Structural Testing and Acceptance of Fabrication & Welding

8/3/2019 Structural Testing and Acceptance of Fabrication & Welding

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STRUCTURAL TESTING ANDACCEPTANCE

FABRICATION AND WELDING


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PRE-TESTING STEEL TESTING AND ACCEPTANCE STRUCTURAL FABRICATION ERECTION WELDING PROCESSES, CONSUMABLES

AND TYPES OF WELDS

FASTENERS, BOLTS AND RIVETS DEFECTS, CAUSES AND REMEDIAL

MEASURES


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Beam (structure)

A beam is a structural element that is capable of withstanding load primarilyby resisting bending. The bending force induced into the material of thebeam as a result of the external loads, own weight and external reactions tothese loads is called a bending moment.

Beams generally carry verticalgravitationalforces but can also be used tocarry horizontal loads (i.e., loads due to an earthquake or wind). The loads

carried by a beam are transferred to columns, walls, or girders, which thentransfer the force to adjacent structural

compression members. In Lightframe construction thejoists rest on the beam.

Beams are characterized by their profile (the shape of their cross-section),their length, and their material. In contemporary construction, beams aretypically made of steel

, reinforced concrete, or wood. One of the mostcommon types of steel beam is the I-beam or wide-flange beam (also

known as a "universal beam" or, for stouter sections, a "universal column").This is commonly used in steel-frame buildings and bridges. Other commonbeam profiles are the C-channel, the hollow structural section beam, thepipe, and the angle.
http://en.wikipedia.org/wiki/List_of_structural_elementshttp://en.wikipedia.org/wiki/Structural_loadhttp://en.wikipedia.org/wiki/Bendinghttp://en.wikipedia.org/wiki/Bending_momenthttp://en.wikipedia.org/wiki/Vertical_directionhttp://en.wikipedia.org/wiki/Gravitationalhttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Horizontal_planehttp://en.wikipedia.org/wiki/Earthquakehttp://en.wikipedia.org/wiki/Columnhttp://en.wikipedia.org/wiki/Wallhttp://en.wikipedia.org/wiki/Girderhttp://en.wikipedia.org/wiki/Compression_memberhttp://en.wikipedia.org/wiki/Light_frame_constructionhttp://en.wikipedia.org/wiki/Light_frame_constructionhttp://en.wikipedia.org/wiki/Joisthttp://en.wikipedia.org/wiki/Materialhttp://en.wiktionary.org/wiki/profilehttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Reinforced_concretehttp://en.wikipedia.org/wiki/Woodhttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/Flangehttp://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Structural_steelhttp://en.wikipedia.org/wiki/Hollow_structural_sectionhttp://en.wikipedia.org/wiki/Pipe_%28material%29http://en.wikipedia.org/wiki/Structural_steelhttp://en.wikipedia.org/wiki/Structural_steelhttp://en.wikipedia.org/wiki/Pipe_%28material%29http://en.wikipedia.org/wiki/Hollow_structural_sectionhttp://en.wikipedia.org/wiki/Structural_steelhttp://en.wikipedia.org/wiki/Structural_steelhttp://en.wikipedia.org/wiki/Structural_steelhttp://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Flangehttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/Woodhttp://en.wikipedia.org/wiki/Reinforced_concretehttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Materialhttp://en.wiktionary.org/wiki/profilehttp://en.wikipedia.org/wiki/Joisthttp://en.wikipedia.org/wiki/Light_frame_constructionhttp://en.wikipedia.org/wiki/Light_frame_constructionhttp://en.wikipedia.org/wiki/Compression_memberhttp://en.wikipedia.org/wiki/Girderhttp://en.wikipedia.org/wiki/Wallhttp://en.wikipedia.org/wiki/Columnhttp://en.wikipedia.org/wiki/Earthquakehttp://en.wikipedia.org/wiki/Horizontal_planehttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Gravitationalhttp://en.wikipedia.org/wiki/Vertical_directionhttp://en.wikipedia.org/wiki/Bending_momenthttp://en.wikipedia.org/wiki/Bendinghttp://en.wikipedia.org/wiki/Structural_loadhttp://en.wikipedia.org/wiki/List_of_structural_elements


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Contents

1 Determination of the bending moment 2 Structural characteristics

3 General shapes

D i i f h b di
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Determination of the bendingmoment

The magnitude of the bending moment along the length of a beamvaries depending on the loading on the beam and the location andtype of supports on which the beam is located. Typically the bendingmoment is calculated by making an imaginary cut through the beamwhere the bending moment and shear force in the beam arerequired to be calculated. The application and mathematical

manipulation of Newton's Laws to tiny elements of material at thecut reveal the existence of the bending moment in the beam. Apositive bending moment induces compressive forces above the socalled neutral axis, while tensile forces are induced in the materialbelow the neutral axis. The compressive and tensile forces result inshortening and lengthening of the material respectively above andbelow the neutral axis resulting in the characteristic bending found inbeams.
http://en.wikipedia.org/wiki/Newton%27s_Lawshttp://en.wikipedia.org/wiki/Newton%27s_Laws


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Structural characteristics Internally, beams experience compressive, tensile and shear

stresses as a result of the loads applied to them. Typically, under

gravity loads, the original length of the beam is slightly reduced toenclose a smaller radius arc at the top of the beam, resulting incompression, while the same original beam length at the bottom ofthe beam is slightly stretched to enclose a larger radius arc, and sois under tension. The same original length of the middle of thebeam, generally halfway between the top and bottom, is the same

as the radial arc of bending, and so it is under neither compressionnor tension, and defines the neutral axis (dotted line in the beamfigure). Above the supports, the beam is exposed to shear stress.There are some reinforced concrete beams that are entirely incompression. These beams are known as prestressed concretebeams, and are fabricated to produce a compression more than theexpected tension under loading conditions. High strength steel

tendons are stretched while the beam is cast over them. Then, whenthe concrete has begun to cure, the tendons are released and thebeam is immediately under eccentric axial loads. This eccentricloading creates an internal moment, and, in turn, increases themoment carrying capacity of the beam. They are commonly used onhighway bridges.
http://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Tension_%28mechanics%29http://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Prestressed_concretehttp://en.wikipedia.org/wiki/Prestressed_concretehttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Tension_%28mechanics%29http://en.wikipedia.org/wiki/Physical_compression


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The primary tool for structural analysis of beams is the Euler-Bernoulli beam equation. Other mathematical methods fordetermining the deflection of beams include "method of virtual work"and the "slope deflection method". Engineers are interested indetermining deflections because the beam may be in direct contactwith a brittle material such as glass. Beam deflections are alsominimized for aesthetic reasons. A visibly sagging beam, thoughstructurally safe, is unsightly and to be avoided. A stiffer beam (highmodulus of elasticity and high second moment of area) producesless deflection. Mathematical methods for determining the beamforces (internal forces of the beam and the forces that are imposedon the beam support) include the "moment distribution method", the

force or flexibility method and the direct stiffness method.
http://en.wikipedia.org/wiki/Euler-Bernoulli_beam_equationhttp://en.wikipedia.org/wiki/Euler-Bernoulli_beam_equationhttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Virtual_workhttp://en.wikipedia.org/wiki/Brittlehttp://en.wikipedia.org/wiki/Stiffnesshttp://en.wikipedia.org/wiki/Modulus_of_elasticityhttp://en.wikipedia.org/wiki/Second_moment_of_areahttp://en.wikipedia.org/wiki/Moment_distributionhttp://en.wikipedia.org/wiki/Flexibility_methodhttp://en.wikipedia.org/wiki/Direct_stiffness_methodhttp://en.wikipedia.org/wiki/Direct_stiffness_methodhttp://en.wikipedia.org/wiki/Flexibility_methodhttp://en.wikipedia.org/wiki/Moment_distributionhttp://en.wikipedia.org/wiki/Second_moment_of_areahttp://en.wikipedia.org/wiki/Modulus_of_elasticityhttp://en.wikipedia.org/wiki/Stiffnesshttp://en.wikipedia.org/wiki/Brittlehttp://en.wikipedia.org/wiki/Virtual_workhttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Euler-Bernoulli_beam_equationhttp://en.wikipedia.org/wiki/Euler-Bernoulli_beam_equationhttp://en.wikipedia.org/wiki/Euler-Bernoulli_beam_equation


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Diagram of stiffness of a simple square beam (A) and universal beam (B). Theuniversal beam flange sections are three times further apart than the solidbeam's upper and lower halves. The second moment of inertia of the universalbeam is nine times that of the square beam of equal cross section (universal


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General shapes

Mostly the beams have rectangular cross sections in reinforcedconcrete buildings, but the most efficient cross-section is a universalbeam. The fact that most of the material is placed away from theneutral axis (axis of symmetry in case of universal beam) increasesthe second moment of area of the beam which in turn increases thestiffness.

A universal beam is only the most efficient shape in one direction ofbending: up and down looking at the profile as an I. If the beam isbent side to side , it functions as an H where it is less efficient. Themost efficient shape for both directions in 2D is a box (a squareshell) however the most efficient shape for bending in any directionis a cylindrical shell or tube. But, for unidirectional bending, the

universal (I or wide flange) beam is king. Efficiency means that for the same cross sectional area (Volume ofbeam per length) subjected to the same loading conditions, thebeam deflects less.

Other shapes, like L (angles), C (Channels) or tubes, are also usedin construction when there are special requirements.
http://en.wikipedia.org/wiki/Reinforced_concretehttp://en.wikipedia.org/wiki/Reinforced_concretehttp://en.wikipedia.org/wiki/Neutral_axishttp://en.wikipedia.org/wiki/Second_moment_of_areahttp://en.wikipedia.org/wiki/Second_moment_of_areahttp://en.wikipedia.org/wiki/Neutral_axishttp://en.wikipedia.org/wiki/Reinforced_concretehttp://en.wikipedia.org/wiki/Reinforced_concrete


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See also

Bending and Bending Moment Bridge Building code Cantilever Classical mechanics Compression member Deflection Elastic modulus or Modulus of elasticity Elasticity (physics) and Plasticity (physics) Free body diagram I-beam

Joist Light-frame construction Materials science and Strength of materials
http://en.wikipedia.org/wiki/Bendinghttp://en.wikipedia.org/wiki/Bending_Momenthttp://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Building_codehttp://en.wikipedia.org/wiki/Cantileverhttp://en.wikipedia.org/wiki/Classical_mechanicshttp://en.wikipedia.org/wiki/Compression_memberhttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Elastic_modulushttp://en.wikipedia.org/wiki/Elasticity_%28physics%29http://en.wikipedia.org/wiki/Plasticity_%28physics%29http://en.wikipedia.org/wiki/Free_body_diagramhttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/Joisthttp://en.wikipedia.org/wiki/Light-frame_constructionhttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Light-frame_constructionhttp://en.wikipedia.org/wiki/Light-frame_constructionhttp://en.wikipedia.org/wiki/Light-frame_constructionhttp://en.wikipedia.org/wiki/Joisthttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/I-beamhttp://en.wikipedia.org/wiki/Free_body_diagramhttp://en.wikipedia.org/wiki/Plasticity_%28physics%29http://en.wikipedia.org/wiki/Elasticity_%28physics%29http://en.wikipedia.org/wiki/Elastic_modulushttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Compression_memberhttp://en.wikipedia.org/wiki/Classical_mechanicshttp://en.wikipedia.org/wiki/Cantileverhttp://en.wikipedia.org/wiki/Building_codehttp://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Bending_Momenthttp://en.wikipedia.org/wiki/Bending


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Moment (physics) Finite element method in structural mechanics Poisson's ratio Post and lintel Second moment of area, sometimes referred to as the moment of

inertia Shear strength and Shear stress Span (architecture) Statics and Statically indeterminate Stress (physics) and Strain (materials science)

Structural analysis and Structural load Tensile strength, Tensile stress and Hooke's law Thin-shell structure Truss Yield (engineering)
http://en.wikipedia.org/wiki/Moment_%28physics%29http://en.wikipedia.org/wiki/Finite_element_method_in_structural_mechanicshttp://en.wikipedia.org/wiki/Poisson%27s_ratiohttp://en.wikipedia.org/wiki/Post_and_lintelhttp://en.wikipedia.org/wiki/Second_moment_of_areahttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Span_%28architecture%29http://en.wikipedia.org/wiki/Staticshttp://en.wikipedia.org/wiki/Statically_indeterminatehttp://en.wikipedia.org/wiki/Stress_%28physics%29http://en.wikipedia.org/wiki/Strain_%28materials_science%29http://en.wikipedia.org/wiki/Structural_analysishttp://en.wikipedia.org/wiki/Structural_loadhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Hooke%27s_lawhttp://en.wikipedia.org/wiki/Thin-shell_structurehttp://en.wikipedia.org/wiki/Trusshttp://en.wikipedia.org/wiki/Yield_%28engineering%29http://en.wikipedia.org/wiki/Yield_%28engineering%29http://en.wikipedia.org/wiki/Trusshttp://en.wikipedia.org/wiki/Thin-shell_structurehttp://en.wikipedia.org/wiki/Thin-shell_structurehttp://en.wikipedia.org/wiki/Thin-shell_structurehttp://en.wikipedia.org/wiki/Hooke%27s_lawhttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Structural_loadhttp://en.wikipedia.org/wiki/Structural_analysishttp://en.wikipedia.org/wiki/Strain_%28materials_science%29http://en.wikipedia.org/wiki/Stress_%28physics%29http://en.wikipedia.org/wiki/Statically_indeterminatehttp://en.wikipedia.org/wiki/Staticshttp://en.wikipedia.org/wiki/Span_%28architecture%29http://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Second_moment_of_areahttp://en.wikipedia.org/wiki/Post_and_lintelhttp://en.wikipedia.org/wiki/Poisson%27s_ratiohttp://en.wikipedia.org/wiki/Finite_element_method_in_structural_mechanicshttp://en.wikipedia.org/wiki/Moment_%28physics%29


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STRENGTH OF MATERIALS

Contents

1 Definitions 1.1 Stress terms 1.2 Strength terms 1.3 Strain (deformation) terms

2 Stress-strain relations 3 Design terms
http://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materials


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In materials science, the strength of a material refers to thematerial's ability to resist an applied stress. The applied stress maybe tensile, compressive or shear.

A material's strength is a function of engineering processes, and

scientists employ a variety of strengthening mechanisms to alter thestrength of a material. These mechanisms include work hardening,solid solution strengthening, precipitation hardening and grainboundary strengthening and can be quantified and qualitativelyexplained. However, strengthening mechanisms are accompaniedby the caveat that mechanical properties of the material maydegenerate in an attempt to make the material stronger. For

example, in grain boundary strengthening, although yield strength ismaximized with decreasing grain size, ultimately, very small grainsizes make the material brittle. In general, the yield strength of amaterial is an adequate indicator of the material's mechanicalstrength. Considered in tandem with the fact that the yield strengthis the parameter that predicts plastic deformation in the material,one can make informed decisions on how to increase the strength ofa material depending its microstructural properties and the desiredend effect. Strength is considered in terms of compressive strength,tensile strength, and shear strength, namely the limit states ofcompressive stress, tensile stress and shear stress, respectively.The effects of dynamic loading is probably the most importantpractical part of the strength of materials, especially the problem of

fatigue. Repeated loading often initiates brittle cracks, which growslowly until failure occurs.
http://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Stress_%28physics%29http://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Strengthening_mechanisms_of_materialshttp://en.wikipedia.org/wiki/Work_hardeninghttp://en.wikipedia.org/wiki/Solid_solution_strengtheninghttp://en.wikipedia.org/wiki/Precipitation_hardeninghttp://en.wikipedia.org/wiki/Grain_boundary_strengtheninghttp://en.wikipedia.org/wiki/Grain_boundary_strengtheninghttp://en.wikipedia.org/wiki/Yield_strengthhttp://en.wikipedia.org/wiki/Deformationhttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Fatigue_%28material%29http://en.wikipedia.org/wiki/Fatigue_%28material%29http://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Deformationhttp://en.wikipedia.org/wiki/Yield_strengthhttp://en.wikipedia.org/wiki/Grain_boundary_strengtheninghttp://en.wikipedia.org/wiki/Grain_boundary_strengtheninghttp://en.wikipedia.org/wiki/Precipitation_hardeninghttp://en.wikipedia.org/wiki/Solid_solution_strengtheninghttp://en.wikipedia.org/wiki/Work_hardeninghttp://en.wikipedia.org/wiki/Strengthening_mechanisms_of_materialshttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Stress_%28physics%29http://en.wikipedia.org/wiki/Materials_science


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However, the term strength of materials most oftenrefers to various methods of calculating stresses instructural members, such as beams, columns andshafts, when the equations of equilibrium are not

sufficient to solve the problem. In such problems, knownas statically indeterminate problems, the elastic or plasticresistance of the material to deformation must beconsidered when calculating stresses. In this sense, theword "strength" could well be replaced by "stiffness", but

the usage goes back to at least 1930 and is not likely togo away any time soon.

St t


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Stress terms

Uniaxial stress is expressed by

where Fis the force [N] acting on an area A [m2]. The area can be

the undeformed area or the deformed area, depending on whetherengineering stress or true stress is used. Compressive stress(or compression) is the stress state when the

material (compression member) tends to compact. A simple case ofcompression is the uniaxial compression induced by the action ofopposite, pushing forces. Compressive strength for materials is

generally higher than that of tensile stress, but geometry is veryimportant in the analysis, as compressive stress can lead tobuckling.

Tensile stressis a loading that tends to produce stretching of amaterial by the application of axially directed pullingforces. Anymaterial which falls into the "elastic" category can generally toleratemild tensile stresses while materials such as ceramics and brittlealloys are very succeptable to failure under the same conditions. If amaterial is stressed beyond its limits, it will fail. The failure mode,either ductile or brittle, is based mostly on the microstructure of thematerial. Some Steel alloys are examples of materials with hightensile strength.

Shear stressis caused when a force is applied to produce a sliding

failure of a material along a plane that is parallel to the direction ofthe applied force. An example is cutting paper with scissors.
http://en.wikipedia.org/wiki/Engineering_stresshttp://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Compression_memberhttp://en.wikipedia.org/wiki/Bucklinghttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Scissorhttp://en.wikipedia.org/wiki/Scissorhttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Bucklinghttp://en.wikipedia.org/wiki/Compression_memberhttp://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Engineering_stress


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A material being loaded in a)compression, b) tension, c) shear.

S h


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Strength terms

Yield strengthis the lowest stress that gives permanent deformationin a material. In some materials, like aluminium alloys, the point ofyielding is hard to define, thus it is usually given as the stressrequired to cause 0.2% plastic strain.

Compressive strengthis a limit state of compressive stress thatleads to compressive failure in the manner of ductile failure (infinitetheoretical yield) or in the manner of brittle failure (rupture as theresult of crack propagation, or sliding along a weak plane - seeshear strength).

Tensile strengthor ultimate tensile strengthis a limit state of tensile

stress thats leads to tensile failure in the manner of ductile failure(yield as the first stage of failure, some hardening in the secondstage and break after a possible "neck" formation) or in the mannerof brittle failure (sudden breaking in two or more pieces with a lowstress state). Tensile strength can be given as either true stress orengineering stress.

Fatigue strengthis a measure of the strength of a material or acomponent under cyclic loading, and is usually more difficult toassess than the static strength measures. Fatigue strength is givenas stress amplitude or stress range ( = max min), usually atzero mean stress, along with the number of cycles to failure.

Impact strength, it is the capability of the material in withstanding bythe suddenly applied loads in terms of energy. Often measured withthe Izod impact strength test or Charpy impact test, both of whichmeasure the im act ener re uired to fracture a sam le.
http://en.wikipedia.org/wiki/Yield_%28engineering%29http://en.wikipedia.org/wiki/Aluminium_alloyhttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Fatigue_%28material%29http://en.wikipedia.org/w/index.php?title=Impact_strength&action=edit&redlink=1http://en.wikipedia.org/wiki/Izod_impact_strength_testhttp://en.wikipedia.org/wiki/Charpy_impact_testhttp://en.wikipedia.org/wiki/Charpy_impact_testhttp://en.wikipedia.org/wiki/Izod_impact_strength_testhttp://en.wikipedia.org/w/index.php?title=Impact_strength&action=edit&redlink=1http://en.wikipedia.org/wiki/Fatigue_%28material%29http://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Shear_strengthhttp://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Aluminium_alloyhttp://en.wikipedia.org/wiki/Yield_%28engineering%29


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Strain (deformation) terms

Deformationof the material is the change in geometrywhen stress is applied (in the form of force loading,

gravitational field, acceleration, thermal expansion, etc.).Deformation is expressed by the displacement field ofthe material.

Strainor reduced deformationis a mathematical term toexpress the trend of the deformation change among the

material field. For uniaxial loading - displacements of aspecimen (for example a bar element) it is expressed asthe quotient of the displacement and the length of thespecimen. For 3D displacement fields it is expressed asderivatives of displacement functions in terms of a

second order tensor (with 6 independent elements). Deflectionis a term to describe the magnitude to which a

structural element bends under a load.
http://en.wikipedia.org/wiki/Deformationhttp://en.wikipedia.org/wiki/Strain_%28materials_science%29http://en.wikipedia.org/wiki/Tensorhttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Tensorhttp://en.wikipedia.org/wiki/Strain_%28materials_science%29http://en.wikipedia.org/wiki/Deformation


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Stress-strain relations

Elasticityis the ability of a material to return to its previous shapeafter stress is released. In many materials, the relation betweenapplied stress and the resulting strain is directly proportional (up to acertain limit), and a graph representing those two quantities is astraight line.

The slope of this line is known as Young's Modulus, or the "Modulusof Elasticity." The Modulus of Elasticity can be used to determinestress-strain relationships in the linear-elastic portion of the stress-strain curve. The linear-elastic region is taken to be between 0 and0.2% strain, and is defined as the region of strain in which no

yielding (permanent deformation) occurs. Plasticityor plastic deformation is the opposite of elastic deformation

and is accepted as unrecoverable strain. Plastic deformation isretained even after the relaxation of the applied stress. Mostmaterials in the linear-elastic category are usually capable of plasticdeformation. Brittle materials, like ceramics, do not experience any

plastic deformation and will fracture under relatively low stress.Materials such as metals usually experience a small amount ofplastic deformation before failure while soft or ductile polymers willplastically deform much more.

Consider the difference between a fresh carrot and chewed bubblegum. The carrot will stretch very little before breaking, butnevertheless will still stretch. The chewed bubble gum, on the otherhand, will plastically deform enormously before finally breaking.

Design terms
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Design terms

Ultimate strength is an attribute directly related to amaterial, rather than just specific specimen of thematerial, and as such is quoted force per unit of crosssection area (N/m). For example, the ultimate tensilestrength (UTS) of AISI 1018 Steel is 440 MN/m. Ingeneral, the SI unit of stress is the Pascal, where 1 Pa =1 N/m. In Imperial units, the unit of stress is given as

lbf/in or pounds-force per square inch. This unit is oftenabbreviated as psi. One thousand psi is abbreviated ksi. Factor of safety is a design constraint that an engineered

component or structure must achieve. FS= UTS/ R,where FS: the Factor of Safety, R: The applied stress,

and UTS: the Ultimate force (or stress). Margin of Safety is also sometimes used to as designconstraint. It is defined MS=Factor of safety - 1

For example to achieve a factor of safety of 4, theallowable stress in an AISI 1018 steel component can be

worked out as R= UTS/ FS= 440/4 = 110 MPa, or R=110106 N/m.

W ldi
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Welding

Arc welding uses a welding power supply to

create an electric arc between an electrode andthe base material to melt the metals at thewelding point. They can use either direct (DC) oralternating (AC) current, and consumable or

non-consumable electrodes. The welding regionis sometimes protected by some type of inert orsemi-inert gas, known as a shielding gas, and/oran evaporating filler material. The process of arc

welding is widely used because of its low capitaland running costs.
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Contents

1 Development 2 Power supplies 3 Consumable electrode methods

4 Non-consumable electrode methods 5 Corrosion issues 6 Safety issues 6.1 Heat and sparks

6.2 Eye damage 6.3 Inhaled matter 6.4 Interference with pacemakers

Development
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Development

While examples of forge welding go back to the BronzeAge and the Iron Age, arc welding did not come into

practice until much later. In 1808, Humphry Davydiscovered the electric arc, initiating the development ofarc welding[1] which continued with the inventions ofmetal electrodes by a Russian (N.G. Slavianoff) and anAmerican (C.L. Coffin) in the late 1800s even as carbonarc welding, which used a carbon electrode, gainedpopularity. Around 1900, A. P. Strohmenger released inBritain a coated metal electrode which gave a morestable arc. In 1919, alternating current welding wasinvented by C.J. Holslag but did not become popular foranother decade.[2]

Competing welding processes such as resistancewelding and oxyfuel welding were developed during thistime as well;[3] but both, especially the latter, faced stiffcompetition from arc welding especially after metalcoverings (known as flux) for the electrode, to stabilize

the arc and shield the base material from impurities,continued to be developed.[4]

During World War I welding started to be used in shipbuilding in
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During World War I welding started to be used in shipbuilding inGreat Britain in place of riveted steel plates. The Americans alsobecame more accepting of the new technology when the processallowed them to repair their ships quickly after a German attack inthe New York Harbor at the beginning of the war.[5] Arc welding was

first applied to aircraft during the war as well, and some Germanairplane fuselages were constructed using this process.[6] In 1919,the British shipbuilder Cammell Laird started construction ofmerchant ship, the Fullagar, with an entirely welded hull;[7] she waslaunched in 1921.[8]

During the 1920s, major advances were made in welding technology,including the 1920 introduction of automatic welding in which electrodewire was continuously fed. Shielding gas became a subject receivingmuch attention as scientists attempted to protect welds from the effectsof oxygen and nitrogen in the atmosphere. Porosity and brittleness were

the primary problems and the solutions that developed included the useof hydrogen, argon, and helium as welding atmospheres.[9] During thefollowing decade, further advances allowed for the welding of reactivemetals such as aluminum and magnesium. This, in conjunction withdevelopments in automatic welding, alternating current, and fluxes fed a

major expansion of arc welding during the 1930s and then during WorldWar II.[10]
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During the middle of the century, many new welding methods wereinvented. Submerged arc welding was invented in 1930 andcontinues to be popular today. Gas tungsten arc welding, afterdecades of development, was finally perfected in 1941 and gasmetal arc welding followed in 1948, allowing for fast welding of non-ferrous materials but requiring expensive shielding gases. Using a

consumable electrode and a carbon dioxide atmosphere as ashielding gas, it quickly became the most popular metal arc weldingprocess. In 1957, the flux-cored arc welding process debuted inwhich the self-shielded wire electrode could be used with automaticequipment, resulting in greatly increased welding speeds. In thatsame year, plasma arc welding was invented. Electroslag weldingwas released in 1958 and was followed by its cousin, electrogaswelding, in 1961.[11]

Power supplies
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Power supplies

To supply the electrical energy necessary for arc welding processes,a number of different power supplies can be used. The mostcommon classification is constant current power supplies andconstant voltage power supplies. In arc welding, the voltage is

directly related to the length of the arc, and the current is related tothe amount of heat input. Constant current power supplies are mostoften used for manual welding processes such as gas tungsten arcwelding and shielded metal arc welding, because they maintain arelatively constant current even as the voltage varies. This isimportant because in manual welding, it can be difficult to hold theelectrode perfectly steady, and as a result, the arc length and thusvoltage tend to fluctuate. Constant voltage power supplies hold thevoltage constant and vary the current, and as a result, are mostoften used for automated welding processes such as gas metal arcwelding, flux cored arc welding, and submerged arc welding. Inthese processes, arc length is kept constant, since any fluctuation inthe distance between the wire and the base material is quickly

rectified by a large change in current. For example, if the wire andthe base material get too close, the current will rapidly increase,which in turn causes the heat to increase and the tip of the wire tomelt, returning it to its original separation distance.[12]
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The direction of current used in arc welding also plays an importantrole in welding. Consumable electrode processes such as shieldedmetal arc welding and gas metal arc welding generally use directcurrent, but the electrode can be charged either positively or

negatively. In welding, the positively charged anode will have agreater heat concentration and, as a result, changing the polarity ofthe electrode has an impact on weld properties. If the electrode ispositively charged, it will melt more quickly, increasing weldpenetration and welding speed. Alternatively, a negatively chargedelectrode results in more shallow welds.[13] Non-consumableelectrode processes, such as gas tungsten arc welding, can useeither type of direct current (DC), as well as alternating current (AC).With direct current however, because the electrode only creates thearc and does not provide filler material, a positively chargedelectrode causes shallow welds, while a negatively chargedelectrode makes deeper welds.[14] Alternating current rapidlymoves between these two, resulting in medium-penetration welds.

One disadvantage of AC, the fact that the arc must be re-ignitedafter every zero crossing, has been addressed with the invention ofspecial power units that produce a square wave pattern instead ofthe normal sine wave, eliminating low-voltage time after the zerocrossings and minimizing the effects of the problem.[15]

Consumable electrode methods
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Consumable electrode methods

One of the most common types of arc welding is shielded metal arcwelding (SMAW), which is also known as manual metal arc welding(MMA) or stick welding. An electric current is used to strike an arcbetween the base material and a consumable electrode rod or'stick'. The electrode rod is made of a material that is compatiblewith the base material being welded and is covered with a flux thatprotects the weld area from oxidation and contamination byproducing CO2 gas during the welding process. The electrode coreitself acts as filler material, making a separate filler unnecessary.The process is very versatile, requiring little operator training and

inexpensive equipment. However, weld times are rather slow, sincethe consumable electrodes must be frequently replaced andbecause slag, the residue from the flux, must be chipped away afterwelding.[16] Furthermore, the process is generally limited to weldingferrous materials, though specialty electrodes have made possiblethe welding of cast iron, nickel, aluminium, copper and other metals.The versatility of the method makes it popular in a number ofapplications including repair work and construction.
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Gas metal arc welding (GMAW) is a semi-automatic or automatic weldingprocess that uses a continuous wire feed as an electrode and an inert orsemi-inert shielding gas to protect the weld from contamination. Whenusing an inert gas as shield it is known as Metal Inert Gas (MIG) welding.

A constant voltage, direct current power source is most commonly usedwith GMAW, but constant current systems as well as alternating currentcan be used. GMAW welding speeds are relatively high due to theautomatically fed continuous electrode, but is less versatile because itrequires more equipment than the simpler SMAW process. Originallydeveloped for welding aluminium and other non-ferrous materials in the1940s, GMAW was soon applied to steels because it allowed for lower

welding time compared to other welding processes. Today, GMAW iscommonly used in industries such as the automobile industry, where it ispreferred for its versatility and speed. Because it employs a shielding gas,however, it is rarely used outdoors or in areas of air volatility.[18]

A related process, flux-cored arc welding (FCAW), uses similar equipmentbut uses wire consisting of a steel electrode tube surrounding a powder fill

material. This cored wire is more expensive than the standard solid wireand generates extra shielding gas and/or slag, but it permits higherwelding speed and greater metal penetration.[1
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Submerged arc welding (SAW) is a high-productivityautomatic welding method in which the arc is struckbeneath a covering layer of flux. This increases arcquality, since contaminants in the atmosphere are

blocked by the flux. The slag that forms on the weldgenerally comes off by itself and, combined with the useof a continuous wire feed, the weld deposition rate ishigh. Working conditions are much improved over otherarc welding processes since the flux hides the arc and

no smoke is produced. The process is commonly used inindustry, especially for large products.[20] As the arc isnot visible, it requires full automatization. In-positionwelding is not possible with SAW.

Non consumable electrode methods
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Non-consumable electrode methods

Gas tungsten arc welding (GTAW), or tungsten inert gas (TIG) welding, is amanual welding process that uses a non-consumable electrode made oftungsten, an inert or semi-inert gas mixture, and a separate filler material.Especially useful for welding thin materials, this method is characterized bya stable arc and high quality welds, but it requires significant operator skilland can only be accomplished at relatively low speeds. It can be used onnearly all weldable metals, though it is most often applied to stainless steeland light metals. It is often used when quality welds are extremely important,such as in bicycle, aircraft and naval applications.[21] A related process,plasma arc welding, also uses a tungsten electrode but uses plasma gas to

make the arc. The arc is more concentrated than the GTAW arc, makingtransverse control more critical and thus generally restricting the techniqueto a mechanized process. Because of its stable current, the method can beused on a wider range of material thicknesses than can the GTAW processand is much faster. It can be applied to all of the same materials as GTAWexcept magnesium; automated welding of stainless steel is one importantapplication of the process. A variation of the process is plasma cutting, an

efficient steel cutting process.[22] Other arc welding processes include atomic hydrogen welding, carbon arc

welding, electroslag welding, electrogas welding, and stud arc welding.

Corrosion issues
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Corrosion issues

Some materials, notably high-strength steels, aluminum, and titaniumalloys, are susceptible to hydrogen embrittlement. If the electrodes used

for welding contain traces of moisture, the water decomposes in the heatof the arc and the liberated hydrogen enters the lattice of the material,causing its brittleness. Electrodes for such materials, with special low-hydrogen coating, are delivered in sealed moisture-proof packaging. Newelectrodes can be used straight from the can, but when moistureabsorption may be suspected, they have to be dried by baking (usually at800 to 1000 F (425 to 550 C)) in a drying oven. Flux used has to bekept dry as well.[23]

Some austeniticstainless steels and nickel-based alloys are prone tointer-granular corrosion. When subjected to temperatures around 700 C(1,300 F) for too long time, chromium reacts with carbon in the material,forming chromium carbide and depleting the crystal edges of chromium,impairing their corrosion resistance in a process called sensitization.

Such sensitized steel undergoes corrosion in the areas near the weldswhere the temperature-time was favorable for forming the carbide. Thiskind of corrosion is often termed weld decay.
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Knifeline attack (KLA) is another kind of corrosion affecting welds,impacting steels stabilized by niobium. Niobium and niobium carbidedissolves in steel at very high temperatures. At some cooling regimes,niobium carbide does not precipitate, and the steel then behaves like

unstabilized steel, forming chromium carbide instead. This affects only athin zone several millimeters wide in the very vicinity of the weld, making itdifficult to spot and increasing the corrosion speed. Structures made ofsuch steels have to be heated in a whole to about 1,950 F (1,070 C),when the chromium carbide dissolves and niobium carbide forms. Thecooling rate after this treatment is not important.[24]

Filler metal (electrode material) improperly chosen for the environmentalconditions can make them corrosion-sensitive as well. There are alsoissues of galvanic corrosion if the electrode composition is sufficientlydissimilar to the materials welded, or the materials are dissimilarthemselves. Even between different grades of nickel-based stainlesssteels, corrosion of welded joints can be severe, despite that they rarelyundergo galvanic corrosion when mechanically joined.[25]

Safety issues
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Safety issues

Welding can be a dangerous and unhealthy practice without the properprecautions; however, with the use of new technology and properprotection the risks of injury or death associated with welding can begreatly reduced.

[edit] Heat and sparks Because many common welding procedures involve an open electric arc or

flame, the risk of burns is significant. To prevent them, welders wearprotective clothing in the form of heavy leathergloves and protective longsleeve jackets to avoid exposure to extreme heat, flames, and sparks.

[edit] Eye damage

The brightness of the weld area leads to a condition called arc eye in whichultraviolet light causes inflammation of the cornea and can burn the retinasof the eyes. Goggles and helmets with dark face plates are worn to preventthis exposure and, in recent years, new helmet models have beenproduced featuring a face plate that self-darkens upon exposure to highamounts of UV light. To protect bystanders, transparent welding curtains

often surround the welding area. These curtains, made of a polyvinylchloride plastic film, shield nearby workers from exposure to the UV lightfrom the electric arc, but should not be used to replace the filter glass usedin helmets.[26]
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In 1970, a Swedish doctor, ke Sandn, developed a new type of weldinggoggles that used a multilayer interference filter to block most of the lightfrom the arc. He had observed that most welders could not see wellenough, with the mask on, to strike the arc, so they would flip the mask up,then flip it down again once the arc was going: this exposed their naked

eyes to the intense light for a while. By coincidence, the spectrum of anelectric arc has a notch in it, which coincides with the yellow sodium line.Thus, a welding shop could be lit by sodium vapor lamps or daylight, andthe welder could see well to strike the arc. The Swedish governmentrequired these masks to be used for arc welding, but they were not used inthe United States. They may have disappeared.[27]

Inhaled matterWelders are also often exposed to dangerous gases and particulate matter. Processeslike flux-cored arc welding and shielded metal arc welding produce smoke containing

particles of various types of oxides. The size of the particles in question tends toinfluence the toxicity of the fumes, with smaller particles presenting a greater danger.Additionally, many processes produce various gases (most commonly carbon dioxideand ozone, but others as well) that can prove dangerous if ventilation is inadequate.Furthermore, the use of compressed gases and flames in many welding processes

pose an explosion and fire risk; some common precautions include limiting the amountof oxygen in the air and keeping combustible materials away from the workplace.[28]
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Interference with pacemakers

Certain welding machines which use ahigh frequency AC current componenthave been found to affect pacemakeroperation when within 2 meters of thepower unit and 1 meter of the weld site


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Rivet

Contents

1 Types 1.1 Solid rivets 1.2 Blind rivets

1.3 Drive rivet 1.4 Flush rivet 2 Sizes 3 Applications 4 Joint analysis 5 Installation 6 Testing 7 High Strength Structural Steel Rivets (ASTM 502A) 8 Alternatives
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A rivet is a mechanical fastener. Before it is installed it consists of asmooth cylindrical shaft with a head on one end. The end oppositethe head is called the buck-tail. On installation the rivet is placed in a

pre-drilled hole. Then the tail is "upset" (i.e. deformed) so that itexpands to about 1.5 times the original shaft diameter and holds therivet in place. To distinguish between the two ends of the rivet, theoriginal head is called the factory head and the deformed end iscalled the shop head or buck-tail.

Because there is effectively a head on each end of an installed rivetit can support tension loads (loads parallel to the axis of the shaft);however, it is much more capable of supporting shear loads (loadsperpendicular to the axis of the shaft). Bolts and screws are bettersuited for tension applications.

Fastenings used in traditional wooden boat building like copper nailsand clinch bolts work on the principle of the rivet but they were inuse long before the term rivet was invented. So, where they are

remembered, they are usually classified among the nails and boltsrespectively.
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TypesThere are a number of types of rivets, designed to meet different cost,

accessibility, and strength requirements. These include solid rivets,blind rivets, multi-grip rivets, grooved rivets, peel type blind rivets, self-

pierce rivets, plastic rivets, tubular rivets, etc.

Solid rivets A typical technical drawing of a universal head solid rivet Solid rivets are one of the oldest and most reliable types of

fasteners, having been found in archaeological findings dating backto the Bronze Age. Solid rivets consist simply of a shaft and headwhich are deformed with a hammer or rivet gun. The use of a rivetcompression or crimping tool can also be used to deform these typeof rivets; this tool is mainly used on rivets closer to the edge since itis limited by its depth of frame. A rivet compression tool does notrequire two people and is generally the most foolproof way to installsolid rivets.

A i l h i l d i f
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A typical technical drawing of auniversal head solid rivet


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Solid rivets are used today in applications where reliability andsafety count. A typical application for solid rivets can be found within

the structural parts of aircraft. Hundreds of thousands of solid rivetsare used to assemble the frame of a modern aircraft. Such solidrivets come with rounded (universal) or 100countersunkheads.Typical materials for aircraft rivets are aluminiumalloys (2017, 2024,2117, 7050, 5056, 55000, V-65), titanium, and nickel based alloys(e.g. Monel). Some aluminum alloy rivets are too hard to buck and

must be softened by annealing prior to being bucked. "Ice box"aluminum alloy rivets harden with age. These rivets are likewiseannealed the then kept under sub-freezing refrigeration (hence thename "ice box") to slow the age hardening process. Steel rivets canbe found in static structures such as bridges, cranes, and buildingframes.

The setting of these fasteners requires access to both sides of astructure. Solid rivets are driven using a hydraulically, pneumatically,or electromagnetically driven squeezing tool or even hand heldhammers. Applications in which only one side is available requirethe use of blind rivets.

Blind rivets
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Blind rivets

Blind rivets are tubular and are supplied with a mandrelthrough the center. The rivet assembly is inserted into a

hole drilled through the parts to be joined and a speciallydesigned tool used to draw the mandrel into the rivet.This expands the blind end of the rivet and then themandrel snaps off. (These are also commonly calledpop rivets from the sound and feel through the setting

tool when the mandrel breaks.) These types of Blindrivets have non-locking mandrels and are avoided forcritical structural joints because the mandrels may fallout, due to vibration or other reasons, leaving a hollowrivet that will have a significantly lower load carryingcapability than solid rivets. Furthermore, because of themandrel they are more prone to failure from corrosionand vibration.

P i h d i f bli d i i ll i f lid
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Prior to the adoption of blind rivets, installation of a solidrivet typically required two assemblers: one person witha rivet hammer on one side and a second person with abucking bar on the other side. Seeking an alternative,

inventors such as Carl Cherry and Lou Huckexperimented with other techniques for expanding solidrivets. Unlike solid rivets, blind rivets can be inserted andfully installed in ajoint from only one side of a part orstructure, "blind" to the opposite side.

Due to this feature, blind rivets are mainly used whenaccess to the joint is only available from one side. Therivet is placed in a pre-drilled hole and is set by pullingthe mandrel head into the rivet body, expanding the rivetbody and causing it to flare against the reverse side. Asthe head of the mandrel reaches the face of the blindside material, the pulling force is resisted, and at apredetermined force, the mandrel will snap at the breakpoint of the mandrel. A tight joint formed by the rivetbody remains, the head of the mandrel remainsencapsulated at the blind side, although variations of this

are available, and the mandrel stem is ejected.
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The rivet body is normally manufactured from one of three methods: Wire, the most common method Tube, common in longer lengths, not normally as strong as wire

Sheet, least popular and generally the weakest option. There is a vast array of specialty blind rivets that are suited for high

strength or plastic applications. Typical types include: - TriFold, a rivet that splits into three equal legs like a Molly bolt. Typically

used in soft plastics where a wide footprint is needed at the rear surface.Used in automotive interiors and vinyl fences.

- Structural rivet(a), an "external" mechanically locked structural blind rivetthat is used where a watertight, vibration resistant connection is ofimportance. Typically used in manufacture or repair of truck bodies. Aspecial nose piece is required to apply this rivet.

- Structural rivet(b), an "internal" mechanically locked structural blind rivetthat is used where a watertight, vibration resistant connection is of

importance. Typically used in manufacture or repair of truck bodies.
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Internally and externally locked structural blind rivets canbe used in aircraft applications because, unlike common"pop-rivets" the locked mandrels can not fall out and arewater tight. Since the mandrel is locked into place theyhave the same or greater load carrying capacity as solid

rivets and may be used to replace solid rivets on all butthe most critical stressed aircraft structures. The typical assembly process requires the operator to

install the rivet in the nose of the tool by hand thenactuate the tool. However, in recent years automated

riveting systems have become popular in an effort toreduce assembly costs and repetitive disorders. The costof such tools range from $1,500 for autofeed pneumaticsto $50,000 for fully robotic systems.


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Drive rivet A drive rivet is a form of blind rivet that has a short mandrel

protruding from the head that is driven in with a hammer to flare outthe end inserted in the hole. This is commonly used to rivet wood

panels into place since the hole does not need to be drilled all theway through the panel, producing an aesthetically pleasingappearance. They can also be used with plastic, metal, and othermaterials and require no special setting tool other than a hammerand possibly a backing block (steel or some other dense material)placed behind the location of the rivet while hammering it into place.

Flush rivet A flush rivet is used primarily on external metal surfaces where good

appearance and the elimination of unnecessary aerodynamic dragare important. A flush rivet takes advantage of a countersink hole,they are also commonly referred to as countersunk rivets.

Countersunk or flush rivets are used all over the outside of manymilitary and commercial aircraft, including the AH-64 Apachehelicopter.

Sizes
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Rivet diameters are commonly measured in 1/32 inch incrementsand their lengths in 1/16th inch increments which are expressed as

"dash" numbers at the end of the rivet identification number. A 'dash3','dash 4' (XXXXXX-3-4) designation indicates 3/32" diameter and4/16" or 1/4" long rivet. Some rivets lengths are also available in"half sizes" and will have a dash number such as -3.5 (7/32") toindicate it as a half size rivet. The letters and numbers that precedethe dash numbers, in the rivets identification number, indicate thespecification under which the rivet was manufactured and the headstyle. On many rivets the size in /32nds may be stamped on the rivethead. Other makings on the rivet head such as small raised ordepressed dimples, or small raised bars indicate the rivet's alloy.

To become a proper fastener, a rivet should be placed in hole ideally4-6 thousandths of an inch larger in diameter. This allows the rivet tobe easily and fully inserted, then setting allows the rivet to expand,

tightly filling the gap and maximizing strength.

Applications


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pp

Before welding techniques and bolted joints weredeveloped, metal framed buildings and structures such

as the Eiffel Tower, Shukhov Tower and the SydneyHarbour Bridge were generally held together by riveting.Also automobilechassis were riveted. Riveting is stillwidely used in applications where light weight and highstrength are critical, such as in an aircraft. Many sheet-

metal alloys are preferably not welded as deformationand modification of material properties can occur.

Common but more exotic uses of rivets are to reinforcejeans and to produce the distinctive sound of a sizzlecymbal.

A riveted buffer beam on a steamlocomotive

Joint analysis
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y

The stress and shear in a rivet is analyzed like a boltedjoint. However, it is not wise to combine rivets with bolts

and screws in the same joint. Rivets fill the hole wherethey are installed to establish a very tight fit (often calledinterference fit). It is difficult or impossible to obtain sucha tight fit with other fasteners. The result is that rivets inthe same joint with loose fasteners will carry more of the

loadthey are effectively more stiff. The rivet can thenfail before it can redistribute load to the other loose fitfasteners like bolts and screws. This often results incatastrophic failure of the joint when the fasteners"unzip". In general, a joint composed of similar fasteners

is the most efficient because all fasteners will reachcapacity simultaneously.

Installation
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Installation

There are several methods for installing rivets. Rivets that are smallenough and soft enough are often "bucked"[1]. In this process theinstaller places a rivet gun against the factory head and holds abucking bar against the tail or a hard working surface. The buckingbar is a specially shaped solid block of metal. The rivet gun providesa series of high-impulse forces that upset the rivet in place. Rivets

that are large or hard may be more easily installed by squeezinginstead. In this process a tool in contact with each end of the rivetclinches to deform the rivet.

Rivets may also be upset by hand, using a ball-peen hammer. Thehead is placed in a special hole made to accommodate it, known asa rivet-set. The hammer is applied to the buck-tail of the rivet, rollingan edge so that it is flush against the fastened material.

Manual installation of a solid rivet

Testing
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A hammer is also used to "ring" aninstalled rivet to test for tightness and

imperfections. The inspector taps the head(usually the factory head) of the rivet withthe hammer while touching the rivet andbase plate lightly with the other hand andjudges the quality of the audibly returnedsound and the feel of the sound travelingthrough the metal to the operator's fingers.

A rivet tightly set in its hole will return aclean and clear ring, while a loose rivet willreturn a recognizably different sound.

High Strength Structural Steel Rivets (ASTM 502A)
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High Strength Structural Steel Rivets (ASTM 502A) Until relatively recently, structural steel connections were either welded or riveted.

High-strength bolts have completely replaced structural steel rivets. Indeed, the lateststeel construction specifications published by AISC (the 13th Edition) no longer

covers their installation. The reason for the change is primarily due to the expense ofskilled workers required to install high strength structural steel rivets. Whereas tworelatively unskilled workers can install and tighten high strength bolts, it took aminimum of four highly skilled riveters to install rivets in one joint at a time.

At a central location near the areas being riveted, a furnace was set up. Rivets wereplaced in the furnace and heated to a glowing hot temperature, at which time thefurnace operator would use tongs to individually remove and throw them to catchers

stationed near the joints to be riveted. The catcher would place the glowing hot rivetinto the hole to be riveted, and quickly turn around to await the next rivet. One workerwould then hold a heavy rivet set against the round head of the rivet, while thehammerer would apply a pneumatic rivet hammer to the unformed head, causing it tomushroom tightly against the joint in its final domed shape. Upon cooling, the rivetwould contract and exert further force tightening the joint. This process was repeatedfor each rivet.

The last commonly used high strength structural steel rivets were designated ASTMA502 Grade 1 rivets. Such riveted structures may be insufficient to resist seismic loading from

earthquakes if the structure was not engineered for such forces, a common problemof older steel bridges. This is due to the fact that a hot rivet cannot be properly heattreated to add strength and hardness. In the seismic retrofit of such structures it iscommon practice to remove critical rivets with an oxygen torch, precision ream the

hole, and then insert a machined and heat treated bolt.
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HIGH TENSILE FASTENERS Indias largest manufacturer and exporter of High Tensile Fasteners, SundramFasteners Limited produces the complete range of standard and special fasteners.High Tensile Fasteners are produced in five state-of-the-art manufacturing facilitiesacross the globe.

OPERATIONAL EXCELLENCE

Pursuit of excellence, over the years, has meant acquiring in-depth expertise inmetal forming, machining, heat treatment and assembly; operator-assured quality;and customer-oriented design and development. As the business has grown with anexpanding global customer base, the Company has steadily invested in creatingadditional capacities at multiple locations. Sundram Fasteners was the first Indianmanufacturing company to be I

Structural Testing and Acceptance of Fabrication & Welding

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