MAE 3272 - Lecture 1B Notes

M&AE 3272; Lecture #1B 27 January 2014

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WSachse; 1/2014;M&AE 3272 1

The Fundamental Materials Triangle

Structure

Internal Structure and Composition of materials dictates their Properties

Material Properties determine the

Processing Operations that can be used

Processing Operations change a material’s

internal structure (“the material’s state evolves”)

Properties

Second Week – Mechanical Property Measurements

M&AE 3272: Mechanical Property

and Performance Laboratory

Processing

WSachse; 1/2014;

Relationships – Two key questions :

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• What’s the relationship between material microstructure and mechanical properties?

• What’s the relationship between material processing (solidification, forming and heat-treating) and the obtained material microstructures - and hence mechanical (and electrical and other) properties?

• For a quick review check-out:

• https://blackboard.cornell.edu/bbcswebdav/pid-1819946-dt-content-rid-

3419254_1/courses/10922_2013SP/Suppl%20Materials%20Lect2%20Material%20Prop

erties.pdf


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WSachse; 1/2014;

Mechanical Properties of Isotropic Materials:

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Elastic Properties (Moduli):• Young’s Modulus, Y

• Bulk Modulus, B

• Shear Modulus, G (or µµµµ)

• Poisson’s Ratio, νννν

Deformation Descriptors:

• Load, P; Stress, σσσσ

• Elongation, δδδδ ; ; ; ; Strain, εεεε

• Reduction of Area, %RA

Inelastic Properties:

• Yield Strength, σσσσys

• Tensile Strength, σσσσTS or σσσσult

• Shear Strength, ττττF

• Fracture Strength, σσσσcrit

Other Properties:

• Ductility

• Toughness

• Hardness

• Flexural Modulus; Strength

• Buckling Strength

WSachse; 1/2014;

Mechanical Properties are Critical -Consequences can be catastrophic!

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Failure of:

• Bridges, Buildings, Structures

• Aircraft

• Medical Devices

Failure of F-15: The Air Force determined that the cause of the accident was a defective metal support beam . . .A failure of the upper right longeron, a critical support structure in the F-15C Eagle, caused the crash of a Missouri Air National Guard F-15C . . .The longeron didn't meet blueprint specifications. This defect led to a series of fatigue cracks in the right upper longeron which expanded under life cycle stress, causing the longeron to fail, thus initiating a catastrophic failure of the entire aircraft.


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WSachse; 1/2014;

Properties of Metals:

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Atomic Scale: Bonding

• Metallic

Microstructure

• Defects and Imperfections

• Crystal grains; Lamella

Useful Characteristics

• Mechanical Properties

• Electrical Conductivity

• Huge Information and Experience Base

• Machinability; Formability

Concerns:

• Fracture

• Fatigue

• Corrosion

• Oxidation

WSachse; 1/2014;

Measurement Challenge:

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You’re given a new super-material, just announced by HRL Laboratories which is claimed to be the lightestmaterial in the world! Ultralight Metallic Micro-lattices.

• Density: <10 mg/cm3

• Periodic array of connected, hollow

Nickel microtubes

• Octahedral unit cell

• Large strain (50%) deformations

• Completely reversible

How would you propose to determine the Young’s Modulusfor the Micro-lattice?

18-Nov-2011


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WSachse; 1/2014;

1. Make a beam specimen, bend it and measure

the deflection.

2. Shake it and measure the modal frequencies.

3. Pull on a chunk of it and measure its stretch.

4. Push on a chunk of it and measure its

contraction.

5. Send a sound wave through it and measure the

travel time.

Measurement Challenge:

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To determine the Young’s Modulus for a specimen of the new Ultralight Metallic Micro-lattice material, your best suggestion would be:

1. Make a beam specimen, bend it and measure

the deflection.

2. Shake it and measure the modal frequencies.

3. Pull on a chunk of it and measure its stretch.

4. Push on a chunk of it and measure its

contraction.

5. Send a sound wave through it and measure the

travel time.

WSachse; 1/2014;

Measurement Results: Young’s Modulus

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Test the Microlattice specimen in compression and record the applied load P and measure the resulting

compression δδδδ of the sample. Stress: σσσσ = P/A

A – Area; L0 – initial thickness. Strain: ε ε ε ε = δ δ δ δ ////L0 ; E=σ/εσ/εσ/εσ/ε


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Your Specimen Materials:

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1050 Steel –

SAE-AISI (American Iron and Steel Institute) Numbering System

XXXX

The first two digits indicate the grades of the steel. The last two digits give the nominal carbon content in 0.01%.

1050 – Plain carbon steel; Non-sulfurized, Mn less than 1%; 0.50% Carbon

• Heated to the Austenizing temperature (723-deg C) and slowly cooled;

• Oil quenched at 845-deg C and tempered at 540-deg C.

WSachse; 1/2014;

Your Specimen Materials:

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6061 Aluminum –

IADS – International Alloy Designation System

The first digit indicate the major alloy; 6=Mg and Si

Second digit gives the impurities and mill data

The next two digits are alloy registration numbers.

This is followed by an index denoting the heat treatment: 0 – Annealed;

Hx – Strain Hardened;

Txx – Thermal treatment (higher number, stronger treatment.)

• O - Heated to recrystallization temperature; cooled to soaking temperature

(413-deg C; 3 hrs) then slowly cool (28-deg/hr) to 260-deg C

• T6 – Solution heat-treated, quenched and furnace aged

(Heated to 529-deg C; quenched; aged at 160-deg C for 18 hrs)


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ASTM Standard E8-04

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1. Scope

3. Terminology

5. Apparatus

6. Specimens

WSachse; 1/2014;

ASTM Standard E8-04

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• Section 5, 5.2 – we will be using wedge grips

• Section 6, 6.2 – we will be using sheet type ½” wide standard specimens

• Section 7, 7.6 – we will be using a rate of separation of the two heads testing speed method. We will be using a rate determined by previous experience.

• Section 7, 7.7 – you will use the appropriate method to determine yield strength, when choice of a method is not clear, use the offset method.


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WSachse; 1/2014;

Measurements: Tensile Test using Instron

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• Activate (1) Hydraulics and (2) Actuators (OFF-LOW-HIGH 5 sec each)

• Warm-up Machine (Sine Wave 2-in Amplitude; 2 Hz; ~5 min)

• Mark on your Specimen where you will attach your Extensometer

• Mount your Specimen with Extensometer in the Testing Machine Grips

• Machine Control is via Instron Console and LabVIEW software

Set Maximum Extension: 1-inch; Maximum Rate: 0.01 in/sec

• Machine Data Collection is via LabVIEW software

Load (lbs) and Extensometer Reading (in)

• Remove specimen from grips; Return ram to initial position

• Download mechanical test data to thumb drive; Upload to LabArchives

• Convert data: σσσσ = P/A (P – Load; A – Cross-section Area of Specimen)

e = ∆∆∆∆L/L0

(∆∆∆∆L – Extensometer Reading; L0

– Initial Gage Length)

• Determine Young’s Modulus, Yield Stress; Ultimate Tensile Strength; Elongation at Fracture; Reduction of Area; Watch Units!

WSachse; 1/2014;

Ductility Measures:Elongation (%EL); Reduction of Area (%RA):

x100A

AARA%

o

fo −=

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• Plastic tensile strain at failure:

Engineering tensile strain, ε

Engineering

tensile

stress, σ

smaller %EL

(brittle if %EL<5%)

larger %EL

(ductile if

%EL>5%)

• Another ductility measure:

• Note: %RA and %EL are often comparable.

--Reason: crystal slip does not change material volume.

--%RA > %EL possible if internal voids form in neck.

Lo LfAo

Af

100xL

LLEL%

o

of −=

Adapted from Fig. 6.13,

Callister 6e.


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WSachse; 1/2014;

Comment on Reduction of Area (%RA):

]6/)4[( 321 www ++×]6/)4[( 321 ttt ++=Area

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• Reduction of Area:

x100A

AARA

o

fo −=%

Lo LfAo

Af

= Thickness

= Widthw

t

WSachse; 1/2014;

Hardness Measurements:

Hardness Testing Methods: Provide a quick and easy determination of a number relatedto the flow stress of a material.

• Rockwell Hardness Test

• Rockwell Superficial Hardness Test

• Brinnel Hardness Test

• Vickers Hardness Test

• Microhardness Test

• Mohs’ Hardness Test

• Scleroscope; other hardness testing methods

M&AE 3272 16


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WSachse; 1/2014;M&AE 3272 17

Hardness: Common Measurement Procedures

WSachse; 1/2014;

Vickers Hardness Measurements:

Vickers Hardness Test:

• Indentation with a diamond indenter (right pyramid, angle 136-degs between faces)

• Load: 1 to 100 kgf for 10-15 seconds; then unload

• Measurement: Two diagonals of indentation measured and averaged

• Determination: Divide Load by area of sloping surfaces of indentation

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WSachse; 1/2014;M&AE 3272 19

Hardness: Common Measurement Procedures

WSachse; 1/2014;

Rockwell Hardness Measurements:

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Scale Indenter

Minor

Load

kgf

Major

Load

kgf

Total

Load

kgf

Value

of E

C Diamond Cone

10 140 150 100

B 1/16” Steel Ball

10 90 100 130

E 1/8”

Steel Ball

10 90 100 130

Rockwell Hardness Scales used in Lab:

Principle: The hardness test method consists of indenting a test material with a diamond cone or hardened steel ball indenter and after unloading measuring the permanent depth of penetration.

Procedure: The indenter is forced into the test material under a preliminary minor load F0 (Fig. 1A) usually 10 kgf. Then the major load is applied resulting in an increased penetration. The permanent increase in penetration is then used to compute the Rockwell Hardness number, HR:

HR = E - e [e: Units of 0.002mm]


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WSachse; 1/2014;

Rockwell Hardness Measurements – TIPS!

Measurement Procedure:• After inserting the indenter, set the

minor load to R.• Set the load selector to the total test

load (e.g. 100 or 150 kgf.)• Press D/B to select test scale• Press AUTO• Place sample on anvil• Press Reset to read 0.0• Turn elevating handle until SET

lights up – If you overshoot the SET position, you will have to unload and repeat the test!

• Press START• Record Hardness value prior to

releasing load.• Release load• Repeat 10 times on each material

NOTE: Stay away from edges, and indents not too close to each other!

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Rockwell Hardness Conversion Chart for Soft Materials

Linear Range: Rockwell B

Determine the Appropriate Hardness Scale to use.Procedure: Use the diamond indenter first; then 1/16”; then 1/8”.(If the test material is too hard, the ball-indenters might get damaged!)

ASTM E18-03:

• Section 5, 5.3 – we will be using a diamond indenter and 1/16 and 1/8-inch dia steel ball indenters

• Section 6, 6.3 and 6.4 – we will be using 1-inch diameter specimens

WSachse; 1/2014;

Ultrasonic Measurements:

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Implementation.

and Signal:

Set-up in B30 Upson:


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WSachse; 1/2014;

Ultrasonic Measurements per ASTM E494:

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Critical Comments:

6. Procedure

Actual Observed:

WSachse; 1/2014;

Ultrasonic Measurementsfor Elastic Modulus Determination:

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Set-up in B30 Upson:

Underlying Equations:

Modulus = Density * Wavespeed2 G = ρ * v

S

2

E = ρ * vS

2 3vL

2 – 4v

S

2

vL

2 – v

S

2( ) ν = {1 −−−− 2(v

S/v

L)2}

2 {1 – (vS/v

L)2}( )

Waves and Signals:

vL

vS h

∆∆∆∆t v = 2h/∆t


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WSachse; 1/2014;

Ultrasonic Moduli Measurement Procedure:

• Determine the density of your specimen(s). Repeat several times.

• Weigh your sample to determine its mass and then measure its diameter and thickness (H) .

• Then compute the volume of your specimen and the error in your volume determination: ∆∆∆∆V/V = 2∆∆∆∆r/r + ∆∆∆∆h/h .

• Couple the P-wave (with couplant; or S-wave transducer with pine tar –removed with alcohol!) to the ultrasonic source/receiver unit. Look for echoes on the oscilloscope display. Vary the pressure on the transducer and observe the cleanest possible echo pattern.

• Measure the wave arrival time for 2H, 4H, 6H, etc. How much do they vary? If you know how, use the delayed sweep of the oscilloscope.

• Can you estimate the error in your arrival time determination?

• Compute the longitudinal wavespeed.

• Repeat for using shear waves.

• Compute the Moduli of your material.

• Can you estimate the error in your modulus determination?

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Procedure:

WSachse; 1/2014;

NEW: Ultrasonic Moduli Determination on LabArchives:

• Logon to LabArchives and in your Module 1 Folder add a `New Item’ where you will do the data input and data analysis.

• Create a spreadsheet for inputting echo arrival times, compute the echo time intervals. Input propagation length and estimated error.

• Compute the wavespeed(s) and the estimated error:

•� � � ∗�

�∆� � �

�∗∆�

�

�

∆�

�

�

• Enter the mass and estimated error; enter diameter and error.

• Compute the Volume and Density and Shear Modulus: Watch Units!

•� � ��∆� � ��∗∆�

�

�

∆�

�

�

M&AE 3272 26

Suggested Procedure: LabArchives Window


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WSachse; 1/2014;

Your Material TestData Sheets:

0f /AA1RA% −=

00ff /L)L(L −=ε

ff00 LALA =

1RA% +=f

fεε

M&AE 3272 27

Expected Reduction

of Area:

Incompressibility:

(Available on Blackboard or

in your LabArchives Folder)

Now available as a

LabArchives Widget !

WSachse; 1/2014;

Your Report Summary:

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Abstract: Mechanical Property Measurements

1. What was (were) the measurement problem(s) you

solved?

2. What procedures did you follow to solve the

problem?

3. What were your principal results?

4. What is the significance or impact of your results?

. . . Written in complete sentence form; 200-500

words (1 page) maximum. No figures.

Create in

MS-WORD;

Place into

your

Electronic

Lab

Notebook


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WSachse; 1/2014;

Tasks to do this Week:

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• Learn all about your specimen materials:Al: 6061-O; 6061-T6; C1050: Annealed; Oil Quenched

• Famililarize yourself with LabArchives. This will save you lots of time later when you process your data.

• Determine Expected Values of Density; Rockwell C; Yield Strength; Ultimate Tensile Strength; Elongation to Fracture; Reduction of Area; Modulus of Elasticity; Bulk Modulus and Poisson’s Ratio. Upload to LabArchives.

• Read the Handout for Module 1 Measurements.

• Peruse the ASTM Standards and read the relevant paragraphs.

• Lab Sections #401, #402, #403, #404, #409, #411 and #413 meet this week. Go to B30 Upson. Please be on-time!

MAE 3272 - Lecture 1B Notes

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