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2Application of Technical DiagnosticsHorst Czichos

2.1 Objects of TechnicalDiagnostics

The objects of technical diagnostics can beillustrated by the life cycle of all man-madetechnical items: from raw materials to engi-neering materials andvia design and produc-tionto structures and systems, and nally, todeposition or recycling, see Fig. 2.1.

Technical diagnostics can be applied inalmost all areas of technology and industry in

order to ensure product quality, economical andefcient processes and, most importantly, toassure safety and reliability. In this section, theobjects of technical diagnosticsengineeringmaterials, structures and systemsare consid-ered in brief.

2.1.1 Engineering Materials

It has been estimated that there are between

40,000 and 80,000 materials which are used orcan be used in todays technology [ 1], they canbe categorized as follows [ 2]:

Natural Materials: Natural materials used inengineering applications are classied intonatural materials of mineral origin, e.g. mar-ble, granite, sandstone, mica, sapphire, ruby,diamond, and those of organic origin, e.g.timber, India rubber, natural bres, like cottonand wool. The properties of natural materialsof mineral origin, as for example high hard-ness and good chemical durability, are deter-mined by strong covalent and ionic bondsbetween their atomic or molecular constitu-ents and stable crystal structures. Naturalmaterials of organic origin often possesscomplex structures with direction-dependentproperties. Advantageous application aspectsof natural materials are recycling andsustainability.

Metallic Materials: In metals, the grains as thebuildings blocks are held together by theelectron gas. The free valence electrons of theelectron gas account for the high electricaland thermal conductivity, and the opticalgloss of metals. The metallic bondingseenas interaction between the total of atomicnuclei and the electron gasis not signi-cantly inuenced by a displacement of atoms.This is the reason for the good ductility andformability of metals. Metals and metallicalloys are the most important group of the so-called structural materials whose specialfeatures for engineering applications are theirmechanical properties, e.g. strength andtoughness.

This chapter considers the objects of technicaldiagnostics and explains Systems Thinking as genericconcept for the application of technical diagnostics intechnology and industry.

H. Czichos ( & )

BHT Berlin, University of Applied Sciences,Luxemburger Strae 20a, 13353 Berlin, Germanye-mail: [email protected]

H. Czichos (ed.), Handbook of Technical Diagnostics ,DOI: 10.1007/978-3-642-25850-3_2, Springer-Verlag Berlin Heidelberg 2013

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Semiconductors have an intermediate position

between metals and inorganic non-metallicmaterials. Their most important representa-tives are the elements silicon and germanium,possessing covalent bonding and diamondstructure and the similarly structured III-V-compounds, like gallium arsenide (GaAs).Being electric non-conductors at absolute zerotemperature, semiconductors can be madeconductive through thermal energy input oratomic doping which leads to the creation of

free electrons contributing to electrical con-ductivity. Semiconductors are important functional materials for electronic compo-nents and applications.

Inorganic Non-metallic Materials: The atomsof these materials are held together by cova-lent and ionic bonding. As covalent and ionicbonding energies are much higher thanmetallic bonds, inorganic non-metallic mate-rials, like ceramics have high hardness andhigh melting temperatures. These materialsare basically brittle and not ductile. Becauseof missing free valence electrons, inorganicnon-metallic materials are poor conductors forelectricity and heat, this qualies them asgood insulators in engineering applications.Concrete, the worlds most used constructionmaterial, is a mixture of coarse aggregates(stone or brick chips) and ne aggregates(generally sand) with a binder material (usu-ally cement), mixed with a small amount of water. Concrete has high compressionstrength, but tension (e.g., due to bending)

will break the microscopic rigid lattice,

resulting in cracking and separation of theconcrete. Thus non-reinforced concrete mustbe well supported to prevent the developmentof tension.

Organic Materials: Organic materials whosetechnologically most important representa-tives are the polymers, consist of macromol-ecules containing carbon (C) covalentlybonded with itself and with elements of lowatom numbers (e.g. H, N, O, S). Intimate

mechanical mixtures of several polymers arecalled blends. In thermoplastic materials, themolecular chains have long linear structuresand are held together by (weak) intermolecu-lar (van der Waals) bonds, leading to lowmelting temperatures. In thermosetting mate-rials the chains are connected in a network structure and do not melt. Amorphous poly-mer structures (e.g. polystyrene PS) aretransparent, whereas the crystalline polymersare translucent to opaque. The low density of polymers gives them a good strength-to-weight ratio and makes them competitive withmetals in structural engineering applications.

Composites are combinations of materialsassembled together to obtain properties supe-rior to those of their single constituents. Aclassic composite material is reinforced con-crete, in which reinforcement grids, plates orbers have been incorporated to strengthenthe concrete in tension. Composites are clas-sied according to the nature of their matrix:metal, ceramic or polymer matrix composites,

Fig. 2.1 The productcycle of technical itemsand the potential of technical diagnostics

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often designated as MMCs, CMCs and PMCs,respectively. Glass ber and Carbon berreinforced composites are denoted GFC andCFC. The potential for a synergy of thecomposite constituents is one reason for the

interest in composites for high-performanceapplications. However, because manufactur-ing of composites involves many steps and islabour intensive, composites may be tooexpensive to compete with metals and poly-mers, even if their properties are superior. Inhigh-tech applications of advanced compos-ites it should also be borne in mind that theyare usually difcult to recycle.Materials result from the processing and

synthesis of matter, based on chemistry, solidstate and surface physics. The microstructure of materials resulting from processing and synthe-sis contains Grains: crystallites made up of identical unit

cells repeated in space, separated by grainboundaries.

Phases: homogeneous aggregations of matterwith respect to chemical composition anduniform crystal structure: grains composed of the same unit cells are the same phase.

Lattice defects: deviations of an ideal crystal

structure: Point defects or missing atoms: vacancies,

interstitial or substituted atoms Line defects or rows of missing atoms:

dislocations Area defects: grain boundaries, phase

boundaries, twins Volume defects: cavities, precipitates.Figure 2.2 illustrates schematically the

microstructure of materials for the example of

metals and alloys.Whenever a material is being created, devel-

oped, or produced the properties the materialexhibits are of central concern. Experience showsthat the properties and performance associatedwith a material are intimately related to itscomposition and structure at all scale levels, but

Fig. 2.2 Schematic overview on the microstructural features of metallic materials and alloys

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Fig. 2.5 Strength-weight map of engineering materials

Fig. 2.4 Data of mechanical, electrical, and thermal properties for the basic types of material



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somewhat different phrasing. According toInternational Standards [ 3], a system can be: Collection of real-world items organised for a

given purpose. A system is characterized byits structure and its behaviour

industrial automation systems (ISO 15704). Set of interdependent elements constituted to

achieve a given objective by performing aspecied function internal combustion engines (ISO 7967).

Assemblage of components performing aspecic function with associated sensors,actuators and interconnections road vehicles (ISO 9141).

Integral part of a nuclear power unit com-

prising electrical, electronic, or mechanicalcomponents (or combinations of them) thatmay be operated as a separate entity to per-form a particular process function nuclear power plants (ISO 6527).

Arrangement of interconnected componentswhich transmits and controls uid power energy hydraulic uid power (ISO 4413).

Assembled section of piping consisting of arepresentative range of pipes, ttings, con-

nections, attachments, supports, penetrationsand associated coatings petroleum and natural gas industries (ISO

14692). Those parts of an installation that, together

with the pump, determine the functional per-formance of the installation liquid pumps and installation (ISO 17769).

Set of interdependent items constituted toachieve a given objective by performing a

specied function space systems (ISO 16091). Delimited group of interrelated, interdepen-

dent or interacting objects that is assessed fora potential risk bases for design of structures (ISO 13824).This collection of denitions shows that dif-

ferent wording is used to dene the variousindustrial systems. Thus, the General SystemTheory has to be considered as a generic base fora methodology of technical diagnostics that canbe applied to structures, systems, and compo-nents in all areas of technology and industry.

2.2 The System Concept

The classical method of scientically analyzingproblems is analytical reductionism. Anentity, i. e. the object of an investigation, couldbe broken down into its individual Parts so thateach Part could be analyzed separately, and thedissections could be added to describe thetotality of the entity. This basic principle of scientic reductionism can be applied ana-lytically in a variety of directions, e. g. resolu-tion of causal relations into separate Parts,searching for atomic units in science or formaterial constants in engineering.

Application of the classical analytical pro-

cedure depends on the condition that interac-tions between the Parts are non-existent or, atleast, weak enough to be neglected for certainresearch purposes. Only under these conditionscan the Parts be singled out and describedmathematically. An equation describing thebehaviour of the Whole is assumed to have thesame form as the equations describing thebehaviour of the Parts, and that partial processescan be linearly superimposed to obtain the total

process.These conditions are not met in a System,

it consist of Parts in interaction forming anentity of organized complexity [ 4]. Systemsthinking focuses on how the thing being studiedinteracts with the other constituents of the sys-tema set of elements that interact to producebehaviourof which it is a part [ 5].

2.2.1 Principles of General SystemTheory

System denition: A system is a set of elementsinterconnected by structure and function .1. Systems Structure

The structure of a system is given byA the set of the elements (components) a i,separated from the environment by a hypo-thetical envelope enclosing the elements,A = {a1, a2, , an},P the relevant (materials) properties of theelements, P = {P(a i)}, i = 1 n,

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R the relations (interactions) between the ele-ments, R = {R(a i$ a j)}, i, j = 1 n, j = i.The normal (nominal) structure of a system is

represented by the set S 0 = {A, P, R}.If the structure of a system changes with time t,

for example due to detrimental changes of ele-ment properties (P)or relations (R)under workingloads L (e. g. force, temperature), the structure ofasystem is load and time dependent and is repre-sented by the set S(t,L) = {A, P(t,L), R(t,L)}.2. Systems Inputs and Outputs

The connections between the structure and itsenvironmentcrossing the hypothetical enve-lope enclosing the structural elementsareclassied as

Inputs {X}: Operating inputs, working loads,auxiliary inputs, disturbances

Outputs {Y}: Functional outputs, loss outputs,noise, wear debrisAll inputs and outputs can be categorized to

belong to the cybernetic categories of energy,matter, information.3. Systems Function

Basic functions of (technical) systems are: Support of (working) loads,

Transfer or transformation of operating inputsinto functional outputs.The function of a system -is borne by the

systems structure. The support of loads requiresappropriate (load-bearing) properties (P) of therelevant systems element. The transfer or trans-formation of operating inputs into functionaloutputs (T) requires appropriate interactions (R)between relevant systems elements to enable thepertinent function.

The behaviour of a system is the manner inwhich the whole or part of a system acts andreacts to perform a function; it can be catego-rized in different states:(a) Steady state

If the inputs and outputs are stationary and thestructure of the system is stable, the functionaloutputs {Y} may be describable as functions of the operating inputs {X} through an algebraicrepresentation of the transfer function (T).(b) Dynamic state

If the inputs and outputs vary with time, thesystemis said tobe ina dynamicstate.Functional

inputoutput relations of a dynamic system can beoften represented by differential equations. (Well-known mathematic modelling examples formechanical systems with stable structures aredifferential equations with mass-spring-damper

characteristics of the systems elements).(c) Stochastic processes

In real systems, the functional inputoutputrelations may be inuenced by stochastic pro-cesses, i. e. dynamic effects of uncertainty andrandom disturbances (noise). In addition, thesystems structure S 0 may be time-dependent dueto detrimental changes of systems elementsproperties P or interactions R, i. e.S0 ? S = {A, P(t), R(t)}. In such cases, an

estimate of the limits of proper systems behav-iour by means of the theory of probabilities maybe attempted.

In characterizing the behaviour of systems bythe terms structure and function theseterms should not be isolated from each otherbecause structure and function of systems areinterconnected. A summarizing overview of thesystem concept is given in Fig. 2.6.

2.2.2 Application of the SystemConcept to the Descriptionof Technical Items

The application of the system concept to thecharacterization of technical items is exempli-ed in Fig. 2.7 for the simplest case of 2-bodysystems, namely a mechanical gear pair and anelectrical transformer,

The function of both systems illustrated in

Fig. 2.7 is to transfer operating inputsspeedand torque in the mechanical system and voltageand current in the electrical systeminto func-tional outputs for the intended technical purpose.In both systems, input energy is dissipated due tofriction or eddy current effects, and the ratiobetween the useful output and the input is theenergy conversion efciency. Regarding thestructures of the systems, a fundamental differ-ence between the electrical and the mechanicalsystem has to be noted [ 6]: In the electrical system, the function of the

system is realized through sub-microscopic



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electronic processes (possibly inuenced byelectromigration, see Sect. 3.3 ), but the(macroscopic) structure of the system remainsconstant with time. If this condition is met, thetransfer function (T) can be worked out

mathematically. This has led to variousapplications of the powerful electrical sys-tems network theory. For condition moni-toring of these systems, the control of thefunctional inputoutput relations may besufcient.

In the mechanical system, however, thestructure of the system may change with timedue to the interfacial Hertzian tribo-contactmechanics of the interacting gears. The tri-

bological processes may cause wear damageof the gear pair (pitting) and these internalstructural changes lead to externally measur-able vibrations and wear debris. This disturbsthe transfer function (T). Therefore, both thesystems inputs {X} and outputs {Y} as wellas the systems structure {S} and its changeshave to be monitored.

2.3 Systems Approach to TechnicalDiagnostics

The systems concept illustrated in Fig. 2.6implies that for technical diagnostics of struc-tures, systems, and components, both Struc-tural Integrity Assessment and FunctionalPerformance Assessment have to be per-formed. This is shown schematically in Fig. 2.8in an overview diagram using the abstract sys-

tems theory symbols.

Consider as an example of systems thinkingin technical diagnostics a rotary machineequipment [ 7]. As exemplied in Fig. 2.9 thetechnical system, characterized by its structureand function (to be specied for the actual

machine type under consideration), may havefaults, for example cracks in critical compo-nents. The associated fault symptoms can beexamined by vibration analysis (measurementsof magnitude/frequency ranges of displacement,velocity, acceleration of stationary and movingmachine parts). A diagnosis may be made afterroot cause analysis and data processing [ 8]. If the causes of faults or failures can be related tothe systems characteristics, structural integrity

assessment and functional performance assess-ment can be made.

Performance parameters for technical sys-tems are exemplied in Fig. 2.10 [9].

Changes of performance parameters observedin condition monitoring can indicate symptomsof fault occurrence. This is illustrated inFig. 2.11 for the example of technical diagnos-tics of a reciprocating internal combustionengine [ 10].

The compilation of Fig. 2.10 shows that(external) functional parameter changes, liketemperature, pressure, fuel ow, can be symp-toms of fault occurrence in the (internal) sys-tems structure, namely detrimental changes of the components of the system and their inter-actions. Combining systems thinking with theconcepts, methods and techniques outlined inthe rst chapter, a general scheme for theapplication of technical diagnostics results,

which is shown in Fig. 2.12 .

Fig. 2.8 Systems approach to technical diagnostics application

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Fig. 2.9 Application of systems thinking in the technical diagnostics of a machine

Fig. 2.10 Examples of condition monitoring parameters for different technical systems

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The methods and techniques for diagnosticsand monitoring are described in detail in Part B of theHandbook. Technical diagnostics of machines

and plants is treated in Part C and structural healthmonitoring is presented in Part D of theHandbook.

Fig. 2.11 Examples of performance parameter changes indicating symptoms of fault occurrence

Fig. 2.12 A general scheme for the application of technical diagnostics



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References

1. Ashby, M.F., Brechet, Y.J.M., Cebon, D., Salvo, L.:Selection strategies for materials and processes.Mater. Design 25 , 5167 (2004)

2. Czichos, H.: Metrology and testing in materialsscience and technology. Measure 4 (4), 4877 (2009)

3. ISO Concept Database (ISO/CDB) (http-// www.iso.org/iso/c#4B3FB3 )

4. von Bertalanffy, L.: General System Theory. Penguin,London (1971)

5. Aronson, D.: Overview of Systems Thinking. NewYork. ( www.thinking.net ) (1998)

6. Czichos, H.: TribologyA Systems Approach to theScience and Technology of Friction, Lubrication andWear. Elsevier, Amsterdam (1978)

7. ISO 13373-1:2002(E): Condition monitoring anddiagnostics of machinesvibration conditionmonitoring

8. ISO 13374-1:2003(E): Condition monitoring anddiagnostics of machinesdata processing,communication and presentation

9. ISO 17359:2003(E): Condition monitoring anddiagnostics of machinesgeneral guidelines

10. ISO 13380: 2002(E): Condition monitoring anddiagnostics of machinesgeneral guidelines onusing performance parameters

Handbook part Topic Chapterno

BMethods and techniques for diagnostics andmonitoring

Overview of diagnostics and monitoring methodsand techniques

4

Stress and strain determination 5Modal analysis 6

Vibration analysis 7

Acoustic emission 8

Nondestructive evaluation 9

Infrared thermography 10

Industrial radiology 11

Computed tomography 12

Embedded sensors 13

Micro-diagnostics 14

Surface chemical analysis 15Subsurface microstructurai analysis 16

CTechnical diagnostics of machines and plants

Principles and concepts of technical failureanalysis

17

Failure analysis: case studies 18

Machinery diagnostics 19

DStructural health monitoring and performancecontrol

Principles, Concepts and Assessment of StructuralHealth Monitoring

20

Buildings 21

Bridges 22

Pipelines 23

Electrical power stations and transmissionnetworks

24

Offshorewind structures 25

Railway systems 26

Guidelines to structural health 27

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