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1、Hardness Training - Basics Methods, application, productsErhard Reimann, Zwick GmbH & Co. KGHardness training at SDL Shanghai, May 2005Basics, standards, methods, related productsIntroduction into hardness test methods, (dis-) advantages & applications 1.1 Definition of Hardness1.2 Hardness Testing
2、of MetalsRockwell, Vickers, Knoop, Brinell, Martens hardness (universal hardness testing)1.3 Hardness Testing of Plastics and RubberBall indentation, Shore, IRHD, Rockwell 2Terminology definition: “Hardness is the resistance that a body offers to indentation by another (hard) body”. Martens, 1900The
3、 technical hardness is a mechanical quantity for describing a material or the state of a material.The hardness cannot be measured directly, it must be derived from primary measurement quantities (e.g. test load, indentation depth, indentation area). Hardness values can only be compared if they have
4、been determined via the same test method with identical test parameters.3An explicit hardness value can only be characterised via the following criteria: definition of the hardness value indentor geometry and material, size and indentation duration at test load, as well as the type of loading, state
5、 and surface quality of the specimen.The following is at the forefront for selection of a hardness test method: economy, time for specimen preparation, availability of machines and devices.4basics overview, methods5Basics, Standards, Methods, related productsIntroduction into hardness test methods,
6、(dis-) advantages & applications 1.1 Definition of Hardness1.2 Hardness Testing of MetalsRockwell, Vickers, Knoop, Brinell, Martens hardness (universal hardness testing)1.3 Hardness Testing of Plastics and RubberBall indentation, Shore, IRHD, Rockwellagenda6Mainly methods with static force applicati
7、on are used for metals. The indentor (ball, cone, pyramid) made of steel, hard metal or diamond is pressed into the surface of the specimen which is placed on a hard and fixed base.The test load is applied bumplessly with a defined application time and duration. The indentation is measured after loa
8、d removal for many test methods.hardness testing of metals7Rockwell - overviewHardness Testing according Rockwell (HR)depth measurement, DIN EN ISO 6508-18Scales - RockwellScale overview Rockwell hardnessIndenter Pre-Load N Total Load N9Anpplication range - RockwellApplication range120- Diamond1/16“
9、 Ball1/8“ Ball120- Diamond1/16“ BallHardness range Hardness Indentation depth 1 Unit Calculation of in HV30 Min. Max. Max. Min. Hardness10Rockwell application examples11Rockwell tipsTips for Rockwell (HR): 1 HR - Unit means 2 or 1m indentation depth no displacement of specimen during testing proper
10、specimen support, no burr no dirt (specimen, diamond) prevent diamond of damage regard correct choice“ of scale regard minimum thickness (indentation depth 1/10 or 1/15) no imprint on support surface regard minimum distance ( 5mm) no shocks, vibrations, strikes12Rockwell product overviewZwick ZHR -
11、ReiheZwick ZHU250Zwick ZHU187,5Zwick ZHU0.2/Z2.5Zwick ZHU2.5/Z2.5Zwick 310613Vickers - overviewHardness Testing according Vickers (HV)optical indentation measurement, DIN EN ISO 6507-1, DIN ISO 451614Vickers tipsTips for Vickers (HV): no shocks, vibration, strikes contact diamond-specimen without sh
12、ock use at least polished surfaces take an appropriate magnification minimise meas. errors horizontal specimen support, no dirt (specimen, diamond) prevent diamond of damage take an appropriate load regard minimum thickness (indentation depth 1/10 or 1,5*d) regard minimum distance ( 3*d) take care o
13、f load dependency of Vickers15Vickers products, overviewZwick ZHV1mZwick ZHV2mZwick ZHU250Zwick ZHU187,5Zwick ZHU0.2/Z2.5Zwick ZHU2.5/Z2.5Zwick ZHV10 AZwick ZHV10 PCZwick products for Vickers hardness testingZwick ZHV20/Z2.5Zwick ZHV30/Z2.516Knoop - overviewHardness Testing according Knoop (HK)optic
14、al indentation measurement, ISO 4545, DIN ISO 451617Knoop advantagesadvantages: Knoop (HK)suitable for small specimen owing to the high diagonal length ratio of approx. 7:1better than Vickers for thin specimen or layers as the indentation is not so deep (by the factor 4) but the diagonal lengths are
15、 the samesuitable for brittle materials owing to the low susceptibility to crackingno influence on the functionality of the test surface owing to the shallow test indentations18Knoop disadvantagesdisadvantages: Knoop (HK)o time consuming to achieve a sufficiently fine test areao sensitivity of the d
16、iamond indentor to damageo time consuming alignment of the test surface to achieve symmetrical test indentations19Knoop products, overviewZwick products for Knoop hardness testingZwick ZHV1mZwick ZHV2mZwick ZHU250Zwick ZHU2.5/Z2.5 Zwick ZHU0.2/Z2.5Zwick ZHV10 AZwick ZHV10 PCZwick ZHV20/Z2.5Zwick ZHV
17、30/Z2.520Brinell overviewHardness Testing according Brinell (HB)optical indentation measurement, DIN EN ISO 6506-121185x Object.90x Objective45x Objective15x ObjectiveApplication range - BrinellApplication range Brinell hardness22Brinell tipsTips for Brinell (HV): no shocks, vibration, strikes conta
18、ct hard-metall ball-specimen without shock use at least dressed to size surfaces take an appropriate magnification minimise meas. errors horizontal specimen support without specimen move no dirt (specimen, diamond) take the loading degree of 10 or 30 regard minimum thickness (1,33*d) no imprint on s
19、upport surface regard minimum distance ( 3*d)23Brinell product overviewZwick ZHU250Zwick ZHU187,5Zwick ZHU0.2/Z2.5Zwick ZHU2.5/Z2.5Zwick ZHV10 AZwick ZHV10 PCZwick ZHV20/Z2.5Zwick ZHV30/Z2.524Martens overview (I)Hardness Testing according Martens (HM, HU)depth measurement, DIN EN ISO 14577-125Struct
20、ure of DIN EN ISO 14577DIN EN ISO 14577 (2003-05): Metallic materials - Instrumented indentation test for determination of hardness and other material parametersPart 1: Test procedure Macro (F 2N; h 6 m), Micro, Nano (h 200 nm)Different geometries of indentersPart 2: Verification and calibration of
21、the testing machineDirect & indirect verificationPart 3: Calibration of reference materialsExamples11.08.202426Content of DIN EN ISO 14577-1 DIN EN ISO 14577 - Part 1: Test procedureA: Material parameterHM, HMS, HIT, EIT, CIT, RIT, indentation workB: Types of control C1: Compliance of machineC2: Are
22、a correction for indenter (h 6 m)D: Diamond indenterE: Influence of surface roughnessF: Theoretical correlation to Vickers hardness11.08.202427Load.- & unload. curvesEvaluation of the loading and unloading curves Some characteristics:- Wplast, Welast- HM = f (Fmax, hmax)- HMs = f (sqrt (loading c.)
23、- HUplast = f (Fmax, hr) - HMit = f (Fmax, hmin) - .loadingunloading28Martens hardnessIndentation modulusIndentation hardnessMaterial parameter of Martens hardnessHM evaluation29Martens 1 ScaleHM-Scale DIN EN ISO 14577Materialsconventional methodsHard metal (z.B. ceramics)SteelNF-MetalePlasticsRubbe
24、rVickersBrinellRockwell A, B, C, D, E, F, G, KKnoopRockwell a a, R, L, M, EBall indentationBarcolBuchholz (nur fr Schichten)IRHD (Internationaler Gummihrtegrad)Shore DShore A1000010001001010N/mm2The instrumented indentation test delivers material-independent comparable hardness numbers.30Martens tip
25、sTips for Martens (HM): no shocks, vibrations, strikes contact diamond-specimen without shock use at least polished surfaces horizontal specimen support, no dirt (specimen diamondt) prevent diamond of damage choose an appropriate load regard minimun distance and -thickness (indent. depth 1/10) inden
26、tation depth 20 x mean roughness value ideal area geometry for h 10 m sufficient31Martens product overviewZwick ZHU0.2/Z2.5Zwick ZHU2.5/Z2.5Zwick products for Martens hardness testing32rebound hardness testing - overviewHardness Testing to Leeb (HL) rebounddynamic method / measurement of energy, AST
27、M A 95633Rckprallhrteprfung advantages, disadvantageadvantages: rebound hardness testing (Leeb, HL)extremely short test timesautomatic test sequencetests in all positions, e.g. also overhead measurement by using correction factorssimple handlingportable devicedirect display of the hardness valuedisa
28、dvantage: o test of specimen that are thin or of low mass is problematic34Leeb products, overviewIndentec Rebound testerZwick DynaPocket, patented35Basics, Standards, Methods, related productsIntroduction into hardness test methods, (dis-) advantages & applications 1.1 Definition of Hardness1.2 Hard
29、ness Testing of MetalsRockwell, Vickers, Knoop, Brinell, Martens hardness (universal hardness testing)1.3 Hardness Testing of Plastics and RubberBall indentation, Shore, IRHD, Rockwellagenda36hardness testing of platics, rubber (I)The hardness of plastics can, in principle, be determined with the me
30、thods of the metals hardness testing. However, the hardness test methods ball indentation hardness, Shore A/D hardness as well as IRHD hardness and Rockwell hardness (scale R.K, ) have proven to be the preferred methods.The reasons for this are, on the one hand, the quite often strongly pronounced,
31、time dependent material behaviour of polymer materials, and, on the other hand, the low contrast ratio of the plastic indentation to the surface.The applied test methods therefore usually include a measurement of the indentation depth under test load and a defined hold time.37hardness testing of pla
32、tics, rubber (II)38ball indentation hardness - overviewHardness Testing according ball indentation (H)depth measurement, DIN EN ISO 2039-139ball indentation hardness advantagesadvantages: ball indentation hardness (H)suitable for hardness tests even under rough conditions owing to the relatively lar
33、ge indentations, suitable for testing the hardness of inhomogeneous and/or anisotropi-cal materials suitable for hardness tests on large finished parts simple and robust indentorcapability of being rationalised or automated by the test sequence and evaluation in the sense of online data processing40
34、ball indentation hardness disadvantagesdisadvantages: ball indentation hardness (H)o limitation when testing small specimen owing to necessary distance(s) ( 10 mm) between the test indentations, as well as the specimen edgeo limiting the applicational range, especially at low hardness; the least pos
35、sible hardness to be determined according to test standard is H 49/30 = 8,5 N/mm (corresponds to, for example, the hardness of soft PVC with approx. 25 - 27% DOP as plasticizer)o no calibrated hardness comparison plates are available41ball indentation hardness H products, overviewZwick ZHU250Zwick Z
36、HU0.2/Z2.5Zwick ZHU2.5/Z2.5Zwick ZHU0.2/Z2.5Zwick ZHU2.5/Z2.5Zwick 310642Shore overviewHardness Testing according Shore hardnessdepth measurement, DIN 53505, ASTM D 2240, ISO 86843Shore advantagesadvantages: Shore method of hardness tests on elastomers used worldwidesmall testers, simple arrangement
37、 resulting in low cost devicessimple operationcan be used in a laboratory with a test stand and defined load application pressure, and can also be used on site by pressing the tester vertically onto the specimen by handtests on specimen or components are possible independent of gravity, even “overhe
38、ad” or on vertical surfacesgood repeatability and compareabilty of the method capability of being rationalised or automated by the test sequence (indentation depth measurement) and evaluation in the sense of online data processing44Shore disadvantagesdisadvantages: Shoreo tests on small parts such a
39、s O-rings are not possibleo fractured surfaces lead to greater test data scattero specimen of thickness 2 mm cannot be tested according to standardo no calibrated hardness comparison plates are availableo testing without a test stand is relatively unexact45Shore products, overviewZwick Shore+ test s
40、tandZwick products for Shore hardness testingZwick 311xShore, analogueZwick 3105 Shore/IRHDfully-automatedZwick Shoredigital46IRHD overviewHardness Testing acc. IRHD (International Rubber Hardness Degree)depth measurement, DIN 53519-2, ISO 48, ASTM D 141547IRHD advantagesadvantages: IRHD better repr
41、oducible test are achieved on concave or convex surfaces than with Shore A hardness teststhe IRHD micro method can be used for small products or for products with dimensions of thickness or diameter down to 1 mm (e.g. O-rings)indentation depth changes owing to relaxation or creep procedures at the t
42、ime of test data recording are relatively small, this is caused by the long load application duration as compared to that for Shore A (application duration 3 s)48Shore disadvantagesdisadvantages: IRHDo test load generation via weights or low load application may cause vibrations, which in turn cause
43、 acceleration to the load application; use a suitable damping systemo no standardised procedure available for indirect, i.e. including all of the devices components, monitoring of the hardness tester via hardness comparison plateso no calibrated hardness comparison plates available for plastics49Sho
44、re, IRHD application areas50IRHD products, overviewZwick 3103Micro-IRHDZwick 3105 Shore/IRHDvollautomatischer Hrteprfer51Rockwell (plastics) overviewHardness Testing according Rockwell (HR)depth measurement, scales: R, L, M, E, K, , ASTM D 78552Rockwell (plastics) advantagesadvantages: Rockwell cove
45、rs a large material range (hardness range); a greater hardness range can be covered through variants with different ball diameters and test loadssuitable for hardness testing even under unsuitable conditionsdevices for hardness tests on metals can be used in principlethe only standardised “ball inde
46、ntation” hardness test method that records solely the remaining deformation portion53Rockwell (plastics) disadvantagesdisadvantages: Rockwello no comparison of test results that have been gained through different scaleso the methods are little used in comparison to others54Rockwell product overviewZwick ZHR - LKPZwick ZHU250Zwick ZHU2.5/Z2.5Zwick 310655
