Indentation methods

The Computation of Polymeric Material s Viscoelastic Properties by Dynamic Indentation Method. 

The paper discusses the application of dynamic indentation method and apparatus for the evaluation of viscoelastic properties of polymeric materials. The three-element model of viscoelastic material has been used to calculate the rigidity and the viscosity. Using a measurements of the indentation as a function of a current velocity change on impact with the material under test, the contact force and the displacement diagrams as a function of time are plotted. Experimental results of the testing of polyvinyl chloride cable coating by dynamic indentation method and data of the static tensile test are presented. 

Obtained results allow to conclude that the dynamic indentation method can be applied to periodical express evaluation of polymeric material state being exposured to the radiation or temperature aging on purpose to early diagnostic of products to avoid emergency situations. 

The technological importance of thin films in snch areas as semicondnctor devices and sensors has led to a demand for mechanical property infonnation for these systems. Measuring the elastic modnlns for thin films is mnch harder than the corresponding measurement for bnlk samples, since the results obtained by traditional indentation methods are strongly perturbed by the properties of the substrate material. Additionally, the behaviour of the film under conditions of low load, which is necessary for the measnrement of thin-film properties, is strongly inflnenced by surface forces [75]. Since the force microscope is both sensitive to surface forces and has extremely high depth resolntion, it shows considerable promise as a teclnhqne for the mechanical characterization of thin films. 

Vickers indentation method will be pursued here (in both its micro- and nanomanifestations). 

ISO 2039-1 2001 Plastics - Determination of hardness - Part 1 Ball indentation method ISO 2039-2 1987 Plastics - Determination of hardness - Part 2 Rockwell hardness ISO 2439 1997 Flexible cellular polymeric materials - Determination of hardness (indentation technique)... 

Marshall, D.B. (1984). An indentation method for measuring matrix-fiber frictional stresses in ceramic composites. J. Am. Ceram. Soc. 67. C259-260. 

Marshall, D.B. and Oliver, W.C. (1990). An indentation method for measuring residual stresses in fiber reinforced ceramics. Mater. Sci., Eng. A 126, 95-103. 

The physical meaning of hardness determined by Bierbaum s method is exactly equal to load P divided by the projected contact surface of pyramid with material under test in the scratch process. It should be mentioned here that the result obtained under Bierbaum s method is roughly directly proportional to the hardness number obtained by the pyramid indenter method, and the relation has the form... 

Khrushchev (1957) considers that the need to measure the force T has not been sufficiently well substantiated, nor has a sufficiently precise and easy in service hardness tester been developed yet for determinations of this type. However, he appreciates the usefulness of scratch hardness tests, especially at low loads, as a non-destructive technique. He recommends these methods as very useful for hardness determination of metallic layers or of materials exposed to abrasive wear under operating conditions (plastics, organic coatings, such as varnishes and paints, etc.). Scratch methods are especially important in tests of anisotropic materials where a change in scratch width is the measure of anisotropy. In static indentation methods, the indentations obtained in anisotropic materials are misformed, varying... 

Comparative values of standards on old Mohs scale obtained by scratch and abrasion methods and by indentation methods compiled by Povarennykh (1963)... 

It is somewhat more difficult to relate dynamic abrasion methods to diamond indenter methods. Since the Scott tower is designed for abrasiveness tests with ceramic glazes, it is obvious that the attempts to correlate abrasiveness derived by this method with hardness, relied on test results for glazes. The hardness of glazes is similar to that of typical glasses, and... 

Khrushchev M. M., Berkovich E. S., 1943, Mikrotverdost, opredelaemaya metodom vdavlivaniya (Microhardness Determined by Indentation Method). Izd. AN SSSR, Moskva. 

PC 2765-70, 1972, SEV. Gruppa 29 (CMEA, Group 29). Izmerenie tverdosti po metodu vdavlivaniya sharika (Hardness Measurements by Ball Indentation Method). 

Srebrodolskii B. I., Yushkin N. R., 1966, Issledovanie tverdosti kristallov samorodnoi sery metodom vdavlivaniya (Hardness testing of brimstone crystals by indentation method. Structure and properties) 35-45, Kiev. 

The phase composition from the surface to the interior of the samples was determined by X-ray diffractometry (XRD) through successive grinding of the surface at 100 pm intervals. The microstructural characterization of the sintered specimens was achieved by scanning electron microscopy (SEM) in backscattered mode. The hardness change from the surface to the interior of the sample was measured by the Vickers indentation method at 19.6 N load. 

Tests such as Vickers, Knoop, and Brinell use an indentation technique that impinges a hard tip (e.g., diamond) into the sample with a known load (Figure 2.35a). After a designated period of time, the load is removed, and the indentation area is measured. The hardness, H, is defined as the maximum load, L, divided by the residual indentation area, (Eq. 11). The coefficient, F, varies depending on which indentation method is used. This value (14.229 for Knoop and 1.854 for Vickers)... 

Indentation methods as a special type of analysis of viscoelastic stress or displacement are studied in Chapter 16. It should be noted that indentation... 

The methods most widely used in determining the hardness of metals are the static indentation methods. These involve the formation of a permanent indentation in the surface of the material under examination, the hardness being determined by the load and the size of the indentation formed. Because of the importance of indentation methods in hardness measurements a general discussion of the deformation and indentation of plastic materials is given in Chapter 2. 

ISO 2439-80 Polymeric Materials, Cellular Flexible —Determination of Hardness (Indentation Method), 4 pp... 

BS 2782 Method 365D, Determination of Hardness by Ball Indentation Method, London (1978). 

Hardness of thin films is measured generally by indentation methods. The relation of the various hardness values obtained by various microhardness measuring techniques is shown in Fig.24. 

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