OS4(2)-5(OS04W0113) Microhardness Measurements as a Tool for Stress Analysis
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概要
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The influence of residual stresses as well as of loading stresses on microhardness is systematically investigated using a combined application of registered microhardness measurements and stress analysis by X-ray diffraction in order to evaluate the ability of the microhardness testing to estimate residual or loading stresses, respectively. Measurements were carried out on steel samples of type S690QL and SAE 1045 using a conventional Vickers indentor as well as a ball indentor. The investigations cover samples subjected to 4-point bending as well as uniaxially loaded samples. By the use of loading devices, which can be mounted both on the hardness testing machine as well as on the X-ray diffractometer, in-situ measurements up to an elasto-plastic loading of the materials enable to distinguish between the effects of loading stresses, residual stresses and strain hardening on microhardness. The 4-point-bending measurements were carried out on a path along the bending height on microhardness. The 4-point-bending measurements were carried out on a path along the bending height on the side face of a bending bar. So for elastically loaded samples the bending experiments covers a wide range of loading stress states from tension to compression, whereas elasto-plastic bending causes an inhomogeneous plastic deformation of the steel specimens and hence results in characteristic macro- and microresidual stress distributions. Measurements carried out on tensile specimens under uniaxial loading were performed to endorse the results of the bending experiments since the heterogeneous loading situation under bending causes an overlapping of different effects. By registered hardness testing various materials parameters can be determined or estimated in addition to the hardness value like e. g. the elastic and plastic parts of the indentation work, an estimation of Young's modulus or parameters characterizing the creep or relaxation behavior of the material of interest. In particular by using a ball indentor methods are proposed in literature which enable the determination of the entire stress-strain-curve. To be consistent the paper deals also with the ability of the indentation tests to determine materials parameters or to characterize the materials behavior in general if loading or residual stresses are present.
- 一般社団法人日本機械学会の論文
- 2003-09-09
著者
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Gibmeier Jens
Inst. Of Materials Engineering Univ. Of Kassel
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Scholtes Berthold
Inst. Of Materials Engineering Univ. Of Kassel