Determination of Residual Stress and Yield Stress Simultaneously by Indentation Method with Dual Indenters
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1049-AA06-08
Determination of Residual Stress and Yield Stress Simultaneously by Indentation Method with Dual Indenters Baoxing Xu, Xinmei Wang, and Zhufeng Yue School of Mechanics, Civil Engineering and Architecture, Northwestern Polytechnical University, Xi'an, 710072, China, People's Republic of ABSTRACT Obtaining residual stress from indentation test requires calculating the contact area between the indenter and the indented material, while yield stress of indented material is to be known in advance. In this work, the dimensional analysis of indentation loading curve was first analyzed, and then a reverse numerical procedure was explored to determine the residual stress and yield stress of materials simultaneously from indentation test. Besides, the calculation of contact area can be also avoided. INTRODUCTION The measurement of residual stress in the surface of materials with indentation test has attracted intensive interests since Sines and Carlson suggested that the residual stress could be measured by utilizing effects of residual stress on the hardness [1]. Recently, several methods have been explored to extract residual stress from indentation load-depth curves [2-6]. Inspired from results of Tsui et al. that residual stress affected the measurement of hardness and elastic modulus using a Berkovich indenter [7], Suresh and Giannakopoulos suggested a method of determination of equi-biaxial residual stress utilizing difference in contact area of stressed and unstressed materials at the same depth with Berkovich indenters [2]. But in fact, the influence of residual stress on contact area is relatively small for the Berkovich indenter, especially when the residual stress is close to yield stress and the pile-up is obvious in materials. Later, Taljat and Pharr suggested that much larger effects from residual stress can be obtained by using blunt, spherical indenters [3]. They performed spherical indentation test on a polished disk of commercial aluminum alloy, which was pre-applied compressive or tensile biaxial stress, and found that indentation load - depth curves shifted to a larger indentation depth when the applied biaxial stress was tensile stress, while compressive stress had opposite effect. Based on these experimental results, Swadener et al put forward a method of measuring residual stresses using spherical indenters [4]. However, this method has the disadvantage that contact area has to be calculated, which is difficult due to the influence of pile- up around indention. Besides, the yield stress of materials needs to be known in advance. Later, in order to avoid the calculation of contact area, Xu et al. give a similar method by using two different sizes of flat cylindrical indenters. But the yield stress still needs to be known in advance [8]. For the indentation test, the unique advantages of dual indenters have been reviewed recently by Chen et al. [9]. In the present study, we show the possibility that residual stress and yield stress can be determined simultaneously with dual indenters from loa
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