An indentation method for evaluating the residual stress of polymeric materials: Equi-biaxial and non-equi-biaxial residual stress states

Akahori, Tomoki; Nagakura, Takumi; Fushimi, Shugo; Yonezu, Akio

doi:10.1016/j.polymertesting.2018.07.024

Cited by 15 publications

(5 citation statements)

References 32 publications

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“…The dimensionless analysis on the micro‐indentation curve of rock is conducted to determine the key influencing factors of the elastoplastic properties, including the initial cohesive force and the residual cohesive force. Previous studies have been conducted to characterize the elastoplastic relationship of the indentation curve (Figure 1) 45‐47 using the shape functions Π i , for example, the total energy during loading, W (the area under the loading curve), the maximum force, P m , the unloading slope, S , the elastic energy, W e (the area under the unloading curve), and the residual or final depth, h f . The basic form of the shape function can be written as,

\prod_{i} = F_{i} false(E, f_{p}, α, h, R, f_{pore} false)

where the total energy W is used in this study, which is defined as,

W = \int_{0}^{h_{max}} F d h = W_{e} + W_{p}

where the impact factor of W in the indentation curve includes the elasticity E and the plastic criterion of the tested material ( f p ); the impact factor of pore structure at the contact zone, f pore ; the indentation depth h ; the conical angle ( α ); and radius of the flat tip ( R ).…”

Section: Methods and Samplementioning

confidence: 99%

Evaluation of elastoplastic properties of brittle sandstone at microscale using micro‐indentation test and simulation

Song

Wang

Sun

et al. 2020

Energy Science & Engineering

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\prod_{i} = F_{i} false(E, f_{p}, α, h, R, f_{pore} false)

where the total energy W is used in this study, which is defined as,

W = \int_{0}^{h_{max}} F d h = W_{e} + W_{p}

Section: Methods and Samplementioning

confidence: 99%

Evaluation of elastoplastic properties of brittle sandstone at microscale using micro‐indentation test and simulation

Song

Wang

Sun

et al. 2020

Energy Science & Engineering

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“…These investigations have all concerned metals, although similar procedures have been applied to polymers. [36] A number of these studies have been purely theoretical, but some have involved experimental indentation of samples in which controlled "artificial" residual stresses have been created by the external application of (equal-or unequal-biaxial) forces [31,32,34,35,37] or via differential thermal contraction between a substrate and a surface layer. [26] The most relevant of these for current purposes are those involving relatively large spherical indenters.…”

Section: Effects Of Residual Stressmentioning

confidence: 99%

The Effect of Residual Stresses on Stress–Strain Curves Obtained via Profilometry‐Based Inverse Finite Element Method Indentation Plastometry

Burley¹,

Campbell²,

Reiff-Musgrove

et al. 2021

Adv Eng Mater

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This paper concerns, the effect of (unknown) residual stresses in the near‐surface region of a sample on outcomes of an indentation plastometry technique for obtaining stress–strain relationships, using relatively large spherical indenters. The technique is based on the iterative finite element method (FEM) simulation of indentation, so as to infer the true stress–strain curve of the material (with the target outcome being the profile of the residual indent). It is expected that residual stress levels (if significant compared with the yield stress) are likely to influence the outcome, and indeed this forms the basis of many attempts to measure residual stresses in this way (using a known stress–strain curve). However, there are important issues of sensitivity here, which affect the reliability of such procedures and are also relevant to the accuracy of stress–strain curves inferred from measurements made on samples containing unknown levels of residual stress. Herein, both experimental work on samples with (equal‐biaxial) residual stresses created by the application of external loads and extensive FEM modeling to explore various scenarios are covered. The main conclusion is that the sensitivities involved are in general very low, particularly with relatively deep indentation. Inferred stress–strain curves are thus likely to be quite accurate, even in the presence of relatively high levels of residual stress. Conversely, the measurement of residual stress levels via this procedure is likely to be rather inaccurate, although the reliability is improved using shallow penetration (low ratio of depth‐to‐indenter radius). It is also noted that tensile residual stresses tend to influence outcomes more strongly than compressive ones.

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“…Researchers have been employing FE methods and novel numerical methods to estimate residual stresses using the indentation technique. Akahori et al 25 proposed a method to evaluate equi-biaxial residual stresses and yield stress using spherical indentation and inverse analysis, they also extended their method for biaxial residual stresses by using Knoop indenter. By employing the imprint of residual deformation and indentation test, the residual stresses were estimated.…”

Section: Introductionmentioning

confidence: 99%

Application of spherical macro-indentation for determination of plastic anisotropy and residual stresses using indentation geometry and inverse analysis

Karbasian

Mahmoudi

2023

Proceedings of the Institution of Mechanical Engineers, Part L:

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The simultaneous determination of mechanical properties and residual stresses using the instrumented indentation technique is more challenging when the anisotropic behaviour of a material is considered. If ignored, it may lead to inaccurate estimation of residual stresses and mechanical properties of materials. In this paper, the existence of in-plane anisotropic plasticity and the equi-biaxial residual stresses were considered in materials simultaneously. These anisotropic plastic properties and residual stresses were extracted for two materials, an aluminium alloy and a stainless steel, using an inverse analysis method and macro-spherical indentation test. The considered anisotropic materials have different yield stresses in both the longitudinal and transverse directions of the part. The inverse analysis method was based on a wide range of finite element (FE) simulations, which included a large number of models covering the properties of different steel and aluminium materials. In this method, the parameters extracted from the load-displacement (P-h) curve for indentation, along with the pile-up around the indentation area after unloading, were considered as the input parameters of the inverse analysis method. The outputs were the mechanical properties of the anisotropic material and the equi-biaxial tensile and compressive residual stresses. The proposed inverse method was based on the analysis of the artificial neural network (ANN). The effectiveness of the inverse method was examined and verified using experimental data which were found to be reliable. The method employed the P-h curve parameters and unloading morphology and was successful to determine the anisotropic plastic properties and residual stresses.

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An indentation method for evaluating the residual stress of polymeric materials: Equi-biaxial and non-equi-biaxial residual stress states

Cited by 15 publications

References 32 publications

Evaluation of elastoplastic properties of brittle sandstone at microscale using micro‐indentation test and simulation

Evaluation of elastoplastic properties of brittle sandstone at microscale using micro‐indentation test and simulation

The Effect of Residual Stresses on Stress–Strain Curves Obtained via Profilometry‐Based Inverse Finite Element Method Indentation Plastometry

Application of spherical macro-indentation for determination of plastic anisotropy and residual stresses using indentation geometry and inverse analysis

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