scholarly journals A New Inverse Method for Determining Uniaxial Flow Properties by Spherical Indentation Test

2021 ◽  
Author(s):  
Guoyao Chen ◽  
Xiaocheng Zhang ◽  
Jiru Zhong ◽  
Kaishu Guan
Keyword(s):  
Inverse Method ◽  
Engineering Application ◽  
Indentation Test ◽  
Experimental Curve ◽  
New Method ◽  
Spherical Indentation ◽  
Fe Model ◽  
Flow Properties ◽  
Indentation Force ◽  
Depth Curves

Abstract This study presents a new inverse method to determine tensile flow properties from a single indentation force-depth curves. A database is established to replace the iterative FE calculations in conventional inverse methods and therefore can process the indentation data more quickly and easily. An axisymmetric FE model is constructed to simulate the elastic-plastic response of indention. Assuming the materials follow Ludwic constitutive model, by systematically changing the material parameters, numerous indentation force-depth curves are extracted from simulation results to establish the database. For a given experimental indentation curves, a mean square error (MSE) is designated to evaluate the deviations between the experimental curve and each curve in the database. Then, the relation of deviations versus stresses are investigated to acquire the true stresses at a series of plastic strain. To validate the new method, three different steels, i.e. A508, 316L and 2.25Cr1Mo are selected. Both simulated indentation curves and experimental indentation curves are used as inputs of the database to inversely acquire the flow properties. The result indicates that the proposed approach provides impressive accuracy when simulated indentation curves is used, but is less accurate when an experimental curve is used. This new method can quickly derive tensile properties without iterative calculations that yield a considerable computational costs and are therefore adaptive to engineering application.

scholarly journals New Inverse Method for Determining Uniaxial Flow Properties by Spherical Indentation Test

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Guoyao Chen ◽  
Xiaocheng Zhang ◽  
Jiru Zhong ◽  
Jin Shi ◽  
Qiongqi Wang ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Inverse Method ◽  
Engineering Application ◽  
Indentation Test ◽  
New Method ◽  
Spherical Indentation ◽  
Flow Properties ◽  
Indentation Force ◽  
Non Destructive ◽  
Depth Curves

AbstractThe spherical indentation test has been successfully applied to inversely derive the tensile properties of small regions in a non-destructive way. Current inverse methods mainly rely on extensive iterative calculations, which yield a considerable computational costs. In this paper, a database method is proposed to determine tensile flow properties from a single indentation force-depth curves to avoid iterative simulations. Firstly, a database that contain numerous indentation force-depth curves is established by inputting varied Ludwic material parameters into the indentation finite elements model. Secondly, for a given experimental indentation curve, a mean square error (MSE) is designated to evaluate the deviation between the experimental curve and each curve in the database. Finally, the true stresses at a series of plastic strain can be acquired by analyzing these deviations. To validate this new method, three different steels, i.e. A508, 2.25Cr1Mo and 316L are selected. Both simulated indentation curves and experimental indentation curves are used as inputs of the database to inversely acquire the flow properties. The result indicates that the proposed approach provides impressive accuracy when simulated indentation curves are used, but is less accurate when experimental curves are used. This new method can derive tensile properties in a much higher efficiency compared with traditional inverse method and are therefore more adaptive to engineering application.

A Novel Method to Extract the Plastic Properties of Metal Materials from a Continuous Spherical Indentation Test

2017 ◽  
Vol 734 ◽  
pp. 206-211 ◽  
Author(s):  
Zhuang Jin ◽  
Jian Ping Zhao
Keyword(s):  
Strain Hardening ◽  
Indentation Test ◽  
New Method ◽  
Spherical Indentation ◽  
Strain Hardening Exponent ◽  
Computational Results ◽  
Plastic Properties ◽  
Novel Method ◽  
Properties Of Materials ◽  
Metal Materials

Cao and Lu had built a method to acquire the properties of materials. But they neglected the influence of strain hardening exponent n by introducing the representative strain which didan’t have any physical meaning. A new method from a continuous spherical indentation test was built, the influence of strain hardening exponent n were considered and the formulas of dimensionless functions defined in their work were improved in this present paper. Then the computational results from the new method and the actual results were compared and the error is about 8%.

Examination of Prestressed Coating/Substrate Systems Using Spherical Indentation—Determination of Film Prestress, Film Modulus, and Substrate Modulus

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
James A. Mills ◽  
Hang Xiao ◽  
Xi Chen
Keyword(s):  
Material Properties ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Indentation Force ◽  
Forward Analysis ◽  
Substrate Properties ◽  
Error Sensitivity Analysis ◽  
Film Substrate

There have been many studies performed with respect to the indentation of thin films affixed to a corresponding substrate base. These studies have primarily focused on determining the mechanical properties of the film. It is the goal of this paper to further understand the role that the film plays and how a potential prestressing of this film has on both the film and substrate base. It is equally important to be able to understand the material properties of the substrate since during manufacturing or long-term use, the substrate properties may change. In this study, we establish through spherical indentation a framework to characterize the material properties of both the substrate and film as well as a method to determine the prestress of the film. It is proposed that through an initial forward analysis, a set of relationships are developed. A single spherical indentation test can then be performed, measuring the indentation force at two prescribed depths, and with the relationships developed from the forward analysis, the material properties of both the film and substrate can be determined. The problem is further enhanced by also developing the capability of determining any equibiaxial stress state that may exist in the film. A generalized error sensitivity analysis of this formulation is also performed systematically. This study will enhance the present knowledge of a typical prestressed film/substrate system as is commonly used in many of today’s engineering and technical applications.

Evaluation of Indentation Test for Measuring Young’s Modulus of Cancellous Bone

2007 ◽  
Vol 544-545 ◽  
pp. 307-310
Author(s):  
Moon Kyu Lee ◽  
Kui Won Choi ◽  
Tae Soo Lee ◽  
H.N. Lim
Keyword(s):  
Porous Materials ◽  
Young’S Modulus ◽  
Cancellous Bone ◽  
Indentation Depth ◽  
Young's Modulus ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Uniaxial Compression Test ◽  
Displacement Curve ◽  
Fe Model

The indentation test has been in the spotlight due to easy and non-destructive testing characteristics. However, there are little studies for the indentation test of porous materials in the evaluation aspect of methodology. The goal of this study was to evaluate a spherical indentation test in the aspect of indenter-size and indentation depth by measuring elastic modulus of porous materials such as a cancellous bone using a FEM. We developed a microstructure-based FE model of cancellous bone with apparent density 0.2~0.8 g/cm3 in order to simulate uniaxial compression test and indentation test in the light of anatomical observation with a scanning electron microscope (SEM). We obtained a load-displacement curve through the indentation simulation and calculated the Young’s modulus of cancellous structure based on Pharr's hypothesis. The result indicated that indenter diameter has to be more than five times of pore size and indentation depth should be about 8% of indenter diameter at least to obtain the appropriate result of the indentation test. It is expected that this result may guide to the design and the simulation of indentation test for porous materials

Spherical indentation for determining the phase transition properties of shape memory alloys

2009 ◽  
Vol 24 (3) ◽  
pp. 1082-1086 ◽  
Author(s):  
Linmao Qian ◽  
Shuang Zhang ◽  
Dongyang Li ◽  
Zhongrong Zhou
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Tensile Tests ◽  
Deformation Analysis ◽  
Spherical Indentation ◽  
Indentation Method ◽  
Indentation Force ◽  
Depth Curves

A spherical indentation method was developed to characterize the phase transition behaviors of shape memory alloys (SMAs). Based on deformation analysis, the measured indentation force-depth curves of SMAs can be converted to their nominal stress-strain curves. The predicted elastic modulus and phase transition stress of SMAs from spherical indentation agree well with those directly measured from tensile tests. This approach should be especially useful for characterizing the phase transition properties of SMA materials of small size or thin films.

Characterisation of Elastoplastic Behaviour Using Spherical Indentation

2006 ◽  
Vol 514-516 ◽  
pp. 744-748
Author(s):  
António Castanhola Batista ◽  
José P. Marinheiro ◽  
Joao P. Nobre ◽  
A. Morão Dias
Keyword(s):  
Inverse Method ◽  
Indentation Test ◽  
Strain Curve ◽  
Tensile Tests ◽  
Spherical Indentation ◽  
Stress Strain Curve ◽  
Hardening Law ◽  
Behaviour Study ◽  
Behaviour Law ◽  
Good Agreement

An inverse method for the characterisation of the elastoplastic behaviour of materials has been studied. The method is based on spherical indentation test data and numerical analysis of the indentation process, enabling to find a characteristic stress-strain curve. This method will be appropriate for elastoplastic behaviour study, mainly on surface hardened materials, when the standard methods cannot be applied. In this work, the method was applied to annealed and quenched steels, with homogeneous properties over the cross section. The obtained results are in good agreement with those obtained from the standard tensile tests. However, if the material does not follow a linear hardening law, the elastoplastic characteristics determined by the inverse method will depend on the indentation depth. For these cases a method for the evaluation of the actual behaviour law has been improved.

Can indentation technique measure unique elastoplastic properties?

2009 ◽  
Vol 24 (3) ◽  
pp. 784-800 ◽  
Author(s):  
Ling Liu ◽  
Nagahisa Ogasawara ◽  
Norimasa Chiba ◽  
Xi Chen
Keyword(s):  
Critical Strain ◽  
Indentation Test ◽  
Strain Curve ◽  
Spherical Indentation ◽  
Plastic Behavior ◽  
Displacement Curve ◽  
Application Range ◽  
Indentation Technique ◽  
Elastoplastic Properties ◽  
Force Displacement

Indentation is widely used to extract material elastoplastic properties from measured force-displacement curves. Many previous studies argued or implied that such a measurement is unique and the whole material stress-strain curve can be measured. Here we show that first, for a given indenter geometry, the indentation test cannot effectively probe material plastic behavior beyond a critical strain, and thus the solution of the reverse analysis of the indentation force-displacement curve is nonunique beyond such a critical strain. Secondly, even within the critical strain, pairs of mystical materials can exist that have essentially identical indentation responses (with differences below the resolution of published indentation techniques) even when the indenter angle is varied over a large range. Thus, fundamental elastoplastic behaviors, such as the yield stress and work hardening properties (functions), cannot be uniquely determined from the force-displacement curves of indentation analyses (including both plural sharp indentation and deep spherical indentation). Explicit algorithms of deriving the mystical materials are established, and we qualitatively correlate the sharp and spherical indentation analyses through the use of critical strain. The theoretical study in this paper addresses important questions of the application range, limitations, and uniqueness of the indentation test, as well as providing useful guidelines to properly use the indentation technique to measure material constitutive properties.

Identification of Hardening Parameters of Metals From Spherical Indentation Tests

2001 ◽  
Vol 123 (3) ◽  
pp. 245-250 ◽  
Author(s):  
S. Kucharski ◽  
Z. Mro´z
Keyword(s):  
Indentation Test ◽  
Strain Curve ◽  
Load Level ◽  
Spherical Indentation ◽  
Indentation Tests ◽  
Geometric Sequence ◽  
Loading And Unloading ◽  
Plastic Hardening ◽  
Hardening Curve ◽  
Two Parameters

The identification method of hardening parameters specifying stress-strain curve is proposed by applying spherical indentation test and measuring the penetration depth during loading and unloading. The loading program is composed of a geometric sequence of loading and partial unloading steps from which the variation of permanent penetration with load level is determined. This data is used for specification of two parameters k and m occurring in the plastic hardening curve εp=σ/k1/m, where εp denotes the plastic strain.

scholarly journals Analysis of depth-sensing indentation tests with a Knoop indenter

2001 ◽  
Vol 16 (6) ◽  
pp. 1660-1667 ◽  
Author(s):  
L. Riester ◽  
T. J. Bell ◽  
A. C. Fischer-Cripps
Keyword(s):  
Elastic Modulus ◽  
Elastic Recovery ◽  
Indentation Test ◽  
New Method ◽  
Short Axis ◽  
Depth Sensing ◽  
Specimen Material ◽  
Indentation Tests ◽  
Conventional Methods ◽  
Knoop Indenter

The present work shows how data obtained in a depth-sensing indentation test using a Knoop indenter may be analyzed to provide elastic modulus and hardness of the specimen material. The method takes into account the elastic recovery along the direction of the short axis of the residual impression as the indenter is removed. If elastic recovery is not accounted for, the elastic modulus and hardness are overestimated by an amount that depends on the ratio of E/H of the specimen material. The new method of analysis expresses the elastic recovery of the short diagonal of the residual impression into an equivalent face angle for one side of the Knoop indenter. Conventional methods of analysis using this corrected angle provide results for modulus and hardness that are consistent with those obtained with other types of indenters.

A New Method Developed for Brittle and Ductile Materials to Evaluate Mechanical Properties of a Lump Specimen in the Use of Indentation Test

2006 ◽  
Vol 129 (2) ◽  
pp. 284-292 ◽  
Author(s):  
Pal Jen Wei ◽  
Jen Fin Lin
Keyword(s):  
Yield Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Elastic Recovery ◽  
Indentation Test ◽  
New Method ◽  
Ductile Materials ◽  
Conventional Material ◽  
Loading And Unloading ◽  
Logarithm Function

In this study, the load-depth (P‐h) relationships matching the experimental results of the nanoindentation tests exhibited at the subregions of small and large depths are obtained, respectively. The relationships associated with these two subregions are then linked by the hyperbolic logarithm function to attain a single expression that is applied in the evaluation of the specimen’s elastic recovery ability, as shown in the unloading process. A new method is developed in the present study to evaluate both Young’s modulus and the yield strength of either a ductile or brittle material through the uses of the appropriate P‐h relationships developed in the load and unloading processes. The results of the Young’s modulus and the yield strength achieved by the present method are compared to those obtained from the conventional material tests for a lump material. The scattering of the experimental data shown in the loading and unloading processes are also interpreted by different causes.

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