scholarly journals An Inverse Method for Measuring Elastoplastic Properties of Metallic Materials Using Bayesian Model and Residual Imprint from Spherical Indentation

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7105
Author(s):  
Mingzhi Wang ◽  
Weidong Wang
Keyword(s):  
Inverse Method ◽  
Measuring Method ◽  
Indentation Load ◽  
Weighting Coefficient ◽  
Spherical Indentation ◽  
Model Parameters ◽  
Metallic Materials ◽  
Elastoplastic Properties ◽  
Indentation Experiment ◽  
Tensile Experiment

In this paper, an inverse method is proposed for measuring the elastoplastic properties of metallic materials using a spherical indentation experiment. In the new method, the elastoplastic parameters are correlated with sub-space coordinates of indentation imprints using proper orthogonal decomposition (POD), and inverse identification of material properties is solved using a statistical Bayesian framework. The advantage of the method is that model parameters in the numerical optimization process are treated as the stochastic variables, and potential uncertainties can be considered. The posterior results obtained from the measuring method can provide valuable probabilistic information of the estimated elastoplastic properties. The proposed method is verified by the application on 2099-T83 Al-Li alloys. Results indicate that posterior distribution of material parameters exhibits more than one peak region when indentation load is not large enough. In addition, using the weighting imprints under different loads can facilitate the uniqueness in identification of elastoplastic parameters. The influence of the weighting coefficient on posterior identification results is analyzed. The elastoplastic properties identified by indentation and tensile experiment show good agreement. Results indicate that the established measuring method is effective and reliable.

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.

Spherical indentation load-relaxation of soft biological tissues

2006 ◽  
Vol 21 (8) ◽  
pp. 2003-2010 ◽  
Author(s):  
Jason M. Mattice ◽  
Anthony G. Lau ◽  
Michelle L. Oyen ◽  
Richard W. Kent
Keyword(s):  
Costal Cartilage ◽  
Kidney Tissue ◽  
Biological Tissues ◽  
Indentation Load ◽  
Spherical Indentation ◽  
Load Relaxation ◽  
Soft Biological Tissues ◽  
Long Time ◽  
Constant Displacement ◽  
Soft Biological Materials

Elastic-viscoelastic correspondence was used to generate displacement–time solutions for spherical indentation testing of soft biological materials with time-dependent mechanical behavior. Boltzmann hereditary integral operators were used to determine solutions for indentation load-relaxation following a constant displacement rate ramp. A “ramp correction factor” approach was used for routine analysis of experimental load-relaxation data. Experimental load-relaxation tests were performed on rubber, as well as kidney tissue and costal cartilage, two hydrated soft biological tissues with vastly different mechanical responses. The experimental data were fit to the spherical indentation ramp-relaxation solutions to obtain values of short- and long-time shear modulus and of material time constants. The method is used to demonstrate linearly viscoelastic responses in rubber, level-independent indentation results for costal cartilage, and age-independent indentation results for kidney parenchymal tissue.

Finite Element Analysis of Ceramic Coating Systems Under Spherical Indentation With Metallic Interlayer: Part I — Uncracked Coatings

2005 ◽  
Author(s):  
Minh-Quy Le ◽  
Jin-Woo Yi ◽  
Seock-Sam Kim
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Coating Thickness ◽  
Radial Stress ◽  
Ceramic Coating ◽  
Ceramic Coatings ◽  
Spherical Indentation ◽  
Model Parameters ◽  
Element Analysis ◽  
Plastic Damage

Spherical indentation problems of ceramic coatings/metallic inter-layer/ductile substrate were investigated numerically by axisymmetric finite element analysis (FEA) for two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel. Various indenter radius-coating thickness ratios and interlayer thickness-coating thickness ratios were used in the modeling. Radial stress distribution and plastic damage zones evolution were discussed in connection with model parameters. The results showed that the suitable metallic interlayer could improve resistance of ceramic coating systems through reducing the peak tensile radial stress on the surface and interface of ceramic coatings and plastic damage zone size in the substrate under spherical indentation.

Plasticity Model and Numerical Simulation of Extruded Oilseeds in Closed Cell

2011 ◽  
Vol 304 ◽  
pp. 235-240
Author(s):  
Xiao Zheng ◽  
Ya Xin Zhang ◽  
Guo Xiang Lin ◽  
Zhi Xian Sun
Keyword(s):  
Numerical Simulation ◽  
Constitutive Equations ◽  
Theoretical Basis ◽  
Inverse Method ◽  
Yield Criterion ◽  
Model Parameters ◽  
Plasticity Model ◽  
Power Curve ◽  
Experimental Stress ◽  
Closed Cell

By using of Kuhn`s yield criterion, plasticity constitutive equations of extruded oilseeds in a closed cylinderical cell were developed. The model parameters were identified from experimental stress—strain using an inverse method. The maximum relative deviations between the measured and the simulated value of soybean and cottonseed are 8.5% and 5.1% respectively, and the average relative deviations are 4.9% and 3.8% respectively. The results of numerical simulation for confined pressing of granular soybeans and cottonseeds in the closed cylinderical cell indicated the following facts that granular soybeans and cottonseeds conform to the model of three power curve, the plasticity constitutive equations can describe the plastic deformation for extruded soybean and cottonseed, and Kuhn`s yield criterion can be used as theoretical basis for plasticity model of granular soybeans and cottonseeds.

Inverse determination of the flow curve in large range of strains for cylindrical tensile specimen

2020 ◽  
Vol 234 (11) ◽  
pp. 2256-2265
Author(s):  
Junfu Chen ◽  
Zhiping Guan ◽  
Changhai Yang
Keyword(s):  
Tensile Test ◽  
Flow Curve ◽  
Inverse Method ◽  
Large Range ◽  
Cylindrical Specimen ◽  
Uniaxial Tensile ◽  
Model Parameters ◽  
Displacement Curve ◽  
Simulation And Optimization ◽  
Load Displacement

In this study, an inverse method with the integration of finite element simulation and optimization algorithms is proposed to determine the flow curve of cylindrical specimen characterized by the modified Voce hardening model. The tensile test is repetitiously simulated with different combinations of model parameters designed through Latin hypercube design method, where the baseline values and variation ranges of model parameters are identified through Leroy–Bridgman method, obtaining different simulated load–displacement curves. The corresponding response is defined as the sum of the absolute area difference between the simulated load–displacement curves and the experimental one. The relationship between the model parameters and the response is established through response surface methodology and the optimal parameters combination in the modified Voce model is then determined through nonlinear programming by quadratic Lagrangian. In the case of uniaxial tensile test of mild steel Q345, the inversely identified flow curve is validated by numerically reproducing the experimental load–displacement curve and necking profile. The results indicate that the proposed inverse method is capable of evaluating the flow curve in large range of strains for cylindrical specimen accurately.

Determination of the Elastic-Plastic Properties of 15Kh2MFA Steel with Austenitic Cladding

2013 ◽  
Vol 586 ◽  
pp. 43-46 ◽  
Author(s):  
Aleš Materna ◽  
Jiri Nohava ◽  
Petr Haušild ◽  
Vladislav Oliva
Keyword(s):  
Tensile Test ◽  
Indentation Test ◽  
Strain Curve ◽  
Indentation Load ◽  
Spherical Indentation ◽  
Compression Tests ◽  
Material Interface ◽  
Plastic Properties ◽  
Longitudinal Orientation ◽  
Sufficient Distance

The spherical indentation response of pressure vessel reactor steel with austenitic cladding is investigated both experimentally and numerically. The instrumented indentation test was performed for both materials at a sufficient distance from the bi-material interface, thus the results can be compared with the bulk data obtained from the standard tensile and compression tests. The stress – plastic strain curve for austenitic cladding estimated by a simplified inverse analysis of the indentation load – penetration curve is shifted to a harder response compared with that determined from the tensile test. One of the possible reasons, anisotropy of the cladding metal, was experimentally observed during the compression tests performed in the longitudinal orientation of the tensile test specimens and in the transverse orientation identical with the direction of the material indentation.

Residual stress model for CaF2

2007 ◽  
Vol 22 (10) ◽  
pp. 2796-2808
Author(s):  
Q. Zhang ◽  
J.C. Lambropoulos
Keyword(s):  
Removal Rate ◽  
Indentation Load ◽  
Contact Radius ◽  
Spherical Indentation ◽  
Stress Distributions ◽  
Element Analysis ◽  
Crystalline Anisotropy ◽  
Crystallographic Planes ◽  
Two Stages

Nanoindentation tests and finite element analysis that considers elastic-mesoplastic deformation for single crystals were used to investigate the mechanical properties of CaF2 under spherical indentation. The goal was to gain a better understanding of microfractures and crystalline anisotropy and their effect on the surface quality of CaF2 during manufacturing. In this analysis, indentations of the three main crystallographic planes (100), (110), and (111) were studied and compared to examine the effects of crystalline anisotropy on the load–displacement curves, surface profiles, contact radius, spherical hardness, stress distributions, and cleavage at two stages, namely at the maximum indentation load and after the load had been removed. Our model results were compared with experimental observation of surface microroughness, subsurface damage, and material removal rate in grinding of CaF2.

THE INVERSION OF VERTICAL MAGNETIC DIPOLE SOUNDING DATA

Geophysics ◽  
1973 ◽  
Vol 38 (6) ◽  
pp. 1109-1129 ◽  
Author(s):  
W. E. Glenn ◽  
Jisoo Ryu ◽  
S. H. Ward ◽  
W. J. Peeples ◽  
R. J. Phillips
Keyword(s):  
Density Matrix ◽  
Magnetic Dipole ◽  
Inverse Method ◽  
Model Parameters ◽  
Curve Matching ◽  
Information Distribution ◽  
Matching Method ◽  
Individual Model ◽  
Vertical Magnetic Dipole ◽  
Standard Deviations

It is demonstrated that the generalized linear inverse theory may be applied to vertical magnetic dipole sounding problems. An analysis of inversion of theoretical data for a two‐layer model illustrates the method and indicates certain features not inherent in the commonly practiced curve‐matching method of interpretation. In particular, the standard deviations of the layered model parameters may be estimated. Also the data may contain varying degrees of information about individual model parameters. Indeed, the information density matrix may be used to optimize the data information distribution by choosing only data that contributes information above some minimal level. The relative importance of the information distribution to the determination of individual model parameters may be assessed using both the structure of the information density matrix and the size of the estimated parameter standard deviations. Data may be removed until the estimated standard deviations of the parameters exceed some critical values. This process may be viewed as a method of experimental design such that information/cost ratios may be maximized. Also, if the economy of the interpretation is a serious consideration, then the same process could be used to eliminate those data that have minimal information and whose exclusion does not significantly effect the parameter resolution. This process would tend to maximize interpretation/cost ratios. Inversion analyses of four sets of data previously interpreted by the curve‐matching method illustrate the inherent features of the inverse method. Results of the inverse method of interpretation may be used to make a statistical evaluation of both the fit between observed and predicted data and the resolution of the model parameters.

scholarly journals Influence of Screen Printed Layers on the Thermal Conductivity of Textile Fabrics

2018 ◽  
Vol 26 (5(131)) ◽  
pp. 70-74
Author(s):  
Ilda Kazani ◽  
Ilda Kazani ◽  
Gilbert De Mey ◽  
Carla Hertleer ◽  
Lieva Van Langenhove ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Measuring Method ◽  
Conducting Layer ◽  
Metallic Materials ◽  
Textile Fabrics ◽  
Electric Conducting ◽  
Smart Textile ◽  
Thermographic Camera ◽  
Textile Fabric ◽  
Screen Printed

In the smart textile field the combination of textile and metallic materials is rising. In order to conduct electricity in textile, different methods are used. This paper deals with a new measuring method to determine the lateral thermal conductivity of a textile fabric. The technique starts by measuring the temperature distribution on the fabric using a thermographic camera. In addition to that, the method outlined in this paper will also allow to determine the change in thermal conductivity when an electric conducting layer has been screen printed on a textile fabric

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