Determining engineering stress–strain curve directly from the load–depth curve of spherical indentation test

2010 ◽  
Vol 25 (12) ◽  
pp. 2297-2307 ◽  
Author(s):  
Baoxing Xu ◽  
Xi Chen
Keyword(s):  
Indentation Test ◽  
Strain Curve ◽  
Spherical Indentation ◽  
Displacement Curve ◽  
Large Set ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Constraint Factors ◽  
Engineering Stress ◽  
Depth Curve

The engineering stress–strain curve is one of the most convenient characterizations of the constitutive behavior of materials that can be obtained directly from uniaxial experiments. We propose that the engineering stress–strain curve may also be directly converted from the load–depth curve of a deep spherical indentation test via new phenomenological formulations of the effective indentation strain and stress. From extensive forward analyses, explicit relationships are established between the indentation constraint factors and material elastoplastic parameters, and verified numerically by a large set of engineering materials as well as experimentally by parallel laboratory tests and data available in the literature. An iterative reverse analysis procedure is proposed such that the uniaxial engineering stress–strain curve of an unknown material (assuming that its elastic modulus is obtained in advance via a separate shallow spherical indentation test or other established methods) can be deduced phenomenologically and approximately from the load–displacement curve of a deep spherical indentation test.

scholarly journals Representative Stress-Strain Curve by Spherical Indentation on Elastic-Plastic Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Chao Chang ◽  
M. A. Garrido ◽  
J. Ruiz-Hervias ◽  
Zhu Zhang ◽  
Le-le Zhang
Keyword(s):  
Strain Curve ◽  
Stress Constraint ◽  
Spherical Indentation ◽  
Stress Strain Curve ◽  
Constraint Factor ◽  
Stress Strain ◽  
Constraint Factors ◽  
Plastic Materials ◽  
Elastic Plastic Materials ◽  
The Relationship

Tensile stress-strain curve of metallic materials can be determined by the representative stress-strain curve from the spherical indentation. Tabor empirically determined the stress constraint factor (stress CF), ψ, and strain constraint factor (strain CF), β, but the choice of value for ψ and β is still under discussion. In this study, a new insight into the relationship between constraint factors of stress and strain is analytically described based on the formation of Tabor’s equation. Experiment tests were performed to evaluate these constraint factors. From the results, representative stress-strain curves using a proposed strain constraint factor can fit better with nominal stress-strain curve than those using Tabor’s constraint factors.

A modified version of MATLAB application window for predicting the weld bead profile and stress–strain plot of AA5052 CMT weldment using ER4043

SIMULATION ◽  
2021 ◽  
pp. 003754972110315
Author(s):  
B Girinath ◽  
N Siva Shanmugam
Keyword(s):  
Strain Curve ◽  
Weld Bead ◽  
Welding Parameters ◽  
Bead Geometry ◽  
Hybrid Technique ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Weld Bead Geometry ◽  
Inference System ◽  
Engineering Stress

The present study deals with the extended version of our previous research work. In this article, for predicting the entire weld bead geometry and engineering stress–strain curve of the cold metal transfer (CMT) weldment, a MATLAB based application window (second version) is developed with certain modifications. In the first version, for predicting the entire weld bead geometry, apart from weld bead characteristics, x and y coordinates (24 from each) of the extracted points are considered. Finally, in the first version, 53 output values (five for weld bead characteristics and 48 for x and y coordinates) are predicted using both multiple regression analysis (MRA) and adaptive neuro fuzzy inference system (ANFIS) technique to get an idea related to the complete weld bead geometry without performing the actual welding process. The obtained weld bead shapes using both the techniques are compared with the experimentally obtained bead shapes. Based on the results obtained from the first version and the knowledge acquired from literature, the complete shape of weld bead obtained using ANFIS is in good agreement with the experimentally obtained weld bead shape. This motivated us to adopt a hybrid technique known as ANFIS (combined artificial neural network and fuzzy features) alone in this paper for predicting the weld bead shape and engineering stress–strain curve of the welded joint. In the present study, an attempt is made to evaluate the accuracy of the prediction when the number of trials is reduced to half and increasing the number of data points from the macrograph to twice. Complete weld bead geometry and the engineering stress–strain curves were predicted against the input welding parameters (welding current and welding speed), fed by the user in the MATLAB application window. Finally, the entire weld bead geometries were predicted by both the first and the second version are compared and validated with the experimentally obtained weld bead shapes. The similar procedure was followed for predicting the engineering stress–strain curve to compare with experimental outcomes.

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.

Strain Localisation during a Tensile Test of Metallic Plates: Experimental and Numerical Results

2009 ◽  
Vol 417-418 ◽  
pp. 569-572
Author(s):  
D.A. Cendón ◽  
Jose M. Atienza ◽  
Manuel Elices Calafat
Keyword(s):  
Tensile Test ◽  
Strain Curve ◽  
Maximum Load ◽  
Surface Strain ◽  
Displacement Curve ◽  
Strain Localisation ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Fields ◽  
Developed Surface

The stress-strain curve of a material is usually obtained from the load-displacement curve measured in a tensile test, assuming no strain localisation up to maximum load. However, strain localisation and fracture phenomena are far from being completely understood. Failure and strain localisation on plane tensile specimens has been studied in this work. A deeply instrumented experimental benchmark on steel specimens has been developed. Surface strain fields have been recorded throughout the tests, using an optical extensometer. This allowed characterisation of the strain localisation and failure processes. Tests have been numerically modelled for a more detailed analysis. Preliminary results show a substantial influence of geometrical specimen defects on the strain localisation phenomena that may be critical on the stress-strain curves obtained and in the failure mechanisms.

Representation of Damage with Fracture-Strain

2014 ◽  
Vol 592-594 ◽  
pp. 1205-1209
Author(s):  
C.S. Surendran ◽  
G. Sasikala
Keyword(s):  
Physical Quantity ◽  
Physical Meaning ◽  
Fracture Strain ◽  
Strain Curve ◽  
Damage Parameter ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Engineering Stress ◽  
Critical Damage

Under the influence of stresses and strains damage is progressively accumulated in the material leading to full damage viz. fracture corresponding to a critical damage parameter. The damage parameter varies in between zero and unity inclusive of both the values corresponding to non damaged and fully damaged condition. Also damage is a tensorial quantity with physical meaning. In order to represent this physical quantity, a damage-D plane is suggested. This is like a co-ordinate system to easy representation of damage as a function of fracture strain. The damage-D plane can be merged with engineering stress-strain curve beyond the UTS where the damage leads to fracture occurs in the material.

Determination of Stress-Strain Curve through Berkovich Indentation Testing

2010 ◽  
Vol 636-637 ◽  
pp. 1186-1193 ◽  
Author(s):  
A.M.S. Dias ◽  
G.C.D. Godoy
Keyword(s):  
Mechanical Properties ◽  
Strain Curve ◽  
Young Modulus ◽  
Displacement Curve ◽  
Indentation Testing ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Research Areas ◽  
Versus Strain

Instrumented indentation testing is a technique widely used in different materials to evaluate the penetration depth in function of the indenter load. Considering Berkovich indenter, this methodology has been used to determine mechanical properties such as hardness, Young modulus and a stress versus strain curve of the elastic-plastic behaviour under compression of the tested materials. However, the implementation of this technique to evaluate mechanical properties and also its results have still brought doubts on research areas. Nowadays, the use of a numerical methodology able to evaluate the stress and strain fields during indentation cycle can lead to a more secure interpretation. The aim of this work was to simulate the Berkovich indentation testing and to propose a methodology to extract the stress-strain curve through experimental and numerical analyses. The obtained numerical results for the load-displacement curve were quite similar to the experimental curve presented in the literature.

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