The Relation of the Vickers Hardness With the Loading Stiffness of Instrumented Vickers Indentation of Metal Substrates

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
E. A. Baxevani ◽  
A. E. Giannakopoulos
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Power Law ◽  
Vickers Hardness ◽  
Material Properties ◽  
Vickers Indentation ◽  
Metal Substrates ◽  
Vickers Indenter ◽  
Indentation Imprint

The present paper presents a relation between the vickers hardness HV and the loading stiffness C of instrumented vickers indentation of metal substrates. The relation is based on the fact that the nonaxisymmetry of the plastic deformation of the vickers indenter leaves the corners of the indentation imprint at the surface of metal substrates after complete unloading. This relation can transform available HV data for metals to C data. It is also shown that the strain hardening details are important in the estimation of material properties and investigators should be cautions when using power-law strain hardening in all cases.

THREE-DIMENSIONAL SIMULATION OF DEFORMATION FIELDS UNDERNEATH VICKERS INDENTER: EFFECTS OF POWER-LAW PLASTICITY

2010 ◽  
Vol 24 (01n02) ◽  
pp. 238-246 ◽  
Author(s):  
NUWONG CHOLLACOOP ◽  
UPADRASTA RAMAMURTY
Keyword(s):  
Yield Strength ◽  
Strain Hardening ◽  
Power Law ◽  
Strain Distribution ◽  
Three Dimensional ◽  
Strain Hardening Exponent ◽  
Al Alloy ◽  
Element Analysis ◽  
Vickers Indenter ◽  
Experimental Heat

The effects of power-law plasticity (yield strength and strain hardening exponent) on the plastic strain distribution underneath a Vickers indenter was systematically investigated by recourse to three-dimensional finite element analysis, motivated by the experimental macro- and micro-indentation on heat-treated Al - Zn - Mg alloy. For meaningful comparison between simulated and experimental results, the experimental heat treatment was carefully designed such that Al alloy achieve similar yield strength with different strain hardening exponent, and vice versa. On the other hand, full 3D simulation of Vickers indentation was conducted to capture subsurface strain distribution. Subtle differences and similarities were discussed based on the strain field shape, size and magnitude for the isolated effect of yield strength and strain hardening exponent.

Effect of Interfaces in the Work Hardening of Nanoscale Multilayer Metallic Composites During Nanoindentation: A Molecular Dynamics Investigation

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
S. Shao ◽  
H. M. Zbib ◽  
I. Mastorakos ◽  
D. F. Bahr
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Strain Hardening ◽  
Power Law ◽  
Indentation Depth ◽  
Constitutive Law ◽  
Atomistic Simulations ◽  
Depth Data ◽  
Strain Data ◽  
Metallic Composites

To study the strain hardening in nanoscale multilayer metallic (NMM) composites, atomistic simulations of nanoindentation are performed on CuNi, CuNb, and CuNiNb multilayers. The load-depth data were converted to hardness-strain data that were then modeled using power law. The plastic deformation of the multilayers is closely examined. It is found that the strain hardening in the incoherent CuNb and NiNb interfaces is stronger than the coherent CuNi interface. The hardening parameters are discovered to be closely related to the density of the dislocations in the incoherent interfaces, which in turn is found to have power law dependence on two length scales: indentation depth and layer thickness. Based on these results, a constitutive law for extracting strain hardening in NMM from nanoindentation data is developed.

Analysis of Indentation Size Effect of Vickers Hardness Tests of Steels

2013 ◽  
Vol 652-654 ◽  
pp. 1307-1310 ◽  
Author(s):  
Nyoman Budiarsa ◽  
Andrew Norbury ◽  
Xiao Xiang Su ◽  
Gareth Bradley ◽  
Xue Jun Ren
Keyword(s):  
Experimental Data ◽  
Size Effect ◽  
Power Law ◽  
Vickers Hardness ◽  
Material Properties ◽  
Indentation Size Effect ◽  
Indentation Load ◽  
Indentation Size ◽  
Load Range ◽  
Hardness Tests

In this work, the indentation size effect (ISE) in Vickers hardness tests of steel with selected heat treatments (annealed or tempered) has been investigated and analysed. Systematical hardness tests were performed within a commonly used micro-load range. The experimental data was analysed according to the Meyer power-law and the proportional specimen resistance (PSR) models and the link between ISE and material properties was discussed. The results showed that the experimental data fitted well with the Mayers power-law (P = A.dn) and the PSR (P/d = al + a2d) models. The ISE index (n) showed a good correlation with the hardness-elastic modulus ratio (H/E), which potentially could be used to predict the relative contributions of the elastic and plastic deformation contact area under indentation load and to normalize the hardness values for inverse material properties .

Influencing Factors for Improving Accuracy in Prediction of Stress Corrosion Crack Growth Rate in Boiling Water Reactor Operational Condition: Part 1—Prediction of SCC Growth Rate in Terms of Vickers Hardness

2010 ◽  
Author(s):  
Yoichi Takeda ◽  
Zhanpeng Lu ◽  
Takeshi Adachi ◽  
Qunjia Peng ◽  
Jiro Kuniya ◽  
...  
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Yield Strength ◽  
Strain Hardening ◽  
Crack Growth ◽  
Vickers Hardness ◽  
316L Stainless Steel ◽  
Strain Hardening Exponent ◽  
Theoretical Formulation ◽  
Prediction Curve

It is known that stress corrosion cracking (SCC) found in the operational power plants show complex cracking behaviors and it’s resulted in complex crack shape e.g. crack branching and its uneven crack front. For the cracking near the weldment, this is due to crack penetrated along the complex distribution of residual stress and strain hardened area. In this investigation, in order to advance the accuracy for crack growth prediction with considering such complex fields, theoretical formulation for SCC growth was further modified. Hardness of the materials, which is a measureable parameter even in operational power plant, was focused on to reflect strain hardening of the component like heat affected zone of the weldments. The theoretical formulation for SCC growth has terms with yield strength of the material and strain hardening exponent to describe crack tip strain rate. Strain hardening was simulated by cross rolling with the range of 4 – 32% as thickness reduction. Correlation between yield strength, strain hardening exponent at 288°C and Vickers hardness was obtained by means of tensile tests and hardness tests on 316L stainless steel. It was observed that a monotonic increase in Vickers hardness and yield strength with degree of reduction in thickness worked by cross rolling. Relationship between Vickers hardness and yield strength was found to have linear correlation. Further confirmation was made by plotting the reported mechanical properties data in terms of Vickers hardness. In addition, linear relationship was found between yield strength and strain hardening exponent. These relationships were introduced into SCC theoretical formulation and a SCC growth rate prediction curve in terms of Vickers hardness was proposed. SCC crack growth evaluation tests with selected work hardened 316L stainless steel were performed in oxygenated pure water environment at 288°C to confirm the predictability of the formulation. The prediction curve had a good agreement with available literature data as well as obtained crack growth rates in the hardness range of 140–300HV which was likely expected one in weld HAZ.

The Effect of Plastic Deformation on the Thermoelastic Constant and the Potential to Evaluate Residual Stress

2011 ◽  
Vol 70 ◽  
pp. 458-463 ◽  
Author(s):  
A. F. Robinson ◽  
Janice M. Dulieu-Barton ◽  
S. Quinn ◽  
R. L. Burguete
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Plastic Strain ◽  
Strain Hardening ◽  
Thermoelastic Stress ◽  
Paint Coating ◽  
Full Field ◽  
Thermoelastic Constant ◽  
Thermoelastic Response ◽  
Measured Change

In some metals it has been shown that the introduction of plastic deformation or strain modifies the thermoelastic constant, K. If it was possible to define the magnitude of the change in thermoelastic constant over a range of plastic strain, then the plastic strain that a material has experienced could be established based on a measured change in the thermoelastic constant. This variation of the thermoelastic constant and the ability to estimate the plastic strain that has been experienced, has potential to form the basis of a novel non-destructive, non-contact, full-field technique for residual stress assessment using thermoelastic stress analysis (TSA). Recent research has suggested that the change in thermoelastic constant is related to the material dislocation that occurs during strain hardening, and thus the change in K for a material that does not strain harden would be significantly less than for a material that does. In the work described in this paper, the change in thermoelastic constant for three materials (316L stainless steel, AA2024 and AA7085) with different strain hardening characteristics is investigated. As the change in thermoelastic response due to plastic strain is small, and metallic specimens require a paint coating for TSA, the effects of the paint coating and other test factors on the thermoelastic response have been considered.

Further analysis of the size effect in indentation hardness tests of some metals

1995 ◽  
Vol 10 (11) ◽  
pp. 2908-2915 ◽  
Author(s):  
M. Atkinson
Keyword(s):  
Size Effect ◽  
Strain Hardening ◽  
Indentation Size Effect ◽  
Plastic Hinge ◽  
Small Scale ◽  
Indentation Hardness ◽  
Vickers Indentation ◽  
Indentation Size ◽  
Hardness Tests ◽  
Indentation Tests

The variation of apparent hardness observed in previously reported Vickers indentation tests of metals is reexamined. Common deseriptions of the effect are shown to be inaccurate: the variation of apparent hardness is monotonic but not simple. The effect is consistent with varying size of a previously postulated “plastic hinge” at the perimeter of the indent. This complexity confers uncertainty on the estimation of characteristic macrohardness from small scale tests. Association of the indentation size effect with friction and with strain hardening is confirmed.

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