Elastic recovery and reloading of hardness impressions with a conical indenter

2002 ◽  
Vol 750 ◽  
Author(s):  
A. C. Fischer-Cripps
Keyword(s):  
Residual Stress ◽  
Test Data ◽  
Elastic Recovery ◽  
Indentation Test ◽  
Nanoindentation Test ◽  
Instrumented Indentation ◽  
Specimen Material ◽  
Elastic Event ◽  
Instrumented Indentation Test ◽  
Elastic Unloading

ABSTRACTThe present work is concerned with the analysis of elastic unloading data in conventional methods of analysis of nanoindentation test data. Experimental and finite element results are used to show that the reloading of a residual impression with and without the presence of residual stress is an elastic event, and further shows that the estimation of modulus and hardness computed using established techniques is in error due to the assumption the sides of the residual impression are straight. This work calls into question the validity of commonly used methods of test and analysis of instrumented indentation test data that use the elastic unloading data as the basis for the calculation of modulus and hardness of the specimen material.

Analyzing the Influence of Test Force on Instrumented Indentation Test

2014 ◽  
Vol 685 ◽  
pp. 245-249
Author(s):  
Yang Liu ◽  
Rong Chen
Keyword(s):  
Test Data ◽  
Coefficient Of Variation ◽  
Indentation Test ◽  
Hardness Test ◽  
Relative Difference ◽  
Indentation Hardness ◽  
Indentation Modulus ◽  
Instrumented Indentation ◽  
Different Levels ◽  
Instrumented Indentation Test

For the problem that the value of test force will influence the result of instrumented indentation hardness test, the relation between test force and instrumented indentation hardness , indentation modulus were investigated. 55 groups of tests were carried out, in which the test force were divided to 11 different levels. On the basis of 110 test data, differences were analyzed and the relation curves were plotted by Origin. And the relative difference value was proposed. Results show that when 19.61N≤Fmax≤98.07N, the change of test force makes little influence on instrumented indentation test (IIT) results and coefficient of variation(CV); when 0.98N≤Fmax≤9.81N or 196.14N≤Fmax≤294.21N, the change of test force makes remarkable influence on IIT results and CV.

Multiscale Mapping of Mechanical Properties by Instrumented Indentation Test

2010 ◽  
Vol 654-656 ◽  
pp. 2316-2321
Author(s):  
Kug Hwan Kim ◽  
Young Cheon Kim ◽  
Seung Kyun Kang ◽  
Kwang Ho Kim ◽  
Dong Il Kwon
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Indentation Test ◽  
Uniaxial Tensile ◽  
Material Surface ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Flow Properties ◽  
Residual Stress State ◽  
Instrumented Indentation Test

The instrumented indentation test (IIT) is a mechanical testing method to determine the hardness and elastic modulus of materials by putting an indenter into a material surface. This technique has now gone beyond normal hardness tests by evaluating additional properties of materials and by allowing testing at much lower forces and indentation depths (micro/nano ranges). This study presents analytic models and procedures for evaluating tensile flow properties and residual stress state using IIT; the tensile flow properties are treated by defining a representative stress/strain beneath a spherical indenter and the residual stress by using a stress-insensitive contact hardness model. The IIT results are compared with those from conventional methods such as uniaxial tensile test and X-ray diffraction. In addition, IIT can be used as a multiscale mapping tool for the mechanical properties of composite materials and constituent phases by using macro/micro/nano indentation system: we made a hardness map of multiphase steel and measured the strength/residual stress distributions of welded pipeline.

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.

Evaluation of Tensile Properties Profile of Weld Zone Using Instrumented Indentation

2010 ◽  
Author(s):  
Seung-Kyun Kang ◽  
Young-Cheon Kim ◽  
Chan-Pyoung Park ◽  
Dongil Kwon
Keyword(s):  
Tensile Properties ◽  
Weld Zone ◽  
Indentation Test ◽  
Tensile Tests ◽  
Structural Safety ◽  
Small Scale ◽  
Stress And Strain ◽  
Instrumented Indentation ◽  
Deformation And Fracture ◽  
Instrumented Indentation Test

Understanding the property distribution in the weld zone is very important for structural safety, since deformation and fracture begin at the weakest point. However, conventional tensile tests can measure only average material properties because they require large specimens. Small-scale tests are being extensively researched to remove this limitation, among such tests, instrumented indentation test (IIT) are of great interest because of their simple procedures. Here we describe the evaluation of tensile properties using IIT and a representative stress-strain approach. The representative stressstrain method, introduced in 2008 in ISO/TR29381, directly correlates the stress and strain under the indenter to the true stress and strain of tensile testing by defining representative functions. Using this technique, we successfully estimate the yield strength and tensile strength of structural metallic materials and also obtain profiles of the weld-zone tensile properties.

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