Determination of Precise Contact Area During Spherical Indentation for Metallic Materials

2005 ◽  
Author(s):  
Sung-Hoon Kim ◽  
Kyung-Woo Lee ◽  
Eun-Chae Jeon ◽  
Dongil Kwon
Keyword(s):  
Contact Area ◽  
Work Hardening ◽  
Fe Simulation ◽  
Flow Properties ◽  
Elastic Deflection ◽  
Wide Range ◽  
Pile Up ◽  
Continuous Indentation ◽  
Work Hardening Exponent

The continuous indentation technique, because it is fast, precise, and nondestructive, has been widely used to determine such mechanical properties as flow properties, residual stress, fracture properties, viscoelastic properties and hardness of materials and structural units. In particular, continuous indentation by a spherical indenter can provide hardness and flow properties such as yield strength, tensile strength, and work-hardening exponent, using the characteristic that strain from the loaded indenter changes with indentation depth. Since the stress and strain values on the flow curve are defined based on the contact area between the indenter and material in the loaded state, accurate determination of the contact area is essential. Determination of the contact area is closely connected with elastic deflection and plastic pile-up/sink-in behavior. In this study, the pile-up phenomenon is considered as two independent behaviors, elastic deflection and plastic pile-up/sink-in, which can each be described by a formula. The formulas can be obtained from FE simulation with conditions reflecting real indentation tests for materials used for various purposes and with a wide range of material properties. By analyzing indentation morphology from the FE simulation, the two phenomena were quantified as formulas. In particular, plastic pile-up/sink-in behavior was formulated in terms of work-hardening exponent and indentation ratio.

Determination of Precise Indentation Flow Properties of Metallic Materials Through Analyzing Contact Characteristics Beneath Indenter

2005 ◽  
Vol 127 (3) ◽  
pp. 265-272 ◽  
Author(s):  
Sung-Hoon Kim ◽  
Min-Kyung Baik ◽  
Dongil Kwon
Keyword(s):  
Fe Simulation ◽  
Indentation Load ◽  
Metallic Materials ◽  
Flow Properties ◽  
Element Analysis ◽  
Property Data ◽  
Testing Data ◽  
Tension Testing ◽  
Continuous Indentation

The continuous indentation technique is widely used for nondestructive evaluation of the mechanical properties of devices and materials. In particular, flow properties can be obtained by using this technique with a spherical indenter. Several formulas have been suggested to determine flow properties, and they commonly require the determination of the precise contact characteristics such as the contact area or depth between material and indenter to obtain the properties accurately. In this study, contact characteristics were determined by analysis of the contact morphology from FEA (finite element analysis) using mechanical property data for several steels. The contact characteristics obtained from FE simulation were compared to an analysis of the parameters of indentation load-depth curves for the steels. The contact characteristics were shown as functions of such parameters as work-hardening exponent and indentation depth. In addition, using indentation morphology from FE simulation, the flow properties were evaluated by analysis of indentation morphology for 18 materials on the basis of the two representative preexisting definitions of stress and strain, and the definitions were verified by comparison of the flow properties with tension testing data.

Nanoindentation by Multiple Loads Methodology: A Pile Up Correction Procedure

2007 ◽  
Vol 345-346 ◽  
pp. 805-808 ◽  
Author(s):  
Miguel Angel Garrido ◽  
Jesus Rodríguez
Keyword(s):  
Element Model ◽  
Spherical Indentation ◽  
Correction Procedure ◽  
Elastic Plastic ◽  
Multiple Loads ◽  
Plastic Materials ◽  
Wide Range ◽  
Pile Up ◽  
Elastic Plastic Materials

Young’s modulus and hardness data obtained from nanoindentation are commonly affected by phenomena like pile up or sink in, when elastic-plastic materials are tested. In this work, a finite element model was used to evaluate the pile up effect on the determination of mechanical properties from spherical indentation in a wide range of elastic-plastic materials. A new procedure, based on a combination of results obtained from tests performed at multiple maximum loads, is suggested.

Analysis of sharp-tip-indentation load–depth curve for contact area determination taking into account pile-up and sink-in effects

2004 ◽  
Vol 19 (11) ◽  
pp. 3307-3315 ◽  
Author(s):  
Yeol Choi ◽  
Ho-Seung Lee ◽  
Dongil Kwon
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Contact Area ◽  
Indentation Depth ◽  
Indentation Load ◽  
Real Contact Area ◽  
Elastic Deflection ◽  
Contact Depth ◽  
Real Contact ◽  
Pile Up

Hardness and elastic modulus of micromaterials can be evaluated by analyzing instrumented sharp-tip-indentation load–depth curves. The present study quantified the effects of tip-blunting and pile-up or sink-in on the contact area by analyzing indentation curves. Finite-element simulation and theoretical modeling were used to describe the detailed contact morphologies. The ratio f of contact depth, i.e., the depth including elastic deflection and pile-up and sink-in, to maximum indentation depth, i.e., the depth measured only by depth sensing, ignoring elastic deflection and pile-up and sink-in, was proposed as a key indentation parameter in evaluating real contact depth during indentation. This ratio can be determined strictly in terms of indentation-curve parameters, such as loading and unloading slopes at maximum depth and the ratio of elastic indentation energy to total indentation energy. In addition, the value of f was found to be independent of indentation depth, and furthermore the real contact area can be determined and hardness and elastic modulus can be evaluated from f. This curve-analysis method was verified in finite-element simulations and nanoindentation experiments.

scholarly journals Finite Element Studies of the Influence of Pile-up on the Analysis of Nanoindentation Data

1996 ◽  
Vol 436 ◽  
Author(s):  
A. Bolshakov ◽  
W. C. Oliver ◽  
G. M. Pharr
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
Peak Load ◽  
Soft Materials ◽  
Modulus Ratio ◽  
Hard Materials ◽  
Plastic Materials ◽  
Wide Range ◽  
Pile Up ◽  
Elastic Plastic Materials

AbstractMethods currently used for analyzing nanoindentation load-displacement data give good predictions of the contact area in the case of hard materials, but can underestimate the contact area by as much as 40% for soft materials which do not work harden. This underestimation results from the pile-up which forms around the hardness impression and leads to potentially significant errors in the measurement of hardness and elastic modulus. Finite element simulations of conical indentation for a wide range of elastic-plastic materials are presented which define the conditions under which pile-up is significant and determine the magnitude of the errors in hardness and modulus which may occur if pile-up is ignored. It is shown that the materials in which pile-up is not an important factor can be experimentally identified from the ratio of the final depth after unloading to the depth of the indentation at peak load, a parameter which also correlates with the hardness-to-modulus ratio.

Effect of Pile-up in Nanoindentation of Micro and Nano crystalline Ni using FEM

2005 ◽  
Vol 880 ◽  
Author(s):  
Raja Mahesh Pothapragada ◽  
Reza A. Mirshams ◽  
Suman Vadlakonda
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Yield Stress ◽  
Contact Area ◽  
Material Properties ◽  
Work Hardening ◽  
Shape Function ◽  
Nano Crystalline ◽  
Pile Up ◽  
Work Hardening Rate

AbstractA much better understanding of the contact mechanics can be obtained through finite element modeling. The experimentally determined tip shape function was included to reproduce the same contact area for a given contact depth as in the experiment. The fundamental material properties affecting pile-up are the ratio of the effective modulus to yield stress Eeff/Y and the work hardening rate.

Determination of the Work Hardening Exponent by the Hollomon and Differential Crussard-Jaoul Analyses of Cold Drawn Ferrite-Pearlite Steels

2006 ◽  
Vol 509 ◽  
pp. 37-42 ◽  
Author(s):  
I. Mejía ◽  
C. Maldonado ◽  
Josep Antonio Benito ◽  
Jordi Jorba ◽  
Antoni Roca
Keyword(s):  
Work Hardening ◽  
True Strain ◽  
Research Work ◽  
Cold Drawing ◽  
True Stress ◽  
Differential Analysis ◽  
Tension Tests ◽  
Slope Change ◽  
Work Hardening Exponent

This research work analyses the effect of cold working level produced by drawing, on the work hardening exponent of 0.18 and 0.43 % C ferrite-pearlite steels. Such analysis is carried out by means of true stress-true strain curves derived from uniaxial tension tests. The work hardening exponent behaviour was determined by using Hollomon and differential Crussard-Jaoul models. It is found that the work hardening exponent decreases as a function of the applied cold-drawing level, and negative values were obtained when differential analysis is used. The results indicate that the Hollomon analysis shows some deviations from the experimentally determined true stress - true strain curves while the differential Crussard-Jaoul analysis fits better when two work hardening exponents are considered. This analysis establishes two exponents for different stages of plastic deformation which are determined by the sharp slope change in the plot of ln (d σ/d ε) - ln ε.

Anisotropy of Nanoindentation – a tool for the determination of nanocrystal orientation ?

2003 ◽  
Vol 779 ◽  
Author(s):  
David Christopher ◽  
Steven Kenny ◽  
Roger Smith ◽  
Asta Richter ◽  
Bodo Wolf ◽  
...  
Keyword(s):  
Crystal Surface ◽  
Scanning Force Microscopy ◽  
Depth Range ◽  
Dislocation Loops ◽  
Force Microscopy ◽  
Pile Up ◽  
Out Of Plane ◽  
Scanning Force ◽  
Dynamics Simulations

AbstractThe pile up patterns arising in nanoindentation are shown to be indicative of the sample crystal symmetry. To explain and interpret these patterns, complementary molecular dynamics simulations and experiments have been performed to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe{110}. The simulations show that dislocation loops start from the tip and end on the crystal surface propagating outwards along the four in-plane <111> directions. These loops carry material away from the indenter and form bumps on the surface along these directions separated from the piled-up material around the indenter hole. Atoms also move in the two out-of-plane <111> directions causing propagation of subsurface defects and pile-up around the hole. This finding is confirmed by scanning force microscopy mapping of the imprint, the piling-up pattern proving a suitable indicator of the surface crystallography. Experimental force-depth curves over the depth range of a few nanometers do not appear smooth and show distinct pop-ins. On the sub-nanometer scale these pop-ins are also visible in the simulation curves and occur as a result of the initiation of the dislocation loops from the tip.

DINAMIKA POLITIK PERSETUJUAN BERSAMA TENTANG PENETAPAN DESA ADAT DI KABUPATEN ROKAN HULU TAHUN 2014

2017 ◽  
Vol 15 (1) ◽  
pp. 21
Author(s):  
Haryo Suganda ◽  
Raja Muhammad Amin
Keyword(s):  
Regulatory Region ◽  
Field Research ◽  
Analysis Techniques ◽  
Political Dynamics ◽  
Political Interests ◽  
Wide Range ◽  
Information Method ◽  
Qualitative Descriptive ◽  
The Village

This study is motivated the identification of policies issued by the regional Governmentof Rokan Hulu in the form of Regulatory region number 1 by 2015 on the determination of thevillage and Indigenous Village. Political dynamics based on various interests against themanufacture of, and decision-making in the process of formation of the corresponding localregulations determination of Indigenous Villages in the Rokan Hulu is impacted to a verysignificantamount of changes from the initial draft of the number i.e. 21 (twenty one) the villagebecame Customary 89 (eighty-nine) the Indigenous Villages who have passed. Type of thisresearch is a qualitative descriptive data analysis techniques. The research aims to describe theState of the real situation in a systematic and accurate fact analysis unit or related research, aswell as observations of the field based on the data (information). Method of data collectionwas done with interviews, documentation, and observations through fieldwork (field research).The results of the research on the process of discussion of the draft local regulations andmutual agreement about Designation of Indigenous Villages in the Rokan Hulu is, showed thatthe political dynamics that occur due to the presence of various political interests, rejectionorally by Villagers who were judged to have met the requirements of Draft Regulations to beformulated and the area for the set to be Indigenous Villages, and also there is a desire fromsome villages in the yet to Draft local regulations in order to set the Indigenous village , there isa wide range of interests of these aspects influenced the agreement to assign the entire localVillage which is in the Rokan Hulu become Indigenous village, and the village of Transmigrationinto administrative Villages where the initiator of the changes in the number of IndigenousVillages in the Rokan Hulu it is the desire of the local Government of its own.

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