scholarly journals Surface Cracking and Degradation of Dense Hydroxyapatite through Vickers Microindentation Testing

2011 ◽  
Vol 66-68 ◽  
pp. 614-619 ◽  
Author(s):  
Aliasghar Behnamghader ◽  
Reyhaneh Neghabat Shirazi ◽  
Alain Iost ◽  
Denis Najjar
Keyword(s):  
Indentation Load ◽  
Serial Sectioning ◽  
Theoretical Relation ◽  
Surface Cracking ◽  
Crack Type ◽  
Microindentation Testing ◽  
Radial Cracks ◽  
Micro Indentation ◽  
Good Agreement ◽  
Median Crack

Surface degradation and cracking of dense hydroxyapatite were evaluated through Vickers micro indentation using indentation loads ranged from 25 gf to 2000 gf. Crack lengths, imprint diameters and the number of lateral cracks and chips were measured using SEM. The crack length-indentation load data were analyzed with regard to the specific relations of Palmqvist and fully developed radial cracks. Crack type transition load from Palmqvist to median crack was experimentally assessed through serial sectioning technique. The analytical estimated transition load, based on the theoretical relation of the indentation load and crack lengths showed a good agreement with one obtained from experimental itinerary. Palmqvist and median cracks were identified in low and medium indentation loads, respectively. High indentation load could also lead to the formation of lateral cracks and chips. The tendency for lateral cracking was evaluated taking into account the number of lateral cracks and chips. The chips were found to be appeared just after test in higher indentation load, whereas in medium loads they could be detectable only after several weeks.

Modeling of contact-induced radial cracking in ceramic bilayer coatings on compliant substrates

2003 ◽  
Vol 18 (5) ◽  
pp. 1275-1283 ◽  
Author(s):  
Chun-Hway Hsueh ◽  
Pedro Miranda
Keyword(s):  
Flexural Rigidity ◽  
Ceramic Coatings ◽  
Analytical Expression ◽  
Bilayer Coating ◽  
Compliant Substrates ◽  
Dental Crowns ◽  
Plates On Elastic Foundation ◽  
Radial Cracks ◽  
Good Agreement ◽  
Bilayer Coatings

Contact-induced radial cracking in ceramic coatings on compliant substrates was analyzed recently. Radial cracks initiate at the coating/substrate interface beneath the contact where maximum flexural tension occurs, and an analytical expression for the onset of radial cracking in monolayer coatings was formulated on the basis of the classical solution for flexing plates on elastic foundation. In the present study, the analytical expression was derived for the case of ceramic bilayer coatings on compliant substrates, which have significant applications in the structure of dental crowns. It was found that the analytical solution for bilayer-coating/substrate systems can be obtained from that of monolayer-coating/substrate systems by replacing the neutral surface position and the flexural rigidity of monolayer coating with those of bilayer coating. The predicted critical loads for initiating radial cracking were found to be in good agreement with existing measurements and finite element results for glass/alumina, glass/glass-ceramic, and glass/Y2O3-stabilized ZrO2polycrystal bilayers on polycarbonate substrates. Limitations of the present analysis are discussed.

Indentation Rate-Dependent Creep Behavior of Sn-Ag-Cu Pb-Free Ball Grid Array (BGA) Solder Joint

2005 ◽  
Vol 502 ◽  
pp. 399-404
Author(s):  
Feng Jiang Wang ◽  
Xin Ma ◽  
Yiyu Qian
Keyword(s):  
Solder Joint ◽  
Hold Time ◽  
Rate Sensitivity ◽  
Ball Grid Array ◽  
Indentation Load ◽  
Indentation Hardness ◽  
Rate Dependent ◽  
Indentation Tests ◽  
Free Solder ◽  
Micro Indentation

Berkovich micro-indentation tests with different loading rates have been performed on the ball grid array solder joint with a Pb-free solder, Sn-4.0Ag-0.5Cu alloy. The resulting indentation load-depth curves are rate dependent and have varying creep penetration depths during the same hold time. Creep indentation hardness and rate sensitivity have been defined from the concept of “work of indentation”. The rate sensitivity of BGA solder joint is 0.0574.

Nanoindentation of a Deformable Substrate Covered by Patterned Nanodot Asperities

2009 ◽  
Author(s):  
Hengyu Wang ◽  
Min Zou ◽  
Robert L. Jackson ◽  
Preston R. Larson ◽  
Matthew B. Johnson
Keyword(s):  
Silicon Substrate ◽  
Experimental Studies ◽  
Indentation Load ◽  
Spherical Indenter ◽  
Experimental Results ◽  
Contact Model ◽  
Asperity Contact ◽  
Deformation Relationship ◽  
Repetitive Pattern ◽  
Good Agreement

This paper presents numerical and experimental studies of nanoindentation of a silicon substrate covered by patterned Ni nanodot asperities. A multi-asperity contact model was developed in this study to simulate the contact between a spherical indenter and the Ni nanodot asperities. In this model, the silicon substrate is considered to be deformable and the nanodots are allowed to interact with each other through the deformation of the substrate. The load-deformation relationship predicted by the model was found to be in good agreement with the experimental results. This model can also be used to predict indentation load-deformation relationships of a deformable substrate covered by nanodots with known size and location distributions, but not necessarily following a repetitive pattern.

scholarly journals Effects of Indentation Load on the Mechanical Behavior of Orthodontic Wire Alloys by Dynamic Micro-Indentation Method

2013 ◽  
Vol 12 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Mariko Nagai ◽  
Yasuhiro Tanimoto ◽  
Toshihiro Inami ◽  
Masaru Yamaguchi ◽  
Norihiro Nishiyama ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Indentation Load ◽  
Indentation Method ◽  
Orthodontic Wire ◽  
Micro Indentation

Hardness of Thin Polymer Coatings on Glass

1990 ◽  
Vol 203 ◽  
Author(s):  
J. E. Ritter ◽  
D.R. Sioui ◽  
W. Gu ◽  
T.J. Lardner
Keyword(s):  
Soda Lime ◽  
Polymer Coatings ◽  
Indentation Load ◽  
Soda Lime Glass ◽  
Epoxy Acrylate ◽  
Glass Substrates ◽  
Thin Polymer ◽  
Pile Up ◽  
Bulk Hardness ◽  
Good Agreement

ABSTRACTFor a soft coating on a hard substrate the overall hardness of the coating/substrate system increases substantially when the indenter penetrates into the substrate sincethe substrate can now directly support some of the indenter load. A model for the overall hardness is developed by accounting for the indentation load shared by the coating andsubstrate. This model accounts for the additional load supported by the coating due to the pile-up of coating material underneath the indenter. The model predicts the overall hardness as a function of coating and substrate bulk hardness and coating thickness. Comparison of the model to experimental data for two polymer coatings (epoxy and epoxy acrylate) on soda-lime glass substrates shows good agreement.

Analytical Study on Micro-Indentation Method to Integrity Evaluation for Graphite Components in HTGR

2006 ◽  
Author(s):  
Junya Sumtia ◽  
Satoshi Hanawa ◽  
Taiju Shibata ◽  
Tatsuya Tada ◽  
Tatsuo Iyoku ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Indentation Depth ◽  
Analytical Study ◽  
Indentation Load ◽  
Strain Condition ◽  
Indentation Method ◽  
Properties Of Materials ◽  
Oxidized Graphite ◽  
The Relationship ◽  
Micro Indentation

An analytical study on micro-indentation method to integrity evaluation for graphite components was carried out. The indentation method is used as simplicity test to measure mechanical properties of materials. This method is thought to be applicable to evaluate the residual stress from the relationship between indentation load and indentation depth. In this study, in order to confirm the applicability of the micro-indentation method for lifetime evaluation of the graphite component, indentation load-depth behavior under stress/strain condition was evaluated taking account of the specified minimum ultimate strength of IG-110 graphite. Moreover, analytical investigations of indentation load-depth behavior for oxidized graphite and oxidized graphite with residual strain were also carried out. As a result, it can be said that the indentation method is potentially applicable to evaluate the integrity of graphite components.

Stress Intensity Factors for Unequal Longitudinal-Radial Cracks in Thick-Walled Cylinders

1991 ◽  
Vol 113 (1) ◽  
pp. 22-27 ◽  
Author(s):  
J. L. Desjardins ◽  
D. J. Burns ◽  
R. Bell ◽  
J. C. Thompson
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Finite Elements ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Two Dimensional ◽  
Intensity Factors ◽  
Radial Cracks ◽  
Good Agreement

Finite elements and two-dimensional photoelasticity have been used to analyze thick-walled cylinders which contain arrays of straight-fronted, longitudinal-radial cracks of unequal depth. The stress intensity factor K1 has been computed for the dominant crack and for some of the surrounding cracks. Cylinders with 2, 4, 6, 8, 16, 36 and 40 cracks have been considered. Good agreement has been obtained between the experimental and the numerical results and, for cylinders with 2 or 4 cracks, with previously published predictions. The results for all of the foregoing cases are used to develop simple, approximate techniques for estimating K1 for the dominant crack, when the total number of cracks is different from those that have been considered herein. Estimates of K1 obtained by these techniques agree well with corresponding finite element results.

scholarly journals Applications of Micro-Indentation Technology to Estimate Fracture Toughness of Shale

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4208
Author(s):  
Qiang Han ◽  
Zhan Qu ◽  
Ping Wang ◽  
Gang Bi ◽  
Guanzheng Qu
Keyword(s):  
Fracture Toughness ◽  
Indentation Test ◽  
Indentation Load ◽  
Wellbore Stability ◽  
X Ray Diffraction ◽  
Theoretical Support ◽  
Macroscopic Fracture ◽  
Magnetic Resonance Scanning ◽  
Micro Indentation ◽  
Selection Of

The fracture toughness of shale is a basic parameter that can provide effective theoretical support for wellbore stability and hydraulic fracturing of a shale reservoir. Due to the composition and microstructure, there are many problems in evaluating the mechanical properties of shale in a macroscopic test. In this paper, the composition and pore distribution of shale were studied by X-ray diffraction and nuclear magnetic resonance. Scanning electron microscopy was used to characterize the pore structure. The setting of experimental parameters and the selection of the indenter were discussed. Micro-indentation technique was proposed and applied to fracture toughness analysis of shale. The results show that Berkovich indenter is more suitable for shale indentation test than Vickers indenter. Fracture toughness of shale indentation is obviously affected by surface roughness and indentation position. Fracture toughness of shale decreases slightly with the increase of the indentation load. The energy analysis result presents that the effect of cracking on the ratio of total/unloading work is minimal when there is no significant stripping on the shale surface. Compared with the experimental method, energy methods can obtain all the analysis parameters from a single indentation test. The results of comparative analysis with macroscopic experiments display that micro-indentation test can effectively predict the macroscopic fracture toughness of shale.

Effects of Surface Stress on the Load-Depth Curves of Depth-Sensing Indentation

2004 ◽  
Vol 841 ◽  
Author(s):  
Q. Wang ◽  
K. Ozaki
Keyword(s):  
Surface Stress ◽  
Fem Simulation ◽  
Indentation Load ◽  
Depth Sensing ◽  
Residual Surface Stress ◽  
Experimental Scheme ◽  
Elastic Unloading ◽  
Depth Curves ◽  
Good Agreement

ABSTRACTBased on the effects of residual surface stress on the unloading curves of indentation load-depth responses, an experimental scheme for determination of the residual stress by depth-sensing indentation is proposed. From the point that the elastic unloading portion of the load-depth curves can be expected to be unaffected by the residual stresses, the formula for evaluating surface stress by indentation is derived based on energy method. The proposed formula is verified by using FEM simulated indentation load-depth responses for different surface stress levels. The levels of surface stress evaluated by the proposed formula show a good agreement with the ones used as input parameters in FEM simulation.

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