Advanced Evaluation Methods of Residual Stress in Bioceramics Wear Surfaces

2010 ◽  
Vol 64 ◽  
pp. 43-48
Author(s):  
Giuseppe Pezzotti
Keyword(s):  
Residual Stress ◽  
Surface Stress ◽  
Electron Probe ◽  
Stress Fields ◽  
Fluorescence Probes ◽  
Surface Residual Stress ◽  
Hip Joints ◽  
Polycrystalline Alumina ◽  
Probe Size ◽  
F Center

Photo- and electro-stimulated probes have been employed for quantitatively evaluating highly graded residual stress fields generated at the surface of alumina hip joints. Optical calibrations revealed large differences in probe size, which strongly affected the detected magnitude of residual stress. A comparison between the responses of Raman and fluorescence probes in polycrystalline alumina showed that the depth of those probes spread to an extent in the order of the tens of microns even with using a confocal probe configuration. On the other hand, the electro-stimulated luminescence emitted by oxygen vacancy sites (F+ center) in the alumina lattice represented a suitable choice for confining to a shallow volume the stress probe. The electron probe enabled confining the measurement depth to the order of the tens of nanometers. Maps of surface residual stress were collected on both main-wear and non-wear zones of an alumina femoral head. A comparison among stress maps taken at exactly the same location, but employing different probes, clarified the averaging probe effects on surface stress magnitude.

Determination of Residual-Stress-Free State and Mapping of Residual Stress Fields Using Speckle Interferometry and Thermal Relaxation

2003 ◽  
Vol 795 ◽  
Author(s):  
Dong-Won Kim ◽  
Jong-jin Kim ◽  
Dongil Son ◽  
Nak-Kyu Lee ◽  
Kyung-Hoan Na ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Speckle Pattern ◽  
Thermal Relaxation ◽  
Free State ◽  
Stress Fields ◽  
Lead Frame ◽  
Surface Residual Stress ◽  
Au Film ◽  
Stress Free State

ABSTRACTWe used an electronic speckle pattern interferometer (ESPI) for nondestructive measurement in-situ displacement fields in microsystems. A four-step phase-shift technique and magnifier with long working distance were adopted to increase displacement resolution to ∼10−2 μm and spatial resolution to ∼2 μm. A thermal vacuum chamber was designed to induce thermal treatments, including annealing. From the identification of the residual-stress-free state, we quantitatively modeled thermal strains/stress fields, relaxation stresses during annealing, and residual stress fields. Thermoelasticity theory was applied to model the relationship between the relaxation stresses and the displacements measured by ESPI during the evolution of the residual-stress-free state. We assessed the surface residual stress fields of indented bulk Cu; a Fe-Ni lead frame of 100 μm width; and 0.5 μm Au film. In the indented Cu, the normal and shear residual stresses around the indented point range from –1.7 GPa to 700 MPa and –800 MPa to 600 MPa, respectively, and the residual stress in the bending area of the Fe-Ni lead frame was estimated at 148 MPa and verified using beam-bending theory. In the Au film, tensile residual stresses are uniformly distributed from 500 MPa to 800 MPa as verified by X-ray diffraction.

An Evaluation of Abrasive Waterjet Peening With Elastic Prestress

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
B. Sadasivam ◽  
A. Hizal ◽  
S. Park ◽  
D. Arola
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Surface Texture ◽  
Surface Stress ◽  
Treatment Process ◽  
Abrasive Waterjet ◽  
Residual Stress Field ◽  
Surface Residual Stress ◽  
Stress Zone ◽  
Study Application

Abrasive waterjet peening (AWJP) has been conceived as a new surface treatment process capable of achieving desired changes in surface texture, chemistry, and residual stress simultaneously. In the present investigation, the influence of elastic prestress on the residual stress resulting from AWJP was studied. Treatments were conducted on steel, as well as nickel and titanium alloy targets subjected to an elastic prestress ranging from 0% to 75% of the material’s yield strength. The results showed that a tensile elastic prestress increases the surface residual stress and the depth of the compressive stress zone. The surface residual stress in each metal increased nonuniformly with magnitude of prestress; the maximum surface residual stress was obtained at an applied prestress between 45% and 60% of the substrate yield strength. Overall, the increases in surface stress and depth that were obtained reached 100% and 50%, respectively. There were no changes to the surface texture caused by the prestress. According to results of this study, application of an elastic prestress can serve as an effective method for improving characteristics of the residual stress field in components treated using AWJP.

Abrasive Waterjet Peening With Elastic Prestress: Effect of Boundary Conditions

2008 ◽  
Author(s):  
Balaji Sadasivam ◽  
Alpay Hizal ◽  
Dwayne Arola
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Boundary Conditions ◽  
Stress Fields ◽  
Abrasive Waterjet ◽  
Surface Residual Stress ◽  
Prosthetic Devices ◽  
Metal Implants ◽  
Removal Technique ◽  
Stored Elastic Energy

Abrasive Waterjet Peening (AWJP) has emerged as a potential surface treatment process for metal implants and prosthetic devices. An elastic tensile prestress has been shown to increase the magnitude and depth of residual stress that can be obtained. In the present investigation, the subsurface residual stress fields resulting from AWJ peening of Ti6Al4V with load control and displacement control elastic prestress were compared. Prestress ranged from 0 to 75% of the material’s yield strength and the subsurface residual stress distribution was quantified using the layer removal technique. Results showed that the surface residual stress was dependent on the boundary conditions for prestress levels less than 60% of the materials yield strength. The magnitude of surface residual stress and the stored elastic energy were up to 50% and 100% larger respectively when load controlled boundary conditions were used. However, the boundary condition did not affect the depth of compressive residual stress.

Surface Stress Concentration Analysis of Shot Peened Aluminium Alloys

2010 ◽  
Vol 449 ◽  
pp. 70-76
Author(s):  
J. Solis-Romero ◽  
J. Oseguera-Peña ◽  
J. Verduzco-Martínez ◽  
J. González-Sánchez
Keyword(s):  
Residual Stress ◽  
Stress Concentration ◽  
Surface Stress ◽  
Aluminium Alloys ◽  
Stress Gradient ◽  
Stress Effect ◽  
Surface Residual Stress ◽  
Closure Stress ◽  
Surface Crack Initiation ◽  
Effect Of Surface

Fatigue limit for surface crack initiation on shot peened Aluminium Alloys resulted to be determined by surface residual stress and stress concentration, according to the magnitude of the applied stress. The effect of surface roughness considered as micro-notches (dents) has been analysed by using the Vallellano and Navarro’s formulation. It was also determined that the stress gradient associated to those dents dominates over the closure stress effect.

Relaxation of Thermal Residual Stress in Laser Irradiated Fused Silica by Annealing Process

2016 ◽  
Vol 874 ◽  
pp. 345-350
Author(s):  
Run Qiang Li ◽  
Peng Yao ◽  
Wei Wang ◽  
Jun Wang ◽  
Chuan Zhen Huang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Stress ◽  
Heat Treating ◽  
Fused Silica ◽  
Annealing Process ◽  
Surface Residual Stress ◽  
Stress Variation ◽  
Annealing Temperatures ◽  
Energy Consuming ◽  
Time And Energy

To relax the surface residual stress of fused silica lens or windows irradiated by CO2 laser, it was proposed to treat it at high temperature above glass strain temperature in the traditional annealing process. However it is a time and energy consuming process, and a distortion will be introduced during the heat treatment. To deal with these problems, annealing temperatures lower than glass strain temperature were applied to the annealing process and a new scheme was designed in this paper. An numerical model was built to simulate the laser induced residual stress and optimize the stress variation in the annealing process. The surface stress of fused silica can be relaxed and deformation induced by heat treating can be ignored.

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