Reduction in Fatigue Life in Cr-Coated Steel Induced by Pulsed Laser Heating

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Jeffrey M. Warrender ◽  
Gregory N. Vigilante
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Pulsed Laser ◽  
Coated Steel ◽  
Propagation Behavior ◽  
Life Tests ◽  
Point Bend ◽  
Thermomechanical Processes ◽  
Laser Heated ◽  
Pulsed Laser Heating

Four-point bend tests were performed on Cr-coated steel specimens that were pulsed laser heated (PLH) with two pulses per area from a millisecond pulse duration laser. Cracks were observed in the PLH specimens extending to the substrate. Specimens subjected to PLH exhibited reduced cycles to failure under all the loadings. This indicates that the PLH process replaces the crack initiation process, and the PLH-formed cracks give the expected crack propagation behavior. This approach provides a method to separately study the effects of crack formation and crack propagation in fatigue life tests. It is especially applicable to situations in which the cracks to be propagated are induced by thermomechanical processes.

The effect of load ratio on fatigue life and crack propagation behavior of an extruded magnesium alloy

2009 ◽  
Vol 31 (11-12) ◽  
pp. 1788-1794 ◽  
Author(s):  
S. Ishihara ◽  
A.J. McEvily ◽  
M. Sato ◽  
K. Taniguchi ◽  
T. Goshima
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Crack Propagation ◽  
Load Ratio ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

scholarly journals Influence of surface residual stresses on the fatigue life and crack propagation behavior of turned Inconel 718 super-alloy

2018 ◽  
Vol 165 ◽  
pp. 18004 ◽  
Author(s):  
Hamid Javadi ◽  
Walid Jomaa ◽  
Elvi Dalgaard ◽  
Myriam Brochu ◽  
Philippe Bocher
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Inconel 718 ◽  
Surface Finishing ◽  
Propagation Behavior ◽  
Surface Residual Stresses ◽  
Crack Propagation Behavior ◽  
Super Alloy

The effects of surface roughness parameters and residual stresses induced by finish turning on fatigue life and crack propagation behavior of Inconel 718 super-alloy are investigated. A criterion serving as a good indicator of surface quality is also discovered. This is carried out for some specific turning conditions in order to control surface characteristics including surface roughness and the bi-axial state of surface residual stresses and to investigate the effects of these characteristics on fatigue behavior. Rotating bending fatigue (RBF) tests are performed on the machined specimens at room temperature. Characterization techniques including X-ray diffraction (XRD), laser confocal microscopy, and opto-digital microscopy are used to investigate surface residual stresses in axial (ARS) and hoop (HRS) directions, surface roughness, and secondary fatigue cracks, respectively. The huge dispersion in fatigue life of smooth turned Inconel 718 with very low arithmetic average roughness (Ra) values indicates that surface finishing is not the only reliable criterion for quality control of machined components. Multivariate statistical analyses show that axial surface residual stress is the most important surface characteristic affecting the fatigue life of machined Inconel 718 for the conditions tested. Changing ARS from compressive to tensile increases the number of secondary cracks and also decreases the fatigue life of turned specimens.

Fatigue Crack Propagation Prediction under Single Overload Variable Loading

2013 ◽  
Vol 275-277 ◽  
pp. 215-219
Author(s):  
Zhi Fang Liu ◽  
Li Xiong Gu ◽  
Zhong Yong Xu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Variable Loading ◽  
Fatigue Crack Propagation Behavior ◽  
Propagation Behavior ◽  
Single Overload ◽  
Crack Growth Curve ◽  
Propagation Prediction

Reasonably predicting the fatigue life of specimens, depends on the research and understanding of the fatigue crack propagation behavior under variable amplitude loading (VAL) rather than under constant amplitude loading (CAL). The present study aims at evaluating residual fatigue life under single overload VAL by adopting a dynamical coefficient mechanics (DCM) model which we have reported. New formulas connecting the crack length with number of cycles and expressions for the fatigue crack propagation (FCP) under single overload VAL have been derived and were used to predict crack propagation. The ratios of predicted-to-experimental lives range from 1.00 to 1.09, which indicates that the results obtained from this DCM model are in good agreement with experimental data from published literatures and cover all stages of fatigue crack growth curve.

Raman Study of Kinetics of Graphitization of Carbon Blacks

2000 ◽  
Vol 73 (2) ◽  
pp. 284-292 ◽  
Author(s):  
T. Waldek Zerda ◽  
Tyler Gruber
Keyword(s):  
Laser Heating ◽  
Continuous Wave ◽  
Fast Rate ◽  
Pulsed Laser ◽  
Reaction Rates ◽  
Carbon Blacks ◽  
Raman Study ◽  
Laser Heated ◽  
Pulsed Laser Heating ◽  
Kinetics Of

Abstract Raman spectra of laser heated carbon blacks provide information on the dynamics of the graphitization process. Continuous wave and pulsed-laser heating is used. It is shown that two ordering mechanisms of distinctly different reaction rates are present during the heat treatment. The dominating mechanism, during the initial stages of graphitization, is characterized by a very fast rate. The rate during the later stages of the process, after the initial first couple of seconds, is orders of magnitude slower.

Effect of Extrusion Ratio on Fatigue Properties of Hot-Extruded Magnesium Alloys

2007 ◽  
Vol 353-358 ◽  
pp. 291-294 ◽  
Author(s):  
Sotomi Ishihara ◽  
H. Shibata ◽  
K. Komano ◽  
Takahito Goshima ◽  
Z.Y. Nan
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Fatigue Limit ◽  
Magnesium Alloys ◽  
Extrusion Ratio ◽  
Fatigue Properties ◽  
Dramatic Effect ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

In the present study, fatigue experiments were conducted using two kinds of extruded magnesium alloys with different extrusion ratios. Effect of the extrusion ratio on fatigue lives and crack propagation behavior was studied in detail. There was no dramatic effect of the extrusion ratio on fatigue life, fatigue limit and crack propagation behavior.

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