scholarly journals Effect of Residual Stress on S–N Curves and Fracture Morphology of Ti6Al4V Titanium Alloy after Laser Shock Peening without Protective Coating

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3799 ◽  
Author(s):  
Xinlei Pan ◽  
Xiang Li ◽  
Liucheng Zhou ◽  
Xiaotai Feng ◽  
Sihai Luo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Compressive Residual Stress ◽  
Fracture Morphology ◽  
High Amplitude ◽  
Laser Shock ◽  
Ti6al4v Titanium Alloy ◽  
Before And After ◽  
Shock Peening

In this paper, the effect of residual stress on the stress–life (S–N) curve and fracture morphology characteristics of Ti6Al4V titanium alloy after laser shock peening (LSP) without protective coating was experimentally investigated. The fatigue test and residual stress measurement were conducted on specimens before and after the LSP process. It was shown that LSP produced a high-amplitude compressive residual stress field on the surface of the specimen. After the LSP process, the fatigue life limit was increased by 16%, and the S–N curve shifted upward. Then, based on the theory of mean stress, the mechanism whereby the compressive residual stress improves the fatigue life of Ti6Al4V titanium alloy was analyzed. It indicated the improvement in fatigue life was because of the high-amplitude compressive residual stress on the surface and in depth induced by LSP to reduce the tensile stress produced by external loading. In addition, the scanning electron microscope (SEM) pattern of fatigue fracture demonstrated distinct differences in the fracture morphology before and after LSP. After LSP, the crack initiation sites of the samples moved to the subsurface where it was difficult for fatigue cracks initiating here. Moreover, after the LSP process, there were high density of fatigue striations and many secondary cracks on the fracture of the treated specimen.

scholarly journals Improvement of Fatigue Life of GH3039 Superalloy by Laser Shock Peening

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3849
Author(s):  
Yang Tang ◽  
MaoZhong Ge ◽  
Yongkang Zhang ◽  
Taiming Wang ◽  
Wen Zhou
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Surface Profile ◽  
Optical Microscope ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Transmission Electron ◽  
Before And After ◽  
Shock Peening ◽  
Improve Fatigue

In order to improve fatigue life of GH3039 superalloy, GH3039 superalloy sheets were treated by laser shock peening (LSP). The microstructure of GH3039 superalloy before and after LSP was characterized using an optical microscope, transmission electron microscope (TEM), and X-ray diffractometer. The fatigue life of the samples with and without LSP was investigated by fatigue experiments. Moreover, surface profile and residual stress were also examined. Experimental results indicated that the grains in the surface layer of the LSP sample were remarkably refined and reached the nanometer scale. The average surface roughness increased from 0.024 μm to 0.19 μm after LSP. The average fatigue life of the laser treated samples was 2.01 times larger than that of the untreated specimens. Additionally, mathematical statistical analysis confirms that LSP has a significant influence on the fatigue life of GH3039 superalloy. The improvement of fatigue life for the laser processed GH3039 superalloy was mainly attributed to compressive residual stress and grain refinement generated by LSP.

Experiment of Laser Shock Processing on AISI 8620 Alloy Steel

2011 ◽  
Vol 464 ◽  
pp. 478-481
Author(s):  
R.H. Shen ◽  
J.Z. Lu ◽  
J.W. Zhong ◽  
L. Zhang ◽  
Kai Yu Luo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Hardness ◽  
Base Material ◽  
High Amplitude ◽  
High Energy ◽  
Laser Shock ◽  
Laser Shock Processing ◽  
Before And After ◽  
Shock Peening ◽  
Shock Processing

Laser shock processing (LSP, also known as Laser shock peening) is applied by using a high energy pulsed laser to create a high amplitude stress wave or shock wave on the surface to be treated. LSP is proved to be superior to conventional treatments such as shot peening in many engineering products. This paper focuses on Laser shock processing and its effects on mechanical properties of material AISI 8620 alloys steel. Experiment results indicated that compared with base material, the surface hardness increased by 13.8%, and compressive residual stress increased by 521%. Statistical method was introduced to analyze hardness and residual stress change before and after the LSP.

scholarly journals Improvement of Damping Property and Its Effects on the Vibration Fatigue in Ti6Al4V Titanium Alloy Treated by Warm Laser Shock Peening

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 746 ◽  
Author(s):  
Xiankai Meng ◽  
Yaomin Zhao ◽  
Jinzhong Lu ◽  
Shu Huang ◽  
Jianzhong Zhou ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Elevated Temperatures ◽  
Damping Ratio ◽  
Fracture Morphology ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Damping Properties ◽  
Ti6al4v Titanium Alloy ◽  
Vibration Fatigue ◽  
Shock Peening

In order to increase the vibration life of Ti6Al4V titanium alloy, warm laser shock peening (WLSP) is used to improve the damping properties and thus decrease the vibration stress in this study. Firstly, the Ti6Al4V specimens are treated by WLSP at different treatment temperatures from 200 °C to 350 °C. Then the damping ratios of untreated and WLSPed samples are obtained by impact modal tests, and the improvement of damping properties generated byWLSP is analyzed by the microstructures in Ti6Al4V titanium alloy. Moreover, the finite element simulations are utilized to study the vibration amplitude and stress during the frequency response process. Finally, the vibration fatigue tests are carried out and the fatigue fracture morphology is observed by the scanning electron microscope. The results indicate that the damping ratios of WLSPed specimens increase with the increasing treatment temperatures. This is because elevated temperatures during WLSP can effectively increase the α phase colonies and the interphase boundaries, which can significantly increase the internal friction of materials. Moreover, due to the increasing material damping ratio, the displacement and stresses during vibration were both reduced greatly by 350 °C-WLSP, which can significantly decrease the fatigue crack growth rate and thus improve the vibration fatigue life of Ti6Al4V titanium alloy.

Fatigue Life Recovery via Laser Shock Peening in Mechanically Damaged Aluminium Sheet; Experiments and Prediction Models

2014 ◽  
Vol 891-892 ◽  
pp. 980-985 ◽  
Author(s):  
Niall Smyth ◽  
Philip E. Irving
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Prediction Models ◽  
Load Cycle ◽  
Laser Shock Peening ◽  
Stress Fields ◽  
Hole Drilling ◽  
Laser Shock ◽  
Aluminium Sheet ◽  
Shock Peening

This paper reports the effectiveness of residual stress fields induced by laser shock peening (LSP) to recover pristine fatigue life. Scratches 50 and 150 μm deep with 5 μm root radii were introduced into samples of 2024-T351 aluminium sheet 2 mm thick using a diamond tipped tool. LSP was applied along the scratch in a band 5 mm wide. Residual stress fields induced were measured using incremental hole drilling. Compressive residual stress at the surface was-78 MPa increasing to-204 MPa at a depth of 220 μm. Fatigue tests were performed on peened, unpeened, pristine and scribed samples. Scratches reduced fatigue lives by factors up to 22 and LSP restored 74% of pristine life. Unpeened samples fractured at the scratches however peened samples did not fracture at the scratches but instead on the untreated rear face of the samples. Crack initiation still occurred at the root of the scribes on or close to the first load cycle in both peened and unpeened samples. In peened samples the crack at the root of the scribe did not progress to failure, suggesting that residual stress did not affect initiation behaviour but instead FCGR. A residual stress model is presented to predict crack behaviour in peened samples.

Massive Parallel Laser Shock Peening: Simulation, Verification, and Analysis

2005 ◽  
Author(s):  
A. W. Warren ◽  
Y. B. Guo ◽  
S. C. Chen
Keyword(s):  
Residual Stress ◽  
Surface Integrity ◽  
Compressive Residual Stress ◽  
Laser Intensity ◽  
Shock Pressure ◽  
Laser Shock Peening ◽  
Massively Parallel ◽  
Laser Shock ◽  
Laser Material ◽  
Shock Peening

Laser shock peening (LSP) is a surface treatment process to improve the surface integrity of metallic components. The nearly pure mechanical process of LSP results in favorable surface integrity such as compressive residual stress and improved surface material properties. Since LSP is a transient process with laser pulse duration time on the order of 40 ns, real time in-situ measurement of laser/material interaction is very challenging, if not impossible. A fundamental understanding of laser/material interactions is essential for LSP planning. Previous finite element simulations of LSP have been limited to a single laser shock location for both two and three dimensional modeling. However, actual LSP are performed in a massively parallel mode which involves almost simultaneous multi-laser/material interactions in order to induce uniform compressive residual stress across the entire surface of the workpiece. The massively parallel laser/material interactions have a significant compound/interfering effect on the resulting surface integrity of the workpiece. The numerical simulation of shock pressure as a function of time and space during LSP is another critical problem. The purpose of this paper is to investigate the effects of parallel multiple laser/material interactions on the stress/strain distributions in the workpiece during LSP of AISI 52100 steel. FEA simulations of LSP in single and multiple passes were performed with the developed spatial and temporal shock pressure model via a subroutine. The simulated residual stresses agree with the measured data in nature and trend, while magnitude can be influenced by the interactions between neighboring peening zones and the locations of residual stress measurement. Design-of-experiment (DOE) based simulations of massive parallel LSP were also performed to determine the effects of laser intensity, laser spot size, and peening spacing on stresses and strains. Increasing the laser intensity increases both the stress magnitude and affected depth. The use of smaller laser spot sizes decreases the largest magnitude of residual stress and also decreases the depth affected by LSP. Larger spot sizes have less energy attenuation and cause more plastic deformation. Spacing between peening zones is critical for the uniformity of mechanical properties across the surface. The greatest uniformity and largest stress magnitudes are achieved by overlapping of the laser spots.

scholarly journals Effect of laser shock peening on residual stress and fatigue life of clad 2024 aluminium sheet containing scribe defects

2012 ◽  
Vol 548 ◽  
pp. 142-151 ◽  
Author(s):  
M. Dorman ◽  
M.B. Toparli ◽  
N. Smyth ◽  
A. Cini ◽  
M.E. Fitzpatrick ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Aluminium Sheet ◽  
Shock Peening

scholarly journals Influence of Laser Shock Peening on Residual stress and Fatigue life of stainless steels

2019 ◽  
Author(s):  
Zbyněk ŠPIRIT ◽  
Jan KAUFMAN ◽  
Josef STREJCIUS ◽  
Michal CHOCHOLOUŠEK ◽  
Josef KOTT
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stainless Steels ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Shock Peening
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