Distribution and Optimization of Residual Stress Fields in Titanium Simulated Blade Treated by Laser Shock Peening

According to the characteristics of mechanical response of titanium alloy, a new constitutive model for ultra-high strain rate deformation in the process of laser shock peening was established. The constitutive model parameters were obtained by the inverse optimization. The propagation characteristic and residual stress-strain distribution under the shock wave were analyzed. The relationship between residual stress and laser power density and laser impacts was indicated via sensitivity analysis of laser parameters. According the above conclusions, the laser shock peening technic on the titanium simulated blades was optimized to obtain the appropriate residual stress distribution. The fatigue test result indicated that the fatigue strength by the optimized technic was improved by 25%, compared to the anterior technic without optimization.

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Prediction of Residual Stress Random Fields for Selective Laser Melted A357 Aluminum Alloy Subjected to Laser Shock Peening

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4044418 ◽

2019 ◽

Vol 141 (10) ◽

Cited By ~ 1

Author(s):

Mohammad I. Hatamleh ◽

Jagannathan Mahadevan ◽

Arif Malik ◽

Dong Qian ◽

Radovan Kovacevic

Keyword(s):

Residual Stress ◽

Random Fields ◽

Joint Probability ◽

High Energy ◽

Laser Shock Peening ◽

Model Parameters ◽

Laser Shock ◽

Near Surface ◽

Numerical Predictions ◽

Shock Peening

Abstract Residual stress (RS) is a major processing issue for selective laser melting (SLM) of metal alloys. Postprocessing by way of heat treatment or hot isostatic pressing is usually required for acceptable mechanical properties. In this work, laser shock peening (LSP) treatment on both SLM and cast aluminum A357 alloys are compared with regard to the development of beneficial near-surface compressive RS. Experiments are conducted using high energy nanosecond pulsed laser, together with a fast photodetector connected to a high-resolution oscilloscope and high-speed camera to identify detailed temporal and spatial laser pulse profiles to improve numerical predictions. Constitutive modeling for SLM A357 alloy is performed using finite element simulation and data obtained from X-ray diffraction (XRD) measurements. Since XRD-RS measurements are accompanied with significant machine-reported error, an effective method is introduced to quantify the material constitutive model uncertainty in terms of a joint probability mass function. Conventionally, most constitutive behavior research for LSP involves deterministic material modeling. Predicted RS using deterministic approaches fail to reflect real-world variations in the materials, laser treatment, or RS measurements. A discretized Bayesian inference is used to quantify the rate-dependent plasticity material model parameters as a joint probability function. RS are then characterized as random fields, which provides far greater insight into the practical ability to attain desired residual stresses. Moreover, for identical LSP treatments, it is determined that the material models are significantly different for the SLM and the conventional cast A357 aluminum alloys, resulting in much lower magnitude of compressive RS in the SLM alloy.

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Effects of Laser Shock Peening on TC11 Titanium Alloy with Different Impacts

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.681.266 ◽

2013 ◽

Vol 681 ◽

pp. 266-270 ◽

Cited By ~ 1

Author(s):

Xiang Fan Nie ◽

Wei Feng He ◽

Liu Cheng Zhou ◽

Yu Qin Li ◽

Yan Chai

Keyword(s):

Residual Stress ◽

Titanium Alloy ◽

Laser Shock Peening ◽

Laser Shock ◽

X Ray Diffraction ◽

Transmission Electron ◽

Shock Peening ◽

Tc11 Titanium Alloy ◽

The Impact ◽

Test Result

The blade, made of TC11 titanium alloy, is prone to result in fatigue failure in the formidable environment in aero-engine. So a higher performance request of the material is brought forward. In this paper, laser shock peening(LSP) as a solution is applied to TC11 titanium alloy and microstructure, residual stress and microhardness with and without LSP were examined and compared via transmission electron microscope(TEM), X ray diffraction(XRD)and microhardness tester. The TEM results indicate that a great high density of dislocations are generated and evolve into the dislocation wall, sub-boundary and grain boundary. The nanocrystallites are formed and become smaller and more uniform with greater impacts. A high compressive residual stress above -540MPa is introduced with an increasing plastically affected layer with different impacts. The microhardness test result shows that LSP can obviously increase the hardness by 20 percent or so, and the affected depth increases with the impact from 600μm to 1200μm.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.891-892.980 ◽

2014 ◽

Vol 891-892 ◽

pp. 980-985 ◽

Cited By ~ 2

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.

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