scholarly journals Phase-field modelling for fatigue crack growth under laser shock peening-induced residual stresses

2021 ◽  
Author(s):  
Martha Seiler ◽  
Sören Keller ◽  
Nikolai Kashaev ◽  
Benjamin Klusemann ◽  
Markus Kästner
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Crack Growth ◽  
Phase Field ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Fatigue Model ◽  
Shock Peening

AbstractFor the fatigue life of thin-walled components, not only fatigue crack initiation, but also crack growth is decisive. The phase-field method for fracture is a powerful tool to simulate arbitrary crack phenomena. Recently, it has been applied to fatigue fracture. Those models pose an alternative to classical fracture-mechanical approaches for fatigue life estimation. In the first part of this paper, the parameters of a phase-field fatigue model are calibrated and its predictions are compared to results of fatigue crack growth experiments of aluminium sheet material. In the second part, compressive residual stresses are introduced into the components with the help of laser shock peening. It is shown that those residual stresses influence the crack growth rate by retarding and accelerating the crack. In order to study these fatigue mechanisms numerically, a simple strategy to incorporate residual stresses in the phase-field fatigue model is presented and tested with experiments. The study shows that the approach can reproduce the effects of the residual stresses on the crack growth rate.

Numerical Analysis of Laser Shock Peening as a Process for Generation of Compressive Residual Stresses in Open Hole Specimens

2011 ◽  
Vol 681 ◽  
pp. 267-272 ◽  
Author(s):  
Goran Ivetic ◽  
Ivan Meneghin ◽  
Enrico Troiani
Keyword(s):  
Fatigue Crack ◽  
Numerical Analysis ◽  
Residual Stresses ◽  
Crack Nucleation ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Fatigue Crack Nucleation ◽  
Open Hole ◽  
Shock Peening ◽  
Compressive Residual Stresses

A numerical analysis of Laser Shock Peening (LSP) process is illustrated, applied to an open hole specimen. This specimen is representative of a section of an aircraft fuselage lap joint, typically prone to fatigue crack nucleation at the rivet holes. The effect of the residual stress field induced by LSP on the fatigue life of open hole specimens is investigated. The results show that significant compressive residual stresses can be introduced in fatigue sensitive areas using LSP, postponing fatigue crack nucleation.

Characterization of TC17 Titanium Alloy Treated by Square-Spot Laser Shock Peening

2013 ◽  
Vol 652-654 ◽  
pp. 2378-2383 ◽  
Author(s):  
Zi Wen Cao ◽  
Shui Li Gong ◽  
Yu Gao
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Stress Gradient ◽  
Laser Shock Peening ◽  
Fatigue Performance ◽  
Specimen Thickness ◽  
Laser Shock ◽  
Shock Peening ◽  
Square Spot

Laser shock peening (LSP) is widely known as a cold-worked surface treatment, and this technology has been to greatly improve the fatigue life of many metallic components. Our works focused on laser shock peening with Nd: glass laser system (pulse duration 30ns) and square laser spot size of 4mm×4mm for TC17 titanium alloy. Surface morphology, residual stresses and fatigue performance had been studied for TC17 alloy specimens and blades processed by LSP treatment. The results show that plastic strains in shocked dents become more homogeneous than ones produced by original circle spot with gaussian energy distribution. Surface residual stresses which measured using x-ray diffraction method showed different characteristic as varying specimen thickness, and LSP with overlapping ratio of 8% provided uniform residual stresses on peened surface. Low fluence peening which was implemented at borderline of peened surface was effective to diminish the stress gradient. Compared with mechanical shot peening, LSP attained smoother surface, lower microhardness and better fatigue performance. In a word, Square-spot LSP is an excellent way to improve fatigue life of titanium blade.

Fatigue Crack Retardation in LSP and Sp Treated Aluminium Specimens

2014 ◽  
Vol 891-892 ◽  
pp. 986-991 ◽  
Author(s):  
Elke Hombergsmeier ◽  
Vitus Holzinger ◽  
Ulrike C. Heckenberger
Keyword(s):  
Fatigue Crack ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Shot Peening ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Propagation Behavior ◽  
Shock Peening ◽  
Compressive Residual Stresses ◽  
Crack Propagation Behavior

Highly loaded aircraft components have to fulfill strict fatigue and damage tolerance requirements. For some components besides the crack initiation mainly the fatigue crack propagation behavior is the main design criteria. To improve the crack propagation behavior of a component several methods are known or have been described in literature. For thin aircraft panels i.e. the application of crenellations [1] or bonded doublers [2, 3] can be a solution. For thick structures mainly the introduction of compressive residual stresses is beneficial. In this paper the potential of compressive residual stresses obtained by Laser Shock Peening (LSP) and Shot Peening (SP) is investigated. By means of Laser Shock Peening the residual compressive stress field can extend much deeper below the treated surface than that produced by conventional Shot Peening (i.e. with steel or ceramic balls) [4, 5]. The effect of such deep compressive stress profile results in a significantly higher benefit in fatigue behavior after Laser Shock Peening or after the combination of Laser Shock Peening and Shot Peening on top. The measurement of residual stresses as a depth profile has been performed by incremental hole drilling (ICHD) and contour method. Finally crack propagation tests have been carried out to validate the process technology approach.

Laser Shock Peening to Repair, Design and Manufacture Current and Future Aircraft Structures by Residual Stress Engineering

2014 ◽  
Vol 891-892 ◽  
pp. 992-1000 ◽  
Author(s):  
Domenico Furfari
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Crack Growth ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Aircraft Structures ◽  
Area Of Interest ◽  
Aircraft Manufacturing ◽  
Stress Engineering ◽  
Shock Peening

This paper will provide an overview on potential applications for the aerospace industry for repairing aircraft as well as to ensure salvage for identified hot spots in terms of fatigue and crack growth performance. Residual stress engineering is a field of engineering aiming to improve the economic and ecological impact of future aircraft structures by controlling the residual stresses induced by Laser Shock Peening (LSP). Managing the residual stresses for designing structures represents an innovative approach for next generation aircraft. Predicting crack turning induced via a LSP treatment and the optimization of the LSP treatment itself for reaching the crack growth design stress for the targeted weight benefit will be discussed. Advanced forming processes in aircraft manufacturing represent another potential area of interest and the benefits and challenges of applying laser peen forming in this context will be presented. The aeronautical industry requirements for future developments of the laser shock process will also be included for applications ranging from the repair environment to design and manufacturing of aircraft structures.

scholarly journals Fatigue Life Extension of AA2024 Specimens and Integral Structures by Laser Shock Peening

2018 ◽  
Vol 165 ◽  
pp. 18001 ◽  
Author(s):  
Nikolai Kashaev ◽  
Sergey Chupakhin ◽  
Volker Ventzke ◽  
Manfred Horstmann ◽  
Stefan Riekehr ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Friction Stir Welding ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Laser Shock Peening ◽  
Specimen Thickness ◽  
Laser Shock ◽  
Friction Stir ◽  
Shock Peening

The goal of the present study is to understand the effects of laser shock peening (LSP)-induced residual stresses on the fatigue crack propagation (FCP) behaviour of the commonly used aircraft aluminium alloy AA2024 in T3 heat treatment condition. LSP treatment was performed using a pulsed Nd:YAG laser on compact tensile C(T)50-specimens with a thickness of 2.0 mm. LSP-treated specimens reveal a significant retardation of the fatigue crack propagation. The fatigue crack retardation effect can be correlated with the compressive residual stresses introduced by LSP throughout the entire specimen thickness. A possible application of the LSP process on a component like panel with three welded stringers representing a part of a fuselage structure was performed as well. The skin-stringer AA2024-AA7050 Tjoints were realised through stationary shoulder friction stir welding (SSFSW), a variant of the conventional friction stir welding process. In this relatively new process, the shoulder does not rotate and therefore does not contribute to the heat generation. Consequently, a reduced and more homogeneous heat input leads to a less affected microstructure and better mechanical properties. The efficiency of the LSP process has been demonstrated resulting in an increase of 200 – 400% in fatigue lifetime.

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