Residual Stress Prediction in Laser Shock Peening Based on Finite Element Analysis and Mechanical Threshold Stress Model PDF Download

Author: Chinmay J. Tophkhane
Publisher:
ISBN:
Category :
Languages : en
Pages : 56

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Book Description
This thesis focuses on a physically based strain rate dependent plasticity model known as the Mechanical Threshold Stress (MTS) model proposed by Follansbee and Kocks. The objective is to develop an algorithm based on the tangent modulus method to resolve the constitutive equation represented by the MTS model and use it to analyze the material response under laser shock peening for the Ni alloy INCONEL 718 (IN718). A user defined subroutine has been developed and integrated with commercial software LS-DYNA. A parametric study is carried out to study the influence of various model parameters on the predicted residual stresses. The developed model is then applied in the study of residual stresses imparted on INCONEL 718 induced by laser shock peening (LSP) process. Finite element analysis is performed for the case of plate made of INCONEL 718 and the residual stress predictions are compared with experimental results. The model predictions are found to be in good agreement with the experimental results. To the best of author's knowledge, this is the first time that an MTS model has been developed for IN 718 with an integrated approach.

Author: Ruidong Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Laser shock peening (LSP) is a mechanical surface treatment that induces plastic deformation and compressive residual stress in the material similar to shot peening. Pressure generated by the pulsed laser is far above the yield stress of the material and pulse duration is on the order of nanosecond. Finite element analysis is applied to simulate LSP and predict plastic deformation and residual stress through different constitutive models. The development of analytical model including model details, loading time history and constitutive model equations and parameters is discussed. Finally, results are presented for different constitutive models and experiment results are discussed.

Author: Adrian T. DeWald
Publisher:
ISBN:
Category :
Languages : en
Pages : 338

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Author: Scott Allen Noll
Publisher:
ISBN:
Category :
Languages : en
Pages : 172

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Book Description
Laser shock peening (LSP) is a material processing technique that imparts compressive residual stresses, which in turn enhance the materials ability to resist crack initiation/propagation. SHOCKWAVE, a finite element program developed at The Ohio State University, is used to predict the residual stress fields for one-sided and two-sided LSP on a common industrial metal, Ti-6A1-4V. Close attention was paid to constitutive modeling, mesh refinement, and correlating the analytical results with experiments. Both one-sided and two-sided LSP techniques were analyzed for multiple peak pressures and base material thickness. The residual stress field was successfully predicted for one-sided LSP and moderately well for two-sided LSP. The challenges for two-sided LSP are discussed and a plan for further investigation is given. Plastic strains are calculated to be on the order of 1-2% penetrating to a depth of 1 to 2 mm. Compressive residual stresses at the surface are found to be 1/3 to 2/3 the yield strength of the metal. Strain rates were calculated at 106 s-1 at the front of the shock wave. To predict the residual stress, the constitutive relations must account for the effect of strain rate for one-sided LSP and also be able to model Baushinger effect for the two-sided LSP.

Author: K. Ding
Publisher: CRC Press
ISBN: 9780849334443
Category : Technology & Engineering
Languages : en
Pages : 182

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Book Description
Laser shock peening (LSP) is a process for inducing compressive residual stresses using shock waves generated by laser pulses. It is a relatively new surface treatment for metallic materials that can greatly improve their resistance to crack initiation and propagation brought on by cyclic loading and fatigue. This book, the first of its kind, consolidates the scattered knowledge about LSP into one comprehensive volume. It describes the mechanisms of LSP and its substantial role in improving fatigue performance in terms of modification of microstructure, surface morphology, hardness, and strength. In particular, it describes numerical simulation techniques and procedures that can be adopted by engineers and research scientists to design, evaluate, and optimize LSP processes in practical applications.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 80

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Book Description
Laser Shock Peening (LSP) is a relatively new material processing technology to enhance the operating service lives of engineering components. It has been applied to metal parts such as aircraft engine turbine blades, compressor blades and medical implants like human hip joints. In this process shock waves are generated in the material using a high powered laser beam which develops residual stresses in the material. It has been proved experimentally that the life cycle of laser shock peened components are higher than conventionally shot peened components. Although LSP process has been found to be effective, improper control of the process will lead to spallation in the material under certain conditions. The spallation within the material in the form of crack significantly reduces the operating life of the component. Currently there is no systematic modeling approach to predict the material response under LSP. As such, the objective of this thesis is to develop a comprehensive model for the predicting the material response as a result of the LSP process. More specifically a pressure model is first established to obtain the pressure loading based on laser pulse intensity. Using the pressure load as input the spallation response is simulated by developing a strain rate and temperature dependent material model. The material model is implemented along with a nucleation and growth based damage model. The material and dynamic fracture model is solved using a semi-implicit forward tangent modulus algorithm. A user defined subroutine (UDM) is written and combined with the analysis tool LS-DYNA. The new model is compared with reported experimental results and a parametric study is done to understand the influence of various processing parameters. The residual stress obtained from simulation is in good agreement with experimental results. The spallation results have not been verified due to lack of experimental data.

Author: Mohammad Issa Hatamleh
Publisher:
ISBN:
Category : Laser peening
Languages : en
Pages :

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Book Description
This work aims to develop a procedure to simulate laser shock peening treatments more efficiently, and to characterize the major differences in laser peening effects for cast and additively manufactured (selective-laser-melted) metallic specimens fabricated from A357 aluminum alloy. In addition, residual stresses (RS) are to be predicted probabilistically as a random field, allowing rigorous determination of RS values for a desired reliability. Laser shock peening (LSP) is a surface treatment technique that induces compressive RS near the surface of target metal components to improve fatigue life. Developing an LSP process using physical experiments is very expensive and time-consuming. To address this issue, finite element methods (FEM) have been widely used to simulate the LSP process and predict RS. Conventionally, almost all material constitutive models used in LSP prediction of RS involve deterministic parameters. Therefore, the predicted RS profiles do not reflect real-world variations in the material or uncertainties in the LSP process. Moreover, prediction of RS as a random field has not been done. While the effect of LSP on cast alloys has been studied extensively, few researchers have investigated the effects of LSP on metallic specimens produced by additive manufacturing processes such as selective laser melting (SLM). Therefore, the objectives of this research are: (1) Develop a procedure to simulate the LSP process with reduced computational time; (2) Conduct experimental and numerical studies to understand the effects of LSP on SLM A357 aluminum alloy; (3) Create a probabilistic approach to quantify the material constitutive model parameters as a joint probability distribution of correlated random variables; and (4) Demonstrate a technique to efficiently generate stochastic maps of the resulting RS random fields, enabling improved reliability analysis for desired RS values. To increase LSP simulation speed, a new systematic procedure is developed using modal analysis and generalized variable damping profiles with the “single explicit analysis using time dependent damping” (SEATD) FEM approach. To begin understanding the effects of LSP on A357 aluminum alloy specimens produced by SLM, true-stress-strain curves of both as-built (AB) and laser shock peened SLM samples are obtained through transverse tensile tests. An initial hypothesis on the effects of LSP during tension testing is formulated and subsequently tested using SEATD approach. To quantify the plasticity-Johnson-Cook (J-C) material model parameters as a joint probability distribution of correlated random variables for heat-treated (HT) and as-built (AB) SLM A357, the Bayesian inference (BI) probabilistic approach is utilized. Also proposed in this work are two BI-quantified-techniques called, respectively, the Multidimensional-BI method and the Spatial-Posterior-Prior-Probability-Mass-Function (SPP-PMF) method. Both can be used to efficiently predict RS as a random field, thus providing far greater insight into the practical ability to attain desired RS. 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 overall magnitude of compressive RS in the SLM-alloy. In addition, stochastic maps of the resulting random stress fields for LSP treatments on specific SLM A357 components are generated using the approach described herein.

Author: Sergey Chupakhin
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
There is a strong economic motivation of the aircraft industry to explore novel residual stress-based approaches for the fatigue life extension, repair, and maintenance of the growing fleet of ageing aircrafts, although the effect of residual stresses is not taken into account by the established damage tolerance evaluation methods. Laser shock peening - the most promising life enhancement technique - has already demonstrated great success in regard to the mitigation of fatigue crack growth via deep compressive residual stresses. However, no comprehensive model exists which allows the prediction of generated residual stress fields depending on the laser peening parameters. Furthermore, the hole drilling method - a well-established technique for determining non-uniform residual stresses in metallic structures - is based on measuring strain relaxations at the material surface caused by the stress redistribution while drilling the hole. However, the hole drilling method assumes linear elastic material behavior and therefore, when measuring high residual stresses approaching the material yield strength, plastic deformation occurs, which in turn leads to errors in stress determination. In the light of these two points, the present work aims to optimize the laser shock peening process in regard to high residual stress profiles, their correct measurement by the hole drilling method and demonstration of the fatigue crack growth retardation through the laser peening treatment on the laboratory scale. First, the methodology for the correction of the residual stresses approaching the material yield strength when measuring by the hole drilling is established and experimentally validated. The correction methodology utilizes FE modelling and artificial neural networks. In contrast to the recent studies, the novelty of this methodology lies in the practical and elegant way to correct any non-uniform stress profile for a wide range of stress levels and material behaviors typically used in industrial applications. Therefore, this correction methodology can be applied in industry without changing the procedure of hole drilling measurement. Second, the laser shock peening process is optimized in regard to the generated residual stress profiles using design of experiments techniques. The strategy involves laser peening treatment with different parameters and subsequent measurement of induced residual stress profiles through hole drilling. The measured stress profiles are subjected to correction using the neural network methodology. After that the regression model is fitted into the experimental data in order to find the relationship between the laser peening parameters and the stress profiles' shapes. In the final stage, it is experimentally demonstrated that the established regression model provides an accurate prediction of the residual stress profile when using defined laser peening parameters and vice versa. Third, the regression model obtained in the design of experiments study is used for generating the desired residual stresses in the C(T)50 AA2024-T3 specimens for the fatigue crack propagation test. Significant retardation of the fatigue crack propagation of specimens due to the presence of deep compressive residual stresses is experimentally demonstrated on the laboratory scale.

Author: Prashanth Kumar Tirukovelluri
Publisher:
ISBN:
Category :
Languages : en
Pages : 376

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Book Description
The objective of the research is to develop a three-dimensional finite element model for predicting residual stresses that evolve during the Laser Powder Deposition of thin-walled builds using commercially available finite element software, ABAQUS/Standard [5]. The research work was started by developing a finite element model of Laser Glazing process, which is relatively simple when compared to Laser Powder Deposition in modeling perspective as there is no dynamic addition of material. The experience gained from modeling of Laser Glazing was applied to develop a finite element model of Laser Powder Deposition for prediction of residual stresses. The numerical model of Laser Glazing is based on sequentially coupled thermo-mechanical theory and Laser Powder Deposition process on fully coupled thermo-mechanical theory. To simplify the models, symmetry of geometry and boundary conditions were taken into account. In both the models temperature dependent material properties were included. Also, latent heat corresponding to melting was taken into account. The material was defined as elastic-perfectly plastic. The results predicted by the thermal model of Laser Glazing are comparable with analytical solution and are also validated with the results obtained from carefully designed experiments. In the case of finite element model of Laser Powder Deposition, it can be concluded that the results obtained are reasonable based on previous experimental studies by others.

Author: Shikun Zou
Publisher: Springer Nature
ISBN: 9819911176
Category : Science
Languages : en
Pages : 398

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Book Description
This book highlights the fundamentals and latest progresses in the research and applications of laser shock peening (LSP). As a novel technology for surface treatment, LSP greatly improves the resistance of metallic materials to fatigue and corrosion. The book presents the mechanisms, techniques, and applications of LSP in a systematic way. It discusses a series of new progresses in fatigue performance improvement of metal parts with LSP. It also introduces lasers, equipment, and techniques of newly developed industry LSP, with a detailed description of the novel LSP blisk. The book demonstrates in details numerical analysis and simulation techniques and illustrates process stability control, quality control, and analysis determination techniques. It is a valuable reference for scientists, engineers, and students in the fields of laser science, materials science, astronautics, and aeronautics who seek to understand, develop, and optimize LSP processes.