Download or read book Finite Element Analysis of Residual Stress Field Induced by Laser Shock Peening written by Taeksun Nam and published by . This book was released on 2002 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamic behavior of Ti-6A1-4V at high strain rates can be investigated by using the split torsional Hopkinson bar experiment and by a longitudinal shock loading simulation in uniaxial strain to obtain material parameters representing rate dependent plasticity. In case of the double-sided laser peening for a thin part, reversal in loading plays a significant role. The stress waves repeatedly recompose the pre-accumulated plastic strains because of the interaction of the primary and reflected stress waves. In an attempt to better represent the material behavior under repeated reversals and collapses in loading, a sequence of bend-reverse bend tests is performed to identify the material parameters of TI-6A1-4V needed for a nonlinear kinematic hardening model (Chaboche model). For a thick part (a semi-infinite domain), single shot as well as multiple shots (at the same location) cases are simulated and compared with measured data for two different loading magnitudes and three different hardening models. Some of the simulation results agree well with the measured data, depending on the choice of hardening model and the treatment of rate dependent material behavior at high strain rates. Only a single shot (on both sides) case is investigated for a thin part (a finite thickness domain) in terms of residual stress distribution. The disagreement between the computed results and the measured data is more pronounced in this case, needing further investigations on both sides of the fields.

Download or read book Residual Stress Prediction in Laser Shock Peening Based on Finite Element Analysis and Mechanical Threshold Stress Model written by Chinmay J. Tophkhane and published by . This book was released on 2012 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Finite Element Modelling of Shot Peening and Strengthening Mechanism Analysis written by Cheng Wang and published by Scientific Research Publishing, Inc. USA. This book was released on 2023-08-25 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: The service performance and life of metal parts are closely related to the surface integrity of materials. Shot peening (SP) is a well-known surface strengthening technique and is widely used for the improvement of the component surface integrity in industrial fields, such as aerospace,vehicle, construction machinery and etc. With the rapid development of science and technology, numerous new SP techniques have been developed from the conventional mechanical shot peening, such as the laser shock peening (LSP), ultrasonic shot peening (USP),surface mechanical attrition treatment (SMAT) and etc. Different from the other mechanical processing techniques, a considerable number of process parameters have an influence on the surface strengthening effects of shot-peened metal parts. Therefore, the selection of the SP process parameters with respect to the different metal parts has always been a challenge. With the rapid development of the computer technology, the numerical simulation has increasingly attracted the more and more attentions both from the academy and the industry. Compared to the experimental investigations, the numerical simulations are not only timesaving and economical, but also can provide an insight into the surface strengthening mechanisms of SP.

Download or read book Laser shock peening Performance and process simulation written by K. Ding and published by CRC Press. This book was released on 2006-01-24 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Analysis of Residual Stress by Diffraction using Neutron and Synchrotron Radiation written by M.E. Fitzpatrick and published by CRC Press. This book was released on 2003-02-06 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: While residual stress can be a problem in many industries and lead to early failure of component, it can also be introduced deliberately to improve lifetimes. Knowledge of the residual stress state in a component can be critical for quality control of surface engineering processes or vital to performing an accurate assessment of component life unde

Download or read book Finite Element Simulation of Laser Shock Peening Process written by and published by . This book was released on 2008 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Practical Residual Stress Measurement Methods written by Gary S. Schajer and published by John Wiley & Sons. This book was released on 2013-09-23 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: An introductory and intermediate level handbook written in pragmatic style to explain residual stresses and to provide straightforward guidance about practical measurement methods. Residual stresses play major roles in engineering structures, with highly beneficial effects when designed well, and catastrophic effects when ignored. With ever-increasing concern for product performance and reliability, there is an urgent need for a renewed assessment of traditional and modern measurement techniques. Success critically depends on being able to make the most practical and effective choice of measurement method for a given application. Practical Residual Stress Measurement Methods provides the reader with the information needed to understand key residual stress concepts and to make informed technical decisions about optimal choice of measurement technique. Each chapter, written by invited specialists, follows a focused and pragmatic format, with subsections describing the measurement principle, residual stress evaluation, practical measurement procedures, example applications, references and further reading. The chapter authors represent both international academia and industry. Each of them brings to their writing substantial hands-on experience and expertise in their chosen field. Fully illustrated throughout, the book provides a much-needed practical approach to residual stress measurements. The material presented is essential reading for industrial practitioners, academic researchers and interested students. Key features: • Presents an overview of the principal residual stress measurement methods, both destructive and non-destructive, with coverage of new techniques and modern enhancements of established techniques • Includes stand-alone chapters, each with its own figures, tables and list of references, and written by an invited team of international specialists

Download or read book Constitutive Modeling of Laser Shock Peening on Additive Manufactured Ti 6Al 4V written by Ruidong Wang and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Laser Shock Peening written by Shikun Zou and published by Springer Nature. This book was released on 2023-06-09 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book On the Optimization of Laser Shock Peening Induced Residual Stresses written by Sergey Chupakhin and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Measurement and Modeling of Laser Peening Residual Stresses in Geometrically Complex Specimens written by Adrian T. DeWald and published by . This book was released on 2005 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Prediction of Residual Stress Random Fields in Selective Laser Melted Aluminum A357 Components Subjected to Laser Shock Peening written by Mohammad Issa Hatamleh and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Residual Stresses 2016 written by Thomas M. Holden and published by Materials Research Forum LLC. This book was released on 2017-03-15 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the proceedings of the International Conference on Residual Stresses 10 and is devoted to the prediction/modelling, evaluation, control, and application of residual stresses in engineering materials. New developments, on stress-measurement techniques, on modelling and prediction of residual stresses and on progress made in the fundamental understanding of the relation between the state of residual stress and the material properties, are highlighted. The proceedings offer an overview of the current understanding of the role of residual stresses in materials used in wide ranging application areas.

Download or read book Finite Element Simulation of Residual Stresses from Welding and High Frequency Hammer Peening written by Gkatzogiannis, Stefanos and published by KIT Scientific Publishing. This book was released on 2022-06-30 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research goal of the present monograph is the establishment of an efficient engineering approach, which will include straightforward but accurate simulation models, in order to estimate the residual stress fields of welded joints introduced during welding and their post-weld treatment with High Frequency Hammer Peening. The present subject lies on the intersection of structural engineering, material science and computational mechanics.

Download or read book Residual Stresses 2018 written by Marc Seefeldt and published by Materials Research Forum LLC. This book was released on 2018-10-10 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: The European Conference on Residual Stresses (ECRS) series is the leading European forum for scientific exchange on internal and residual stresses in materials. It addresses both academic and industrial experts and covers a broad gamut of stress-related topics from instrumentation via experimental and modelling methodology up to stress problems in specific processes such as welding or shot-peening, and their impact on materials properties. Chapters: Diffraction Methods; Mechanical Relaxation Methods; Acoustic and Electromagnetic Methods; Composites, Nano and Microstructures; Films, Coatings and Oxides; Cold Working and Machining; Heat Treatments and Phase Transformations; Welding, Fatigue and Fracture: Stresses in Additive Manufacturing.

Download or read book Modeling Simulation and Optimization written by Biplab Das and published by Springer Nature. This book was released on 2021-03-17 with total page 802 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes selected peer-reviewed papers presented at the International Conference on Modeling, Simulation and Optimization, organized by National Institute of Technology, Silchar, Assam, India, during 3–5 August 2020. The book covers topics of modeling, simulation and optimization, including computational modeling and simulation, system modeling and simulation, device/VLSI modeling and simulation, control theory and applications, modeling and simulation of energy system and optimization. The book disseminates various models of diverse systems and includes solutions of emerging challenges of diverse scientific fields.

Download or read book Infuence of Curved Geometries on the Fatigue Life of Laser Peened Components written by Anoop Vasu and published by . This book was released on 2014 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Generating compressive residual stresses at the critical stress locations can prevent or delay structural component failure. Laser peening is a well-known method for inducing compressive residual stresses. The plastic deformation created by the planar shock waves near the surface regions is the major cause for the generation of compressive residual stresses. Apart from the planar waves, release waves at the border of impact are generated that act against the plastic deformation created by planar waves. This decrease of plastic deformation reduces the compressive residual stress generated near the surface regions of peened components. Laser peening of curved geometries creates compressive residual stresses - which is dissimilar to flat geometries - because of the influence of release waves on different curvatures. This research investigates the effects of reduction in the amount of plasticity in convex, concave, and flat geometries using the plastic dissipation energy as the measure of plastic deformation imparted on the component. Finite element models are created in Abaqus to predict the effects of "reduced plasticity" in residual stresses generated on curved geometries of laser peened components. An analytical formulation is derived based on the plasticity incurred inside the material and the results are compared with the prediction by numerical simulation. The consistency in the analytical formulation with the simulation model indicates the behavior of laser peening for curved geometries. However, the compressive residual stresses can relax due to the loading conditions and thus reduce the laser peening effectiveness. Under such a condition, re-peening or re-laser peening a component already in service can further increase its component life. This research develops a method to predict the optimal re-peening time for maximum fatigue life under realistic loading conditions. An optimization problem is set up to illustrate the application of this method to an aircraft lug problem. A novel surrogate modeling technique called the Sorted k-fold Approach (SKA) is developed to perform the optimization. Results from the investigation indicate that re-peening the component ~50-55% of its expected fatigue life maximizes the component's fatigue life. The proposed approach, proven to be able to obtain optimal process parameters for improving the fatigue resistance of the component, can significantly reduce the costs for experimental testing.