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Numerical analysis of multi-layered laser cladding for die repair applications to determine residual stresses and hardness
摘要： Laser cladding provides numerous advantages over the traditional, ad-hoc and imprecise deposition techniques for the repair of critical structural components such as dies and molds used in cold working industries. A necessity of a good quality laser cladding is to offer durable and reliable adhesion to the substrate with reduced dilution and absence of pores, cracks, and delamination. The process can add to complications due to addition of the second layer on the surface of the first clad layer that can generate local variation in shrinkage, layers of additive material are added onto the non-planar domain and the additional distance from the substrate. Consequently, residual stresses previously induced in a first clad layer and substrate region can alter. Largely, tensile residual stresses in the clad layer or clad-substrate interface region can lead to accelerated fatigue failure. Prediction and mitigation of tensile residual stresses still remain important issues in multi-layer laser cladding. Finite element modelling is an appropriate way to estimate the residual stress profile and microstructural changes for the prediction of optimal process parameters. The current work focuses on the development of a coupled metallo-thermomechanical finite element model in ABAQUS? for multi-layered laser cladding of CPM9V powder on H13 tool steel. The residual stress evolution along the cross-section has been characterized at different process conditions and the optimal conditions corresponding to mitigation of tensile residual stresses have been identified. The hardness can be affected due to the deposition of an additional layer and tempering can occur in clad or substrate which needs to be understood. The micro-hardness values are estimated using the numerical model and compared with the measured data using a Vickers hardness tester. It has been observed that the peak magnitude of tensile residual stress in the clad region with multiple layers is lower than the peak residual stresses in single layer clad of the same height along with the hardness.
关键词： residual stress,multi-layered deposition,Additive manufacturing,metallo-thermomechanical model,micro-hardness
更新于2025-09-12 10:27:22
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Non-dimensional process maps for normalized dilution limits in laser direct metal deposition
摘要： The quality and integrity of laser direct metal deposition (DMD) processes primarily depend on the substrate dilution and the nature of residual stresses in the deposited layer. An adequate amount of melting of the substrate is required to ensure the formation of sound metallurgical bond between the deposited layer and substrate. Insufficient melting and excessive dilution may lead to adverse effects. Furthermore, the dilution also controls the location of the melt front in substrate where maximum tensile residual stresses occur. The presence of tensile residual stresses in the deposited layer may be detrimental to service life, especially, for components repaired using DMD. These challenges can be overcome by predicting and controlling the dilution and the nature of residual stress as a function of process parameters. To model the direct metal deposition process, a 3D coupled metallo-thermomechanical finite element model is employed to predict the temperature and the residual stress due to thermomechanical interactions and metallurgical transformations and the substrate dilution. Non-dimensional process parameters affecting the dilution in laser DMD have been identified using Buckingham-Π theorem. The metallo-thermomechanical model is used to develop empirical relationships via regression to correlate the dimensionless process parameters with the dilution. These correlations are employed in developing the isopleths in the form of process maps, which could predict regions of inadequate fusion and excessive dilution (unduly large substrate melting). It may be noted that the limiting value of dilution corresponds to the condition where the entire deposited layer (cladding) is under compressive residual stresses. Any dilution higher than this will result in excess substrate melting which is undesirable. The limiting values of normalized dilution are estimated to be 1 and ~1.3 corresponding to complete deposit-substrate fusion and presence of entirely compressive residual stress in deposition, respectively. These process maps are designed to provide a theoretical framework for understanding the influence of process parameters and provide informed decisions on the selection of appropriate process parameters for ensuring the quality and integrity of the deposition.
关键词： Laser cladding,residual stress,metallo-thermomechanical finite element model,process maps,dilution,non-dimensional parameters
更新于2025-09-12 10:27:22
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Finite element prediction and validation of residual stress profiles in 316L samples manufactured by laser powder bed fusion
摘要： Laser powder bed fusion (LPBF) processes continue to grow in popularity and much progress has been made in recent years. However, due to the extreme thermal gradients present, significant residual stresses are inevitable and can be detrimental during component service. Critical to mitigating these stresses effectively is the ability to model the thermo-mechanical process accurately and efficiently. A simplified FE modelling methodology has been developed and applied to a cylindrical component built in both the horizontal and vertical orientations. The resulting distortion of the parts following a slitting process was compared with those predicted by the model and good agreement to within 5% was found. The final stress fields in the components were predicted by the model and then examined to assess the principal stresses driving the distortion and the causes of difference in results between the two build orientations.
关键词： LPBF,residual stress,finite element modelling,Laser powder bed fusion,distortion
更新于2025-09-12 10:27:22
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Stress distribution in laser metal deposited multi-layer thick-walled parts of Ti-6Al-4V
摘要： The laser metal deposition is an additive manufacturing technology enabling the production of large scale complex parts without additional treatment like welding or machining. The study of the origin of the stress field during laser metal deposition is essential for solving a number of problems, including: the assessment of cold and hot cracking; prediction of the fatigue resistance, and the stress corrosion cracking. The quantitative study of transient and residual stresses in build parts is necessary for optimising the parameters of processing and post-production stress relieving heat treatment. Residual stress field in laser metal deposited 50-layer (4-pass per layer) wall of Ti-6Al-4V was analysed experimentally using neutron diffraction and numerically using finite element simulation. Long dwell time between passes and a rigid substrate was used in order to simulate conditions of large scale parts fabrication. An analysis of the calculated and experimentally measured residual stress field showed that near the edges of the buildup there is a region where all three components of stress field are tensile, and normal stress exceeds the yield stress by more than 25%. Moreover, normal plastic strain in this area are also tensile and reaches 2.5-3%. The longitudinal tensile stress closes to yield stress on almost the entire length of the several last layers near the top of the buildup. Residual stress field calculated using neutron diffraction data according to interplanar lattice distance obtained assuming plane stress approach has a satisfactory agreement with FE simulated results.
关键词： Neutron diffraction,Laser metal deposition,Simulation,Residual stress,Titanium alloy
更新于2025-09-12 10:27:22
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Multi-Objective Optimization of Residual Stress and Cost in Laser Shock Peening Process Using Finite Element Analysis and PSO Algorithm
摘要： Laser shock peening (LSP) is an effective process utilized for surface enhancement of metal parts so that generating compressive residual stresses (RS) on the surface improves fatigue life of the material. The main affecting parameters on surface negative residual stress are laser power, laser beam size and shape, peening pitch and pattern. Varying these parameters alters the magnitude and depth of RS as well as the cost of LSP. An integrated method for simulation of optimum LSP process is presented in this paper, in which Particle Swarm Optimization (PSO) technique was employed utilizing Python coding in ABAQUS finite element environment to maximize the uniformity of compressive RS and minimize LSP cost on an Inconel 718 super-alloy specimen. The mentioned affecting parameters were selected as optimization parameters, and minimum acceptable amounts and depth of compressive RSs were two main design constraints. Simulation results were compared with previously published experimental ones, and optimum LSP variables were finally determined and presented for certain amount of design constraints. It was revealed that, relatively small circular laser beam, shot by square scanning pattern, leads to generate the most uniform RS with minimum LSP cost.
关键词： Particle swarm multi-objective optimization,Laser shock peening,Residual stress,Python coding,Finite element simulation
更新于2025-09-12 10:27:22
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Effect of Welding Speed on the Prediction Accuracy of Residual Stress in Laser Welded 1.2?mm Thick Dual Phase Steel
摘要： Post-weld residual stress and distortion are significant issues in laser welding as they reduce fatigue strength and toughness. In the present work, cold rolled dual phase steel sheets of 1.2 mm thickness were laser welded in both bead on plate and butt configurations. The optimum heat input was observed to be approximately 25 kJ/m for visually defect free weld with narrow weld bead and through-thickness penetration. A novel attempt was made to increase the welding speed whilst maintaining the optimum heat input. It was observed that, high welding speed led to high residual stress, resulting in longitudinal cracks, whereas the speed at a limiting value of 0.08 m/s was found to be beneficial longitudinal cracks. Literature suggests researchers have for welding without already proposed different mathematical models on keyhole mode laser welding that can predict the residual stress and deformation. However, most of them failed to predict it repetitively, especially for thin sheets. This work tried to find the range of the rationality of this argument. For low-speed condition, residual stress values was substantially wide, making it difficult to predict actual residual stress with the aid of mathematical models. The range of residual stress values was found to be much lower for the optimum heat input and high-speed condition, resulting into better prediction accuracy. Residual stress values were also validated using kernel average misorientation (KAM) study.
关键词： Heat input,Dual phase steel,Kernel average misorientation,Residual stress,Laser welding,Key-hole mode,Welding speed,Weld longitudinal crack
更新于2025-09-12 10:27:22
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Modeling and optimization for laser cladding via multi-objective quantum-behaved particle swarm optimization algorithm
摘要： The process parameters of laser cladding have significant effects on the quality of the laser clad coating. Generally, optimizing one property usual lead to deterioration in some other performances. In this study, the influence of key parameters to preparing the CoCr1.5FeNiNb0.5 coating, namely laser beam power, scanning speed and defocus, on the dilution and residual stress were systematically researched. The polynomial model for the parameters on dilution and residual stress was designed by response surface methodology and the effect of each parameter on the responses was investigated. Then the quadratic models were used as the constraint functions and multi-objective quantum-behaved particle swarm optimization was applied to find the minimum dilution and residual stress. At last, the optimal process parameters were predicted by this algorithm and the high entropy alloy coating was manufactured. The CoCr1.5FeNiNb0.5 HEA coating consisted of FCC and Laves phase.
关键词： Dilution,Residual stress,Response surface methodology,Laser cladding,Multi-objective
更新于2025-09-12 10:27:22
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Stress-controlled decomposition routes in cubic AlCrN films assessed by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction
摘要： The dependence of decomposition routes on intrinsic microstructure and stress in nanocrystalline transition metal nitrides is not yet fully understood. In this contribution, three Al0.7Cr0.3N thin films with residual stress magnitudes of ?3510, ?4660 and ?5930 MPa in the as-deposited state were in-situ characterized in the range of 25–1100 °C using in-situ synchrotron high-temperature high-energy grazing-incidence-transmission X-ray diffraction and temperature evolutions of phases, coefficients of thermal expansion, structural defects, texture as well as residual, thermal and intrinsic stresses were evaluated. The multi-parameter experimental data indicate a complex intrinsic stress and phase changes governed by a microstructure recovery and phase transformations taking place above the deposition temperature. Though the decomposition temperatures of metastable cubic Al0.7Cr0.3N phase in the range of 698–914 °C are inversely proportional to the magnitudes of deposition temperatures, the decomposition process itself starts at the same stress level of ~?4300 MPa in all three films. This phenomenon indicates that the particular compressive stress level functions as an energy threshold at which the diffusion driven formation of hexagonal Al(Cr)N phase is initiated, provided sufficient temperature is applied. In summary, the unique synchrotron experimental setup indicated that residual stresses play a decisive role in the decomposition routes of nanocrystalline transition metal nitrides.
关键词： thin films,AlCrN,phase decomposition,thermal expansion,microstructure,in-situ XRD,residual stress
更新于2025-09-12 10:27:22
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Influence of multiple laser impacts on thin leading edges of turbine blade
摘要： Laser shock peening is a mechanical surface improvement treatment used to enhance the fatigue life of critical components. This paper investigates the influence of multiple square laser impacts to study their special effect on the diverse mechanical behaviours of the thin leading edge surface of turbine blades. Most works existing in the literature have presented experimental investigations. The originality of our paper is to validate and numerically simulate the proposed model. Indeed, a 3D finite element method of a thin leading edge specimen, Ti–6Al–4V, of a turbine blade is numerically simulated using the ABAQUS software. The mechanical surface modifications (residual stresses, equivalent plastic strains and Johnson–Cook superficial damage) induced by the multiple square laser impact are examined in detail. The main purpose of this investigation is to determine the effects of single-sided and double-sided laser shock peening.
关键词： turbine blade,thin leading edge,Ti–6Al–4V,multiple square laser impacts,finite element method,equivalent plastic strain,Laser shock peening,Johnson–Cook superficial damage,compressive residual stress
更新于2025-09-12 10:27:22
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Residual stress and welding distortion of Al/steel butt joint by arc-assisted laser welding-brazing
摘要： The thermo-elastic?plastic finite element method (FEM) is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas (TIG) arc-assisted laser welding-brazing (A-LWB) butt joint. The influence of material nonlinearity, geometrical nonlinearity and work hardening on the welding process is studied, and the differences in the welding temperature field, residual stress and welding distortion by A-LWB and by single laser welding-brazing (SLWB) are analyzed. The results show that the thermal cycle, residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments, which verifies the effectiveness of FEM. Compared with the SLWB, A-LWB can make the high-temperature distribution zone of weld in width direction wider, decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress. And the welding deformation also decreases to some extent.
关键词： arc-assisted laser welding-brazing (A-LWB),residual stress,welding distortion,Al/steel,temperature field,finite element method (FEM)
更新于2025-09-12 10:27:22