查看更多>>摘要：This research presents an innovative approach to accurately predict the nugget diameter in resistance spot welding(RSW)by leveraging machine learning and trans-fer learning methods.Initially,low-fidelity(LF)data were obtained through finite element numerical simulation and design of experiments(DOEs)to train the LF machine learn-ing model.Subsequently,high-fidelity(HF)data were col-lected from RSW process experiments and used to fine-tune the LF model by transfer learning techniques.The accuracy and generalization performance of the models were thor-oughly validated.The results demonstrated that combining different fidelity datasets and employing transfer learning could significantly improve the prediction accuracy while minimize the costs associated with experimental trials,and provide an effective and valuable method for predicting criti-cal process parameters in RSW.
查看更多>>摘要：Wax pattern fabrication in the investment casting of hollow turbine blades directly determines the dimension accuracy of subsequent casting,and therefore significantly affects the quality of final product.In this work,we develop a machine learning-based multi-objective optimization framework for improving dimension accuracy of wax pat-tern by optimizing its process parameters.We consider two optimization objectives on the dimension of wax pattern,i.e.,the surface warpage and core offset.An active learn-ing of Bayesian optimization is employed in data sampling to determine process parameters,and a validated numeri-cal model of injection molding is used to compute objec-tive results of dimension under varied process parameters.The collected dataset is then leveraged to train different machine learning models,and it turns out that the Gauss-ian process regression model performs best in prediction accuracy,which is then used as the surrogate model in the optimization framework.A genetic algorithm is employed to produce a non-dominated Pareto front using the surrogate model in searching,followed by an entropy weight method to select the most optimal solution from the Pareto front.The optimized set of process parameters is then compared to empirical parameters obtained from previous trial-and-error experiments,and it turns out that the maximum and average warpage results of the optimized solution decrease 26.0％and 20.2％,and the maximum and average errors of wall thickness compared to standard part decrease from 0.22 mm and 0.051 7 mm using empirical parameters to 0.10 mm and 0.035 6 mm using optimized parameters,respectively.This framework is demonstrated capable of addressing the chal-lenge of dimension control arising in the wax pattern pro-duction,and it can be reliably deployed in varied types of turbine blades to significantly reduce the manufacturing cost of turbine blades.
查看更多>>摘要：The stress-life curve(S-N)and low-cycle strain-life curve(E-N)are the two primary representations used to characterize the fatigue behavior of a material.These mate-rial fatigue curves are essential for structural fatigue analy-sis.However,conducting material fatigue tests is expensive and time-intensive.To address the challenge of data limita-tions on ferrous metal materials,we propose a novel method that utilizes the random forest algorithm and transfer learning to predict the S-N and E-N curves of ferrous mate-rials.In addition,a data-augmentation framework is intro-duced using a conditional generative adversarial network(cGAN)to overcome data deficiencies.By incorporating the cGAN-generated data,the accuracy(R2)of the random forest algorithm-trained model is improved by 0.3-0.6.It is proven that the cGAN can significantly enhance the predic-tion accuracy of the machine-learning model and balance the cost of obtaining fatigue data from the experiment.
查看更多>>摘要：This paper presents a new machine learning-based calibration framework for strength simulation mod-els of self-piercing riveted(SPR)joints.Strength simula-tions were conducted through the integrated modeling of SPR joints from process to performance,while physical quasi-static tensile tests were performed on combinations of DP600 high-strength steel and 5754 aluminum alloy sheets under lap-shear loading conditions.A sensitivity study of the critical simulation parameters(e.g.,friction coefficient and scaling factor)was conducted using the controlled variables method and Sobol sensitivity analysis for feature selection.Subsequently,machine-learning-based surrogate models were used to train and accurately represent the mapping between the detailed joint profile and its load-displacement curve.Calibration of the simulation model is defined as a dual-objective optimization task to minimize errors in key load displacement features between simulations and experiments.A multi-objective genetic algorithm(MOGA)was chosen for optimization.The three combinations of SPR joints illustrated the effectiveness of the proposed framework,and good agreement was achieved between the calibrated models and experiments.
查看更多>>摘要：The exoskeleton is employed to assist humans in various domains including military missions,rehabili-tation,industrial operation,and activities of daily living(ADLs).Walking is a fundamental ADL,and exoskeletons are capable of reducing the activation and metabolism of lower extremity muscles through active assistance during walking.To improve the performance of active assistance strategy,this article proposes a framework using an active hip exoskeleton.Subsequently,it correlates to an already established Bayesian-based human gait recognition algo-rithm,with a particular focus on linear and circular walk-ing within industrial and ADL contexts.In theorizing this strategy for exoskeletons,this study further reveals,in part,the activation characteristics of human hip muscles for the instruction and regulation of active assistance duration and onset timing.This proposed active assistance strategy pro-vides new insights for enhancing the performance of assis-tive robots and facilitating human-robot interaction within the context of ADLs.
查看更多>>摘要：Al-Si alloys manufactured via high-pressure die casting(HPDC)are suitable for a wide range of applications.However,the heterogeneous microstructure and unpredicta-ble pore distribution of Al-Si high-pressure die castings result in significant variations in the mechanical properties,thus leading to a complicated microstructure-property relationship that is difficult to capture.Hence,a computational framework incorporating machine learning and crystal plasticity method is proposed.This framework aims to provide a systematic and comprehensive understanding of this relationship and enable the rapid prediction of macroscopic mechanical properties based on the microstructure.Firstly,we select eight variables that can effectively characterize the microstructural features and then obtain their statistical information.Subsequently,based on 160 samples obtained via the Latin hypercube sampling method,representative volume elements are con-structed,and the crystal plasticity fast Fourier transformation method is executed to obtain the macroscopic mechanical properties.Next,the yield strength,elastic modulus,strength coefficient,and strain-hardening exponent are used to charac-terize the stress-strain curve,and Gaussian process regression models and microstructural variables are developed.Finally,sensitivity and univariate analyses based on these machine-learning models are performed to obtain insights into the microstructure-property relationships of the HPDC Al-Si alloy.The results show that the Gaussian process regression models exhibit high accuracy(R2 greater than 0.84),thus confirming the viability of the proposed method.The results of sensitivity analysis indicate that the pore size exerts the most significant effect on the mechanical properties.Further-more,the proposed framework can not only be transferred to other alloys but also be employed for material design.
查看更多>>摘要：Precipitation is a common phenomenon that occurs during heat treatments.There is internal stress around the precipitate owing to the lattice misfit between the pre-cipitate and matrix.This internal stress has a significant influence not only on the precipitation kinetics but also on the material properties.The misfit stress can be obtained by numerically solving the mechanical equilibrium equations.However,this process is complex and time-consuming.We developed a new approach based on deep learning to acceler-ate the solution process.The training data were first gener-ated by a phase-field model coupled with elastic mechanical equilibrium equations,which were solved using the finite difference method.The obtained precipitate morphologies and corresponding stress distributions were input data for training the physics-informed(PI)UNet model.The well-trained PI-UNet model can then be applied to predicting stress distributions with the precipitate morphology as the input.Prediction accuracy and efficiency are discussed in this study.The results showed that the PI-UNet model was an appropriate approach for quickly predicting the misfit stress between the precipitate and matrix.
查看更多>>摘要：The majority of vehicle structural failures origi-nate from joint areas.Cyclic loading is one of the primary factors in joint failures,making the fatigue performance of joints a critical consideration in vehicle structure design.The use of traditional fatigue analysis methods is constrained by the absence of adhesive life data and the wide variety of joint geometries.Therefore,there is a pressing need for an accurate fatigue life estimation method for the joints in the automotive industry.In this work,we proposed a data-driven approach embedding physical knowledge-guided parameters based on experimental data and finite element analysis(FEA)results.Different machine learning(ML)algorithms are adopted to investigate the fatigue life of three typical adhesive joints,namely lap shear,coach peel and KSⅡ joints.After the feature engineering and tuned process of the ML models,the preferable model using the Gaussian process regression algorithm is established,fed with eight input parameters,namely thicknesses of the substrates,line forces and bending moments of the adhesive bonded joints obtained from FEA.The proposed method is validated with the test data set and part-level physical tests with complex loading states for an unbiased evaluation.It demonstrates that for life prediction of adhesive joints,the data-driven solutions can constitute an improvement over conventional solutions.
查看更多>>摘要：In lightweight automotive vehicles,the applica-tion of self-piercing rivet(SPR)joints is becoming increas-ingly widespread.Considering the importance of automo-tive service performance,the fatigue performance of SPR joints has received considerable attention.Therefore,this study proposes a data-driven approach to predict the fatigue life and failure modes of SPR joints.The dataset comprises three specimen types:cross-tensile,cross-peel,and tensile-shear.To ensure data consistency,a finite element analysis was employed to convert the external loads of the different specimens.Feature selection was implemented using vari-ous machine-learning algorithms to determine the model input.The Gaussian process regression algorithm was used to predict fatigue life,and its performance was compared with different kernel functions commonly used in the field.The results revealed that the Matern kernel exhibited an exceptional predictive capability for fatigue life.Among the data points,95.9％fell within the 3-fold error band,and the remaining 4.1％exceeded the 3-fold error band owing to inherent dispersion in the fatigue data.To predict the failure location,various tree and artificial neural network(ANN)models were compared.The findings indicated that the ANN models slightly outperformed the tree models.The ANN model accurately predicts the failure of joints with varying dimensions and materials.However,minor deviations were observed for the joints with the same sheet.Overall,this data-driven approach provided a reliable predictive model for estimating the fatigue life and failure location of SPR joints.
查看更多>>摘要：The structural optimization of electric vehicles involves numerous design variables and constraints,mak-ing it a complex engineering optimization task over the past decades.Many population-based evolutionary algorithms encounter issues such as converging to local optima and lacking population diversity when tackling such optimi-zation problems.Consequently,the solutions obtained for the optimization may be flawed or suboptimal.To address these problems,an improved genetic algorithm(GA)based on reinforcement learning is proposed in this paper.The proposed method introduces a population delimitation method based on individual fitness ranking.The popula-tion is divided into two parts:the excellent population and the ordinary population,and different selection and cross-mutation methods are applied to each part separately.More efficient crossover and mutation methods are then applied to the ordinary population to enhance the generation of excellent individuals.Furthermore,the proposed approach replaces the traditional fixed crossover and mutation rates with a dynamic selection method based on reinforcement learning to enhance optimization efficiency.A markov deci-sion process model is constructed based on GA environment in this context.The population state determination method and reward method are designed for reinforcement learn-ing in the GA environment,dynamically selecting the most appropriate genetic parameters based on the current state of the population.Finally,the uncertainty in the manufac-turing process is introduced into the optimization problem and the case study results demonstrate that the proposed reinforcement learning-based GA significantly outperforms other evolutionary algorithms when applied to solving the structural optimization of electric vehicles.
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