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The yield behavior of aluminum alloy 5754-H111 under different stress conditions for three kinds of plastic work is studied using an anisotropic Drucker model. It is found that when the plastic work is 30 MPa, the anisotropic Drucker model has the most accurate prediction. Comparing the Hill48 and Yld91 models with the Drucker model, the results show that both the anisotropic Drucker and Yld91 models can accurately predict the yield behavior of the alloy. Cylinder drawing finite element analysis is performed under the AFR, but it is not possible to accurately predict the position and height of earing appearance. The anisotropic Drucker model is used to predict the earing behavior under the non-AFR, which can accurately predict the earing phenomenon. Numerical simulation is conducted using three different combinations of yield functions: the anisotropic yield function and the anisotropic plastic potential function (AYAPP), the anisotropic yield function and the isotropic plastic potential function (AYIPP), and the isotropic yield function and the anisotropic plastic potential function (IYAPP). It is concluded that the influence of the plastic potential function on predicting earing behavior is more critical than that of the yield function. [ABSTRACT FROM AUTHOR]

Biodynamic modelling of seat-occupant systems can assist in seat comfort design. A finite element (FE) model of the seated human body, including detailed modelling of the lumbar spine, was established to reflect the human response to vibration and biodynamic response of the lumbar spine under whole-body vibration (WBV). The lumbar spine model was established and validated against the in-vitro results and calculated data. The posture of the lumbar spine was adjusted according to the radiological research results, and the adjusted model was combined to establish a FE model of the seated human body. The present seated human model with backrest inclination angles of 10, 20, and 30°, validated by comparing the measured apparent mass and seat-to-lumbar spine transmissibility, was used to calculate the biodynamic response of the lumbar spine with three inclined backrests under WBV. The results showed that the model could characterise the apparent mass, seat-to-lumbar spine transmissibility, and the biodynamic response of the lumbar spine. Practitioner summary: Biodynamic models can represent dynamic characteristics of the human body exposed to vibration and assist in seat comfort design. The three-dimensional FE model of the human body can be used to explore the human response to vibration and the biodynamic response of the lumbar spine under WBV. [ABSTRACT FROM AUTHOR]

Tikhonov regularization is frequently used to solve the ill-conditioned inverse problem in load identification, and the regularization parameter which plays a significant role in Tikhonov regularization is usually determined by L-curve method. However, two corners appear on the L-curve at some situations, which cause the L-curve method to fail to determine a proper regularization parameter. To improve the accuracy of load identification, a new form of regularization parameter which is based on the largest singular value of the impulse response function matrix and signal-to-noise ratio is developed, and a modified L-curve is plotted. When the norm of the solution and the norm of the residual are balanced, a proper regularization parameter is determined through the modified L-curve. Both simulation and experimental results show that the identified load by the modified L-curve is closer to the actual load than L-curve. It also reveals that the modified L-curve is reasonable and the new regularization parameter is correct, and the accuracy of load identification is improved effectively. [ABSTRACT FROM AUTHOR]

Deconvolution beamforming has gotten increased attention as a way to improve the spatial resolution of delay-and-sum beamforming. It has the ability to decrease sidelobes and increase resolution. However, compared to conventional beamforming, the extra computation of the deconvolution method is a drawback. A more efficient approach is developed to improve the computing speed of the deconvolution method. Specifically, when tackling deconvolution problems, this method improves computational performance by combining Fourier operation with a fast gradient algorithm called the double momentum gradient algorithm. We compare the proposed method with two known effective deconvolution methods, namely the fast Fourier transform non-negative least squares algorithm and the fast iterative shrinkage threshold algorithm. The results of simulation and experiment reveal that the proposed method tends to give a better spatial resolution within a short computational time and is more suitable for engineering applications. [ABSTRACT FROM AUTHOR]

In this article, an optimization procedure of composite structures is proposed and applied to a vehicle subframe redesign. The process is divided into two stages and surrogate models are built by Gaussian Process Regression. The modified Fast Flexible Filling designs is used to deal with the non-rectangular design region problem. And combined with the adaptive sampling method, uniform training and test points which increase the accuracy of surrogate models are obtained. The two established surrogate models are solved by non-dominated sorting genetic algorithm-II and particle swarm optimization algorithm, respectively. The redesigned subframe exhibits significantly weight reduction and performance improvement. [ABSTRACT FROM AUTHOR]

Load identification in structural dynamics is an ill-conditioned inverse problem, and the errors existing in both the frequency response function matrix and the acceleration response have a great influence on the accuracy of identification. The Tikhonov regularized least-squares method, which is a common approach for load identification, takes the effect of the acceleration response errors into account but neglects the effect of the errors of the frequency response function matrix. In this article, a Tikhonov regularized total least-squares method for load identification is presented. First, the total least-squares method which can minimize the errors of the frequency response function matrix and acceleration response simultaneously is introduced into load identification. Then Tikhonov regularization is used to regularize the total least-squares method to improve the ill-conditioning of the frequency response function matrix. The regularization parameter is selected by the L-curve criterion. To validate the performance of the regularized total least-squares method, a load identification simulation with two excitation loads is studied on a plate based on the finite element method and a load identification experiment with two excitation loads is conducted on an aluminum plate. Both simulation and experiment results show that the excitation loads identified by the regularized total least-squares method match the actual loads well although there are errors existing in both the frequency response function matrix and acceleration response. In experiment, the average relative error of the regularized total least-squares method is 13.00% for excitation load 1 and 20.02% for excitation load 2, whereas the average relative error of the regularized least-squares method is 35.86% and 53.09% for excitation load 1 and excitation load 2, respectively. This result reveals that the regularized total least-squares method is more effective than the regularized least-squares method for load identification. [ABSTRACT FROM AUTHOR]

A structural multi-objective topology optimization method integrating the solid isotropic material with penalization (SIMP) approach, compromise programming method and criteria importance through intercriteria correlation (CRITIC) method is proposed. The SIMP approach performs topology optimization. The compromise programming method builds a comprehensive objective function to handle the multi-objective optimization. The CRITIC method, which reflects the contrast intensity and conflicting character of objectives, is applied to determine the weight coefficients of objectives. The conceptual design of a vehicle shock tower is taken as a numerical example. Comparison of the original design and the optimized conceptual design indicates that the stiffness and frequency performance of the shock tower clearly improve as the total weight reduces. Meanwhile, comparison of the weight coefficients and corresponding optimization results produced by the subjective method, CRITIC method, grey comprehensive relational analysis and entropy weight method proves that the CRITIC method is feasible and superior in structural multi-objective topology optimization. [ABSTRACT FROM AUTHOR]