Xu Han

Crashworthiness optimization design of honeycomb sandwich panel based on factor screening

This paper presents a crashworthiness robust optimization design of aluminum honeycomb sandwich panel with regular hexagonal core cell based on explicit finite element analysis. First, the crashworthiness of honeycomb sandwich panel and the bare honeycomb core are compared with each other in the aspects of specific energy absorption and peak crushing force. The comparative results show that honeycomb sandwich panel can absorb more energy than the bare honeycomb core, though the peak crushing force of honeycomb sandwich panel is larger. Then the factor screening experiments are carried out to find out variables that have significant effects on the crashworthiness of honeycomb sandwich panel. The ultimate purpose of factor screening experiments is to decrease the computational expense by reducing the number of design variables. Finally, the dual response surface method and the crossed array design are employed to formulate the complex robust optimization design problem. The regression expressions of specific energy absorption and peak crushing force are defined as the objective and constraint function respectively in the robust design of crashworthiness optimization.

Optimization design of corrugated beam guardrail based on RBF-MQ surrogate model and collision safety consideration

Multiobjective optimization design was made for two corrugated beam guardrails.RBF surrogate model based on collision safety consideration was used for regression analysis.Comparative studies were made between W-beam guardrail and Thrie-beam guardrail. As the main safety facility on the highway, a guardrail system is very essential for the highway traffics safety. In this paper, the Finite Element (FE) models of the vehicle and the corrugated beam guardrail system were created. Two types of widely used corrugated beam semi-rigid guardrails were simulated, which were the W-beam guardrail and the Thrie-beam guardrail. The collision between the corrugated beam guardrail systems and the vehicle body was analyzed. In the collision process, the snagging effect of the post to the vehicle body was also concerned. Under the considerations of the collision safety and the mechanism of the snagging effect, the multiobjective optimization problem was defined with dimensional sizes of guardrails to be the design variables. And the radial basis function (RBF) was applied to construct the regression models of the analytical objective, which increased the accuracy of fitting. The Pareto set and the optimal solution were obtained. After the optimization design, the W-beam guardrail and Thrie-beam guardrail were both greatly improved, that increased the collision safety between the corrugated beam guardrail and the vehicle body. This kind of analytical method can also be used for the crashworthiness optimization between any other cars and guardrails.

Real-Time Composition Monitoring Using Support Vector Regression of Laser-Induced Plasma for Laser Additive Manufacturing

Laser additive manufacturing has gained widespread adoption in recent years. However, process diagnosis and process control lag behind the progresses of other key technologies, which make the product quality control a challenging problem. This work proposes an operating parameter conditioned support vector regression (SVR) method that uses processing parameter conditioned kernel function to achieve a processing parameter independent in-situ composition prediction. Two different features of laser-induced plasma, spectral line-intensity-ratio, and both spectral line-intensity-ratio and spectral integrated intensity were used to train the SVR. Composition measurements using a calibration curve method, partial least square regression, and artificial neural networks are also performed for comparison. The results show that the SVR with both spectral line-intensity-ratio and spectral integrated intensity as inputs has the best performance due to linearly separable point clusters in the high-dimensional space. Laser power independent composition prediction is achieved and real-time composition predictions are validated. It is proved that the operating parameter conditioned SVR provides a more accurate, a more universal, and an operating parameter independent prediction. Moreover, operating parameter conditioned SVR provides a potential data-driven-based approach for real-time composition monitoring of the laser additive manufacturing process.

OPTIMIZATION DESIGN OF NJ SHAPED GUARDRAIL BASED ON COLLISION SAFETY CONSIDERATION

Cross-sectional shapes and dimensions of concrete guardrails directly influence climbing angles and directions of a car when a collision between concrete guardrail and car occurs. At the same time, contacting and climbing angles and directions influence the peak crushing force and the peak acceleration of a car body during a collision. Therefore, cross-sectional shapes and dimensions of concrete guardrails can influence the severity of injuries sustained when a collision between concrete guardrail and car occurs. In this study, the passive safety of a car body is considered in optimizing the cross-sectional dimensions of a New Jersey (NJ) concrete guardrail based on numerical simulations and surrogate model techniques. Optimal Latin hypercube design is used to get sampling points, and multi-island genetic algorithm is utilized to obtain the optimal size of NJ concrete guardrail in the optimization process. After simulating the collision between car and optimal NJ shaped guardrail, the results show that the peak acceleration of optimal results reduces significantly by 28% compared with the initial value, and the peak interface force decreases from 378.6 kN to 241.5 kN.

Identification of dynamic load for prosthetic structures

Dynamic load exists in numerous biomechanical systems, and its identification signifies a critical issue for characterizing dynamic behaviors and studying biomechanical consequence of the systems. This study aims to identify dynamic load in the dental prosthetic structures, namely, 3-unit implant-supported fixed partial denture (I-FPD) and teeth-supported fixed partial denture. The 3-dimensional finite element models were constructed through specific patients computerized tomography images. A forward algorithm and regularization technique were developed for identifying dynamic load. To verify the effectiveness of the identification method proposed, the I-FPD and teeth-supported fixed partial denture structures were investigated to determine the dynamic loads. For validating the results of inverse identification, an experimental force-measuring system was developed by using a 3-dimensional piezoelectric transducer to measure the dynamic load in the I-FPD structure in vivo. The computationally identified loads were presented with different noise levels to determine their influence on the identification accuracy. The errors between the measured load and identified counterpart were calculated for evaluating the practical applicability of the proposed procedure in biomechanical engineering. This study is expected to serve as a demonstrative role in identifying dynamic loading in biomedical systems, where a direct in vivo measurement may be rather demanding in some areas of interest clinically.