一种精确积分的四边形四结点等参单元

针对平面问题四边形四结点单元，提出一种新的等参变换方法。采用平行四边形母单元和相应的形函数，推导出四边形四结点等参单元刚度矩阵的精确积分解。理论和数值分析表明，该方法从根本上克服了数值积分带来的误差，计算单元刚度矩阵的速度比传统的高斯两点积分方法快近三倍。     

稀土元素在铬钒共渗中的作用

研究了稀土元素在铬钒共渗过程中的作用。结果表明,稀土元素能有效地改善铬钒共渗层结构,提高共渗层生长速度和性能。讨论了稀土元素的催渗机理。     

有限元结构分析神经网络计算

采用精确积分四边形单元刚度矩阵,构造一种多层反馈神经网络以实现平面问题有限元结构分析,其中间层神经元联接权值为求解问题的单元刚度矩阵。分析和数值仿真结果表明,该神经网络稳定收敛于有限元模型解,为有限元结构分析并行计算提供一种新的方法。     

用于复合材料板、壳结构的退化的等参壳元

研究了用于复合材料板、壳结构分析的退化的等参壳元．数值计算结果表明,该单元不仅适合厚的和中厚的复合材料板、壳结构的分析,而且在采用了“节减积分”或“选择积分”技术之后,也同样适合复合材料薄板和薄壳的计算．     

火炮整体动态分析与土壤的耦合作用

本文以85加农炮为实例,根据实测结果,估计了土壤的物理参数,从而确定了火炮的边界条件;用塑性杆元及线性阻尼器模拟了驻退机、复进机的作用;在此基础上,建立了火炮整体的有限元模型。所得计算结果与实测结果符合较好。     

二维周期钢管阵列带隙特性计算中的时域有限差分算法

通过选取合适的离散时间间隔,解决了大密度、弹性常数差界面上时域有限差分(FDTD)算法的不稳定现象。进而采用改进的O(2,4)精度FDTD算法,计算了由空气中二维周期钢管正方阵列组成的晶格常数为103mm的声子晶体的Г Х方向禁带,计算结果与测试结果吻合较好。     

基于ANSYS的预应力CFRP布加固混凝土梁有限元分析

采用ANSYS有限元分析软件,对卸载或不卸载时预应力碳纤维(CFRP)布加固梁进行仿真分析,并在有限元分析中提出了施加预应力的方法(升温法),以及利用单元的生与死实现不卸载时加固的方法。通过实例对比分析表明,基于ANSYS的有限元分析结果与试验分析结果吻合较好,可在一定程度上有效替代试验分析方法,从而减少试验所需的时间和费用,对后续的CFRP布加固混凝土结构的研究工作具有一定的参考价值。     

Optimization of buckling load for laminated composite plates using adaptive Kriging-improved PSO: A novel hybrid intelligent method

An effective hybrid optimization method is proposed by integrating an adaptive Kriging (A-Kriging) into an improved partial swarm optimization algorithm (IPSO) to give a so-called A-Kriging-IPSO for maxi-mizing the buckling load of laminated composite plates (LCPs) under uniaxial and biaxial compressions. In this method, a novel iterative adaptive Kriging model, which is structured using two training sample sets as active and adaptive points, is utilized to directly predict the buckling load of the LCPs and to improve the efficiency of the optimization process. The active points are selected from the initial data set while the adaptive points are generated using the radial random-based convex samples. The cell-based smoothed discrete shear gap method (CS-DSG3) is employed to analyze the buckling behavior of the LCPs to provide the response of adaptive and input data sets. The buckling load of the LCPs is maximized by utilizing the IPSO algorithm. To demonstrate the efficiency and accuracy of the proposed methodology, the LCPs with different layers (2, 3, 4, and 10 layers), boundary conditions, aspect ratios and load patterns (biaxial and uniaxial loads) are investigated. The results obtained by proposed method are in good agreement with the literature results, but with less computational burden. By applying adaptive radial Kriging model, the accurate optimal results-based predictions of the buckling load are obtained for the studied LCPs.     

Bionic stab-resistant body armor based on triangular pyramid structure

A stab-resistant substrate was designed and realized with a triangular pyramidal structure, inspired by the biological armor model in nature. The stab-resistance behavior and dynamic response mechanisms were studied through numerical simulation and experimental testing of a knife impacting a substrate, and an optimal structural design was obtained accordingly, with a tilted angle of 22.5° and optimal thickness of 1.2 mm. It was shown that the triangular pyramidal structure generated twice the internal energy of the knife than the flat substrate due to the dispersing effect of the structure. The force parallel to the inclination caused a significant scratch on the substrate surface, while the force perpendicular caused obvious substrate deformation. A new riveting method was used to form the total layer, which passed the GA 68—2008 standard. The stab-resistant clothing coupled with the reduced wearing burden could provide effective protection and avoid fatal injuries on security personnel working in dangerous environments. The method provided may enlighten the future design and manufacturing of stab-resistant clothing.     

Dynamic necking of a near α titanium alloy at high strain rates:Experiments and modelling

The tensile behaviour of near α Ti3Al2.5 V alloy, conceived for applications in aerospace and automotive engineering, is characterized from quasi-static to high strain rates. The material is found to present noticeable strain rate sensitivity. The dynamic true strain rate in the necking cross-section reaches values up to ten times higher than the nominal strain rate. It is also observed that beyond necking the dynamic true stress-strain curves present limited rate dependence. The experimental results at different strain rates are used to determine a suitable constitutive model for finite element simulations of the dynamic tensile tests. The model predicts the experimentally macroscopic force-time response, true stress-strain response and effective strain rate evolution with good agreement.