Topology optimization for crashworthiness of thin-walled structures under axial crash considering nonlinear plastic buckling and locations of plastic hinges

Although topology optimization is established for linear static problems, more effort is required for solving nonlinear plastic problems. A new topology optimization approach with equivalent static loads (ESLs) is suggested to find the optimum topologies and locations of plastic hinges of thin-walled crash boxes by considering crash-induced deformation, the main crash energy-absorbing mechanism. Together with finite element method crashworthiness analyses, considering all nonlinearities with rate-dependent plasticity, the method was developed using an appropriate time-incremental scheme of ESLs without removing any high values of loads. Analyses show that the crash boxes with optimum topologies have energy-absorbing capabilities equivalent to the original structure. The proposed method is evaluated for two crashes: a crash box at low speed and a double cell subjected to high-speed collision. The results indicate that this method captures nonlinear crushing behaviours and accurate locations of plastic hinges where, if proper reinforcements are made, energy absorption can be enhanced.     

一种新型包装专用蜡的研制

为了根据某瓦楞纸箱生产厂的实际生产条件制备一种耐热、耐低温、防水、透气等性能优异的包装专用蜡，将58号全炼蜡和70号微晶蜡混合物作为基础蜡料，分别考察添加剂、助剂、抗氧剂等对基础蜡料滴熔点、运动黏度及外观等的影响，确定了最佳制备配方：合成蜡、添加剂B、助剂1、助剂2、抗氧剂加入量（w）分别为基础蜡料质量的9.8%，6.5%，1.5%，2.1%，0.1%。在温度为160 ℃、时间为30 min、搅拌速率为200 r/min条件下制备的包装专用蜡具有熔点高、黏附性强、光泽性好的优点，满足该瓦楞纸箱生产厂的质量和外观要求。     

旋挖钻机设备油液智能分析与健康监测

为了对直升机盒段件入水载荷进行分析，开展了模型垂直入水冲击试验，同时采用有限元-光滑粒子流体动力学（finite element method-smooth particle hydrodynamics，简称FEM-SPH）耦合数值方法进行仿真分析，计算了不同材料构型和速度下的过载、压力及应变结果。与试验结果进行对比表明，仿真结果与试验值吻合较好，预测的结构失效破坏模式与试验结果基本一致，可为真实直升机入水冲击的结构设计提供参考。     

铸造式和焊接式主轴箱体的动态特性对比分析

利用有限元法和试验模态法对立式加工中心的铸造式和焊接式两种结构的主轴箱体进行了模态分析,分别获得了其前六阶固有频率和振型。通过对比两种方法获得的结果,验证了有限元分析模型的有效性。研究表明,两种主轴箱体的阻尼比接近,但焊接式主轴箱体的各阶固有频率均要高于铸造式主轴箱体的各阶固有频率。并且铸造式主轴箱体的固有频率更接近于机床主轴的常用工作频率,焊接式主轴箱体的则远离此频率。因此对于常用主轴转速而言,焊接式主轴箱体的动态性能要优于铸造式主轴箱体的动态性能。     

Analysis of nonlinear thermal radiation and higher‐order chemical reactions on the non‐orthogonal stagnation point flow over a lubricated surface

A numerical study is performed to discuss the heat and mass transfer on oblique stagnation point flow over a lubricated surface with nonlinear thermal radiation and higher‐order chemical reactions. The problem is formulated using basic conservation laws of mass, momentum, energy, and mass concentration in terms of partial differential equations along with nonlinear boundary conditions. These governing equations are transformed into ordinary differential equations by means of similarity transformations. The system of resulting ordinary differential equations are solved numerically by an implicit finite difference scheme known as the Keller–box method. The quantities elaborated in the problem, such as velocity, temperature, skin friction, and local Nusselt and Sherwood numbers are analyzed for several values of involved parameters. The obtained results are presented through various graphs and tabular data and showed a good agreement with the existing results in the literature, which are the subcases of the present work. The heat transfer rate enhances with nonlinear thermal radiation and mass transfer rate decreases with increasing the order of chemical reaction.     

铝合金拐臂盒件铸造工艺优化

铝合金拐臂盒铸件轴孔处容易产生缩松缺陷,对此进行了原因分析和工艺改进。依据铸造凝固理论结合实际生产经验,采用不同热导率的金属材料的冷铁及增加工艺补贴等方法,对铸造工艺进行优化。优化后经过X光无损检测及机加工验证,成功解决了轴孔处缩松的铸造缺陷。