一种集群式指状电磁铁的结构设计及研究

合理的磁路结构及均匀的磁场强度对磁流变抛光效果起着至关重要的作用，基于电磁铁的特性并结合集群磁流变技术，设计了一种集群式指状电磁铁。详细分析了集群式指状电磁铁的结构设计，通过Ansoft有限元仿真对集群式指状电磁铁的结构进行仿真及优化。优化结果显示：当凹槽间隙为1 mm、凹槽深度为2 mm且凹槽进行圆弧处理时，两磁极磁指区域表面可以获得比较均匀的面域磁场。经试验证明，磁极头磁指处磁感应强度的测试曲线与仿真曲线趋势吻合度达87.5%，符合集群效应，磁场强度满足集群磁流变抛光的要求。     

Three‐dimensional analyses of in‐plane and out‐of‐plane crack‐tip constraint characterization for fracture specimens

Three‐dimensional elastic–plastic finite element analyses have been conducted for 21 experimental specimens with different in‐plane and out‐of‐plane constraints in the literature. The distributions of five constraint parameters (namely T‐stress, Q, h, T_z and A_p) along crack fronts (specimen thickness) for the specimens were calculated. The capability and applicability of the parameters for characterizing in‐plane and out‐of‐plane crack‐tip constraints and establishing unified correlation with fracture toughness of a steel were investigated. The results show that the four constraint parameters (T‐stress, Q, h and T_z) based on crack‐tip stress fields are only sensitive to in‐plane or out‐of‐plane constraints. Therefore, the monotonic unified correlation curves with fracture toughness (toughness loci) cannot obtained by using them. The parameter A_p based on crack‐tip equivalent plastic strain is sensitive to both in‐plane and out‐of‐plane constraints, and may effectively characterize both of them. The monotonic unified correlation curves with fracture toughness can be obtained by using A_p. In structural integrity assessments, the correlation curves may be used in the failure assessment diagram (FAD) methodology for incorporating both in‐plane and out‐of‐plane constraint effects in structures for improving accuracy.     

Development of a creep‐free stress‐strain law for fire analysis of steel structures

This paper presents a practical procedure for obtaining creep‐free stress‐strain laws for steel exposed to fire, on the basis of codified stress‐strain laws that consider creep implicitly. The applicability of the proposed procedure has been tested on two commonly used stress‐strain laws for steel at elevated temperature, the Eurocode 3 law and a Ramberg–Osgood model, both of which have implicit consideration of creep. The simulation of two published steel coupon experiments on steel of grades S275 and S355 shows that both the Eurocode and Ramberg–Osgood stress‐strain laws produce inaccurate predictions of creep in fire at elevated temperatures. The proposed procedure was thereby used to extract the implicit creep according to the heating rates of the transient coupon tests and to derive the creep‐free stress‐strain laws. It has been shown that, by combining the creep‐free stress strain law obtained by the proposed methodology with an explicit creep model, a more realistic prediction of steel behaviour in the selected coupon test studies can be achieved. Copyright © 2015 John Wiley & Sons, Ltd.     

对称边界条件下轨道炮有限元／边界元仿真

基于deal．ii编写了电磁轨道炮有限元仿真程序，建立了拉格朗日运动坐标下电磁轨道炮的有限元仿真模型；通过使用有限元边界元耦合方法可以对电磁轨道炮的边界条件进行计算，而无需对轨道炮周边的空气划分网格，是一种处理电磁场边界问题的有效方法；但是，由于边界元方法，使用的是满秩矩阵，在三维情况下计算量大，利用轨道炮的对称性，使用对称边界条件，减少了参与计算的网格数目，从而减少计算量。     

弹带宽度对弹丸挤进过程的影响分析

弹丸挤进过程是火炮发射继点火传火之后的起始阶段，弹带结构对弹丸挤进过程有一定的影响。针对某大口径火炮，基于 Hypermesh和 Abaqus建立5种宽度弹带的挤进过程有限元模型，采用载荷幅值子程序的方法，联合求解内弹道方程组和非线性有限元过程，计算火药燃气压力作为载荷边界条件，进行数值模拟计算。研究结果表明，在相同装药条件下，弹带宽度对挤进终了速度影响较小。较宽弹带受到挤进阻力和摩擦力较大，对应的挤进压力较大，全弹带挤进耗时较长。综合考虑身管寿命、火炮保养和弹带制造成本，59 mm是5种工况中较为理想的弹带宽度。     

A computational framework for scale‐bridging in multi‐scale simulations

A computational framework for scale‐bridging in multi‐scale simulations is presented. The framework enables seamless combination of at‐scale models into highly dynamic hierarchies to build a multi‐scale model. Its centerpiece is formulated as a standalone module capable of fully asynchronous operation. We assess its feasibility and performance for a two‐scale model applied to two challenging test problems from impact physics. We find that the computational cost associated with using the framework may, as expected, become substantial. However, the framework has the ability of effortlessly combining at‐scale models to render complex multi‐scale models. The main source of the computational inefficiency of the framework is related to poor load balancing of the lower‐scale model evaluation We demonstrate that the load balancing can be efficiently addressed by recourse to conventional load‐balancing strategies. Copyright © 2016 John Wiley & Sons, Ltd.     

热轧微合金高强钢卷冷却过程温度场数值模拟

钢卷冷却过程中温度的变化对组织的形成、二次相的析出以及晶粒尺寸起着至关重要的作用，因此，获得钢卷冷却过程的温度场变化规律有重要的现实意义。计算符合实际冷却工艺的比热容及建立钢卷内表面换热系数和钢卷层与层之间热阻的模型，采用Deform-2D软件对微合金高强钢卷自然空冷过程进行数值模拟。比较模拟温降曲线与试验数据，验证了该模型的正确性，并研究分析了钢板厚度和卷取温度对钢卷冷却温度场的影响。结果表明，钢板厚度越大，钢卷温度分布越不均匀，卷取温度越高，钢卷发生相变的时间越长，但钢卷各部位冷速不会因此而改变。     

光纤Bragg光栅可变灵敏度液位传感器设计

为了实现对液位的多灵敏度状态下监测,设计了一种利用光纤Bragg光栅(FBG)的可变灵敏度液位传感探头.将薄膜片上的液体压力通过传压杆传送给悬臂梁,将FBG粘贴于悬臂梁上表面,利用灵敏度变换阀改变悬臂梁长度而改变传感器的灵敏度.对悬臂梁进行有限元仿真优化计算,得到悬臂梁的变形特性.悬臂梁长度分别调节为100,90,80 mm状态下,最大变形出现在悬臂梁尖端,分别为4.266,3.457,2.736 mm,裸光栅粘贴处,对应的灵敏度分别为2.0,1.5,1.0 mm/m,实现灵敏度变换.     

高温条件下沥青路面车辙问题研究

该文基于有限元软件，通过耦合气候温度和太阳辐射，使用连续变温方法分别计算车辙问题。通过研究发现沥青路面的车辙变形规律与温度场分布规律相近，主要是沥青路面与轮胎之间的剪切变形不断积累最终导致车辙的形成。     

轴承预紧力对陶瓷电主轴特性影响分析?

基于170 SD30 SY无内圈陶瓷电主轴转子具有比重轻、耐磨、高弹性模量等优良的综合特性，对不同预紧力载荷下的主轴前端振动位移进行仿真分析；在ANSYS中求解因预紧力在轴承处摩擦产生的温升，并导入整个模型当中，研究整个温度场的分布；对轴承在不同预紧力工况下的使用寿命进行计算分析；依据上述仿真和计算分析，并考虑合理的工况条件下选择合理的预紧力，在该预紧力下进行了振动和温升的实验测量，与仿真进行对比，验证仿真的正确性，从而证明选取预紧力的正确性。