三维CAD环境下压力中心的快速求解

在综合分析了目前压力中心求解方法的基础上,提出了以求解工艺件所受压力束面的重心来求解压力中心的方法,该方法将工艺件轮廓线所受均布载荷等效为同重量压力束面的载荷,将压力中心的计算转化为轮廓线所受压力束面重心的计算,进而在三维CAD环境下通过计算面的重心,快速地实现了压力中心的精确求解。在CATIA平台上实现了通过压力束面重心求解压力中心的方法,并以实例验证了该方法的有效性和实用性。     

基于CATIA的冲模压力中心快速定位的研究

目前冲模系统中压力中心的求解方法通常采用解析法和作图法。计算量大。操作繁琐。笔者提出了计算工艺件壳体重心求解压力中心的方法，在CATIA平台上实现了冲模压力中心的快速定位，操作简单方便，工作效率较高。     

用MasterCAM快速确定冲裁压力中心

在模具设计中，冲裁模压力中心通常采用解析法或图解法求解。文中提出一种用MasterCAM绘图软件在设计制图时直接求解的方法，快速直接，简单方便，精度较高。     

管路计算的直接图表法

一、前言在管路计算中,常遇到下列二种情况: (1)已知管径、管长和允许的压力损失,求流速; (2)已知管长、流速及允许的压力损失,求管径。由于流速或管径未知,不能计算雷诺准数Re,因此无法判断流动类型,以求得摩擦系数λ。这时,管路计算常采用试差法。试差法虽能求解,但由于计算繁杂,给工程计算带来很多不便。为避免求解隐函数,作者经分析计算并给出相应的Re-λRe~2及Re-λRe~(-1)关系图,采用直接图表法求解流速或管径。该图的原始数据系采用电子计算机求得,图表中     

基于AutoCAD2000的冲模压力中心确定方法

在冲模设计中。冲模压力中心通常采用计算法(解析法)或作图法求解。文章提出了一种基于AutoCAD中“工具”的压力中心确定方法。快速直接。简单方便。精度较高。并举出应用实例。此方法可以替代原有方法。值得推广。     

基于转矩平衡和模拟退火的级进模压力中心优化研究

针对级进模压力中心的求解及优化,提出应用转矩平衡原理建立带料压力中心求解模型的方法,推导出了压力中心与滑块中心偏离值、滑块中心两侧转矩偏移等量随时间变化的计算公式。在中心偏移优化法的基础上,提出了一种使滑块中心两侧转矩偏移最小的优化方法,建立了相应的目标函数与约束函数。结合有限元模拟技术,计算了各工序中凸模的冲压力随时间的变化情况,并使用模拟退火算法,迭代求解了最优带料压力中心偏移值。以壳形电子零件的级进模为例,与理论计算作比较,验证了上述方法的有效性。     

面域法求解冲模压力中心

在冲裁时,模具压力中心可视为用均细杆按分离曲线所围成构件的重心,其冲裁力按刃口长度分布;在校平时,模具压力中心则与相应轮廓均质薄板的重心重合,其压力中心按受压面积分布。因为工序类型不同,则工作压力的分布情况不同,压力中心的求法也就不同。下面就CAD面域法求解模具压力中心的方法论述如下。 1.开式剪切 设有一半径为R、顶角为2α的圆弧,见图1。 面域法就是把AB弧视为中性层,通过编辑,将AB弧转化成一个细长的封闭图形,再生成面     

冲裁模刃口尺寸的尺寸链计算法

本文分析讨论了按传统方法在设计计算冲模刃口尺寸方面存在的问题．提出了运用尺寸链原理来求解刃口尺寸的新方法,以使计算简便,所确定的刃口尺寸更为合理．     

冲裁模刃口尺寸的链计算法

本文分析讨论了按传统方法在设计计算冲模刃口尺寸方面存在的问题，提出了运用尺寸链原理来求解刃口尺寸的新方法，以使计算简便，所确定的刃口尺寸更为合理。     

计算应力强度因子的无网格-直接位移法

目前计算裂纹尖端应力强度因子的无网格法一般均采用。积分方法，但由于该方法为间接求解，降低了求解精度与求解效率。文中采用无网格—伽辽金方法，选取带有扩展基的奇异基函数，以精确计算裂纹尖端位移场，并借鉴有限元法中计算应力强度因子的直接位移法，提出一种计算含裂结构裂纹尖端应力强度因子的新方法，即无网格—直接位移法。数值计算结果表明，该方法具有简捷、高效的特点，可以准确计算裂纹尖端应力强度因子。     

SIMUUTION OF ELECTROMAGNETIC TUBE BULGING BASED ON LOOSE COUPLING METHOD

A loose coupling method is used to solve the electromagnetic tube bulging. ANSYS/ EMAG is used to model the time varying electromagnetic field with the discharge current used as excitation, in order to obtain the radial and axial magnetic pressure acting on the tube, the magnetic pressure is then used as boundary conditions to model the high velocity deformation of tube with DYNAFORM. The radial magnetic pressure on the tube decreases from the center to the tube end, axial magnetic pressure is greater near the location equal to the coil height and slight in the other region. The radial displacement of deformed workpieces is distributed uniformly near the tube center and decreases from the center to the end; Deformation from the location equal to coil height to the tube end is little. This distribution is consistent with the distribution of radial pressure; Effect of the axial magnetic pressure on deformation can be ignored. The calculated results show well agreements with the experimental results.     

基于胎压监测的自卸车车载称重系统设计

提出了一种基于胎压监测的车载称重系统解决方案。在车辆胎压实时监测的基础上,通过胎压变化测量车辆载重反应车辆的超载情况,并通过控制车辆熄火、取力器工作、气路建立以及车载仪表显示等多种方法进行超载管控,此外通过GPS／GPRS实现车辆的定位以及与车辆远程控制中心的通信。     

Mechanical error analysis of disk cam mechanisms with a flat-faced follower

By employing the concept of equivalent linkage, this paper presents an analytical method for analyzing the mechanical errors of disk cam mechanisms with a flat-faced follower. The resulting error equations do not really involve the location of the curvature center of the cam profile, and locating the curvature center of the cam profile is not essential. The resulting errors are significantly affected by the pressure angle, and the smaller pressure angle will result in the smaller mechanical error. In the worst case, owing to the joined effects of various design parameters, the accuracy of the follower motion may degrade considerably. For the oscillating follower case, all acceleration error functions have a sudden change at every beginning and at every end of the motion even though the theoretical follower displacement is cycloidal motion.     

Dynamic Analysis of Plain Bearings in a Positive-Displacement Rotary Compressor

This paper discusses the dynamic performance of plain bearings in a positive displacement rotary compressor. It includes dynamic bearing loads produced by rotor unbalance and cyclical loads produced by gas compression forces acting on the rotor. With the aid of the short-bearing approximation, bearing center loci and oil film pressure distributions are determined. The optimum location of oil film feed groove for the bearings of such a compressor is discussed.     

Sliding of a solid body supported by a round platform on a horizontal plane with orthotropic friction. Part 1. Regular load distribution

The problem of stopping a solid body supported by a round platform on a horizontal plane is discussed assuming that the pressure is distributed regularly and the force of friction features orthotropic properties. The assumption of location of the instant center of speeds at the moment of stopping is proven. The obtained results can be applicable to simulation of the motion of a solid body supported by a round platform during the solution of problems of erosive wear.     

购物中心选址分析

适当的用地和合适的位置是购物中心开发的先决条件,购物中心对区位有严格要求,这关系到未来商业经营的成败。用地的地理位置和周围地区的经济状况与人口状况决定购物中心能否生存。文章选取购物中心为研究对象,详细分析了购物中心的选址问题,这一问题的提出将对购物中心的规划和建筑设计产生深远的影响。     

西门子系统中孔心坐标的确定

在加工中心加工中,有很多情况要使用预制孔或基准孔定位,而孔心位置的确定对加工起着至关重要的作用。以西门子802D系统为例,以一种简单的方法快速准确地确定孔心坐标。     

Sliding of a solid body borne on a circular area over a horizontal plane with orthotropic friction. Part 2. Pressure distribution according to the Bussinesque law

The problem of stopping of a solid body when it is borne on a round-shaped horizontal plane is studied, assuming that the pressure is distributed according to the law of Bussinesque and the forces of friction are characterized by orthotropic properties. An inference on the location of the instant center of velocities at the moment of stopping is proven. The obtained results may be of practical use in the simulation of the motion of a solid body borne on a round area for solving contact problems and investigating erosive wear.     

基于Moldflow的魔方中心轴注射分析与优化设计

应用Moldflow软件对魔方中心轴的注射成型过程进行浇口位置、充填、冷却和翘曲等模拟分析。通过在不同注射工艺条件下进行对比分析,确定了注射的最佳工艺参数:充填时间为2 s,注射+冷却时间为8 s,模具温度为40℃,熔体温度为240℃,注射压力为100 MPa。应用UG软件建立了注射模具的实体模型,解决了传统注射模具设计方法存在设计周期长、成本高且质量难以保证等问题。     

Static and Dynamic Slider Air-Bearing Behavior in Heat-Assisted Magnetic Recording Under Thermal Flying Height Control and Laser System-Induced Protrusion

The air bearing’s response to regions of elevated temperature on its bounding surfaces (the slider and disk) may be an important consideration in the head–disk interface design of heat-assisted magnetic recording (HAMR) systems. We implement the general non-isothermal molecular gas lubrication equation into an iterative static solver and dynamic air-bearing solver to evaluate the effect of localized heating of the air-bearing surface (ABS) due to the near-field transducer (NFT). The heat-dissipating components in our simplified HAMR design are the NFT, laser diode, and thermal flying height control (TFC) heater. We investigate the effect of each HAMR slider component on ABS temperature and thermal deformation and the slider’s flying height. The NFT induces a localized thermal spot and protrusion on the larger TFC bulge, and it is the location of maximum temperature. This ABS temperature profile alters the air-bearing pressure distribution, increasing the pressure at the hot NFT location compared with predictions of an isothermal air-bearing solver, so that the center of the pressure acting on the ABS is slightly closer to the trailing edge, thereby decreasing the pitch angle and increasing the minimum flying height. Other researchers have shown that the NFT’s thermal response time may be much faster than its protrusion response time (Xu et al. in IEEE Trans Magn 48:3280–3283, 2012). The slider’s dynamic response to a time-varying NFT thermal spot on the ABS while the combined TFC and NFT induced thermal protrusion remains constant is investigated with our dynamic air-bearing solver. We simulate the slider’s step response to a suddenly applied ABS temperature profile and a pulsed temperature profile that represents laser-on over data zones and laser-off over servo zones. The sudden (step) or rapid (pulse) increase in ABS temperature induces a sudden or rapid increase in pressure at the NFT location, thereby exciting the air bearing’s first pitch mode. For the slider design and simulation conditions used here, the result of the pitch mode excitation is to alter the position of the center of pressure in the slider’s length direction, thereby changing the pitch moment. In response, the pitch angle and minimum flying height change. The step response decays after approximately 0.15 ms. Because the laser duty cycle is much shorter than this response time, a periodic disturbance is predicted for the center of pressure coordinate, pitch angle, and minimum flying height. The peak-to-peak minimum flying height modulations are relatively small (only up to 0.126 nm); more significantly, the time-averaged minimum flying height increases 0.5 nm for the NFT that reached 208 °C compared to simulations of the isothermal ABS at ambient temperature.