Factors affecting stretching limits of Aluminum sheet

The purpose of the present paper is to study methods to improve the stretching limit of metal sheet. The factors affecting the stretching limit were sheet thickness, blank diameter, blank holding pressure, and forming rate. Punch radius, die radius, and clearance between a punch and a die were retained constant. Tested materials were softened and half hardened types of aluminum sheet. The effect of lubrication was also studied. Lubricants used were a press working oil and graphite. Stretching by two types of punch shape, a spherical head punch and a truncated cone one, was tried in order to research the effect of punch shape. The half hardened aluminium, which has a larger n-value, showed the larger stretching limit. The larger thickness gave rise to the larger stretching limit. Flow characteristic of materials was poorer in larger diameter of a blank, so its stretching limit was lower. A bit lower holding pressure, which allows drawing of materials to some extent, yielded larger stretching limit than rigid holding. The forming rate did not so much affect stretching limit. Concerning the effect of lubrication, applied position of lubricants was important.     

A novel approach for predicting the tensile strength of brazed joints

A method for predicting the tensile strength of brazed joints is presented. A finite element method (FEM) of analysis is used, taking into account the failure within the soft interlayer metal region of the joint. A modified failure criterion is derived in consideration of void growth and incorporated into the FEM analysis. The predicted tensile strength is discussed and compared with experimental results obtained from titanium joints brazed with aluminum.     

Conjugated heat transfer to laminar flow with internal heat source in a parallel plate channel

A steady heat transfer problem was analyzed as a conjugated problem between a fully-established laminar flow and the duct wall, under two kinds of boundary conditions at the outer wall surface. The internal heat generation is described as a linear function of the fluid temperature. The influence of the heat conduction in the wall was found to be important for the case with small wall conductance under a boundary condition of the first kind, and also for the large wall-conductance case under the second condition. Such influence is more significant for the case with an internal heat source.     

中型载货车车身扭转刚度对车辆侧翻特性的影响

因为较小的轮距和车辆质心高度的比值,较长的轴距和较大的惯性距,控制货车车辆侧翻操纵稳定性是最重要的特性。而较长的轴距,造成车身扭转刚度降低。因此,要研究其对车辆侧翻特性的影响。我们进行了对中型载货汽车的仿真分析和试验,用改变车辆参数研究车辆的频率响应特性。结果表明,车身扭转刚度降低,增大前倾角的稳态增量,不影响车辆运动的侧滑和侧翻特性。因此,即使车身扭转刚度不可避免地较低,采用增大前悬架的侧倾刚度,减小前倾角,可保持合适的车辆操纵稳定性。     

饱和砂土液化后的剪切吸水效应

饱和土在自然排水条件下随着剪切作用而发生的含水量增大的行为和过程被称为剪切吸水现象。本文发展了一种新的试验方法,成功地再现了从较松到密实状态的饱和砂土在振动液化后的剪切吸水现象,探讨了剪切吸水速率对饱和砂土液化后应力应变关系的影响。试验结果表明,具有相同密度的饱和砂土,其液化后的应力应变关系随剪切吸水速率的不同而呈现出硬化、理想塑性及软化的不同变化。文中给出了判定这些不同的液化后应力应变响应产生的条件