英语翻译

题目

英语翻译
2.Thermal Modelling of Grinding
The finite element model proposed is based on Jaeger's model [2]; it is a 2D model and the grinding wheel is considered to be a moving heat source,see Fig.1.The heat source is characterised by a physical quantity,the heat flux,q,that represents the heat entering an area of workpiece per unit time and is considered to be of the same density along its length,which is taken equal to the geometrical contact length,l.which is calculated from the relation where a is the depth of cut and d ,is the diameter of the gringing wheel .The real contact length is expected to be large owing to the deflection of the grinding wheel and the workpiece in the contact area.Nevertheless,as a first approximation,the geometrical and real contact lengths are considered to be equal.The heat flux can be calculated from the following equation Where is the percentage of heat flux entering the workpiece,the tangential force per unit width of the workpiece,the peripheral wheel speed and the geometrical contact length.The proportion of the heat flux entering the workpiece can be calculated by a formula suggested by Malkin [3,4] for grinding with aluminium oxide wheels,as where is the energy required for chip formation,having a constant value of about 13.8 J mm-3 for grinding all ferrous materials and u is the total specific grinding energy required for grinding,calculated from where is the workspeed and,consequently,as in Jaeger's model,the speed of the moving heat source.Note that,in both Eqs (2) and (4),the value of ,is required in order to calculate the heat flux and the total specific grinding energy,respectively; it can be calculated from where is the power per unit width of the workpiece,which was measured during the testing of the different grinding wheels.Therefore,from Eqs (2)一(5),the heat flux can be calculated for every case.The kind of modelling suggested in this paper is suitable for a grinding process with a very small depth of cut,since there is no modelling of the chip.In any other case,other assumptions must be made for the chip in order to provide a valid model,since the heat carried away by the chip cannot be neglected.Furthermore,the two coef- ficients of the workpiece material that are related to temperature,i.e.the thermal conductivity and the specific heat capacity,along with the density of the workpiece must be inserted as inputs to the program.For the material used in the wheel testing,those quantities were taken from the FEM program data bank.The first two were considered to be temperature dependent.

答案

积的模型[2]提出的有限元模型的基础上,它是一个二维模型,被认为是一个移动的热源和砂轮,见图.1.热源的特点是一个物理量,热通量,Q,表示进入了一个面积在单位时间内工件的热,被认为是相同的密度沿其长度,这是采取的几何接触长度等于湖这是从关系,其中一个是削减和D的深度计算,gringing轮的直径.真正的接触长度预计要大,由于砂轮和工件的接触面积的挠度.然而,作为第一个近似,几何和真正接触长度被认为是平等的.进入工件,每单位宽度的工件,外围轮速度和几何的接触长度的切向力的热通量的百分比在哪里从下面的公式可以计算热流.进入工件的热通量的比例建议由一个公式可以计算出马尔金[3,4]与三氧化二铝轮磨,芯片形成所需的能量,有一个恒定值约13.8 J毫米磨有色金属材料和U 3是总具体磨进行研磨所需的能源,其中是计算的workspeed,因此,在Jaeger的模式,移动热源的速度.需要注意的是,在式（2）和（4）的价值,是必需的,以计算热通量和总额比磨削能,分别是每单位宽度的力量在哪里,它可以计算工件,这是在测试不同的砂轮测量.因此,从式（2）一（5）,热通量,可以计算出每一种情况下.本文提出一种建模是适合一个非常小的深度与切的研磨过程的,因为没有芯片的建模.在任何其他情况下,其他的假设必须作出的芯片,以提供一个有效的模型,因为热量由芯片进行了不可忽视.此外,两个工件材料与温度有关的系数ficients,即导热系数和比热容,以及工件的密度必须插入作为程序的输入.轮测试中所用的材料,这些数量有限元程序的数据银行.前两个被认为是随温度变化的.