各位前辈，帮小弟翻译一篇机械专业英语课文！
作者：cad 提交日期：2009-7-6| 分类: | 访问量：
各位前辈，帮小弟翻译一篇机械专业英语课文！
建议先自己翻译，碰到有疑问的再具体求助。
By：terry_d
书到用时方恨少。。。。单词都能看懂，可连在一块就不知道啥意思了。
在此小弟恳求各位前辈了，还请版主支持一下！！！
文章如下：
Deep Drawing
In sheet metal,drawing is a process of forming flat sheet metal into hollow shapes by mean of a punch that causes the metal to flow into the die cavity .If the depth id one or more times the diameter,the process is called deep drawing.The forming of shallow shapes is something referred to as stamping,but the distinction is not clear since stamping is also used to describe cutting flat figures or patterns.
In deep-drawing,also called cup or radial drawing,a parallel-walled cup is created from aflat blank (fig8-6).the blank may be circular,rectangular,or of a more complex outline.
the blank is drawn down into the die cavity by action of the punch.deformation is restricted to the flange and draw radius.No deformtion occurs under the bottomof the punch.as the punch forms the cup,the amount of materialin flange decreases.
In drawing,the limit of defoormation is reached when the load required to deform the flange becomes greater than the local-carrying capacity of the cup wall.The hold-down pressure on top of the blank must be sufficient to keep the material from wrinkling as it goes into the die.The deformation limit(limiting drawing ratio or LER)is the maximum blank diameter that can be drawn into a cup without failure.The percentage of reduction can be caluculated as follows:
%Reduction=(D-d)*100/D
The calculations is usually made with the cup-wall inside diameter,which would also be the draw-punch diameter.A drawing ratio or percentage reduction of 48 is considered excellent on the first draw.Succeeding draw must be reduced.That is the perecntage reducetion that can be expected under favorable conditions without annealing,for a second draw would be about 30% and about 20% for a third draw.
Most drawing operations start with a sheet metal blank whose surface are is only slightly larger than the finished product,allowing just enought material to hold the blank during the drawing operations and for trimming after drawing.
There should be no appreciable change in the thickness of the material between the blank and the finished part.When it is desirable to reduce the metal thickness,it may be done in secondary operations as in ironing.
The die cushion,which is umderneath the press bed,holds the blank against the punch in the initial stage of operation.Then as the punch descends,the cushion also moves down,maintaining contact with the blank.When the stroke is completed,the die cushion returns to its original position,flush with the top of the punch.This action strips the part off the punch.Presses are not ordinaril equipped with a die cushion,but this attachment greatly extends the versatility of the press.The cushion may be spring,air,or hydraulically actuated.
As the metal starts to move into the die ,bending occurs.Greater depth is obtained by drawing or pulling in metal form the flange region.The bottom of the cup is compledted in the first stage.Very large,compressive forces occur in the flange and die radius area.Normally,wrinkles would start to form as the metal is pulled over the die radius.Fortunately,the proper application of a blank holder can keep the wrinkles form forming.However,if the blank-holding pressure is too great,the metal will tear.
The final stage is a continuation of the two previous stages of bending,compressing,ivercoming friction,and starightening.
Important variables of the drawing operation are firction,squeezing force,and formability of the metal.
The amount of friction encoutered will be dependent on the surface finish of the metal and die components and blank-holding force.Friction is usuall reduced by the use of the proper drawing compounds.
The squeezing force that takes place in the flange and draw redius is related to the percentage reduction of area,ductility of the metal,yield strength,blank thickness,temperature,and the depth of draw.How sell the metal forms will be governed by the strain-hardening exponent and average strain ratio.
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话是这样说没错，可是你好歹总能用工具书把每个单词的意思查出来吧，自己组合一下，如果有专业术语再来问吧
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Deep Drawing
深冲压
In sheet metal,drawing is a process of forming flat sheet metal into hollow shapes by mean of a punch that causes the metal to flow into the die cavity .If the depth is one or more times the diameter,the process is called deep drawing.The forming of shallow shapes is something referred to as stamping,but the distinction is not clear since stamping is also used to describe cutting flat figures or patterns.在板金上，拉伸是一个通过冲床将平板金属冲入模腔拉成中空形状工件的工艺过程。如果拉伸深度是直径的一倍或者更大倍数的时候，这个过程就叫做深冲压。形成中空形状的形式和印花有点相似，但是区别并不明显，因为印花也是用来描述切削平直图形或者图案。
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在钣金上，冲压成型是一个通过冲床使平钣金金属进入型腔而形成凹形的过程。如果冲压深度是直径的一倍或几倍，这样的过程称为深冲压。形成凹形的过程和模锻有些相似，这两者之间的区别不是很明显
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最后一段：
The squeezing force that takes place in the flange and draw redius is related to the percentage reduction of area,ductility of the metal,yield strength,blank thickness,temperature,and the depth of draw.How sell the metal forms will be governed by the strain-hardening exponent and average strain ratio.
在凸、凹缘半径处的挤压力与断面收缩比、金属延展性、屈服强度、边厚度、温度及冲压深度有关。如何选模由加工硬化指数和平均应变比例所决定。
*本文摘自：http://www.jxcad.com.cn/read.php?tid=509490&fpage=2
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