英语翻译(2).mechanical strengths .A material can be subjected to

英语翻译
(2).mechanical strengths .A material can be subjected to a number of different types of forces .They may be tension ,shear ,torsion ,compression ,or a combination of these forces .Each possible force causes a material to respond in a different way .A material ,therefore,has several different mechanical strengths .The strength depends on the force applied.
The most common mechanical strengths are :
A.tensile strength the maximum tension load a material can withstand before fracturing .Tensile strength is the easiest strength to measure and ,therefore ,is widely used .
B.Compression strength the ability t resist forces which tend to squeeze the material into a new shape .It is basically the opposite of tensile strength .Excessive compression force will cause the material to rupture .
C.Shear strength the ability to resist fracture under shear forces .The shear force is caused by offset forces applied in opposite directions .These forces cause the grains or molecules of the material to slide by one another and eventually fracture .
D.Torsion strength the ability to resist twisting forces .Forces which exceed the torsion strength will cause the material to rupture .
E.Flexure strength the ability of a material to resist the combination of tensile and compression forces .As seen in fig .1.2,when a material is bent ,the material on the inside of the bend must compress while that on the outside portion must stretch .A material must have flexure strength to undergo bending processes .
F.Fstigue strngth the ability to resist forces which vary in direction and /or magnitude .Typical of forces which cause fatigue are constant beding back and forth ,applying and releasingtension forces ,or torsion forces .
G.Impact strength the ability to resist a rapidly applied load .This is a more specific measure of tension or compression strengths .Impact strength determines the ability to absorb a tension or compression load which is quickly applied .Impact strength is often called toughness .The action of a hammer on a nail applies such impacts .forging dies must have high impact strength.
(3).Plastic flow of material in addition to the mechanical properties involving strength ,material have characteristics that govern their be their behavior during the plastic defomation stage .these properties are usually called ductility and creep .
Ductility is the plastic flow characteristic of a material under mormal temperature .The higher the ductility of a material the greater is its ability to be formed without fracturing.Highly ductile materials can be easily bent ,drawn into wire ,or extruded .

机械强度.一种材料可以遭受很多不同种类的作用力.他们可能是拉力,剪力,压力或者是他们的联合.每个可能的力造成材料的不同回应方式.因此,一种有几个不同的“机械强度”.这些强度是建立在说加载的载荷上的.
最典型的机械强度有：
A、抗拉强度 一种材料在断裂前能抵抗的最大拉应力.抗拉强度是最容易测量的强度,因此,它被广泛的应用.
B、抗压强度 抵抗挤压材料变成新形状趋向应力的能力.从根本上是与抗拉强度相反的.极大的挤压应力会造成材料破裂.
C、剪应力 抵抗在遭受剪应力断裂的能力.大小相等的力作用于相反的方向时会产生剪应力.这些力会造成材料的晶粒或者分子从这个滑动到那个上,最后断裂.
D、抗扭强度 抵抗切向应力的能力.超过抗扭强度的力会使材料断裂.
E、抗弯强度 材料抵抗拉应力和压应力共同作用的能力.由图1.2可以看到,当弯曲一个材料时,被弯曲材料的内部肯定受压,以此同时,外面的部分被拉伸.当遭到弯矩时,材料肯定出现抗弯强度.
F、疲劳强度 抵抗方向变力.造成疲劳的典型应力为往复来回地变动的恒力.或者弯应力.
G、抗“冲击强度”（不够专业的翻译） 抵抗忽然迅速加上载荷的能力.它是抗拉强度和抗压强度更具体的测量.冲击强度决定了吸收迅速加上的拉力或者压力的能力.锻模必须有很高的抗冲击强度.
（3）材料的塑性流动 除了涉及强度的机械性能外,材料有统治他们在塑性变形阶段行为的特征.这些性能通常被称为延展性和CREEP.
延展性是材料普通温度下粘性流动的特征.越高的延展性越高的可加工性（没有断裂发生的）.高延展性的材料容易弯曲,拉成电线或者拉伸成实体.