Value - значение, величина

fabricated member or product - производимая промышленная деталь

eyebar - стержень с проушиной

ferrous and non-ferrous metals - черные и цветные металлы

sample - образец, проба

cast iron - чугун

tile - керамическая плитка

N 9

MECHANICAL PROPERTIES FOR THE ELASTIC RANGE

(I)

The tensile mechanical properties of materials for the elas­tic range are those which represent ability to resist loads and deformations and capacity to absorb energy in the elastic range.

Elastic strength. A material has a high elastic strength if it resists loads without yielding and without being permanently deformed. Elastic strength is measured by the stress which re­presents the transition from the elastic range (where the strains are small and recoverable) to the plastic range (where the strains become large aid are partly nonrecoverable). The initial part of the plastic range is designated as the region where yielding of the material takes place.

The proportional limit is the elastic strength and is defined as the stress value beyond which the stress is no longer propor­tional to the strain. An exact determination of the stress cor­responding to the elastic limit is difficult because the change from the curve to the straight line is very gradual and the exact location of the point of transition is not definite. Another elastic strength value is the elastic limit which is defined as the maximum stress that can be applied to a material without producing a permanent plastic deformation when the load is re­moved. The proportional elastic limits are called ideal strength values. These strength values are seldom found because of the difficulties involved in their evaluation and the inaccuracies in the values determined. Fоr these reasons, elastic strength is designated by one of the following so called plastical elas­tic strength values. In all cases some geometrical construction is used to define the transition from the straight-line elas­tic to the curved plastic part of the stress-strain diagram.

Notes:

Tensile mechanical properties - механические свойства материалов на растяжение

elastic range - упругая область, область упругого поведения

elastic strength - предел упругости

load - нагрузка

yielding - текучесть

plastic range - область пластичности

N 10

MECHANICAL PROPERTIES FOR THE ELASTIC RANGE

(II)

A lower yield point exists for some materials because the movement of the end of the specimen, as produced by the testing machine, does not proceed as rapidly as the plastic deformation of the specimen. This condition results in a decrease in the load and hence a lowering of the stress from the upper to the lower yield point. The foregoing explanation is confirmed by the fact that in a rapidly applied impact test of the same material, a lower yield point does not exist. For materials which exhibit both an upper and lower yield point, the lower yield point is used to define the elastic strength since its magnitude is less influenced by test variables than is the upper yield point.

Stiffness. A material has a high stiffness value when its deformation in the elastic range is relatively small. The pro­perty of stiffness is very important in certain designs where the deformations must be kept small. For example, in some ma­chine tools a slight deflection resulting from lack of stiff­ness could result in inaccurate machining.

N о t e s :

a lower yield point - нижний предел текучести

rapidly applied impact - быстро приложенный удар