The elasticity and resistance of the materials of engineering . 5 = Gcp^ or, G = 9 (3) It will be seen hereafter that there are certain limits ofstress within which Eqs. (i), (2) and (3) are essentially true,but beyond which they do not hold ; this limit is called the limit of elasticity, and is not in general a well definedpoint. Art. 3.—Lateral Strains. If a body, like that shown in Fig. i, be subjected to ten-sion, all of its oblique cross sections, such as EE and GH, willsustain shearing stresses in consequence of the componentsof the tension tangential to those oblique sections. The
The elasticity and resistance of the materials of engineering . 5 = Gcp^ or, G = 9 (3) It will be seen hereafter that there are certain limits ofstress within which Eqs. (i), (2) and (3) are essentially true,but beyond which they do not hold ; this limit is called the limit of elasticity, and is not in general a well definedpoint. Art. 3.—Lateral Strains. If a body, like that shown in Fig. i, be subjected to ten-sion, all of its oblique cross sections, such as EE and GH, willsustain shearing stresses in consequence of the componentsof the tension tangential to those oblique sections. These Art. 3.] LATERAL STRALNS. 5 tangential stresses will cause the oblique sections, in bothdirections, to slide over each other. Consequently tJie normalcross sections of the body will be decreased; and if the normal. cross sections of the body are made less, its capacity of resist-ance to the external forces acting on AB and CD will be cor-respondingly diminished. If the body is subjected to compression, oblique sections ofthe body will be subjected to shears, but in directions oppositeto those existing in the previous case. The effect of suchshears will be an increase of the lateral dimensions of the bodyand a corresponding increase in its capacity of resistance. These changes in the lateral dimensions of the body aretermed *lateral strains; they always accompany direct strainsof tension and compression. It is to be observed that l^ateral strains decrease 3. bodysresistance to tension, but increase its resistance to , that if they are prevented, both kinds of resistance areincreased. Consider a cube, each of whose edges is a, in a body sub-jected to tension. Let r represent the ratio between thelateral and direct strains, and let it be supposed to be the samein all direction
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