. The strength of materials; a text-book for engineers and architects. so Fig. 195.—Stresses in Eccentrically Loaded Tie-bar. exception of that at the highest load, in which the materialbegins to yield at the edges and the straight line bends over asshown. In this case the test-piece showed residual stress atthis edge after the load had been removed. In experiments upon models of standard cement briquettesProfessor Coker found t that the maximum stress was about1*75 times the mean stress (cf. p. 78). * Engineering, January 6, Ibid., December 13, 1912. THE TESTING OF MATERIALS 413 Fig. 1
. The strength of materials; a text-book for engineers and architects. so Fig. 195.—Stresses in Eccentrically Loaded Tie-bar. exception of that at the highest load, in which the materialbegins to yield at the edges and the straight line bends over asshown. In this case the test-piece showed residual stress atthis edge after the load had been removed. In experiments upon models of standard cement briquettesProfessor Coker found t that the maximum stress was about1*75 times the mean stress (cf. p. 78). * Engineering, January 6, Ibid., December 13, 1912. THE TESTING OF MATERIALS 413 Fig. 196 ^ shows the results of the experiments by thesame investigator upon the distribution of stresses in. Fig. 196.—Effect of Holes on Stress in Beams, rectangular beams with holes cut through them. In theupper specimen a hole is in the centre and in the lower oneholes are formed half way between each edge and the neutralaxis. In this case it wiU be noted that the maximum stress* Engineering, March 3, 1912. 414 THE STRENGTH OF MATERIALS does not occur at the outermost fibre, but at the outer edge of each hole. Professor Coker and Mr. W. A. Scoble, ,* have also experimented upon the stresses in tie-bars with holes in them , ...,.., T-p width of plate such as occur m riveted lomts. it c = -,• -^ y ^—r- ^ diameter of hole and f is the mean stress over the whole width of plate, they find that their results for one central hole may be expressed by the formula maximum stress _ 3 c mean stress c + 1 Also if a is the radius of the hole, the longitudinal stress ata distance r from the centre of the hole on a normal section ofthe plate is expressed by the formula /, 2+^:+ 3 a* where p is
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