KONSTRUKSI MESIN (3 SKS) MODUL 11 TEGANGAN DAN REGANGAN DOSEN: JAMIATUL AKMAL, S.T., M.T. PROGRAM KULIAH SABTU MINGGU JURUSAN TEKNIK MESIN FAKULTAS TEKNOLOGI INDUSTRI UNIVERSITAS MERCU BUANA http://www.mercubuana.ac.id JAKARTA 2007 Tegangan dan Regangan From statics, one can only determine the internal member forces and/or moments in structural members subject to some loading. However the behaviour of a

Plotting the variation of axial force against the elongation results in the diagram in Figure 2.1 where there are three curves corresponding to the three bars. We do not get a unique plot. If we were to plot the variation of the average intensity of the force defined by force per http://www.mercubuana.ac.id

AA P dF .dA If the stress is uniform, then P = A or = P/A Otherwise, we can only say that the average stress = P/A When referring to normal stresses in more than one direction, a subscript may be used to indicate the direction on which the stress is acting. For example, x denotes the normal stress in x-direction. Note that the normal stress distribution in an axially loaded member may be taken as being uniform, except in the immediate vicinity of the points of application of loads, provided the loading is centric (applied through the centroid of the cross section of the member). If the loading were eccentric, the resulting stress distribution would be non-uniform and would cause bending. In the immediate vicinity of concentrated loads, and near points where the cross section of the member changes abruptly, there will develop some stress concentration, which may be taken into account using stress concentration factors. Shearing Stress (Shear Stress): Shear stress is defined as the intensity of shearing force acting on a plane at a point. The Greek letter tau ( ) is used to denote shear stress. Examples: Shear stress may occur as a result of torsional loading, transverse loading and is also induced in connections (rivets, bolts etc.). Axial loading also causes shearing stress in oblique planes. Sign Convention & Notation: It is common practice to indicate the direction of the shear stress using two subscripts. For example, xy indicates the stress acting in the y direction on (x-plane) a perpendicular to the x-axis. The sign convention that is used in most texts is shown in the diagram. Here the stresses are shown to act in the positive co-ordinate directions on positive faces, and negative co-ordinate directions on negative faces.. http://www.mercubuana.ac.id