Trục Torsionally tải là một trong các cấu trúc được sử dụng phổ biến nhất trong kỹ thuật. Ví dụ, trục ổ đĩa của một ổ đĩa tiêu chuẩn phía sau bánh xe ô tô, mô tả trong hình. 1, phục vụ chủ yếu để truyền tải xoắn. Những đường hầm này hầu như luôn luôn rỗng và vòng tròn trong mặt cắt, truyền tải điện từ các truyền khác biệt giữa các khớp quay được chuyển hướng đến các bánh xe ổ đĩa. . | SHEAR AND TORSION David Roylance Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge MA 02139 June 23 2000 Introduction Torsionally loaded shafts are among the most commonly used structures in engineering. For instance the drive shaft of a standard rear-wheel drive automobile depicted in Fig. 1 serves primarily to transmit torsion. These shafts are almost always hollow and circular in cross section transmitting power from the transmission to the differential joint at which the rotation is diverted to the drive wheels. As in the case of pressure vessels it is important to be aware of design methods for such structures purely for their inherent usefulness. However we study them here also because they illustrate the role of shearing stresses and strains. Figure 1 A drive shaft. Shearing stresses and strains Not all deformation is elongational or compressive and we need to extend our concept of strain to include shearing or distortional effects. To illustrate the nature of shearing distortions first consider a square grid inscribed on a tensile specimen as depicted in Fig. 2 a . Upon uniaxial loading the grid would be deformed so as to increase the length of the lines in the tensile loading direction and contract the lines perpendicular to the loading direction. However the lines remain perpendicular to one another. These are termed normal strains since planes normal to the loading direction are moving apart. 1 Figure 2 a Normal and b shearing deformations. Now consider the case illustrated in Fig. 2 b in which the load P is applied transversely to the specimen. Here the horizontal lines tend to slide relative to one another with line lengths of the originally square grid remaining unchanged. The vertical lines tilt to accommodate this motion so the originally right angles between the lines are distorted. Such a loading is termed direct shear. Analogously to our definition of normal stress as force per unit area1 or ơ P A we
