机械设计05_弯曲剪切和扭转.pptVIP

05 Bending, Shear and Torsion Bending of Straight Beams: Deformed Beams Straight Beams: Moments of Inertia Straight Beams: Normal Stresses Straight Beams: Normal Stress Distribution Shear Stress in Beams: Shear Stress Shear Stress in Beams: First Moment of Area Shear Stress in a Narrow Rectangular Beam I Beam: Shear Stress txy I Beam: Shear Stress txz in the Flange Example Example: Solution Strategy Example: Solution Shear Strain and Stress for Circular Shafts Shear Stress Distribution for Circular Shafts Thin-Walled Hollow Shafts Applications: Design of Transmission Shafts Example Example: Analysis Model Example: Internal Forces Example: Critical Points Example: Bending Moment and Torque at Point B Example: Stresses Components Example: Maximum Normal Stress at E Example: Maximum Shear Stress at E Example: Maximum Normal Stress at F Example: Maximum Shear Stress at F Example: Summary Curved Beams: Assumptions Neutral Axis Curved Beams in Bending: Normal Stress Curved Beams in Bending: Example Curved Beams in Bending: Example – Stress Esc TOPIC School of Engineering Mechanical Engineering ME 461 Design ? Tulong Zhu, All rights reserved. Shigley, Fig. 4-15 The neutral plane passes through the centroid of the cross sectional area . Stress (strain) is zero at the neutral plane. Deformed Beams The material is isotropic, homogeneous and linear elastic. The beam is initially straight. Plane cross sections remain plane during bending (i.e., the deformation due to transverse shear is ignored). The beam axes are the principal axes of the section, i.e., Iyz = 0. The beam would fail by bending rather than by crushing, wrinkling (local buckling) or global buckling. Assump-tions There is at least one set of coordinate system about which Iyz = 0. The axis about which Iyz = 0 is called the principal axis. If the section is symmetric about an axis, this axis is a principal axis. For most shapes, there are only two mutually perpendicular principal axes. Definition Principa