Chap' 6

1
Chap. 6 Introduction to Deformable Body
Mechanics
2
6.1 Overview

• Deformable body
• Rigid body
• Statically indeterminate problems in rigid body
  analysis

6.2 Applied Forces and Deformations

• Two types of motion
• Position of the body changes over the time.
  (temporal changes)
• Local changes within the body (deformations)
• Deformations
• Even in the static equilibrium, there is some
  local shape change within the body.
• The extent of the shape change may depend on the
  magnitude, direction, and duration of the applied
  forces, material properties of the body and
  environmental conditions such as heat and
  humidity.

3
6.3 Internal force s and moments

• internal force, internal moment
• free-body diagram
• axial or normal force
• tensile
• compressive
• shear force
• twisting torque
• bending moment

Free-body diagram
internal forces and moments
4
6.4 Stress and Strain

• The design of a structure is safe against the
  combined effects of applied forces and moments.
• mechanical properties of materials

• Stress

• Strain

5
6.5 General Procedure

• General procedure to solve deformable body
  mechanics
• Static analyses
• to determine external reaction forces and
  moments
• free-body diagram and equilibrium conditions
• Analyses of internal forces and moments
• method of sections
• to determine critical load conditions using
  shear force diagram and bending moment diagram
• Stress analyses
• stress and strain
• Material selection
• safety of the structure based on the max
  stresses
• dAlembert principle