TABLE OF CONTENTS Mechanical assembly is a subset of the classical theory of statics that is, the description of bodies that may experience external forces and torques but do not accelerate. Statics deals with all the items listed in Figure 3-1: connective systems like pipes, structures like bridges and car bodies, and mechanisms like engines (as long as they are not operating or are moving very slowly).
The theory of statics permits the engineer to calculate the positions of all the parts in the item being analyzed as well as any internal stresses and strains. The analysis requires consideration of the following factors, which are called the principles of statics:
Geometric compatibility: All the parts should have consistent locations with respect to each other; that is, it should be possible to utilize information about the size and shape of the parts, as well as information about contact between them, to calculate the location of any part based on knowledge of the location of any other part.
Force moment equilibrium: The sum of all forces applied to the parts should be zero, as should the sum of all moments. The same principle applies to each individual part in the assembly with respect to any internal forces and torques that act between the parts.
Stress strain temperature relations: Based on the properties of the materials, all deformations caused by the applied or internal forces and torques can be calculated, along with any deformations that arise from changes in temperature.
