ABSTRACT
This chapter introduces the neutral axis for a beam as an axis passing through the centroid of the section at which the bending stress is zero. It applies simple bending theory to a beam subjected to a bending moment. The chapter evaluates the second moment of area for a beam section. It analyses the stresses in a shaft subjected to torsion. The chapter evaluates the second polar moment of area for solid and hollow shafts of circular cross-section. It takes that knowledge a stage further by considering the stresses resulting from either the bending of beams or torsion in shafts. If the stresses in the beam vary from compressive on one side to tensile on the other, there must be a position where the stress, and the strain, is zero. The stress-strain relationship for the material remains within the elastic region and is the same in both tension and compression.
