Forging new generations of engineers Stress Principles of EngineeringTM Lesson 5.2 – Strength of Materials Forging new generations of engineers Project Lead The Way, Inc. Copyright 2007

Stress

Stress: Stress in a structure is calculated once the applied forces are known and the shape or geometry of a part is chosen. Stress in a part must be below the allowable stress of the material, or the part fails. Allowable stress depends on several factors which will be shown later in this lesson.

Stress:  Before After Axial   Shear Twisting, bending, & torsion forces also factors in (but require the Calculus).   

Stress: Axial Shear

Types of Loading Formula Axial  = P / A where: A is the cross section area Shear  = P / A Formulas shown can be used to calculate average stress on the cross section P

Stress: Twisting and Torsion

Pure Bending Compression M M Tension M is a moment or torque. M creates axial compressive (-) stress on the top surface and axial tensile (+) stress on the bottom surface. The axial stress crosses through zero at the location of the centroid of the cross section, this location is called the neutral axis.