# Physics : Mechanical Properties Of Materials

2190 WordsNov 30, 20169 Pages
Erin Ross ENG 305 11/16/2016 Mechanical Properties of Materials INTRODUCTION Before anything is built, first the proper materials must be chosen. Some people only consider the strength of a material when choosing. Other properties can be taken into account, though. The ductility or brittleness of a material could play a role depending on the project. The hardness of a material is important for durability. There are multiple properties that can describe a material, and engineers must consider all of them before deciding on a material. If a material is not properly chosen, the object being made may not work correctly. When in the process of making an object, properties must, also, be remembered. An archery bow, for example, would not work correctly if it were pre-bent. A bow starts out straight and is bent. This is done to create strain energy and this is what throws the arrow. Most properties stem from engineering stress and engineering strain. These are important when describing materials. Engineering Stress Stress is defined as force per unit area. Stress can be described as normal or shear stress. When the stress is normal, the material is stretching or compressing. Shear stress will shear the material. Normal stress gets its name because this stress is normal, or perpendicular, to the plane, while shear stress is parallel to the plane. Normal stress and shear stress can be calculated using the following equations: σ=F/A_0 τ=F/A_0 where σ is the normal stress, F is