“ STRENGTH OF MATERIALS ”
Engineers conduct tests on different materials such as concrete , steel , wood , etc . to determine a material ’ s strength . “ The strength of a material measures how much stress can be applied to an element before it deforms permanently or fractures ” ( fictiv ). There are two important values of strength that are tested for , yield strength and ultimate strength .
“ Yield strength is defined as the amount of stress ( yield point ) that a material can undergo before moving from elastic deformation into plastic deformation ”( engbox ).
Yield strength is the stress value where the material begins to permanently deform . Values less than the yield strength will cause the material to have an elastic behavior . Much like a rubber band being pulled apart , the sides of the band stretch . However , when tension is removed the band returns back to its original dimensions . Exceeding the yield strength and the rubber band will permanently stretch or even break . Yield strength is frequently used for calculating allowable load in materials and mechanical components . The yield strength could be 3 or 4 times greater than the necessary design load depending on the factor of safety .
“ The ultimate strength refers to the maximum stress a material can receive before failure occurs ” ( fictiv ).
Ultimate strength is the stress value when a material actually breaks under the applied stress . The value can be closer to the yield strength depending on how brittle the material is . For example , glass is so brittle the yield and ultimate strength are the same . On the other hand , steel is very ductile and will have more strength as it plastically deforms .
Citations : https :// www . fictiv . com / articles / engineering-fundamentals-refresh-strength-vs-stiffness-vshardness
https :// www . engineeringtoolbox . com / young-modulus-d _ 417 . html