![]() ![]() Conversely, a homogeneous material with defects only on its surfaces (e.g., due to scratches) might have a higher tensile strength than flexural strength. Therefore, it is common for flexural strengths to be higher than tensile strengths for the same material. However, if the same material was subjected to only tensile forces then all the fibers in the material are at the same stress and failure will initiate when the weakest fiber reaches its limiting tensile stress. When a material is bent only the extreme fibers are at the largest stress so, if those fibers are free from defects, the flexural strength will be controlled by the strength of those intact 'fibers'. In fact, most materials have small or large defects in them which act to concentrate the stresses locally, effectively causing a localized weakness. The flexural strength would be the same as the tensile strength if the material were homogeneous. Most materials generally fail under tensile stress before they fail under compressive stress, so the maximum tensile stress value that can be sustained before the beam or rod fails is its flexural strength. These inner and outer edges of the beam or rod are known as the 'extreme fibers'. At the outside of the bend (convex face) the stress will be at its maximum tensile value. At the edge of the object on the inside of the bend (concave face) the stress will be at its maximum compressive stress value. 1), it experiences a range of stresses across its depth (Fig. When an object is formed of a single material, like a wooden beam or a steel rod, is bent (Fig. 2 - Stress distribution through beam thickness
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