granite rock formation in chilean patagonia. inorganic minerals formed oxidation in earth s atmosphere, granite consists of crystalline silica sio2 , alumina al2o3.
the mechanical properties of materials describe characteristics such strength , resistance deformation. example, steel beams used in construction because of high strength, meaning neither break nor bend under applied load.
mechanical properties include elasticity , plasticity, tensile strength, compressive strength, shear strength, fracture toughness, ductility (low in brittle materials), , indentation hardness. solid mechanics study of behavior of solid matter under external actions such external forces , temperature changes.
a solid not exhibit macroscopic flow, fluids do. degree of departure original shape called deformation. proportion of deformation original size called strain. if applied stress sufficiently low, solid materials behave in such way strain directly proportional stress (hooke s law). coefficient of proportion called modulus of elasticity or young s modulus. region of deformation known linearly elastic region. 3 models can describe how solid responds applied stress:
elasticity – when applied stress removed, material returns undeformed state.
viscoelasticity – these materials behave elastically, have damping. when applied stress removed, work has done against damping effects , converted heat within material. results in hysteresis loop in stress–strain curve. implies mechanical response has time-dependence.
plasticity – materials behave elastically when applied stress less yield value. when stress greater yield stress, material behaves plastically , not return previous state. is, irreversible plastic deformation (or viscous flow) occurs after yield permanent.
many materials become weaker @ high temperatures. materials retain strength @ high temperatures, called refractory materials, useful many purposes. example, glass-ceramics have become extremely useful countertop cooking, exhibit excellent mechanical properties , can sustain repeated , quick temperature changes 1000 °c. in aerospace industry, high performance materials used in design of aircraft and/or spacecraft exteriors must have high resistance thermal shock. thus, synthetic fibers spun out of organic polymers , polymer/ceramic/metal composite materials , fiber-reinforced polymers being designed purpose in mind.
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