数控技术应用专业英语教学课件作者刘小芹3.mechanicalproperties课件幻灯片.pptVIP

 English on Mechanical Engineering Lesson 3 Mechanical Properties of Metals Text Mechanical properties are the characteristic responses of a material to applied forces. Knowledge of mechanical properties of materials is essential in order to construct a mechanically sound structure such as a bridge on the river. Mechanical properties can be determined by conducting experimental tests on the material samples. Some important mechanical properties of materials are: strength (in tension, compression, shear, bending and torsion), stiffness (strength), ductility, impact strength, hardness and toughness. Materials Sustain Loads On Tension Materials Sustain Loads On Shear Materials Sustain Loads on bending Materials Sustain Loads on torsion Text 1. Strength The Strength of a material may be defined as the ability of the material to sustain loads without undue distortion or failure. Material should be adequately strong when subjected to tension, compression, shear, bending or torsion as per the intended use. For example, the crankshaft of an automobile should have sufficient torsion strength.  2. Stiffness Stiffness is the ability of a material or shape to resist elastic deflection. For identical shapes, the stiffness is proportional to the modulus of elasticity. A material which deforms less under a given load is stiffer than one which deforms more. 3.Ductility Ductility refers to the capacity of a material to undergo deformation under tension without rupture as in a wire drawing operation. Text 4. Impact Strength Impact strength is the strength of a material when subjected to high rates of loading, usually in bending, tension or torsion. The amount of energy required to fracture the material by a single blow is measured by means of a Charpy impact test. 5. Hardness Hardness is the resistance of a material to plastic deformation usually by indentation. However,