Electrical, Mechanical, and Thermophysical Properties of Materials

Material properties depend on many frictors, indudii how the material vras prcKessed, its age, its exact chemical composidon, and any nonhomogendty or defect within die material. Material properdes also chai with temperature and time as the material t es. Most companies that sdl materials will provide upon request informadon on the important properdes of dieir manufactured materials. Keep in mind that when practicing as an engineer, you should use the manufricturer s material property values in your des calculadons. The proper values fr other textbooks should be used as typical values—not as exact 

In the previous chapters, we have eiqilained what some properdes of materials mean. The meanit of diose properdes and other properdes that we have not explained already are summarized next. 

Electrical Resistivity The value of electrical resisdvity is a measure of the resistance of material to the flow of electrid. For example, plastics and ceramics typically have high resisdtdty, whereas metals ically have low resisdvity, and among the best conductors of electricity are silver and copper. 

Density Density is defined as mass per unit volume it is a measure of how compact the material is fi r a ven volume. For example, die average density of aluminum alloys is 2700 %/m and compared to steel densi of 7850 l m aluminum has a density that is approximately one-third the density of steel. 

Modulus of Elasticity (Young s Modulus) Modulus of elasticity is a measure of how easily a material will stretch vdien pulled (subject to a tensile force) or how well the material will shorten len pushed (subject to a compressive fiirce). The latter the value of the modulus of elasticity is, the la r the required fiirce would be to stretch or shorten the material. For example, the modulus of elasddty of aluminum alloy is in the range of 70 to 79 GPa, whereas steel has a modulus of elasticity in the range of 190 to 210 GPs therefore, steel is approximately 3 times stififer than aluminum alleys. 

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