5 ) ) INTRODUCTION Engineering materials are used to manufacture the products, dictates which manufacturing process or processes are to be used to provide it the desired shape.
6 ) ) 2. PROPERTIES OF MATERIALS The various engineering material properties are given as under. 1. Physical properties 2. Chemical properties 3. Thermal properties 4. Electrical properties 5. Magnetic properties 6. Optical properties, and 7. Mechanical properties
7 ) ) 2.1. Mechanical Properties Mechanical properties describe how a material responds to an applied force, include strength and ductility. Mechanical properties describe how a material behaves when it is exposed to a sudden, impact, fatigue, creep or wear.
8 ) ) Strength Strength is a measure of how the material resists being misshapen or deformed, when acted under force. Tensile strength إجهاد الشد Tensile strength إجهاد الشد The ability of the material to withstand pulling forces or tension forces. Compressive strength إجهاد الضغطCompressive strength إجهاد الضغط It is the ability of the material to withstand squeezing forces or compression forces.
9 ) ) Fig. 1.1 Schematic universal tensile testing machine Fig. 1.2 Stress strain curve for ductile material
10 ) ) Tensile testing machine
11 ) ) Torsional properties Torsional properties إجهاد الإلتواء It is the ability of a material to withstand twisting forces Hardness Hardness الصلادة It is the ability of a material to withstand being scratched Toughness Toughness المتانة A measure of how much energy is required to break a material Stiffness Stiffness الجساءة It is the ability to resist bending deformation Ductility المطيلية It is the ability to be elongated Brittleness Brittleness القصافة It is the ability to be resist fracture or deformation.
12 ) ) 1.CLASSIFICATION OF ENGINEERING MATERIALS A large numbers of engineering materials exists in the universe such as metals and non metals (leather, rubber, asbestos, plastic, ceramics, organic polymers, composites and semiconductor). Some commonly used engineering materials are broadly classified as shown in 1.3.
13 ) ) Fig. 1.3 Classification of engineering materials
14 ) ) Ferrous (a) Ferrous metals are those which have the iron as their main constituent, such as pig iron, cast iron, wrought iron and steels. Non-ferrous (b) Non-ferrous metals are those which have a metal other than iron as their main constituent, such as copper, aluminum, brass, bronze, tin, silver zinc, invar etc Steels Steel is an alloy of iron and carbon with carbon content maximum up to 1.7%. The carbon occurs in the form of iron carbide, because of its ability to increase the hardness and strength of the steel.