Metal / Metallic materials Generally classified as ferrous and nonferrous Ferrous materials consist of steel and cast ir

1. Engineering materials • Metal / Metallic materials • Generally classified as ferrous and nonferrous • Ferrous materials consist of steel and cast iron • Eg. Carbon steel, high alloy steel, stainless steel • Nonferrous materials consist of the rest of the metals and alloys • Eg. Aluminum, magnesium, titanium & their alloys • Materials from each group are further classified and given certain designation according to the ASTM standard

2. Engineering materials • Each has their own unique number/code that represent main alloying elements, cast or wrought and in case of plain carbon – amount of carbon. • Steel can be classified or grouped according to some common characteristic. • The most common classification is by their • Composition • Example : 10xx, 15xx • Strength • Most common material used in construction of structure such as bridge, building and ships

3. Engineering materials • Low yield strength, less < 40 psi • Eg : A36 – Carbon steel plates, bars and shapes • High strength, between 40 psi and 120 psi • Eg. A440- Carbon steel plates, bars and shapes of • high tensile strength • Ultra-high strength > 200 psi • Product shape, finish processing and quality descriptors • Typical product classification of flat hot-rolled carbon & low alloy steel • According to the thickness and width

4. Engineering materials • For ‘shape’ product forms • eg. I beam and special shapes ( designed for specific application ), bar ( also included round, squares, hexagon in cross section ) • Finishing process • The last processing that the steel undergone. • The mot common are hot-rolled, cold—rolled or cold finished, annealed, normalized, quenched and tempered, coating process.

5. Engineering materials • Design and selection for metals • One of the major issues for structural components is deflection under service load. • A function of the applied forces and geometry, and also stiffness of material. • So suitable material and design are needed. • Load carrying capacity of component can be related to the yield strength, fatigue strength or creep strength depending on loading & service condition. • All are structure sensitive. • Changed, chemical composition of the alloy, method and condition of manufacturing, as well as heat treatment

6. Engineering materials • Electrical & thermal conductivities • Thermal conductivity, K • Is measure of the rate at which heat is trnasfered through a material • Manufacture of component where electrical conductivity is primary requirement • Al & Co • Corrosion resistance & specific gravity limits the materials.

7. Engineering materials • Manufacturing consideration • Wrought m/str usu stronger and more ductile than cast. • Precision / size tolerances, surface finish, heat treatment – stress relief etc., other secondary treatment & finishing. • Weldability – a function of material composition. So structure involve welding of the components need to consider. Also for other joining means. • Machinability – improvement by heat treatment or alloying elements. • Economic aspects - perform function at lowest cost.

8. Engineering materials • Design for polymer • Polymer – low density, good thermal & electrical insulation, high resistance to most chemicals and ability to take colours and opacities. • But if unreinforced bulk polymer are mechanically weaker, lower elastic moduli & high thermal expansion coefficients. • Improvement – Reinforced variety of fibrous materials • Composites (PMC). • Advantages : ease of manufacturing & versatility. • Can manufacture into complicated shapes in one step with little need for further processing or surface treatment.

9. Engineering materials • Versatility : ability to produce accurate component, with excellent surface finish and attractive color, at low cost and high speed • Basic manufacturing processes for polymer parts are extrusion, molding, casting and forming of sheet. • Thermoset & thermoplastic • Differ in the degree of their inter-molecular bonding • Rubber are similar to plastic in structure and the difference is largely based on the degree of extensibility or stretching. • Design : avoid limitations, must remember that strength & stiffness vary with T, many have low impact strength, i.e brittle so avoid stress raisers.

10. Engineering materials • Design consideration for polymer • Structural part • When the parts is to carry load • Should remember the strength and stiffness of plastics vary with temperature. • Long term properties • Eg. Creep behavior • Stress raiser

11. Engineering materials • Design for ceramics • Ceramics – inorganic compounds of one or more metals with a nonmetallic element. Eg Al2O3, SiC, Si2N3. • Crystal structure of ceramic are complex • They accommodate more than one element of widely different atomic size. • The interatomic forces generally alternate between ionic & covalent. • usually heat & electrical insulators. • Strong ionic & covalent bonds give high hardness, stiffness & stability (thermal & hostile env.). • (1) Amorphous or glass, (2) crystalline (arrange) & (3) crystalline bonded by glassy matrix.

12. Engineering materials • Whitewares, glass, refractories, structural clay products & enamels. • Disadvantages • Brittleness, low mechanical & thermal shock • Design consideration for ceramics • Sensitive to stress concentration • Avoid stress raiser during design. • Dimensional change take place during drying and firing, should be consider • Large flat surface can cause wrapping • Large changes in thickness of product can lead to nonuniform drying and cracking.

13. Engineering materials • Design for composite • A composite material can be broadly defined as an assembly two or more chemically distinct material, having distinct interface between them and acting to produce desired set of properties • Composites – MMC, PMC & CMC. • The composite constituent divided into two • Matrix • Structural constituent / reinforcement • Properties / behavior depends on properties, size & distribution, volume fraction & shape of the constituents, & the nature and strength of bond between constituents.

14. Engineering materials • Mostly developed to improve mechanical properties i.e strength, stiffness, creep resistance & toughness. • Three type of composite • (1) Dispersion-strengthened, (2) Reinforcement – continuous & discontinuous (3) Laminated. • Designing with composite • A composite materials usually are more expensive on a cost. • Important factors when designing with composite materials is that their high strength are obtained only as a result of large elastics strains in the fiber • Fatigue behavior at low stress level because fibrous composites may have many crack, which can be growing and propagate through the matrix