Material Selection for Product Development
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This document discusses material selection for product development. It outlines several key factors that influence material selection, including required properties, cost considerations, manufacturing processes, and failure analysis. Material selection is an important part of the engineering design process. The document provides details on selecting materials based on strength, toughness, fatigue resistance, corrosion resistance, and other mechanical properties to meet requirements while balancing various constraints.
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Material Selection for Product Development
- 1. MATERIAL SELECTION FOR PRODUCT DEVELOPMENT by Devan P D Assistant Professor Kumaraguru College of Technology Coimbatore
- 4. Material Selection Materials selection is an important part of a larger process of creating new solutions to problems. This larger process is called “Engineering Design”. (or) Material selection is an integral part of design process.
- 5. Factors Influencing Material Selection
- 6. Why do we need to select a new Material ? ▪ When the product is new (never produced before), the decision to select a new material is obvious.
- 7. Cont.. ●With existing products (Material Substitution), selecting a new material is due to the following: ▪ Reduce material cost ▪ Reduce production cost ▪ Accommodate some changes in function ▪ Solve some material processing problems ▪ Take advantage of new materials or processing methods ▪ Incorporate failure analysis recommendations
- 8. Motivation for Selection •What materials are available; •What processes for shaping these materials are available and how this affects their properties; •The cost of the materials in relation to each other, their processing and their properties. •There are two basic situations that necessitate materials selection that we shall consider: • Development of a new product; • Improvement of an existing product.
- 9. Cost for Selection • At initial, the material is selected for a particular application is based on the required properties. • But final decisions will always involve considerations of cost which in many cases will be the dominant criterion.
- 10. Service Requirements and Failure Analysis • Majority of decisions on materials selection should be taken by the design team based on a quantitative analysis. •The designer should have clear idea of the properties required in his materials and the modes of failure to be avoided in service. • Selected material has to fulfill all the various demands anticipated in service for a particular design. • Combination of properties which it is impossible to achieve fully in any one material and a compromise has to be reached.
- 11. Causes of Failure in Service •Errors in design •Defects introduced during fabrication •Deterioration in service •Inherent defects in a material properly selected •Corrosion
- 12. Selection of Mechanical Properties •Strength •Toughness •Fatigue •Creep
- 13. Strength ●(1) Static strength - the ability to resist a short term steady load at normal room temperature; ●(2) Fatigue strength - the ability to resist a fluctuating or otherwise time-variable load; ●(3) Creep strength - the ability to resist a load at temperatures high enough for the load to produce a progressive change in dimensions over an extended period of time.
- 14. Cont.. • Strength of a material generally requires the determination of its stress-strain curve either in tension, compression or shear: from this several parameters of strength can be taken. • Most strength data for metals are obtained in tension. •concrete and ceramics are commonly tested in compression. • Plastics are frequently tested in flexure. •Most ductile materials, mechanical properties in compression are sufficiently close to tensile properties.
- 15. Cont.. •Presence of internal flaws from which cracks can propagate readily in tension but less easily in compression. • Casted metal- Stronger in compression than in tension. • Cast irons and concrete- they are much stronger in compression than in tension. •Wood- Fails in compression by separation and buckling of its fibres.
- 16. Materials selection criteria for static strength • Strength of a component can be increased simply by making it large. • In a compound structure, it is more convenient to cope with the higher loads by increasing the cross-sectional area of the members. •Thermoplastic applications the need for increased strength may ●be accommodated by local thickening of sections.
- 17. Cont.. ●There are three reasons for seeking to employ materials of increased strength: ●(a) decreased volume, ●(b) decreased weight, ●(c) decreased cost.
- 18. Toughness • Toughness is resistance to fracture. • Fracture occurs by the advance of a crack, and the micro mechanisms of crack advancement are many and varied. The most important micro mechanisms of fracture are ●(1) cleavage, ●(2) microvoid coalescence, ● (3) stress-corrosion, ● (4) fatigue, ●(5) creep rupture.
- 19. Cont... ●Cleavage - This is fracture occurring by separation at crystallographic planes of low indices ●Microvoid coalescence- This is crack advancement by the coalescence of voids produced by the tearing away of second phase particles. ●Stress-corrosion cracking- much of the energy for crack growth is provided by chemical corrosion reactions occurring at the crack tip. ●Fatigue- Fatigue is crack growth induced by cyclic or fluctuating stresses.
- 20. Cont.. •Strength and toughness is indirectly proportional relationship. ●Selection for toughness must then be based upon the designer's assessment of the relative severity Toughness of the duty that the material has to perform.
- 21. Fatigue • Fatigue is a dangerous form of fracture which occurs in materials when they are subjected to cyclic or otherwise fluctuating loads. ●Initiation of a crack can occur in two main ways: ●(1) By formation of slip bands, due to crystallographic slip in a surface grain, followed by development of a narrow crack which eventually deepens into a crack crystallographic plane. It is greatly accelerated by the presence of geometric stress concentrations. ●(2) As a result of severe strain incompatibility across inclusions or hard second-phase particles. This process tends to occur in metallurgically hardened alloys in which the matrix is resistant to the crystallographic slip required to form a slip band crack.
- 22. Cont…. • In specimens without stress concentrations Stage I growth can occupy up to 90% of the total life of the specimen. •Stage II crack growth and as the transition occurs the direction of crack growth changes so as to maximize the crack opening displacement during subsequent growth.
- 23. Corrosion Resistance • Corrosion is the result of chemical reaction at the interface between the material and the associated environment. • The corrosion reaction is dominated by the chemical nature of the environment and the effective concentration of reactive species. • The amount of pollution in the atmosphere can also affect the corrosion rate. •For metals immersed in water, the corrosion depends on the substances that are dissolved or suspended in the water.
- 24. Material Selection and Manufacturing Process • There is no profit in selecting a material which offers ideal properties because that it cannot be manufactured economically into the required form. •Processing also influences material properties. • Nickel-base alloys or high strength alloys are too hard and it is difficult to machine. Therefore, it is formed by casting or by powder metallurgy.
- 25. Cont... •Natural stone can only be cutting. •Concrete can only be cast. •Timber can sometimes be shaped by steaming and bending but more normally only by cutting and adhesive joining.
- 26. Purpose of materials processing ●Materials processing has three principal aims. ●(1) Shape and dimensions ●(2) Properties ●(3) Finish
- 27. Shape and dimensions ●These are obtained by three basic methods: ● (1) Flow processes, ● (2) Fabrication (the assembly of ready-made constituent parts by joining) ●(3) Machining.
- 28. Flow processing ●This method can be used to shape liquids, fluids and solids: it includes • Liquid casting of metals, •Injection moulding of plastics, • Slip casting of ceramics, •Densification of powder-metallurgy compacts.
- 29. Fabrication •This is accomplished by mechanical, metallurgical or chemical methods of joining. •Mechanical methods, include riveting and bolting and other diverse methods of clipping and fixing. •Metallurgical techniques embrace welding, brazing and soldering. •Chemical methods involve the use of adhesives, glues or cements
- 30. Machining •Its flexibility and convenience, and for its ability to make up for the shortcomings of other processes. • Machining has the ability to combine high quality with large throughput. • Machining is used for the bulk manufacture of a part which has a shape inappropriate for any other forming process.
- 31. Properties •The properties of an engineering part derive mainly from the basic nature of the material of which it is made. •Properties can generally be greatly modified during the successive stages of a manufacturing process. Finish This includes engineering tolerances, surface quality, surface protection and appearance.
- 32. Factors to be considered ●1) how many are required, ● (2) the size and weight per piece, ● (3) the geometrical complexity, ●(4) the required dimensional tolerances ● (5) the desired surface finish.