Why Materials Selection?
Material selection is one of the foremost functions of effective engineering design as it determines the reliability of the design in terms of industrial and economical aspects. A great design may fail to be a profitable product if unable to find the most appropriate material combinations. So it is vital to know what the best materials for a particular design are. How we are going to get an idea about the best materials for a design? In this aspect engineers use several facts of materials to come to the most reasonable decision. They are mainly concentrated on the properties of the materials which are identified as the potential materials for that specific design.
1. Mechanical properties
When a certain design is going to be actually produced it must be subjected to a number of manufacturing practices depending on the material and the design process. At the completion of production it must be totally fit for the service phase, too. In order to predict the reliability of both of these requirements, the materials must be able to withstand a certain load. Therefore the material must possess a certain strength and stiffness. Selected materials are examined for strength and stiffness values, and then potential materials are further inspected for other desired properties.
Material selection is one of the prime concerns in mechanical engineering design as mechanical engineers possess great deals with various loads and temperature variations. Material selections in engineering designs such as civil engineering structures also are very crucial.
2. Wear of materials
Wear is a problem when the materials are contacting each other in a product. So it must be ensured that the selected materials have sufficient wear resistance. One of the best examples for this is designing gears to cope with wear. There are many production techniques available to improve the wear resistance and make the material is more suitable for the application. This is also very important factor to consider when selecting a material for a particular design. In the engineering design process this has to be considered with great care.
The importance of material selection in engineering is clearly visible in corrosive environments. Also it is an important engineering design criterion for designs open to the environment for a longer period of time. Some materials are very likely to be corroded in the service depending on the service environment. Metals like iron are heavily prone to corrosion if it not prepared to resist corrosion. Therefore it must be assured that the material is capable of being employed for the particular design before selecting it. Painting or any other surface coating method, cathodic protection, etc. are possible ways to minimize the effect and increase the service life.
4. Ability to manufacture
Although the material is well capable of using for the design, it may be difficult to manufacture. This is particularly applicable in mechanical engineering design. If this selection criteria is neglected the manufacture process might be very costly making it unprofitable as a commercial product. So before selecting the materials this fact also must be considered. These facts are widely varied with the type of manufacturing method. For an example, when producing a gear its dimensions must be very accurate. Otherwise the application may not provide the expected performance. To make the dimensions more accurate it has to be machined in the production. So the selected material must able to be machined with a minimum cost. Otherwise there is no point of selecting that material for that particular gear.
Cost is a critical fact to consider when selecting materials for a certain design for most products because they are facing a severe competition in the market. So you may see that most of the metal or other valuable materials are replaced by plastics in most of the designs which they are applicable such as mechanical engineering designs. The cost factor can be neglected when performance is given the top priority. When estimating costs, all the associated cost factors must be considered to get a more reasonable value. It may involve the transportation, processing, etc. costs.
These are the main facts to consider when selecting a material for a design, but there are a number of other factors which become essential depending on the particular product. In some occasions particular properties of the material may become the dominant factor over other properties. For example, electrical conductivity is vital for an electrical application so it must be given the priority. In mechanical engineering, designing for light weight is important for certain body parts of vehicles where aluminum is used instead of steel. An inability to meet the maximum operating temperature may be the reason to exclude the most profitable material for a certain high temperature design. Once a short list of materials is selected, the best possible candidate that gives the maximum performance with minimum cost must be determined.
The end of material selection is not the end of the design process. The best material may be yet to come. Also it has to perform desired functions satisfactorily, not for just one or two days, but for a long period of time. In this tough test, the design may fail comprehensively. Therefore the designer has to consider the ways to improve the performance in all possible aspects. So the design process and the material selection is a continuous process unless the manufacturer has no intention to survive the ever-challenging market battleground.