What is meant by the material selection procedure?

The term material selection means to select the right material for various engineering applications. There are various engineering materials available and each has different individual properties. Thorough knowledge of the material properties and behavior is crucial in the design process. For instance, a structural member, such as a beam, is used to support vertical shear loads by the building itself. To withstand such loads, the material of the beam must possess adequate strength and stiffness to resist any deformation that might lead to the formation of cracks.

The material selection involves the right decision making, proper problem evaluation, estimating design requirements, identification of critical areas, and proper engineering knowledge. Certain specific properties of materials are meant for certain specific engineering applications. So, engineers should wisely choose the materials.

Mechanical properties of materials

There are specific mechanical properties of materials that must be suitably used by engineers so as to accomplish the design requirements of a project. Some of the properties are discussed below:

Tensile strength

In the materials selection process, the tensile strength associated with a component is a fundamental criterion. The component should have enough tensile strength to withstand external loads. For instance, the components of trusses are under compressive and tensile loads, and weak material properties will result in a low tensile strength of the material. The members of the trusses are specially made of metals and certain aluminum alloys. They should also have adequate corrosion properties.

Flexural strength

In the materials selection process, the flexural strength is also an important criteria; it is associated with members which are under bending moments. A column used in the foundation applications are under high compressive loads that leads to buckling condition. These members should have a good flexural strength so as to withstand the buckling loads. Materials selection process should be such that it provides good resistance to deformation or buckling.

Fatigue strength

To have a good fatigue strength, the materials selection process should be such that the components under cyclic loadings have excellent endurance properties. Engineers must do a proper fatigue test analysis of the material before subjecting the material to practical use. The requirement of good fatigue properties is essential to minimize the initiation of cracks that might lead to fatigue failure.

Materials should be less brittle

A concrete is a brittle substance. Under the application of periodic loadings, it develops cracks suddenly. Hence, engineers of the design team must ensure the use of proper material selection. The use of the right concrete materials and reinforcements, helps to meet the design requirements, minimize the brittleness, and withstand seismic loads. Seismic loads are loads from an earthquake that are periodic in nature.

Machinability

It is one of the primary aspects of the material selection process. The material selected for various engineering applications must possess the property of machinability. Certain metals used in the manufacturing domain and analysis are to be cut and trimmed for different processing purposes. Metals with low machinability aids difficulty in processing. Hence, material selection plays a major role even in the analysis domain. Machinability can be enhanced by improving the material properties of the parent metal. This can be done, mixing the parent metal with other substances, such as in composites. Composites find their wide application in various engineering domains such as in the aerospace and automobile industries.

Improving material properties

When the material selection process is inadequate in meeting the design and metallurgical needs, the material properties can be enhanced by certain additional processes. Some of the processes are outlined below:

Heat treatment

Low thermal resistance and strength are the characterizations of poor material properties. These properties can be improved by the heat treatment process. In the heat treatment process, the material is subjected to a high-temperature furnace and cooled either slowly in open air or rapidly in water. This process helps to improve the material properties, and also helps to derive other mechanical properties as well.

Coatings

Materials such as stainless steel used in many engineering applications are coated with other elements or metals, primarily known as electroplating. This process aids in improving corrosion resistance of the material. This process can also be termed as a substitution process because the parent metal is substituted by other metals, which are deposited at the surface of the parent metal.

Alloying

By definition, alloying is a process when two or metals in the molten state are fused to form a new metal, which has a different set of properties from its constituent elements. This can lead to material properties enhancement.

Performance index of materials

The performance index is a measure that determines how good a material can perform under the given external influences, such as loads and bending moments. The performance index helps to evaluate and determine the workability and durability of the given material when subjected to engineering applications. The material selection process plays a key role in the evaluation of the performance index of the material.

The above figure shows a black carbon fiber composite that is extensively used in automobile applications. A right decision-making skill of an engineer leads to the right material selection. This ultimately leads to the safety of individuals and property.

Context and Applications

The topic of material selection finds its application in various engineering domains such as construction engineering, aerospace engineering, automobile engineering, and mechanical engineering.

This topic is taught in various applied science and engineering degree courses of bachelor science and master of science. The topic is found as a chapter bearing the name, 'material selection process, in the subject of materials science and engineering.

• Bachelors in Civil Engineering
• Bachelors in Automobile Engineering
• Bachelors in Mechanical Engineering
• Bachelors in Aerospace Engineering

Practice Problems

1. Which of the following is a part of the material selection process?

1. Decision making
2. Estimating design requirements
3. Problem evaluation
4. All of these

Correct option- d

Explanation:  A proper material selection involves the right decision-making, proper problem evaluation, and estimating design requirements.

2. Which of the following is the name of the process that requires the coating of metals to improve the corrosion properties?

1. Electrolysis
2. Electroplating
3. Galvanization
4. Nitriding

Correct option- b

Explanation: Electroplating involves coating the metallic surface with a suitable metal that improves the corrosion resistance of the materials.

3. Which of the following is a mechanical property that plays a major role in the material selection process?

1. Corrosion resistance
2. Fatigue strength
3. Tensile strength
4. Both b and c

Correct option- d

Explanation: Mechanical properties such as tensile strength and fatigue are two of the fundamental properties to be considered in the material selection process.

4. Which of the following is true for heat treatment?

1. It improves the strength of the material.
2. It improves the corrosion resistance.
3. It also induces new properties of the material.
4. Both a and c

Correct option- d

Explanation: Heat treatment improves the mechanical strength of the material along with, induces additional properties to the material.

5. Which of the following is true for machinability?

1. A low machinability signifies good workability.
2. A high machinability allows the material to be cut and machined to meet the design needs.
3. A low machinability means the material flexible and has high elastic modulus.
4. None of these

Correct option- b

Explanation: A high machinability indicates good workability, this allows the material to be cut and machined to meet design dimensions.