Engineering Materials - Research Paper Example

ENGINEERING MATERIAL By Location Table of Contents 0 Definition of terms 2 1 Metallic materials 5 2 Ceramics 6 1.3 Polymers 7 1.5 Generate and process test data (on graph) 9 1.6 Investigate and assess the quality of suitable data from three different sources 9 2.0 Task 2 9 2.1 Advantages of Brinell hardness testing 9 2.2 Effect of heat treatment process on the structure, properties and behavior of the parent material 10 2.3 How liquid processing method and mechanical processing methods affect the structure, Properties and behaviour of the parent material 11 3.0 Task 3 12 3.1 Methods of NDT Visual, Liquid penetration, Magnetic, Ultrasonic, Eddy current and X-ray 12 3.2 Analysis of the functions of a product in terms of the materials’ constraints on its design 14 3.3 Required properties for the product and select the most appropriate materials and processing methods 14 4.0 Task 4 15 4.1 Forms of steel 15 5.0 Task 5 16 5.1 In-service failure 16 5.2 Failure of the retracting lever 17 5.3 Methods of investigating material failure 17 5.4 Improving service life of the retracting lever 17 References 18 1.0 Definition of terms 1. Proportional limit In a stress-strain curve, proportional limit refers to the limit in which below, the material shows the expected direct relation between stress and strain (Hooke’s law). The straight line from starting point of the curve to the point marked proportional limit shows the behavior. 2. Yield stress In materials, it refers to the minimum stress necessary to induce a plastic deformation in a material. The material loses the ability to go to the original shape after removal of the forces. 3. Ultimate stress It refers to the point during the application of stress on a material at which the material fails and thus breaks. From this point, the curve starts going down indicating that a small increment of little strain requires a relatively smaller stress. 4. Fracture Fracture refers to the point whereby the material breaks and separates at a point due to the constant addition of stress beyond what the material can support. The bondage between the molecules is broken. Stress-strain curve regions 1. Elastic region In this region, the material can regain its original shape after the removal of the loading or rather the stress. At this juncture, the material obeys Hooke’s law and the stress and strain relate proportionally, and the constant of proportionality is the modulus of elasticity. The structure of the particles is not altered which explains the reason the material regains it original shape after the removal of the stress. 2. Yielding region It is the region just after the elastic limit. It is characterized by the graph flattening indicating destroyed proportionality between the stress and strain. Plastic deformations creep in, and the material loses the ability to regain fully its shape and size after the stress has been released. It takes place due to rearrangement of the molecular or atomic structure that allows for the new shape and size. 3. Strain hardening region Found just after the yielding region. It is characterized by a slight rise of the curve to the ultimate stress point. The behavior is due to the strength of the deformed atoms or molecules having a slight ability to withstand more stress up to the point beyond which complete deformation takes place. The rise of the curve in this region is what is termed as strain hardening. 4. Necking region It is the region beyond the ultimate stress point. In this region, a further increase of the stress leads to a reduction of the cross section of the material only in some parts and not the entire material. The constrictions formed are what is referred to as necking. It is the continuous reduction of the cross section area that leads to the breakage and thus separation of the material. 1.1 Metallic materials Metallic properties for consideration during the selection of the material Tensile strength that on the graph is the ultimate stress point Electrical conductivity affected by the atomic structure of the material The melting point or rather temperature effect on the strength of the material Thermal conductivity depending on the use of the material Reactivity Metallic materials are ductile thus has the ability to deform plastically up to some extent. On the graph, it is represented by the region beyond the proportional limit where the elastic limit has been exceeded. Force beyond the elastic limit affects the mobility of the atoms and dislocations thus the inability to regain the original shape after the force has been removed. The attained structure and affected mobility supports the load but not elastically according to Hooke’s law to a point where beyond necking takes place and the covalent and ionic bonds between the atoms gets broken. 1.2 Ceramics Mechanical properties crucial for the selection of the material Materials for a particular use is selected depending on the use and physical aspects that are going to affect the desirable mechanical properties if the material. Strength of the material Temperature effect on the strength Electrical conductivity Thermal conductivity Reactivity Ceramics is material that made by a combination of metallic and non-metallic materials. Ceramics can be amorphous or crystalline in nature is having either ionic or covalent bonds. The type of bond in this material makes it break just beyond the elastic limit. The material lacks the property of plastic deformation and thus low toughness displaying catastrophic failure when the elastic limit is exceeded. Furthermore, this type of material tends to be porous which acts as stress concentrators reducing the toughness of the material. 1.3 Polymers Properties for selection of material Strength. Polymers have poor tensile strength. Electrical and thermal conductivity (Good insulators to both heat and electricity) Reactivity (Resistant to corrosion) Effect of temperature on strength Polymers have low densities Polymers are made of hydrocarbons. Carbon atoms attach to another carbon atom to form a long chain that forms what is known as the backbone of the polymer. The two main types of bonds in a polymer include covalent bonds between carbon atoms and molecular bonds. The molecular bonds between the layers of molecules are weak which explains the weak and sudden breaking of polymers after the yield strength. Beyond the yield strength, the molecular bonds break the molecular slides over each other thus the sudden drop in strength after the yield strength. 1.4 Composites Properties for selection of composite material Strength (composites have very high strength) Weight Resistance to corrosion Electrical and thermal conductivity Composite material are that material made by a combination of more than one type of material according to desirable qualities. A good example of the composite material is concrete. The tensile and compressive strengths of the two combined material gives the final product a desirable strength depending on the use of the material. Most materials have covalent bonds that are hard to break. One element of the material resists the tensile force while the other resists the compressive strength. 1.5 Generate and process test data (on graph) The data on the preceded discussion are generated for the development of the graphs. The graphs indicate a difference I yield strength between the materials being tested and the plasticity. The breaking point explains a lot when it comes to material selection and choice. 1.6 Investigate and assess the quality of suitable data from three different sources The quality of data is crucial in for the production of dependable results. Several factors must be in line while checking for the accuracy of the information. The gradient of the curve at the proportional limit should represent the modulus of elasticity and if this is not achieved recollection of data is imperative. Suitable data should display desired characteristics or rather close to the hypothesis. 2.0 Task 2 2.1 Advantages of Brinell hardness testing The method can be used to test almost all metals. The method is used to test high strength material, and almost all metal have a high strength thus the method can be applied. The method tests a wider area of the sample compared to other methods because it uses a sphere. Other methods of testing hardness employ pins or cones that concentrate load at a point. The method gives hardness on a linear scale that is easier to understand and faster especially when it comes to design works. Limitations Material to be tested must be thick as the indentation should not exceed thickness of the material The method is limited in the sense that it cannot measure cylindrical objects. The indent size of the ball gives different readings thus one does not know which size of the sphere to use for most accurate results. 2.2 Effect of heat treatment process on the structure, properties and behavior of the parent material Heat treatment The heat treatment process has several effects on the initial properties of the material depending on the attained temperature of heating and rate of cooling. The heating process takes place after raising the temperature to the desirable level where the material becomes molten, or semi-molten. The rate of cooling affects the metallurgical restructuring takes place that in essence affects properties such as frictional resistance and lateral strength. Faster cooling does not allow for proper organization of the building structures of the material that leads to altered properties. In steel, heat affects the ductility and hardness making it harder and less ductile. Anti-corrosion treatment It refers to the treatment undertaken to prevent the material from corrosion by the chemical. It involves the application of a coating layer of a material that is resistant to corrosion and applied to materials such as stainless steel, aluminum, and copper. The applied coating can affect some properties of the material such as appearance, electrical conductivity, and temperature resistance depending on the material used for coating. Some of the material acts as insulators which make the parent material resistant to conducting heat or electricity. Alloying The method involves a combination of one material and the other to improve or rather alter the quality to a desirable standard. It involves the heating of a material to a molten state and addition of another material that is the annealed for restructuring. The altered properties can be hardness, electrical and thermal conductivity by the provision of more valence electrons that allow for the conduction of heat and electricity. 2.3 How liquid processing method and mechanical processing methods affect the structure, Properties and behaviour of the parent material 1. Liquid processing method The method involves the altering the properties of the material using liquids and in the liquid state. Some liquid treatment also takes place when the parent material is in solid state. When applied to the metals to obtain certain shape it is called casting, and when applied to plastics it is called molding. Liquid additives are added in this state to improve properties such as strength, appearance, and electrical conductivity. Furthermore, the lubricants added on the solid material reduce the resistance to friction. In other forms, a liquid may be added the parent material in a molten state to remove impurities and thus improve the quality of the final product. 2. mechanical processing methods The mechanical process involves the alteration of the property of the material without altering the chemical composition. The most commonly used method is the heating and cooling process that alters the microscopic structure of the material. The alteration leads to change in some of the properties of the material such as the lateral strength, electrical conductivity, ductility, and appearance. How the composition and structure of metal alloys, polymers, and polymer matrix composites influence the properties of the parent material Metal alloys are made by a combination of metal and metal or metal with other compounds to achieve desirable characteristics. Property of the material gets improved to the intended level for particular use. The strength is increased by reducing porosity and bond strength between the atoms. Provision of valence electrons improves electrical conductivity. Polymers are made of repeating series of molecules that are attached by molecular bonds. Most polymers have weak yield strength due to the weak molecular bonds. Lack of valence electrons also makes the polymer poor conductors of heat and electricity. Composites are materials made by a combination of two or more primary material to improve the quality of the final product. The desired properties of resistance in the composite material include things such as tensile stress, compressive stress, corrosion, electrical conductivity, and thermal insulation. A good example of this is reinforced concrete. 3.0 Task 3 3.1 Methods of NDT Visual, Liquid penetration, Magnetic, Ultrasonic, Eddy current and X-ray a) Visual testing- it is broadly applied when checking for welded joints. It involves keen observation of the observer on any defaults available in the welded joints. Several things are inspected for the same. These include strength, porosity, distribution, and tightness. The method was used because of its cost effectiveness and simplicity when it comes to application. b) Liquid penetration- the test is performed to ensure the material being test is free from minor cracks and voids that can compromise the strength. An example of is the rails. The metals should be free from cracks and crevices, and the test gives desirable results. The method was used due to the simplicity of application and the presence of quality penetrants that are environmentally friendly. c) Magnetic- the method involves the application of magnetic field on the material. The induced magnetic flux together with iron filling on the surface of the material would detect any discontinuity since air does not support magnetic flux as steel. Applied in vehicle manufacturing industries. The method was applied due to the cost and high level of precision that can be attained. The material being tested is magnetic, and thus the method is desirable. d) Ultrasonic- the method involves the use of an instrument that generates an ultrasonic pulse that pass through a material. A receiver detects discontinuity of the pulse and the material is changed or meant. It is applied to companies that manufacture airplanes and aircraft parts due to the high level of sensitivity. The method was used due to the high level of precision attainable by the sophisticated machines that can detect even small crevices in the material e) Eddy current- the method involves testing discontinuities in the magnetic material by inducing eddy currents through the use of a solenoid. Variations in the eddy currents detected by a receiver can be used to detect flaws in a material. Used in aircraft manufacturing companies. The method was applied because the company deals with magnetic materials, and the method is suitable and precise in testing magnetic materials. f) X-ray- the method is used to develop radioscopic images of materials and detect porosity and discontinuity that cannot be detected with naked eyes. It is a very sensitive method and it is applied in pipeline companies that undertake the test of materials beneath the surface. The method was used because physical contact with the material is not needed for the testing to take place. Most pipelines are laid underground, and thus the method is effective. 3.2 Analysis of the functions of a product in terms of the materials’ constraints on its design A selection of material or a particular use is based on the desirable characteristics of the material. A good example of this is the piston of a car. The major thing is that the material making a particular component should be easily to handle or rather workability. The material made should be storable without the deterioration of quality with time. Production of the material at any stage should not negatively impact the environment or affect the wellbeing of the user or worker. The recovery of the material in terms of recycling should be achievable. 3.3 Required properties for the product and select the most appropriate materials and processing methods The piston of a car especially a heavy commercial vehicle is subjected to various forces. The material should have high tensile and compressive strengths for the effective utilization of energy from the burnt fuel. The material making the component should be light and hard to resists wear and tear as the moving parts come into contact with one another. Furthermore, the material should have a high melting point so as to maintain a high strength even when the temperature is raised as the vehicle moves. The preferable processing method of the material is casting of iron. Annealing should be applied to ensure sufficient cooling and arrangement of the microstructure for it to attain the proper strength. Casting method has two main limitations Achieving dimensional accuracy is a problem especially when producing in large scale. It is hard to avoid defects when using this method, and some of the pistons produced can underperform or rather be a waste. The technique requires high temperatures and the cooling system releases hot water to the environment which is dangerous. Furthermore, the energy required to raise the temperature leads to environmental pollution. 4.0 Task 4 4.1 Forms of steel Martensite It is formed by the increased rate of cooling or rather quenching of austenite. The carbon atoms are denied a chance to move out of the crystalline structure in a high amounts to form cementite. Face-centered austenite is changes to a body-centered tetragonal that has a high amount of carbon. The material has very high strength and improved ductility. Austenite-Also known as gamma iron, it is formed on an alloy of iron and another material that can be non-metallic such as carbon. Mostly, the material exists above the eutectoid temperature that is 730 degrees Celsius. It is non-magnetic and has a high strength. Cementite The material is also known as iron carbide and involves a combination of iron and carbon. It has an orthorhombic structure due to the arrangement of the combination. It is a hard material and brittle material. It is always classified as a ceramic. Perlite It is a type of material that is composed of alternating layers of alpha-ferrite and cementite. The long chains of interconnected layers are connected in three dimensions that explain the rough nature. The material is hard and has high plasticity that explains the use in making guitar wires. 5.0 Task 5 a) The material that is suited for this purpose is titanium or an alloy of titanium b) The choice of material is based on the mechanical property of titanium since it is light in weight and has a high strength. c) The treatment that the material can undergo is alloying and coating with another metal so as to improve the characteristics of the material. Alloying can be achieved by melting the material and mixing with other material like iron or carbon to give it a better quality. d) The part can be formed by casting. It involves making manipulating the material in molten state to achieve the desired shape. Cutting with a laser can also be achieved by manipulating the material in a solid state. e) Coating is one of the surface processes that can be done to reduce corrosion as it covers the material. The other method is plating which involves attaching a plate of inert material on the surface that prevents exposure of the material. 5.1 In-service failure Metals can experience fatigue failure and corrosion after continued use and exposure to the environment. Metals can be redesigned by creating an alloy and coating that will ensure it is lighter and resistant to corrosion. Ceramics experiences brittle fatigue as the materials are hard and have low plasticity compared to the metal. Ceramics can also experience a fracture. Redesigning a ceramic would mean increasing the plasticity due to the dynamic loads when the plane is landing or leaving. Polymers experience fatigue and brittle failure especially at low temperatures as the molecular bonds between the molecules get broken. Composites are prone to brittle failure, but it all depends on the material combination. Composites materials have very high yield strength and the breakpoint is catastrophic. 5.2 Failure of the retracting lever The retracting lever may fail due to fatigue and corrosion. The dynamic loads and continuous exposure to the first moving that also causes changes in pressure can cause the failure of the lever due to cracks and fractures. 5.3 Methods of investigating material failure Several methods are available for investigation material failure. Sounding is one of the methods in which a specialized tool is used to hit the material, and the produced sound can tell whether the material has fractures or spaces in between. Subjecting a used material to test on strength help determine the reduction in material strength and thus can be used to predict the service life of a particular material. 5.4 Improving service life of the retracting lever It can be achieved through alloying of the material to make is strong and resistant to rust and corrosion. Furthermore, it can be improved by providing a plate coat that prevent the lever from wear and tear when coming into contact with another and there is a generation of friction. References Ashby, M. and Jones, D. (2012). Engineering materials 1. Boston, Mass.: Butterworth-Heinemann. Read More