The Process of Selection of Materials - Term Paper Example

 MATERIAL SELECTION Table of Contents Page No Table of Contents………………………………………………………………...……ii Table of Figures……………………………………………………………………….iii Introduction……………………………………………………………………..…….1 The Use of Cambridge Material Selector and Granta Charts………………….….…..4 CES Selector…………………………………………………………………….……4 Granta MI……………………………………………………………………………..4 Selection Procedure…………………………………………………………………...5 Selection from Metal Alloys Candidates……………………………………………..7 Eco Design……………………………………………………………………………8 General Criteria for Typical Material Selection………………………………….…...9 Component Manufacturing Process: Casting…………………………………………9 Cost of Manufacturing Considerations…………………………………………..…..10 Reference……………………………………………………………………….……14 Table of Figure Fig. 1………………………………………………………………………………6 Fig. 2………………………………………………………………………………7 1.0 Introduction The process of selection of materials for certain engineering applications is a crucial step in designing the application or systems. As far as product design is concerned, the major objective of selecting the right material involves minimization of costs while at the same time trying to achieve the goals of the product performance and efficiency. The first step in systematic selection of materials for any engineering application starts with the material properties consideration as well as consideration of other factors such as costs of the material to be selected. A thermal blanket, for instance ought to have a poor thermal conductivity for minimizing the rate of heat transfer for a certain temperature difference (Lawton, 2004). The systematic selection of materials for these applications demands one to consider various criteria, which is definitely a more complex process. A rod that is supposed to be stiff as well as light needs a material which has high modulus of elasticity (Young’s Modulus) coupled with low density. For cases where the said rod needs to be pulled in tension the specific modulus which is modulus divided by the materials density would be employed in determining the most appropriate materials. Since the bending stiffness of the plate scales at the thickness (cubed), then the most appropriate material for the stiff as well as light material is found by determining the cube root of the stiffness divided by the materials density (Lawton, 2004). Comprehending the necessary material selection process is very significant in engineering design and applications. Material selection happens to be the basic of all engineering principles and applications in addition to engineering design. The process of material selection is defined by application requirements, physical properties and principles of the candidate material and possible material selection. The application requirements refer to the design or the specific function. Requirements are specific to certain applications. Possible materials refer to the kind of material that would be employed in the application. They are usually defined by the application requirements (Lawton, 2004). Physical principles usually refer to the approach of changing a material which is understood through material science techniques. Employing physical principles of material science can help in changing the properties of the specific materials. There are usually three common physical principles that can be used for strengthening of functional materials including composites, densification, and alloying. Several techniques of manufacturing are used in strengthening as well as forming materials used in engineering applications. Provided with the necessary application requirements, physical principles and possible materials, the most appropriate material for any engineering application can be selected. The first step is to consider the application requirements, and then we decide on the possible material which can be employed in that specific application. The necessary changes to be made in the material properties are considered and appropriate decisions made upon them. Out of the possible materials provided, the best material that fulfils the given requirements of that specific application is chosen. 2.0 The Use of Cambridge Material Selector and Granta Charts. CES Selector This is part of granta’s collection of software meant for management and use of material information. It is a focus PC-based instrument which provides graphical and intensive material analysis for enabling easy process of material selection a swell as decisions for material substitution. Granta MI on the other hand is an enterprise system which is used for management of all data related to the candidate materials. It offers secure, browser-based access and controlled data. In addition to this, it offers browser-based material selection technology deployment which assists the designers as well as engineers in making every day’s decisions regarding selection of materials. When employed together, both CES selector and GRANTA MI provides a complete solution to the process of selecting the appropriate material for an application. In this way hey assist the organization in making implementing strategic material decisions. 2.10 The Selection Procedure Combination of several material properties, the approach of processing them and the functions they are supposed to serve in the specific application in addition to their desirable shape were be crucial in defining the process of the materials election. CES thus provided database a swell as information regarding material processing and information regarding all the required applications. In order to find a short list of the application candidate materials, the basic information related to the materials are gotten from the database. After this the candidates which are not appropriate for the specific applications are eliminated. The remaining candidate materials then continued to be considered as candidates until indicated as being unsuitable after a very careful analysis (Williams,1992). This was the only approach of improving the chances of getting the most appropriate material for the said application. In spite of the fact that material limits including temperature of the service as well as the need to have transparency can have effect in limitation of the process considerations, they are not supposed to be part of the final selection process. In the final stages of material selection, there was need to employ optimization criteria such as specific stiffness (E/p) which would allow one to rank candidate materials. Information of the materials were received from the CES database although other reliable sources such as the data sheets by manufactures are useful in determination of the precise properties, prices as well as candidate materials availability. The material selection charts condensed the information into compact and easily accessible form. The charts revealed the correlations between the properties of the materials which assist in estimation and evaluation of data thus lending themselves to the optimization techniques. One approach used in selecting suitable material for the said component to consider the material’s stiffness, where the young’s modulus of the material was plotted on one axis while its density plotted on the other. Given that the material for the required component was supposed be above 5500C, a minimum tensile strength of 300 MPa and a minimum Yield Strength of 300MPa with a Maximum thermal expansion of 15 ustrain/0C , the required data points were plotted on the graph by the CES Selector for every candidate material considering Metal alloys, ceramics and polymers. Using this approach enabled easiness in finding the suitable material that had the highest stiffness as well as the one with the lowest density but having the best ratio () (Faulkner, 1995). Employing the scale on the two axes enabled the right selection of the most appropriate material that possessed the suitable plate stiffness (). Fig 1. Graph of Young’s Modulus against Density for the Metals, ceramics and Polymers. Metals which had higher stiffness were indicated by blue squares as ceramics are represented by green while polymers are represented by red. Metal alloys indicated the required properties hence were selected as possible candidates. The plot below indicates the same materials database of a number of materials. The families of the various materials such as metals, polymers, and foams were represented by some bigger bubbles. This graph was created with the use of CES selector software as well as necessary data from Granta Design. Fig. 2. Graph of Density against young’s Modulus 2.2 Selection from Metal Alloys Candidates The properties of engineering materials were normally indicated as material selection charts which are usually accessible and summarize the range of the properties as well as the specific classes of these materials for several applications in engineering systems and processes. The properties of the materials were usually influenced by the nature of the bonding of the atoms as well as the mass of these atoms which are involved in the packing. The materials nature of the packing was also considered in defining the properties of the needed materials. The charts were used in estimation and validation of the data related to these materials (Pool, 1997). Through such an approach, they offered hint regarding the potential application of the material in the engineering processes. The charts therefore served as the basis for all significant procedure in selection of materials for design from several metal alloy candidates. Using the CES, as the material database, one has access to a huge number of authenticated as well as detailed information regarding the materials in all relevant classes. This process involved more than just the profile of the material properties. The capability of shaping the said materials into the wanted form and shape would also have significant impact in the application. In development or forming of a component like this one indicated, the alternative one which would replace it would need to have the capability of resisting bending moment (which is a property of stiffness). The resistance to bending of several shapes was found by employing the second moment of Inertia. A cylindrical tube would have a high second moment of inertia for bending in all directions. Employing a certain material for he component members, it would be advantageous if the said material is shaped into tube shape. In this case steel and aluminum materials were given the first consideration as they indicated the said properties. The creation of better approaches for production of such materials with tube shapes out of several components and going ahead to join them would lead to making the particular materials more desirable to employ in such application. Since both Aluminum and steel alloys had the indicated properties and passed the tests, steel Alloys: Cast Iron was selected as the most appropriate candidate as it indicated higher physical properties than aluminum alloys. 3.0 Eco Design The Edupack software was employed in calculating the energy as well as the carbon footprint for the said component considering the steel alloy material at different stages of the alloys life cycle. It was used to select and investigate several materials and as well compare their environmental impact of the candidate materials as well as processes (GRANTA, 2010). This enabled us in making fast and approximate estimates of the impact of the material to the environment in the initial stages of design phase and helped in avoiding the later-stage challenges. The designer through this approach would be in a position to provide the best combination of the product performance as well as Eco design (IDSA, 2009). 4.0 Report on Criteria for The Material Selection. 4.10 Overview of Steel Alloy: Cast Iron 4.20 Background Study Discovery of steel started in 1900 but this came about through accumulation of efforts of various people in early 1820s. It started with invention of Bessemer process as it become material that was cheaply produced. Refinements such as steelmaking of basic oxygen which reduced the cost of production but increased the metal quality. It has currently emerged as a major component. Steel is an alloy which comprises of iron and some small contents of carbon with contents of about 2.1% by weight although this depends on the grade of the material. Carbon in alloy of steel has been the most cost-effective iron alloys. Other elements used in steel alloys include chromium, vanadium, manganese and tungsten. The Carbon elements are used as hardening agents which prohibit dislocations in the crystal lattice of iron atom from sliding past each other. The amount of elements in the steel alloy improves qualities such as ductility, hardness and tensile strength. Cast iron has higher content of carbon and have lower melting point and are easy to cast. 4.30 Requisition of Cast Iron Cast Iron is a readily available material in most hardware stores. To acquire the right cast iron material, one would need to get the specifications of the required material component. Since the required component needs to be of wall thickness of 10 mm, 200 mm in depth and 0.75 mm in diameter the cast iron material to be purchased has to be having the same dimensions. Cast Iron was selected as the most suitable candidate as it had qualified properties for the component requirements and could easily be manufactured. The cost of cast Iron is lower as compared to other metal alloys. It is also environmentally friendly as it releases les gases to the atmosphere. Cast Iron is also a durable metal which is able to exist for the required duration. 4.40 Component Manufacturing Process: Casting The manufacturing process for the component would involve casting of cast iron: Melting the metal at a temperature above 550 0 C to form a molten liquid metal. This would be poured in a replica container having the dimensions as the indicated component and dimension with some allowances due to expansion and contraction. The metal would then be allowed to solidify and then machined in a lather machine. Necessary facing, turning and finishing would be done on this component. 4.50 General Material Selection Criteria. While considering the material to select for an application, one has to consider such factors as the materials temperatures, pressure, fluid flow rate, stress analysis of the material, chemical environment and if the said material is in a position to withstand these conditions without failure. These service conditions don’t have to account for possible worse conditions as a result process upset and other unknown uncertainties. Another major consideration is the specific physical properties which the material must meet. These include a wide range of material section criteria such as fracture toughness, strength-to-weight ratio or density, resistance to corrosion, thermal and electrical conductivity, wear resistance and ability to be machined (Miller, 1999). One has to consider also if the said material has been dictated by applicable specifications, codes as well as local preferences and practices including ASTM, TEMA, ASME and Mil-Specs. There is need to check out whether there are good reasons for the local practices or preferences. A Major consideration to make while selecting an appropriate material for any application also includes the possible service life of the material. Will this be an ideal result or a definite requirement and will it be justified economically. The most possible material failure modes in the specific application ought to be put into consideration also. These include fatigue, corrosion as well as material wear. Other factors besides the selected material which might affect to a great extent the overall reliability of the material hence the application include quality of fabrication, on-site installation difficulties, design quality and maintenance completion difficulties during use. One has also to consider if a system approach has been used in evaluating the application as well as other attention on the said material. Consideration of the causes of failure in the specific application is crucial. Once this one has been established then it would be easy for one to find the most appropriate material which has the necessary features that can overcome these failures (Lawton, 2004). Another factor that one has to put into consideration while analyzing the selection of a material for a particular application would be the possibility as well as desirability of employing non-metallic material entirely or partially. Can this non metallic material serve the desired purpose on its own or when constituted on the metallic materials system. Welding is another factor to be put into consideration during the material selection process. In can the material or the alloy selected is in apposition to be easily welded but with special skills and precautions needed, one has to consider if the needed in-house personnel or the contract expertise are available for the operation and can be relied on for the satisfactory results (Farr, 1993). In cases of known corrosive conditions, if alternative corrosion control measures are practical. For instance, is the coating to be used suitable? Can an alloy which is resistant to corrosion suit to a carbon steel substrate to be employed instead of a solid plate which includes a more expensive alloy. Also one has to look at the suitability of the chemical corrosion inhibitor. Will it be suitable and possible to the application? The application in this case ought to allow the employment of cathodic safeguard for control of corrosion. Backs (2000) indicate that Economic consequences of a certain failure of the material’s part or the entire component would need to be considered. What would be the economic effects is the component or part of it fails? Will the failure be inconvenient but impose little or insignificant impact to the engineering application or will it have effect on the whole application such that the entire ,continuous production process or an engineering system demands to be shut down because of this failure. What would be the cost per time period in case the whole application or system fails? Will the costs of lost production be defined as the first costs of materials which can be an alternative to the one chosen? Will there be a severe safety hazard in case a failure results? (Dieter,1997). Would conduct a pre-fabricated spare in the organization’s invention come out to be practical as well as justifiable regarding the cost of the possible failure? Would it be practical to get only the required material which is considered long-time (or durable in this case) from the inventory then conduct the necessary fabrication only if a failure happens. One has to consider also if the initial cost of material would influence the decision of the selection process or if this would be controlled by the life-cycle using alternative materials which can be used in the specific application (Cheng,1965). This is a development or rather adaptive design which takes an existing design and improves it via better selection of materials. The development design comes up with a variant design under which a change of dimension or scale becomes necessary for a change of the said materials. Under every design stage (from conceptual to detailed), the most appropriate material is required, the nature of the data differs and become more accurate and less broad towards the final stages of the material selection. This final stage of design is done with the help of the specifications of the manufacturers. It might require in-house evaluation of the crucial properties. 4.60 Cost of Manufacturing Considerations Massey (2000) holds that, in materials selection process, the cost of the candidate materials playa a crucial role. The easiest approach to find the weight of cost against the materials properties is to establish a monetary metric meant for materials properties. For instance, the life cycle evaluation indicates that the net present value of lowering an object by 1 kg approximates to about $ 5. This implies that the material substitution that lowers the said weight can go at $5 for every kg of the weight reduced, which is more than the original material. This may however be affected by other factors including time dependence energy, geography, maintenance, geography as well as other costs incurred in the operations in addition to variation in discount rates(Attfield, 2000). With the increase of energy prices coupled with increase in technology, there is therefore need to substitute the high energy consuming materials. In addition to cost per kg evaluation, another crucial factor to consider as per as cost of the material is concerned include cost per unit of function. For instance, in cases where the objective of the design is the plate’s stiffness of the material, it would be appropriate to include material that has the optimal combination of Young’s Modulus, density as well as price. Since optimization of complex combination of price and technical properties becomes a tedious and hard technique to attain manually, rational selection of appropriate materials include the employment of material selection software (Attfield, 2000). References Attfield, J. 2000. Wild Things: The Material Culture of Everyday Life. Berg. Backs, R. 2000. Engineering Psychophysiology: Issues and Applications. Mahwah NJ: Lawrence Erlbaum Associates. Cheng, C. 1965. Scientific and Engineering Manpower in Communist China, 1949-1963. New York: National Science Foundation. Dieter, M. 1997. Overview of the Materials Selection Process: Materials Selection and Design. Cambridge: Cambridge University press. Farr, J. 1993. Personnel Selection and Assessment: Individual and Organizational Perspectives. Mahwah NJ: Lawrence Erlbaum Associates. Faulkner, W. 1995. Knowledge Frontiers: Public Sector Research and Industrial Innovation in Biotechnology, engineering Ceramics and Parallel Computing. Oxford: Oxford University Press IDSA. 2009. Ecodesign. Available at: http://www.idsa.org/whatsnew/sections/ecosection/selectedlinks.html [Accessed March 11, 2010] Lawton, B. 2004. The Early History of Mechanical Engineering. New York: Brill. Massey, A. 2000. Hollywood beyond the Screen: Design and Material Culture. Berg. Miller, A. 1999. The Material Life of Human Beings: Artifacts, Behavior and Communication. London: Routledge. Pool, R. 1997. Beyond Engineering: How Society Shapes Technology. Oxford: Oxford University Press. Williams, G. 1992. Natural Selection: Domains, Level and Challenges. Oxford: Oxford University Press. GRANTA. 2010. Teaching Sustainable Engineering and Eco Design. Available at: http://www.grantadesign.com/education/eco/index.htm [Accessed March 11, 2010] . Read More