History Of Materials In The Aviation Industry Engineering Essay

History Of Materials In The Aviation Industry Engineering Essay Aircraft materials have faced an overwhelming phase of change since the takeoff of the first designed aircraft to the skies. This has seen aircraft designers changing the design materials from merely wood and fibre in the early days to composite materials and aluminium alloys in modern days aircrafts. Composite materials and aluminium alloys were introduced in the industry rapidly. Due to advancement in technology the use of wood in manufacturing aircraft structures is now history. This review covers the use of composite materials and aluminium alloys in the design of modern aircrafts, both civil and military. It also compares the usage of these two materials in aircraft structures. Table of Contents INTRODUCTION Aircraft materials have faced an overwhelming phase of change since the takeoff of the first designed aircraft to the skies. This has seen aircraft designers changing the materials of design from merely wood and fibre in the early days to composite materials and aluminium alloys in modern days aircrafts. Early aircrafts were constructed mainly of wood and fabric, the Wright flyer (1903) is an example. Manufacturers preferred relatively light and strong wood such as spruce and fabrics, which were normally linen or something similarly close-weaved. These materials were selected looking at different characteristics which include among other the weight, strength, cost and availability of the material. Due to advancement in technology the use of wood in manufacturing aircraft structures is now a thing of the past. The use of metals in aircraft structures had to await modern material development processes such as alloy development. This processes produced stronger and better materials which allowed high speed flight. Materials produced were better as they allowed heavy loads and they showed better resistance to stress corrosion cracking. The introduction of computers has been of massive input in the field of aerospace. These seen engineers perform deep analysis of strain; stress and fatigue on new materials before there are introduced in aircraft structures. And as a result, the number of aircraft accidents reduced drastically. This review aims to cover the use of composite materials and aluminium alloys in the design of both civil and military modern aircrafts, and compare the usage of the two materials in aircraft structures. COMPOSITE MATERIALS Composites have been the most important materials to have been introduced in the aviation sector since the use of aluminium in the early years. Wright et al (2003) defines composite materials as, a combination of linear elements of one material in a matrix of one another material. This implies that composites are engineered materials made from two or more ingredients with significantly differing properties, either physical or chemical. The application of composite date back in the 1940s to the F-15 (US Air Force) fighters, which used boron/epoxy empennages. Initially the percentage by weight of composite materials used was 2%.Since then, the use of composites has rapidly accelerated. In 1981, the British aerospace- McDonnell Douglas AV-8B Harrier flew with over 25% of its structures made of composite materials (Schmitt, 2008). This shows that composite materials were introduced at a very high rate in the aviation industry. Though composites have been introduced in aviation with such a fierce rate, it was proved they are expensive to produce. They are also hard to inspect for flaws and some easily absorb moisture. Despite the above mentioned disadvantages, composites still play a major role in modern day aircrafts. This is so because of their greater strength and lighter weights. Callus (2007) claims that regardless of the disadvantages of composites, they were introduced because they allowed a quantum leap in aircraft performance. Performance is in the form of light weight, ability, useful payload and super high speeds. USES OF COMPOSITES IN AIRCRAFT STRUCTURES Since each aircraft is unique, it is impossible to generalise where various materials are being used in current aircrafts, but reference to a specific example illustrates the trend. Figure 1 below shows composite materials used in Boeing 787. http://people.bath.ac.uk/ck258/new%20materials%20documents/Composite%20materials_files/image002.jpg Figure 1. Composite materials used in Boeing 787 structures. Adapted from: http://people.bath.ac.uk/ck258/new%20materials%20documents/Composite%20materials.htm The above figure clearly gives a clear indication of the introduction of composites in aircraft structures. It can be confidently stated that composites form about 50% of the weight of the materials used in modern day aircrafts. This can be seen from the pie chart in figure 1. The commonly used composites are fibreglass, carbon laminate composites and carbon sandwich composite. Some composites include the Titanium and polymer matrix composites. COMPOSITION OF COMPOSITES Composite materials are made of two materials, one acting as the matrix and the other as the reinforcement material. These constituent materials determine the mechanical properties of the composite. The matrix has a lower density, stiffness and strength than the reinforcement material, and as a result the reinforcement of the matrix, to provide the majority of the strength and stiffness of a composite is accomplished by the fibres. They can be metallic, organic, synthetic or mineral. American Composite Manufacturers Association (2004) considers epoxy resins as one of the well known matrix material to have been used in a wide range of composite parts and structures. It further states that a major advantage of using Epoxy resins over other matrix materials is their lower shrinkage. http://navyaviation.tpub.com/14018/img/14018_593_1.jpg Figure 2. Aircraft advanced composite application usage. Adapted from: http://navyaviation.tpub.com/14018/css/14018_593.htm The table shows that the in early aircrafts composites were introduced in smaller quantities. This is the case with the F-14 aircraft which was first introduced in September 1974 (Hickman, 2012). Comparing the percentage of composite materials of the F-14 with the F/A-18, which was introduced in January 1983, one can notice that the F/A-18 contained a higher percentage of composites which is 20% as compared to the 0.04% of the F-14. This 19.96% difference may have been due to the introduction of modern material development processes. The mostly used reinforcement fibres are: glass fibre, carbon pitch based, Boron chemical vapour deposition (CVD) fibres, Alumina, Aramid, Carbon Polyacrylonitrile (PAN) and Polyethylene. Baker, Dutton and Kelly (2004, pp. 57) claim glass fibres are used mostly in airframes of gliders and in secondary structures such as fairings. The trio further explain that this is the case because this is where their low specific stiffness is not a problem in the design process, and because of their low cost as compared to high performance fibres. Such high performance composites include carbon fibre reinforced carbon. This is a composite material made from carbon fibre reinforcement in a carbon matrix. Diagram of carbon-reinforced carbon Figure 3. Material properties of a carbon fibre reinforced carbon. Adapted from: http://www.materialsviews.com/understanding-carbon-reinforced-carbon According to Grolms (2011), carbon fibre reinforced carbon is used mainly in high performance and high cost applications in aerospace technology. He further explains that this composite material is used widely in nose cones, wing leading edges in space shuttles and in aircraft brake systems. ALUMINIUM ALLOYS Aluminium has been the main structural element since 1930. This was made possible by its lightness as compared to other metals which are referred to as heavy, steel for example. Also, aluminium has been selected because of its indomitable strength to weight ratio. Although aluminium is not the strongest of the pure materials, its alloys use other elements to bridge the gap and improve its strength. Starke and Staley (1995) claims that aluminium is still selected as a structural material for the fuselage, wings and supporting structure for commercial airliners because of its well known performance characteristics, known fabrication costs, design experience and established manufacturing methods and practices. The duo continue on saying low specific gravity of aluminium leads to high specific properties giving aluminium alloys an upper hand in weight critical applications. Weight and strength Figure 4. Weight and Strength- aluminium is approximately one third as dense as steel. Aluminium alloys have tensile strengths of between 70 and 700 MPa. Adapted from: http://www.powerofaluminium.com/page.asp?node=45sec=Properties . Aluminium alloys were mainly created to tackle the weight problems of aircraft structures, but due to modern research and studies they have been recently studied for use in liquid oxygen and hydrogen fuel tanks, application which Starke and Staley (1995,pp.167) referred to as cryogenic. The development of aluminium-lithium alloy replaced the conventional airframe alloys. Its lower density property was thought to reduce the weight and accelerate the performance of aircrafts. This development, lead to the introduction of commercial alloys 8090, 2090 and 2091 in the mid 1980s (Davis, 1993). Weldalite 049 and CP276 were introduced shortly thereafter. Davis (1993) further says that aluminium alloys have a superior fatigue crack propagation resistance as compared to other alloys. This is due to high levels of crack tip shielding, meandering crack path and the resultant roughness induced crack closure (Davis, 1993). ANALYSIS AND COMPARISON OF ALUMINIUM ALLOYS AND COMPOSITES USES IN AIRCRAFT STRUCTURES The future of aluminium alloys in the aerospace industry seems brighter than that of its competitors, the composite materials. Even though the use composite materials is continuously growing, it recently became clear that aluminium alloys will in the near future be the winners of the fierce competition between the two materials. The airbus A380 give a clear indication of this. It shows that 61% of its structure is composed of aluminium alloys, 22% being composites, 10% is titanium and steel, and 3% of the structure is made of fibre metal laminates (Key to Metal, 2012). http://ars.els-cdn.com/content/image/1-s2.0-S1359645403005020-gr10.jpg Figure 5: Material distribution for Airbus A380 by percentage, Adapted from: http://www.sciencedirect.com/science/article/pii/S1359645403005020 It appears the rivalry between composites materials and aluminium alloys in the manufacturing of aircraft structures will continue to exist even in the future. This report claims aluminium alloys have the upper hand due to the fact that aluminium is less expensive as compared to composites, and recycling aluminium is not that difficult as compared to recycling composites, meaning that aluminium alloys are more environmental friendly. To support this claim, Arval (2010) pointed out that Bombardier has chosen Airware, a new aluminium alloy, for its upcoming CSeries, and Airbus has also shown that new aluminium alloys may be feasible for its next aisle aircraft. CONCLUSION In this report, the use of composite materials in aircrafts has been thoroughly discussed, pointing out their advantages and their disadvantages. The report identifies the main disadvantage of using composites in aircrafts being its high cost. The other disadvantage of using composite mentioned is their repair problems. It has been proved that composite can give a headache when it comes to repairing from ground damages, which usually avail themselves during baggage loading and other ground accidents. Nevertheless, the report also states that composites are still playing a major role in the aviation industry. This is due to their remarkable strength and their lighter weight. Also outlined in the report is the use of aluminium alloys in modern day aircrafts. Indicated in the report is that, even though aluminium alloys are not currently the main material for aircraft structure, they are awaited by a bright future. New aluminium alloys have been opted over composites for new aircraft technologies because they are recyclable, less expensive, and their characteristics and damage tolerance are well known. The development of new aviation materials since the 1980s was a major achievement in the industry since the number of aviation accidents reduced significantly. Carrying out more research on new aviation materials can see aircraft accidents reducing to probably zero, and this is a call for researchers to concentrate more on new aviation materials.

Designing a Manufacturing Process Toshiba´s Notebook Computer Assembly Line Essay

Whenever a new model is introduced at Toshiba, management attempts to improve the assembling process in terms of increasing productivity and decreasing costs. Attentiveness is directed towards reducing the amount of components and simplifying production and assembly. Manufacturing engineering manager Toshihiro Nakamura introduced a prototype assembly sheet concerning the new notebook model. The following precedence graph examines the process sheet. Task numbers: 1-17; task time in seconds (in brackets). The assembly line consists out of 6 workstations. Labour time (in seconds) for each workstation is indicated in brackets. Workstation 1, task 1 (75). Workstation 2, tasks 2 and 3 (85). Workstation 3, tasks 4, 5 and 6 (97). Workstation 4, tasks 7, 8 and 9 (105). Workstation 5, tasks 10-15 (101). (Workstations 6, 7 and 8 are operating the software load). The final workstation 9 handles tasks 16 and 17 (120). The sum of task time therefore equals 583 seconds. The assembly line is designed assuming that one notebook would be assembled every 2 minutes by six workers. Therefore, daily capacity of the assembly line would be 225 units (450 minutes operating time per day), assuming that on each one of the six workstations a computer is positioned at the beginning of the day. Initial production for the new model is 150 units per day, increasing to 250 the following week and eventually up to 300 units, depending on process success. The bottleneck in this assembly  line is located between workstation 4 and 5. Workstation 4 completes its tasks (7, 8, and 9) within 105 seconds whereas workstation 5 finishes after 101 seconds. This results in a slack of 4 seconds per unit at workstation 5. A potential solution to this problem might be assigning higher skilled staff to workstation 4 in order to push on assembly time. More detailed recommendations will follow. This bottleneck constitutes the major issue within this production process and will be examined in more detail in the following. Analysing the major issues concerns calculating potential slack times at workstation 5 regarding different amounts of units being produced. With the initial production of 150 units per day, a slack of 600 seconds (10 minutes) at workstation 5 would appear per day. It takes 3 minutes to finish one unit, assuming that 150 units are produced per day with an operating time of 7.5 hours. Producing 250 units per day means that one unit is assumed to be finished after 1.8 minutes or 108 seconds. When production increases up to 300 units per day, operating time per unit would be 1.5 minutes or 90 seconds. Hence, increasing production results in increased slack times at workstation 5. With a production of 250 units per day, slack time would be 1000 seconds or 16.67 minutes. Within those 16.7 minutes of slack time, 9.3 units could have been produced. With a production of 300 units per day, slack time would even increase up to 20 minutes in which 13.3 units could have been produced. These calculations clearly illustrate inefficiency at workstation 4 which results in major costs due to relatively high idle times. Extrapolating these numbers up to a working week, assuming that 5 days à ¡ 7.5 hours the assembly line is in operation, significantly high slack times and therefore unnecessary costs arise. Assuming a production of 250 units per day, slack time at station 5 per week would be 83.5 minutes in which an additional 46 units could have been produced. Efficiency of the assembly line will be calculated in the following with regard on different amounts of units being produced. Eventually the optimal number of units to reach an efficiency of 100% will be calculated. With 250 units produced per day, a cycle time of 108 seconds per unit results. Hence, using the formula for calculating the line ´s efficiency, (sum of task times = 583 seconds/6 workstations x 108 seconds cycle time) results in an efficiency rate of m89.97% (~ 90%). Running at a maximum capacity of 300 units per day (583/6Ãâ€"90), line efficiency would be 107.96% which is not close to reality. Relative to its use of labour, an efficiency of ~ 108% producing at maximum capacity is not achievable. More workers would be needed and staff would have to work on one task simultaneously. An efficiency of 100% can be reached with a daily production of 277 units per day assuming that the assembly line maintains its initial set up of 6 workstations with the same labour time. The actual efficiency rate (with 277 units produced per day) constitutes 99.66% which is the maximum that can be reached. In order to dispense the previously discussed issue of inefficiency at workstation 4, several recommendations will be highlighted. Firstly, the easiest solution in relation to not changing the assembly set up would be to assign more skilled workers to station 4 in order to speed up the assembling process. Going hand in hand with this assumption is that the supporter might help staff at workstation 4. The problem is though, that the supporter ´s task certainly is to help out the assembly workers where help is needed but his/her task is not to stay in one spot at all times. Moreover, redesigning the assembly set up might benefit workstation 4. The redesign is concerned with the optimal placement of staff. In the case of Toshiba ´s assembly line it might be helpful to expand the section of workstation 4 in order to place one or two additional workers. Another possible solution might be to place additional staff not just on one side of the conveyer belt but on the other one as well. Especially in the section of workstation 4 additional help from across might be a solution. The assembly line has space for a total of 12 positions. Not all are being used. Another potential determination might be to split up workstation 4 into two and place the new one in a free spot. Regarding the calculations of slack times and efficiency with different amounts of units being produced, one can conclude that Toshiba ´s assembly line is relatively efficient but has space to improve. Workstation 4 represents the main problem of this case but several potential solutions were presented. Overall efficiency of this assembly line is quite high and appropriate. (All calculations were made without considering any break times)

College Essay Samples Background Story Reviews & Tips

College Essay Samples Background Story Reviews & Tips Whenever you opt to ask us for skilled guidance, don't hesitate to get in touch with our support managers. There's, naturally, a limit on the variety of pages even our finest writers can produce with a pressing deadline, but usually, we can satisfy all the clients seeking urgent assistance. Whether you should locate a strategy to fulfill your school or visa requirement, or simply to supply you with the coverage you require, start looking so that you can discover a plan and get same-day coverage! In order to construct a logical chain, you are in need of a plan of writing. The major part and conclusion are the two most necessary elements of the essay that show your knowledge of the topic. Some individuals have short attention span so that you will need to have the writing skills to produce your point with only a few words. In Harrison Bergeron, everybody is wrong to believe that everyone can be equal. Narrative writing has become the most simple sort of work. Personal narrative essays are about personal experience that's presented in the very first individual. Use a brief anecdote, a brief you're writing. If the writer is just discussing his ideas, the reader isn't going to anticipate a finished work. A thriving personal essay is in somewhere to station powerful and strong messages to the reader. The primary aim of the introduction is to bring the reader to the most important part. Another benefit of our website is the quickness. Thus, our principal feature is to supply quality stories. What You Should Do to Find Out About College Essay Samples Background Story Before You're Left Behind One have to bear in mind a specific regularity in the usage of verbal forms. Also remember this kind of essay requires you to write from your own standpoint, so utilize suitable words to express your own mindset. Our private essays are composed to satisfy your needs so that it's possibl e to secure your dreams. The introduction and conclusion shouldn't be more than 25% of the full work, the principal part being 75% of the job. Be certain to use the wording of exactly the question you're working on. A huge conclusion section is a huge minus, which says that you cannot summarize your thoughts concisely. Stubborn individuals continue to make the very same decision repeatedly even when initial evidence provides a better solution. Thus, there are several ways an essay can be written. The essay has to be viewed via the program. Of all Of the forms of essay, writing a brief essay may appear to be the easiest. Beginning an essay with a succinct story has become the most common and effective of such procedures. All you need to do is specify if you would like your article to be delivered. Short essays, as its name implies, needs to be concise and succinct. All you need to do is specify if you'd like your essay to be sent. All you need to do is specify if you prefer your essay to be sent. The Battle Over College Essay Samples Background Story and How to Win It Writing is quite a strong tool. In spite of exceptional grades a poorly written essay will provide you with a lousy name. Writing a persuasive essay can be challenging because you're not merely presenting the research materials you have gathered but you're trying to influence your readers. Writing the college application essay can be among the most daunting pieces of applying to college. Imagine the attribute of writing you'll receive from an inexpensive essay writing service. Buy essays from us and you could always be sure of excellent paper that may assure you quality grade. You should start your work with the analysis of the topic, on the grounds of the analysis of the topic of the essay, you opt for the material, the key facts, and the essential points of your paper. The actual folks highly praise our essay help site. The Nuiances of College Essay Samples Background Story Each paragraph starts with a topic sentence in which you state your case or objective. The topic is followed by many sentences that provide evidence and analysis to back up your argument. Ultimately, a concluding sentence provides a transition to the subsequent paragraph. When writing your body paragraphs, make certain each paragraph is all about one specific message. The Lost Secret of College Essay Samples Background Story Sample college admission essays give applicants an opportunity to figure what things to write and what things to avoid. The conclusion should have a synthesis or a concise summary. How to be a better leader essay. How to compose a fantastic thesis and intro paragraph. Students lead busy lives and frequently forget about a coming deadline. Let's say you pay for over 10 orders for the length of a class. Your orders will be done exactly as you desire.

Fluid Mechanics Free Essay Example, 2000 words

1.60 cfs c. 1.28 cfs b. 1.43 cfs d. 1.15 cfs Computations d = 8† = 0.67 ft, r = 0.333 ft L = 5,400.00 ft H = 40.5 ft n = 0.013; n value for new cast iron pipe Solve for C using Mannings formula C =  Area = Ï€(r)2 =Ï€(0.333)2 = 0.3483 ft2 R =  R =  R =  =  = 0.1665 Q = Av Q = A  Q = 0.3483 Q = 1.12 cfs 10. a symmetrical trapezoid plate has the following dimensions: the width of the parallel sides are, respectively, 2.50 ft and 4.50 ft. The perpendicular distance between those is 1.50 ft. The plate is submerged in a liquid in a vertical position with the parallel sides horizontal and the shorter parallel side at the top and exactly in the surface of the liquid will be a. 5.43 cu. We will write a custom essay sample on Fluid Mechanics or any topic specifically for you Only $17.96 $11.86/pageorder now Ft c. 6.93 cu. Ft b. 4.31 cu. Ft d. 7.68 cu. Ft Computations: Static Moment of the plate w/ respect to the surface of the liquid Static moment of the rectangle = 2.5 (1.5)  = 2.8125 Static moment of the 2 triangles = (1)(1.5) = 1.50 Total Static moments = 2.8125 + 1.50 = 4.31 cu. ft 11. The diameter of a new cast iron pipe in which water is flowing is 6.0 in. ,and the estimated velocity is 5.83 fps. The friction factor, determined from table 4 and expressed to four decimal places, is a. 0.0239 c. 0.0233 b. 0.0236 d. 0.0129 The answer of this problem can be taken from table 4 in the textbook. 12. the pipe described in question 11 contains four 90 ° elbows and two y’s. The sum of the minor losses in head caused by these fittings is a. 7.20 ft c. 4.33 ft b. 6.00 ft d. 3.80 ft Computations: Diameter = 6 inches = 0.5 ft. , r =. 25 ft A = Ï€ r2 A = 3.1416(0.25) A = o. 20 ft2 Q = Av Q = 0.20 ( 5.83) Q = 1.20 cfs Qtotal = sum of Q1 - Q6 Q total = 7.20 cfs 13. In the Hazen-William formula, the value of the factor C for a certain pipe may be taken as 145. The diameter of the pipe is 16 in. Its length 6400 ft, and the head tending the cause flow is 52.0 ft. The rate of discharge for the pipe in gallons per minute is a. 4100.00 gpm c. 2650.00 gpm b. 3380.00 gpm d. 1900.00 gpm Computation: Diameter = 16 inches, radius = 8 inches = 0.666 ft. Area = Ï€ r2 = 1.3932 ft2 R =  R =  R = 0.3326 V = 1.318 C (R)0.63 (S)0.54 V =  V = 7.0904 fps Q = Av Q = 0.4435 (7.0904) Q = 9.88 cfs = 9.88 (7.477) (60) Q = 4432 gpm ≈ 4100.00 gpm 14.