In Mass Boom Wing Structure Engineering Essay

In Mass Boom Wing Structure Engineering Essay Wing structure is a main part of the aircraft which transmits resist applied loads and provide and maintain aerodynamic shape. Mass Box beam Box beam Multi-spar Delta Wing http://www.free-online-private-pilot-ground-school.com/images/wing-components.gif FIGURE 1: Wing components (http://www.free-online-private-pilot-ground-school.com/aircraft-structure.html) 1.1 Mass boom structure In mass boom wing structure there are flanges with one or two spares to bear the bending and the torsional load is carried by spar webs. The outer wing is only works against the buckling due to shear forces with help of the ribs and span wise stiffeners. Mass boom structure is mostly use on slow aircraft with thick wings and low wing loadings. (Torenbeek.E 1999, p259) C:UserscompaqDesktopCapturen.PNG FIGURE 3: Typical single spar Mass boom structure (SYNTHESIS OF SUBSONIC AIRPLANE DESIGN, 1988) Advantages in Mass boom structure Tapered booms are uncomplicated to manufacture and might be modified to the local stress level preferred. High stress levels are achievable. Disadvantages of Mass boom structure Failure of spar boom is catastrophic, due to the absence of fail-safe characteristics; the mass boom wing structure is no longer used in new transport aircraft designs. Due to the high stress in the spar boom the deflections under bending loads are large. The skin plays no part in, the absorbing the bending moment so that is not used very efficiently. If two-spar configuration is used, the spar height is less than the airfoil thickness. The forces in the spar booms due to bending are thus increased and more material will be required. Many ribs are required to stabilize the spar booms. The skin will be buckle when loaded if no stringers are used; this will adversely affected the aerodynamic cleanness. (Torenbeek.E 1999, p260) 1.2 Box beam structure In box beam construction there are thin skins or webs and stringer jointed in box shape. This wing designed to carry shear, bending and torsional loads. Box beam structures incorporate skin panels, which are stressed only to take shear forces, but also the end load due to bending. From the point of view of fail-safe design and stressed skin structure is much better than the mass boom type. (Torenbeek.E ,1999, p260) This method is more suitable for aircraft wings with medium to high load intensities and differs from the mass boom concept in that the upper and lower skins also contribute to the span wise bending resistance. Another difference is that the concept incorporates span wise stringers to support the highly-stressed skin panel area. The resultant use of a large number of end-load carrying members improves the overall structural damage tolerance. http://www.scribd.com/doc/39959654/WING Advantages of box beam structure The advantages of the box beam will be evident when considerable skin thickness is required to obtain sufficient tensional rigidity on wing design for high speed and thin, high aspect ratio wings. In lightly loaded wings, however the stress level in the upper skin will be kept fairly low to avoid buckling and the differences in weight will be small as compared with the mass boom type. Disadvantages of box beam structure Interactions among the ribs and stringers are a main advantage of the box beam, because of these ribs has to go by the stringers or path of the load can be fail. Also this structure has many joints which make the wing structure heavy. It needs more assemble time, increases complexity, stress concentration areas and manufacturing cost.( http://www.scribd.com/doc/30983628/olaestruclayout-1#) 2. MATERIAL SELECTION FOR THE WING STRUCTURE Several significant factors considered when selecting materials for aircraft structural applications. http://www.scielo.oces.mctes.pt/pdf/ctm/v20n3-4/v20n3-4a11.pdf Materials properties such as: à ¢Ã¢â€š ¬Ã‚ ¢ Ultimate stress à ¢Ã¢â€š ¬Ã‚ ¢ Yield stress à ¢Ã¢â€š ¬Ã‚ ¢ Stiffness à ¢Ã¢â€š ¬Ã‚ ¢ Temperature limits à ¢Ã¢â€š ¬Ã‚ ¢ Corrosion resistance à ¢Ã¢â€š ¬Ã‚ ¢ Fatigue resistance à ¢Ã¢â€š ¬Ã‚ ¢ Fracture toughness à ¢Ã¢â€š ¬Ã‚ ¢ Fragility at low temperatures à ¢Ã¢â€š ¬Ã‚ ¢ Crack growth resistance à ¢Ã¢â€š ¬Ã‚ ¢ Ductility à ¢Ã¢â€š ¬Ã‚ ¢ Maintainability à ¢Ã¢â€š ¬Ã‚ ¢ Reliability à ¢Ã¢â€š ¬Ã‚ ¢ Fabricability The main group of materials used in aircraft construction has been: à ¢Ã¢â€š ¬Ã‚ ¢ Wood à ¢Ã¢â€š ¬Ã‚ ¢ Steel à ¢Ã¢â€š ¬Ã‚ ¢ Aluminum alloys à ¢Ã¢â€š ¬Ã‚ ¢ Titanium alloys à ¢Ã¢â€š ¬Ã‚ ¢ Fiber reinforced composites Aluminium alloys usage in structural parts In aircraft structures Aluminium alloys are mainly used since its a relatively low-cost, simply produced and machined. Rib is a structural part of the wing to which keeps the aerodynamic profile, and oppose the distributed aerodynamic pressure loads along with the skin, distribute concentrated loads into the structure redistribute stress around any discontinuities Increase the column buckling strength of the stringers through end restraint.( http://www.scribd.com/doc/30983628/olaestruclayout-1#) Increase the skin panel buckling strength. Group 7000 aluminium alloy used in Compression applications like this, where static strength is more important than fatigue or damage tolerance. It is also used in Upper wing surfaces and beams. Wing Spars Transmit bending and tensional loads. Produce a closed-cell structure to provide resistance to torsion, shear and tension loads. (http://www.scribd.com/doc/30983628/olaestruclayout-1#)These usually comprise thin aluminium alloy webs and flanges, sometimes with separate vertical stiffeners riveted to the webs. The flanges are extruded or machined and bolted or riveted onto the webs. Skin is to form impermeable aerodynamic surface, Transmit aerodynamic forces to ribs stringers, Resist shear torsion loads.( http://www.scribd.com/doc/30983628/olaestruclayout-1#) Aluminium alloy used to manufacture the wing. Aluminium alloys and their recommended applications Material Recommended Application 2024-T3, T42, T351, T81 Use for high strength tension application; has best fracture toughness, slow crack growth rate and good fatigue life. 2224-T3, 2324-T3 8% improvement strength over 2024-T3; fatigue and toughness better than 2024-T3. 7075-T6, T651, T 7351 Have higher strength than 2024, lower fracture toughness, and use for tension applications where fatigue is not critical. 7079-T6 Similar to 7075 but has better thick section properties than 7075. 7150-T6 11% improvement strength over 7075-T5. Fatigue and toughness better than 7075-T6. 717-T6, T651 Use for compression application. Aluminium-Lithium 10% lighter, 10% stiffer and superior fatigue performance than other AL alloys. PM Aluminium Higher strength, good fatigue life, good toughness, higher temperature capability and superior corrosion resistance. TABLE 2: ALUMINIUM ALLOYS AND THEIR RECOMMENDED APPLICATIONS (FROM AIRFRAME STRUCTURAL DESIGN, SECOND EDITION 2002, p 102) Wood The first aircraft were constructed from wood since Wood has a good Strength/weight ratio about 0.1 same as aluminum alloys. http://www.scielo.oces.mctes.pt/pdf/ctm/v20n3-4/v20n3-4a11.pdf Steel Steel are applied in various components in an aircraft. Steel is used for highly stressed Components because of its high strength. Titanium Titanium has an excellent relation stress/weight, good Resistance to corrosion and good creep proprieties. Its uses are limited for special proposes. http://www.scielo.oces.mctes.pt/pdf/ctm/v20n3-4/v20n3-4a11.pdf 3. BENDING MOMENT REDUCTION OF THE WING The bending-moment is the force at each location on the spar that bends the wing upward during normal non-inverted flight, the force rotating the wing around the fuselage. The bending-moment is zero at the wing-tip and maximum at the root. But its value is not proportional across the span. In other words, it is not half as much at the wing mid-point as it is at the root. In fact, the mid-point bending-moment is only about a 1/4 of the root value. A340-200 is a modern passenger transport design which has box beam structure wing with 197ft wing span and 610,000 lb maximum takeoff weight.( http://en.wikipedia.org/wiki/Airbus_A340#Specifications) Bending moment = (Total weight*Total wing span)/8 FIGURE 5: BENDING MOMENT VS SPAN POSITION The  maximum bending moment  magnitude occurs at the  wing  root Wing weight is linearly proportional to the wing root bending moment. Therefore if we reduce the weight of the aircraft by using light material it can reduce the maximum bending moment on the wing root. Also the wing span is proportional to bending moment; the bending moment can be reduced by reducing the wing span of the aircraft. Wing with high aspect ratio with entire swept box structure wing moves towards the root and therefore forward of the aircraft. Then in order to maintain balance smaller wing lift and larger tail plane lift will be required. The inboard shift in the lift will decrease the wing root bending moment. When engines are mounted on the wings, their weight is obviously going to be borne by the wing structure, along with inertia loads as the aircraft maneuvers. Thrust forces from the engines will also be carried by the wings. With pod-mounted engines the thrust force is bellow the wing and so this tends to twist the wing. This can be used to balance the effect of the aerodynamics of the wing which creates a nose down pitching moment. Another advantage of wing mounted engines is that their weight is close to the area in which lift is produce. This reduces the total fuselage reducing the shear force and bending moment at the wing attachment to the fuselage. So putting the engines on the wings provides bending relief. (Wilkinson 2009,p 32) Outboard fuel tanks reduce the wing bending moment. If the landing gear is not mounted under the wing it reduces the wing weight and it also reduce the bending moment of the wing. Braced wings reduce the wing weight by 30% and it helps to reduce the bending moment of the wing. C:UserscompaqDesktopUntitled.png FIGURE 6: LOADING EFFECTS ON A WING 4. EFFECTS OF WING THICKNESS TO WING WEIGHT The thickness of the airfoil affects the drag, maximum lift, stall characteristics and the structural weight. The thickness is generally given as a ratio of the chord which is referred to as the thickness ratio or the thickness to chord ratio (t/c). An airfoil with a high thickness ratio decrease wing weight since both bending and torsional thickness increase with increasing the thickness. (Roskam, J, 2002, p69) Wing weight is strongly affected by thickness, particularly for cantilever wings. Thicker is lighter FIGURE 7: Effect of Thickness Ratio on Wing Weight (Airplane Design, 2002) GD method (Roskam, J, 2002, p69) to estimate the wing weight of the commercial transport aircrafts Ww = {0.00428(S0.48) (A) (MH) 0.43 (WTO nult) 0.84 ( Ã‚ ¬) 0.14}/ [{100 (t/c) m }0.74 (Cos Æ’â„ ¢1/2)1.54 ] (Roskam, J, 2002, p69) Definition of terms and data of Boeing 747-400 Ww = Structural weight of the wing S = Wing area in ft2 = 6027.78  ft2 A = Wing aspect ratio = 7.4   WTO = Takeoff weight in lbs = 875,000  lb nult = design ultimate load factor = 1.5  Ã‚ ¬ = Wing taper ratio = 0.37 (t/c) m = Maximum wing thickness ratio Æ’â„ ¢1/2 = Wing semi-chord sweep angle = 33.50 MH = Maximum Mach number at sea level = 0.885 This equation is valid only in the following parameter ranges MH from 0.4 to 0.8 (t/c)m from 0.08 to 0.15 and A from 4 to 12 Ww = {0.00428(60280.48) (7.4) (0.885) 0.43 (875000ÃÆ'- 1.5) 0.84 (0.37) 0.14}/ [{100 (t/c) m }0.74 (Cos 33.50)1.54 ] When (t/c)m is 0.08,Ww = 36747.3657 When (t/c)m is 0.15 Ww = 23078.37734 From the above calculations we can come to a conclusion that the thicker wing is lighter than the thinner wing. 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Jack: Almost the Hero of Lord of the Flies :: Lord of the Flies Essays

Jack: Almost the Hero of Lord of the Flies Jack Merridew is the devil-like figure in the story, Lord of the Flies. Jack is wicked in nature having no feelings for any living creature. His appearance and behavior intimidates the others from their first encounter. The leading savage, Jack leans more towards hunting and killing and is the main reason behind the splitting of the boys. It has been said that Jack represents the evilness of human nature; but in the end, Jack is almost a hero. With his totalitarian leadership, he was able to organize the group of boys into a useful and productive society From the beginning of the novel Jack intimidates the other boys with his flaming red hair, his long black cape, and the brutal way he shouts orders to his choir. Although he is not a good-looking boy, he is amazingly arrogant. He always has to look good in people's eyes. Not that he cares if people like him, but more that they respect him. The only way he knows how to gain people's admiration is by getting them to fear him. He spots Piggy as an easy target and immediately starts to humiliate him in front of the others: "You're talking too much," said Jack Merridew. "Shut up, Fatty."(21) He sizes up Piggy right from the beginning knowing that Piggy wouldn't stand up to him and by making fun of him he was letting the other boys know that he not one to be messed with. When he feels that people are about to think him to be weak or gutless, he uses his knife as if it were a symbol of his superiority: "Jack slammed his knife into a trunk and looked round challengingly"(33). His knife gives him power, a weapon that he would use against anyone who dares to mock him. He shows early on how he has no sympathy for anyone. For example, when Simon passed out from heat exhaustion on the beach Jack showed no compassion: "Let him alone.He's always throwing a faint."(20) Simon was not a stranger, he was a boy that Jack has spent a great deal of time with and yet he displays no feelings for him at all. He demonstrates a great deal of power over his choir. He orders them around as if they were puppets that he controls by working their strings and making them dance at will.

B Wordsworth

â€Å"B. Wordsworth† is the creation of V. S. Naipaul about the story of a boy and a man who felt like being a poet but, unfortunately, could never be one. As one of the most widely read and perhaps interpreted writers of Caribbean descent, V. S. Naipaul presents a poetic view of the challenges of being part of Caribbean society during that time. It reflects the impact that a foreign culture and a foreign language had upon the natives. Yet, it does not condemn this fact but rather embraces it in an unfamiliar way.The main character, B. Wordsworth, is a tramp, a vagabond who resides in a very simple one room hut that is surrounded by weeds, trees and bushes that are overgrown. He not only lives a life of modesty and simplicity but he also has an unusual appreciation for nature. This is shown by his comments on the stars and during the time when he shows the young boy the different trees. The thing that made him different, however, was the fact that while he was a man of simple means he spoke English in a peculiar, unnatural manner.It is this fact which draws the attention of the young boy and invites the scorn of his mother. A critical analysis of the circumstances and the events that transpire in the story will reveal that there is an internal struggle that the characters have to face. The misplaced English that the boy speaks as compared to the flawless English of B. Wordsworth mirrors the social climate in the Caribbean during that time.This contrast also reveals the irony that exists in the life of not only the boy but also the vagabond as the realization of having a dream but not the capacity to pursue such dawns upon him in the twilight of his years. B. Wordsworth and perhaps the boy who followed his dream wanted to be poets but could never be one. The seemingly poetic language of the boy and the poetic nature of B. Wordsworth show that the poetry existed not in language but in his lifestyle. The magically garden that existed amidst the concrete jun gle is a testament to this but is sadly one that was torn down only to exist in the boys memory.

Reflection of Cannibalistic Societies through Diary of a...

The meager image depicted by Lu Xuns Diary of a Madman projects an illustration of society that stresses submission to authority, and the ultimate compliance to tradition. Lu Xun battles the idea that society is constantly being manipulated and controlled by the masses of people who know no better than to follow tradition. His story Diary of a Madman gives the representation of a culture that has not only failed, but failed by the cannibalistic nature of humans corrupting them-selves over and over again therefore feeding upon themselves. The analysis of Diary of a Madman gives way to a new interpretation of societies of the past, present, and future. Following the idea that history tends to repeat itself, I have paralleled the†¦show more content†¦The content of the story is divided into thirteen chapters that project images of society in discrete ways. The preface of the story begins explaining the story of two male siblings who remain nameless and identity less throug hout the story. The men can be seen as society as a whole, without a name, without an identity, without individuality. The identity of a culture is very important to give separation between individuals, but in the story there is no distinct characteristic described that can set these two men apart from any other two men. Without the individualism of nations, cultures, and people, identity can never be established or characterized. As the story unfolds the main character, the diarist, announces the idea that one must always be in a constant state of awareness, always ready for attack. The thought that someone could cast a look of fear upon another, but at the same time reflect an attitude of complete hostility towards another begins the diarist?s paranoia for others. Paranoia is a theme that runs wild in the ?Diary of a Madman?, disillusioning the diarist into feeling that he is going to be attacked by others, or even worse eaten. This false belief that people are plotting against the diarist is the central story line of the story. Although the idea of cannibalism may not be a worry in today?s society, the paranoia of society still exists. For example, the paranoid society of Nazi