In Mass Boom Wing Structure Engineering Essay

In throng Boom telephone extension Structure Engineering EssayWing structure is a main part of the aircraft which transmits go applied packs and provide and maintain aerodynamic shape.Mass Box institutionaliseBox beamMulti-sparDelta Winghttp//www.free-online-private-pilot-ground-school.com/images/ reference-components.gifFIGURE 1 Wing components (http//www.free-online-private-pilot-ground-school.com/aircraft-structure.html)1.1 Mass sweep through structureIn aggregative inflate 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 hook deposits with help of the ribs and span wise stiffeners. Mass holloa structure is broadly speaking use on slow aircraft with thick wings and low wing loadings. (Torenbeek.E 1999, p259)CUserscompaqDesktopCapturen.PNGFIGURE 3 Typical single spar Mass boom structure (SYNTHESIS OF SUBSONIC AIRPLANE DESIGN, 1988)Advantag es in Mass boom structureTapered booms are uncomplicated to manufacture and might be modified to the topical anesthetic stress level preferred. High stress levels are achievable.Dis receiptss of Mass boom structureFailure 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 chthonian bending loads are bountiful. The skin plays no part in, the absorbing the bending turn so that is not used very efficiently. If two-spar soma is used, the spar height is less than the airfoil oppressiveness. 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 structureIn box beam constructi on 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, moreover 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 append 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 geomorphological damage tolerance. http//www.scribd.com/doc/39959654/WINGAdvantages of box beam structureThe advantages of the box beam will be evident when abundant skin thickness is required to obtain sufficient tensional rigidity on wing design for high speed and thin, high aspect proportion wings. In lightly loaded wings, however the stress level in the upper skin will be kept fairly low to distract buckling and the differences in weight will be small as compared with the mass boom type.Disadvantages of box beam structureInteractions 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 call for more assemble time, increases complexity, stress concent ration areas and manufacturing cost.( http//www.scribd.com/doc/30983628/olaestruclayout-1)2. MATERIAL SELECTION FOR THE WING STRUCTURESeveral 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 crowning(pren ominal) stress Yield stress Stiffness Temperature limits Corrosion resistance Fatigue resistance Fracture toughness Fragility at low temperatures Crack harvest-feast resistance Ductility Maintainability Reliability FabricabilityThe main group of materials used in aircraft construction has been Wood Steel Aluminum alloys Titanium alloys Fiber reinforced composites aluminium alloys usage in structural partsIn 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 nigh 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 aluminum alloy used in Compression a pplications 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 applicationsMaterialRecommended Application2024-T3, T42, T351, T81Use for high strength tension application has trounce fracture toughness, slow crack growth rate and good fatigue life.2224-T3, 2324-T38% improvement strength over 2024-T3 fatigue and toughness better than 2024-T3.7075-T6, T651, T 7351Have higher strength than 2024, lower fracture toughness, and use for tension applications where fatigue is not critical.7079-T6Similar to 7075 but has better thick section properties than 7075.7150-T611% improvement strength over 7075-T5. Fatigue and toughness better than 7075-T6.717-T6, T651Use for compression application.Aluminium-Lithium10% lighter, 10% stiffer and superior fatigue performance than other AL alloys.PM AluminiumHigher 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, assist EDITION 2002, p 102)WoodThe 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.pdfSteelSteel are applied in va rious components in an aircraft. Steel is used for highly stressedComponents because of its high strength.TitaniumTitanium has an delicate 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.pdf3. BENDING MOMENT REDUCTION OF THE WINGThe 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 level best at the root. But its value is not proportionate 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 _A340Specifications)Bending moment = (Total weight*Total wing span)/8FIGURE 5 BENDING MOMENT VS SPAN POSITIONThemaximum bending momentmagnitude occurs at thewingrootWing weight is linearly proportional to the wing root bending moment. Therefore if we lop 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 reduction 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. whence in order to maintain balance smaller wing lift and larger tail plane lift will be required. The inboard swag 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 b e 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 appendix 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.CUserscompaqDesktopUntitled.pngFIGURE 6 LOADING EFFECTS ON A WING4. EFFECTS OF WING THICKNESS TO WING angleThe thickness of the airfoil affects the drag, maximum lift, stall char acteristics 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 lighterFIGURE 7 Effect of Thickness proportionality on Wing Weight (Airplane Design, 2002)GD method (Roskam, J, 2002, p69) to estimate the wing weight of the commercial transport aircraftsWw = 0.00428(S0.48) (A) (MH) 0.43 (WTO nult) 0.84 () 0.14/ 100 (t/c) m 0.74 (Cos 1/2)1.54 (Roskam, J, 2002, p69)Definition of cost and data of Boeing 747-400Ww = Structural weight of the wingS = Wing area in ft2 = 6027.78ft2A = Wing aspect ratio = 7.4WTO = Takeoff weight in lbs = 875,000lbnult = design ultimate load factor = 1.5 = Wing taper ratio = 0.37(t/c) m = Maxi mum wing thickness ratio1/2 = Wing semi-chord sweep angle = 33.50MH = Maximum Mach number at sea level = 0.885This equation is valid only in the following parameter rangesMH from 0.4 to 0.8(t/c)m from 0.08 to 0.15 and A from 4 to 12Ww = 0.00428(60280.48) (7.4) (0.885) 0.43 (875000- 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 = 36747.3657When (t/c)m is 0.15 Ww = 23078.37734From the above calculations we can come to a conclusion that the thicker wing is lighter than the thinner wing.(1494 Words)