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LANDING GEAR SHOCK ABSORBER DESIGN Presented by : 1.Maruf Khondker (L) ID : A.K.M Lutful kabir ID : Amen Younes ID : Md Shelimuzzaman ID : Shafiul Islam ID : CONCORDIA UNIVERSITY MECH 7501, SUMMER 2009 Presented to : Professor DR. S.V. HOA

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Introduction Configuration Design and Analysis Finite Element Analysis (FEA) Material Selection and Manufacturing Weight Estimation and Comparison. Conclusion. 45 Second Video OUTLINES

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INTRODUCTION Landing gear is a critical part & has significant effect on aircraft performance. The basic function is to support aircraft, absorb & dissipate impact kinetic energy. Early build airplanes conventionally used metal skids as landing gear. It is able to supports the airplane weight but is not able to absorb the landing shock. Oleo Pneumatic shock absorber is selected for high efficiency as they can absorb & remove vertical kinetic energy simultaneously. Composites are being increasingly used due to weight saving,reduction in fabrication cost, specific stiffness & strength properties.

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Aircraft Choosing I.Beech craft Model 99.

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II.Hawker 850 XP. Aircraft Choosing

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Shock Absorber dimension calculations I.Shock absorber choosing. Type: Oleo-pneumatic shock absorber Reason: High efficiency. absorb and remove vertical kinetic energy simultaneously.

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Shock Absorber dimension calculations II.Landing gear Load distribution

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Shock Absorber dimension calculations II.Main shock strut calculations: a.Stroke calculation. b.Piston outside diameter. c.Inside cylinder diameter. d.Total cylinder length.

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Shock Absorber dimension calculations Result of Dimension Calculations

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STRESS ANALYSIS AND LAMINATE DESIGN Methodology: Netting theory. Classical Lamination Theory (Layer by layer analysis.)

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Procedure: I.Lay-up sequence choosing. II.Strain in the laminate. III.Off-axis & On-axis stress for each ply. IV.Hill-Tsai Criterion. V.Evaluation STRESS ANALYSIS AND LAMINATE DESIGN

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Results

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STRESS ANALYSIS AND LAMINATE DESIGN

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Summary of Analysis

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Different material has different properties. That are needed for various applications require the material should be chosen according to the choice of a given application. Depending on a selection of a material, the design, processing, cost, quality and performance of the product change Material selection is important to redesign an existing product for better performance, lower cost, increased reliability, decreased weight, etc MATERIAL SELECTION

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Material should be selected such that it can store the greatest elastic potential energy per unit volume without failure. Component Specification Shock resistance of landing Resist the vibrations during the flight Thermal requirements: -60°C

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Reinforcement system I.Carbon fibers (UHM) high strength and stiffness (E = 500 GPa) tolerance to high temperatures and corrosion low weight expensive II.Glass fiber ( R glass) High strength Medium stiffness (86 GPa) Corrosion resistance Fatigue resistance Low cost w.r.t carbon fiber Matrix system Epoxy: good mechanical properties (E = 4.5 GPa) humidity resistance adhere very well to reinforcement fibers expensive MATERIAL SELECTION

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COMMON MATERIAL USED IN LANDING GEAR Aircraft materials are of high specific strength, and corrosion-resistant alloys Steel : provides low volume (as size is important) and high strength, can be made corrosion resistant. But the disadvantage is the weight of the steel. Most common landing gear steels are 4130, 4340, 4330V and 300M. Aluminum alloys are lighter weight in combination with high specific strength. But this alloy is very prone to stress concentration T736 are being used in the landing gear for its better strength and stress-corrosion immunity. titanium alloys, light weight and reduced corrosion susceptibility. Example Boeings 777 are using main gear structures that are mainly forged from the titanium alloy Ti-10V-2Fe-3Al from the mid-1990s. Magnesium was used previously for the landing gear wheels, but now it is discarded due to the fire hazard and susceptibility to corrosion.

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MATERIAL APPLICATIONS IN LANDING GEAR

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SCHEMATIC OF LANDING GEAR

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BONDING BONDING LENGTH CALCULATION Consider : 3000 N-m Bonding Length Calculated 37 mm Considered in Design 40 mm

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MANUFACTURING PROCESS We selected the Fiber placement technology for manufacture of the cylindrical part of the landing gear. The fiber placement technology allows the fiber placement at any angle in conformance with the local load conditions. Parts like drag brace, torque links are made by Resin Transfer moulding because it can be done at moderate pressure consequently reduces the cost.

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FEA

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FINITE ELEMENT ANALYSIS 1 (METAL LINER ONLY) Metal Liner Standard Steel Gauge 25( 1 mm ) Pressure 3000 PSI (20.68 MPA) Max Axial Stress 117 Mpa Max Radial Stress 83.5 Mpa Max Hoop Stress 1085 Mpa Max Hoop Stress 1085 Mpa > Rupture = FAIL

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FINITE ELEMENT ANALYSIS 2 (HYBRID : COMPOSITE + METAL LINER) Pressure 3000 PSI (20.68 MPA) Max Hoop Stress 986 Mpa << Rupture = OK Max Displacement mm

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FINITE ELEMENT ANALYSIS 3 (HYBRID : COMPOSITE + METAL LINER) Pressure 7000 PSI (48 MPA) Max Hoop Stress 2301 Mpa Rupture = FAIL Max Displacement mm

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FINITE ELEMENT ANALYSIS 3 ( METAL only – PISTON MADE OF FULL METAL ) Pressure 7000 PSI (20.48 MPA) Max Hoop Stress 949 Mpa Rupture = FAIL Max Displacement mm Max Hoop Stress 949 MPa

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FINITE ELEMENT ANALYSIS 4 ( METAL only – PISTON MADE OF FULL METAL ) Pressure 3000 PSI (20.64 MPA) Max Hoop Stress 307 Mpa << Rupture = OK Max Displacement mm

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MaterialWall Thickness (mm) Pressure (Psi) Max Hoop Stress (Mpa) Rupture (Mpa) Max Displacem ent (mm) Metal Liner Composite + Metal Composite + Metal Metal Only SUMMARY OF FINITE ELEMENT ANALYSIS

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CONSIDER FULLY METAL MANUAL CALCULATION Kg METAL LINER Kg3.949 Kg COMPOSITE Kg % of weight reduction = ( – )/ = WEIGHT REDUCTION CALCULATION USING CATIA Upper Torque Link (Steel + Composite) CYLINDER (Steel + Composite) Bottom Torque Link (Steel + Composite) % 40 % 47 % 57 %

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CONCLUSION ADVANTAGES: LESS WIGHT. CORROSIVE RESISTANCE. NO RUST. DISADVANTAGE HIGH COST. LOW PRODUCTION RATE. DEFLECTION HIGHER THAN METAL.

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45 Second Video

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