LANDING GEAR SHOCK ABSORBER DESIGN CONCORDIA UNIVERSITY MECH

LANDING GEAR SHOCK ABSORBER DESIGN CONCORDIA UNIVERSITY MECH 7501, SUMMER 2009 Presented to : Professor DR. S. V. HOA Presented by : 1. 2. 3. 4. 5. Maruf Khondker (L) A. K. M Lutful kabir Amen Younes Md Shelimuzzaman Shafiul Islam ID : 9204040 ID : 9059180 ID : 6014860 ID : 9008837 ID : 4806972

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

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

Aircraft Choosing I. Beech craft Model 99. Small size civilian air craft Crew One Capacity 15 passengers Length 44 ft 6¾ in (13. 58 m) Wingspan 45 ft 10½ in (13. 98 m) Height 14 ft 4⅓ in (4. 37 m) Empty weight 5, 533 Ib (2, 515 kg) Loaded weight 10, 400 Ib Max takeoff weight 11, 300 Ib (4, 727 kg) Power plant Pratt & Whitney PT 6 A-20, -27

Aircraft Choosing II. Hawker 850 XP Luxurious & Mid-size airplane Crew Two Capacity 8 to 15 passengers Length 51 ft 2 in (15. 60 m) Wingspan 54 ft 4 in (16. 56 m) Height 18 ft 1 in (5. 51 m) Empty weight 15, 670 Ib (7, 108 kg) Max Landing weight 23, 350 Ib (10, 591 kg) Max takeoff weight 28, 000 Ib (12, 701 kg) Power plant Honeywell TFE 731 – 5 BR

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

Shock Absorber dimension calculations II. Landing gear Load distribution

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

Shock Absorber dimension calculations Result of Dimension Calculations Beech craft Model 99 Item Nose landing gear Main landing gear Load at fully compressed position, Ib 3, 420 9, 125 Piston outside diameter, in 1. 7 2. 7 Cylinder inside diameter, in 1. 95 3. 15 Total stroke, in 12 12 Total cylinder length, in 16. 6 20 Hawker 850 XP Item Nose landing gear Main landing gear Load at fully compressed position, Ib 7, 980 22, 800 Piston outside diameter, in 2. 6 4. 4 Cylinder inside diameter, in 2. 9 4. 9 Total stroke, in 8 8 Total cylinder length, in 15. 15 20

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

STRESS ANALYSIS AND LAMINATE DESIGN q 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 Results

STRESS ANALYSIS AND LAMINATE DESIGN

STRESS ANALYSIS AND LAMINATE DESIGN

STRESS ANALYSIS AND LAMINATE DESIGN Summary of Analysis

MATERIAL SELECTION q 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. q Depending on a selection of a material, the design, processing, cost, quality and performance of the product change q Material selection is important to redesign an existing product for better performance, lower cost, increased reliability, decreased weight, etc

MATERIAL SELECTION q Material should be selected such that it can store the greatest elastic potential energy per unit volume without failure. q Component Specification • Shock resistance of landing • Resist the vibrations during the flight • Thermal requirements: -60°C<T<60 °C • Withstand water, humidity • Surface has to resist the impact during the landing • Smooth surface

MATERIAL SELECTION q. 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 q. Matrix system Epoxy: • good mechanical properties (E = 4. 5 GPa) • humidity resistance • adhere very well to reinforcement fibers • expensive

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, 4330 V and 300 M. • Aluminum alloys are lighter weight in combination with high specific strength. But this alloy is very prone to stress concentration. 7175 -T 736 are being used in the landing gear for its better strength and stress-corrosion immunity. • titanium alloys , light weight and reduced corrosion susceptibility. Example Boeing’s 777 are using main gear structures that are mainly forged from the titanium alloy Ti-10 V-2 Fe-3 Al from the mid-1990 s. • Magnesium was used previously for the landing gear wheels, but now it is discarded due to the fire hazard and susceptibility to corrosion.

MATERIAL APPLICATIONS IN LANDING GEAR Material Steel Applications Bogies, pistons, braces, links, switch brakets, plug, axle, shaft, spring, plate, clamp, sleeve, arm(tube), pin, bushing, Aluminum arm, collar, shimm, wheel, adapter assembly Titanium Main landing gear structure Magnesium No use right now due to fire hazard Aluminum Bronze Extremely used for upper and lower shock strut bearings Beryllium Brake heat sink material and bushing material Aircraft wheels, main landing gear parts including outer Composite material cylinder, pistons, side braces, torque arms, trailing arms, springs, wing panels, stabilizers and control surfaces

SCHEMATIC OF LANDING GEAR

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

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.

FEA

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 > Rupture = FAIL

FINITE ELEMENT ANALYSIS 2 (HYBRID : COMPOSITE + METAL LINER) Pressure 3000 PSI (20. 68 MPA) Max Hoop Stress 986 Mpa << Rupture = OK Max Displacement 0. 247 mm

FINITE ELEMENT ANALYSIS 3 (HYBRID : COMPOSITE + METAL LINER) Pressure 7000 PSI (48 MPA) Max Hoop Stress 2301 Mpa ≈ Rupture = FAIL Max Displacement 0. 576 mm

FINITE ELEMENT ANALYSIS 3 ( METAL only – PISTON MADE OF FULL METAL ) Pressure 7000 PSI (20. 48 MPA) Max Hoop Stress 949 MPa Max Hoop Stress 949 Mpa ≈ Rupture = FAIL Max Displacement 0. 343 mm

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 0. 104 mm

SUMMARY OF FINITE ELEMENT ANALYSIS Material Metal Liner Composite + Metal Only Wall Pressure Thickness (Psi) (mm) Max Hoop Stress (Mpa) Rupture Max (Mpa) Displacem ent (mm) 1 5 3000 1085 986 1000 2500 2. 25 5 7000 2301 2500 0. 576 5 3000 307 1000 0. 104 0. 247

CYLINDER (Steel + Composite) WEIGHT REDUCTION MANUAL CALCULATION 11. 519 Kg CONSIDER FULLY METAL LINER 1. 4673 Kg COMPOSITE % of weight reduction = (11. 519 – 6. 5950)/11. 519 3. 949 Kg = COMPOSITE 6. 5950 Kg 42. 75 % CALCULATION USING CATIA Bottom Torque Link (Steel + Composite) Upper Torque Link (Steel + Composite) 40 % 47 % 57 %

CONCLUSION q ADVANTAGES: ØLESS WIGHT. ØCORROSIVE RESISTANCE. ØNO RUST. q DISADVANTAGE ØHIGH COST. ØLOW PRODUCTION RATE. ØDEFLECTION HIGHER THAN METAL.

45 Second Video