LANDING GEAR SHOCK ABSORBER DESIGN

Presented by :

1. Maruf Khondker (L) ID : 92040402. A.K.M Lutful kabir ID : 90591803. Amen Younes ID : 60148604. Md Shelimuzzaman ID : 90088375. Shafiul Islam ID : 4806972

CONCORDIA UNIVERSITYMECH 7501, SUMMER 2009

Presented to :

Professor DR. S.V. HOA

IntroductionConfigurationDesign and AnalysisFinite Element Analysis (FEA)Material Selection and ManufacturingWeight Estimation and Comparison.Conclusion.45 Second Video

OUTLINES

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.

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 PT6A-20, -27

II. Hawker 850 XP.

Aircraft Choosing

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 TFE731 – 5BR

Shock Absorber dimension calculations

I. Shock absorber choosing.Type: Oleo-pneumatic shock absorberReason:

High efficiency. 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

Beech craft Model 99Item 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 XPItem 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

Result of Dimension Calculations

STRESS ANALYSIS AND LAMINATE DESIGN

Methodology:

Netting theory.

Classical Lamination Theory (Layer by layer analysis.)

nnfnffn

nnfnffn

tttttth

rP

tttttth

rP

22

2221

21121

22

2221

21121

sin...sinsin)(

cos...coscos)(2

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

STRESS ANALYSIS AND LAMINATE DESIGN

Results

STRESS ANALYSIS AND LAMINATE DESIGN

STRESS ANALYSIS AND LAMINATE DESIGN

STRESS ANALYSIS AND LAMINATE DESIGN

Summary of Analysis

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

MATERIAL SELECTION

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<T<60 °C

• Withstand water, humidity

• Surface has to resist the impact during the landing

• Smooth surface

Reinforcement systemI. 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 systemEpoxy:

• good mechanical properties (E = 4.5 GPa)• humidity resistance• adhere very well to reinforcement fibers• expensive

MATERIAL SELECTION

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. 7175-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 Boeing’s 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.

Material Applications

SteelBogies,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

Composite materialAircraft wheels, main landing gear parts including outer cylinder, pistons, side braces, torque arms, trailing arms, springs, wing panels, stabilizers and control surfaces

MATERIAL APPLICATIONS IN LANDING GEAR

SCHEMATIC OF LANDING GEAR

BONDING

BONDING LENGTH CALCULATION

mml

factorsafetygconsiderin

mmlm

NMN

r

MlW

averrage

t

697.365.1465.24

5.1

465.24

1041085.692

3000

22

6232

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

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 ≈ Rupture = FAIL

Max Displacement 0.343 mm

Max Hoop Stress 949 MPa

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

Material Wall Thickness

(mm)

Pressure (Psi)

Max Hoop Stress (Mpa)

Rupture (Mpa)

Max Displacement (mm)

Metal Liner 1 3000 1085 1000 2.25 Composite +

Metal 5 3000 986 2500 0.247

Composite + Metal

5 7000 2301 2500 0.576

Metal Only 5 3000 307 1000 0.104

SUMMARY OF FINITE ELEMENT ANALYSIS

CONSIDER FULLY METAL

MANUAL CALCULATION

11.519 Kg

METAL LINER 1.4673 Kg 3.949 KgCOMPOSITE COMPOSITE 6.5950 Kg

% of weight reduction = (11.519 – 6.5950)/11.519 =

WEIGHT REDUCTION

CALCULATION USING CATIA

Upper Torque Link (Steel + Composite)

CYLINDER (Steel + Composite)

Bottom Torque Link (Steel + Composite)

42.75 %

40 %47 %

57 %

CONCLUSION ADVANTAGES:

LESS WIGHT. CORROSIVE RESISTANCE. NO RUST .

DISADVANTAGE HIGH COST. LOW PRODUCTION RATE. DEFLECTION HIGHER THAN METAL.

45 Second Video