# Finite Element Analysis

1. May 31, 2009

### gimini75

Hello

I have an assignemt to analysis a landing gear for the cyclone earoplane, an initial design being supplied, I have being askedto check for the suitability of the part, the conditions are:

Aircraft mass with fuel: 43000 lbs
Landing speed: 65 Knots
Maximum deceleration: 3g
Each part takes 25% of the landing load (see the picture attached)
External diameters cannot be exceed or pitch between lug centres changed.
Factor of safety for landing load: 1.5
Maximum number of landings: 500000

Here what I have done, I converted all units to (N, mm), the mass of the aeroplane is (0.45 x 43000 = 19350 Kg), speed (=65 x 0.514 = 33.41 m/s), Force (= 19350 x 3g = 564.47 kN), I found force in Y direction = 516.115
X = 238.555 kN (Fx=Fcos25), but when I run the vo mises ProMechanica analysis I found (40190 N/mm2, which is to high as I have to choose a material from a list provided to me, the max is (H950 with 1517 MPa), now I dont understand what mistake I have made for my analysis, I appreciate any help from you.

Thanks

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Last edited: May 31, 2009
2. Jun 2, 2009

### nvn

(1) What are the cross-sectional dimensions, cross-sectional area, and moment of inertia of the part? (2) What is the length of the part? (3) How many stress cycles, n, occur per landing? (4) What is the fatigue strength of H950 at 500 000*n stress cycles? At least answer items 1 and 2.

3. Jun 3, 2009

### gimini75

Hi

Thanks for your reply, I have attached the dimensions of the landing gear which you asked for.

Thanks

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4. Jun 3, 2009

### nvn

gimini75: What is the name of the material for H950? I think H950 is the hardness. But what is the name of that material?

Ensure all of your input units are N and mm, not kN. Ensure your software expects all input values in N and mm. Also, see if your output display is showing MPa or Pa. Is your output display showing units of MPa or Pa?

5. Jun 3, 2009

### gimini75

Hi

The materials is Hardening Stainless Steel bar, all my units are in N and mm, just one thing else I don't know how to use the number of landings in my calculations as I don't have any other information about it.

Thanks

6. Jun 3, 2009

### nvn

Give us the name of the stainless steel material. Which stainless steel? Also, please answer my last question in post 4.

7. Jun 3, 2009

### gimini75

Hi

The materials is AMS 5629 (13/8 PH VAR).

Thanks