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Hi Guys, I appreciate your replies. I'd like to provide additional information: The original material drawing called for PH13-8Mo stainless steel, solution treated according to AMS 5629, with a subsequent heat treatment to condition H1000 (205 KSI minimum UTS) per AMS 2759/3. We received...

Hello Everyone, I'm reaching out for your input. My background is in fatigue life assessments, not materials engineering, so I'd value your thoughts on these statements: Risks Associated with Machining Pre-Hardened PH13-8Mo: Increased Residual Stresses: Machining hardened material generates...

Hello, We need to design a fuse pin for a main landing gear. The goal is to achieve controlled shear failure to protect the aircraft. Our focus is on achieving a predictable failure in shear mode rather than tension or bending, as shear failure provides more controlled separation. To control the...

Based on the e-mail reply that I received from Battel Columbus "The equation included with each MMPDS S/N curve is the typical regression line, 50% survival. And, the 97.7% survival probability can be computed, by subtracting 2.0 x the standard error of the estimate from the typical line."...

Hi, I would like to know what is the Certainty of Survival for the S-N (stress-life) Curves presented in MMPDS? Thanks, A.

Perfect. Thank you.

Yes, I agree with you. I also noticed that there are no S/N curves for 7050-T7451 in MMPDS-15. I sent an email about these S/N Curves to Battelle Memorial Institute, and I didn't receive any answer until now.

Thank you for your reply. I think that 800 cpm (cylces per minute) is equivalent to 800 /60 = 13.3 Hz (cycles per second) versus 20 Hz (not 20,000 Hz).

Figure 3.7.5.2.8(b): Product Form = 4.25 to 8.50 inches thick Specimen Details: Unnotched 0.25 inch diameter Surface Condition: Polished, final surface finish unspecified Test Parameters: Loading - Axial, Frequency - 20 Hz, Temperature - RT, Environment - Air No. of Heat/Lots: Unspecified Sample...

Figure 3.7.5.2.8(b): Product Form = 4.25 to 8.50 inches thick Specimen Details: Unnotched 0.25 inch diameter Surface Condition: Polished, final surface finish unspecified Test Parameters: Loading - Axial, Frequency - 20 Hz, Temperature - RT, Environment - Air No. of Heat/Lots: Unspecified...

Hi Guys, I recently noticed that there is significant difference between the predicted life with S/N curves shown in Figures 3.7.5.2.8(b)and 3.7.5.2.8(e) in MMPDS-09. Both of them are "for unnotched 7050-T7451 plate, long transverse direction, t/4 specimen locations". The second one is giving...

Hi Guys, I recently noticed that there is significant difference between the predicted life with S/N curves shown in Figures 3.7.5.2.8(b)and 3.7.5.2.8(e) in MMPDS-09. Both of them are "for unnotched 7050-T7451 plate, long transverse direction, t/4 specimen locations". The second one is giving...

Hi Guys, I noticed that on page A-7 of MMPDS-15, it is written that "S/N Curves are for a 50 percent probability of survival. We usually assume conservatively few fatigue penalization factors (such as anodizing + shot-peening, surface finish, ...). But, I would like to know if you apply another...

O.K., thanks. For 17-7PH the recommended range is 45% (not 35%).

Thanks again for your reply. We use the Tensile Strength shown in Table 4A of AMS 5678F (SAE). In this document, it is not mention Ultimate or Limit. But, for a wire diameter of (4.57mm to 5.26mm), manufactured from 17-7PH, CH900, the Tensile Strength are Min. 1738 MPa Max. 1944 MPa I think...

Thanks for your reply. I am using Fsy (limiting shear stress from Figure 4 of ESDU 83002). If I understood correctly then you are proposing 0.4 Fty for this check. By the way, where do you get Fty for spring wire? I have seen Tensile Strength in AMS5678F for 17-7PH. I thought that those Tensile...

Hello, We usually calculate Margins of Safety for compression spring as shown below: Stress = 8 K Force Dmean / (pi*d^3) (Calculated Stress at max. operating deflection) K = (4C-1)/(4C-4) + 0.615/C (Spring Stress Correction Factor) C = Dmean / d (Spring Index) M.S. = TDS Ftu / Stress...

Yes, basically, customer is asking for deflection of LG by including the flexibility of backup structure. So, we need to have their feedback to include the appropriate stiffness (using CBUSH or ...) into LG FEM at attachment points.

Thank you rb1957. Unfortunately, we don't have access to FEM of Aircraft. I proposed both above approaches to our customer. I thought that they should be able to assume some reasonable boundary conditions to estimate reasonably the stiffness of Aircraft Structure at attachment point to Landing...

Hi Guys, I understood that if we have a Nastran Model of Aircraft then one way to find out stiffness of Aircraft Structure at attachment point to Landing Gears is using following cards: ASET1 123 GRID1 GRID2 ... GRIDn (to have 3 x 3 stiffness matrix) PARAM,EXTOUT,DMIGPCH I also think that we...