# bhumkaromkar

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1. ## Fatigue life calculations

@Prakash Pagadala What if i have Stress at 1000 cycles and not at 1 cycle. In that case I have to use Point, 1 segment method for SN curve in Fatigue Process Manager. Do i have to multiply this stress@ 1000 cycles by 2 for SR1000 input? Kindly revert back at your earliest convenience.
2. ## Fatigue analysis MATFAT parameters

@Prakash Pagadala @Rahul R Hello Sir, I have doubt regarding MATFAT parameters in opti. Can you please tell me the SRI1, b1, Nc1, FL parameters values for following Material stress data: Alternating Stress(Amplitude) Life 4000 MPA 1 855 MPA 1000 86.2 MPA 1000000 86.2MPA is the fatigue strength/endurance strength of the material. Please guide me to calculate the MATFAT parameters from given material data. I am confused about where to double the values for stress range and where not to. If you will elaborate with the given data it will help me a lot. Kindly reply at your earliest convenience. Thanking you in anticipation. Regards, omkar Bhumkar
3. ## FL value in MATFAT

Hello, In fatigue analysis in Optistruct, Do we also have to multiply the fatigue strength value by 2 while defining FL in MATFAT like we are doing for SRI1 value?(stress range= 2* stress amplitude) e.g if the fatigue strength of a material is 100 MPA then do i have to put 200 for FL in MATFAT? TIA
4. ## Fatigue life calculations

@Rahul R Do we also have to multiply the fatigue strength value by 2 while defining FL in MATFAT like we are doing for SRI1 value? e.g if the fatigue strength of a material is 100 MPA then do i have to put 200 for FL in MATFAT? TIA

6. ## Fatigue Load case i/p

@Prakash Pagadala I have sent you .out file on your File Transfer link. Kindly review the file. TIA
7. ## Fatigue Load case i/p

@Prakash Pagadala I created control card of Global output request for FOS. But when i review results in Hyperview it only shows Life and damage option. Where can i see FOS? TIA
8. ## Fatigue Load case i/p

@Prakash PagadalaThank you for the reply. Can you also tell me if we can get other outputs too from this card for fatigue sub case? Like stress , strain?

Hello, I am doing fatigue analysis using SN life approach....I wanted to know what is the effect of frequency of loading cycle on fatigue life and damage? For example if the frequency of load cycle is doubled what will be the life and damage? Thanks in advance.
10. ## Fatigue Load case i/p

@Prakash Pagadala I did not get this point: Yes, but comment 2 says " Repeat number (N#) has no effect on the results of a Factor of Safety (FOS) analysis" If you are not interested in results you can go ahead for only life prediction. I did fatigue analysis on a component by both methods: 1. By increasing the number of cycles in .csv file 2. By changing N# (number of repeats in FATSEQ) Results by both the methods are same i.e. Life and damage o/p is same. Optistruct fatigue does not give any other o/p except these two stated above. How do we calculate FOS analysis?
11. ## Optistruct Fatigue Analysis Output options

In SN life fatigue analysis carried out in optistruct, we get output of life and damage only. How to get dispacement and stresses induced due to fatigue loading in output? Thanks in advance.
12. ## Fatigue analysis Minimum life is coming less than 1

I used following values YS= 340 MPA UTS = 497 MPA Values calculated in Fatigue process manager for SN curve Plot (Estimated based on UTS option) SR1 = 2118.71 B1= -0.125 NC1 = 1e6 B2, FL, SE are OFF.
13. ## Fatigue analysis Minimum life is coming less than 1

@ Prakash Pagadala I am using SN life method for stress calculation. For this SR1, B1 and NC1 values are directly estimated using UTS in fatigue process manager. I have used this approach. Are their any additional values needed ? TIA.
14. ## Fatigue analysis Minimum life is coming less than 1

Hello all, I have done static analysis of the structure using static load case of 971N. I have applied Fully reversible sinusoidal curve (100 cycles) for fatigue analysis in optistruct. SN curve is calculated in optistruct using UTS. After analysis i am getting minimum number of cycle as 1.581e-2 which seems unrealistic. What can be the problem?
15. ## Optistruct User Manual

Hello all, I have recently started exploring Fatigue and Modal Analysis in optistruct. I wanted to know if there is any User manual where meanings of different variables in cards are explained as in LS Dyna User Manual. Thanks in Advance.
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