Learning Forum

[louiee1907]

Hello,

Even though I change the my mean stress correction theroy from Gerber to Goodman, neither damage nor life result change. In addition, I want to see damage colour in model however I can not see, I just see von-misses result colur from static structural analysis.

How can I solve these problems? Can you help me, please?

[Ashish Khemka]

Hi,

Did the discussion here help you to get an answer to this query? Please comment.

Calculating Cycle (ansys.com)

Regards,

Ashish Kumar

[louiee1907]

Hi,

Calculating Cycle (ansys.com) this discussion helped me different problem. I analyzed fatigue life and damage in nCode DesignLife. Even though I changed from life to damage, there is no change the colour on the model, so damage result colour is same life result colour despite of different result

[danielshaw]

What are the maximum damage and minimum life results reported in DataValueDisplay?

[louiee1907]

Maximum damage is 0.05 and minimum life is 700 repeats. I can see them as number, however both damage and life colours are same in FE model result. For example, cube's surface has same colour, even though I choose damage or life

[danielshaw]

If RMB>Properties on the image, you can change the color scheme.

[louiee1907]

Sir, can you help me about my other topics, please? I cannot edit time as 0.2 in TimeSeries Input. 

[danielshaw]

I do not understand the question.  Why are attempting to edit "time"?

[louiee1907]

I have acceleration-time data. When I put it in nCode DesignLife, time between each acceleration is 1 second, however I want to edit as 0.2 seconds. How can I do it? Acceleration changes Y axis properly, and in my data X axis(time second) is 0,0.2,0.4 , however in the Time series input the time changes 0,1,2.. I want to change it from 0,1,2 to 0,0.2,0.4. Is it possible or time is not necessary? Can you explain me, please?

[danielshaw]

It is not necessary.  With time series load mapping, time is just used as a counter for graphing the time series data.  It is not an "actual" solver time used in the fatigue calculations.

[louiee1907]

Thank you so much sir, I learn much information thanks to you. I put just acceleration data in time series input and I calculated life on model, however I still could not calculate as hours. The life is 240000 repeats and my test duration is 5200 second. When I calculate(240000*5200)/3600 , the result is so enormous. How can I calculate the result correctly?

Secondly, as you know,  in my static structural there are moment and acceleration load. I cannot choose just acceleration time series (stress) in load mapping. What should I do?

[danielshaw]

Just because the predicted failure time is enormous does not mean that it is incorrect.  The fatigue simulation indicates that the 5200 second test produces very little fatigue damage.  Since that test represents 5200 seconds of operation, the fatigue result basically predicts infinite life.

There are various methods to define a result set as non-varying.  The simplest method is probably to use the “static” option in the time series load mapper.  The static option in the time series load mapper represents a constant stress.  You need to define 2 result sets in the time series load mapper; one result set contains the acceleration stresses the other one contains the moment load stresses.  You link the times series file to the acceleration result set and specify the moment result set to be “static”.

[louiee1907]

 

Thank you so much.

My distance between each acceleration is 0.2 seconds. The simulation sees this as 1 second, not 0.2 seconds, but you said the time is unnecessary. Actually, I entered 90000 acceleration data as time-series input. I’m a little confused here. Is not enough?

Is it true analysis? Normally, I would put these two loadings in a single structural analysis, but it appeared as a single stress result in the fatigue analysis. So I split this in half but I’m not sure it’s correct. Otherwise, I cannot select the moment as ‘static’.

 

[danielshaw]

The fatigue results are independent of actual time.  Consider a loading scenario that produces 2 result sets with fatigue damage caused by the stress difference between those sets.  It does not matter if the stresses occur .2 seconds apart or 1 second apart (or any other time difference).  The time between the result sets does not affect the calculated fatigue damage.

The static stress must be saved in a separate result set.  It does not matter if that result set is from a unique system or from the same system as the acceleration loading.  You could use 2 systems, or you could use 1 system with multiple result sets.  DesignLife translates all imported results sets into one results file.

[louiee1907]

Thank you so much, sir. I understood how DesignLife works, however I found a life result as cycle. How can I translate it as hours? I just want to know it. I tried to search every article, but I couldn't find anything to convert as hours.

[danielshaw]

For time-based loading (Constant Amplitude, Time Series, and Time Step), DesignLife calculates the life as repeats of the loading cycle.  Thus, for time series loading, life is reported as repeats of the load history.  If you know the relationship between the load history and actual time, you can easily convert the loading cycle repeats to time.  If you want DesignLife to do the conversion, you can set the Number of equivalent units in the DesignLife post-processor. DesignLife will just multiply the calculated repeats by the NumEquivUnits value and report that value.

 

 

[louiee1907]

Thank you very much. I really appreciate. Lastly, There is acceleration load which is 9800 m/s^2 in static structural. When I put my acceleration data to time series input, must it be as 9800 mm/s^2? I put as 9800/9800 = 1 in time series input, so my input datas change from 1 to -1 not 9800 to -9800. What should my load be?

 

[danielshaw]

The data in the time series input file are scale factors used to multiply the calculated stresses from the results file.  So, if you want the stress produced by 9800 mm/s^2 to be used in the fatigue calculations, you can either apply an acceleration value of 9800 in the FE model and define a scale factor of 1 in the time series input file or apply an acceleration value of 1 in the FE model and a scale factor of 9800 in the time series input file; or any other combination FE loading and time series scale factors that produces a net value of 9800.

[louiee1907]

I've been asking you for days, thank you very much.