Ansys nCode Design life

[morris9791]

Dear Experts,

Does anyone know the basic price of this new Fatigue predictor integrated into Ansys WB provide by HBM-ncode?

Thanks
Eddie

 

[aeroafrix2]

I guess you can contact the guys that owns the software ncode here :

http://www.ncode.com/

For all I know, ncode isnt a new software for fatigue,as it has being around for some time now as a standalone product, however many companies found it difficult to integrate into their existing suites of CADs, moreso there are so many inherent flaws in some of the assumption made in the code as you would have to basically reconfigure much of the software to meet the internal design philosophy of your company. That was exactly what our company had to do and we basically had to write several macros in house and coupled it with ncode to run some of our "classical" fatigue analysis. FE fatigue too you would have to tweak certain things and also have good understanding of the workings behind for you to actually get meaningful results.

 

[morris9791]

Thanks,

Thats disappointing! It looked impressive on the Ansys website, i guess thats marketing
Can you recommend any other programs? Currently we used an excel based program which is outdated and only does very simple fatigue calcs.

Thanks
Eddie

 

[aeroafrix2]

Hi ya Eddie,
Sorry if my last post seems to convey wrong impression about nCode. That wasnt what I actually intended, as I only wantd you to understand that you should be prepared to do abit more work on the package. Beside, nCode are quite helpful with onsite assistance in configurations to meet your reqirements. Apart from "in house" fatigue codes written by experts, nCode is one of the most widely used fatigue codes at last in Europe.

Like you already know, fatigue analysis involves several assumptions and variables which as an analyst you would have to tweak to get meaningful results from your analysis.Some of the flaws in the assumptinos I mentioned in my earlier post ( in our case) was largely due to the 'strict' nature of our fatigue design philosophy which for some others might not be something of grave concern.

If you ask me again I think I will stil recommend nCode fatigue suites 'cos it is easy for you to run external macros with it and since you guys already have an in house spreadsheet, with good support from nCode I think you can work with them to have your own nCode suites tweaked (or shall i say customized) to meet your company fatigue design philosophy. Lastly, if i may say this, I do not think there is any fatigue codes you can buy off the shelf that wouldnt require you doing some customization, like I already mentioned, your fatigue design intent is always going to be somewhat different fom the base line approach with which these codes are sometimes written.

If I may ask, do you guys do "Classical" fatigue with Stress Life approach or "Full field" F.E fatigue using Strain Life approach?

 

[morris9791]

Dear aeroafrix2

That sounds a lot better
We mainly use strain life approach but it is not full field.
Our spreadsheet does not calculate fatigue for the different types of cycle regimes etc.

I am wondering how i can convince the boss to invest in this product!!

Thanks

 

[aeroafrix2]

@morris9791,
"..Our spreadsheet does not calculate fatigue for the different types of cycle regimes etc..." Sorry I did not get what you mean here.Did you mean to say that your Fatigue spreadsheet does not use a cyclic load history when estimating the fatigue life of your component? I would assume your company's strain life approach is a classical method where by for a given "serve"load case,a Kt value is used to estimate the "peak" stress amplitude and the spreadsheet then uses the stress value to estimate the strain amplitude using Ramberg-Osgoods cyclic material equation. The spreadsheet then calculates the Fatigue life based on this estimated strain amplitude using Mason-Coffin equations hence things like mean stress effects are taken care off using some conservative factors?

As par convincing your boss about getting this package, it depends on where Fatigue of components ranks in the certification of your manufactured parts before any competent certification authority. In aerospace industry for example, you must be able to prove vigorously to CAA or FAA that your part meets the qualifying design "life" before such a part can be certified for in service. More so the certification authority an/or the purchasing tier1 company will specify how such qualification should be achieved and in most cases, a full field F.E. analysis will be required. Again, it depends if failure of your component is fatigue critical, if the fatigue cycle is Low or High etc. Other than some of these reasons, Cost becomes another factor! I think you could ask nCode for a tral demonstration ( which I think will be at no cost to your company) and see if they could demonstrate how nCode will give you an edge over your current fatigue tools

 

[morris9791]

aeroafrix2

Currently our program only does constant amplitude, proportional loading with Smith- Watson-Topper, Morrow mean stress corrections for strain life calcs.
We do not incorporate the Ramberg-Osgoods cyclic material equation to calculate strain amplitude. Basically, our program is very limited and simplistic.
Currently we would like to be able to predict component life for different and independent loading scenarios and cumulative damage from duty cycles etc.

I believe that fatigue strength of our components is ranked very high in our product certification.
As much as I’d like more comprehensive software it will be impossible to convince my boss because of so called budgetary restrictions…frustrating to say the least!!!

 

[aeroafrix2]

morris9791
I understand where you are coming from! It gets my head doing in when I hear budgetary constraints especially when it comes to getting the right analysis tools.

"..We do not incorporate the Ramberg-Osgoods cyclic material equation to calculate strain amplitude.." Care to exlain then how your spreadsheet calculates your strain amplitudes?

sorry I found that statement contradicts what you said here

"..Currently our program only does constant amplitude, proportional loading with Smith- Watson-Topper, Morrow mean stress corrections for strain life calcs..."

Life Prediction I would have thought should be based on the worst case scenario of events in the component load history ( i.e mission mix events) and I am not sure how beneficial and cost effective it will be for you to carry out life prediction for different and independent loading scenario since fatigue life prediction itself is by and large a statistical event. Again you care to give shed some reasons why you guys are looking at carrying such life predictions?

Since you already mentioned that your components are fatigue critical in design, I would assumed that your company must have used this same spreadsheet in carrying out fatigue analysis of parts that have undergone certification. If that is the case, why bother incurring additional cost in purchasing a fatigue analysis software suites when what you have presently can achieve meets the requirements of your certification and/or purchasing authority.

 

[morris9791]

aeroafrix2

I am not familiar with the Ramberg – Osgoods cycle…!

That is what I meant, I would like to have the correct tools that predicts ‘mission mixed events’ or duty cycles, damge accumulation etc.
Currently we can only predict life of a component subjected to a single loading event despite the fact it will certainly see other types of loading. Broadly speaking our method involves loading the part, looking for the highest and lowest Von mises stresses, determine whether compressive or tensile. Then input these into our program with a surface finish correction factor and calculate life.

What are your thoughts on this method?

Thanks