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@tbuelna, corrosion underneath chrome is really not new especially for landing gear structures when chrome has been applied to the coating surface with incorrect thickness. Nickel under chrome usually comes handy, however, new environmental regulations in aerospace is pushing most OEM to look...

I think EASA policy is quite straight forward with flying with known cracks in that provided that the cracks are proven to be benign and when the primary structure is subjected to loads up to the Ultimate loads to be experienced in-service it does not result in adverse performance of flight. An...

If you are well grounded in fatigue damage and crack growth predictions, static strength analysis using both classical and Finite Element methods, then you should do very well in Aero-structures. Also, the area on the aircraft you end up will also influence how successful your previously...

Has anyone come across this FE mesh convergence approach which is based on the ratio of the un-averaged min/maximum principal stress ratios at the element corner nodes or at integration points?

I think it is all fallacy that Airframers do not want stress analyst who are PhD holders. I am sorry to say this, most of the major commercial/military aircraft projects ongoing currently need stress analyst who can jump on a project and get going very quickly, hence emphasis are placed of...

@missil3 You stated: "We use equivalent plastic strains for rupture in our dynamic analysis, this is backed up by our experimental results database" My question for you is: Does your allowable strain not derived from a uni-axial stress strain testing, hence how sure are you that such a strain...

@rb1957 "I believe von mises assumes a linear stress/strain curve" ... that's what i meant with "von mises is based on elastic strain energy"... Don't you think this statement is highly misleading? Is Yielding not a purely non-linear phenomenon in most metals commonly used in designs i.e...

I think I would like to convince myself that my stress-strain data obtained via test follow the trend expected. So my question is, does your stress strain data as obtained represent the stress-strain data obtained elsewhere?

@rb1957, "i use von mises as a conservative failure model"... If one may ask, ( not an academic question but one of practical interest), Von Mises beyond yield is conservative to what? If the Von Mises derived stress beyond yield tells you nothing about rupture, how then can one say it is...

@rb1957, Why would you use Von Mises beyond yield when clearly the mathematical formulation and physical justification is only valid as an indicator of the 'on-set' of yielding and as such beyond that, its actual meaning seriously I do not know. @inline, What component of plastic strain are...

@ ESPcomposite, Thank is also my understanding. Pertaining to max or min Principal stresses, aren't they suppose to be less than Von Mises? Again is there any validity in their use against rupture?

thread727-253537 thread727-253537 I know in this forum the issue of Von Mises stress has been discussed time and time again,(e.g http://www.eng-tips.com/viewthread.cfm?qid=253537) however having gone through most of the threads, I am still left wondering about the validity of Von Mises stress...

If you are analyzing this by classical method, draw a free body diagram of all forces and moments, indicating all boundary conditions. Knowing the centroid or neutral axis of your geometry, you can simply solve the problem classically. Also bear in mind, you mind have secondary deformation...

It all depend on the way your flight control system is designed and several aircraft parameters. If you are working in a professional design group, then the guys in flight physics should be able to tell the worst in-flight handling maneuvering that gives the most severe loading inline with the...

If your stresses are higher than your yield stress, and your plasticity is localized, surely you should be using a strain life analysis rather than stress life? I thought Goodman's diagram helps you to determine your "equivalent" stress amplitude to correct for your "mean stress" effect for...

Thanks SWComposite, I have always thought that was the main reason but I thought there was more justification behind the 3 seconds.

What is rationale behind holding structures under Ultimate load test for 3 seconds accroding to FAR 25 or EASA CS25 Aircraft certification requirements? In terms of structural failures, what is the 3 seconds no failure at ultimate load testing requirement meant to demonstrate? I have asked this...

Hi all and the experts in house, I have two questions regarding FE Fatigue; In order to do fatigue analysis in most Axial FE Fatigue codes, various Unit load cases are often created based on 'Linear' FEA assumptions - (usually linear material model based on monotonic material Stress-Strain...

Thank rb1957, I quite understand that, but then, how do you define your failure strain? is it overly conservative to assume this to be the strain at Ultimate Stress for a ductile material?

Hello all, How do you determine your reserve factor from a non-linear FEA (material)? Generally, most non-linear FEA I have come across tend to use a non-linear material true stress-strain curve for non-linear FEA (material). And there after extract the Maximum Strains, derive the 'equivalent...