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drawoh. Well you don't have a board of known stiffness. All the components will alter the PCB stiffness.

IRstuff, thanks for your feedback. No, not at all. But I'm wondering: how can I get the correct stiffness of the components without coming down to the nitty gritty details of each component with soldering and cabling. Do you have any good suggestions on how to do this? Or anyone else on the...

Yes, that's the thing. This is not an accurate model, because I don't have the stiffness of the components.

Hi there I've been searching and wondering how to correctly FE-model a populated PCB with components. I get excellent input from Steinberg book, but how to model thia with FE is still a mystery. The Componens will add both mass and stiffness to the PCB, and to model this corectly without using...

Thank you. 3DDave

Hi Does anyone have experience with shock loads from MIL-S-901 testing? We have been asked to do an analysis of ahip board equipmnet mounted in a navy vessel. What g-levels do we apply?? Thanks for any help. Rgds Bernt

Hi I just wonder what the error #1466 means: "BEGIN BULK" encountered while reading continuation for control card. My Job stops, and I am not able to get results. Any help is appreciated:-)

Is it one single shock mount you are applying? In order for you to select the correct shock mount, you need to know the dynamic behavior of your electronic component. And compare that to the shock. Shock duration (gives you the frequency), shock wave form etc. Generally, you will need to...

Intersting discuasionQ! But how do we define "accurate"? I bet that no matter how accurate you set up your FEM model, it will never copy the reality. And reality is also relative depending om how well you manufacture the part and how accurate the system is assembled. After all, FEM is only a...

Well. Maybe it is just me being used to working with defence materials. Both Def-Stan and MIL-STD-810 operates with a shock duration of 11ms.

Why is 11ms on shock loads "Standard"?

Yes, I have to switch back to the original. But for us, Airbus is several links away back from where we are. This is a MEDEVAC helicopter, and our immediate contact is the helicopter operators. But we will get through the jungle in the end. Thanks for any input.

Yes, now I looked at MIL-STD-810G. And G gave some good info. Previously I used F version, and that was more confusing. Thank you.

Yes, I guess that's where I have to go. Thanks.

Hi I need to find the vibration levels for payload for an Airbus helicopter. I have search both European and US Standards, but I cant find something useful. I know the rpm and No of blades for the main rotor, but I assume there's a lot of other vibration sources like the tail rotor, engine, gear...

Thank you, Jeff. That's what I thought was the best method.

Hi everybody. Is there a good method of adding the static g-forces to a vertical frequency dependent SRS analysis?

Hi Is it possible that a SRS input of 2G responds with almost 0 stresses. (actually 0,004MPa) The SRS has a max acce between 0,6 and 0,9 Hz, whereas the lowest natural frequency of the system is at 4,2 Hz. Appreciate any help here.

In the last century, we had to tweak and save elements to get answers. The computers wouldn't swallow anything. That was a very good lesson learnt. You couldn't just use as many elements you wanted. Learning to see where you could expect stress raisers, bolted connections etc, has helped me to...

I would appreciate some help regarding analysis of SRS in MSC/NASTRAN. I have generated a SRS from a (close to) a half sine shock in the time domain, and want to use this as an input in MSC/NASTRAN sol 103. What about the damping? I alredy defined a damping when generated the SRS (The SRS was...