Learning Forum

[charlietran]

Hi guys!nWe are doing a vibration simulation of a 15 tons truck traveling through unpaved road. Some electronic devices were mounted on the chassis frame of this truck. The weight of these devices is about 4 tons. We need to protect some PCB boards from high vibration acceleration, so we must determine the maximum drive speed at this type of unpaved road. Due to the lack of measured vibration data, we use vibration profiles from MIL-STD-810H for input loading. But for now, some difficulties were occurred. First, the weight of devices forms high proportion of truck mass, so it is very difficult to apply input vibration profile (to which part of devices and which profile to be used?). Second, If we use vibration profile of composite wheeled vehicle (page 514.8C-14, MIL-STD-810H) as input profile, then how to tailor this profile in case of big weight of mounted devices?. Please, could anyone advise me to overcome this problem? Thank in advance!n

[peteroznewman]

nI haven't read page 514.8C-14 of MIL-STD-810H, but I expect it is an acceleration vibration profile for the truck frame. Why would you need to tailor this profile? Wouldn't you just use it, since you have no measured data?nA device frame is bolted to the truck frame. That device frame has a subframe that holds electronics, the subframe holds some electronics boards that are fragile.nI suggest you build a model of the device frame, subframe and electronic boards. Don't model the truck frame. The mass and stiffness of all these parts must be properly represented. Large pieces of hardware that are bolted to the device frame can be represented as a point mass. Build that model and run a Modal analysis and a Random Vibration analysis where you use the vibration profile. This will show the stress in the PCB boards.nn