Units Confusion

[mdristy]

In Mechanica, I am using Force units of in-lbm/sec^2. Length units of inches. Mass units of lbm. (Mechanica defaults)


When I want to apply a pressure load of 2,000 psi to a surface, do I have to actually enter the value of the pressure times the acceleration due to gravity? (ie: 2000 x 386.1)


It seems my displacements are coming out about 380 times to low, so I suspect this is the case. But I find the Mechanica units to be confusing...


The weird thing is the stesses (von Mises) were coming out about right, so I'll then have to divide the stresses by 386.1! annoying!


What am I doing wrong?


I am using Mechanica integrated with Wildfire 2.0.

 

[mdristy]

Okay. I just found out that by changing the model units to "IPS" (Edit/Setup/Units...) it takes care of all the confusion. Just make sure to then go and update the pressure values you used in your Mechanica model. The unit conversionprocess will have decreased them by 386.1 (the acceleration due to gravity). Then everything works out cleanly.