CAD Models for Lego components can be found at: http://gicl.cs.drexel.edu/repository/data/repository/Lego/ There are many models in various subdirectories. STEP, VRML and I-DEAS formats should be available.
.sat, .stp, and .wrl files for lego parts are located in http://gicl.cs.drexel.edu/repository/data/repository/Lego/Drexel_GICL/
Importing .stp files to Adams
Inside a particular model (mine is called legos),
go to File/Import set the file type to STEP (.stp) set File To Read to your .stp file (from the web repository, save the .stp file to your local machine) remove whatever is in the "relative to" textbox, double click there, click on your model name (.legos for me) in part name, double click, then click on ground under your model name (legos for me)
leave all other options as defaults, click OK
If you cannot see your part, click on View/Part Only.
This will import your part as a shell and attach it to the ground.
These directions are very hackish, feel free to improve them.
Additional Directions from going from STP file to Adams via Pro-E:
picked a lego file (24 tooth gear) 3648.stp right click on the link and save as 24tgear.stp in pro-e, open files, open file of type step, open 24tgear.stp, open as a part save a copy of the file: export as parasolid, had clicked on solids and shells in adams, import file of type parasolid
right click on the imported part, select part menu, part 3 for me, modify
under mass properties, geometry and density, enter 1060 (which is density of lego plastic (1020-1060 kg/m^3)), and then click apply create a construction marker geometry, put it at the center of the 24 tooth gear right click on the gear again, select part menu, part 3, modify, mass properties, user input, center of mass marker (delete what is there), double click in the area then select the marker (marker11 for me) that you added, also add this as the initial inertia reference
Some parts do not exist in .stp format, and some do not have informative labels.
Here is a start of a label map for the parts:
axles, numbers increase with increasing size, not a very exact scale
somewhere b/w 3 and 5 3737.stp
somewhere b/w 3 and 4 32073.stp
round to round 3673.stp
round to axle 3749.stp
round to tiny round 4274.stp
bricks with round crossholes
10x1x1 9 holes 2730.stp
1x2x1 1 hole 3700.stp
1x4x1 3 holes 3701.stp
1x6x1 5 holes 3894.stp
1x8x1 7 holes 3702.stp
1x12x1 11 holes 3895.stp
1x14x1 13 holes 32018.stp
1x16x1 15 holes 3703.stp