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Firstly, tubes in a frame will experience various forces and moments when analyzing the load case requirements. (see the ASC regulations)
- Force → load applied at a point, causes pressure and by extension stress (over an area), displacement, work, etc.
- Moment → measure of a force times a perpendicular distance from a point (I.e. tendency of a force to rotate around an axis of an arbitrary point)
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- Bending moments (forces that cause a rotation around a fixed point, causing bending) can cause bending stress (this is the root of most all problems in frame design)
- Bending moments have a lot to do with load pathing (i.e. if your tubing and therefore your load path is a straight line, no bending moment is caused (forces are only axial), but as soon as you introduce an angled path, bending moments are caused)
Torsional Forces
- Torsional (or twisting) forces occur when torque is applied about the longitudinal axis of a part
- A good way to visualize this would be when the driver takes a turn, where one wheel must travel a farther distance than the other, meaning there is a differential in the forces on either side, causing a torque
Supports will come in later when you take Statics/are introduced to Ansys (FEA).
- Supports assume infinite stiffness in specific degrees of freedom. Some supports (like fixed) have reactionary forces and moments in all DOF, some like (roller and pinned) have reactionary forces and moments in only specific DOF
- All that matters is that different types of supports resist different types of forces/moments, which you can use to solve/isolate forces and understand the reactions happening in a system
- Supports are integral to setting up a simulation right. If you have too many constraints, your sim will be too stiff and you will have inaccurate results. Too little constraints, same problem, inaccurate results, that can cause you to falsely presume your part is safe/effective.
Two Force Members
- A two force member in our case would be a tube with forces only acting in two locations, with the forces being equal opposite and colinear. Two forces are
Truss Structures
- In our case, a truss structure is structure made to take high loads while utilizing 2 force members, thus taking high axial loads, while minimizing bending loads.
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