General Mechanical

General Mechanical

Which boundary condition is correct Fixed support or Frictionless support?

    • sakthi arumugam

      A stand simply placed on the ground and load applied at the corner of the table. Which boundary condition is correct Fixed support or Frictionless support and which type of connection is correct (rough or frictionless) between ground and stand base. if load exceeds , table should upset. so which boundary condition is correct. This very basic support.

      @peteroznewman #peteroznewman


    • peteroznewman

      I will assume the table top is bolted to the stand.  I will assume the mass of the blocks, the table top and the stand are all correctly modeled.  The analysis needs the Inertial load of Standard Earth Gravity to pull all that mass downward to create a reaction force on the bottom of the stand. I will assume the Y axis points up.

      While you could model the ground and rough contact, that is more work than necessary. Also, you can't use Static Structural because there is no solution after the load passes the tipping over load, so you have to sneak up on that and the solution ends with a failure to converge, so the results are messy.

      The simple way to find the load when the table tips over is to suppress the ground body and put a Revolute Joint to Ground on the left edge of the stand. Select a vertex on the right edge of the stand to apply a Displacement of Y = 0 leaving X and Z Free.  Apply a large Force to the face of the block on the corner of the table.  Under the Solution branch, insert a Probe for the Reaction Force on the Displacement.  Solve.

      For a small Force, the Reaction Force will be upward and the Force on the table is below the tipping load. For a large Force, the Reaction Force will be downward and the Force on the table is above the tipping load.  The Force when the Reaction Force is 0 is the critical load when the table will tip over.

      This analysis is not really a Stress analysis, it is a Statics problem and could be solved without Ansys.

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