I am trying to simulate bolt tightening in a truss-type structure with ABAQUS. I have used the solid 3D modeling part for simulating parts of the structure. I have created two steps: step 1 is defined Static General for analysis bolt loads and Step 2 is the Frequency for gaining modal parameters. In both steps NIgeon is off. There are 26 bolts and I have created bolt load for each bolt with Interior Surface method. Although I set up the model carefully, after just three increments the analysis aborted due to errors. Before stopping the analysis, some warnings occur including:

• The aspect ratio for 160 elements exceeds 100 to 1. The elements have been identified in element set WarnElemAspectRatio.
• The system matrix has 104 negative eigenvalues.
• Displacement increment for contact is too big.
• The strain increment has exceeded fifty times the strain to cause first yield at 1272 points.
• The strain increment is so large that the program will not attempt the plasticity calculation at 29 points.