5. Conclusion
Failure causes of the co-fracture of sixteen connecting bolts of a filter press were investigated. Fracture surfaces of the bolts showed distinct fatigue characteristics and thus the fracture cause was determined to be progressive growth of the fatigue cracks. It was shown that, probably low tightening torques were used for the assembly. Accordingly, the bolts failed due to the separation between members and thus the increased alternative stress on the bolts to beyond the fatigue limit of the material, which favors the conditions for failure by the fatigue mechanism. Also, stress concentration atthe bolt roots and surface defects seem to be important parameters in promotion of crack initiation.
