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Analysis of the Reduction of Bolt Pre-tightening Force When Using the Hydraulic Stretcher

The final pre-tightening force on the bolt is smaller than the design value , as when the nut is tightened using the Hydraulic Stretcher, there is reduction of bolt pre-tightening force. In the design procedure, the value difference is an important reference in determining the oil pressure applied by the hydraulic stretcher. The methods of the finite element analysis and testing were adopted to study the value difference. The results show that the reduction reaches 10% of the designed value, and shoud be paid attention to.