Fastener pre-stressing joint

Abstract

Fastener joints induce static pre-stresses into a fastener that clamps the joint in a magnitude equal and direction opposite from bending stresses induced in the fastener by application loading. Such joints include angling the bolts seats of a connecting rod bearing cap inwardly, creating a relief at the bolted interface between the cap and the rod adjacent to the main bore of the connecting rod or skewing the threaded holes in the rod body inwardly as they extend from the bolted joint faces.

1 . In a joint between at least two parts clamped by a fastener having a shank in tension that holds the parts together, the improvement wherein the joint induces a bending stress in the fastener shank in a plane of bending when the fastener is assembled to the joint, the bending stress induced by the joint being substantially inversely proportional to a bending stress induced in the plane of bending by a maximum application load that the fastener shank is subjected to in service so as to reduce the maximum stress when the maximum application load is applied.  
   
   
       2 . The improvement of  claim 1 , wherein the bending stress induced by the joint is of a magnitude and direction to produce a substantially uniform stress distribution across the fastener shank in the plane of bending when the maximum application load is applied.  
   
   
       3 . The improvement of  claim 1 , wherein the joint has a seat that the fastener bears against to induce tension in the shank and the seat is skewed at an angle other than 90 degrees to an axis of a fastener hole in the parts through which the shank extends in a direction so as to induce bending stresses in the shank of the fastener opposite in direction to bending stresses induced by the maximum application load.  
   
   
       4 . The improvement of  claim 1 , wherein the joint has joint faces that face one another and are held together by the fastener, a portion of the joint faces defining between them an unsupported gap that induces bending stresses in the shank of the fastener opposite in direction to bending stresses induced by the maximum application load.  
   
   
       5 . The improvement of  claim 1 , wherein a hole that extends in the parts and receives the fastener shank has a first portion in one of the parts and a second portion in the other part, wherein the first portion is skewed relative to the second portion so as to induce bending stresses in the fastener opposite in direction to bending stresses induced by the maximum application load.  
   
   
       6 . The improvement of  claim 5 , wherein the second portion is threaded.  
   
   
       7 . The improvement of  claim 5 , wherein the first portion is adjacent to a fastener seat that is substantially perpendicular to an axis of the first portion.  
   
   
       8 . The improvement of  claim 1 , wherein the joint is a joint in a connecting rod connecting a bearing cap to a rod portion of the connecting rod.