Methods and systems for mitigating residual tensile stresses

Abstract

Residual tensile stresses can be mitigated through methods and systems provided by the present invention. Such a method can include securing a metal member ( 10 ) to a substrate and at least partially surrounding a portion of the metal member ( 10 ) with a cooling fluid ( 18 ). As a result, the cooled portion of the metal member ( 10 ) contracts a predetermined amount. Once cooled, the metal member may be fixed, preferably welded, to another metal member in a constrained relationship. As the portion of the metal member is returned to its original temperature, expansion of the metal member acts to mitigate residual tensile stresses in the metal assembly. Tensile stress in restrained members, cambering, and structural deformation can be readily controlled in an assembled structure.

1 . A system for mitigating residual tensile stresses comprising:
 a) a fluid containment vessel having an interior volume capable of retaining a cooling fluid therein and configured to enclose at least a portion of a first member; and   b) a cooling source operatively connected to the fluid containment vessel, said cooling source containing the cooling fluid.   
   
   
       2 . The system of  claim 1 , wherein the first member is a metal member and the system further comprises a welding apparatus capable of joining the first metal member to a second metal member. 
   
   
       3 . The system of  claim 1 , wherein the fluid containment vessel includes a contact cooler which comprises an open-sided shell which encloses the interior volume upon contact with the portion of the first member. 
   
   
       4 . The system of  claim 3 , further comprising a cooling fluid outlet operatively connected to the open-sided shell to allow removal of the cooling fluid. 
   
   
       5 . The system of  claim 3 , further comprising a low temperature sealant material placed between edges of the open-sided shell and the portion of the first member. 
   
   
       6 . The system of  claim 1 , wherein the fluid containment vessel includes an enclosure configured to surround the portion of the first member with the cooling fluid. 
   
   
       7 . The system of  claim 6 , further comprising a removable filler configured to occupy space within the enclosure to reduce usage of cooling fluid. 
   
   
       8 . The system of  claim 1 , wherein the fluid containment vessel further includes interchangeable inserts, said inserts being adjustable to allow insertion of various shaped members into the fluid containment vessel. 
   
   
       9 . The system of  claim 1 , wherein the first member comprises a weldable material selected from the group consisting of copper, titanium, aluminum, carbon steel, tin, iron, and alloys or composites thereof. 
   
   
       10 . The system of  claim 1 , wherein the cooling fluid is selected from the group consisting of liquid nitrogen, liquid helium, liquid argon, liquid oxygen, liquid carbon dioxide, and combinations thereof. 
   
   
       11 . The system of  claim 1 , wherein the cooling fluid is liquid nitrogen. 
   
   
       12 . The system of  claim 1 , wherein the fluid containment vessel is formed of metal, plastic, ceramic, polymeric foam, composites thereof, or combinations thereof. 
   
   
       13 . The system of  claim 12 , wherein the fluid containment vessel is formed of polymeric foam. 
   
   
       14 . The system of  claim 13 , wherein the polymeric foam is polystyrene, polyurethane, polyolefin or polyisocyanurate. 
   
   
       15 . The system of  claim 1 , wherein the fluid containment vessel includes a metal lining.