Method and devices to limit a creep of mechanical fasteners

Abstract

A method and devices to limit or to exclude operating creep of mechanical fasteners is disclosed. The method consists in use of mechanical fasteners such as bolts, gaskets, screws, washers and other power elements manufactured from shape memory alloys having temperature interval of martensitic phase transformations corresponding to the operating temperature of industrial equipment. The power elements are previously shape-memorized either to tension or to compression, flexion, torsion, or to their combinations under temperature of martensite state with suitable quantity of conserved residual shape-memorized deformation obtained during loading-unloading of the power elements. Further constrained recovery of shape-memorized deformation under operating temperature generates reactive shape-recovering forces having direction inverse to the direction of operating creep. The process of creep limitation is called “Method of “negative creep”.

1 . A method to provide an active behavior of mechanical fasteners to limit or to exclude their operating creep due to external and/or internal loadings and elevated operating temperature of industrial equipment.  
   
   
       2 . A method according to  claim 1  wherein said mechanical fasteners are the bolts, gaskets, screws, washers or other fastening power elements.  
   
   
       3 . A method according to  claim 2  wherein said bolts, gaskets or other fastening power elements are manufactured from shape memory alloys having temperature interval of martensitic phase transformations corresponding to interval of operating temperatures of industrial equipment.  
   
   
       4 . A method according to  claim 3  wherein said bolts, gaskets or other fastening power elements are previously shape-memorized either to the tension or to compression, flexion, torsion, or to their combinations obtaining conserved residual shape-memorized deformations under temperatures of martensite state during loading-unloading.  
   
   
       5 . A method according to  claim 1  wherein said mechanical fasteners interact with adjacent rigid component parts of said industrial equipment under temperatures of martensitic phase transformation to provide a constrained recovery of conserved residual shape-memorized deformation that generates a reactive shape-recovering forces having direction inverse to the direction of operating creep of said mechanical fasteners.  
   
   
       6 . A method according to  claim 1  that is called the “Method of “negative creep”.  
   
   
       7 . A device to limit or to exclude operating creep of mechanical fasteners including bolts manufactured from shape memory alloy and previously shape-memorized to the compression.  
   
   
       8 . A device according to  claim 7  including the gasket manufactured from shape memory alloy and previously shape-memorized to the tension.  
   
   
       9 . A device according to  claim 7  including the gasket manufactured from typically used material.  
   
   
       10 . A device including the bolts manufactured from typically used structural steel and gasket manufactured from shape memory alloy and previously shape-memorized to the tension.  
   
   
       11 . A device according to  claim 10  wherein the bolts have internal axial hollow channel adapted to place and to fix firmly a shank manufactured from shape memory alloy and previously shape-memorized to the compression.  
   
   
       12 . A device according to  claim 11  wherein the gasket is manufactured from typically used material.