Control devices for cold-working structures

Abstract

Control systems for indenters used in cold working processes, and in particular, for StressWave cold working of metal workpieces. Load on an indenter is increased by increasing the force applied, such as by pressure in a hydraulic reservoir acting on a piston. When the load reaches a desired limit, as may be calibrated by the pressure in the fluid reservoir responsive to the piston being driven by the indenter, then a pressure relief valve allows the fluid to flow from the cylinder to a hydraulic reservoir, thus allowing the indenter shaft to move away from the workpiece. Then, on recycle of the apparatus, an automatic control system reacts to such movement and pumps fluid back to the reservoir, and thus returns the indenter shaft to a pre-determined position. In one embodiment, the pressure relief valve is integrated into, or attached to, the indenter. Other embodiments are disclosed for control of various compound or simple indenters.

1 . Tooling for working a structure to improve the fatigue strength at a selected location in said structure, said structure comprising a first surface, a second surface, and a body therebetween, said tooling comprising: 
 a first compound indenter, said first compound indenter comprising a first primary indenter, said first primary indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said first surface of said structure to impart a residual stress profile in said body of said structure;    a first secondary indenter, said first secondary indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said first surface of said structure to impart a residual stress profile in said body of said structure,    wherein said contacting end of said primary indenter comprises a first shaped surface having a preselected profile, and wherein said contacting end of said first secondary indenter comprises a second shaped surface having a preselected surface profile; and    wherein said first primary indenter and said first secondary indenter are configured for companion engagement with said structure, and wherein first primary indenter acts on said first secondary indenter through a load transfer mechanism.    
     
     
         2 . Tooling as set forth in  claim 1 , wherein said first primary indenter further comprises a flange member for applying load to said load transfer mechanism.  
     
     
         3 . Tooling as set forth in  claim 1  or in  claim 2 , wherein said load transfer mechanism comprises a spring.  
     
     
         4 . Tooling as set forth in  claim 1  or in  claim 2 , wherein said load transfer mechanism comprises a substantially non-compressible fluid.  
     
     
         5 . Tooling as set forth in  claim 2 , wherein said first primary indenter comprises a sufficiently large flange surface area so that the load transferred is sufficient for the secondary indenter to penetrate a preselected workpiece.  
     
     
         6 . Tooling as set forth in  claim 2 , wherein said first secondary indenter comprises sufficiently load receiving surface area to receive load from said load mechanism so that the load transferred is sufficient for the secondary indenter to penetrate a preselected workpiece.  
     
     
         7 . Tooling as set forth in  claim 1 , wherein said load transfer mechanism additionally performs the function of removing said first primary indenter from a dimple in said workpiece.  
     
     
         8 . Tooling as set forth in  claim 7 , wherein said load transfer mechanism additionally performs the function of removing said second primary indenter from a dimple in said workpiece.  
     
     
         9 . Tooling as set forth in  claim 7  or in  claim 8 , wherein said load transfer mechanism comprises a spring.  
     
     
         10 . A hydraulic control system for an indenter having a frame, in which a primary indenter shaft is supported hydraulically by a first piston movable in a first hydraulic cylinder, said system comprising: 
 a tank for hydraulic fluid,    a first pump unit and first line which leads hydraulic fluid from the tank into the first cylinder;    a first return line which leads hydraulic fluid from the first cylinder into the tank, and    a first pressure relief valve connected to the first inlet line and having associated therewith an opening pressure at which the first relief valve opens, and a first by-pass line connected between the first relief valve and tank, such that when the pressure in the first hydraulic cylinder exceeds the opening pressure of the first relief valve, fluid flows from the first hydraulic cylinder through the first relief and through a first return line to the tank.    
     
     
         11 . A system in accordance with  claim 10 , wherein the first by-pass line is integrated the indenter frame.  
     
     
         12 . A system in accordance with  claim 11 , further comprising 
 a first transducer which monitors a height position of the primary indenter shaft, and    a control unit connected to the first transducer and to the first pump unit such that when the pressure in the first hydraulic cylinder is below the opening pressure of the first relief valve, the control unit operates the first pump unit to automatically position the primary indenter shaft at a predetermined position.    
     
     
         13 . A system in accordance with  claim 11 , wherein the first by-pass line is placed in the frame of the indenter.  
     
     
         14 . A system in accordance with  claim 13 , further comprising 
 a first transducer which monitors a height position of the primary indenter shaft in the indenter frame, and    a control unit connected to the first transducer and to the first pump unit such that when the pressure in the first hydraulic cylinder is below the opening pressure of the first relief valve, the control unit operates the first pump unit to automatically position the primary indenter shaft at a predetermined position.    
     
     
         15 . A system in accordance with  claim 10 , further comprising 
 a first transducer which monitors a height position of the primary indenter shaft in the indenter frame, and    a control unit connected to the first transducer and to the first pump unit such that when the pressure in the first hydraulic cylinder is below the opening pressure of the first relief valve, the control unit operates the first pump unit to automatically position the primary indenter shaft at a predetermined position.    
     
     
         16 . A system in accordance with  claim 10 , wherein the first pressure relief valve is integrated into the indenter frame.  
     
     
         17 . A system according to  claim 10 , further comprising 
 a secondary indenter having a secondary indenter shaft portion, said secondary indenter shaft hydraulically supported by a second piston moveable in a second hydraulic cylinder;    a second pump unit and second line which leads hydraulic fluid from the tank into the second hydraulic cylinder;    a second return line which leads hydraulic fluid from the second cylinder into the tank, and    a second pressure relief valve connected to the second inlet line and having associated therewith an opening pressure at which the second relief valve opens, and a second by-pass line connected between the second relief valve and tank, such that when the pressure in the second hydraulic cylinder exceeds the opening pressure of the second relief valve, fluid flows from the second hydraulic cylinder through the second relief valve and through a second return line to the tank.    
     
     
         18 . A system in accordance with  claim 17 , wherein the second by-pass line is integrated the indenter frame.  
     
     
         19 . A system in accordance with  claim 18 , further comprising 
 a second transducer which monitors a height position of the secondary indenter shaft, and a control unit connected to the second transducer and to the second pump unit such that when the pressure in the second hydraulic cylinder is below the opening pressure of the second relief valve, the control unit operates the second pump unit to automatically position the secondary indenter shaft at a predetermined position.    
     
     
         20 . A system in accordance with  claim 19 , wherein the second by-pass line is placed in the frame of the indenter.  
     
     
         21 . A system in accordance with  claim 20 , further comprising a second transducer which monitors a height position of the secondary indenter shaft in the indenter frame, and 
 a control unit connected to the second transducer and to the second pump unit such that when the pressure in the second hydraulic cylinder is below the opening pressure of the second relief valve, the control unit operates the second pump unit to automatically position the secondary indenter shaft at a predetermined position.    
     
     
         22 . A system in accordance with  claim 17 , further comprising 
 a second transducer which monitors a height position of the secondary indenter shaft in the indenter frame, and    a control unit connected to the second transducer and to the second pump unit such that when the pressure in the second hydraulic cylinder is below the opening pressure of the second relief valve, the control unit operates the second pump unit to automatically position the secondary indenter shaft at a predetermined position.    
     
     
         23 . A system in accordance with  claim 17 , wherein the second pressure relief valve is integrated into the indenter frame.