Deep rolling tool and method

Abstract

An embodiment of a tool assembly includes a hub connected to a distal end of a spring-loaded shaft assembly disposed along a first axis. An upper hub portion is adjacent to the distal end of the spring-loaded shaft assembly aligned with the first axis, and a lower hub portion extends along a second axis, forming a nonzero angle relative to the first axis. A roller disk is joined to the lower portion of the hub, and is rotatable about the second axis parallel to the second portion of the hub. A load cell is disposed along the first axis between a proximal end of the shaft and the roller disk, and is adapted to measure a downward force applied along the shaft assembly.

1 . A tool assembly comprising:
 a spring-loaded shaft assembly disposed along a first axis;   a hub connected to a distal end of the spring-loaded shaft assembly, the hub having an upper hub portion adjacent to the distal end of the spring-loaded shaft assembly aligned with the first axis, and a lower hub portion extending along a second axis, the second axis forming a nonzero angle relative to the first axis;   a roller disk joined to the lower portion of the hub, the roller disk having a working surface about its perimeter and being rotatable about the second axis parallel to the second portion of the hub; and   a load cell disposed along the first axis, the load cell adapted to measure a force applied along the shaft between a proximal end of the shaft assembly and the roller disk.   
     
     
         2 . The assembly of  claim 1 , wherein the spring-loaded shaft assembly comprises a flexible shaft. 
     
     
         3 . The assembly of  claim 1 , wherein the spring-loaded shaft assembly comprises:
 a rigid shaft; and   a resilient element disposed at a distal end of the spring-loaded shaft assembly proximate to the hub.   
     
     
         4 . The assembly of  claim 3 , wherein the rigid shaft is supported by a linear bearing arranged along the first axis. 
     
     
         5 . The assembly of  claim 3 , wherein the resilient element comprises a plurality of stacked Belleville washers. 
     
     
         6 . The assembly of  claim 3 , wherein the load cell is contiguous with the resilient element. 
     
     
         7 . The assembly of  claim 1 , wherein the load cell is in communication with a monitor adapted to receive signals corresponding to an instantaneous load on the resilient element. 
     
     
         8 . The assembly of  claim 7 , wherein the monitor is part of a machine controller with closed-loop feedback logic, the machine controller adapted to vary an applied force on the tool along the first axis based on one or more of the received signals. 
     
     
         9 . The assembly of  claim 1 , wherein the upper hub portion and the lower hub portion define a right angle, such that the roller disk is rotatable about the second axis perpendicular to the first axis. 
     
     
         10 . The assembly of  claim 1 , wherein the working surface includes a profile along its width such that an effective radius of the roller disk varies along a width thereof. 
     
     
         11 . The assembly of  claim 10 , wherein the working surface of the roller disk is crowned from a center to opposing first and second edges. 
     
     
         12 . A method comprising:
 supporting a workpiece in a fixture, the workpiece having a first nonplanar surface: and   performing a first rolling operation on the first nonplanar surface, the first rolling operation comprising:
 applying a downward force to a proximal end of a spring-loaded tool shaft aligned with a first axis, the downward force applied along the first axis such that the downward force is transferred through the shaft to a hub disposed at a distal end of the shaft assembly; 
 transmitting the transferred downward force from an upper portion of the hub aligned with the first axis to a lower portion of the hub parallel to a second axis, the second axis forming a nonzero angle relative to the first axis, about which a roller disk is supported by one or more bearings, such that a resulting compressive force is applied to the first nonplanar surface of the workpiece via a working surface of the roller disk; and 
 operating a load cell disposed along the first axis to generate signals corresponding to an instantaneous load on the spring-loaded tool shaft. 
   
     
     
         13 . The method of  claim 12 , wherein the working surface includes a profile along its width such that an effective radius of the roller disk varies along a width thereof, such that the resulting compressive force applied to the first nonplanar surface varies along the width of the working surface. 
     
     
         14 . The method of  claim 13 , wherein the working surface of the roller disk is crowned from a center to opposing first and second edges. 
     
     
         15 . The method of  claim 12 , wherein the deep rolling tool shaft comprises:
 a rigid shaft extending along the first axis; and   a resilient element disposed at a distal end of the rigid shaft adjacent to the hub.   
     
     
         16 . The method of  claim 12 , and further comprising:
 transmitting the signals to a controller for monitoring the applied compressive forces during the first rolling operation.   
     
     
         17 . The method of  claim 12 , and further comprising:
 varying the downward force based on the signals generated by the load cell such that the resulting compressive force is within a predetermined range along a tool rolling path.   
     
     
         18 . The method of  claim 12 , and further comprising using the tool to perform a second rolling operation on a second nonplanar surface of the workpiece, wherein the second nonplanar surface is directly opposite the first nonplanar surface. 
     
     
         19 . The method of  claim 18 , wherein the workpiece comprises a fan blade for a gas turbine engine. 
     
     
         20 . The method of  claim 19 , wherein at least one of the first nonplanar surface and the second nonplanar surface includes a junction between an airfoil and a dovetail root.