text: The cold work produced from this process is typically minimal, similar to the cold work produced by laser peening, only a few percent, but a great deal less than shot peening, gravity peening or, deep rolling. Cold work is particularly important because the higher the cold work at the surface of a component, the more vulnerable to elevated temperatures and mechanical overload that component will be and the easier the beneficial surface residual compression will relax, rendering the treatment pointless.  In other words, a component that has been highly cold worked will not hold the compression if it comes into contact with extreme heat, like an engine, and will be just as vulnerable as it was to start.  Therefore, LPB and laser peening stand out in the surface enhancement industry because they are both thermally stable at high temperatures.  The reason LPB produces such low percentages of cold work is because of the aforementioned closed-loop process control.  Conventional shot peening processes have some guesswork involved and are not exact at all, causing the procedure to have to be performed multiple times on one component.  For example, shot peening, in order to make sure every spot on the component is treated, typically specifies coverage of between 200% (2T) and 400% (4T).  This means that at 200% coverage (2T), 5 or more impacts occur at 84% of locations and at 400% coverage (4T), it is significantly more.  The problem is that one area will be hit several times while the area next to it is hit fewer times, leaving uneven compression at the surface.  This uneven compression results in the whole process being easily "undone", as was mentioned above.  LPB requires only one pass with the tool and leaves a deep, even, beneficial compressive stress.
  The LPB process can be performed on-site in the shop or in situ on aircraft using robots, making it easy to incorporate into everyday maintenance and manufacturing procedures.  The method is applied under continuous closed loop process control (CLPC), creating accuracy within 0.1% and alerting the operator and QA immediately if the processing bounds are exceeded.  The limitation of this process is that different CNC processing codes need to be developed for each application, just like any other machining task.  The other issue is that because of dimensional restrictions, it may not be possible to create the tools necessary to work on certain geometries, although that has yet to be a problem.