An apparatus and method are provided for changing physical characteristics of a workpiece which may have been pre-loaded before being further processed. The workpiece is supported in a fixed position during processing. A driven member applies multiple impacts to one surface of the workpiece. The driven member is operated within adjustable parameters. A controller, having the adjustable parameters, is operatively connected to the driven member for causing the driven member to apply multiple impacts against a surface of the workpiece while under the control of the pre-adjustable parameters for changing physical characteristics of the workpiece.