Ultrasonic impact methods for treatment of welded structures
This invention provides methods of treatment for work products of materials such as steel, bronze, plastic, etc. and particularly welded steel bodies by pulse impact energy, preferably ultrasonic, to relax fatigue and aging and extend expectant life. The treatment may occur (a) at original production, (b) during the active life period for maintenance or (c) after failure in a repair stage. The ultrasonic treatment improves the work product strength. In welded products residual stress patterns near the weld sites are relaxed and micro-stress defects such as voids and unusual grain boundaries are reduced. The basic method steps are non-destructive in nature, inducing interior pulse compression waves with ultrasonic transducers and accessory tools impacting an external product surface with enough impulse energy to heat and temporarily plasticize the metal interior and relax stresses. The nature of the work product interior structure being treated is determined by sensing the mechanical movement at the impact surface of the work body to produce feedback frequency and phase signals responsive to input impact signals. These signals automatically conform driving pulse energy frequency and phase to the input transducers to match the mechanical resonance frequency of the working transducers and increase efficiency of energy transfer. Such feedback signals also are available for automated procedures which can improve product quality and consistency.
1. A load bearing work product body of a solid structural material comprising an interior structural zone constructed and arranged by controlled introduction of pulses of energy of ultrasonic waves into said interior structural zone through periodic ultrasonic mechanical impulse impacts normal to an exterior work product body surface providing compression waves providing relaxed residual stress patterns and reformed grain boundary structure in said zone thereby providing a work product body with a strength greater than that present therein prior to said periodic ultrasonic mechanical impulse impacts.
2. The work product body of claim 1 , wherein said zone further includes a white layer.
3. A product body with an internal body structure with increased life and load bearing strength therein comprising stress concentration regions of an internal body structure constructed and arranged by a controlled impulse producing instrument in normal periodic mechanical contact with an external surface in vicinity of said regions providing first a multiplicity of shock pulses of a magnitude and sequential relationship to induce temperatures to a predetermined depth in said structure and thereafter in a dynamic treatment zone, a compression wave pattern gradient of greater magnitude at a surface zone which receives said multiplicity of shock pulses than at remote unstressed locations in said product body, and subsequently reconstructed compression wave distribution patterns to provide said internal body structure with higher fatigue strength and load bearing capacity than present prior to provision in said internal structure of said reconstructed compression wave distribution patterns, wherein said compression wave distribution patterns provide relaxed and redistributed residual crystalline structure in said product body due to presence therein of reduced work product voids or bubbles, reworked grain structure and residual stress patterns.