Views:31 Author:Yvonne Han Publish Time: 2019-10-12 Origin:Site
Why use ultrasonic impact gun to eliminate stress?
Metal structure parts are generally welded by welding. During the metal filling process, there are residual heights, pits, undercuts and various welding defects at the joints, causing severe stress concentration and a certain welding residue. Pulling stress.
Residual tensile stress is extremely unfavorable to the fatigue strength of the welded structure, which easily leads to cracking, accelerated stress corrosion and welding deformation;
At the same time, a large number of studies have shown that there are welding defects at the weld toe, which are relatively sharp, causing stress concentration to cause fatigue cracks to prematurely initiate, leading to cracking of the weld.
Tensile residual stress exists in the stress concentration, and the fatigue strength will decrease. According to statistics, about 80% of the failures of mechanical parts are fatigue damage, and there is no obvious deformation before the damage, so fatigue damage often causes major accidents.
Stress corrosion cracking is a phenomenon in which cracks are generated by the combination of tensile residual stress and chemical corrosion, which occurs under the combination of certain materials and media. The greater the tensile residual stress, the shorter the time for stress corrosion cracking.
When there is residual stress inside the deformed object, the object will produce corresponding elastic deformation or lattice distortion. If the residual stress equilibrium state is destroyed, it will cause changes in the shape and shape of the object;
When the sum of the stress generated by the external load and the residual stress of a certain area in the structure reaches the yield point, the material in this area will undergo local plastic deformation, losing the ability to further withstand the external load, resulting in the effective cross-sectional area of the structure. Small, the stiffness of the structure is also reduced.
How to solve this problem?
The ultrasonic impact stress relieving device utilizes a high-power impact tool to impact the surface of the metal object at a frequency of more than 20,000 times per second, and causes a large compression plastic deformation of the metal surface layer under high energy, high efficiency and high focusing energy; The shock wave changes the original stress field and produces a certain amount of compressive stress, which strengthens the impact portion.