How does surface treatment shot blasting equipment improve the fatigue life of metal parts through "cold working strengthening"?
Publish Time: 2025-10-14
Metal parts subjected to long-term alternating loads are prone to microcracks in stress concentration areas, ultimately leading to fatigue fracture. To enhance the durability and safety of parts, surface treatment shot blasting equipment is widely used in the strengthening of key components. Its core principle is to introduce a beneficial compressive stress layer on the part surface through "cold working strengthening," significantly delaying crack initiation and propagation, thereby significantly improving fatigue life. This technology has become an indispensable key process in modern high-end manufacturing.1. Cold Working Strengthening: From Surface Plastic Deformation to Residual Compressive StressShot peening is a mechanical surface strengthening process. Surface treatment shot blasting equipment uses a high-speed rotating impeller or compressed air to continuously bombard the surface of a metal part with a large number of tiny projectiles at high kinetic energy. Upon impact, the surface metal undergoes plastic deformation in a very short period of time, forming countless tiny dents. Because metal materials have elastic recovery capabilities, the underlying matrix attempts to return to its original shape, but the plastically deformed surface cannot rebound, resulting in a layer of residual compressive stress.2. How does residual compressive stress inhibit fatigue cracks?Metal fatigue cracks typically originate from stress concentration points at or near the surface. Under alternating tensile stress, microcracks gradually propagate, eventually leading to fracture. The residual compressive stress layer formed by shot peening acts as a "preload" on the component surface, effectively offsetting the externally applied tensile stress. When the component is operating, the external tensile stress must first overcome the surface compressive stress before the material enters a tensile state. This significantly reduces the actual alternating stress amplitude and significantly delays crack initiation. Even if microcracks have already occurred, the compressive stress layer will hinder their propagation path, forcing the crack to deflect or stop, thereby extending the fatigue life of the component. Research has shown that properly shot peened parts such as gears, springs, and blades can increase their fatigue life by 50% to over 300%.3. Precision Equipment Control: Ensuring Consistent Strengthening ResultsSurface treatment shot blasting equipment uses CNC systems to precisely control the shot material, particle size, velocity, angle, coverage, and treatment time. For example, shot kinetic energy is controlled by adjusting the impeller speed or air pressure; robot trajectory programming ensures uniform coverage of complex curved surfaces; and shot peening intensity is quantified by measuring "arc height" using Almen test pieces, achieving process standardization. The equipment is also equipped with a shot circulation system that automatically separates broken shot from dust, ensuring uniformity and cleanliness of the shot blasting media and avoiding surface damage.4. Wide Application: From Aircraft Engines to Automotive SuspensionsIn the aviation sector, key components such as turbine blades, landing gear, and fasteners must undergo shot peening to withstand extreme alternating loads. In the automotive industry, shot peening is widely used on high-stress parts such as suspension springs, torsion bars, gears, and connecting rods to improve safety and reliability. In wind turbine equipment, shot peening of main shafts and gearboxes extends maintenance cycles and reduces operating costs.5. Environmental Protection and Intelligent DevelopmentEnclosed shot blasting chambers effectively control dust and noise, complying with occupational health and environmental standards. New-generation equipment, integrating sensors and AI algorithms, monitors shot blasting quality in real time, enabling closed-loop control and predictive maintenance, driving the development of intelligent and digital surface treatment.Surface treatment shot blasting equipment uses "cold working strengthening" to introduce a residual compressive stress layer on the metal surface, fundamentally improving the part's resistance to fatigue failure. This is more than just a surface treatment process; it's also a crucial technical means to ensure the long life and high reliability of high-end equipment.
