Suspension spring reinforcement
Thanks to the high-stress and lightweight design, the weight of the suspension spring has been greatly reduced in recent years, and the stress of the new suspension spring >1000Mpa is very common. The service of the spring under such high stress has exceeded the limit that the material can withstand, so it must be supplemented by other strengthening means (such as throwing/spraying).
The host manufacturer adopts very strict test standards for automotive suspension springs. The longest one test period is 70 days (10 weeks). It should be based on suspension springs operating under high stress conditions. Once the surface is stressed and corroded. That is, corrosion fatigue failure occurs, and the broken spring port may cause significant safety and personal accidents if the tire is broken.
The throwing/spraying is the most effective means of strengthening the suspension spring. The fatigue life of the high-stress spring can be increased by more than 5 times after proper shot peening. The throwing/spraying of the suspension spring is mostly using steel wire cutting pills. Shot peening (different pellet diameters) is commonly used. The compressive strength and depth of the spring surface are an important indicator of the shot peening effect. Good shot peening surface stress is at least -600Mpa, -800Mpa can be reached at 50um from the surface, the surface compressive stress of the stress peening spring can reach -800Mpa or more, and -1200Mpa can be reached at 50um from the surface.
At present, well-known suspension spring manufacturers at home and abroad, such as Liaoyang Kesuo, generally use a continuous through-roller frame reinforcement device, and the workpiece is conveyed through a hanging conveyor chain. Each part must be in three shot blasting positions, and three shot peening cycles are performed according to the set time. After the reinforcement is completed, the head is stopped, the discharge door is opened, the strengthened workpiece is automatically hoisted, the new workpiece enters, and the new cycle begins. The equipment has a capacity of up to 500 pieces per hour.
Leaf spring reinforcement
The leaf spring can be individually reinforced by a continuous pass shot peening device to expose the leaf spring geometry concave surface under high speed pill flow. A typical model consists of a throwing head for projecting the top of the leaf spring, with a throwing head on the side and spraying the left and right sides of the leaf spring.
The standard leaf spring reinforcement unit has a 10 ft/min pass rate. If a higher production speed is required, the number of throws can be increased and the motor frequency can be adjusted. Under working conditions, the leaf spring is repeatedly affected by uniaxial bending stress and is therefore sometimes stress-strengthened. In the strengthening process, the simulated leaf spring will be subjected to "stress strengthening" in the future use, so that it can be shot peened while applying a "static stress" in the direction of the load. After the strengthening is completed, the applied static stress is released. Experiments have shown that stress strengthening can extend the service life of leaf springs more than conventional strengthening.
Round spring reinforcement
The round spring, due to its spiral geometry, is more difficult to strengthen than to flatten the leaf spring. In addition, the strengthening effect of the cross-section of the round spring must be strictly evaluated to fully understand the resistance of the round spring to fatigue fracture.
The round springs are individually fed into the blasting chamber through a continuous conveyor chain system. The blasting chamber is equipped with a set of parallel roller tables. At the same time, the roller table is continuously rolled, and the round spring is rotated to move forward. This way of rotation allows the high-speed pill to flow through the loops of the round spring and onto the metal surface of the inner ring, where the stress of the round spring is most concentrated.
For applications with high capacity requirements, a reinforced device that can spray two round springs at the same time is available. The latest research and development results are based on the original shot peening equipment, combined with a number of nozzles, for the specific target of the round spring (stress concentration pleasing) more targeted, firepower concentrated shot peening.
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