Shaft pin design knowledge

Shaft pin type components are usually used after machining and are used in bearings. In the bearing industry, some of them call him a roller needle or a roller.

Shaft-pin parts usually exhibit delayed fracture under stress. There have been automobile galvanized parts such as springs, washers, screws, and leaf springs, and fractures have occurred successively within hours after the assembly of the pin parts, and the fracture ratio has reached 40% to 50%. The cadmium plated parts of a special product had appeared batch cracking during the use process, and had organized nationwide research to develop a strict dehydrogenation process. In addition, there are some hydrogen embrittlement does not appear to delay the phenomenon of fracture, such as: plating hanger (steel wire, copper wire) due to multiple plating and pickling plating, hydrogen permeability is more serious, often occur in the use of a fold will occur Brittle fracture phenomenon; shotgun precision forging mandrel, after repeated chrome plating, smashed to break; some quenched parts (large internal stress) will produce cracks when pickling. These parts are heavily infiltrated with hydrogen and cracks do not occur without external stress. It is no longer possible to use the pin to restore the original toughness.

When the shaft pin is in the anti-reduction design of the pin, the shaft pin friction type connection is the limit state of the maximum possible friction force provided by the bolt tightening force between the contact surface of the plate and the external shear force, that is, the connection is ensured during the entire period of use. The internal and external shear forces do not exceed the maximum friction. The plate does not undergo relative slip deformation (the gap between the screw and the hole is always maintained in the original amount), and the connected plate is subjected to the force of elasticity as a whole. In the shear design, the external shear force is allowed to exceed the maximum friction force in the high-strength pin-pinned type connection. At this time, relative slip deformation occurs between the connected plate members until the bolt rod contacts the hole wall, and then the connection is determined by the bolt. The shear force of the shaft, the pressure on the wall of the hole and the friction between the contact surfaces of the plates jointly transmit the force. Finally, the shear state of the shaft or the pressure on the wall of the hole is used as the limit state of the shear connection.