The latest category car body oil machine rod large hardness bolt material bending fastening case analysis

Example of high-strength bolt fastening of connecting rods. Calculation example of high-strength bolts HXN5 locomotive diesel engine connecting rod bolt material is alloy structural steel. The strength yield limit σy after heat treatment is 1100MPa, bolt size M24×2. Bolt tightening adopts corner method, fastening The relationship between the corner and the preload. Fig. 2 Relationship between tightening angle and preloading forceFig. 3 Torque angle of four connecting rod bolts of diesel engine connecting rod Note: The highest torque of the system is controlled at 1250Nm, and the actual maximum torque is 1233Nm when the angle is 145°.

According to GE's relevant operating specifications, the tightening wrench system is controlled by a microcomputer, and the microcomputer display screen simultaneously displays the bolt angle torque curve. Before the torque wrench tightens the connecting rod bolts, firstly lubricate the threaded joint surface, the bearing surface should be oil-free, and then tighten the four connecting rod bolts in the diagonal order in 280Nm torque, and then tighten the torque. When the bolt angle is 145°, the torque Tfy1 should be around 1100Nm, and the system maximum torque Tfy2 should be controlled at 1250Nm. Figure 3 is an image of the four connecting rod bolts of the diesel engine connecting rod according to GE's relevant operating specification <4>.

The analysis is the relationship between the corner torque of the No. 1 connecting rod bolt when tightened according to GE's relevant operating specifications. According to China's GB/T16823.3D1997 "Bolt Fastener Tightening Test Method", the definition of the yielding tightening axial force: When the gradient of the curve changes drastically, the axial force value at this point is the yielding tightening axial force value Ffy. According to the definition, the curves from the middle and the middle can be seen that during the tightening process, the angular torque relationship curve does have a sudden change from the elastic zone to the plastic zone. Therefore, it can be judged that the curve is the appearance of the plastic fastening of the bolt. .

The calculation is based on the formula of the yielding tightening axial force and the yielding tightening torque in the General Rules for Fastening of Threaded Fasteners, and the bolt is in the theoretical calculation of the plastic fastening load. Ffy=σyAs/1+32dA×Pπ+μsd2secα′2(1)Tfy=KFfyd(2) where: Ffy is the yielding tightening axial force, kN; Tfy is the yielding tightening torque, Nm; σy is the bolt yielding limit of 1100MPa As is the bolt nominal stress cross-sectional area 384mm2<4>; dA is the bolt nominal stress equivalent diameter 221118mm; P is the pitch 2mm; μs is the thread friction coefficient, take 0105～0110; μw is the bearing surface friction coefficient, take 0110; d2 For the thread diameter 221701mm; α' is the thread flank angle 300°; K is the torque coefficient; d is the bolt nominal diameter 24mm.

When taking μs as the intermediate value, that is, μs=0108, μw=0110, substituting into equation (1): Ffy=1100×384/1+32221118×2π+0108×221701×11552=388295N=3881295kN from “Threaded Fasteners” Appendix A of the General Rules for Fastening finds K=01123, then: Tfy=01123×3881295×24=11461247Nm 1 2 Prove that the theoretical calculation results are consistent with GE's relevant operational specifications.

When taking μs as the limit value, ie μs=0110, μw=0110, substituting into equation (1): Ffy=3761234kN from GB/T16823.2D1997 "Threaded fastener fastening rules" <2> Appendix A found K= 01134, then Tfy=01134×3761234×24=12091969Nm 1 2 Prove that the theoretical calculation results are consistent with GE's relevant operational specifications.

Conclusion Through the above analysis and calculation, combined with the bolt operation specification provided by GE, it is verified that GE has rationally applied the bolt plastic fastening bearing theory to maximize the strength of the connecting rod bolt. With the continuous expansion of imported technology and localization, as well as the increasing introduction of China's imported equipment and the increasing level of cold and hot technology, it is necessary to draw on and apply the international research results on the twist-pull relationship of threaded fasteners.

Hex Nuts

Hex Nut is a kind of nut, which is screwed together with bolt or screw for fastening. All manufacturing machinery must use a kind of component. According to different materials, it can be divided into carbon steel, stainless steel, non-ferrous metal (such as copper) and other types.we have the perfect after-sales service and technical support.