The combined ring rolling process and the stiffness condition

Different from the conventional ring rolling mill, the combined ring rolling mill has not only one main roll and one mandrel to enlarge the ring blank, but also two assistant rolls to deform the ring blank with the main roll continuous feeding. The novel ring rolling process can have three working modes: 1) conventional ring rolling; 2) cross rolling with three rolls surrounding the ring blank; 3) conventional ring rolling with cross rolling. Moreover, the new ring rolling process allows the transferring from one working mode to another. The process and the mill provide more flexibility for manufacturing different ring products. The stiffness condition at different working modes and the smoothly transferring conditions are first studied carefully. Then the combined ring rolling model for deep groove ring is established and evaluated

Numerical simulation of the dynamic recrystallization behaviour in hot precision forging helical gears

In hot precision forging helical gears, the dynamic recrystallization phenomena will occur, which affect the microstructure of the formed part and in turn decide their mechanical properties. To investigate the effect of deformation temperature on the dynamic recrystallization in hot precision forging helical gears, a three dimensional (3D) finite element (FE) model was created by coupling the thermo-mechanical model with the microstructure evolution model developed based on the hot compressive experimental data of 20CrMnTiH steel. The hot precision forging process was simulated and the effect laws of the deformation temperature on the microstructure evolution the formed part were investigated. The results show that the dynamic recrystallization volume fraction and the average grain sizes increased with the increasing deformation temperature and the higher deformation temperature is beneficial to dynamic recrystallization and grain refinement

Numerical simulation of the dynamic recrystallization behaviour in hot precision forging helical gears

In hot precision forging helical gears, the dynamic recrystallization phenomena will occur, which affect the microstructure of the formed part and in turn decide their mechanical properties. To investigate the effect of deformation temperature on the dynamic recrystallization in hot precision forging helical gears, a three dimensional (3D) finite element (FE) model was created by coupling the thermo-mechanical model with the microstructure evolution model developed based on the hot compressive experimental data of 20CrMnTiH steel. The hot precision forging process was simulated and the effect laws of the deformation temperature on the microstructure evolution the formed part were investigated. The results show that the dynamic recrystallization volume fraction and the average grain sizes increased with the increasing deformation temperature and the higher deformation temperature is beneficial to dynamic recrystallization and grain refinement

The combined ring rolling process and the stiffness condition

Different from the conventional ring rolling mill, the combined ring rolling mill has not only one main roll and one mandrel to enlarge the ring blank, but also two assistant rolls to deform the ring blank with the main roll continuous feeding. The novel ring rolling process can have three working modes: 1) conventional ring rolling; 2) cross rolling with three rolls surrounding the ring blank; 3) conventional ring rolling with cross rolling. Moreover, the new ring rolling process allows the transferring from one working mode to another. The process and the mill provide more flexibility for manufacturing different ring products. The stiffness condition at different working modes and the smoothly transferring conditions are first studied carefully. Then the combined ring rolling model for deep groove ring is established and evaluated

Effect of Cold Ring Rolling on the Wear Resistance of GCr15 Bearing Steel after Quenching and Tempering

In this work, the effects on dry wear behavior of cold ring rolling (CRR) of GCr15 bearing steel, after quenching and tempering (QT) heat treatment are investigated. The effects on steel microstructures and wear mechanisms of CRR with different austenitizing times are also discussed. The results show that, with a short austenitizing time of 10 min, CRR can increase the retained austenite content, decrease the undissolved carbide content and improve the hardness of the specimen, thus reducing ploughing and fatigue flaking, and decreasing the wear loss of the CRR specimen. With the longer austenitizing time of 20 min, the retained austenite content increases, the undissolved carbide content decreases, and the hardness increases significantly, both in specimens with and without CRR, so that ploughing, fatigue flaking, and wear loss can all be decreased. However, with an austenitizing time of less than 20 min, the effects of CRR on retained austenite content, undissolved carbide content, and hardness are not significant. Thus, CRR of less than 20 min cannot further improve wear morphology or decrease wear loss

A Novel Force Variation Fine-Blanking Process for the High-Strength and Low-Plasticity Material

High forming force is often needed when high-strength and low-plasticity materials are processed by fine blanking. Too high forming force increases the load of the die and greatly increases the risk of die failure. If the forming force is reduced, the material will fracture prematurely, which will lead to poor quality parts. Aiming at this problem, a new force variation load fine-blanking technology is proposed in this paper. During the loading process, the forming force does not remain constant but changes with the blanking stroke. A 2D finite element fine-blanking model was established for the TC4 material. The mechanism of force variation fine blanking is also revealed. This paper proposes a method to design the loading route of the forming force with variable load. This method combines finite element simulation with neural network and a multi-objective genetic algorithm. Finally, the application of variable load fine blanking production and the application of traditional fine blanking production parts are verified by the experimental method. The same results are obtained from both simulation and experiment. It is found that the variable load fine blanking process can greatly reduce the load of the die on the premise of ensuring the quality of fine-blanking parts

A three-dimensional viscoelastic analysis of thermoplastic resin matrix composite laminates during hot stamping

In this paper, a three-dimensional thermo-viscoelastic constitutive equation is used to simulate and analyze the hot stamping process of thermoplastic resin matrix composites. Dynamic mechanical analyzer (DMA) was used to measure the relaxation behavior of resin matrix at different temperatures. Then, the relaxation times and the weight factors of the resin matrix were obtained by regression analysis of the data of the resin matrix relaxation behavior using genetic intelligent algorithm. According to the classical Maxwell model with N Maxwell elements and representative volume element (RVE), the integral constitutive model was established, and the corresponding integral finite element program was incorporated into commercial software ABAQUS with an UMAT subroutine.Thermal expansion was also taken into account in the present model. The constitutive model and its finite element program in this paper were verified by experiments with a self-designed hot stamping die for thermoplastic composites.In addition, the simulation results were compared with the actual failure areas to further verify the applicability of the constitutive model adopted in this paper. The results indicate that the ball edge of the hemispherical part is easy to be damaged