Jian Li Song

Parameters and Experiments on the Precision Forming Process of Spline Cold Rolling

Cold rolling precision forming process of spline is one of the high-efficiency, precision and non-chip forming advanced manufacturing technologies. It has the characteristics such as high forming efficiency, energy-saving, low material consumption and better forming properties of components. The process and principle of involute spline cold rolling precision forming was analyzed. A measuring and testing system for the force and energy parameters in the forming process was set up, and the real-time variation curves of the torque moment of the spindle and the radial feeding force were obtained. Also, the influencing rules of process parameters on the maximum radial feeding force and spindle torque were investigated. Finally, Precision forming experiments of involute spline cold rolling were carried out with optimized parameters. Precision measuring and hardness testing of the tooth outline section shows that the components obtained by the experiments were free of defects. Compared with the spline components obtained from conventional cutting process, the hardness and wear ability was greatly improved, which is suitable for the requirement of application.

Cracking Mechanism of Laser Cladding Rapid Manufacturing 316L Stainless Steel

Laser cladding rapid manufacturing technology is a kind of new developed advanced manufacturing technology integrating the advantages of rapid prototyping manufacturing and laser cladding surface modification. Due to the complex thermo-physical and metallurgical factors in the deposition process, the cladding layer is liable to crack, which seriously impedes the industrial application of this technology. Experiments of laser cladding rapid manufacturing 316L stainless steel were carried out. The cracking behavior and phenomena has been observed, cracking mechanism of 316L stainless steel was investigated by means of microstructure characterization and phase analysis with optical microscopy (OM), X-Ray diffraction (XRD), scan electronic microscopy (SEM) and phase diagram analysis. Factors influencing the cracking susceptibility has also been studied. Results show that the cracks of 316L stainless steel were hot solidification cracks caused by the high residual stress and separating of the liquid films among dendrites. Through the optimization of process parameters, adding protective atmosphere, etc. cracking sensitivity has been effectively reduced and crack free 316L stainless steel components have been obtained.

Process and Properties on the Precision Forming of Spline Cold Rolling

Cold rolling precision forming process of spline is one of the high-efficiency, precision and non-chip forming advanced manufacturing technologies. It has the characteristics such as high forming efficiency, energy-saving, low material consumption and better forming properties of components. The principle and the force of involute spline cold rolling precision forming process were analyzed. Forming experiments of involute spline cold rolling were carried out, and the microhardness map of the tooth outline was gained. The rule of the metal flow in the deforming area and the forming mechanics of the microstructure were analyzed. The influence of plastic deformation on the forming properties was also conducted. Experimental results showed that dramatic plastic deformation has taken place on the upper surface of the workpiece during the cold rolling process of spline, while the influence on the inner materials were very small. The grains were distributed as a flow line pattern along the tooth profile, and the grains in the plastic deformation zone presented a fine and long fibrous state. The hardness on the section of the tooth outline is regularly distributed. Compared with the spline components obtained from conventional cutting method, the hardness of the spline was greatly increased, therefore, comprehensive mechanical property such as wear resistance and impact resistance were largely improved. Precision measuring and hardness testing of the tooth outline section showed that the components obtained by the experiments were free of defects, and the application requirement can be satisfied.

Researches on Dressing Diamond Grinding Wheels on Line by a Diamond Pen Aided with Laser Beam Preheating Based on Optical Fiber Delivering

The dressing on line of diamond grinding wheels used in NC optical curve grinding machines are very difficult. A method has been researched in this paper that is dressing the diamond grinding wheels by a diamond pen aided with laser beam preheating . Its principle has been stated. The temperature mathematics model of laser beam preheating diamond grinding wheels has been set up. The temperature field of resin substrate diamond grinding wheels has been calculated. Through the analyses on the results of the temperature field, it has been known that the distance between laser beam preheating central and the diamond pen dressing point be very small. A new method that is delived laser beam by optical fiber in dressing on line of diamond grinding wheels by a diamond pen aided with laser beam preheating has be proposed. Uasing this new method, a high precision and high efficiency in dressing diamond grinding wheels on line can be fulfiled.

Numerical Simulation of the Temperature Field in Multi-Layer Powder-Feeding Laser Cladding Forming

The numerically simulation of temperature field was carried out by the ANSYS software in multi-layer powder-feeding laser cladding forming.3-D finite element model was found, which nonlinear characteristics of the material thermal properties and the boundary conditions of the convective transfer heat was considered; The process of powder falling into the substrate and cladding element growing was accomplished by “Element Birth and Death technology” in the process of numerical simulation. The result shown that the primarily solidified cladding layer to the following cladding layer has a preheating function in the process of multi-layer laser cladding forming, the initial temperature of following cladding layer is higher than primarily melted cladding layer; The thermal cycling curves of the molten pool nodes takes on periodic variation and basic similar in every layer cladding; The end effect problem is apt to happen in cladding layer, which the phenomenon of edge collapsing or partially burnt is formed; The temperature gradient distribution is divided into two parts, the temperature gradient level distribution along the laser scanning direction in the top and perpendicular distribution in the bottom, The temperature gradient appearances mutation and maximum value in the junction of the substrate and cladding layer, which the crack is apt to be caused in this region.

Modal Analysis on the Inclined Double-Column and Pre-Stress Combined Frame Structure of the 80MN Rapid Forging Hydraulic Press

In this paper, the first 80MN rapid forging hydraulic press in China was developed. The inclined double-column and pre-stress combined frame structure and the direct Pump-driven technologies were adopted for the first time in the design of this press. The linkage driving with the full-hydraulic orbital manipulator has been realized. A rapid forging frequency of 75~80 /min and a finishing precision of ±1mm for hot-state forgings can be obtained. The three dimensional full-contact solid model of the double-column combined frame structure of the 80 MN rapid forging hydraulic press has been set up. The modal analysis of the pre-tightened frame has been carried out with the FEM analysis software ANSYS. The first five-order inherent frequencies and the corresponding natural modes have been obtained, the mode shapes of various orders have also been analyzed in detail. It is shown from the research results that the inherent frequency of the frame is larger than the impact frequency. Therefore, resonant vibration of the structure will not occur. The analysis results will have an important significance for the understanding of the dynamic performance of the rapid forging hydraulic press, optimization of the structure design of the press and the decrease of vibration and noise pollution.

Experimental Study on the Laser Rapid Forming Repairing of 45 Steel and 2Cr12 Components

Laser rapid forming is a kind of new developed technology combining laser surface modification and rapid prototyping technology. It provides a powerful tool for the manufacturing and repairing of metal components. Laser rapid forming repairing experiments of 45 and 2Cr12 steel have been carried out with 316L stainless steel powder. Microstructure and properties of the repaired components are analyzed and tested with optical microscopy (OM), scanning electron microscopy (SEM) and electronic tensile experimental machine etc. Repaired components of different materials have been metallurgically bonded with the deposited layers, with fine microstructure, better mechanical properties and free of defects.

Synchronized Hydraulic Bulging Forming Technology of Three-Layer-Metal Tubes

Synchronized hydraulic bulging forming technology on three-layer-metal tubes was studied. The possibility of three-layer-metal tubes formed by hydraulic bulging method was discussed and proved by elastic-plastic theory. The calculation formulas about the bulging pressure, the residual contact stress and the relationship between them were derived and the main process parameters were analyzed. Finite element analysis was carried out on bulging forming process using MSC. Marc. Practical bulging forming experiments were conducted and well compounded three-layer-metal tubes with tight interfaces were obtained. Through the comparison of the results of theoretical analysis, numerical simulation and practical experiments, proper parameters for the bulging process were obtained and the theoretical analysis was verified and proved.

Optimization of Laser Cladding Forming Parameters by Numerical Simulation to Minimize the Cracking Posibilitys

Laser cladding forming (LCF) is one of the new developed advanced manufacturing technologies. It integrates the advantages of rapid prototyping manufacturing and laser cladding surface modification, and three dimensional near-net-shape metal components can be directly manufactured without dies. Due to the dramatic heating and cooling characteristics of laser cladding forming process, the cladding layers is liable to crack, which greatly impedes the further and wider application of this technology. In this paper, numerical simulation on the three-dimensional transient temperature field and stress field of powder-delivery LCF has been carried out with parametric programming methods. The temperature field, temperature gradient and cooling rate of the laser cladding layer have been obtained. The influences of laser power and scanning speed on the temperature gradient and cooling rate of the cladding layers, especially the cooling rate of solid-liquid interface of the melt pool have been studied, which is tightly correlated with the cracking generation of the deposited layers. According to the simulation, process parameters were optimized to minimize the cracking possibility; LCF experiments have also been conducted to verify the simulation results.

Mechanics Analysis on Bar Cutting Based on High Speed and Restrained State

There are many problems in the common baiting methods, such as bad cross-section quality, low efficiency and so on. In order to overcome these disadvantages, a new bar cutting technology based on high speed and restrained state is put forward in the paper. The cutting process and cutting mechanics were analyzed. The stressing intensity factor and fracture toughness were introduced to analyze the influence of loading velocity on the cutting surface quality. By means of the dislocation theory, the influence of loading velocity on the fracture process was researched. Numerical simulation and experiments were carried out, and the results were conformed well with the theoretical ones.