Advanced Materials Research Vols. 314-316

Abstract: The extrudate swell of the polymer extrusion process was studied with the experiment and simulation method. The extrudate swell process was recorded by the high-speed photography apparatus. The swell rate at the different time was calculated. It is found that the extrudate swell rate increase at the first five seconds. The maximum swell rate is about 4.37%. The three-dimensional numerical simulation model of the experiment die path was founded. The extrusion process including the extrudate swell was simulated used the Finite Element Method. Such simulated results as the velocity vector, the shear rate profile and the end of the swell zone were analyzed. The extrudate swell end got by the simulation is similar with the experiment result.

Abstract: In order to predict the evolution of microstructure and grain size in TC6 alloy blade finish forging process and optimize the parameters, a series of constitutive equations for dynamic recrystallization and grain growth were developed and implemented into a 3D FE simulator. The grain size has been illustrated for the upsetting of TC6 alloy and the calculated grain size is in a good agreement with the experimental results, which shows that the microstructure prediction tool was validated and reliable. Then the distribution of stress, strain, temperature and microstructure, grain size and deformation has been predicted in TC6 alloy blade forging successfully using the 3D FEM at 930°C deformation temperature, 250°C die temperature and 50mm/s deformation velocity. The results show that the temperature of blade edge is higher than that of center because heat transfer, friction work and deformation work. The equivalent stress and strain have the same distribution as temperature after forging and the refined grain is obtained because of dynamic rescrystallization occurred with larger deformation. The uniform distribution of grain size are obtained in the blade and the shape after finish forging under the condition of technology parameters meet the user’s requirement comparing the calculated deformation with experimental results.

Abstract: In order to investigate the impact factor of hot rolled aluminum alloy, a experiment was finished in a factory, to determine the effects of hot-rolled aluminum alloy plate with the system deformation resistance coefficient of the various factors and to mark the influence about the temperature to the hot rolling deformation resistance; Then, established the mathematical models of 1100,3003,5052 series hot rolled aluminum alloy plate's deformation resistance; The data calculated by the theoretical mathematical models is in good agreement the measured data. So this mathematical have the importance actual significance to actual production.

Abstract: In the multistage machining processes (MMPs), SPC is widely utilized to control the quality of machining processes and diagnose the processing error. But there is a defect, that it can not compensate the error when the machining process is abnormal. For this issue, a new method of quality diagnosis and error compensation is proposed based on EPC (engineering process control). A new framework for processes quality diagnosis and error compensation about the description of machining processes and controlling mechanism of machining process quality is proposed first. And the mapping model of machining error propagation is introduced to explore the model of the error compensation decision. From theoretical level, modeling level and solution level, the mapping model from the decision model based on EPC to SPC is studied, in which the key technologies are the machining error propagation model and the error compensation model. Therefore, the machining error propagation network is utilized to build the error propagation model, and an adaptive control method based on the stability theory is introduced to make error coordination optimization.

Abstract: The effect of wall conditions on co-rotating conical twin-screw extrusion of rigid polyvinyl chloride (PVC-R) is studied. The relationship between the shear stress at the screw surface and the slip velocity of the flowing melt obeys Navier’s linear law. When the volumetric flow rate is 3.83×10-5 m3/s, the pressure difference between the entrance and exit of the metering section of co-rotating conical twin-screw extruder is calculated under different wall conditions by using the evolution technique in POLYFLOW. The 3D isothermal flow fields of PVC-R are also calculated. The results show that when the slip coefficient is smaller than 104 , the pressure difference is constant, corresponding to the full slip condition. When the slip coefficient is larger than 104 , with the slip coefficient decreasing, the pressure difference, and the gradients of velocity, pressure and shear rate decrease. The residual stress of the product is thus reduced. Therefore, increasing wall slip is good for the stability of polymer extrusion and the product quality. The dispersive and the distributive mixing of the twin-screw extruder under different slip conditions are also studied. Results show that when the slip coefficient is 107 , it is good for the co-rotating conical twin-screw PVC-R mixing extrusion.

Abstract: To simulate preheating and postweld heat treatment of Q345 steel pipe welding, the finite element model was established. The welding process was simulated by method of the ANSYS element birth and death technique. In this paper, to obtain the distribution of the temperature field and stress field in different situations, preheating processes with two different values of temperature and postweld heat treatment process were simulated respectively. The results show that preheating can homogenize residual stress distribution of the weldment and decrease the residual stress. The heat treatment reduces the residual stress in inner and outer walls by 24% and 70% respectively and the stress distribution is more even and stress concentration is reduced.

Abstract: For modern hot tandem mill, various shape control means are equipped, so its shape control ability is strong. How to reasonably distribute every stand’s shape control ability is a difficult problem. If the distribution scheme is unreasonable, every stand’s shape control ability maybe waste or offset each other, eventually product’s shape quality is inevitable unsatisfactory. To achieve high precision shape control, a reasonably shape control strategy is necessary, whose job is to make use of every stand’s utmost shape control ability, with a constraint that every stand’s flatness must not be buckling, finally ensuring product’s flatness and crown meet industrial demand simultaneously. A quantitative shape control strategy is put forward by this essay, which is verified on a 1750mm hot tandem mill, the result show its practicability to improve product’s shape quality.

Abstract: Oxygen cutting is the principal method for temporary hatch opening in hull structure. Residual stresses induced by oxygen cutting have a large influence on subsequent sealing and structure safety. Based on oxygen cutting theory, a heat source model was proposed with the combination of preheating flame and reaction heat between iron and oxygen, and a model was presented to simulate the cutting process on the basis of thermal elastoplastic FEM analysis, including the temperature and stress distribution. An oxygen cutting experiment was performed, in which an infrared radiation was used for surface temperature measurement. The residual stresses were measured by impact-indentation measurement. As a result, the calculation results were consistent with experiment values. The research concluded that there is a region in which the tensile stresses values exceed the yield point of material along the kerf, and the width of this region will be influenced by cutting velocity, opening dimension and longitudinal constraints.

Abstract: In this paper, rigid plastic finite element method simulation of AZ31 wrought magnesium alloy radiator isothermal extrusion is studied according to the stress - strain data of magnesium alloy obtained from isothermal compression experiments and the mathematical model of warm forming by the regression. And the paper focuses on the AZ31 magnesium alloy during isothermal extrusion, the deformation force and metal flowing law. The simulated stress field, strain field, velocity field, load changes and so on from simulation can predict the defect in deformation, and offer the reliable reference basis for such parts processing in isothermal extrusion.

Abstract: In order to study the effect which weak intercalated layer produces in the rock during the process when explosives transferring the energy, this research uses ANSYS/LS-DYNA toexplore the numerical simulation of the law which the stress wave of weak intercalated layer rock with different thickness propagates and decays. It also compares the effect to stress wave in certain position when the thickness of the intercalated layer is different or inexistent. The outbreak pheno-menon of the rock with weak intercalated layer occurs in the blasting process is analyzed as well, so the effect of weak intercalated layer should be fully considered when arranging blast hole around the tunnel. Then the research provides the theoretical basis for selecting blasting parameters.