Papers by Author: Ming Shao

Abstract: The semi-solid thixo-extruded process of AZ91D magnesium alloy with 9 % plastic deformation was investigated. The effect of isothermal time on the thixo-extruded formability of AZ91D magnesium alloy was analyzed. The relationship between isothermal time and microstructure, mechanical property was also researched. The results showed that with increasing the isothermal time from zero to 60 min on 575 °C, the filling distance was increased firstly and then decreased, the solid volume fraction was decreased firstly and then increased, the tensile strength and elongation were also increased firstly and then decreased. However, the increasing isothermal time would lead to decrease of shape factor but the coarsening of particle size. When the isothermal time was 30 min, the solid volume fraction was lowest and the filling distance was greatly increased obviously.

Abstract: The semi-solid rheoforming process of AZ91D alloy with 9 % plastic deformation was investigated. The effect of holding time on the rheoforming formability of AZ91D alloy was analyzed. The relationship between holding time and microstructure, mechanical property was also researched. The results show that with increasing of holding time from 0 to 60 min at 575 °C, the filling distance increases firstly and then decreases, the solid fraction decreases firstly and then increases, the tensile strength and elongation are also increase firstly and then decrease. However, the increasing of holding time would lead to shape factor decreasing but particle coarsening. When holding time is 30 min, the solid fraction is lowest and the filling distance increases greatly. Compared to the conventional casting sample, the tensile strength and elongation of the rheoforming parts increase 43.9 % and 187.5 %, respectively.

Abstract: The semisolid shear rheological properties of AZ91D alloy were tested. The effect of holding time on the rheological characteristics was investigated. The results show that: during the shear rheological test at 570 °C, a critical shear stress and a maximum shear stress are happened. And with the holding time increasing, solid fraction decreasing and solid particles distributing more uniformly, the rheological rate increases, but the critical shear stress and the maximum shear stress decrease.

Abstract: The pruning of branches in loquat trees is the main part of the consumption of labor in production, so the use of branch intelligent pruning device can effectively reduce the labor intensity and cost. Identification of branches is the key technology of intelligent pruning branches, and it is the first step of intelligent pruning equipment research. A recognition method of branch images was introduced in this paper. With this approach, we used open operation to deal with the images after the segmentation which was performed by using color aberration, and the image noises were eliminated basing on comparison of connected areas. For faulted branches which were caused by leaves shield or strong illumination, they could be filled by expanding at the designated place, and then the integrated frameworks of branch images were obtained. At last, both the positions of the center points and the diameters of loquat branch images were determined based on the characteristics of the branch image edges. Experiments showed that the accurate identification rate of branch feature images and branch center coordinates were 89.3% and 84.6%.

Abstract: Injection device is one of key parts of Squeeze Casting Machine, and scrapping problem is the pivotal knot of leading to injection device’s malfunction and lifetime cutting of shot sleeve. This paper computes out the displacement values of shot sleeve and plunger tip in radius direction through FEM, and makes qualitative investigation on scrapping problem of injection device.

Abstract: This paper focused on the Cu alloy elements macro segregation of large squeeze casting wheel hub, analysed element segregation on the wheel axle, wheel arm and wheel rim. Three positions on the hardness and mechanical properties were tested, researched the influence of element segregation on the hardness and mechanical properties.

Abstract: The spout at the connection of the pipe and the chamber is easily clogged when a large amount of molten metal is conveyed to the chamber in squeeze casting for large parts. In order to reduce the chances of clogging and clean up quickly when clogged, a quickly removable pipe is designed. The pipe is heated through thermal conduction by resistance wire, and thermal equilibrium is used to derive the power of heating element. Solid-state regulator is applied to control the heating power. Molten aluminum is conveyed from furnace to chamber using electromagnetic pump. The experiment shows that the molten metal flowing through the pipe is smooth, and the temperature of molten metal can be maintained stability.

Abstract: As a forming process, squeeze casting is completed in the corresponding manufacturing system. The paper deals with the overall design of the manufacturing system-the forming system for squeeze casting. To construct a practical manufacturing system for this technology, the forming control process of squeeze casting is analyzed, where the key factors are identified to determine the production quality. Then the design principles for the forming system for squeeze casting are built and its functional requirements are attained. And an overall structure for this forming system is presented including the die design system, the design and management system of process parameters and the squeeze casting equipment system. This structure decreases the difficulties and the cost of building the physical system.

Abstract: Fretting wear behavior of 40CrNiMoA steel was studied on a SRVⅣoscillating friction and wear tester. The results indicate that the fretting wear volume increase with test frequency, load and amplitude increasing. Meanwhile, the fretting wear mechanism is directly related to test frequency, load and amplitude. When they are small, the main fretting wear mechanism is abrasive wear, with these test parameters increasing, the main fretting wear mechanism turns to a combination of abrasive wear and adhesion wear. Based on the experimental results, the anti-fretting wear measures of steel worm gear pairs used in mechanical tracked regulator of tracked vehicle are discussed.

Abstract: High velocity compaction (HVC) is one of the latest technologies of powder metallurgy (PM), while the prices threshold of Hydropulsor’s HVC presser limited massive application of this technique in vast minor PM enterprises in Mainland China. In the light of this, the paper delivers a new design of HVC apparatus which adopts mechanical springs groups instead of hydraulic cylinder as hammer driver. The virtual prototype and simulation of new HVC apparatus is brought about. The result of simulation shows that new design can basically meet the demand of HVC.