Applied Mechanics and Materials Vols. 217-219

Abstract: Technological processes such as forging, die forging, pile driving, etc., are realized as a result of a collision between two bodies. The bodies’ rebound after the collision takes place due to the use of part of the energy of the hit for their elastic deformation. The paper presents results from an experimental research on the possibilities of the decrease of rebound, by the use of an additional force during the hit. A laboratory test-stand is described in which an additional force is created by the use of a cold rocket engine, working with compressed air.

Abstract: With the aesthetics’ enhancement, there is a growing demand for the use of restorative ceramics in dental surgery. However, ceramic materials are hard and brittle, and problems such as surface damage, crack, and fatigue were easily produced in dental abrasive finishing. Consequently, these flaws could cause the strength decrease of the ceramic, which manifest the shortage of the lifespan in dental. Contraposing these problems, a high-speed handpiece with diamond burs was used when finishing the leucite glass ceramic in the dental surgery. In this paper, finishing force, specific energy and surface integrity including the roughness and morphology were observed. the results revealed that both normal and tangential forces increased with the increasing of feed rate and depth of cut, while there is an apparent decrease of the specific energy. These two parameters were bigger in the up finishing than that of down finishing. Finishing parameters have little effect on surface roughness, according to the observation of a scanning electron microscope. It is easily found that the finished surface was consisting of brittle fracture and plastic deformation. For comprehensive, good surface quality could be obtained in the down cutting other than up cutting.

Abstract: Steelmaking Plant of PZH Steel improves the hitting ratio of independent converter model, by optimizing the terminal controlling model of molten steel, stabilizing the charging load in BOF, accelerating the turnover rapid of ladle, improving the quality of semi-steel into the furnace and optimizing the management of production organization. So the ratio of the direct-tapping is improved and increases to more than 50% now from 25% on average in 2011.

Abstract: Constitutive equations and dynamic recrystallization (DRX) model of GH4169 alloy were investigated using compression tests with temperature 940(°C)-1060(°C) and strain rate 0.001(s-1)-0.1(s-1). A coupled numerical simulation between thermal-mechanical and microstructure evolution was realized through embedding the developed user subroutines into the FEM software DEFORM-3D system. The simulated results show that higher speed of upper die is useful to the DRX but much higher and lower speed of upper die go against improving the finer and uniform of grain size in the blade. Furthermore, the grains are finer and uniform in the blade body compared with those of blade rabbet and damper platform. The experimental results of microstructure under the same forging condition were studied and the average grain degrees in the blade are over 9. The calculated results of microstructure have a good agreement with the measured value from experimental data and the prediction error is less than 7.0%. Therefore, the DRX model and developed program is reliable to optimize and improve the parameters in the blade finish forging.

Abstract: This research presents the chip breaking detection system by monitoring the cutting temperature during the in-process turning. The effects of cutting parameters on the cutting temperature and the chip formation are investigated. The in-process monitoring of chip formation is developed to detect the continuous chip, the mixed chip and the broken chip by utilizing the ratio of the maximum variance of the dynamic cutting temperature to the average variance of the dynamic cutting temperature. The broken chip formation is required for the reliable turning operation. The new algorithm is proposed to obtain the broken chip by changing the cutting conditions during the cutting process referring to the cutting temperature. It has been proved by series of cutting experiments that the broken chip can be well identified by the proposed method.

Abstract: The demand for complex sheet parts has increased more and more in the modern lightweight construction, especially in the automotive industry. Complex drawn sheet parts can be usually achieved in one step with using the hydroforming technology. As the demand for the complex products increase, the need of hydroforming process will greatly expanded around the world due to its many advantages. Complex parts have many convex and/or concave features on it. The shapes, dimensions and the positions of the features are important for manufacturing high quality products. So understanding these geometrical parameters on the product quality has great importance. In this study, the effects of the geometrical parameters of the complex stepped parts on the manufacturability by using sheet hydroforming process were numerically investigated for AA5754 aluminum alloy and some of results were experimentally confirmed.

Abstract: In this paper a method of ultrasonic elliptical vibration cutting has been applied to precision boring of micro hole due to its superior performances such as low cutting force, high quality surface finish and long tool life. A transducer with the longitudinal excitation is carried out to machining(boring) micro hole of 1Cr18Ni9Ti workpiece. The cutting force and surface quality are studied in detail.The workpiece with surface roughness of Rz 0.4μm is achieved.The results showed that the ultrasonic elliptical vibration transducer can be applied rationally in micro hole precision boring.

Abstract: The application of compact spinning technology with suction groove for ramie was studied. This technology improved ramie yarn hairiness, breaking strength and so on. The performance of the yarn hairiness was analyzed in detail through contrast test of the compact spinning technology with suction groove and the traditional ring spinning for ramie fiber. At the same time, the comprehensive performances of ramie yarn spinning by the two kinds of spinning technologies were contrasted and analyzed. The results showed that the spinning technology with suction groove can be significantly improved ramie yarn properties: hairiness and breaking strength etc. In the spinning technology with suction groove, the optimal technological parameter for producing least yarn hairiness, A1 B1 C1 D1, is acquired, where the spindle speed A is 6600 r/min, twist B is 608 T/m, the value of negative pressure C is -3.1 kPa, and traveler D is 21 # (yarn Nm 36).

Abstract: This paper presents the development and performance assessment of a novel 5-axis ultra-precision micro-milling machine (UltraMill) which enables ultra-precision micromachining of high precision 3D miniature components and micro features. An integrated design approach with motion accuracy, dynamic stiffness and thermal stability prioritized has been proposed and applied to analyze and optimize key machine components and their integration. Direct drives and aerostatic bearings with the squeeze oil-film damper are employed in the micro-milling machine throughout, which offers higher motion accuracy, improved dynamics and loading capacity. Micro-milling trials were performed on OFHC copper using tungsten carbide, CVD diamond and single crystal diamond micro tools. Both micro featured profiles and micro machined surfaces were measured to validate the proposed machine specifications and performance.

Abstract: The engineering ceramic material is hard to machining with the hard and brittle characteristics, so we are using a precision machining method of the rotary ultrasonic assisted grinding. In this paper, a research on the rotary ultrasonic assisted grinding mechanism of zirconia ceramic material is described. We use an experimental method of the orthogonal combination to complete an experiment of the rotary ultrasonic grinding of zirconia ceramic material. According to the experiment, we explore how the various grinding parameters affect the surface roughness, and determine a set of the optimal grinding parameters.