Advanced Materials Research Vols. 189-193

Abstract: The analytic formula of the thickness demarcation circle during hydroforming of double-cone tube is derived by using the mechanical analysis and the total strain theory. The effect of friction coefficient, expansion coefficient, ratio of axial stress to internal pressure, length of feeding zone, and initial thickness of tube on the thickness distribution can be given by this formula quantitatively, and the analytic results were compared with the FEM analysis and experimental results. The results show that with the increasing of friction coefficient, the ratio of axial stress to internal pressure, the relative length of feeding zone, the distance between thickness demarcation circle and tube end decreased, that means the increasing of length of the thinning zone, and with the increasing of relative thickness of tube blank, the distance between thickness demarcation circle and tube end increased, that means decreasing of length of the thinning zone.

Abstract: In this paper, finite element models of the strip shape during cold rolling of thin strip in both symmetrical and asymmetrical rolling cases have been successfully developed, and the effects of rolling parameters on strip shape such as the thickness distribution along the strip width have been obtained. The strip edge drop and shape are discussed under both symmetrical and asymmetrical rolling conditions. Simulation results show that the asymmetrical rolling can reduce the strip edge drop dramatically, which is useful in improving the strip shape and reducing the energy cost during cold rolling of thin strip. The developed finite element model has been verified with the experimental value. The obtained results are applicable to control the rolled thin strip shape in practice.

Abstract: Through analyzing cell direct assembly process requirements and existing hydrogel materials properties, employing the discrete/deposit rapid prototyping technique, developed a cell direct assembly technology adopting the hybrid of gelatin-based hydrogels. The cell assembly technology skillfully combined with the sol/gel transition mechanism about chemical and physical crosslink of gelatin-based hydrogels, in consideration of the main forming factors, through controlling the extruded materials rheological properties and optimizing the forming process, thereby achieved a promising assembling process with high cell survival rate and its corresponding biological viability. The technology can form a predefined three-dimensional structure with certain shape and size, suitable for variety of natural polymer materials (the most similar with extracellular matrix, such as fibrin, sodium alginate, chitosan, hyaluronic acid) with gelatin coupling forming; therefore, it satisfied majority cells needs of choosing the gelatin-based composite hydrogels reasonably. With the limitative extrusion pressure, more than 90% of the cells survived through this process and performed metabolic functions during a long term culture. This technology is a front research of biotechnology manufacturing science, is an important expansion of manufacturing technology.

Abstract: In order to realize high efficiency and flexible manufacturing for rotary surfaces, efficient spinning technology (EST) is researched. It is the combination of multi-point forming and traditional spinning. Principle of EST is described, traditional spinning method is compared with it, and characteristics of it are analyzed. Finite element analysis (FEA) model of disc-shape part is established, EST process is analyzed, equivalent stress and plastic strain distributions are analyzed. EST equipment is developed, and the experiments are made. Results indicate: EST process consists of four stages; equivalent stress in sheet metal’s center region and bendable rollers active region exceeds yield stress, and plastic deformation is generated; experimental result accords with simulation result. Feasibility of EST is validated by simulation and experimental results.

Abstract: The global manufacturing trend is now focusing towards miniaturization. Microminiature Powder Injection Molding (μPIM) is a viable technology to fabricate complex and high performance miniaturized components. The μPIM technique was used to produce the near-net shape micro components in this study. Fine stainless steel powder with particle size of 5μm was mixed with a ternary water-based binder system. Micro dumbbells with the largest dimension of 9mm were replicated. In order to obtain successful and well molded micro dumbbells, the Design of Experiments (DOE) technique was applied to investigate the optimal parameters in injection molding process. Injection parameters such as injection pressure (A), injection temperature (B), powder loading (C), mold temperature (D), injection time (E) and holding time (F) were optimized by using stainless steel feedstocks. Taguchi approach is chosen and the results were evaluated with signal-to-noise (SN) ratio and analysis of variance (ANOVA). The results show that the feedstocks could be replicated by using μPIM method with the application of Taguchi approach.

Abstract: In recent years, the number of automobiles has been steadily increasing, which has significantly impacted on the society and human life, and led to many social problems such as fuel crisis, environment pollution. Therefore, lightweight designing becomes a focused issue. Lightweight materials application, optimized structure design and advanced manufacturing process are the main ways to achieve the lightweight. However, low plasticity and ductility of high strength steel constrain the application of high strength steel. In this paper, the basic principle of roll forming for automotive parts is investigated, and it is innovatively applied in the hot roll forming process of the ultra high strength steel.

Abstract: This paper presents the effect of ambient temperature and operation conditions (compression ratio, turbine inlet temperature, air to fuel ratio and efficiency of compressor and turbine) on the performance of gas turbine power plant. The computational model was developed utilizing the MATLAB codes. Turbine work found to be decreases as ambient temperature increases as well as the thermal efficiency decreases. It can be seen that the thermal efficiency increases linearly with increases of compression ratio while decreases of ambient temperature. The specific fuel consumption increases with increases of ambient temperature and lower turbine inlet temperature. The effect of variation of SFC is more significance at higher ambient temperature than lower temperature. It is observed that the thermal efficiency linearly increases at lower compressor ratio as well as higher turbine inlet temperature until certain value of compression ratio. The variation of thermal efficiency is more significance at higher compression ratio and lower turbine inlet temperature. Even though at lower turbine inlet temperature is decrement the thermal efficiency dramatically and the SFC decreases linearly with increases of compression ratio and turbine inlet temperature at lower range until certain value then increases dramatically for lower turbine inlet temperature.

Abstract: The drill bit for underground casing drilling was taken as object of study, and systemic research have been done for N80 casing drilling in Radial water jet deep penetration perforation. A new drill bit was designed after researched the actual drilling conditions, the characteristic of current commonly used drill bits and the property of blades edge materials. The reasonable original-edge angle, cutting parameters have been obtained for the new drill bit. We choose some other commonly used drill bit, and then contrast experiments result have been done by the new drill bit. The test results show that the new drill bit have the advantages of centering reliable, drilling smooth and sub-chip completely, and it can meet the requirements of the down hole casing drilling.

Abstract: It is necessary to supply enough grinding fluid during grinding process to lower grinding temperature. But, there is little grinding fluid into the contact area actually due to the airflow layer with high pressure around grinding wheel. In this paper, the finite element analysis and simulation on airflow field in the grinding zone is performed based on hydrodynamics. The performance and the influencing mechanism of the airflow field on effective grinding fluid are analyzed further. The research works show that it is important to design the grinding wheel and fluid jet parameters reasonably for increasing the proportion of effective grinding fluid.

Abstract: Dry electrostatic cooling (DESC) assisted machining is one of the green machining technologies that uses ionized air flow as lubricating and cooling medium in the machining process. The influence of discharge parameters on the efficiency of ion transport and ozone concentration in the DESC is experimentally researched. The results show that the efficiency of ion transport increases with the rising of the discharge current and air pressure, but decreases with the rising of the distance from the nozzle and the nozzle diameter. The tungsten electrode is used to obtain high ozone concentration with the nozzle diameter of 2-4mm, air pressure of 0.2-0.4MPa, and the distance from the nozzle within 0.5mm. Experimental research on the DESC assisted machining for hardened steel GCr15 shows that cutting force decreases by 7%-28%, tool wear reduces by 30-50%, and tool life is 1.5-3.3 times more than dry cutting. Better results are achieved when increasing the cutting speed.