Key Engineering Materials Vols. 462-463

Abstract: Based on the assumption of one-dimensional specimens and stress distribution hypothesis，SHPB experiment is used to analysis dynamic characteristics of materials. But it is impossible for the transverse inertia and the friction on the surfaces of specimen. A model is established in order to evaluate the degree of influence of horizontal specimen inertia and friction on the experimental results. Moreover, the model is applied to discuss the transverse inertia effect influence on elastic modulus of materials.

Abstract: In view of the bottleneck of the interfaces between Forward Engineering (FE) and Reverse Engineering (RE) softwares, the method of extracting feature for hybrid modeling of FE and RE is attempted to present based on secondary development for UG NX by using VC++. The method is proved through two simple surface modeling.

Abstract: In order to research the surface integrity of SEAM, the surface figure, surface heat-affected zones (HAZ ) and surface hardness are analyzed. The author mainly researches the influence factors of water pressure, air pressure, cathode feed rate and relative line speed on processing indictor. The orthogonal experiment results indicate that the main influence factors of surface roughness and HAZ are air pressure, gap voltage and cutting depth. In SEAM, certain scope pressure atomization of dielectric liquid has deionization and arc-extinguishing effect, and takes away melted metal and heat from the discharge channel in time. Workpiece surface will be smoothness. However, the enlarged air pressure will break normal electrode discharge and make the surface smoothness worse. The research of influence of gap voltage on surface quality are accomplished.

Abstract: The dynamic analysis of the 750Kw wind turbine blade was presented based on Reverse Engineering. Because of complex shape, the model of wind turbine blade is a bottleneck of restriction development on the dynamic characteristic research of blade. The work attempted a new way to build the blade 3D model and completed the dynamic analysis. At first, the point cloud data of blade were gained using ATOS optical scanner. Secondly simplified, smoothed and partitioned in Imageware, point cloudy data were created into curves. Then the curves were imported into UG, the 3D model of blade was attained through curve fitting. At last the dynamic analysis of the blade was completed in ANSYS Workbench. The analysis adopted BlockLanczos method to extract the mode and get the natural frequency and eigenmode from the first to sixth modes. The paper ascertained the first and second wave eigenmodes, the first swing and the first torsion eigenmode. Calculations showed that eigenvalue of wave vibration and swing vibration were lower, torsion vibration eigenvalue was higher. In the vibration of the blade, the couple vibration of wave and swing taked major role, and the influences of torsional vibration were not great. The results showed the wave and swing vibration were predominated, the torsional vibration can be neglectful. The paper developed some new methods, established foundations for the further research of large wind turbine blade in the future.

Abstract: With the necessity and importance of reconstructing medical image model on the medical application and research, a variety of methods reconstructing human body tissues were introduced according to different original data and application purposes. The different reconstruction processes of human pelvic tissues, molar and incisor models are detailed. This proves the validity and feasibility of the different means.

Abstract: The piston is a key moving-part of the reciprocating piston compressor with a high failure rate. Because of the difficult exact calculation of machinery dynamic, the traditional and common way to find the reason of fracture is based on metal-lographic phase of piston material. The C102B reciprocating piston compressor is an important equipment in methanol plant. In this paper, in connection with the piston fracture of the C102B fresh air compressor on service , besides a lot of analysis on metal-lographic phase, the 3-D model of piston and cylinder were built-up, and the two dangerous places where the piston suffered max-force were found. Bases on ANSYS and FEM technology, the value of max-force on piston at the two places were carried out. Finally, the reasons of piston fracture of the C102B fresh air compressor were found and some preventive suggestion was proposed.

Abstract: The important thing in micro-machining is its accuracy. The Micro-Electrical Discharge Machining (micro-EDM) is a promising method in micro-machining, because (1) the process is independent on the hardness of the workpiece but only depends on its thermal conductivity and melting point and (2) it can be used to machine materials with highly complex geometrical shapes using a simple-shaped tool electrode. However, the process in micro-EDM is not totally well-known, especially related to the formation of discharge pulse energy and the fracture phenomena. In the micro-EDM processes, the formation of discharge pulse energy is a complex phenomenon, since it is related to many parameters such as discharge gap, charge voltage, capacitance, and tool electrode wear. In this paper, the Acoustic Emission (AE) sensor is used to detect the changes of discharge pulse energy during machining of brass using micro-EDM. The results shows that the AE signals can detect and explain the fracture phenomena during the micro-EDM processes.

Abstract: In this work, an inductively-coupled rf plasma reactor was utilized in the nitriding process for surface hardness improvement of aluminium-copper alloy 2011. Substrate bias at 400V was used in the pre-sputtering step to eliminate the aluminium oxide on the samples. Plasma nitriding was carried out in a N2-H2 admixture at total pressure of 1 torr. The process length was varied from 9 to 36 hours while the input rf power and substrate temperature were varied from 100 to 300 W and kept at 400 oC, respectively. A negative bias voltage up to 400 V was used in the nitriding process. Glancing incident-angle x-ray diffraction (GIXRD) results showed the hexagonal crystal structure of AlN on samples. The roughness increased slightly when the voltage increase up to 400V and was investigated by Scanning Electron Micrograph (SEM). Electron Probe Microscopy Analysis (EPMA) and Energy Dispersive X-ray Analysis (EDX) were used to detect the N atoms in specimens. Significant increases of surface hardness are observed after plasma nitriding.

Abstract: Metal-organic framework MOF-5 (i.e. IRMOF-1) with the chemical structure of Zn4O(BDC)3 were successfully synthesized using room temperature synthesis approach of direct-mixing method ans liquid-crystal templating method. The metal clusters organic linker used was benzenedicarboxylic acid (BDC). Direct-mixing approach resulted in MOF-5 with tetragonal cell while the liquid-crystal templating method resulted in cubic structure. The metal/linker ratios were varied from 0.1 to 1 to study the effect of metal linker on the formation of MOF-5 materials and their characteristics. The crystallinity of the evacuated framework MOF-5 materials were increased when the metal/organic linker ratios were increased from 0.3 to 0.5. However, the cubic structure of the evacuated framework was relatively disrupted at metal/linker ratio 0.7.

Abstract: Fracture toughness KC and fatigue crack growth behavior of commuter train’s rail track material used in Klang Valley, Malaysia was investigated. Two different tests were performed in accordance to ASTM E399 and E647 testing procedures using single edge notch bend (SENB) and compact tension (CT) specimens, respectively. The results showed that the average KC value of the rail track material was 51.7 MPa√m. On the other hand, from the fatigue crack growth test, both longitudinal (LD) and short-transverse (TD) direction specimens demonstrated identical Paris’ Law constants C and m of 1.3 x 10-12 m/cycle and 3.54, respectively. Prediction of bending fatigue life of rail track material using the above obtained parameters showed a good agreement with the experimental results.