Key Engineering Materials Vol. 522

Abstract: From the perspective of forming bone scaffold, the technologic parameters of LDM which have important influence on the shape of the deposition material are studied. Through building experimental platform and using chitosan solution as experimental material, the influence of the temperature and the layer height on the lap of every fiber layer are firstly discussed in detail. Besides, the effects of nozzle diameter, the velocity of receiving device, the pressure of feeding device are also discussed. Then the above mentioned process parameters are all optimized, which make the forming mechanism of LDM to be clear. Finally, based on the optimal parameters, the scaffold with self-designed pore size and a high degree of pore interconnectivity, which meeting the requirements of the structure of tissue engineering are fabricated.

Abstract: Green manufacturing is a new model to solve current environmental problems in manufacturing, and the process route determination of the product machining process is one of the key problems. According to the existing machining process and equipment of mine fans impellers, analytic hierarchy process (AHP) is used to assist in building the optimized decision-making model and multi-criteria assessment indicator system and help draw decision. It is concluded that processing technology route of using steel plate stamped is better than that of using aluminum ingot cast for mine fan impellers. The decision coincides with fan impellers actual production.

Abstract: The filling method of the cross section of the plasma arc welding based rapid prototyping was investigated. Veritable parameters filling method was proposed to improve the building quality. Optimizing model was established according to veritable parameters filling method and filling parameters such as width of deposited tracks and scan spacing were optimized. The process parameters were chosen from the database according to the optimized data. Experimental results showed that the building precision of the deposited layer using optimized parameters was obviously higher than those using non-optimization parameters.

Abstract: An ideal scaffold should mimic the morphology of the natural extracellular matrix and have good mechanical properties and biologically functional. So, the key point of fabricating of scaffolds is to realize the composition of scaffolds by materials having different physical and biological properties and control porous structure accurately. In this study, we propose a novel technology combining a low-temperature deposition, electrospinning process and freeze-drying to produce a hierarchical 3D biomedical scaffold consisting of micro-sized highly porous chitosan-gelatin strands and nanosized PCL fibers network. Scanning electron microscopy analysis showed that the scaffold composed of parallel aligned micro-strands in a grid-like arrangement layer by layer, along the thickness direction intercalated by a network with randomly distributed nanofibers. The stand of macro-scaffold composed of natural-derived biomaterials and nanofibers composed of synthetic biomaterials were bonded together firmly to form a stable network structure.

Abstract: Laser cladding technique was used to form Ni3Si intermetallic coating by Ti addition on Ni-based superalloy substrate. The coating was investigated by optical microscopy and X-ray diffraction (XRD). The clad coating was dense, compact and smooth. An excellent bonding between the coating and the substrate was ensured by a strong metallurgical interface. The laser clad Ni3Si-Ti intermetallic coating has a rapidly solidified microstructure consisting of Ni (Si), Ni3Si (L12) and Ni31Si12 . The grain refinement effect has been achieved due to the occurrence of Ti in cladding layers. By increasing the proportion of Ti, the hardness decreased as the Ti content increasing, the peaks intensity of Ni31Si12 decreased.

Abstract: Accurate and automatic processing of the stone contour such as the straight line, circle and arc shape is achieved by CNC bridge cutting machine based on the GTS motion control card. Difficult problems of sawing curve contour have been solved with the method of the tool tangential following, in addition, high efficiency and high precision in milling procedure are ensured as a result of the velocity look-ahead. The operation of the automatic tool changer among saw tool, milling tool and grind tool in the machining process is achieved by the method of translating tool carrier. Selective processing of the stone contour is achieved by point selection or region selection, therefore, more flexible processing is realized. The highly automated and integrated processing of the stone contour is realized.

Abstract: In view of the processing characteristic of large equipment, The CNC system of the fine milling machine tool for the large double-sided of aluminum ingot is designed, the hardware of the system is introduced, the software is illuminated mainly, the system is configured based on SCOUT, and the control programs of the manual and automatic processing are designed. Based on WINCC Flexible, the operating system which can meet the multi-interface easy to operate and live real-time monitoring is designed. As the result of the commissioning, the system is stable and reliable.

Abstract: Artificial neural network (ANN) and inverse method were employed in modeling the rheological behavior of the AZ80 magnesium. The hot deformation behavior of extruded AZ80 magnesium was investigated by compression tests in the temperature 350-450 and strain rate range 0.01-50 s^-1. Investigation of flow stress curves and microstructure of the compression specimen illustrate occurrence of dynamic recrystallization. The inverse method of non-liner regression was used to determine the parameters of the suggested constitutive equation. The maximum relative errors at different temperatures and different strain rates between experimental and predicted flow stresses by ANN and inverse method were compared. The results show the ANN derives statistical models have better similar prediction ability to those of inverse method, especially at high strain rate. This indicates that ANN can be used as an alternative modeling tool for high temperature rheological behavior studies.

Abstract: Under atmospheric pressure diamond is a metastable phase of carbon, which on heating can spontaneously transforms into a thermodynamically stable phase of carbon, graphite. No matter in diamond and in graphite, the six-fold ring is the smallest ring structure; they are very simillar in shape. The graphitization occurs when the rings of {111} plane are flattened. The {111} plane of diamond is the one that would graphitize preferentially and the (001) planes are most resistant to high temperature thermal graphitization.

Abstract: The ultrasonic polishing test of the nanoZrO₂-Al₂O₃ composite ceramics is done under the two-dimensional ultrasonic polishing device, which is developed by us. In this process, the ultrasonic amplitude-frequency characteristic testing is done by the DASP software. There are certain amplitudes at some frequency points, which can be seen from the spectrum and the three-dimensional spectral array maps, but only one the largest amplitude appears. This shows the resonance points appear when the ultrasonic is passed to the nanocomposite ceramic plate after it is amplified by the horn. This phenomenon is analyzed by the second-order surface wave theory and the waves are surface waves, which are generated by surface waves. These explain the good polishing surface quality and high efficiency under the two-dimensional ultrasonic polishing in the same conditions.