Advanced Materials Research Vol. 500

Abstract: The titanium diboride reinforced titanium nitride-based ceramic cutting tool composite materials were fabricated by a new technology namely in situ synthesis followed by hot-pressed sintering. The experimental results showed that the highest density and the best mechanical properties of the composite material were obtained when the content of Ni was 5wt%. X-ray diffraction (XRD) was used to identify the phases of the composite. Microstructures of the composite were observed by means of scanning electron microscope (SEM). It is concluded that the sintered material was pure, no harmful reaction products was found; with the increase of Ni content, the proportion of short rod-like TiB₂ increased, fracture toughness of the composite materials were improved because lots of TiB₂ were pulled out; bridging phenomenon of short rod-like particles and metal particles were observed in the crack propagating process. The main toughening mechanisms of the composites were deflection and bridging of the crack as well as grains pulling out.

Abstract: In this paper, the pure chitin fiber spunlace nonwoven was made from raw material chitin 100 fiber, and its processing technique was improved from traditional one. The performance comparison tests under different processes and traditional process were conducted, test results showed that pure chitin fiber spunlace nonwoven made under improved process studied in this paper had better mechanical properties and fabric quality.

Abstract: In this paper, a kind of 304 austenitic stainless steel sheets has been investigated, and systemic tests were conducted to study the law and mechanics of work hardening of 304 austenitic stainless steel. The results of microstructure analyzing of 304 austenitic stainless steels showed that when it was deformed by means of tensile testing at room temperature, obvious work hardening was caused by the changes of structure during the deformation. The strain-induced α-martensite, ε-martensite and deformation twins enhanced flow stress obviously, which is the main reason for the strong work hardening in FCC metals and alloys with low stacking fault energy as 304 austenitic stainless steel.

Abstract: This method of parallel computing into nanoindentation molecular dynamics simulation (MDS), the author uses a nine-node parallel computer and takes the single crystal aluminum as the experimental example, to implement the large-scale process simulation of nanoindentation. Compared the simulation results with experimental results is to verify the reliability of the simulation. The method improves the computational efficiency and shortens the simulation time and the expansion of scale simulation can significantly reduce the impact of boundary conditions, effectively improve the accuracy of the molecular dynamics simulation of nanoindentation.

Abstract: The work in the optimization of the simulation of nanoindentation based on the molecular dynamics was mainly introduced in this paper. One optimization method, freeze atoms method was proposed according to the characteristics of nanoindentation process itself, then did the simulation calculation through the use of freeze atoms method and the traditional calculation method, It was found that the difference between simulation results and experimental results of hardness decreased gradually with enlarge the scale of molecular dynamics simulation (with increase of the indentation depth), from 32.39% of 5nm decreased to 14.6% of 25nm. By comparison, it was found that the optimized algorithm could improve the efficiency of simulation in large-scale molecular dynamics simulation., confirmed the correctness and effectiveness of freeze atoms method.

Abstract: A crankshaft dynamic balance system designed based on VB is proposed in this thesis. The imbalance can be measured by using computing software and signal processing technology. The development principle, method, hardware and software system are all introduced. The modular design is used in software system. The touch-screen device is used to realize the data display, storage and analysis. And the imbalance mass and position can be displayed on the virtual instrument interface. Real-time monitoring and accurate information can be completed by the system. The experiment result shows this system is easy in operating, high in capability/price ratio and high in balancing precision. It can meet the producing demands and has good market prospects.

Abstract: Accuracy of the Stewart parallel manipulator is utmost important in assembly quality control procedures, and it's also difficult to demonstrate the inner relations quantitatively between errors of pose and of actuators. A novel methodology is proposed in this paper. Firstly the experiment area planning approach is proposed according to the pose and strut symmetries of the manipulator, and the uniform experiment design is conducted to investigate indexes of accuracy sensitivity. The regression equations are established to analyze the significance of various factors according to experiment results.

Abstract: Abnormal vibration was found in a rocket engine test, to guarantee the stability of the rotor when its working, in this paper, by studying the turbine assembly process and pump assembly process, research of the factors such as correlation among the assembly torque, the pre-tightening force, part parameters and assembly parameters etc was applied. By studying the assembly process of turbine pump shaft, analyzing the of the role of the turbine shaft Parts parameters in the assembly process, by selecting the shaft parts and assembly experiments, theoretical basis and data preparation are provided to improve the quality of the turbopump assembly.

Abstract: A calculation of an axial compressor characteristics is made based on Elman neural network. The experimental data provided by manufacturers are used for the neural network training.To establish the function model to obtain the pressure ratio and efficiency respectively. The result show that Elman neural network both have a good precision for prediction of interpolation and extrapolation.

Abstract: Rapid growth in modern technology places greater requirements on electronic products' performance and quality. For a PCB (printed circuit board) assembly of SMT (surface mounting technology) electronic components, restricted by its limited vision in image collection, a high-pixel CCD (charge coupled device) can only screen local images, and they need to be mosaiced, through matching and alignment, into a complete image, which is to be matched and aligned with a standard image then for image analysis. Therefore, image matching and alignment are of crucial importance to both the precision of image mosaic and the quality of SMT components. This paper proposed a sub-pixel based method, by which local images are marked, matched and aligned into a mosaiced image, which is matched and aligned with a standard image. The error analyses of matching and alignment for four common markers, i.e. circle, ellipse, square and rectangle, show that a square or rectangle marker is preferred for SMT electronic components; when the marker's center point serves as alignment point and the marked data are processed by sub-pixel algorithm, the alignment error can be reduced to about 0.2 pixel point, besides the sub-pixel based method can greatly improve precision when noise is fixed.