Advanced Materials Research Vols. 1120-1121

Abstract: The precision of cutter grinding decides the level of cutting machining technology, and the precision of cutter is effectively improved through grinding by CNC technology. This paper first analyzed the key parameters of cutter grinding, and realized the functions of CNC five-axis grinding turning tool through design of the structure of CNC five-axis machine tool and building of the control system, to simplify the structure of machine tool, use open CNC control system, and reduce the cost of whole machine, convenient for promotion and use.

Abstract: Picoliter or femtoliter droplets generated with high frequency is very useful for many applications in different valuable fields, such as microarray generation, drug delivery or biochips. Pulsed electrohydrodynamic inkjet printing (Pulsed EHDP) is an advanced technology which is used for generating fine droplets in recent years. Apparently, the deposition frequency of droplets is a key parameter, and it is influenced by various factors. In this paper, the effect of duty cycle and voltage frequency on deposition frequency is investigated in the pulsation mode. A simple scaling law is proposed to demonstrate relationships between these two parameters and deposition frequency. Results show that volume of the liquid accumulated at the apex of the nozzle changes during the non-electric field period, which affects taylor cone deformation time and deposition frequency. High deposition frequency can be achieved by increasing the duty cycle up to 0.7, and choosing voltage frequency between 10Hz to 40Hz. These analysis is valuable for understanding Pulsed EHDP deeply and fabricating the micro/nanoapplications.

Abstract: Reduced-iron used rotary spray cooler atomizes cooling water and sprays them directly to the outer wall of the cooler, which is called indirect cooling method for which the motion law of the materials in the cooler will have a great influence on the design and the cooling efficiency of the equipment. Based on the DEM simulation, the motion of materials in the cross section is investigated in two dimensions, and the influences of rotation speed, lifters, particles diameter and drum fill are discussed. The research results will guide the operation in real practice and help to optimize the design and control of the equipment to some extent.

Abstract: Nondestructive determination of Au in gold ornaments mainly takes density method and X ray fluorescence spectrometer with energy dispersion (EDXRF), which exists disadvantages. This paper based on the principle of crystallography, deduced the mathematical relationship between the crystallographic parameters, the density and the impurities content in gold jewelry alloys, then introduced the results by density testing and determination of Ag and Cu by EDXRF into the mathematical relationship, and obtained the gold weight percent in gold jewelry alloys. The results show that obtained the gold weight percent and determination of Au by fire assay are almost consistent, which the error is less than 0.12 %, so establishes a synthesis method of determination of Au by EDXRF and density testing, solves the disadvantages which EDXRF only detects on gold jewelry surface and small area, and density testing cannot detect gold jewelry alloy and demands that jewelry shape is simple, and provides an effective synthesis way for determination of Au in gold jewelry alloys.

Abstract: Fluid-solid coupling numerical method of propellers is applied to make numerical calculations of propellers made of different materials without considering the material anisotropic. Comparative analysis of hydrodynamic performance and wake flow field of the propellers are carried on under typical working conditions. The influence of the key parameters of material on the efficiency of marine propellers is analyzed. The results show that the material with greater elasticity makes the magnitude of speed increase,especiously the axial velocity. On the other hand, compared with the strong rigidity material propeller, the small rigidity material propeller increases a little in the highest value of propeller efficiency curve.

Abstract: Traditional ultrasonic methods are popular in identifying easily detectable cracks, but are not good enough in minute crack detection. Early damage identification is important in preventing larger crack development and future catastrophes. Highly sensitive and precise actuator/sensor is employed to improve the detection capability of these minute cracks. The Orthotropic Piezoelectric Composite Material (OPCM) has been developed as a functional material that can be conveniently used as a highly sensitive actuator/sensor. Comparing the OPCM with the traditional elements, the former has the ability of exciting and receiving focus power and directional strain waves. They have been used in non-destructive technology in many structural engineering inspections. Using the filtering capabilities of the OPCM sensor and Hilbert-Huang Transform (HHT) method, the experimental results show that by using the multi-actuator and sensor, the simulated cracks inside aluminum plane specimen can be successfully identified.

Abstract: In this research, a vapor chamber embedded in the base of a heat sink was experimentally analyzed for the application in thermal management of microelectronics. The vapor chamber was produced by a copper and molybdenum alloy with length of 240 mm, width of 54 mm, thickness of 3 mm, and capillary structures composed by copper screen meshes. The working fluid used was de-ionized water. The pure aluminum heat sink was cooled by air forced convection and the evaporator vapor chamber was heated using an electrical resistor simulating integrated circuit power dissipation. The experimental tests were done in a suction type wind tunnel with open return for a heat load varying from 20 to 80 W and for an airflow velocity varying from 1 to 4 m/s. The experimental results showed that the considered vapor chamber worked successfully, maintaining low operating temperature.

Abstract: Contact resistance is one of the key parameters of main bus bar. The bus performance is decided by the value of Contact resistance. By test of the typical rectangular copper bus-bar, it is analyzed that the effects of force on DC contact resistance. The results show that metal surface contact resistance decreases with the increment of pressure. The resistance is mental nature property, which is determined by material’s performance. At the same time the effect of contact distance is studied in detail.

Abstract: This thesis is aimed to the external instantaneous high energy heat source, according to enclosed metal cavity, porous medium in the cavity, porous media can by phase change heat transfer characteristic of variegated medium coupling state target’s special requirements in the field of aerospace, it is innovatively to put forward a kind of applicable to simulate sealed coupling target, under the condition of instant high energy heat source excitation, By heat source-metal cavity-porous medium—porous medium’s phase-changeable phase change process heat-transfer characteristic numerical calculation model-creation approach, in use of the metal cavity, in the porous medium incompressible flow phase transition of working medium’s heat energy conservation, momentum conservation and mass conservation principle, it is to establish analysis model of coupled heat transfer characteristics of multiple parts, in order to acquire the full target area of airtight coupling state targets, temperature field, pressure field, velocity field and phase change of phase transition of working medium characteristics change with time and space change numerical value to analog result. The study results points out: when the incentive heat source keep constant, the change rule of full target area temperature, pressure flow rate and phase change characteristic parameters is in conformity with theory of heat transfer medium. The heat transfer model can be popularized and applied to the optimization design of incentive heat source, and comprehensive performance optimization of enclosed coupling state objects.

Abstract: The friction welded joints made by GH4169 heat metal alloys are detected by U1traPAC system of the ultrasonic wave explore instrument. Aimed at the blemish signal characteristics, this article introduce Support Vector Machine (SVM) theory, which is based on statistical theory and structural risk minimization principle, to carry out multi-classification study of the detection signal. We decompose de-noising signals with wavelet packet transform, and extract energy eigenvalues according to "energy- defects". In accordance with designed "1-to-v" SVMs scheme, we respectively input normalized eigenvector to the SVM model to obtain the Forecast data. It is verificated that the limited existing data and information is well used by SVM and the signal is accurately been classificated. All of these verify that SVM has a strong generalization ability.