Applied Mechanics and Materials Vols. 313-314

Abstract: For manufacturing the special shape micro-structures with hard and brittle materials , the ultrosonical combined electrical micro-machining method is proposed and improved. The ultrasonical combined synchronous electrochemical micro-machining system is built and optimized, which machining parameters can be adjusted in a big ranges, and the synchronous target between the ultrasonical vibration and the voltage of micro-PECM(Micro-pulse electrochemical machining) can be realized. The micro-machining electrodes are manufactured in round sections by combined micro electrical-discharged machining (EDM).The mechanism tests of ultrasonic vibration combined electrical pulse micro-machining tests are carried. It is adopted that the low amplitude of electrical voltage (no more than 6V) and the static electrolyte with lower electrical conduction rate, the good machining accuracy and surface quality are acquired. The regular morphology array micro-round holes are manufactured successfully on friction units' working surface, which can save oil , improve the friction performances and prolonging working life of important friction units. In additional, the fixed holes satisfying the precision needs are machined on the hard and brittle piezo-ceramics pieces, which are often used in many important micro-precise piezo-ceramics sensor. It is proved that ultrasonic combined electrical micro-machining is an effect method for to machine the special shape micro-structures.

Abstract: The demands of Prognostics and Health Management (PHM) for the air cooling equipment are constantly growing in the industrial field. However, most studies on PHM of fans are still in the exploratory stage, the failure modes and working conditions are mostly single and ideal. It proposed a PHM method for the brushless DC fan. Firstly it makes an analysis on the failure mode of the air cooling equipment. Secondly, two kinds of the prognostic tests are made, including fault simulation test and accelerated life test. After that, a prognostics method based-on the combination of reliability and data-driven models are proposed. The test results show that the proposed prediction method has a strong practical value.

Abstract: In order to providing the reference of improving the reliability of the tools, this paper analyze the stress of steel bar cutting tool and reinforcement which is used in the construction equipment in the process of cutting . Finite element method is used to build a 3d model of 60 t hydraulic shearing machine. And stress situation of steel bar and shear blade is analysized in the shearing process. Then inspect if cutting tools is reliable and improving measures are put forward.

Abstract: Continuous development of science and technology, the human ability to conquer nature and continuously improve, but also rapid growth in social demands, significantly reduced the amount of available resources. Earth-shallow layer drying up of resources of our human life, forcing people to the underground exploration of the deeper substance to meet human needs. This requires adaptation of deep drilling tool for drilling needs good equipment, deep-hole wireline coring drilling equipment in adapting to constantly update and be perfect with this demand.

Abstract: Mathematical models and statistical models of effectiveness were set up during the technology preparation period. A model and flow was set up based on the system parameters and using regulation applying the theory of Monte-Carlo sampling, discrete event simulation and mathematical statistical. Results of its application show that the model can not only simulate effectiveness of equipment weapon, but also can analysis sensitivity, can offer auxiliary decision-making during the technology preparation period.

Abstract: With the aid of the thermal model, thermal resistance matrix of emitter-segmented power HBT is proposed to represent thermal effects. The effect of 2-dimensional (2-D) inter-segment spacing on thermal stability of device is studied. It is shown that the increase of inter-segment spacing could effectively decrease thermal coupling resistance, lower temperature of center segments, and hence improves the thermal stability. Furthermore, a novel emitter-segmented power HBT with 2-D non-uniform segment spacing is proposed, in which the non-uniformity of segment temperature is improved by 75.26% and the maximum power level difference of emitter segment is improved by 55.84%, when compared with uniform segment spacing HBT. Therefore the technique of 2-D non-uniform segment spacing is a better method for enhancing the thermal stability of power HBTs.

Abstract: The brake disc is one of the most important components of the braking system, so studying its dynamic characteristics is particularly important. In this paper, based on the 3D model, the theory modal analysis of break disc is conducted with ANSYS software and the modal experiment analysis is carried out through LMS(Lab Impact Testing system). The experimental results are in good consistency, which shows that the finite element model built in the paper is reasonable. This paper provides theoretical reference for vibration and noise reduction of the brake disc.

Abstract: By using the classic control theory, the paper deduced a calculation formula on the Reproducibility Error of parts processing in the technology system, the flexible clamp system , with the clamping device on the gas power, and analyzed its influencing factor with examples.

Abstract: An experimental investigation into free underexpanded jets is described. In this paper the experiment took the axis-symmetry unexpended jets as the object, used the typical "Z" schlieren system and replaced the edge with rainbow filter.The rainbow schlieren method is used to obtain measurements in underexpanded jets with nozzle pressure ratios ranging from 2.97 to 19.80. Obtaining the result of that the influence of pressure ratio on jet structure. This paper provides an operation method in the concrete and some useful reference for the rainbow schlieren technique.

Abstract: Theperformances of the turning center will be influenced by its thermalcharacteristics seriously, and accurately predict thermal characteristic of themachine tool is helpful to improve the design level. The headstock of a high precision turning center has been regarded as the researchobjects, and its thermal properties and influence on the performance of the turningcenter are studied. First based the finite element analysis model that has beenconstructed, the steady temperature field distribution and thermal equilibriumtime of the headstock are calculated, and then the temperature field andthermal deformation have been calculated also, and analysis to identify thetrend of the headstock heat distortion are also been done. Some of the keyfactors on the thermal performance of turning center are also studied. Thestudy lays a foundation for the thermal error compensation of the headstock.