Applied Mechanics and Materials Vols. 34-35

Abstract: Bearing failure is one of the foremost causes of breakdown in rotating machinery. To date, Envelope detection is always used to identify faults occurring at the Bearing Characteristic Frequencies (BCF). However, because the impact vibration generated by a bearing fault has relatively low energy, it is often overwhelmed by background noise and difficult to identify. Combined the results of extensive experiments performed in a series of bearings with artificial damage, this research investigates the effect of many influencing factors, such as demodulation methods, sampling frequency, variable machine speed and the signals collected in different directions, on the effectiveness of demodulation and the implications for bearing fault detection. By understanding these effects, a more skillful application of the envelope detection in condition monitoring and diagnosis is achieved.

Abstract: In the field of RPM( rapid prototyping manufacturing), accuracy and efficiency have become the bottleneck that slows down its development, so how to improve parts precision has been one of the hot research questions. A variety of factors are analyzed which have effect on parts precision , such as extrusion temperature, envelope temperature, extrusion velocity, filling velocity, slicing orientation, slicing thickness, filament-width compensation, and delay time, and then corresponding measures to improve parts precision is presented.

Abstract: Internet gives the manufacturing a new way to confront the challenges from the protean market. Applications including web techniques such as XML, Web Services, and the industrial techniques OPC UA & FDT/DTM, contribute to the reforming of the manufacturing. It leads to a new revolution and orients the manufacture to network manufacturing, cooperative manufacturing and even so-called the cloud manufacturing (the integration of the manufacturing and cloud computing) based on SOA in order to outrival other companies in the drastic competitions. This paper describes a new type of the co-service supporting based on SOA for Complex Equipments & Field Devices following a lead system which has been built in the frame of the project “Sino-German cooperation to advance the technique’s advantages: co-service supporting of the complex devices“.

Abstract: The super plastic diffusion bonding behavior of 00Cr25Ni7Mo3N duplex stainless steel was performed on Gleeble-1500 hot simulator. The microstructure of the bonding interface region was studied by using optical microscope (OM), scanning electron microscope (SEM). The mechanical property of the joint was characterized by tensile strength tests. The results indicate that the strength of joint was improved with the increase of the bonding temperature, the applied pressure and the hold time. The suitable bonding temperature is higher about 100°C than its super plastic temperature. The initial bonding boundary were disappeared and the voids were closed by hot plastic deformation under the bonding condition like T=1323K, P=20MPa, t=12min. At the same condition, the grain grew up across the interface by atomic diffusion and the interfacial migration, and the strength of joints was high as 440MPa.

Abstract: Rock macro mechanic character is decided by rock composite and meso configuration. LuHui granite minerals composite, micro configuration and the rock thermal cracking in differ temperature are observed by micro-photometer in meso. LuHui granite is composited by kinds of minerals, and its minerals’ inhomogeneity is visible, the change of cementation among rock crystal grains, dislocation and micro cracking in crystal is produced in crystal grains under temperature. By means of experiment, the development of granite micro cracks and interior configuration, and change laws of micro cracks were observed. The quantitative analysis of the micro mechanism and laws of granite thermal crack was made, granite cracks number increases acutely in 240-260 degree C after a narrow range fluctuation in 80 degree C. Finally, the thermal cracks threshold of granite was determined primarily.

Abstract: Reliability research on machining center has great significance for the quality improvement of the machining center and its mechanical products. The long cycle and insufficient accuracy of collecting data is the main problem of the current reliability research on machining center. By means of building a test-bed and simulating the environment and running conditions of live using in the specialized laboratory, the simulation reliability tests, accelerated and enhancement tests are carried out. This paper aims to solve the above mentioned limitations and offer a more effective method for reliability tests on machining center.

Abstract: We calculate the temperature of excited plasma, found that will be enhanced with pulse energy increased. The delay time and the pulse energy were very important to the LIBS signal and define the -0.5μs was very suitable to this experiment, determined the intensity of emission spectra was linear to the pulse energy when the delay time was fixed. By change the delay time, got the emission of bivalence ionization of Zn was just less than 500ns.At last, we had researched the effect of element concentration and the thickness of film on signal intensity. When the concentration of Al being increased from 2.5% to 5%, the intensity of signal enhanced double. At the same time the content of Zn being decreased from 78% to 76%, the intensity of signal had just no change.

Abstract: A comparison on geometrically nonlinear analysis of composite girder cable-stayed bridge is presented. The spatial nonlinear analysis model named double-girder is established, the geometrically nonlinear behavior of whole bridge is analyzed under dead load plus live load in normal service stage, the nonlinear analysis involves cable sag, large displacement and beam-column, the three nonlinear factors effect on internal force and deformation of side tower, main girder are investigated. The results show that the effect of geometric nonlinearity is small on bending moment and deformation of side tower, and also small on vertical deflection of main girders, but nonlinear effect is large on bending moment of main girders. Results obtained in this research and conclusions made provide valuable insight and guidelines for the design of composite girder cable-stayed bridge with three towers.

Abstract: In this paper, the reason was analyzed that the aerodynamic efficiency of the traditional vertical axis wind turbine (VAWT) was always low, and a new type of VAWT—Guiding VAWT was introduced. On that basis, a new blade shape called as combined blade for Guiding VAWT was proposed and numerical investigation was complemented on its aerodynamic performance by CFD (Computational Fluid Dynamics) technique. This Guiding VAWT includes two components: guiding impeller and rotating impeller, which are both combined blade in shape. The guiding blade is combined by three sections: inlet radial section, middle arc section and outlet linear section. The wind blade is combined by two sections, inlet arc section and outlet linear section. The combined guiding blade may not only avoid the wind impeller from the direct impact by the coming flow on its convex surface of the blade so as to decrease the drag torque but also improve the effective impact by the coming flow on the concave surface of the blade, both of which contribute the enhancement for the driving torque of the wind turbine. Results indicate: This new type of Guiding VAWT with combined blade has a wider operating range, higher aerodynamic efficiency than the traditional VAWTs. And more, this paper introduced the airfoil blade into this new type of VAWT and numerically validated that even though the flow inside VAWT was a large separated flow with variable attack angles, the aerodynamic advantage of the airfoil blade could still be shown to some extent, which hoped to further enhance the aerodynamic efficiency of the VAWT. Additionally, this new type of VAWT has a two dimensional structure for convenient manufacture, which has the latent energy to be popularized.

Abstract: Rock is a natural heterogeneous material and presents complicated behaviors in the fracturing process. It is prevail to study the basic failure mechanism of rocks via numerical simulation. Based on the elasto-plastic cellular automaton (EPCA) model, this paper simulates single pre-fractured rock fracturing process with consideration of rock heterogeneity on the meso-scale. In this model, the Weibull’s distribution, which characterizes heterogeneity with the homogeneous index m and the random seed parameter s, is adopted to describe the distribution of mechanical parameters of rock specimens such as cohesive strength, Young’s modulus, etc. Pre-existing crack rock specimens with different homogeneous index or the different random seed are simulated by EPCA under uniaxial compression. Numerical results show that heterogeneity has great influence on pre-fractured rock failure process, final failure modes, and the uniaxial compressive strength.