Abstract:Based on the tooth cutting principle and manufacturing method of Oerlikon's hypoid gear, the structure and assembly location of three-faced blade is analyzed and the method to establish the mathematical model of three-face cutter head and plate (SPIRON) by the normal benchmark of the NS plane of tool is proposed. According to the manufacturing coordinate systems through HFT methods, the mathematical models of pinion with generating method and gear with shaping method is established on the basis of the NS benchmark. Furthermore, the technological process of Oerlikon's hypoid gear modeling based on the three-face cutter is proposed. The two compare methods were made between the mathematical tooth flank by tooth surface mathematical model and 45 point tooth surface by the KIMOS of both pinion and gear and the contact pattern with actual and theory. Results reveal that the geometry and tooth line of theoretical tooth surface of gear and pinion corresponds well with the actual tooth surface, the maximum the concave error of pinion was 0.007 5 mm,the maximum convex error of gear about 0.002 3 mm. The contact pattern is consistent between the contact patterns of tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) by KIMOS and calculated by the initial element method, it verified the precision of the mathematical model.

Abstract:This paper proposed a new power-split hybrid electrical powertrain to reduce electric loss of single-mode power split hybrid electric vehicle (PSHEV). Different from traditional dual-mode power split mechanism with multi-planetary gear set and multi-clutch, this powertrain is a dual-mode configuration with a single planetary gear set, realizing mode switching by a Synchronizer. The backward simulation method based on global optimization energy management strategy was used to optimize the parameters of the proposed powertrain and Toyota Hybrid System (THS). The optimization results analyzed by energy flow method show that the proposed power split powertrain can reduce the power loss compared with that of THS.

Abstract:In order to predict the heat generation of each heat source and the temperature distribution of components of a dual clutch transmission, a coupled model to simulate the bearing forces, power loss and heat transfer of the transmission was developed based on the theory of thermal network, and validated by comparing the simulation results of the total power loss and the temperature of some chosen tested points under steady and transient operation conditions with the experimental results. The results show that the numerical total power loss is in good agreement with the test results under steady operation condition, and the variation trend of the numerical results under transient condition is same as the test results; the numerical temperature of each tested point under steady and transient working conditions is in good agreement with the test results.

Abstract:Due to their dense gears or field load fluctuations, traditional tractors often need cyclic shifts, which affects the quality of work. Therefore, the adaptive shift control strategy is proposed for different field working conditions. Overshifting is avoided by skipping in start or acceleration conditions; when the load fluctuation is small, the fuzzy-PID control is used to meet the speed requirement; when the load fluctuation is large, the speed requirement is met by correcting the shift law. The strategy was verified by the MATLAB/Simulink simulation platform and the results show that the modified shifting schedule can avoid too fast shift frequency, reduce the speed fluctuation, thereby improving the fuel economy.

Abstract:The battery and supercapacitor hybrid energy storage system can not only fully utilize the physical characteristics of power-type energy storage devices, but also optimize the charging and discharging process of batteries, and it is one of the development trends of energy storage technology in the future. A dual decoupling control strategy with master-slave structure is proposed to meet the requirements in isolated operation of microgrid. The coupling relationship between bus voltage and disturbance input is eliminated by power feedforward, and the influence of coupling disturbance input on the terminal voltage of supercapacitor is restrained, thus allowing the terminal voltage to be effectively maintained in a norm. The problem of supercapacitor overcharge and overdischarge under the traditional control strategy is solved, and the control process is simplified. The stable operation of the microgrid is ensured, the charging and discharging current of the batteries changes smoothly, the change rate of the output current of the batteries decreases, and the service life of the batteries is prolonged. The reliability of the micro-grid island operation energy storage system is improved. Finally, simulation analysis is carried out and the correctness of the proposed control strategy is verified.

Abstract:When there are inter-harmonics in the grid signal, the fast detection using discrete spectrum analysis causes the accuracy to decrease due to the negative frequency spectrum leakage interference after the discrete Fourier transform(DFT). In order to effectively eliminate the negative frequency spectrum leakage interference, the analytical expression of the spectrum containing the negative frequency component is established, and the improved three-line interpolation DFT based on the maximum side-lobe attenuation window is derived to realize the fast and high-precision detection of inter-harmonics. The systematic error and noise sensitivity of the new algorithm are analyzed. The simulation results show that the new algorithm can not only effectively eliminate the negative frequency spectrum leakage interference, but also has strong robustness to additive white noise. When the inter-harmonics are lower than one frequency resolution, the new algorithm can still achieve high detection accuracy.

Abstract:Insulation clearance should be taken into account in the tower design of transmission lines in an ice zone, which is closely related to the jump height of conductor lines after ice shedding. Because the existing formulas for jump height of conductor lines after ice shedding are inapplicable to the lines with large span length and evelation difference, this research focuses on the finite-element simulation of dynamic responses of transmission lines with large span length and elevation difference after ice shedding, and obtains the numerical data in relation to the jump height, its sag before and after ice-shedding, line span and evelation difference. Based on the numerical simulation results, an improved formula for jump height of transmission lines is proposed with nonlinear regression analysis, and the fomula is applicable to all the transmission lines with different span length and elevation.

Abstract:The mechanical properties of the bonded joints, riveted joints and hybrid joints between carbon/glass fiber reinforced polymer (FRP) and steel plate were systematically studied by simulation and experiment, in which cohesive zone damage model, metal failure criterion and Hashin failure criterion were employed to simulate the cohesive failure of adhesive layer, rivet rupture and FRP damage, respectively. On this basis, the finite element model of hybrid joints was established by combining the three failure criteria, and the mechanical properties of the hybrid joints during tensile tests were predicted. The results show that the finite element model can accurately predict the maximum load, failure displacement, failure modes and complex failure process of the hybrid joints tests. It is noticeable that the glass fiber as braided yarn is torn in the hybrid braided FRP for the joints with adhesive layer. Besides, the effect of the adhesive thickness on the mechanical properties of the hybrid joints was also studied. With the increase of the adhesive thickness, the maximum load of the joint increases first and then decreases, and the area of the damage zone around the rivet hole of FRP plate increases gradually.

Abstract:Sandwich structures with excellent mechanical properties and multifunctional potentials can be applied as favorable impact protective structures. Low velocity impact resistance of woven fiber reinforced polypropylene honeycomb sandwich panel was experimentally studied using drop weight tester. Effect of impact energy on structural response under four sides fixed condition was investigated by changing drop height. Under the same impact energy, the effects of core height and core layer number on the impact resistance were also studied. Finite element model of honeycomb sandwich panel subjected to low velocity impact was established by ABAQUS and compared with experimental results in terms of load-time curves and failure modes. It was found that local depression of upper face sheet and core collapse were the dominate failure modes and a significant rebound of honeycomb sandwich panel was found when face sheet was not penetrated.

Abstract:Accurate simulation of the delamination growth behavior in composite multidirectional laminates is important for the designs of composite structures. According to the failure mechanism of multidirectional laminates, a novel three-linear cohesive zone model has been established in our previous work, in order to include the influence of fiber bridging on the delamination growth behavior in simulation. Based on that, numerical researches on the critical parameters in the novel three-linear cohesive zone model are performed in this study using two-dimensional finite element method. A value scheme of the critical parameters suitable for the simulation on the delamination growth in composite multidirectional laminates is obtained. The simulated results using the value scheme have good agreements with the experimental results, validating its effectiveness in the novel three-linear cohesive zone model.

Abstract:In this paper, some boundednesses and inadequacies of the traditional fluctuation theory were pointed out. Then the establishment and derivation process of a modified elastic wave theory was given. The conversion process of wave equation from tensor state to column coordinate system was completed and the wave equation under column coordinate system was obtained. The relationship between the fluctuation variables and the load and velocity on the loading surface was established, revealing the influence of the boundary condition on the fluctuation variables when the stress wave reflection occurred on the free surface. By using Matlab programming, propagation process of the stress wave was calculated in the hollow cylindrical structure with an infinite length in the z direction of the geometric model and so was its reflection when encountering with the boundary. The calculation results showed the propagation process of stress wave in the structure with time, during which the stress wave would produce two waves on the loading surface, namely the volume wave and the deformation wave, and four waves would be reflected when encountering the boundary. At the same time, the volume wave and the first part of the deformation wave would be combined to form a composite pulse moving at the same wave speed.

Abstract:Wet bulb globe temperature (WBGT) is the thermal environmental index that acquired the ISO7243 authentication of the international standard system,which is adopted by countries including America, Australia, Japan and China, etc. Currently, most of the simplified calculation of the outdoor WBGT is summarized or verified based on the actual measurement in low altitude areas. To research the simplified calculation method of outdoor WBGT for areas with low latitude and high altitude, taking Guiyang, a typical city with low latitude and high altitude, as an example, we conducted Pearson correlation analysis and hierarchical regression analysis on the air temperature, solar radiation, relative humidity, wind speed, air pressure and WBGT of different altitudes in summer. The result shows that except the wind speed, other four parameters are of linear dependence with WBGT, and can be brought into the regression model. In the hierarchical regression, adding in air pressure can improve the prediction approach of air temperature, solar radiation and relative humidity to WBGT, the regression model has statistical significance and so does the influence of the four independent variables added into the model on WBGT. In the outdoor thermal environment evaluation and actual measurement, empirical formulas need to be verified first when adopted in different regions, and it is suggested to add the air pressure parameters in WBGT calculation model to improve the prediction accuracy at high altitude.