Abstract:

Abstract:3D contact finite element model of output helical gear pair of wind turbine speed-increase gearbox is built to calculate stress-strain of gear pair under static load. S-N curves of gear pair materials are calculated based on fatigue test constants of materials. After carrying out rain-flow counting for load histories of real load spectrum in 20 working conditions of the gearbox，the relation of load cycles，mean value and amplitude of the load are obtained. Fatigue life of helical gear pair is analyzed with FE-SAFE to study the influence of magnitude of load，residual stress，tooth surface roughness and profile modification to fatigue life of gear pair. The results indicate that there are a few short life points at places where stress concentrates；the life of gear pair extends with the decrease of load or tooth surface roughness；residual tensile stress leads to a reduction of fatigue life while residual pressure stress leads to extension；the life of gear pair extends with proper tooth modification.

Abstract:On the basis of failure data gathered from 5 NC machine tools of one type in one year，a two-parameter Weibull distribution model is established，and this model has passed linear correlation test and hypothesis testing. On the principle of the most effectiveness，the best preventive maintenance intervals model on the state of reparative maintenance is brought forward，and the best preventive maintenance intervals of this type have been calculated. In the end，an appropriate maintenance plan is brought forward according to the best preventive maintenance intervals，and the maintenance cost is greatly reduced and the availability of this type of NC machine tool are kept at the same time.

Abstract:The welding residual stress and strain of cellular ice-maker plate are considered during 304 stainless steel laser welding process. The different welding powers lead to different sizes of laser welding seam. The influence of different welding seam sizes on the maximum bearing load and deformation of cellular ice-plate is studied in laser welding with a new analysis method. And some deformation controlling methods and a new welding procedure for cellular ice-maker plate are proposed. It is showed when the welding power is 1.4 kW and 1.8 kW，the ratio of longitudinal bending deflection is about 1.000∶1.328，which is equal to the ratio of longitudinal shrinkage stress respectively，and then the measured value of residual stress ratio is about 1.000∶1.391，which is similar to the calculated value. The research shows that the maximum bearing load has a certain relationship with the welding seam geometry，and the new function equation between the maximum bearing load and welding seam geometry is submit during 304 stainless steel laser welding process. The cycle welding sequence of inside and outside is proposed，which not only can reduce the occurrence of the welding deformation，but also do not affect the welding efficiency，so the quality of the cellular ice-maker plate is increased greatly.

Abstract:For predicting the running-in process of wet clutch test，a method based on multifractal spectrum and its parameters are proposed to predict the running-in state，combining with the geometry features of friction torque signal in test. Firstly，the concept of multifractal spectrum based on the box-counting method is introduced；and then the inherent relationship between the multifractal parameters and friction torque is discussed；finally，friction torque signals from a certain type wet clutch running-in test are analyzed and depicted by the multifractal spectrum and its parameters. The analytical results show that the geometry features of friction torque signals can be quantitatively described through multifractal spectrum and its parameters，and the breadth and fractal dimension difference of maximum-minimum probability subset of multifractal spectrum gradually decrease with the running-in process，while the minimum singularity exponent increases gradually with the running-in process. Therefore the running-in state of wet clutch can be effectively predicted by the multifractal spectrum of friction torque in test.

Abstract:In order to quickly and accurately locate the fault of CNC software and improve the reliability of CNC system，an improved algorithm of similar path and fuzzy judgment is introduced into the fault location of CNC software. Firstly，according to the execution information recorded by monitor，the failed path is generated；secondly，the similar path set can be obtained from control flow graph and failed path；then the search scope of suspicious codes can be reduced by program slicing；finally，the fuzzy mathematics is performed to judge suspicious codes. In addition，the experiment on the NURBS interpolation injected bugs is carried out. The experiment results indicate that the proposed method is effective in locating the fault of the CNC software.

Abstract:There is a lot of non-stationary signals in gear vibration signals，which is analyzed by using Gabor spectrum. To resolve the problem of the choice of window，a method based on entropy is proposed to select the optimal Gabor window width，and the time-frequency resolution of Gabor transform is improved. Since the spectrum has its specific mechanism of crossing-item，the Gabor spectrum is calculated in the region of the key support area and the crossing-item is effectively removed，then the Gabor spectrum is used to analysis the time-frequency distribution of vibration signals of gear，and this method is compared with traditional analysis methods. The result shows that the Gabor spectrum can intuitively react abnormal gear and energy changes with time，and easily diagnose the gear fault.

Abstract:The topology optimization of the internal structure of a simple expansion chamber muffler is realized by using two-dimensional finite element and combined with a gradient-based optimization algorithm，the method of moving asymptotes. Then，on the basis of topology optimization，the size optimization is further studied. The change of the expansion chamber’s internal structure causes the change of transmission loss. United COMSOL with MATLAB programming，numerical results show that on the target wave number，the acoustical performance of the optimized muffler is much better than that of a simple expansion chamber muffler.

Abstract:The principle and the structure of oil shock absorber determine the inevitable occurrence of abnormal sound of cavitation. Through establishing the mechanical model and simulation, this paper analyzes the cause of abnormal sound of cavitation, uses shock absorber abnormal sound detection device to test shock absorber piston rod acceleration signal, compares the test result with simulation, and verifies the correctness of the analysis. Diagnosis about the abnormal sound absorber of the cavitation can be carried out through the analysis of shock absorber piston rod acceleration power spectrum and bispectrum. The results show that the energy of the shock absorber piston rod acceleration power spectrum and bispectrum is obviously different from those of the normal shock absorber after the cavitation occurs, and the abnormal sound can be reduced by replacing oil.

Abstract:In industrial cycling cooling water system, the dirt of heat exchanger causes enormous economic losses, and the traditional anti-scaling method has disadvantages, such as secondary pollution, poor results and high cost, etc. While the anti-scaling of electromagnetic field is convenient, pollution-free and low cost. These are advantages that other methods don’t have. A high-frequency electromagnetic device with DDS and amplifier technology for different water is designed, and its output is single frequency and sweep of the square wave signal within the scope of 0~1 MHz. A dynamic circulating water system is set up in laboratory to simulate industrial water cycling system. The research results show that external high-frequency electromagnetic field slows down the crystallization rate. Part of original calcite comes into aragonite. In addition, the effect of anti-scaling is effected by the concentration and output frequency, while the higher output frequency doesn’t always obtain better result, and the concentration of calcium should not be more than 5 mmol/L.

Abstract:As flashover accidents because of strong wind and storm frequently appear in our country, storms are thought to be one cause of flashover between tower and conducting wires in transmission lines.The influence of rainfall intensity,rainwater resistivity and air temperature on AC discharge characteristic of rod-plane(rod-rod) air gap is mainly investigated.The experimental result shows that,rainfall intensity and rainwater resistivity can reduce AC discharge voltage of rod-plane(rod-rod) air gap,and rainfall intensity has the most obvious effect on AC discharge voltage of rod-plane air gap;when rainfall intensity ranges from 2 to 14 mm/min,AC discharge voltage maximum reduction of 0.4,0.6,0.7 m rod-plane gap is respectively 6.73%,6.54%,6.02%,and maximum reduction of rod-rod gap is respectively 2.66％,3.22%,3.07%;the influence of rainfall intensity on AC discharge voltage of rod-plane is bigger than rod-rod’s;AC discharge voltage of rod-plane air gap increases with the increase of air temperature,and the maximum amplitude is 7.03%.

Abstract:Focusing on the problem of computer operation without hand for the disabled people, a new method of mouse control based on visual analysis of the face poses is proposed. First, the face images from CCD camera are obtained and the face areas are located based on AdaBoost algorithms with Haar features. Then, 5 feature points including 2 eye corners, 2 mouth corners and nose tip are detected with image analysis. After that, with help of the feature points in a predefined frontal face image, the face poses are estimated in the real-time face images. Finally, the 3 deflection angles are adopted to define human computer interactive information, which can be used to determine positions and operations of the mouse in the human computer interactive interface. The experimental results demonstrate the efficiency of our method that the face poses can be estimated accurately as well as the operation information to the mouse be achieved rapidly. It is valuable in human computer interaction for the disabled people.

Abstract:In industrial production, neglected loading of metal parts is very normal. It not only causes the quality reduction of products, but also affects production rate. Based on the theory of electromagnetic induction, by supervising the assemblage process of metal parts, it is able to count the number of assembled metal parts so that automatic online monitoring of neglected loading can be achieved. The feasibility of using the eddy current method to monitor the motions of metal parts is analyzed theoretically and MATLAB is utilized to simulate. On the basis of theoretical analysis, the specific eddy current type transducer, the appropriate signal-processing circuits and the software are designed. A testing system is established for analog. This method can effectively solve the problem of neglected loading by artificial factors, save the costs of factories, raise the FPY of products.

Abstract:Low cycle fatigue(LCF)properties of H-beam as hot-rolled and welded are studied, and the cyclic stress-strain relationship and cyclic response characterization are determined. Based on the Coffin-Manson formula, the strain-fatigue life relationship is obtained. Finally, the cyclic toughness, which is the product of strain range at LCF life of 100 cycles and the stress amplitude, are calculated. The test results show that the cyclic toughness as welded H-beam is 62% of that as hot-rolled. Hot-rolled materials exhibit cyclic stability, and welded materials show cyclic softening followed by fracture. The scanning electron microscope(SEM) micrograph of fracture surfaces reveals that the fatigue crack initiates from the coarse grain area of welding joint, and the fine dimple is observed in the fracture surface, which indicates the welding joint remains a good ductility.

Abstract:By analyzing the system of argon stirring molten steel in ladle, many affecting factors are determined. The model of characteristic number about describing mixing effect of steel stirred by argon in the ladle is gotten by dimensional analysis. Taking a ladle furnace of some steel plant as prototype, hydraulics simulation experiment is designed by generalized similarity principle. The equation for characteristic number about the mixing effect of steel in the ladle is gotten by stepwise regression, which is suitable for ladles whose geometric structure are similar to the ladle in this study. The results could be gotten as follows. The four decisive characteristic numbers that are considered are all significantly effective to H0. And gas-liquid density ratio πρ is the most remarkable among them. When doing some hydraulics experiment to simulate the phenomenon of molten steel stirred by argon from the bottom of ladle, using some conventional gas instead of argon could result in a great difference between the decided characteristic numbers of model and prototype.

Abstract:To increase desulfurization efficiency of oxidizing roasting in muffle furnace, microwave is used to roast the high-sulfur bauxite. The influences of roasting temperature and time on sulfur content are investigated, and the final phases are recognized by XRD analysis. The results show sulfur content is less than 0.7% after being roasted at 400 ℃ for 2 min. If it’s roasted at higher temperature for longer time, like 550 ℃ for 10 min, the sulfur content decreases to 0.23%. Sulfide ion can be dissociated by microwave and diffuses to the surface to form sulfur dioxide. This process will accelerate dissociation further so as to increase desulfurization efficiency.

Abstract:To reveal the effect of clay on the dispersibility of polycarboxylate superplasticizer(PC), the fluidity and viscosity of cement paste are chosen as performance indexes to study the effect of clay on the rheological properties of cement paste mixed with PC. The influence of filtrate of clay on molecular structure and the regularity of adsorption of PC on the surface of clay particles in alkaline environment are also analyzed by IR and UV. The results show that PC has no dispersing effect on the cement paste when clay content reaches to 15%. Increasing the dosage of PC can reduce the negative impact of clay. The filtrate of clay can’t change the molecular structure of PC and doesn’t affect the dispersibility of PC. In simulated alkaline environment (saturated solution of calcium hydroxide), the adsorption speed of clay on PC is rapid, whose adsorption capacity of clay on PC is about 4 times of cement’s, and clay will have been reached its equilibrium adsorption amount in the initial period (within 6 min).

Abstract:Based on the domestic experimental data of multi-storey concrete frame structures, the relationship between curvature ductility of concrete frame column and structural displacement ductility is proposed. 32 sets experimental data of system displacement ductility and the corresponding storey displacement ductility, which are mainly obtained from beam hinge yield mechanism and failure mechanism, are collected, and statistical property of system placement ductility is analyzed. Curvature ductility of concrete frame column is derived from storey displacement ductility factor by the classical analytic solution, and relationship between curvature ductility of frame column and structural displacement ductility is established. Correlation coefficient (R) for fitting power exponent function model and sample test data is 0.775. Results of nonlinear numerical analysis examples show that statistical function model is able to direct the ductility control design of concrete frame column.

Abstract:In order to overcome the existing problems of low automation, high cost and difficult to implement in the area of landslide monitoring, this paper presents a new method of RSSI (Received Signal Strength Indicator)based positioning technology without any one-off instruments to monitor landslide surface displacement. By adding weighted factors, the improved positioning algorithm can estimate the parameters of the path loss model dynamically and calculates the communication distance of network nodes in real-time, which can improve positioning precision and reduce the impact of environmental changes on it. The MATLAB experiments show that, compared with the traditional RSSI based localization algorithm using fixed pass loss model, the improved algorithm could significantly reduce the average error.

Abstract:The technology of coal dust explosion suppression is an important means for coal dust explosionproofing. The core of this technology is to develop the inhibitor with effective explosion suppression performance. Firstly, the mechanisms of 3 inhibitors are analyzed, namely physics-based, chemical-based and mixture-based mechanisms. Secondly, the existing inhibitors are categorized and the basic property of the novel inhibitor is put forward. Then, the technology of synergistic mixtures is adopted to tap inhibitors by choosing 3 monomers (aluminum hydroxide, ammonium polyphosphate and diatomaceous earth) and synthesizing, and finally get 3 new inhibitors A, B and C. Utilizing 20 L spherical explosion test system, based on the index of parameters of explicability, the effect of the novel inhibitor is verified by explosion testing. The results indicate mixtures of inhibitors obtain good results, realize synergism and perform much better than traditional inhibitors.

Abstract:Experiments of outburst coal’s gas seepage and deformation under cyclic loading of the stationary gas pressure and different confining pressures are made by “fluid-solid-heat coupling with axis servo seepage system of coal”. The results show that loading route has a significant effect on mechanical properties of coal sample. Although the complete stress-strain curves and one cyclic loading curve present similarity in the overall trend, the stress peak value of coal sample under cyclic loading is lower. Under cyclic loading, the stress-strain curves during loading and unloading don’t overlap. They connect to form a hysteretic loop. The permeability is in close relation with the damage deformation process of coal sample. Under cyclic loading, permeability is increasing during the unloading and decreasing during the loading. The permeability-strain curves during loading and unloading form a hysteretic loop, which is corresponding with the hysteretic loop of stress-strain curves of coal sample.

Abstract:A mathematical model of rock breaking under pulsed jet is established by introducing the Johnson-Holmquist-Concrete constitutive relation and the smoothed particle hydrodynamics method. Based on this model, the formation, propagation and attenuation of stress wave during rock breaking by pulsed jet are simulated. The relations between pressure and time at different points on rock surface and the curve of peak stress wave versus distance to action spot are obtained. Destruction behaviors of rock under pulsed jet and effects on stress wave effect from jet velocity and lithology are studied according to the above calculation results, analysis results show that stress wave effect of pulsed jet acts locally and the peak stress wave shrinks sharply as the acting distance increases. The rock breaking mechanism of stress wave is tensile failure during the high speed process of load-unload. Power and effect range of stress wave is in high direct proportion with jet velocity. There is a threshold velocity before the macroscopic failure. Rocks of different lithologies have different destruction types under pulsed stress wave of pulsed jet. Destruction type of low strength rock like sandstone is crack propagation under the tensile stress during the high speed process of load-unload, while the destruction type of high strength brittle rocks like granite and limestone is vertical failure of stress concentration.

Abstract:Under the operation of multifunctional device for water lifting and aeration(MDWLA), in situ simulation experiment is made by use of the oligotrophic biofilm process for pretreatment of micro-polluted raw water in order to investigate the removal effects of nitrogen and organic matter. The experimental results show that the combined technique of water-lifting aeration and oligotrophic biofilm process is feasible, and the removal rate of ammonia, nitrate, total nitrogen and TOC in steady running period range from 82%~100%, 62%~79%, 71%~80% and 73%~80%, respectively, under the condition of temperature 10~23 ℃, dissolved oxygen 4.0~6.0 mg/L, NH +4-N 0.230 mg/L, NO -2-N 0.010 mg/L, NO -3-N 1.125 mg/L, TN 2.010 mg/L, CODMn 3.140 mg/L and BOD5 1.540 mg/L for source water, also the nitrite is poorly detected and the ratio of BOD5 to CODMn is in the range of 0.05 to 0.20. Obviously, the nitrogen removal effects can meet the requirements of class Ⅲ of surface water quality according to GB3838—2002 and the biological stability can be improved under stable operation condition of the combined process. Lastly, the changes of oligotrophic denitrifying bacteria number and biological phase, and water purifying mechanism of oligotrophic biofilm system are also discussed.

Abstract:The project problem because of wall rock’s deformation fracture in deep-buried and high geostress conditions is very prominent at Jinping hydropower Ⅱ station underground engineering. According to the characteristics of the bedded marble collected from Jinpiing Ⅱ hydropower station auxiliary traffic tunnel in deep-buried area, three-point bending experiment on different bedded direction specimens with SEM high temperature testing system is carried out to test the stress of bedded marble in different directions and the failure mechanism and deformation features of homogeneous marble. In the test, there are 3 groups of specimens, include parallel bedded specimen, vertical bedded specimen and homogeneous marble specimen. The results show that: bedded marble’s bedded feature is because of the banded structure feature between dolomite mineral particles and calcite mineral particles; the fracture mechanism and strength parameter of bedded marble depend on different force directions and mineral composition. Because of the cement capacity between dolomite minerals and particles size, homogeneous marble specimen has the lowest strength. The marble specimens’ deformation shows 3 stages, and because of different fracture mechanisms, the plastic deformation of parallel bedded specimens is more obvious than that of vertical bedded specimen. While the deformation of homogeneous marble can be divided into 2 stages, i.e. before and after peak stage, and the after peak stage shows the complete deformation development process.

Abstract:Short-term memory measurement is an important method to determine study fatigue as it pertains to learning outcome. This project examines the impact of classroom-lighting on circadian rhythm. A learning-recognition model using two-character Chinese word cards formed the basis of this study. Utilizing the discriminating ability in Signal Detection Theory as an index, students’ brain fag (mental exhaustion and fatigue), short-term memory and recognition ability are tested and analyzed. The subjects are placed under T5 fluorescent lamps of 3 typical colour temperatures and with 4 luminance levels. Within a certain length of time, students’ brain fag and recognition ability of short-term memory differs under different spectrum conditions and luminance levels. Low colour temperature and low luminance has a wake-up effect that improves short-term memory. Medium colour temperature is the optimum that can keep brain function appropriately excited. Under high luminance level, brain fag is more serious and learning efficiency is lower. Brain fatigue is most pronounced under high colour temperature. Obviously longer exposure time to the Chinese characters will result in higher recognition ability. This study has important implications in how to improve learning through properly designed lighting conditions.