Search

Modified nanocellulose fibers (MCNFs) were added to the high energy nitroamine gun propellant to explore its influence on the mechanical and energy properties of the gun propellant. In this paper, nanocellulose fibers (CNFs) and MCNFs with a content of 1% were added in the high energy nitroamine gun propellant formula. The mechanical properties, fracture surface structure and energy performance are characterized by the impact strength test equipment, universal material experiment machine, scanning electron microscope (SEM) and closed vessel test. The results show that in terms of low-temperature tensile properties, low-temperature compression properties, and low-temperature impact resistance, the MCNFs-containing propellant samples increased by 2.97%, 1.94%, and 20.4%, respectively, compared with the CNFs-containing propellant samples. The difference in energy properties between the two is not significant. Compared with CNFs, MCNFs can better combine with nitrocellulose matrix in microstructure.

According to the multiple matching principles of hydraulic torque converter and engine, a multi-objective optimization mathematical model is established. Genetic Algorithm is used to optimize the matching mathematical model, because the search process is not easy to fall into local optimum. The matching example of YJSW315 type hydraulic torque converter and WD615.67G3-28 type engine is optimized. The design variables’ optimization results are obtained and the figure of optimization results is shown. The matching evaluation indicators of automobile power performance and economy are compared before and after optimization. We can find out that maximum output of hydraulic torque converter torque, highly effective rotational speed range, highly effective torque range, average power output of full working condition range and efficient working condition range are all increased, at the same time, average fuel consumption rate of full working condition range and efficient working condition range are decreased. In accordance with the optimization results, we can see that GA can be used to optimize the matching of engine and hydraulic torque converter.

A measurement and analysis system is designed base on the requirement of digital upgrade to the KY231 Material strain tester. This system is made up of two parts :The analyze system based on the LABWINDOWS and the measurement system based on STM8S207. The physical quantities (such as stress, pressure, deformation, etc.) of the metal specimen are acquired, displayed and analyzed digitally in this system, meanwhile the experimental data and curves can be stored in the systerm and compared to the historical data saved in the previous files. Because the USB interface is too complex to the MCU systerm form the aspart of the programming and circuit design, the PL2303 is used to simulate USB interface as virtual RS232 for the communication between the measurement system and the analyze system.

This dissertation is centered about the research on the quartz-tube roasting lighter for electric heater by the simulative test methods. The experiments are carried out and accomplished in a large space laboratory. It turns out that the burning possibility are directly related to three aspects, including the power of electric heating, the distance between the lighter and electric heating, and, most importantly,the surrounding combustible condition. When the lighter is heated by electric heating and get blasted, combustible tend to be caught fire instantly if it is near to the lighter and the cause of fire, vice versa.

When fire breaks out, the gas composition and concentration as well as smoke concentration of burning part vary from those in normal environment. The gas and smoke absorbed during solidification of short circuited melted mark occurred in such environment will certainly have an effect on grain shape, grain size, holes distribution and impurity element distribution of organization of melted mark. The gas in the environment has a certain influence on the organization of short circuited melted mark, but the influence is smaller than that of smoke. The reason may be that the gas is mingled with certain amount of tiny smoke particles inevitably which play a role in the solidification of melted mark. Compared with short-circuit samples in normal atmosphere, carbon content of short-circuit samples increases and oxygen content decreases in the environment of smoke.

Fire scene investigation on fire caused by the wall socket,extracted the copper bead and aluminum wire material evidence,observe and analysis,include the macro analysis and metallographic analysis, and then confirmed the reason.Through the identification of the extracted fire material evidence,macro features are all electric heated,the metallographic analysis to determine the nature of the melted marks respectively for primary short circuit melted marks and over load melted marks and short circuit spatter melted mark. These three kinds of trace is in line when the electrical fault occurred formed, and a primary short circuit melted marks provides the most direct strong scientific basis for the cognizance of the fire,and determined the fires is caused by the faulted wall socket.

The sampling flow will be decreased by the weakness of filterable membrane permeability after the dust sampler working for period of time. It seriously affects the measurement accuracy, so keeping the dust sampler working under the constant gas flow is important. Gas flow can be adjusted accurately in time to ensure constant flow based on single neuron adaptive PLC algorithm and PWM technique. Apply ZigBee wireless communication technology on indoor positioning and remote monitoring.

In order to assess the comprehensive quality of Jeep front-flank bracket rationally and effectively, use K means cluster method to analyze the cluster of condition attribute data, data separated into categories will be discretizated into integer according to the characteristics of the data distribution. In order to reduce the workload of detection and avoid the interference of complex data, use rough set toolbox to reduce attributes and get core data. In order to guarantee the result correct and avoid local optimal solution, the Genetic algorithm that can realize the parallel search is used to seek the optimal solution interval, the Simplex search optimization method is used to determine the optimal solution. In order to reflect the quality holographicly, use weibull distribution that has a wide applicability to calculate the similarity, that this process use the Adaptive integration method and Cubic spline interpolation to eliminate the accumulation error and guarantee the accuracy of calculation results. The method proposed in this paper can reduce the workload of measurement and calculation, save effectively time, improve the testing efficiency, in theory and practice, this paper realize the beneficial exploration around the comprehensive quality assessment of Jeep front-flank bracket.

The Sampling flow will be decreased because the permeability weakness of filterable membrane after the dust sampler working for a period of time. It seriously affects the accuracy of measurement, so we should keep the dust sampler working under the constant gas flow. The stable, rapidness and accuracy constant sampling can be achieved based on the application of fuzzy-PID algorithm and the adoption of PWM technique. It has carried on design to the dust sampler control system from selecting the hardware and designing the software to data processing and errors analysis, and discussing the preferable performance of the dust sample control system.

The safe current carrying capacity of iron wire is far less than copper wires. In the simulation experiments, use iron wire replace copper wire and use welding machine as electric equipment, even the flaming. Normal operating electric homework, the whole iron wire overheat and cause carbonization of insulation layer and even set on fire because of line’s overload, and lead to short circuit between wire. Extract fire material evidence, observe and analysis. Summed up the microstructure characteristics of the sample. Apparent characteristics of short circuit melting mark organization is:wire matrix is widmanstatten structure and ferrite, the transition region is mainly widmanstatten structure; overload melted mark organization is mainly cast structure, there was more casting .

Nowadays, technology rapid development, the living standard of people also is rising, household devices gradually to the trend of electrification development, in the meantime, the fire also increase annually in caused by electrical equipment. The solar energy water heater used more widely, because the product quality, installation and improper use fire in the number of rising sharply. Among them, caused by electric heating cable fault accounts for a bigger chunk of fire, so the identification of electric heating cable fire are particularly important. We can made comprehensive Analysis on electric heating cable trace utilize the technical means of macroscopical method and metallographic method etc., judge its melting nature, can provide strong technical support for fire investigation.

The methods of work this identification system is that distill wheel speed characteristics to standard signal then stored in the system. When the first anti-lock loop begin to input the initial velocity to identification model then extract theoretical value of the system and input the actual speed then calculate the similar with theoretical speed. The maximum similarity value is the identification when the pavement is true. After that every cycle identifies monitoring (again identify based on new data) that is establishing state observer. Though it is inaccurate due to various interference identifications or when the adhesion coefficient of pavement has changed ABS will determine quickly make the work more reasonable. Choose normal distribution and exponential distribution of statistical principles to identify the pavement and modify the identification model with gamma membership function. Tire model choose H.B.Pacejka model suitable for programming. It will use Gauss numerical integration and rational interpolation to increase the timeliness of identification. The method this paper described is suitable for the identification of low road.

Electrical wiring is the main fireorigin on electrical fire, and aluminum wire laying lines used more fire hazard. The melting mark formed in process of fire is the important material evidence to analysis the cause, but the aluminum wire melting mark organization feature is also different in different solidification conditions, therefore, to identify the mark characteristics formaed in different environment conditions has become a important task of fire evidence identification. Prepared fire sample melting by the means of simulation test, and observed to analysis the experimental sample, then summarizes the influence of solidification environment on microstructure characteristics of aluminum wire trace sample. Through the analysis found that, because of the influence of subcooled temperature, make the most of the organization of melt mark cooled in the air have oversize equiaxial crystal organization, almost no holes; and the dip in water cooling of melting mark is formed in larger subcooling, so the organization have more than a small columnar crystal and cellular crystal, and have more small holes exist. These features of aluminum conductor mark can provide strong technical support for fire investigation.

An experimental investigation was conducted on 4100 engine to study the influences of different percentages of methanol in DME/diesel blended fuel on combustion and emission performance. The result indicates that a certain amount of methanol in DME/diesel blended fuel can reduce production cost, improve the engine's power performance at the same time, but when the methanol percentage is increased (over 2%), the power performance will decrease. With the increase of methanol proportions, the maximum cylinder pressure is slightly increased, the peak of heat-release curves are declined and delayed, the cylinder temperature is decreased, the ignition timings are delayed and the combustion duration is shortened. In addition, NOx emissions were further reduced, but the HC emission, the CO emission and the soot emission has a little rise.

This paper makes study on the 42CrNiMo gear contact fatigue strength, applying the rapid measure method of the gear contact fatigue stress value with a few gear samples to get the estimated value of the gear fatigue limit value precisely and rapidly. And the gear fatigue life curve and fatigue damage accumulation curve are got by MATLAB simulation. Comparing with the traditional test method, this method can reduce the cost and save the time.

In order to meet the need of identifying obstacles and navigating for the Coal Mine Detection Robot which is used to rescue life and detect environment from coal mine disaster, binocular stereo vision is researched and 3D model of objects around the robot is reconstructed by means of two cameras of visual system built in the robot. The two cameras are calibrated and two projection matrices of them are obtained. Then, two images of the same scene are obtained by the two cameras. The matching points of two-dimensional coordinate are got through Harris corner extraction and stereo matching. According to the principle of binocular vision, equations are obtained and solved by least square method, which can calculated the discrete points of 3D coordinate.

A variable-grain strategy is proposed to solve the complicated problem of optimization design on high-speed transmission helical gears with multiple objectives and restrictions. Based on the theory of gear meshing noise and the superiority criteria, a multi-objective evaluation index system is brought forward which gives consideration to the increase of the contact ratio and the decrease of the noise generated by the slide ratio of the tooth flank meshing and the mutation of friction torque, and then the variable-grain multi-objective optimization models of high-speed helical gears are established. The coarse-grained model is utilized in the early design to efficiently determine the direction to the optimal solution. Then the grain is refined and the fine-grained model can be utilized to acquire the optimal result.

This paper introduces the installment method of experimental machine and gears, and the definition of stress levels, based on the contact fatigue experiment of 18Cr2Ni4WA carburizing and quenching gears, the few experimental points combination method was applied. The experimental points data was obtained by failure criteria. The S-N curve is fitted according to experiment data, and the experimental points data processing method is also explained in the paper.

In order to meet high-volume, low-cost reducer and ensuring quality in the production of reducer, a new design method is necessary. This paper applies the design method of ‘modular’ in high-volume reducer production, preferred numbers and mechanical optimization design thought, then based on access database and VB programming software research modular design process of the volume reducer. Higher degree basic modular parameters of volume reducer are obtained.

For early failure problems, which are broken teeth of the first transmission driving gear in the test, this paper studies the problem in the failure mechanisms such as chemical composition analysis, fracture surface analysis as well as the metallographic structure morphology inspection analysis of failure gear. The results show that the main reasons causing abnormal fracture of the failure gear are the insufficient root shot peening strengthening, the small fillet of the spline groove and the inadequate rim thickness of the rim. This paper uses the finite element method to analyse the contact stress of failure gear and puts forward an improving design method.

A variable-grain strategy is proposed to tackle the complex problem of optimization design of fine-pitch gear with multiple objectives and restrictions involved. Multi-objective optimization mathematical models of various grains are established, in order to ensure the tooth profile optimal and reduce the noise generated by the slide of tooth flank meshing and the mutation of friction torque as criteria to evaluate different schemes. The coarse-grained model is utilized in the early design to efficiently determine the direction to the globally optimal solution. Then more accurate model can be utilized and finally the optimal scheme can be acquired on the basis of the fine-grained model. Based on the theory of meshing noise and the superiority criteria, the algorithm is put forward for the fine-pitch gear design problem, and the Pareto optimal sets are obtained.

Tooth contact analysis is an effective tool for meshing analysis of the double circular arc profile spiral bevel gear (DCAPSBG), as well as the basis for loading tooth contact analysis and finite element analysis. Applying the principle of tooth contact analysis (TCA) and the tooth profile characteristic of the DCAPSBG, this paper introduced and discussed the key contents and method of TCA computer programming for numerical simulation analysis of the transmission meshing quality of DCAPSBG. The TCA program developed in this paper, which had been verified by real examples, provided an effective approach for the design of DCAPSBG.

Firstly the engine models with different types of crankshaft are built, and the load condition of the crankshaft is simulated .After comparing the simulation results, a conclusion is obtained that the model with beam crankshaft or flexible crankshaft corresponds with actual situation. Then the selection of the balance target is discussed .At last, using a certain 60°V8 engine as an example, two kinds of counterweight arrangement schemes are studied, and the simulation results shows that both schemes can achieve good balance effect.

In view of the characteristics of the low-noise and high-strength of auto gears, this paper proposes a new method of optimization of fine-pitch tooth profile. Based on the constant gear-pair parameter values of transmission ratio, modulus, pressure angle, the method takes the optimal contact ratio as design object, sets up the constraint conditions such as noise limit index, non-interference, non-undercutting, and non-sharpened in the tip, and optimizes the addendum coefficient and coefficient so as to increase the contact ratio. In addition, this paper makes a finite element strength analysis on the design result, and the result shows that the new method can not only reduces noise but also improves gear strength of fine-pitch gear.

With the ESE module of FIRE software, this paper establishes the diesel engine model of 4100, and verifies the correctness with the test result. Based on this, the paper carries on a simulation on three high proportions of DME-diesel D65, D75 and D85, and makes a contract with diesel on the mean pressure, mean temperature, mass fraction, accumulated heat release, as well as the mass fraction of NOx and soot. The result shows that the higher proportional, the lower mean pressure in-cylinder. Also the result shows that NOx growth will come to a “freezing period” when it comes to a certain temperature, while soot growth is growing first and oxygenated later, and with the increase of DME proportion, NOx grows later and its mass fraction is lower. Besides, the mass fractions of soot of three kinds of mixed fuels are far below diesel’s, D85’s is the lowest.

Following spatial mesh principle, the gear cutting meshing equation was established in the paper through analyzing the relation between the machining principle of the double circular arc profile spiral bevel gear and the movement of the machine tool. The parameters of cutter head and the machine tool’s movement were then obtained through the equation. VERICUT was applied to build the three-dimensional virtual simulation machining model by which the gear geometry parameters, cutter parameters and machining tool movement parameters were calculated for a given gear to be processed and virtual simulation machining proceeded to prove the validity of the model.

Tooth contact analysis (TCA) is an effective tool for meshing analysis of the double circular arc profile spiral bevel gear (DCAPSBG), and it is the basis of loading tooth contact analysis and finite element analysis. The TCA application is developed by Visual Basic and MATLAB mixed programming method, this paper compared the results of the TCA application analysis with the results of contact area check experiment on one pair of gears with given parameters. The TCA application had been verified by real experiment, this provided an effective approach for the design of DCAPSBG.