Applied Mechanics and Materials Vols. 249-250

Abstract: To comprehensive evaluate the safety working status for hoisting mechanism of crawler crane based on fault analysis for hoisting mechanism of crawler crane, this paper builds a model of state comprehensive for hoisting mechanism of crawler crane and builds a fuzzy comprehensive set of safe working state for hoisting mechanism of crawler crane based on the 3-scale AHP(Analytic Hierarchy Process), then gets the weight of each index. With the help of the score of index graded by experts, safe working state comprehensive evaluation for hoisting mechanism can be gotten. The results of the engineering example shows that compared with 9-scale AHP, 3-scale AHP overcome the difference of subjective understanding, and save the inspection process of complex consistency, the method is concise and feasible, and the results reflect that it is same with the objective reality.

Abstract: The telescopic boom of truck crane has bearing and luffing functions. It not only requires higher carrying capacity, but also requires higher reliability in the various working conditions. For scientific evaluating the reliability of the telescopic boom structure, the stochastic finite element method is used to calculate the structure performance function probability. Taking 50t truck crane telescopic structure as an engineering practical example, the feasibility and practicability of the method have been verified (tested/proved).

Abstract: Based on ABS System,a regenerative and pneumatic baking system was proposed,which can adjust pneumatic braking force precisely through ABS valve in order to guarantee the distribution of braking force. A control strategy using logic threshold was made,considering ECE regulation,control logic of ABS system,braking torque of motor and charging-discharging characteristic of battery. A co-simulation model was built with the platform of Simulink-AMESim and the simulation was performed under different braking intensity and driving cycles. The results indicate that the vehicle can achieve good braking regeneration effect with ensuring braking stability .Ratio of energy recycling can achieve 16.26% in London bus driving cycles.

Abstract: A piezoelectric vibration table was designed for seeding precisely small size of vegetable seed, tree seed, flower seed, etc., it worked under the converse piezoelectric effect of piezoelectric element, piezoelectric vibration driving system produced mechanical micro-displacements with applied electric field, micro-displacements amplified by amplification mechanism driven the seed dish vibrating, producing the boiling movement beneficial to sucking seeds. The mathematical model of piezoelectric vibration was established, static and dynamic state properties of vibration table were analyzed and tested. Experimental results showed that piezoelectric vibration system had a higher drive capacity when 90～110 V electric voltage was loaded, vibration amplitude was above 1.31 mm, vibration frequency was at 13～55Hz and adjustable (resonant frequency about at 25Hz). The piezoelectric vibration table is expected to reach to favorable dynamic characteristics and higher seeding performance, runs smoothly, and meets the agronomic demands for precise tray seeding.

Abstract: Based on domestic and foreign research situations of variable-rate fertilizing technology, the overall structure and working mechanism of variable-rate fertilizing machine were described, control content and strategy of control system were studied, AT89C5 SCM was used as a core control element in control system, control system hardware and software were designed and integrated. Variable-rate fertilizing experiments in space and paddy field showed that working efficiency of the spreader was up to 6 hm2/h, fertilizing error was less than 5%, fertilizing stability variation coefficient was less than 6.2%, working performance and control system design of the fertilizer can satisfy the demand of variable-rate fertilization in paddy field.

Abstract: In order to solve the problems of low-ground-clearance , backward manure regulation technology and low working efficiency presented in paddy fertilizing machine，a self-propelled spreader for rice variable-rate fertilization was designed, whole structure and working mechanism of the machine were introduced, hydraulic drive system of fertilizing device, fertilization disc and regulation device for fertilizing orifice were designed, key structures and parameters of the device were determined. Function relationship between orifice length and manure flow-rate was studied, linear equation was decided for variable-rate fertilization. Variable-rate fertilizing experiment shown that the velocity of fertilization disc changed about 0～900r/min continuously，the angle for pushing fertilizer board was at -20°～40°, the design for fertilization device can meet variable-rate fertilization requirements of widespread distribution and high efficiency in paddy fields.

Abstract: In order to improve performances of a virtual prototype, modeling and analysis are necessary before a system is produced and put into use. Firstly, structure and control schematics of electric vehicle with the steer by wire system and brake by wire system integrated are analyzed. Then, dynamics models of brake by wire system including the motor, planetary gear reducer, ball screw, etc. are built using Matlab software. Finally, effects of brake by wire system parameters such as motor parameters on system performance such as time domain and frequency domain response characteristics are analyzed using modern control theory. The results show that the modeling and analysis helps to find the performance sensitive parameters ,which will be used for parameter optimization design of brake by wire system.

Abstract: The expression of reliability estimation method for fatigue life of machine parts was derived, and two kinds of stress cycles (reversed cycle and un-symmetric reversed cycle) were considered. An iteration method is presented and the corresponding computer program named STRENGTH-2 is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are close to experimental results. The proposed method can be convenient to carry out the fatigue reliability design for machine parts under the action of uni-axial and multi-axial loadings, and promote the popularization and application of existing anti-fatigue design method. It has the high value of engineering application.

Abstract: Two methods acquiring p-S-N curve for machine parts are given, namely directly searching out the p-S-N curve of the material from material database and using the idealized p-S-N curve. Reliability estimation methods of fatigue life of machine parts are derived under uniaxial constant amplitude load. Two kinds of circumstances (fixed stress and probabilistic stress) and two kinds of stress cycles (reversed cycle and unsymmetric reversed cycle) are considered. An iteration method is presented and the corresponding computer program is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are closer to experimental results. The suggested method can be convenient to fatigue reliability design of machine parts. It has good stimulative effect on popularization and application of existing anti-fatigue design method for machine parts, and high value of engineering application.

Abstract: Optimization of closure law is the priority selection in solving the guaranteed regulation calculation problems due to its simplicity and economy. This present study deals with the optimization of two-stage closure law of wicket gates, which has more advantages in control pressure and speed rise. The mathematical model of transient process is established by introducing the method of characteristic, whose correctness is validated by the field test. Then the model is applied to a specific hydropower station that only can employ closure law optimization to coordinate the contradiction between pressure and speed rise, for two-stage closure optimization. The achievements of the study can serve as a reference for similar projects.