Abstract: The cooling characteristic of sprag nozzles for different costructions are researched.The water distribution of spray flow, spray angles and water droplet seize in different spray condition are measured. The influence of nozzles ceonstruction and spray parameters on cooling characteristic are iscussed.
Abstract: In this paper, a study of three-dimensional flow field in the mold region by means of mathematical modeling is reported.The mathematical model consists of time-average turbulent Reynolds equations and the k-e two equations model of turbulence.The Artificial Damping and compressibility method which is developed by Gao Ge is used to solve these equations.The computed resultsfor the velocity field has been found to be in good agreement with the data——measured in experiments.It only takes 8min.26sec.for three-dimensional turbulent flow field of 10×10×20=2000 cells on M-150 electronic Computer.The results show that the convergence rate increases by a few order of magnitude as Compared with the conventional SOR method. A new experienced value of C2(c2=2.23) was obtained when the k-ε two equations turlulent model was calculated.
Abstract: Spiral seed squeezing machines are commonly used in our country to produce vegetable oil.The spiral squeezing sleeves slipped onto the axis are the main parts doing the work of squeezing the seeds.The wear life of them shall be very important to the effective service of the machine The wear failure analysis of these sleeves was done in this paper.The squeezing chamber in the machine can be divided into 3 zones, namely, "feeding zone", "presqueezing zone" and "squeezing zone".Because the squeezing pressure in the last zone is high and the seeds become highly compacted "non-compressible bodies" the sleeves in that zone are sustaining high stress grinding wear and wears fast This is proved by the wear morphology of these sleeves.Wear failure analysis is mainly done on them.The SEM examinations of the wear face and section through the subsurface show that the wear mechanisms of the sleeves are; deformation wear mechanism,cutting wear mechanism, tearing wear mechanism and fatigue wear mechanism by non-compressible bodies and high pressure erosive wear mechanism by liquid oil produced. The main causes of failure are the former two mechanisms.Alloy white cast iron con taining carbide of high hardness and having high macro-hardness was suggested to make those sleeves to replace carburized steel and proved to be much more cost effective.
Abstract: This paper deals with the effects of cobalt on the mechanical properties of Fe-Cr-Ni-Co base superalloy Refractoloy26.Cobalt is replaced by nickel to produce 0,7,14 and the standard 20 pct cobalt versions of the alloy. Tensile properties at room temperature and elevated tempratures,temperature dependence of Young's modulus and shear modulus, and the creep properties at 565℃ and varied applied stresses are experimentally determined. The results ndicate that lowering cobalt content has a little influence on the tensile properties, but a great influence on the creep rate and the stress rupture life. It is proved that the creep properties of the alloys depend directly on the ivalues of stacking fault energy in matrices. The possilility of lowering cobal content in Refractoloy 26 also has been discussed.
Abstract: Room temperature anisotropy field of 85KOe and magneto-crystalline an-isotropy constant of 4.2×107 erg/cm3 for sintered Fe76Pr16B8 bulk permanent magnets were measured.The energy product of the sintered magnet is up to 34MGOe.The influences of process factors such as sintering temperature and annealing temperature and time etc. on magnetic properties were studied.
Abstract: In order to obtain the strengthening effect of sintered steel phosphorus is used as one of the alloying elements.In present work the distribution of phosphorus in Fe-P-C-Cu-Mo alloy containing 0.6%P and its effect on properties were studied by means of Auger electron spectroscopy, scanning electron microscopy,mechanical properties test machine etc.lt is found that when the above alloy,is sintered at 1080-1200℃ the concentration of phosphorus at grain boundaries is higher than that at intracrystalline.At above sintering temperature range the lower the sintering temperature is,the higher the concentration of phosphorus at grain boundaries will be. The effect of grain boundary segregation of phosphorus on the impact toughness is concealed by the structure of as-sintered alloy which contains a large amount of ferrite.The fracture surface of alloys sintered at 1080-1240℃ is of intracrystalline. In addition, it was found that after tempering the effect of distribution of phosphorus on the way of fracture and the mechanical properties is very great. The specimens were tempered at 200℃ the dissolved molybdenum will inhibit phosphorus segregation towards the grain boundaries and the fracture surface is of transgranular. Tempering at 400℃ decreases the impact toughness and causes intergranular fracture because during tempering at 400℃ molybdenum is in the form of molybdenum carbde (Mo2c) and phosphorus dominantly segregates into grain boundaries. During tempering at 600℃ the trend of phosphorus segregation towards the grain boundaries decreases and phosphorus mainly precipitates on the internal pore surfaces. The specimens tempered at 600℃ will have high impact toughness and the fracture surfaces of above specimens are dimpled ductile fracture.
Abstract: The approaches of intuitive derivation are presented for the various equivalent cuircits of a transistor from its physical model.These approaches only use the concept of equivalent transformation of circuits,and avoid the tedious mathematical derivation. They have the advantages of having clear physical meaning and exposing clearly the relationships among various equivalent circuits.
Abstract: In this paper starting with the basic matrix equations of the motor,we xamined and obtained the mathematical model of the Commutatorless Motor and consequently its simplified transfer function The effects of some factors on the dynamic characteristics of the Commutatorless Motor were discussed. The structure and the characteristics of closed loop control system of the Commutatorless Motor were expounded,some methods were also presented to improve the dynamic characteristics of the system.
Abstract: This paper discribes a design method of multivariable self-tuning controllers for a class of multivariable systems which the number of inputs is uneq ual to the number of outputs.In a quadratic cost function,the control signaland the output derivations from the time varying reference signals are penalized.The optimal control strategy is developed by minizing the cos function.Combining the the equation of the optimal control strategy and the optimal predictor of the auxiliary outputs,the equation of the estimation of the parameters and the structure of the self-tuning controller are obtained. The closed-loop system of the self-tuning controller can trace the time varying reference signals and also adapt to the unstable open-loop systems.
Abstract: In this paper,a new internal sorting algorithm is presented which is especially suited for sorting record set in which the total number of key values is much smaller than that of records Viz.many records have the same value. If we assume the total number of records to be sorted is N and the total number of key values is M,the sorting efficiency-the total number of comparisons-of classical algorithms (e. g. quicksort,heapsort) is O(N·log2N), unrelated to M. Under the same assumption,the sorting efficiency of the new algorithm presented in this paper that uses one kind of queue with single pointer data structure, through two passes, is 2·N·log2M.If some conditioing are added,only one pass is needed and the efficiency is N·log2M.The moving total number of the new algorithm is N·M/4,and the extra memory space required is M,pointers and M key value locations.
Abstract: This paper presents a formula which can be used to calculate dynamic eguations of goint-typical robot manipulator.This formula is simple, direct, especially is suitable for calculation with computer.In this paper the process to use this formular is also introduced with a simple example.
Abstract: Potentiodynamic scanning method was used to study influence of environmental factors on the pitting potentials of types NHB-1、NHB-3、316L and 304 stainless steel. The changing ranges of temperature、PH and Nacl concentration were 0°-90℃、2-2 and 1%-5%,respectively. The experimenta 1 results showed that below certain temperature(It can be called Eb's as tran-siton temperature) the Eb rapidly decrease with the temperature increase while over this temperature,the Eb slowly decrease with the temperature increase in studied conditional ranges, preferential adsorption of Cl-、O2 and H2O on passivating films can be used to explain this pheiomenon. Increasing NaCl concentration,the Eb tend to decrease. The Eb increase with PH increase in neutral and acid solution.pitting corrosion was not found for the types of NHB-1 and NHB-3 stainless steel at Low temperature and for the types of NHB-1 and 316L stanless steel at PH12.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
