Abstract: A two-dimensional mathematical model describing the colling and reheating characteristics of slab ingots has been established.Based on this model, the simulative calculation has been carried out for the colling process of the slab ongot weighted 10.866 ton from pouring to charging and the reheating process if them in the soaking pits with one burner at one side wall. The parameters, such as the thermal states of slab ingots in colling and reheating processes, the reheating time and the reheating stratagy which have to be controlled for the reheating and rolling of slab ingots with a liquid core have been given from the calculating results.By comparison the actural data to the outputs of the model, this model is availiable for the industrial processes. These researches memtioned above are the theoretical basis for the industrial test and the actural production. The 51 charges of slab; ingots (total weighted 6769 ton) have been tested at Benxi Iron & Steel Company, the test results show that the research is succeessed in saving power and the economic benefit is remarkable, such as: (1) Raisng the production of the soaking pits by 1.5 times, (2) Descreasing the heat comsumed by producing 1 ton slab ingots by 0.795×106 kJ: (3) Saving power 3.12 kW h/t (ingot); (4) Descreasing the oxide of steel by 0,5%.
Abstract: Coal-Water Slurry is a kind of solid-liquid suspensions, which has the characteristics of thixotropy.In this paper,the breaking up and the recovering of the structure of CWS is studied first.Then, a easy and simple, but accurate and reliable quantitative method of experiment is introduced to describe the thixotropy of CWS. Studies of thixotropic characteristics of CWS will be in progress from two fields.One is the study of the process of thixotropy, the other is the study of results of thixotropy. In this paper, coefficient A(named structure breaking-up coefficieut) related to time is used to describe the process of thixotropy of CWS; another quantity AT (named absolute quantity of thixotropy) is used to describe the results of thixotropy of CWS. Three factors——shear rate, concentration and temperature of CWS which affect the thixotropy of CWS mainly-are studied. It is discovered that the increase in concentration and shear rate, and the decrease in temperature cause the increase of thixotropy of CWS while the process of thixotropy will be prolonged.
Abstract: In this work, the tension equation taking into account the workpiece section varying along the length has been derived strictly.By the method of using the original algebraical equations which express the rolling process, the static continuous rolling process of 5 # steel angles for φ250×6 +φ300×1 small bar mill has been simulated.
Abstract: In this paper, the sintering mechanism of GF3 high-speed steel powders has been investigated by means of a cylinderically converging explosive method with a ring-shaped flyer.It has been shown that shock waves produce high temperature and high pressure in a few microseconds, which leads to that melting occurs at the interface of the metallic powders and caructure causes inter-particle welding resultion in microcrystaline structure and sintering of powder particles in the rapid solidifying process followed.
Abstract: The topological properties of annealed pure iron have been experimentally investigated by means of serial sectioning method, with emphasis on the characteristics of their distributions. The average values of basic topological parameters have been found close to those of Coxeter's statistical honeycomb or tetrakaidecahedra.The experimental distribution of the number of edges per grain face is lognormal with a mode of four.Empirical linear relations between the number of grain faces (or grain edges and grain corners) and spatial diameters of grains have been established.The experimental results also support the existing empirical linear relations between the geometric standard deviation of the distribution of grain volume and that of the distribution of the number of edges per grain face or the fraction of grain faces with no more than three edges.
Abstract: This paper investigated high temperature HCF, static and dynamic creep behaviours in GH33A superalloys with and without Mg and Zr.HCF notch sensitivity in the two alloys was analysed.Results show that a small amount of Mg and Zr can improve neither HCF properties nor fatigue notch sensitivity. Notch fatigue limit depends on smooth fatigue limit, grain size and notch geometric parameters Kt and λ (stress concentration coeffecient and stress gradient).A small amount of Mg and Zr can intensively prolong secondary creep stage and well develop tertiary creep stage, and so increase stress rupture life and stress rupture ductility significantly.The benificial effect still exists under dynamic creep condition.
Abstract: The Cu K edge EXAFS of amorphous alloy CuxZr1-x(X=33,50) and Cu80 Ti20 were measured.The structural parameters such as distance between atoms and coordination numbers were obtained. In this paper, investigation of the chemical short range order in the systems of Cux Zr1-x and CuxTi1-x is carried out, and the results are presented.There is no chemical short range order ia 50 at% Cu alloy,while increasing the copper content in this kind of systems increases the tendency to order with unlike atoms and decreasing the copper content willincrease the tendency to order with like atoms.
Abstract: Method of modelling is a major question of the time series analysis. Two modelling methods of autoregressive (AR) model based on the LS approach are proposed in this paper.By means of reserving a few data to enter calculating successively,the matrix XTX can be inversed recursively by the inver-sing formula of block matrix or result from the Crout resolving method. Moreover, a quick scalar product algorithm, advanced by S. Winograd, is employed and the relations between vectors or matrices are applied for reducing computational operations.The operations have been largely reduced so that they are less than the operations of normal LS approach, and they can be compared with the famous Marple algorithm and Burg's maximum entropy spectral analysis method.
Abstract: The hobbing machine can hob components such as gears and worm gears with 5 grade accuracy and high accuracy SG-71 worm gearing, if it is provided with the correcting mechanism to compensate its transmission error. We have measured the composition error of the generating gearing chain on the Y3180 hobbing machine, have used FFT program to obtain the frequency spectrum figure, have found out sourc.es of several errors and magnitude of their effects.And then according to these factors we have designed the correcting mechanism, which consists of the correcting cam, the swing arm of the cam and the correcting eccentric gear unit,by using CAD technology. This results in the reduction of lowfrequency error and short-period error.This method can be applied to design the cam of the relieving mechanism of SG-71 worm, so that the inlet relieving and the outlet relieving can be ground in one operation, the production rate can be raised. The short-period error can be compensated and the working stability of SG-71 worm gearing can be increased, if the correcting eccentric gear unit is used.
Abstract: This paper provides kinematic and dynamic analysis for robots with the structure of single-closed kinematic chain.The single-closed kinematic chain is divided into left and right paths for establishing the motion equations of an intermediate link,and then the displacement,velocity and acceleration of the passive joints are derived. On the ground of these equations, the formulas of calculating velocity and acceleration of each link are obtained. Finally, the inverse dynamics of the robots is modelled, using Kane's dynamical equations.
Abstract: This paper proves the existence of mixed linear optimal control in a quadratic criterion, by analysing the characteristics of linear differential operator A and using the properties of semigroups of compact operators and Picard theorem, for one-dimensional diffusion processes. And then, according to the reference[3], the optimal control law has been given in detail. Besides, the results given in the references[1-2]are discussed as the special cases in the paper.
Abstract: Potentiostatic method is mainly used to study the nucleation and growth of molybdenum and their effects on electroplating. It has been shown that the rate-determining step of cathodic reaction in the initial stage is hemispherical nucleation with diffusion controlled growth and the quality of electroplates can be improved by controlling the factors effecting this step. Increase of applied overpotential results in increase of nucleus density rapidly, which is favourable for getting an electroplate with coherent nature.fine grains and smooth surface. Under constant potential a higher temperature leads to a higher nucleus density, which is in favour of electroplating. Increase in concentration of molybdenum usually leads to decrease of nucleus density whether Constant potential or constant current is kept in the electroplating.
Abstract: The mechanism of the effect of various additives on the electrolytic deposition of amorphous Ni-P alloy has been investigated using A C impedance technique. The results show that the detergent,as one of the additives in Ni-P electroplating bath,can improve the quality of the coatings, favouring the formation of amorphous structure. A C impedance technique is an effective technique for studying the mechanism of electroplating process.
Abstract: The diffusivities of hydrogen in as-quenched and annealed metallic glass Fe39Ni39Si8B12Mn2 were measured by volumenometric methode under different temperatures near room temperature. The activation energy of diffusion was calculated from the results obtained. The structural relaxation caused by annealing tends to decrease the frequency's factor DO and the activation energy, The resonant frequencies of the flexural vibration of the samples during the aging were also measared after charging hydrogen. Some closs relation between the resonant frequencies and the hydrogen contents was observed. It shows that the existence of hydrogen in metallic glass tends to decrease the value of roung's modulus and the reduction of which is proportional to the hydrogen content in sample.
Abstract: Using electrochemical method the Fe-P coating of amorphous alloy was prepared.The effect of different electrodepositional conditions on the composition of phosphrous in alloy had been studied. We determined the corrosive behavior and polarization curve of the amorphous alloy. The results indeca-ted that the alloys in acid solution were rather active at the initial period, the phosphorus in amorphous alloy accelerated the process of corrosion,richened the content of phosphorus on the surface and the alloy turned into a passive state.The crystalline temperature and the hardness of the amorphous electro-depositional coating were determined.
Abstract: This paper, on the basis of authors paper[2], Studies further thesystem $\left\{ {_{\frac{{{\rm{dy}}}}{{{\rm{dt}}}}{\rm{=a - }}{{\rm{x}}^{\rm{2}}}{\rm{y}}}^{\frac{{{\rm{dx}}}}{{{\rm{dt}}}}{\rm{=b - }}{{\rm{x}}^{\rm{2}}}{\rm{y}}}} \right.\;\;\;\;\;\;\;(1)$and a result is abtained that if a - b ≤ (a + b)3 holds, system (1) has no limit cycle.It also points out the position of limit cycles of the system (1) when a-b>(a + b)3 holds how it changes with the parameters a, b.
Abstract: Using fractional linear function (also called pseudolinear function) to approximate a function f (x) at a specific point Xo, a iteration scheme for the solution of equation f (x)=0 is developed the variant of the method includes the well-known Hally method. Under the appropriate condition the quadratie convergence is proved.
Abstract: In this paper, Using the Lagrangian equations, the dynamics equations of Steel Robot-1 manipulator of our university is established to explain the physical sense of dynamic equations. By means of the kinetic energy and the potential energy of the manipulator mechanism, the simple relation between the joint torques and the joint angular accelerations are found out. Paul's approximate method is used to simplify the process of the derivation for applying actually.
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
