1990 Vol.3(1)
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THE WORKPIECE TEMPERATURE DISTRIBUTION IN CONTACT ZONE AND BURN MECHANISM DURING CREEP FEED GRINDING
1990, 4(1).
Abstract:
On the basis of improved experiments, in-depth researches on the temperature in contact zone and its variance regularity during creep feed grinding were carried out. The most important experiment result is the workpiece surface tem-perature space-time destribution in contact zone during creep feed grinding. It bring forth new ideas which can be used to explain clearly the temperature characteristics and burn mechanism during creep feed grinding. The conclusion shows that the workpiece burn during creep feed grinding is a typical gradual process with obvious premonition. Therefore the prediction and monitoring of workpiece burn in production can be easily realized.
On the basis of improved experiments, in-depth researches on the temperature in contact zone and its variance regularity during creep feed grinding were carried out. The most important experiment result is the workpiece surface tem-perature space-time destribution in contact zone during creep feed grinding. It bring forth new ideas which can be used to explain clearly the temperature characteristics and burn mechanism during creep feed grinding. The conclusion shows that the workpiece burn during creep feed grinding is a typical gradual process with obvious premonition. Therefore the prediction and monitoring of workpiece burn in production can be easily realized.
1990, 4(1).
Abstract:
This paper deals with the system with planetary transmission, which chiefly consists of the fixed axis transmission and the planetary transmission. Considering the transmission loss, the rigid dynamic equations for the fixed axis transmission and for the planetary transmission are built respectively by using transfer matrix method and lagrange equation. Finally, through combination of these two portions, the rigid dynamic equation of the whole system is extablished.
This paper deals with the system with planetary transmission, which chiefly consists of the fixed axis transmission and the planetary transmission. Considering the transmission loss, the rigid dynamic equations for the fixed axis transmission and for the planetary transmission are built respectively by using transfer matrix method and lagrange equation. Finally, through combination of these two portions, the rigid dynamic equation of the whole system is extablished.
1990, 4(1).
Abstract:
This article studies the erosion distributions and locations of the maximum erosion point due to solid particles impacting on the outside wall in 90-deg variable rectangular-section bends. The particle trajectory computations are based on two gas flow fields, I.e., potential flow and potential plus secondary flow. Finnie's model is used to compute the erosion rate. The computed results are compared with the experimental results for three 90-deg bends with radius ratio R/D of 0.8, 1.2 and 1.6. It indicates that the erosion distributions and maximum erosion locations obtained from computations are in better agreement with experimental data, if the secondary flow is taken into account.
This article studies the erosion distributions and locations of the maximum erosion point due to solid particles impacting on the outside wall in 90-deg variable rectangular-section bends. The particle trajectory computations are based on two gas flow fields, I.e., potential flow and potential plus secondary flow. Finnie's model is used to compute the erosion rate. The computed results are compared with the experimental results for three 90-deg bends with radius ratio R/D of 0.8, 1.2 and 1.6. It indicates that the erosion distributions and maximum erosion locations obtained from computations are in better agreement with experimental data, if the secondary flow is taken into account.
1990, 4(1).
Abstract:
Proceeding from angle changing feature of vibration drilling, zero-phase-difference vibration chip breaking theory is developed for the first time. The theory is suitable for the ductile metal drilling and is in good agreement with experimental results.
Proceeding from angle changing feature of vibration drilling, zero-phase-difference vibration chip breaking theory is developed for the first time. The theory is suitable for the ductile metal drilling and is in good agreement with experimental results.
1990, 4(1).
Abstract:
This paper is concerned with the dynamic merit of robot and the method for the optimization of dynamics in robot design. The optimization of robot dynamics in the worst case design can be put into three categories: 1. Acceleration performance index; 2. Velocity performance indes; 3. Comprehensive performance index. The optimization problem has been expressed as the imnimum with respect to the design parameters and constraints of these performance indices. At last, a simple two-degree-of-freedom mechanism arm is used to illustrate this method.
This paper is concerned with the dynamic merit of robot and the method for the optimization of dynamics in robot design. The optimization of robot dynamics in the worst case design can be put into three categories: 1. Acceleration performance index; 2. Velocity performance indes; 3. Comprehensive performance index. The optimization problem has been expressed as the imnimum with respect to the design parameters and constraints of these performance indices. At last, a simple two-degree-of-freedom mechanism arm is used to illustrate this method.
1990, 4(1).
Abstract:
With the help of direct observation of wear, the processes and mechanism of the wear particle formation and growth were studied. The results showed that the final formation for wear particle usually went through the following stages; The unclear wear particle formation stage characterized by metal plastic flowing of wear surface and dominated by cellular substructure cracking process of the plastic flowing layer; The new born nuclear wear particle growth stage through debris mutual transfer at the iterfaces; The plowing growth stage of the wear particles which have achieved their critical size of mutual transfer growth; The second plowing growth stage of the cracked accumulating layer of wear particle. It was the processes of the wear particle formation and growth that predominated the wear behavior.
With the help of direct observation of wear, the processes and mechanism of the wear particle formation and growth were studied. The results showed that the final formation for wear particle usually went through the following stages; The unclear wear particle formation stage characterized by metal plastic flowing of wear surface and dominated by cellular substructure cracking process of the plastic flowing layer; The new born nuclear wear particle growth stage through debris mutual transfer at the iterfaces; The plowing growth stage of the wear particles which have achieved their critical size of mutual transfer growth; The second plowing growth stage of the cracked accumulating layer of wear particle. It was the processes of the wear particle formation and growth that predominated the wear behavior.
1990, 4(1).
Abstract:
The pure squeeze theory of elastohydrodynamic lubrication in point contacts has been developed in this paper. Accurate viscosity-pressure relationship proposed by Roelands is used in the study. The numerical results show that while a spherical body is dropping vertically toward a flat surface of a half-infinitive solid covered with a thin layer of lubricant, it is only in the final stage of dropping that the squeeze action is significant. In this stage very high pressure, sometimes being more than 3 Gpa, may be generated in the film, causing a surface concave in the central region of conjunction. The shape and the depth of this concave changes little since it fully formed. In the case the mass of the sphere is small and the dropping height of it is not large, the high pressure can rebound the sphere before impact so that to avoid the metal-to－metal contact of the surfaces.
The pure squeeze theory of elastohydrodynamic lubrication in point contacts has been developed in this paper. Accurate viscosity-pressure relationship proposed by Roelands is used in the study. The numerical results show that while a spherical body is dropping vertically toward a flat surface of a half-infinitive solid covered with a thin layer of lubricant, it is only in the final stage of dropping that the squeeze action is significant. In this stage very high pressure, sometimes being more than 3 Gpa, may be generated in the film, causing a surface concave in the central region of conjunction. The shape and the depth of this concave changes little since it fully formed. In the case the mass of the sphere is small and the dropping height of it is not large, the high pressure can rebound the sphere before impact so that to avoid the metal-to－metal contact of the surfaces.
1990, 4(1).
Abstract:
A new method for locus synthesis of planar four-bar linkage is presented. A digital atlas of coupler curves is set up in a micro computer by describing the curve with a group of characteristic numbers. Treated with fuzzy mathematics, a curve in the atlas similar to the desired locus and the dimensions of the four-bar linkage which generates the curve can be found conveniently.
A new method for locus synthesis of planar four-bar linkage is presented. A digital atlas of coupler curves is set up in a micro computer by describing the curve with a group of characteristic numbers. Treated with fuzzy mathematics, a curve in the atlas similar to the desired locus and the dimensions of the four-bar linkage which generates the curve can be found conveniently.
1990, 4(1).
Abstract:
In this paper, constitutive equations and failure strain were used to simulate the quasi-solid stress, strain and hot cracking during solidification in Al-5.14% Cu alloy casting with hot spot and restricted ends. The influence of temperature difference, length and temperature profile of hot spot region have been investigated. Results of investigation indicate that hot spot has important influence on the quasi-solid stress and strain during solidification, and is a main factor in causing hot cracking.
In this paper, constitutive equations and failure strain were used to simulate the quasi-solid stress, strain and hot cracking during solidification in Al-5.14% Cu alloy casting with hot spot and restricted ends. The influence of temperature difference, length and temperature profile of hot spot region have been investigated. Results of investigation indicate that hot spot has important influence on the quasi-solid stress and strain during solidification, and is a main factor in causing hot cracking.
1990, 4(1).
Abstract:
This paper presents a new method on the principle of absolute spectral line intensity. In this method a supernarrow band-pass filter is used instead of a spectromter, arc images taken by infrared image technique are fed into a computer throuth A/D interface to be processed, then physical characteristics such as temperature field and conductivity of the TIG welding arc plasma are obtained. The temperature field and rediation intensity distribution of TIG welding arc plasma are displayed on a color screen after being pseudocolored. The whole measurement is completed by a computer. It takes only two seconds to obtain all the information. Experiments show that this method is fast and simple, correct and visual. It helps to make real-time measurement and control of arc. It opens up a new way to the development of new welding technique and equipment.
This paper presents a new method on the principle of absolute spectral line intensity. In this method a supernarrow band-pass filter is used instead of a spectromter, arc images taken by infrared image technique are fed into a computer throuth A/D interface to be processed, then physical characteristics such as temperature field and conductivity of the TIG welding arc plasma are obtained. The temperature field and rediation intensity distribution of TIG welding arc plasma are displayed on a color screen after being pseudocolored. The whole measurement is completed by a computer. It takes only two seconds to obtain all the information. Experiments show that this method is fast and simple, correct and visual. It helps to make real-time measurement and control of arc. It opens up a new way to the development of new welding technique and equipment.
1990, 4(1).
Abstract:
In this paper by means of the formation of an equivalent physical model the expressions of differential efficiency calculation of differential gear trains have been derived, and the curves deduced from these expressions have been presented. Both of them are a version of representation of the variation regularity mentioned above. They could be used as references in efficiency calculation for the application of differential gear trains.
In this paper by means of the formation of an equivalent physical model the expressions of differential efficiency calculation of differential gear trains have been derived, and the curves deduced from these expressions have been presented. Both of them are a version of representation of the variation regularity mentioned above. They could be used as references in efficiency calculation for the application of differential gear trains.
1990, 4(1).
Abstract:
Using electric contact method via embedded wire in a small hole drilled on gear tooth surface, the turning angles of the gear at open and close circuit can be obtained respectively and the width of instantaneous contact locus then be converted. The measured widths of contact locus of gears with different helical angles and under different loads may be formularized, and the equation of contact stress is then derived. The teeth surface contact fatique test of 16 gears made of tempered 45 steel and 14 gears made of tempered 40Cr steel are performed on a test stand with lock-in torgue whose center distance being of 120mm; their limited contact fatigue stresses obtained in the test can be used, combining with the stress equation in calculation on contact fatigue strength of model JB2940-81 W-N gears.
Using electric contact method via embedded wire in a small hole drilled on gear tooth surface, the turning angles of the gear at open and close circuit can be obtained respectively and the width of instantaneous contact locus then be converted. The measured widths of contact locus of gears with different helical angles and under different loads may be formularized, and the equation of contact stress is then derived. The teeth surface contact fatique test of 16 gears made of tempered 45 steel and 14 gears made of tempered 40Cr steel are performed on a test stand with lock-in torgue whose center distance being of 120mm; their limited contact fatigue stresses obtained in the test can be used, combining with the stress equation in calculation on contact fatigue strength of model JB2940-81 W-N gears.
1990, 4(1).
Abstract:
This paper presents a new model for research of mechanisms with clearances based on Kane's method. As an example, a planar crank-and-rocker mechanism with a clearance is studied. The deduced dynamic equations are exact and simple. Some dynamic properties of the mechanisms at high speed are discovered by numerical results. The model can be easily applied to the study of spatial mechanisms with clearances.
This paper presents a new model for research of mechanisms with clearances based on Kane's method. As an example, a planar crank-and-rocker mechanism with a clearance is studied. The deduced dynamic equations are exact and simple. Some dynamic properties of the mechanisms at high speed are discovered by numerical results. The model can be easily applied to the study of spatial mechanisms with clearances.
1990, 4(1).
Abstract:
Casting under pulsating electromagnetic field is a process in which a mould is put in a copper coil to which pulsating current is connected, after pouring liquid metal into the mould, to produce a pulsating electromagnetic field which exerts pulsating electromagnetic pressure on the liquid metal, so that defects in the casting are eliminated and the cast crystal structure refined. It has been found that solidification under the pulsating electromagnetic field can completely eliminate the macro dispersed shrinkage and micro dispersed shrinkage of Al-5% Cu alloy, increase the compactness of Al alloy by 0.9% and shorten the relative intrusive depth of shrinkage in pure aluminium sample from 0.56 to 0.05. Washing the channel repeatedly between dendrites in liquid-solid region by the metal liquid, caused by the electromagnetic pressure is the main factor in eliminating dispersed shrinkage, and the facilitating of the settling of grains is the reason for the shortening of intrusive depth of shrinkage. The practical experiments were carried out in Harbin Steam Turbine plant and some perfect results were gained.
Casting under pulsating electromagnetic field is a process in which a mould is put in a copper coil to which pulsating current is connected, after pouring liquid metal into the mould, to produce a pulsating electromagnetic field which exerts pulsating electromagnetic pressure on the liquid metal, so that defects in the casting are eliminated and the cast crystal structure refined. It has been found that solidification under the pulsating electromagnetic field can completely eliminate the macro dispersed shrinkage and micro dispersed shrinkage of Al-5% Cu alloy, increase the compactness of Al alloy by 0.9% and shorten the relative intrusive depth of shrinkage in pure aluminium sample from 0.56 to 0.05. Washing the channel repeatedly between dendrites in liquid-solid region by the metal liquid, caused by the electromagnetic pressure is the main factor in eliminating dispersed shrinkage, and the facilitating of the settling of grains is the reason for the shortening of intrusive depth of shrinkage. The practical experiments were carried out in Harbin Steam Turbine plant and some perfect results were gained.
1990, 4(1).
Abstract:
A new criterion of fracture mechanics-stochastic characteristics for ceramic tool fracture based on the analysis of its fracture features in intermittent turning, is proposed in the paper. A series of experiments on mechanical performance for ceramic tool as well as cutting tests on tool life by fracture have been done. The stresses in tool tip are analysed by finite element method. All of these show that the modified distribution function of theoretical tool life by fracture derived from the mentioned new criterion presents a good agreement with the experimental results. SEM analysis on the tool fracture faces indicates the late fracture of ceramic tool appears in fatigue features.
A new criterion of fracture mechanics-stochastic characteristics for ceramic tool fracture based on the analysis of its fracture features in intermittent turning, is proposed in the paper. A series of experiments on mechanical performance for ceramic tool as well as cutting tests on tool life by fracture have been done. The stresses in tool tip are analysed by finite element method. All of these show that the modified distribution function of theoretical tool life by fracture derived from the mentioned new criterion presents a good agreement with the experimental results. SEM analysis on the tool fracture faces indicates the late fracture of ceramic tool appears in fatigue features.
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