1989 Vol.2(2)
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1989, 3(2).
Abstract:
1989, 3(2).
Abstract:
This paper deals with the theoritical basis and calculating method of hydrogen removal process from large forgings. Hobson's calculating method was revised and complemented. We consider that the calculations of hydrogen removal effects in hot working processes must be done in accordance with the hydrogen content of steel and hydrogen distribution character in large forgings. Is was found that the calculating results comformed to the actual situation pretty well when the revised calculating method was widely tried out in industry. It can be used in the production process of large forgings.
This paper deals with the theoritical basis and calculating method of hydrogen removal process from large forgings. Hobson's calculating method was revised and complemented. We consider that the calculations of hydrogen removal effects in hot working processes must be done in accordance with the hydrogen content of steel and hydrogen distribution character in large forgings. Is was found that the calculating results comformed to the actual situation pretty well when the revised calculating method was widely tried out in industry. It can be used in the production process of large forgings.
1989, 3(2).
Abstract:
An investigation has been made on the relationship between microstructure and fatigue property of an ultra-high strength low-carbon martensitic steel. Results of the experiment show that the experimental steel has an excellent fatigue strength and high resistance to fatigue crack propagation when tempered at low temperature. The dominant microstructural feature that contributes to delay the nucleation of fatigue crack is fine and dispersed carbides in dislocated martensite, whereas the orientation difference between adjacent martensite packets, martensite laths and retained austenite in the form of thin interlath film are factors that control tha rate of fatigue crack propagation. Factors affecting deterioration of fatigue behavior in tempered martensite embrittlement have also been analysed and discussed.
An investigation has been made on the relationship between microstructure and fatigue property of an ultra-high strength low-carbon martensitic steel. Results of the experiment show that the experimental steel has an excellent fatigue strength and high resistance to fatigue crack propagation when tempered at low temperature. The dominant microstructural feature that contributes to delay the nucleation of fatigue crack is fine and dispersed carbides in dislocated martensite, whereas the orientation difference between adjacent martensite packets, martensite laths and retained austenite in the form of thin interlath film are factors that control tha rate of fatigue crack propagation. Factors affecting deterioration of fatigue behavior in tempered martensite embrittlement have also been analysed and discussed.
1989, 3(2).
Abstract:
The stochastic models of the usual joints are first extablished through introducing the concepts of Clearance Characteristic Element and Clearance Space. After deriving the probability density function of the joint clearance and making the probabilistic analysis of the resulted kinematic errors, the sampling formulas of the independent variables of the joint clearances are further deduced. Through Monte Carlo simulation, the statistical characteristics and frequency histograms of the kinematic errors are then analysed on computer.
The stochastic models of the usual joints are first extablished through introducing the concepts of Clearance Characteristic Element and Clearance Space. After deriving the probability density function of the joint clearance and making the probabilistic analysis of the resulted kinematic errors, the sampling formulas of the independent variables of the joint clearances are further deduced. Through Monte Carlo simulation, the statistical characteristics and frequency histograms of the kinematic errors are then analysed on computer.
1989, 3(2).
Abstract:
The authors present a hydraulic expanding device of reducing load and put forward the principle of plastic forming, the calculation formulae for designing devices and the qualitative analysis for pressurizing process. In cooperation with the units concerned, the authors revealed the inherent forming law of the hydraulically expanded retaining rings by reducing load method after a series of simulated tests. The laws have direct guide significane on theory and practice for manufacturing 300,000kW retaining rings, as well as the larger one. Some of theoritical studies and experimental verifictions are valuable for this field.
The authors present a hydraulic expanding device of reducing load and put forward the principle of plastic forming, the calculation formulae for designing devices and the qualitative analysis for pressurizing process. In cooperation with the units concerned, the authors revealed the inherent forming law of the hydraulically expanded retaining rings by reducing load method after a series of simulated tests. The laws have direct guide significane on theory and practice for manufacturing 300,000kW retaining rings, as well as the larger one. Some of theoritical studies and experimental verifictions are valuable for this field.
1989, 3(2).
Abstract:
This paper lays stress on an analysis of the mechanism indicating how the noise in the swash plate type piston pumps occurs. Approaches to reduce the noise, a derivation of the formulae for the calculation of the low-noise type of the orifice and triangular groove of the value plate, a calculation, with the help of computer, of the liquid pressure changes in piston chamber, and finally, a confirmation through experiments of the correctness of the design method discussed.
This paper lays stress on an analysis of the mechanism indicating how the noise in the swash plate type piston pumps occurs. Approaches to reduce the noise, a derivation of the formulae for the calculation of the low-noise type of the orifice and triangular groove of the value plate, a calculation, with the help of computer, of the liquid pressure changes in piston chamber, and finally, a confirmation through experiments of the correctness of the design method discussed.
1989, 3(2).
Abstract:
The research and development of turbomachines requires the understanding of the complex three dimensional flow through blade passages including the boundary layers. The non-contact laser anemometry provides the necessary information concerning the velocity and turbulence components even when rotor operates at high rotational speed. This paper mainly reviews systems of laser anemometry having been applied successfully to turbomachinery over last ten years. The characteristic parameters of each system including Laser-Dopplar Anemomtry (LDA) and Laser Two-focus Velocimeter (L2FV) and typical xamples are shown. Finally, some conclusions are drawn considering the advantages and disadvantages of LDA and L2FA for this special application.
The research and development of turbomachines requires the understanding of the complex three dimensional flow through blade passages including the boundary layers. The non-contact laser anemometry provides the necessary information concerning the velocity and turbulence components even when rotor operates at high rotational speed. This paper mainly reviews systems of laser anemometry having been applied successfully to turbomachinery over last ten years. The characteristic parameters of each system including Laser-Dopplar Anemomtry (LDA) and Laser Two-focus Velocimeter (L2FV) and typical xamples are shown. Finally, some conclusions are drawn considering the advantages and disadvantages of LDA and L2FA for this special application.
1989, 3(2).
Abstract:
This paper shows that the 'grindability' of curved surface is an important conecption. From the point of view of grindability, it is concluded that the curved surfaces with special shape are generally ungrindable. They can only be substituted by the approximate curved surfaces ground out, and the key problem is how to grind out the approximate curved surfaces satisfying the required accuracy in engineering. In order to slove this problem, the principle of anomalous conjugation is presented in this article. The groud approximate curved surfaces can substitute the required curved surfaces optimumly, if the principle is applied to it . It has been tested and verified that the principle of anomalous conjugation is applied successfully to the grinding of some complex curved surfaces on cutting tools.
This paper shows that the 'grindability' of curved surface is an important conecption. From the point of view of grindability, it is concluded that the curved surfaces with special shape are generally ungrindable. They can only be substituted by the approximate curved surfaces ground out, and the key problem is how to grind out the approximate curved surfaces satisfying the required accuracy in engineering. In order to slove this problem, the principle of anomalous conjugation is presented in this article. The groud approximate curved surfaces can substitute the required curved surfaces optimumly, if the principle is applied to it . It has been tested and verified that the principle of anomalous conjugation is applied successfully to the grinding of some complex curved surfaces on cutting tools.
1989, 3(2).
Abstract:
The strain energy model (SEM), including both strain energy partitioning (SEP) and strain energy frequency separation (SEFS) developed by the present authors which are the syntheses and modifications of strain range partitioning (SPR), frequency separation (FS) and Ostergren Model, is presented. In comparing the abilities of the above five methods to predict the creep-fatigue lives of three different strength and ductility materials Cr18Ni9Ti, GH36A and GH33A with three different processings. The authors postulate that SEP and SEFS have better predictabilities than the others and thus more significant physical meanings. Finally, the analyses of time-dependent fatigue of GH33A at 700℃ showed the close dependence with the lives.
The strain energy model (SEM), including both strain energy partitioning (SEP) and strain energy frequency separation (SEFS) developed by the present authors which are the syntheses and modifications of strain range partitioning (SPR), frequency separation (FS) and Ostergren Model, is presented. In comparing the abilities of the above five methods to predict the creep-fatigue lives of three different strength and ductility materials Cr18Ni9Ti, GH36A and GH33A with three different processings. The authors postulate that SEP and SEFS have better predictabilities than the others and thus more significant physical meanings. Finally, the analyses of time-dependent fatigue of GH33A at 700℃ showed the close dependence with the lives.
1989, 3(2).
Abstract:
Based on R.H.Yü's Empirical Electron Theory of Solids and Molecules, the austenite structure in industry alloys is analyzed by using the Bond Length Difference (BLD) method. Combined with obtained information of Valence Electron Structure (VES) of the materials, the following are proposed: 1. C-Me segregation regions exist in the austenite of Fe-C-Me alloys. 2. C-Me segregation resists phase transformation. The structures, morphologies and properties of transformed products can be changed by the murual action of such resistance and driving force of phase transformation. 3. New explainations on some metallography problems can be made from C-Me segregation: ⑴ The formation residual austenite; ⑵ The incompleteness of bainite transformation in some alloys and bainite morphology variation; ⑶ The formation of both dislocation and twin martensite.
Based on R.H.Yü's Empirical Electron Theory of Solids and Molecules, the austenite structure in industry alloys is analyzed by using the Bond Length Difference (BLD) method. Combined with obtained information of Valence Electron Structure (VES) of the materials, the following are proposed: 1. C-Me segregation regions exist in the austenite of Fe-C-Me alloys. 2. C-Me segregation resists phase transformation. The structures, morphologies and properties of transformed products can be changed by the murual action of such resistance and driving force of phase transformation. 3. New explainations on some metallography problems can be made from C-Me segregation: ⑴ The formation residual austenite; ⑵ The incompleteness of bainite transformation in some alloys and bainite morphology variation; ⑶ The formation of both dislocation and twin martensite.
1989, 3(2).
Abstract:
The compositions and structutes of grinding oxide films on the surface for both precise and plain bearings of GCr15 steel have been investigated by means of Auger electron spectroscopic depth profile analysis as well as deconvolution and the peak decomposition investigation of X-ray photoelectron spectroscopic depth profile. The results show that grinding oxide films are mixture of Fe and its oxides, and the bearing with superior mechanical properties possesses the thinnest oxide film.
The compositions and structutes of grinding oxide films on the surface for both precise and plain bearings of GCr15 steel have been investigated by means of Auger electron spectroscopic depth profile analysis as well as deconvolution and the peak decomposition investigation of X-ray photoelectron spectroscopic depth profile. The results show that grinding oxide films are mixture of Fe and its oxides, and the bearing with superior mechanical properties possesses the thinnest oxide film.
1989, 3(2).
Abstract:
The synthetic effects of alloys on matrix structure and mechanical properties of as-cast austempered ductile cast iron (ADI) have been comprehensively studied. The researches show that it is feasible to obtain as-cast ADI by adding alloys. The tensile strength can reach over 900MPa and the elongation over 3%. The as-cast ADI has good low-temperature impact toughness. At -40℃, the impact toughness (CVN) is 4.6 J. In as-cast condition, the fracture toughness is 54 MPam1/2 and can be enhanced nearly 20% after tempering at 325℃. The researches show that retained austenite (Ar) has a favourable effect on mechanical properties.
The synthetic effects of alloys on matrix structure and mechanical properties of as-cast austempered ductile cast iron (ADI) have been comprehensively studied. The researches show that it is feasible to obtain as-cast ADI by adding alloys. The tensile strength can reach over 900MPa and the elongation over 3%. The as-cast ADI has good low-temperature impact toughness. At -40℃, the impact toughness (CVN) is 4.6 J. In as-cast condition, the fracture toughness is 54 MPam1/2 and can be enhanced nearly 20% after tempering at 325℃. The researches show that retained austenite (Ar) has a favourable effect on mechanical properties.
1989, 3(2).
Abstract:
Numerical simulation with rigid plastic finite element method and experimental investigation with visioplasticity method and Morie technique were used to study the effect of die profiles on the flow during metal extrusion. Velocity, strain rate, stress and temperature field in the workpieces extruded with conical die, cosine curved die, constant strain rate curved die, hyperbolic curved die, elliptical curved die and Richmond curved die as well as newly designed sine curved die were calculated. Boundary conditions of F.E.M.were checked with Morie pattern. Results show that among the seven kinds of dies, the best one is the newly designed sine curved die and the next is the cosine curved die. These dies carry out lower extrusion load and more homogeneous strain distributions.
Numerical simulation with rigid plastic finite element method and experimental investigation with visioplasticity method and Morie technique were used to study the effect of die profiles on the flow during metal extrusion. Velocity, strain rate, stress and temperature field in the workpieces extruded with conical die, cosine curved die, constant strain rate curved die, hyperbolic curved die, elliptical curved die and Richmond curved die as well as newly designed sine curved die were calculated. Boundary conditions of F.E.M.were checked with Morie pattern. Results show that among the seven kinds of dies, the best one is the newly designed sine curved die and the next is the cosine curved die. These dies carry out lower extrusion load and more homogeneous strain distributions.
1989, 3(2).
Abstract:
Starting from the basic theories of plasticity for continuous media and using superplastic constitutive equations with varying m value, the coefficient of height limit D for free bulging at constant pressure, the coefficient of radius limit D' for filling the grooves at constant pressure and a simple method of deciding the limit height and the limit radius by D and D' are proposed. The theoretical conclusions have been proved identical to experimental results. So, D and D' can be taken as the important technical parameters for superplastic bulging.
Starting from the basic theories of plasticity for continuous media and using superplastic constitutive equations with varying m value, the coefficient of height limit D for free bulging at constant pressure, the coefficient of radius limit D' for filling the grooves at constant pressure and a simple method of deciding the limit height and the limit radius by D and D' are proposed. The theoretical conclusions have been proved identical to experimental results. So, D and D' can be taken as the important technical parameters for superplastic bulging.
1989, 3(2).
Abstract:
By using a new test method "plane strain compression in different orientations", the authors have studied the anisotropic hardening effect of α-brass subjected to several plastic strain paths and determined the loading function of composite model. The conclusion shows that this testing method is suitable for studing of large plastic deformation and that the function of composite model for α-brass subjected to various strain paths is always suitable.
By using a new test method "plane strain compression in different orientations", the authors have studied the anisotropic hardening effect of α-brass subjected to several plastic strain paths and determined the loading function of composite model. The conclusion shows that this testing method is suitable for studing of large plastic deformation and that the function of composite model for α-brass subjected to various strain paths is always suitable.
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