1989 Vol.2(1)

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A STUDY FOR THE FILM FORMATION OF ROUGH SLIDER BEARING
1989, 3(1).
[Abstract](2135) [PDF 100KB](96)
Abstract:
It has been proved in industry that the lubrication behaviour of a metal friction pair may be greatly improved by controlling its surface topography. With the average flow model applied to calculate the film formation of rough slider bearing, this mechanism has been successfully expounded in present work.
THE EFFECTS OF TEMPERATURE AND CREEP DAMAGE ON CREEP CRACK GROWTH IN HK40 STEEL
1989, 3(1).
[Abstract](2155) [PDF 227KB](115)
Abstract:
Creep crack growth rates are investigated in compact tension specimens of cast HK40 steel at 830, 850, 871 and 890℃; Apparent activation energies for creep and creep crack growthe are measured in the temperature range 830 890℃; Over limited ranges of stress and temperature, the values of the two energies are close. The creep crack growth behavior of cast is different from that of the creep damaged specimens. The creep crack growth rate of cast specimen increases more quickly than that of creep damaged specimens with the increase of the stress intensity factor. The fine secondary carbides make the creep crack growth rate increase and the time to rupture shorten.
EFFECT OF VOIDS FORMATION ON THE FORMABILITY OF A DUAL-PHASE STEEL
1989, 3(1).
[Abstract](2203) [PDF 358KB](79)
Abstract:
The Dual-Phase steels are high strength steels with the formability of conventional steels of much lower strength, the properties having been associated with a two phase structure of ferrite and martensite. The failure mode of Dual-Phase steel sheet during the forming processes was by plastic instability and voids formation. Forming Limit Diagram (FLD) and the volume fraction of voids were determined in a Mn-Si Dual-Phase steel with different volume fraction of martensite. The effect of voids formation on the critical failure strain has been discussed with the aid of damage mechanics.
A NUMERICAL METHOD FOR SIMULATION OF PRESSURE FORMING OF VISCO-PLASTIC SHEET METAL UNDER PLANE STRAIN CONDITION
1989, 3(1).
[Abstract](2169) [PDF 261KB](63)
Abstract:
A numerical method for simulating the pressure forming of visco-plastic sheet metal under plane strain condition was presented based on the authors' previous work and the related publications. The proposed method is not only able to simulate the process under constant pressure but also to determine the optimal loading pattern in order to keep the strain rate approximately unchanging during the processes. The results obtained by applying the proposed method to some processes were consistent with the data in the publications. The achievements of this study may serve as a guide to define the process parameters for the relevant processes.
SOLIDIFICATION PROCESS OF COMPACTED/VERMICULAR (CV) GRAPHITE CAST IRON
1989, 3(1).
[Abstract](2228) [PDF 340KB](77)
Abstract:
Precipitation of graphite durign eutectic reaction in compated / vermicular (CV) cast irion is clarified by investigation on the solidification process of cast iron treated with various vermicularizing agents. It is found that the eutectic solidfication process consists of two stages: in the first stage, spheroidal graphite is formed and then encircled by austenite shell; in the second stage, vermicular graphite is formed, and due to partial remelting of the austemite shell, the vermicular graphite comes into contact with liquid iron and grows. The investigation shows that spheroidal graphite formed during the first stage of eutectic solidification becomes the starting point of CV graphite.
BAUSCHINGER EFFECT AND BACK STRESS IN DUAL PHASE STEEL
1989, 3(1).
[Abstract](2230) [PDF 404KB](72)
Abstract:
The Bauschinger effect and back stress in Mn-V heat treated dual phase steel have been investigated. The influence of reverse flow and aging at 175℃ on the Bauschinger effect and back stress, and relationship between back stress and microstructural parameters have been measured. The results show that there are Bauschinger effect and permanent softening in the dual phase steel studied. The Bauschinger effect is mainly related to mobile dislocations and dislocation configurations with directionality in their resistance to motion and the back stress in the matrix due to prestrain. Only when the dislications are mobile, the back stress can facilitate dislocations to reverse motion resulting in the decrease of yield stress during the reverse flow and rounding off of reverse fow curve as well as producing Bauschinger effect. The relationship between the back stress and microstructural parameters of dual phase steel were calculated by using the back stress hardening model evolved by Brown and Stobbs for describing back stess hardening mechanism. The calculated results have good corelation with measured results. It shows that the back stress hardening mechanism in dual phase steel bears analogy with that in dispersion hardened alloys. The aging at 175℃ can dispel Baauschinger effect but does not change the value of back stress in dual phase steel. However, the reverse flow can simultanuously decrease or dispel Bauschinger effect and back stress in dual phase steel.
SIMULATION OF CUP-ROD COMPOUND EXTRUSION PROCESS USING UBEF
1989, 3(1).
[Abstract](2219) [PDF 248KB](106)
Abstract:
In this paper, the process of simulating deformating force and metal flow in forming process using UBET is stated and the basic equations of UBET are developed. According to Minimum Upper Bound Power Principle, the deformation force and metal flow in cup-rod compound extrusion for different parameters, such as different reduction rate and different conical angles are simulated using UBET. The deformation models and formulas for calculating flow-out quantities to two ends of exit are also given. The results of experiments show that the theoretical prediction is close to the practice.
THE RATIONAL CONSTRUCTION AND THE TOOTH PROFILE ON CYCLOID DISK OF A LARGE CYCLOID GEARING
1989, 3(1).
[Abstract](2204) [PDF 348KB](118)
Abstract:
On the basis of comprehensive theoretical analysis of the research and experimental achievements resulted at home and abroad since 1972, especially to that of our own since 1977, this article present not only a rational and practical scheme for the construction of large scale cycloid gearings, but also a method of modification for tooth profile of the cycloid disk by use of only conventional technological process to obtain a novel and ideal one. Thus, the tooth surface scoring will be effectively avoided, and the transmitting power as well as the life of the epicyclic arm bearings will considerably increase without increasing its radial size.
THE COMPUTER-AIDED DESIGN OF CYLINDRICAL DIES FOR SHEET BENDING
1989, 3(1).
[Abstract](2226) [PDF 199KB](113)
Abstract:
An idea for the computer-aided design of cylindrical dies for sheet bending is proposed to compensate for the amount of springback in the die design. To implement this idea, some new algorithms are adopted: ⑴ Lagrange interpolation for the real stress-strain relationship of arbitrary materials. ⑵ Piecewise curve spline fit for the curvature function. ⑶ Least square collocation-Powell method in solving non-linear differential equations. Thus, the final shape of a die can be easily obtained by going through this procedure, if the material and the geometry of the workpiece are specified. The idea proposed here can be extended to design more complicated dies.
THE INFLUENCE OF SLIDING SPEED ON THE SCUFFING OF LUBRICATED SURFACES
1989, 3(1).
[Abstract](2267) [PDF 528KB](149)
Abstract:
The scuffing behaviour of steel surfaces lubricated by oil not only depends on the failure of oil film, but also on forming effective reaction film on the surfaces. In this paper, the influence of sliding speed on the scuffing of steel surfaces has been described. At lower sliding speed, when the oil film was broken down the scuffing might not occur and the reaction film could be the scuffing would take place. At high sliding speed, it was easy of scuffing when the oil film was failed, in this case both the surface temperature and the friction coefficient just before scuffing were lower than those of lower sliding speed.
STUDY OF DIFFUSION WEAR IN MILLING TITANIUM ALLLOYS
1989, 3(1).
[Abstract](2203) [PDF 463KB](73)
Abstract:
In this paper diffusion wear in milling of titanium alloys has been investigated. At high speed milling, tool wear is mainly caused by diffusion. The wear pattern is characterized by the combined action of the extension of the cratering wear on the rake face and the glacien wear on the flank. The evidence of diffusion of cobalt and carbon at the interface between the milling cutter and the workpiece has been obtained. It was demonstrated for the first time that a rich carbon layer was formed at the tool / work interface and poor carbon layer was found in a sub-surface layer under the tool flank as the diffusion wear took place. Wear occurred due to brittleness and weakeming in the surface layer can be fully explained by the above mentioned reasons.
STUDY OF A LOW NOISE RELIEF VALVE
1989, 3(1).
[Abstract](2204) [PDF 374KB](158)
Abstract:
This paper deals with the study of the low noise relief valve Type YF-L20H-Y2(A). It describes a noise source that old valve has, the means of decreasing its noise and gives structural principle of this new type of the valve and its computer aided design. Using the program that determines frequency behaviors from the block-diagram directly, the dynamic analyses are carried out on computer. The experiments and manufacture of new valves are in progress. In this paper, sound power level, sound pressure level and other imporatnt quality indexes of the new low noise relief valve are given. Its noise level and other important quality indexes of the new low noise relief valve are given. Its noise level of the low noise relief valve comes up to existing international advanced standards which the same type products have.