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1.
The wear failure course of gas-valve/valve-seat in engine was investigated with a simulating tester. The results show that the failure of the contact conical surface is mainly caused by the elastic and plastic deformation and the fatigue micro-crack and spalling. The creep-deformation and corrosion atmosphere accelerated wear failure course at the high temperature. The wear failure course of the gas-valve/valve-seat in engine follows general wear rules of mechanical elements, but the rate of wear in the sharp wear stage is faster. 相似文献
2.
Microstructure and wear resistance of electro-thermal explosion sprayed stellite coating used for remanufacturing 总被引:1,自引:0,他引:1
Electro-thermal explosion directional spraying was used to prepare the stellite coating on substrate of the AISI 1045 steel.
The morphologies of cross-section and worn scar, porosity, distribution of elements, micro-hardness and wear resistance of
the coating were determined by means of SEM, EDAX, micro-hardness tester and sliding wear tester. Because of the compact construction,
good bonding and high hardness, the coating is characterized by good wear resistance. The results show that the mainly failure
mode of the stellite coating is micro-plowing.
Foundation item: Project(2003AA331130) supported by Hi-tech Research and Development Program of China; Project(50235030) supported by the
National Natural Science Foundation of China 相似文献
3.
Wang Hai-dou Xu Bin-shi Wei Shi-cheng Zhang Xian-cheng Jin Guo Jiang Yi 《中南工业大学学报(英文版)》2005,12(2):30-33
The guide-pieces, used in the process line of steel rolling, were the important components. The guidepieces, which were slide
contacting with the rolled-piece, had a high temperature and high speed. The wear was very serious. The results from failure
analysis showed that there were three failure forms in the guide-pieces: the first was the wear during heat friction, the
second was the heat fatigue under the cycle of deep heating and deep cooling, and the third was the impact rupture. Among
them, the wear was the main reason. To the wear of guidepieces, there were four mechanisms, namely abrasive wear, adhesive
wear, fatigue wear and corrosion wear. The failure analysis to the guide-piece laid the foundation for its remanufacturing.
Foundation item: Project(50235030) supported by the National Natural Science Foundation of China 相似文献
4.
The severe wear of separating ring is considered to be a main reason which leads to the improper declutch of the main clutch
of heavy vehicles. The wear mechanism of the separating ring is not well understood. Scanning electron microscopy and transmission
electron microscopy were employed to analyze the surface features and dislocation characteristics of the separating ring.
The typical features of furrows and rolled tongue-like metal were found on the surface of separating ring by scanning electron
microscopy observation, which can be considered as a major indication of the grain-abrasion. A zone of high density dislocation
was noted on the subsurface of the separating ring by transmission electron microscopy observation, which implies the contribution
of the severe impact on the surface of the separating ring in the wear process. The influences of the structure of the separating
ring, the service condition and the in-service stress distribution on the wear behavior, were also analyzed. The results show
that the failure of separating ring results from the impact wear and grain-abrasion together with the plastic deformation.
Foundation item: Project(41327040101) supported by the Pre-research Fund of General Armament Department; project(51489010104QT0101) supported
by the Fund of State Key Laboratory of Re-manufacture Technology 相似文献
5.
An automatic brush-plating system was developed for component remanufacturing. With this system, Ni/nano-alumina composite
coatings from an electrolyte containing 20 g/L nano-alumina particles were prepared. Microstructure, surface morphology, microhardness
and wear resistance of automatically plated coating and manually plated coatings were investigated comparatively. The results
show that the automatically plated coatings are relatively dense and uniform and have lower friction coefficient of 0.089
under lubricant condition, when compared with manually plated coatings with friction coefficient of 0.14.
Foundation item: Project(50235030) supported by the National Natural Science Foundation of China; Project(G1999065009) supported by the National
Basic Research Program of China 相似文献
6.
Ni/n-SiO2 composite coating was electrodeposited by brush-plating with pulse-reverse current(RC). The morphology, hardness, and tribological
properties of the coating were investigated and compared with those of Ni and composite coatings electrodeposited with direct
current (DC). The results indicate that Ni/n-SiO2 composite coating electrodeposited by RC, because of RC and the nano powders, has denser coating, finer crystal grains, higher
hardness (HV650.0, nearly 1.5 times higher than that of Ni coating electrodeposited by DC) and lower friction coefficient
(nearly 0.62), as a result, in the wearing experiment, the Ni/n-SiO2 composite coating electrodeposited by RC has the least worn loss. So this kind of coating has better wear resistance. And
RC electro brush-plating can be used as a new technology of brush-plating in the area of wear resistance.
Foundation item: Project (50235030) supported by the National Natural Science Foundation of China; Project (51489020104JS9102) supported
by the National Key Laboratory for Remanufacturing 相似文献
7.
Virtual manufacturing is fast becoming an affordable technology with wide-ranging applications in modern manufacturing. Its
advantages over existing technology are primarily that users can visualize, feel involvement and interact with virtual representations
of real world activities in real time. In this paper, a virtual cutting system is built which can simulate turning process,
estimate tool wear and cutting force using artificial neural network etc. Using the simulated machining environment in virtual
reality (VR), the user can practise and preview the operations for possible problems that might occur during implementation.
This approach enables designers to evaluate and design feasible machining processes in a consistent manner as early as possible
during the development process.
Foundation item: Projects (50475117, 50175081) supported by the National Natural Science Foundation of China; project (033181611) supported
by the Science and Technology Commission of Tianjin Municipal 相似文献
8.
Fe-Al/Cr3C2 coatings were sprayed on low steel by high velocity arc spraying(HVAS) technology. The influences of oxides on erosion, corrosion and wear behavior for high velocity arc sprayed Fe-Al/Cr3C2 coatings were studied. The results show that HVAS-sprayed Fe-Al/Cr3C2 coatings have good erosion, heat corrosion and wear resistance. The erosion resistance improves with the increase of the temperature. On one hand, the ferrous oxides are incompact, so they peel off the surface of the coatings easily during the high temperature erosion. On the other hand, compact Al2O3 films on the surface can protect the coatings. 相似文献
9.
This paper used Baumel Jr. and Seeger’s approach estimating fatigue parameters of 48MnV with 3Cr13 coatings. The fatigue life
of the crankshaft of a six-cylinder engine, repaired by twin arc spraying 3cr13 deposits, is respectively calculated using
different damage model such as S-N method, normal strain approaches, SWT-Bannantine approaches, shear strain approaches, and
fatemi-Socie method based on dynamical simulation and FE analysis of crankshaft. The results indicate that the traditional
calculation is conservative and that the life of crankshaft repaired by arc spraying is sufficient.
Foundation item: Project (50235030) supported by National Natural Science Foundation of China 相似文献
10.
C/C-SiC composites with SiC island distribution were prepared via a new processing route. The fabrication process mainly included
silicon infiltration by ultrasonic vibration, chemical vapor deposition (CVD), siliconizing, liquid phase impregnation and
carbonization. The wear and friction properties were tested by an MM-1000 wet friction machine. The results show that SiC
phases are mainly distributed between carbon fibers and pyrocarbons as well as among the pryocarbons. The dynamic friction
coefficient of the composites decreases gradually from 0.126 to 0.088 with the increase of the surface pressure from 0.5 to
2.5 MPa at the same rotary speed. Furthermore, under the constant surface pressure, the dynamic friction coefficient increases
from 0.114 to 0.126 with the increase of the rotary speed from 1 500 to 2 500 r/min. However, the coefficient decreases to
0.104 when the rotary speed exceeds 4 500 r/min. During the friction process, the friction coefficient of C/C-SiC composite
is between 0.088 and 0.126, and the wear value is zero after 300 times brake testing.
Foundation item: Project(2006CB600901) supported by the Major State Basic Research and Development Program of China; Project(0991015) supported
by Guangxi Science Found, China; Project(200808MS083) supported by Guangxi Education Department Found 相似文献
11.
The life cycle index of remanufactured engines was assessed by using the method of life cycle assessment (LCA). A remanufactured
engine of a certain domestic brand was taken as researching object. Engine reproducing engineering was investigated from three
aspects which were energy, material and environment. The application of LCA on remanufacturing engines was discussed in detail
with a practical case. The results indicate that remanufacturing an engine can save 55 kg steels, 8.3 kg aluminum and 113
kW · h electric powers and reduce emissions of 565 kg CO2, 6.09 kg CO, 1.01 kg NO
x
, 3.985 kg SO
x
and 288.725 kg solid waste. The remanufacturing of engines possesses great economic value and practicability.
Foundation item: Project (50235030) supported by the National Natural Science Foundation of China 相似文献
12.
The surface modified nanocopper particles were prepared with chemical reduction method. The wear test was carried out on a
T-11 ball-on-plate friction and wear tester made in Poland. The material of the upper sample was GCr15 and the counterpart
was AISI-1045 steel. The morphologies of the worn surfaces of the samples were observed by optical microscope and scanning
electron microscope, while the element distributions on the worn surfaces were determined by means of electron microprobe
analysis. As the results, a film mainly made of Cu is formed on the worn surface. The film on the surface of the still upper
sample is thicker than that formed on the revolving counterpart. At the edge of the groove of the worn surface made by the
milling before test there is Cu element observed obviously, but there is not any Cu element in the bottom of the groove. A
possible action mechanism of the film is suggested. The friction movement can induce reactivity of the metal and continuously
produce activation surface. It benefits the film formed by nano-Cu in lubricant on the worn surface. Hardness and modulus
of nano-Cu films were successfully measured and analyzed by the nanoindentation instrument. The results show that the hardness
and modulus of the films are lower than those of the initial surface.
Foundation item: Project (50235030) supported by the National Natural Science Foundation of China; Project (G1999065009) supported by the
National Key Basic Research Special Foundation 相似文献
13.
The end-of-life vehicle recycling was studied based on the disassembly. The end-of-life recycling and the disassembly were
reviewed and discussed. A disassembly experiment of an end-of-life engine was carried out, which strictly recorded the process
of dismantling. Based on the results, a model of the end-of-life recycling was presented. In this model, the end-of-life parts
were classified by three ways which included to recycle directly, to recycle after remanufacturing and to discard. By using
this model, the dismantling efficiency and the recycling rate can be improved. Also, it obtains a good result after used in
a dismantling factory.
Foundation item: Key Project (50235030) supported by the National Natural Science Foundation of China 相似文献
14.
Directly searching method for slip plane and its influential factors based on critical state of slope 总被引:3,自引:1,他引:2
In order to determine the slip plane of slope directly by the calculation results of strength reduction method, and analyze
the influential factors of slope stability, a numerical model was established in plane strain mode by FLAC3D for homogeneous
soil slope, whose parameters were reduced until the slope reached the critical state. Then FISH program was used to get the
location data of slip plane from displacement contour lines. Furthermore, the method to determine multiple slip planes was
also proposed by setting different heights of elastic areas. The influential factors for the stability were analyzed, including
cohesion, internal friction angle, and tensile strength. The calculation results show that with the increase of cohesion,
failure mode of slope changes from shallow slipping to the deep slipping, while inclination of slip plane becomes slower and
slipping volume becomes larger; with the increase of friction angle, failure mode of slope changes from deep slipping to shallow
slipping, while slip plane becomes steeper and upper border of slip plane comes closer to the vertex of slope; the safety
factor increases little and slip plane goes far away from vertex of slope with the increase of tensile strength.
Foundation item: Project(20060533071) supported by the Doctoral Program Foundation of Higher Education of China; Project (20060400264) supported
by China Postdoctoral Science Foundation; Project (50774093) supported by the National Natural Science Foundation of China;
Project (1343-74236000014) supported by Graduate Student Innovation Foundation of Hunan Province, China 相似文献
15.
Nie Xin-min Gui Rong Zhao Hong-shan Ma Da-long Li Deng-qing Yuan Hong Huang Zu-fa 《中南工业大学学报(英文版)》2005,12(1):310-312
Objective Tacrolimus is an immunosuppressive drug with narrow therapeutic range and wide interindividual variation in its pharmacokinetics.
Tacrolimus is a substrate of cytochrome P450(CYP)3A5. The aim of this study was to evaluate whether the A6986G polymorphism
is associated with tacrolimus concentration /dose ratio. Methods Fifty-two Chinese renal transplant patients were enrolled in this study. Their body weight, dosage and concentration of tacrolimus
were observed. CYP3A5 genotype was determined by polymerase chain reaction followed by restriction fragment length polymorphism
analysis. Results A significant association was found between tacrolimus levels per dose/kg/d and CYP3A5 gene A6986G polymorphism (P<0.001). The CYP3A5 * 3 * 3 patients have a significantly higher tacrolimus level/dose than CYP3A5 * 1 * 1 and CYP3A5 * 1
* 3. Conclusions CYP3A5 gene A6986G polymorphism is associated with tacrolimus pharmacokinetics and dose requirements. Pharmacogenetic methods
could be employed prospectively to help the dose selection and to individualize immunosuppressive therapy according to the
result.
Foundation item: Project (03GZ3072) supported by the Science and Technology Department of Hunan Province; project (2004035206) supported by
the China Postdoctoral Foundation and project (30300383) supported by the National Natural Sciences Foundation of China 相似文献
16.
In order to improve the friction-wear properties of the C/C composites for aircraft brake pairs, the friction behavior of samples with infiltrating Si was investigated. The influence of Si smearing thickness on friction properties was studied in detail. The results show that with the increase of Si smearing thickness and β-SiC content, the friction coefficient reduces from 0. 40 to 0. 30; the linear wear of stators increases from 2. 0 μm to 18. 9 μm per cycle, and that of rotors increases from 1. 4μm to 22. 6 μm per cycle; mass wear of stators increases from 20. 6 mg to 126. 9 mg per cycle, and that of rotors increases from 13. 7 mg to 166. 2 mg per cycle. On the other hand, when a large number of inhomogeneous β-SiC particulates are performed, friction surfaces of the samples flake off layer by layer and many nicks are observed. 相似文献
17.
A new method was proposed to predict the limited compaction grouting pressure for the soft soils. Theoretical basis of the
method considered the conical shear failure above the grout bulb. Using the Mohr-Coulomb yield criterion as the initial yield
function, the limited compaction grouting pressure was determined, according to the softening elastic-plastic model based
on the conventional triaxial compression tests to simulate the strain softening soils. The small strain in the elastic zone
and large stain in the plastic zone and the rational yield function for the strain softening phase stage, the analytical solutions
to the compaction grouting pressure were presented. The results indicate reasonable agreement and show a good potential of
the proposed method for rationally optimizing the design of compaction grouting operations.
Foundation item: Project (200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China; Project
(09JJ1008) supported by Hunan Provincial Natural Science Foundation of China 相似文献
18.
Sand-wear resistance of nano scale alumina particle reinforced nickel matrix composite coating (n-Al2O3/Ni) prepared by brush electroplating technique was investigated via wear tests in sand-contaminated oil lubricant, comparing
with that of AISI1045 steel and brush electroplated Ni coating. Effects of testing load, sand content and sand size on worn
volume of the three materials, and also coating surface roughness on worn volume of the brush electroplated coatings were
accessed. Results show that the worn volume of all the three materials increases with increasing of testing load, sand content
and sand size. In the same conditions, n-Al2O3/Ni composite coating has the smallest worn volume while AISI1045 steel has the largest because of the n-Al2O3 particle effects. As to n-Al2O3/Ni and Ni coatings, the surface-polished coatings have obviously lower worn volume than the as-plated coatings. The brush
electroplated n-Al2O3/Ni composite coating was employed to remanufacture the sand-worn bearing seats of a heavy vehicle and good results were gained.
Foundation item: Project (50235030) supported by the National Natural Science Foundation of China; Project (51489020104ZD0401) supported
by the National Key Laboratory for Remanufacturing; Project(51418060105JB3058) supported by National Defence Foundation 相似文献
19.
Design of wear-out-failure in-situ repair parts by environment-friendly nanocopper additive 总被引:1,自引:0,他引:1
Oleic acid surface-modified Cu nanoparticles with an average size of 20 nm were prepared by liquid phase reducing reaction.
The tribological performance and mechanism of nanocopper as additive were studied by means of tribotester, scanning electron
microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and nanoindentation instrument. The results indicate that the
modified nanocopper additive can significantly improve the wear resistance and reduce friction coefficient of base oil. A
copper protective film is formed and contributes to the excellent tribological properties of nanocopper additive. On the basis
of the film forming mechanism, a new in-situ repair method was designed and used to repair wear-out-failure injection pump
plunger and barrel. Furthermore, the current research progress of nanoparticles as green energy-saving lubricating oil additives
were presented.
Foundation item: Project (50235030) supported by the National Natural Science Foundation of China 相似文献
20.
Ge Sheng-lei Xie Ding-hua Chen Zhu-chu Xiao Zhi-qiang Yang Xin-min 《中南工业大学学报(英文版)》2005,12(1):313-316
Objective This pilot-study was designed to evaluate the feasibility of cell transplantation into guinea pig cochlea. Methods Marrow stromal cells were labeled with DAPI, and then implanted into the cochlea of guinea pig. The existence and differentiation
trend were observed roughly two weeks later by histologic analysis. Results Transplant-derived marrow stem cells survived in cochlea two weeks later with a trend of attaching to cochlear architecture
but not differentiate into neuron. Conclusions Transplant-derived marrow stem cells can survive in cochlea, and cell transplantation may be a useful strategy in inner ear
diseases.
Foundation item: Project (30000094) supported by the National Nature Science Foundation of China; project supported by the Postdoctoral Foundation
of Central South University 相似文献