Magnesium is an exceptionally lightweight metal as the “21st century the most potential for development and future of the green engineering materials”.It presents a great potential as medical implant material in our body,such as low price,good biocompatibility, good biodegradability as well as participates the metabolism as the positive ion which just inferior to potassium ion,sodium ion and calcium ion in the cell.However,the chemical property of magnesium alloy is so active that it has to suffering the challenge for meeting the requirements of corrosion resistance,abrasion resistance and fatigue resistance.So some surface treatments should be applied to meet the use of long-term implantation. Micro-arc oxidation（MAO）present a great potential as a surface treatment technology, through MAO,in-situ-grown ceramic coating is directly formed on the surface of magnesium alloy,by which its corrosion resistance,abrasion resistance and fatigue resistance are greatly improved.This research will introduce the AZ91D magnesium alloy into the field of oral implants,Micro-arc oxidation technology will be used to AZ91D magnesium alloy surface modification.With the method of experiment and numerical modeling,the corrosion resistance,abrasion resistance and fatigue resistance of AZ91D magnesium alloy with and without Micro-arc Oxidation Coating in oral environment is studied.The main results are as follows:（1）The corrosion resistance of AZ91D magnesium alloy with and without Micro-arc Oxidation Coating is investigated under the experiments of immersion corrosion and electrochemical corrosion.The result indicates that in the immersion corrosion experiment, within 60 days,the weightlessness of untreated samples is 20.97 times that of micro-arc samples,the electrochemical corrosion experiment enhanced the corrosion electric potential E₀ of AZ91D magnesium alloy from-1.45V which without Micro-arc Oxidation Coating in artificial saliva to -0.44V which with Micro-arc Oxidation,corrosion current density I₀ from 7.5×10^-5A/cm² without Micro-arc Oxidation Coating to 5.0×10^-7A/cm² with Micro-arc Oxidation.The corrosion resistance of AZ91D magnesium alloy is greatly improved with Micro-arc Oxidation Coating.（2）The X-ray diffraction（XRD）analysis shows the ceramic coating is mainly composed of some oxides which are similar to spine,such as Mg₂Al₄Si₅O₁₈, Mg_0.87Al_1.83O_3.61,MgSiO₃ and Mg₂Al.Besides this,the ceramic coating also contains some multiple oxides which have magnesium and aluminum in them,the ceramic coating combine tightly with magnesium alloy,it can separate corrosive agent with bulk material, improve the performance of corrosion resistance and abrasion resistance of AZ91D magnesium.（3）The abrasion resistance of AZ91D magnesium alloy with and without Micro-arc Oxidation Coating in the artificial saliva is studied by the wear experiment using the facility of MM-200 which is produced by Nanjing University of Science & Technology. The result shows that the volume loss of AZ91D magnesium alloy without Micro-arc Oxidation Coating is greater than Ti6A14V alloy,the micro-oxidation magnesium alloy is the least.The abrasion resistance of AZ91D magnesium alloy is greatly improved with Micro-arc Oxidation Coating.（4）The abrasion resistance of AZ91D magnesium alloy with and without Micro-arc Oxidation Coating in the artificial saliva is also researched by numerical simulation using the method of finite element.The result shows the similar tendency that the abrasion resistance of AZ91D magnesium alloy is greatly improved with Micro-arc Oxidation Coating.（5）After the AZ91D magnesium alloy is Micro-arc Oxidation treated,the affection to fatigue resistance of the ceramic coating’s thickness and Young’s modulus is studied by finite element.The conclusion is that under the specifically condition of oral environment, the thickness and Young’s modulus of ceramic coating have no essential influence to the fatigue of tooth material.The model will not be destroyed under the cyclic load of infinite times in oral cavity.It is suitable to be denture material to repel fatigue.

Energy-absorbing, thin-walled, impact-resistant metal structures have been widely used in aircrafts, automobiles, trains and ships and other transportation apparatus as the parts of energy dissipation of impact kinetic energy. Therefore, extensive attentions have been drawn on performance investigations of energy absorption of various forms of thin-walled metal structures.This thesis is funded by The National Science Foundation of China (Projects 10332010, 10721062) and The National Basic Research Program of China (Project 2006CB601205).The light-weight, thin-walled metal structures are studied in this paper. A new type of energy -absorbing structure is proposed to investigate the structural deformation mechanism and energy absorption under transient axially compressive impact loadings.The research work can be summarized as follows:(1) System description and analysis of theoretical models of cylindrical metal shell under axial compressive loadings, and numerical simulations for three thin-walled metal structures possessing the same cross-sectional areas loaded by transient axial pressures. The patterns of deformation and performances of energy absorption are compared and analyzed, respectively.(2) Numerical simulation for complicated energy absorption of a truss- reinforced sandwich-type cylinder tube with large displacement and large strain. The numerical model is established based on the nonlinear finite element theory. The property of energy absorption under axial impact loadings is investigated with the proposed model. Various impact speeds and internal truss layouts are used to study how they affect the capability of energy absorption of the compound tube. The numerical results present a valuable reference to design light weight composite structures with the best performance of energy absorption under impact circumstance.(3) Numerical modeling of a cylinder tube with a finite length of crack is presented based on the fracture mechanics theory with an appropriate criterion for fracture. The deformation and damage are predicted and numerically analyzed considering nonlinear transient axial compressive loadings.

Thin-walled workpieces of 45Cr hardened steel are selected as the study object and the problems about the process quality and efficiency of these workpieces are the primary study subject. The aim of research is improving its processing technology, selecting a suitable cutting tool and optimal cutting parameters , increasing productivity and reducing production costs which are achieved by the experimental researchs of turning process, theoretical analysis and turning process of FEM.This paper study says:(1) The cutting performance of cermets tools are studied. The content includes: based on the processing characteristics, several new types of cermets tools are chosed by analysing the material properties of 45Cr hardened steel, and the cutting performance is studied; the cutting force and wear mechanisms of cermets tools, the influence of the chip breaking groove types on the cutting performance and the workpieces quality are developed by doing the single factor experiments of cutting force and tool wear experiment about the thin-walled workpieces; the suitable cermets tool is eventually elected for 45Cr hardened steel workpieces, the cutting force model of cermets tool are found and the appropriate chip breaking groove is elected. This research results can provide a theoretical basis for the selection of a suitable cutting tools.(2) The optimization parameters of the turning process about thin-walled workpieces of 45Cr hardened steel are studied. The optimal cutting parameters are obtained by the taguchi method, the principal component analysis and the response surface methodology, and the optimum objective are cutting force, cutting power, surface roughness and material removal rate, and then the purpose of improving the thin-walled workpieces of the processing quality, reducing production costs and increasing tool life are confirmed through the optimal cutting parameters of the tests.(3) Cutting process of FEM is simulated. A cutting model of the thin-walled workpieces is established by Ansys9.0, the simulation of deformation and stress distribution abou the workpieces under the conditions of clamping, semi-finished process and finished process are achieved. The thermal deformation of the cutting area is simulated, and the contrast result of the wokpieces simulation by using the original fixture and the improved fixture are showed, which is helpful for the in-depth study of the finite element simulation of optimization methods in processing technology.

As a new mechine method,plunge milling is approved by more and more industry because of its high machine efficiency. In the research of the plunge milling, the cutting temperature is very important, the distribution of the cuting temperature is one of the mostly gist of the techniques analysis in the plunge milling. But the research on plunge milling is underway no matter in domestic or abroad. Therefore, take the Titanium alloy as the research object, the distributing of temperature field in the plunge milling are studied in this paper.Firstly, in allusion to the machining characteristic of the plunge milling, theoretical model of the, work piece temperature field is established by using the method of heat source base on the theory of metal cutting and hear transfer.Secondly, semi-artificial thermocouple method which is nipped metal thread in work piece and the infrared thermograph are used to measure cutting field temperature of work piece. The data which are measured by infrared thermograph can prove those which are measured by semi-artificial thermocouple method correctly and reliably. The concrete works are as follows:Finally,used the software ABAQUS to carry out the finite element simulation analysis of the cutting temperature field of the work piece by the method of the given heat source. The comparison of the results of the theoretical model and the finite element simulation and the data of the experiment showed that they had good concordanc.These conclusions could provide plunge milling, tool designing, production practice and surface quality controlling with important indication.

The pressure vessel containing pit defects brings stress concentration at the place of pit because of break of geometrical figure, it makes a certain influence on the security and used life of vessel. According to above consideration, carrying out the following research about the pressure vessel containing pit defects.Firstly, choosing pits in the different situation and different dimension, owing to existing pits, according to request of GB/T19624-2004 Safety Assessment for Pressure Vessels Containing Defects, need carry through safety assessment for the pits which satisfy G₀>0.1.The results indicate that researchful pits are in the allowable range of safety assessment.Seccondly, fatigue analysis is based on the statics analysis, so, making use of finite element software MSC.Patran to carry through statics analysis for the vessels which contain different kind of pits, and making ues of Excel to carry through multianalysis, gainedingaregressive formulas. The results indicate that along with the increase of Z/δ_n, maximal principal stress and stress concentration factor are power increases and along with the increase of X/（?）_n , maximal principal stress and stress concentration factor are power decreases.Thirdly, according to the statics analysis, making use of fatigue design curve in JB 4732 and fatigue analysis software MSC.Fatigue to carry through fatigue life analysis for the vessels which contain different kind of pits, and making ues of Excel to carry through multianalysis, gaineding aregressive formulas. The results indicate that along with theincrease of Z/δ_n, design fatigue life and MSC fatigue life are power decreases and along with the increase of X/（?） , design fatigue life and MSC fatigue life are power increases.

Warm extrusion is one of new technology of finishing rough part between cold extrusion and hot extrusion, but at present one of the potential problem is bad early failure which is occured in its die. In order to put the new technology into practice, it is necessary to research generally on basic parameters and find prime factors of influcing die early failure during warm extrusion process.With the fast development of computer hard, finite element method and computer graphics, the computer aided engineering technology based on numerical simulation is used widely in metal plastic forming field, which actualizes computer emulation of metal forming process.In this paper, based on the detail reviews of the development of warm extrusion die at home and abroad, the forming process of warm extrusion of the yoke is simulated by DEF0RM-3D software with rigid-visco plastic finite element method, stress distribution in different stroke of male die is discussed, and variation law is researched of which the stress of die is increasing with the extrusion force increasing.In this paper, the influence of extrusion temperature, extrusion velocity and the temperature of die preheating to die failure are researched. The research has found that:1.The temperature field of workpiece is uneven during extrusion process. It is apparently higher in the part of smart distortion and contact friction with die than others.2.The reason of die failure is the plastic deformation and the crack because of rapidly cold and hot during extrusion process, when the load and stress is over its allowable load and stress .3.Extrusion force, the load of female die and die stress are bigger when metal overflowed die space and the flow direction of metal is opposite with the movement direction of male die.4. Extrusion force falls down, the stress of female die is low and the trend of plastic distortion is small when extrusion is over with extrusion temperature increasing; however, the higher the temperature of female die surface is, the bigger the trend of plastic distortion is fatigue because of cold and hot, the higher extrusion temperature is.5.The lower the temperature of female die, the smaller the trend of fatigue because of cold and hot, the faster extrusion velocity is; however, the higher the stress of female die is, the smaller the trend of plastic distortion is, the faster extrusion velocity is.6. The lower extrusion force is, the lower the stress of female die is, the smaller the trend of plastic distortion is, the bigger the temperature of die preheating is; however, the higher the temperature of female die surface is, the bigger the trend of fatigue because of cold and hot, the higher the temperature of die preheating is.Hereby, it provided a gist for establishing correctly precautionary technology about die early failure and improving die life.

Warm extrusion die is endured high temperature, high pressure and local stress concentration during it is working, which makes the stress distribution inside the die not uniform, and makes the service life of the warm extrusion die very short. With the development of theories in the fields of heat conduction, elasticity and plasticity mechanics, optimal design and numerical calculation analysis technology, the traditional structure design and intensity check method has left many problems to be researched ulteriorly on the stress distribution inside the die, the accurate calculation and analysis can be made for the finite element model of warm extrusion die with the help of numerical calculation methods, resulting in the actual distribution of stress and strain inside the die. That supplies true and reliable dates used for the intensity calculation, thereby the distribution of stress and strain can be obviously improved, resulting in improvement of the carrying capacity and service life of the die to a large extent.In this paper, the magnetism yoke warm extrusion die is used as research object, the finite element of warm extrusion die is established, the thermal field, thermal stress field, coupled thermal-mechanical strain and coupled thermal-mechanical stress of warm extrusion die are analyzed, structure optimal design has achieved, resulting in some research results as follows.1. Base on the theories in the fields of heat conduction, elasticity and plasticity mechanics, mathematical models about temperature fields and thermal stress fields of warm extrusion dies are built up and boundary conditions under actual physical working environment are determined, the finite element method is used to calculate the temperature fields and thermal stress fields of the warm extrusion die, which discusses the main failure causes of warm extrusion die.2. The intensity calculation and analysis of magnetism yoke warm extrusion die is done accurately and therefore the values of Von Mises stress and strain inside the die as well as their distribution can be acquired during extrusion process.3. The research is done on the analysis and choice of major structure parameters of warm extrusion die, when the whole die cann’t meet the requirement of intensity, the combined die is used to enhance intensity. the research has optimized the combined die under coupled thermal-mechanical condition by ANSYS Parametric Design Language and gets the best data of combined die inside and outside layers dimensions and surplus value.4. The optimal structure of warm extrusion die has achieved.The research results in the paper can be used to do accurate intensity analysis and structure optimal design of warm extrusion dies under actual physical conditions, which is helpful to get rid of the traditional “trial and error” design model of warm extrusion die and establishes the basis of enhancing the quality of die design and shorting design period.

The steel silo is widely used to store dispersed materials in many aspects of industry, such as mining, metallurgy, chemical, electric power, agriculture and the alike. Unlike traditional reinforced concrete silo,the steel silo has many merits such as lightly deadweight, short cycle of construction, investment effectively, craft readily to be modified. Therefore, in recent years, steel silos are used to store the sandy alumina (dry powder) in aluminum smelting industry, the development of which has led to yearly increment of the total production of alumina and the requirement of large-scale, gargantuan steel silo.Recently, the norms and standards between different countries about the design of large-scale steel silo are not identical—-especially stored material loads acting on steel silos and seismic analysis of the whole-silos. Nevertheless, engineering incidents as crack, breakdown still take place in the applying of them.This article takes a large-scale alumina steel silo as its research object,and has established a three dimensional silo model using the general finite element software ANSYS. Detailed calculation and analysis of this structure subject to static and dynamic loading is implemented with finite element simulation.(1) A static analysis considering the most unfavorable situation is studied, calculating the stored material loads, wind loads and snow loads according to the standard, and find that stored material loads is the most effective to other loads when alumina filled up the silo.(2) Assume the alumina powder as a continuous medium, establish a contact silo model. By comparing with result of the former model the result of model considering the alumina powder as equivalent load, the equivalent mechanical parameters of alumina powder are concluded.(3) Dynamic analysis is carried out to obtain the fundamental frequency and vibration modes of this structure, and also obtain the dynamic response under seismic effect through the response spectrum analysis.(4) The time-history analysis is used to calculate the dynamic response of the structure under the three typical seismic waves. The result shows that when considering the seismic as eight-intensity-resistance and rare earthquake, some part of the structure would get into plastic yield.In conclusion, anti-seismic performance of structure is evaluated, and feasible suggestion to further strengthen structure is proposed.

In recent years, planetary rolling process on continous casting of copper tube billiet, which gradually replaces the tradional extrusion process, is an critical technology on short-stage process of copper tube, thus production efficiency maxima bump, product quality fitness, stabilized. However, its dying and processing mostly rest up on limited experience and heuristic foundation. Debugging cycle length, outlay, the product performance and vice had no control, yielding stability and rate of finished products in addition treat ramp out.In order to improve the copper alloy rotating performance of three-roll rotary rolling mill and the efficiency of rotating mill.In this paper, first, the structure principle for the three-roller planetary mill, the rolling mechanism and the movement are introduced. Moreover, relation between the offset angle、the inclined angle and rolling process and distort characteristic of workpiece were detailedly discussed. Whereafter, this paper also is focused on using the finite element method to simulate and analyze the planetary rolling process. A basic geometric model of the planetary rolling millthat considers roll profiles and offset angle of the rolls was constructed. Subsequently, plastic pug is used to simulate the process of copper alloy rotary, also an orthotropic simulating experiment of three-roll planetary mill is processed by orthotropic experimental method. A research about the relationship between parameters (deflecting angle of the roller、the rotating speed of the roller、the friction coefficient of the roller、the initial temperature of plastic pug) of rotating process and the screw-pitch of plastic pug. The results of the experiment are as follows:The effect of product improves greatly when the roller has a 7°deflecting angle; The higher the rotating speed of roller, the better the processing effect. the friction coefficient of the roller and the initial temperature of plastic pug have a great effect on the rotating process, so lower friction coefficient and higher initial temperature are demanded.

Because of the notable advantage of bolt support at technical and economical, now, it has developed a main form of mine laneway and underground engineering in most countries of the world. But, as the complexity of laneway support system, so it is difficulty to determine parameters of anchor support, and difficulty to widely apply in engineering.The paper expounded the development of laneway support at home and abroad, the development of laneway support theory, and the mechanical character of the rock. Base on these, an asymmetry three-dimension model is founded, and to optimize design parameters of bolt support. The paper separately analyze the influence of support time to distortion, the influence of laneway excavation to distortion, the influence of parameters (length, diameter and space between) of bolts to distortion, and the influence of pre-strength of bolts to support effect. Finally, base on the prophase analysis, an asymmetry optimize design project is put forward.After calculate completely, we can distinctly make out the effect of support through displacement maps, stress maps and plastic strain maps of laneway wall rock. And then, pick up displacements of appoint points on the side of laneway, plot the displacement map, quantificational compare support effect of different projects (here the quantificational analysis to models unequal to the quantificational analysis to prototype), then we can find reasonable parameters of support, apply it to engineering practice. It provided a safe and credible method on bolt support design.