| Fatigue life of the production is an important index of moderndesign. Recently years, the market contest of automobile industry ismore and more intense. Update and change generation is more and morerapid, It is increasingly regarded by automobile production company andresearch and development personnel to the essentiality of fatigue lifeestimate of components and parts in production design. And the analysisand forecast of fatigue life of automobile components and parts, whichbase on FE have been applied in overseas automobile company. Comparingthe method with the traditional method which can just "check up", cannot "forecast", It can provide the fatigue life distributing figureof components and parts surfaces, can compare the fatigue lifedifference due to different design under definite load chart, can judgefatigue life weakness position of components and parts in design phase,and can avoid unreasonable life distribution in advance. So this methodcan reduce the quantity of trial sample machines and sample parts, canreduce the exploitation period of production, accordingly depress theexploitation cost, and enhance the market contest power.At present, cold extrusion shaping process is among the bestprocess of the net shaping in material forming processes. The processis high accuracy, stable quantity and very suitable for production inbulk. With the development of the automobile, especially the car, itis required that higher performance, lower cost, the less consumes. Theadopting cold extrusion shaping process makes net shape the importantand complicated car parts are the development trend of the automobilemanufacturing industry nowadays. Another advantage of cold extrusionshaping process lies in products themselves, especially surface and asubsurface of the parts can keep the cold-harden appearance. Itsresidual press stress of the surface not only can raise the hardnessand strengths of the materials, but also can raise fatigue life of theparts. But, at present, cold extrusion process design is the entry-levelstage and still depended on the engineer's personal empirical. How tobuild up the relation between cold extrusion process and fatigue life,when we draw up cold extrusion process, can predict its performance andfatigue life in advance, have already become study process, materialand intelligences analysis system of the experts need the problem forresolution urgently. Up to now, various cold extrusion process integration system orcold extrusion process parameter fuzzy optimization projects withoutability to analyze the parts'the foece and fatigue life after coldextrusion process. So at present, Based on the research of coldextrusion process and fatigue life intelligent analysis system stillblank. This paper discuss the process establish "intelligent analysissystem of automobile parts of cold extrusion process and the fatiguelife", according to the process of shaping up, force and fatiguedestroy of cold extrusion parts, I hold the engineering problem of coldextrusion automobile parts as a system, hold the residual stress as abridge, base on plastoelasticity theories, elasticity mechanicstheories and fatigue failure theories, use MSC.SuperForm,MSC.Marc和MSC.Fatigue and so on software as a platform, establish intelligentanalysis system of automobile parts of cold extrusion process and thefatigue life. Mostly research work of the paper as follows: ⑴Through researching the analysis function and interfacefunction of various software, put forward the base of theory andtechnology premise condition of establishing system. Cold extrusion plastic deformation can produce residual pressurestress on parts surface and subsurface, the many -year study showed,this residual stress is the chiefly factor of influence gap partsfatigue performance, different cold extrusion process parameter mustbe produce different residual pressure stress field distributing,consequently make different fatigue life of parts, and the mostreasonable process parameter must be produce the most reasonableresidual stress field distributing, consequently make the longestfatigue life of parts, based on above consideration, It is provided withfar-reaching realism significance to research the relation of coldextrusion process parameter and fatigue life, according to the residualstress as a bridge. But the research treat of cold extrusion process,the check of residual stress and lots of fatigue trial, so It is verydifficult to develop this research in finite cost and trial condition. In recent years, the rapid development of numerical simulationtechnology and computer technology provide new idea for development ofthe research. Elastoplasticity FE numerical simulation can reserveresidual stress, can put up force analysis too, and fatigue imitateanalysis can forecast fatigue life, based on above FE analysis, so itwill be premise condition that the system can or not build whether ornot these software can interface each other. With the continual updateof version, the interface function update continually too, consequentlyIt is possible to make positive pass between FE model and residual stress.Based on above analysis, through researching the analysis and interfacefunction of various software, the author decided use the analysis systemwhich is made of MSC.SuperForm,MSC.Marc,MSC.fatigue three software. (2) System theory, general structure frame, function and keytechnology problem Through the process research of cold extrusion from figuration touse, We know that automobile cold extrusion parts can just completewhole lifecycle including three phase: the first phase cold extrusionforming; the second phase force produce elastic deformation; the thirdphase accumulative damnification fatigue destroy. Referring to themainly principles are too mainly as follows three fields: cold extrusionforming numerical simulation principle ----metal bulk forming 3D bigdeformation elastoplasticity FE method; fact force numericalsimulation principle ----3D linear elasticity FE method; high cyclefatigue life forecasting principle ----nominal stress method (S-Nmethod). So the system makes into three functions module namely coldextrusion numerical simulation module, fact force numerical simulationmodule and fatigue life forecasting module, they and analysis flow makeup of system whole frame. The numerical simulation process exist below 5 field keytechnology problem: geometry description of die cavity, contactanalysis including boundary condition, contact algorithm and contactdefinition and so on, material model, mesh regeneration and frictionmodel etc. For different problem type, the resolvent of these keytechnologies is different. So we must be use given analysis in givensituation, the paper with example explains the resolution method of keytechnology, which have been referred in spline extrusion. (3) Aim at involute transmission shaft, establishing systemanalysis flow The section has analyzed the condition of spline cold extrusionforming, according to circle symmetrical characteristic of splinestructure and analysis style, has built hexahedron with eight nodes 3Delastoplasticity FE model, through define initial condition, boundarycondition, material model, contact condition, friction factor and jobcondition, put up spline cold extrusion numerical simulation, put upquality analysis for the result, and have obtained spline deformationprinciple through across-vertical every position slice. Secondly,reserved and transferred FE model and residual stress field after coldextrusion, in software, put up torsion force analysis, obtainstress-strain field. Finally, through interface technology the resultis transmitted into MSC.Fatigue software, combining fact materialfatigue performance data and load-time course etc., obtain fatigue lifenumerical and its distributing, sequentially establish the principlebetween the residual stress which is reserved by cold extrusion historyand fatigue life. (4) Aim to fatigue life, optimize cold extrusion spline processparameter For one thing research the influence different length of billetto spline extrusion power, the most equivalent plastic strain andsimulation time, find out cold extrusion spline belong to forwardextrusion, its deformation course is metal steady flow, and obtain theconclusion that spline length has not influence to extrusion power andthe dimension of stress and strain, according to the characteristic offorming and simulation, adopt billet with 40mm in length, reducesimulation time, improve the efficiency of numerical simulation. Startwith the lost steady phenomenon billet is upsetting easily at cavitydie entrance, research the influence billet diameter, working landwidth, cavity die entrance half angle and friction factor etc. to splineformability, extrusion power, die force, equivalent plastic strain andequivalent stress, optimize the most excellent billet diameter withφ30mm, the most excellent working land width with 5mm, the mostexcellent cavity die entrance half angle with 22.5°, the most excellentfriction factor with 0.1. Compare formability, equivalent plasticstrain, extrusion power and die force of spline with α=21.8°withspline with =22.5, every result is very near, Given that p ≤σS exist αwhen αis within certainty range, namely for cold extrusion spline,both all is reasonable cavity die entrance half angle, In order tooptimize process parameter from fatigue life point of view, the paperaccord system analysis flow, FE model and residual stress after splinecold extrusion introduce into MSC.Marc software, put up torsion forceanalysis, and coupling stress field and torsion FE model introduce intoMSC.Fatigue software, put up fatigue life calculation, obtain fatiguelife and its distribution. Fatigue destroy position of spline with bothangles are the transition position from final extrusion to light shaft,The result with compare show, the least life of spline with α=22.5°is bigger than the least life of spline with α=21.8°. so, the mostexcellent value of cavity die entrance half angle is α=22.5°. (5) Use optimization result guide process and die model, put upspline cold extrusion process trial and fatigue trial Through cold extrusion process trial, It is close to fact extrusionpower of spline with α=21.8°and fact extrusion power of spline withα=22.5°, the trend of simulation extrusion power and fact extrusionpower is rough accordant, simulation extrusion power is a little biggerthan fact extrusion power and calculation extrusion power, so thenumerical simulation to spine cold extrusion is reasonable and correct;... |
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