本文選題：有限元　切入點：薄壁件　出處：《武漢理工大學》2015年碩士論文

【摘要】：由于對產(chǎn)品功能、質量等性能的特殊要求,薄壁件在航空以及造船等行業(yè)廣泛存在,其結構主要由側壁或腹板組成,結構形狀復雜。這樣的零部件的輪廓尺寸相比截面尺寸要大很多,有的還對平面度和變形精度要求較高,因此加工起來剛度穩(wěn)定性較低,往往需要采用特殊的加工工藝及誤差控制方法,導致加工效率較低且制造成本較高。采用計算機輔助工程(Computer Aided Engineering,CAE)可有效緩解這一問題。本文首先簡單介紹了切削加工仿真需要的關鍵有限元法(Finite Element Method,FEM)技術和切削加工特點,分析和闡述了國內(nèi)外解決復雜非線性熱-力仿真分析問題常采用的Johnson-Cook材料塑性模型、Johnson-Cook材料失效模型、ABAQUS/Explicit仿真環(huán)境中的損傷演化模型,以及切削中刀具和工件材料的接觸特點、仿真軟件對于接觸特性的計算特點和相應的摩擦模型建立。其次,分別采用以上涉及到的相關方法和技術對簡化二維正交切削和三維斜角切削模型作了相應的仿真分析,模擬了不同形貌切屑的成形過程以及加工中生熱和應力-應變問題,分析了不同切削厚度、不同切削速度、不同刀具角度對切削力和切削溫度的影響。驗證了該仿真方法的可行性。然后,運用上述方法對薄壁板的三維切削加工模型進行了仿真模擬。本文全部模型都是基于各項同性材料,仿真過程中不考慮刀具的磨損和變形以及切削液的影響。由于薄壁零部件剛性差,在加工過程中很容易產(chǎn)生“讓刀”變形現(xiàn)象,所以分別針對“僅底端約束”、“底部和兩端面約束”這兩種約束狀態(tài)的薄壁板的切削加工模型進行了仿真模擬,分析了其加工過程中的加工誤差以及相應的切削熱大小、應力分布情況等。經(jīng)仿真分析,與后一個模型相比,僅底端約束的模型的薄壁板更容易產(chǎn)生切削變形,加工誤差更大,其加工變形誤差從板的上端往下逐漸減小,并且由于加工過程中薄板上端的撓曲變形和兩端撓曲變形的綜合作用,最終在薄壁板底端正中間產(chǎn)生一個“凹坑”狀區(qū)域;底部和兩端均約束的模型在薄壁板的正中間才產(chǎn)生最大加工變形誤差,并且誤差從上往下呈逐漸減小的趨勢。在本文最后,針對某鏡座零部件的鏡框臺階面的切削加工進行了仿真模擬。提取加工面的變形誤差繪制成曲線圖,并與實驗結果進行對比分析,結果表明:采用ABAQUS/Explicit能夠有效對薄壁零部件的切削加工進行有限元仿真計算。
[Abstract]:Due to the special requirements for the function and quality of products, thin-walled parts are widely used in aviation and shipbuilding industries, and their structures are mainly made up of side walls or web plates. The shape of the structure is complex. The contour size of such parts is much larger than the cross-section size, and some require higher flatness and deformation accuracy, so the stiffness stability is low when machined. Special processing techniques and error control methods are often required. As a result of low machining efficiency and high manufacturing cost, this problem can be effectively alleviated by using computer Aided engineering (CAE). This paper first introduces the key finite element method finite Element method for machining simulation and the characteristics of cutting machining. The damage evolution model of Johnson-Cook material failure model in Abaqus / explicit simulation environment, and the contact characteristics of cutting tools and workpiece materials in cutting are analyzed and expounded, which are often used to solve complex nonlinear thermo-mechanical simulation problems at home and abroad, such as Johnson-Cook material plastic model and Johnson-Cook material failure model. The simulation software is used to calculate the contact characteristics and establish the corresponding friction model. Secondly, the simplified two-dimensional orthogonal cutting model and the three-dimensional diagonal cutting model are simulated and analyzed using the methods and techniques mentioned above. The forming process of chips with different morphologies and the problems of heat generation and stress-strain in machining are simulated. The different cutting thickness and cutting speed are analyzed. The effects of different tool angles on cutting force and cutting temperature are verified, and the feasibility of the simulation method is verified. The three-dimensional machining model of thin-walled plate is simulated by using the above method. All the models in this paper are based on the same materials. In the simulation process, the wear and deformation of the tool and the influence of the cutting fluid are not considered. Due to the rigidity of the thin-walled parts, it is easy to "make the knife" deform in the process of machining. Therefore, the machining models of thin-walled plate with "only bottom constraint" and "bottom and end face constraint" are simulated, and the machining error and the corresponding cutting heat are analyzed. Through simulation analysis, compared with the latter model, the thin-walled plate with only the bottom end constraint is more likely to produce cutting deformation, and the machining error is larger, and the machining deformation error decreases gradually from the top end to the bottom of the plate. And because of the comprehensive action of bending deformation at the upper end of thin plate and flexural deformation at both ends of the thin plate during the machining process, a "pit" region is finally produced in the middle of the bottom end of the thin-walled plate. The model with both bottom and end constraints produces the maximum machining deformation error in the middle of the thin-walled plate, and the error decreases gradually from top to bottom. At the end of this paper, The cutting process of the mirror frame step surface of a mirror seat component is simulated. The deformation error of the machining surface is drawn into a curve, and the results are compared with the experimental results. The results show that ABAQUS/Explicit can effectively simulate the machining of thin-wall parts by finite element method.
【學位授予單位】：武漢理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG506
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本文編號：1657229