【摘要】：氣缸蓋作為內燃機中結構和載荷最復雜的零件之一,容易形成不同位置不同程度的破壞,成為制約發(fā)動機壽命的重要因素。本文以蠕鐵氣缸蓋作為研究對象,從細觀損傷力學的角度出發(fā),運用GTN損傷模型對缸蓋損傷進行分析,利用有限元逆向法結合試驗和仿真確定模型中的損傷參數(shù)。采用了缸蓋火力板結構模擬件,基于GTN損傷模型對缸蓋進行損傷分析,通過孔洞體積分數(shù)的演變從細觀損傷的角度描述了材料宏觀裂紋的產生。主要研究方法和結論如下:利用用于材料試驗的單向拉伸圓試棒,在室溫、300℃、500℃下進行了單向拉伸試驗,得到了各溫度下的應力應變關系曲線。對拉伸試件初始階段、頸縮階段、斷裂階段切取用于掃描電鏡觀測的切片,得到掃描圖像,再利用圖像處理軟件IPP進行處理,初步得到孔洞長大過程參數(shù)0f=0.00328,cf=0.021,Ff=0.0412。建立拉伸試件的有限元模型,利用有限元逆向法通過正交試驗對孔洞形核參數(shù)的取值進行計算分析,最終確定了n?=0.1,ns=0.075,nf=0.025。在此基礎上,對室溫下的GTN損傷參數(shù)進行溫度修正,以高溫下的試驗應力應變曲線為參照,調整GTN參數(shù)使仿真值吻合試驗值,在此過程中確定了nf、nS和n?對材料仿真計算的力學行為的影響。制備了與缸蓋火力板等效的結構模擬件,分別討論了孔洞體積分數(shù)與等效塑性應變以及頸縮后Mises等效應力的關系,通過分析得到孔洞體積分數(shù)與等效塑性應變的變化趨勢基本一致;孔洞不斷增大,損傷不斷累積,材料承載能力下降,最先達到臨界孔洞體積分數(shù)的節(jié)點應力最早開始下降。從孔洞體積分數(shù)的演化預測孔洞體積分數(shù)最先達到破壞體積分數(shù)的進氣門鼻梁區(qū)首先出現(xiàn)裂紋,從細觀損傷角度解釋了缸蓋宏觀裂紋的產生。
[Abstract]:As one of the most complicated parts in internal combustion engine, cylinder head is easy to be destroyed in different positions and degrees, and becomes an important factor restricting engine life. In this paper, the damage of vermicular iron cylinder head is analyzed by using GTN damage model from the point of view of mesoscopic damage mechanics, and the damage parameters in the model are determined by finite element reverse method combined with test and simulation. The damage analysis of cylinder head based on GTN damage model is carried out by using the cylinder head fire plate structure simulator. The macroscopic crack generation of material is described from the point of view of mesoscopic damage through the evolution of pore volume fraction. The main research methods and conclusions are as follows: uniaxial tensile tests were carried out at room temperature, 300 鈩，

本文編號：2273534