發(fā)布時間：2018-08-04 13:58

【摘要】：在運用TBM進(jìn)行隧道開挖的工程中,刀盤上的刀座是最常發(fā)生疲勞破壞的結(jié)構(gòu),破壞形式多表現(xiàn)為沿焊縫的疲勞裂紋和刀座的過載變形,并最終導(dǎo)致刀座性能失效。刀座的失效會對滾刀的安裝精度和工作狀態(tài)造成影響,改變滾刀的受力特性,并加速滾刀的破壞,最終影響掘進(jìn)效率。因此,針對刀座焊接疲勞壽命預(yù)測及其焊接結(jié)構(gòu)的改進(jìn)具有重要的工程實際意義。本文圍繞TBM刀座焊接疲勞壽命預(yù)測和焊接結(jié)構(gòu)改進(jìn)的問題,進(jìn)行了一系列研究。(1)根據(jù)TBM刀盤板厚超厚特點,基于平面應(yīng)力條件的小時間裂紋擴(kuò)展模型不再適用,故引入塑性約束因子α來改變材料屈服應(yīng)力值,將內(nèi)部裂紋和沿板厚方向擴(kuò)展的裂紋尖端平面應(yīng)力/應(yīng)變狀態(tài)的轉(zhuǎn)變進(jìn)行等效。根據(jù)不同板厚試樣的裂紋擴(kuò)展疲勞試驗,得到α與板厚t的關(guān)系方程：α=0.73t-0.943,提出了適用于大板厚的應(yīng)力/應(yīng)變轉(zhuǎn)換的小時間尺度三維約束裂紋擴(kuò)展模型。另外,將焊接殘余應(yīng)力對焊縫區(qū)應(yīng)力特征的影響考慮在內(nèi),對小時間裂紋擴(kuò)展模型進(jìn)一步改進(jìn),使其適用于焊縫裂紋擴(kuò)展壽命的預(yù)測。(2)采用C(T)焊接試樣進(jìn)行焊縫疲勞裂紋擴(kuò)展壽命試驗,記錄了裂紋擴(kuò)展長度α0與載荷循環(huán)次數(shù)N的關(guān)系數(shù)據(jù),并運用修正后的壽命預(yù)測模型對C(T)試樣的焊縫疲勞裂紋擴(kuò)展壽命進(jìn)行預(yù)測,理論預(yù)測結(jié)果與疲勞試驗數(shù)據(jù)對比結(jié)果顯示,疲勞試驗結(jié)果處于理論預(yù)測壽命的0.5-2倍范圍內(nèi),在工程中是可接受的,證明了壽命預(yù)測模型和方法的有效性。(3)根據(jù)工程實例中TBM刀座的結(jié)構(gòu)和載荷特點,以及刀座正面焊縫常出現(xiàn)疲勞裂紋的情況,對刀座正面焊縫形式進(jìn)行改進(jìn),將角焊縫改為對接焊縫,為節(jié)省仿真計算成本,設(shè)計縮尺簡化模型代替現(xiàn)役刀座和新型刀座的結(jié)構(gòu)特點,對刀座縮尺簡化結(jié)構(gòu)的殘余應(yīng)力場進(jìn)行仿真分析,對比兩種結(jié)構(gòu)的殘余應(yīng)力場,得出新型結(jié)構(gòu)的殘余應(yīng)力場對提高疲勞性能更有利。(4)運用提出的壽命預(yù)測模型對刀座縮尺結(jié)構(gòu)的焊縫裂紋擴(kuò)展壽命進(jìn)行了預(yù)測。根據(jù)相似理論,反推得到工程實例刀座的焊縫裂紋擴(kuò)展壽命,得到現(xiàn)役刀座焊接結(jié)構(gòu)的壽命為6.04km,新型刀座焊接結(jié)構(gòu)的壽命為7.74km,與現(xiàn)役結(jié)構(gòu)相比,新型結(jié)構(gòu)的焊縫疲勞裂紋擴(kuò)展壽命預(yù)測提高了28%,設(shè)計的新型刀座焊接結(jié)構(gòu)比現(xiàn)役刀座焊接結(jié)構(gòu)有更好的疲勞性能。
[Abstract]:In the engineering of tunnel excavation with TBM, the tool holder on the cutter head is the most common structure with fatigue failure. The failure forms are mostly the fatigue crack along the weld seam and the overload deformation of the tool holder, and finally lead to the failure of the tool holder performance. The failure of the tool holder will affect the installation accuracy and working state of the hob, change the mechanical characteristics of the hob, accelerate the destruction of the hob, and ultimately affect the tunneling efficiency. Therefore, the prediction of welding fatigue life of tool holder and the improvement of welding structure have important engineering significance. This paper focuses on the prediction of fatigue life of TBM tool holder and the improvement of welding structure. (1) according to the characteristics of TBM cutter plate thickness and super-thickness, the small time crack propagation model based on plane stress condition is no longer applicable. Therefore, the plastic constraint factor 偽 is introduced to change the yield stress value of the material, and the transformation of the plane stress / strain state of the crack tip along the plate thickness is equivalent to that of the inner crack. According to the fatigue test of crack propagation of specimen with different thickness of plate, the equation of 偽 and thickness t is obtained: 偽 0.73t-0.943. A small time scale confined crack propagation model is proposed for the stress / strain conversion of large plate thickness. In addition, the influence of welding residual stress on the stress characteristics of weld zone is taken into account, and the small time crack propagation model is further improved. It is suitable for the prediction of weld crack growth life. (2) the fatigue crack growth life test of weld seam is carried out with C (T) welding specimen, and the relation data between crack propagation length 偽 0 and load cycle number N are recorded. The modified life prediction model is used to predict the fatigue crack propagation life of weld seam of C (T) specimen. The results of theoretical prediction and fatigue test show that the fatigue test results are within the range of 0.5-2 times of the theoretical predicted life. It is acceptable in engineering, which proves the validity of life prediction model and method. (3) according to the structure and load characteristics of TBM tool holder in engineering example, fatigue crack often appears in the front weld of tool holder. In order to save the cost of simulation, a simplified model was designed to replace the active tool holder and the new type tool holder in order to save the cost of simulation. The residual stress field of the simplified structure is simulated and analyzed, and the residual stress field of the two structures is compared. It is concluded that the residual stress field of the new structure is more favorable to improve the fatigue performance. (4) the life prediction model is used to predict the crack propagation life of the weld seam of the tool holder scale structure. According to the similarity theory, the weld crack propagation life of the tool holder in engineering example is obtained. The service life of the welding structure is 6.04km, and the life of the new type welding structure is 7.74km, which is compared with the active structure. The prediction of fatigue crack propagation life of the new type structure has been improved by 28%. The designed new type of tool holder welding structure has better fatigue performance than the existing tool holder welding structure.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：U455.3

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本文編號：2164104