發(fā)布時間：2018-05-15 06:08

  本文選題：起重機 + 箱形梁��； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：起重機械作為特種設(shè)備的主要類別之一,對釋放勞動力、實現(xiàn)自動化、提高作業(yè)效率發(fā)揮著極其巨大作用,已在人類社會生產(chǎn)、生活的眾多領(lǐng)域普遍應(yīng)用。起重機金屬結(jié)構(gòu)作為大型焊接結(jié)構(gòu),在生產(chǎn)、裝配與使用過程中,受各種因素地影響,不可避免的會出現(xiàn)缺陷(如裂紋)。這些裂紋的存在給服役起重機的安全使用埋下了較大隱患。在起重機作業(yè)過程中,一旦裂紋擴展,使得結(jié)構(gòu)斷裂失效,將導(dǎo)致不可預(yù)知的事故。故從起重機服役安全的角度,對含有裂紋缺陷的起重機進行安全評估具有重要現(xiàn)實意義。本文針對服役起重機的安全性,以某36t門式起重機箱形梁為研究對象,參照英國標準BS7910《金屬結(jié)構(gòu)中缺陷驗收評定方法導(dǎo)則》,基于線彈性斷裂力學(xué)理論、可靠性理論、以及疲勞損傷理論等,采用理論分析與有限元數(shù)值模擬等技術(shù)手段,對含有裂紋缺陷的箱形梁進行了概率安全評估和疲勞壽命估算的研究。論文的主要內(nèi)容包括:(1)以BS7910標準為參考,介紹了失效評定圖技術(shù)以及該標準中的三個評估等級及其特點。還介紹了可靠性分析中的一些常見分布類型,以及可靠性指標求解的相關(guān)過程與常用方法。(2)利用有限元分析軟件ABAQUS建立了起重機箱形梁的整體有限元模型和裂紋子模型,采用相互作用積分法分別計算了箱形梁下蓋板和腹板上,不同尺寸參數(shù)下的貫穿斜裂紋以及相應(yīng)簡化等長裂紋尖端的應(yīng)力強度因子KI。通過將KI值進行比較分析,驗證了將起重機箱形梁中的實際裂紋簡化成等長裂紋進行斷裂分析是合理可行的。(3)基于失效評定圖技術(shù)和可靠性基本理論,建立了起重機箱形梁結(jié)構(gòu)概率安全評定的方法與流程;并且利用有限元分析結(jié)果和Monte Carlo隨機抽樣方法,對含裂紋缺陷的某36t門式起重機箱形梁結(jié)構(gòu)進行了算例分析。算例分析表明該評定方法是可行的;并由參數(shù)敏感性分析得到斷裂韌性,屈服強度與一次薄膜應(yīng)力對箱形梁失效概率影響較大,評定時需優(yōu)先考慮這些參數(shù)。(4)針對起重機箱形梁結(jié)構(gòu)及其受力情況復(fù)雜的特點,提出了一種以疲勞試驗數(shù)據(jù)為基礎(chǔ)的等效裂紋法來估算疲勞壽命。通過將該方法的計算結(jié)果與文獻中的試驗結(jié)果數(shù)據(jù)進行對比分析,新方法對于常幅載荷作用下的疲勞壽命估算是有效可行的,但在變幅載荷作用下的疲勞壽命估算還需更深入地研究。該估算方法可為起重機的設(shè)計制造提供一定的參考。
[Abstract]:As one of the main types of special equipment, hoisting machinery plays an extremely important role in releasing labor force, realizing automation and improving work efficiency. It has been widely used in many fields of human society production and life. Crane metal structure as a large welded structure, in the production, assembly and use of the process, affected by a variety of factors, the inevitable defects (such as cracks). The existence of these cracks buries a great hidden danger for the safe use of the crane in service. In the process of crane operation, once the crack expands, the structure will break and fail, which will lead to unpredictable accidents. Therefore, from the point of view of crane service safety, it is of great practical significance to evaluate the safety of cranes with crack defects. Aiming at the safety of the crane in service, taking the box girder of a 36t portal crane as the research object, referring to the British standard BS7910 "guidelines for the acceptance and Evaluation of defects in Metal structures", based on the theory of linear elastic fracture mechanics and reliability theory, Based on the theory of fatigue damage, the probabilistic safety assessment and fatigue life estimation of box beams with crack defects are studied by means of theoretical analysis and finite element numerical simulation. The main contents of this paper are as follows: (1) taking the BS7910 standard as the reference, the paper introduces the failure assessment chart technology, three evaluation grades and their characteristics in this standard. This paper also introduces some common distribution types in reliability analysis, as well as the related process and common methods of reliability index solving.) by using finite element analysis software ABAQUS, the integral finite element model and crack sub-model of crane box-beam are established. The stress intensity factors (Ki) at the bottom cover plate and web plate of box beam with different parameters are calculated by the interaction integration method. The stress intensity factors (Ki) at the tip of the oblique crack and the corresponding simplification of the tip of the equal-length crack are simplified. By comparing and analyzing the KI value, it is proved that it is reasonable and feasible to simplify the actual crack in the box girder of crane to equal length crack for fracture analysis. The method and flow of probabilistic safety assessment of crane box-girder structure are established, and a case study of a 36t portal crane box girder structure with crack defects is carried out by using the results of finite element analysis and Monte Carlo random sampling method. The example analysis shows that the method is feasible, and the fracture toughness is obtained by parameter sensitivity analysis, and the yield strength and the first film stress have great influence on the failure probability of box beam. These parameters should be considered first. (4) in view of the complexity of crane box-beam structure and its mechanical condition, an equivalent crack method based on fatigue test data is proposed to estimate fatigue life. By comparing the calculated results with the experimental data in literature, the new method is effective and feasible for fatigue life estimation under constant amplitude loading. However, the estimation of fatigue life under variable amplitude loads needs to be further studied. This method can provide a certain reference for the design and manufacture of crane.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TH21

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