摘 要
盤式制動(dòng)器是海洋鉆井絞車制動(dòng)系統(tǒng)的核心部件，其在制動(dòng)工作時(shí)由于熱疲勞而出現(xiàn)裂紋甚至斷裂，因此開展海洋鉆井絞車盤式制動(dòng)器熱疲勞失效機(jī)理研究，對(duì)確保鉆井作業(yè)人員和設(shè)備的安全具有重要的意義。本文以水冷盤式制動(dòng)器為研究對(duì)象，運(yùn)用有限元的方法研究了水冷盤式制動(dòng)器的熱-機(jī)耦合特性，并以此為基礎(chǔ)分析了制動(dòng)盤熱疲勞裂紋形成機(jī)理。論文的主要研究?jī)?nèi)容及創(chuàng)新工作如下：
(1) 闡述了論文研究的基礎(chǔ)理論，包括摩擦生熱理論、熱傳導(dǎo)理論和熱-機(jī)耦合分析理論，給出了溫度場(chǎng)熱傳導(dǎo)的有限元求解方法和熱-機(jī)耦合條件下溫度場(chǎng)與應(yīng)力場(chǎng)的有限元描述。
(2) 根據(jù)水冷盤式制動(dòng)器結(jié)構(gòu)特點(diǎn)，建立了制動(dòng)系統(tǒng)的熱-機(jī)耦合理論分析模型，并確定了其熱分析的初始條件和邊界條件。利用Pro/E軟件建立了制動(dòng)系統(tǒng)實(shí)際尺寸三維建模，利用有限元前處理軟件Hypermesh對(duì)其進(jìn)行網(wǎng)格劃分，并運(yùn)用非線性有限元分析軟件ABAQUS建立了制動(dòng)器的熱-機(jī)耦合分析模型。
(3) 根據(jù)海洋鉆井絞車的緊急制動(dòng)工況和連續(xù)制動(dòng)工況各自的特點(diǎn)，運(yùn)用ABAQUS軟件，分別對(duì)兩種工況進(jìn)行了數(shù)值模擬，得到了制動(dòng)盤溫度場(chǎng)和應(yīng)力場(chǎng)的分布特性和變化規(guī)律，并通過改變工況參數(shù)和材料參數(shù)等方式，研究了溫度場(chǎng)和應(yīng)力場(chǎng)的影響因素。
(4) 基于制動(dòng)過程的熱-機(jī)耦合分析結(jié)果，分析了水冷式制動(dòng)盤的失效機(jī)理，并確定了制動(dòng)盤的危險(xiǎn)部位和載荷譜，應(yīng)用局部應(yīng)力應(yīng)變法建立制動(dòng)盤熱疲勞壽命預(yù)測(cè)模型，分析了不同制動(dòng)形式下制動(dòng)盤熱疲勞壽命和影響因素。
研究表明：在制動(dòng)過程中，制動(dòng)盤的溫度場(chǎng)與應(yīng)力場(chǎng)是相互耦合的，較大的制動(dòng)盤比熱容、導(dǎo)熱系數(shù)大和較低的熱膨脹系數(shù)、彈性模量有利于降低制動(dòng)盤溫度極值和應(yīng)力極值；冷卻水速度越大對(duì)制動(dòng)盤的冷卻效果越明顯，但當(dāng)速度達(dá)到一定數(shù)值時(shí)，冷卻效果就不再非常明顯；在節(jié)點(diǎn)的三向應(yīng)力中，周向應(yīng)力是產(chǎn)生表面裂紋的主要分量；下鉆速度是影響制動(dòng)盤熱疲勞壽命的主要因素。

關(guān)鍵詞 水冷盤式制動(dòng)器；熱-機(jī)耦合；數(shù)值模擬；失效機(jī)理；壽命預(yù)測(cè)


Abstract
The disc brake is one core component in the ocean drilling equipments. The practical results show that the crack or fracture induced by thermal fatigue is the main failure mode of the brake. Therefore, to carry out the failure mechanism research of the disc brake has a very important significance in safeguarding the safety of drilling workers and equipments. Aiming at a water-cooling disc brake of offshore drilling drawworks, the thermo-mechanical coupling characteristics of the water-cooling disc brake were simulated by the method FEM. Based on the above results, the formation mechanism of thermal fatigue cracks of the brake disc was analyzed. The main research and innovation work include:
(1) The basic theory used in this thesis was elaborated, including friction heat theory, thermal conduction theory, and thermo-mechanical coupling analysis theory. The finite element solution method of heat transfer and the finite element description of temperature field and stress field under thermo-mechanical coupling conditions were also given in the thesis.
(2) Thermo-mechanical coupling theoretical analysis model of the brake system was established according to the structural features of water-cooling disc brake, then the initial and boundary conditions of thermal analysis were determined. Three dimension modeling software Pro/E was used to build the real dimension brake disc system. The software Hypermesh was applied to mesh the brake system. And the FEA software ABAQUS was adopted to build up the thermo-mechanical coupling model.
(3) According to the characteristics of emergency braking and repeated braking, the two braking conditions were simulated respectively by using software ABAQUS, and the distribution characteristics and variation disciplinarian of temperature field and stress field of the brake disc were obtained. The factors of temperature field and stress field were discussed through changing the working parameters and material parameters, etc.
(4) Based on the results of thermo-mechanical coupling analysis during braking, the failure mechanism of water-cooling brake disc was analyzed. Then dangerous parts and load spectrum of the brake disc were determined. Thermal fatigue life prediction model of the disc was established by the local stress and strain law. The thermal fatigue life of the brake disc and its factors in different braking forms were also analyzed.
The research showed that temperature field and stress field during braking were coupled. The higher specific heat, thermal conductivity and the lower thermal expansion coefficient, elasticity modulus could help decrease the maximum values of the temperature and stress of the brake disc. The greater the rate of cooling water was, the more obvious the cooling effect of the brake disc was, but when the rate of cooling water reached a certain value, and the cooling effect was unobvious. In the three-dimensional stress, circumferential stress was the main reason for causing the initial cracks on the surface of brake disc. The velocity of round trip was a major factor in influencing thermal fatigue life of the brake disc.

Keywords water-cooling disc brake; thermo-mechanical coupling; numerical simulation; failure mechanism; life prediction



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