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  本文選題：高強螺栓 + 應(yīng)力集中　； 參考：《湖南大學(xué)》2013年碩士論文

【摘要】：高強螺栓連接以其強度高、可拆卸等優(yōu)點而成為了一種重要的鋼結(jié)構(gòu)連接形式。由于該連接受力機理復(fù)雜,目前仍有較多問題值得探討。我國現(xiàn)行規(guī)范一方面低估了某些情況下的承載力,例如,高強螺栓承壓型連接的抗剪承載能力規(guī)定；另一方面,現(xiàn)行規(guī)范缺乏對某些情況下承載力的規(guī)定,例如,規(guī)范缺少高強螺栓在受拉情況下疲勞計算的規(guī)定。本文采用理論推導(dǎo)及數(shù)值試驗的方法,對這兩個問題進行了深入的研究,獲得了如下成果： (1)采用虛功原理推導(dǎo)了預(yù)拉力模擬方法,該方法可以較為準(zhǔn)確的模擬預(yù)應(yīng)力的工作。 (2)采用了數(shù)值試驗的方法研究了承壓型高強螺栓的受力過程。研究表明當(dāng)連接的承載力由螺栓強度控制時,若不考慮構(gòu)件間的摩擦力,則高強螺栓承壓型連接的承載力會被低估。本文對這種連接方式的抗剪承載力提出了為合理的計算方法。 (3)通過理論推導(dǎo)及數(shù)值試驗的方法研究了螺栓桿的應(yīng)力集中系數(shù)。在忽略螺紋升角的情況下,根據(jù)變形協(xié)調(diào)條件研究了螺栓桿的軸力梯度變化。采用數(shù)值計算確定常用螺栓球的螺紋位移系數(shù)及螺紋力計算公式。采用局部建模,通過迭代計算的方法確定螺栓桿應(yīng)力集中系數(shù)。與完整模型的計算結(jié)果比較表明該方法的計算結(jié)果具有較高的精度,且計算效率高。 (4)針對應(yīng)用最普遍的40Cr鋼制高強螺栓,在計算出的螺栓螺紋應(yīng)力集中系數(shù)的情況下,采用2種S-N曲線法對高強螺栓的疲勞壽命進行了估算。并結(jié)合等壽命曲線綜合考慮了應(yīng)力幅和應(yīng)力比的影響,推導(dǎo)出了螺栓疲勞的設(shè)計公式。將估算結(jié)果與國內(nèi)已有的實驗數(shù)據(jù)進行對比,估算結(jié)果偏于安全,且在高周期疲勞中精度較好。 (5)采用斷裂力學(xué)分析了螺栓螺紋根部表面Ⅰ型裂紋的應(yīng)力強度因子,對帶有不同長度初始裂紋的螺栓進行了壽命估算,研究了不同長度裂紋對高強螺栓疲勞壽命的影響。并按照工程中假設(shè)初始裂紋為0.5mm時的疲勞壽命為螺栓的疲勞壽命,與實驗數(shù)據(jù)對比表明假設(shè)初始裂紋為0.5mm的估算壽命偏于安全且精度較好。并且證明了初始裂紋長度對螺栓疲勞壽命有著不可忽視的影響。
[Abstract]:High-strength bolt connection has become an important form of steel structure because of its high strength and detachability. Due to the complex mechanical mechanism of the connection, there are still many problems to be discussed. On the one hand, the current code of our country underestimates the bearing capacity in some cases, for example, the shear bearing capacity of high-strength bolt bearing connections; on the other hand, the current code lacks the provisions on the bearing capacity in some cases, such as, The specification lacks provisions for fatigue calculation of high-strength bolts under tension. In this paper, the theoretical derivation and numerical test are used to study these two problems, and the results are as follows: 1) the simulation method of pretension force is deduced by using the principle of virtual work, which can simulate the work of prestress accurately. (2) the stress process of high-strength bolt with bearing pressure is studied by numerical test. The results show that when the bearing capacity of the connection is controlled by the bolt strength, the bearing capacity of the high-strength bolt bearing joint will be underestimated if the friction between the members is not taken into account. This paper presents a reasonable calculation method for the shear capacity of this connection. The stress concentration factor of bolt rod is studied by theoretical derivation and numerical test. In this paper, the axial force gradient of bolt rod is studied according to the deformation coordination condition, while the screw lift angle is ignored. The displacement coefficient of thread and the calculation formula of thread force are determined by numerical calculation. The stress concentration factor of bolt rod is determined by means of local modeling and iterative calculation. The comparison of the results with the complete model shows that the proposed method has high accuracy and high efficiency. The fatigue life of high strength bolts made of 40Cr steel is estimated by using two S-N curve methods under the calculated stress concentration factor of bolt thread. Considering the influence of stress amplitude and stress ratio, the design formula of bolt fatigue is deduced. The estimated results are compared with the experimental data available in China. The estimated results are relatively safe and have good accuracy in high cycle fatigue. In this paper, the stress intensity factor of mode I crack at the root of bolt thread is analyzed by fracture mechanics. The life of bolt with initial crack of different length is estimated, and the influence of crack of different length on fatigue life of high strength bolt is studied. The fatigue life of bolts is assumed to be the fatigue life of bolts when the initial crack is assumed to be 0.5mm. The comparison with the experimental data shows that the estimated life of the initial crack assuming that the initial crack is 0.5mm is more safe and accurate. The effect of initial crack length on the fatigue life of bolts is proved.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU391

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本文編號：1875349