本文選題：循環(huán)載荷 + 應(yīng)力—應(yīng)變關(guān)系��； 參考：《武漢理工大學(xué)》2014年碩士論文

【摘要】：在船舶安全性評估中，船體梁極限承載能力的研究是其中一個(gè)非常重要的方面，而如今的評估方法都是以靜力極限強(qiáng)度為準(zhǔn)則的。當(dāng)船體結(jié)構(gòu)遭受到較大的交變載荷的作用時(shí)，會(huì)導(dǎo)致船體梁危險(xiǎn)斷面處某些縱向構(gòu)件發(fā)生一定程度的屈服或屈曲破壞及塑性變形，從而使得該斷面的極限承載能力降低。其最終結(jié)果是，船體梁在某一次未達(dá)到一次性縱向極限彎矩的載荷作用下就有可能發(fā)生破壞，基于靜力極限強(qiáng)度準(zhǔn)則會(huì)過高評估船體結(jié)構(gòu)的極限強(qiáng)度，不符合實(shí)際情形。因此需要引入基于循環(huán)載荷作用下的船體極限承載能力的遞增塑性破壞準(zhǔn)則，考慮循環(huán)載荷下船體結(jié)構(gòu)響應(yīng)。 船體加筋板是船舶的主要承載構(gòu)件，其一次性加載下極限強(qiáng)度已經(jīng)被廣泛研究，而對循環(huán)載荷作用下的加筋板的性能分析研究還很少。本文通過大量的有限元計(jì)算，修正了Rahman法的加筋板應(yīng)力-應(yīng)變公式，并推導(dǎo)出了循環(huán)載荷下加筋板的應(yīng)力-應(yīng)變關(guān)系，這對于循環(huán)載荷載荷下加筋板變形性能的研究具有重要意義。最后以循環(huán)載荷下加筋板單元性能為基礎(chǔ)，進(jìn)而探討循環(huán)載荷下船體梁彎矩-曲率變化關(guān)系，本文的主要研究工作如下： 1）介紹一次性加載下加筋板單元應(yīng)力-應(yīng)變關(guān)系的兩種計(jì)算方法：Rahman法和FEM非線性有限元法。將兩種方法計(jì)算結(jié)果進(jìn)行對比，驗(yàn)證其準(zhǔn)確性和可靠性，，并分析兩種方法的優(yōu)劣。 2）基于FEM非線性有限元方法的結(jié)果，修正Rahman法的理論計(jì)算公式，并進(jìn)行誤差分析，得到更為準(zhǔn)確的計(jì)算加筋板單元應(yīng)力-應(yīng)變曲線的簡單關(guān)系式。 3）分析循環(huán)載荷作用下加筋板的變形性能，基于修正Rahman法的簡單計(jì)算公式，得到循環(huán)載荷作用下加筋板單元的應(yīng)力-應(yīng)變關(guān)系。并提出了兩種典型的循環(huán)加載歷程：單向遞增循環(huán)模式和雙向遞增循環(huán)模式。給出算例分別計(jì)算兩種循環(huán)歷程下加筋板單元的應(yīng)力-應(yīng)變曲線，并與有限元結(jié)果進(jìn)行比較驗(yàn)證。 4）在傳統(tǒng)逐步破壞法基礎(chǔ)上，引入循環(huán)載荷下結(jié)構(gòu)的遞增累積塑性破壞概念，采用循環(huán)載荷下結(jié)構(gòu)單元的應(yīng)力-應(yīng)變關(guān)系，改進(jìn)計(jì)算程序，得到循環(huán)彎曲簡化方法計(jì)算程序。使用修改后的程序?qū)蓚�(gè)箱型梁模型和一條散貨船實(shí)船算例進(jìn)行計(jì)算，探討兩種典型循環(huán)歷程下船體梁的極限承載性能，并與非線性有限元軟件的計(jì)算結(jié)果進(jìn)行對比，驗(yàn)證本文程序的準(zhǔn)確性。
[Abstract]:In ship safety assessment, the study of ultimate load-bearing capacity of hull girder is one of the most important aspects, and the present assessment methods are based on static ultimate strength. When the hull structure is subjected to a large alternating load, it will lead to some longitudinal members in the dangerous section of the hull beam to yield or buckle to a certain extent and plastic deformation, thus reducing the ultimate bearing capacity of the section. The ultimate result is that the hull beam may be destroyed under a load which does not reach the one-off longitudinal ultimate bending moment, and the ultimate strength of the hull structure will be evaluated too high based on the static ultimate strength criterion, which is not in line with the actual situation. Therefore it is necessary to introduce an incremental plastic failure criterion based on the ultimate load-carrying capacity of the ship under cyclic load and to consider the response of the hull structure under cyclic load. Hull stiffened plate is the main bearing member of the ship. The ultimate strength under one-time loading has been widely studied, but the performance analysis of stiffened plate under cyclic load is rare. In this paper, the formula of stress-strain of stiffened plate by Rahman method is modified by a lot of finite element calculation, and the stress-strain relation of stiffened plate under cyclic load is deduced. This is of great significance to the study of deformation properties of stiffened plates under cyclic loading. Finally, based on the performance of stiffened plate element under cyclic load, the relationship between bending moment and curvature of hull girder under cyclic load is discussed. The main research work of this paper is as follows: 1) two calculation methods of stress-strain relationship of stiffened plate element under one time loading are introduced: the method of: Rahman and the nonlinear finite element method of FEM. The calculation results of the two methods are compared to verify their accuracy and reliability. 2) based on the results of FEM nonlinear finite element method, the theoretical calculation formula of Rahman method is modified, and the error analysis is carried out. A more accurate formula for calculating the stress-strain curves of stiffened plate elements is obtained. 3) the deformation performance of stiffened plates under cyclic loading is analyzed, based on the simple formula of modified Rahman method. The stress-strain relationship of stiffened plate elements under cyclic loading is obtained. Two typical cyclic loading processes are proposed: unidirectional incremental cycle mode and bidirectional incremental cyclic mode. Examples are given to calculate the stress-strain curves of stiffened plate elements under two cycles, and the results are compared with those of the finite element method. 4) on the basis of the traditional progressive failure method, The concept of incremental cumulative plastic failure of structure under cyclic load is introduced. The stress-strain relationship of structural elements under cyclic load is adopted to improve the calculation program, and the simplified method of cyclic bending is obtained. The modified program is used to calculate two box girder models and a bulk carrier real ship, and the ultimate load-bearing performance of the hull girder under two typical cyclic histories is discussed, and the results are compared with the results of nonlinear finite element software. Verify the accuracy of this program.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U661.4

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