本文選題：斷裂過程區(qū) + 尺寸效應(yīng)�。� 參考：《北京建筑大學(xué)》2017年碩士論文

【摘要】：準脆性材料(巖石,混凝土等材料)所具有的強度等物理特性與構(gòu)件的空間尺寸以及結(jié)構(gòu)構(gòu)件所受荷載的加載率有關(guān),而不是簡單的經(jīng)典彈塑性力學(xué)假設(shè)的理想值的大小。準脆性材料表現(xiàn)出來的材料強度與材料內(nèi)部的結(jié)構(gòu)構(gòu)造特性相關(guān),而且與施加在構(gòu)件上的荷載加載率,以及與結(jié)構(gòu)試件的尺寸大小也是有關(guān)系的。在時間和空間維度上,材料的物理特性都會存在一定的影響因素。然而,關(guān)于巖石,混凝土的結(jié)構(gòu)尺寸與動力荷載之間聯(lián)系的分析理論相對較少,兩者的關(guān)聯(lián)性沒有充分的研究,造成了很多實際的問題。例如,對于結(jié)構(gòu)發(fā)生破壞的進程沒有被充分的認識,以導(dǎo)致無法進一步使工程結(jié)構(gòu)的設(shè)計更加安全可靠。戚承志教授,成功分析出了在I型尺寸效應(yīng)下,結(jié)構(gòu)的強度與應(yīng)變率以及構(gòu)件大小的內(nèi)在聯(lián)系,并且證明應(yīng)變率變化過程中存在臨界應(yīng)變率,另外求解出了結(jié)構(gòu)應(yīng)變率和破碎的巖石的塊體大小的關(guān)系式,證明了準脆性材料的I型尺寸效應(yīng)與應(yīng)變率效應(yīng)是統(tǒng)一的。本文主要是結(jié)合巖石類的結(jié)構(gòu)層次,考慮裂紋尖端存在的斷裂過程區(qū),進而參考戚承志教授對Ⅰ型(無裂紋試樣)尺寸效應(yīng)和應(yīng)變率關(guān)聯(lián)的研究,應(yīng)用Hu,Duan的邊界效應(yīng)公式,對有Ⅱ型尺寸效應(yīng)和應(yīng)變率效應(yīng)進行研究,主要研究成果包括:(1)依據(jù)動態(tài)裂紋尖端應(yīng)力場和摩爾強度準則,求解出了裂紋的斷裂過程區(qū)尺寸�；贔reund求解出的變速動態(tài)裂紋尖端的應(yīng)力場,結(jié)合摩爾強度準則,求解出來裂紋尖端斷裂過程區(qū)的形狀和大小。得出結(jié)論:在裂紋起裂過程中,裂紋尖端的斷裂過程區(qū)隨著應(yīng)變率的增大而增大;在裂紋傳播過程中,裂紋尖端的斷裂過程區(qū)面積隨著裂紋傳播速度的增大而增大;裂紋傳播相比裂紋起裂過程,斷裂過程區(qū)增大的幅度更大。(2)結(jié)合Hu,Duan的邊界效應(yīng)公式,理論推導(dǎo)出了帶裂紋體的起裂韌度與加載率的關(guān)系,傳播韌度與裂紋速度的關(guān)系,實現(xiàn)了Ⅱ型尺寸效應(yīng)和應(yīng)變率效應(yīng)關(guān)聯(lián)研究。得出結(jié)論:含有裂紋的準脆性材料試件,試件的起裂韌度隨著應(yīng)變率的提高而增大,在裂紋傳播過程中,試件的傳播斷裂韌度隨著裂紋速度的提高而增大,試件的傳播韌度要大于起裂韌度。所得到的理論結(jié)果與實驗結(jié)果相符。(3)結(jié)合動態(tài)裂紋尖端的能量釋放率,推導(dǎo)出了裂紋尖端斷裂過程區(qū)尺寸與裂紋速度的關(guān)系,帶入邊界效應(yīng)公式,計算出了試件的斷裂韌度與裂紋速度的關(guān)系,從能量的角度,驗證了前面的理論結(jié)果。即隨著裂紋的速度的增加,裂紋長度的增加,裂紋尖端的能量釋放率不斷增大,可以發(fā)現(xiàn)裂紋尖端的斷裂過程區(qū)的面積隨裂紋速度增加而增大,進而材料抵抗裂紋擴展的阻力增大,表現(xiàn)出了試件的斷裂韌度隨著裂紋速度增大而增大。
[Abstract]:The physical properties of quasi-brittle materials (such as rock, concrete, etc.) are related to the spatial size of the members and the loading rate of the structural members, rather than the ideal values of simple classical elastoplastic mechanics assumptions. The strength of the quasi-brittle material is related to the structural characteristics of the material, the loading rate applied on the members, and the size of the structural specimen. In the dimension of time and space, there are some influence factors on the physical properties of materials. However, there are relatively few theories about the relationship between the structure size and the dynamic load of concrete, and the correlation between them is not fully studied, which has caused many practical problems. For example, the process of structural failure is not fully understood, resulting in a failure to further make the design of engineering structures more secure and reliable. Professor Qi Chengzhi has successfully analyzed the intrinsic relationship between the strength of the structure and the strain rate and the size of the member under the model I size effect, and has proved that the critical strain rate exists in the process of strain rate variation. In addition, the relationship between the strain rate of structure and the block size of broken rock is obtained. It is proved that the I size effect and strain rate effect of quasi-brittle materials are unified. In this paper, considering the fracture process zone at the crack tip, and referring to Professor Qi Chengzhi's research on the correlation between the size effect and strain rate of model 鈪，

本文編號：2012661