應(yīng)力腐蝕耦合作用下的斷裂力學(xué)問題

內(nèi)容概要

　　作者在留學(xué)美國布朗大學(xué)期間，在導(dǎo)師的指導(dǎo)下，從1997年開始從事這個領(lǐng)域的研究工作（主要是數(shù)值計算工作），其間獲美國國家計量局陶瓷研究所的資助。2002年完成博士論文后，作者在加州Irvine分校從事相關(guān)的博士后研究。在此期間，作者用自己開發(fā)的軟件模擬了在應(yīng)力和腐蝕耦合作用下脆性材料表面微裂縫的擴展過程，同時也研究了初始裂縫在兩種脆性材料（復(fù)合材料）界面時的情形?！　　稇?yīng)力腐蝕耦合作用下的斷裂力學(xué)問題》整理匯集了作者這些年的研究成果。因為已發(fā)表的大部分文章是用英文寫就的，故作者最終選擇了英文作為《應(yīng)力腐蝕耦合作用下的斷裂力學(xué)問題》書寫的語種。限于作者的認(rèn)識水平和分析能力，書中難免有不足甚至謬誤之處，敬請批評、指正?！　∽髡咭貏e感謝我的博士導(dǎo)師--布朗大學(xué)的Bower教授，和博士后學(xué)習(xí)實踐期間的指導(dǎo)教授--美國工程院院士Atluri博士在這些年中的指導(dǎo)和幫助。同時，作者要感謝浙江大學(xué)出版社編輯王鐠博士為《應(yīng)力腐蝕耦合作用下的斷裂力學(xué)問題》出版做出的努力，以及浙江海洋學(xué)院趙秋亮老師的文字錄入工作。

書籍目錄

Chapter 1　INTRODUCTION1.1　Stress corrosion problem in history1.2　Charles and Hillig's model1.3　Brief description of work reported in this book　　Chapter 2　NUMERICAL APPROACH2.1　Model description2.2　Numerical procedure2.3　Convergence studies2.3.1　Effect of finite boundaries and mesh sizes2.3.2　Effect of time step sizeChapter 3　RESULTS AND DISCUSSION WITH HOMOGENEOUS3.1　Dimensionless analysis　3.2　Results and discussion　3.2.1　Introduction　3.2.2　Stress corrosion studies for typical material3.2.3　Stress driven corrosion problem in general3.2.4　Further studies of steady state crack growth3.3　Conclusions　Chapter 4　CRACK PROPAGATION ON THE INTERFACE BETWEEN TWO BRITTLE SOLIDS4.1　Introduction　4.2　Description of model and numerical procedureChapter 5　SUMMARIZATIONREFERENCES

章節(jié)摘錄

　　Usually for time dependent numerical simulation， the time stepΔt must be chosen with care. Our algorithm for integrating the surface corrosion equation with respect to time is conditionally stable and the stability of the algorithm is greatly improved if the numerical parameterθ = 1 is set .Nevertheless， instabilities may be still occur if At happens to be too large. The difficulty is caused by the terms involving curvature in Eq. （2.10）： small changes in the position of the points on the void surface can lead to large changes in curvature， so small time steps must be taken to compute the rate of change of curvature accurately. The elastic fields in the solid， however， alter more slowly as the surface of the void evolves .In order to make simulation calculations maneuverable without loss of accuracy， the convergence studies by systematically testing various time step sizes through the process of computation have been conducted and finally an approach of automatic adjustment of time step size is implemented. Through convergence study （see following section）， we find that， after every time step， if the maximal Ah exceeds a mesh height or more near the crack tip， the rate of convergence for the numerical solutions decreases dramatically and consequently the result becomes not reliable. If we， however， set all the time step sizes too small， it turns to be not practical due to the very long time needed for computation. Then we enable the code to adjust time step size automatically by monitoring Ah. if the maximal Ah is around 30%~40% of its corresponding mesh size after one time step， computation for next time step will be allowed to continue. Otherwise， the code will adjust time step size correspondingly and re-compute this step till the maximal Ah match the criteria above. For calculation of next time step， this new adaptive time step size will be first tried and automatic adjustment of time step size will be re-activated if necessary. This procedure is repeated through computing the progressive change in shape of the void.Meanwhile， we have devised a re-start function in this FEM code.　Usually in time dependent simulation， computation could be terminated unexpectedly for some reasons such as mesh construction problem due to the complicate geometric shape on the boundaries， etc. It is， however， not necessary to resume the calculation from the initial step if the results of first many steps are assured to be acceptable. We may write the information of all variables during the calculation into a file that is named as re-start file.

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