热预应力内压厚壁圆筒自增强技术研究与仿真-电路空与系统专业毕业论文.docx

ABSTRACT Autofrettage technique is usually adopted by internally pressurized thick-walled cylinders to increase bearing capacity and extend fatigue life when subjected to high or ultrahigh pressure．Hydraulic autofrettage and swage autofrettage are the most common methods，but there are certain difficulties in these autofrettage process．The thermal autofrettage is achieved by creating temperature gradient in the wall of the cylinder．It is easy to handle，safe and inexpensive．Therefore，it is of great importance to investigate the theory ofthermal autofrettage and analyze the effects of temperature gradient on bearing capacity． Basic research on some important phases of the thermal autofrettage for internally pressurized thick-walled cylinder is carried out with the combination of theory method and numerical simulation，which could provide a theoretical guide for the application of thermal autofrettage． The primary investigation contents ofthis paper are as follows： First，the theory of thermo—elastic stresses was systematically studied． On the basis of the elastic—perfectly plastic material，The calculation formulas such as threshold temperature differences of initial yielding—at inner wall，the total stresses due to internal working pressure and thermal load the relationships between the maximum bearing capacity after autofrettaged and temperature gradient were obtained by using the yield criterion of Tresca．The distribution rules of thermo-elastic stresses and the influence of temperature gradient on bearing capacity were summarized．Second，mechanical models of elastic and plastic zone were built．On this basis，the formulas of thermal stresses，residual thermal stresses and total stresses under plane stress condition for the phases of elasto-plastic deformation were obtained．The numerical solutions of ⅡI 万方数据  elasto-plastic interface and threshold temperature difference of initial yielding at the outer wall were solved，the distribution curves of stresses were shown by MA