【作者】 李兆锋；

【导师】 江楠；

【作者基本信息】 华南理工大学 ， 安全技术及工程， 2011， 硕士

【摘要】 压力容器安全性与经济性并重的设计理念已成为当前压力容器设计的发展趋势,奥氏体不锈钢是一种较为理想的低温压力容器材料,韧塑性好但屈服强度低,使得按常规设计不能充分发挥其承载能力,造成材料和资源浪费。将应变强化轻型化技术应用于奥氏体不锈钢低温容器,通过消耗材料的部分塑性,显著提高屈服强度,可达到节省材料、节能减排的目的。本文围绕国产奥氏体不锈钢应变强化低温容器的安全性,分析应变强化对材料力学性能、容器整体安全裕度的影响,并采用有限元分析手段对复杂结构容器的应变强化过程进行数值模拟。主要的研究内容和结论如下:(1)通过预应变拉伸试验得出了国产奥氏体不锈钢材料(牌号06Cr19Ni10)合适的应变强化范围,并分析了应变强化量、加载方式、保压过程对材料性能的影响。结果表明:应变强化量的增加对抗拉强度影响不大,4%~10%预应变强化范围内材料的塑性损失量约等于预应变量;保压过程基本不影响材料性能的改变。(2)运用有限元法模拟分析了应变强化对容器塑性失稳压力的影响。结果表明加载路径不同对容器的极限承载能力无影响,应变强化后压力容器的设计按强化前的尺寸进行设计是合理的;同时考虑预应变后容器几何形状改变和材料应力应变曲线改变的情况下,圆筒容器的塑性失稳压力无明显下降,球壳容器的下降趋势较为明显。(3)定量分析了预应变后容器的安全裕度。结果表明预应变后球壳容器安全裕度的下降程度比圆筒容器大。经4%~10%预应变后,圆筒容器的最小安全裕度由按常规设计的4.76降至2.21,与国内外标准中的最低安全裕度要求相当;球壳容器的最小安全裕度由按常规设计的4.43降为1.83。应变强化技术更适合圆筒容器。(4)利用建立的非线性有限元模型对复杂结构低温容器的应变强化过程进行数值模拟,得出了容器典型部位的应力应变随载荷的变化规律。对容器的安全裕度分析表明,按应变强化设计后容器仍具有较高的强度裕度和塑性储备。为避免应变强化后不必要的塑性变形,在有限元分析的基础上探讨了以筒体主体环向应变为关键控制参数的设计方法。更多还原

【Abstract】 The design concept that safety and economy are equal important for pressure vessels has become the development trend of pressure vessels design method. Austenitic stainless steel is an ideal material for cryogenic vessel, with excellent toughness and plasticity but low yield strength, so the conventional design method can’t make full use of its carrying capacity and results to material and resource waste. Applying strain hardening technology to austenitic stainless cryogenic vessels, which can increase the yield strength greatly by consuming the plasticity of material, could save material and energy and reduce emission.This thesis focuses on the safety of strain hardening cryogenic vessels with austenitic stainless steel, mainly analyzes the impact between strain hardening and performance of material, integral safety margin of vessels. And the strain hardening process of pressure vessels with complicated structure is numerical simulated by using finite element(FE)method.The main efforts and results of this study are as follows:(1)This study gets appropriate strain hardening range of domestic austenitic stainless steel by pre-strain tensile test and analyzes the impact of different strain hardening quantity and loading method and pressure-keeping process on material’s performance. The result is that, strain hardening increasing has little impact on tesile strength, plasticity loss is almost equal to pre-strain when strain quantity is between 0.04 to 0.1, and pressure-keeping process almost doesn’t change the material properties.(2)This study analyzed the impact of strain hardening on the plastic instability pressure by using FE numerical simulation method. The ultimate bearing capacity of pressure vessels has nothing to do with the loading path, so the method which the design of strain hardening vessels’demission based on the initial ones is reasonable. Considering the change of both geometry of vessels and stress-strain curve after being hardened, the decrease of plastic instability pressure for cylinder vessels is not significantly, but for the spherical vessels is more obvious.(3)This study quaintly analyzed the safety margin of vessels after strain hardening. The result is the decline trend of safety margin for spherical vessels is greater than cylinder. After strain hardening range between 0.04 and 0.1, the minimum safety margin of cylinder vessels decreases from 4.76 by conventional design to 2.21, which also could meet the demand of international pressure vessels standards, and the minimum safety margin of spherical vessels decreases from 4.43 to 1.83. So the strain hardening technology is more suited to cylinder than spherical vessels.(5)This study numerical simulates the strain hardening process of cryogenic vessels with complicated structure by using the non-linear finite element model and gets the variation pattern for stress and strain of typical position on vessel with the change of internal pressure. The result of safety margin to this vessel by strain hardening design is that it still has good strength and plasticity reserves. Based on the FE analysis, the hoop strain of the main part of the cylinder body could used as a key controlling factor for avoiding unnecessary plastic deformation after strain hardened.更多还原