压力容器焊缝咬边疲劳裂纹的启裂寿命

针对某企业空气球罐焊缝咬边在压力波动时的受力情况,首先建立带咬边结构的受力模型,利用西田正孝的图表方法和有限元法分别计算咬边引起的弹性应力集中系数,然后计算出咬边尖端的名义应力,进而利用小缺口启裂寿命经验估算式估算咬边的疲劳裂纹启裂寿命。再采用与实物等厚度、与真实咬边等尺寸的模拟试样,进行与实际结构等应力范围条件下的模拟疲劳试验。结果表明,试验寿命与根据经验估算式得到的估算寿命非常接近,从而为咬边疲劳裂纹启裂寿命研究提供了理论依据和试验数据。在考虑一定的安全系数后,对所分析的球罐给出的剩余总寿命为9年,至启裂的剩余寿命为6年。

INITIATION LIFE OF WELD UNDERCUTS FATIGUE CRACK IN PRESSURE VESSEL

Aiming at the pressure condition of the weld undercuts of the air spherical tank under the fluctuant pressure in an enterprise, the mechanics model of the structure with undercuts is built, the graphology and finite element method are respectively used to calculate the elasticity stress concentration factor, then the nominal stress about the undercut tip is calculated. Then the initiation life of fatigue crack is estimated according to the experimental estimate expression. Using the samples with equal thickness to the tank and with the same size as the real undercuts, a simulation fatigue testes are performed under the stress range of an actual structure. As a result, the estimating life according to the experimental estimate expression approaches to the experimental life. Sequentially, theoretical basis and the experimental data for study on fatigue crack initiation life of the undercut is provided. Considering some safety factor, the remain life of the tank is 9 years, the remain initiation life of fatigue crack is 6 years.