船舶结构低周疲劳强度分析方法

摘要

为了分析船舶结构低周疲劳强度,以连续介质损伤力学和热力学为基础,将损伤耗散势和塑性应变理论相结合,建立了船舶结构低周疲劳强度模型.分别采用船用高强度402钢疲劳试验结果、Manson-Coffin方程法、通用斜率法及高周疲劳S-N曲线外推法对推导模型的适用性和实用性进行评估,并讨论了船舶结构低周疲劳损伤临界值.比较结果表明,文章推导的模型可以使用应力形式准确地评估船舶局部结构的低周疲劳寿命和损伤,能够方便地对低周疲劳强度进行校核.根据推导模型,低周疲劳强度与等效平均应力幅(ˉσa)和钢材低周疲劳试验特性参数K,m有关,船舶常用钢材的低周疲劳损伤临界值可取为0.3.%A model to analyze the low-cycle-fatigue strength of ship structures was presented. It combined dissipation energy of continuum mechanics with plastic mechanics, and is based on continuum damage mechanics and thermodynamics theories. The applicability of the model has been verified by fatigue test results of high strength steel 402, the Manson-Coffin equation, the universal slopes method, and a method of extrapolating a high-cycle-fatigue S-N curve in a low cycle life region. The convenience of assessing the low-cycle-fatigue strength and damage of local ship structures precisely was proven. It was also implied by the models that the low-cycle-fatigue strength was related to the effective mean amplitude and steel fatigue test constants K and m. The damage limit of steel which is commonly used in shipbuilding was shown to be 0.3.