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表面粗糙度缺陷是影响金属材料疲劳性能的重要因素,尤其针对高强度钢FV520B-Ⅰ。但目前基于表面粗糙度的FV520B-Ⅰ高周疲劳研究得到开展,也没有建立相应的寿命预测模型。本文首先针对不同粗糙度件下的疲劳试件进行了疲劳实验,对粗糙度作用下断口处的疲劳裂纹萌生区域和扩展区域的形貌特征进行了观察,分析了粗糙度影响的FV520B-Ⅰ疲劳失效行为和疲劳性能。由于疲劳失效机理不同,目前存在的FV520B-Ⅰ超高周疲劳寿命预测模型并不适用于高周疲劳情况,因此需要提出一个新的针对粗糙度影响下的FV520B-Ⅰ高周疲劳寿命预测模型。结合Murakami条件疲劳强度模型和经典的Basquin公式得到疲劳寿命预测基础模型。以疲劳实验数据为基础拟合得到了与FV520B-Ⅰ相关的未知模型参数,建立了针对FV520B-Ⅰ的粗糙度影响下的疲劳寿命预测模型,并提出了疲劳强度系数与应力幅值之间满足线性关系。明确粗糙度影响下的FV520B-Ⅰ高周疲劳行为机理能够有效的提高实际工况中疲劳寿命预测的准确性,同样丰富了FV520B-Ⅰ的疲劳研究。
Surface roughness defects are important factors affecting the fatigue properties of metallic materials, especially for high-strength steel FV520B-Ⅰ. However, the research on FV520B-Ⅰ high cycle fatigue based on surface roughness has been carried out at present, and no corresponding life prediction model has been established. In this paper, the fatigue tests of fatigue specimens under different roughness were carried out firstly. The appearance of fatigue crack initiation zone and extension zone under the action of roughness was observed. The fatigue of FV520B-Ⅰ Failure behavior and fatigue performance. Due to the different mechanism of fatigue failure, the existing FV520B-Ⅰ ultra-high cycle fatigue life prediction model is not suitable for high cycle fatigue conditions. Therefore, a new FV520B-Ⅰ high cycle fatigue life prediction model under the influence of roughness needs to be proposed. Combined with Murakami condition fatigue strength model and classic Basquin formula, the fatigue life prediction basic model is obtained. Based on the fatigue experimental data, the unknown model parameters related to FV520B-Ⅰ were fitted and the prediction model of fatigue life under the influence of roughness of FV520B-Ⅰ was set up. The fatigue strength coefficient and the stress amplitude were satisfied Linear relationship. The mechanism of FV520B-Ⅰ high-cycle fatigue under the influence of definite roughness can effectively improve the accuracy of prediction of fatigue life under actual conditions and also enrich the fatigue study of FV520B-Ⅰ.