基于表面和内部损伤的压缩机叶片疲劳性能研究
发布时间：2018-08-04 13:37
【摘要】：高强度钢FV520B-I被应用于各类大型机械设备的核心部件的制造,例如离心压缩机的叶片。以实际工况中的压缩机叶片为例,其疲劳寿命为10-20年,经过疲劳分析为超高周疲劳。经过研究发现,损伤是影响超高周疲劳性能最明显的因素,包括表面粗糙度以及内部夹杂物等都是容易引起疲劳失效的位置。损伤的存在使得材料或者零部件的疲劳强度降低,这个过程中还伴随着实际工况中的应力比等因素的综合影响,最终导致疲劳寿命减小并发生不可逆的疲劳失效。虽然在疲劳研究领域已经提出了各类疲劳寿命预测模型以及疲劳强度计算公式,也建立了比较成熟的理论,但是目前还没有针对FV520B-I开展不同损伤形式的疲劳性能研究。同时针对实际工况参数影响下的FV520B-I疲劳性能研究也没有得到广泛的开展,不能为理论研究以及实际应用提供有效的研究依据。本文将结合成熟理论与疲劳实验研究影响FV520B-I疲劳寿命以及疲劳强度的各类因素,建立考虑表面粗糙度和内部夹杂物两种损伤的疲劳寿命以及疲劳强度计算模型,为实际工况中的FV520B-I及相关零部件的疲劳分析和再制造提供理论依据,丰富FV520B-I的疲劳研究。本文首先从疲劳理论的研究背景出发,了解现阶段的疲劳研究取得的成果,明确针对FV520B-I疲劳研究的意义。其次,从疲劳实验出发,开展了FV520B-I的疲劳实验,得到了疲劳实验数据,包括应力幅值和疲劳寿命,从而得到应力-寿命曲线。并针对试件断口以及表面进行分析,得到相应的夹杂物尺寸和表面粗糙度值,为后续的研究提供数据基础。进一步以离心压缩机实际工况为基础建立有限元模型,分析叶片存在疲劳裂纹情况下的应力分布,为后续建立疲劳强度模型打下基础。第三章中结合实际压缩机叶片工作的实际参数分析了影响金属材料疲劳寿命和疲劳强度的各类因素,明确了各个参数对疲劳强度的影响机制,根据经典疲劳理论得到了应力比以及尺寸变化对疲劳强度影响的修正参数具体表达式。针对表面粗糙度影响系数进行了实验,明确了不同表面粗糙度时的粗糙度系数。第四章和第五章中分别以表面粗糙度和内部非金属夹杂物为主要研究对象建立表面粗糙度和内部非金属夹杂物与疲劳强度以及疲劳寿命之间的计算模型。并针对表面粗糙度影响情况开展了补充实验来证明模型的精确性。进一步根据实际的工况参数确定应力比、氢元素等影响参数的具体值。并根据疲劳实验中的工况进行了考虑内部非金属夹杂物情况下相应的疲劳强度以及疲劳寿命计算,验证了疲劳强度计算模型的适用性。
[Abstract]:High strength steel FV520B-I is used in the manufacture of core components of large mechanical equipment, such as centrifugal compressor blades. The fatigue life of compressor blade is 10-20 years, which is analyzed as ultra-high cycle fatigue. It is found that the damage is the most obvious factor affecting the fatigue performance of ultra-high cycle, including the surface roughness and internal inclusions, which are easy to cause fatigue failure. The existence of damage reduces the fatigue strength of the material or parts, which is accompanied by the comprehensive influence of the stress ratio in the actual working conditions, which ultimately leads to the reduction of fatigue life and the occurrence of irreversible fatigue failure. Although various fatigue life prediction models and fatigue strength calculation formulas have been put forward in the field of fatigue research, and more mature theories have been established, there is no research on fatigue performance of different damage forms of FV520B-I at present. At the same time, the research on fatigue properties of FV520B-I under the influence of actual working condition parameters has not been widely carried out, which can not provide an effective research basis for theoretical research and practical application. In this paper, the fatigue life and fatigue strength of FV520B-I are studied with mature theory and fatigue experiment, and the fatigue life and fatigue strength calculation model considering surface roughness and internal inclusions are established. It provides theoretical basis for fatigue analysis and remanufacture of FV520B-I and related parts in actual working conditions, and enriches the fatigue research of FV520B-I. Based on the research background of fatigue theory, this paper first understands the achievements of fatigue research at the present stage, and clarifies the significance of FV520B-I fatigue research. Secondly, the fatigue experiment of FV520B-I is carried out, and the fatigue test data, including the stress amplitude and fatigue life, are obtained, and the stress-life curve is obtained. Based on the analysis of the fracture and surface of the specimen, the inclusion size and the surface roughness are obtained, which provides the data basis for further research. The finite element model is established on the basis of the actual condition of centrifugal compressor, and the stress distribution in the presence of fatigue crack is analyzed, which lays the foundation for the subsequent establishment of fatigue strength model. In chapter 3, the factors affecting fatigue life and fatigue strength of metal materials are analyzed according to the actual working parameters of compressor blades, and the influence mechanism of each parameter on fatigue strength is clarified. According to the classical fatigue theory, the modified parameter expression of the effect of stress ratio and size change on fatigue strength is obtained. The influence coefficient of surface roughness is tested, and the roughness coefficient of different surface roughness is determined. In the fourth and fifth chapters, the surface roughness and internal non-metallic inclusions are taken as the main research objects, respectively, and the calculation models between surface roughness and internal non-metallic inclusions, fatigue strength and fatigue life are established. A supplementary experiment was carried out to prove the accuracy of the model according to the influence of surface roughness. Furthermore, the specific values of the stress ratio, hydrogen element and other influencing parameters are determined according to the actual operating condition parameters. The fatigue strength and fatigue life are calculated under the condition of internal non-metallic inclusions, and the applicability of the fatigue strength calculation model is verified.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH45
本文编号：2164052
[Abstract]:High strength steel FV520B-I is used in the manufacture of core components of large mechanical equipment, such as centrifugal compressor blades. The fatigue life of compressor blade is 10-20 years, which is analyzed as ultra-high cycle fatigue. It is found that the damage is the most obvious factor affecting the fatigue performance of ultra-high cycle, including the surface roughness and internal inclusions, which are easy to cause fatigue failure. The existence of damage reduces the fatigue strength of the material or parts, which is accompanied by the comprehensive influence of the stress ratio in the actual working conditions, which ultimately leads to the reduction of fatigue life and the occurrence of irreversible fatigue failure. Although various fatigue life prediction models and fatigue strength calculation formulas have been put forward in the field of fatigue research, and more mature theories have been established, there is no research on fatigue performance of different damage forms of FV520B-I at present. At the same time, the research on fatigue properties of FV520B-I under the influence of actual working condition parameters has not been widely carried out, which can not provide an effective research basis for theoretical research and practical application. In this paper, the fatigue life and fatigue strength of FV520B-I are studied with mature theory and fatigue experiment, and the fatigue life and fatigue strength calculation model considering surface roughness and internal inclusions are established. It provides theoretical basis for fatigue analysis and remanufacture of FV520B-I and related parts in actual working conditions, and enriches the fatigue research of FV520B-I. Based on the research background of fatigue theory, this paper first understands the achievements of fatigue research at the present stage, and clarifies the significance of FV520B-I fatigue research. Secondly, the fatigue experiment of FV520B-I is carried out, and the fatigue test data, including the stress amplitude and fatigue life, are obtained, and the stress-life curve is obtained. Based on the analysis of the fracture and surface of the specimen, the inclusion size and the surface roughness are obtained, which provides the data basis for further research. The finite element model is established on the basis of the actual condition of centrifugal compressor, and the stress distribution in the presence of fatigue crack is analyzed, which lays the foundation for the subsequent establishment of fatigue strength model. In chapter 3, the factors affecting fatigue life and fatigue strength of metal materials are analyzed according to the actual working parameters of compressor blades, and the influence mechanism of each parameter on fatigue strength is clarified. According to the classical fatigue theory, the modified parameter expression of the effect of stress ratio and size change on fatigue strength is obtained. The influence coefficient of surface roughness is tested, and the roughness coefficient of different surface roughness is determined. In the fourth and fifth chapters, the surface roughness and internal non-metallic inclusions are taken as the main research objects, respectively, and the calculation models between surface roughness and internal non-metallic inclusions, fatigue strength and fatigue life are established. A supplementary experiment was carried out to prove the accuracy of the model according to the influence of surface roughness. Furthermore, the specific values of the stress ratio, hydrogen element and other influencing parameters are determined according to the actual operating condition parameters. The fatigue strength and fatigue life are calculated under the condition of internal non-metallic inclusions, and the applicability of the fatigue strength calculation model is verified.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH45
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