Fracture Mechanics Methodologies for Structural Integrity Assessments and Fatigue Life Predictions under Multi-axial Non-proportional Loading

多轴非比例载荷下结构完整性评估和疲劳寿命预测的断裂力学方法

• 批准号: RGPIN-2015-03994
• 负责人: Wang, Xin
• 金额: $ 1.6万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=678693
• 关键词: Fracture; Mechanics; Methodologies; Structural; Integrity

Safe operations of high-performance structural components such as those in nuclear pressure vessel, gas pipeline, offshore and aircraft industries are of significant practical interest. Failures of any of those components are major concerns since they can result in injury to the public, damage to the environment and high repair costs. Structural integrity assessments and fatigue life predictions aimed at quantifying the impact of defects in those components play a key role in ensuring the safe service of those high-performance structures. Current fracture-mechanics based procedures use results of laboratory tests on small-scale specimens to correlate and predict the response of full scale structural components. Significant developments in constraint-based fracture mechanics have taken place in recent years to ensure reliable transferability of properties obtained from laboratory tests to the full scale components. In those developments, the differences between the crack tip triaxial stress states (so-called "constraint") in test specimens and full scale components was quantified.****However, all these developments have been focused on the cases where external loading are proportionally applied, and thus the stress components in the structural body remain proportional during the loading process. The present methodologies cannot properly address the effects of multi-axial loading that are applied non-proportionally. Multi-axial non-proportional loading occurs routinely in engineering structures, and the proper quantification of its effect on fracture and fatigue behaviors is of practical significance. It is proposed here to develop fracture mechanics methodologies that accounted for the effect of multi-axial non-proportional loading. In particular, the effect of non-proportional loading on constraint will be studied extensively. Two-parameter approach will be extended with an additional parameter that quantifies the non-proportional loading. Numerical simulations, employing micromechanical models, and experimental testing of various laboratory specimens under multi-axial non-proportional loading will be carried out to quantify the effects on brittle, ductile fracture and fatigue behaviors. Procedures of failure assessment and fatigue life predictions will be developed that is capable of addressing the non-proportional loading effects. The outcome of the research will enable more reliable assessments and fatigue life predictions for high performance engineering structural components under complex loading conditions.**

核压力容器、天然气管道、海上和飞机工业等高性能结构部件的安全运行具有重大的实际意义。 这些组件中的任何一个发生故障都是主要问题，因为它们可能导致公众受伤、环境破坏和高昂的维修成本。 旨在量化这些部件缺陷影响的结构完整性评估和疲劳寿命预测在确保这些高性能结构的安全使用方面发挥着关键作用。 当前基于断裂力学的程序使用小尺寸样本的实验室测试结果来关联和预测全尺寸结构部件的响应。 近年来，基于约束的断裂力学取得了重大进展，以确保从实验室测试获得的性能能够可靠地转移到全尺寸部件。 在这些开发中，对测试样本和全尺寸部件中的裂纹尖端三轴应力状态（所谓的“约束”）之间的差异进行了量化。****但是，所有这些开发都集中在按比例施加外部载​​荷的情况下，因此结构体中的应力分量在加载过程中保持成比例。 目前的方法不能正确解决不按比例施加的多轴载荷的影响。 工程结构中经常发生多轴非比例载荷，适当量化其对断裂和疲劳行为的影响具有实际意义。 这里建议开发考虑多轴非比例载荷影响的断裂力学方法。 特别是，将广泛研究非比例载荷对约束的影响。 双参数方法将通过量化非比例载荷的附加参数进行扩展。 将采用微机械模型进行数值模拟，并对多轴非比例载荷下的各种实验室样本进行实验测试，以量化对脆性、延性断裂和疲劳行为的影响。 将开发能够解决非比例负载效应的失效评估和疲劳寿命预测程序。 研究成果将为复杂载荷条件下的高性能工程结构部件提供更可靠的评估和疲劳寿命预测。**