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Method for calculating ultrahigh-cycle fatigue crack initiation time

A fatigue crack and time calculation technology, applied in the direction of measuring devices, instruments, scientific instruments, etc., can solve the problems that the estimated contribution of remaining life is not direct enough, coupling effect is not considered, and the crack growth rate is not constant.

Active Publication Date: 2015-05-13
SOUTHEAST UNIV +1
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Problems solved by technology

However, the above model does not consider the coupling effect, and the model does not express the relationship between crack growth and existing crack length, so, on the one hand, the estimated contribution to the remaining life of existing cracks in real production is not direct enough
On the other hand, it also contradicts the phenomenon that the real crack growth rate is not constant

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  • Method for calculating ultrahigh-cycle fatigue crack initiation time
  • Method for calculating ultrahigh-cycle fatigue crack initiation time
  • Method for calculating ultrahigh-cycle fatigue crack initiation time

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Embodiment Construction

[0047] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

[0048] The internal structure of the material is not uniform, and the environment of each lattice is not the same. Under the alternating load, the component bears the force, the component undergoes slight deformation, and absorbs a large proportion of energy in the form of potential energy. Stress concentration at some places, dislocations occur in some minority lattices, molecular spacing changes, local temperature rises, thermal expansion occurs, and thermal stress occurs. At the same time, due to local temperature rises, the mechanical properties of materials in local areas change, yield strength and cracks The threshold value is getting smaller, resulting in very small cracks; the generation of cracks requires the formation of surface energy on the one hand, and on the other hand, the generation of strain, the formation of potentia...

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Abstract

The invention belongs to the fields of quantitative description and life calculation and analysis of ultrahigh-cycle fatigue damage coupling mechanisms of iron system materials and in particular relates to a method for calculating ultrahigh-cycle fatigue crack initiation time. The method comprises the following steps: by adopting principles such as an energy conservation principle, elastic mechanics and fracture mechanics, taking a hollow shaft as an example, establishing a three-dimensional transient temperature field, providing a quantitative model and time calculation method in the ultrahigh-cycle fatigue crack initiation process under the coupling effect, giving novel crack initiation basis, and performing allowable stress design reasoning. The propagation of cracks is discontinuous, the change of outside action time and change of the crack length are in the same direction, and the change speed is influenced by surface energy and yield limit. The scheme has the advantages that the method is based on the quantitative model of the crack initiation under the multi-factor coupling effect when the material interior crack size is zero. The method directly contributes to estimating the observable crack scale and crack initiation time in actual production and is scientific.

Description

technical field [0001] The invention belongs to the field of life calculation and analysis of ultra-high-cycle fatigue coupling damage of iron series materials, and in particular relates to a calculation and analysis method for ultra-high-cycle fatigue crack initiation time. Background technique [0002] The life prediction of ultra-high cycle fatigue has important guiding significance for component design and equipment maintenance. However, due to the complexity of its mechanism, there are still deviations between the existing theory and practical data. Therefore, the existing theory needs to be improved. , especially in the crack initiation model, the existing quantitative models are very lacking. It generally assumes that there are cracks in the material, so most of the research is on the crack growth model. Even in the research on the growth model, it is mainly a static model and a single factor model. . [0003] Therefore, in theory, there is a lack of a quantitative r...

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Application Information

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IPC IPC(8): G01N3/00
Inventor 方叶祥汤文成
Owner SOUTHEAST UNIV
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