This problem involves the complex mechanism of small-crack growth which is different from long crack growth behavior. This behavior is known as the small crack effect and it indicates that the crack closure phenomenon may not exist in small crack growth regions or it can be negligible.
The paper is organized as follows. However, the difference of growth behavior between small crack and long crack is not considered in this method. Liu and Mahadevan [ 5 ] recently proposed a method to predict the fatigue life of smooth specimens based on the equivalent initial flaw size EIFS.
Newman developed a strip yield model to quantify the crack closure level [ 1011 ]. These issues make fatigue life prediction based on crack growth analysis difficult.
Therefore, the EIFS concept is considered to be a good way to solve these problems. In this paper, a general method is proposed to predict fatigue life based on the crack closure model and the EIFS, in which the small crack effect is also considered.
One of the main problems of this method is how to evaluate the initial flaw size IFS appropriately. Though some researchers doubted the contribution of crack closure to crack growth and the existence of the crack closure phenomenon [ 121314 ], plenty of experimental research, numerical, and theoretical analysis on long cracks have shown that the crack closure phenomenon does exist and has a significant effect on fatigue crack growth [ 9101115161718192021222324 ].
Introduction Life prediction and failure analysis are indispensable and critical for engineering structural materials, but continue to be challenging issues. Because of this, the fatigue crack growth method based on linear elastic fracture mechanics LEFM is becoming a more important and promising alternative for total fatigue life analysis.
But most of the existing methods are lack of theoretical foundation and are sometimes unreliable [ 4 ]. A good agreement is observed between model predictions and experimental data.
Experimental data for smooth and circular-hole specimens in three different alloys AlT3, AlT6 and Ti-6Al-4V under multiple stress ratios are used to validate the method. Crack closure considering the small crack effect may reflect real crack propagation characteristics.
The general material crack propagation model can be expressed as d. Finally, some discussion and conclusions are drawn based on the current study.
Additionally, estimation of the actual IFS is another challenge. In the validation section, Semi-circular surface crack and quarter-circular corner crack are assumed to be the initial crack shapes for the smooth and circular-hole specimens, respectively.
In the current study, several methods are employed to estimate the value of initial flaw size, such as nondestructive evaluation NDE [ 2 ] and empirical approaches [ 3 ]. Next, a total fatigue life prediction model considering the crack closure, is established; then, a large number of experimental data, for smooth and circular-hole specimens on three different alloys AlT3, AlT6 and Ti-6Al-4Vunder multiple stress ratios collected from the open literature, are employed to validate the proposed model.
Different effects of crack closure on small crack growth region and long crack growth region are considered in the proposed method. The crack closure phenomenon caused by plasticity was first observed by Elber [ 9 ]. Many complicated crack growth phenomena such as the overload retardation effect and the loading sequence effect, etc.
Several crack growth models are available to describe crack growth behavior, such as the Forman model and the Walker model. Failure analysis and fatigue life prediction are necessary and critical for engineering structural materials.
Some conclusions and future work are given. Small-crack growth is a very complicated process, and it is difficult to establish an accurate quantitative expression to describe the growth behavior of a real small crack.
The detailed analysis and discussion are performed on the proposed model. First, a brief review of the concept of EIFS and the framework of fatigue life prediction based on crack growth analysis method, is addressed. In this paper, a general methodology is proposed to predict fatigue life of smooth and circular-hole specimens, in which the crack closure model and equivalent initial flaw size EIFS concept are employed.
In other words, crack closure may just exist in the long crack growth regime but not in the small crack growth region. In addition, Newman et al. The cumulative fatigue damage theories and the traditional S-N curve method, such as the stress-based approach [ 1 ], are often used for fatigue life prediction in engineering practice.For predicting the fatigue life of composites, the input parameters may include static and cyclic properties of the composite material under consideration, its lay.
Model for Predicting Fatigue Life of Nanomaterials. Print Reference this. Disclaimer: Develops a model for predicting fatigue life of nanostructured chip-to-package copper interconnections; Dissertation Writing Service Dissertation Examples Example Engineering Dissertations Dissertation Help Engineering Essays.
Get help with your. Failure analysis and fatigue life prediction are necessary and critical for engineering structural materials. In this paper, a general methodology is proposed to predict fatigue life of smooth and circular-hole specimens, in which the crack closure model and equivalent initial flaw size (EIFS) concept are employed.
Different effects of crack closure on small crack growth region and long crack. Understanding and Predicting the Toxicity of Manufactured Nanomaterials Supporting/Contributing Agency: U.S.
EPA To understand and ultimately predict the potential complex interplay between man-made nanomaterials and the health of living organisms, experimental and computer modeling Molecular model of a cell membrane and a carbon nanotube.
Fatigue life prediction for a bridge should be based on the current condition of the bridge, and various sources of uncertainty, such as material properties, anticipated vehicle loads and environmental conditions, make the prediction very challenging.
This paper presents a new approach for probabilistic fatigue life prediction for bridges using finite element (FE) model updating based on. Predicting fatigue resistance of nano-twinned materials: Part I – Role of cyclic slip irreversibility and Peierls stress.Download