Linear elastic fracture mechanics is applied to analyze the lifespan of fatigue crack growth of specimen, which is under constant amplitude load. The nucleation phase typically represents the longest period of fatigue life, although local irregularities could significantly shorten the nucleation period. Plaque fatigue crack growth per pressure pulse was estimated using an. Oct 24, 2014 failure and fatigue crack propagation analysis with marc msc software. Low cycle fatigue crack propagation resistance of materials for large welded structures. A recent paper by pearson1 reports the results of crack propagation experiments on various metals, of which youngs moduli e range from 6. Kfc, corresponding to the final fracture in fatigue, was also determined. Based on the baseline model, we investigated the influence of calcification on rupture path and fatigue life by adding a circular calcification and changing its location within the fibrous cap area. For other components the crack growth life might be a substantial portion of the total life of the assembly. In this study, we explore the fatigue process in human carotid artery plaques using in vivo highresolution mr imaging by assessing the propagation of cracks leading to plaque rupture. The software of fatigue is used to calculate the lifespan of a center crack plate steel specimen. How does calcification influence plaque vulnerability.
In the patient group with fc defect, for each plaque one mr slice with presence of fc rupture or ulceration figure 1 was used for the fatigue simulation and the ulceration was replaced by lrnc with the assumption that the ulceration was the result of escaped lrnc 2123. There may be instances when the bolt or rivet holes. For fatigue, fatiguecrack propagation, and fracture data, however, design allowable values are usually not available and the data are presented in terms of typical or average values. Designing safe products requires the knowledge of failure mechanisms of the materials used, and understanding of contributing factors like the loads that could initiate a crack. Probabilistic assessment of creepfatigue crack propagation in. Fatigue failure slides share and discover knowledge on.
Fatigue crack propagation analysis of plaque rupture. This could be due the presence of residual stresses that increase the load ratio effectively applies to the fatigue crack. Assuming an initial flaw of 1mm, and using paris law, a crack propagation analysis by integration would give 10,000 cycles before the crack becomes. Crack propagation and residual static strength of fatigue cracked titanium and steel cylinders. The influence of metallurgical structure on the mechanisms of fatigue crack propagation. But whether or not the calcifications have a negative effect on plaque vulnerability is still under debate. In the current study, we investigated the influence of calcium deposition on plaque rupture from the fatigue crack growth point of view. Fractals and catastrophe analysis of fatigue crack. Calcification is commonly believed to be associated with cardiovascular disease burden. Fatigue process in atherosclerotic plaques studied by developing a 2d fatigue crack propagation model for investigating the plaque initiation, crack path and crack growth rate for an idealized. Mean or pulse pressure did not affect initiation location.
Mribased fatigue analysis predicts plaque vulnerability. Failure and fatigue crack propagation analysis with marc msc software. Significant grain flow along the crack path is seen due to higher crack tip stresses. The crack may be initiated by fatigue, or may be preexisting from manufacture, or may be caused by an impact, or similar event e. Cracks extended radially and fatigue crack growth rate increased with increase in pulse pressure. Fatigue and plaque rupture in myocardial infarction. Part of the problem for fatigue and fatiguecrack propagation is that these behaviors are influenced by a wide range of parameters that include cyclic stress, meanstress, cyclic frequency, temperature, environment, product form and orien tation with respect to loading, structural geometry size, shape, and notch con figuration, metallurgical and surface effects associated with heat treatment, microstructure, and machining practices. Fatigue crack propagation analysis of plaque rupture, asme j. Incremental crack propagation was dynamically simulated based on stress distributions. It is suggested that crack propagation analysis can lead to a better recognition of factors involved in. Materials and methods 1mri acquisition twenty seven patients table 1 with atherosclerotic carotid artery disease were included in this study. Fatigue crack growth and fracture mechanics analysis of a working roll surface layer material is presented in this paper. Pdf stress analysis of fracture of atherosclerotic plaques. Solid mechanics fatigue crack propagation anders ekberg 3 20 crack growth as a function of.
Paris law was used to determine the fatigue crack growth rate. Rupture of atheromatous plaque is the major cause of stroke or heart attack. For some components the crack propagation life is neglected in design because stress levels are high, andor the critical flaw size small. Plaque fatigue crack growth per pressure pulse was estimated using an adapted parisrelation. An idealized baseline model containing no calcification was first built. The correlation between fatigue crack propagation and stress intensity factor is analyzed. Fatigue crack growth rate, dadn, of two high strength steels were examined in a laboratory air at different stress ratios, covering almost the entire range of stress intensity. Fractals and catastrophe analysis are applied to analyze photos of the law of crack of three sets of fatigue samples under different stress cycles. Im a bit puzzled about fatigue and crack propagation. Review, analysis, and discussion of the fatigue crack growth problem significance of fatigue cracks in microrange and macrorange j. It is suggested that crack propagation analysis can lead to a better recognition of factors involved in plaque rupture and more accurate determination of. Department of transportation research and special progrems adninistration volpe national transportation systems center kcndell square, cdridge, ma 02162 8. Stress analysis of carotid plaque rupture based on in vivo high resolution mri. Further validation studies on the 3d printed arteries are necessary for better understanding the factors contributing to plaque rupture.
Dislocations play a major role in the fatigue crack initiation phase. From fatigue research it is known that fatigue life can often be divided into three periods. Fracture mechanics theory was introduced to describe the stress status at the crack tip and paris law was used to calculate the crack growth rate. Assuming that crack propagation initiated at the sites of stress. Fatigue and plaque rupture in myocardial infarction request pdf. By the use of fracture mechanics principles it is possible to predict the number of cycles spent growing a crack to some specified length or to final failure. Fatigue crack growth once a crack is present in a material, it will tend to grow under the influence of cyclic loading. It is suggested that crack propagation analysis can lead to a better recognition of factors. Part of the problem for fatigue and fatiguecrack propagation is that these behaviors are influenced by a wide range of parameters that include cyclic stress. Fatigue crack growth under pulsatile pressure and plaque rupture. Fatigue fracture toughness and crack propagation rate. Fatigue crack propagation in structures with simulated rivet forces.
It is suggested that crack propagation analysis can lead to a better recognition of factors involved in plaque rupture and more accurate determination of vulnerable plaques. Fatigue crack propagation fatigue material fracture. Stp415 fatigue crack propagation astm international. It is clear that the maximum fatigue crack propagation. The research is done on a hot strip mill working roll where high chromium steel is used for rolls shell material. Stress analysis of fracture of atherosclerotic plaques. Fatigue rupture analysis and the fatigue life were used to evaluate the rupture risk. Paris law in fracture mechanics is adopted to determine the fatigue crack growth rate. It is proven that in fretting fatigue failure scenario after nucleating crack at contact interface, in early stage of crack propagation its behavior is governed by frictional shear stress at the contact interface. Moreover, increasing the mean or pulse pressure decreased the number of cycles to rupture. Research open access in vivo mribased simulation of fatigue. The majority of the fatigue life may be taken up in the propagation of a crack. Given a sn curve, this one will predict for a specific level of stress what number of cycles are required to failure, lets say 10e6 cycles. The fatigue crack propagation lifespan of the engineering structure is studied.
Fatigue rupture analysis and the fatigue life were used to evaluate the rupture. Analysis of the fatigue crack propagation lifespan based on. Failure and fatigue crack propagation analysis with marc. K in experiments, crack propagation has been measured as a function of the stress intensity factor i ii iii log da dn log. To obtain corresponding parameters, a rectangular single edge notched bend specimens senb, according to. Schijve 415 discussion 458 fatiguecrack propagation in some ultrahighstrength steelsr.
With this relevance, in vivo imagebased mechanical analysis has been employed. Modified paris law was used to govern crack propagation and the. Considering that the cardiovascular system is a classic fatigue environment, plaque rupture was treated as a chronic fatigue crack growth process in this study. Talda, and cheyu li 460 discussion 480 the effect of grain size on fatigue crack propagation in copper. K below which fatigue cracks will not propagate at the other extreme, k max will. Sep, 20 rupture of atheromatous plaque is the major cause of stroke or heart attack. Compared with metal whose fatigue behavior has been widely quantified, plaque is a more complex structure with various atherosclerotic components and anisotropic material properties. When one measures fatigue crack propagation rate, a crack increment, ha, and its corresponding increment in load cycles, an, are measured. The life of a fatigue crack has two parts, initiation and propagation. For undestroyed samples, the law of crack appears and develops, and the fractal dimension tends to be constant eventually.
Prediction of atherosclerotic plaque life perceptions from. This project is being conducted under the advisory guidance of the committee on ship structural design of the national academy of sciencesnational research council. The initial fracture propagation by fatigue resulted from the growth of multiple cracks in the thickness direction, followed by positive interaction of these closely spaced microcracks leading to a large equivalent crack size. Keywords atherosclerotic plaque myocardial infarction fracture mechanics fatigue finite element method. Here, we built an idealized model in which only one calcification is included. Oct 01, 20 fatigue crack propagation analysis of plaque rupture. The results indicate that the law of crack has fractal characteristics. Marc simulation of failure and crack propagation in fea. Stages of fatigue failure fatigue failure two main fracture zones smooth surface crystalline surface 1 crack initiation 2 crack propagation 3 catastrophic rupture atta ul haq gik institutefall 20 7 8. Fatigue crack propagation must be caused by a shear andor a normal separation mode. Analysis of fatigue crack propagation in gusset plates bhairav k thakkar1 gusset plates are used commonly in truss joints. The simplest form of joints in a truss system consists of bolted or riveted connections. Introduction fracture mechanics fatigue crack propagation.
Rupture of atherosclerotic plaque with resulting thromboembolism is a. Fatigue is one of the primary reasons for the failure of structural components. The evidence of previous plaque rupture and intraplaque. The methodology will then allow us to quantify the influence of this and other parameters associated with the fatigue behavior of welded joints. Crack propagation versus fiber alignment in collagen gels. Fatigue process in atherosclerotic plaques studied by developing a 2d fatigue crack propagation model for investigating the plaque initiation, crack path and crack growth rate for an idealized plaque model based on paris law resulted in minimum fatigue life for the cracks initiated in the midcap zone, shoulder region and backside zone 14 and. Fatigue analysis was performed based on the plaque geometry derived from in vivo mri of the carotid artery at the point of maximum stenosis. It was demonstrated that cracks begin at the lumen wall at areas of stress concentration, depending on the shape of the lumen, thickness of the fibrous cap and stiffness of the plaque components. While on the subject of dislocations, it is appropriate to briefly discuss fatigue.
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