This project is being conducted under the advisory guidance of the committee on ship structural design of the national academy of sciencesnational research council. Schematic representation of a fatigue fracture surface in a steel shaft, showing the initiation region, the propagation of fatigue crack with beam markings, and catastrophic rupture when the crack length exceeds a critical value at the applied stress 36. Fracture mechanics analysis of fretting fatigue considering. An engineering study to investigate fatigue crack in n 9 cyclically loaded wing boxes reported the following crack lengths in mm. Microstructure is the principal independent variable which can be used to control the fatigue crack growth rate fcgr once loading conditions and environment are established. Fatigue crack growth once a crack is present in a material, it will tend to grow under the influence of cyclic loading.
Research open access in vivo mribased simulation of. K region i, crack propagation is difficult to predict since it depends on microstructure and flow properties of the material here, the growth may even come to an arrest crack growth rate is sensitive to the size of the grains. There is reason to believe that analysis of plaque motion may provide new. 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 crack propagation, computational fluid dynamics, and structural. As a result, the fibrous cap becomes weak and can rupture. Atherosclerotic plaque rupture pathologic basis of plaque. A recent paper by pearson1 reports the results of crack propagation experiments on various metals, of which youngs moduli e range from 6. Considering that the cardiovascular system is a classic fatigue environment, plaque rupture was treated as a chronic. Fatigue rupture analysis and the fatigue life were used to. Fatigue fracture toughness and crack propagation rate.
Introduction fracture mechanics fatigue crack propagation. Atherosclerosis plaque rupture, heart attack and stroke risk. Calculate the sample mean and sample standard deviation. Mechanisms of plaque rupture cardiovascular research oxford.
Fatigue presentationmae160 chap14 fatigue material. Also indicated are the rates of crack growth per cycle derived from staticload fracture data. Microstructure and the fracture mechanics of fatigue crack. During the fracture of low cycle fatigue, the cleavage nucleation leads to the formation of fatigue crack initiation region, the fatigue crack growth exhibits a mixed transgranular and intergranular crack growth mode, and in the final rupture region, the fracture surface of low cycle fatigue of tc25 titanium alloy appears as a typical semi. The total fatigue life is the sum of crack initiation life and crack propagation life. The simplest form of joints in a truss system consists of bolted or riveted connections.
Fatiguecrack propagation behavior of several pressure vessel. Microstructure affects the fcgr through its influence on strain distribution slip character, slip length, plastic zone size, and crack path. Paris law in fracture mechanics is adopted to determine the fatigue crack growth rate. The plaque is similar in size and echogenicity to that of the asymptomatic plaque shown in figure 3. Fatigue and plaque rupture in myocardial infarction. Volume i1 treats exclusively the subject of damage tolerance evaluation of airframes 14. Oct 16, 2015 atherosclerosis plaque rupture, heart attack and stroke risk detecting tool developed. Investigations on the fatigue crack propagation threshold in. Solid mechanics fatigue crack propagation anders ekberg 4 20 crack growth in region i for small.
Fatigue crack initiation and propagation life prediction of. In carotid plaques, rupture sites are also associated with plaque inflammation and indeed, in 70% of the ruptured plaques that were encountered in our series, the rupture site was found in the upstream shoulder. However, in con ducting fatigue analyses on pressure vessel and piping components, it is often conservative to ignore the crack initiation process, assume that the component already contains a pre existing crack or defect, and use the analysis technique of fracture me. Growth of coronary plaque presents clinically as angina when coronary flow is decreased. Kfc, corresponding to the final fracture in fatigue, was also determined. Prediction of atherosclerotic plaque life perceptions. The fatigue hypothesis of plaque rupture and atherosclerosis.
Atherosclerotic plaque is subjected to a repetitive deformation due to arterial pulsatility during each cardiac cycle and damage may be accumulated over a time period causing fibrous cap fc fatigue, which may ultimately lead to rupture. The correlation between fatigue crack propagation and stress intensity factor is analyzed. Fatigue rupture analysis and the fatigue life were used to evaluate the rupture risk. Whether analysis of plaque motion in patients with carotid artery. Stress analysis of fracture of atherosclerotic plaques. In the current study, we investigated the influence of calcium deposition on plaque rupture from the fatigue crack growth point of view. Fatigue crack propagation fatigue material fracture. It is suggested that crack propagation analysis can lead to a better recognition of factors involved in plaque rupture and more.
Thus, fatiguecrackpropagation results are usually presented in terms of crack. Fatigue and fatigue crack growth behavior of tool steel. Atherosclerotic plaque rupture is a catastrophic event that contributes to mortality. 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. The fatigue cracks are simultaneously generated by cracking of carbides, debonding of carbide metallic matrix interfaces or by crack initiationinthematrix4. In this study, we investigate the fatigue process in human carotid plaques using in vivo carotid magnetic resonance mr imaging. Solid mechanics fatigue crack propagation anders ekberg 1 20 fatigue crack propagation repetition crack initiation and growth small cracks shear driven interact with microstructure mostly analyzed by continuum mechanics approaches large cracks tension driven fairly insensitive to microstructure mostly analyzed by. Fracture mechanics analysis of fretting fatigue considering small crack effects, mixed mode, and mean stress effect. Materials and methods 1mri acquisition twenty seven patients table 1 with atherosclerotic carotid artery disease were included in this study. The process of atherosclerotic plaque rupture with superimposed thrombosis is. It can make you feel unwell and like youre not in control of your recovery. Prediction of atherosclerotic plaque life perceptions from.
Various fracture criteria and crack growth rules are studied. Failure and fatigue crack propagation analysis with marc. Calcification is commonly believed to be associated with cardiovascular disease burden. Atherosclerotic plaque rupture is a significant cause for the majority of acute events such as ischaemic stroke and myocardial infarction. Fatigue crack propagation must be caused by a shear andor a normal separation mode. Moreover, increasing the mean or pulse pressure decreased the number of cycles to rupture.
Fatiguecrack propagation is more complicated than fatigue because different life curves fig. Pdf stress analysis of fracture of atherosclerotic plaques. The pulsatile blood flow in the arteries generates mechanical stresses that affect the rupture of the atherosclerotic plaque. Poststroke fatigue psf is a frequent, disabling symptom that lacks a consensual definition and a standardized evaluation method.
The process of atherosclerotic plaque rupture with superimposed. The remaining fatigue life of plaque thus may be used to evaluate the rupture risk 30, 31. Here, we built an idealized model in which only one calcification is included. Subject terms dmmge tolerance, fracture mechanics, crack initiation, toughness, stress. But whether or not the calcifications have a negative effect on plaque vulnerability is still under debate. In the present work here, the fatigue crack propagation threshold of a surface crack for an armco iron loaded in the vhcf regime was investigated by a new approach which combines the fracture surface analysis and the temperature recording on the surface during the test by an infrared camera. Fatiguecrack propagation how is fatiguecrack propagation. The evidence of previous plaque rupture and intraplaque. Fatigue life prediction has become important because of complex nature of fatigue as it is influenced by several factors, statistical nature of fatigue phenomena and time consuming fatigue tests.
The nucleation phase typically represents the longest period of fatigue life, although local irregularities could significantly shorten the nucleation period. Stressrelaxation and cyclic behavior of human carotid plaque. 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. Mechanisms of plaque vulnerability and rupture prediman k. Oct 24, 2014 failure and fatigue crack propagation analysis with marc msc software. Considering that the cardiovascular system is a classic fatigue environment, plaque rupture was treated as a chronic fatigue crack growth process in this study. Plaque rupture has become identified as a critical step in the evolution of atherosclerotic plaque. Modified paris law was used to govern crack propagation and the propagation direction. 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. Oct 01, 20 fatigue crack propagation analysis of plaque rupture. Mribased fatigue analysis predicts plaque vulnerability. Cracks extended radially and fatigue crack growth rate increased with increase in pulse pressure.
The multiple causes of psf have not been formally characterized. Rupture of atheromatous plaque is the major cause of stroke or heart attack. Analysis of fatigue crack propagation in gusset plates bhairav k thakkar1 gusset plates are used commonly in truss joints. Rupture of atherosclerotic plaque with resulting thromboembolism is a predominant cause of. Fatigue failure being the accumulation of the damage due to repeated loading that occurs when the stresses are much lower than those needed to rupture the plaque with normal loading. It is suggested that crack propagation analysis can lead to a better recognition of factors.
Further validation studies on the 3d printed arteries are necessary for better understanding the factors contributing to plaque rupture. Fatigue crack propagation analysis of plaque rupture qut. Plaque fatigue crack growth per pressure pulse was estimated using an adapted. Fatigue analysis was performed based on the plaque geometry derived from in vivo mri of the carotid artery at the point of maximum stenosis. Fatigue crack propagation for pmma and pvc fatigue crack growth rate dadn in alumina as a function of the maximum stress intensity factor kmax under fully reversed cyclic loads v 5 hz. From fatigue research it is known that fatigue life can often be divided into three periods. Fourdimensional ultrasonographic characterization of plaque. Plaque rupture plays a role in the majority of acute coronary syndromes. Atherosclerosis plaque rupture, heart attack and stroke risk detecting tool developed. Failure and fatigue crack propagation analysis with marc msc software. There may be instances when the bolt or rivet holes. Fatiguecrack propagation behavior of several pressure. The crack may be initiated by fatigue, or may be preexisting from manufacture, or may be caused by an impact, or similar event e.
Though a lot of fatigue models have been developed and used. Detection of fatigue cracks and torque loss in bolted joints. Rupture of atheromatous plaque is the major cause of stroke or heart. Research open access in vivo mribased simulation of fatigue. 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. With this relevance, in vivo imagebased mechanical analysis has been employed to. Comparing to the previously used stress analysis, this fatigue model provides some possible explanations of plaque rupture at a low stress level in a pulsatile cardiovascular environment, and it. Fatigue crack propagation rate how is fatigue crack. Incremental crack propagation was dynamically simulated based on stress distributions.
Health monitoring of structural and biological systems 2007. Motion analysis of a symptomatic ica plaque that caused stroke through embolism into the ipsilateral middle cerebral artery. Cyclic plastic zone is the region ahead of a growing fatigue. Sep, 20 rupture of atheromatous plaque is the major cause of stroke or heart attack. Abstractthe analysis of plaque mechanics along the longitudinal axis. How does calcification influence plaque vulnerability. Paris law was used to determine the fatigue crack growth rate. A technique of fracture analysis used to determine the stress level at which preexisting cracks of known size will propagate leading to fracture. Analysis on low cycle fatigue life and fatigue fracture. When one measures fatigue crack propagation rate, a crack increment, ha, and its corresponding increment in load cycles, an, are measured. Inthis study, fatigue andfatigue crack growth behavior of krupp 2510 steel was investigated in. Preventing fatigue crack propagation in aircraft structures is an important element of aircraft safety.
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