Search results for "Crack"
showing 9 items of 209 documents
Simulation of Fatigue Delamination Growth in Composites with Different Mode Mixtures
2007
A numerical model, obtained by implementing a cyclic damage model in the framework of an interface element, is here proposed to reproduce the crack growth in laminated composites subjected to cyclically repeated loads. This model, which differs from the few studies in the literature on the topic, applies not only to single fracture modes but also to mixed modes, and to constant or variable crack growth rates. The applied load (in terms of force or displacement) is assumed to oscillate between a minimum and a maximum constant value. The Paris curve can be reproduced with accuracy once some parameters in the numerical model are tuned with experiments. These parameters are preliminarily found…
CT imaging findings of abdominopelvic vascular compression syndromes: what the radiologist needs to know.
2020
AbstractAbdominopelvic vascular compression syndromes include a variety of uncommon conditions characterized by either extrinsic compression of blood vessels by adjacent anatomical structures (i.e., median arcuate ligament syndrome, nutcracker syndrome, May-Thurner syndrome) or compression of hollow viscera by adjacent vessels (i.e., superior mesenteric artery syndrome, ureteropelvic junction obstruction, ureteral vascular compression syndromes, portal biliopathy). These syndromes can be unexpectedly diagnosed even in asymptomatic patients and the predisposing anatomic conditions can be incidentally discovered on imaging examinations performed for other indications, or they can manifest wit…
Das »Nußknacker-Syndrom« der Vena renalis (Arteria-mesenterica-superior-Syndrom) als Ursache gastrointestinaler Beschwerden
2008
History and clinical findings Since the age of 19 a now 22-year-old man had complained of intermittent abdominal pain, irregular stools and paroxysmal tachycardia. The only preceding illness had been a single episode of iron-deficiency anemia. A laparoscopy, done 8 months after the onset of symptoms, had revealed an inflamed Meckel's diverticulum which was surgically removed. After transient improvement the symptoms recurred 5 months postoperatively. On admission to clarify the cause of the symptoms he had discrete abdominal pain on pressure, but physical examination was otherwise unremarkable. Investigations Routine biochemical tests and endoscopy were normal. Abdominal computed tomography…
Association of Dunbar, May-Thurner and Nutcracker Compression Syndromes in One Patient
2020
Abstract We report a case of Dunbar syndrome, May–Thurner syndrome and Nutcracker syndrome diagnosed in one patient with clinical presentation and imaging findings on Doppler ultrasonography. Dunbar syndrome or truncus coeliacus compression syndrome is an under-diagnosed vascular compression syndrome with a lot of controversy around it because of insufficient differentiation from celiac artery stenosis. May–Thurner syndrome or iliac vein compression syndrome is an anatomically variable condition of venous outflow obstruction caused by extrinsic compression by the right common iliac artery as it crosses the iliac vein anteriorly. In Nutcracker syndrome due to compression the outflow from the…
A model for predicting the mixed-mode fatigue crack growth in a bonded joint
2013
Bonded joints are highly sensitive to the presence of defects and to the degradation phenomena, and this aspect represents the primary obstacle to their use in different structural engineering applications. Delamination in a bonded joint represents, in fact, one of the primary, most common and insidious causes of damage. In this paper, a numerical–experimental study on the crack propagation along the adhesive layer of a bonded joint specimen is carried out. Experimental study is focused on the evaluation of the damage modalities of a bonded joint when the specimens are subject to fatigue load. Experimental tests are compared with the results of several numerical analysis performed in ANSYS …
Residual Stress Effects on Fatigue Crack Growth in Ti-6Al-4V Friction Stir Welds
2008
Recent studies have illustrated a predominant role of the residual stress on the fatigue crack growth in friction stir welded joints. In this study, the role of the residual stress on the propagation of fatigue cracks orthogonal to the weld direction in a friction stir welded Ti-6Al-4V joint was investigated. A numerical prediction of the fatigue crack growth rate in the presence of the residual stresses was carried out using AFGROW software; reasonable correspondence between the predictions and the experimental results were observed when the effects of residual stress were included in the simulation.
Error analysis and calibration for a novel pipe profiling tool
2020
Integrity of industrial pipework is ensured through routine inspection. Internal visual inspection tools are capable of characterising degradation in the form of corrosion, pitting, erosion and cracking. The accuracy of such inspection systems has a direct impact on decisions regarding the remaining lifetime of the asset. By minimising error margins, the asset may be operated with confidence for longer, with less uncertainty. This paper considers a probe system consisting of a laser profiler and camera that produces a textured 3D model of the internals of 2 – 6 inch pipework. The accuracy of the system is defined by the ability to extract laser projections from an image as it travels down t…
Estudio y optimización de nuevos catalizadores para la producción selectiva de olefinas ligeras
2017
El cambio climático ha sido calificado como el mayor de los problemas a los que se enfrenta la humanidad actualmente. Sus consecuencias pueden ser extremas y pueden poner en peligro a todas las especies que habitan este planeta. La solución implica necesariamente un esfuerzo global, tanto a nivel político como científico. Afortunadamente, los químicos e ingenieros químicos tienen a su alcance poderosas herramientas con las que contribuir, incluyendo la química sostenible y, en particular, la catálisis. La catálisis permite hacer un uso más eficiente de los recursos que requieren de una transformación química. Los recursos fósiles son la principal reserva de carbono al alcance del ser humano…
The effect of defect location on coating fragmentation patterns under biaxial tension
2005
Fragmentation of a coating possessing orthogonal preferential crack propagation directions is modeled for equibiaxial tensile loading. Two plausible cracking scenarios are compared, caused by flaws randomly distributed over the area of the coating or along the coating fragment edges. The two fragmentation scenarios considered are shown to yield qualitatively different fragment patterns.