Search results for "Fracture"
showing 10 items of 873 documents
Adaptive Planning in-Service Inspections of Fatigued Structures in Damage Tolerance Situations via Observations of Crack Growth Process
2017
From an engineering standpoint the fatigue life of a fatigued structure consists of two periods: (i) crack initiation period, which starts with the first load cycle and ends when a technically detectable crack is presented, and (ii) crack propagation period, which starts with a technically detectable crack and ends when the remaining cross section can no longer withstand the loads applied and fails statically. The main aim of this paper is to present more accurate innovative stochastic fatigue model for adaptive planning inspections of fatigued structures in damage tolerance situations via observations of crack growth process during a crack propagation period. A new crack growth equation is…
Trauma in cirrhosis: an indicator of the pattern of alcohol abuse in different societies.
1991
While some morbidities associated with the excessive use of alcohol are related to the total amount of alcohol consumed--cirrhosis being an example--other pathologies, such as trauma and those of psycho-social origin, are mainly related to the frequency of acute alcoholic intoxication rather than to the total amount consumed. The balance between these two types of alcohol-associated morbidities can provide an indication of the relative frequency of intoxication, and thus of the pattern of alcohol abuse in a population. Since trauma is highly associated with acute alcoholic intoxication, the prevalence of bone fractures was determined in cirrhotics in nine countries. The prevalence of rib an…
Dilatation Sites: Fibrous Veins, Strain Shadows, Strain Fringes and Boudins
1998
Many deformed rocks contain sites with a deviant mineralogy and fabric, interpreted as an effect of rearrangement of material by local dilatation and precipitation during deformation. Such ‘dilatation sites’ can be isolated and elongate (veins), flanking rigid objects (strain shadows) or occur in the neck of boudinaged layers or elongate crystals (Fig. 6.1). Strain shadows are also referred to in the literature as pressure shadows. Most veins and many strain shadows and boudin necks have sharp contacts with the wall rock and may form by precipitation of material from an aqueous solution in a fracture, as outlined below. Such sites are usually filled with polycrystalline material which may b…
: Looking through the gaps of the digital divide in Higher education
2007
A partir de una muestra de 719 estudiantes de la Universidad de Chile en 2004, este artículo analiza las diferencias existentes respecto de capitales culturales materiales e incorporados relacionados con el acceso y uso de las nuevas tecnologías de la información y comunicación (NTICs). Bajo diferentes métodos de análisis cuantitativo se pone de manifiesto la existencia de niveles de brecha digital para tales herramientas, brecha que estaría relacionada especialmente al género pero también a la condición socioeconómica. Esta última variable, aunque presente, muestra efectos más bien indirectos no pareciendo influir en las actitudes y disposiciones de los estudiantes respecto al uso de las N…
Effect of cyclic loading on fracture strength and microleakage of a quartz fiber dowel with different adhesive, cement and resin core material combin…
2010
Background: This study evaluated the performance of different adhesive-cement-core combinations coupled with quartz fiber dowels after cyclic loading and fracture strength tests and assessed the microleakage using dye penetration method. Methods: Forty maxillary canines (n=10 per group) were restored with fiber dowels (Quartz fiber DT Light Post) and four adhesive-cement-core material combinations [(Group 1: All-Bond 2+C&B (root) / All-Bond 2+Biscore (core); Group 2: All-Bond 2+Bisfil 2B (root) / All-Bond 2+Bisfil 2B (core); Group 3: Scotchbond 1+RelyX ARC (root) / Scotchbond 1+Supreme (core); Group 4: RelyX Unicem (root) / Scotchbond 1+Filtek Supreme (core)]. The specimens were initially c…
A comparative study of mechanical resistance of two reciprocating files
2019
Background To evaluate the cyclic fatigue resistance of two different Nickel-Titanium instruments, Reziflow (Komet, Brasseler GmbH & Co., Lemgo, Germany) and WaveOne Gold (Dentsply Maillefer, Ballaigues, Switzerland). Material and Methods Two groups of 20 different NiTi endodontic instruments of identical tip size of 0.25 mm were tested; Reziflow and Wave-One Gold primary. Cyclic fatigue testing was performed in a stainless steel simulated root canal manufactured by reproducing the instrument’s size and taper. A simulated root canal with a 90 degrees angle of curvature and 5 mm radius of curvature was constructed for the instruments tested. The centre of the curvature was 5 mm from the tip …
Numerical simulation of fatigue-driven delamination using interface elements
2005
This paper presents a computational technique for the prediction of fatigue-driven delamination growth in composite materials. The interface element, which has been extensively applied to predict delamination growth due to static loading, has been modified to incorporate the effects of cyclic loading. Using a damage mechanics formulation, the constitutive law for the interface element has been extended by incorporating a modified version of a continuum fatigue damage model. The paper presents details of the fatigue degradation strategy and examples of the predicted fatigue delamination growth in mode I, mode II and mixed mode I/II are presented to demonstrate that the numerical model mimics…
Effet de l'orientation des fibres des plis adjacents sur la résistance au délaminage en mode I pur = Effect of the fibre's orientation of adjacent pl…
2009
National audience; Ce travail concerne l'étude de l'effet de l'orientation des fibres des plis adjacents à la fissure dans une éprouvette DCB (Double Cantilever Beam) sur la résistance au délaminage en mode I pur. Afin d'isoler l'influence de l'orientation l'étude porte sur des stratifiés particuliers ayant tous les mêmes matrices de comportement global A B D. Les résultats expérimentaux montrent une grande variation de résistance au délaminage GIC et des courbes R selon l'orientation des plis situés de part et d'autre du plan de fissure. Une modélisation par éléments finis permet de mettre en évidence l'importance de l'état de contraintes locales et donc de l'endommagement au voisinage du …
Reduced Peak Bone Mass in Young Adults with Low Motor Competence
2023
Although suboptimal bone health has been reported in children and adolescents with low motor competence (LMC), it is not known whether such deficits are present at the time of peak bone mass. We examined the impact of LMC on bone mineral density (BMD) in 1043 participants (484 females) from the Raine Cohort Study. Participants had motor competence assessed using the McCarron Assessment of Neuromuscular Development at 10, 14, and 17 years, and a whole body dual-energy X-ray absorptiometry scan at 20 years. Bone loading from physical activity was estimated from the International Physical Activity Questionnaire at the age of 17. The association between LMC and BMD was determined using general …
Role of Negative Pressure Therapy as Damage Control in Soft Tissue Reconstruction for Open Tibial Fractures.
2017
AbstractThe concept of damage control orthopaedics (DCO) is a strategy that focuses on managing orthopaedic injuries in polytrauma patients who are in an unstable physiological state. The concept of DCO is an extension of damage control surgery or damage limitation surgery (DCS/DLS). Recently, it has become clear that certain patients, following extensive soft tissue trauma, could benefit from the idea of DCS. In the management of severe lower extremity trauma with exposed fracture sites, aggressive early wound excision debridement, early internal fixation, and vascularized wound coverage within a few days after trauma were proposed. A negative-pressure dressing can be easily and rapidly ap…