Search results for "Fracture"

Some Optimization Problems

2013

In this chapter, the problems of safety analysis and optimization of a moving elastic plate travelling between two rollers at a constant axial velocity are considered. We will use a model of a thin elastic plate subjected to bending and in-plane tension (distributed membrane forces). We will study transverse buckling (divergence) of the plate and its brittle and fatigue fracture caused by fatigue crack growth under cyclic in-plane tension (loading). Our aim is to find the safe ranges of velocities of an axially moving plate analytically under the constraints of longevity and stability. In the end of this chapter, the expressions for critical buckling velocity and the number of cycles before…

Bartotraumatic Blowout Fracture After Sneezing: Cone Beam CT demonstration

2013

Rarely a blowout orbital fracture is related to sneezing in patients with no history of trauma or sinus surgery. A case of barotraumatic, pure and isolated blowout fracture of the right orbit after sneezing diagnosed by CBCT is reported. A forty-year-old man complained sudden right diplopia after vigorous sneezing. On MRI a reduced size and an altered shape of the right maxillary sinus, a slightly increased vertical diameter of the right orbit, a round shape of the inferior rectus muscle on coronal sections, and a right maxillary haemosinus were observed. A strong peripheral enhancement of the maxillary sinus wall was evident. One week after the patient was submitted to a maxillofacial CBCT…

Characterization of major discontinuities from borehole cores of the black consolidated marl formation of Draix (French Alps)

2012

A quantitative description of rock discontinuities present in subsurface cores that were drilled (down to 20 m) in the marls of the Laval and Moulin catchments near Draix (France) is presented. Three kinds of discontinuities are studied: those fully open, those open but filled with clay rich material and those sealed with calcite. With a laser profiler, the topography of facing sides of typical discontinuities was measured with a normal resolution of 1 µm. The probability distribution of the elevation of each surface are obtained and shown to be normal. Possible self-affine scaling invariance of the topography were explored. The mineralogical content of an interface between the marl bulk an…

Randomized, Double-Blind, Clinically Controlled Trial of Intranasal Calcitonin Treatment in Patients with Hip Fracture

2002

The objective of this study was to evaluate the short-term outcome of intranasal calcitonin treatment of elderly hip fracture patients on pain, bone loss, functional recovery, and length of hospital stay. In addition, we wanted to compare the effect of calcitonin with placebo on fusion of hip fractures treated with internal fixation using a screw or a nail. In a randomized, double-blind, clinically controlled trial, 260 independently living patients (aged 65 years or older) with acute hip fracture were randomly assigned to intranasal calcitonin 200 IU daily for 3 months or matching placebo nasal spray. Analyses were completed on an intention-to-treat basis. Three months after the operation,…

Boundary elements analysis of adhesively bonded piezoelectric active repair

2009

Abstract This paper presents the analysis of active piezoelectric patches for cracked structures by the boundary element method. A two-dimensional boundary integral formulation based on the multidomain technique is used to model cracks and to assemble the multi-layered piezoelectric patches to the host damaged structures. The fracture mechanics behavior of the repaired structures is analyzed for both perfect and imperfect interface between patches and host beams. The imperfect interface, representing the adhesive between two different layers, is modeled by using a “spring model” that involves linear relationships between the interface tractions, in normal and tangential directions, and the …

Does Optimal Volume Fraction in Percutaneous Vertebroplasty Prevent Cement Leakage?

2018

Microstructure and mechanical effects of spark plasma sintering in alumina monolithic ceramics

2013

The specific effects of spark plasma sintering (SPS) on the creep behavior, microstructure and mechanical properties of alumina monolithic ceramic were investigated. SPS introduces strains that concentrate at grain boundaries and inhibit crack growth, resulting in an improvement in the flexural strength and fracture toughness. However, creep blocks grain boundary movements and decreases the reliability of the material. These strains can be removed by a post-sintering thermal treatment, which plays an important role in the distribution of dislocations.

Fracture resistance and the mode of failure produced in metal-free crowns cemented onto zirconia abutments in dental implants.

2019

The purpose of the investigation was to analyze fracture resistance and mode of failure of zirconium oxide (zirconia) abutments placed on dental implants bearing crowns of different esthetic materials: zirconia, lithium disilicate (LDS), and nano-ceramic resin, for replacing single teeth in the anterior sector. Eighty implant-abutment-crown units were divided into four groups: Group T-MC (control): 20 metal-ceramic crowns cemented onto titanium abutments; Group Z-Z: 20 zirconia crowns on zirconia abutments; Group Z-LD: 20 lithium disilicate crowns on zirconia abutments; and Group Z-NCR: 20 nano-ceramic resin crowns on zirconia abutments. Specimens underwent a fatiguing process (dynamic load…

A fatal iatrogenic right vertebral injury after transoral odontoidectomy and posterior cervical stabilization for a type II odontoid fracture.

2014

Abstract The authors present a singular case of an iatrogenic right vertebral artery injury, involving a 67 year-old man, who reported a type II odontoid fracture (Anderson and D'Alonzo Classification) and posterior atlantoaxial dislocation following a road traffic accident. A small injury involving the right vertebral artery occurred as a consequence of transoral odontoidectomy and posterior cervical stabilization. It was caused by bone spicules of spinal origin and their presence was confirmed by the histological section of the right vertebral artery at the level of C1–C2. The case confirms how iatrogenic vertebral artery injuries during cervical spine surgery may be potentially lethal, e…

MoSi2 laser cladding—A new experimental procedure: double-sided injection of MoSi2 and ZrO2

2003

International audience; In the last decade, development of low density advanced material systems for service at temperatures up to 1300 °C was one of the goals of many researches. This kind of material should mainly have moderate fracture toughness and should exhibit oxidation resistant behaviour at low and intermediate temperature. One of the most studied materials continues to be the intermetallic compound MoSi2. The molybdenum disilicide has been considered as an attractive candidate due to its melting point (2030 °C) and excellent oxidation resistance at high temperatures. The main problem associated with the MoSi2 layer synthesized using laser beam is the layer fragility. To avoid this…