Search results for "Fracture"
showing 10 items of 873 documents
Influence of custom-made and prefabricated insoles before and after an intense run
2017
[EN] Each time the foot contacts the ground during running there is a rapid deceleration that results in a shock wave that is transmitted from the foot to the head. The fatigue of the musculoskeletal system during running may decrease the ability of the body to absorb those shock waves and increase the risk of injury. Insoles are commonly prescribed to prevent injuries, and both custom-made and prefabricated insoles have been observed to reduce shock accelerations during running. However, no study to date has included a direct comparison of their behaviour measured over the same group of athletes, and therefore great controversy still exists regarding their effectiveness in reducing impact …
Interfacial fracture toughness of universal adhesive systems treated with an antioxidant
2017
Background Secondary caries, degradation of the dentin-resin interface and fracture of the restoration are the most common forms of failure. The aim of this study was to assess the interfacial fracture toughness of three different adhesive approaches and to compare their fracture toughness after surface treatment with antioxidant. Material and methods Seventy two dentin blocks with 3×4mm dimension and 3mm thickness were prepared and attached to precured 3×4×12mm composite blocks from both sides. Six adhesive groups (N=12), All-bond universal, Scotchbond universal and Clearfil SE bond with or without antioxidant treatment (Sodium Ascorbate 10% )were applied to dentin surfaces, a 160µ polyeth…
The Italian observational study on severe osteoporosis (ISSO): 24-month results on incidence of fractures and adherence to treatment
2016
Objective To estimate the proportion of patients with very severe osteoporosis (those covered by the reimbursement criteria of the Italian National Health Service) experiencing new vertebral and non-vertebral fragility fractures in the first 24 months of a new anti-osteoporosis treatment. Methods Prospective observational study in men and post-menopausal women (aged > 21 years) initiating anti-osteoporosis treatment for very severe osteoporosis. Eligibility was based on teriparatide (TPD) reimbursement criteria in Italy: Incident of vertebral or hip fracture during anti-resorptive treatment (minimum 1 year), or at least three prevalent severe vertebral fractures, or two prevalent severe ver…
Modelling unilateral damage effect in strongly anisotropic materials by the introduction of the loading mode in damage mechanics
1999
Abstract Damage weakens the mechanical characteristics of materials. But this weakening can disappear if the cracks close again: this is called the unilateral effect of damage. We propose a model of this phenomenon using damage mechanics in the case of a diffuse network of identical microcracks. The microcracks state is defined with two internal state variables. These two variables are control parameters of the geometry of the microcracks. They also define the loading mode in damage mechanics as in fracture mechanics. In order to limit the anisotropy induced by the microcracks, hence by the loading, we suppose that the geometry of damage spreads into preferential directions. Therefore, this…
Surgical treatment of solitary sternal metastasis from breast cancer Case report
2016
Bone metastasis is a frequent and early complication of breast cancer. This case report describes a technique for a partial exeresis of the sternum and the reconstruction of the pleura with autologous dermis from the lower abdomen and the loss of substance with a myocutaneous flap.We describe the case of a 50-year old woman with a sternal excavated lesion with pathologic fracture due to an invasive adenocarcinoma, treated with a partial exeresis of the sternum and the reconstruction with a myocutaneous flap.The patient doesn't show evidence of recurrent disease and the stability of her chest well preserved.Metastatic breast cancer to the sternum, if detected early and treated aggressively, …
Interdependence Between Tool Fracture and Wear
1985
Wear and fracture are the main causes of tool scrapping. However fracture plays a major role for increasing values of the hardness and brittleness of tool materials or when low-cobalt tungsten carbides are used or in interrupted cutting conditions where it is the most relevant factor for tool scrapping. In order to obtain the optimal values of the cutting speed both these factors should be considered. The hypothesis of stochastic independence among them simplifies the mathematical formulation of the optimization problem; but experimental investigations do not agree with this assumption and, as a matter of fact, the probability density function of tool fracture results to be dependent on the…
Fatigue crack growth in welds based on a V-notch model for the short crack propagation at the toe
2018
Abstract This work presents a new fatigue crack growth prediction model for non-load-carrying fillet welded steel joints. For this joint configuration the fatigue cracks will emanate from the weld toe region. Due to the presence of a V-notch in this region the crack initiation point becomes a point of singularity for the stress field. This may in many cases make it difficult to determine the Stress Intensity Factor Range (SIFR) for small cracks by conventional methods based on Linear Elastic Fracture Mechanics (LEFM). The present approach solves this problem by using the Energy Release Rate (ERR) to determine the SIFR in the small crack growth regime. The model is fitted to crack growth cur…
Experimental Tests of Fatigue Induced Delamination in Gfrp and Cfrp Laminates
2007
This work deals with the experimental analysis of the delamination phenomena in various composite materials under different loading conditions. Quasi-static and fatigue tests are performed on specimens made of glass-fibre reinforced plastic (GFRP) and carbon-fibre reinforced plastic (CFRP). In particular, under both quasi-static and fatigue loading, single fracture modes I and II (using standard DCB and ENF test configurations) and mixed modes I+II (using the MMB test configuration) with several mode mixtures, have been analysed. Further experiments of delamination growth with mode mixture that varies with the crack length, will be performed.
Thermodynamics and continuum fracture mechanics for nonlocal-elastic plastic materials
2002
Nonlocal elasticity is used as an improved elasticity model which engenders no crack-tip stress singularities and thus makes applicable the classical stress-based failure criteria. Considering nonlocal-elastic plastic materials exposed to softening by particle decohesion in a process surface and to subsequent surface separation by fracture, fracture mechanics is addressed within the framework of irreversible internal-variable thermodynamics in the hypothesis of small strains and arbitrary (but sufficiently regular) fracture surface (crack surface plus process surface). The state equations and the energy dissipation densities are derived for the bulk material and for the process surface, for…
Crack growth analysis at adhesive–adherent interface in bonded joints under mixed mode I/II
2008
The propagation of an interface crack subjected to mixed mode I/II was investigated for two 2024-T351 aluminum thin layers joined by means of DP760 epoxy adhesive produced by 3M©. On the basis of beam theory, an analytical expression for computing the energy release rate is presented for the mixed-mode end loaded split (MMELS) test. The analytical strain energy release rate was compared by finite element (FE) analysis using the virtual crack closure technique (VCCT). Several fatigue crack growth tests were carried out in a plane bending machine to compare the experimental energy release rates to those of the analytical and FE solutions. Experimental results showed the relationship between t…