Search results for "Cyclic load"
showing 10 items of 22 documents
On the estimation of the fatigue cycle distribution from spectral density data
1999
This paper deals with the fatigue life prediction of components and structures subjected to random fatigue, i.e. to cyclic loading whose amplitude varies in an essentially random manner. In particular, this study concentrates on the general problem of directly relating fatigue cycle distribution to the power spectral density (PSD) by means of closed-form expressions that avoid expensive digital simulations of the stress process. At present, all the methods proposed to achieve this objective are based on the use of a single parameter of the PSD. In this work, by numerical simulations and theoretical considerations, it is shown that the statistical distribution of fatigue cycles depends on f…
Steel-concrete bond in lightweight fiber reinforced concrete under monotonic and cyclic actions
2005
Experimental results of the local bond stress-slip relationship of reinforcing bars embedded in lightweight fiber reinforced concrete with expanded clay aggregates are presented. The effect of the following parameters were investigated: - dimension of specimens; - anchorage length; - percentages of hooked steel fibers; - geometrical ratio of transverse reinforcement; - confinement external transverse pressure. Prismatic specimens with deformed steel bars embedded for a fixed length equal to five and eight equivalent diameters were tested under both monotonic and cyclic reversal imposed displacements at the tip of the bars, in controlled displacement tests. The influence of the above mention…
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…
Fatigue resistance of fiber post and cement/build-up materials.
2004
Objectives:The purpose of this study was to evaluate the fatigue resistance to cycling loading of teeth restored with fiber post and different build-up systems. Methods: Forty human, sound single-rooted teeth were selected and stored in 0.02% thymol solution. The crowns were removed by cutting the teeth at the cement-enamel junction, thereafter endodontic treatment was performed using the vertical condensation technique. The roots were partially embedded in epoxy resin and randomly assigned to four groups. The specimens were restored with the same type of quartz fiber posts (DT Light Post, RTD, Grenoble, France), but different cements and build-up systems were used: 1)All-Bond2+C&B Cement+B…
Effect of endodontic treatment on fatigue resistance of fiber posts bonding
2003
Objectives: The aim of this study is to evaluate the effect of the endodontic treatment on the fatigue resistance of endodontic post adhesive interfaces. Materials and methods: 50 single-rooted human teeth have been severed at the cement-enamel junction and randomly assigned to 5 groups receiving different endodontic treatments as follows: 1) distilled water + gutta-percha (control); 2) NaOCl 5% + gutta-percha and Pulp Canal Sealer EWT (Kerr); 3) NaOCl 5% + gutta-percha and Top Seal (Dentsply-Maillefer); 4) NaOCl 5% and EDTA 10% (alternatively) + gutta-percha and Pulp Canal Sealer EWT; 5) NaOCl 5% and EDTA 10% (alternatively) + gutta-percha and Top Seal. Subsequently, Light-Post DT #2 quart…
Incremental Delamination Processes under Cyclic Loading
2012
Mechanical resistance of zirconium implant abutments: A review of the literature
2010
The increase of aesthetic demands, together with the successful outcome of current implants, has renewed interest in the search for new materials with enough mechanical properties and better aesthetic qualities than the materials customarily used in implanto-prosthetic rehabilitation. Among these materials, zirconium has been used in different types of implants, including prosthetic abutments. The aim of the present review is to analyse current scientific evidence supporting the use of this material for the above mentioned purposes. We carried out the review of the literature published in the last ten years (2000 through 2010) of in vitro trials of dynamic and static loading of zirconium ab…
Application of an energy model for fatigue life prediction of construction steels under bending, torsion and synchronous bending and torsion
2003
Abstract The paper contains a mathematical model of the material’s behaviour under cyclic loading taking into account the dynamics of the fatigue process, including the number of cycles to failure, induced by the mean stress value. The coefficients in the proposed model have been obtained from experimental tests under symmetrical and nonsymmetrical loading (with the stress ratio R =0). The proposed model has been used in order to modify an energy criterion with the aim of accounting for the influence of the mean stress on the fatigue life. The fatigue tests have been performed for structural steels 10HNAP and 18G2A subjected to cyclic bending, torsion and synchronous bending with torsion, b…
Cohesive-frictional interface model with oligocyclic degradation of surfaces roughness
2008
The present work is devoted to the constitutive modelling, through the classical interface kinematical formulation, of the mechanical behaviour of the internal adhesive layers, connecting different bodies. The proposed interface constitutive model couples a cohesive behaviour with a frictional one and it is able to follow the transition from the sound condition to the fully cracked one by means of a specific interpretation of the damage variable. In the fully cracked condition, the dilatancy exhaustion and the frictional strength degradation are also modelled.
An Interface Mechanical Model with a Cohesive to Frictional Transition
2009
A thermodynamically consistent mechanical interface model is presented. The model is based on the interface damage mechanic theory applied in a special fashion such that the interface damage variable is also used as a parameter which drives the continuous and smooth transition from the sound initial cohesive state to the final fully fractured frictional state. Interface damage activation and fictional sliding are promoted by a damage activation function and a Coulomb frictional yielding function. The main features of the model are discussed in details and some numerical results for the material response are shown in monotonic and cyclic loading regimes.