Search results for "Fracture"
showing 10 items of 873 documents
Fracture behavior and mechanical, thermal, and rheological properties of biodegradable films extruded by flat die and calender
2020
The development of biodegradable materials for tailored applications, particularly in the field of polymeric films and sheets, is a challenging technological goal as well as a contribution to help protect the environment. Poly(lactic) acid (PLA) is a promising substitute for several oil-based polymers; however, to overcome its thermal and mechanical drawbacks, researchers have developed solutions such as blending PLA with polybutylene adipate terephthalate (PBAT), which is capable of increasing the ductility of the final material. In this study, PLA/PBAT binary blends, with minimum possible content of nonrenewable materials, were examined from processing, thermal, morphological, and rheolog…
Fatigue crack growth of new FML composites for light ship buildings under predominant mode II loading condition
2019
The use of light but strong materials is largely studied in various area of the shipbuilding, this because the need of reducing the weight, and especially the weight of all the structures above the main deck assume primary importance for the stability. Traditionally in fast boats like fast ferries, hydrofoils, patrol boats, the typical materials are Aluminum alloy or composites, both those materials have advantages and disadvantages, but the new development of technologies made possible to combine them, in order to have a new material, combining the advantages of both, in terms of fatigue resistance, firefighting characteristics. In this paper, predominant mode II fatigue delamination tests…
Investigation on fracture of epoxy-filled composites by acoustic emission
2016
Acoustic emission (AE) technique is widely used to monitor failure processes in composite materials includ-ing development of cracks and plastic deformations within the polymer matrix, fracture and debonding of inclusions, etc. In this study, the AE technique was applied investigating failure character of epoxy polymers with different content of nanofiller – fine polyethersulfone (PES) powder. Variation of material properties of the epoxy with 0, 5%, 7.5%, 10%, and 12.5% concentration (by weight) of the PES was assessed experimentally. Correlation between the PES content and the modulus of elasticity was found negligible. The same was characteristic for the tensile strength. Whereas, such a…
Modeling the Fatigue Damage Evolution in Welded Joints
2017
The present paper presents a two-phase model for the fatigue damage evolution in welded steel joints. The argument for choosing a two-phase model is that crack initiation and subsequent crack propagation involve different damage mechanisms and should be treated separately. The crack initiation phase is defined as the number of cycles to reach a crack depth of 0.1 mm. This phase is modelled based on the Dang Van multiaxial stress approach. Both a multiaxial stress situation introduced by the acting loads and the presence of the multiaxial welding residual stresses are accounted for. The local notch effect at the weld toe becomes very important and the irregular weld toe geometry is character…
Modelling of the fracture toughness anisotropy in fiber reinforced concrete
2015
Steel fiber reinforced concrete is potentially very promising material with unique properties, which currently is widely used in some applications, such as floors and concrete pavements. However, lack of robust and reliable models of fiber reinforced concrete fracture limits its application as structural material. In this work a numerical model is proposed for predicting the crack growth in fiber reinforced concrete. The mixing of the steel fibers with the concrete usually creates nonuniform fibers distribution with more fibers oriented in horizontal direction, than in vertical. Simple numerical models of fiber reinforced concrete require a priori knowledge of the crack growth direction in …
Effect of retention design of artificial teeth and implant-supported titanium CAD-CAM structures on fracture resistance
2014
Background For implant-supported hybrid prostheses, high mastication forces and reduced acrylic resin thickness over a metal substructure often cause failures arising from tooth or resin fractures. To assay fracture resistance of artificial teeth and resin in implant-supported hybrid prostheses in relation to the titanium structure and retention design supporting teeth. Material and Methods 40 specimens bearing incisors were divided into four groups according to the titanium structure supporting the teeth and the type of load force applied: Group I (Control; n=10): Application of static loading to ten incisors set over a metal structure with internal retention. Group II (Control; n=10): App…
Are Metal-Free Monolithic Crowns the Present of Prosthesis? Study of Mechanical Behaviour
2019
Purpose: To analyze in vitro the mechanical behavior of five types of complete coverage crowns fabricated from different materials. Materials and methods: Seventy-five full coverage crowns were divided into five groups according to material: Group I, metal core with feldspathic ceramic covering (MC- control group)
Bond strength of metal-ceramic systems in three-point flexure bond test
1995
This study deals with a three-point flexure test for the metal-ceramic bond involving geometrically simple specimens (alloy strips partly coated with ceramic) that can be fabricated with reasonable expenditure and sufficient reproducibility. The calculation of the stress distribution in such specimens with the aid of the finite-element method (FEM) is presented. The aim of this numerical analysis is: to investigate the stress distribution in a ceramometallic specimen with dimensions that, in a large number of experiments, have proven to lead to debonding at one end of the ceramic veneer instead of a crack in the middle of the veneer; and to assign a bond strength to the measured critical be…
Sejas un žokļu traumas Paula Stradiņa Klīniskajā Universitātes slimnīcā
2020
Sejas un žokļu traumu ietekme uz hospitalizācijas ilgumu un neiroloģisko simptomātiku Paula Stradiņā Klīniskajā Universitātes slimnīcā. Viena no plašākajām traumu kategorijām, kas tieši pieder pie jebkuras valsts galvenajām sociālekonomiskajām problēmām un skar visus pasaules iedzīvotāju slāņus, un ir galvaskausa, sejas un apakšžokļu traumas. Sejas traumas ir bieži izplatītas, jo seja ir visatklātākā un neaizsargātākā ķermeņa daļa ar nelielu aizsargpārklājumu. Mutes dobuma un augšžokļa sejas traumas, papildus sejas estētikai, ietekmē tādas funkcijas kā elpošana, košļāšanas, rīšanas un runas funkcijas. Darba mērķi: noskaidrot FISS skalas ietekmi uz pareģojošo pacientu hospitalizācijas ilgumu…
Generalized Fatigue Criterion of maximum shear and normal strains on the fracture plane for materials under multiaxial random loadings
1991
A generalized fatigue criterion for materials under multiaxial random loadings is presented. The criterion is based on the assumption that shear and normal strain on the expected fracture plane – shear strain in one direction on this plane is considered – determine the fracture plane. It has been shown that the well known fatigue criteria of maximum normal strain, maximum shear strain and the criterion of maximum shear and normal strains on the critical shear plane result from the newly formulated criterion.