Search results for "creep"
showing 10 items of 167 documents
How does shear zone nucleate? An example from the Suretta nappe (Swiss Eastern Alps)
2016
In order to address the question of the processes involved during shear zone nucleation, we present a petro-structural analysis of millimetre-scale shear zones within the Roffna rhyolite (Suretta nappe, Eastern central Alps). Field and microscopic evidences show that ductile deformation is localized along discrete fractures that represent the initial stage of shear zone nucleation. During incipient brittle deformation, a syn-kinematic metamorphic assemblage of white mica + biotite + epidote + quartz precipitated at ca. 8.5 ± 1 kbar and 480 ± 50 °C that represent the metamorphic peak conditions of the nappe stacking in the continental accretionary wedge during Tertiary Alpine subduction. The…
Recyclable and Light-Adaptive Vitrimer-Based Nacre-Mimetic Nanocomposites.
2021
Nacre's natural design consists of a perfect hierarchical assembly that resembles a brick-and-mortar structure with synergistic stiffness and toughness. The field of bioinspired materials often provides attractive architecture and engineering pathways which allow to explore outstanding property areas. However, the study of nacre-mimetic materials should not be limited to the design of its architecture but ought to include the understanding, operation, and improvement of internal interactions between their components. Here, we introduce a vitrimer prepolymer system that, once integrated into the nacre-mimetic nanocomposites, cures and cross-links with the presence of Lewis acid catalyst and …
Mechanical properties of injection-molded binary blends of polyethylene with small additions of a liquid-crystalline polymer
2011
The results of the investigation of the mechanical properties of polyethylene (PE) blends with small (<3 wt %) additions of thermotropic liquid-crystalline polymers (LCPs) are reported. PE/LCP compositions with various LCP weight contents were obtained by thermoplastic mixing in a two-stage process. Short-term and long-term mechanical behavior of various PE/LCP compositions were analyzed. Data on the influence of LCP addition on the tensile elastic modulus [or Young's modulus (E)], stress at yield (σY), stress at break (σB), strain at yield, strain at break, and deformation at long-term (1000-h) tensile creep were obtained. The experimental results of the investigation show that even small …
The Rehabilitation of Segmental Bridges Subjected to Time-dependent Deflections Through Additional Prestressing
2022
Segmental bridges built by cantilevering with in-situ casting in the ‘60s-‘80s of the XX Century present a central hinge on the main span or a central simply supported span between the two cantilevers (drop-in span). Due to time-dependent phenomena like creep of concrete and to unexpected loss of prestressing, several bridges of this typology show an abnormal deflection at hinges causing discomfort of traffic as well as insufficiencies of checks at Service and Ultimate Limit States. Moreover, these bridges are today at the end of their nominal service life, impacting significantly on Italian road network. A methodology for retrofitting these bridges by partial recovering of deflection and o…
Microstructure and fabric development in ice: Lessons learned from in situ experiments and implications for understanding rock evolution
2014
Abstract In this contribution we present a review of the evolution of microstructures and fabric in ice. Based on the review we show the potential use of ice as an analogue for rocks by considering selected examples that can be related to quartz-rich rocks. Advances in our understanding of the plasticity of ice have come from experimental investigations that clearly show that plastic deformation of polycrystalline ice is initially produced by basal slip. Interaction of dislocations play an essential role for dynamic recrystallization processes involving grain nucleation and grain-boundary migration during the steady-state flow of ice. To support this review we describe deformation in polycr…
Origin of the fast magnetization relaxation at low temperatures in HTS with strong pinning
2010
The temperature T variation of the normalized magnetization relaxation rate S in high-temperature superconductors (HTS) with strong vortex pinning exhibits a maximum in the low-T range. This was reported for various HTS, and the origin of the faster relaxation at low T appearing in standard magnetization relaxation measurements was usually related to specific pinning properties of the investigated specimens. Since the observed behaviour seems to be characteristic to all HTS with enhanced pinning (generated by random and/or correlated disorder), we show that the S(T) maximum can be explained in terms of classic collective vortex creep. The influence of thermo-magnetic instabilities in the lo…
Structural performances of pultruded GFRP emergency structures – Part 1: Experimental characterization of materials and substructure
2019
Abstract This paper presents an experimental study in the field of structures made of pultruded fiber reinforced polymers (FRP) elements to be used for emergency purposes. A preliminary design of a 3D pultruded glass fiber reinforced polymer structure is presented with the mechanical characterization of the constituting elements. The axial and flexural properties of laminate and I-shaped GRFP profiles are discussed considering the short term creep. In a companion paper, the benefits, the limits and the reliability of the structure analyzed for emergency applications are discussed. In details, the numerical structural analysis of the full-scale 3D model is described followed by the experimen…
Effect of carboxymethyl cellulose concentration on rheological behavior of milk and aqueous systems. A creep and recovery study
2009
Carboxymethyl cellulose (CMC) is an anionic polysaccharide used mainly as stabilizer and thickener agent. The purpose of this study was to investigate the effect of CMC concentration on viscoelasticity of dairy and aqueous model systems through the analysis of creep and recovery tests. The viscoelastic properties of different concentrations of CMC (0.75, 1.00, 1.25, and 1.50% w/w) in two milk systems (skimmed milk and whole milk) were compared with those of the same concentration of biopolymer in aqueous solution. Creep curves were fitted to a six parameter mechanical model (Burger + Kelvin-Voigt), whereas an empirical equation was used for recovery. The creep and recovery properties of sam…
Field-driven domain wall motion under a bias current in the creep andflow regimes in Pt/[CoSiB/Pt](N) nanowires
2016
AbstractThe dynamics of magnetic domain wall (DW) in perpendicular magnetic anisotropy Pt/[CoSiB/Pt]N nanowires was studied by measuring the DW velocity under a magnetic field (H) and an electric current (J) in two extreme regimes of DW creep and flow. Two important findings are addressed. One is that the field-driven DW velocity increases with increasing N in the flow regime, whereas the trend is inverted in the creep regime. The other is that the sign of spin current-induced effective field is gradually reversed with increasing N in both DW creep and flow regimes. To reveal the underlying mechanism of new findings, we performed further experiment and micromagnetic simulation, from which w…
Hillslope evolution by nonlinear creep and landsliding: An experimental study: Comment and Reply
2002
[Roering et al. (2001)][1] describe very careful and interesting experiments that beautifully illustrate the transition from steady downhill creep at low gradients to highly dynamic transport on steep slopes. They interpret this behavior in terms of a single nonlinear diffusion coefficient,