The Experts below are selected from a list of 16548 Experts worldwide ranked by ideXlab platform
Carlos M Lopez - One of the best experts on this subject based on the ideXlab platform.
-
normal shear cracking model application to discrete crack analysis
Journal of Engineering Mechanics-asce, 1997Co-Authors: Ignacio Carol, Pere C Prat, Carlos M LopezAbstract:A simple but general model for normal/shear cracking in quasi-brittle materials is presented. It is defined in terms of the normal and shear stresses on the average plane of the crack and the corresponding normal and shear relative displacements. A crack surface in stress space determines crack initiation under Pure Tension, shear-Tension, or shear-compression loading. Two independent fracture energy parameters are used: the classical Mode I fracture energy GfI, and the asymptotic Mode II fracture energy GfIIa under very high shear-compression and no dilatancy. The cracking model proposed can be implemented in two ways: directly as the constitutive law of an interface element in the context of discrete crack analysis, or as the law of a generic cracking plane in a multicrack formulation in the context of smeared crack analysis. In this paper, the first approach is presented and examples are given of numerical constitutive testing and verification with experimental data.
-
normal shear cracking model application to discrete crack analysis
Journal of Structural Engineering-asce, 1997Co-Authors: Ignacio Carol, Pere C Prat, Carlos M LopezAbstract:A simple but general model for normal/shear cracking in quasi-brittle materials is presented. It is defined in terms of the normal and shear stresses on the average plane of the crack and the corresponding normal and shear relative displacements. A crack surface in stress space determines crack initiation under Pure Tension, shear-Tension, or shear-compression loading. Two independent fracture energy parameters are used: the classical Mode I fracture energy and the asymptotic Mode II fracture energy under very high shear compression and no dilatancy. The cracking model proposed can be implemented in two ways: directly as constitutive law of an interface element in the context of discrete crack analysis, or as the law of a generic cracking plane in a multicrack formulation in the context of smeared crack analysis. In this paper, the first approach is presented and examples are given of numerical constitutive testing and verification with experimental data.
Ignacio Carol - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of mixed-mode fracture in concrete using interface elements and a cohesive crack model
Sadhana, 2012Co-Authors: Víctor O. García-Álvarez, Ravindra Gettu, Ignacio CarolAbstract:The paper presents a model, based on nonlinear fracture mechanics, for analysing crack propagation in quasi-brittle materials, such as concrete. The work is limited to two-dimensions, and therefore, the fracture modes of interest are mode I (Pure Tension) and mode II (Pure shear). The constitutive model has been implemented in the context of the finite element method using interface elements. The fracture is simulated through a discrete crack represented by the interface with a cohesive crack stress-separation relation derived from the model, which is based on a fracture criterion, together with a flow rule and a softening law. The model is used for simulating results from an experimental study on beams with centric and eccentric notches of high and normal strength concretes, and explaining other test results available in the literature.
-
normal shear cracking model application to discrete crack analysis
Journal of Engineering Mechanics-asce, 1997Co-Authors: Ignacio Carol, Pere C Prat, Carlos M LopezAbstract:A simple but general model for normal/shear cracking in quasi-brittle materials is presented. It is defined in terms of the normal and shear stresses on the average plane of the crack and the corresponding normal and shear relative displacements. A crack surface in stress space determines crack initiation under Pure Tension, shear-Tension, or shear-compression loading. Two independent fracture energy parameters are used: the classical Mode I fracture energy GfI, and the asymptotic Mode II fracture energy GfIIa under very high shear-compression and no dilatancy. The cracking model proposed can be implemented in two ways: directly as the constitutive law of an interface element in the context of discrete crack analysis, or as the law of a generic cracking plane in a multicrack formulation in the context of smeared crack analysis. In this paper, the first approach is presented and examples are given of numerical constitutive testing and verification with experimental data.
-
normal shear cracking model application to discrete crack analysis
Journal of Structural Engineering-asce, 1997Co-Authors: Ignacio Carol, Pere C Prat, Carlos M LopezAbstract:A simple but general model for normal/shear cracking in quasi-brittle materials is presented. It is defined in terms of the normal and shear stresses on the average plane of the crack and the corresponding normal and shear relative displacements. A crack surface in stress space determines crack initiation under Pure Tension, shear-Tension, or shear-compression loading. Two independent fracture energy parameters are used: the classical Mode I fracture energy and the asymptotic Mode II fracture energy under very high shear compression and no dilatancy. The cracking model proposed can be implemented in two ways: directly as constitutive law of an interface element in the context of discrete crack analysis, or as the law of a generic cracking plane in a multicrack formulation in the context of smeared crack analysis. In this paper, the first approach is presented and examples are given of numerical constitutive testing and verification with experimental data.
Julian J. Rimoli - One of the best experts on this subject based on the ideXlab platform.
-
A reduced-order model for the dynamic and post-buckling behavior of tensegrity structures
Mechanics of Materials, 2016Co-Authors: Julian J. RimoliAbstract:Traditional approaches for modeling the behavior of tensegrity structures have their origin either on form-finding applications or on the desire to capture their quasi-static behavior. As such, they generally assume that (i) bars are perfectly rigid, (ii) cables are linear elastic, and (iii) bars experience Pure compression and strings Pure Tension. In addition, a common design constraint is to assume that the structure would fail whenever any of its bars reaches the corresponding Euler buckling load. In reality, these assumptions tend to break down in the presence of dynamic events. In this work, we develop a physics-based reduced-order model to study aspects related to the dynamic and nonlinear response of tensegrity-based structures. With very few degrees of freedom, our model captures their buckling and post-buckling behavior as well as their dynamic response. We then adopt our model to show how, under dynamic events, buckling of individual members of a tensegrity structure does not necessarily imply structural failure. Our research suggests that efficient structural design of impact-tolerant tensegrity structures could be achieved by exploiting rather than avoiding the buckling behavior of its compression members.
William M Shih - One of the best experts on this subject based on the ideXlab platform.
-
self assembly of three dimensional prestressed tensegrity structures from dna
Nature Nanotechnology, 2010Co-Authors: Tim Liedl, Bjorn Hogberg, Jessica D Tytell, Donald E Ingber, William M ShihAbstract:Tensegrity, or Tensional integrity, is a property of a structure indicating a reliance on a balance between components that are either in Pure compression or Pure Tension for stability. Tensegrity structures exhibit extremely high strength-to-weight ratios and great resilience, and are therefore widely used in engineering, robotics and architecture. Here, we report nanoscale, prestressed, three-dimensional tensegrity structures in which rigid bundles of DNA double helices resist compressive forces exerted by segments of single-stranded DNA that act as Tension-bearing cables. Our DNA tensegrity structures can self-assemble against forces up to 14 pN, which is twice the stall force of powerful molecular motors such as kinesin or myosin. The forces generated by this molecular prestressing mechanism can be used to bend the DNA bundles or to actuate the entire structure through enzymatic cleavage at specific sites. In addition to being building blocks for nanostructures, tensile structural elements made of single-stranded DNA could be used to study molecular forces, cellular mechanotransduction and other fundamental biological processes.
Marino Quaresimin - One of the best experts on this subject based on the ideXlab platform.
-
multiaxial fatigue of a short glass fibre reinforced polyamide 6 6 fatigue and fracture behaviour
International Journal of Fatigue, 2010Co-Authors: M De Monte, E Moosbrugger, K Jaschek, Marino QuaresiminAbstract:Abstract The multiaxial fatigue behaviour of a short glass fibre reinforced polyamide 6.6 (PA66-GF35) is investigated on hollow tubular specimens in the range of fatigue lives between 10 2 and 10 7 cycles. Fatigue experiments included Pure Tension, Pure torsion, combined Tension–torsion at different biaxiality ratios and phase shifting angles between the stress components. Tests were carried out with load ratio R = 0 and R = −1 at room temperature as well as at 130 °C. The influence of biaxiality ratio, phase angle between load components and load ratio is discussed. An extensive analysis of the fracture behaviour is performed on the specimens to recognise the crack nucleation and propagation mechanisms; failure modes were evaluated via optical and scanning electron microscopy.
-
multi axial fatigue behaviour of a severely notched carbon steel
International Journal of Fatigue, 2006Co-Authors: B Atzori, Filippo Berto, Paolo Lazzarin, Marino QuaresiminAbstract:Abstract The paper deals with multi-axial fatigue strength of notched specimens made of C40 carbon steel (normalised state), subjected to combined Tension and torsion loading, both in-phase and out-of-phase ( Φ =0 and 90°). V-notched specimens have been tested under two nominal load ratios, R =−1 and 0, while keeping constant and equal to the unity the biaxiality ratio, λ =σ a / τ a . All specimens have the same geometry, with notch tip radius and depth equal to 0.5 and 4 mm, respectively, while the V-notch angle is equal to 90°. The results determined are discussed together with those deduced under Pure Tension or torsion loading on plain and notched specimens as well as on small shafts with shoulders. The application of an energy-based approach allows all the fatigue data obtained from the notched specimens to be summarised in a single scatter band, in terms of the total strain energy density evaluated at the notch tip against cycles to failure.
