The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Darren J Stefanyshyn - One of the best experts on this subject based on the ideXlab platform.

  • forefoot Bending Stiffness running economy and kinematics during overground running
    Footwear Science, 2015
    Co-Authors: Ryan Madden, Joh W Wannop, Masanori Sakaguchi, Elias K Tomaras, Darren J Stefanyshyn
    Abstract:

    Previous research has shown that altering forefoot (FF) Bending Stiffness can enhance running economy; however, the mechanism behind the changes in running economy remains unknown. Therefore, the purpose of this study was to investigate the relationship between forefoot Bending Stiffness, running economy, and lower limb kinematics during overground running. Eighteen aerobically fit recreational male athletes performed overground running using a portable metabolic analysis system to measure oxygen consumption in two footwear conditions with different forefoot Bending Stiffness. Sagittal plane kinematic data of the metatarsophalangeal, ankle, and knee joints were recorded using a high-speed camera. On average, there was no difference in running economy when running in the Stiff shoe (O2 = 38.1 ± 5.4 mL/kg/min) compared to the Control shoe (O2 = 37.7 ± 5.8 mL/kg/min, p = 0.11). On an individual basis, 10 athletes (Responders) improved their running economy with increased FF Bending Stiffness (∆O2 = −2.9%), w...

  • shoe midsole longitudinal Bending Stiffness and running economy joint energy and emg
    Medicine and Science in Sports and Exercise, 2006
    Co-Authors: Jeanpierre R Roy, Darren J Stefanyshyn
    Abstract:

    ABSTRACTPurpose:It has been shown that mechanical energy is dissipated at the metatarsophalangeal (MTP) joint during running and jumping. Furthermore, increasing the longitudinal Bending Stiffness of the midsole significantly reduced the energy dissipated at the MTP joint and increased jump performa

  • increased shoe Bending Stiffness increases sprint performance
    Sports Biomechanics, 2004
    Co-Authors: Darren J Stefanyshyn, Ciro Fusco
    Abstract:

    The purposes of this investigation were to determine if increasing the Bending Stiffness of sprint shoes increases sprinting performance and to determine whether simple anthropometric factors can be used to predict shoe Bending Stiffness for optimal performance. Thirty-four athletes were tested using four different shoe conditions--a standard condition consisting of their currently used footwear and three conditions where the Bending Stiffness was increased systematically. The sprinters performed maximal effort 40 m sprints and their sprint times were recorded from 20 to 40 m. On average, increasing the shoe Bending Stiffness increased sprint performance. The Stiffness each athlete required for his or her maximal performance was subject specific but was not related to subject mass, height, shoe size or skill level. It is speculated that individual differences in the force-length and force-velocity relationships of the calf muscles may influence the appropriate shoe Stiffness for each athlete to obtain their maximal performance.

  • influence of midsole Bending Stiffness on joint energy and jump height performance
    Medicine and Science in Sports and Exercise, 2000
    Co-Authors: Darren J Stefanyshyn, Benno M Nigg
    Abstract:

    STEFANYSHYN, D. J. and B. M. NIGG. Influence of midsole Bending Stiffness on joint energy and jump height performance. Med. Sci. Sports Exerc., Vol. 32, No. 2, pp. 471–476, 2000.Purpose:A substantial amount of rotational energy is lost at the metatarsophalangeal joint during running and jumping. We

Andreas Menzel - One of the best experts on this subject based on the ideXlab platform.

  • fibre reinforced composites with fibre Bending Stiffness under azimuthal shear comparison of simulation results with analytical solutions
    International Journal of Non-linear Mechanics, 2017
    Co-Authors: Tobias Asmanoglo, Andreas Menzel
    Abstract:

    In Ref. [1], Spencer and Soldatos proposed an enhanced modelling approach for fibre-reinforced composites which accounts for the fibre-Bending Stiffness in addition to the directional dependency induced by the fibres. Although analytical solutions for simple geometries have been derived over the past years, often subject to specific assumptions such as small deformation kinematics, the application to more general and non-academic boundary value problems is desirable. Motivated by the latter, the numerical solution of the general system of partial differential equations by means of a multi-field finite element approach is proposed in Ref. [2] and the principal model properties are studied for a specific form of the elastic energy potential. In the present contribution a comparison of the numerical solution by means of the multi-field finite element approach against the analytical solution is presented for the azimuthal shear deformation of a tube-like structure. To this end, the general deformation pattern and especially the distribution of the stress and couple stress tensor are taken into account. We find that, although the analytical solution is derived subject to the assumption of small deformations, whereas the numerical solution is based on the finite strain counterpart of the theory, the simulation results are quasi identical, which verifies the numerical framework proposed.

  • a multi field finite element approach for the modelling of fibre reinforced composites with fibre Bending Stiffness
    Computer Methods in Applied Mechanics and Engineering, 2017
    Co-Authors: Tobias Asmanoglo, Andreas Menzel
    Abstract:

    Abstract The implementation of an enhanced modelling approach for fibre-reinforced composites is presented which may, in addition to the directional dependency induced by the fibres, allow the capturing of the fibre-Bending Stiffness. The theoretical framework is based on the introduction of higher-order gradients of the motion function as additional arguments of the energy function such that size effects can be taken into account. However, the application of higher-order gradients within a finite element framework requires particular care with respect to continuity requirements. In this contribution the usage of a mixed-type multi-field finite element formulation and the fulfilment of the continuity requirement only in a weak sense is proposed. Based on a particular specification of the energy function representative boundary value problems are discussed to assess the model’s properties. It is then shown that a model which is based on one additional invariant compared to the classic structural tensor approach allows, in principle, to incorporate effects which are due to the fibre-Bending Stiffness.

Peter Goldsmith - One of the best experts on this subject based on the ideXlab platform.

  • A comparison of forefoot Stiffness in running and running shoe Bending Stiffness.
    Journal of biomechanics, 2005
    Co-Authors: Mark Arthur Oleson, Daniel H. Adler, Peter Goldsmith
    Abstract:

    This study characterizes the Stiffness of the human forefoot during running. The forefoot Stiffness, defined as the ratio of ground reaction moment to angular deflection of the metatarsophalangeal joint, is measured for subjects running barefoot. The joint deflection is obtained from video data, while the ground reaction moment is obtained from force plate and video data. The experiments show that during push-off, the forefoot Stiffness rises sharply and then decreases steadily, showing that the forefoot behaves not as a simple spring, but rather as an active mechanism that exhibits a highly time-dependent Stiffness. The forefoot Stiffness is compared with the Bending Stiffness of running shoes. For each of four shoes tested, the shoe Stiffness is relatively constant and generally much lower than the mean human forefoot Stiffness. Since forefoot Stiffness and shoe Bending Stiffness act in parallel (i.e., are additive), the total forefoot Stiffness of the shod foot is dominated by that of the human foot.

Masoud Motavalli - One of the best experts on this subject based on the ideXlab platform.

  • electrostatically tunable Bending Stiffness in a gfrp cfrp composite beam
    Smart Materials and Structures, 2007
    Co-Authors: Andrea Bergamini, R Christen, Masoud Motavalli
    Abstract:

    The suppression of vibrations in structures is commonly considered a useful measure for the extension of their lifetime, when high amplitude vibrations are observed. In the experiments presented in this work, the modification of the Stiffness of a beam as a means to suppress vibrations due to resonance is proposed as an alternative to the introduction of discrete damping devices. The Stiffness of a beam is modified by applying an electric field between the main element of the structure and additional stiffening elements applied to its surface, thus coupling the latter to the former by transfer of shear stresses. The effect of electrostatic tuning of the Bending Stiffness (and consequently of its eigenfrequencies) of a large size GFRP–CFRP beam is shown by the shift of the resonance peak for the first Bending mode to higher frequencies. The discrete character of the Stiffness increase in multi-layer beams (n≥3) is postulated.

  • a sandwich beam with electrostatically tunable Bending Stiffness
    Smart Materials and Structures, 2006
    Co-Authors: Andrea Bergamini, R Christen, B Maag, Masoud Motavalli
    Abstract:

    The tuning of the Bending Stiffness of structural elements is of interest for, among other things, the suppression of vibrations related to resonance phenomena. For a given cross-sectional area and geometry, the variation of the elastic properties of the material composing the structure provides a viable approach to this task. Only very limited options are available for such changes in material properties. The use of NiTi shape memory alloys has been proposed for this purpose. A new, energetically less expensive method for the modification of the Bending Stiffness of sandwich beams is presented. The proposed method makes use of electrostatic forces to modify the transfer of shear stresses at the interface between the faces and the core of the sandwich. Changes in Bending Stiffness of up to 18 times could be obtained for a prototype beam. A simple model for describing the behavior of the beam is presented.

C. Pozrikidis - One of the best experts on this subject based on the ideXlab platform.

  • effect of membrane Bending Stiffness on the deformation of capsules in simple shear flow
    Journal of Fluid Mechanics, 2001
    Co-Authors: C. Pozrikidis
    Abstract:

    The effect of interfacial Bending Stiffness on the deformation of liquid capsules enclosed by elastic membranes is discussed and investigated by numerical simulation. Flow-induced deformation causes the development of in-plane elastic tensions and Bending moments accompanied by transverse shear tensions due to the non-infinitesimal membrane thickness or to a preferred configuration of an interfacial molecular network. To facilitate the implementation of the interfacial force and torque balance equations involving the hydrodynamic traction exerted on either side of the interface and the interfacial tensions and Bending moments developing in the plane of the interface, a formulation in global Cartesian coordinates is developed. The balance equations involve the Cartesian curvature tensor defined in terms of the gradient of the normal vector extended off the plane of the interface in an appropriate fashion. The elastic tensions are related to the surface deformation gradient by constitutive equations derived by previous authors, and the Bending moments for membranes whose unstressed shape has uniform curvature, including the sphere and a planar sheet, arise from a constitutive equation that involves the instantaneous Cartesian curvature tensor and the curvature of the resting configuration. A numerical procedure is developed for computing the capsule deformation in Stokes flow based on standard boundary-element methods. Results for spherical and biconcave resting shapes resembling red blood cells illustrate the effect of the Bending modulus on the transient and asymptotic capsule deformation and on the membrane tank-treading motion.

  • Effect of membrane Bending Stiffness on the axisymmetric deformation of capsules in uniaxial extensional flow
    Physics of Fluids, 2001
    Co-Authors: Sehoon Kwak, C. Pozrikidis
    Abstract:

    The effect of interface Bending Stiffness on the axisymmetric deformation of liquid capsules enclosed by elastic membranes subject to uniaxial extensional flow is considered. Flow-induced deformation causes the development of membrane in-plane elastic tensions and Bending moments due to the noninfinitesimal thickness of the membrane or to a preferred equilibrium configuration of an interfacial molecular network, accompanied by transverse shear tensions. The elastic tensions are related to the surface deformation by means of Mooney’s linear constitutive law for thin elastic sheets, and the Bending moments are related to the membrane resting shape and to the instantaneous principal curvatures by means of constitutive equations. Interfacial force and torque balances are used to relate the jump in hydrodynamic traction across the interface to the elastic tensions and Bending moments. A numerical procedure is implemented for simulating the capsule deformation in uniaxial extensional Stokes flow based on a boun...