Showing papers on "Torsion (mechanics) published in 2015"
TL;DR: In this paper, the Visco-Plastic Self Consistent (VPSC) model was used to simulate a vast number of mechanical responses and crystallographic characteristics including stress-strain curves in tension, compression in three directions, and free-end torsion, texture evolution at different strains, lateral strains of compression samples, twin volume fraction, and axial strain during the torsions experiment.
180 citations
TL;DR: In this paper, a torsion vibration isolator with quasi-zero stiffness (QZS) is proposed to attenuate the transmission of torsional vibration along a shaft system, which also plays a role of coupling between shafts.
111 citations
Book•
30 Jul 2015
TL;DR: In this paper, the authors introduce stress, strain, and constitutive relations in equilibrium, universal solutions, and inflation, and propose a semi-empirical method to solve the problem of controlling volume.
Abstract: 1 Introduction.- 2 Stress, Strain, and Constitutive Relations.- 3 Equilibrium, Universal Solutions, and Inflation.- 4 Extension and Torsion.- 5 Beam Bending and Column Buckling.- 6 Some Nonlinear Problems.- 7 Stress, Motion, and Constitutive Relations.-8 Fundamental Balance Relations.-9 Some Exact Solutions.-10 Control Volume and Semi-empirical Method.-11 Coupled Solid-fluid Problems.-12 Epilogue
107 citations
TL;DR: In this paper, a set of experimental setups, as well as a convenient and accurate method of stress-strain state modeling based on the finite element method have been developed, which can be used as a solid basis for optimization of various cabling concepts.
Abstract: For high current superconductors in high magnet fields with currents in the order of 50 kA, single ReBCO coated conductors must be assembled in a cable. The geometry of such a cable is mostly such that combined torsion, axial and transverse loading states are anticipated in the tapes and tape joints. The resulting strain distribution, caused by different thermal contraction and electromagnetic forces, will affect the critical current of the tapes. Tape performance when subjected to torsion, tensile and transverse loading is the key to understanding limitations for the composite cable performance. The individual tape material components can be deformed, not only elastically but also plastically under these loads. A set of experimental setups, as well as a convenient and accurate method of stress–strain state modeling based on the finite element method have been developed. Systematic measurements on single ReBCO tapes are carried out combining axial tension and torsion as well as transverse loading. Then the behavior of a single tape subjected to the various applied loads is simulated in the model. This paper presents the results of experimental tests and detailed FE modeling of the 3D stress–strain state in a single ReBCO tape under different loads, taking into account the temperature dependence and the elastic-plastic properties of the tape materials, starting from the initial tape processing conditions during its manufacture up to magnet operating conditions. Furthermore a comparison of the simulations with experiments is presented with special attention for the critical force, the threshold where the tape performance becomes irreversibly degraded. We verified the influence of tape surface profile non-uniformity and copper stabilizer thickness on the critical force. The FE models appear to describe the tape experiments adequately and can thus be used as a solid basis for optimization of various cabling concepts.
105 citations
TL;DR: In this paper, the authors apply a phenomenological higher-order theory of distortion gradient plasticity to the torsion problem, here assumed as a paradigmatic benchmark of small-scale plasticity.
Abstract: Under small strains and rotations, we apply a phenomenological higher-order theory of distortion gradient plasticity to the torsion problem, here assumed as a paradigmatic benchmark of small-scale plasticity. Peculiar of the studied theory, proposed about ten years ago by Morton E. Gurtin, is the constitutive inclusion of the plastic spin, affecting both the free energy and the dissipation. In particular, the part of the free energy, called the defect energy, which accounts for Geometrically Necessary Dislocations, is a function of Nye's dislocation density tensor, dependent on the plastic distortion, including the plastic spin. For the specific torsion problem, we implement this distortion gradient plasticity theory into a Finite Element (FE) code characterised by implicit (Backward Euler) time integration, numerically robust and accurate for both viscoplastic and rate-independent material responses. We show that, contrariwise to other higher-order theories of strain gradient plasticity (neglecting the plastic spin), the distortion gradient plasticity can predict some strengthening even if a quadratic defect energy is chosen. On the basis of the results of many FE analyses, concerned with (i) cyclic loading, (ii) switch in the higher-order boundary conditions during monotonic plastic loading, (iii) the use of non-quadratic defect energies, and (iv) the prediction of experimental data, we mainly show that (a) including the plastic spin contribution in a gradient plasticity theory is highly recommendable to model small-scale plasticity, (b) less-than-quadratic defect energies may help in describing the experimental results, but they may lead to anomalous cyclic behaviour, and (c) dissipative (unrecoverable) higher-order finite stresses are responsible for an unexpected mechanical response under non-proportional loading.
96 citations
TL;DR: In this paper, the authors investigate the mechanical behavior of balsa wood as a function of density, which varies from roughly 60 to 380 kg/m3 in axial compression, bending, and torsion, while in radial compression, the modulus and strength vary nonlinearly.
84 citations
TL;DR: In this article, the elastostatic problem of functionally graded circular nanobeams under torsion, with nonlocal elastic behavior proposed by E ringen, is preliminarily formulated.
Abstract: The elastostatic problem of functionally graded circular nanobeams under torsion, with nonlocal elastic behavior proposed by E ringen , is preliminarily formulated. Exact solutions are detected for nanobeams with arbitrary axial gradations of elastic properties and radially quadratic distributions of shear moduli. Extension of the treatment to nonlocal viscoelastic composite circular nanobeams is then performed. An effective solution procedure based on L aplace transform is developed, providing a new correspondence principle in nonlocal viscoelasticity for functionally graded materials. Displacements, shear strains and stresses are established for nonlocal viscoelastic nanobeams made of periodic fiber-reinforced materials, with polymeric matrix described by a M axwell model connected in series with a V oigt model.
83 citations
TL;DR: This report presents clear tensile ductility in a Zr-based BMG via a high-pressure torsion (HPT) process and provides insights into the basic functions of hydrostatic pressure and shear strain in the microstructure and mechanical properties of HPT-processed BMGs.
Abstract: Work-Hardening Induced Tensile Ductility of Bulk Metallic Glasses via High-Pressure Torsion
78 citations
TL;DR: In this paper, the authors exploit a dedicated material calibration to predict an extreme loading condition: the damage of a helicopter tail rotor transmission shaft due to a small arm ballistic impact, which is a typical material point in the damage area undergoes complex stress and strain history, starting from a large compressive stresses through shear deformation during crack extension all the way to the tensile fracture of the remaining ligament.
74 citations
TL;DR: In this paper, the response of a multi-strand wire rope subjected to axial tension and axial torque is presented, and a new method to compute local deformation parameters (two curvatures and a twist defined by Love, 1944) is introduced.
71 citations
TL;DR: In this article, an effective solution procedure based on an analogy between functionally graded orthotropic Saint-Venant beams under torsion and inhomogeneous isotropic Kirchhoff plates, with no kinematic boundary constraints, is proposed.
Abstract: Exact solutions of elastic Kirchhoff plates are available only for special geometries, loadings and kinematic boundary constraints. An effective solution procedure, based on an analogy between functionally graded orthotropic Saint-Venant beams under torsion and inhomogeneous isotropic Kirchhoff plates, with no kinematic boundary constraints, is proposed. The result extends the one contributed in Barretta (Acta Mech 224(12):2955–2964, 2013) for the special case of homogeneous Saint-Venant beams under torsion. Closed-form solutions for displacement, bending–twisting moment and curvature fields of an elliptic plate, corresponding to a functionally graded orthotropic beam, are evaluated. A new benchmark for computational mechanics is thus provided.
TL;DR: In this article, the elastostatic problem of a functionally graded K irchhoff plate, with no kinematic constraints on the boundary, under constant distributions of transverse loads per unit area and of boundary bending couples is investigated.
Abstract: The elastostatic problem of a functionally graded K irchhoff plate, with no kinematic constraints on the boundary, under constant distributions of transverse loads per unit area and of boundary bending couples is investigated. Closed-form expressions are provided for displacements, bending–twisting curvatures and moments of an isotropic plate with elastic stiffness and boundary distributed shear forces, assigned respectively in terms of the stress function and of its normal derivative of a corresponding S aint -V enant beam under torsion. The methodology is adopted to solve circular plates with local and E ringen -type elastic constitutive behaviors, providing thus new benchmarks for computational mechanics. The proposed approach can be used to obtain other exact solutions for plates whose planform coincides with the cross-section of beams for which the P randtl stress function is known in an analytical form.
25 Feb 2015-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, an incremental high pressure torsion is introduced as a novel severe plastic deformation process, which is capable of delivering specimens having an extraordinarily high aspect-ratio of thickness to diameter.
Abstract: High pressure torsion is known as one of the most popular severe plastic deformation processes. However, it has certain size limitations, especially regarding the thickness of the processed samples. In this contribution incremental high pressure torsion is introduced as a novel severe plastic deformation process. This further development of conventional high pressure torsion is capable of delivering specimens having an extraordinarily high aspect-ratio of thickness to diameter. The features of this process combined with a case-study on a pure copper specimen with a deformed diameter of 50 mm and a thickness of 40 mm is presented.
TL;DR: In this article, the boundary layer effect exhibited by the shear stress field, expressed in terms of the torsional warping function, near the cross-section boundary is investigated.
TL;DR: In this article, the axial distributions of longitudinal and shear moduli inducing an axially uniform warping field were analyzed for linearly elastic isotropic beams, with both cross-sectional and axial inhomogeneities.
TL;DR: In this article, a Mg-Zn-Zr alloy was processed by high-pressure torsion for up to 2 turns at room temperature to produce significant grain refinement together with enhanced plasticity and strength.
TL;DR: T theoretical and experimental investigations indicate that by optimizing the refractive index difference between the core and cladding, core ellipticity andCladding diameter, the twist sensitivity could be further improved.
Abstract: A highly sensitive optical fiber twist sensor has been proposed by employing a Sagnac interferometer based on polarization-maintaining elliptical core fibers (PM-ECFs). The twist effects have been theoretically analyzed and experimentally demonstrated. Based on the photoelastic effect, the resonance wavelength linearly shifts with the increment of twist and the wavelength shift is also dependent on the torsion direction. The maximum torsion sensitivities reach 18.60nm/(rad/m) for clockwise (CW) torsion direction and 15.83nm/(rad/m) for anticlockwise (ACW) torsion direction, respectively. To eliminate the temperature cross-sensitivity effect, a sensor matrix for simultaneous measurement of twist and temperature has also been obtained. Moreover, theoretical and experimental investigations indicate that by optimizing the refractive index difference between the core and cladding, core ellipticity and cladding diameter, the twist sensitivity could be further improved.
TL;DR: A novel optical fiber torsion sensor head is proposed, where a section of polarization-maintaining fiber is spliced between single mode fiber, and a twist taper is fabricated by a commercial electric-arc fusion splicer in the middle of the PMF.
Abstract: A novel optical fiber torsion sensor head is proposed. A section of polarization-maintaining fiber (PMF) is spliced between single mode fiber (SMF), and a twist taper is fabricated by a commercial electric-arc fusion splicer in the middle of the PMF. The asymmetric characteristics are obtained by the twist taper so that a fiber torsion sensor with directional discrimination is fabricated. Due to the characteristics of the asymmetric structure, the torsion sensitivity for the twist rate from 0 rad/m to -8 rad/m reaches 2.392 nm/rad·m-1, and for the twist rate from 0 rad/m to 8 rad/m reaches 1.071 nm/rad·m-1 respectively.
TL;DR: In this paper, cyclic torsion fatigue tests were performed with VDSiCr spring steel with shot-peened surface in the HCF and very high cycle fatigue (VHCF) regime and cracks were preferentially initiated internally in the matrix, below the surface layer with compression residual stresses, and less frequently at the surface.
TL;DR: In this paper, the buckling analysis of thin-walled functionally graded (FG) sandwich box beams is investigated, where the Euler-Bernoully beam theory for bending and the Vlasov theory for torsion are applied.
Abstract: Buckling analysis of thin-walled functionally graded (FG) sandwich box beams is investigated. Material properties of the beam are assumed to be graded through the wall thickness. The Euler-Bernoully beam theory for bending and the Vlasov theory for torsion are applied. The non-linear stability analysis is performed in framework of updated Lagrangian formulation. In order to insure the geometric potential of semitangental type for internal bending and torsion moments, the non-linear displacement field of thin-walled cross-section is adopted. Numerical results are obtained for FG sandwich box beams with simply–supported, clamped–free and clamped–clamped boundary conditions to investigate effects of the power-law index and skin-core-skin thickness ratios on the critical buckling loads and post-buckling responses. Numerical results show that the above-mentioned effects play very important role on the buckling analysis of sandwich box beams.
TL;DR: In this article, a method to measure both the free stroke and blocked torque in a one-end-tethered polyamide fiber was proposed. And the analysis allowed the prediction of torsional stroke under any external loading condition based on the fundamental characteristics of the actuator.
TL;DR: In this paper, the authors studied possible equilibrium magnetization states in the helix wire with different anisotropy directions, and showed that the curvature and torsion also influence the spin-wave dynamics in the magnet wire, acting as an effective magnetic field.
Abstract: A magnetic helix wire is one of the simplest magnetic systems which manifests properties of both curvature and torsion. Possible equilibrium magnetization states in the helix wire with different anisotropy directions are studied theoretically. There exist two equilibrium states in the helix wire with easy-tangential anisotropy: a quasitangential magnetization distribution in the case of relatively small curvatures and torsions, and an onion state in the opposite case. The curvature and torsion also essentially influence the spin-wave dynamics in the helix wire, acting as an effective magnetic field. Originated from a geometry-induced effective Dzyaloshinskii interaction, this magnetic field leads to a coupling between the helix chirality and the magnetochirality and breaks mirror symmetry in the spin-wave spectrum: the modification of magnon dispersion relation is linear with respect to the torsion and quadratic with respect to the curvature. All analytical predictions on magnetization statics and dynamics are well confirmed by direct spin-lattice simulations.
TL;DR: In this article, a model for estimating fatigue life under multiaxial stress states, based on critical plane concepts, taking into account the effect of mean shear stress, was proposed.
TL;DR: In this article, a three-dimensional thermomechanical constitutive model based on the microplane theory is proposed to simulate the behavior of shape memory alloy tubes, which is capable of predicting both superelasticity and shape memory effect by providing closed-form relationships for calculating the strain components in terms of the stress components.
Abstract: In this study, a three-dimensional thermomechanical constitutive model based on the microplane theory is proposed to simulate the behavior of shape memory alloy tubes. The three-dimensional model is implemented in ABAQUS by employing a user material subroutine. In order to validate the model, the numerical results of this approach are compared with new experimental findings for a NiTi superelastic torque tube under tension, pure torsion, and proportional tension–torsion performed in stress- and strain-controlled manners. The numerical and experimental results are in agreement indicating the capability of the proposed microplane model in capturing the behavior of shape memory alloy tubes. This model is capable of predicting both superelasticity and shape memory effect by providing closed-form relationships for calculating the strain components in terms of the stress components.
TL;DR: In this article, a structural analysis of Guastavino staircases based on a circular plan-form is presented, based on the assumption that the material is unilateral, namely a No-Tension material in the sense of Heyman.
TL;DR: In this article, an equivalent one-dimensional beam model immersed in a three-dimensional space is proposed to study the aeroelastic behavior of tower buildings: linear and nonlinear dynamics are analyzed through a simple but realistic physical modeling of the structure and of the load.
Abstract: In this paper, an equivalent one-dimensional beam model immersed in a three-dimensional space is proposed to study the aeroelastic behavior of tower buildings: linear and nonlinear dynamics are analyzed through a simple but realistic physical modeling of the structure and of the load. The beam is internally constrained, so that it is capable to experience shear strains and torsion only. The elasto-geometric and inertial characteristics of the beam are identified from a discrete model of three-dimensional frame, via a homogenization process. The model accounts for the torsional effect induced by the rotation of the floors around the tower axis; the macroscopic shear strain is produced by bending of the columns, accompanied by negligible rotation of the floors. Nonlinear aerodynamic forces are evaluated through the quasi-steady theory. The first aim is to investigate the effect of mechanical and aerodynamic coupling on the critical galloping conditions. Furthermore, the role of aerodynamic nonlinearities on the galloping post-critical behavior is analyzed through a perturbation solution which permits to obtain a reduced one-dimensional dynamical system, capable of capturing the essential dynamics of the problem.
TL;DR: In this article, the problem of mixed mode (I + III) brittle fracture of polycrystalline graphite is investigated systematically for the first time, and a new complete set of experimental data is provided considering different geometrical configurations by varying the notch opening angle and the notch tip radius.
TL;DR: In this paper, the static strength of the considered specimens is assessed through an approach based on the strain energy density averaged over a control volume, where the center of the control volume is located on the notch edge where the principal stress reaches its maximum value.
Abstract: The present paper summarizes some recent experimental, theoretical and numerical results on brittle fracture of isostatic polycrystalline graphite. The analyses have been carried out on V-notched samples under mixed mode (I+II), torsion and compression loading, considering various combinations of the notch tip radius, opening angle and notch tilt angle. The static strength of the considered specimens is assessed through an approach based on the strain energy density averaged over a control volume. The center of the control volume is located on the notch edge, where the principal stress reaches its maximum value. The correct orientation is obtained by a rigid rotation of the crescent-shaped volume while the size depends on the fracture toughness and the ultimate strength of the material. This methodology has been already used in the literature to analyze U- and V-shaped notches subject to mode I loading with very good results and advantages with respect to classic approaches. The results reported in this new work show, also under mixed mode loading conditions, a good agreement between experimental data and theoretical predictions.
TL;DR: In this paper, an extensive experimental investigation is carried out on a stack of two dry-jointed tuff blocks subjected to different loading conditions implying interactions among shear, torsion and bending moments.
TL;DR: In this article, a numerical model and numerical procedures are presented to solve self-contact in beams under loop formation, where the authors showed that friction may influence loop and snarling formation.
Abstract: Many engineering scenarios involve contact between beam structures or, eventually, self-contact. Specifically when dealing with a beam submitted to large torsion loads and considering large displacements and rotations, it is possible to occur self-contact. Beams with low bending stiffness loaded with large torsion can present a loop, followed by self-contact and sometimes a snarl formation. This work presents a numerical model and numerical procedures to solve such a kind of self-contact in beams under loop formation. Numerical examples are presented in the context of initially straight nitinol beams. Numerical tests showed that friction may influence loop and snarling formation. Numerical models could predict self-contact occurrence events with good agreement with experimental results already published in literature. Snarling patterns (when occurred) were also predicted correctly, but with delay when compared to experiments. This delay showed to be friction-dependent.