Large Rotation Deformation Research Articles

A force-resisting rotary friction damper (RFD): Verification and comparison with traditional RFD

A force-resisting rotary friction damper (RFD) is proposed in this paper, which can be applied where there is a large rotational deformation. Its exclusive configuration lies in that multiple bolts are symmetrically arranged on concentric circles centered on the hinge pin to apply preload, resulting in: [i] an independent force-transfer capability decoupled with the moment to meet shear or axial forces-transfer demands and [ii] providing larger friction bending-moment with smaller compressive stresses on friction shim and lower maximum stress on the steel plate compared to the traditional RFD under the same preload and friction coefficient. A prototype of the proposed RFD was manufactured and tested twice without tightening the bolts again and replacing the friction shims by cyclic loading to investigate its mechanical property and recoverability. The test results showed that the moment–angle hysteretic curve of the proposed RFD was an ideal rectangle, indicating a reasonable mechanism. The variation of the friction bending-moment was within 4.00 % between the two-time tests, indicating that the proposed RFD has satisfactory recoverability and can uninterruptedly provide energy absorption during dense aftershocks. Then, a refined finite element model was established and calibrated by the test results. For the numerical prototype studied, the friction bending-moment of the proposed RFD was approximately 35 % larger than that of the traditional RFD while its maximum pressure on friction shim was about 40 % of the corresponding traditional RFD. The difference in the friction moment between the theoretical and numerical results was within 4.50 %. The concept of the force-resisting RFD was justified.

Experimental and finite element analysis of modular prefabricated composite beam-column interior joints

This contribution presents quasi-static tests of three modular prefabricated composite beam-column interior joints (MPCIJs), analyzing the strain distribution, ductility, energy consumption, strength, and stiffness degradation . Three finite element models were established by ABAQUS and compared with quasi-static test results to verify their correctness. The stress mechanism of different materials in MPCIJs was further analyzed. Results showed that the absolute value of the plastic drift ratio was 6.41–8.01% rad, the ductility coefficient was 3.50–4.50, and the equivalent viscous damping coefficient was 0.32–0.33. The overall degradation performance of MPCIJs strength and stiffness were relatively stable. MPCIJs achieved good seismic performance and large rotational deformation capacity. The stress (strain) in the joint module, consistent with the ‘diagonal compression bar’, was diagonally distributed. The high-stress connection bolt at the column end is located on both sides of the centerline along the direction of the beam length. The internal stress of concrete follows an antisymmetric distribution along the diagonal direction and diffuses outward at an angle of 45°. • A new type of modular composite joint is proposed. • Physical tests and finite element analysis of composite joints are carried out. • Verify the correctness of the modular composite joint finite element model. • The stress mechanism of joints with different composition materials is clarified. • The modular composite joint meets the requirements of seismic fortification.

Full-automatic seed point selection and initialization for digital image correlation robust to large rotation and deformation

Accurate initial guess plays a key role to realize full-automatic digital image correlation (DIC) analysis, especially when large rotational deformation presents in deformed images. In this work, an efficient, robust and full-automatic initial guess approach combining the speeded-up robust features (SURF) algorithm and the reliability-guided displacement tracking (RGDT) strategy is proposed, which can not only automatically select and update seed point, but also can effectively deal with target images with large deformation and rotation. The scale- and rotation-invariant SURF algorithm can extract and match a certain number of feature points from two images even though the significant deformation and rotation present. The Euclidean distance and deformation information (including displacement and major orientation rotation angle) of the best-matched point are used to choose the seed point and determine its initial guess, respectively. Then, the RGDT strategy is then employed to continue the DIC analysis of rest calculation points. Compared with existing path-dependent initial guess using RGDT, the proposed method not only can automatically select seed points without manual intervention, but also can provide accurate initial value estimation for the deformed images in the presence of large rotation and/or deformation. Furthermore, it has evident efficiency advantages over existing path-independent initial guess methods based on SIFT and RANSAC. The robustness and effectiveness of the proposed method are validated by numerical simulation tests and real experiments.

A study on the false volume expansion problem under rigid large rotation based on the modified symmetric and anti-symmetric decomposition method

During the simulation of large rotation deformation by the discontinuous deformation analysis method or numerical manifold method, a false volume expansion problem appears. A theoretical and experimental study on the false volume expansion problem based on the modified symmetric and anti-symmetric decomposition (MSAD) is given, reveals the intrinsic cause, and gives an insight into the false volume expansion problem. It is theoretically proven that MSAD will never lead to the false volume expansion problem, and it is also verified by two numerical experiments of large rotation deformation in both static and dynamic situations. The MSAD method can accurately distinguish rotation and strain from the incremental deformation gradient tensor and realize the objective update of rotational stress. Using the MSAD method, larger rotational deformation is allowed for each incremental step; thus, fewer calculating steps and higher computational precision can be achieved, indicating that large rotational deformation problems can be solved in a more accurate and efficient manner. The combination of the MSAD method and the Bathe implicit time integration scheme provides good numerical stability and high computational precision and satisfies the conservation of kinetic energy and momentum for conservative systems.

Experimental investigation on behavior of reinforced concrete interior beam column joints retrofitted with fiber reinforced polymers

This experimental study is undertaken to study the behavior of RC interior beam-column joints which lack in shear reinforcement and strengthened by FRPs and additional tie bars. The samples are constructed with transverse beams and slab. Total eight models have been prepared of which three joints have been strengthened by carbon FRP (CFRP) fabrics, two joints have been strengthened by CFRP plates and one model has been strengthened by adding tie bar into the joint. The samples have been subjected to incremental cyclic loading provided by hydraulic jacks under constant axial or gravity load and their load-deformation behaviors have been measured by dial gauges and video extensometer. The behaviors of the strengthened joints are compared with the control models. The joints without shear reinforcement undergo brittle failure under cyclic loading. But their ductility increases with increased concrete strength. The joints strengthened by the CFRPs show better load bearing capacity with enhanced ductile behavior. Location of the plastic hinges shifts from column to beam in case of the joints strengthened by CFRP plates and fabrics. The joint strengthened by additional tie bar and micro-concrete undergo large rotational deformation before they fail. Joints strengthened by CFRP fabrics exhibit better ductility and strength than those of the joints retrofitted by CFRP plates and tie bars. Joints strengthened by CFRP plate exhibited high rotational stiffness and are effective in resisting the diagonal crack travelling to transverse beams.

Behaviour and modelling of connections in cold-formed steel single C-section portal frames

The flexural behaviour of eaves, apex and base connections for cold-formed steel single C-section portal frames is investigated through a series of connection tests and analyses of corresponding finite element models. The moment-rotation characteristics of the eaves, apex and base connections from the respective connection tests and the numerical models indicate good agreement between. The attainment of ultimate load by the eaves and the apex connection was normally preceded by significant deformation of connecting brackets. The eaves connections reached its ultimate load capacities upon fracture of screws or ply bearing of M8 bolts on the C-section lips while the apex connections attained their ultimate load capacities with the formation of inelastic buckling near the compression flange-web junction of one of the adjoining beams. The base connection tests exhibited large rotational deformation and capacity to deform with inelasticity mostly concentrated in the connector bracket. Based on the tests and numerical analyses, simplified nonlinear moment-rotation relations are established for eaves, apex and base connections.

Effects of z-pin’s porosity on shear properties of 2D C/SiC z-pinned joint

In this paper, 2D C/SiC z-pinned joint is prepared via chemical vapor infiltration. Effects of z-pin’s porosity on shear properties of z-pinned joint are investigated from the failure mode and the shear damage mechanisms. The results show that the average joint shear strength decreases asymptotically from 249.9MPa to 97.2MPa as the total porosity of 2D C/SiC z-pin increases from 14.4% to 27.3%. For each porosity, the joint shear strength is between the tensile strength and the in-plane shear strength of 2D C/SiC, which is rationalized by the rigid body sliding model of 2D C/SiC. Because high porosity leads to large rotational deformation of transverse fibers, a critical porosity about 17.7% is observed from shear-controlled failure to bending-controlled failure. A cohesive fracture model is developed to build the relation between the joint shear strength and the mechanical properties of 2D C/SiC. Very good accuracy is obtained.

Deformations of flexible and foldable electro-active composite structures

This paper presents numerical analyses of elastic and viscoelastic smart flexible and foldable composite structures under electric field actuation. The studied composites comprise of multiple distributed piezoelectric patches bonded to the surfaces of in-active thin planar structures (substrates). Upon applications of electric field input, the planar structures can undergo three-dimensional large rotational deformations while their strains and stretches remain relatively small. A nonlinear time-dependent electro-mechanical coupling relation for the piezoelectric patches is considered to simulate more precisely response of piezoelectric materials when subjected to large magnitude of electric field. Co-rotational Lagrangian finite element approach is used for solving the governing equations of the deformations of flexible and foldable electro-active composite structures. Various three-dimensional shape changes of originally planar structures are achieved with different arrangements of integrated patches and subjected to different magnitude of electric fields. The effect of viscoelastic substrates and time-dependent electro-mechanical coupling of piezoelectric materials on the deformed shapes is also studied. This analysis can help designers in simulating desired deformed shapes and determining external stimuli to be prescribed prior to fabricating smart and flexible composites.

Delaunay graph and radial basis function for fast quality mesh deformation

A novel mesh deformation technique is developed based on the Delaunay graph mapping (DGM) method and the radial basis function (RBF) method. The algorithm combines the advantages of the efficiency of DGM mesh deformation and the better control of the near surface mesh quality from the RBF method. The Delaunay graph is used to divide the mesh domain into a number of sub-domains. On each of the sub-domains, the radial basis function is applied to build a much smaller sized translation matrix between the original mesh and the deformed mesh, resulting in a similar efficiency for the mesh deformation as compared to the fast Delaunay graph mapping method. Furthermore, by separating the translation and rotation motion, the mesh quality near the wall can be substantially improved for extremely large rotational deformation. The paper will show how the near-wall mesh quality is controlled and improved by the new method while the computational time is maintained to be comparable to the original Delaunay graph mapping method.

Modal method for dynamics analysis of cantilever type structures at large rotational deformations

The modal warping method is extended to a floating frame of reference formulation to combine modal warping formula with rigid body simulation. The highly nonlinear mass matrix because of the inertia coupling between the reference and the elastic displacements is approximated using the linear theory of elastodynamics. By kinematics analysis of infinitesimal deformation, the calculation of rotation deformations is derived. Then modal warping method is used to model deformations for numerical accuracy and computation efficiency. The rigid-flex multibody model for a leaf spring landing gear system is developed. The accuracy of the proposed method is examined by experimental/simulation comparison.

Distributed haptic interactions with physically based 3D deformable models over lossy networks.

Researchers have faced great challenges when simulating complicated 3D volumetric deformable models in haptics-enabled collaborative/cooperative virtual environments (HCVEs) due to the expensive simulation cost, heavy communication load, and unstable network conditions. When general network services are applied to HCVEs, network problems such as packet loss, delay, and jitter can cause severe visual distortion, haptic instability, and system inconsistency. In this paper, we propose a novel approach to support haptic interactions with physically based 3D deformable models in a distributed virtual environment. Our objective is to achieve real-time sharing of deformable and force simulations over general networks. Combining linear modal analysis and corotational methods, we can effectively simulate physical behaviors of 3D objects, even for large rotational deformations. We analyze different factors that influence HCVEs' performance and focus on exploring solutions for streaming over lossy networks. In our system, 3D deformation can be described by a fairly small amount of data (several KB) using accelerations in the spectral domain, so that we can achieve low communication load and effective streaming. We develop a loss compensation and prediction algorithm to correct the errors/distortions caused by network problem, and a force prediction method to simulate force at users' side to ensure the haptic stability, and the visual and haptic consistency. Our system works well under both the client-server and the peer-to-peer distribution structures, and can be easily extended to other topologies. In addition to theoretical analysis, we have tested the proposed system and algorithms under various network conditions. The experimental results are remarkably good, confirming the effectiveness, robustness, and validity of our approach.

A frame-invariant scheme for the geometrically exact beam using rotation vector parametrization

While frame-invariant solutions for arbitrarily large rotational deformations have been reported through the orthogonal matrix parametrization, derivation of such solutions purely through a rotation vector parametrization, which uses only three parameters and provides a parsimonious storage of rotations, is novel and constitutes the subject of this paper. In particular, we employ interpolations of relative rotations and a new rotation vector update for a strain-objective finite element formulation in the material framework. We show that the update provides either the desired rotation vector or its complement. This rules out an additive interpolation of total rotation vectors at the nodes. Hence, interpolations of relative rotation vectors are used. Through numerical examples, we show that combining the proposed update with interpolations of relative rotations yields frame-invariant and path-independent numerical solutions. Advantages of the present approach vis-a-vis the updated Lagrangian formulation are also analyzed.