Showing papers on "Hinge published in 2022"

Theoretical analysis on the lateral drift of precast concrete frame with replaceable artificial controllable plastic hinges

Abstract: This research proposed a calculation method for the deformation of the frame system with the artificial controllable plastic hinges (APHF). The lateral deformation amplification coefficient was introduced to regulate the deformation value of APHF. Based on the equivalent system method, the relation between the rotational stiffness of the artificial controllable plastic hinge and the lateral deformation amplification coefficient was analyzed. According to the structural performance requirements, the rotational stiffness limit of the artificial controllable plastic hinge can be obtained to avoid the APHF deformation exceeding the demand limits. Based on the APHF experiment, the APHF model was developed using Opensees. Subsequently, the dynamic response analysis was performed to further explore the deformation mechanism of APHF. The seismic response analysis results indicated that the inter-story drift of APHF was more evenly distributed, which avoided the formation of vulnerable structural layers, compared with RC frame. The artificial controllable plastic hinge effectively reduced the base shear of the frame structures.

Analytical modelling and experiments for hybrid multiaxis flexure hinges

Abstract: Hybrid multiaxis flexure hinges with a generalized elliptical-arc hybrid fillet (EAHF) notch contour are herein developed and investigated. Analytical closed-form equations of compliance, rotational precision, and maximum stress under spatial combined loads are formulated. The presented analytical equations are confirmed by finite element analysis and experiments. The performances of the hybrid multiaxis flexure hinges are investigated by means of a parameter study with a focus on the effects of the hybrid filleted notch. It is found that the notch transformation of the multiaxis flexure hinges between transverse symmetric and asymmetric (or hybrid) only change their rotation centre and shearing compliances but hardly change their rotational compliances. In conclusion, the presented EAHF contour provides a generalized model for designing hybrid multiaxis flexure hinges, while the developed analytical equations are sufficient for quick, systematic evaluations of hinge performance.

A Snakeskin‐Inspired, Soft‐Hinge Kirigami Metamaterial for Self‐Adaptive Conformal Electronic Armor

Abstract: A majority of soft‐body creatures evolve armor or shells to protect themselves. Similar protection demand is for flexible electronics working in complex environments. Existing works mainly focus on improving the sensing capabilities such as electronic skin (E‐skin). Inspired by snakeskin, a novel electronic armor (E‐armor) is proposed, which not only possesses mechanical flexibility and electronic functions similar to E‐skin, but is also able to protect itself and the underlying soft body from external physical damage. The geometry of the kirigami mechanical metamaterial (Kiri‐MM) ensures auxetic stretchability and meanwhile large areal coverage for sufficient protection. Moreover, to suppress the inherent but undesired out‐of‐plane buckling of conventional Kiri‐MMs for conformal applications, soft hinges are used to form a distinct soft (hinges)‐rigid (tiles) configuration. Analytical, computational, and experimental studies of the mechanical behaviors of the soft‐hinge Kiri‐MM E‐armor demonstrate the merits of this design, i.e., stretchability, conformability, and protectability, as applied to flexible electronics. Deploying a conductive soft material at the hinges enables facile wiring strategies for large‐scale circuit arrays. Functional E‐armor systems for controllable display and sensing purposes provide simple examples of a wide spectrum of applications of this concept.

Detecting Hinge Joint Damage in Hollow Slab Bridges Using Mode Shapes Extracted from Vehicle Response

Abstract: Hinge joint damage is the main defect affecting the safety of assembled hollow slab bridges. The timely discovery of hinge joint damage is significant for guaranteeing the structural safety of assembled hollow slab bridges. This paper presents a damage detection approach for hinge joints of hollow slab bridges using mode shapes extracted from moving vehicle responses. A stationary excitation vehicle equipped with a shaker excites a bridge, another vehicle moves along the driving path, and its acceleration is collected to extract the mode shape, which is called the stationary excitation extraction mode (SEEM) method. First, the theoretical analysis model of the proposed method is established to analyze the response of the vehicle–bridge system, and the mode shape is extracted from vehicle acceleration by the Hilbert transform. An algorithm that requires no baseline is adopted to detect damage from the extracted mode shape. Then a procedure for damage detection in field testing is proposed in which the determination of important parameters is explained, including excitation frequency, moving vehicle departure time, and narrowband filtering. Finally, factors that affect the accuracy of the approach are studied by numerical analysis, including road roughness, vehicle speed, damage degree, and damage location. The results demonstrate that the damage detection approach for hinge joints is feasible at low vehicle speeds.

Vibration characteristics of thin plate system joined by hinges in double directions

Abstract: This study investigates the free vibration characteristics of a double-direction (D-D) solar array structure connected with flexible hinges. We propose the more accurate continuity conditions in the theoretical model. The Kirchhoff plate theory is adopted to derive the energy equations of the structure. The Chebyshev polynomials are introduced as admissible functions to construct the dynamic model of each solar panel. The Lagrange multiplier method is employed to describe the continuity conditions of the flexible hinges. The natural frequencies and corresponding global mode shapes of the structure are calculated using the Rayleigh–Ritz method. Furthermore, a comparison with the results obtained from ANSYS is performed to confirm the validity of the present method. Finally, investigations are carried out to illustrate the effect of the structural parameters on the natural frequency and mode shape of the structure. A comparison study shows that the present continuity conditions can significantly improve the accuracy of the results. Different from the single direction solar panels structures, there exist coupling effect between x- and y-direction solar panels in D-D solar array structures. Moreover, unique frequency stability phenomenon and coplanar phenomenon of solar panels are discovered in D-D solar array structures. In addition, the results of frequency curves, mode shapes, and modal assurance criterion (MAC) values reveal that the variation of the hinge torsional stiffness and the solar panel aspect ratio induce a series of frequency veering and mode shift phenomena. Particularly, the mechanism of these phenomena is explored. The present theoretical study can significantly improve the calculation efficiency, and is convenient to analyze the parameter influence law, which outperforms the finite element analysis.

Selective hinge removal strategy for architecting hierarchical auxetic metamaterials

Abstract: Abstract Mechanical metamaterials are man-made structures capable of achieving different intended mechanical properties through their artificial, structural design. Specifically, metamaterials with negative Poisson’s ratio, known as auxetics, have been of widespread interest to scientists. It is well-known that some pivotally interconnected polygons exhibit auxetic behaviour. While some hierarchical variations of these structures have been proposed, generalising such structures presents various complexities depending on the initial configuration of their basic module. Here, we report the development of pivotally interconnected polygons based on even-numbered modules, which, in contrast to odd-numbered ones, are not straightforward to generalize. Particularly, we propose a design method for such assemblies based on the selective removal of rotational hinges, resulting in fully-deployable structures, not achievable with previously known methods. Analytical and numerical analyses are performed to evaluate Poisson’s ratio, verified by prototyping and experimentation. We anticipate this work to be a starting point for the further development of such metamaterials.

Seismic fragility estimates of steel diagrid structure with performance-based tests for high-rise buildings

Abstract: During seismic performance-based design for building structures, the accuracy of limit states criteria is directly related to its real damage state and retrofitting measures after the earthquake. As a new type of structures, diagrid structure has a special way of bearing force. Firstly, in order to accurately estimate the deformation capacity and energy dissipation mechanism under horizontal loads, four plane specimens of steel diagrid structure are designed and seismic performance-based tests under horizontal quasi-static cyclic load are carried out. Secondly, according to the yield strength and horizontal ultimate deformation capacity of diagrid structure, combined with pushover method, the limit state values of four performance levels of diagrid structure are determined. Finally, the seismic fragility of a diagrid structure for high-rise building is analyzed. The results suggest that the bottom tilted columns have obvious deformation visible to the naked eye before failure, and some failure warnings can be given in advance. It is difficult to realize the “beam hinge” mechanism in diagrid structure, and the cumulative damage of “column hinge” is its main failure mode. The bottom tilted column is the first place where plastic hinge occurs. In addition, the recommended value of inter-story drift ratio for judging the yield of steel diagrid structure is 1/128 by these experimental results, and the recommended value of inter-story drift ratio for collapse resistance is 1/85. Based on these experimental results, the probability of diagrid structure in each performance state can be estimated reasonably and effectively.

Detecting Hinge Joint Damage in Hollow Slab Bridges Using Mode Shapes Extracted from Vehicle Response

Abstract: Hinge joint damage is the main defect affecting the safety of assembled hollow slab bridges. The timely discovery of hinge joint damage is significant for guaranteeing the structural safety...

Cryomicroscopy reveals the structural basis for a flexible hinge motion in the immunoglobulin M pentamer

Abstract: Abstract Immunoglobulin M (IgM) is the most ancient of the five isotypes of immunoglobulin (Ig) molecules and serves as the first line of defence against pathogens. Here, we use cryo-EM to image the structure of the human full-length IgM pentamer, revealing antigen binding domains flexibly attached to the asymmetric and rigid core formed by the Cμ4 and Cμ3 constant regions and the J-chain. A hinge is located at the Cμ3/Cμ2 domain interface, allowing Fabs and Cμ2 to pivot as a unit both in-plane and out-of-plane. This motion is different from that observed in IgG and IgA, where the two Fab arms are able to swing independently. A biased orientation of one pair of Fab arms results from asymmetry in the constant domain (Cμ3) at the IgM subunit interacting most extensively with the J-chain. This may influence the multi-valent binding to surface-associated antigens and complement pathway activation. By comparison, the structure of the Fc fragment in the IgM monomer is similar to that of the pentamer, but is more dynamic in the Cμ4 domain.

Determining Orders of Modes Sensitive to Hinge Joint Damage in Assembled Hollow Slab Bridges

Abstract: Hinge joint damage is the main defect that affects the safety of assembled hollow slab bridges. There are some studies on vibration-based damage detection for hinge joints. However, the effect of hinge damage on the modal parameters of bridges lacks in-depth analysis. The sensitivities of different order modes to hinge damage are dissimilar. This study determines the orders of modes sensitive to hinge damage in assembled hollow slab bridges, which is instructive for vibration-based hinge damage detection. First, the effect of the degree and location of the damage on the frequencies and curvature mode shapes is theoretically analyzed using a novel equivalent model. The orders of the modes sensitive to hinge damage are determined. Then, the numerical analysis of a bridge is performed. The equivalent model is proven to accurately reflect the dynamic characteristics by comparing it to the entity reference model. Various scenarios are established to quantitatively analyze the influence of joint damage on the partial order frequencies and mode curvatures. The accuracy of the sensitivity analysis is verified. Damage detection based on frequencies and curvature mode shapes sensitive to hinge damage is discussed briefly.

Experimental Demonstration of Bulk-Hinge Correspondence in a Three-Dimensional Topological Dirac Acoustic Crystal.

Abstract: Three-dimensional topological Dirac semimetal (DSM) is a vital state to explore topological phases and phase transitions. However, its bulk-boundary correspondence is elusive. Here, we experimentally investigate the higher-order hinge states in an acoustic DSM. Not only removable trivial surface states but also robust nontrivial hinge arcs are observed, attributed to the direct correspondence between bulk polarization and hinge charge. We further reveal that a pair of zigzag and bearded hinges possess arcs located in complementary momentum regions. Our work provides solid proof of the bulk-hinge correspondence in DSM and sheds light on the study of topological hierarchy across dimensions.

Approaches for Minimizing Joints in Single-Degree-of-Freedom Origami-Based Mechanisms

Abstract: Origami patterns have been used in the design of deploy- able arrays. In engineering applications, paper creases are often replaced with surrogate folds by providing a hinge-like function to enable motion. Overconstraint ob- served in multi-vertex origami patterns combined with imperfect manufacturing may cause the resulting mech- anisms to bind. The removal of redundant constraints de- creases the likelihood of binding, may simplify the over- all system, and may decrease the actuation force by re- ducing friction and other resistance to motion. This pa- per introduces a visual and iterative approach to elim- inating redundant constraints in origami-based mecha- nisms through joint removal. Several techniques for joint removal are outlined and illustrated to reduce overcon- straints in origami arrays.

Mechanical Performance of Lightweight-Designed Honeycomb Structures Fabricated Using Multijet Fusion Additive Manufacturing Technology.

Abstract: Cellular structures including three-dimensional lattices and two-dimensional honeycombs have significant benefits in achieving optimal mechanical performance with light weighting. Recently developed design techniques integrated with additive manufacturing (AM) technologies have enhanced the possibility of fabricating intricate geometries such as honeycomb structures. Generally, failure initiates from the sharp edges in honeycomb structures, which leads to a reduction in stiffness and energy absorption performance. By material quantity, these hinges account for a large amount of material in cells. Therefore, redesigning of honeycomb structures is needed, which can improve aforementioned characteristics. However, this increases the design complexity of honeycombs, such that novel manufacturing techniques such as AM has to be employed. This research attempts to investigate the optimal material distribution of three different topologies of honeycomb structures (hexagonal, triangular, and square) with nine different design configurations. To achieve this, higher amount of material was distributed at nodes in the form of fillets while keeping overall weight of the structure constant. Furthermore, these design configurations were analyzed in terms of stiffness, energy absorption, and the failure behavior by performing finite element analysis and experimental tests on the samples manufactured using Multijet fusion AM technology. It was found that adding material to the edges can improve the mechanical properties of honeycombs such as stiffness and energy absorption efficiency. Furthermore, the failure mechanism is changed due to redistribution of material in the structure. The design configurations without fillets suffer from brittle failure at the start of the plastic deformation, whereas the configurations with increased material proportion at the nodes have larger plastic deformation zones, which improves the energy absorption efficiency.

Hinge point emergence in mammalian spinal neurulation

Abstract: Significance Spinal neural tube folding shows a transition from medial to dorsolateral neural plate bending sites (hinge points) along the embryo’s body axis. While hinge points are considered an important driving force in neural tube closure, their biomechanical origin is poorly understood. Here we use a computational model based on mouse and human embryo imaging data to show that the median hinge point emerges in simulations combining mesoderm expansion, nonneural ectoderm expansion, and neural plate adhesion to the notochord. Furthermore, dorsolateral hinge points emerge through a medial pulling force exerted by dorsal nonneural ectoderm (zippering). This indicates that spinal neural tube folding could be primarily driven by mesoderm expansion and zippering, with hinge points passively emerging in response to extrinsic forces.