Bending Deformation Characteristics Research Articles

Analyzing the bending deformation of van der Waals-layered materials by a semi-discrete layer model

Van der Waals (vdW)-layered materials, such as graphite, exhibit unique mechanical properties owing to their structural and mechanical anisotropies. This study reports the development of a mechanical model that reproduces the characteristics of the nonlinear and reversible bending deformation of vdW-layered materials, while taking into account the microscopic mechanism of the discrete interlayer slips. The vdW-layered material was modeled as a stack of interacting discrete deformable layers (semi-discrete layer model), and the interlayer interaction was modeled using a cohesive zone model that reproduced the localized interlayer slip. Using the finite-element method, out-of-plane bending deformation analyses were performed on the cantilevers of the highly oriented pyrolytic graphite (HOPG) and MoTe2, and the validity of the model was verified by comparing it with the experimental results. The model accurately reproduced the loading and unloading behaviors in the experiments for the submicron HOPG cantilevers or the large nonlinear and reversible deformation with a hysteresis loop. Furthermore, the model reproduced well the characteristics of the bending experiments for the micro-MoTe2 cantilevers, or the intermittent decrease in stiffness during the loading process and deformation restoration during the unloading process. These results demonstrated that the designed semi-discrete layer model can be universally applied to reproduce the bending deformation characteristics of a variety of vdW-layered materials and can be employed to effectively elucidate the underlying deformation mechanisms.

Study on Shear Behavior and Failure Characteristics of Bolted Anisotropic Rock Joints

Anisotropic discontinuity exists widely in rock masses of mines, tunnels, slopes, water conservancy and hydropower projects. The shear characteristics of bolted anisotropic rock joints are extremely important for the stability design of engineering rock mass. However, few scholars have studied the bolted anisotropic rock joint. The different rock properties on both sides of the rock joint, especially the different rock strengths, will greatly affect the deformation characteristics and failure mode of the rock mass. Based on this, a series of shear tests were carried out on the bolted anisotropic rock joint under different normal stresses, and the characteristics of shear stress-shear displacement curve, shear strength, failure characteristics of the rock joint and deformation characteristics of the bolt are discussed. λ is defined as the strength ratio of upper and lower rock on the structural surface. The results show that the effect of λ on the shear stress-shear displacement curve is not obvious at the pre-fracture stage. The shear stress-shear displacement curve at the pre-breaking stage of the bolt presents a softening stage when the normal stress is equal to 0.5 MPa, tends to be horizontal when the normal stress is equal to 1 MPa and presents a hardening stage when the normal stress is greater than 1 MPa. After the bolt is broken, the shear stress-shear displacement curve presents a stepped-down descent. With the increase in λ, the breaking shear stress of the bolt increases. Elliptic failure occurs on the surface of the bolted anisotropic rock joint, and the length of the major axis of the ellipse decreases with the increase in λ value and normal stress. The bolts with different λ values of anisotropic rock joint show "Z-shaped" tensile bending deformation characteristics after shear fracture, and the horizontal and vertical components of the bolt deformation decrease with the increase in λ value and normal stress. The fracture shear displacement of the bolt increases with the increase in normal stress and decreases with the increase in λ value. The research results are helpful to further understand the shear mechanical characteristics and differences of bolted rock joints and provide a reference for solving the engineering problems of the composite layered rock mass.

Study on mechanical properties of the cross arm-insulator system under strong wind load

High-voltage transmission tower-line systems in coastal areas are often affected by strong winds, which leads to structural damage to the towers. Detailed analysis of the damage mechanism of towers is very useful to ensure the safety and stability of the power system. This paper examines the mechanical properties of the cross-insulator structure under horizontal wind load, and then the load-carrying capacity and deformation performance were analyzed based on ABAQUS. The results show that the structure is stable under the load, and the main structure is basically in the elastic working stage with insignificant flexural and torsional effects. On the contrary, the local stress of the combined link rod connected with the insulator is large; the bending deformation characteristics of the combined link rod are obvious under the maximum horizontal load the insulator can withstand. This result can provide a reference for cross-arms structural safety design.

Bending deformation characteristics of high-pressure soft actuator driven by water-hydraulics for underwater manipulator

In the field of marine research, the soft actuator has a better flexible grasping effect and adaptability to the target object compared with the traditional rigid manipulator. In this paper, a soft actuator based on water-hydraulic technology is proposed. The material parameters of the Yeoh 3rd-order model is determined based on uniaxial testing, and a mathematical model of the input pressure and deformation of the water-hydraulic soft actuator (WHSA) is established. The optimal structural parameters of the rectangular chamber WHSA are selected by orthogonal test. The bending deformation of WHSA under different pressure conditions is simulated with thermoplastic polyurethane (TPU) as the material. The deformation of WHSA under different pressure is measured experimentally to verify the consistency of the simulation and theoretical results and the rationality of the design. Meanwhile, the pressure-holding experiment and grasping experiment of WHSA are conducted, which confirmed the important application value and application potential of WHSA in the underwater manipulator with better flexibility and adaptability in comparison with traditional rigid manipulators.

Flexible actuator by electric bending of saline solution-filled carbon nanotubes

As a two-phase hybrid material, liquid-filled carbon nanotubes (CNTs) provide a great opportunity to design dexterous flexible nano-manipulator actuated by electric field. Here, we report a group of saline solution-filled CNTs with the end constraint can realize 360° all-round bending in a suitable electric field. The molecular dynamics (MD) simulation results show that saline solution-filled CNTs can be bent under the axial-lateral compound electric field, whereas the bending deflection increases with the increase of salinity, CNTs length and electric intensity. The deformation mechanism of saline solution-filled CNTs under the electric field is clarified by exploring the movement and distribution of salt ions in CNTs under the axial electric field. Moreover, based on the bending deformation characteristics of saline solution-filled CNTs, the MD simulations for the two-finger and four-finger nano grippers grasping diamond balls are carried out to demonstrate the micromanipulation functions of saline solution-filled CNTs. The findings will provide an important theoretical basis for the design and application of micromanipulation devices based on low dimensional carbon materials.

Bending Deformation Characteristics and Performance Limitation of Polyethylene Reinforced with Short Glass Fiber Pipes and Electrofusion Joints

Bending Deformation Characteristics and Performance Limitation of Polyethylene Reinforced with Short Glass Fiber Pipes and Electrofusion Joints

Bending Deformation Characteristics of Polyethylene Reinforced with Short Glass Fiber Pipe

Bending Deformation Characteristics of Polyethylene Reinforced with Short Glass Fiber Pipe

Wood Composite Plates with Reversible Humidity-driven Deformation

Four types of beech/spruce composite plates were fabricated from beech with different wood textures under different initial ambient relative humidity, and the impacts of the changes in ambient relative humidity on the deformation characteristics and mechanical properties of the composite plates were studied. It was found that the reversible bending deformation of the composite plates can be achieved by adjusting the ambient humidity. The bending deformation characteristics of the composite plates were related to the initial fabrication conditions and humidity expansion characteristics of the wood, and conformed to the improved Timoshenko theoretical model for bilayer humidity expansion materials. The experiments on humidity-driven deformation of the counter-balanced composite plates showed that external load would hinder the deformation of the composite plates driven by the ambient humidity, but the composite plates still had a good load-bearing capacity.

A nonlinear semi-continuum model for silicon micro/nanosheets and its application in bending and vibration

Background: This paper is concerned with a nonlinear semi-continuum model for an ultrathin structure. The basic equations of the theoretical model for silicon micro/nanosheets are derived, and the geometric nonlinearity is introduced in the model. Methods: From two different approaches including the new strain energy and the new external potential energy, we establish the nonlinear semi-continuum theoretical model of silicon micro/nanosheets, respectively. A new dimensionless nonlinear semi-continuum parameter is defined. Based on the theoretical model, the characteristics of bending deformation and free vibration are revealed. Results: The relationships between bending deflection and atomic layers in thickness direction as well as the relaxation coefficient between atomic layers are analyzed. The resonance frequencies of free vibration and their relationship with atomic layers are calculated. By introducing the specific property parameters of silicon micro/nanomaterials, several numerical calculations have been carried out. Conclusion: The theoretical results are compared with other studies in the literature, such as nonlinear finite element method (FEM), experimental and classical results, to validate the semi-continuum model established in the present research. This work can provide new ideas for the mechanical analyses of micro/nanomaterials and structures, and the results could be foundations for the design and application of silicon micro/nanosheets.

이중 볼 맨드릴에 의한 동파이프의 굽힘변형 특성 연구

이중 볼 맨드릴에 의한 동파이프의 굽힘변형 특성 연구

동파이프의 굽힘변형 특성에 대한 연구

동파이프의 굽힘변형 특성에 대한 연구

Time-varying Characteristics of Bending Deformation for Bridge under the Action of Moving Vehicle Loads

This paper takes the three-span bridge under the two vehicles moving along opposite directions as an example. By using the Singular Function to list the moment equation of the whole bridge, the integral rule of Singular Function and the force, and displacement boundary conditions, the deflection equation of bridge under corresponding vehicles is deduced. Furthermore, the deflection curve of the bridge at each time under the action of one vehicle, dual-vehicles and multi-vehicles moving along the forward direction and reverse motion is obtained by using Mathcad software. Comparing the influence of different vehicle speeds and shifting direction on the bending moment and deflection regularity of bridge’s each section, the relative position relationship between the cross section and the vehicle is studied when the deflection of each section is maximized during the vehicle movement. With the increase of vehicle speed, the maximum value of section deflection increases first and then decreases. When the vehicle is moving along opposite direction, the distance between the section and the vehicle decreases first and then increases with the movement of the vehicle when the deflection of each section reaches the maximum. When the vehicle is moving in the same direction, no matter the vehicle is approaching or crossing the cross section, the deflection of the section reaches the maximum, and the distance between the section and the vehicle is very small. To the middle section of the bridge, the distance increases rapidly, and then the distance between the cross-section and the vehicle linearly reduced trend.

Transverse bending deformation analysis of 3D surface part in continuous roll forming process

This paper introduces a newly developed technique called continuous roll forming process which is applied to manufacture 3D surface part with various shapes, especially for doubly curved parts. In continuous roll forming process, the twin bendable rolls are placed to form a nonuniform roll gap. The bendable rolls rotate in opposite directions around the bend axis with equal angular velocity. The sheet metal is bitten into the roll gap by friction force and compressed nonuniformly across its width. At the present, how to precisely predict transverse bending deformation of 3D surface part has become a critical issue for guiding practical forming in the continuous roll forming process. This work focuses on analysis of the transverse bending deformation characteristics in continuous roll forming process.

Effect of strain rate on the compressive deformation behaviors of lotus-type porous copper

Abstract Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10−3–2400 s−1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar (SHPB) were used to investigate the effect of strain rate on the compressive deformation behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate (< 1.0 s−1), the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s−1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.

Test Study on Bending Deformation Performance and its Size Effect Characteristics of RC Cantilever Beams

Studies on size effect around deformation performance of RC members are carried out relatively fewer at present. This article evaluated bending deformation capacity and size effect characteristics of RC cantilever beams by means of test method. And decomposed various deformation components with size effect factors considered, including bending, shear and bar-slip deformation and so on. The article focus on discussing bending deformation components at different loading stage and putting forward corresponding distribution functions. Calculation and experimental results show that bending deformation characteristics have significant differences on specimen dimensions, especially in nonlinear loading stage after longitudinal reinforcement yielding. Large size members have a significant concrete crushing process. ductility reserves show a growing trend with specimens size increasing. Bending deformation ability depends on average stiffness along overall beam before longitudinal reinforcement yielding. After plastic hinge forming, its bending performance will be decided by average stiffness within hinge region equivalent length.

Relationships between Spring-Back and Microstructure of Ti-15V-3Cr-3Sn-3Al Titanium Alloy Sheet during Bending Process

Evolutions of microstructure, micro-hardness in the central deformation area and spring-back, were studied in different bending conditions of Ti-15V-3Cr-3Sn-3Al titanium alloy sheet. The results show that, with the increase of bending deformation, i.e. increase of bending angle or decrease of bending radius, the grain area, the grain feret diameter ratio and micro-hardness in the central deformation area all show nearly linear growth trends. The spring-back angle has no clearly correlation with the degree of bending deformation. While the spring-back rate correlates positively with the length of deformation-affected zone, which can reflect the characteristics of bending deformation more intuitively than that of spring-back angle.

Bending deformation characteristics of actuator with anion exchange polymer membrane and polyaniline electrode

To remove the metal electrode and comprise all-organic ionic polymer actuators, tri-layer actuators with anion exchange membranes and conducting polymer electrode were purposely fabricated by the simple attaching method with or without an adhesive layer. Three grades of Neosepta were used as the anion exchange membrane, and polyaniline (PANi) as the electrode. Despite the oxidation/reduction occurring, PANi functioned as the electrode for the actuators. The bending displacement of 7 mm was measured, which was comparable to that of the typical Nafion actuator. As the initial bending direction was the same as an actuator with a cation exchange membrane, the bending characteristics of the actuators and structural change in PANi during actuation were investigated. Open image in new window

Time-Varying Characteristics of Bending Deformation of Work-Piece in the Turning Process

Based on the geometrical description of work-pieces cutting process, the time-varying differential equations of deflection curve under two different conditions were obtained using the singular function: one with thimble and one without thimble constraint. Using the Mathcad software, we have solved the time-varying differential equations analytically and have studied the deflection changing of work piece with the position of turning tool and given the distribution characteristic for the time-varying deflection of each section. The results indicate that (1) the deflection of an arbitrary section is time-varying due to the time-varying position of the turning tool and the time-varying inertia moment; (2) for the shaft with thimble constraint, the position of the maximal deflection is not at the section with turning tool; (3) for the shaft without thimble constraint, when the turning tool is at the free end, the deflection at each section of the work-piece is the maximal compared with the other positions of turning tool.

OS2111 脳ベラ用精密鋳造TiNi形状記憶合金の曲げ変形特性(OS21-3 形状記憶材料の機能特性,OS-21 形状記憶材料の開発,機能特性および応用)

In order to develop a brain spatula or a brain refractor made of a shape memory alloy (SMA), the bending deformation characteristics of the brain spatula of TiNi SMA made by the precision casting were discussed. The results obtained can be summarized as follows. (1) The relationship between force and deflection obtained from the cyclic three-point bending test changes slightly except for a first cycle. (2) The fatigue life in pulsating-plane bending is longer than that in alternating-plane bending. (3) The relationship between dissipated work W_d and the number of cycles to failure N_f can be expressed by a unified power function for alternating- and pulsating-plane bendings.

Swinging motion control of suspended structures: Principles and applications

This paper discusses the development of non-linear differential equation modeling and characteristic analysis of control force for motion control of suspended structures, and proposes an innovative passive control system for suppressing swinging motion of similar structures. Based on the classical Lagrangian principle, the system EOM can be established with respect to two basic motion modes: planar motion and swinging motion. The analytical results indicate that different control systems should be considered owing to the diverse motion characteristics of the suspended system. Furthermore, theoretical results show that the tuned mass damper (subsequently abbreviated as TMD) cannot be used for swinging motion control, due to the coupling effect between linear stroke of TMD mass and angular velocity of suspended structure. Then, based on thorough numerical analysis, the concept of tuned rotary inertia damper (subsequently abbreviated as TRID) control system is proposed, and the differential equations of motion, denoting the motion law of the whole system, are studied. In addition, optimization issues of TRID control are equivalent to the classical optimization problem of TMD control. At last, conclusions were extended to vibration or motion control of typical civil engineering structures, such as high-rising tower structures with prior bending deformation characteristics and long-span bridges with rotation vibration characteristics. Once the structural motion or vibration is similar to the single pendulum or inverted pendulum, the planar TMD control system will lose its effectiveness and the innovative TRID system should be considered for suppressing swinging motion of such structures. Copyright © 2009 John Wiley & Sons, Ltd.