scholarly journals Deformation and Mechanical Properties of a Constant-Friction-Force Energy-Absorbing Bolt

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Tao Song ◽  
Tianbin Li ◽  
Lubo Meng ◽  
Chunchi Ma ◽  
Chaofei Li ◽  
...  
Keyword(s):  
Energy Absorption ◽  
Friction Force ◽  
Displacement Curve ◽  
Pull Out ◽  
Constant Friction ◽  
Combined Action ◽  
Face Plate ◽  
Energy Absorbing ◽  
Rock Tunnels ◽  
Force Displacement

The conventional bolts used in surrounding rock tunnels with large deformation often fail. As a solution to this problem, we developed an extensible bolt with energy-absorbing and constant-friction-force (EACF) characteristics. The EACF bolt mainly comprises a damping device, a hollow threaded bolt, a tightening nut, and a face plate. To reveal its working mechanism, the bolt was tested in terms of its friction, displacement, and energy absorption through a modified tensile test device in a laboratory. The static pull-out test results showed that the axial force-displacement curve of the bolt can be mainly divided into three stages: a conical extrusion stage, an elongation stage, and an elastic failure stage. The EACF bolts exhibited stable energy absorption behaviors when subjected to static loading. The maximum constant friction force could be adjusted by increasing the size and diameter of the straight section of the damping block, and the maximum elongation could be adjusted by increasing the length of the damping cylinder. When the properties of the bolt materials are kept constant, increasing the diameter of the damping block can help achieve a high constant resistance. The proposed EACF bolt has reliable deformation and energy-absorption properties, which ensure its stability when employed in tunnels under the combined action of support and surrounding rocks.

scholarly journals Study on improvement of prefolded energy absorption device to constant resistance and its mechanical properties

2021 ◽  
Vol 104 (3) ◽  
pp. 003685042110368
Author(s):  
Dong An ◽  
Jiaqi Song ◽  
Hailiang Xu ◽  
Jingzong Zhang ◽  
Yimin Song ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Energy Absorption ◽  
Compression Test ◽  
Side Wall ◽  
Concave Side ◽  
Displacement Curve ◽  
Static Compression ◽  
Constant Resistance ◽  
The Impact ◽  
Force Displacement

When the rock burst occurs, energy absorption support is an important method to solve the impact failure. To achieve constant resistance performance of energy absorption device, as an important component of the support, the mechanical properties of one kind of prefolded tube is analyzed by quasi-static compression test. The deformation process of compression test is simulated by ABAQUS and plastic strain nephogram of the numerical model are studied. It is found that the main factors affecting the fluctuation of force-displacement curve is the stiffness of concave side wall. The original tube is improved to constant resistance by changing the side wall. The friction coefficient affects the folding order and form of the energy absorbing device. Lifting the concave side wall stiffness can improve the overall stiffness of energy absorption device and slow down the falling section of force-displacement curve. It is always squeezed by adjacent convex side wall in the process of folding, with large plastic deformation. Compared with the original one, the improved prefolded tube designed in this paper can keep the maximum bearing capacity ( Pmax), increase the total energy absorption ( E), improve the specific energy absorption (SEA), and decrease the variance ( S2) of force-displacement curve.

scholarly journals Why Should the “Alternative” Method of Estimating Local Interfacial Shear Strength in a Pull-Out Test Be Preferred to Other Methods?

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2406
Author(s):  
Serge Zhandarov ◽  
Edith Mäder ◽  
Uwe Gohs
Keyword(s):  
Shear Strength ◽  
Interfacial Shear Strength ◽  
Traditional Approach ◽  
Interfacial Shear ◽  
Frictional Stress ◽  
Displacement Curve ◽  
Pull Out ◽  
Alternative Method ◽  
Fiber Reinforced Materials ◽  
Force Displacement

One of the most popular micromechanical techniques of determining the local interfacial shear strength (local IFSS, τd) between a fiber and a matrix is the single fiber pull-out test. The τd values are calculated from the characteristic forces determined from the experimental force–displacement curves using a model which relates their values to local interfacial strength parameters. Traditionally, the local IFSS is estimated from the debond force, Fd, which corresponds to the crack initiation and manifests itself by a “kink” in the force–displacement curve. However, for some specimens the kink point is hardly discernible, and the “alternative” method based on the post-debonding force, Fb, and the maximum force reached in the test, Fmax, has been proposed. Since the experimental force–displacement curve includes three characteristic points in which the relationship between the current values of the applied load and the crack length is reliably established, and, at the same time, it is fully determined by only two interfacial parameters, τd and the interfacial frictional stress, τf, several methods for the determination of τd and τf can be proposed. In this paper, we analyzed several theoretical and experimental force–displacement curves for different fiber-reinforced materials (thermoset, thermoplastic and concrete) and compared all seven possible methods of τd and τf calculation. It was shown that the “alternative” method was the most accurate and reliable one, while the traditional approach often yielded the worst results. Therefore, we proposed that the “alternative” method should be preferred for the experimental force–displacement curves analysis.

Evaluation of Crushing Response of Limited Bonding of a Composite Core With a Cross Tube

2020 ◽  
Author(s):  
Sean Jenson ◽  
Muhammad Ali ◽  
Khairul Alam
Keyword(s):  
Energy Absorption ◽  
Axial Loading ◽  
Absorption Capacity ◽  
Displacement Curve ◽  
Progressive Deformation ◽  
Finite Element Software ◽  
First Case ◽  
Short Period ◽  
Deformation Modes ◽  
Force Displacement

Abstract Rectangular and round tubular structures are typically used in a vehicles’ front structure to increase the energy absorption capacity in the event of an accident. There is significant interest in lighter structures for improving automobiles’ fuel efficiency with the challenge of maintaining or preferably exceeding the energy absorption properties of the structure. The structural members are designed to take on the challenge of absorbing maximum amount of energy in a relatively short period of time, while also maintaining reactive forces below damaging levels as they undergo progressive deformation under axial loading. The type of deformation mode is critical as it defines the overall configuration of force-displacement curve. There are different types of deformation modes for cross tube under axial loading. Likewise, cellular structures exhibit distinct deformation modes under in-plane loading. The work presented here investigates the effects of bonding of composite cellular core structure on deformation modes of cross tubes under axial loading. The numerical simulations were performed in ABAQUS finite element software. Four cases were considered for analysis. The first case did not contain core bonding. The second case consisted of 3 bonding sites. In the third case, 5 bonding zones were defined and in the final case, 7 bonding sites were assigned. Bonding of the composite core resulted in an increase of up to 39.2% energy absorption as compared to the unbonded case. The results show discrete bonding of composite cellular core with the tube has significant effect on progressive deformation of tubes and therefore, presents an opportunity to re-configure force-displacement curve for improved protection of automobile structures under impact loading.

The Pull-Out Method For On-Site Estimation of the Elastic Modulus of Concrete

2005 ◽  
Vol 40 (6) ◽  
pp. 505-511 ◽  
Author(s):  
P Antonaci ◽  
P Bocca
Keyword(s):  
Elastic Modulus ◽  
Concrete Strength ◽  
Displacement Curve ◽  
Concrete Mass ◽  
Existing Structures ◽  
Pull Out ◽  
Site Evaluation ◽  
Displacement Transducers ◽  
Force Displacement

The paper describes a new experimental mechanical method for the on-site evaluation of the elastic modulus of concrete. It is based on a modification of the well-known pull-out test, which is currently used for the estimation of concrete strength. The method consists in pulling out a metal insert embedded in the concrete mass and measuring the force-displacement curve consequent to the extraction. Three displacement transducers were used in order to correctly detect the displacement of the insert. Moreover, an adequate number of loading-unloading cycles was performed in order to stabilize the system and eliminate possible phenomena of mutual sliding between the mechanical parts of the apparatus and between the insert and the concrete mass. By performing a certain number of pull-out tests the stiffness value of the system is obtained. The material deformability is then estimated through an appropriate correlation curve between pull-out stiffness and elastic modulus, which has been worked out on the basis of finite element simulations and experimental results. The proposed method offers interesting possibilities of application for the characterization of existing structures at affordable costs.

The Simulation Study for Energy-Absorbing Properties of the Railway Vehicle’s Anti-Climber with Different Vertical Offsets

2013 ◽  
Vol 300-301 ◽  
pp. 160-165
Author(s):  
Wen Bin Wang ◽  
Jun Jie Jiang ◽  
Qian Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Simulation Study ◽  
Passive Safety ◽  
Displacement Curve ◽  
Linear Finite Element ◽  
Improvement Method ◽  
Energy Absorbing ◽  
Force Displacement ◽  
Cross Structure

Anti-climber is one of the most important passive safety devices for railway vehicles. Based on the non-linear finite element method, properties of the anti-climber with different vertical offsets are simulated by the software LS-DYNA. The force-displacement curve is mainly analyzed, and the energy absorbed by the anti-climber is also calculated in order to assess the properties. At last, an improvement method with a cross structure inside the anti-climber is designed for the offset problem and is proved effective by the simulation.

Negative stiffness honeycombs for recoverable shock isolation

2015 ◽  
Vol 21 (2) ◽  
pp. 193-200 ◽  
Author(s):  
Dixon M Correa ◽  
Timothy Klatt ◽  
Sergio Cortes ◽  
Michael Haberman ◽  
Desiderio Kovar ◽  
...  
Keyword(s):  
Energy Absorption ◽  
High Energy ◽  
Negative Stiffness ◽  
Static Displacement ◽  
Content Type ◽  
Beam Geometry ◽  
Displacement Behavior ◽  
Shock Isolation ◽  
Energy Absorbing ◽  
Force Displacement

Purpose – The purpose of this paper is to study the behavior of negative stiffness beams when arranged in a honeycomb configuration and to compare the energy absorption capacity of these negative stiffness honeycombs with regular honeycombs of equivalent relative densities. Design/methodology/approach – A negative stiffness honeycomb is fabricated in nylon 11 using selective laser sintering. Its force-displacement behavior is simulated with finite element analysis and experimentally evaluated under quasi-static displacement loading. Similarly, a hexagonal honeycomb of equivalent relative density is also fabricated and tested. The energy absorbed for both specimens is computed from the resulting force-displacement curves. The beam geometry of the negative stiffness honeycomb is optimized for maximum energy absorption per unit mass of material. Findings – Negative stiffness honeycombs exhibit relatively large positive stiffness, followed by a region of plateau stress as the cell walls buckle, similar to regular hexagonal honeycombs, but unlike regular honeycombs, they demonstrate full recovery after compression. Representative specimens are found to absorb about 65 per cent of the energy incident on them. Optimizing the negative stiffness beam geometry can result in energy-absorbing capacities comparable to regular honeycombs of similar relative densities. Research limitations/implications – The honeycombs were subject to quasi-static displacement loading. To study shock isolation under impact loads, force-controlled loading is desirable. However, the energy absorption performance of the negative stiffness honeycombs is expected to improve under force-controlled conditions. Additional experimentation is needed to investigate the rate sensitivity of the force-displacement behavior of the negative stiffness honeycombs, and specimens with various geometries should be investigated. Originality/value – The findings of this study indicate that recoverable energy absorption is possible using negative stiffness honeycombs without sacrificing the high energy-absorbing capacity of regular honeycombs. The honeycombs can find usefulness in a number of unique applications requiring recoverable shock isolation, such as bumpers, helmets and other personal protection devices. A patent application has been filed for the negative stiffness honeycomb design.

scholarly journals Numerical simulation of fiber-matrix debonding in single fiber pull-out tests

2020 ◽  
Vol 2 (1) ◽  
pp. 21-35
Author(s):  
Lukas Hoppe
Keyword(s):  
Crack Initiation ◽  
Cohesive Zone ◽  
Single Fiber ◽  
Displacement Curve ◽  
Fe Model ◽  
Pull Out ◽  
Peridynamic Model ◽  
Reference Experiment ◽  
Fiber Matrix ◽  
Force Displacement

The present work deals with the numerical crack simulation of fiber-matrix debonding in single fiber pull-out tests. For this purpose, two models are used: a finite element model (FE model) with the cohesive zone approach and a peridynamic model. For calibration a reference experiment is applied. In addition analytical equations are used for reference values. The influence of the model parameters and the material parameters of the cohesive zone model on the force-displacement curve is investigated. Besides the free fiber length, the critical interface strength, the critical energy release rate as well as the initial interface stiffness have a great influence on the force-displacement curve of the pull-out test. From the crack simulation it can be seen that Mode I has an influence on the crack initiation, but further crack growth after initiation is dominated by Mode II. The FE model can be calibrated in a way that the crack initiation point and the maximum force correspond to the reference experiment. The peridynamic model depicts a comparable crack formation process.

Numerical simulation of hybrid composite tubes under oblique compression

2017 ◽  
Vol 14 (2) ◽  
pp. 173-177 ◽  
Author(s):  
Al Emran Ismail ◽  
N. Nezere
Keyword(s):  
Energy Absorption ◽  
Kinematic Hardening ◽  
Shell Element ◽  
Steel Tube ◽  
Finite Element Program ◽  
Content Type ◽  
Contact Algorithm ◽  
Element Program ◽  
Energy Absorbing ◽  
Force Displacement

Purpose An energy-absorbing device is an important tool that is capable of increasing the survivability of passengers in vehicles. Generally, empty metallic tubes are used, and it is found that the energy absorption capability is lower than the energy obtained using composite materials. Therefore, this paper numerically presents the crushing performances of hybrid tubes under axial and oblique compressions. Design/methodology/approach Three important parameters are used such as fiber thicknesses, fiber orientations and oblique compression angles. Epoxy-reinforced fibers are wrapped around the steel tubes and it is then modeled numerically using the ANSYS finite element program. Belytscho – Tsay shell element is used to model the composites, while a bilinear kinematic hardening model is used to model the steel tube. A proper contact algorithm is implemented to prevent interpenetration among elements and surfaces. Findings A proper contact algorithm is implemented to prevent interpenetration among elements and surfaces. Hybrid tubes are quasi-statically crushed and force–displacement curves are extracted and analyzed. Originality/value It is found that the introduction of oblique compressions has induced bending moments and therefore decreases the energy absorption capability. Varying fiber orientations also insignificantly changed the crushing performances. However, wrapping carbon/epoxy composite that is capable of strengthening the tubes, is also subjected to oblique compression compared with the glass/epoxy composites.

Evaluation Method of U-Bolt Energy Absorption

2009 ◽  
Author(s):  
Eiji Shirai ◽  
Tetsuya Zaitsu ◽  
Kazutoyo Ikeda ◽  
Toshiaki Yoshii ◽  
Masami Kondo ◽  
...  
Keyword(s):  
Energy Absorption ◽  
Evaluation Method ◽  
Design Procedure ◽  
Piping System ◽  
Design Technique ◽  
Dynamic Tests ◽  
Key Issues ◽  
Static And Dynamic Tests ◽  
Force Displacement ◽  
Rigid Design

At domestic PWR plants in Japan, one of the major key issues is earthquake-proof safety [1–3]. Recently, a design procedure using energy absorption, not conventional rigid design, was authorized according to revised review guidelines for aseismic design (JEAC4601). Therefore, we focused on the design technique that utilizes energy absorption effects to reduce the seismic responses of the piping system with U-Bolt, by the static and dynamic tests of simplified piping model supported by U-Bolt. The force-displacement characteristics and a fatigue diagram were obtained by the tests.

scholarly journals Young’s Modulus of Polycrystalline Titania Microspheres Determined by In Situ Nanoindentation and Finite Element Modeling

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Peida Hao ◽  
Yanping Liu ◽  
Yuanming Du ◽  
Yuefei Zhang
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Deformation Mechanisms ◽  
Displacement Curve ◽  
Element Simulation ◽  
Nanoindentation Experiment ◽  
Force Displacement

In situ nanoindentation was employed to probe the mechanical properties of individual polycrystalline titania (TiO2) microspheres. The force-displacement curves captured by a hybrid scanning electron microscope/scanning probe microscope (SEM/SPM) system were analyzed based on Hertz’s theory of contact mechanics. However, the deformation mechanisms of the nano/microspheres in the nanoindentation tests are not very clear. Finite element simulation was employed to investigate the deformation of spheres at the nanoscale under the pressure of an AFM tip. Then a revised method for the calculation of Young’s modulus of the microspheres was presented based on the deformation mechanisms of the spheres and Hertz’s theory. Meanwhile, a new force-displacement curve was reproduced by finite element simulation with the new calculation, and it was compared with the curve obtained by the nanoindentation experiment. The results of the comparison show that utilization of this revised model produces more accurate results. The calculated results showed that Young’s modulus of a polycrystalline TiO2microsphere was approximately 30% larger than that of the bulk counterpart.

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