Displacement Diagrams Research Articles

Applied element modelling of unreinforced and reinforced concrete masonry walls under blast loading

Masonry walls are the first defense line against exterior explosions in buildings; however, no adequate guidelines are currently available for the analysis and design of these walls under such extreme loading. In this paper, a comprehensive applied element model (AEM) is developed and validated to investigate the behaviour of both reinforced (RMWs) and unreinforced (URMWs) concrete masonry walls under blast loading. A single degree of freedom (SDOF) model is also developed to estimate their pressure-impulse diagram for concrete masonry walls. The developed models are utilized to conduct a parametric study by analyzing 30 walls with different design parameters (boundary conditions, dimensions, compressive strength, as well as reinforcement ratio) under various blast loadings. Crack pattern, fundamental period, support rotation, as well as pressure–displacement and pressure-impulse diagrams for the analyzed walls were compared. The boundary conditions and compressive strength had the most and least significant influence on the behaviour of walls. The two-sides-supported walls experienced severe cracks compared to the four-sides-supported walls. Fundamental period decreased by 74% when the wall thickness increased from 100 mm to 250 mm for either URMWs or RMWs. Resistance of a wall with dimensions of 3 × 7 m was less than that of a 5 × 2 m wall by 81% and 77% for URMW and RMW, respectively. The SDOF model showed that URMWs and RMWs with dimensions of 5 × 2 m had the maximum pressure-impulse response limit compared to the other walls. The average increase in the support rotation was 200% and 380% when the charge weight increased from 5 kg to 15 kg for URMWs and from 15 kg to 150 kg for RMWs, respectively. Using reinforcement ratio greater than 0.85% considerably improved the performance of RMWs.

KINEMATIC CALCULATION OF VARIABLE CURVATURE FIST MECHANISM WITH CONVEX PROFILE

In order to take into account more boundary conditions, a new modified equation was obtained to establish the profile of the fist by adding a constant to the equation obtained from the solution of the differential equation of curvature (i.e., k < 0 - convex profile surface as a special case). Based on this equation, the expression defining the movement of the pusher based on the rotation angle of the fist was deduced. The kinematic report of the punching mechanism was performed on the basis of a modified formula. During the kinematic calculations, it was found that there are no jumps in the displacement, velocity and acceleration diagrams of the pusher, that is, the mechanism works smoothly. In order to verify that the curvature takes a negative value along the profile, the equation of the curvature was deduced, its graph was plotted and its accuracy was confirmed.

Laboratory Analysis of an Asphalt Mixture Overlay Reinforced with a Biaxial Geogrid

Geosynthetic materials have been demonstrated to be an accurate element in civil engineering, specifically in the field of pavement. Regarding the implementation of these materials in asphalt mixture layers, geosynthetics, such as geotextile and geogrid, have been used to delay the crack propagation and/or increase the fatigue life. However, the use of these material is based on the experience learned in the field or results obtained from testing on a reduced scale in the laboratory. This research work aims at evaluating the influence that geogrids have as a reinforcement to asphalt mixture layer samples. Within this context, in this work, two types of large-scale samples (with and without reinforcement) are subjected to a monotonic load under two support conditions (simple support and granular base). The results were summarized with the load-line displacement diagram, where parameters such as the peak load, displacement, stiffness, and work of fracture were analyzed. The results reveal that the asphalt layer with geogrid experiences a double benefit since it withstands greater magnitudes of load and delays the appearance of rutting problems. To conclude, the geogrid as a reinforcement for asphalt mixture layers strongly impact their mechanical behavior, increasing the service life of the pavement structure.

Gait analysis using physical examination and digital techniques

Gait examination is an important component of the patient assessment prior to movement therapy. With the advancement of video technology and computer science, digital analysis of gait has become possible. This research aims to physically examine gait and analyze video recordings using dedicated software. A voluntary group of 10 individuals diagnosed with coxarthrosis or gonarthrosis constituted the study group, while the control group comprised 10 individuals without lower limb musculoskeletal disorders. The mean age of the study group was 57 ±4.03 years, and the mean age of the control group was 54.2 ±3.16 years. The research involved conducting physical examinations of gait and recording walking sessions with body markers. The software facilitated the presentation of marker displacements on diagrams in both vertical and horizontal planes. Visual analysis and a two-sample t-test were employed. The physical musculoskeletal examination successfully identified causes of claudication. Significant differences were observed between the two groups across all kinematic gait indicators. The mean stance width in the test group was 17.65 ±3.09 cm, while the control group averaged 8.75 ±1.23 cm (p < 0.001). The walking speed, assessed using a two-sample t-test, also yielded a significant difference (p < 0.001). Key diagrams representing the groups during functional analysis were presented. Visual analysis revealed distinct variations in marker frequency and vertical and horizontal displacements between the groups. The study group exhibited notable deviations in the displacement diagrams on the affected side of the body. The average of the maximum and minimum points on the charts demonstrated a significant difference between the groups in terms of body displacement. The identified differences in gait between the two groups align with the results of the physical examination. The graphical representation of disparities in body displacement between the two halves of the body in the study group indicates the future potential of digital gait analysis for practical applications and monitoring the effectiveness of physiotherapy.

EFFICACY OF POROUS MEDIA ON FLUID-INDUCED VIBRATION OF A FLUCTUATING CYLINDER

In this research, the numerical simulation of the vibrations caused by the release of the vortex from the surface of the two-degrees-of-freedom circular cylinder, under the elastic support with the porous cover, has been done. The laminar flow around the cylinder is considered and the Reynolds number is < 250. The effect of the porous layer is investigated by considering its different thicknesses. In order to solve continuity and momentum equations for incompressible, unsteady, and two-dimensional flow, the finite volume numerical method based on the SIMPLE algorithm has been used. In addition, to simulate the fluid-structure interaction, the solver of the equations of motion of the rigid body in the flow direction and perpendicular to it is coupled with the computational fluid dynamics solver. The efficacy of the porous coat on the locking zone was investigated by comparing the transverse-longitudinal displacement diagrams and aerodynamic coefficients. The results show that, by adding the porous layer, the amplitude of transverse and longitudinal oscillations, the length of vortices, the drag and lift force are reduced. Up to 97% reduction of transverse vibrations in the porous state has been observed.

Numerical analysis and experimental verification on crack growth and fatigue life in double-edge cracked metal plates

The aims of the work were first to obtain the fatigue crack growth and life numerically and empirically and then compare the numerical results and experimental data. Grade 1 titanium plates with both symmetrically and anti-symmetrically waisted cracks were due to tension tests first to receive the load versus displacement diagrams and mechanical properties of strength and stiffness. Next from cyclic tests the load versus cycles curves were constructed and fatigue life obtained. The numerical analysis using finite element method and ANSYS workbench was to yield the numerical results of crack growth and life. From fracture mechanics, the critical crack length was considered as final failure, and then, the modified numerical results were received. The estimated crack growth rates showed that at high load ratios the rates were faster and the lives shorter; however, at low load rations both were reverse. The results in load versus cycles curves from two numerical method were found within acceptable errors with the experimental data.

Simulation Calculation of New Steel Tube Structure based on Vortex-Induced Vibration Control Technology of Steel Tube Tower

This paper proposes a new three-tube structure to replace the original steel tube. The vortex-induced vibration of the three-tube structure is simulated by two-way fluid-structure coupling. With the control variable method, the simulation calculation of multiple groups of three-pipe structures under uniform incoming flow at different wind speeds is carried out. By analyzing the vortex kinetic energy diagram and displacement diagram, the best outer diameter and tube center distance of the three-tube structure to suppress vortex-induced vibration in the leeward direction are obtained. By summarizing the situation of a symmetrical vortex, the conditions of the symmetrical vortex are understood. Then, by comparing the amplitude of the vortex-induced vibration of the original structure with that of the three-tube structure, the three-tube structure is further optimized to obtain a new structural design that can effectively control vortex-induced vibration.

Possibilities of personalized finite element segmental analysis of the cervical spine for predicting the course of dorsopathy

Introduction. The use of mathematical modeling methods in clinical practice will make it possible to identify the pathogenetic forms of dorsopathies and thus reasonably use the concept of targeted treatment in the management of patients of this category.Aim. To evaluate the possibilities of finite element segmental analysis of the cervical spine for personalized treatment and prediction of the course of dorsopathies.Material and methods. Based on the combined data of computed and magnetic resonance imaging of the patient (female, born in 1951), a model of the C5 – C7 segment was generated, including: vertebrae C5, C6, C7, IVD, anterior and posterior longitudinal ligaments, two pairs of facet joints, spinal cord, nuchal ligament. Computer modeling and finite element method were used to analyze the stress-strain state of the cervical spine of a patient with degenerative-dystrophic changes in the C2 – C7 segments. In the Abaqus/CAE 6.14 software, finite element analysis of the C5 – C7 stress-strain state was carried out in the state of flexion, rotation and compression. The data obtained during compression were compared with previous experiments in silico and in vitro for the norm.Results. For each state, stress and displacement diagrams, load-displacement curves, stress profiles in the MPD were obtained. The axial mobility of the segment under compressive load is two times lower compared to the norm under the same boundary conditions and material models. The degree of involvement of the spinal cord in conflicts with the surrounding anatomical structures was studied. When the model was rotated to the right, conflicts were observed between the spinal cord roots and the bone structures of the vertebrae in the foraminal zones, as well as at the level of the C5 – C6 and C6 – C7 discs with the left posterolateral surfaces of the fibrous rings. When the model was turned to the left, conflicts of the spinal cord were observed in all foraminal zones, as well as at the level of the C6 – C7 disc with the left posterolateral surface of the fibrous rings. Based on the data on stresses in the studied segment, further development of dorsopathies and degenerative changes in the cervical spine was predicted.Conclusions. The use of finite element segmental analysis of the cervical spine creates objective prerequisites for the formation of a combined personalized treatment and prediction of the course of dorsopathies.

Fatigue failure of hybrid nanocomposite laminates with kinked single- and double-edged cracks

Mechanical properties and fatigue responses of hybrid Ti/APC-2 neat and nanocomposite laminates with kinked single- and double-edged cracks were investigated. Through the tensile tests the load vs. displacement diagrams, the mechanical properties and the failure mechanisms were received. Also, for cyclic tests the fatigue responses of load vs. cycles curves, fatigue life and the process of failure mechanisms were obtained. The length of cracks increasing and kink angles decreasing, their mechanical properties were decreased. The mechanical properties and fatigue life of nanocomposite laminates were improved slightly over those of neat laminates. It was attributed to uniformly spreading the nanoparticles, not concentrated at the tips of cracks and along the path of crack growth. The stress intensity factors (SIFs) at the tips of kinks were obtained for applications. The two crack tips run around until they merge together with a small broken ellipse.

Design and kinematic analysis of the four-level rigid trunk mechanism based on 4-SPS/U

A four-level rigid trunk mechanism based on 4-SPS/U, with SPS as the driving branch and U pair as the middle constrained driven branch, is innovatively proposed in this paper. Based on the innovative design of this trunk mechanism, it can improve the flexibility of the hexapod mobile robot's posture adjustment and changes in various motion modes such as walking, water propulsion, climbing and rolling. Firstly, the screw theory is adopted to calculate the degree of freedom of the trunk mechanism. Secondly, a combination of closed vector method and the characteristic structure configuration decoupling method has been applied to constructing the inverse kinematics solution, and deriving the velocity and acceleration models as well as analyzing the high posture flexibility in workspace of the trunk mechanism. Thirdly, theoretical simulation data diagram of the movement branch chain displacement, end height, speed and acceleration of the trunk mechanism are calculated through theoretical numerical examples, and the excellent motion characteristics of the 4-SPS/U-based four-level rigid trunk mechanism are analyzed . Finally, a quantitative comparison was made between the theoretical simulation data and the experimental data of the experimental prototype. The error rates of the variation curves of the displacement length, height, velocity and acceleration of the driving branch chain were 0.8%, 0.2%, 0.5% and 0.9%, which verified the correctness and reliability of the theoretical derivation.

Kinematics of Bennett Mechanism, Negative Angular Velocity

This article provides reasoning and research of spatial mechanisms. The creation of the first simple Bennett mechanism obtained through the pyramid of its base and sides is described. In the pyramid, the angles of inclination and heights of the sides are determined to obtain standard equalities. Thanks to all the parameters, the theoretical link lengths that have practical values are determined. All parameters of length and angles are presented on the structural diagram for each received mechanism. On the basis of two identical, but mirrored mechanisms, a five-bar Bennett mechanism is synthesized. The five-link mechanism is obtained by mutual integration of two identical links, for which the calculation method is described. The article contains a calculation to determine the length and angle of the frame. The frame is obtained by the specified parameters of the ghost angle, the parameters of the two mirrored links derived into one expression. The specified inequality is used for a five-link mechanism in which it is obtained by a driving and a driven full-turn link. The text defines the main kinematic parameters of the links that make a complete turn around its axis without contact. All parameters of the mechanism are metered intuitively. Principle kinematic parameters of the mechanism: angular displacement, angular velocity and angular acceleration are determined. The kinematics is determined with respect to the driving and driven link, taking into account the angular displacement, speed and acceleration. For a more accurate calculation, the dependence of the additional ghost angle of the mechanism on the kinematic parameters is considered. The obtained data are visualized using diagrams of relationships of the rotation of the input link to the output using the Maple application. In trigonometric functions, there is a negative and a positive value determined by the quadrants on the sectors of the circle. Diagrams of angular displacement and angular velocity according to the calculations show negative numerical values. The angular acceleration of the driven link during the rotation of a full turn of the driving link of the mechanism changes its acceleration 4 times. The analysis of the data obtained allows us to conclude that the driven link will rotate jerkily, at these moments there is a possibility of destruction of the mechanism and an increase in the load on the driven link and imbalance of the mechanism.

Experimental and numerical analyses of damaged-steel plate reinforced by CFRP patch in moisture and the acidic environment under tensile test

The FRP materials and their adhesively bonded joints to steel plates are vulnerable to harsh environments. So far, various researches have been studied on the effect of humid environments but the impact of acidic ones needs to be investigated. In the present paper, the strength of the damaged-steel plate strengthened with one sided CFRP patches exposed to distilled water and concentrated sulfuric acid environments is studied experimentally. Moreover, some numerical studies have been carried out in Abaqus software. The damage shape of the steel plate is considered a central hole with two narrow notches on two sides of this hole. To prepare CFRP patches for the experimental tests, vinyl ester resin resistant to humid and acidic environments was used. The simple tensile test at room temperature is studied for evaluation of the magnitude of reinforcement. The results of these specimens compared to non-patched dry specimens show noticeable strengthening with at least 40 and 50 percent increase in load-carrying capacity and displacement, respectively. Moreover, the comparison between the tensile test results of patched-specimens immersed in distilled water and concentrated sulfuric acid (for the duration of 8 weeks) with the dry patched ones show less than 4 percent decrease in load carrying-capacity. Comparison studies between the numerical and experimental results show that load–displacement diagrams and the failure modes are in good consistency with each other.

Failure-Mode Shift of Metal/Composite L-Joint with Grooved Structure under Compressive Load.

Bond length and bond interface morphology have a great influence on the performance of metal/composite hybrid joints. In this paper, a metal/composite L-joint with groove structure was designed, and seven groups with different bonding lengths were fabricated using the VARI (Vacuum Assisted Resin Infusion) process to study the effect of different bonding lengths on the performance of the joint. In the simulation analysis of the metal/composite L-joint, the stiffness equivalence method was adopted, and the groove structure was equivalent to a 0-thickness element layer. The applicability of the simulation method was verified by comparing the ultimate load, displacement and failure mode of the test and simulation. Furthermore, the simulation method was used to simulate more compression experiments of metal/composite L-joints with different bonding lengths, and prediction diagrams of failure displacement and failure mode were produced. According to the prediction map, when the bonding length is 100.00 mm, the metal/composite L-joint has better compressive properties.

ASSESSMENT OF SHEAR STRENGTH PARAMETERS OF SOIL FROM LOAD MICROPILE TESTS

Design and evaluation of the bearing capacity of micropiles are based on shear strength parameters of the soil within which a micropile is installed. These parameters are mostly received from laboratory tests or as an expert evaluation relying on soil description, classification and collected experience. This paper presents an approach that determines cohesion and angle of internal friction from diagrams of displacement on load, these being obtained by compression and traction load tests of real micropiles installed in the known soil. Furthermore, the diagrams are interpreted by the Mohr-Coulomb strength criterion and the desired values of shear strength are thus derived by using it.

Micro-mechanical FE modelling and constitutive parameters calibration of masonry panels strengthened with CFRP sheets

This paper describes the development of a micro-mechanical Finite Element model apt to reproduce the behavior of masonry walls reinforced with Carbon Fiber Reinforced Polymer (CFRP) sheets, monotonically loaded by out of plane actions. According to the results of previous experimental programs carried out by the Authors, in the case of CFRP sheets bonded parallel to the bed joints, such walls behave like un-connected masonry portions (similar to strengthened masonry beams). For this reason, only such effective part was considered in both the experimental program (already published by the Authors) and the numerical simulations. Both simply bonded and anchored CFRP reinforcements have been considered in the paper.Particular attention was paid to the definition of the constitutive parameters, calibrated on the basis of several experimental campaigns previously performed by the Authors. Since fracture energy of bulk materials and adhesive tangential strength of the reinforcement are generally thought of as difficult to experimentally determine and can be affected by uncertainties, a sensitivity analysis concerning such parameters is described in the paper.The numerical predictions have been compared to the experimental outcomes in terms of load displacement diagrams, stress distribution and damage evolution; the proposed numerical model seems to well reproduce the general experimental behavior.

Comparison of the High Cycle Fatigue Behavior of the Orthodontic NiTi Wires: An in Vitro Study

Objective: To compare the high-cycle fatigue behavior of four commercially available NiTi orthodontic wires. Material and Methods: Twelve NiTi orthodontic wires, round, 0.016-in, three per brand, were selected and divided into four groups: G1 - Heat-activated NiTi, G2 - Superelastic NiTi, G3 - Therma-Ti, and G4 - CopperNiTi. The atomic absorption spectrometry method was used to determine the chemical composition of investigated NiTi wires. We also performed a fatigue test at three-point bending using a universal testing machine for 1000 cycles in a 35 °C water bath. For the first and thousandth cycle, the average plateau load and the plateau length were determined in the unloading area of the force versus displacement diagram. In addition, we calculated the difference between the average plateau load of the first and thousandth cycle (∆F), as well as the difference between the plateau length of both cases (∆L). Results: According to our results, there were no significant differences between the average plateau load of the first and thousandth cycles of each group (p>0.05) and in the plateau length of the first and thousandth cycles of the groups (p>0.05). Conclusion: There were no significant differences between the groups changing the superelasticity property after high-cycle fatigue.

Passenger rover model in Matlab-SimMechanics environment

The paper presents the concept of the supporting structure and modeling of the main components of the rover, which can transport people and work in autonomous mode. This is ensured by an appropriate design of the rover's support frame and drive wheel system. The paper presents a computer model of selected fundamental drive components affecting the traction capabilities of the vehicle, namely the differential, frame, and wheels. The modeling was performed in a Matlab-SimMechanics environment. In this environment, the model was also assembled into a functional whole, which allows simulating the rover's operation in different terrain conditions. This is presented in the final part of the paper, where the simulation of overcoming an obstacle by the rover presented in this paper is presented. One of the studied cases, an urban obstacle in the form of stairs, was chosen. Displacement diagrams of individual structural elements of the rover prove its high traction and stability capabilities.

Kinematic Simulation of Automatic Conveying and Stamping Machine based on UGNX

This paper designed a kind of automatic conveying and stamping machine, which was mainly used for drawing thin sheet metal. UGNX software was used to design the motion law of the mechanism and the simulation mechanism. The time displacement diagram obtained by theoretical calculation and simulation was compared to verify the correctness of theoretical analysis and the rationality of the design. The comparison shows that the device meets the requirements of theoretical calculation. The device has the characteristics of simple structure, high efficiency and easy operation, which provides a reference for the subsequent realization of conveying and stamping devices with different requirements.

Numerical analysis of eco-friendly ductile cementitious composite influence on structural masonry reinforcement

The behaviour of structural masonry walls reinforced with a ductile sustainable cementitious coating, called Eco-friendly Ductile Cementitious Composite (EDCC) is evaluated through Finite Element Modelling (FEM). EDCC is a sustainable material composed mostly by fly-ash and sand, with low cement content, used to repair masonry structures: it has excellent ductile behaviour due to the presence of polymeric fibres. Numerical models that can accurately simulate EDCC-reinforced masonry behaviour under compressive, flexural and shear loads were validated using previous experimental tests. A literature review was completed about the parameters defined for the component materials, interfaces and strategies that can be implemented to model structural masonry walls accurately, with the finite element method. Subsequently, the models were calibrated, comparing the results of stress vs strain or force vs displacement diagrams of experimental tests with numerical simulations. The models were able to simulate the masonry behaviour, with consistent results and failure modes. Parametric modelling was implemented to develop a formula capable of predicting the compressive load capacity of masonry walls strengthened with EDCC.

Experimental investigation of a spherical rubber isolator for use in low income countries

This paper presents an experimental study of a low-cost seismic isolator that can be used for the protection of low-rise houses in low-income countries. The isolator is based on rolling of a rubber sphere on flat or spherical concrete surfaces. Using a closely spaced grid of such spheres may allow for avoiding of the diaphragm slab at the isolation level, or of reducing its thickness. Avoiding the cost of this extra slab is crucial for building seismically isolated low-rise dwellings economically feasible in low-income regions of the globe.The effects of the geometry of the rolling surface (i.e., flat or concave), of the diameter of the rolling sphere (i.e., 25, 50 or 100 mm), and of the applied compressive load on the seismic behavior of such isolation bearings were investigated. Initially, the rubber isolators were subjected to monotonic uniaxial compression to examine their behavior under vertical loading. Subsequently, cyclic tests were performed to obtain the lateral force–displacement diagram of the isolation system. Finally, a slab supported by 4 isolators was subjected to a group of 61 ground motions. Eight different configurations were tested, leading to a total of 488 dynamic tests.It was found that the restoring force of such systems can originate not only from the curvature of the concrete surface, but also from the vertical motion induced by the drastic change of the shape of the rubber spheres, as well. In fact, for the configurations tested, the vertical motion sourcing from shape of the deformed sphere was much larger than the vertical motion sourcing from the curvature of the concrete surfaces.Moreover, equations offering the coefficient of friction as a function of the vertical load, the size and the deformation of the sphere were derived. This is crucial for design, as the governing parameter for the design of the rubber spheres is not material failure, but excessive compressive deformation that leads to undesirably high rolling friction. Dynamic tests proved that the proposed low-cost rolling rubber isolators can substantially reduce the accelerations transmitted to the superstructure The cost of the tested 25 mm, 50 mm and 100 mm diameter natural rubber spheres is 0.6 $, 3 $ and 17$, respectively.