Direction Of Shear Force Research Articles

Cilia-Inspired Magnetic Flexible Shear Force Sensors for Tactile and Fluid Monitoring.

Recently, there has been a burgeoning interest in flexible shear force sensors capable of precisely detecting both magnitude and direction. Despite considerable efforts, the challenge of achieving accurate direction recognition persists, primarily due to the inherent structural characteristics and sensing mechanisms. Here, we present a shear force sensor constructed by a magnetically induced assembled Ni/PDMS composite membrane, which is magnetized and integrated with a three-axis Hall sensor, facilitating its ability to simultaneously monitor both shear force magnitude (0.7-87 mN) and direction (0-360°). The cilia-inspired shear force magnetic sensor (CISFMS) exhibits admirable attributes, including exceptional flexibility, high sensitivity (0.76 mN-1), an exceedingly low detection limit (1° and 0.7 mN), and remarkable durability (over 10,000 bending cycles). Further, our results demonstrate the capacity of the CISFMS in detecting tactile properties, fluid velocity, and direction, offering substantial potential for future developments in wearable electronics.

Experimental Investigations on Tensile and Shear Behavior of the Interface Between UHP-ECC and Concrete

Ultra-high performance engineered cementitious composite (UHP-ECC), which is known for its exceptional compressive strength, tensile strength, and ductility, has been emerged as a promising option for repairing and strengthening reinforced concrete (RC) structures. The bond between UHP-ECC and normal concrete is the key issue for the material to be successfully implemented. This paper presents an experimental investigation focused on understanding the tensile and shear behavior of the bonding interface between UHP-ECC and concrete. A total of 78 specimens were prepared and tensile splitting tests and push-out tests were carried out. The study examined key parameters including the strength of the concrete substrate, the roughness of the interface, and the moisture condition at the interface. Various failure modes are observed in the specimens under tensile splitting force and direct shear force, and it is found that the influence of the key parameters varied depending on the type of failure mode. In specimens experiencing full interface debonding or interface failure combined with substrate cracks, the roughness of the interface and the moisture degree have a significant impact on the tensile and shear strength. Conversely, in specimens with full substrate disruption, the strength of the substrates plays a more significant role. Additionally, the study reveals that the grooving treatment is highly effective in improving the shear strength of the interface, but its impact on enhancing the tensile strength is comparatively less pronounced. Prediction models for the tensile and shear strength of the interface are established and verified against the test results. The proposed models provide valuable insights into the behavior of the UHP-ECC to concrete interface and can aid in predicting its performance in practical applications.

Two-dimensional (2D) axis-pin force sensor and its characterization on the shear force direction

The characterization of the shear force direction is an imperative technical problem to be solved for the axis-pin force sensor. In the present work, a two-dimensional axis-pin force sensor has been designed. The layout of the sensor is to open horizontal blind holes and vertical blind holes at intervals of 90 degrees along the circular direction on the surface of the axis-pin. Then the variation law of the circumferential strain of blind holes along with the shear force direction is first studied through the FEA simulation. It is found that the sum of the circumferential strains of two horizontal blind holes or vertical blind holes varies in sine and cosine pattern with the shear force direction. On this basis, the mathematical model of shear force direction characterized by circumferential strains of blind holes is derived. Eventually, the prototype of the axis-pin force sensor was made to verify this law. The experimental results showed that the accuracy of the shear force and direction measured by the sensor can reach ± 8% and ± 5% respectively, which meet the requirements of the practical application. This method eliminates the theoretical error caused by the use of correction coefficients and nonlinear model approximation, which provides a theoretical basis for the development of two-dimensional axis-pin force sensors.

Investigation on the shear performance of circumferential joints of segments in super‐large cross‐section shield tunnels

AbstractTo investigate the shear performance of the circumferential joints equipped with inclined bolts and distributed mortises and tenons, a 3D refined numerical calculation model was established. After verification with the full‐scale tests, the shear mechanical behavior of the circumferential joints under shear force in different directions and different longitudinal force was investigated. The results have proven that the evolution of joint dislocation with shear force can be divided into three stages, and the shear stiffness of circumferential joints varies greatly in these three stages. The direction of shear force mainly affects the shear stiffness of the second stage. The mechanical behavior of bolts under shear force in different directions shows significant differences, which is the main reason for the difference of shear stiffness of joints. The failure characteristic of the circumferential joint is mainly the concrete crushing at the mortise. The longitudinal force mainly affects the shear stiffness of the first stage.

Influence of the second phase on relative fracture behavior of friction stir welded 7A52 aluminum alloy

The mechanical properties of welded joints play a decisive role in service life of the materials, and the second phase particles significantly affect the fracture behavior of the welded joint. In present work, 7A52 aluminum alloy welded joints were prepared by friction stir welding (FSW), the morphologies of different second phases distributed in the joints were observed by SEM, TEM, EBSD and the fracture behavior of the advance side was investigated by in-situ tensile testing. The results show that the fracture is located at the thermo-mechanically affected zone of advance side, where are serious crystal mutation and second phase segregation. Because of poor mechanical properties of the incoherent Mg2Si phase, the cracking initiated at the interface and showed a characteristic with multi-directional cracking. The incoherent AlFe phase cracked along the direction of shear force, and the separated phase interface provided the main cracking propagation path, which would reduce the energy consumption in the process of cracking propagation and accelerate the propagation speed. The semi-coherent AlMgCu phase with excellent mechanical properties hindered the movement of dislocations and improved the mechanical properties of the joints.

Flexible three-dimensional force sensor of high sensing stability with bonding and supporting composite structure for smart devices

Characteristics, such as large measurement range, good repeatability and stability, are the guarantee for a wide application of flexible three-dimensional force sensors in robots and other smart devices. In this research, a flexible three-dimensional force sensor is presented, whose structure includes force-sensitive cells, fixed under the bump and a support layer, filled around the force-sensitive cells. This setup allows the sensor to quickly recover, after the force is released, to ensure its excellent performance. The production method is very simple and has the advantage of large-scale and low-cost manufacturing. The sensor exhibited good repeatability and stability, after 25 000 cycles of loading and releasing, under 8 N force. Meanwhile, it has a large measuring range, which is 0–15 N in the direction of normal force and 0–5.5 N in the direction of shear force. The sensitivity of the sensor in the x, y, and z directions is 1.5321 V−1 N−1, 1.501 29 V−1 N−1, and 0.936 87 V−1 N−1, respectively. The load response time of the sensor is 33 ms and the unload recovery time of 18 ms. Regarding practical applications, the sensor shows good prospects. For example, the sensor and its array can be installed on the manipulator to sense the magnitude and location of the three-dimensional force; in the case of the flexible smart keyboard, the presented sensor array can save space significantly and recognize multiple specific input features, in order to enhance information security; while as a car controller, it is multi-functional integrated and portable, thus showing great potential as replacement to the traditional operating methods.

Assessment of glenoid baseplate initial micromotion and fixation strength in reverse total shoulder arthroplasty designs using a direct shear force methodology.

In a reverse total shoulder arthroplasty, the altered glenohumeral joint center of rotation subjects the glenoid baseplate to increased shear forces and potential loosening. This study examined glenoid baseplate micromotion and initial fixation strength with the application of direct shear force in a Sawbone model. The reverse total shoulder arthroplasty systems examined were the DJO Reverse® Shoulder Prosthesis, the Exactech Equinoxe® Reverse System, and the Tornier AequalisTM Reverse Shoulder Prosthesis. Specimens were cyclically tested with increasing shear loads until 150 µm of displacement between the implant and glenoid was achieved, and subsequently until failure, classified as either 1 cm of implant/glenoid displacement or fracture. The average load withstood for the 150 µm threshold for DJO, Tornier, and Exactech was 460 ± 88 N, 525 ± 100 N, and 585 ± 160 N, respectively. The average total load at device failure for DJO, Tornier, and Exactech was 980 ± 260 N, 1260 ± 120 N, and 1350 ± 230 N, respectively. The Exactech implant design trended toward requiring more load to induce micromotion at each threshold and to induce device failure, most commonly seen as inferior screw pull out. This study proposes design features that may enhance fixation and suggests little risk of initial micromotion or failure during initial post-operative recovery.

Design of a three-dimensional capacitor-based six-axis force sensor for human-robot interaction

Multi-dimensional force sensing capability of the robot plays a critical role in its interaction with the human and environment. The six-axis force sensor as a typical representative of the multi-axis force sensor, however, has not been extensively used in the field of human-robot interaction due to its high price. A low cost, a good sensing accuracy, and a high integration level six-axis force sensor is highly desirable to create. In this paper, to weaken the crosstalk phenomenon between the six-axis and optimize the sensitivity of overall system, a 3D capacitor structure with a cross-shape configuration of the shear force sensing cell was proposed. Eight electrodes were arranged on three perpendicular planes of the Cartesian coordinate system independently. The cross-shape differential capacitor was designed to achieve the improvement of sensitivity along the shear force direction. With Polyoxymethylene (POM) selected as the substrate material, a monolithic spatial structure was manufactured using CNC technology, and then conductive copper paint was sprayed on the specific surfaces of this 3D structure. The cost-effective prototype sensor has been manufactured without the manual work and experimentally validated by comparing it with a commercial six-axis force sensor. The characteristics of the prototype were analyzed in terms of its linearity, interference error, hysteresis, time domain response, SNR, offset repeatability and time drift. Finally, to verify the instrumented six-axis force sensor further, a controlled lab test was performed to measure the interaction forces with the Baxter Research Robot in a simulated scenario.

Tactile Interaction Sensor with Millimeter Sensing Acuity.

In this article we report on a 3 × 3 mm tactile interaction sensor that is able to simultaneously detect pressure level, pressure distribution, and shear force direction. The sensor consists of multiple mechanical switches under a conducting diaphragm. An external stimulus is measured by the deflection of the diaphragm and the arrangement of mechanical switches, resulting in low noise, high reliability, and high uniformity. Our sensor is able to detect tactile forces as small as ~50 mgf along with the direction of the shear force. It also distinguishes whether there is a normal pressure during slip motion. We also succeed in detecting the contact shape and the contact motion, demonstrating potential applications in robotics and remote input interfaces. Since our sensor has a simple structure and its function depends only on sensor dimensions, not on an active sensing material, in comparison with previous tactile sensors, our sensor shows high uniformity and reliability for an array-type integration.

An experimental and analytical investigation of reinforced concrete beam-column joints strengthened with a range of CFRP schemes applied only to the beam

This paper investigates the experimental and analytical behaviour of beam-column joints that are subjected to a combination of torque, flexural and direct shear forces, where different Carbon Fibre Polymer (CFRP) strengthening wraps have been applied only to the beam. These wrapping schemes have previously been determined by the research community as an effective method of enhancing the torsional capacities of simply supported reinforced concrete beams. In this investigation, four 3/4-scale exterior beam-column joints were subjected to combined monotonic loading; three different beam wrapping schemes were employed to strengthen the beam region of the joint. The paper suggests a series of rational formulae, based on the space truss mechanism, which can be used to evaluate the joint shear demand of the beams wrapped in these various ways. Further, an iterative model, based on the average stress-strain method, has been introduced to predict joint strength. The proposed analytical approaches show good agreement with the experimental results. The experimental outcomes along with the adopted analytical methods reflect the consistent influence of the wrapping ratio, the interaction between the combined forces, the concrete strut capacity and the fibre orientation on the joint forces, the failure mode and the distortion levels. A large rise in the strut force resulting from shear stresses generated from this combination of forces is demonstrated and leads to a sudden-brittle failure. Likewise, increases in the beams’ main steel rebar strains are identified at the column face, again influenced by the load interactions and the wrapping systems used.

Study on the Strength Performance of Recycled Aggregate Concrete with Different Ages under Direct Shearing.

In order to study the mechanical properties of recycled aggregate concrete (RAC) at different ages, 264 standard cubes were designed to test its direct shear strength and cube compressive strength while considering the parameters of age and recycled aggregate replacement ratio. The failure pattern and load–displacement curve of specimens at direct shearing were obtained; the direct shear strength and residual shear strength were extracted from the load–displacement curves. Experimental results indicate that the influence of the replacement ratio for the front and side cracks of RAC is insignificant, with the former being straight and the latter relatively convoluted. At the age of three days, the damaged interface between aggregate and mortar is almost completely responsible for concrete failure; in addition to the damage of coarse aggregates, aggregate failure is also an important factor in concrete failure at other ages. The load–displacement curve of RAC at direct shearing can be divided into elasticity, elastoplasticity, plasticity, and stabilization stages. The brittleness of concrete decreases with its age, which is reflected in the gradual shortening of the elastoplastic stage. At 28 days of age, the peak direct shear force increases with the replacement ratio, while the trend is opposite at ages of 3 days, 7 days, and 14 days, respectively. The residual strength of RAC decreases inversely to the replacement ratio, with the rate of decline growing over time. A two-parameter RAC direct shear strength calculation formula was established based on the analysis of age and replacement rate to peak shear force of RAC. The relationship between cube compressive strength and direct shear strength of recycled concrete at various ages was investigated.

Influence of shielding gas composition on molten metal flow behavior during plasma keyhole arc welding process

The purpose of this investigation is to elucidate the behavior of molten metal flow inside weld pool during welding of Plasma Keyhole Arc Welding (PKAW). An observation of the behavior of three-dimensional (3D) molten metal flow inside weld pool during welding was carried out with the support of an advanced X-ray observation system. The results showed that the metal flow in pure Ar shielding gas case was in upward direction from bottom surface toward top surface of weld pool behind the keyhole. Meanwhile, the molten metal flow in Ar shielding gas mixed with 0.5 % O2 case was in downward direction from top surface toward bottom surface. The variation of convection flow inside weld pool as described above is a result of the variation of keyhole diameter and inclination angle of keyhole wall (keyhole profile) with (1) large around the top surface but narrow around the bottom surface in case of pure Ar and (2) narrow around the top surface but large around the bottom surface in case of Ar mixed with 0.5 % O2, which affect the direction and magnitude of shear force acting on weld pool surface. Consequently, only the very slight increase of oxygen content in argon shielding gas due to lowering of shielding effect is found to significantly affect material and heat transport process in PKAW. The results also imply that when argon shielding gas with small amount of oxygen is used, deep and narrow weld penetration is more easily obtained similarly with AA-TIG welding process. However, its mechanism is suggested to be mainly related to the change in shear force due to keyhole shape deformation by the decrease of the surface tension rather than the change in direction and magnitude of Marangoni force.

Shear connection of prefabricated slabs with LWC - Part1: Experimental and analytical studies

This paper studies the shear strength and load-slip behaviours of a recently developed novel steel-concrete composite flooring system (PUSS) with two different types of shear connectors while also using lightweight concrete. PUSS consists of a T-ribbed lightweight concrete floor and C-channel steel edge beams. The proposed shear connection system is using either web-welded shear studs only, or combined with horizontally lying steel dowels. This unique system further minimises its structural depth and results in ultra-shallow floors.Eight full-scale push-out tests were conducted to investigate the connection under the direct shear force with three different concrete types (normal concrete, lightweight and ultra-lightweight concretes) and two different shear connection systems (web-welded shear studs only and horizontally lying steel dowels together with web-welded shear studs). Three types of failure were recorded from the push-out tests; shear failure with bending near the roots of the connectors, shear failure of the weld toe of shear studs, and concrete cracking. Among the conclusions, it was validated that the compressive strength of the concrete significantly influences the ultimate shear strength capacity loads while it is influencing the failure mode of the connection. The failure mechanisms of the shear connectors were extensively studied, which led to the development of a calculation method for the shear strength and load–slip behaviours of the new connectors embedded in lightweight concrete. The analytical results are compared with those predicted by modern codes of practices and available methods from the literature. It is concluded that the proposed formulae offer a reliable prediction.

Improving performance of friction stir welded AZ31/AM60 dissimilar joint by adjusting texture distribution and microstructure

Inhomogeneous deformation, which was usually found during the deformation of friction stir welding (FSW) Mg alloys joints, could deteriorate the joint performance. This work aims to understand the effect of microstructure and texture distribution in joint on mechanical properties and deformation behavior of the FSW dissimilar Mg alloys joints. Two kinds of AZ31/AM60 dissimilar Mg alloys joints were obtained via FSW at two sets of welding parameters (higher rotation rate and welding speed (HRW), lower rotation rate and welding speed (LRW)). Electron backscatter diffraction measurements were conducted to examine the microstructure and texture distribution of these two joints. The results showed that the joint with finer grains, weaker texture and higher nugget zone (NZ) interface angle was obtained with HRW. The weaker texture and finer microstructure were beneficial to the homogeneous deformation of the joint. The larger angle between the NZ interface and the transverse direction (about 75°) made it away from the maximum shear force direction (45°) to avoid premature fracture. With these advantages, the mechanical properties of the joint with HRW were better than that with LRW. The yield strength, ultimate strength and elongation were improved 14.4%, 19.7% and 63.7%, respectively. In addition, the grain size of AZ31 of NZ in two joints was smaller than that of AM60. All the joints fractured at the AM60 side near the NZ boundary during the tension tests. This was mainly attributed to the larger grain size and higher Schmid factor of basal slip at the AM60 side near the NZ interface. This study provided some insights in understanding the improvement of the dissimilar FSW Mg joint performance by controlling texture distribution and microstructure.

Experimental and numerical study on static behavior of grouped large-headed studs embedded in UHPC

The static behavior of grouped large-headed studs (d = 30 mm) embedded in ultra-high performance concrete (UHPC) was investigated by conducting push-out tests and numerical analysis. In the push-out test, no splitting cracks were found in the UHPC slab, and the shank failure control the shear capacity, indicating the large-headed stud matches well with the mechanical properties of UHPC. Besides, it is found that the shear resistance of the stud embedded in UHPC is 11.4% higher than that embedded in normal strength concrete, indicating that the shear resistance was improved. Regarding the numerical analysis, the parametric study was conducted to investigate the influence of the concrete strength, aspect ratio of stud, stud diameter, and the spacing of stud in the direction of shear force on the shear performance of the large-headed stud. It is found that the stud diameter and stud spacing have an obvious influence on the shear resistance. Based on the test and numerical analysis results, a formula was established to predict the load-slip relationship. The comparison indicates that the predicted results agree well with the test results. To accurately predict the shear resistance of the stud embedded in UHPC, a design equation for shear strength is proposed. The ratio of the calculation results to the test results is 0.99.

Mechanically fastened shear connectors in prefabricated concrete slabs – experimental analysis

Nowadays, in prefabricated composite construction, composite action between steel beam and concrete slab is often achieved with positioning of shear connectors in envisaged openings of concrete slabs. Prefabricated concrete slabs are used for composite steel-concrete buildings and bridges, both for the construction of new structures and for renovation of existing ones, significantly reducing construction time. Development of different types of shear connectors represent alternative solution to the traditionally used headed studs, considering their shear resistance, stiffness and ductility. New types of shear connectors tend to reduce the construction time and overall construction cost. Mechanically fastened shear connectors represent a viable alternative to headed studs, considering their fast installation process and shear resistance. X-HVB shear connectors are attached to the steel beam with two cartridge fired pins. The first step towards extensive implementation of X-HVB shear connectors in composite construction is to understand their behaviour through experimental investigation. Results of the push-out tests, in accordance to Eurocode 4, with X-HVB 110 shear connectors positioned in envisaged openings of prefabricated concrete slabs are presented in this paper. The experimental investigation comprised three different specimen\'s layout. Group arrangement of X-HVB shear connectors in envisaged openings included specimens with minimal recommended distances and specimens with reduced distances between connectors in both directions. Influence of different installation procedures on overall behaviour of the connection is presented, as well as the orientation of shear connectors relative to the shear force direction. Influence of variations is characterized in terms of failure mechanisms, shear resistance and ductility.

Study on shear behavior of inclined cross lag screws for glulam-concrete composite beams

The mechanical performance of shear connectors has an important effect on the load bearing capacity and the bending stiffness of timer-concrete composite (TCC) beams. Most studies reported so far have focused on the shear behavior of the single inclined screw working only under shear–tension stress. However, there are few researches on the shear behavior of inclined cross screws. In this paper, a total of thirty-six push-out tests were conducted to investigate the shear behavior of the inclined cross lag screws for glulam-concrete composite beams. Based on the push-out test results, the influences of concrete strength, screw diameter, penetration length of screw into timber, screw inclination angle and screw arrangement with respect to the shear plane on the shear bearing capacity and slip modulus were investigated in detail. Two types of failure mechanisms of inclined cross lag screws were observed from the push-out tests: cone expulsion of concrete ahead of the shear-compression loaded screw and the shear-tensile loaded screw withdrawn from timber. When the inclined screws worked only under shear-compression load, the screw connectors were in the worst stress state. Since the direction of interface shear force in timber-concrete composite beams changed constantly under seismic load, the optimal screw arrangement was the crossed screws working simultaneously under shear-compression and shear–tension load. In addition, the analytical models were proposed to predict the shear bearing capacity and slip modulus of the inclined cross screws, and the calculated results were in good agreement with the test results.

Evaluation of rolling shear modulus and strength of Japanese cedar cross-laminated timber (CLT) laminae

Cross-laminated timber (CLT) panels are fabricated with their layers stacked crosswise. Owing to the low shear modulus and strength in the rolling shear direction, the shear properties of cross-layers influence the overall deflection and shear capacities of CLT panels. The aim of the present study is to determine the rolling shear properties of Japanese cedar and investigate how annual ring patterns and lamina geometry influence shear properties. Using a test configuration similar to the standard shear test configuration prescribed in European Standards (EN 408), a single lamina shear test was conducted. To investigate the influence of thickness-to-width aspect ratio of the lamina on the rolling shear properties, samples with three different widths, including 62, 88, and 112 mm, with a constant thickness of 24 mm were tested. The geometrical features of the annual ring patterns of each test sample were measured. The mean rolling shear moduli were 72, 91, and 109 MPa, and the mean rolling shear strengths were 1.54, 1.83, and 2.02 MPa for the 62-, 88-, and 112-mm sample widths, respectively. Shear strength was highly correlated with shear modulus. The mean shear modulus and strength, in addition to the 5% quantile, increased with an increase in lamina width. Across all sample widths, rolling shear modulus and strength decreased with an increasing radial distance from the pith. Using the principle of continuum mechanics, the influence of the annual ring angle relative to the shear force direction was examined quantitatively using the finite element method. The results suggest that shear modulus and its variance are influenced greatly by the annual ring structure.

LEM-DEM coupling for slope stability analysis

Slope stability analysis is a keen area of interest to researchers of geotechnical engineering and geological hazards. To date, the most popular approach applied in slope engineering design is the limit equilibrium method (LEM). However, for this method, some assumptions are required when obtaining the sliding force and the resistance force on the slide face. The discrete element method (DEM) presents an advantage in the calculation of the interaction forces between adjacent blocks without assumptions. This paper introduces a new slope stability analysis based on coupling of both approaches, herein referred to as LEM-DEM. The main LEM-DEM procedure is to transform the slice model of a slope in LEM into the DEM model and obtain the sliding force and the resistance force to calculate the factor of stability (Fos). The sensitivity analysis of the parameters in DEM, such as normal and shear stiffness, was conducted to illustrate that LEM-DEM suggests higher contact stiffness. A comparison between the Fos values in DEM and LEM-DEM was also conducted to indicate the rationality and advantages of LEM-DEM, especially for a gentle slope with a changing shear force direction in the slice model where the interslice forces in LEM are unreasonable. Furthermore, this study carried out a 3D landslide stability analysis extension, along with the results, for the proposed method.

Growth Enhancement of Probiotic Pediococcus acidilactici by Extractive Fermentation of Lactic Acid Exploiting Anion-Exchange Resin.

Fermentation employing lactic acid bacteria (LAB) often suffers end-product inhibition which reduces the cell growth rate and the production of metabolite. The utility of adsorbent resins for in situ lactic acid removal to enhance the cultivation performance of probiotic, Pediococcus acidilactici was studied. Weak base anion-exchange resin, Amberlite IRA 67 gave the highest maximum uptake capacity of lactic acid based on Langmuir adsorption isotherm (0.996 g lactic acid/g wet resin) compared to the other tested anion-exchange resins (Amberlite IRA 410, Amberlite IRA 400, Duolite A7 and Bowex MSA). The application of Amberlite IRA 67 improved the growth of P. acidilactici about 67 times compared to the control fermentation without resin addition. Nevertheless, the in situ addition of dispersed resin in the culture created shear stress by resins collision and caused direct shear force to the cells. The growth of P. acidilactici in the integrated bioreactor-internal column system containing anion-exchange resin was further improved by 1.4 times over that obtained in the bioreactor containing dispersed resin. The improvement of the P. acidilactici growth indicated that extractive fermentation using solid phase is an effective approach for reducing by-product inhibition and increasing product titer.