Increment Of Force Research Articles

Electronic Speckle Pattern Interferometry for fatigue crack monitoring

This study aims to monitor the fatigue crack tip through a contactless optical method. A Middle Tension (MT) specimen is initially prepared by submitted it to a cyclic fatigue loading, in order to generate a crack with a specified length. Then, the cracked specimen is statically loaded under a uniaxial tensile condition, and Electronic Speckle Pattern Interferometry (ESPI) is employed to monitor the crack tip. During specimen loading with incremental force values, the behavior of the cracked area is monitored, with displacement and deformation fields acquired for each load increment. The obtained data is used to calculate fracture parameters, such as the Stress Intensity Factor (SIF). For that purpose, an overdeterministic algorithm was developed to calculate SIFs for each measured crack length. The main contribution of the present work is the adoption of a high-resolution optical contactless technique to monitor the fatigue crack tip. The obtained SIF values are compared to the reference solution proposed by ASTM E647 and an acceptable agreement has been verified.

Comparative Analysis of Machine Learning Methods for Predicting Robotized Incremental Metal Sheet Forming Force.

This paper proposes a method for extracting information from the parameters of a single point incremental forming (SPIF) process. The measurement of the forming force using this technology helps to avoid failures, identify optimal processes, and to implement routine control. Since forming forces are also dependent on the friction between the tool and the sheet metal, an innovative solution has been proposed to actively control the friction forces by modulating the vibrations that replace the environmentally unfriendly lubrication of contact surfaces. This study focuses on the influence of mechanical properties, process parameters and sheet thickness on the maximum forming force. Artificial Neural Network (ANN) and different machine learning (ML) algorithms have been applied to develop an efficient force prediction model. The predicted forces agreed reasonably well with the experimental results. Assuming that the variability of each input function is characterized by a normal distribution, sampling data were generated. The applicability of the models in an industrial environment is due to their relatively high performance and the ability to balance model bias and variance. The results indicate that ANN and Gaussian process regression (GPR) have been identified as the most efficient methods for developing forming force prediction models.

The Regularity of Stress Shielding in Internal Fixation Characterized by Hydromechanics.

Stress shielding is an important factor in the internal fixation of a fracture. To explore the regularity of stress shielding in internal fixation, a simplified model of a comminuted femoral shaft fracture bridged by a locking plate was established and finite element analysis was performed to analyze the load distribution between the plate and femur from the proximal end of the femur to the fracture line and investigate the stress shielding degree of the plate on the bone. The stress, deformation, and axial compressive force distribution of four internal fixation schemes under compression were obtained, and the stress shielding degrees on each section was calculated. To compare the regularity of stress shielding and flow distribution, the relationship between the compressive force increment and stress shielding degree was established. The normalized curves of compressive force increment with the plate section position were compared with the flow distribution in a Z-type manifold, a parallel pipe system similar to an internal fixation system in structure and working characteristics. For quantitative comparison, the similarity between normalized curves of the compressive force increment and simulated flow distribution was calculated. The regularity of load distribution along the section position of the plate was similar to the flow distribution in the Z-type manifold. Therefore, the flow distribution pattern of the Z-type manifold can be used to characterize the regularity of load distribution in internal fixation. This study provided a new method to characterize the stress shielding degree of a locking plate on bone.

The sliding mode and dissipative force of moving nanodroplets on smooth and striped hydrophobic surfaces

The motion of nanodroplets on hydrophobic surfaces is ubiquitous in a broad range of applications such as nanofluidic devices. The dissipative force and sliding mode are two vital factors for the utilization of moving nanodroplets. However, the kinetics of moving nanodroplets is different from millimeter-sized droplets due to their extremely small size, and the dissipative force and sliding mode of nanodroplets have not been clearly understood. In this work, the dissipative force and sliding mode of moving nanodroplets on smooth and striped hydrophobic surfaces are investigated via molecular dynamics simulation. We find that the dissipative force has a more significant effect on nanodroplets than millimeter-sized droplets, and the nanodroplets show a combination of rolling and slipping motion on the hydrophobic surfaces. We report that the dissipative force of moving nanodroplets can be divided into the viscous force and the hysteresis force, and the viscous force is the major resistance to the motion of nanodroplets. We demonstrate that the sliding mode of nanodroplets is jointly determined by the significant slippage and the enhanced viscous effect, and the large shear rate of nanodroplets can promote slipping by increasing the surface slip length. Furthermore, the effects of striped structure on the moving nanodroplets are studied. On the one hand, the striped structure increases the apparent contact angle of nanodroplets and thus reduces the dissipative force. On the other hand, the slip length of the striped surface can be lower than that of the smooth surface under the action of large Laplace pressure of nanodroplets, leading to the increment of the dissipative force and the enhancement of rolling.

A Novel Incremental Iterative Force Recovery Method for Second-Order Beam-Column Elements in Plastic Hinge Analysis of Steel Frames

This paper is concerned with an incremental iterative force recovery method in the second-order plastic hinge analysis of steel frames mainly modelled by a single element per member. Second-order beam-column elements are preferred in the direct analysis of steel frames due to their high accuracy and efficiency. However, formulations of these elements are complicated, and therefore they may have a problem of getting element force recovery in inelastic analysis. To overcome this difficulty, a novel incremental iterative force recovery method for second-order beam-column elements is proposed to perform plastic hinge analysis. The proposed method is derived more strictly and has good performance. Also, the section assemblage approach and the refined plastic hinge method are adopted in this study to consider the gradual degradation of section stiffness in the plastic hinge analysis. To verify the accuracy, efficiency and robustness of the proposed method, several benchmark examples are analyzed by the proposed method and compared with solutions reported by early researchers.

Impact of entropy optimized Darcy‐Forchheimer flow in MnZnFe2O4 and NiZnFe2O4 hybrid nanofluid towards a curved surface

AbstractThe theme of this article is to scrutinize the entropy analysis for Darcy‐Forchheimer flow of hybrid nanoliquid towards a stretched curved surface. Manganese and nickel ( and ) zinc ferrites are taken as nanoparticles. Here engine oil () is used as base liquid. Dissipation and radiation effects in energy equation are incorporated. The basic modeling of entropy analysis is developed through second law of thermodynamics. The governing nonlinear partial system (PDEs) of the flow are converted to ordinary one (ODEs) through utilizing suitable variable. The resultant system is consequently solved through one of numerical method (ND‐solve method). Graphical illustrations of velocity field, thermal field and entropy rate versus dimensionless variables for both manganese and nickel zinc ferrites/engine oil nanoparticles are discussed. Computational results of Nusselt number and drag force for both and nanoparticles against flow parameters are studied in tabulated form. A reverse trend holds for velocity through curvature and porosity variables. Higher Forchheimer number diminishes the velocity profile. Larger approximation of radiation has similar effect on thermal field and entropy rate. Higher volume fraction enhances the entropy rate and velocity profile. An intensification in porosity variables rises entropy rate. An increment in drag force is noticed for volume fraction. Higher curvature variable improves the heat transfer rate.

Changes in physico-mechanical properties of water caltrop fruit (Trapa natans L.) during the drying process

The cosmopolitan water caltrop plant (Trapa natans L.) produces nuts, which in the maturing process develop very hard pericarps. This hardness, together with structure and shape (external spikes) of pericarp and seed, and the water contained in the fruit are responsible for their mechanical properties. This study determined the force needed to break Trapa natans nuts at various drying stages, with tests having been carried out at weekly intervals until the fruit dried completely. The amount of force necessary for cracking nuts at each of the 6 drying stages was determined, as well as the work of crushing calculated until the greatest compressive force (crushing force) was reached. The force needed to rupture the hydrated fruit in the horizontal plane was higher than that necessary for the rupture of dried fruit. The experiment showed that the maximum force needed to crush the fruit was 828.7 N and occurred when crushing the fruit after 2 weeks of drying, while the largest calculated crushing work was 2185.5 mJ for the same fruit. Other strength parameters were introduced to characterize mechanical properties of water caltrop in a more extensive scope. These are hardness defined as a ratio of compressive force increment to strain increment, specific crushing energy defined as a ratio of crushing work to water caltrop’s mass, and unit crashing force defined as a ratio of crushing force to caltrop’s thickness. All these parameters reached their highest mean values for pericarps after 2 weeks of desiccation. Mass measurements were also applied in modelling the desiccation process by the exponential function. The very dense pericarp material, after reaching maturity, slightly changes during drying. It can be used industrially as an extremely durable and biodegradable biological material. Results also suggest that the great evolutionary success of the species may result from the ability of the pericarp to protect its seeds, leading to the spread of this species in aquatic environments.

Crack tip monitoring by multiscale optical experimental techniques

This study focuses on the development of a complementary fatigue crack-tip evaluation approach with multiscale optical techniques with different resolutions. A middle tension (MT) specimen, of aluminium alloy AA6082-T6, was prepared and submitted to a cyclic fatigue loading to generate a fatigue crack. Then, it was statically loaded under a uniaxial tensile condition, and two non-contact full-field optical techniques, Digital Image Correlation (DIC) and Electronic Speckle Pattern Interferometry (ESPI), were employed to acquire the experimental data. While the specimen is loaded with incremental force values, the behaviour of the cracked area is monitored, with displacement and deformation fields acquired for each force increment. The obtained data is thereby used to calculate the Stress Intensity Factor (SIF) and monitor the crack opening evolution. An overdeterministic algorithm was developed for the SIF determination. The main contribution of the present work is the development of a complementary multiscale methodology, which employs available techniques with different resolutions to monitor the tip of a fatigue crack, drawing a comparison between calculated parameters for each system to shift from one technique to the higher resolution one and validating the proposed methodologies. The obtained SIF values are compared to the reference solution proposed by ASTM E647, and an acceptable agreement has been verified amongst the results.

Structural stress analysis and surface settlement study of a subway station in Beijing

Taking a PBA construction method station of Beijing subway as the engineering background, Simulation of station construction process by MIDAS / GTS NX finite element software, and compare the simulation results with the on-site monitoring data. The stress of steel tube column and side pile, the main load components of the station, and the surface settlement caused by construction are analyzed. The analysis results show that (1)During the second lining construction stage, the axial force increments of steel tube columns and side piles are the largest, and the axial force increments account for 59.10 % and 51.98 %, respectively. This stage is the key stage to control the axial force;(2)The horizontal displacement curves of steel tube column and side pile show ‘bulging’ form, and the maximum value is located near the middle of steel tube column and side pile;(3)The transverse surface settlement is symmetrically distributed along the center line of the station, and the maximum value is 47.9 mm, which is located near the center line of the station. The larger settlement is mainly distributed in the range of 20 m from the center line of the station.

Combined active-passive heat transfer control using slotted fins and oscillation: The cases of single cylinder and tube bank

In heat transfer augmenting methods such as radial fins, the heat transfer enhancement commonly leads to the drag force increment. In the present paper, slots are inserted over the fins to simultaneously reduce the drag coefficient. Turbulent convection heat transfer around a cylinder, as well as oscillating bundle of tubes including the slotted radial fins have been investigated. The governing equations are solved in two-dimension utilizing OpenFOAM software based on k-ω SST closure model. The cases with various slot location, slot width, the number of the slots, the fin height, and the oscillation frequencies are examined. In all cases, the Reynolds number is taken to be equal to 5000. Presence of three slots on the fins reduces the drag coefficient by 23% and augments the Nusselt number by 76%. In order to enhance the heat transfer from the bundle of tube, oscillation of tubes and utilization of the slotted fins are applied. The optimum situation occurs for a sample with the oscillating third column which shows 3% increment in heat transfer relative to that of the fixed case. This is while adding the slotted fins to the oscillating tube bank increases the heat transfer up to 2.5 times.

Bond characteristics between concrete and near-surface mounted carbon fiber reinforced polymer cords

ABSTRACT Previous studies showed that near-surface mounting (NSM) strengthening technique with rigid CFRP materials has potential advantages over the externally bonded reinforcing (EBR), therefore, it becomes efficient methodology for concrete strengthening. However, rigid NSM-CFRP cannot be wrapped around a deteriorated structural element; the need for the existence of flexible material has appeared. Therefore, in this study the flexible NSM-CFRP (cord) is investigated as strengthening technique instead of rigid NSM-CFRP. The aim of this study is to recognize the parameters affecting the bond performance of carbon fiber-reinforced concrete (CFRP) cord and concrete. These parameters are cords’ bonded length, the ratio between cord’s width and depth, concrete compressive strength, number of CFRP cords used and the distance separating cords in multi-cord specimens. Fifty-four concrete prisms were cast from 25 MPa and 50 MPa concrete compressive strengths. Thirtyeight prisms reinforced by a single cord with various cord sizes were prepared. Twelve and four specimens were reinforced with two and three cords, respectively. In the case of multi-cord specimens, a unified bond length and cord’s aspect ratio were carried out. The main parameter to be studied in this case is the cords’ separating spacing. The test results indicated that increasing (NSMCFRP) cords bonded length, concrete compressive strength, number of applied CFRP cords, the spacing between cords and reducing cords’ aspect ratio (width/depth ratio) cause an increment in the pull-out force, and then a better strengthening is achieved. Rupture was the predominant failure mode for specimens with the same bond and equal cord dimension, while debonding of the CFRP cords is the most frequent failure mode for multi-cords specimens with greater spacing.

Irreversibility analysis for axisymmetric nanomaterial flow towards a stretched surface

• Hydromagnetic axisymmetric flow of nanomaterial by a nonlinear stretched sheet is addressed. • Dissipation and radiation effects are scrutinized in heat equation. • Thermophoresis and Brownian motion are scrutinized. • Irreversibility analysis is scrutinized. Magnetohydrodynamic axisymmetric flow of viscous nanoliquid towards a variable stretching sheet is scrutinized. Flow is generated due to nonlinear stretching. Joule heating, heat flux and dissipation are analyzed in heat expression. Random and thermophoresis diffusions are considered. Physical description of entropy generation is also accounted. Entropy generation and heat transfer analysis are scrutinized through thermodynamics laws. Furthermore chemical reaction along with Arrhenius activation energy is addressed. Ordinary differential system is obtained through suitable variables. Homotopic convergent solutions for nonlinear system is developed. Influence of flow variables on entropy rate, velocity, Bejan number, concentration and temperature are analyzed. Further velocity gradient and heat and mass transfer rates are discussed. Reduction in velocity is noticed for magnetic variable. Thermal field has an enhancing trend for magnetic and Eckert number. Larger thermophoresis variable rises the temperature. An increment in entropy rate is observed for magnetic parameter. An increment in drag force is seen for magnetic variable.

Novel Model for Limit-Equilibrium Analysis of Slope Stability with a Nonlinear Strength Criterion

Slope stability has always been a concern of the geotechnical engineering community, and geotechnical scholars have continued to explore the reasonable failure mechanism of slopes and make the theoretical models of slope stability more reliable. This work established a novel model for limit-equilibrium (LE) analysis of slope stability with a nonlinear strength criterion. In this theoretical model, the thrust line of interslice force and corresponding increment are reasonably simplified. Then, the formula of normal stress on slip surface is derived by assuming the increment of normal interslice force. Meanwhile, strength reduction technology is applied to reduce the shear strength of the geotechnical body on the slip surface with slope factor of safety (FOS) to obtain shear stress on the slip surface. Thereafter, mechanical equilibrium conditions satisfied by the whole slope sliding body and newly introduced equation about increments of interslice force are used to solve LE stability of the slope. For stability analysis of a slope with a nonlinear strength criterion via a simple and feasible calculation process, an iterative loop solution strategy is adopted in the analysis. After comparison and analysis of several slope examples, the feasibility and rationality of the present method are verified. Moreover, the present method has high efficiency in terms of calculation speed.

Secondary breakup of shear thickening suspension drop

To explore the effect of shear thickening behavior on the secondary deformation and breakup of cornstarch–water suspension droplets, an experimental investigation is conducted by using a high-speed camera. The experimental results demonstrate suspension droplets that exhibit discontinuous shear thickening (DST) exhibit a hardened deformation mode when they fall into the airflow field. When the droplets are in a hardened deformation mode, the windward side of the droplet deforms into a sheet, while the leeward side remains hemispherical until the droplet leaves the airflow field. The dimensionless number N is established to describe the relative magnitude of the increment of the viscous force and aerodynamic force during the secondary breakup process. Based on the suggested dimensionless number N and the Weber number We, the secondary deformation and breakup regime map of Newtonian fluids and DST suspensions is also proposed.

Cathode Spot Velocity of Atmospheric Arc Plasma after Arc Ignition Affected by Self and External Electromagnetic Force between Parallel Electrodes Using 3D Numerical Simulation

For visually and quantitatively elucidating the contribution of self and external electromagnetic forces of the cathode spot area to the cathode spot movement, a three‐dimensional electromagnetic thermal fluid simulation program was used to simulate the arc movement between parallel electrodes. According to the analysis results, the cathode spot first step occurred when the electromagnetic force balance of cathode spot area was broken, and the direction of total electromagnetic force at the right side control volume pointed forward. When the current path changes from straight to reentry model, the cathode spot movement became faster because of the self electromagnetic force derived from electrodes. The rapid of cathode spot first step significantly increased along with the arc current increasing, and the increment of self electromagnetic force was more significant than the external electromagnetic force. In conclusion, the application of external magnetic field or the self magnetic field derived from the parallel electrodes benefit to break the electromagnetic force balance of cathode spot area and promote the rapid of cathode spot first step. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A temporal–spatial hybrid dynamic algorithm strategy for inelastic earthquake response analysis of super high‐rise building structures

SummaryBased on the understanding about the spatial distribution of plasticity development in super high‐rise building structures excited with strong earthquakes, a temporal–spatial hybrid dynamic algorithm (TSHDA) strategy is specifically proposed with the combination of the previously developed bilateral algorithm switch mechanism. The coupling response of partitioned subdomains and interfaces by the nodal partition strategy is solved using the iterative interfacial prediction–correction procedure. Four implicit and two explicit algorithms are selected and implemented on a finite element analytical platform, generating a total of eight alternative hybrid algorithms. A performance evaluation is carried out on a high‐rise reinforced concrete frame structure, and a super high‐rise frame core‐tube structure indicates that using the TSHDA strategy can achieve a more desirable balance among accuracy, stability, and efficiency. Such strategy is believed to be elaborately tailored for those mega structures with some strengthened stories distributed along height. The computational accuracy is well maintained by the bilateral algorithm switch which can substantially reduce the error accumulated in the determination of the incremental internal force vectors of subdomains and interfaces. The hybrid DKNR + CA algorithm, that is, the combination of the Krylov subspace accelerated Newton (KNR) algorithm with Chang's algorithm (CA), demonstrates comparatively desirable accuracy and superior efficiency.

An analytical method for continuously predicting mechanics and residual stress in fillet surface turning

A novel and effective approach for determining mechanics and residual stress when turning a component with curved surfaces is presented in this paper. This predictive approach is based on a three-dimensional analytical model to study the distributed mechanics and residual stress caused by vary cutting condition during the machining process. The variation of uncut chip area in this process can be divided into several stages based on different tool-workpiece contact and the discretization of cutting edge is conducted at an arbitrary tool position. The chip flow direction is calculated through the equilibrium of the incremental interaction forces. The cutting force can be determined by integrating the force components along the cutting edge, with each incremental force component obtained based on a fully analytical model. Distributed heat source intensity is considered to model the temperature rise at an arbitrary point in workpiece. The residual stress in curved surface machining is obtained considering the loading-unloading-relaxation procedure at the engagement of cutting edge and machined surface. Finally, Finite Element (FE) modeling and experiments are performed to validate the correctness and robustness of the analytical model proposed in this paper. The results of predicted chip flow direction, cutting force, temperature, and residual stress show good agreement with the simulated and measured results.

Development of Enhanced Two-Time-Scale Model for Simulation of Ship Maneuvering in Ocean Waves

In this study, a modified two-time-scale model is proposed to overcome the limitations of the existing maneuvering analysis model. To this end, not only wave conditions but also all directions of ship operation velocities are considered in estimating wave drift force and moment. Subsequently, the increment of the drift force and moment induced by steady drift and yaw motion of a ship is imposed up to the first derivative of Taylor series expansion. By introducing this bilinear model, the burden of the drift force computation is reduced so that a more realistic and efficient seakeeping-maneuvering coupling analysis can be performed. A turning circle simulation in a regular short wave is carried out using the modified two-time-scale model. Then, the performance is validated by comparing its results with the direct coupling model. Moreover, quantitative improvement of the present numerical scheme and the influence of the operation velocities on ship maneuvering performance are discussed.

Experimental investigations on a deep excavation support system with adjustable strut length

Conventional deep excavation support systems (diaphragm wall with inner strut) have fixed length of struts, which can lead to a significant discrepancy between deformations of actual and designed diaphragm wall systems. As a result, failure of support system is likely to occur during the deep excavation. In this paper, a novel deep excavation support system with adjustable strut length was proposed, whereby the construction risk during deep excavation can be effectively reduced. An intelligent adjustment method of coordinated deformation of deep excavation support system was proposed as well. Model tests were carried out to investigate the influence of inner strut length on the mechanical and deformation characteristics of the system consisting of inner strut, diaphragm wall and soil behind diaphragm wall. The inner strut forces, lateral earth pressure on the diaphragm wall, the ground settlement and the deformation of the diaphragm wall were measured and analyzed. Results show that control the horizontal displacement of the braced excavation strictly will lead to the increment of axial force and the axial compression ratio of strut, which pose a threat to the safety of the strut system. By contrast, a reasonable adjusted length of inner strut is favorable to the safety of construction.

Interaction of chloramphenicol with titin I27 probed using single-molecule force spectroscopy.

Titin is a giant elastic protein which is responsible for passive muscle stiffness when muscle sarcomeres are stretched. Chloramphenicol, besides being a broad-spectrum antibiotic, also acts as a muscle relaxant. Therefore, it is important to study the interaction between titin I27 and chloramphenicol. We investigated the interaction of chloramphenicol with octamer of titin I27 using single-molecule force spectroscopy and fluorescence spectroscopy. The fluorescence data indicated that binding of chloramphenicol with I27 results in fluorescence quenching. Furthermore, it is observed that chloramphenicol binds to I27 at a particular concentration ([Formula: see text] 40 μM). Single-molecule force spectroscopy shows that, in the presence of 40 μM chloramphenicol concentration, the I27 monomers become mechanically stable, resulting in an increment of the unfolding force. The stability was further confirmed by chemical denaturation experiments on monomers of I27, which corroborate the evidence for enhanced mechanical stability at 40 μM drug concentration. The free energy of stabilization for I27 (wild type) was found to be 1.95 ± 0.93 kcal/mole and I27 with 40 μM drug was 3.25 ± 0.63 kcal/mole. The results show a direct effect of the broad-spectrum antibiotic chloramphenicol on the passive elasticity of muscle protein titin. The I27 is stabilized both mechanically and chemically by chloramphenicol.