Increase In Lateral Force Research Articles

Dynamic Analysis of the Guiding Shoe considering Contact Gap and Pose Disturbance

The pose disturbance of the guide shoe under complex working conditions can lead to collision, impact, and wear failure between the guide shoe and the pin row. To explore the damage law of pose disturbance on the guiding shoe, a rigid‐flexible coupling dynamic model of the walking mechanism considering the contact gap between the guiding shoe and the pin row was constructed. The contact characteristics of the guiding shoe under different poses were analyzed. The results indicate that the swing around the x‐axis has the most significant impact on the guiding shoe, with stress concentration primarily occurring near the corner of the trench. The posture of swinging solely around the y‐axis weakens the supporting effect of the guide shoe, resulting in stress concentration on the end face of the left side face. Swinging around the z‐axis results in stress concentrations on the upper faces of the shoe. Research shows that the angular velocity of the guiding shoe around the x‐axis and z‐axis is highly sensitive to variations in traction speed. In addition, an increase in lateral force weakens the support effect of the guiding shoe, resulting in elevated contact force on the lower side of the guiding shoe and increased y‐direction load on the walking wheel. The research results provide a reference for exploring the influence of walking unit postures on the failure of the guiding shoe and for improving shearer traction reliability.

Ensuring the safety of rolling stock movement when entering transition curves

The main factor in the issue of the safety of the rolling stock movement in the rail track is the change in the magnitude of the lateral forces arising from the interaction of the wheel with the rail. The dynamics of changes in lateral forces directly depends on the increase in rolling stock speeds in curves and, especially, in transition curves. To prevent the sudden appearance of centrifugal force, the outer rail is elevated, the track is broadened when moving from a straight line to a circular curve and a transition curve of variable curvature r = l / p, where p is the variable radius of the curve. Within the transition curve, the current elevation h of the outer rail over the inner rail must be proportional to the current curvature value, including at the end of the transition curve, all these factors leading to a sharp dynamic increase in lateral forces. In this case, the elevation h0 of the rail and the curvature r0 = 1/R are the parameters of the circular curve. Due to the fact that r, h and track width S are variables within the transition curve, in case the widening in a circular curve is intended when moving along the transition curve, additional forces and moments arise not present either on a straight line or on a circular curve. It is necessary for any additional force factors (forces and moments) to change gradually and be equal to zero at the beginning (BTC) and end (ETC) of the transition curve, and for the absolute values and intensities (gradients) of their changes within the transition curve not to exceed the allowable values, which is provided by complying with the requirements specified in table.1.

Influence of Gravity Framing on the Collapse Probability of Steel Buildings with Special Moment Frames

This paper presents the influence of gravity framing on the collapse risk of steel frame buildings with perimeter special moment frames (SMFs) designed in Turkey. For this, four- and eight-story buildings have been designed considering the related current specifications and codes. Header end-plate connections are used for the beam-to-column joints of the gravity frame system. A nonlinear analytical model that simulates the hysteretic behavior of header end-plate connections is calibrated with past experimental data. Nonlinear static pushover analysis (NSPA) and nonlinear response history analyses (NRHAs) were implemented for both four-story and eight-story SMFs with and without the gravity framing to quantify their collapse performance and monitor the system-level seismic response of the building through collapse. The advantage of presence of the gravity framing is investigated and differences in structural responses between the models are also examined. When the models were excited by different ground motions, median responses of the detailed models showed an increase in lateral force carrying capacity and a decrease in first-story drift demand, compared to the nonlinear static pushover analyses results. Furthermore, the results demonstrate that gravity frames in a structure profoundly decrease the possibility of collapse.

MODIFICATION OF MOMENTUM DISTRIBUTION WITHIN THE THREE NOZZLES OF THE WATERJET AZIMUTH PROPULSION SYSTEM

This paper focuses on the thrust direction misalignment and lateral force caused by the rotational flow at the impeller outlet of the waterjet azimuth propulsion system. Momentum distribution within the three nozzles is found to be the direct reason. Two methods, i.e. area match between the left nozzle and right nozzle and adding guide vanes inside the middle nozzle are proposed and their effects are analysed respectively based on numerical simulation. Results show that an appropriate area ratio can eliminate thrust direction misalignment with a small increase in lateral force. Guide vanes can effectively reduce lateral force by 56% without affecting aligned thrust direction.

Impact of lateral load transfer in heavy road vehicles at horizontal curves on the distress of asphalt pavements

The distress of asphalt pavements on horizontal curves can be relatively higher because of the lateral load transfer and the increase in lateral forces on vehicles during their cornering manoeuvre. In this study, the lateral load transfer in horizontal curves and its effect on pavement disstress is evaluated using a commercial vehicle dynamics software, IPG TruckMaker®. Road profiles were generated with a straight section followed by a horizontal curve. A sensitivity analysis was conducted by varying the radii of horizontal curves, road-surface roughnesses, vehicle speed, and its laden weight. The results were compared with results from static analysis and an analytical model. The curved section was found to sustain about two to six times more damage. Further, layered elastic analysis of the curved section showed higher shear stresses at the layer interface. This emphasises the need for a separate design of pavements on a horizontal curve.

Multiscale mechanical and tribological characterizations of additively manufactured polyamide 12 parts with different print orientations

The use of additive manufacturing for prototyping and manufacturing purposes is becoming a crucial topic in both industry and research. Multi Jet Fusion printing technology possesses advantages in fabricating engineering-quality parts, but the dependency of their mechanical characteristics on process parameters is not well understood. In this work, multiscale mechanical analyses were conducted with the goal of investigating the effect of build orientation on Multi Jet Fusion manufactured polyamide 12 samples. Tensile tests of samples printed in two orientations showed that build orientation resulted in different strain and stress behaviors, with vertical samples having 25% smaller fracture strains, but slightly higher (5.8%) fracture stresses than horizontal samples. Nanoindentation showed vertical samples with reduced elastic modulus (Er) values double that of horizontal, and with hardness values nearly 30% larger. Nanoscratch tests showed that vertical samples had an almost 50% increase in lateral forces. Experimental and numerical creep analyses demonstrated higher creep resistance of vertical samples as compared to the horizontal specimens. Additionally, macroscale friction measurements showed that the friction coefficient of horizontal samples was independent of the direction of sliding while coefficient of friction for vertical samples showed a 60% drop when sliding directions were varied. These results point to a dependence on print orientation in the resulting mechanical and tribological properties.

Sustainable Seismic Design

Traditional design of a seismic resistant system for a building structure has often relied on structural damage as the intended response of the structure to limit the increase in lateral force and to dissipate energy. The goal of this traditional design approach was life-safety, i.e. to prevent building collapse. Following this approach, a major seismic event can cause significant damage to the structure. This in turn requires extensive repair, or if the damage is severe enough, for the structure to be demolished. More recently, an alternative design approach has emerged that is intended to provide structures that remain damage free and self-center (i.e. exhibit no residual drift) after the earthquake. This paper describes this alternative approach, and discusses opportunities for improved sustainability through damage-resistant seismic design and renewable materials.

Structure and nanotribology of thermally deposited gold nanoparticles on graphite

We present experiments involving the structural and frictional characterization of gold nanoparticles (AuNP) thermally deposited on highly oriented pyrolytic graphite (HOPG). The effect of thermal deposition amount, as well as post-deposition annealing on the morphology and distribution of gold on HOPG is studied via scanning electron microscopy (SEM) measurements, while transmission electron microscopy (TEM) is utilized to confirm the crystalline character of the nanoparticles. Lateral force measurements conducted via atomic force microscopy (AFM) under ambient conditions are employed to investigate the nanotribological properties of the gold nanoparticles as a function of normal load. Finally, the increase in lateral force experienced at the edges of the nanoparticles is studied as a function of normal load, as well as nanoparticle height. As a whole, our results constitute a comprehensive structural and frictional characterization of the AuNP/HOPG material system, forming the basis for nanotribology experiments involving the lateral manipulation of thermally deposited AuNPs on HOPG via AFM under ambient conditions.

Transverse Crack Propagation Characteristics of Rail Bottom under Wheel-Rail Force

The finite element model of multi-span continuous beam track is established to research the stress and strain fields of rail under the wheel-rail force. On this basis, according to the practical observation of crack shape, a three-dimensional semi-elliptical crack model was established, the singular element method was employed to simulate the stress field singularity of crack tip, and the transverse crack propagation characteristics of rail bottom under wheel-rail force was studied. The results show that: with the increase of wheel-rail force (vertical, lateral and longitudinal force), KI shows an increasing trend, and with the increase of lateral force, the increase rate of KI is maximum; with the increase of vertical force, both of the KII and KIII show a decreasing trend. However, with the increase of lateral and longitudinal force, both of them show an increasing trend. From the range of stress strength factor of crack tip, the amplitude of KI at the crack tip of rail outer edge is maximum , but the crack tip amplitude of KII and KIII is maximum at partial to the rail centerline.

Transverse Crack Propagation Characteristics of Rail Bottom under Wheel-Rail Force

The finite element model of multi-span continuous beam track is established to research the stress and strain fields of rail under the wheel-rail force. On this basis, according to the practical observation of crack shape, a three-dimensional semi-elliptical crack model was established, the singular element method was employed to simulate the stress field singularity of crack tip, and the transverse crack propagation characteristics of rail bottom under wheel-rail force was studied. The results show that: with the increase of wheel-rail force (vertical, lateral and longitudinal force), KI shows an increasing trend, and with the increase of lateral force, the increase rate of KI is maximum; with the increase of vertical force, both of the KII and KIII show a decreasing trend. However, with the increase of lateral and longitudinal force, both of them show an increasing trend. From the range of stress strength factor of crack tip, the amplitude of KI at the crack tip of rail outer edge is maximum , but the crack tip amplitude of KII and KIII is maximum at partial to the rail centerline.

Sub-scale simulation and measurement of railroad wheel/rail adhesion under dry and wet conditions

The adhesion characteristics of railroad wheels against rails were simulated using a sub-scale wheel/rail configuration. The apparatus consists of a small roller to simulate the locomotive or rolling stock wheel and a large roller to simulate the rail. The scale of the wheel/rail profiles, relative to full size, is 1:4. Results indicated that this laboratory test can be used to adequately simulate and evaluate the adhesion behavior of the wheel/rail interface under various conditions. Under dry conditions, the adhesion coefficient of wheel/rail has a sharp initial increase of between 0% and 1.5% as creep ratio increases, and then a slight reduction of up to 5%. The presence of water or oil markedly decreases the adhesion coefficient of wheel/rail. With an increase of speed and due to the water volume in the wheel/rail surface, the adhesion coefficient drops. With an increase of lateral force, the adhesion coefficient of wheel/rail increases. Axle load has no obvious effect on the adhesion coefficient in the presence of water. Tree leaves have an important effect on the adhesion coefficient and should be cleared away from the contact surface of wheel/rail if water is present. Further work on improving adhesion and damage of wheels on rails should be studied and explored under a range of low adhesion conditions.

Ground reaction forces analyses during the gait of healthy individuals with and without the use of a calcaneus insole

The foot forms the base of propulsion and balance during the gait. It is well known that excessive or prolonged pronation and supination changes the gait’s mechanical movement. Hence, the use of corrective insoles is recommended when calcaneus alterations (valgus and varun) are present. Objetive: The main purpose of this article was to analyze the effects of a calcaneus insole on normal individuals on the Ground Reaction Force variables. Method: The experiment used ten adults (31.9 ± 6,7 years, 65.9 ± 15.4 kg and 1.7 ± 0.1 m) and registered no apparent changes in gait or pathologies that have an effect on the locomotor system. The following gait conditions were analyzed and compared: barefoot, using a sport shoe, and using the sport shoe with insole. The variables analyzed were vertical, medial lateral, and anterior-posterior dynamic ground reaction forces. An ANOVA one-way was used in order to compare the three different conditions. Statistically significant differences were revealed between the conditions of barefoot and sport shoe with insole for the vertical GRF during initial contact Fz1 (F2,59 = 3.4; p < 0.0406) and for the GRF anterior-posterior in the terminal stance phase Fy2 (F2,59 = 3.63; p < 0.0332). Results: These results indicated that the use of an insole increased the vertical impact on the locomotor system during the response to load phase, probably because of its greater stiffness compared to the barefoot or sport shoe trials. The insole also changed the GRF anterior-posterior during the terminal stance that corresponded with the acceleration/propulsion gait phase. Conclusion: Just based on the analysis of the dynamic variables, it was concluded that the use of insoles did not induce any significant increase in lateral forces that would indicate the reduction of excessive pronation or supination during the response load phase. The use of an insole produced a significant dynamic effect on the pronation/supination only in the propulsive gait phase.

Grip and detachment of locusts on inverted sandpaper substrates

Locusts (Locusta migratoria manilensis) are characterized by their strong flying and grasping ability. Research on the grasping mechanism and behaviour of locusts on sloping substrates plays an important role in elucidating the mechanics of hexapod locomotion. Data on the maximum angles of slope at which locusts can grasp stably (critical angles of detachment) were obtained from high-speed video recordings at 215 fps. The grasping forces were collected by using two sensors, in situations where all left legs were standing on one and the right legs on the other sensor plate. These data were used to illustrate the grasping ability of locusts on slopes with varying levels of roughness. The grasping morphologies of locusts' bodies and tarsi were observed, and the surface roughness as well as diameters of their claw tips was measured under a microscope to account for the grasping mechanism of these insects on the sloping substrate. The results showed that the claw tips and part of the pads were in contact with the inverted substrate when the mean particle diameter was in the range of 15.3–40.5 µm. The interaction between pads and substrates may improve the stability of contact, and claw tips may play a key role in keeping the attachment reliable. A model was developed to explain the significant effects of the relative size of claw tips and mean particle diameter on grasping ability as well as the observed increase in lateral force (2.09–4.05 times greater than the normal force during detachment) with increasing slope angle, which indicates that the lateral force may be extremely important in keeping the contact reliable. This research lays the groundwork for the probable design and development of biomimetic robotics.

Numerical simulation of the seismic behavior of self-centering steel beam-column connections with bottom flange friction devices

A new type of steel moment resisting frame with bottom flange friction devices (BFFDs) has been developed to provide self-centering capacity and energy dissipation, and to reduce permanent deformations under earthquakes. This paper presents a numerical simulation of self-centering beam-column connections with BFFDs, in which the gap opening /closing at the beam-column interfaces is simulated by using pairs of zero-length elements with compression-only material properties, and the energy dissipation due to friction is simulated by using truss elements with specified hysteretic behavior. In particular, the effect of the friction bolt bearing against the slotted plate in the BFFDs was modeled, so that the increase in lateral force and the loss of friction force due to the bolt bearing could be taken into account. Parallel elastic-perfectly plastic gap (ElasticPPGap) materials in the Open System for Earthquake Engineering Simulation (OpenSees) were used with predefined gaps to specify the sequence that each bolt went into the bearing and the corresponding increase in bending stiffness. The MinMax material in OpenSees is used to specify the minimum and maximum values of strains of the ElasticPPGap materials. To consider the loss of friction force due to bolt bearing, a number of parallel hysteretic materials were used, and the failure of these materials in sequence simulated the gradual loss of friction force. Analysis results obtained by using the proposed numerical model are discussed and compared with the test results under cyclic loadings and the seismic loading, respectively.

Nano-scratching in solution to the single-crystal Ta (100) subjected to anodic oxidation

A single crystal-tantalum (100) surface was anodically oxidized at 5.0 V (SHE) for 1 h in pH 8.4 borate buffer solution. Nano-scratching in solution at a constant normal force of 300 µN was performed on the tantalum (100) surface kept at 5.0 V (SHE) after anodic oxidation. Nano-scratching in air was also performed on the tantalum (100) surface after anodic oxidation. A stick–slip was always observed in lateral force versus lateral displacement curves during nano-scratching in solution. The degree of stick–slip, however, decreased with increasing scratching rate. The average friction coefficient obtained with nano-scratching in solution was significantly larger than that obtained with nano-scratching in air and increased linearly with the logarithm of time required for scratching. In contrast, the friction coefficient obtained with nano-scratching in air was independent of the time required for scratching. The protrusion at the scratching end of the groove produced by nano-scratching in solution was observed from the AFM image, while no protrusion was observed for nano-scratching in air. It has been proposed that the protrusion consists of anodic oxide accumulated on the moving front of the indenter tip during nano-scratching in solution and contributes to the increase in lateral force, i.e. friction coefficient.

Influence of Molecular Weight on Nanoscale Modification of Poly(methyl methacrylate) Due to Simultaneous Mechanical and Chemical Stimulation

We report observations of poly(methyl methacrylate) films modified by the synergistic effect of solvent exposure and mechanical stress applied by the tip of an atomic force microscope (AFM). We show that these modifications are sensitive to polymer molecular weight as well as solvent strength and the force applied by the tip. Small-area scanning often produces localized patches of raised material as well as depressed areas. The volume change associated with the depressed areas generally increases with increasing solvent strength, increasing applied normal force, and decreasing polymer molecular weight. In contrast, the volume change associated with the raised patches is greatest for 25-145K Mw films in 60 and 100% ethanol solutions. In each case, the normal force applied by the AFM tip must exceed a threshold to significantly modify the surface; this threshold is associated with an increase in lateral force applied by the AFM tip during small-area scanning. We attribute the raised patches to mechanically enhanced swelling due to diffusion of solvent into near-surface material. Permanent net volume loss, when observed, is attributed to localized polymer dissolution.

INVESTIGATION OF LATERAL FORCES WHILE PERFORMING VOLUN-TARY FORWARD STEPPING WITH and WITHOUT USING A CANE IN HEALTHY ADULTS and HEMIPLEGIC PATIENTS WITH STROKE.

Hypothesis: This study investigated differences in the lateral forces while performing voluntary forward stepping with and without a cane in healthy adults and hemiplegic patients with stroke. Number of Subjects: Five hemiplegic patients with stroke (mean age=55.9 ± 11.5yrs) and five age-matched healthy adults (mean age=56.0 ± 7.0yrs) participated in this study. Materials/Methods: Four conditions, stepping forward with the left and right leg, and with and without using a cane, were tested. Ground reaction forces underneath the lower extremities and the cane were collected by two force plates and an instrumented cane, respectively. The loading duration (from onset of the increase in lateral force toward the stepping leg to the first zero crossing of the lateral force), unloading duration (onset of the increase in lateral force toward the stance leg to the second zero crossing of the lateral force), force impulses during the loading and unloading durations, and the rate of lateral force transfer prior to foot liftoff were analyzed. Results: Compared with healthy adults, patients with stroke showed longer loading duration (P = 0.003), smaller force impulse in the loading phase (P = 0.024), and slower rate of lateral force transfer (P = 0.001) when stepping with the unaffected leg without a cane; and showed longer loading (P = 0.003) and unloading durations (P = 0.01), and smaller force impulses in the unloading phase (P = 0.001) while stepping with the affected leg without a cane. Without using a cane, patients with stroke also showed longer unloading duration (P = 0.017), faster rate of lateral force transfer (P = 0.009), greater force impulse in the loading phase (P = 0.021), and smaller force impulse in the unloading phase (P = 0.017) while stepping forward with the affected leg than with the unaffected leg. While using a cane to perform the stepping, most of these patients decreased the generation of force impulses in the loading and unloading phase although the amount of the decreases did not reach a significant level (loading phase P = 0.059;unloading phase P = 0.071). No significant change was observed for the rate of lateral force transfer between the no cane and cane use conditions for the patient group either. Conclusions: To achieve a safe lateral weight transfer required prior to and during a forward stepping movement, patients with stroke appeared to lengthen the loading and unloading durations in order to compensate for their decreased ability to generate lateral impulses in the loading and unloading phases, respectively. Using a cane might partially contribute to the lateral impulse generation required for performing the stepping movement such that the impulses generated by the lower extremities decreased slightly. Clinical Relevance: For patients with stroke to step forward, the use of a cane might potentially decrease the difficulty of the lower extremities to perform the lateral weight shifting required prior to and during this movement.

Hydrodynamics of caudal fin locomotion by chub mackerel, Scomber japonicus (Scombridae).

As members of the derived teleost fish clade Scombridae, mackerel exhibit high-performance aquatic locomotion via oscillation of the homocercal forked caudal fin. We present the first quantitative flow visualization of the wake of a scombrid fish, chub mackerel Scomber japonicus (20-26 cm fork length, FL), swimming steadily in a recirculating flow tank at cruising speeds of 1.2 and 2.2FL s(-1). Thrust was calculated from wake measurements made separately in the horizontal (frontal) plane and vertical (parasagittal) planes using digital particle image velocimetry (DPIV) and compared with drag measurements obtained by towing the same specimens of S. japonicus post mortem. Patterns of flow indicated that the wake consisted of a series of linked elliptical vortex rings, each with central jet flow. The length of the minor axis (height) of the vortex rings was approximately equal to caudal fin span; the length of the major ring axis was dependent on swimming speed and was up to twice the magnitude of ring height. Profiles of wake velocity components were similar to theoretical profiles of vortex rings. Lift, thrust and lateral forces were calculated from DPIV measurements. At 1.2FL s(-1), lift forces measured relative to the X axis were low in magnitude (-1+/-1 mN, mean +/- S.D., N=20) but oriented at a mean angle of 6 degrees to the body axis. Reaction forces tend to rotate the fish about its center of mass, tipping the head down. Thus, the homocercal caudal fin of S. japonicus functions asymmetrically in the vertical plane. Pitching moments may be balanced anteriorly via lift generation by the pectoral fins. Thrust estimates for the two smallest fish based on DPIV analysis were not significantly different from drag measurements made by towing those same animals. At a speed of 1.2FL s(-1), thrust magnitude was 11+/-6 mN (mean +/- S.D, N=40). Lateral force magnitudes were approximately double thrust magnitudes (22+/-6 mN, mean +/- S.D., N=20), resulting in a mean mechanical performance ratio (thrust/total force) of 0.32 at 1.2FL s(-1). An increase in speed by a factor of 1.8 resulted in a mean increase in thrust by a factor of 4.4, a mean increase in lateral forces by a factor of 3, no change in the magnitude of lift produced and an increase in mean mechanical performance to 0.42. The relatively high lateral forces generated during swimming may be a necessary consequence of force production via propagated waves of bending.

Effect of aggregation state on nanotribological behaviors of organosilane monolayers

Nanotribological behaviors of organosilane monolayers prepared by the Langmuir–Blodgett (LB) and chemisorption methods are discussed in terms of their aggregation states. Aggregation structure of the LB n-octadecyltrichlorosilane (OTS-C18) monolayers changed from a rectangular to an amorphous phase via a hexagonal phase with increasing temperature. A distinct lateral force decrease accompanies the phase transition. The LB alkyltrichlorosilane monolayers with longer alkyl chains were in a crystalline state at 293 K. The lateral force of the LB alkyltrichlorosilane monolayers at 293 K increased with increasing chain length. The n-triacontyltrichlorosilane LB monolayer (TATS-C30) in a rectangular phase showed higher lateral force than that of the alkyltrichlorosilane with shorter alkyl chains in a hexagonal phase. The lateral force of the OTS-C18 monolayer prepared by the LB method was higher than that of the chemisorbed one because of the higher packing density of alkyl chain for the LB monolayer, though both monolayers are in a hexagonal phase at 293 K. A large increase in lateral force was observed for the 18-nonadecenyltrichlorosilane (NTS) after oxidation of vinyl end groups.

Keratocytes generate traction forces in two phases.

Forces generated by goldfish keratocytes and Swiss 3T3 fibroblasts have been measured with nanonewton precision and submicrometer spatial resolution. Differential interference contrast microscopy was used to visualize deformations produced by traction forces in elastic substrata, and interference reflection microscopy revealed sites of cell-substratum adhesions. Force ranged from a few nanonewtons at submicrometer spots under the lamellipodium to several hundred nanonewtons under the cell body. As cells moved forward, centripetal forces were applied by lamellipodia at sites that remained stationary on the substratum. Force increased and abruptly became lateral at the boundary of the lamellipodium and the cell body. When the cell retracted at its posterior margin, cell-substratum contact area decreased more rapidly than force, so that stress (force divided by area) increased as the cell pulled away. An increase in lateral force was associated with widening of the cell body. These mechanical data suggest an integrated, two-phase mechanism of cell motility: (1) low forces in the lamellipodium are applied in the direction of cortical flow and cause the cell body to be pulled forward; and (2) a component of force at the flanks pulls the rear margins forward toward the advancing cell body, whereas a large lateral component contributes to detachment of adhesions without greatly perturbing forward movement.