Resultant Force Vector Research Articles

Triaxial Load Testing of Metal and FRP Roof-to-Wall Connectors

The allowable capacity of conventional roof-to-wall metal connectors is based on results of unidirectional component tests that do not simulate triaxial aerodynamic loading effects induced by high-wind events. The results of wind and wind-driven rain tests conducted at a full-scale facility were used to create a database on aerodynamic and aerohydrodynamic load effects on roof-to-wall connectors. Based on these results, three axial mean force components (triaxial mean loads) were combined into a series of resultant mean force vectors. A new test protocol was then developed for roof-to-wall connectors under simulated triaxial loading as opposed to simple uniaxial loading. The findings confirm that current testing methods tend to overestimate the actual load capacities of metal connectors. The performance of a nonintrusive roof-to-wall connector system using fiber-reinforced polymer (FRP) ties was also tested and compared with that of a traditional metal connector under simulated aerodynamic loads. The test...

Specific machining forces and resultant force vectors for machining of reinforced plastics

When machining fiber reinforced plastics, the machining forces may induce workpiece damage if they exceed the workpiece's anisotropic strength values. Knowledge of the resultant force vectors is therefore important to allow optimization of tool geometry and machining strategy. This article deals with experimentally obtained machining forces on short glass fiber reinforced polyester. Specific cutting, passive and axial forces have been determined for varied parameters of cutting velocity, cutting depth, cutting edge rounding and tool inclination. Generic multivariate regression models have been calculated, which, implemented in a kinematic simulation, allow calculation of machining forces (and direction) for arbitrary milling operations.

Analysis of machining strategies for fiber reinforced plastics with regard to process force direction

Mechanical machining of composites, especially the machining of holes for bolts or rivets, poses challenges due to the anisotropic material structure. Machining forces may damage the workpiece permanently. Chipping or delamination are severe damages, primarily occurring at the workpiece's surface layers. Prior research has shown that machining induced damages can be significantly reduced by using machining strategies, which aim at directing the resultant process force vectors toward the center of the workpiece. This article presents detailed analyses of two such machining strategies with regard to the process force direction. A combined process of circular and spiral milling as well as five-axial wobble milling is analyzed. The influences of process and workpiece parameters (feed, tool inclination, tool spiral angle, cutting edge radius) on the resultant machining force vector are determined.

The mechanics of azimuth control in jumping by froghopper insects

Many animals move so fast that there is no time for sensory feedback to correct possible errors. The biomechanics of the limbs participating in such movements appear to be configured to simplify neural control. To test this general principle, we analysed how froghopper insects control the azimuth direction of their rapid jumps, using high speed video of the natural movements and modelling to understand the mechanics of the hind legs. We show that froghoppers control azimuth by altering the initial orientation of the hind tibiae; their mean angle relative to the midline closely predicts the take-off azimuth. This applies to jumps powered by both hind legs, or by one hind leg. Modelling suggests that moving the two hind legs at different times relative to each other could also control azimuth, but measurements of natural jumping showed that the movements of the hind legs were synchronised to within 32 mus of each other. The maximum timing difference observed (67 micros) would only allow control of azimuth over 0.4 deg. to either side of the midline. Increasing the timing differences between the hind legs is also energetically inefficient because it decreases the energy available and causes losses of energy to body spin; froghoppers with just one hind leg spin six times faster than intact ones. Take-off velocities also fall. The mechanism of azimuth control results from the mechanics of the hind legs and the resulting force vectors of their tibiae. This enables froghoppers to have a simple transform between initial body position and motion trajectory, therefore potentially simplifying neural control.

Influence of neck rotation and neck lateroflexion on mandibular equilibrium

Neuromuscular interaction between neck and jaw muscles has been reported in several studies. However, the influence of experimentally modified posture of the neck on jaw muscle activity during isometric biting was not investigated so far. The aim of the present study was to test by the aid of simultaneous electromyographic and intraoral bite force measurements whether neck rotation and lateroflexion, in contrast to a straightforward neck position, change the isometric cocontraction patterns of masticatory muscles under identical submaximum bite forces of 50-200 N. Electric muscle activity of all masticatory muscles and changes of the reduction point (RP) of the resultant bite force vectors were examined. An anteroposterior displacement of the RPs could be observed for the rotated and lateroflexed neck position in comparison with the straightforward position. On the other hand, the results revealed no significant differences between bilateral muscle activation under the different test conditions. These findings suggest a force transmission between the neck and the masticatory system, but no essential activity changes in the masticatory muscles under short time posture modification of the neck.

Formulation of a Three-Dimensional Movable Magnetic Levitation System and its Performance in Tests

This paper describes a new formulation to the three-dimensional movable magnetic levitation system using I-shaped electromagnets and a lower dimensional technique at a suitable selected operating point. In the formulation, an attractive force per unit was first derived to assume that an I-shaped electromagnet and a floating object were present as a magnetic charge model. Then, the resulting force vector was determined on the geometric configuration of I-shaped electromagnets. Model-following servo controllers designed for each state equation in the x-, y-, and z- directions, which were derived from the proposed formulation and lower-dimensional technique, successfully stabilized the maglev system.

Body position determines propulsive forces in accelerated running

Rapid accelerations during running are crucial for the performance in a lot of sports. While high propulsive forces are beneficial to forward acceleration, vertical forces have to be small to attain high stride frequencies. However, propulsive and vertical force components cannot be altered independently, because the resultant force vector affects the angular momentum of the body. Therefore we hypothesized that propulsive forces in accelerated running mainly depend on body position regardless of performance level. In our cross-sectional study 28 male and 13 female physical education students performed submaximal and maximal accelerations. Ground reaction forces and whole body kinematics were recorded. Higher accelerations were generated by lower, but more forward oriented forces. The orientation of the maximum force vector strongly correlated with the forward lean of the body at toe-off ( r = 0.93 , p ≤ 0.001 ) . All subjects demonstrated similar propulsive forces at equal body positions. This indicates an external constraint of propulsive force application by the mechanical requirement of running to maintain a stable body posture. Faster subjects utilized a more posterior foot plant or a longer ground contact time. Both strategies facilitated greater forward leans of the body which finally resulted in greater propulsive forces. Consequently, maximizing forward propulsion requires optimal, not maximal force application.

Small unilateral jaw gap variations: equilibrium changes, co‐contractions and joint forces

After complex prosthetic reconstructions, small differences in vertical distances between the left and right side of the jaw may occur during jaw closing, nevertheless providing bilateral tooth contacts in intercuspation by small deformations of the mandible. Their effects on the co-contraction of the masticatory muscles, the temporomandibular joint reaction forces, and the point of application of the resultant bite force vector in the maxillary occlusion plane - the so-called reduction point - have not been investigated, thus far simultaneously in one sample. The main goal of this study was to investigate variations of these measures in an experimental intercuspation simulated by one anterior and two posterior force transmission points.

The simulation of the geometry of a tuna purse seine under current and drift of purse seiner

It was necessary to obtain a more practical interactive precise model of the three-dimensional (3-D) geometry during purse seine operations considering movements of fishing vessel and details of the sea condition. The changes in the shape of a purse seine from shooting to pursing during pelagic skipjack fishing was recorded in the Southwest Pacific Ocean by photographs of the scanning sonar with in situ measurements of water flow by a current meter. The modeling of 3-D geometry during purse seining was established using finite element methods, as resultant force vector from flow drag, buoyancy, sinking force, tension of pulling or pursing acting on net panels in connection with drift of fishing vessel with time elapsed from the start of shooting to the end of pursing. The simulation results were matched closely by field measurements as a heart-like shape in upper net near floatline and a water-drop shape in purse line following drift of ship towards inside net circle during pursing. This model of a purse seine can be extended to almost any kind of purse seine generating real fishing parameters and to modeling fish capture process.

DTI‐based muscle fiber tracking of the quadriceps mechanism in lateral patellar dislocation

To determine the feasibility of using diffusion tensor MRI (DT-MRI) -based muscle fiber tracking to create biomechanical models of the quadriceps mechanism in healthy subjects and those with chronic lateral patellar dislocation (LPD). Four healthy (average 14.5 years old; BMI 21.8) and four chronic LPD (average 17.3 years old; BMI 22.4) females underwent DT and axial T1W MRI of the thighs. The anatomical and physiologic cross-sectional areas (ACSA and PCSA, respectively) and pennation angle were calculated of the vastus lateralis oblique (VLO) and vastus medialis oblique (VMO) muscles. The predicted resultant force vector on the patella was calculated. The VLO pennation angles in healthy and LPD subjects were 18.7 and 14.5 degrees, respectively (P=0.141). The VMO pennation angles in healthy and LPD subjects were 11.4 and 14.8 degrees, respectively (P=0.02). The ACSA and PCSA VLO:VMO ratios in healthy and LPD subjects were 1.9:1.6 and 2.1:1.6, respectively (P=0.025 and 0.202, respectively). Regardless of whether ACSA or PCSA was used to predict resultant lateral force vectors, the values differed between healthy and LPD subjects (approximately 2 and approximately 5.3 degrees, respectively; P<0.05). Chronic LPD patients had more laterally directed predicted resultant force vectors than healthy subjects. Our preliminary results suggest that biomechanical models of the quadriceps mechanism in patients with chronic LPD and healthy subjects can be created in healthy subjects and patients with chronic LPD using DT-MRI.

Tension patterns of the anteromedial and posterolateral grafts in a double‐bundle anterior cruciate ligament reconstruction

The two functional bundles of the anterior cruciate ligament (ACL), namely, the anteromedial (AM) and posterolateral (PL) bundles, must work in concert to control displacement of the tibia relative to the femur for complex motions. Thus, the replacement graft(s) for a torn ACL should possess similar tension patterns. The objective of the study was to examine whether a double-bundle ACL reconstruction with the semitendinosus-gracilis autografts could replicate the tension patterns of those for the intact ACL under controlled in vitro loading conditions. By means of a robotic/universal force moment sensor (UFS) testing system, the in situ force vectors (both magnitude and direction) for the AM and PL bundles of the ACL, as well as their respective replacement grafts, were determined and compared on nine human cadaveric knees. It was found that double-bundle ACL reconstruction could closely replicate the in situ force vectors. Under a 134-N anterior tibial load, the resultant force vectors for the intact ACL and the reconstructed ACL had a difference of 5 to 11 N (p > 0.05) in magnitude and 1 to 13 degrees (p > 0.05) in direction. Whereas, under combined rotatory loads of 10-N-m valgus and 5-N-m internal tibial torques, the corresponding differences were 10 to 16 N and 4 degrees to 11 degrees, respectively. Again, there were no statistically significant differences except at 30 degrees of flexion where the force vector for the AM graft had a 15 degrees (p < 0.05) lower elevation angle than did the AM bundle.

Interaction force diagrams: new insight into ligand-receptor binding

A method is described to calculate and visualize the interaction forces of ligand-receptor complexes. Starting from an X-ray crystallographic structure, a "thawing" procedure results in a force-field energy-minimized geometry which is close to the crystallographic starting point. By subtracting non-bonded interactions of the ligand with each amino acid residue and using the resulting force vectors to describe the slope of the remaining potential, two types of interaction force diagrams are created; the first shows the direction of the force vectors in 3D and the second shows the magnitude of the force vectors. The latter representation leads to definition of an 'Interaction Force Fingerprint' (IFFP) which is characteristic of the ligand-receptor binding. IFFPs are used to discuss ligand binding in the human estrogen receptors ERalpha and ERbeta, and provide new insight into ligand selectivity between receptor isoforms.

Open-Loop Control of a Multifin Biorobotic Rigid Underwater Vehicle

This paper presents an open-loop control system for a new experimental vehicle, named the biorobotic autonomous underwater vehicle (BAUV). The rigid cylindrical hull of the vehicle is attached with six strategically located fins to produce forces and moments in all orthogonal directions and axes with minimal redundancy. The fins are penguin-wing inspired and they implement the unsteady high-lift principle found widely in swimming and flying animals. The goal has been to design an underwater vehicle that is highly maneuverable by taking the inspiration from nature where unsteady hydrodynamic principles of lift generation and the phase synchronization of fins are common. We use cycle-averaged experimental data to analyze the hydrodynamic forces and moments produced by a single foil as a function of its kinematic motion parameters. Given this analysis, we describe a method for synthesizing and coordinating the sinusoidal motion of all six foils to produce any desired resultant mean force and moment vectors on the vehicle. The mathematics behind the resulting algorithm is elegant and effective, yielding compact and efficient implementation code. The solution method also considers and accommodates the inherent physical constraints of the foil actuators. We present laboratory experimental results that demonstrate the solution method and the vehicle's resulting high maneuverability.

Rock mass deformation modeling using the non-Archimedean analysis

The non-Archimedean space is a multi-scale one. The paper shows that this face is applicable to developing mathematical models of rocks exhibiting a hierarchy of structural levels. A closed model, considering anisotropy and weakening of a rock mass, is constructed. The equations in terms of displacements and the resultant internal force vector are derived. The authors have obtained the numerical solution to the problem on deformation of a rock mass around extended galleries, and showed how the areas of weakening and residual strength evolve. The energy flow lines are plotted.

Are sound dogs mechanically symmetric at trot?

A two-year-old, sound Labrador Retriever was determined to be 'right hind limb dominant' by comparison of total hind limb moments of support using inverse dynamics. Net joint moments at the hip, tarsal and meta-tarsophalangeal joints were larger on the right side. Vertical joint reaction forces at the stifle were larger on the right, and horizontal stifle joint reaction forces were smaller on the right. The crus segment was more cranially inclined on the right side through most of stance, but the angle of the resultant stifle joint reaction force vector against the long axis of the crus segment was identical between the right and left sides. The cranially inclined crus segment orientation on one side, coupled with the larger vertical joint reaction force, may result in an internal asymmetry in stifle joint mechanics, although the effects of this on cruciate ligament stresses remain to be determined.

Changes in the perceived head transversal plane and the subjective visual horizontal induced by Coriolis stimulation during gondola centrifugation

For studying the influence of the vertical semicircular canals on spatial orientation in roll, the subjective visual horizontal (SVH) and the subjective transversal plane of the head (STP) were measured in a situation where the vertical canals sense a roll-velocity stimulus while the otolith organs persistently signal that the head is upright in roll. During gondola centrifugation (resultant gravitoinertial force vector 2.5 G, gondola inclination 66 degrees) subjects were exposed to controlled rotational head movements (angular speed 27 degrees/s, magnitude 40 degrees) about the yaw (body z-) axis, produced by means of a motor-driven helmet. This causes a roll-plane Coriolis stimulus to the canals, while the otoliths persistently sense upright head position in roll. The subjects reported intense sensations of rotation and tilt in the roll plane. This was reflected in tilts of both the SVH and STP. The initial tilt of the SVH was 13.0 +/- 9.7 degrees (mean +/- S.D., n=10). The STP was changed in the opposite direction. The initial tilt was 23.8 +/- 12.2 degrees (mean +/- S.D., n=5). The changes in the SVH and STP were not of equal magnitude. A few subjects who had almost no deviations in the SVH showed pronounced tilts of the STP. The time constant for exponential decay of the tilts of the SVH and STP was on average approximately 1 minute. These findings indicate that a difference in activity of the vertical canals in the right versus left ear may cause substantial tilts of the SVH even if there is no asymmetry in the activity of the otolith system. Further, the canal stimulus may induce a tilt of the fundamental egocentric frame of reference.

Minimally invasive endoscopic reconstruction technique of acute AC-joint dislocations: a cadaver study

The treatment of acute Rockwood type III AC-joint dislocations is controversial. Problems related to open surgery are soft tissue healing, residual instability and the necessity of hardware removal. After non-operative therapy the cosmetic result may be problematic and in some cases symptomatic instabilities occur. The goal of the present cadaver study was to develop a new, minimally invasive technique for acute AC-joint reconstructions and to analyse its potential risk for neurovascular injuries. The surgical technique was based on an arthroscopically assisted reconstruction of the coracoclavicular ligaments with a suture anchor (Arthrex, Naples, FL, USA) and a supplemental stabilization of the AC-joint capsule with a suture cerclage (Fibre Wire 2, Arthrex) performed on ten cadaveric shoulder specimens. After surgery all specimens were dissected to analyse the anatomy of the coracoclavicular ligament complex, the position of anchors and sutures and to measure the distance to the neurovascular structures at risk. The supraspinatus muscle was never injured by the Neviaser approach. The insertion of the suture anchors never failed, resulting in a secure and reproducible anchor position. The mean distance between the coracoid and suprascapular nerve was 1.8 cm (1.5-2.2), between the coracoid and the suprascapular artery 1.5 cm (1.3-1.9). These structures were never injured. The resulting force vector of the suture located between the anchor and the drill hole was close to the anatomic force vector of the coracoclavicular ligament complex. The suture cerclage was always correctly positioned. The presented technique is at minimal risk for the surrounding neurovascular structures and allows for a minimally invasive and anatomically correct reconstruction of the AC-joint. Further biomechanical analysis is needed to evaluate the strength of the reconstruction technique. The proposed technique might be a reasonable alternative to existing invasive techniques of open reconstruction of acute type III AC-joint dislocations in high-demand patients.

Activity patterns of the masticatory muscles during feedback‐controlled simulated clenching activities

In 10 normal subjects, the electromyographic (EMG) activities of the masseter, anterior and posterior temporalis, medial pterygoid, inferior lateral pterygoid, as well as the anterior digastric, were bilaterally recorded during clenching with various resulting force vectors. The intraoral force transfer was achieved with a three-component force transducer. The direction and magnitude of the force vectors were controlled by visual feedback. The goal of the study was to investigate how various clenching directions at constant magnitude of force influence the EMG activity in the masticatory muscles during gradual increase of the horizontal force component. Depending on the force direction and the individual muscle, an increase or decrease of activity was observed during clenching with increasing horizontal force components at constant magnitude of force. The inferior lateral pterygoid exhibited the highest activation (about 80% of maximal voluntary clenching) of all masticatory muscles. The medial pterygoid showed the greatest range of variation in activation behavior, and it was the most active muscle in relation to all clenching directions. In conclusion, the results show that with growing horizontal force components at constant magnitude of force, all muscles demonstrated an increase or decrease of activity in several clenching directions.

Differential activity patterns in the masseter muscle under simulated clenching and grinding forces

The aim of this study was to investigate (i) whether the masseter muscle shows differential activation under experimental conditions which simulate force generation during clenching and grinding activities; and (ii) whether there are (a) preferentially active muscle regions or (b) force directions which show enhanced muscle activation. To answer these questions, the electromyographic (EMG) activity of the right masseter muscle was recorded with five intramuscular electrodes placed in two deep muscle areas and in three surface regions. Intraoral force transfer and force measurement were achieved by a central bearing pin device equipped with three strain gauges (SG). The activity distribution in the muscle was recorded in four different mandibular positions (central, left, right, anterior). In each position, maximum voluntary contraction (MVC) was exerted in vertical, posterior, anterior, medial and lateral directions. The investigated muscle regions showed different amount of EMG activity. The relative intensity of the activation, with respect to other regions, changed depending on the task. In other words, the muscle regions demonstrated heterogeneous changes of the EMG pattern for the various motor tasks. The resultant force vectors demonstrated similar amounts in all horizontal bite directions. Protrusive force directions revealed the highest relative activation of the masseter muscle. The posterior deep muscle region seemed to be the most active compartment during the different motor tasks. The results indicate a heterogeneous activation of the masseter muscle under test conditions simulating force generation during clenching and grinding. Protrusively directed bite forces were accompanied by the highest activation in the muscle, with the posterior deep region as the most active area.

A Basic Power Decomposition in Lagrangian Mechanics

A Basic Power Decomposition in Lagrangian Mechanics