Force In Radial Direction Research Articles

Hoek-Brown failure criterion for damage analysis of tunnels subjected to blast load

In this study, a rock tunnel subjected to blast load is modeled mathematically. For this purpose, a cylindrical shell element is used and the motion equations are derived by energy method and Hamilton's principle. In the inner surface of tunnel, different blast holes are considered and its force in radial direction is coupled by motion equations. The structural damping of the structure is assumed by Kelvin-Voigt model. Hoek-Brown failure criterion is utilized for explosion damage analysis of the tunnel. The motion equations are solved numerically by differential quadrature method (DQM). The effect of different parameters such as depth of tunnel, number and diameter of blast holes, type of stone, geological strength index (GSI) and density of stone, type and mass of explosive material are studied on the damage factor of Hoek-Brown criterion. Numerical results show that with increasing the density of explosive material, number and diameter of blast holes, the thickness of damage is increased in the tunnel. In addition, the depth of damage is decreased with increasing strength, GSI, density of rock and depth of tunnel.

Experimental and numerical investigation of particle distribution behaviors in a rolling circulating fluidized bed

Dynamic properties of particle distribution behaviors in the circulating fluidized bed with rolling motion have been clarified by both Electrical Capacitance Tomography (ECT) experiment and CFD-DEM simulation. In the present study, the amplitude and period of the rolling motion were maintained at Θ=±π/12rad (±15°) and T=5s, respectively. Limestone particles (Geldart group B) were used as the circulating particles. As a result, the rolling motion causes little impact to the flow directional profiles of particle volume fraction due to the negligible inertial forces and changes of gravity component. However, both the experimental and simulation results indicate that the rolling motion has a dominant influence on the particle distribution un-uniformity in the radial direction. An obvious periodical variation of the particle volume fraction appears under the rolling motion due to the significant effect of the resultant force of the gravity component and inertial forces in radial direction, whereas this phenomenon did not appear under the upright condition in any previous studies.

Computation of Radial Electromagnetic Forces on Power Transformer LV Windings due to Short-Circuit Currents

The short-circuit electromagnetic force in radial direction induces critical mechanical stress on a power transformer. In this paper, the radial short-circuit forces which are exerted on transformer low voltage (LV) windings are investigated. Firstly, the mechanisms of leakage flux and short-circuit electromechanical forces in transformer coils are analyzed. Afterwards, based on IEC standards followed by short-circuit tests, calculations of radial short-circuit forces and evaluations of the ability to withstand short currents in LV windings are developed. The case studies and comparisons with improved measures show that the evaluation and calculation method is feasible and effective, and this method also offers three useful ways to strengthen the ability to withstand short-circuit currents for transformer windings.

Development of Dynamic Loading Device for Rotating Spindle of Machine Tools

High performance milling spindles, which have high rigidity and high speed, are required for high productive machining. In order to evaluate the rigidity change of the spindle, authors has been developed a magnetic loading device. This device provides attractive force in radial direction to a dummy tool attached to a spindle. By using this device, the static stiffness of the rotating spindle has been successfully evaluated. However the loading rate could not be controlled due to the electric response lag caused by the magnetic field. To solve this problem, electric response of the coil-tool system with the air gap is analyzed and the dynamic response is estimated. The air-gap's influence on the load was also evaluated. Based on the analysis, a dynamic loading test is designed carried out for the measurement of the rigidity of a machine tool spindle.

Axial force measurement for esophageal function testing

The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophageal function is normally evaluated by means of manometry even though it reflects the squeeze force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe with combined axial force and manometry recordings showed that axial force amplitude increased by 130% in contrast to an increase of 30% using manometry. Using axial force in combination with manometry provides a more complete picture of esophageal motility, and the current paper outlines the advantages of using this method.

Development of a Grip Force Sensor in Golf Swing

Gripping force during golf swing has close relationship with the performance and the feeling of the club. Friction on the grip surface must be an important factor as well as the normal force. In order to elucidate the gripping force on both pressure and friction, a sensor chip was developed that detects the force in radial direction (Fz), tangential direction (Fx), and axial direction (Fy). Using a sensor grip equipped with four sensor chips, gripping force on finger and palm in swing action was measured. The forces change at five periods on swing start, downswing start, wrist release, impact and after impact. In downswing, the axial friction is larger than the tangential one on the left hand. On the other hand, the tangential friction is larger than the axial one on the right hand. This indicates that the left hand makes the centripetal force to rotate the club and the right hand controls the head surface direction around the shaft axis.

Photophoresis and the Pile‐up of Dust in Young Circumstellar Disks

A rapidly growing number of observations reveal ever more structure in young circumstellar disks that are presumed to be forming planetary systems. Prominent features observed are ring-shaped dust distributions with sharp inner edges around stars like the young, main-sequence star HR 4796A. Models aiming to explain the formation of these dust rings by grain migration incorporate radiation pressure of the central star as one shaping force in radial direction. However, the radiometric effect of photophoresis has been ignored, so far, in this context. This effect is based on a radiation-induced temperature gradient on the surface of a particle and the consequential nonuniform interaction with surrounding gas. The resulting force is able to effectively influence the motion of particles in gaseous environments, but so far photophoresis has been limited to applications in the field of aerosol science. Here we present calculations that underline the relevance of the photophoretic force for the dynamics of particles in gas-rich, optically thin circumstellar disks. Depending on the gas pressure, photophoresis can be stronger than radiation pressure, gas drag, and gravity by orders of magnitude. Then the motion of particles ranging in size from 1 μm to 10 m will be dominated by photophoresis. Since the photophoretic force is a function of the gas density, it provides an efficient mechanism for fast radial migration of particles to a definite distance from the star where the gas density reaches a value at which photophoresis is in equilibrium with all other forces at work. By this effect, material is swept out from the inner region of the disk and piled-up in a more or less confined belt around the star. Thus, the formation of ringlike structures of the dust distribution can most naturally be explained without any further assumptions. Since photophoretic pile-up also works for larger bodies, it might even trigger the formation of Kuiper belts.

Void initiation close to a macro-inclusion during single pass reductions in the hot rolling of steel slabs: A numerical study

The work is focussed on the start of void formation close to a hypothetical single macro-inclusion in the hot rolling of steel slabs. The inclusion is chosen to be either three times harder or three times softer than the surrounding matrix. A commercial FE-code LS-Dyna3D has been utilized for the numerical analysis. Process data from the Swedish company “SSAB Tunnplåt AB” are used. The initial inclusion geometry is assumed to be cylindrical with an extension through the entire width of the slab. Different distances from the slab surface, on the vertical symmetry plane in rolling direction, are chosen as locations for the enclosure. Influence of different single pass reductions and roll radii are analysed. The only boundary force used on the matrix/inclusion interface is referred to friction. By treating a very big inclusion and neglecting bonding forces in radial direction, a worst-case scenario means to be studied. Two indices, one describing the deformation of the inclusion and one the surrounding matrix are used to estimate the likelihood for start of void formation. If the matrix index is bigger than that of the inclusion, voids are assumed to be initiated. This hypothesis gives trusty results. Near the hard particle, voids are likely to be formed. It became clear that the risk is smaller when large rolls are used. Furthermore, the threat for start of void formation turned out to be slighter for high reductions and in the vicinity of the slab surface. Soft particles were just elongated and no risk for void formation could be predicted.

ゴルフスウィングにおけるグリップ圧力と摩擦力の測定(ゴルフ(1))

In this paper, we investigate the gripping force in golf swing, which is considered to have close relationship with performance and feeling of the club. The sensor grip using the force sensor chip was developed which can detect the gripping force in radial direction (Fz), tangential direction (Fx). and axial direction (Fy). The sensor grip was attached on the shaft of the test club and the dynamic: gripping force on some part of finger and palm in swing action was examined. Some remarkable results of change in radial and frictional force were obtained as follows. (1) Using a parallel structure plates, we were able to manufacture the reliable sensor chip. Which detects forces in radial direction, tangential direction, and axial direction. (2) In golf swing, the force changes in five periods at swing start, down swing, rist release, impact, and after impact. (3) On the left hand, large axial force is applied as a drawing force for the swing. In the right hand, large tangential force appeared as a force to control of the head face direction. (4) Near the impact, the reduction of the axial force in the left little appeared which may cause the head move straight.

19S ゴルフスイングにおけるグリップ力の測定

In this paper, we investigate the gripping force of golf which is considered to have close relationship with performance and feeling of the club. The force sensor cell composed by bridge structure featured small light and strain gages was newly designed in order to detect the gripping force in golf swing. The sensor grip using the force sensor cell was developed which can detect the gripping force in radial direction (Fz), tangential direction (Fx) and thrust direction (Fy). The sensor grip was attached on the shaft of the test club and the dynamic gripping force on some part of finger and palm in swing action was examined. Some remarkable results of change in radial and frictional force were obtained as follows. (1) The gripping forces of three direction show the tendency to change rapidly at around the impact point. (2) The force of frictional direction (Fx, Fy) in swing were large on the all measured points. (3) The force of radial direction on the palm of left hand was detected steadily. (4) The force of tangential direction on the palm of left hand and the middle finger of right hand were detected markably at back swing and impact. (5) The thrust direction force on the thumb of right hand was detected stably in down swing. It is considered that these results will offer the many useful data in order to develop the advanced sports gear which have funtional design and appropriate specification for each player.

Physical properties of an exact spherically symmetric solution with shear in general relativity

The properties of an exact spherically symmetric perfect fluid solution obtained in non-comoving coordinates are examined. This solution contains shear, and the pressure and the density are positive in the interior of the fluid. Their respective gradients with respect to comoving radial coordinate are equal and negative, and the speed of sound in this fluid is less than the speed of light in vacuum and is increasing outwards. There is a singularity at the center of the fluid since the pressure and the density become infinite there, though their ratio becomes unity. This singularity is naked, since there does not exist a trapped surface in the fluid outside this singularity. The circumference is an increasing function of radical comoving coordinate, and the mass function is positive and is increasing outwards. There are no tidal forces in radial direction, but the tidal forces normal to this direction are non-vanishing. We also give the kinematic quantities for this fluid. However, it is not possible to match this solution with an exterior vacuum Schwarzschild solution. Moreover, the dominant energy condition produces imaginary values for the sound speed.