Maximum Vertical Load Research Articles

Determination of Minimum Required Halo Pin Force

The motivation for this study is to provide design guidance for a new halo system that minimizes pin loosening. If halo pin loosening can be substantially decreased with a new halo system, then the current standard of care of overtightening halo pins will not be necessary. Accordingly, there is a need to determine the halo pin force that should be applied to ensure adequate fixation. A biomechanical test was performed using cadaver head constructs, a custom halo fixture, and a tensile testing machine in an attempt to determine the relationship between the force required to dislodge a halo ring and the initial halo pin force. Three cadaver head constructs were tested at initial pin forces of 120, 240, and 360 N. For each test, the halo was pulled from a cadaver head with a displacement rate of 2.5 mm/min until the halo ring disengaged from the head. The vertical force that caused disengagement of the halo from the head was determined from the resulting load-displacement curves. A linear regression of the data predicts disengagement forces of 80, 320, and 570 N, respectively, for initial pin forces of 120, 240, and 360 N. The 95% prediction interval of disengagement forces for initial pin forces of 120, 240, and 360 N were +/-130, 120, and 130 N, respectively. A previously published study reported the maximum vertical load on a halo orthosis during patient usage to be 186 N. The lower 95% prediction interval from this study indicates that an average initial pin force of 230 N is necessary to prevent halo pin disengagement from a 186-N vertical load.

A RoBall with an elastic restoring force

We present recent research on the development of the seismic isolator, the RoBall, a rubber container holding a number of metal balls. This version of the RoBall, which in addition to friction includes an elastic restoring force and contains 7 metal balls, took a maximum vertical load of -0.5 MPa and had a force-displacement wavelength of - 450 mm.

重粘土壌におけるトラクタ作業の所要動力測定システムの開発

A measurement system that measures the power requirement of a work machine was developed to clarify the conditions of applicability of pan breakers and trenchers. These implements are used for the improvement of field drainage in the Jahgaru soil region. This measurement system is composed of a multi-channel data logger, a notebook computer, a clinometer, an ultrasonic distance meter that measures the depth of work, a three-point linkage type traction resistance meter, and a torque meter that measures the power requirement. The traction resistance meter that was prepared for a trail product had an error rate within 5%; the range of the maximum vertical load was 5kN, and the maximum moment 20kN·m in the horizontal load was in the range 0-30kN. The time series of the traction resistance, PTO axis torque, work depth, and inclination (pitching) could be measured simultaneously, which facilitated the understanding of the local change in the state of work and the power requirement since this measurement system was used in measuring the work of trenchers.

Suction effects on rockfill compressibility

A conceptual mechanism of rockfill deformation was postulated by Oldecop & Alonso (2001) on the basis of the observed rockfill behaviour in suction-controlled oedometer tests. Rockfill mechanical behaviour was linked to water action by means of some crack propagation phenomena, usually known as subcritical crack growth (Atkinson, 1984). For most rocks, the propagation velocity of cracks depends on the applied loads and the chemical action of water contained within the rock particles. Water action is conveniently measured by the relative humidity or by the total suction. It is believed that such phenomena are involved in rockfill particle breakage, an experimental fact that is well recognised as being part of rockfill volumetric deformation under a wide range of stress states (Kjaernsli & Sande, 1963; Sowers et al., 1965; Fumagalli, 1969; Marsal, 1973). A phenomenological constitutive model was proposed (Oldecop & Alonso, 2001) for one-dimensional compression, in which total suction and total stress are the relevant variables. This initial approach was based on a reduced number of laboratory tests, in which the vertical stress was limited to a maximum of 1 MPa. A new experimental programme was performed on the same material, using a newly developed testing device. A large-diameter (300 mm) oedometer, specially designed for the control of relative humidity by means of an air-flow circulation through the specimen, was built. The maximum vertical load was extended to 2·8 MPa in order to investigate the material behaviour in a load range common to rockfill dam structures. New features of rockfill behaviour were observed during this experimental programme. These are described in the paper. Moreover, the previously proposed constitutive model has been reformulated in order to extend its capabilities to cover these new features.

Suction effects on rockfill compressibility

A conceptual mechanism of rockfill deformation was postulated by Oldecop & Alonso (2001) on the basis of the observed rockfill behaviour in suction-controlled oedometer tests. Rockfill mechanical behaviour was linked to water action by means of some crack propagation phenomena, usually known as subcritical crack growth (Atkinson, 1984). For most rocks, the propagation velocity of cracks depends on the applied loads and the chemical action of water contained within the rock particles. Water action is conveniently measured by the relative humidity or by the total suction. It is believed that such phenomena are involved in rockfill particle breakage, an experimental fact that is well recognised as being part of rockfill volumetric deformation under a wide range of stress states (Kjaernsli & Sande, 1963; Sowers et al., 1965; Fumagalli, 1969; Marsal, 1973). A phenomenological constitutive model was proposed (Oldecop & Alonso, 2001) for one-dimensional compression, in which total suction and total stress are the relevant variables. This initial approach was based on a reduced number of laboratory tests, in which the vertical stress was limited to a maximum of 1 MPa. A new experimental programme was performed on the same material, using a newly developed testing device. A large-diameter (300 mm) oedometer, specially designed for the control of relative humidity by means of an air-flow circulation through the specimen, was built. The maximum vertical load was extended to 2·8 MPa in order to investigate the material behaviour in a load range common to rockfill dam structures. New features of rockfill behaviour were observed during this experimental programme. These are described in the paper. Moreover, the previously proposed constitutive model has been reformulated in order to extend its capabilities to cover these new features.

Aircraft Landing Impact Parametric Study with Emphasis on Nose Gear Landing Conditions

A parametric approach to simulation of landing impact, with pitching and heaving degrees of freedom of the aircraft motion, has been used to determine the response of the main and nose gears. Compared to each gear's independent behavior, there are important differences in the landing conditions and in the resulting vertical loads and displacements when these aircraft motions are included. For main gears, the maximum vertical loads are almost linearly dependent on the sinking speed, but there is some variation in the proportion of kinetic energy absorbed. For nose gears, no similar validity exists, compared with the single gear results. Correlation with aircraft sinking speed is absent, but the response is sensitive to the values of initial pitch angle and pitch inertia. This is associated with the equivalent mass and its motion at this location, which are greatly affected by these input quantities and by the aircraft scale.

Structural safety assessment under the low temperature of KSTAR superconducting magnet-supporting post

A magnet-supporting post installed between the lower TF coil cooled by 4.5 K supercritical helium and the cryostat base is one of the most important components of the superconducting magnet-supporting structure for KSTAR Tokamak. This structure should be flexible to absorb thermal shrink of the magnet and should also be rigid to support the magnet weight and the plasma disruption load. The post was designed with stainless steel (SS) 316 LN and carbon fiber reinforced plastic (CFRP) that has low thermal conductivity and high structural strength at low temperature. In order to verify the fabricability and the structural safety, a whole scale prototype of the KSTAR magnet-supporting post was manufactured and tested. Both static and compressive cyclic load tests under the maximum plasma vertical disruption load and the magnet dead weight were performed. The test results showed that the magnet-supporting post of KSTAR Tokamak was fabricable and structurally rigid.

体操競技における着地動作および着地荷重の解析

For the purpose of studying evaluation methods of shock absorption and stability of gymnastics landing mats, we did experiments of jumps and landings in men's gymnastic vault with five toy-level male gymnasts. The landing performances and landing loads on four common skills were examined by 3-D high-speed video analysis and measurement of landing load with force plate. Consequently, we clarified the ranges of and the correlations between the parameters, namely, velocity and angle of the center of gravity, angular velocity of spin and twist, and maximum vertical and, horizontal load, etc. in the landing. The results were as follows: 1) The verticla velocity of the center of gravity on landing averaged from -5.2 to -6.0m/s in each vaulting skill. The horizontal velocity (longitudinal direction) averaged from 3.4 to 3.9m/s. 2) The angular velocity of spin on landing averaged 310, 620, 550, 500deg/s in 'Handspring forward and salto forward tucked', 'Cuervo stretched', 'Kasamatsu stretched' and 'Kasamatsu stretched with 1 / 1 twist', respectively. The angular velocity of twist averaged 20, 90, 215, 265deg/s. 3) The landing angles were different according to the landing direction. Namely, the landing angle of' Cuervo stretched', 'Kasamatsu stretched' and 'Kasamatsu stretched with 1 / 1 twist' averaged from 50 to 55 deg, and that of' Handspring forward and salto forward tucked' averaged 70 deg. 4) The extents of maximum vertical load, in the four skills ranged from 5.0kN to 9.5kN and their weight-ratios ranged from 8 r to 15. The maximum horizontal load extents ranged from 0.8kN to 3.8kN and their weight-ratios ranged from 1.5 to 6.5.

Effects of external trunk loads on lumbar spine stability

Stability of the lumbar spine is an important factor in determining spinal response to sudden loading. Using two different methods, this study evaluated how various trunk load magnitudes and directions affect lumbar spine stability. The first method was a quick release procedure in which effective trunk stiffness and stability were calculated from trunk kinematic response to a resisted-force release. The second method combined trunk muscle EMG data with a biomechanical model to calculate lumbar spine stability. Twelve subjects were tested in trunk flexion, extension, and lateral bending under nine permutations of vertical and horizontal trunk loading. The vertical load values were set at 0, 20, and 40% of the subject’s body weight (BW). The horizontal loads were 0, 10, and 20% of BW. Effective spine stability as obtained from quick release experimentation increased significantly ( p<0.01) with increased vertical and horizontal loading. It ranged from 785 (S.D.=580) Nm/rad under no-load conditions to 2200 (S.D.=1015) Nm/rad when the maximum horizontal and vertical loads were applied to the trunk simultaneously. Stability of the lumbar spine achieved prior to force release and estimated from the biomechanical model explained approximately 50% of variance in the effective spine stability obtained from quick release trials in extension and lateral bending (0.53< R 2<0.63). There was no such correlation in flexion trials. It was concluded that lumbar spine stability increased with increased trunk load magnitude to the extent that this load brought about an increase in trunk muscle activation. Indirectly, our data suggest that muscle reflex response to sudden loading can augment the lumbar spine stability level achieved immediately prior to the sudden loading event.

Basin formation behind an active subduction zone: three‐dimensional flexural modelling of Wanganui Basin, New Zealand

AbstractSouth Wanganui Basin is a Plio‐Pleistocene basin formed behind the Hikurangi subduction zone of the North Island, New Zealand. The active Benioffzone lies about 30–40 km beneath the centre of Wanganui Basin. We attribute the development of this basin primarily to frictional shear between the subducted Pacific plate and overriding Australian plate. This frictional interaction harnesses part of the ‘slab pull’ force of plate tectonics to deform the overriding plate and create the basin. The overall shape of the basin is modified to a lesser extent by the effects of uplift around the basin margin and by in‐plane compressional stress. A quantitative three‐dimensional model, based on flexure of a thin elastic sheet with spatially varying rigidity, is used to test the implications of our hypothesis. A maximum vertical loading stress of about 85 MPa is required to produce the vertical deformation in Wanganui Basin, and that in turn implies about 170 MPa of shear stress at the inclined subduction thrust. A vertical stress of 85 MPa applied over a 40‐km‐wide subduction thrust represents about 50% of the magnitude theoretically present in the ‘slab pull’ force. The effective elastic thickness (Te) of the flexed plate that provides the best fit to the observed deformation is 10 ± 5 km; such a low value of 7“e is attributed to the high plate curvature and high strain rates associated with Wanganui Basin. Constraints on our analysis are provided by seismic reflection, seismicity, gravity, geodetic and geological data. A similar situation to Wanganui Basin, in which a high‐friction subduction thrust induces shortening and flexure of the overlying crust, may be found in the Puget Sound area of Washington State, USA.

支台歯形成時の切削圧の測定

When a vital tooth is cut or ground with air turbine handpiece, the load applied on the tooth should be controlled to be moderate, because too high a grinding load may cause pain or pulpal damage of the patient. In this study, the applied revolution and load in tooth-grinding were measured with use of a testing apparatus designed for giving instruction to dental students in proper grinding technique. The data were compared between the dentists in our department (skilled group) and the students (unskilled group). The results were summarized as follows : 1. Recorded load in tooth-grinding 1) The maximum vertical load detected was less than 100 g in the skilled group. 2) The unskilled group showed higher load than the skilled group. 3) In the unskilled group, the load was lower in woman group than in man group. 4) In the skilled grrup, there was no significant difference in the load for grinding between the dentists having 1 to 4 years' experience and those over 7 years'. 2. Recorded revolution in tooth-grinding 1) There was no significant difference in the average revolution of the air turbine between the unskilled and skilled groups. 2) In the unskilled group, the revolution was higher in woman group than in man group. 3) In the skilled group, there was no significant difference in the revolution between the dentists having 1 to 4 yearas' experience and those over 7 year'. 3. Correlation between recorded load and revolution in tooth-grinding 1) In all the groups, the load for grinding was negatively correlated with the revolution detected. 2) The skilled group showed a common tendency to increase the load for grinding more than the unskilled group as the revolution was decreased.

Experimental production of forward dislocation in the human cervical spine.

Entire human cadaveric cervical spines with the basiocciput were subjected to load in a compression apparatus to simulate the clinical situation of forward dislocation. The movements were recorded by lateral cineradiography. Vertical load was measured by a potentiometric transmitter synchronised with each frame of the cineradiograph. The lower part of the spine was flexed and fixed, and the upper extended and free to move forward. Vertical compression then produced bilateral dislocation of the facets without fracture. If lateral tilt or axial rotation occurred as well, a unilateral dislocation was produced. The maximum vertical load was only 145 kilograms, and coincided with the rupture of the posterior ligament and capsule and the stripping of the anterior longitudinal ligament, but this occurred before dislocation. The low vertical load indicates a peculiar vulnerabiity of the cervical spine in this position and correlates well with the minor trauma often seen in association with forward dislocation.

Dual extremum principles relating to optimum beam design

Of concern is a cantilever beam resting on an elastic foundation and supporting a load at the free end. The beam is of rectangular cross section and of constant height but variable width. It is required to taper the beam for maximum strength. This means that the beam is to support a maximum vertical load W at the free end when the free end is given unit deflection. The constraint is that the weight of the beam should not exceed a given bound K. It is shown that the optimum taper should be so chosen that the curvature of the beam is constant. This yields the solution of the problem in terms of explicit formulas. For more general constraints, an inequality is found which gives upper and lower bounds for the maximum load W even though explicit formulas are not available.