Axial Force Measurement Research Articles

Biologically-Inspired Bodies Under Surface Waves—Part 1: Load Measurements

Measurements have been carried out in a tow tank on cylindrical bodies submerged in proximity of traveling surface waves. Two bodies are considered: a reference plain cylinder and another cylinder containing a pair of wings (or hydrofoils) below the cylinder, not above. The latter body owes its origin to certain species of fish which has small wings for maneuverability. The wavelength of the surface waves (λ) is of the order of the cylinder length (L) or higher (1 < λ/L < 10). Temporal measurements of axial and vertical forces and pitching moments, phase matched to the surface elevation of traveling waves, have been carried out. The time periods of the waves and depth of water pertain to deep water and intermediate depth waves. The forces and moments exhibit characteristic phase relationship with water elevation. Towing affects only vertical forces in the speed range of 0 to 1 m/s. The effect of towing and surface waves on vertical forces is roughly additive. Within the low speed range of towing evaluated, the effects of surface waves dominate those of towing. The presence of the hydrofoil and intermediate depth waves bring in some additional effects which are not well understood. In intermediate depth waves, a small plain cylinder may encounter a resonance with traveling waves which can be averted by attaching a pair of small wings to dampen pitching moment and make it speed invariant, although at a cost of increased vertical forces.

A Plexiglas Research Pump With Calibrated Magnetic Bearings/Load Cells for Radial and Axial Hydraulic Force Measurement

A research pump intended for both flow visualization studies and direct measurement of hydrodynamic radial and axial forces has been developed. The impeller and the volute casing are constructed from Plexiglas which facilitates optical access for laser velocimetry measurements of the flow field both inside the impeller and in the volute casing. The pump housing is designed for flexibility allowing for each interchange of impellers and volute configurations. The pump rotor is supported by three radial magnetic bearings and one double acting magnetic thrust bearing. The magnetic bearings have been calibrated to characterize the force versus coil current and air gap relationship for each bearing type. Linear calibration functions valid for rotor eccentricities of up to 2/3 of the nominal bearing clearances and force level of ±58 N (13 lbf) and ±267 N (60 lbf) for the radial and axial bearings, respectively, were found. A detailed uncertainty analysis of the force calibration functions was conducted such that meaningful uncertainty bounds can be applied to in situ force measurements. Hysteresis and eddy current effects were quantified for each bearing such that their effect on the in situ force measurements could be assessed. By directly measuring the bearing reaction forces it is possible to determine the radial and axial hydraulic loads acting on the pump impeller. To demonstrate the capability of the magnetic bearings as active load cells representative hydraulic force measurements for a centered 4 vane 16 degree log spiral radial flow impeller operating in a single tongue spiral volute casing were made. At shut-off a nondimensional radial thrust of 0.084 was measured. A minimum nondimensional radial thrust of about 0.007 was observed at the nominal design flow. The nondimensional radial thrust increased to about 0.019 at 120 percent of design flow. The nondimensional axial thrust had a maximum at shut-off of 0.265 and decreased steadily to approximately 0.185 at 120 percent of design flow. Two regions of increasing axial thrust, in the flow range 75 to 100 percent of design flow, were observed. The measurements are compared to radial and axial force predictions using classical force models. The direct radial force measurements are compared to a representative set of radial force measurements from the literature. In addition, the directly measured radial force at design flow is compared to a single representative radial force measurement (obtained from the literature) calculated from the combination of static pressure and net momentum flux distribution at the impeller exit.

A new mathematical model to predict cavern diameters in highly shear thinning, power law liquids using axial flow impellers

An axial force model is described for predicting cavern diameters in highly shear thinning liquids using axial flow impellers. The model has been verified experimentally by measuring cavern sizes in viscous and shear thinning Carbopol solutions with SCABA 3SHP1 impellers. The proposed force model considers the total momentum imparted by the impeller as the sum of both tangential and axial components and assumes a torus-shaped cavern. It combines torque and axial force measurements with the simple power-law equation to predict the cavern diameter with the cavern boundary defined by a limiting velocity. The proposed new model is capable of predicting the measured cavern diameters for Re > 20 and is valid for sizes greater than the impeller diameter but less than the vessel diameter. This approach is also shown to be superior to the traditional Elson and Nienow yield stress model in extremely shear thinning fluids whose flow curve can be well-fitted by the power-law equation. In principle, the model can also be applied to caverns generated by radial flow impellers.

Influence of milling regime on properties of samarium-cobalt powder : N.M.Taliyan et al. Poroskovaya Metall., no 5/6, 1996, 100–103. (In Russian.)

The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants. A hex bolt sample was prepared in the following steps: 1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area; 2) nickel(Ni) film coating as a glue layer on the surface of the bolt; and 3) Ag-Pd alloy coating on the Ni film. The films were deposited by using a direct current(DC) magnetron sputtering system. The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient, which was determined using axial force measurement. A 500 nm-thick Ag-Pd (80:20, molar ratio) alloy film has the lowest friction coefficient of 0.109. A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd (80:20) alloy film or N-5000 oil. In a cycle, the bolts were inserted into a block using a torque wrench, which was followed by heating and disassembling. After only one cycle, it was not possible to remove the bolts coated with the N-5000 oil from the block. However, the bolts coated with the Ag-Pd (80:20) alloy could be easily removed up until 15 cycles.

Wear of alumina ceramics with added oxides of copper, nickel and boron : V.N.Pavlikov et al. Poroshkovaya Metall., no 5/6, 1996, 118–123. (In Russian.)

The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants. A hex bolt sample was prepared in the following steps: 1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area; 2) nickel(Ni) film coating as a glue layer on the surface of the bolt; and 3) Ag-Pd alloy coating on the Ni film. The films were deposited by using a direct current(DC) magnetron sputtering system. The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient, which was determined using axial force measurement. A 500 nm-thick Ag-Pd (80:20, molar ratio) alloy film has the lowest friction coefficient of 0.109. A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd (80:20) alloy film or N-5000 oil. In a cycle, the bolts were inserted into a block using a torque wrench, which was followed by heating and disassembling. After only one cycle, it was not possible to remove the bolts coated with the N-5000 oil from the block. However, the bolts coated with the Ag-Pd (80:20) alloy could be easily removed up until 15 cycles.

Structural transformation of iron powders mechanically processed in nitrogen : D.Shaham et al. (Technion, Haifa, Israel.) Mater. Lett., vol 27, 1/2, 1996, 41–45

The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants. A hex bolt sample was prepared in the following steps: 1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area; 2) nickel(Ni) film coating as a glue layer on the surface of the bolt; and 3) Ag-Pd alloy coating on the Ni film. The films were deposited by using a direct current(DC) magnetron sputtering system. The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient, which was determined using axial force measurement. A 500 nm-thick Ag-Pd (80:20, molar ratio) alloy film has the lowest friction coefficient of 0.109. A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd (80:20) alloy film or N-5000 oil. In a cycle, the bolts were inserted into a block using a torque wrench, which was followed by heating and disassembling. After only one cycle, it was not possible to remove the bolts coated with the N-5000 oil from the block. However, the bolts coated with the Ag-Pd (80:20) alloy could be easily removed up until 15 cycles.

Force, Torque, and Stress Relaxation with Direct Laryngoscopy

In Response: We appreciate the interest in our report of force and torque with direct laryngoscopy. Our laryngoscope handle measured both axial force and torque as shown in Figure 2of our paper [1]. We calibrated the handle with known torques of 0 and 5.6 newton-meters (n-m) by applying a known force, 44.5 newtons (n), at a known moment arm, 0.125 m. Static load testing using varying forces and moment arms confirmed accurate torque readings over the entire calibration range. Dr. Bucx and Dr. Snijders are correct that axial force is sufficient to calculate torque when the effective moment arm of the applied force is known. However, there is no empiric or a priori argument to justify a fixed value of the moment arm during laryngoscopy in patients. Oral structures can exert force along the length of the blade in an unrestricted fashion. For this reason, resolution of force and torque requires at least two transducers. No previous investigators have reported the torque involved in direct laryngoscopy of human subjects. The laryngoscope handle using three transducers described by Chilcoat et al. [2] could measure torque, but to our knowledge, the investigators never reported torque measurements in human subjects. Bucx et al. [3] reported measurements of axial force and discussed how torque could be calculated. Bucx and Snijders correctly state that exerting force on the maxillary incisors would invalidate our data. However, in no case did the laryngoscope blade contact the maxillary incisors during the measurement period. Edward D. Hon, MD Carson City, NV 89702 Randolph H. Hastings, MD, PhD Department of Anesthesiology Department of Veterans Affairs University of California, San Diego San Diego, CA 92161-5085

Three-component force balance for flows of millisecond duration

The authors investigate the feasibility of a new type of multiple-component force balance for measurements on models in hypervelocity hows of millisecond duration. The balance extends the concept of the single component stress-wave force balance to measurement of axial force, normal force, and pitching moment. Numerical modeling of the performance of the balance shows that coupled deconvolution techniques can be used to decouple the signals from axial strain measurements in the balance to determine the applied loads. Experiments performed in the T4 free-piston shock tunnel on a sharp cone at incidence indicate that the prototype balance performs satisfactorily, forces being measured to within 11% of their theoretical values, and the location of the line of force being measured to within 2.1% of the theoretical location as a fraction of model chord.

Mechanical properties of sintered parts made from new low alloy prealloyed powders : M. Yoshida et al (Kobe Steel Ltd Hyogo, Japan)

The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants. A hex bolt sample was prepared in the following steps: 1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area; 2) nickel(Ni) film coating as a glue layer on the surface of the bolt; and 3) Ag-Pd alloy coating on the Ni film. The films were deposited by using a direct current(DC) magnetron sputtering system. The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient, which was determined using axial force measurement. A 500 nm-thick Ag-Pd (80:20, molar ratio) alloy film has the lowest friction coefficient of 0.109. A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd (80:20) alloy film or N-5000 oil. In a cycle, the bolts were inserted into a block using a torque wrench, which was followed by heating and disassembling. After only one cycle, it was not possible to remove the bolts coated with the N-5000 oil from the block. However, the bolts coated with the Ag-Pd (80:20) alloy could be easily removed up until 15 cycles.

Tribological properties of rapidly solidified ternary aluminium-silicon alloys : K. Kondoh, Y. Takeda, (Sumitomo Electric Industries Ltd, Itami City, Japan)

The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants. A hex bolt sample was prepared in the following steps: 1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area; 2) nickel(Ni) film coating as a glue layer on the surface of the bolt; and 3) Ag-Pd alloy coating on the Ni film. The films were deposited by using a direct current(DC) magnetron sputtering system. The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient, which was determined using axial force measurement. A 500 nm-thick Ag-Pd (80:20, molar ratio) alloy film has the lowest friction coefficient of 0.109. A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd (80:20) alloy film or N-5000 oil. In a cycle, the bolts were inserted into a block using a torque wrench, which was followed by heating and disassembling. After only one cycle, it was not possible to remove the bolts coated with the N-5000 oil from the block. However, the bolts coated with the Ag-Pd (80:20) alloy could be easily removed up until 15 cycles.

Application of hot isostatic pressing to preparation of sintered steels : J. Karwan-Baczewska et al (University of Mining and Metallurgy, Crakow, Poland)

The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants. A hex bolt sample was prepared in the following steps: 1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area; 2) nickel(Ni) film coating as a glue layer on the surface of the bolt; and 3) Ag-Pd alloy coating on the Ni film. The films were deposited by using a direct current(DC) magnetron sputtering system. The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient, which was determined using axial force measurement. A 500 nm-thick Ag-Pd (80:20, molar ratio) alloy film has the lowest friction coefficient of 0.109. A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd (80:20) alloy film or N-5000 oil. In a cycle, the bolts were inserted into a block using a torque wrench, which was followed by heating and disassembling. After only one cycle, it was not possible to remove the bolts coated with the N-5000 oil from the block. However, the bolts coated with the Ag-Pd (80:20) alloy could be easily removed up until 15 cycles.

Gastric axial forces in experimentally delayed and accelerated gastric emptying.

The aim of this study was to assess the relationship between altered axial forces and gastric emptying of solids by experimentally inhibiting or stimulating gastric axial forces by intraduodenal lipid or intravenous erythromycin, respectively. In 15 healthy volunteers, we simultaneously measured gastric emptying of solids by scintigraphy, gastroduodenal motility by manometry, and forces along the longitudinal axis of the distal stomach by an axial force transducer. When 25% of the radiolabel had emptied from the stomach, subjects (n = 5 in each group) received normal saline (controls), intraduodenal lipid, or intravenous erythromycin. The test period consisted of the infusion period (10 min) and the subsequent 30 min. Lipid significantly reduced and erythromycin increased axial forces compared with control (lipid: median 0.6 N [0-1.4 interquartile range (IQR)]; erythromycin: median 18.2 N (16.5-20.5 IQR); control: median 4.7 N (3.9-5.2 IQR); P < 0.01). Similarly, antral phasic pressure activities were different relative to control. Gastric axial forces correlated significantly with gastric emptying (Spearman rank correlation = 0.86; P < 0.01). These data are consistent with the hypothesis that axial forces affect gastric emptying of solids and suggest that measurement of axial forces provides an assessment of overall gastric propulsion during the emptying of solids.

Measurement of axial forces during emptying from the human stomach.

Our aim was to measure axial forces in the stomach and to evaluate their relation to circumferential contractions of the gastric walls and the emptying of gastric content. We used a combination of simultaneous radioscintigraphy, gastroduodenal manometry, and an axial force transducer with an inflatable 2-ml balloon fluoroscopically placed in the antrum. In vitro studies demonstrated that the axial force transducer records only antegrade forces along the longitudinal axis of this probe in an intensity-dependent manner. In vivo studies were performed in five healthy subjects for at least 3 h after ingestion of radiolabeled meals. When administered separately, the emptying of liquids or solids from the stomach is associated with generation of antral axial forces and coincident phasic pressure activity; however, almost 20% (average) of gastric axial forces during emptying of liquids or solids are unassociated with proximal or distal antral pressure activity ("isolated" forces). High amplitude antral axial forces and pressures occur during both lag and postlag emptying phases. During emptying of liquids, there is a trend for axial forces to be coincident more often with proximal than with distal antral pressure activity and vice versa for the emptying of solids (P = 0.015). These data suggest that when placed in the antrum, the transducer can semiquantitatively record axial forces during gastric emptying. By combining these observations with the data from in vitro studies, it appears that axial forces predominantly result from traction on the balloon by the longitudinal vector resulting from circumferential gastric contractions. The combination of radioscintigraphy and measurement of antral axial forces is a promising method to evaluate mechanical forces involved in the emptying of the human stomach.

On Some Issues in Triaxial Extension Tests

Abstract Results of triaxial extension tests on dry sand are presented. Special attention is paid to the factors influencing the results in triaxial extension tests. It is found that factors such as accuracy of the axial force measurement, axial force carried by the rubber membrane surrounding the specimen, gravity, and inhomogeneous deformation have a much larger influence on the results in triaxial extension tests than in triaxial compression tests. Accurate measurement of the axial force is achieved by placing the load cell inside the pressure chamber. The influence of the confining pressure on the axial force measurement is avoided through a proper construction. The force carried by the rubber membrane is corrected with reference to the result of a tension test on a strip of rubber membrane. The effect of gravity is accounted for by adding the axial stress due to gravity to the applied axial stress. The inhomogeneous deformation is traced by three lateral strain collars placed along the specimen height. Results of triaxial extension tests cannot be appreciated if these influential factors are not taken into account. The failure mode of the specimen is found to be influenced largely by the initial density. Inhomogeneous deformation in the form of necking develops in the upper part of dense specimens and in the middle of loose specimens. For dense specimens, the necked region becomes wider with advanced deformation and develops into one single or two intersecting shear bands. For loose specimens, however, no shear bands can be observed.

Physiological, morphological, and histochemical properties of cat external anal sphincter.

The contractile properties, morphology, and the distribution of striated muscle fiber types of the external and sphincter (EAS) were determined using axial force measurements, fiber size cross-sectional area measurements, and histochemistry. Electrical stimulation of motor axons in pudendal nerve at supramaximal intensities (10 V, 0.05 ms duration) elicited twitch contractions of EAS. The time to peak force after a single pulse ranged from 37 to 42 ms. The time for relaxation to half-maximal twitch force ranged from 20 to 29 ms. Repetitive stimulation of motor axons (0.1-3.0 Hz) produced potentiation and fatigue of single twitch contractile force, suggesting that the EAS of the cat is comprised predominantly of fast-twitch muscle fibers. Confirmation of skeletal muscle fiber types was determined by histochemistry. Frozen serial cross sections of EAS were incubated to demonstrate succinic dehydrogenase (SDH) and myosin adenosine triphosphatase after alkaline preincubation (pH 10.4). Based on these reactions, muscle fibers were classified as fast glycolytic (FG) (high ATPase, low SDH), fast oxidative-glycolytic (FOG) (high ATPase, high SDH), and slow oxidative (SO) (low ATPase, high SDH). The mean percentage +/- SE of each histochemical type was the following: FG, 73.5 +/- 3.9; FOG, 22.8 +/- 3.7; and SO, 3.7 +/- 0.6. These results indicate that the predominant fiber type for the EAS is FG. The EAS of the cat is considered a nominally fast-twitch muscle.

Axial force measurements for the friction welding of aluminium tubes

Abstract Friction welding experiments were performed in a rigid centre lathe for pure aluminium tubes of thicknesses t = 4.5 and 6 mm. The effects of rotational speeds N in the range 800–2240 rev min-1 and tube vertical end chamfer angles α = 15°, 30°, 45° and 60° on the maximum axial intertube force Fa were investigated. The axial force Fa increased with increasing tube wall thickness t. Fa reached a maximum with increasing spindle speed N and chamfer angle α. The recorded maximum axial forces were found to range between 240 and 175 kgf. A force of 240 kgf was recorded at N = 1600 revmin-1, t = 6 mm and α = 45°.

The prediction and measurement of axial forces, bending moments and accelerations in an engine connecting rod

The graphs, numbered 1–5 reproduced below, were omitted from the above paper. Any inconvenience to the readers is regretted.The author wishes also to acknowledge with grateful thanks the assistance given to him by, the Department of Mechanical Engineering, Lanchester College of Technology, Coventry, where the work was carried out.

The prediction and measurement of axial forces, bending moments and accelerations in an engine connecting rod

An engine connecting rod was fitted with two accelerometers, an axial force bridge and a bending moment bridge. These transducers enabled the acceleration components (along the connecting rod axis and perpendicular to it), the axial force and the bending moment, to be measured at the transducer locations.A theoretical method of analysis was carried out and a computer programme was developed, for use on a PET computer, to execute the repetitive calculations of the above mentioned quantities.The connecting rod was fitted into a Ford two‐litre OHC automotive engine. A few components were manufactured to complete the test rig.Three engine tests were conducted using combinations of engine load and cylinder gas pressure. The outputs from the transducers were recorded on photographic film from a galvanometer recorder. The traces were then analysed to reveal the variation of the dynamic properties with crankshaft angle.The experimental and theoretical results of the three tests were compared. The experimental accelerations and axial force were in close agreement with the predicted results. However, the experimental and the predicted bending moment distribution, did not agree at all well.

Wind-tunnel measurements of dynamic reefing line force in ribbon parachutes

This paper presents the results of a series of wind-tunnel tests conducted to measure the force in ribbon parachute reefing lines. Three-foot diameter ribbon parachute models with porosities of 10-25% were tested in the Vought Systems Low-Speed Wind Tunnel. Simultaneous measurement of parachute axial force and reefing line force allowed the latter to be expressed either as a percent of axial force or as a dimensionless force coefficient. Maximum reefing line forces for 15, 20, and 25% porosity chutes were 4-5% of the axial force. Forces for the 10% porosity chute were considerably higher. The 10% porosity chute also showed a significant dynamic effect, with maximum values considerably higher than those in steady state.

Arterial wall mechanics and composition and the effects of smooth muscle activation.

A comparison of passive mechanics and the effects of smooth muscle (SM) activation has been made in canine carotid and iliac arteries. Measurements of external diameter and axial force were made on isolated cylindrical segments in response to internal pressure variations. Data were obtained during maximal norepinephrine (NE) and potassium (K) activation, and following metabolic inhibition of SM. These data were used to determine wall tangential stress-strain relations. The maximum increase in wall stress after K and after NE was greater for the iliacs and occurred at smaller values of wall strain. Passive stress-strain curves for the iliacs were likewise shifted to smaller strains, suggesting an important role of passive wall elements in setting the length of contractile elements. Diameter responses to K at low values of pressure were the same for iliacs and carotids, but were better maintained at higher pressure levels for the iliacs. Similar findings were found for iliac responses to NE and K. The results suggest that at low values of wall stress, active diameter responses are not strongly dependent on the maximum isometric stress development. However, higher pressure-diameter responses are also determined by the force-generating capacity of SM.