Low-speed Test Research Articles

Evaluating Low-Speed Rear-End Impact Severity and Resultant Occupant Stress Parameters

Automotive Systems Analysis, Inc. (ASA) and Lowell Hicks, Inc. (LHI) have developed a ground-up set of sensor instrumentation and recording method to document vehicle-artifact/occupant-stress parameters occurring from a continuing series of low-speed rear-end multi-vehicle impact tests (approximately 2 to 8 MPH). This work has four goal areas: 1) calculate impacted vehicle (TARGET) barrier equivalent velocity (BEV) from isolator Artifacts; 2) correlate calculated BEV' to occupant stress; 3) calibrate injury potential of occupant stress impulse; 4) compare occupant stress with everyday volunteer activities. The test collision series now includes several different vehicle pairs with varying impact/escape speeds, weight ratios, and parallel parameters from a driver side manikin and passenger side volunteer. Observable physical vehicle isolator artifacts (piston stroke scrapes) were compared with computer-recorded linear sensor time traces, and these data were fitted to a 'calculated BEV' worksheet/algorithm. The worksheet/algorithm method shown here was found to be reasonably repeatable, per vehicle model and series tested. Next, manikin and volunteer occupant stress data, measured along with TARGET vehicle BEVs, were charted and compared with injury-threshold-impulse criteria referenced in the literature. Lastly, the occupant-stress impulses were compared with sample stress impulses for various volunteer physical activities, as a practical calibration of vehicle occupant stress.

Axial compressor performance during surge

There is limited information available in the literature about flow conditions in axial compressors during surge. This article presents detailed measurements from a low-speed test rig instrumented to pick up details of axial and circumferential flow disturbances. The results show that is initiated by rotating stall, and that the ensuing cycle is a sequence of well ordered cause-and-effect events. The differences in cycle behavior between classic surge and deep surge are investigated, and it is shown that the shape of the compressor characteristic determines which of these will occur. From the results it is also concluded that some important factors, such as overall pressure rise and size of hysteresis loop, have not received sufficient attention in existing techniques for predicting the rotating stall/surge boundary. In line with these findings an Appendix by E. M. Greitzer presents a more general version of the B Parameter, which takes into account the influence of compressor design variables on the stalling behavior of the compressor.

The Unstable Behavior of Low and High-Speed Compressors

By far the greater part of our understanding about stall and surge in axial compressors comes from work on low-speed laboratory machines. As a general rule, these machines do not model the compressibility effects present in high-speed compressors and therefore doubt has always existed about the application of low-speed results to high-speed machines. In recent years interest in active control has led to a number of studies of compressor stability in engine-type compressors. The instrumentation used in these experiments has been sufficiently detailed that, for the first time, adequate data are available to make direct comparisons between high-speed and low-speed compressors. This paper presents new data from an eight-stage fixed geometry engine compressor and compares them with low-speed laboratory data. The results show remarkable similarities in both the stalling and surging behavior of the two machines, particularly when the engine compressor is run at intermediate speeds. The engine results also show that, as in the laboratory tests, surge is precipitated by the onset of rotating stall. This is true even at very high speeds where it had previously been thought that surge might be the result of a blast wave moving through the compressor. This paper therefore contains new information about high-speed compressors and confirms that low-speed testing is an effective means of obtaining insight into the behavior of high-speed machines.

Quasi Static Derailment of a Railway Vehicle, Comparison Between Experimental and Simulation Results

SUMMARY This paper describes an ORE B55 derailment test of a CORAIL passenger coach of the SNCF network, equipped with measurement wheelsets. This low speed test is simulated with the VOCO code. Experiments and simulations were executed for a co-operation between SNCF and INRETS-LTN, to evaluate the Dynamic Railway code VOCO, especially about wheel-rail contact conditions.

Fully parallel superconducting analog-to-digital converter

The authors present measurements that follow up on a design of a 3-b wideband analog-to-digital converter (ADC) given by E. Fang et al. (IEEE Trans. Magn., vol.27, no.3, p.2891-4, 1991). The original design has been modified, and some circuit parameters have been changed to optimize the margins. Based on this modified design, the authors have fabricated and were able to demonstrate the functionality not only of simple logic gates, including inverters, AND, OR, NAND, NOR, and XOR, but also of much more complicated combinations, including a complete 2-b ADC and a complete 3-b binary encoder. After a brief description of the design and modifications, low-speed tests of these circuits are presented and discussed. Simulations have shown that the complete 3-b ADC can work up to 5 GHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Correlation of High-Speed Tensile Strength with Collagen Content in Control and Lathyritic Rat Skin

Severity of lacerative skin injury depends on the applied load and the resistance of the tissue. At low (static) rates of loading there is a high degree of correlation between skin tensile strength and the degree of collagen crosslinking, with little added strength due to collagen interactions with the glycosaminoglycan matrix. We examined the effects of high (ballistic) rates of loading in order to determine the contributions to strength made by both the degree of collagen crosslinking and the collagen-matrix interaction. Tensile failure experiments were conducted using the dorsal skin of rats 1.5-6 months of age. Test specimen orientations were cut parallel and transverse to the body axis at cephalad and caudad locations on the dorsum. Tensile strength was measured at nominal strain rates of 30%/sec (low speed) and 6000%/sec (high speed) using both control and lathyrogen fed rats. Biochemical analyses were conducted to determine the amount of total and crosslinked (insoluble) collagen. In low-speed tests, there was a significant correlation ( r ⩾ 0.900) between collagen content and skin tensile strength measured both transverse and parallel to the spine. The degree of correlation was higher with insoluble ( r = 0.973) collagen content than with total ( r = 0.901) collagen. The effect of a lathyrogen diet produced a significant ( P < 0.001) reduction (two- to threefold) in tensile strength compared to control. In both high- and low-speed groups, tensile strength was greatest in the transverse samples with a significant correlation to collagen content ( r ⩾ 0.858). In the high-speed experiments, the skin tensile strength was significantly ( P < 0.001) increased (two- to threefold) compared to low-speed results at each age tested. Because this increase occurred in identical tissues, these data support our hypothesis that the more dynamic strength properties of skin involve the influence of matrix interactions with collagen.

Manufacturing and testing of an air-core compulsator driven 0.60 caliber railgun system

A laboratory-based, small-caliber, electromagnetic launcher and compensated pulsed alternator power supply are being tested. The objective of the program is to develop a compact, lightweight testbed capable of accelerating a salvo of three 32 g masses to 2 km/s at a rate of 10 Hz. The 0.60 caliber, augmented railgun is powered by an 850 kg self-excited, air-core compulsator which develops 674 MW peak power delivered through a solid-state, silicon-controlled rectifier closing switch. The incremental test plan is scheduled to bring the system to full power levels during the summer of 1992. Critical component fabrication and assembly details of the compulsator and supporting subsystems are presented. Early system commissioning and test data are presented, including low-speed (8000 r/min) tests of the compulsator involving external excitation of the field coil.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Similarity Transformations for Compressor Blading

Improving the performance of high-speed axial compressors through low-speed model compressor testing has proved to be economical and effective (Wisler, 1985). The key to this technique is to design low-speed blade profiles that are aerodynamically similar to their high-speed counterparts. The conventional aerodynamic similarity transformation involves the small disturbance potential flow assumption; therefore, its application is severely limited and generally not used in practical design. In this paper, a set of higher order transformation rules are presented that can accommodate large disturbances at transonic speed and are therefore applicable to similar transformations between the high-speed high-pressure compressor and its low-speed model. Local linearization is used in the nonlinear equations and the transformation is obtained in an iterative process. The transformation gives the global blading parameters such as camber, incidence, and solidity as well as the blade profile. Both numerical and experimental validations of the transformation show that the nonlinear similarity transformations do retain satisfactory accuracy for highly loaded blades up to low transonic speeds. Further improvement can be made by only slightly modifying profiles numerically without altering the global similarity parameters.

Effect of high-intensity endurance training on isokinetic muscle power

The purpose of this study was to determine the effects of high-intensity endurance training on isokinetic muscle power. Six male students majoring in physical-education participated in high intensity endurance training on a cycle ergometer at 90% of maximal oxygen uptake (VO2max) for 7 weeks. The duration of the daily exercise session was set so that the energy expenditure equalled 42 kJ.kg-1 of lean body mass. Peak knee extension power was measured at six different speeds (30 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees.s-1) with an isokinetic dynamometer. After training, VO2max increased significantly from mean values of 51.2 ml.kg-1.min-1, SD 6.5 to 56.3 ml.kg-1.min-1, SD 5.3 (P less than 0.05). Isokinetic peak power at the lower test speeds (30 degrees, 60 degrees and 120 degrees.s-1) increased significantly (P less than 0.05). However, no significant differences in muscle peak power were found at the faster velocities of 180 degrees, 240 degrees, and 300 degrees.s-1. The percentage improvement was dependent on the initial muscle peak power of each subject and the training stimulus (intensity of cycle ergometer exercise).

The effects of orientation and location on the strength of dorsal rat skin in high and low speed tensile failure experiments.

The tensile strength of skin is associated, in part, with its potential for laceration from impact. The quasi-static tensile strength of skin depends on orientation. The objective of this study was to determine whether the strength of skin in high speed tensile failure experiments exhibits a similar dependence on orientation. Tensile experiments were conducted at 6000 percent/s and 30 percent/s on dorsal skin of rats aged 1-6 months. Experiments were performed on specimens cut perpendicularly and longitudinally to the spine at cranial and caudal locations. The tensile failure properties depended on location, orientation, age and strain rate. The strength was dependent on orientation to the same degree in high and low speed tests. This helps explain why accident statistics show that skin lacerates preferentially on the body.

The identification of linear and non-linear models of a turbocharged automotive diesel engine

The identification results obtained from a study on a Leyland TL11 turbocharged, direct injection diesel engine are presented. Two sets of data corresponding to low and high engine speed tests, which were recorded from experimental trials on the engine, are analysed. The identification of both linear and non-linear difference equation models are described to represent the relationship between the fuel rack position (input) and the engine speed (output).

The changes in surface properties during running-in process under rolling/sliding condition.

Changes in surface properties during the running-in process, especially those in surface topography and surface hardness, were examined using a two-disc type of machine. The loads applied were lower than the shakedown limit of a test material. Two differen running-in tests were conducted i. e. a low-speed test in which the in which the contact condition was severe, even at an initial stage, and a high-speed test in which the initial thick oil film thickness became thinner and the contact condition became more severe with time. After running-in, the roughness and correlation distance of disc surface were reduced and increased, respectively. The final surface topography was controlled by the initial surface topography and the final film parameter. The surface hardness was also increased after running-in. Consequently, the scuffing resistance of discs was enhanced through the running-in process. The high speed test was excellent in improving surface topography and increasing surface hardness compared with the low speed test where the wear of rubbing surfaces was increased.

High-Speed High-Current Copper Finger Brushes for Pulsed Homopolar Generator Service

ln continuing research into higher energy density, higher current rated pulsed homopolar generators (HPG's), solid copper fingers are explored as sliding electrical contacts to slip speeds of 300 m/s and collector area current densities above 75 MA/m2. Achieving increased compactness in HPG's is easily accomplished by spinning the inertial energy storage flywheel to higher tip speeds but generally involves brush operation at higher Slip speeds. Sintered copper-graphite brushes presently limit slip velocity to 220 m/s and collector area current densities to 7-15 MA/m2, if a reasonable brush wear rate is expected. Development of copper finger brushes began in 1981 by Marshall who performed low speed (15 mm/s) testing at current densities above 450 MA/m2. Based off encouraging results obtained by Marshall, the present investigation focused on characterization of copper finger brushes in an actual HPG operating environment. Experimental data were collected using the Compact HPG System Tester, a working 5-MJ HPG which can deliver current pulses in excess of 1 MA into resistive loads for the evaluation of brush performance. The copper finger brushes tested successfully transferred 1.15 MA at a slip speed of 100 m/s and currents of 600 kA at 180 m/s. Experimental evaluation of effective contact resistance as functions of slip speed, Current transferred, and brush normal force was performed, and the results are discussed. Interfacial heat fluxes due to friction and contact voltage drop for the test conditions were also determined, and then extrapolated to operating levels of 300 m/s and 3 MA. These projections were used to determine the feasibility of rejecting the heat flux through direct injection (transpiration) cooling methods. Although problems with coolant delivery and hydrodynamic forces do exist, the approach holds promise in the continuing effort to extend pulsed HPG brush operating limits.

Ice penetration tests

Exploratory tests of ice penetration were made by driving small blunt cylinders into semi-infinite ice at normal incidence. Three types of laboratory tests were made: (1) drop-weight impact (impact speed 1.4–3.1 m/s), (2) high-speed ballistic penetration (impact speed 83–434 m/s), (3) deep penetration at low speed (0.42–4.23 m/s). Penetration by indenters and projectiles could be characterized by the energetics of the process, with little variation of specific energy as penetration speed changed by orders of magnitude. For blunt penetrators entering ice at −5°C, specific energy was typically in the range 1.5–15 MJ/m 3. Low speed tests provided data on penetration force (and energy) as a function of displacement. The test results were compared with other published laboratory data, and with field test results for bigger projectiles.

A Laser System For Cryogenic Wind Tunnels

Cryogenic wind tunnels have been under active development for several years only. The main advantage of this type of tunnels is the possibility of obtaining high values of Reynolds number on relatively small test models. Moreover, it offers massive reduction of energy required in transonic and low speed testing. The basic idea of the cryogenic wind tunnel is to obtain flow at very low temperature in the order of 120 °k . This temper-ature is reached by injecting liquid nitrogen in the circuit of the tunnel. In order to reach correct simulation of flow on the tested model, the particles of liquid nitrogen must be evaporated completely on entering the test section of the cryo-genic wind tunnel. This paper presents a laser system developed to determine the size-distribution of liquid nitrogen particles carried in the airstream of a pilot cryogenic wind tunnel. The developed sys-tem could be used to determine size distribution functions of particles in aerosols, combustion and in a two-phase-flow ( liquid-gas) generally. It is actually feasible to be applied in this area of experimental investigations.

Speeded performance following head injury in children.

Fifty-one children who has sustained head injuries were divided into mildly, moderately and severely injured groups according to neurological criteria. The groups were matched for age, sex, and injury-test interval. Approximately 1 year after their injuries, patients were tested on speeded and nonspeeded measures of motor, visual-motor, and visual-spatial functioning as well as on the WISC-R. The performance of the mildly and moderately injured groups was similar, with both groups performing significantly faster than the severely injured group on measures of speeded performance. There were few significant differences between groups on measures requiring little speed. In contrast to the results for the other two groups, the severely head-injured group performed significantly worse on the highly speeded tests than on the low speed tests. The findings are discussed in relation to the literature on the cognitive sequelae of head injuries.

Octane Number Requirement Survey of 1982 Japanese Passenger Cars

The Sub-Committee of Octane Number Requirements (ONR) of the Japan Petroleum Institute has made a 1982 ONR survey on 120 Japanese passenger cars, including 39 cars with automatic transmission of 15 different models.Since the 1975 ONR survey, the minimum mileage required to keep stable ONR has been increased to over 6, 000km.Test vehicles and engine types are shown in Table 1.Primary Reference Fuel (PRF) and two types of unleaded Full Boiling Range Reference Fuel (FBRRF), cracked type and mixed type, have also been used as reference fuels.The blending proportions for preparing the FBRRF and properties of the blending stocks are shown in Tables 2 and 3, respectively.The low speed test method was mainly carried out on ten chassis dynamometers belonging to the participant companies and partly at the test track of the Japan Automobile Research Institute.The simulated road load on the chassis dynamometers was set arbitrarily by each participant but the inertia weight on the chassis dynamometer was set equal to the total vehicle weight.The determination of knocking was performed according to the JPI Standard Method 6R-6-77.The low speed knocking was identified in engine speed range from 1, 000rpm to 4, 000rpm during acceleration at the highest gear position.The test results obtained were treated statistically according to the JPI Standard 6R-2-72 in order to calculate the car satisfaction distribution for each of the given octane number fuels.For these statistical data, ONRs of 94 cars surveyed in 1981 were incorporated in the calculations, since the 1982 model cars contain the ones similar to those of the 1981 model cars which have been already tested.These results are shown in Table 8 and illustrated in Fig. 1.The low speed ONRs of 1982 model cars for 50% and 90% market satisfaction with the PRF were 90.8 and 95.7 octane numbers, respectively.The ONR distributions of 1982 model cars are summarized in Tables 5 and 6.

A comparison of dense gas dispersion model simulations with burro series LNG spill test results

The predictions from three vapor dispersion models for cold dense gas releases are compared with the results from several 40 m3 LNG spill experiments conducted at China Lake, California, in 1980. The models vary considerably in the degree to which they approximate important physical phenomena and include restricting assumptions. The simplest model (GD), a modified Gaussian plume model, predicted a vapor cloud that was always too high and too narrow by a factor of 1.5 to 3. The second model (SLAB), a layer-averaged conservation equation model with one independent spatial variable (downwind distance), generally predicted the maximum distance to the lower flammability limit (LFL) and cloud width quite well. SLAB assumes the vertical concentration distribution is nearly uniform so that the vertical concentration gradient (∂c/∂z) is essentially zero from the ground up through most of the cloud and then very steep at the top of the cloud. This was generally not the case in these experiments, especially in the high wind speed tests, where the vertical concentration gradient was found to be more gradual throughout the cloud. The final model (FEM3) is a fully three-dimensional conservation equation model that generally predicted the concentration distribution in time and space rather well. A particular achievement of this model was the prediction of a bifurcated cloud structure observed in one experiment conducted with a low ambient wind speed. Both the SLAB and the FEM3 models accurately predicted the length of time required for the cloud to disperse to a level below the LFL, even in the low wind speed test where the vapor cloud lingered over the source region for a considerable length of time after the LNG spill was terminated.

The Influence of Inlet Conditions on the Performance of Annular Diffusers

Low speed tests have been carried out to investigate the performance and mechanism of flow in two annular diffusers having center bodies of uniform diameter and conically diverging outer walls. In the first part of the investigation the diffusers were tested over a range of naturally developed inlet velocity profiles ranging from near-uniform to fully developed flow. Information is presented concerning the pressure recovery, total pressure loss, and characteristics of the outlet flow. Measurements have also been made of the mean velocity profile and turbulence structure at a number of stations along the length of the diffusers. The second part of the test program was devoted to studying the effects of increased inlet turbulence. The results show a marked improvement in the stability of the outlet flow and gains in pressure recovery, up to a maximum of 20 percent, with only small increases in total pressure loss.

Low-Speed Test Limit of V/STOL Model Located Vertically Off-Center

A vertically off-centered V/STOL model - a 2-ft-diam three-bladed aluminum propeller operating in a rotor mode - is tested in an 8 by 12 ft wind tunnel with and without ground plane along with an associated 3 by 4.5 ft test section insert. The objective was to assess the effect of the vertically off-centered model on the low-speed test limit. The aerodynamic data of the model at a constant negative angle of attack (-3 deg) are recorded at selected tunnel dynamic pressures to provide adequate data points to define the model lift variation with respect to the tip speed ratio. The adverse effect of the rotor low-speed test limit is observed in the form of lift change with respect to the tip speed ratio. A major conclusion is that for rotors tested with a ground plane or in the vicinity of the floor, the ratio of distance between floor and model to rotor radius defines the low-speed test limits.