1、BRITISH STANDARD AUTOMOBILE SERIES BS AU 164:1977 ISO3784:1976 Specification for Measurement of impact velocity in collision tests on road vehicles UDC 629.113:614.864:531.66:531.112.082BSAU164:1977 This BritishStandard, having been prepared under the directionof the Automobile Standards Committee,
2、was published under the authority ofthe Executive Board on 31January1977 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference AUE/-/1/6 Draft for comment75/73852 DC ISBN 0 580 09990 3 Foreword This BritishStandard was prepared under the authority of the A
3、utomobile Standards Committee and is identical with ISO3784:1976 “Road vehicles Measurement of impact velocity in collision tests”, prepared by Technical Committee ISO/TC22, Road vehicles, of the International Organization for Standardization. Terminology and conventions. The text of the Internation
4、al Standard has been accepted as suitable for publication, without deviation, as a BritishStandard. Certain terminology and conventions are used, however, that are not strictly appropriate in a BritishStandard, and attention is therefore drawn to the following. Wherever the words “International Stan
5、dard”, relating to this publication, appear, they should be interpreted as “BritishStandard”. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point (a full stop on the baseline) as the decimal marker. A British Standard does not purpo
6、rt to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front co
7、ver, pagesi andii, pages1 to3 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBSAU164:1977 BSI 0
8、2-2000 i Contents Page Foreword Inside front cover 1 Scope and field of application 1 2 Performance 1 3 Methods of measurement 1 Annex Typical methods of measurement of velocity 2ii blankBSAU164:1977 BSI 02-2000 1 1 Scope and field of application This International Standard lays down the accuracy of
9、 measurement of the impact velocity in collision tests on road vehicles. In addition, some typical methods suitable for the measurement of this impact velocity are described in the Annex. These methods are intended to facilitate the comparison of data obtained in similar tests by different laborator
10、ies. 2 Performance 2.1 The accuracy of velocity measurement shall be1%. 2.2 The impact velocity measurement shall be made within0,2s prior to impact. 3 Methods of measurement Typical methods for measuring impact velocity are described in the Annex. Other methods may be used provided they meet the re
11、quirements of2.1 and2.2.BSAU164:1977 2 BSI 02-2000 AnnexTypical methods of measurement of velocity Velocity measurement methods can be classified in three general categories: a) Doppler effect method; b) summation of the units of distance in a given time (fifth wheel method); c) measurement of the t
12、ime needed to cover a given distance. A.1 Doppler effect method This effect utilizes the apparent frequency variation of a wave in motion. This variation is proportional to the speed of the body in relation to the observer and is governed by the following formula: where f is the apparent frequency;
13、f 0 is the emitted frequency; v 1 is the speed of the wave emitted in an ambient medium; v 2 is the speed of the vehicle. The emitted electromagnetic waves which are generally used are situated in two different wavelength bands: a) centimetric waves: radar with an accuracy that is only of the order
14、of2%; b) micrometric waves: the laser. The laser system, more perfected than the radar system, permits measurements with an error less than1%. It should be noted, however, that the cost of this type of equipment is very high. A.2 Summation of the units of distance in a given time (fifth wheel method
15、) A wheel attached to the rear of the vehicle by an articulated yoke is maintained in contact with the ground by a spring. Mounted axially on this wheel is a disc containing slits spaced regularly around the circumference. A photoelectric transmitter-receiver system is located on either side of the
16、disc. Passage of the slits in front of a photoelectric cell activates a series of impulses corresponding to the distance covered. The summation of these data permits direct reading from a galvanometer, or a recording on an ultra-violet oscillograph. Careful machining permits an accuracy of the order
17、 of1%. An alternative method is to use an induction proximity sensor in place of the photoelectric receiver. Its advantages are simpler assembly and resistance to weather. A further variation involves attaching the transmitter directly to a rear wheel of the vehicle instead of the fifth wheel. In th
18、is case it is difficult to calibrate the system and there must be no tyre slip at the road surface. However, the calibration must be carried out carefully. A.3 Measurement of time needed to cover a given distance The following typical methods are in general use: A.3.1 System using a photoelectric ba
19、rrier A transmitter and a receiver are located on either side of a shutter in a U-shaped arrangement fixed rigidly on the vehicle. The transmitter consists of a lamp emitting a light beam with essentially parallel rays which illuminate a photoelectric cell which constitutes the receiver. Successive
20、cutting of the light beam by the arms of the U start and stop a digital chronometer. The transmitter is placed approximately1m from the receiver. A diaphragm can be placed on the receiver to limit parasitic reflections. The cutting of the beam is effected by means of a shutter in a U shape mounted o
21、n the side of the vehicle. This mounting should be very rigid in order to avoid any deflection tending to spread or tilt the two arms, thus altering their separation. The spacing between the arms of the U should be known within approximately0,2%. The U is painted matt black to avoid any reflections.
22、 The passage of the first arm of the shutter through the barrier produces a variation in voltage at the amplifier. This difference in potential applied at entrance A of a digital chronometer whose time base is regulated to10 5 s, initiates the time recording. When the second arm obscures the receive
23、r, it produces a new voltage variation at entrance B of the chronometer, stopping the recording. The accuracy with this system is very high and can be better than1%. A.3.2 System with induction proximity sensor The receiver is of a cylindrical form and has dimensions of approximately60mm in length w
24、ith a diameter of11mm. The receiver includes an electronic amplifier within the sensor. The sensor is an oscillator which is stopped when a metallic body passes in front of the active extremity of the receiver. The power supply required by this receiver is24V d.c. The output current can attain40mA f
25、rom a receiver having a resistance of6007, with a response time of150s. A digital chronometer is started and stopped by the metallic body passing close by. f v 1 f 0 v 1 v 2 - =BSAU164:1977 BSI 02-2000 3 The accuracy of this system is better than1%. Durability is also very good due to the fact that
26、there is no direct contact. This procedure can only be utilized if the vehicle is perfectly guided, the maximum detection distance being5mm. A.3.3 Equipment utilizing electromagnetic beam barriers Two centimetric transmitters and two receivers are located on each side of the test track at an interva
27、l of at least1m. Passage of the vehicle interrupts the beams. Interruption of the first beam actuates the circuit of the chronometer; interruption of the second stops the circuit. The major drawback of this system is its high cost. Assuming that the axes of the beams from the two transmitters are pe
28、rfectly parallel, the principal source of error comes from measurement of the spacing of the receivers. It is considered that this system provides an accuracy better than1%. A.3.4 Cinematographic procedure The impact velocity can also be measured by use of high-speed cinematography, of the order of5
29、00 to2000 images per second. A clearly visible target is placed on the vehicle and its displacement in relation to a ground target is measured on a certain number of film images. The time is derived on the basis of the camera time based on an impression on the margin of the film of a small flash eve
30、ry0,01s or0,001s, contingent on the film speed chosen. To obtain the time measurement, another method can be utilized by filming a disc operated by a small synchronous motor. The accuracy of this procedure depends on: a) the grain of the film, which can cause blurring of the image; b) the time base
31、of the camera. Analysis of the films must be effected with equipment permitting positioning of the film within 15m, a resolution of1/20mm in X and Y and22 of angle in . In order to minimize parallax errors, the cameras must be positioned as far away as possible and be equipped with long focal length
32、 lenses compatible with the field to be filmed. To obtain accuracies of1%, very detailed attention to equipment and technique is required. A.3.5 System of plates actuated by the vehicle wheels A.3.5.1 Metallic plates Two flexible metallic plates, separated from each other and arranged across the tes
33、t track, are put in contact by the pressure of the front wheels of the vehicle. Coupled with a direct current generator, this contact actuates a digital chronometer. Thepassage of the rear wheels re-closes the contact and stops the chronometer. Knowing the time required to cover a given distance, i.
34、e.thewheelbase of the vehicle, it is simple to derive the velocity. This procedure is not very precise owing to the disparity of the pressures engendered by the front wheels and the rear wheels. This drawback leads to the use of a variation of this procedure which consists in placing two identical s
35、ets of plates across the track. The actuation and stopping of the chronometer are then caused by the front wheels alone. If the contact is subjected to repeated actuation and wear is not apparent, it is possible that after several tests the velocity measurement would be affected by erratic release.
36、A.3.5.2 Pneumatic plates In this version, the receiver consists of a rubber tube closed at one end. Passage of the vehicle over the tube produces a pressure variation, which actuates an electrical contact formed from a movable element and a stationary element. Time measurement is achieved in the sam
37、e manner as with the metallic plates equipment.BS AU 164:1977 ISO3784:1976 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international
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