SU1151856A1 - Stand for impact-testing of safety helmets - Google Patents

Abstract

STAND FOR IMPACT TESTS OF PROTECTIVE COSKETS, having a base, a head model for mounting a protective helmet on it, a force sensor mounted on the base under the head model, a drummer, a mechanism for dropping a drummer on a helmet, an accelerometer located on the drummer, and a recording device with which through a matching amplifier and an integrating device is connected to the accelerometer and through another matching amplifier - a force sensor, characterized in that, in order to increase the informativeness of the tests by measuring the maximum displacement helmets on impact, it is equipped with two memory blocks, a zero indicator, a maximum indicator and a subtraction unit, the integrating device is made in the form of two successively connected integrators, the output of the first integrator is connected to the indicator inputs, the output of the second integrator is connected to the information inputs of memory i, the control input of each of which is connected to the output of the corresponding (Lea indicator, and the output - to one of the inputs of the subtraction unit, the output of which is connected to a recording device.

Description

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O5 The invention relates to mechanical testing of products and can most effectively be used in impact testing of protective helmets. A test stand for impact testing of protective helmets is known, comprising a base, a head model for mounting a protective helmet on it, a force sensor mounted on the base under the head model, a drummer, a hammer dropping mechanism onto the helmet and a recording device to which a force sensor 1 is connected via a matching amplifier The disadvantages of the stand are that it does not allow to determine the relative damping capacity and the safe clearance of the protective helmet. The closest in technical essence to the present invention is a shock test stand of protective helmets containing a base, a head model for mounting a protective helmet on it, a force sensor mounted on the base under the head model, a drummer, a mechanism for dropping a drummer on a helmet, an accelerometer located on the drummer. and a recording device with which an accelerometer is connected through a matching amplifier and an integrating device and a force sensor 2 through another matching amplifier. A disadvantage of the known test bench is that it does not allow to determine the maximum movement of the helmet on impact, i.e. the safe clearance of the protective helmet. The purpose of the invention is to increase the informativeness of the tests by measuring the maximum movement of the helmet on impact. The goal is achieved by the fact that the test bench for protective helmets, having a base, a head model for mounting a protective helmet on it, a force sensor mounted on the base under the head model, a drummer, a mechanism for dropping a drummer on a helmet, an accelerometer placed on the drummer and a recording device The accelerometer is connected to it via a matching amplifier and an integrating device and a force sensor through another matching amplifier; it is equipped with two memory blocks, a zero indicator, a maximum indicator and 6 the subtractor, the integrating device is made in the form of two series-connected integrators, the output of the first integrator is connected to the indicator inputs, the output of the second integrator is connected to the information inputs of the memory blocks, the control input of each of which is connected to the output of the corresponding indicator, and the output to one of inputs of the subtraction unit, the output of which is connected to the registering device. FIG. 1 is a block diagram of a crash test bench for safety helmets; in fig. 2 - the dependence of the signal U at the output of the accelerometer on the time; in fig. 3 - time dependence of the signal C / at the output of the first integrator; in fig. 4 dependence of the signal Us at the output of the second integrator on time. The test bench for protective helmets contains base I, model 2 heads for mounting protective helmet 3 on it, force sensor 4 mounted on base 1 under model 2 heads, drummer 5, dropping mechanism (not shown) of drummer 5 on helmet 3, placed Accelerometer 6 is on drummer 5; a recording device 7 with which an accelerometer b is connected through a matching amplifier 8 and an integrating device made in the form of two series-connected integrators 9 and 10 and a force sensor 4 through another matching amplifier 1I. The bench also contains two memory blocks 12 and 13, an indicator 14 zero, a maximum indicator 15 and a subtractor 16, with the output of the first integrator 9 connected to the inputs of indicators 14 and 15, the output of the second integrator 10 to the information inputs of memory 12 and 13 , the control input of each of which is connected to the output of the corresponding indicator 14 or 15, and the output to one of the inputs of the subtraction unit 16, the output of which is connected to the recording device 7. The stand works as follows. During the tests, a protective helmet 3 is put on the model 2 of the head and is mounted on the base of 1 stand. Using the dropping mechanism, the hammer 5 is dropped onto the protective helmet 3, and at the moment of their collision the force sensor 4 generates a signal proportional to the force acting on the head model 2, which after amplification by the matching amplifier 11 is recorded by the recording device 7. The accelerometer 6 generates the signal Ug proportional to the acceleration of the striker 5 when falling and hitting the helmet 3, (Fig. 2), which, after amplification by the matching amplifier 8, enters the input of the recording device 7. The ratio of the registered max The value of the force in the impact process and the corresponding acceleration moment, taking into account the mass of the striker, makes it possible to determine the damping of the protective helmet 3. The signal of the accelerometer 6 after amplification by the amplifier 8 also goes to the integrating device containing two series-connected integrators 9 and 10, where after the first integrating by integrator 9, it is converted into a signal Ut, (FIG. 3), proportional to the speed of the hammer 5, and after the second integration by integrator 10, into a signal Us {FIG. 4), proportional to the displacement of the hammer 5. The signal U, proportional to the speed of the hammer 5 before the impact, increases, reaching a maximum at the moment

ti, immediately preceding the impact of the impactor 5 with the helmet 3, and upon impact decreases to zero during braking on impact. The maximum indicator 15 at time ti, when the signal reaches the maximum value at the output of the first integrator 9, generates a signal that goes to the control input of the memory 13, as a result of which the memory 13 captures the signal Usi from the second integrator 11, corresponding to this moment ti (Fig. 4). When the signal and "at the output of the first integrator 9 becomes close to zero and equal to the threshold of the indicator 14 zero (time t2), the indicator 14 zero produces

a signal arriving at the control input of the second memory block 12, which will capture the value of the signal Us2 of the integrator 10 corresponding to this instant t2. The signals Uji and Us2 from outputs 12 and 13 of the memory are fed to the corresponding input of subtraction unit 16, the output of which receives the difference signal LJs2-Uii, proportional to the maximum movement of helmet 3 upon impact, which is recorded by means of a recording device 7.

The invention allows for shock testing of protective helmets to determine both the damping and the maximum movement of protective helmets upon impact.

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Claims (1)

STAND FOR SHOCK TESTS OF PROTECTIVE HELMETS, having a base, a head model for installing a protective helmet, a force sensor mounted on the base under the head model, a hammer, a mechanism for dropping the hammer on the helmet, an accelerometer placed on the hammer and a recording device with which the matching amplifier and integrating device is connected to the accelerometer and through another matching amplifier is a force sensor, characterized in that, in order to increase the information content of the tests by measuring the maximum movement of the helmet upon impact, it is equipped with two memory blocks, a zero indicator, a maximum indicator and a subtraction unit, the integrating device is made in the form of two successively connected integrators, the output of the first integrator is connected to the inputs of the indicators, the output of the second integrator is to the information inputs of the memory blocks, the control input of each © which are connected to the output of the corresponding indicator, and the output to one of the inputs of the subtraction unit, the output of which is connected to the recording device. Figure 1>