JB/T 7079-1993 Spring-driven impact tester and its calibration JB/T7079-1993 standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Spring-driven impact tester and its calibration JB/T7079
This standard refers to the International Electrotechnical Commission (IEC) Publication 817 "Spring-driven impact tester and its calibration". 1 Subject content and scope of application
This standard specifies the structure, use and calibration of spring-driven impact testers. This standard applies to spring-driven impact testers that test the mechanical strength of electrical equipment by impacting the test sample. 2 Reference standards
GB9342 Plastic Rockwell hardness test method
3 Structure
3.1 The structure of the spring-driven impact tester (hereinafter referred to as impact tester) is shown in Figure 1. The impact tester consists of three main parts: the main body, the impact element and the spring-loaded release cone. Release dimensional body
α19.2±0.1
27.5±0.1
Dimensional body spring
818.5±0.1
Release rod
Spring
Figure 1 Spring-driven impact tester
Release mechanism spring
Release claw
Spherical firing knob
3.2·The main body includes: housing, impact element guide sleeve, release mechanism and all parts rigidly fixed thereon. The mass of this assembly is 1250±10g.
3.3The impact element includes: hammer head, hammer shaft and spherical firing knob. The mass of this assembly is 250±1g. The top of the hammer head is a hemispherical surface made of polyamide with a Rockwell hardness of HRR100. The radius of the hemispherical surface is 10mm. The assembly position of the hammer head on the hammer shaft should be such that when the impact element is released, the distance from the top of the hammer head to the front plane of the cone is approximately the spring compression shown in Table 1. The Rockwell hardness of polyamide is measured by Rockwell hardness tester R scale according to GB9342. Approved by the Ministry of Machinery Industry on October 8, 1993
1994-0101 Implementation
JB/T 7079-~1993
3.4 ​​The mass of the cone is 60g. When the release claw is in the release position of the impact element, the pressure of the cone spring is about 5N. The force of the release mechanism spring should be adjusted to just keep the release claw in the meshing position and it is required that this force should not make the force of releasing the impact element exceed 10N.
3.5 The adjustment device of the hammer shaft, hammer head and spring should be configured so that when the top of the hammer head passes about 1mm before the impact surface, the hammer spring releases all its accumulated energy.
In the last 1mm of the impact element's movement before it impacts, the free moving mass has only kinetic energy and no other stored energy except friction. After the top of the hammer head passes the impact surface, the impact element should be able to continue to move freely without hindrance for at least 8mm. The impact tester is calibrated according to Chapter 5. So that when the impact tester is kept in a horizontal position, the impact element has the kinetic energy value specified in Table 1 just before the impact.
The impact energy for various types of equipment is specified by the relevant standards. Table 1
Energy just before impact
0.2±0.02
0.35±0.03
0.50±0.04
0.70±0.05
1.00±0.05
The kinetic energy E just before impact can be calculated by the following formula: E=0.5FC×10-3(J)
Where: F——Force applied when the hammer spring is compressed to the specified value (N) C—Compression of the hammer spring (mm)
The actual value of the kinetic energy just before impact should be obtained by the method described in Chapter 5. Approximate value of spring compression
In order to avoid frequent adjustment and calibration, it is recommended to set up a set of impact testers for each kinetic energy value and calibrate each impact tester.
4 Operation of the impact tester
The impact is applied by pushing the release cone of the impact tester in a direction perpendicular to the relevant surface against the appropriate part of the test sample. The pressure should be slowly increased when pushing the cone so that the cone moves backward relative to the impact tester body until it contacts the release lever, which activates the release mechanism and allows the hammer to impact. The specimen is fixed or placed on a rigid support surface as a whole as in normal use. Before applying the impact, the fixing screws of the base, cover and similar parts of the specimen are tightened with a torque equal to that applied in normal use. Note: To ensure that the specimen is supported permanently, it may be necessary to place it on a brick, concrete or similar solid surface, covered by a polyamide board close to the wall. In this case, care should be taken that there is no obvious air gap between the wall and the board. The polyamide board must have a Rockwell hardness of HRR100 and a thickness of at least 8 mm, and the area of ​​the plane is not subjected to excessive mechanical stress due to improper support. For similar equipment, concrete blocks with a mass of not less than 15 kg can be used as permanent supports. The number of impacts on the sample, the location of the impact and the torque of tightening the screws are specified by the standards of the relevant samples. 5 Correction
5.1 Structure of the correction device
The main component of the correction device is the pendulum shown in Figure 2, which is fixed to the spring made of spring steel at the lower end. The dimensions of the spring are listed in Figure 3.
Figure 2 Pendulum
The spring does not need to be quenched.
JB/T7079—1993
Figure 3 Steel spring
Figure 4 shows the assembled correction device, except for the frame. The main parts are bearing a, damping pointer b, release base c and release device d. Figure 5. is an enlarged view of these parts. In order to obtain suitable friction characteristics of the pointer. A piece of thick fabric is placed between the metal surfaces of the bearing, and the carbon spring steel wire is bent to apply a small force to the fabric.
Since the release device must be removed during the correction of the correction device, the fixation of the release device to the release base is connected by screws. Figure 4 Correction device
a-bearing b-damping pointer e-release base d-release device 85
5.2 Correction method of correction device
Auni pointer
JB/T7079-1993
Release base
Figure 5 Detail of correction device
The correction device is calibrated with a special impact element that is not in the impact tester. d
Release device bzxz.net
The impact element is suspended by 4 linen threads b, and the suspension point is located at the same level 2000mm above the contact point when the spring C and the impact element are in the static position.
The impact element should be able to swing towards the spring, and the contact point in the dynamic situation should be no more than 1mm below the static contact point. Then the suspension point should be raised by a distance equal to the distance between the two contact points. When adjusting the suspension system, the axis of the impact element should be at right angles to the impact surface of the spring, and the axis of the impact element should be in a horizontal position at the moment of impact.
The calibration device should be placed in such a position that when the impact tester is calibrated, the head of the impact element of the impact tester is exactly located at the static position of the impact element of the calibration device when the impact is applied. In Figure 6, only the pendulum part is listed. An error of 1 mm in the vertical direction will cause a loss of about 0.8% calibration error. Before calibration, the release device should be removed from the calibration device. Two linen threads can also be used to hang the impact element, but it is necessary to ensure that the axis of the impact element is at right angles to the spring plane of the pendulum. And adjust it so that after the impact, the impact element returns exactly to the track before the impact. In addition, it should be noted that the line closest to the head of the impact element should be sufficiently far from the top of the impact element to avoid interfering with the pendulum and the damping pointer.
In order to obtain reliable conclusions, the calibration device should be rigidly fixed to a support such as a member of a building. Calibration is performed with an impact energy of 1J, which can be obtained by dropping the impact element 408±1mm. The drop height is measured at the center of gravity of the impact element. The drop height can be conveniently measured using two glass tubes d. The two glass tubes are connected by a hose, and one of the glass tubes is fixed and attached with a ruler.
The impact element can be kept at a high position with a thin wire f, and it can be released when the thin wire is broken. As shown in Figures 4 and 7, a circular plate is used to make an impact energy scale. A circle is drawn on the scale plate. The center of the circle coincides with the center of the pendulum's bearing point and the radius of the circle is larger than the tip of the damping pointer. When the damping pointer contacts the stationary pendulum, the position of the damping pointer on the scale is the OJ point. The 1J point on the scale is obtained by swinging the suspended impact element from a height of 408 ± 1mm ​​to the spring impact point of the pendulum. 86
JB/T70791993
10 impact operations are to be performed, and the average value of the 10 indications of the damping pointer is the point of 1 value. The other points on the scale are determined as follows: draw a straight line through the center of the circle and point OJ, project point P from point 1J on the circle onto this line, divide the line segment OP10 into equal parts, draw perpendiculars to OP through each of the equal parts, and the intersection of these perpendiculars with the circle corresponds to the impact energy values ​​of 0.1, 0.2, 0.3 up to 0.9J. The same method can also be used to extend the scale to points beyond 1J. 160
Figure 6: Calibration Preparation of the calibration device
5.3 Use of the calibration device
Figure 7 Graduation of the scale plate
In order to obtain correct results, the calibration device should be rigidly fixed to the support. For example, on the components of a building. When calibrating the impact tester, it should be placed on the base and then operated three times with the release device. The impact tester should not be directly operated by hand. Each operation should turn the impact element to a different position. The average of the three readings of the calibration device is considered to be the actual value of the impact energy of the impact tester.
Additional Notes:
This standard was proposed and managed by the National Electric Tool Standardization Committee. This standard was drafted by the Shanghai Electric Tool Research Institute of the Ministry of Machinery Industry. The main drafter of this standard was Lu Tiemin.
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