HG 2724.7-1995 Test method for rubber filaments Determination of tensile stress HG2724.7-1995 Standard download decompression password: www.bzxz.net

Chemical Industry Standard of the People's Republic of China
HG/ T 2724.7 ---1995
idt 1S0 2321: 1983
Test Methods for Rubber Wire
Determination of Tensile Stress
Published on 1995-06-30
Ministry of Chemical Industry of the People's Republic of China
Implementation on 1996-01-01
This standard is formulated by adopting the ninth part of the international standard ISO2321:1983 "Test Methods for Rubber Wire": It is equivalent to it in technical content and writing rules. By adopting international standards and formulating test methods suitable for rubber wire in my country, it lays the foundation for formulating product standards in the future and adapting to the needs of international trade, technology and economic exchanges as soon as possible. Because the test device in the original standard has the following deficiencies, it has been improved: 1. Single chain structure, and no provisions on the length of the fixture (iron bar), which causes measurement errors. Now we use double chain structure, the error is small
2. Spring force measurement, and the data has no self-locking device, which is easy to produce visual errors. Now we use force sensor, digital display, plus self-locking device, the reading is intuitive and the error is small. This standard is issued by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Latex Industry Research Institute of the Ministry of Chemical Industry. The drafting unit of this standard is the Latex Industry Research Institute of the Ministry of Chemical Industry. The main drafters of this standard are Kang Ronghua, Wen Sizheng, and Xia Yingyuan.
ISO Foreword
ISO (International Organization for Standardization) is a worldwide federation of national standards associations (ISO member groups). The work of formulating international standards is carried out through ISO technical committees. Any member group interested in the projects established by the technical committee has the right to participate in the committee. All political and non-governmental international organizations that have contact with ISO can participate in this work. The draft international standards adopted by the technical committees should be sent to all member groups for approval before they can be approved as international standards by the ISO Council.
International Standard ISO2321 was formulated by ISO/TC45 Rubber and Rubber Products\Technical Committee. This second edition is in accordance with the first part of ISO Technical Working Guidelines 6.11.2 of the International Standard was submitted directly to the ISO Council. The first edition replaces the first edition (i.e. ISO 2321:1975) and is approved by the following national member bodies: Belgium
Bulgaria
Canada
Czech Republic
Federal Republic of Germany
Ireland
Israel
Italy
For technical reasons, the following national members have expressed disapproval of this document: United States
Portugal
Romania
This International Standard also replaces Annex 1-1975, Annex 2-[980 and Annex 3-198046
1 Scope
Chemical Industry Standard of the People's Republic of China
Test methods for rubber threads
Determination of tensile stress
This standard specifies the test method for tensile stress of rubber threads. This standard applies to threads made of natural rubber and synthetic polyisoprene rubber. 2 Cited standards
HG / T 2724. 7 —1995
idtISO 2321:1983
The following standards contain provisions that constitute the provisions of this standard through reference in this standard. When the standard is published, the versions shown are valid. All standards will be revised. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB2941-91. Standard temperature, humidity and time for environmental conditioning and testing of rubber specimens (ISO 47t: 1983. ISO 1826: 1981)
HG/T2412.3--92 Test methods for rubber filaments - Determination of density of rubber filaments (ISO 2321: 1983) 3 Terms and symbols
The following definitions are adopted in this standard:
3.1 Initial tensile stress
The tensile stress when an unstressed rubber filament is stretched to a specified elongation is the ratio of the applied force to the initial cross-sectional area of ​​the specimen, in MPa, and is represented by the symbol GMn. 3.2 Relaxation treatment (mechanical conditioning)
An adaptive treatment of the rubber filament to eliminate the influence of storage on the physical properties of the rubber filament and to simulate its conditions for use as much as possible. This treatment is usually done before the test by repeatedly lengthening and retracting the specimen within a slightly larger range near the estimated value point. 3.3 Schwartz value
For the rubber thread after relaxation treatment, at a given elongation, the average value of the stress in the tensile state and the stress in the retracted state is expressed in MPa and denoted by the symbol SV. c is the pre-elongation and n is the elongation when the reading is taken. Both are expressed as a percentage of the initial length. c and n must be integer multiples of 100%. Unless otherwise specified, C=+100% should be selected. During the test, the preferred values ​​are 300% and 500% depending on the type of rubber thread.
3.4 ​​Schwartz hysteresis ratio
For the rubber thread after relaxation treatment, at a given elongation, the ratio of the load in the retracted state to the load in the tensile state. It is represented by the symbol SHR, c is the pre-elongation, n is the elongation when reading, both are expressed as a percentage of the initial length, c and n must be integer multiples of 100%. Unless otherwise specified, c=+100% should be selected. During the test, according to the type of rubber wire, the preferred value of n is 300%500%,
4 Determination of initial tensile stress, Schwartz value, and Schwartz hysteresis ratio 4.1 Apparatus
Approved by the Ministry of Chemical Industry of the People's Republic of China on June 30, 1995, and implemented on January 1, 1996
HIG/T 2724. 7 1995bZxz.net
The test apparatus should be able to stretch and retract the specimen at a given elongation within a rate range of 100±30mm/s, and be able to indicate the load on the cover at any position during the cycle.
Figure 1 shows a schematic diagram of the structure of a suitable device 17
1-frame: 2-lower in-position switch; 3-lower sprocket: 4-chain tea; 5-driven gear; 6-lower shaft; 7-motor 8-upper in-position switch; : 9-in-position baffle; 10-photoelectric switch: 11-lower hanging hook; 12-upper hook 13-photoelectric baffle plate; 14-upper sprocket; 15-upper shaft; 16-sensor; 17-digital display instrument Figure 1 Determination device for fixed tensile stress
This device consists of two chain links (4) and four sprockets (3) and (14) bypassed by them. The lower sprocket (3) is driven by a reversible motor. This motor must have rapid braking and rapid reversal. The rubber ring is stretched between the two hooks (11) and (12) to ensure that the load capacity is met and the overtravel is not exceeded. The lower hook (11) is connected to the chain and the upper hook (12) is connected to the force sensor (16). The signal is then converted to a digital display (17) to read out the load. This device can indicate the load at any position of the balance ring.
4.2 Test steps
4.7.1 Test according to the specification of B2941. 4.2.2 Determine the density of the sample according to the provisions of HG/T2412.3. 4.2.3 Prepare three samples, each of which includes one or more rubber rings with a circumference of 1001mm and the number of turns should be suitable for 48
HG / T 2724. 7 - 1995
Testing capacity of rubber wire count and device.
4.2.4 Before placing the rubber wire on the two hooks, it should be rotated around the fingers so that it is evenly distributed between the hooks. Perform six stretching and retraction cycles continuously according to the elongation. Read the readings at the first cycle (secondary length) and the sixth cycle (extension and retraction) at n elongation. It is allowed to stop the cycle for a short time when reading. 5.1 Cross-sectional area
Calculate according to formula (1)
Where: S—cross-sectional area of ​​the sample, mm\:
-mass, g;
-density of the sample determined according to the provisions of I1G/T2412.3, Mg/m2 (=g/cm\); L is the length of the rubber wire when measuring mass, which is 1m.
5.2 Initial tensile stress GMn, expressed in MPa, is calculated by formula (2):
Schwartz value SV, expressed in MPa; Schwartz hysteresis ratio SHR is expressed in percentage and calculated by formula (3) and formula (4) respectively:
Wherein: F is the load at n elongation (first cycle) during elongation, N; F2 is the load at # elongation (sixth cycle) during elongation, N; F is the load at n elongation (sixth cycle) during retraction, N; S is the initial cross-sectional area of ​​the specimen, mm\;
The number of turns of the test rubber wire.
The initial tensile stress of the rubber wire, Schwarz value and Schwartz hysteresis ratio are expressed by the median value of the three specimens. Test report
The test report should include the following contents:
The source of the specimen and identification mark;
b. Based on the standard:
Test temperature and humidity;
Specimen type;
Test method and device adopted;
Rates of stretching and retracting of rubber wire;
Test results.
Test date:
Tester.
HG /T 2724. 7—1995
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