This standard is applicable to the determination of shear elastic modulus, shear proportional limit, shear strength and shear stress-strain curve of resin castings used in fiber reinforced plastics. GB/T 4726-1984 Torsion test method for resin castings GB/T4726-1984 Standard download decompression password: www.bzxz.net

Scope of application
National Standard of the People's Republic of China
Test method for torsion test of resin castings
Standard method of torsion test for resin castingsUDC 678.5. 017
GB 4726—84
This standard is applicable to the determination of shear elastic modulus, shear proportional limit, shear strength and shear stress-strain curve of resin castings used for fiber reinforced plastics.
2 Test specimens
2.1 The geometric shape and size of the test specimens are shown in the figure (the shape and size of the central holding part are allowed to vary with the chuck of the testing machine). 2'0 =ztp-
110± 0.5
Test specimen geometric shape and size diagram
2.2 The number of test specimens shall comply with GB2567 "General Rules for Test Methods for Mechanical Properties of Resin Castings". 3 Test conditions
The rest74
3.1 Test environment conditions shall comply with GB2567.
3.2 Test equipment is in accordance with GB2567. The accuracy of the torsion angle deformer used is less than ±1% compared with the mirror torsion angle instrument. 3.3 The loading speed is 30~150kgfcm/min (or 20°~60°/min). 4 Test steps
4.1 Sample preparation is in accordance with GH2567.
4.2 Sample appearance inspection is in accordance with GB2567.
4.5 Number the qualified samples, measure the diameter of any flange in the working section of the sample (two orthogonal diameters should be taken when measuring each place, and the calculated diameter is the square root of the product of the two diameters, that is, √D.·Dg), and take the arithmetic mean. The measurement accuracy is 0.02mm. 4.4 Clamp the sample so that the central axis of the sample is aligned with the center line of the chuck. 4.5 Install the torsion angle deformer in the working section of the sample, apply the initial load (about 5% of the failure load), and check the measurement system to make it work normally. 4.6 Install the protective cover, calibrate the alarm point, and record the initial reading. 4.7 Load the balancing spoon continuously, load (or torsion angle) at a certain interval. Record the corresponding torsion angle (or load), record at least 5 times within the proportional limit, and record at least 8 times from the proportional limit to failure. If the testing machine is equipped with an automatic recording device, record the complete torque-torsion angle curve.
1984-10-20 issued by the National Bureau of Standards
1985-09-01 implementation
GB 4T26-84
4.8 Specimens with obvious internal defects or broken outside the upper working section should be discarded. If there are less than 5 valid specimens in the same batch, the test should be repeated. 5 Test results
5.1 The apparent shear stress is calculated according to formula (1): T
Where, t, — apparent shear stress, kgf /cm2 (MPa) M torque, kgf.cm;
D — diameter of the specimen, cm.
Note 1MPa = 1N /mm2~10.2kgt/cm? 5.2 The shear strain is calculated according to formula (2):
Where··D
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Shear strain #
Where—Relative rotation angle of the sections at the two ends of the gauge length on the specimen, degree! L—Gauge length, cm.
5.3 Shear stress is determined by formula (3):
Where: f——shear stress, kgf/cm (MPa) dt.
——the slope of the tangent line at a point on the apparent shear stress-strain curve. (1)
5. Draw a shear stress-strain curve For the torque-torsion angle curve read or automatically recorded, calculate and draw the apparent shear stress-strain (T.-) curve according to formula (1) and (2), and then modify this curve according to formula (3) to obtain the shear stress-strain (-r) curve, see Appendix A (Supplement). 5. Shear proportional limit: The maximum stress on the straight line segment on the apparent shear stress-strain (t, -r) curve is the shear proportional limit Tp [kgf/cm2 (MPa)].
5.6 Shear strength: The maximum stress on the shear stress-strain (-) curve after correction according to formula (3) is the shear strength [kgf/cm2 (MPa)].
5.7 The shear modulus is calculated according to formula (4): G:
Where: G is the shear modulus, kgf/cm2 (MPa), At is the stress increment on the straight line segment of the shear stress-strain curve, kgf/cm22 (MPa) Ar is the strain increment corresponding to Ar.
6 Test report
The test report is in accordance with GB2567.
GB 4726-84
Appendix A
Graphing method
(Supplement)
A.1 Draw the apparent shear stress-strain (T.-r) curve (see figure). To ensure the accuracy of the curve, it is stipulated that the shear stress of 100kgF/cm should not be less than 2cm on the ordinate, and the shear strain of 1% should not be less than 2cm on the abscissa. A.2 Take any point a1 on the curve segment of the above curve graph, and draw a tangent line through point a1 to intersect the axis at Ai. From the figure, we can get: OA, =te-r
A.3 Intercept point B, on 0A, so that AB, =
, and draw a line parallel to Aa from B, intersecting the ordinate c,a of point a1 at point b, cb is the shear stress corresponding to the shear stress-strain (-) curve. A4 Then take ten points a1 on the apparent shear stress-strain (t.-r) curve, and determine ten points b; by the method of finding one point, the number of points i should be at least 8. Connect b, b; to form a shear stress-strain (r) curve. To,
Shear strain +%
G 726-84
This standard was proposed by the State Building Materials Industry Bureau, and the Fiber Additive Standardization Sub-Technical Committee was composed of the Shanghai Fiberglass Research Institute of the State Building Materials Industry Bureau and the main drafters of the standard are Wang Zheng and Yang Chengtong.
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