Test Method for Tensile Strength Estimate by Disc Compression of Manufactured Graphite

Abstract The use of pulsed NMR analysis under proper operating conditions has proven to be useful for controlling various polymer compositions in the manufacture of EPDM. It can be used in determining the amount of oil incorporated into oil-extended EPDMs. At higher oil contents, the differences in EPDM properties will affect this test method, which will require a separate calibration curve for each type of polymer. It can be used to measure the propylene content of EPDM. Comparison data have shown that this technique is more accurate in predicting crystallinity or propylene content than the standard IR method within the propylene range of 22 to 41%. Pulsed NMR can also be used to predict uncured EPDM compound tensile strength and EPDM/PP compression-molded tensile strength. Since these properties are affected by the crystallinity of EPDM, of which percent ethylene is the major contributor, then tensile strength can be determined indirectly. Based on the tensile and SER correlation, it seems obvious that this technique is measuring the spin-spin relaxation times of the crystalline phase, whereas the ir method is only measuring propylene content.

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Dynamic Fracture Toughness and Dynamic Tensile Strength of the Rock from Different Depths of Beijing Datai Well

Advances in Civil Engineering ◽

10.1155/2018/2567438 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Ke Man ◽

Xiaoli Liu

Keyword(s):

Fracture Toughness ◽

Tensile Strength ◽

Dynamic Fracture ◽

Empirical Relation ◽

Dynamic Fracture Toughness ◽

Rock Failure ◽

Test Method ◽

Strength Increase ◽

Dynamic Tensile Strength ◽

Different Depths

From the standard test method suggested by ISRM and GB/T50266-2013, the uniaxial static tensile strength, dynamic tensile strength, and dynamic fracture toughness of the same basalt at different depths have been measured, respectively. It is observed that there may be an empirical relation between dynamic fracture toughness and dynamic tensile strength. The testing data show that both the dynamic fracture toughness and dynamic tensile strength increase with the loading rate and the dynamic tensile strength increases a little bit more quickly than the dynamic fracture toughness. With an increasing depth, the dynamic tensile strength has much more influence on the dynamic fracture toughness, as which it is much liable to bring out the unexpected catastrophes in the engineering projects, especially during the excavation at deep mining. From the rock failure mechanisms, it is pointed out that the essential reason of the rock failure is the microcrack unstable propagation. The crack processes growth, propagation, and coalescence are induced by tensile stress, not shear stress or compressive stress. The paper provides estimation of the dynamic fracture toughness from the dynamic tensile strength value, which can be measured more easily.

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