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Model
No. CU-NR (low carbon steel)
V-Notched Rail Shear Test Fixture shown
with This ASTM standard (Reference 1) is the result of studies initiated at the University of Wyoming and later continued at the University of Utah to combine the best features of the Iosipescu Shear (ASTM D 5379) and Two-Rail Shear (ASTM D4255) test methods into a unified test. The 90-degree v-notch configuration of the Iosipescu Shear test, and the clamped rail configuration of the Two-Rail Shear test have been combined. A potential problem with the standard Iosipescu Shear test method when testing some materials is crushing of the edges of the specimen in the regions where it is loaded by the fixture. The Two-Rail Shear test method utilizes loading rails clamped onto two edges of the specimen by six bolts that pass through holes in the specimen. In addition to the cost and potential specimen damage when preparing these holes, slipping of the specimen in the rails can lead to premature bearing failures as the bolts contact edges of the specimen holes, thus nullifying the test. As indicated in the above photograph, tungsten carbide particle-coated grip plates are pushed against the specimen by bolts threaded into holders. This eliminates the need for holes in the specimen, and permits high shear loads to be applied. The ASTM D 7078 standard specimen is 3” long (the same as the standard Iosipescu specimen), but 2.22” wide (versus 0.75” for the standard Iosipescu specimen), resulting in a much larger gage section (1.22” wide versus 0.45”). The specimen notch depth-to-width ratio of 0.225 is nearly the same as the 0.200 for the Iosipescu specimen, thus preserving the gage section geometry. One inch of each end of the specimen is gripped by the fixture. That is, the specimen is gripped up to the notches, resulting in 1” of specimen being exposed between the grips. Note in the following photograph the cutout in the lower grip assembly (shown at the left). This is to permit raising the lower grip mounted in the testing machine after the
specimen has been installed in the upper grip. This cutout permits installing a specimen without having to remove the fixture from the testing machine, which is sometimes desirable, e.g., when performing elevated temperature or cryogenic tests Special configuration fixtures can also be designed and fabricated. The following photograph shows a specially designed adjustable gage section width fixture.
Nonadjustable fixtures for non-standard (fixed) gage section widths can also be fabricated. As another option, a pair of specimen installation alignment jigs can also be provided, as indicated in the following two photographs. These jigs can be used to aid in centering the specimen notches between the rails while aligning it. After specimen installation, the jigs are removed.
Use of Specimen Installation Alignment Jigs Sources of Additional Information: 1) ASTM Standard D7078-05 (2005), "Standard Test Method for Shear Properties of Composite Materials by the V-Notched Rail Shear Method," American Society for Testing and Materials, West Conshohocken, Pennsylvania (first published in April 2005). 2) 2) Adams, D.O., Moriarty, J.M., Gallegos, A.M., and Adams, D.F., “Development and Evaluation of a V-Notched “Rail Shear Test,” Proceedings of the 2002 SAMPE Technical Conference, Baltimore, MD, November 2002. 3) 3) Adams, D.O., Gallegos, A.M, Moriarty, J.M., and Adams, D.F., “A V-Notched Rail Shear Test for Composite Laminates,” Proceedings of the 2002 SEM Annual Conference, Milwaukee, WI, June 2002. 4) 4) Hussain, A.K., and Adams, D.F., “The Wyoming-Modified Two-Rail Shear Test Fixture for Composite Materials,” Journal of Composites Technology and Research, Vol. 21, No. 4, October 1999, pp. 215-223. 5) 5) Hussain, A.K., and Adams, D.F., “Experimental Evaluation 9of the Wyoming-Modified Two-Rail Shear Test Method for Composite Materials,” Experimental Mechanics, Vol. 44, No. 4, August 2004, pp. 354-364. 6) 6) Hussain, A.K., and Adams, D.F., “Analytical Evaluation of the Two-Rail Shear Test Method for Composite Materials,” Composites Science and Technology, Vol. 64, 2004, pp. 221-238. Top of Page | Home Page | General Info | Company Profile |Product Index Copyright 2005 - Wyoming Test Fixtures, Inc.
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