1. Field of the Invention
The present invention pertains to the testing of engineering materials and, more particularly, to the testing of tensile properties of metal plate.
2. Discussion of the Prior Art
Interest in the anisotropy of engineering materials and, particularly, the current problems of lamellar tearing of rolled steel plate, as noted in "Commentary on Highly Restrained Welded Connections," AISC Engineering Journal, 3rd Quarter 1973, "Lamellar Tearing and the Slice Bend Test," M. L. Drury and J. E. M. Jubb, Welding Journal, Feb. 1973, "A Quantitative Weldability Test for Susceptibility to Lamellar Tearing," R. P. Oats and R. D. Stout, Welding Journal, Nov. 1973 and "Lamellar Tearing", J. E. M. Jubb, Welding Research Council Bulletin No. 168, Dec. 1971, make it highly desirable to have a simple, quick and reliable test to determine the ultimate tensile strength, the tensile yield strength and the tensile elongation before necking in the short transverse (Z) direction of steel plate to be welded in critical structural connections. It is especially desirable to have a test which can be performed on the site of fabrication or erection of large steel structures. Such a test should avoid difficult machining and joining procedures in the preparation of sample specimens and should employ test equipment small enough to be transported by passenger vehicles.
In the past, a variety of test sample designs and procedures have been employed by different research workers to measure the short transverse properties of relatively thin rolled plate. For tensile tests, either the specimens are miniature tensile bars or have ends added by welding or brazing. Other tests employ simpler specimens which are shaped as rings, flat plates and the like, but such specimens do not provide information in terms of the conventional tensile properties desired by designers.
A double ligament tensile impact test was described in "Measurement of Short-Transverse Tensile-Impact Energy of Rolled Steel Plate," E. D. Oppenheimer and J. T. Berry, ASME Pressure Vessel and Piping Conference, 1968. The two-ligament design was necessary for impact testing in order that the restraining ligament forces on the center segment be balanced and, therefore, no guidance device be needed to prevent rotation of the center segment during fracture. The use of a guidance device, such as a restraining clamp with slide or the like, would add sufficient mass to the moving segment of the specimen to severely degrade the test results.
Further work on slow strain rate tensile ligament testing as described in "The Evaluation of Anisotropy and Plane Strain Properties of Cast and Wrought Materials," R. G. Kumble, PhD. Thesis, University of Vermont, May 1973 and "The Double Ligament Tensile Test: Its Development and Application," E. D. Oppenheimer, R. G. Kumble and J. T. Berry, ASME Winter Annual Meeting, Nov. 1974, was performed using the original double ligament specimens because tooling and specimens existed and the design was suited to research work on very thin (1/4 inch) plate. However, while the results were excellent, this specimen has obvious practical drawbacks when applied to industrial problems such as on-site use, simple preparation of specimens of small size, as set forth above. Further disadvantages stem from the fact that, even when the specimens are of larger size, it is essential that close tolerances be held so that both ligaments are, as nearly as possible, of equal strength. Close dimensional control of the location of the ligaments with respect to each other must be exercised. For common structural sizes, for example 1 inch thick plate, the test apparatus becomes very bulky and heavy.