Last updated on September 3rd, 2023 at 11:39 am
Description of Shirley Stiffness Tester
The stiffness tester consists of a platform with smooth low friction and flat surfaces such as glossy metal or plastic. The platform is supported by two side pieces made of plastic. Index lines are engraved on these side pieces, inclined at an angle of 41.50 below the platform surface plane. At this angle f (ϴ) = 0.5. A mirror is associated with the instrument to enable the operator to view both index lines from a convenient position. A scale is supplied with the instrument to estimate the bending length and is graduated in cm. It also works as a template for cutting the samples of size.
The sample is conditioned in the standard testing atmosphere and using the template, specimens are cut to the size of 6 inches X 1 inch. Four specimens in the warp way and weft way are prepared for the test. If the fabric is not uniform or a high degree of accuracy is required, more samples can be tested. The specimens are cut in such a way that the warp specimens do not contain the same warp yarns and the weft specimens contain different weft yarns. Selvedges, end pieces, creased or folded places must be avoided and the specimens must be handled as little as possible.
The test is carried out in the standard testing atmosphere. The tester is set on a table so that the horizontal platform and the index lines are at eye level.
The specimen is placed on the platform with the template at the top of it so that the leading edges coincide. Both are slowly pushed forward until the leading edges of the specimen and the template project beyond the edge of the platform. With the eye in a position so that the index line coincides, the sliding of the specimen is stopped when it cuts both index lines.
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If the specimen has a tendency to twist, the reference point at the center of the leading edge is taken. For the specimens which twist more than 450, this method should not be used. Then the bending length can be read from the scale (template) opposite a datum line engraved on the side of the platform.
Four readings are taken from each specimen, with each side up, first at one end and then another. Mean values for the bending length in warp and weft ways are calculated and the flexural rigidity and the bending modulus are determined.
This instrument is used in the finishing departments where the control of the process is used and to note the effects of varying the process.