1、 The following commercial specification is adopted from the military document. Revision A includes all known accepted revisions, amendments, notices, and Department of Defense (DoD) engineering changes previously developed for this item. Revision B and forward include changes adopted to reflect tech
2、nology and design evolution. STIFFNESS OF CLOTH, DIRECTIONAL; CANTILEVER BENDING METHOD 1. SCOPE 1.1 This method is intended for determining the directional flexstiffness of cloth by employing the principle of cantilever bending of the cloth. Small differences in stiffness may be determined by this
3、method, but it is not well suited for testing extremely pliable fabrics. 2. TEST SPECIMEN 2.1 Unless otherwise specified in the procurement document, the specimen shall be a rectangle of cloth 2 inches by 1 inch (51 mm by 25 mm) with the long dimension parallel to the yarns to be tested. The specime
4、n shall be cut from the smoothest area possible which has not been previously folded or in any manner deformed. 3. NUMBER OF DETERMINATIONS 3.1 Unless otherwise specified in the procurement document, ten specimens in each of the warp and filling directions shall be tested from each sample unit. 4. A
5、PPARATUS (see FIGURE 1) 4.1 Specimen vise. A Specimen vise, “V”, at least 1 inch (25 mm) wide, to which the pointer indicator “I2” is attached, and which can be rotated in a clockwise direction alternately by means of a hand crank or motor about the point 0, at a rate of 60 degrees per minute. 4.2 P
6、endulum weighing system. A pendulum weighing system, including an angular deflection scale pointer indicator “I1”, adjustable bending plate “Q” for contacting the free end of the specimen, and a series of detachable weights “M” calibrated to the pendulum system. This system shall be pivoted for near
7、ly frictionless rotation about the point 0. 4.3 Angular deflection scale. An angular deflection scale calibrated in degrees of arc which will indicate the difference in the angles through which the vise has been turned and DISTRIBUTION STATEMENT: All Rights Reserved. No Part of this publication may
8、be reproduced without prior written permission from Parachute Industry Association. Additional copies may be purchased on-line from PIA Specifications and Products at: . PIA-TEST METHOD-5202B 25 November 2013 Superseding PIA-TEST METHOD-5202A 20 July 2009 PIA-TEST METHOD-5202B the load of the pendul
9、um has been deflected. 4.4 Fixed load scale. A fixed load scale which measures the deflection 0 of the pendulum system, calibrated to read directly 100 L sin O, where L is the distance between the center of rotation 0 and the center of the applied load M. Thus, M times the load scale reading divided
10、 by 100 gives the bending moment directly. 5. PROCEDURE 5.1 Unless otherwise specified in the procurement document, the specimens shall be conditioned and tested under Standard Atmospheric Conditions as specified in Section 4 of this Standard. 5.2 The machine shall be placed in a test position and l
11、eveled. A suitable moment weight shall be placed on the pendulum and then, if necessary, the load scale adjusted to indicate zero. The moment weight applicable to a given cloth may be determined by trial. The bending plate shall be set to a 1/2 inch (13 mm) span between the edge of the vise and the
12、nearest edge of the bending plate. The motor shall be started and kept running throughout the test since its vibration minimizes friction effects in the weighing system. However, during the initial portion of the test it shall be disengaged. 5.3 The specimen shall be clamped firmly in the vise and t
13、he long edge parallel to the face of the dial plate. Care shall be taken that the specimen is not unduly deformed in handling. The face surface of the specimen (weave face, finished side, coated side, etc.) shall be placed upward in the vise. 5.4 Sufficient load shall be applied to the specimen by t
14、urning the hand crank to show a one percent load reading. The angle pointer shall then be set to zero and subsequent load readings reduced by one division. 5.5 The motor engaging lever shall be held down and the load scale readings taken at 10 degree intervals up to 90 degree deflection or until the
15、 angle of bend specified for the test is reached. 5.6 Calculation of results. 5.6.1 The stiffness shall be calculated in one or more of the following ways as specified in the procurement document. 5.6.1.1 Bending moment inch-pounds (Nm). The bending moment shall be the load that is applied when the
16、specimen is bent to a 60 degree angular deflection and shall be calculated as follows: Bending moment, inch-pounds = load scale reading x moment weight 100 Bending moment, Nm = Bending moment, inch-pounds x 0.113 Page 2 of 4 PIA-TEST METHOD-5202B 5.6.1.2 Load scale reading, percent (percentage of th
17、e maximum bending moment). The load scale reading when the specimen is bent to a 60 degree angular deflection shall be recorded. 5.6.1.3 A plot of the data shall be made on coordinate paper with the “load scale readings” at every 10 degrees up to 90 degrees and the calculated corresponding “bending
18、moment” as the ordinate, and the “angular deflection” as the abscissa. 5.6.1.4 Load, pounds (mg). The pounds (mg) load shall be that applied when the specimen is bent to a 60 degree angular deflection and shall be calculated as follows: Load, pounds (mg) = Load scale reading X moment weight 100 X 0.
19、5 in. (12.7 mm) 6. REPORT 6.1 The stiffness of the sample unit shall be the average of the results obtained from the specimens tested in each of the warp and filling directions, respectively, and shall be reported to the nearest 0.001 pound (1 mg) for pounds (mg) load, and to the nearest scale divis
20、ion for the load scale reading. 6.2 The report shall include the moment weight, length of span, and specimen dimensions. 6.3 Each individual value used to calculate the average shall also be reported. 7. NOTES 7.1 A cantilever bending machine of the type described in this method is manufactured by t
21、he Tinius Olsen Testing Machine Co., 2100 Easton Road, Willow Grove, PA 19090. (THIS SPACE LEFT INTENTIONALLY BLANK) Page 3 of 4 PIA-TEST METHOD-5202B FIGURE 1 * Notice: This document has been adopted from the original Mil-Spec of the same number, and is being maintained as a commercial specificatio
22、n by the Parachute Industry Association. Orders, inquires and comments should be addressed to PIA, Specification Committee via e-mail: or to our website at: . Copyright 2004-2013 Parachute Industry Association. Disclaimer: This document is published by the PIA to provide technical and engineering s
23、tandards that can be used for reference by all those who may benefit from them. The use of this document is entirely voluntary, and its applicability and suitability for any particular use, including any patent or trademark infringement arising there from, is the sole responsibility of the user. The original Government document was scanned. The PIA reviews each technical publication periodically, at which time it may be reaffirmed, revised, or canceled. The PIA invites your written comments and suggestions. Page 4 of 4
