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Aviation History
1917
1917 - 1225.PDF
NOVEMBER 22, 1917. Tensile Test.—(b) To determine whether a specimen hasa yield point equal to or greater than that specified the procedure shall be as follows : A line shall be described on thetest piece with a punch mark as centre, and with a radius of about 2 ins. (50,8mm.) when possible; the specified loadshall then be applied, removed, and a second line scribed with the same radius and the same centre ; if two lines are thenseen on the test piece, indicating that permanent elonga- tion has occurred, it shall be considered that the specimenhas not passed the yield-point test. If the manufacturer 1.—I.A.S.B. standard tensile test specimen for bars. desires, the yield point may be determined by an approved autographic or extensometer method. (c) The elastic or the proportional limit, when called for, shall be determined with an extensometer reading to at least 0.002 ins. (0.05 mm.). It shall be attached to the specimen at the gage marks and not to the shoulders of the specimen nor to any part of the testing machine. The elastic limit is defined as the greatest load per unit of original cross-section which does not produce a permanent set. The proportional limit is the load per unit of original cross-section at which the deformation ceases to be propor- tional to the load. Bend Test.—(d) The specimens shall be bent cold in the bend test. (e) (Bars). Bars will be bent around a pin of radius equal to the bar diameter or thickness until the sides are parallel ; A c Fig. 2.—Bending test operation. The distance X shall conform to value called for in detail specifica- tions for sheets. unless otherwise noted the bar must withstand such bending without developing cracks or signs of failure. (f) (Sheets). The test comprises two distinct operations, both of which are performed by the use of a press, or, in the absence of this, by using a knife-edge and hammer. First, the strip is placed in position AB (Fig. 2«) on block having a V-shaped groove. The knife-edge is placed as shown and pressure is applied by means of either press or hammer until the test specimen assumes the shape A'MB'. After this block is removed the bending is finished as indicated in Fig, 26, with or without the interposition of a spacer. The spread of the ends of the test piece varies with the quality and thickness of the sheets. The specimens must be bent as indicated without breaking and after test shall not show hair lines, cracks, or other defects. Impact Test.—(g) Impact tests shall be carried out with an impact testing machine of the pendulum type. Brinell Hardness Test.—(h) The hardness test shall be made with a 10-millimetre diameter ball, using a pressure of 3,000 kgs. for steel and one of 500 kgs. for softer metals. This pressure shall be applied for 30 seconds. Test Specimens.—(i) Tension, bend, and impact test specimens shall be taken from the rolled or forged material, except that in the case of irregularly shaped forgings they may be taken from a full-sized prolongation. Specimens shall not be annealed or otherwise treated, except as provided in the individual specifications. (j) Tension, bend, and impact test specimens for rolled material which is to be annealed or otherwise treated before use shall be cut from properly annealed or similarly treated short lengths of the full section of the piece, and for forged material from the treated forgings. ' (k) The axis of tension, bend, and impact test specimens for rolled bars and forgings of uniform cross-section over i£ ins. (38.10 mm.) in thickness or diameter and for forgings of irregular section, when practicable, shall be located at a point midway between the centre and surface when solid and at any point between the inner and outer surfaces of the wall when bored, and shall be parallel to the axis of the piece in the direction in which the metal is drawn. (/) Tension test for specimens for bars shall conform to the dimensions shown in Fig. 1. The ends shall be of a form to fit the holders of the testing machine in such a way that the load shall be axial ; test specimens representing heat-treated or brittle materials shall have threaded ends or ends so made as to permit' of testing material, using a ball-and-socket chuck. (m) Tension and bend test specimens for plates, sheets, and shapes shall be of the full thickness of material as rolled. Tensile-test specimens for sheets or plates shall be machined to the form and dimensions shown in Fig. 4. Bend- test specimens for sheets shall have a width of 1.5 in. (38.10 mm.) and a minimum length of 8 ins. (203.2 mm.) Test 3 mm (.078") t 039") Lengto dependent upon I .nel 10 o (.393')'j type of testing oaonlne Fig. 3.—I.A.S.B. standard impact test specimen. The faces are to be true and parallel. The base of the notch is to be of uniform depth and per-pendicular to the long axis of the specimen. For unheat-treated material the notch is to be drilledand slotted. For heat-treated material the notch may be ground or milled. specimens shall not be hammered in order to straighten them, nor may they be tempered, annealed, or otherwise treated unless specifically noted. Impact-test specimens are to be rectangular in section and shall be notched on one side. They are to have the form shown in the sketch, Fig. 3- SELECTION OF TEST SPECIMENS—6. A sufficient number of test specimens will be selected by the inspector from each lot of material submitted to satisfy him of the quality of the material. If any test specimen shows defective machining or develops flaws, it may be discarded ; in which case the manufacturer and the purchaser or his representative shall agree upon the selection of another specimen in its stead. MARKING AND IDENTIFICATION—7. (a) It shall be the duty of the manufacturer to provide that manufacturing identi- fication marks, such as heat numbers, shall be readily avail- able at the time_pf inspection of the finished material to the inspector, and "Sltrier that materials shall be grouped when possible by heat or melt numbers. Fig. 4.—I.A.S.B. standard tensile test specimen for sheets. Test specimens in accordance with the above sketch shall apply to sheet one-fifth in. (5.08 mm.) (No. 6 U.S. standard gauge) and up in thickness. Below one-fifth in. (5.08 mm.) in thickness w and d shall be one-half in. (12.70 mm.), h £ in. (12.70 mm.), and wn 1 in. (25.40 mm.). The percentage of elongation may be determined on either 2 or 4 ins. (50.80 mm. or 101.60 mm.). Soft materials of light gauge are apt to fail in detail under the pin. Specimens representing these materials may be gripped in the jaws of the testing machine. Drilling is omitted. The specimens may be reduced in width by not more than 0.003 in' (°-°8 mm.) over the centre half of the gauge length in order that fracture may occur there. 1225 . . .tfcjrf. -, ,-T.,,. L .» ..TJ*.J. ...M^A
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