1、 ENGINEERING MATERIAL SPECIFICATION Date Action Revisions 2006 09 26 Revised Inserted 3.0; Deleted 3.1, 3.6 & 4 2000 09 25 Revised Updated A. Cockman 1987 12 01 Released CF4R RD 107002-87 Printed copies are uncontrolled Copyright 2006, Ford Global Technologies, LLC Page 1 of 3 ELECTROGRAPHITE BRUSH
2、MATERIAL, 2500 - 6500 micro ohm.cm ESF-M99G150-A SPECIFIC RESISTANCE 1. SCOPE The material defined by this specification is an electrographite brush. 2. APPLICATION This specification was released originally for material used as an electrographite brush in alternators for long life trucks. 3. REQUIR
3、EMENTS Material specification requirements are to be used for initial qualification of materials. 3.0 STANDARD REQUIREMENTS FOR PRODUCTION MATERIALS Material suppliers and part producers must conform to the Companys Standard Requirements For Production Materials (WSS-M99P1111-A). 3.2 SPECIFIC RESIST
4、ANCE 2500 - 6500 micro ohm.cm Test Method: The apparatus consists of 2 jaws which can be closed firmly against the ends of the test specimen. The jaws should be faced with silver-plated copper gauze, backed with resilient pads to insure uniform current distribution into the ends of the piece. The si
5、ze of the test specimen is immaterial, providing it fulfills the following requirement for accurate results. The length should be at least 4 times the width and thickness dimensions and the spacing between pointers should be no more than 1/2 the length of the specimen. For a test specimen the specif
6、ic resistance is defined as follows: E x A r = - x 1000 I x L where: r = specific resistance in micro ohm.cm E = millivolt drop between pointers A = cross-sectional area, cm2 I = current in amperes L = pointer spacing, cm ENGINEERING MATERIAL SPECIFICATION ESF-M99G150-A Printed copies are uncontroll
7、ed Copyright 2006, Ford Global Technologies, LLC Page 2 of 3 The convenient method for obtaining readings of specific resistance that are a multiplier of the potential drop in millivolts is to proceed as follows: For SI units, use voltmeter (or millivoltmeter) pointers that are accurately spaced 2 c
8、m apart. Set the current at 1.97 times the value of the cross-sectional area of the specimen in square centimeters: E x A E x A r (micro ohm.cm) = - x 1000 = - x 1000 = 254E I x L 1.97A x 2 If the specimen is not long enough to use a 2 cm spacing between pointers, another method is to make the point
9、er spacing equal to the width of the specimen, and the current setting 3.94 times the thickness, then: E x A E x W x T r (micro ohm.cm) = - x 1000 = - x 1000 = 254E I x L 3.94T x W 3.3 SCLEROSCOPE HARDNESS 45 - 85 Test Method: Use a Shore Scleroscope instrument with a diamond-pointed steel hammer st
10、andardized for carbon. Mount and level the instrument on a firm support. The anvil of the instrument must be kept clean at all times. The material is placed on the anvil, and the tube is lowered firmly against the test piece. At least 6 readings (in different areas) should be taken on each specimen
11、to obtain average hardness. 3.4 APPARENT DENSITY 1.60 - 1.90 g/cm3 Test Method: The apparent density is the density of the mass, including the voids or pores, and is expressed in the following manner: Weight in Air Apparent Density = - Weight in Air - Weight in Water The specimen to be tested must f
12、irst be coated with a thin coating of grease to prevent water absorption. The piece is then weighed in air and the value recorded. It is then weighed while completely submerged in water, with special care being taken to eliminate all air bubbles from the specimen. Alternate Method: Finish the specim
13、en to such a shape that the volume can be accurately measured. Then, if the specimen is weighed (g) and such weight divided by the volume (cm3) the result is numerically equal to the apparent density by the formula: Weight, g Apparent Density = - Volume, cm3 ENGINEERING MATERIAL SPECIFICATION ESF-M9
14、9G150-A Printed copies are uncontrolled Copyright 2006, Ford Global Technologies, LLC Page 3 of 3 3.5 TRANSVERSE STRENGTH, min 19.6 MPa The transverse strength refers to the strength of the material when tested as a simple beam under load. Test Method: The specimen is supported at each end by a 1.6
15、mm radius knife-edge. A load is gradually applied at a point exactly midway between the supports through a third 1.6 mm radius knife-edge until rupture occurs. Calculate the transverse strength as follows: 3 x L x P S = - 2 x h x b where: S = maximum stress, MPa L = length between supports, mm h = thickness of specimen, mm b = width of specimen, mm P = load at instant rupture occurs, N For SI units, by using a length between supports of 20 mm and a test specimen 5 mm thick by 6 mm wide and long enough to overlap supports, the formula reduces to: 3 x 20 x P S = - = 0.2P 2 x 5 x 5 x 6
