1、Designation: B 478 85 (Reapproved 2003)Standard Test Method forCross Curvature of Thermostat Metals1This standard is issued under the fixed designation B 478; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of crosscurvature of thermostat metals.NOTE 1This test method is not limited to thermos
3、tat metals and canbe used for other materials for which the cross curvature must bemeasured accurately.NOTE 2This standard includes means for calculating cross curvaturefor widths other than that of the specimen having the same radius ofcurvature.1.2 The values stated in inch-pound units are to be r
4、egardedas the standard. The metric equivalents of the inch-pound unitsmay be approximate.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to become familiarwith all hazards including those i
5、dentified in the appropriateMaterial Safety Data Sheet for this product/material as pro-vided by the manufacturer, to establish appropriate safety andhealth practices, and determine the applicability of regulatorylimitations prior to use.2. Terminology2.1 thermostat metala composite material, usuall
6、y in theform of sheet or strip, comprising two or more materials of anyappropriate nature, metallic or otherwise, which by virtue ofthe differing expansivities of the components, tends to alter itscurvature when its temperature is changed.2.2 cross curvaturethe deviation from flat across thewidth, m
7、easured as a chord height. It is expressed in inches ormillimetres.3. Summary of Test Method3.1 The test method for cross curvature consists of measur-ing the chord height deviation from flat across the width of aspecimen of thermostat metal (Fig. 1).NOTE 3The highest point will normally be at or ne
8、ar the center of thespecimen.4. Significance and Use4.1 This procedure provides the means for defining themagnitude and direction of cross curvature (an inherent prop-erty in thermostat metal).5. Apparatus5.1 FixtureA typical cross curvature fixture is shown inFig. 2. It consists of a base which has
9、 a flat ground surface onits top side. For convenience a granite surface plate, as ispictured, can be used. To it are attached side frames to supportrod or bar tracks which are parallel to the top surface of thebase. On the tracks is assembled a movable carriage formounting a micrometer depth gage.5
10、.2 Micrometer Depth Gage, for measuring the position ofthe specimen to the nearest 0.0001 in. (0.0025 mm). The tip ofthe gage rod shall be radiused.5.3 Electronic Contact Indicator, sensitive, low-current, togive a signal when the micrometer depth-gage rod completesthe electrical circuit across the
11、indicator terminals by touchingthe specimen or the parallel.5.4 Parallel, hardened and ground steel,14 by38 by 6 in. (6by 10 by 150 mm).NOTE 4Parallelism of the rods, on which the micrometer carriagetraverses, to the steel parallel when laid on the surface plate shall be suchthat when the carriage i
12、s traversed and micrometer readings are takenalong the length of the parallel, no reading shall be different from anyother reading by more than 0.0002 in. (0.005 mm).1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of S
13、ubcommitteeB02.10 on Thermostat Metals and Electrical Resistance Heating Materials.Current edition approved June 10, 2003. Published July 2003. Originallyapproved in 1968. Last previous edition approved in 1985 as B 478 85 (1997)e1.FIG. 1 Specimen Relationships1Copyright ASTM International, 100 Barr
14、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Sampling6.1 The method of sampling shall be mutually agreed uponbetween the manufacturer and the purchaser.7. Preparation of Sample for Measurement7.1 The most important step in preparing the specimen formeasurement is cu
15、tting it to length. The length shall beapproximately equal to the width. The minimum length of aspecimen shall be34 in. (20 mm). It must be cut in a mannerthat will not tend to alter the inherent cross curvature. It isrecommended that a shear with sharp blades and the properclearance be used. The sh
16、earing should impart no burrs to thespecimen. It is recommended that after shearing the specimento length the specimen be allowed to set for 10 min beforetesting so that it can stabilize its shape. The specimen shall beflat longitudinally.8. Procedure8.1 Lay the steel parallel on the surface plate w
17、ith the14 -in.(6-mm) face down and its length parallel to the travel of themicrometer and directly under the tip of micrometer gage rod.Take a base reading of the micrometer depth gage by slidingthe micrometer carriage over the parallel and turning themicrometer thimble down until contact of the tip
18、 of the rod ismade with the parallel as is indicated by the electronic contactindicator. Back off the micrometer thimble and move thecarriage away. Lay the specimen on the parallel so that the twoside edges of the specimen contact the parallel, the convex sideof the specimen is up, and the specimen
19、is centered to avoidtilting or uneven contact to the parallel. Then move themicrometer carriage over the sample and take a micrometerreading at the highest point on the specimen. Remove thespecimen and determine its thickness within 60.0001 in.(60.0025 mm) by means of micrometer calipers havingradiu
20、sed anvils. Take all measurements at a temperature of 756 1F (24 6 0.5C) with sufficient time allowed for the sampleto have reached temperature stabilization.NOTE 5When low expansion side of the thermostat metal is convex,the results obtained shall be referred to as positive ( + ) and when the highe
21、xpansion side is convex, the results obtained shall be referred to asnegative ().9. Calculation9.1 Calculation of cross curvature is as follows:C 5 B 2 H 2 twhere:C = cross curvature, in. (or mm)B = base reading of micrometer depth gage, in. (or mm),H = micrometer depth gage reading at highest point
22、 ofspecimen, in. (or mm),t = specimen thickness, in. (or mm).NOTE 6Cross curvature varies by the square of the width for the sameradius of curvature. For example, if the cross curvature of a strip 3.00 in.(76.2 mm) is 0.09 in. (2.3 mm), the cross curvature of a strip 1.00 in. (25.4mm) wide having th
23、e same radius of curvature would be 0.01 in. (0.3mm). This relationship may be influenced by mechanical distortion of theedges in slitting or trimming to width for strips of low width-thicknessratio.10. Report10.1 The report shall include the following:10.1.1 Type of material,10.1.2 Thickness of spe
24、cimen,10.1.3 Width of specimen,FIG. 2 A Typical Design of ApparatusB 478 85 (2003)210.1.4 Percentage reduction of specimen,10.1.5 Test temperature,10.1.6 Base reading of micrometer depth gage,10.1.7 Micrometer depth gage reading at highest point onspecimen, and10.1.8 Cross curvature (including posit
25、ive or negative sign).11. Precision and Bias11.1 The reliability of the results of the measurement ofcross-curvature depends primarily on the method of samplepreparation and the test conditions. The most common sourcesof variation in the test results relate to the quality of the shearededge of the t
26、est specimen, and the uniformity of the testtemperature.11.2 Quantitative determination of precision and bias is inprogress.12. Keywords12.1 chord height; cross curvature; thermostat metalASTM International takes no position respecting the validity of any patent rights asserted in connection with an
27、y item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical
28、 committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration a
29、t a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor
30、Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).B 478 85 (2003)3
