1、Designation:B47885(Reapproved 2016)Standard Test Method forCross Curvature of Thermostat Metals1This standard is issued under the fixed designation B478;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A numb
2、er in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of crosscurvature of thermostat metals.NOTE1This test method is not limited to thermostat metals and
3、canbe used for other materials for which the cross curvature must bemeasured accurately.NOTE2This 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 regardedas standa
4、rd.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.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
5、 to become familiarwith all hazards including those identified in the appropriateSafety Data Sheet(SDS)for this product/material as providedby the manufacturer,to establish appropriate safety and healthpractices,and determine the applicability of regulatory limi-tations prior to use.2.Terminology2.1
6、 thermostat metal,na composite material,usually inthe form of sheet or strip,comprising two or more materials ofany appropriate nature,metallic or otherwise,which by virtueof the differing expansivities of the components,tends to alterits curvature when its temperature is changed.2.2 cross curvature
7、,nthe deviation from flat across thewidth,measured 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).NOTE3The h
8、ighest point will normally be at or near 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.
9、2.It consists of a base which has 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 formounti
10、ng a micrometer depth gage.5.2 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 electric
11、al circuit across the indicator terminals by touchingthe specimen or the parallel.5.4 Parallel,hardened and ground steel,14by38by 6 in.(6by 10 by 150 mm).NOTE4Parallelism of the rods,on which the micrometer carriagetraverses,to the steel parallel when laid on the surface plate shall be suchthat when
12、 the carriage is 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).6.Sampling6.1 The method of sampling shall be mutually agreed uponbetween the manufacturer and the purchaser.7.Preparatio
13、n of Sample for Measurement7.1 The most important step in preparing the specimen formeasurement is cutting it to length.The length shall beapproximately equal to the width.The minimum length of aspecimen shall be34in.(20 mm).It must be cut in a mannerthat will not tend to alter the inherent cross cu
14、rvature.It isrecommended that a shear with sharp blades and the properclearance be used.The shearing should impart no burrs to the1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.10 on Thermostat Meta
15、ls and Electrical Resistance Heating Materials.Current edition approved May 1,2016.Published May 2016.Originallyapproved in 1968.Last previous edition approved in 2008 as B478 85(2008).DOI:10.1520/B0478-85R16.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2
16、959.United States1 specimen.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 with 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 ove
