1、Designation: D6991 17Standard Test Method forMeasurements of Internal Stresses in Organic Coatings byCantilever (Beam) Method1This standard is issued under the fixed designation D6991; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number 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 procedure for measurementsof internal stresses in organic coatings by using
3、the cantilever(beam) method.1.2 This method is appropriate for the coatings for whichthe modulus of elasticity of substrate (Es) is significantlygreater than the modulus of elasticity of coating (Ec) and forwhich the thickness of substrate is significantly greater thanthickness of coating (see Note
4、7 and Note 8).1.3 The stress values are limited by the adhesion values ofcoating to the substrate and by the tensile strength of thecoating, or both.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not
5、 purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and todetermine the applicability of regulatory limitations prior touse.1.6 This international st
6、andard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2.
7、 Referenced Documents2.1 ASTM Standards:2D823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic, Nonconductive Coa
8、t-ings Applied to Non-Ferrous Metals3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 cantilever, na beam or member securely fixed at oneend and hanging free at the other end.3.1.2 deflection, nthe displacement of a beam from itsoriginal position by an applied force.3.1.2.1 Disc
9、ussionThe deflection of the beam is used tomeasure that force acting on the tip.3.1.3 internal stress, na stress system within a solid that isnot dependent on external forces.4. Test Method4.1 Internal stresses in coatings are determined by thecantilever method (Fig. 1). Substrate A in the shape of
10、arectangular cantilever beam is clamped by its end B in a specialfixture E. Coating (F) is applied to one side of the beam.Internal stresses occur in the film when it is being cured(drying, cross-linking, etc.). When there is sufficient adhesionbetween the coating and the substrate, the stresses ben
11、d thecantilever beam, forcing its free end D to be deflected from itsoriginal position by a distance of h. The deflection of the beamis measured under an optical microscope and internal stress iscalculated using the equation for the cantilever method. See Eq1 in Section 9, (Formula 1).5. Significanc
12、e and Use5.1 Stresses in coatings arise as a result of their shrinkage orexpansion if expected movements are prevented by coatingadhesion to its substrate.5.2 There are several causes leading to arrival of stresses inthe coatings: film formation (cross-linking, solventevaporation, etc.); differences
13、 in thermal expansion coefficientsbetween coating and substrate; humidity and water absorption;environmental effects (ultraviolet radiation, temperature andhumidity), and others.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Application
14、s and is the direct responsibility ofSubcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved May 1, 2017. Published August 2017. Originallyapproved in 2005. Last previous edition approved in 2010 as D6991 05 (2100).DOI: 10.1520/D6991-17.2For referenced ASTM standar
15、ds, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1
16、9428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Tec
17、hnical Barriers to Trade (TBT) Committee.15.3 Knowledge of the internal stresses in coatings is veryimportant because they may effect coating performance andservice life. If the internal stress exceeds the tensile strength ofthe film, cracks are formed. If stress exceeds adhesion betweencoating and
18、substrate, it will reduce adhesion and can lead todelamination of coatings. Quantitative information aboutstresses in coatings can be useful in coating formulation andrecommendations for their application and use.5.4 This method has been found useful for air-dry industrialorganic coatings but the ap
19、plicability has not yet been assessedfor thin coatings (thickness = 80 mm (3 in.).Notes:1. Use rectangular pressure shim 19 by 12.7 by 1.6 mm (34by12 by116 in.) between clamp and sample;2. Use stainless steel for all parts to avoid corrosion;3. Polish support base and clamping surface area to maketh
20、em parallel;4. Polish both sides of the pressure shim;5. Make clamping screw perpendicular to the clampingsurface.X2. PRECISION DATAASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard
21、 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 committee and must be reviewed every five years andif n
22、ot 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 at a meeting of theresponsible technical committee, which
23、 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 Drive, PO Box C700, West Conshohocken, PA 19428-2959,Uni
24、ted 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). Permission rights to photocopy the standard may
25、also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ X2.1 Repeatability of Stress Measurements Within One Lab by One OperatorStress Readings, psiPanel ID DFT, mils 1st2nd3rd4th5th6th7th8th9th10thaverage stdvcoef.Var, %5A 3.0 708 885 7
26、08 708 708 885 708 531 531 885 726 131 185B 2.8 1155 1155 1155 963 963 1155 963 963 963 963 1040 99 109A 3.5 1022 1314 1314 1022 1022 1022 876 876 876 876 1022 169 169B 3.5 584 584 584 584 584 438 584 438 438 438 526 75 1417A 4.2 694 810 694 694 578 578 578 578 578 578 636 82 1317B 3.2 490 490 653 4
27、90 490 490 490 490 490 490 506 52 1020A 3.6 846 846 987 846 846 846 846 705 705 705 818 89 1120B 3.0 885 708 531 708 708 531 708 708 708 708 690 100 1524A 3.0 1062 1062 1062 1062 1062 1062 885 1062 1062 1062 1044 56 524B 2.8 963 963 963 963 770 963 770 578 963 770 867 136 1626A 3.6 987 846 846 846 846 846 846 846 987 846 874 59 7Pooled 102 psi 130.7 MPaD6991 175
