# ASTM F2433-05 (Reapproved 2013)

Designation: F2433 − 05 (Reapproved 2013)Standard Test Method forDetermining Thermoplastic Pipe Wall Stiffness1This standard is issued under the fixed designation F2433; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, 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 determination of the load-deflection behavior of thermoplastic pipe wall sections underparallel plate loading conditions.NOTE 1—These are not full pipe section tests, but pipe wall segmenttests. The results of these tests will be different from pipe stiffness tests perTest Method D2412, although they may be proportional. This test providesquite different information, including , stress relaxation under constantstrain, and comparisons of the function and stiffness of different pipe walldesigns or materials.1.2 This test method covers a loading test for determiningthe wall stiffness of a thermoplastic-pipe wall under a com-bined load of bending and compression. Changes in pipe wallprofile geometry under load may also be determined.1.3 This test method covers thermoplastic pipe.1.4 The characteristics determined by this test method arewall stiffness and changes in profile wall dimensions at specificdeformations.1.5 The characteristics determined by this test method arewall stiffness, profile wall efficiency, and for some wallelements stability at specific Strain levels.1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.7 The text of this specification references notes andfootnotes that provide explanatory material. These notes andfootnotes (excluding those in tables and figures) shall not beconsidered as requirements of the specification.1.8 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD695 Test Method for Compressive Properties of RigidPlasticsD883 Terminology Relating to PlasticsD1600 Terminology forAbbreviated Terms Relating to Plas-ticsD2122 Test Method for Determining Dimensions of Ther-moplastic Pipe and FittingsD2412 Test Method for Determination of External LoadingCharacteristics of Plastic Pipe by Parallel-Plate LoadingF412 Terminology Relating to Plastic Piping Systems2.2 AASHTO Standards:M 252 Standard Specification for Corrugated PolyethyleneDrainage Pipe3M 294 Standard Specification for Corrugated PolyethylenePipe, 300- to 1500-mm Diameter33. Terminology3.1 Definitions—Definitions are in accordance with Termi-nology F412, and abbreviations are in accordance with Termi-nology D1600, unless otherwise specified.3.2 Definitions of Terms Specific to This Standard:3.2.1 chord shortening, n—the ratio of the reduction in pipesection chord shortening to the initial chord length expressed asa percentage.3.2.2 ∆y, n—measured change in chord length (in thedirection of load application) expressed in millimeters (inches).3.2.2.1 compressive deformation, n—the measured changeof the inside diameter in the direction of load applicationexpressed in millimeters (or inches).3.2.3 load (F), n—the force applied to the wall section toproduce or maintain a given percent chord length shortening atany given unit of time; expressed as Newtons per meter(pounds-force per linear inch).1This test method is under the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved Aug. 1, 2013. Published October 2013.Originallyapproved in 2005. Last previous edition approved in 2009 as F2433–05(2009). DOI:10.1520/F2433-05R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3Available from American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http://www.transportation.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.4 mean radius (r), n—the mid-wall radius determined bysubtracting the average wall thickness from the average outsidediameter and dividing the difference by two; expressed inmillimeters (or inches).3.2.5 time-independent pipe stiffness K(0), n—the valueobtained by dividing the force per unit length on the curvedbeam specimen by the resulting deflection in the same units atthe % deflection prescribed and extrapolating the linear portionof the curve of stiffness versus % deflection to the moment ofapplication of load.3.2.6 time-dependent residual curved beam stiffness K(t)and residual pipe stiffness K(t), n—the value obtained bydividing the force per unit length on the curved beam specimenby the constant target deflection in the same units, at any timet, t 0.3.2.7 modulus of relaxation, n—the residual pipe stiffnessversus log(time).3.2.8 residual pipe stiffness K(50y), n—the value obtainedby extrapolating values of residual pipe stiffness versus time to50 years.3.2.9 compliance C(t), n—the inverse of stiffness K(t).3.2.10 liner cracking or crazing, n—the occurrence of abreak or network of fine breaks in the liner visible to theunaided eye.3.2.11 wall cracking, n—the occurrence of a break in thepipe wall visible to the unaided eye.3.2.12 wall delamination, n—the occurrence of any separa-tion in the components of the pipe wall visible to the unaidedeye.3.2.13 rupture, n—a crack or break extending entirely orpartly through the pipe wall.4. Summary of Test Method4.1 The test is conducted by applying a controlled, nearlyinstantaneous, load to the longitudinally cut edges of curvedbeam sections cut from short lengths of pipe until a prescribedshortening of the chord connecting the longitudinal edges isachieved and held constant for prescribed intervals. Load anddeformation data establish the time-independent measure ofcurved beam wall stiffness at the instant of load application, themeasure of efficiency of the profile wall geometry, stability ofthe profile wall, a modulus of relaxation and long-termestimates of residual pipe wall stiffness.4.2 Alength of a 10 to 120° arc segment of a pipe wall, fromone diameter length to one meter long is loaded across its chordlength between two freely rotating end plates at a controlledrate of approach to one another. Load-deflection data of thewall section in combined bending and compression are ob-tained. Change in pipe wall thickness at the center of thesection (springline) is determined. If cracking, crazing,delamination, rupture, or buckling occurs, the correspondingload, deflection, and/or time are recorded.NOTE 2—If this test method is incorporated in a product standard itwould be necessary to define the arc length to be tested. There are,however, many reasons various arc lengths might be tested, especially asa research or product development tool. Large arc lengths are primarily inbending, while short arc lengths are primarily in compression.5. Significance and Use5.1 The performance under bending and compression loadof a thermoplastic plastic pipe wall design obtained by thismethod can be used for the following:5.1.1 To determine the stiffness of the pipe wall section.This is a function of the pipe dimensions, the wall design, thearc length tested, and the physical properties of the material ofwhich the pipe is made.5.1.2 To compare the characteristics of various thermoplas-tic pipe wall designs.5.1.3 To compare the characteristics of various plastics inpipe form.5.1.4 To study the interrelations of dimensions, materials,and deformation properties of thermoplastic pipe designs.5.1.5 To measure the deformation and load-resistance at anyof several significant events which may occur during the test.5.1.6 To provide a reasonable quality control/quality assur-ance test for very large diameter plastic pipes.5.2 The time-dependent pipe wall stiffness of a thermoplas-tic pipe obtained by this test method may used for thefollowing:5.2.1 To predict the residual stiffness of the pipe wall inbending and compression at all times after initial loading.5.2.2 For purposes of design, to determine a modulus ofrelaxation under sustained loads.5.2.3 To quantify the influence of material formulations ofthermoplastics on the modulus of relaxation.5.2.4 To study the influence of geometric patterns of wallprofiles on the modulus of relaxation.5.3 The time-independent reduction of wall thickness atspringline may be used for the following:5.3.1 For pipe wall stiffness, to quantify the efficiency of allwall profiles of any material composition and a given geometrywith that of a solid uniform thickness wall.6. Apparatus6.1 Testing Machine—A properly calibrated compressiontesting machine of the constant-rate-of-crosshead movementtype meeting the requirements of Test Method D695 shall beused to make the tests. The rate of head approach shall be 63.56 2.5 mm (2.5 6 0.1 in.)/s. The machines must be capable ofholding a required percent chord shorting for an extendedperiod of time.6.2 Loading Grips—The load shall be applied to the speci-men through two parallel-axis grips. These assemblies shall beflat, smooth, and clean. Specimen contact surfaces of platenshall be coated with a PTFE spray lubricant. The thickness ofthe platens shall be sufficient so that no bending or deformationoccurs during the test, but it shall not be less than 12 mm (0.5in.). The nominal length of each grip shall equal or exceed thespecimen length but shall not be less than 1040 mm (41 in.).Upper and lower grips shall be free to rotate about an axis inthe plane of the applied and reacting line loads. Recommendedarrangement of loading frame, upper and lower grips with testspecimen are shown in Fig. 1.6.3 Deformation Indicator—The change in total wall (majorwall for profile wall pipe) thickness at springline, shall beF2433 − 05 (2013)2measured with a suitable instrument meeting the requirementsof 4.1.2 of Test Method D695, except that the instrument shallbe accurate to the nearest 0.025 mm (0.001 in.). The instrumentshall not affect in any way the load-deflection measurements.6.4 Load Sensor—The change of load with time during theperiods of displacement (loading) and during the period ofconstant displacement shall be digitally recorded with a preci-sion of no less than 4 significant figures and at time intervals asnoted in 9.3. The sensing element shall have a precision of62 % of maximum recorded value.6.5 Temperature Recorder—Ambient temperature shall becontinuously recorded using a sensor capable of recording to1°C (1.8°F).6.6 Reaction Frame—The reaction frame shall be suffi-ciently rigid such that the movement of the stationery platenshall not exceed 0.05 % of the displacement of the movingplaten.7. Test Specimens7.1 Test specimens shall be cut from the pipe wall, with thecuts through the wall radial and parallel through the samplelength. Test specimens may be the required arc length indegrees 61° arc sections of the wall, as agreeable to themanufacturer and the purchaser, but not less than 10 degreesnor greater than 120 degrees. Test specimens should be aminimum of 600 mm (24 in.) long, and may be as much as 900mm (36 in.), and for corrugated or profile pipe should besquarely cut in the corrugation or profile valley.NOTE 3—Standard arc lengths for specimens should be 120°, 90°, and30°, though other arc lengths may be used within the range of 120° to 10°,as determined by the needs of the owner, researcher, or testing laboratory.8. Conditioning8.1 Condition the pipe wall section for at least 24 h in air ata temperature of 23 6 2°C (73.4 6 3.6°F), and 50 6 5%relative humidity and conduct the test in a room maintained atthe same temperature.8.2 When a referee test is required, condition specimens forat least 40 h at 23 6 2°C (73.4 6 3.6°F), and 50 6 5 % relativehumidity per Practice D618 Procedure A and conduct the testunder the same conditions.9. Procedure9.1 Before placing each test specimen in the test apparatusmake the following measurements:9.1.1 Measure, to the nearest 1 mm (0.04 in.), the longitu-dinal length with equally spaced parallel measurements at midand quarter points of the arc of the curved beam. Determine thelongitudinal length by averaging the three measurements.9.1.2 For specimens prepared from AASHTO M 252M andAASHTO M 294M Type C pipes, at each of three pointsapproximately located on a mid-longitudinal line of the corru-gated wall, one point located at mid-length and two pointsFIG. 1 Recommended Arrangement of Loading Frame, Upper expressed as Newtons permeter (pounds-force per linear inch), and∆y = measured change in chord length (in the direction ofload application) expressed in millimeters (inches).FIG. 2 Photographs of Specimen in Load Frame (continued)F2433 − 05 (2013)5NOTE 4—Immediately after the moment of initiation of continuousapplication of load, the load of record incorporates the influences of thecontinuing application of load and the relaxation of previously appliedload. The net load at any time t, t 0, is characterized as the residual load;the quantity, load per unit length divided by the associated displacementis characterized as the residual stiffness. These definitions also applyduring the extended period when displacements are held constant withoutfurther application of load.10.1.2 For the interval beginning at the instant of loadapplication and ending when the deflection of the curved beamreaches 10 % shortening of the chord, plot, on cartesiancoordinates, curved beam stiffness, K(t) versus % deflection.10.1.3 Through the points between 2 % deflection and 8 %deflection fit a least squares estimate of a straight line.10.1.4 Calculate the intercept, K(0) at time t =0.NOTE 5—Stiffness versus deflection is typically a smooth curve. Theeffective zero point of zero time is established by deleting the stiffness-time record prior to, and immediately after, the application of loadrecorded and extrapolating the initial straight line portion of the curvebackwards to zero load.10.2 Estimate the residual pipe wall stiffness, K(t),of300mm (12 in.) diameter solid wall pipes after 50 years, K(50y),and after 100 years, K(100y).10.2.1 Calculate and plot the residual stiffness, K(t) versus1/log(t), t = time in seconds, for all points beginning at the timeof 10 % displacement of the curved beam extending through aperiod of no less than six (6) weeks.10.2.2 Using the method of least squares linear regre