1、TIA/EIA TELECOMMUNICATIONS SYSTEMS BULLETIN ITM-13 Measuring Dynamic Strength and Fatigue Parameters of Optical Fibers By Two-Point Bending TSB62-13 MAY 2000 TELECOMMUNICATIONS INDUSTRY ASSOCIATION “ Representing the telecommunications industn in asoctition with the Electronic industrier Alliance El
2、ectronic Industries Alliance STD-EIA TSB62-L3-ENGL 2000 H 3234600 0656568 162 .I NOTICE TWEIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement o
3、f products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of TWEIA from manufacturing or selling products not conforming to s
4、uch Standards and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than TIA/EIA members, whether the standard is to be used either domestically or internationally. Standards, Publications and Bulletins are adopted by EL4 in accordan
5、ce with the American National Standards Institute (ANSI) patent policy. By such action, TIA/EIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard, Publication, or Bulletin. Technical Bulletins are distinguished from TWEN St
6、andards or Interim Standards, in that they contain a compilation of engineering data or information useful to the technical community, and represent approaches to good engineering practices that are suggested by the formulating comi ttee. This Bulletin is not intended to preclude or discourage other
7、 approaches that similarly represent good engineering practice, or that may be acceptable to, or have been accepted by, appropriate bodies. Parties who wish to bring other approaches to the attention of the formulating committee to be considered for inclusion in future revisions of this Bulletin are
8、 encouraged to do so. It is the intention of the formulating committee to revise and update this Bulletin from time to time as may be occasioned by changes in technology, industry practice, or government regulations, or for other appropriate reasons. (From Project No. 4757, formulated under the cogn
9、izance of the TIA FO-6.6 Subcommittee on Fibers and Materials.) Published by TELECOMMUNICATIONS INDUSTRY ASSOCIATION 2000 Standards and Technology Department 2500 Wilson Boulevard Arlington, VA 22201 PRICE: Please refer to the current Catalog of ELECTRONIC INDUSTRIES ALLIANCE STANDARDS and ENGINEERI
10、NG PUBLICATIONS or call Global Engineering Documents, USA and Canada (1-800-854-7179) International (303-397-7956) All rights reserved Printed in U.S.A. STD-EIA TSBbZ-Lg-ENGL 2000 I 3234600 0656569 UT9 I TINEIA-TSB-62-13 ITM-13 Measuring dynamic strength and fatigue parameters of optical fibers by t
11、wo-point bending CONTENTS Number Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Section 7 Figure 1 Figure 2 Figure 3 Annex A Title Page I iii I 3 3 6 7 10 13 Schematic of two-point bending unit 4 Schematic of surface plate; (a) plan, (b) section - 4 Weibull plot of two-point bending dat
12、a - 9 I STD.EIA TSBb2-13-ENGL 2000 m 3234600 065b570 810 TINEIA-TSB-62-13 ITM-I 3 Measuring dynamic strength and fatigue parameters of optical fibers by two-point bending Foreword (This foreword is informative and is not part of this standard.) This document comes from TIA Standards Proposal 4757, a
13、nd was formulated under the cognizance of TIA FO-6.6 Subcommittee on Optical Fibers and Cables, and TIA FO-6.6.8, Working Group on Optical Fiber Reliability. This ITM is part of the series of test procedures included within Recommended Standard E IARI A-TS B-62, There is one informative annex. Key w
14、ords: distribution. bending, strength, fatigue, failure stress, stress corrosion parameter, Weibull iii Previous page is blank STD-EIA TSBb2-33-ENGL 2000 3234b00 0656573 757 W TINEIA-TSB-62-13 ITM-I 3 Measuring dynamic strength and fatigue parameters of optical fibers by two-point bending I Introduc
15、tion 1.1 Intent This procedure provides a method for measuring the strength and dynamic fatigue of optical fiber in two-point bending in a specified environment. The stress is increased at a nominally constant rate until breakage occurs. This test can be applied to fibers in ambient conditions or to
16、 fibers that are in various aging conditions exposed to alternative environments. Two-point bending avoids difficulties that may be associated with gripping some fibers in tensile testing. It utilizes many samples of short lengths of fiber simultaneously, facilitating comparison of different fiber s
17、amples and reducing scatter in the data. It can measure strength and fatigue in different environments since the fiber and surface plates can be immersed in the environment of interest. However, compared with tensile testing, the effective fiber lengths under stress are very short. Changes in the fa
18、ilure stress distribution that occur by changing stress rate can be used to measure the stress corrosion parameter n . For Weibull distributions, procedures are given to determine the Weibull dynamic shape parameter md and scaling parameter So. Some distributions are not Weibull, such as bimodal Wei
19、bull distributions, but can be related to Weibull. This method is not intended for the evaluation of the second (low-strength) Weibull mode. See FOTP-28 for this. 1.2 Scope This procedure is appropriate for coated and uncoated fibers, but is not appropriate for jacketed or “tight buffered“ fibers. I
20、t measures the strength and the stress corrosion parameters of optical fiber at specified constant strain rates. The ITM is useful in comparing the effects of different environmental treatments. It is a destructive test, and is not a substitute for prooftesting. This method tests the fatigue behavio
21、r of fibers by varying the strain rate. The test is applicable to fibers and strain rates for which the relationship of log of failure stress vs. log of stress rate is essentially linear. Other approaches are feasible for non-linear results. The test environment and any preconditioning or aging is c
22、ritical to the outcome of this test. There is no agreed upon model for extrapolating the results for one environment to another 1 STD-EIA TSBb2-L3-ENGL 2000 3234b00 0656572 b93 = TINEIA-TSB-62-13 environment. For failure stress at a given stress rate, however, as the relative humidity increases, fai
23、lure stress decreases. Both increases and decreases in the measured stress corrosion parameter and strength distribution parameters have been observed as the result of preconditioning at elevated temperature and humidity for even a day or two. Agreement between the results of ITM-13 and the results
24、of FOTP-28 is a matter for study, and the results of this ITM are not to be used directly to predict fiber reliability. I .3 Background This test is based on the theory of fracture mechanics of brittle materials and on the power-law description of flaw growth (see TSB-61). Although other theories ha
25、ve been described elsewhere, the fracture mechanics/power-law theory is the most generally accepted. There are several other fatigue tests that are related to this test: 0 Static fatigue in tension 0 Dynamic fatigue in tension 0 0 Static fatigue in bending Static fatigue in two-point bending While t
26、hese tests theoretically measure the same properties, differences between the measured values have been observed. 1.4 Other A typical population consists of fiber that has not been deliberately damaged or environmentally aged. A typical fiber has a nominal diameter of 125 pm, with a 250 pm or less n
27、ominal diameter acrylate coating. Default conditions are given for such typical populations. Atypical populations might include alternative coatings, environmentally aged fiber, or deliberately damaged or abraded fiber. 1.5 Hazards This test involves bending sections of optical fiber until breakage
28、occurs. Upon breakage, glass fragments can be distributed in the test area. Protective screens are recommended. Safety glasses shall be worn at all times in the testing area. 2 STD-EIA TSBb2-13-ENGL i000 3234h00 Ob56573 52T = TINEIA-TSB-62-13 2 Normative references Test or inspection requirements in
29、clude, but are not limited to, the following references: Standard Test Procedures for Fiber Optic Fibers, Cables, Transducers, Sensors, Connecting and Terminating Devices, and Other Fiber Optic Components FOTP-28 (TINEIA-455-28C) Measuring dynamic strength and fatigue parameters of optical fibers by
30、 tension FOTP-161 (EIA/TIA-455-161) Procedure for Measuring High Temperature and Humidity Aging Effects on Mechanical Characteristics of Optical Fibers FOTP-173 (EIMIA-455-173B) Coating Geometry Measurement for Optical Fiber Side- View Method FOTP-176 (EIA/TIA-455-176) Measurement Method for Optical
31、 fiber Geometry by Automated Gray-Scale Analysis TSB-61 (TINEIA-61) Power-law theory of optical fiber reliability 3 Apparatus A possible test apparatus is schematically shown in Figures I and 2. This equipment is designed to measure the strain/stress required to break an optical fiber in a two-point
32、 bending geometry by measuring plate separation at failure. 3.1 Stepper motor control Use a device that allows accurate, reliable, repeatable motorized control of a translation stage. Use a maximum step length of 1 pm. A step length of 0.1 pm could be used for higher accuracy. in preparation 3 STDmE
33、IA TSBb2-13-ENGL 2000 3234b00 Ob5b574 4bb II TINEIA-TSB-62-I 3 Movable PI mri coating , the cross- sections may typically be rectangular or semi-circular. With an uncoated bare fiber, there may be no groove used, and the plate surface must be highly polished to avoid damage to the fiber. 3.3 Plate s
34、eparation and velocity Place the fiber between two plates at a separation of 1 O to 15 mm, including groove depths d, , unless otherwise specified in the Detail specification. Bring these together by the computer- controlled stepper motor at a constant plate velocity (specified below) until the fibe
35、r breaks. (Comparable constant strain or constant stress rates may also be used.) For slower rates, fibers may be preloaded at 1000 pmls to about 50% of their expected failure strain. The latter may be estimated from tests at higher rates. Unless otherwise specified in the Detail Specification, For
36、dynamic strength measurements: 0 Use a plate velocity of 1 O0 pm/s. For dynamic fatigue measurements: 0 Use plate velocities of 1, IO, 100, and 1000 pm/s. Note: For dynamic strength, some slight variations are expected depending on the method chosen. For dynamic fatigue, the results are not sensitiv
37、e to whether the rates are constant in plate velocity or fiber stress or strain, as long as one method is used over all stress rates. 3.4 Fiber failure detecting system One of the following techniques may be used to detect fiber failure. In each case, the computer records the plate separation at the
38、 time of each failure. It may stop the plate motion appropriately. 0 An acoustic emission detector or transducer. It detects the sound of breakage. For simultaneous multiple breaks, the sound intensity may be calibrated. 0 A force (pressure) transducer incorporated into the stationary plate to measu
39、re force exerted on the fiber. It detects when the force decreases at breakage. For simultaneous multiple breaks, the force decrease may be calibrated. 0 An optical power monitor for light launched in the fiber. It detects zero transmission at breakage. Simultaneous multiple breaks are readily detec
40、ted. Obtain the plate separation d, at fracture. 5 STD-EIA TSB62-13-ENGL 2000 m 3234600 0656576 237 = TINEIA-TSB-62-13 3.5 Characterization of stress rate For the stress corrosion parameter, characterize the stress rate for each nominal strain rate, coating, and environmental treatment. For non-typi
41、cal weak fiber, a stress rate measurement for each individual specimen is recommended. Prepare a plot of applied stress CJ vs. time t using tensile load measurements and equations in 6.1. Let t(o) represent the time at a given stress level, and let of be the failure stress of a typical specimen. The
42、n the stress rate for the stress corrosion parameter, a sample size of 15 per strain rate is often used. Any deviation from these values are to be specified in the Detail Specification. 4.3 Environment There are two key environmental considerations: aging environment and test environment. Fiber agin
43、g is sometimes required, for example per FOTP-161. Even brief accelerated aging may produce increases or decreases in the measured strength and stress corrosion parameter of some fibers. The causes of these phenomena are not well understood. As a consequence, extrapolation methodologies from acceler
44、ated aging environments to other environments are under study. After extensive aging, the coating surface friction may be altered. The stress rate characterization in 3.5 should be done for each aging condition, coating type, and nominal strain rate. After any aging and before any testing, fiber spe
45、cimens should be pre-conditioned in the test environment for at least 12 hours. The typical test environment is 23 OC. (12“) and 50 % R.H. (+5%). Alternative environments, such as high non-precipitating relative humidity, can yield significantly different stress corrosion parameters and failure stre
46、ss values. 5 Procedure 5.1 Preliminary steps 5.1.1 For calibration, set the distance reading between the plates to zero when the faces of the plates (which should have been carefully cleaned) are completely touching. When contact is made, the readout on the stepper motor controller should be zero. V
47、erify the plate separation value d when the fiber breaks by checking the distance with a gauge block. The zero position should be repeatable to 15 pm. 5.1.2 Age the specimens if required. 5.1.3 Precondition the specimens. 5.1.4 For characterization of the stress corrosion parameter on deliberately d
48、amaged fiber, randomize the fiber sections among the stress rates. 7 TINEIA-TSB-62-13 5.2 Procedure for single or multiple specimens 5.2.1 Carefully grasp both ends of the test specimen, bend it carefully, insert it between the plates, in one set of grooves (if used), and pull it upwards to position
49、 as shown in Figure 2. Do not touch the bent fiber (gage length) with fingers when handling or loading fibers. The apex of the fiber should always be at the same position in the fixture to minimize the effect of nonparallel plates. Fiber orientation, whether up or down, does not matter. 5.2.2 Repeat with additional specimens. Note: For an uncoated bare fiber, only one specimen is typically used because relatively more care is needed in handling and because a fracture of one specimen would likely trigger failure of others. Ungrooved highly polished pla
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