1、 Institute of Environmental Sciences and Technology Design, Test, and Evaluation Division IEST-RP-DTE032.2 Recommended Practice 032.2 Pyroshock Testing Techniques Arlington Place One 2340 S. Arlington Heights Road, Suite 100 Arlington Heights, IL 60005-4516 Phone: (847) 981-0100 Fax: (847) 981-4130
2、E-mail: iestiest.org Web: www.iest.org 2 IEST 2009 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE032.2 This Recommended Practice is published by the Institute of Environmental Sciences and Technology (IEST) to ad-vance the technical and engineering sciences. Use o
3、f this document is entirely voluntary, and determination of its appli-cability and suitability for any particular use is solely the responsibility of the user. Use of this Recommended Practice does not imply any warranty or endorsement by IEST. This Recommended Practice was prepared by and is under
4、the jurisdiction of Working Group 032 of the IEST Design, Test, and Evaluation Division. Copyright 2009 by the Institute of Environmental Sciences and Technology First printing, October 2009 ISBN 978-0-9841330-2-4 PROPOSAL FOR IMPROVEMENT: The Working Groups of the Institute of Environmental Science
5、s and Tech-nology are continually working on improvements to their Recommended Practices and Reference Documents. Suggestions from users of these documents are welcome. If you have a suggestion regarding this document, please use the online Proposal for Improvement form found on the IEST website at
6、www.iest.org. Institute of Environmental Sciences and Technology Arlington Place One 2340 S. Arlington Heights Road, Suite 100 Arlington Heights, IL 60005-4516 Phone: (847) 981-0100 Fax: (847) 981-4130 E-mail: iestiest.org Web: www.iest.org IEST-RP-DTE032.2 Institute of Environmental Sciences and Te
7、chnology IEST 2009 All rights reserved 3 Pyroshock Testing Techniques IEST-RP-DTE032.2 CONTENTS SECTION 1 SCOPE 5 2 REFERENCES 5 3 TERMS AND DEFINITIONS 6 4 BACKGROUND AND OVERVIEW . 7 5 PYROTECHNICALLY EXCITED NEAR-FIELD SIMULATION 21 6 MECHANICALLY EXCITED MID-FIELD AND FAR-FIELD SIMULATION . 23 7
8、 STANDARD SHOCK-TESTING MACHINES WITH CLASSICAL PULSE TESTS (NOT RECOMMENDED) 31 8 MECHANICALLY EXCITED NEAR-FIELD SIMULATIONS . 31 FIGURE 1 TYPICAL ACCELERATION-TIME HISTORY FOR A PYROSHOCK 7 2 ACCELERATION SRS AND TIME HISTORY FOR A NEAR-FIELD PYROSHOCK (DAMPING = 5%) 9 3 ACCELERATION SRS AND TIME
9、 HISTORY FOR A FAR-FIELD PYROSHOCK (DAMPING = 5%) 9 4 NEAR-FIELD PYROSHOCK DATA WITH ERRONEOUS ACCELEROMETER OFFSET . 11 5 NEAR-FIELD PYROSHOCK DATA CORRECTED WITH WAVELETS 13 6 NEAR-FIELD PYROSHOCK DATA REPEATABILITY FOR A PLATE (16 TESTS) 15 7 NEAR-FIELD PYROSHOCK DATA REPEATABILITY FOR A NASA STR
10、UCTURE (48 MEASUREMENTS: SIX LOCATIONS MEASURED FOR EIGHT TESTS) 16 8 NEAR-FIELD PYROSHOCK NOISE CHANNEL DATA 18 9 ORDNANCE-GENERATED PYROSHOCK SIMULATOR 21 10 SCALED TESTS USING REPRESENTATIVE STRUCTURE 22 11 BOUNDED IMPACT TEST METHOD IMPLEMENTED ON A STANDARD DROP TABLE 23 12 FULL-SCALE PYROSHOCK
11、 SIMULATION WITH RESONANT SIMULATOR. MEASUREMENTS AT COMPONENT LOCATIONS CONFIRM SIMULATION SUCCESS . 24 13 MIPS SIMULATOR . 25 14 ACCELERATION SRS AND TIME-HISTORY FROM A TUNED RESONANT FIXTURE (DAMPING = 5%) 26 15 RESONANT PLATE TEST METHOD (PLATE IS FREELY SUSPENDED) . 27 16 RESONANT BAR TEST MET
12、HOD (BAR IS FREELY SUSPENDED) 27 17 TUNABLE RESONANT BEAM TEST METHOD . 28 18 TRIAXIAL ACCELERATION MEASUREMENTS FOR THE UNIQUE RESONANT FIXTURE SURVEY WITH THREE-AXES RESPONSE . 29 4 IEST 2009 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE032.2 19 TRIAXIAL ACCELE
13、RATION SRS CALCULATIONS FOR THE UNIQUE RESONANT FIXTURE WITH THE ACTUAL TEST UNIT 30 20 KNEE FREQUENCY IN THE SRS FOR THE UNIQUE RESONANT FIXTURE WITH THE ACTUAL TEST UNIT 31 TABLE 1 COMPARISON OF PUBLISHED PYROSHOCK DEFINITIONS . 8 APPENDIX A BIBLIOGRAPHY . 32 IEST-RP-DTE032.2 Institute of Environm
14、ental Sciences and Technology IEST 2009 All rights reserved 5 Institute of Environmental Sciences and Technology Design, Test, and Evaluation Division Recommended Practice 032.2 Pyroshock Testing Techniques IEST-RP-DTE032.2 1 SCOPE This Recommended Practice (RP) provides an over-view of pyroshock te
15、sting concepts and compares pro-visions from other pyroshock documents. Much of this RP is devoted to acquisition and analysis of pyroshock data because proper time-history data acquisition and test specification development are common test indus-try problems. To avoid corrupted pyroshock data and r
16、esulting inaccurate pyroshock specifications, recom-mended practices for instrumentation and data acquisi-tion systems are given. If pyroshock testing equipment is used to simulate the detonation of a pyrotechnic device, a unique, custom design is usually required, with a few exceptions. There is no
17、 universal pyroshock testing technique or equipment that can handle all specifications and all dimensions for units under test, whether test units are individual components, subsystems, or complete sys-tems. This RP includes examples of different concepts and equipment configurations and notes any l
18、imita-tions. Several sections are devoted to the design and use of resonant fixtures for pyroshock simulations. Additionally, this RP contains an example of a three-dimensional pyroshock simulation with one impact to a resonant fixture that can provide a realistic simula-tion of pyroshock and preven
19、t mechanical failure caused by overtesting with single-axis sequential test procedures. CAUTION: Testing in accordance with this RP may involve hazardous materials, operations, and equip-ment. This RP does not purport to address all of the safety problems associated with its use. It is the re-sponsi
20、bility of the user to consult safety guidelines and establish appropriate safety practices, and to determine the applicability of regulatory limitations prior to use of this RP. 2 REFERENCES The following documents are incorporated into this RP to the extent specified herein. Users should apply the
21、most recent editions of the references. See Appendix A for informative references cited in this RP and addi-tional resources. IEST-RD-DTE012: Handbook for Dynamic Data Ac-quisition and Analysis. ISO 18431-4: Mechanical vibration and shockSignal processingPart 4: Shock-response spectrum analysis MIL-
22、STD-810: Environmental Engineering Consid-erations and Laboratory Tests, Method 517, Pyro-shock. NASA-STD-7003: Pyroshock Test Criteria. 2.2 Sources and Addresses IEST Institute of Environmental Sciences and Technology Arlington Place One 2340 S. Arlington Heights Road, Suite 100 Arlington Heights,
23、IL 60005-4516 Phone: (847) 981-0100 Fax (847) 981-4130 www.iest.org ISO In US, documents may be obtained from: IEST Arlington Place One 2340 S. Arlington Heights Road, Suite 100 Arlington Heights, IL 60005-4516 Phone: (847) 981-0100 Fax (847) 981-4130 www.iest.org Outside U.S.: Documents available f
24、rom representative ISO member organization 6 IEST 2009 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE032.2 US Military Standards Standardization Document Order Desk 700 Robbins Avenue Bldg. #4, Section D Philadelphia, PA 19111-5094, USA http:/dodssp.daps.dla.mil/
25、NASA Technical Standards NASA Headquarters Washington, DC 20546-0001 Phone: (202) 358-0001 Fax: (202) 358-4338 http:/standards.nasa.gov 3 TERMS AND DEFINITIONS damping ratio For a system with viscous damping, the ratio of the actual damping coefficient to the critical damping coefficient or the frac
26、tion of critical damping. = c/ccis the symbol typically used. dB A decibel for acceleration or an acceleration-based shock response spectrum (SRS) in this case is defined as: 20 log10(new level/nominal level). The nominal level for acceleration is almost always 1 g. dB/octave A slope used for an acc
27、eleration-based SRS. An octave is a doubling in frequency. A pyroshock slope is 9 to 12 dB/octave or 1.5 to 2 decades in amplitude to one decade in frequency. Fourier transform; discrete Fourier transform (DFT) The representation of a time-history by a harmonically related series of sines and cosine
28、s. The digitally sam-pled time-history is represented by the DFT. g The acceleration of gravity: 9.8 m/sec (386 in./sec, or 32.2 ft/sec). g-level Acceleration time-history amplitude of a pyroshock as measured by an accelerometer calibrated in gs. knee frequency The dominant frequency in a pyroshock
29、SRS, at which the slope for the SRS changes from an approximate +9 dB/octave slope to an approximately horizontal slope with peaks at the major local structural frequen-cies. All pyroshock SRS have a knee frequency, even if not properly measured or quantified. maximax SRS The maximum of the positive
30、 and negative primary and of the positive and negative residual. Nyquist frequency The highest frequency identified in a DFT, equal to one-half of the sample rate. pseudo-velocity A widely used approximation for a relative velocity SRS is given by the relative displacement SRS multip-lied by 2fn. Fo
31、r hard impact and pyroshock transients, a relative velocity or pseudo-velocity SRS generally covers a much narrower dynamic range than either an absolute acceleration or a relative displacement SRS. pyroshock (also called pyrotechnic shock) The result of an explosive event, such as an explosive char
32、ge to separate two stages in a multi-stage rocket, and the resulting high-frequency (as high as 1 MHz), high-magnitude material stress phenomenon that prop-agates throughout the structure. pyroshock, far-field Pyroshock sufficiently distant from the pyrotech-nic source that significant energy has tr
33、ansferred into the lower frequency structural response. Far-field pyroshock contains lower frequency and lower g-level energy than mid-field pyroshock; most of the energy is usually concentrated at one or a few frequencies at 3 kHz or less that corre-spond to dominant structural mode(s). Additional-
34、ly, some energy is dissipated by friction, material deformation, and heating and is not manifested in the lower structural frequency response. pyroshock, mid-field Pyroshock at a distance from the pyrotechnic source where significant energy is still contained in material stress-wave propagation, but
35、 some energy has transferred into the lower frequency structural response. Mid-field pyroshock contains lower frequency and lower g-level energy than near-field pyroshock; most of the energy is usual-ly concentrated at frequencies between 3kHz and 10 kHz. pyroshock, near-field Pyroshock close to the
36、 pyrotechnic source, at a point before significant energy is transferred to the modal structural response. This type of pyroshock is dominated by material stress-wave propagation from the source, and contains very high frequency and very high g-level energy, which is distributed over a wide frequenc
37、y range and is not generally dominated by a few selected frequencies. Q The quality factor, 1/2. Typically, Q = 10 for an acce-leration-based pyroshock SRS. shock response spectrum (SRS) The maximum response of a single-degree-of-freedom system to a shock input, plotted as a function of the IEST-RP-
38、DTE032.2 Institute of Environmental Sciences and Technology IEST 2009 All rights reserved 7 natural frequency of the system with a constant damp-ing value. The response and the input may be accelera-tion, velocity, or displacement. The damping value used for an SRS specification may affect the abili
39、ty to meet that specification. Typically the maximum of the positive and negative SRS (maximax) is plotted, but many specifications require the positive SRS and nega-tive SRS to be calculated separately and shown on the same log-log plot. In all cases, the SRS should be cal-culated according to ISO
40、18431-4. single degree of freedom Motion described by a single coordinate. slew rate The maximum slope or rate of change of a sinusoidal wave form. 4 BACKGROUND AND OVERVIEW Pyroshock (also called pyrotechnic shock) testing may be required for test items, subsystems, and full-scale or complete syste
41、ms that must withstand an explosive event, such as an explosive charge to separate two stages in a multi-stage rocket, and the resulting high-frequency (as high as 1 MHz), high-magnitude materi-al stress phenomenon that propagates throughout the structure. Pyroshock was once considered a relatively
42、mild environment due to the relatively low velocity change (as compared to impact mechanical shock) and high-frequency content involved. Although pyroshock rarely damages structural members, pyroshock can easily cause failures in electronic test items that are sensitive to the high-frequency pyrosho
43、ck energy. Many flight failures have been attributed to pyroshock compared to other types of shock or vibration sources. In one case, an extensive database of the failures due to pyroshock has been compiled.1The types of failures caused by pyroshock commonly include relay chatter, separation of smal
44、l-circuit test items, and the dislodg-ing of contaminants (e.g., solder balls) that cause short circuits. Designers should rely on testing of systems and components exposed to pyroshock because of the absence of adequate analytical techniques to predict high-frequency structural response. Implementa
45、tion of a qualification test program can reduce failures caused by pyrotechnic shock. Figure 1 shows a typical pyroshock acceleration-time history and displays the general characteristics of a pyroshock. The initial pyroshock acceleration magni-tude may be as high as 200,000 g or higher, as it is a
46、function of the measurement technique and digital sig-nal processing as well as the source type and size or strength, intervening structural path characteristics (in-cluding structural type and configuration, joints, fasten-ers, and other discontinuities), and distance from the source to the respons
47、e point of interest. The pyroshock acceleration-time history is a decaying oscillatory acce-leration transient that decays to a few percent of the maximum within a few (typically no more than 20) msec. The characteristics of the pyroshock accelera-tion-time history, i.e., the magnitude and frequency
48、 content, vary with the distance from the pyroshock event. As discussed in this RP, the pyroshock frequen-cy content is assessed with the shock response spec-trum (SRS). In this document, three types of pyroshock Figure 1Typical acceleration-time history for a pyroshock. IEST2009 Allrightsreserved8
49、IEST 2009 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE032.2 are distinguished: near-field, mid-field, and far-field. Although the differences among the three types of py-roshock are not always clearly defined for a particular structure, the major differences are defined here in terms of their corresponding test techniques. The three types of pyroshock should be used as guidelines and not rigid definitions of acceleration amplitude or SRS frequency characteristics. The acceleration time history and resulting SRS for a l
