1、MIL-M-L9863D 53 9999906 0477045 O NON-MEASUREMENT SENSITIVE Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Commander, Naval Sea Systems Command, SEA 5523, Department of the Navy, Washington, DC
2、 20362-5101 by using the self-addressed Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter. n MIL-M-l9863D(SH) 8 Mav 1991 SUPERSEDING 1 April 1966 (See 6.14) MIL-M-l9863C(SHIPS) MILITARY SPECIFICATION MOUNT, RESILIENT: TYPE 5B5,OOOH This s
3、pecification is approved for use by the Naval Sea Systems Command, Department of the Navy, and is available for use by all Departments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope. This specification covers the type 5B5,OOOH resilient mount assembly together with tests for evaluatin
4、g the rubber stocks and the completely assembled mount. a resonant frequency of 5 . The film thickness of the oil and ozone coating shall be measured on the coated metal steel plate to determine conformance with the requirement of table II. The thickness of the coating shall be determined by either:
5、 using a magnetic type thickness gauge 15 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-M-LS63D 53 9999906 0477060 7 MIL-M-l9863D(SH) in accordance with ASTM D 1186, using a micrometer to measure the thickness of the steel plate before and afte
6、r the coating is applied, or by other valid and accurate procedures. (The manufacturer shall not determine the coating thickness by measuring the thickness of different coated and uncoated steel plates, unless he demonstrates that his procedure is valid and accurate.) 4.6.11 Impact resilience test.
7、Impact resilience tests shall be in accordance with ASTM D 1054. Two specimens shall be tested and the results averaged. 4.6.12 Specific gravity. - The specific gravity of the rubber samples shall be determined according to ASTM D 792 on specimens cut from 0.08 by 6 by 6 inch (2 by 150 by 150 mm) sh
8、eets. The average of three measurements shall be used to determine conformance with 3.2.2.5. 4.6.13 Test for deflection at 5.000 pounds load. A universal type testing machine shall be used. A mount without snubber cones shall be secured on a jig. It shall be subjected to four loading cycles in the a
9、xial direction (see 6.5.1). Three loadings shall be at a rate not greater than 0.3 inch per minute. The fourth loading cycle shall be at a rate of 0.05 inch per minute. The deflection at 5,000 pounds load for the fourth loading cycle shall be measured to the closest 0.001 inch. While deflected, the
10、mount shall be examined for a break or separation between the component parts. 4.6.14 Dynamic stiffness test. Dynamic stiffness shall be measured for the mount in the axial direction at loads of 3,500 and 5,000 pounds to determine conformance with 3.4.1. 4.6.14.1 General procedure. There are two bas
11、ic types of tests for determining these properties: resonant and nonresonant methods. An example of each method is given in 4.6.14.2 and 4.6.14.3. Although the manufacturer is not required to use these exact procedures, his test procedures shall follow the guidelines given in ASTM D 2231 and IS0 285
12、6, and in addition, where mechanical mobility is measured, ASA 31 and ASA 32. instrumentation should have the following general characteristics: In accordance with ASTM D 2231, (a) Adequate sensitivity and resolution for transducers, signal (b) Adequate dynamic range and signal to noise ratio for th
13、e range of (c) Flat frequency response and good amplitude linearity within the (d) Essentially no zero drift or calibration change within the test (e) Low sensitivity to changes in temperature. conditioners, and readout instrumentation. specimen stiffnesses to be measured. range of measurements. per
14、iod. The test machine should be decoupled from the floor with soft mounts where possible to minimize the effect of background vibration on the measurement results. The components of the test machine in series with the specimens should be very stiff to minimize systematic error in the measurement. Wh
15、ere systematic 16 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NIL-N-39863D 53 W 9999906 0477063 9 H error in the dynamic stiffness measurement due to machine flexibility exceeds 1 percent, the results should be corrected for this effect (see 4.6.
16、14.4.4). For both resonant and nonresonant tests, the measurements shall be conducted using sinusoidal vibration with a displacement amplitude of approximately 0.008 inches (0.2 mm) peak-to-peak. For nonresonant tests, the nominal frequency of excitation shall be 6 hertz for all mounts except the 73
17、450, 7E450BB, and 533500 mounts where the nominal shall be 7 hertz and 5 hertz respectively. facturer shall include a detailed description of his test equipment and procedures used to measure dynamic stiffness or resonance frequency, The Government reserves the right to perform these tests on mounts
18、 offered for qualification. When qualifying the manu- 4.6.14.2 Resonant methods. Figure 1 shows a typical apparatus for the direct measurement of resonance frequency of a mount. The test load is applied to the mount by weights suspended from a steel rod. electromagnetic shaker and impedance head att
19、ached to the bottom of the rod using swept sinusoidal vibration with a sweep rate low enough to achieve quasi-steady- state response. The instrumentation of figure 1 is used to measure the ratio of velocity to force, or mechanical mobility of the system. of acceleration to force (accelerance) or dis
20、placement to force (dynamic compliance) could be used in lieu of mobility.) The fundamental resonance frequency of the system occurs at the lowest frequency corresponding to a maximum in the mobility, accelerance, or dynamic compliance ratios as applicable. Because of flexibility in the components o
21、f the test apparatus that are in series with the mount (test frame, hanger rod, and so forth), the system resonance frequency that is measured will be lower than the (true) resonance frequency of the mount-mass system that would be measured with a rigid apparatus. in measuring resonance frequency ex
22、ceeds 1 percent, the measurement must be corrected to determine conformance with 3.4.1. A procedure for obtaining the corrected resonance frequency is given in 4.6.14.4.4. measurement error to be less than 1 percent (and not require correction), the static stiffness of the test apparatus must be at
23、least 50 times greater than the dynamic stiffness of the mount being tested. In practice, most measurements made using the system of figure 1 to test mounts will require correctlon since the stiffness of the hanger rod itself, usually the most flexible element of the system, is generally less than 5
24、0 times stiffer than the mount. In no case, however, shall measurement systems be used which result in stiffness ratios less than 30. The system is excited with an (Alternatively the ratio Where such systematic error It is noted that for the 4.6.14.2.1 Optional instrumentation. In lieu of using an i
25、mpedance head as shown in figure 1, separate force and motion transducers may be used. system operates in a closed loop mode using the signal from the force transducer to control a shaker and maintain constant input force to the system while conducting the frequency sweep. transducer is a maximum is
26、 considered to be the system resonance frequency, The requirements as in 4.6.14.2 apply in determining if a correction must be made to the measurements in determining conformance with 3.4.1. One such The frequency at which the signal from the motion 4.6.14.3 Nonresonant methods. These methods are ba
27、sed on the transmitted force principle and used a linear dynamic model consisting of a parallel combination of an ideal spring and dashpot to represent an elastomeric specimen. Although a more exact model includes a mass term, it may be omitted with 17 Provided by IHSNot for ResaleNo reproduction or
28、 networking permitted without license from IHS-,-,-MIL-M-L9863D 53 = 9997906 0477062 O negligible error for relatively light specimens, stiff load cells, and low excitation frequencies. The method requires the measurement of two independent quantities: the sinusoidal displacement or velocity across
29、the specimen and the resulting force transmitted through the specimen as well as the phase relationship between them. is the closed-loop servohydraulic test machine shown schematically in figure 2. The machine consists of a load frame, hydraulic actuator, load cell, and associated hydraulic and elec
30、tronic components which permits a static load to be applied to a rubber specimen while an oscillatory vibration is superimposed upon it. The machine operates in a closed-loop mode utilizing the feedback signal from either the force or motion transducer to control the hydraulic actuator. Tests are us
31、ually conducted in the force control mode so that a constant load is maintained on the specimen while it creeps. Electronic circuitry controlling the servo valve permits the operator to independently vary the vibration frequency, amplitude, and static load applied to the specimen. Dynamic stiffness
32、is calculated from the measured force and displacement signals as follows: A commonly used type of equipment for conducting such measurements K = (F/X) COS where: K = Uncorrected dynamic stiffness of specimen, lbf/in (kN/m). F = Amplitude of sinusoidal force transmitted through the specimen, X = Amp
33、litude of sinusoidal displacement applied to specimen, in 4 = Phase angle between force and displacement phasors. C = Scaling factor determined by the procedure given in 4.6.14.4.2. lbf (kN). (m) * As in the case of resonant testing, flexibility in components of the test apparatus that are in series
34、 with the specimen (primarily the load cell and test frame) can result in measured values of dynamic stiffness for the specimen that are lower than if the apparatus were rigid. Where an overall system calibration (which includes machine flexibility) using steel coil springs is not performed (see 4.6
35、.14.4.2) and the basic sensitivities of the transducers are used instead to calculate dynamic stiffness, the measurements shall be corrected to determine conformance with 3.4.1 if the systematic error exceeds 1 percent. Procedures for correcting such errors are given in 4.6.14.4.4. For such systems
36、it is noted that the static stiffness of the test apparatus must be at least 100 times the dynamic stiffness of the specimen in order to limit the error to 1 percent (and require no correction). Regardless of the type of calibration used, however, measurement systems which result in stiffness ratios
37、 less than 30 shall not be used. 4.6.14.4 Calibration of test systems. All systems used to conduct resonance frequency or dynamic stiffness measurements shall be calibrated before use. Although the calibrations discussed in this section are combined system calibrations, basic calibrations should be
38、performed on the individual components of the measurement system (transducers, signal conditioners, and so forth) if difficulties are encountered with the combined system calibration and should in any case be conducted at regular intervals. 18 Provided by IHSNot for ResaleNo reproduction or networki
39、ng permitted without license from IHS-,-,-MIL-N-LSb3D 53 9999906 0477063 2 4.6.14.4.1 Resonance frequency. For measurement of resonance frequency using mobility methods, the operational calibration procedures given in ASA 31 shall be followed. This method involves driving through the impedance head
40、into a freely suspended mass while utilizing the same gains on the force and acceleration channel as will be used in later measurements. measured mobility or accelerance shall be multiplied to obtain the correct value (1/2 xfm) or l/m, as appropriate) for the known mass, m, is calculated and applied
41、 to the subsequent measurements. A scaling factor by which the 4.6.14.4.2 Dvnamic Stiffness. For measurement of dynamic stiffness using servohydraulic test equipment, overall system calibration shall be performed using steel coil springs of known spring rate. Calibration springs shall be selected on
42、 the basis of linear force-deflection properties and shall be used alone or in parallel combinations to produce a spring rate comparable to the dynamic stiffness of the sample to be tested. load within its linear range and apply a sinusoidal vibration of approximately the same amplitude and frequenc
43、y as will be used later in testing the mount samples. Using the same gains as for later measurement on samples, measure the transducer signals proportional to the amplitudes of the transmitted force, the displacement applied to the specimen, and their relative phase. These quantities may then be sub
44、stituted into the equation of 4.6.14.3 to obtain a scaling factor by which the measured stiffness, K, shall be multiplied to equal the known spring rate of the calibration springs. The scaling factor is then applied to subsequent measurements on mount samples. When testing mounts that are softer or
45、stiffer than the springs used to obtain the scaling factor, a new calibration should be conducted using springs of the appropriate stiffness in order to avoid overcorrecting or undercorrecting the measurements. This is especially important for measurement systems that approach the 30 to 1 minimum al
46、lowable stiffness ratio of 4.6.14.3. The procedure is to load the spring(s) to a static 4.6.14.4.3 Measurement of machine stiffness. The stiffness of those components of the test machine in series with the specimen shall be determined experimentally in accordance with the procedures of 4.6.14.4.3.1
47、or 4.6.14.4.3.2 as appropriate. 4.6.14.4.3.1 Resonant freuuencv test equipment. For test systems used to measure resonance frequency (figure i), the rubber test specimen shall be replaced by a stiff steel spacer, the shaker and impedance head removed, and a downward force applied to the bottom of th
48、e hanger rod using a calibrated load cell or proving ring. indicator. The force applied shall be sufficient to insure good resolution for both the force and deflection readings. Several points shall be taken to insure that the force-deflection relationship is linear. The resulting spring rate of the
49、 system shall be used to determine if the measurement system meets the stiffness requirements of 4.6.14.2 as well as the amount (if any) of correction to to be applied to the resonance frequency measurements. Deflection at the bottom of the rod is measured with a dial 4.6.14.4.3.2 Dynamic stiffness test equbment. For test systems used to measure the dynamic stiffness of mounts (figure 2), test machine stiffness can be determined using the internal transducers of the machine itself. Operating in the 19 Pr
