GB/T 13665-1992 Test method for damping capacity of metallic damping materials - Torsion pendulum method and bending resonance method
Some standard content:
UDC669：620.178.5:534.833
National Standard of the People's Republic of China
GB/T 13665—92
Test method for damping capacity of metallic damping materials-Torsion pendulum method and Flexural resonance method
Published on August 19, 1992
Implemented on March 1, 1993
Published by the State Administration of Technical Supervision
National Standard of the People's Republic of China
Test method for damping capacity of metallic damping materiais-Torsion pendulum method and Flexural resonance method method1 Subject content and scope of application
GB/T13665-92
This standard specifies the principle outline, test equipment, sample requirements, test procedures and test result calculation of the torsion pendulum test method and bending resonance method for testing the damping capacity of metal damping materials. The torsion pendulum method in this standard is applicable to the determination of the damping capacity of metal damping materials in the low frequency range (0.1-10 Hz) of torsional vibration at room temperature.
Bending resonance method is applicable to the determination of the damping capacity of bending vibration in the audio frequency range. 2 Terms
Damping capacity: When a metal material is isolated from the outside world, the ratio of the energy lost in one vibration cycle in mechanical vibration to 2 times the energy stored in the material itself (unit is pi). Damping capacity is dimensionless. The damping capacity measured by the torsion pendulum method is represented by the symbol "D,". The damping capacity measured by the bending resonance method is represented by the symbol "D,". 3 Torsion pendulum method
3.1 Principle of the method
3.1.1 When the sample is subjected to free decay vibration on the torsion pendulum, its vibration amplitude will gradually decay. The damping capacity of the sample and the two adjacent amplitudes have the following relationship (see Figure 1):
D, = Iln A,
Where: D,---measured damping capacity; A, amplitude of the nth vibration, n=2.3, is the number of vibrations; A+1--amplitude of the n+1th vibration.
Approved by the State Administration of Technical Supervision on August 19, 1992 (1)
Implemented on March 1, 1993
3.1.2 Test apparatus see Figure 2
r (displacement)
GB/T13665-92
t(time)
1 Light source: 2-Pendulum; 3 Inertial arm: 4-Suspension wire; 5-Pulley; 6-Counterweight: 7-Small mirror; 8 Pendulum; 9-Sample; 10-Upper and lower chucks; 11-Base; 12-Sensor; 13 Amplitude and frequency measuring device
The sample is fastened between the upper chuck and the lower chuck. During measurement, a pure torsional torque is applied to the inertial arm to make it reach a certain torsion angle. 2
GB/T 13665-92
After the torsional moment is removed, the sample vibrates with the torsional vibration of the pendulum. The vibration of the pendulum can reflect the light from the light source to the sensor through a small mirror, or other sensors can be used to directly receive the vibration signal, and the amplitude and frequency values are recorded by the amplitude and frequency measuring device. 3.2 Test device
In order to ensure that the sample performs pure free torsional motion, the torsion pendulum test device should pay attention to avoid external mechanical vibration interference and meet the following requirements. 3.2.1 The weight of the two pendulums is equal, the material of the inertia arm is uniform and balanced to the center, and the vertical deviation of the inertia arm and the pendulum is not more than 13.2.2 The lower chuck should be fixed vertically on the base of the specimen table. The suspension system is required to be vertical so that the eccentricity of the upper chuck and the lower chuck is less than 1mm.
3.2.3 The linearity of the sensor is better than 1%. The minimum resolution of the amplitude and frequency measuring device The scale is 1% of the full scale. The effective number of the frequency measurement shall not be less than three.
3.2.4 The weight of the counterweight is slightly higher than the weight of the entire pendulum. 3.2.5 Use a soft hanging wire, and the friction between the pulley and the shaft is as small as possible. 3.3 Specimens and their preparation
The specimen is required to have uniform material, no macroscopic defects, no axial deflection, and its dimensions are as follows (tolerance ± 0.1mm): length: 70.0~100.0mm,
width: 2.0~4.0mm;
thickness: 0.5~~1.5mm; the ratio of width to thickness is required to be greater than 3; surface roughness R.<6.3μm.
3.4 Test procedure
3.4.1 Fasten the specimen between the upper chuck and the lower chuck, and the entire swinging part has no contact with other objects. 3.4.2 Adjust the pendulum distance (or weight) symmetrically and select the vibration frequency. 3.4.3 Measure the effective length of the sample between the upper and lower chucks. 3.4.4 Apply a torsional moment along the axial direction of the sample to the inertial arm so that the maximum strain amplitude of the sample is no more than 1×10*4. 3.4.5 Release the applied torque to make the torsion pendulum produce free torsional vibration, and measure the amplitude change and vibration frequency by the amplitude and frequency measuring device. 3.4.6 For the same sample, at least three measurements should be taken to obtain the average value to improve the accuracy. 3.5 Calculation of test results
3.5.1 In order to improve the measurement accuracy, the nth amplitude A, and the n+th amplitude A+ (see Figure 1) can be measured, and the damping capacity can be calculated according to the following formula:
D, = ln An
Wherein: the amplitude ratio A,/A+ is within the range of no more than 3. ·(2)
3.5.2 The maximum strain amplitude (shear strain) max of the specimen has the following relationship with the effective length L (mm) of the specimen; the thickness of the specimen (mm); and the torsion angle (radian):
4 Bending resonance method
4.1 Principle overview of the method
(3)
4.1.1 When the specimen is subjected to strong bending vibration under the condition that both ends are free, its damping capacity has the following relationship with the frequency difference Af at half the resonance amplitude and the resonance frequency f. (Figure 3): D. =
Where: D,--measured damping capacity;
Af--resonance amplitude-half frequency difference f2-fi, Hz; f.-resonance frequency value, Hz.
（4）
GB/T13665-92
Where: AT——Period difference at half of the resonance amplitude T2—TS;IAT!
a(amplitude)
4.1.2 The suspension bending resonance method is adopted. The test device is shown in Figure 4. 3
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Transducer"
Oscilloscope
Transducer 2
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The signal generator generates an audio sine electrical signal, which is converted into an alternating mechanical force by transducer 1 to excite the sample vibration. Transducer 2 restores the mechanical vibration of the sample into an electrical signal, which is amplified by the amplifier and displayed on the indicating instrument 2. Change the frequency of the signal generator output signal. When it is consistent with the resonant frequency of the sample, the maximum value (resonant amplitude) of the received signal is observed on the indicating instrument 2. The frequency at this time is measured by a frequency meter, that is, the resonant frequency F of the sample. Keep the reading of indicating instrument 1 constant, increase and decrease the output signal frequency of the signal generator near the resonant frequency. When the indicating instrument 2 shows that the signal amplitude is half of the maximum value, measure the corresponding frequency, that is, the two frequencies f and f2 at half of the resonant amplitude. The excitation signal output by the signal generator and the amplified receiving signal can also be input into the oscilloscope. The oscilloscope displays the Lissajous figure to assist in observing and judging the resonant state of the sample. 4.2 Test device
The instrument should avoid external mechanical vibration interference and meet the following requirements. 4
GB/T 13665-92
4.2.1 Vernier caliper: used to measure the suspension point position of the sample. The minimum division is not greater than 0.05mm. 4.2.2 Signal generator: used to generate audio sinusoidal electrical signals, with a frequency range of 20Hz to 20kHz, a frequency stability of not less than 1×10-\/h, and an amplitude stability of not less than 1%. 4.2.3 Frequency meter: used to measure frequency, and should have the function of measuring signal period. The frequency stability of the crystal oscillator should be not less than 5×10-1/d, and the number of displayed digits should be not less than seven.
4.2.4 Transducer: used to excite and receive the mechanical vibration of the sample, and perform electrical energy to mechanical energy conversion. The linearity of the transducer is better than 1%. 4.2.5 Amplifier: used to amplify the received vibration signal. The linearity of the amplifier is better than 1%. 4.2.6 Indicator: Indicator 1 is used to indicate the amplitude of the driving signal; Indicator 2 is used to indicate the amplitude of the amplified vibration signal. The accuracy of the indicator should be able to reach Class 1 or equivalent digital equipment. 4.2.7 Oscilloscope: used to observe and judge the resonance state of the sample. 4.3 Sample and its preparation
A rectangular strip sample is used, and the material is required to be uniform, without macro defects, and without axial deflection. Its external dimensions are specified as follows (tolerance ±0.1mm):
Length: 80.0~200.0mm;
Thickness: 2.0~~3.0mm;
Width: 4.0~5.0mm;
Surface roughness R, <1.60 μm.
4.4 Test procedure
4.4.1 Measure the length L of the sample with a vernier caliper. 4.4.2 The suspension wires are suspended at 0.224L from the two end points of the sample, with a deviation of no more than 0.5mm. 4.4.3 Use a soft suspension wire with a length of 20 to 30mm. The suspension wire and the sample should not contact other parts of the device. The suspension wire is required to be perpendicular to the axis of the sample and the sample should be kept horizontal. 4.4.4 In order to improve the frequency measurement accuracy, the method of measuring the signal period is adopted. According to Article 4.1.2 of this standard, the resonant frequency f., the frequencies fi and f2 at half the resonant amplitude are measured. At the same time, the corresponding period values T, T1, and T2 are measured. 4.4.5 For the same sample, at least three measurements should be taken to obtain the average value to improve the accuracy. 4.5 Calculation of test results
Substitute the measured values of T., T1, and T2 of the sample into formula (5) to obtain the damping capacity Dr. 5. Presentation of test results
The damping capacity measurement report shall include the following contents: the commissioning unit, metal grade, sample number, sample size, sample state, room temperature, vibration frequency and maximum amplitude of the torsion pendulum method, resonance frequency of the bending resonance method, damping capacity, number of this standard, inspector, inspection date, etc. 6. The damping capacity value measured according to the method of this standard shall have three significant figures, and its standard error shall not exceed 5%. Additional remarks:
This standard is proposed and managed by China State Shipbuilding Corporation. This standard was drafted by Luoyang Ship Material Research Institute of China State Shipbuilding Corporation and Institute of Solid State Physics of Chinese Academy of Sciences. The main drafters of this standard are Meng Xianliang, Zhu Zhengang, Shi Chunyi, Wen Yiting, Xie Pingmei, Zhang Jiaxiang, Liu Xijun, Zhang Junxu and Zhu Xianfang.
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