GMW-14738-2007.pdf
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1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure Materials GMW14738 Master Test Procedure for Determination of Dynamic Stiffness and Loss Angle of Elastomeric Components Copyright 2007 General Motors Corporation All Rights Reserved May 2007 Originating Department: North American Engineering Standards
2、 Page 1 of 8 1 Scope Note: Nothing in this standard supersedes applicable laws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. The purpose of this procedure is to determine the dynamic stiffness and l
3、oss angle (viscoelastic properties) of elastomeric components used in vehicles when subjected to forced sinusoidal oscillations in the temperature range of -50 to +150C. 1.2 Foreword. The dynamic stiffness and loss angle characteristics of elastomeric components in the vehicle chassis are important
4、contributors to vehicle noise and vibration isolation as well as ride and handling performance. 1.3 Applicability. This procedure is appropriate for the evaluation of all elastomeric components. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 Exte
5、rnal Standards/Specifications. DIN 53513 SAE J1085 ISO 10846 VDA 675480 2.2 GM Standards/Specifications. GMW14203 2.3 Additional References. None. 3 Resources 3.1 Facilities. All facilities shall be free of extraneous noise and vibration sources. 3.2 Equipment. 3.2.1 Test Device. The test device sha
6、ll be capable of applying both a static and a sinusoidal force to the elastomeric component simultaneously. The static force, dynamic deflection and its frequency and the temperature of the elastomeric component shall all be capable of being controlled and variable. The device consists of the testin
7、g machine (load-frame, actuators, and sensors), and measuring and analysis systems. 3.2.1.1 Testing Machine. For the parameter determination of elastomeric parts, a testing machine has to be chosen according to the part- specific conditions. The given static and dynamic loads for the elastomeric par
8、ts have to be applied by the testing machine. The machine typically has a servo hydraulic cylinder; sometimes an electro- dynamic system is used. A testing machine for elastomeric parts must generally exhibit the following performance capability: Force 10 kN Displacement 10 mm Note 1 Frequency 0.01
9、to 600 Hz Note 1: 20 mm desired Common transducer signals used in forced non- resonant systems for obtaining data are load, displacement, and/or velocity. Each transducer should be calibrated to the following minimum accuracies: Force measurement 0.5% of full scale for each calibrated range Displace
10、ment 0.5% of full scale for each calibrated range Velocity 0.1% of full scale for each calibrated range Readout instrumentation for load, displacement, and velocity transducers should provide a sufficient number of ranges so that it will not be necessary to use less than 20% of the range. The load-f
11、rame carries the test fixture, test piece, and sensors and reinforces them against the test machine, so that the elastomeric part can be stressed by the test machine. 3.2.1.2 Measuring System. The measuring system mostly consists of converter systems for force and deflection, corresponding measuring
12、 amplifiers, downstream A/D converters and the analysis processor. Error margins are specified in Table 1. GMW14738 GM WORLDWIDE ENGINEERING STANDARDS Copyright 2007 General Motors Corporation All Rights Reserved Page 2 of 8 May 2007 Table 1: Error Margins Frequency The tolerated error of the freque
13、ncy is 2% of the measured value Dynamic Stiffness f 300 Hz f 300 Hz Tolerated error is 2% of the display values of the dynamic stiffness Tolerated error is 5% of the display values of the dynamic stiffness Loss Angle f 300 Hz f 300 Hz Loss angle 20 degrees Tolerated error is 0.2% of the display Loss
14、 angle 20 degrees Tolerated error is 1% of the display Tolerated error is 5% of the display 3.2.1.3 Analysis System. Analysis systems are used for the determination, storage and presentation of the measurements. The measurements may be evaluated by Fast Fourier Transform (FFT) (using Fundamental Fre
15、quency), Sine Regression, or DIN 53513 analysis. 3.2.1.3.1 Sample Points. Digital analyzing methods can cause results to be affected by distortion of the oscillating force due to nonlinear spring characteristics. The number of sample points must be chosen such that the determination of the dynamic s
16、tiffness and the loss angle fulfils the required accuracy. There must be 100 to 200 sample points per wave. 3.2.1.3.2 Hysteresis Loop. Another source for error is caused by the rheology of the elastomer material. A displacement of the average value during the measurement may occur and the force- def
17、lection-diagram must be adjusted. The analysis system must be capable of closing the hysteresis loop with a straight-line approximation. 3.2.1.3.3 Fixture Correction. The analysis system must allow a correction of the dynamic stiffness to account for the measured machine and fixture stiffness. Corre
18、ction must be performed if the dynamic stiffness of the elastomeric part is 1% of the machine and fixture stiffness. If the dynamic stiffness of the elastomeric part is 10 % of the machine and fixture stiffness, the result must be rejected. 3.2.2 Part Conditioning. For testing that requires controll
19、ed pre-conditioning and test temperatures, the following capabilities are required: Table 2: Part Conditioning Preconditioning-Chamber for Recirculating Air Operation: Temperature range: (continuously controlled) -50 to 250C Temperature constancy: 2C Temperature variation rate for the empty chamber
20、1.5C/minute Temperature-Variation-Chamber for Recirculating Air Operation for use with the Test Machine: Temperature range: (continuously controlled) -50 to 250C Temperature constancy: 2C Temperature variation rate for the empty chamber 1.5C/minute 3.3 Test Vehicle/Test Piece. This procedure applies
21、 to all elastomer components including bushings, mounts, hangers and snubbers. 3.4 Test Time. Calendar time: 2 to 3 days Test hours: 4 to 8 hours Coordination hours: 1 to 2 hours 3.5 Test Required Information. Different information is required based on the purpose of the testing (e.g. for developmen
22、t or for validation). This information is generally specified in the appropriate statement of requirements (SOR) document. The following items are generally required: 3.5.1 Number of test pieces. 3.5.2 Required pre-conditioning temperature. 3.5.3 Required test temperature. 3.5.4 Direction of force a
23、pplication (in local coordinate system). 3.5.5 Static Force (Mean preload). 3.5.6 Dynamic Deflection (mm Peak to Peak). 3.5.7 Frequency (frequency range) (Hz). 3.5.8 Frequency increment (Hz). 3.6 Personnel/Skills. Elastomer testing is quite complex. Several parameters must be adjusted and tracked fo
24、r accurate results. It is highly recommended that a person with significant -,-,- GM WORLDWIDE ENGINEERING STANDARDS GMW14738 Copyright 2007 General Motors Corporation All Rights Reserved May 2007 Page 3 of 8 experience ( 3 years) in elastomer testing perform the test. 3.7 Additional Information. Fo
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