1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW14738 Master Test Procedure for Determination of Dynamic Stiffness and Loss Angle of Elastomeric Components Copyright 2013 General Motors Company All Rights Reserved March 2013 Page 1 of 10 1 Scope Note: Nothing in this standard supercedes applicabl
2、e 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 loss angle (viscoelastic properties) of elastomeric components used in ve
3、hicles when subjected to forced sinusoidal oscillations in the temperature range of -50 C to + 150 C. 1.2 Foreword. The dynamic stiffness and loss angle characteristics of elastomeric components in the vehicle chassis are important contributors to vehicle noise and vibration isolation as well as rid
4、e 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 External Standards/Specifications. DIN 53513 ISO 10846 SAE J1085 VDA 675
5、480 2.2 GM Standards/Specifications. GMW14116 GMW14203 3 Resources 3.1 Facilities. All facilities shall be free of extraneous noise and vibration sources. 3.1.1 Calibration. The test facilities and equipment shall be in good working order and shall have a valid calibration label. 3.1.2 Alternatives.
6、 Alternative test facilities and equipment may also be used. However, all measuring variables as specified in this standard shall be determined correctly with respect to their physical definition. 3.2 Equipment. 3.2.1 Test Device. The test device shall be capable of applying both a static and a sinu
7、soidal 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 testing machine (load-frame, actuators, and sensors), an
8、d 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 parts have to be applied by the testing machine. The m
9、achine 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 ( 20 mm is desired). Frequency: 0.01 Hz to 600 Hz. Copyright General Mo
10、tors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14738 Copyright 2013 General Motors Company All Rights Reserved March 2013 Page 2 of 10 Common transducer sig
11、nals 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. Displacement: 0.5% of full scale for each calibrated range.
12、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-frame carries the test fixture, test piece, senso
13、rs, 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 amplifiers, downstream analogue digital (A/D) conv
14、erters and the analysis processor. Error margins are specified in Table 1. Table 1: Error Margins Frequency The Tolerated Error of the Frequency 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%
15、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 Tolerated error is 5% of the display Loss Angle 20 degrees Tolerated error is 1% of the display 3.2.1.3 Analysis System. Analysis systems are used for the determin
16、ation, storage and presentation of the measurements. The measurements may be evaluated by Fast Fourier Transform (FFT) using Fundamental Frequency, 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 oscilla
17、ting force due to nonlinear spring characteristics. The number of sample points must be chosen such that the determination of the dynamic stiffness 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 i
18、s caused by the rheology of the elastomer material. A displacement of the average value during the measurement may occur and the force-deflection-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 Correct
19、ion. The analysis system must allow a correction of the dynamic stiffness to account for the measured machine and fixture stiffness. Correction 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 p
20、art is 10% of the machine and fixture stiffness, the result must be rejected. 3.2.2 Part Conditioning. For testing that requires controlled pre-conditioning and test temperatures, the capabilities in Table 2 are required. Copyright General Motors Company Provided by IHS under license with General Mo
21、tors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14738 Copyright 2013 General Motors Company All Rights Reserved March 2013 Page 3 of 10 Table 2: Part Conditioning Preconditioning-Chamber for Recirculating Air Operat
22、ion Temperature range: (continuously controlled) -50 C to 250 C Temperature constancy: 2 C Temperature variation rate for the empty chamber: 1.5 C/minute Temperature-Variation-Chamber for Recirculating Air Operation for use with the Test Machine Temperature range: (continuously controlled) -50 C to
23、250 C Temperature constancy: 2 C Temperature variation rate for the empty chamber: 1.5 C/minute 3.3 Test Vehicle/Test Piece. This procedure applies 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 Coordin
24、ation hours: 1 to 2 hours 3.5 Test Required Information. Different information is required based on the purpose of the testing (e.g., for development or for validation). This information is generally specified in the appropriate statement of requirements (SOR) document. The following items are gener
25、ally 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 application (in local coordinate system). 3.5.5 Static Force (Mean preload). 3.5.6 Dynamic Deflection: (millimeter, peak to peak). 3.5.7 Frequency: (freq
26、uency range, hertz). 3.5.8 Frequency Increment (hertz). 3.6 Personnel/Skills. Elastomer testing is quite complex. Several parameters must be adjusted and tracked for accurate results. It is highly recommended that a person with significant experience (more than three years) in elastomer testing perf
27、orm the test. 3.7 Additional Information. For further background information with respect to the preparation and testing of Elastomeric Isolators, refer to SAE J1085, VDA 675480, and ISO 10846. 4 Procedure 4.1 Preparation. Test pieces shall be clean and free from debris. Virgin pieces must be allowe
28、d to age between manufacturing and testing for a minimum of 24 h. For initial approval and arbitration purposes, the minimum time period between vulcanization and testing shall be seven days. For quality control purposes the minimum period shall be 72 h. Pieces that have undergone some permanent def
29、ormation (such as that due to an assembly operation) must be allowed 24 h before testing to permit relaxation of any internal stresses that may exist. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted witho
30、ut license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14738 Copyright 2013 General Motors Company All Rights Reserved March 2013 Page 4 of 10 If the test piece is required to be pressed into a fixture, then a suitable lubricant shall be used and sufficient time allowed for the lubricant to h
31、ave dried before commencing any tests. The test device shall be warmed up per manufacturer recommendations to stabilize measurements sensors and hydraulic systems. A 30 minute warm up run time for hydraulic systems is recommended if not known. Sensors may take several hours or days to stabilize if t
32、he electronics have been turned off. 4.2 Conditions. 4.2.1 Environmental Conditions. Testing may be performed at ambient (room) temperature or at other specified temperatures. 4.2.1.1 Ambient Temperature Testing. The test specimen must be maintained at ambient temperature between 20 C and 26 C for 8
33、 h prior to testing. The ambient temperature during testing shall be maintained between 20 C and 26 C unless otherwise specified. 4.2.1.2 Other Temperature Conditions. The test samples and fixtures may be temperature conditioned in the preconditioning chamber prior to conducting the test to shorten
34、the duration the test sample is in the test device. If various test temperatures are to be used, then the testing at the lower temperatures shall commence first. The test samples and fixtures shall be conditioned to one of the requirements specified in Appendix A, Table A1 and subsequently tested at
35、 that temperature as follows. 4.2.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. This master test procedure provides the basis for determination of dynamic
36、stiffness and loss angle for elastomeric components. Recommendations for test operating conditions for specific elastomeric applications are referenced in Appendix B, Table B1. 4.3 Instructions. If various dynamic deflections or frequencies are to be used, then the smaller deflection or lower freque
37、ncy tests shall be conducted first to minimize the effects of heat buildup. If the force or the force measurement equipment is influenced by the weight of the test sample and/or its fixtures, compensation shall be made prior to the commencement of the test. Example: To get an accurate preload with h
38、eavy fixtures and/or test samples, zero the load cell with only the portion of the fixture and test specimen that is attached to the load cell. The remaining part of the fixturing should not be zeroed out. 4.3.1 Setup. Attach the temperature conditioned test sample at the required test temperature t
39、o the load cell and the test machine by means of the necessary fixtures, so that the force imposed upon the test sample is not more than 10 N, ensuring at same time that the test sample maintains the test temperature during test procedure. Set the force and displacement indicators to zero (0). 4.3.2
40、 Preload. Apply the static force Fm (preload) to the test sample within a period of 2 s and allow 6 s to elapse before rechecking for consistency. Determine the static deflection lm. 4.3.3 Precondition. Run one (1) low frequency (0.5 Hz) cycle to maximum load/deformation. Note: This will affect the
41、dynamic performance if eliminated. 4.3.4 Dynamic Test. Test varies based on type of sequence desired. 4.3.4.1 Single Frequency. Set desired test condition (frequency, mean preload/deflection, and dynamic deflection). Maintain mean preload and dynamic deflection for a minimum of two minutes. Collect
42、data. 4.3.4.2 Sweep. Set desired test condition (frequency, mean preload/deflection, and dynamic deflection). Maintain mean preload and dynamic deflection for 5 s. Collect data for 5 s. Continue to next frequency and repeat until full range of frequencies, amplitudes, and preloads are tested. 4.3.5
43、Analyze Data. Determine the loss angle and the force with the approved digital analysis methods (Fundamental Frequency based Fast Fourier Transform (FFT), Sine Regression, or DIN 53513 analysis methods) as outlined in 5.1.1. Copyright General Motors Company Provided by IHS under license with General
44、 Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14738 Copyright 2013 General Motors Company All Rights Reserved March 2013 Page 5 of 10 5 Data 5.1 Calculations. 5.1.1 Loss Angle (). In cases where linearity of th
45、e spring-characteristic of the test sample exists, the value of the loss angle is indicated by the phase-angle present between the measured dynamic force and the dynamic deflection (see Figure 2). In cases where the loss angle is 90 degrees, any of the three (3) recommended procedures (FFT, Sine Reg
46、ression, or DIN 53513) may be used for calculation. In cases where the loss angle is 90 degrees, only the FFT and Sine Regression may be used. In cases where considerable non-linearity of the spring-characteristic of the test sample exists, the value of the loss angle is calculated from the hysteres
47、is loop obtained as shown in Figure 1 and the equation (the DIN 53513 method). oiaiwi ljFj lo o ph y s te r e s isofa r e aAj )(a r c s i nExam p l e: A w Figure 1: Area of Hysteresis Loop 5.1.2 Dynamic Stiffness or Complex Spring Rate (K or K*). K* shall be calculated from the measured values as fo
48、llows: )( )(* d e fle c tio nofa m p litu d elo a m p litu d elo a dFaK 5.1.3 Damping Coefficient (C). C shall be calculated from the measured values as follows: /)sin(*KC 5.2 Interpretation of Results. Results shall be interpreted according to the appropriate specification documents. 5.3 Test Docum
49、entation. Unless otherwise specified by the requirements document or the individual test requestor, test documentation shall include the following. 5.3.1 Part name. 5.3.2 Part number or drawing number. 5.3.3 Test specification number. 5.3.4 Additional identification. 5.3.5 Grade of elastomer. Copyright General Motors Company Provided by IHS under license with Gene
