1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising theref
2、rom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2008 SAE International All rights reserved. No part of this publication ma
3、y be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA)
4、Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR1228AAEROSPACEINFORMATIONREPORTAIR1228A Issued 1972-11 Reaffirmed 2007-08 Revised 2009-01 Super
5、seding AIR1228 (R) Standard Impulse Machine Equipment and Operation RATIONALEThis document has been revised to describe current technology in impulse machine design. 1. SCOPE This SAE Aerospace Information Report (AIR) establishes the specifications and descriptions of the critical components and op
6、erational guidelines for the standard hydraulic impulse machine for testing hydraulic hose assemblies, tubing, coils, fittings and similar fluid system components. This revision to the AIR1228 provides a description of a system that meets the requirements for specifications including: AS603, AS4265,
7、 and ARP1383. This impulse system utilizes closed loop servo control with specifically generated command signal waveforms.Data accuracy and integrity are emphasized in this revision. Knowing the uncertainty of the pressure measurement is important whether using a resonator tube system, as described
8、in the original release of this document, or a closed-loop systems as described in this release. The accuracy of the data measurement system and consistency of the pressure waveform are fundamental to test validity, regardless of the system type. This is discussed in more detail in Section 5.The sta
9、ndard impulse test system is established for the following purposes: A. As referee in the event of conflicting data from two or more nonstandard impulse machines. Such a referee system might be built by an impartial testing activity. B. A design guide for future test systems being built by manufactu
10、rers and users, or the upgrading of present systems. C. A design guide for higher pressure test systems or special purpose machines being designed. It is not the intention of this document to obsolete present resonator type machines. The specification for the resonator type machine is available in t
11、he original release of this document. A simple block diagram of the revised system is shown in Figure 1. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR1228A Page 2 of 33FIGURE 1 - SIMPLE BLO
12、CK DIAGRAM OF SERVO CONTROLLED IMPULSE SYSTEM The simplified block diagram shown in Figure 1 does not use a resonator tube as in the original release of the specification. To eliminate undesired resonances the hydraulic system is as closely coupled as possible. In this design, the pressure waveform
13、is created in closed loop proportional control via the command signal generated by the test controller system. If the test controller is a computer with an impulse specific software application, it is possible to control all parameters ofthe specified waveform, within the capabilities of the hydraul
14、ic system. These parameters include things such as rise rate, damping, secondary oscillation amplitude, etc. In a resonator tube system, it is difficult to make adjustments to these parameters. 2. REFERENCES 2.1 Applicable Documents 1. Keller, George R., Hydraulic System Analysis, Penton/IPC, 1969 2
15、 Merritt, Herbert E., Hydraulic Control Systems, John Wiley and Sons, Inc., 19673. DAzzo and Houpis, Linear Control System Analysis and Design, 1981 4. Nelson and Englund “Proposed revisions to AIR1228, AS4265, and AIR4298“, SAE G-3 Conference, 3/14/2005 5. Mills Jr., Blake D., “The Fluid Column”,
16、American Journal of Physics, April 1960 Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR1228A Page 3 of 332.2 U.S. Government Publications Available from US Government Printing Office, 732 Nor
17、th Capitol Street, NW, Washington, DC 20401, 202.512.0000, http:/www.gpo.gov/.MIL-PRF-5606 Hydraulic Fluid, Petroleum Base MIL-PRF-83282 Hydraulic Fluid, Fire Resistant, Synthetic Hydrocarbon Base MIL-PRF-87257 Hydraulic Fluid, Fire Resistant; Low Temperature, Synthetic Hydrocarbon Base, Aircraft an
18、d Missile2.3 Definitions General: The impulse test system can be divided into four subsystems. HYDRAULIC SYSTEM The hydraulic system provides the power for generating the impulse pressure waveform. Hydraulic components include the hydraulic power supply (HPS), supply and return lines, accumulators,
19、servovalve, intensifier, and test manifold as described in Figure 2. If the test pressure is higher than the HPS output, the system utilizes an intensifier. If the test pressure is lower than the HPS output, the system operates without an intensifier (also called straight servovalve). The system sho
20、wn in Figure 2 can be switched to either mode with three manual valves. This document will use “servovalve“ to represent all types of valves that can be used in a proportional manner for pressure testing. CONTROL SYSTEM The control system includes the test controller and the servo-controller in Figu
21、re 1. Physically this can be one integrated unit, or it can be comprised of several interconnected subsystems. This system controls the HPS, generates the pressure waveform signal in accordance with standard specifications, closes the control pressure control loop (servo-controller), and ensures pre
22、ssures are within the test specification.INSTRUMENTATION SYSTEM The instrumentation system consists of the pressure transducers, cabling, signal conditioning, amplifiers and filters used to convert the pressure measurement into electrical signals as shown in Figure 3. The amplifiers and signal condi
23、tioning may be integral with the pressure transducers. When using computerized data acquisition, the analog-to-digital converters and associated software application are also considered part of the instrumentation system. TEST ENCLOSURE OR ENVIRONMENTAL CHAMBER The test enclosure provides a safety b
24、arrier for testing high pressure specimens. When required, the enclosure may be an environmental chamber capable of controlling the test temperatures of the air surrounding the test specimens (and the fluid temperatures inside the test articles) within the parameters of the test document.3. DETAILED
25、 DESCRIPTION OF HYDRAULIC COMPONENTS Figure 2 shows the general arrangement of hydraulic components in the impulse system. The system shown is capable of straight servovalve operation for low pressure testing and intensifier operation for higher test pressures. Operation can be switched to either mo
26、de with three manual valves. The servovalve and intensifier are shown in a 3-way configuration as described in the servovalve section. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR1228A Pag
27、e 4 of 335000 PSIHYDRAULIC POWER SUPPLY (HPS)RETURN LINE ACCUMULATORPRESSURE LINE ACCUMULATORINTENSIFIER CENTER CHAMBER ACCUMULATORINTENSIFIER FOR 5000-25,000 PSI TESTSSERVOVALVEEQUALDISTRIBUTION MANIFOLDTESTARTICLESSTRAIGHTSERVO LINEFOR 50-5000 PSI TESTSTESTARTICLEFILL LINECONTROLLERPBLEEDSBACKPRES
28、SURE VALVEPMPISTONHOLD UP LINE FORSTRAIGHT SERVOSINE WAVE SOURCESIGNAL CONDITIONINGAMPLIFIERSDATA AQUISITIONNOTE: ACCUMULATOR DUMP VALVES NOT SHOWNPRESSURE REDUCERFIGURE 2 - HYDRAULIC SCHEMATIC 3.1 Hydraulic System Sizing The test system size is typically determined by desired test volume, by availa
29、ble power for the HPS or by cost. One of these three factors typically determines the other two. In determining the test volume, or “specimen load“ one must consider the quantity required by the test specification and how many specimens can be run concurrently. From an operational standpoint, it is
30、most efficient to maximize the number of specimens run under a single condition which leads to larger test system size. All components need to be sized relative to each other. Undersized components will limit desired performance, while oversized components cost more and may have adverse effects on p
31、erformance. The system must be designed for both pressure and flow requirements3.2 Closed Loop Control In the resonator impulse system designed for AS603 type testing, a solenoid valve is used and the supply pressure to the solenoid is the same as the desired plateau pressure. To start the waveform
32、the solenoid valve is turned on, and goes to the fully open position until the end of the plateau pressure waveform timing and then completely closes. In a closed-loop system, a servovalve is used instead of a solenoid valve. The servovalve opening can be controlled precisely and varied in accordanc
33、e with the difference between the desired pressure output and the actual pressure output.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR1228A Page 5 of 33In a closed-loop control system where
34、 the desired pressure rise times are less than twice the time it takes the servovalve to open, the orifice area when plotted versus time will resemble an inverted “V“ as shown in Graph 1. In this graph the loop gain of the control system was set as high as possible without causing over-shoot of the
35、pressure wave. The command signal is a step (square wave) 4500 psi input. The servovalve appears to open 0.0025 s after the command and the pressure begins to rise within a millisecond after that. At the start of the commanded rise, the orifice area will start increasing, and mid-way through the pre
36、ssure rise it will start to close again. The supply pressure to the servovalve is usually at least 500 psi higher than the maximum desired pressure. When the desired pressure in the test volume is reached, the servovalve will once again be closed, trapping the added volume of fluid inside the test s
37、pecimens. This sequence will be referred to later in this document when an example is presented with rough calculations for sizing the servovalve and related components. It is apparent from examining the valve area trace in Graph 1, that the valve dynamics play a significant role in the ability to m
38、eet pressure impulse rise times that are up to twice the time it takes to fully open the valve.GRAPH 1 - CLOSED LOOP CONTROL WITH SHORT RISE TIMES Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE
39、AIR1228A Page 6 of 33When the servovalve is used in a closed-loop control system where the rise times are more than twice as long as the time it takes the servovalve to open, the valve will open completely and stay in that position while the pressure increases and then it will begin to close again.
40、In tests with this range of rise rates, the maximum flow rating of the servovalve becomes more important than the valve dynamics in determining rise rate. This is shown in Graph 2.GRAPH 2 - CLOSED LOOP CONTROL WITH LONG RISE TIMES Graphs 1 and 2 show that the servovalves need to be sized in terms of
41、 their maximum ratings as well as their response. This is true of other components as well. One purpose of this document is to help choose the components that will provide the specified parameters for a wide variety of test applications. Table 1 shows an example of a 35 gpm HPS system with a variety
42、 of specimen volumes, typical component sizing and test system performance.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR1228A Page 7 of 33TABLE 1 - HYDRAULIC SYSTEM SIZING Copyright SAE Int
43、ernational Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR1228A Page 8 of 33The hydraulic pressure in a typical impulse system runs at two levels, the pump output pressure (supply pressure), and peak impulse pressure at
44、 the test specimen which is controlled by the servovalve. The pump will typically run at a constant value between 2000 psi (minimum pressure for servovalve pilot stage in most impulse applications) and 5000 psi. This supply pressure should not vary more than a couple hundred psi or it will affect th
45、e operation. A large variation may be eliminated with the proper accumulator. See the “accumulator section“ for more information on accumulator sizing. By maintaining a separate supply pressure to the servovalve pilot stage, the supply pressure to the servovalve final stage may be adjusted for the t
46、ype of component that is being tested.The pressure at the test specimens can run at radically different ranges to give a wide spectrum of test flexibility. The pressure at the test specimens can be varied from 100 psi (straight servovalve) to 20 000 psi (with an 8:1 intensifier). With the straight s
47、ervovalve configuration, the pressure down stream of the pressure reducer (shown between the servovalve and the pump in Figure 2) can run as low as 100 psi for reservoir testing (ARP1383) or fuel system component testing. With the reducer set at the 1000 to 2000 psi range, aluminum hydraulic return
48、lines can be tested with the AS603 wave form. With the HPS running at the 2000 psi range, 1500 to 2000 psi titanium return tubes can be tested with the AS603 wave form. With the HPS running at 5000 psi, all 3000 psi components can be tested at 4500 with the AS603 wave form. With an 8:1 intensifier in the system, test pressures up to 20 000 can be achieved for the AS4265 wave form. The components used in the impulse test systems must be sized with these pressures in mind. The flow in the system also runs at two rates, the low
