ASD-STAN PREN 4859-2017 Aerospace series - Sensor based clamp load determination high tensile bolts - Technical specification (Edition 1).pdf

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1、 ASD-STAN STANDARD NORME ASD-STAN ASD-STAN NORM ASD-STAN prEN 4859:2017 Edition 1 2017-11 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATION Rue Montoyer 10 - 1000 Brussels - Tel. + 32 2 775 8126 - Fax. + 32 2 775 8131 - www.asd-stan.orgICS: Descriptors: ENGLIS

2、H VERSION Aerospace series Sensor based clamp load determination / high tensile bolts Technical specification Luft- und Raumfahrt Sensor basierende Vorspannkraftmessung / hochfeste Schrauben Technische Lieferbedingungen Srie arospatiale Dtermination de la tension de serrage avec capteur / Boulons fo

3、rtement contraints Spcification technique This “Aerospace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (The AeroSpace and Defence Industries Association of Europe - Standardization). It is published for the needs of the European Aerospace Industry. It has been technical

4、ly approved by the experts of the concerned Domain following member comments. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After e

5、xamination and review by users and formal agreement of ASD-STAN, the ASD-STAN prEN will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement

6、the EN at national level by giving the EN the status of a national standard and by withdrawing any national standards conflicting with the EN. ASD-STAN Technical Committee approves that: “This document is published by ASD-STAN for the needs of the European Aerospace Industry. The use of this standar

7、d is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” ASD-STAN reviews each standard and technical report at least every five years at which time it may be revised, reaffirm

8、ed, stabilized or cancelled. ASD-STAN invites you to send your written comments or any suggestions that may arise. All rights reserved. No parts of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, reco

9、rding, or otherwise, without prior written permission of ASD-STAN. Order details: E-mail: salesasd-stan.org Web address: http:/www.asd-stan.org/ Edition approved for publication 1stNovember 2017 Comments should be sent within six months after the date of publication to ASD-STAN Mechanical Domain Cop

10、yright 2017 ASD-STAN prEN 4859:2017 (E) 2 Contents Page Introduction 3 1 Scope 4 2 Normative references 4 3 Terms and definitions . 4 4 Clamp load measurements on bolts . 4 4.1 Configuration of thin film transducer based sensor bolts 4 4.2 Determination of the clamp load on thin film transducer base

11、d sensor bolts . 6 4.3 Basic components of an ultrasonic measurement system . 7 4.4 Geometrical requirements on sensor bolts . 8 5 Certification and quality assurance for thin film transducer based sensor bolts 10 5.1 Qualification . 10 5.1.1 Purpose 10 5.1.2 Conditions . 10 5.1.3 Product Qualificat

12、ion 11 5.1.4 Manufacturers approval . 11 5.2 Acceptance 11 5.2.1 Purpose 11 5.2.2 Conditions . 11 5.3 Quality system certification . 11 5.3.1 Purpose 11 5.3.2 Requirements and procedure 11 5.4 Inspection and test report 11 5.5 Environmental durability . 11 6 Application restriction . 12 7 Technical

13、requirements and test methods . 12 Bibliography . 19 prEN 4859:2017 (E) 3 Introduction Aerospace and Defence Standardisation (ASD-STAN) draws attention to the fact that it is claimed that compliance with this document may involve the use of a patent concerning “Connector component with temperature-r

14、esistant sensor element” EP 2010883 B1, US 8,177,464 B2. ASD-STAN takes no position concerning the evidence, validity and scope of this patent right. The holder of this patent right has assured ASD-STAN that he / she is willing to negotiate licenses under reasonable and non-discriminatory terms and

15、conditions with applicants throughout the world. In this respect, the statement of the holder of this patent right is registered with ASD-STAN. Information may be obtained from: Intellifast GmbH Siemensstrasse 18 67346 Speyer Germany Attention is drawn to the possibility that some of the elements of

16、 this document may be the subject of patent rights other than those identified above. ASD-STAN shall not be held responsible for identifying any or all such patent rights. prEN 4859:2017 (E) 4 1 Scope This European standard specifies the technical, qualification and quality assurance requirements fo

17、r sensor based clamp load measurement systems for high tensile bolts and other clamp load sensitive elements. Primarily for aerospace applications, it is applicable to such products when referenced on the product standard or drawing. 2 Normative references The following documents, in whole or in par

18、t, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 2424, Aerospace series Marking of aerospace pro

19、ducts EN 10204, Metallic products Types of inspection documents 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 Thin film ultrasonic transducer this kind of transducer applied to one of the two bolt ends converts an electrical pulse in an ult

20、rasonic wave travelling through the bolt body and transforms the reflected ultrasonic wave back into an electrical echo signal; the thereby used physical principles are the piezoelectric effect and its reversion 3.2 Sputtering PVD (physical vapour deposition) process to apply thin films onto a subst

21、rate; under vacuum and by means of physical methods the base material becomes transformed into the gas phase; the condensing particles form the target layer on the substrate; sputtering is used to apply thin film ultrasonic transducer on bolts 3.3 Clamp load needed axial force in a bolt to secure a

22、save operation in a bolted joint 4 Clamp load measurements on bolts 4.1 Configuration of thin film transducer based sensor bolts Three layers coated onto the top of the bolt (a) form an ultrasonic thin film transducer. Applied in a vacuum process the transducer becomes a permanent part of the bolt (

23、see Figure 1). The transducer consists of a piezoelectric thin film (b), followed by a protection layer (c) and an electrode metallization (d). Figure 2 shows different sensor bolts equipped with a thin film transducer. prEN 4859:2017 (E) 5 Key (a) top of the bolt (b) piezoelectric thin film (c) pro

24、tection layer (d) electrode metallization Figure 1 Thin film transducer configuration Figure 2 Samples of sensor bolts with thin film transducer In addition to the thin film transducer method, there are other systems to measure the clamp load in bolts. Examples are strain gages, electromagnetic acou

25、stic transducers (EMAT) or conventional piezoelectric transducers (glued on transducer, hand held transducer). This standard describes the requirements, test procedures etc. for thin film transducer based sensor bolts. prEN 4859:2017 (E) 6 4.2 Determination of the clamp load on thin film transducer

26、based sensor bolts The ultrasonic clamp load determination in sensor bolts is based on the pulse echo method. This technique works similar to systems like sonar or ultrasonic based material testing. The thin film transducer placed at one of the bolt ends receives an alternating current (AC) pulse. T

27、he transducer follows the change of the electrical voltage by changing its length. The coupling of the transducer with the bolts surface leads to an ultrasonic wave traveling through the bolt. The ultrasonic waves are reflected by the opposite side of the bolt and travel back in direction of the tra

28、nsducer (see Figure 3). There, an echo signal can be detected. The transducer works as both, as sender and receiver. t is the time period between pulse sending and receiving the echo. Figure 3 Determination of the clamp load in a bolt using a thin film ultrasonic transducer The time-of-flight (TOF)

29、of an ultrasonic pulse traveling along the bolt axis shows a marked dependence on the applied tensile stress. In addition to the strain approximately given by Hooks law, there is a decrease in sound velocity, the latter of which remarkably accounts for 75 % (for steel) of the total time-of-flight in

30、crease. Fortunately, both effects act in the same direction and are sufficiently linear so that the changes in TOF between an unloaded and a loaded state can be used as a direct measure of the applied load. The TOF dependence on load can be described with low (first or second) order polynomials: = 1

31、 = 1 ( ) = 1 + 22where F load kN; TOF measured time-of-flight difference ns; BTOF measured time-of-flight under no-load conditions ns; FTOF measured time-of-flight under load conditions ns; k1, k2material- and bolt- dependent linear and quadratic load scale factors. prEN 4859:2017 (E) 7 The desired

32、scale factors k1and k2can be obtained by using a load cell or a tensile testing machine as reference for the applied loads and an ultrasonic measurement system to determine the time-of-flight value for the different load steps. Temperature variations affect ultrasonic TOF measurements by changing th

33、e length of the inspected material according to the thermal expansion law. To eliminate this influence, all time-of-flight values determined and stored in the measuring device must be compensated for the current temperature. One way to do the temperature compensation is to refer all measured time-of

34、-flight values to 0 Celsius. The dependence of the time-of-flight on temperature can be described by a low order polynomial with sufficient accuracy. For short bolts, for materials with a highly linear thermal expansion and for small temperature ranges during TOF measurements, the TOF correction to

35、0 Celsius using a first order polynomial (straight line) is recommended. See the following formula: =(1 + 1)For long bolts, for materials with non-linear thermal expansion behavior and for large temperature ranges during TOF measurements, correction to 0 Celsius using a second order polynomial (para

36、bola) is recommended. The following formula can be used: =(1 + 1 + 22)where TOF measured time-of-flight ns; TOFkorrtime-of-flight corrected to 0 Celsius ns; TEMP material temperature during time-of-flight measurement C; C1, C2material- and bolt- dependent temperature calibration factors. The specifi

37、c material- and bolt- dependent temperature calibration factors (C1, C2in the formulae above) can be determined by measuring the raw (uncorrected) time-of-flights while stepping through the desired temperature range in 10K steps. The temperature stepping requires a programmable climate chamber which

38、 allows specific (constant) temperatures to be realized for sufficiently long time spans so that the bolt definitely reaches thermal equilibrium at the given temperatures while the TOFs are measured with the ultrasonic measurement system. Evidence for thermal equilibrium can be gained from the const

39、ancy of the TOF values once the temperature level has been reached. 4.3 Basic components of an ultrasonic measurement system The minimal configuration for an ultrasonic measurement system consists of an ultrasonic unit (1) that generates the ultrasonic pulses and receives the echoes. This unit is co

40、axially (3) connected with the bolt to be measured (2) and communicates with the processing unit (4). The processing unit (4) controls the ultrasonic unit (1), displays the load values and is the interface for the user. A temperature probe (5) sitting on the joint measures the current bolt temperatu

41、re. The ultrasonic unit (1) and the processing unit (4) are often combined to one device. This minimal configuration allows the permanent monitoring of one test joint. prEN 4859:2017 (E) 8 For the case that more than one bolt need to be measured, the ultrasonic measurement system can be expanded wit

42、h a multiplexor. This allows the sequential (one after another) monitoring of several test joints. For simultaneous load determination the ultrasonic measurement system must contain several ultrasonic units (1). All units work in parallel. For this reason, this system is much faster than a system ba

43、sed on a multiplexor configuration. The configuration with several ultrasonic units is called a multi-channel system. Key (1) ultrasonic unit (2) bolt to be measured (3) coaxial cable (4) processing unit (5) temperature probe Figure 4 Basic components of an ultrasonic measurement system 4.4 Geometri

44、cal requirements on sensor bolts The proper determination of the clamp load requires a sufficient echo quality. The magnitude and the form of the received echo are strongly dependent on the bolt geometry. The propagation of ultrasonic waves follows geometrical rules. Similar to the optics the angle

45、of incidence equals the emergent angle for the reflection at any boundary surface. The transducer as integrating element collects all the different echo fractions receiving at the same time to one echo signal. To avoid any disturbing interference during the echo formation a flat bolt reflection end

46、is needed. The bolt head surface with the transducers on top and the bolt reflection end should parallel. This supports the ultrasonic waves to come back on a direct way from the reflection end to the transducer. In some configurations bolts might be bent. In this case the bolt head surface and the

47、reflection end are no longer parallel. This could lead to disturbed echoes or to a complete loss of the echo signal. This effect can be minimized by applying a convex end to the bolt reflection end. The radius helps to focus prEN 4859:2017 (E) 9 the ultrasonic waves and works similar to a parabolic

48、mirror. In a first estimation the value for the reflection end radius can be assumed as the half of the bolt length. The flat area where the sensor shall be placed will be polished to have a maximum roughness of Rz5. The thickness of the sensor will not exceed a normal embossed head marking of the b

49、olt. Figure 5 Samples of bolts with convex and with flat shank end For newly designed bolts a small recess at one of the bolts ends is recommended to protect the sputtered transducer from mechanical damaging (Figure 6). The active transducer area lies deepened in a recess (a). The two electrical contacts of the transducer are marked with (b) and (c). The transducer front side contact is (b). (c) represents