1、ASD STANDARD NORME ASD ASD NORM prEN 3475-418 Edition P 1 September 2006 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATION Gulledelle 94 - B-1200 Brussels - Tel. + 32 2 775 8126 - Fax. + 32 2 763 3565 - www.asd-stan.orgICS: 49.060 Descriptors: Aerospace indust
2、ry, aircraft equipment, electrical cable test ENGLISH VERSION Aerospace series Cables, electrical, aircraft use Test methods Part 418: Thermal endurance for conductors Srie arospatiale Cbles lectriques usage aronautique Mthodes dessais Partie 418 : Endurance thermique des conducteurs Luft- und Raumf
3、ahrt Elektrische Leitungen fr Luftfahrtverwendung Prfverfahren Teil 418: Thermische Gebrauchsdauer fur Leiter 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
4、 the needs of the European Aerospace Industry. It has been technically 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
5、 or functionally, without re-identification of the standard. After examination and review by users and formal agreement of ASD-STAN, it will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (
6、EN). The CEN national members have then to implement 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. Edition approved for publication 30 September 2006 Comments should be sent within six months after the d
7、ate of publication to ASD-STAN Electrical Domain Copyright 2006 by ASD-STAN Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-prEN 3475-418:2006 2 Conte
8、nts Page Foreword2 1 Scope 3 2 Normative references 3 3 Introduction3 3.1 General3 3.2 Theory.3 3.3 Technical consequences on conductors 4 4 Preparation of specimens.4 4.1 Specimens4 4.2 Conditioning.4 4.3 Initial measurement .4 5 Apparatus .4 6 Method 5 7 Requirements.5 Foreword This standard was r
9、eviewed by the Domain Technical Coordinator of ASD-STANs Electrical Domain. After inquiries and votes carried out in accordance with the rules of ASD-STAN defined in ASD-STANs General Process Manual, this standard has received approval for Publication. Copyright Association Europeene des Constructeu
10、rs de Materiel Aerospatial Provided by IHS under license with AECMA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-prEN 3475-418:2006 3 1 Scope This standard specifies a test method to value the thermal endurance of bi-metal conductors, by valuation of the influen
11、ce of metallic migration on the electrical resistance per unit length. It shall be used together with EN 3475-100. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated refer
12、ences, the latest edition of the referenced document (including any amendments) applies. EN 3475-100, Aerospace series Cables, electrical, aircraft use Test methods Part 100: General. EN 3475-301, Aerospace series Cables, electrical, aircraft use Test methods Part 301: Ohmic resistance per unit leng
13、th. 3 Introduction 3.1 General Various bi-metal conductors exist among which the most usual are tin-coated copper, copper clad steel and copper clad aluminium. Inter-metallic compounds may appear at the interface of the various layers of such conductors. As these compounds have generally an increasi
14、ng growth rate when exposed to elevated temperature, the characteristics of the cables (mechanical and electrical) can be affected depending on the time and the temperature of exposure. A good example is tin-coated copper where the diffusion of tin into copper is a fast, well-known and important phe
15、nomenon between ambient temperature and 230 C. 3.2 Theory The inter-metallic layer formation at the interface of the various layers in the wires is due to a diffusion mechanism in association with solubility phenomenon. The diffusion rate is characterized by a coefficient of diffusion of the two met
16、als in contact at a given temperature. This coefficient of diffusion has generally the form of an Arrhenius law and is given by the formula. TRQeDoD.= where R is the ideal gas constant; Q is the activation energy for the diffusion process; and T is the absolute temperature; Do is a constant given fo
17、r a couple of diffusion. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-prEN 3475-418:2006 4 Furthermore, in the case of the electrical wires, the ca
18、lculation shows that there is a relation between the coefficient of diffusion D and the time t of exposure at different temperatures: D.t = Const So that D1.t1 = D2.t2 This say that it is possible to calculate an equivalent time of exposure at a higher temperature but this must be done at a temperat
19、ure for which the solubility limit and the metallurgic mechanisms involved are not too different, generally in a domain below 280 C. If the test temperature is too high there is a risk of obtaining a degradation mechanism not representative of reality. For example, on a copper clad aluminium conduct
20、or to assess the behaviour for: 10 000 hours at 180 C, a test of 2 200 hours at 200 C can be performed; 140 000 hours at 150 C, a test of 2 500 hours at 200 C can be performed. 3.3 Technical consequences on conductors When appeared, such inter-metallic compounds will affect the mechanical and electr
21、ical behaviour of the conductor. Even if all these characteristics do not evolve proportionally in relation with its thickness, it has been shown that an easy way to survey the growth of the inter-metallic part is to measure the increase of the linear resistance. 4 Preparation of specimens 4.1 Speci
22、mens A sufficient length shall be taken from the same batch of a finished cable. Generally, the test is run on gauge 20. 4.2 Conditioning This length shall not be bent with a radius less than 50 times the overall diameter of the cable, during temperature exposure. 4.3 Initial measurement On this ini
23、tial length take a minimum length of three meters to make three samples of at least one meter, make three measurements of the electrical resistance per unit length, according to EN 3475-301. Record the arithmetic mean value, of this sampling corrected to 20 C, as the initial measurement without ther
24、mal ageing. NOTE The temperature correction coefficient is generally given in the relevant conductor product standard. 5 Apparatus An air-circulating oven shall be required for this test. Its size must be sufficient to hold all necessary specimens during the complete duration of the test. Copyright
25、Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-prEN 3475-418:2006 5 6 Method The initial length shall be placed in the oven for the time and the temperature sp
26、ecified in the product standard. Each month, or specified period in the concerned product standard, after having cut 10 cm at the extremity one specimen of three meters minimum length shall be removed from the oven and cooled for at least 1 h at ambient temperature. Then, make three samples of at le
27、ast one meter and performed three measurements of the electrical resistance per unit length, according to EN 3475-301. Record the arithmetic mean value as the value of the concerned sampling corrected to 20 C. All specimens shall be kept in order if necessary to be able to measure the thickness of t
28、he inter-metallic interface. 7 Requirements a) the electrical resistance increase of each mean measurement shall be less than x % of the initial mean measurement. b) the electrical resistance increase of each mean measurement shall be less than y % of the maximum resistance requested in the product standard. x and y values shall be specified in the product standard. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-
