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 prEN 3475-418:2006 2 Contents 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 Conditionin
8、g.4 4.3 Initial measurement .4 5 Apparatus .4 6 Method 5 7 Requirements.5 Foreword This standard was reviewed 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
9、, this standard has received approval for Publication. 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 influence of metallic migration on the electrical resistance per unit length. It shall be used together
10、 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 references, the latest edition of the referenced document (including any amendments) applies. EN 3475
11、-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 length. 3 Introduction 3.1 General Various bi-metal conductors exist among which the most usual are
12、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 increasing growth rate when exposed to elevated temperature, the characteristics of the cables (mechanic
13、al 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 phenomenon between ambient temperature and 230 C. 3.2 Theory The inter-metallic layer formation at
14、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 metals in contact at a given temperature. This coefficient of diffusion has generally the form of a
15、n 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 for a couple of diffusion. prEN 3475-418:2006 4 Furthermore, in the case of the electrical wires,
16、the calculation 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 te
17、mperature 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 c
18、onductor 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
19、electrical 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
20、 Specimens 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 th
21、is initial 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 withou
22、t thermal 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. prEN
23、 3475-418:2006 5 6 Method The initial length shall be placed in the oven for the time and the temperature specified 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
24、 removed from the oven and cooled for at least 1 h at ambient temperature. Then, make three samples of at least 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 c
25、orrected to 20 C. All specimens shall be kept in order if necessary to be able to measure the thickness of the 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.
