IEC 61631 pdf download – Test method for the mechanical strength of cores made of magnetic oxides

IEC 61631 pdf download – Test method for the mechanical strength of cores made of magnetic oxides
1 scope
This International Standard specifies a test method for the mechanical strength of cores madeof magnetic oxides.This test method is suitable for most of the E-cores，ETD-cores andl-cores but other core types such as U-cores could be tested according to a derived methodagreed by the parties concerned.
2Normative references
The following referenced documents are indispensable for the application of lEC 61631.Fordated references,only the edition cited applies. For undated references,the latest edition ofthe referenced document (including any amendments) applies.
IEC 61246:1994，Magnetic oxide cores (E-cores) of rectangular cross-section and associatedparts – Dimensions
EN 10002-2:1992,Tensile testing of metallic materials – Part 2: Verification of the forcemeasuring system of the tensile testing machine
ISO 4677-1:1985,Atmospheres for conditioning and testing – Determination of relative humidity -Part 1: Aspirated psychrometer method
ISO 4677-2:1985,Atmospheres for conditioning and testing – Determination of relative humidity -Part 2: Whirling psychrometer method
3Definitions
For the purpose of this International Standard, the following definition applies.
3.1
mechanical strength
the maximum recorded force at the instant of fracture of a magnetic oxide core when it isloaded in bending
4Apparatus
4.1Test core support and loading wedge
Test cores shall be supported on free moving roller bars or on a flat support depending on theirsize (see 6.2). The loading wedge and the roller bars or the flat support shall be made ofhardened steel with a hardness of 40 HRC to 60 HRC.The loading wedge and the roller barsshall have a radius of 2 mm.The loading wedge shall be connected to a device for measuringand recording the load applied.
4.2Testing device
The testing device shall be a mechanical testing machine capable of applying a force to theloading wedge high enough to break the test core.The machine shall be capable of applyingthe force at a constant loading-rate.The machine shall be equipped with a device for recordingthe peak load applied to the test core.The accuracy of the machine shall be in accordance withEN 10002-2,Grade 1 (accuracy 1 % of the indicated load). Force calibration of the machineshall be checked in accordance with EN 10002-2.
4.3Humidity measuring device
A humidity measuring device shall be as specified in lSO 4677-1 or ISO 4677-2 and shall becapable of measuring relative humidity to an accuracy of 12 %.
5Test cores
The test cores shall be selected as agreed between the parties concerned. They may bemachined to the specified, dimensions, because any machined surface plays an important rolein the mechanical strength (see Introduction).
5.1 Number of test-cores
For material development,characterization or quality checking,the minimum number of testcores shall be five pieces. For statistical evaluation of strength-data (for example，Weibullparameters), the minimum number shall be 30.
NOTE For comparison of data for different materials, it is important that the number of specimens is high enoughto obtain results with sufficient statistical confidence. Since the confidence limits, in general, depend on the numberof test results and their dispersion, the number of test specimens should be decided on the basis of statisticalconsiderations.
5.2Precautions
The prepared test cores should be handled with care to avoid introduction of additionaldamage.Test cores should be kept separately at all times,and should be wrapped individuallyfor transport.
6Testing
6.1Test conditions
The test shall be carried out at an ambient temperature between 15 C and 35 °C. Thetemperature shall not vary by more than 3 °C during the course of a test series.The relativehumidity shall be between 45 % and 85 % and shall not vary by more than 10 % during thecourse of a test series.
6.2Test procedures6.2.1General
The test core shall be arranged in the test apparatus in accordance with 6.2.2，6.2.3，6.2.4,6.2.5 or 6.2.6 as applicable (see figures 1 to 5).
The E-test and W-test can be used for material related purposes,while the M-test and T-testcan be used for process related purposes.The l-test is only recommended for flat shaped testcores such as antenna rods. A preloading force of 5 N to 25 N shall be applied because theupper and lower faces of the test cores are never absolutely parallel.Then the test force shallbe applied at a loading rate of between 5 mm/min and 20 mm/min until the test core fractures.The load at the instant of fracture shall be recorded.The fractured fragments shall be identifiedand preserved for later fractographic examination.