ISO 7257:2016
Aircraft — Hydraulic tubing joints and fittings — Rotary flexure test
ISO 7257:2016 specifies a flexure test procedure to determine and classify the fatigue strengths of reconnectable or permanent hydraulic tube joints.
The procedure is intended for conducting flexure tests of fittings and joints with high-strength hydraulic tubes of various alloys such as corrosion resistant steel, Nimonic?[1], titanium and aluminium alloy hydraulic tube for use on commercial and military aircraft.
A mean stress is applied by holding system pressure in the specimens and then flexing in a rotary bending test machine.
[1] Nimonic? is the trademark of a product supplied by Special Metals Corporation. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent products can be used if they can be shown to lead to the same results.
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Foreword
Introduction
1 Scope
2 Requirements
2.1 Flexure test device
2.2 Flexure test specimen
2.3 Specimen length and deflection requirements
2.3.1 Specimen length
2.3.2 Stress determination
2.3.3 Deflection
2.4 Method of classification of fittings according to S/N flexure performance
2.5 Method of determining deflection/fatigue strength
3 Procedure
3.1 Preparation for test
3.1.1 Instrumentation, strain gauges
3.1.2 Rotary flexure test set-up centring
3.1.3 Flexure stress measurement
3.1.4 Flexure deflection measurement
3.1.5 Operating pressure
3.2 S/N testing
3.3 Deflection/fatigue testing
4 Formula
5 Equipment
Bibliography
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Foreword
Introduction
1 Scope
2 Requirements
2.1 Flexure test device
2.2 Flexure test specimen
2.3 Specimen length and deflection requirements
2.3.1 Specimen length
2.3.2 Stress determination
2.3.3 Deflection
2.4 Method of classification of fittings according to S/N flexure performance
2.5 Method of determining deflection/fatigue strength
3 Procedure
3.1 Preparation for test
3.1.1 Instrumentation, strain gauges
3.1.2 Rotary flexure test set-up centring
3.1.3 Flexure stress measurement
3.1.4 Flexure deflection measurement
3.1.5 Operating pressure
3.2 S/N testing
3.3 Deflection/fatigue testing
4 Formula
5 Equipment
Bibliography