ISO 9538:2017 pdf download

ISO 9538:2017 pdf download.Aerospace series — Hydraulic tubing joints and fittings — Planar flexure test
1 Scope
This document specifies a flexure test procedure for reconnectable and permanent hydraulic tube joints.
This procedure is intended for conducting flexure tests on fittings with high-strength hydraulic tubes made of corrosion-resisting steel, titanium and aluminium for use on commercial and military aircraft.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Device for flexure test
The test device should be similar to that shown in Figure 1. It shall consist of a vibrator, a manifold to receive at least six test specimens, and a hydraulic supply unit capable of constantly maintaining the static operating pressure during testing, including monitors inducing the shutdown of the system in the event of pressure drop.
5 Flexure test specimens
The test specimens shall consist of the tube fitting to be tested (for example straight union), the test tube and the fitting to seal the tube.
6 Stress determination
The maximum permissible flexure fatigue stress of the test tubing is determined for the combined stress level.
The combined stress, σ f , is composed of the tensile stress, σ p , resulting from the internal pressure and the wall thickness of the tube, and the bending stress, σ b .
Strain gauges shall be used to demonstrate the bending stress, and the deflection can be checked during testing by means of angle gauges.
A typical stress cycle is illustrated in Figure 3.
The bending stress, σ b , is determined by the maximum permissible flexure fatigue stress of the test tube and shall be specified for each application.
7.3 Bending stress calibration of test specimen
Submit the prepared tube to a static load (F) corresponding to the specified bending stress (see Clause 4) in order to produce the required moment. After the tube bending setting is complete, introduce the specified pressure and read the stress transmitted by the strain gauge on an oscilloscope. Start the vibrator and increase the vibration amplitude of the vibrator until the oscillograph shows the previously determined stress value. The angle gauge allows the deflection(s) to be read for further control. The angle gauge shall be mounted at the end cap of the test specimen. To control the deflection of the test specimen, a suitable stroboscope with variable flash frequency shall be used.