ISO 9538-2017 PDF

Full title and description

St ISO 9538-2017 — Aerospace series — Hydraulic tubing joints and fittings — Planar flexure test. Specifies a dynamic flexure (fatigue) test procedure for reconnectable and permanent hydraulic tube joints and fittings used with high‑strength hydraulic tubes in commercial and military aircraft.

Abstract

Defines the test apparatus, specimen preparation, instrumentation and test procedure for planar flexure testing of hydraulic tubing joints and fittings (steel, titanium, aluminium). Intended to assess flexure fatigue performance under combined internal pressure and bending loads to validate joint integrity.

General information

• Status: Withdrawn (revised by ISO 9538:2025).
• Publication date: April 2017 (2017-04).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 49.080 — Aerospace fluid systems and components.
• Edition / version: Edition 2 (2017).
• Number of pages: 6.

Scope

Applies to planar flexure testing of reconnectable and permanent hydraulic tube joints and fittings used with high‑strength hydraulic tubes made of corrosion‑resisting steel, titanium and aluminium for use on commercial and military aircraft. The standard covers test specimen configuration, dynamic test setup, calibration and acceptance criteria for fatigue performance.

Key topics and requirements

• Purpose: assess flexure/fatigue resistance of hydraulic tubing joints and fittings under combined internal pressure and bending.
• Test device and setup: vibration‑based planar flexure rig, hydraulic supply and pressure monitoring, manifold for multiple specimens and shutdown capability; vibrator capable of relevant test frequencies.
• Specimens: include test fitting and tube assembly with end fittings/seals representative of service joins.
• Instrumentation: strain gauges on specimens, deflection/angle measurement and calibration procedures; gauge placement specified by tube size.
• Frequency and tuning: recommendations on specimen natural frequency and test frequency to avoid resonance; dynamic tuning and static calibration steps described.
• Stress determination and calibration: combined mean axial (from internal pressure) plus bending stress determined by calibrated strain readings.
• Acceptance criteria: specimens are expected to survive the specified endurance (typical industry criterion expressed in the procedure is on the order of 10^7 cycles with no leakage or failure).

Technical details and procedural parameters summarized from the published standard and technical catalogues.

Typical use and users

Used by aerospace OEMs, component and hydraulic‑system suppliers, flight‑hardware test laboratories, design and qualification engineers, and regulatory/airworthiness authorities for qualification and verification of hydraulic tube joints and fittings. Also used by test laboratories establishing fatigue test programs for aerospace hydraulic components.

Related standards

Revises ISO 9538:1996 and has been revised by ISO 9538:2025; related documents are other aerospace series standards for hydraulic tubing, fittings and coupling performance and associated test methods developed by ISO/TC 20/SC 10.

Keywords

hydraulic tubing, fittings, planar flexure test, flexure fatigue, aircraft hydraulic joints, strain gauges, aerospace qualification, reconnectable joints.

FAQ

Q: What is this standard?

A: ISO 9538:2017 specifies a planar flexure (dynamic fatigue) test method for hydraulic tubing joints and fittings in aerospace applications.

Q: What does it cover?

A: It covers test apparatus, specimen preparation, instrumentation and procedures to evaluate flexure fatigue performance of reconnectable and permanent hydraulic tube joints and fittings under combined internal pressure and bending.

Q: Who typically uses it?

A: Aerospace OEMs, suppliers of hydraulic tubing and fittings, qualification and test laboratories, and engineers responsible for component verification and airworthiness substantiation.

Q: Is it current or superseded?

A: ISO 9538:2017 is listed as withdrawn and has been revised by ISO 9538:2025; users should consult the 2025 revision for the current requirements.

Q: Is it part of a series?

A: Yes — it is part of the ISO "Aerospace series" of standards dealing with hydraulic tubing joints and fittings and is maintained by ISO/TC 20/SC 10 (aerospace fluid systems and components).

Q: What are the key keywords?

A: hydraulic tubing, fittings, flexure test, fatigue, aerospace, reconnectable joints, strain gauges, planar flexure.