ISO 12111:2011

Overview

ISO 12111:2011 - Metallic materials - Fatigue testing - Strain-controlled thermomechanical fatigue testing method - defines a standardized method for performing strain-controlled thermomechanical fatigue (TMF) tests on uniaxially loaded metallic specimens. The standard covers simultaneous, cyclic control of mechanical strain and temperature, allowing any constant cyclic amplitude, mechanical strain ratio and temperature–strain phasing. It targets reproducible generation, monitoring and reporting of TMF data for materials subject to combined thermal and mechanical cycling (commonly in the low‑cycle fatigue domain).

Key topics and technical requirements

• Scope and definitions: Terms for total, thermal and mechanical strain; cycle, amplitude, range, phase angle and fatigue life are defined to ensure consistent usage.
• Apparatus:
  • Tension–compression testing machine with smooth, backlash‑free start-up (hydraulic or electromechanical).
  • Force measuring system compliant with ISO 7500‑1 Class 1.
  • Strain measurement (extensometer) conforming to ISO 9513 Class 1 (Class 0.5 recommended for gauge lengths <15 mm).
  • Heating system and instrumentation for accurate temperature control and monitoring.
  • Grips and load‑train alignment requirements to limit bending and ensure reproducible loading.
• Specimen requirements: Geometry, machining, surface condition, marking, storage and dimensional checks for uniaxial TMF specimens.
• Procedure and control:
  • Laboratory environment, specimen mounting, temperature control and gradients.
  • Mechanical strain control and thermal strain compensation.
  • Specification of temperature/mechanical strain phasing (phase angle) and command waveforms.
  • Start, monitoring, interruption and failure criteria for TMF tests.
• Data handling and reporting: Preliminary data, reduction/analysis of recorded data, and a structured test report (aim, material, specimen, equipment, methodology, termination criteria, deviations and results presentation).

Applications and users

ISO 12111 is used by:

• Materials testing laboratories and R&D groups conducting TMF experiments.
• Design and fatigue engineers in aerospace, power generation (turbines), automotive and industrial sectors evaluating material life under combined thermal/mechanical loads.
• Failure analysts and suppliers validating materials/components for high‑temperature cyclic service. Practical outcomes include validated fatigue life data, fatigue design inputs for components operating under simultaneous strain and temperature cycles, and consistent inter‑laboratory comparisons.

Related standards

• ISO 7500‑1 - force measuring system verification
• ISO 9513 - calibration of extensometer systems
• ISO 12106 - axial strain‑controlled fatigue testing
• ISO 23718 - mechanical testing vocabulary

Keywords: ISO 12111, TMF testing, thermomechanical fatigue, strain‑controlled, fatigue testing, metallic materials, extensometer, phase angle, low‑cycle fatigue.