ASTM E2368 is a standard practice for strain-controlled thermomechanical fatigue (TMF) testing of materials under uniaxial loading, where temperature and mechanical strain are varied in a controlled, repeatable cycle.
This standard is typically used when fatigue life and damage mechanisms are influenced by both cyclic mechanical strain and cyclic temperature (including the phase relationship between them). If you need help deciding whether TMF testing applies to your program or how to align a lab setup with the edition you’re citing, talk with our team.
ASTM E2368: Standard Practice for Strain Controlled Thermomechanical Fatigue Testing
ASTM E2368 provides a structured approach for generating TMF data on test specimens using strain control while independently controlling the specimen temperature through a defined thermal cycle.
Because E2368 is a practice (not a material specification), the exact temperature/strain limits, waveform details, and end-of-test criteria are typically defined by the test plan, contract requirements, or the material development program while staying consistent with the practice’s framework.
Quick Definition
Document type: Standard practice.
In plain terms: A controlled lab approach for running uniaxial, strain-controlled fatigue cycles while also cycling temperature, so you can evaluate fatigue behavior under combined thermal + mechanical cycling.
What This Standard Covers
ASTM E2368 focuses on strain-controlled TMF testing where the specimen gage section is intended to experience a controlled mechanical strain history at the same time as a controlled temperature history.
Key boundaries: It applies to specimen testing (not full-scale components) and is written around uniaxial loading with cyclically repeatable parameters (temperature range, strain range, and their phase relationship held consistent through the test).
Why This Standard Matters in Testing
For elevated-temperature applications, fatigue damage is often shaped by the interaction of temperature-dependent mechanisms (for example, microstructural evolution and time/temperature effects) with cycle-dependent fatigue mechanisms. TMF testing is commonly selected when isothermal fatigue data alone does not represent the combined thermal-mechanical service condition.
In practical terms, E2368 helps laboratories and engineering teams standardize how TMF cycles are controlled and reported so results can be compared within a program and across labs more consistently.
Common Materials, Product Types, or Applications Covered
ASTM E2368 is commonly associated with structural alloys and engineered materials used in cyclic, elevated-temperature environments where both temperature and mechanical loading vary during operation.
Common application areas: High-temperature machinery and hardware where start/stop, ramping, or duty-cycle changes create coupled thermal and mechanical cycling (for example, hot-section or near-hot-section metallic materials development and qualification programs).
Common Test or Verification Workflow
TMF programs built around ASTM E2368 often follow a workflow like the one below, with details tailored to the material system and the objective of the work.
- Define the thermal cycle (minimum/maximum temperature, heating/cooling rates, dwell(s) if used) and the mechanical strain cycle (minimum/maximum strain, waveform, and any holds).
- Define temperature–strain phasing (for example, whether peak strain occurs near peak temperature or offset from it) and keep it consistent for the test series.
- Prepare and instrument the specimen for both strain control and temperature measurement in/near the gage section, then stabilize and verify control performance before starting the life test.
- Run cyclic loading under strain control with synchronized temperature cycling while recording cyclic response and tracking life or a defined end point.
- Report the test conditions and results in a way that makes the thermal-mechanical history and control method unambiguous for comparison.
Equipment Commonly Used for This Standard
ASTM E2368 is equipment-intensive because it requires closed-loop strain control while also imposing a controlled thermal cycle. The most important selection factor is whether the system can maintain stable, synchronized control of strain and temperature over the intended ranges for the full test duration.
Common equipment elements: A fatigue-rated axial test frame and controller capable of strain-controlled cyclic loading; a high-temperature heating solution (commonly a furnace or induction heating, depending on the temperature profile and lab approach); high-temperature strain measurement suitable for the gage section (often a high-temperature extensometer or equivalent validated strain measurement approach); temperature measurement and control hardware (for example, thermocouples and a temperature controller); and grips/fixtures designed to survive the thermal environment while maintaining alignment and minimizing unintended bending.
If you’re selecting a TMF-capable frame, furnace/heating package, and high-temperature strain measurement for your temperature range and cycle profile, you can request a detailed quote for a configuration matched to your specimen type and control requirements.
How to Read This Designation or Revision
ASTM E2368 is the fixed designation for this standard practice. When written with a year suffix (for example, E2368-25), the suffix identifies the edition year tied to that published version.
TMF control language and referenced verification practices can change between editions, so quotes, compliance statements, and lab procedures should be tied to the exact edition specified in the purchase order, contract, or test plan.
Related Standards, Methods, or Frameworks when useful
TMF testing is also addressed by other frameworks in industry and research, and programs may reference multiple documents depending on customer requirements and the region of use.
Common cross-references: ISO 12111 is frequently cited alongside ASTM E2368 for strain-controlled thermomechanical fatigue testing. When multiple documents are invoked, align the control definitions, reporting expectations, and any acceptance criteria to the governing requirement set for the program.
Talk with us about an ASTM E2368 testing setup
If you’re planning TMF work and want to confirm practical details like strain measurement approach at temperature, heating method tradeoffs, and controller capability for temperature–strain phasing, contact our team to discuss your test window and the edition you need to follow.