Overview
ISO/TR 12112:2018 - Metallic materials - Principles and designs for multiaxial fatigue testing - is a Technical Report from ISO that provides guidance on the general principles of multiaxial fatigue testing and practical design recommendations for classes of multiaxial testing machines and test specimens. Published in 2018 by ISO/TC 164/SC 4, the document synthesizes around 80 years of multiaxial fatigue research to support laboratories, researchers and engineers in reproducing realistic multiaxial stress–strain states in metallic components.
Key topics and technical content
The report focuses on methodology, machine and specimen design, and analysis approaches for multiaxial fatigue testing:
- Methodology and objectives: simulating realistic dynamic stress–strain conditions, controlling stress or strain depending on constraint and low-cycle fatigue (LCF) vs high-cycle regimes.
- Historical development: evolution of specimen and machine designs and lessons learned, including limitations of early approaches.
- Specific multiaxial test methods: descriptions and guidance for common loading combinations such as:
- Bending + torsion
- Axial + torsion
- Axial + internal / external pressure and combined loadings
- Cruciform specimens for LCF and crack-growth studies
- Specimen design guidance: design considerations, recommended geometries and comparison with existing practices (e.g., ASTM E2207 is referenced).
- Machine design and instrumentation: guidance on frames, load cells, pressure systems, strain measurement, control systems, data acquisition and software.
- Multiaxial fatigue analysis and failure criteria: use of computer-aided design, fatigue life prediction approaches, and criteria to interpret multiaxial failure modes.
- Crack growth monitoring and measurement for cruciform and fracture-oriented tests.
Note: ISO/TR 12112 is a Technical Report (guidance) and contains no normative references; it is intended to inform rather than prescribe mandatory requirements.
Practical applications and users
ISO/TR 12112 is useful for:
- Materials and fatigue researchers developing multiaxial test programs
- Test-house managers selecting or designing multiaxial testing machines and specimens
- Automotive, aerospace, energy and pressure-vessel engineers validating component behavior under realistic multiaxial loading (shafts, turbine disks, pressurized vessels)
- Engineers performing fatigue life prediction, crack-initiation and crack-growth studies
- Standards developers and academics seeking a consolidated historical and practical reference on multiaxial fatigue testing.
Related standards
- ASTM E2207 (referenced in the report for specimen comparisons)
- Other ISO mechanical testing standards developed by ISO/TC 164 (see ISO catalog for related fatigue and mechanical test standards).
Keywords: ISO/TR 12112:2018, multiaxial fatigue testing, metallic materials, specimen design, axial + torsion, cruciform, fatigue life prediction, machine design, biaxial stress.