Overview
ISO/TTA 5:2007 - Code of practice for creep/fatigue testing of cracked components is an ISO Technology Trend Assessment (ISO/TTA) that documents recommended, standardized techniques for measuring and analysing time-dependent fracture behaviour of cracked components. It focuses on Creep Crack Initiation (CCI), Creep Crack Growth (CCG) and Creep‑Fatigue Crack Growth (CFCG) using a wide range of pre‑cracked standard and non‑standard specimen geometries. Published as a second‑edition (2007), this ISO/TTA is a pre‑standardization guidance document intended to harmonize test methods and inform future standards and life‑assessment codes.
Key topics and technical requirements
- Test scope and objectives: Guidance on producing validated test data relevant to industrial life‑assessment and R&D needs.
- Specimen and geometry guidance: Recommendations for specimen selection, machining, crack‑plane orientation, side‑grooving and pre‑cracking methods to introduce sharp, flat crack fronts.
- Experimental setup and monitoring: Procedures for specimen heating, loading, displacement measurement, temperature control and initial pre‑load.
- Crack measurement techniques: Use of direct measurements and electrical methods such as Potential Drop (PD) for in‑test crack length monitoring and post‑test crack front measurement.
- Data collection and logging: Minimum data capture, data smoothing, PD signal preparation, and recommendations on the number and duration of tests to address variability.
- Data analysis parameters: Fracture‑mechanics parameters including stress intensity factor (K), J‑integral, C parameter*, Q* and the Time‑Dependent Failure Assessment Diagram (TDFAD); guidance on validity checks, small‑scale creep, steady‑state creep and transition criteria.
- Reporting and uncertainty: Recommended reporting elements and considerations for sensitivity and accuracy limits of CCI/CCG/CFCG results.
Applications
ISO/TTA 5:2007 is practical for:
- Materials and mechanical engineers performing high‑temperature fracture testing.
- Test laboratories developing creep and creep‑fatigue test programs.
- Component life‑assessment and fitness‑for‑service analysts using experimental parameters (C*, K, J) as inputs to predictive models.
- R&D teams validating new alloys, welds or component designs against time‑dependent crack initiation and growth.
- Standards developers seeking harmonized prestandard data and methods for future formal standards.
Who should use it
- Materials scientists, fracture mechanics specialists, mechanical test engineers, quality assurance teams, and regulators concerned with high‑temperature structural integrity and life assessment.
Related standards
ISO/TTA documents are prestandardization guidance; users should apply ISO/TTA 5:2007 alongside established fracture‑mechanics and creep testing standards and national codes used for component life assessment and fitness‑for‑service evaluations.
