LOW CYCLE FATIGUE TESTS WITH THE USE OF MINIATURIZED TEST SPECIMENS

Determination of mechanical properties with the use of sub-sized specimens is topic a high interest nowadays. The application of the sub-sized samples is quite wide for all cases where only limited amount of the experimental material is available such as evaluation of additively manufactured products properties, residual life of in-service components, properties determination of developed nano-structured materials, assessment of dilatometric samples used for thermal and thermo-mechanical treatment development, local properties of components, weld joints and so on. Concerning this large application field it would be very useful to prepare standard for small size samples especially for the most demanded material properties: tensile properties, notch impact transition temperature, fatigue properties, fracture toughness and creep. Current paper is going to deal with the low fatigue (LCF) properties assessment with the use of miniaturized specimens'. There were proposed specimen geometries with the use of FEM analysis and testing procedures for considered mini-specimens tests were developed. In the case of strain controlled LCF tests, contactless testing system had to be established for testing of small sized specimens, where it is not possible to apply standard mechanical extensometers for test control. Moreover, LCF procedure for high temperature tests was also successfully established here. The LCF results were subsequently used for Manson-Coffin parameters determination. Results of low cycle tests for several steels are confronted with the results of standard sized specimens with very good agreement for all considered conditions.