Development of a Novel Method for Simultaneously Testing Multiple Specimens to Evaluate Tension-Tension Fatigue Life

The aim of this study is to develop a novel method for rapidly evaluating the tension–tension fatigue life of metals. Fatigue failure, which occurs when materials gradually weaken and fracture under repeated loading, is a critical concern in designing safe and reliable structures such as airplanes, cars, and bridges. Traditional fatigue testing methods are slow, costly, and typically limited to one specimen at a time. To address this, a high-throughput testing method was developed that allows multiple small-scale specimens to be tested simultaneously while following international testing standards. Using stainless steel sub-sized specimens scaled at 1:5 relative to the ASTM E8 standard, an innovative four-specimen series assembly was designed to create different stress levels under a single applied load. Three multi-specimen, load-controlled fatigue testing strategies were introduced, and 57 specimens were tested individually and in assemblies. Digital Image Correlation (DIC) was used to monitor the strain response of each specimen in real time. The results show that this method can reduce testing time by up to 75% and material usage by 80%, while maintaining accuracy and reliability comparable to conventional single-specimen testing.