Experimental investigation on low cycle fatigue properties and constitutive models of wire arc additively manufactured carbon steels

Wire arc additive manufacturing (WAAM) is a metal 3D printing technology widely recognized for its potential in structural engineering. However, knowledge about mechanical response of WAAM carbon steels under plastic loading remains relatively scarce. Clarification of strain-life relationships and constitutive model parameters under cyclic loading is essential. In this study, low cycle fatigue (LCF) tests and cyclic loading tests were conducted of WAAM carbon steels, including both as-built and machined coupons of ER70S-6 normal-strength and ER110S-G high-strength steels. A total of 36 LCF coupons and 24 cyclic loading coupons were tested and presented. Based on the LCF test results, strain-life relationships were established and fatigue failure mode was also analysed. The findings revealed that, under identical surface conditions, the WAAM ER70S-6 normal-strength steel exhibited superior LCF performance compared to the ER110S-G high-strength steel. Across all types of LCF coupons, surface undulation emerged as the primary factor contributing to fatigue failure, exerting a more pronounced influence than internal material defects such as porosity or inclusions. For both as-built and machined WAAM normal-strength steels, the hysteresis curves displayed smooth and full shapes, indicating efficient energy dissipation and robust deformation capability. In accordance with the calibrated Chaboche hybrid hardening model parameters, the hysteresis curves calculated by ABAQUS were in good agreement with the test curves, demonstrating the model's capability to predict the cyclic behavior of WAAM carbon steels with a good precision. A comprehensive understanding of the mechanical response of WAAM carbon steels in plastic stage forms the foundation for subsequent design implementation of additively manufactured steel structures. This study enriches the existing WAAM experimental data pool, thereby supplementing the current knowledge base and facilitating the broader application of WAAM technology in structural engineering.