Metal AMS
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49 - Fatigue life assessment of WAAM ER70S-6 steel


The three main factors that influence the fatigue life of metal AM parts are, in decreasing order of their influence, surface roughness, defects, and microstructure. Modelling of the entire fatigue life of parts with defects to obtain crack initiation and crack propagation information with respect to detailed stress and strain fields remain largely neglected. Preliminary FE analyses showed that scatter in fatigue life could be attributed to pore size and location. Subsurface pores centred at a distance of one diameter from the free surface showed the shortest initiation life compared to surface hemispherical pores and internal pores. To analyse the impact of imperfections on crack initiation and crack propagation lives of the mild steel ER70S6 manufactured by WAAM method, the X-ray CT scan was employed in order to detect potential manufacturing defects. The CT results showed that only two specimens out of six had significant defects which could shorten the overall fatigue life. The selected defects were then processed and incorporated into FE analysis. The combination of the X-ray CT-scanned geometries of the defects and the FEA approach helped to bridge the research gap and to model crack propagation in WAAM ER70S6 steel by adopting certain assumptions. Furthermore, six CT-scanned and 14 unscanned specimens were subjected to high-cycle fatigue tests aimed at obtaining the S-N curve of the WAAM ER70S6 steel. Fractography analysis helped to determine the causes of fatigue failures and classify the defects into three categories. By using the scanning electron microscope and employing the striation counting method on the failed specimens with clear fatigue fracture surface, the crack initiation and crack propagation fatigue life was compared with the numerical results on the specimens with the CT-scanned defects.


CETIM-Matcor Technology & Service Pte Ltd, Singapore, Singapore

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49 - Fatigue life assessment of WAAM ER70S-6 steel



11:35 am -11:55 am


Room 7