Prof. Mohammad Azadi
Prof. Mohammad Azadi
Semnan University, Iran
Title: A statistical analysis on loading parameters and 3D-printing variables on fatigue lifetimes of PLA-TPU bi-material polymers under bending cycles

Generally, using different polymeric materials besides each other, as bi-materials, leads to improving the performance of the mechanical structures. One polymer has proper strength and the other one has appropriate ductility. These polymeric components can be fabricated by 3D printing. In this research, samples of PLA-TPU bi-material polymers were additively manufactured under different infill (60 and 80%) and TPU percentages (0, 25, and 50%). Then, these specimens were tested under bending cyclic loads, considering various stress levels (5.0 and 7.5 MPa) and loading frequencies (20 and 100 Hz). Based on obtained fatigue lifetimes, a statistical analysis was finally done by the Design-Expert software. The objective was to find the significant factor on the output of fatigue lifetime in bi-material samples. Then also, the predicted fatigue lifetimes were inside the scatter band of ±1.35 versus 100% of the experimental data, which illustrated proper regression modeling, as depicted in the following figure. Moreover, the effective parameters on the lifetime were the loading frequency and the TPU percentage, since the delamination between layers of PLA and TPU was the predominant failure mechanism.

Keywords: Statistical analysis; Loading parameters; 3D-printing variables; Fatigue lifetime; PLA-TPU bi-materials


Figure 1: The predicted and actual values of the logarithm of fatigue lifetimes in PLA-TPU bi-materials

Mohammad Azadi was born in Shiraz, Iran in 1983. He received BSc and MSc degrees in mechanical engineering from Shiraz University, Shiraz, Iran and K.N. Toosi University of Technology, Tehran, Iran, respectively, in 2006 and 2008; then, the PhD degree in mechanical engineering from Sharif University of Technology, Tehran, Iran, in 2013. During his PhD, he has awarded an exchange program by the Ministry of Science, Research and Technology in Iran and also Irankhodro Powertrain Company (IPCO), in order to perform a fatigue testing project at the University of Leoben (Montanuniversität), Leoben, Austria, 2012.

From 2008 to 2015, he has worked as a validation engineer in engine testing laboratory in IPCO, Tehran, Iran and for the last two years, he was a project manager of a national turbo-charged engine. Since 2015, he has been an Assistant Professor in the Faculty of Mechanical Engineering, Semnan University, Semnan, Iran. Now, he is an Associate Professor, since 2019. He is now a vice chancellor of research and technology in the department.

He is the author of five chapter-books, three book translations, two conference proceedings, more than 170 journal articles, about 130 conference papers, and 14 Iranian patents. He has been also funded to perform various research projects by Iranian universities and industries; in addition to one international project, entitled "Iran-Austria Impulse" on the thermo-mechanical fatigue behaviors of metal-matrix nano-composites with the University of Leoben, in Leoben, Austria. As another international collaboration, an investigation on fatigue properties of surface-modified magnesium alloys was performed with the Russian Academy of Sciences, Tomsk, Russia. He was also involved in a project between the university and the industry on AZ91 magnesium alloy for the possibility of manufacturing the automotive components, in IPCO and the University of Leoben in Austria.

He is the editor-in-chief of the International Journal of Additive-Manufactured Structures and also, an editor in PLOS One, Frontiers in Mechanical Engineering, International Journal of Engineering, and Mechanics of Advanced Composite Structures, plus a reviewer in different ISI journals, such as the International Journal of Fatigue, Materials Science and Engineering A, etc.

His research interests include solid mechanics, fatigue, fracture, creep, corrosion, and wear plus to numerical methods, surface engineering, materials characterization, design of experiments, with the application of engine, aerospace, and automotive industries, besides biomechanics. The main field of study is fatigue in materials, epically light metals. Nowadays, he is working on additive manufacturing to fabricate composites and nano-composites by 3D-printing, in order to evaluate fatigue properties of materials. Moreover, 4D-, 5D-, and 6D-printing is also interested besides the bi-/multi-material meta-materials with topology optimization.