Welcome to Fatigue & Fracture Lab

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Welcome to the Fatigue and Fracture Research  Lab  At the forefront of materials durability research, our lab investigates how structures respond to cyclic loading, uncovering the mechanisms that govern fatigue life and fracture behavior. Combining hands-on testing with theoretical modeling, our team investigates stress-driven failure modes, engineered defects, and architected material systems. We push the boundaries of what materials can endure—from polymers and polymer composites to metals and lightweight metamaterials.

 

We generate reliable fatigue and fracture data to help engineers design safer components. Our team specializes in coupon-level testing, analysis, and modeling for metals, thermoplastics, and carbon-fiber reinforced polymers including FFF/AM materials. We partner with industry and agencies to turn rigorous experiments into actionable S–N/ε–N curves, design allowables, and failure insights.   Research Area:

Lab Director: Mohammad Amjadi, Ph.D., P.E. Assistant Professor of Mechanical Engineering   Arkansas Tech University  1811 North Boulder Ave.   Corley 222  Russellville, AR 72801  Phone: 479-964-0583, Ext. 4204 Email: mamjadi@atu.edu  Google Scholar    LinkedIn
Former Students:  Brayden May (Currently Tooling and Process Engineer at Taber Extrusions) Brayden May is undergraduate alumni, majoring in Mechanical Engineering. His research focused on the fatigue behavior of 3D-printed thermoplastics, contributing to advancements in additive manufacturing techniques and material durability testing.
Minh Tran (Currently Development Engineer at First Solar) Minh Tran is a Mechanical Engineering graduate student doing research on fatigue behavior of porous titanium and thermoplastic cellular structures. Minh's research aims to enhance the performance and durability of materials used in advanced engineering applications. In addition to his academic work, Minh gained valuable industry experience during a summer internship at AESC US headquarters in Smyrna, Tennessee. As an electric vehicle (EV) and energy storage systems (ESS) battery cell process engineer intern, Minh developed an automated packaging machine capable of processing 15 battery cells per minute, improving efficiency and safety.
Genya Ohama: A Bachelor's student majoring in Mechanical Engineering at Arkansas Tech University, conducted fatigue testing experiments on 17-4 Stainless Steel material produced by binder jetting.

 

Standards-Aligned Methods (e.g., ASTM E466 axial fatigue, ASTM E606 strain-controlled fatigue; ASTM D7791-style methods for polymers/composites where applicable) MONOTONIC TESION TESTING Determine elastic modulus, 0.2% offset yield strength, ultimate tensile strength, fracture stress, total elongation, and ductility. FATIGUE TESTING Measure life under cyclic loading to develop S–N or ε–N curves, endurance limits, and mean-stress/frequency effects for design allowables. FRACTURE TOUGHNESS TESTING Fracture Toughness Testing provides information about a material’s resistance to crack extension under a steadily increasing load. FATIGUIE CRACK GROWTH TESTING Measure crack-growth kinetics under cyclic loading (da/dN vs. ΔK or ΔJ) to support life prediction and damage-tolerance analysis. HARDNESS TEST Indentation-based assessment of strength and wear resistance (methods selected per material; e.g., Rockwell, Vickers, or Shore). FRACTOGRAPHY Examine fracture surfaces to locate initiation sites and identify failure mechanisms (e.g., ductile tearing, brittle cleavage, fatigue striations) for root-cause analysis.

1. Servopulser Servo Dynamic Systems EHF-E SERVOPULSER, 50KN, ± 50 mm from Shimadzu     Features include: Up to ±50 kN axial force capacity GRIP SET, SPLIT FLANGE, 50KN Crack growth and fracture toughness grip set and sensor Wide range of grips, fixtures, and accessories
3. Axial Extensometers  For different specimen sizes: Epsilon-Model 3542 Epsilon-Miniature Axial Extensometers – Model 3442
3. Rotating Bending
4. Optical Microscopy
5. Hardness Tester
6. Infrared Camera

 

Iowa State University  Auburn University University of Arkansas for Medical Sciences, Biomechanics lab

Conferences: 

1. Amjadi, M, Brayden May, Genya Ohama, and Minh Hoang Tran; “Fatigue Behavior of Additively Manufactured PA6-GF TPMS Structures using FDM”, the ASTM International Conference on Advanced Manufacturing, Atlanta, GA, 2024.
2. Molaei, R, Amjadi, M; “Fatigue Behavior of Additively Manufactured Titanium TPMS Structures using Selective Laser Melting”, the ASTM International Conference on Advanced Manufacturing, Atlanta, GA, 2024.
3. Amjadi, M; Molaei, R, “A Comparison between Additive Manufacturing and Injection Molding Techniques”, the ASTM International Conference on Advanced Manufacturing, Washington, DC, 2023.
4. Amjadi, M.; Fatemi, A.,” A Critical Plane Fatigue Damage Model for Multiaxial Fatigue Life Prediction of Injection MoldedShort Fiber Reinforced Thermoplastic Composites”. 13th International Conference on Multiaxial Fatigue and Fracture (ICMFF13), New Orleans, LA, USA, 2022.
5. Amjadi M, Fatemi A., “Multiaxial Fatigue Behavior of Thermoplastics; Experimental Study and Modeling”. New trends in fatigue and fracture - NT2F19, Tucson, Arizona, USA, 2019.
6. Amjadi, M.; Fatemi, "Fatigue Behavior of High-Density Polyethylene: Effects of Temperature, Mean Stress, and Manufacturing Method," 12th International Fatigue Congress (FATIGUE 2018), Poitiers Futuroscope-France, May 2018.

Journal Publications:

• Amjadi, M.; Fatemi, A.,” A critical plane approach for multiaxial fatigue life prediction of short fiber reinforced thermoplastic composites”. Composites Part A: Applied Science and Manufacturing, 2024. 180: p. 108050.
• Amjadi, M.; Fatemi, A.,” A Fatigue Damage Model for Life Prediction of Injection Molded Short Fiber Reinforced Thermoplastic Composites”. Polymers. 2021, 13, 2250. 
• Amjadi, M.; Fatemi, A.,”Tensile Behavior of High-Density Polyethylene Including the Effects of Processing Technique, Thickness, Temperature, and Strain Rate”. Polymers 2020, 12, 1857. 
• Amjadi, M.; Fatemi, A.,” Creep and fatigue behaviors of High-Density Polyethylene (HDPE): Effects of temperature, mean stress, frequency, and processing technique”. International Journal of Fatigue. 2020; 141: 105871. doi: 10.1016/j.ijfatigue.2020.105871.
• Amjadi, M.; Fatemi, A. Creep behavior and modeling of high-density polyethylene (HDPE). Polymer Testing 2021, 94, 107031, doi: 10.1016/j.polymertesting.2020.107031.
• Amjadi, M.; Fatemi, A.,” Multiaxial Fatigue Behavior of Thermoplastics Including Mean Stress and Notch Effects: Experiments and Modeling”. International Journal of Fatigue. 2020; 136: 105571. doi: 10.1016/j.ijfatigue.2020.105571.
• Amjadi, M.; Fatemi, A.,” Multiaxial Fatigue Behavior of High-Density Polyethylene (HDPE) Including Notch Effect: Experiments and Modeling”. ICMFF12 - 12th International Conference on Multiaxial Fatigue and Fracture; MATEC Web of Conferences. 2019; 300: 05001. doi: 10.1051/matecconf/201930005001.
• Amjadi M, Nikkhoo M, Khalaf K, et al., “An in silico parametric model of vertebrae trabecular bone based on density and microstructural parameters to assess risk of fracture in osteoporosis”. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. 2014;228(12):1281-1295. doi:10.1177/0954411914563363.

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