714 M A T E R I A L S E V A L U A T I O N • J U L Y 2 0 2 1 Radiographic Testing Applied Technical Services Inc.: Atlanta, GA atslab.com/training. n Atlas API Training: atlasapitraining.com. n Decibel NDE Inspection & Training Institute: Kerala, India Banbury, UK Osaka, Japan Ahmadi, Kuwait Port Harcourt, Nigeria Muscat, Oman Doha, Qatar Jubail, Saudi Arabia Dammam, Saudi Arabia Seoul, South Korea Dubai, UAE Abudhabi, UAE decibelnde.com. n Fujifilm NDT Training Services: Valhalla, NY Suwanee, GA Lake Forest, CA Trumbull, CT Mentor, OH fujifilmndttraining.com. Hellier: Houston, TX Anaheim, CA hellierndt.com. n Institute of Nondestructive Testing & Training: Mumbai, India Navi Mumbai, India Pune, India Goa, India Bangalore, India Delhi, India Karnataka, India Dammam, Saudi Arabia Khobar, Saudi Arabia Jubail, Saudi Arabia Alberta, Canada indtt.org. n Kraft Technology Resources LLC: Tiki Island, TX ndtbootcamp.com. Mistras Group Inc.: Heath, OH mistrasgroup.com. Moraine Valley Community College: Palos Hills, IL morainevalley.edu/ndt. NDE Professionals Inc.: Portland, OR ndeprofessionals .com. NWIS Training Inc.: Burton, TX nationalwelding.com. Test NDT LLC: Brea, CA testndt.com. Trinity Institute of NDT Technology: Bangalore, India trinityndt.com. n Waygate Inspection Academy: Cincinnati, OH Houston, TX San Carlos, CA waygateinspectionacademy .com. Welder Training & Testing Institute: Allentown, PA ndtinstitute.com. n WorldSpec Online NDT Training, a division of Hellier NDT: worldspec.org. Thermal/Infrared Testing n Decibel NDE Inspection & Training Institute: Kerala, India Banbury, UK Osaka, Japan Ahmadi, Kuwait Port Harcourt, Nigeria Muscat, Oman Doha, Qatar Jubail, Saudi Arabia Dammam, Saudi Arabia Seoul, South Korea Dubai, UAE Abudhabi, UAE decibelnde.com. Hellier: hellierndt.com. n Institute of Nondestructive Testing & Training: Mumbai, India Navi Mumbai, India Pune, India Goa, India Bangalore, India Delhi, India Karnataka, India Dammam, Saudi Arabia Khobar, Saudi Arabia Jubail, Saudi Arabia Alberta, Canada indtt.org. n The Snell Group: Barre, VT Charleston, SC Chesapeake, VA Chicago, IL Cincinnati, OH Detroit (Madison Heights), MI Durham, NC Hagerstown, MD Houston, TX Indianapolis, IN Kansas City, MO Knoxville, TN Louisville, KY Minneapolis, MN Omaha, NE Phoenix, AZ San Antonio, TX thesnell group.com. Ultrasonic Testing Applied Technical Services Inc.: Atlanta, GA atslab.com/training. n Atlas API Training: atlasapitraining.com. n Decibel NDE Inspection & Training Institute: Kerala, India Banbury, UK Osaka, Japan Ahmadi, Kuwait Port Harcourt, Nigeria Muscat, Oman Doha, Qatar Jubail, Saudi Arabia Dammam, Saudi Arabia Seoul, South Korea Dubai, UAE Abudhabi, UAE decibelnde.com. Hellier: Houston, TX Anaheim, CA hellierndt.com. n Institute of Nondestructive Testing & Training: Mumbai, India Navi Mumbai, India Pune, India Goa, India Bangalore, India Delhi, India Karnataka, India Dammam, Saudi Arabia Khobar, Saudi Arabia Jubail, Saudi Arabia Alberta, Canada indtt.org. n Kraft Technology Resources LLC: Tiki Island, TX ndtboot camp.com. Mistras Group Inc.: Heath, OH Kent, WA mistrasgroup.com. Moraine Valley Community College: Palos Hills, IL morainevalley.edu/ndt. NDE Professionals Inc.: Portland, OR ndeprofessionals .com. NWIS Training Inc.: Burton, TX nationalwelding.com. n TechKnowServ Corp.: State College, PA techknowserv.com. Test NDT LLC: Brea, CA testndt.com. Trinity Institute of NDT Technology: Bangalore, India trinityndt.com. n Waygate Inspection Academy: Cincinnati, OH Houston, TX San Carlos, CA waygateinspectionacademy .com. Welder Training & Testing Institute: Allentown, PA ndtinstitute.com. Visual Testing Applied Technical Services Inc.: Atlanta, GA atslab.com/training. n Atlas API Training: atlasapitraining.com. n Decibel NDE Inspection & Training Institute: Kerala, India Banbury, UK Osaka, Japan Ahmadi, Kuwait Port Harcourt, Nigeria Muscat, Oman Doha, Qatar Jubail, Saudi Arabia Dammam, Saudi Arabia Seoul, South Korea Dubai, UAE Abudhabi, UAE decibelnde.com. Hellier: Houston, TX Anaheim, CA hellierndt.com. n Institute of Nondestructive Testing & Training: Mumbai, India Navi Mumbai, India Pune, India Goa, India Bangalore, India Delhi, India Karnataka, India Dammam, Saudi Arabia Khobar, Saudi Arabia Jubail, Saudi Arabia Alberta, Canada indtt.org. n Kraft Technology Resources LLC: Tiki Island, TX ndtbootcamp.com. Mistras Group Inc.: Heath, OH mistrasgroup.com. NDE Professionals Inc.: Portland, OR ndeprofessionals .com. n TechKnowServ Corp.: State College, PA techknowserv.com. Test NDT LLC: Brea, CA testndt.com. Trinity Institute of NDT Technology: Bangalore, India trinityndt.com. n Waygate Inspection Academy: Cincinnati, OH Houston, TX San Carlos, CA waygateinspectionacademy .com. n WorldSpec Online NDT Training, a division of Hellier NDT: worldspec.org. w calendar

J U L Y 2 0 2 1 • M A T E R I A L S E V A L U A T I O N 715 ME TECHNICAL PAPER w A B S T R A C T Tubular structures are critical components in infra- structure such as power plants. Throughout their life, they are subjected to extreme conditions or suffer from defects such as corrosion and cracks. Although regular inspection of these components is necessary, such inspection is limited by safety- related risks and limited access for human inspec- tion. Robots can provide a solution for automatic inspection. The main challenge, however, lies in integrating sensors for nondestructive evaluation with robotic platforms. As part of developing a versatile lizard-inspired tube inspector robot, in this study the authors propose to integrate electro- magnetic acoustic transducers into a modular robotic gripper for use in automated ultrasonic inspection. In particular, spiral coils with cylin- drical magnets are integrated into a novel friction- based gripper to excite Lamb waves in thin cylindrical structures. To evaluate the performance of the integrated sensors, the gripper was attached to a robotic arm manipulator and tested on pipes of different outer diameters. Two sets of tests were carried out on both defect-free pipes and pipes with simulated defects, including surface partial cracking and corrosion. The inspection results indicated that transmitted and received signals could be acquired with an acceptable signal-to- noise ratio in the time domain. Moreover, the simulated defects could be successfully detected using the integrated robotic sensing system. KEYWORDS: electromagnetic acoustic transducers, Lamb waves, robotic sensing, nondestructive evaluation, tubular structures Introduction Power plants, which provide energy to surrounding cities, are important to everyday life and work, and tubular structures are critical components of these plants. Throughout their life, these tubular structures experience extreme conditions or suffer from defects such as corrosion, cracks, and stress corro- sion cracks. Therefore, it is necessary to regularly inspect them to ensure structural integrity. This is especially impor- tant because even small defects in the tubes can result in cata- strophic failure and power outages for weeks. However, frequent inspection of these structures is problematic due to various reasons. For example, most power plants that need to be inspected cannot be shut down as they are critical to the functioning of surrounding communities. In addition, safety risks, high temperatures, and limited access to these structures (hard-to-reach places) inhibit human inspection. In this context, robotic inspection is a potential route to mitigating some of the safety restrictions faced by humans furthermore, robotic inspection would facilitate structural inspection in a timely and cost-effective manner. Tubular structures can be difficult to inspect because they often involve time-consuming testing methods for verifying their integrity. Two major types of robots being used for this purpose are in-pipe and out-pipe robots (Roh et al. 2009 Roh and Choi 2005 Lee 2013 Qiao et al. 2013). The first type, in-pipe robots, focuses on inspecting the insides of pipe the main limitation faced by these robots is that the power plant must be shut down during inspection, which affects plant Integrating Electromagnetic Acoustic Transducers in a Modular Robotic Gripper for Inspecting Tubular Components by Hamidreza Nemati*, Fernando Alvidrez*, Ankit Das†, Nihar Masurkar†, Manoj Rudraboina†, Hamid Marvi†, and Ehsan Dehghan-Niri‡ Materials Evaluation 79 (7): 715–727 https://doi.org/10.32548/2021.me-04223 ©2021 American Society for Nondestructive Testing * Intelligent Structures and Nondestructive Evaluation (ISNDE), Civil Engineering Department, New Mexico State University, Las Cruces, NM 88003, USA † School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287, USA ‡ Intelligent Structures and Nondestructive Evaluation (ISNDE), Civil Engineering Department, New Mexico State University, Las Cruces, NM 88003, USA niri@nmsu.edu