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Savas Dilibal

University of Akron, Mechanical Engineering, Faculty Member

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www.adaptronics.tech
Address: Akron, Ohio, United States

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University of Cologne

Armando Marques-Guedes

UNL - New University of Lisbon

Minas Liarokapis

The University of Auckland

Indian Institute of Technology Delhi

Visvesvaraya Technological University

Sarah M O H A M E D el hawary

De Montfort University

Giuseppe Carbone

University of Calabria

National Institute of Technology Rourkela

Pablo Alvarez-Alonso

University of Oviedo / Universidad de Oviedo

Richard Crawford

The University of Texas at Austin

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Papers by Savas Dilibal

Additively Manufactured Soft Pneumatic Gripper Integrated Remotely Operated Underwater Vehicle (ROV) for Grasping Archeological Remains

Effect of Wire Electrical Discharge Machining on the Surface of Ebm-Additive Manufactured Niti Alloys

International journal of 3d printing technologies and digital industry, Dec 30, 2021

Nickel-titanium (NiTi) shape memory alloys are used in varied engineering products, such as biome... more Nickel-titanium (NiTi) shape memory alloys are used in varied engineering products, such as biomedical device and mechatronic actuator applications. The conventional machining technology are utilized in the limited fields due to their effects on the hardness and brittleness of the machined alloys. However, the wire electrical discharge machining (WEDM) technology is one of the most preferred postprocessing tool to obtain a surface with high quality. The electrical current and voltage values with pulse on and pulse off time are the crucial parameters for WEDM. These parameters should be optimized before wire electrical discharge machining process. Electron beam melting (EBM)-based additive manufacturing of the nickel-titanium powders provides obtaining bulk NiTi shape memory alloys using high energy electron beams. In this study, the application of WEDM which is used as a post-processing tool is evaluated for the EBM-based additive manufactured NiTi samples. Additionally, the scanning electron microscopy, elemental analysis and microhardness characteristics results of the wire electrical discharge machined NiTi samples are carefully investigated.

Corrigendum to “On the volume change in Co–Ni–Al during pseudoelasticity” [Mater. Sci. Eng. A 528 (2011) 2875–2881]

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, May 1, 2011

CoNiAl alloys are a new class of shape memory alloys, which exhibit pseudoelastic strains as high... more CoNiAl alloys are a new class of shape memory alloys, which exhibit pseudoelastic strains as high 6% over a broad range of temperatures. Based on the crystallographic lattice constants, a substantial volume change upon transformation is expected at the mesoscopic level, yet it has not been measured previously. Transformation strains are established in three mutually orthogonal directions in the [0 0 1]-oriented CoNiAl single crystals under compression. Experiments reveal that the transformation volume change is approximately 2% based on determination of strains on transformed and untransformed locations. Despite the high volumetric strain, the pseudoelastic stress-strain response represents full recoverability with small stress hysteresis. Additional factors that influence pseudoelasticity behavior are discussed particularly the M d − A f interval and the flow resistance, which are both higher for CoNiAl compared to other shape memory alloys.

Nikel-Titanyum Şekil Bellekli Alaşımların Süperelastik Davranışına Isıl İşlemin Etkisi

Politeknik dergisi, Sep 15, 2017

Şekil bellekli alaşımlar (ŞBA), mikroyapıda östenit ve martenzit fazlar arasında tersinir termoel... more Şekil bellekli alaşımlar (ŞBA), mikroyapıda östenit ve martenzit fazlar arasında tersinir termoelastik faz dönüşümü ile makroyapıda şekil belleği ve süperelastik davranış gösterebilen intermetalik malzemelerdir. Nikel-titanyum (NiTi) ŞBA`lar süperelastik özelliği sebebiyle başta biyomedikal uygulamalar olmak üzere birçok alanda hızla yaygınlaşmaktadır. Bu çalışmada, atomik olarak % 50.8 nikel içeren NiTi numunelere uygulanan ısıl işlemin, alaşımın faz dönüşüm sıcaklığı ve süperelastik davranışına etkisi incelenmiştir. Yapılan diferansiyel taramalı kalorimetri (DSC) analizleri ve çekme testlerinde elde edilen sonuçlar karşılaştırılmıştır. Çözeltiye alma ve yaşlandırma ısıl işlemlerinin, NiTi numunelerin süperelastik davranış gösterme karakteristiğini artırdığı deneysel sonuçlarla gözlemlenmiştir.

Finger-like manipulator driven by antagonistic nickel-titanium shape memory alloy actuators

Shape memory alloy (SMA) actuators generally have a fast response time when heated. However, the ... more Shape memory alloy (SMA) actuators generally have a fast response time when heated. However, the return stroke during cooling can be slow and has been a hindrance to the application of SMA actuators in different areas such as robotic hands. Thus, a novel finger-like antagonistic SMA actuator design is presented in this paper. By using different thermal shape setting processes, one SMA actuator was designed to take a curved shape when heated. This actuator was antagonistically coupled to a different actuator that took a straight shape when heated. Thus, alternately heating each actuator caused the finger-like manipulator to flex and extend rapidly. A comparison study was performed between the novel antagonistic design and a single actuator which showed that the both designs applied approximately the same force with the same velocity when flexing. However, the antagonistic design was able to extend, or open, more rapidly with statistical significance. This was demonstrated for 1.5mm, 1.9mm, and 3.0mm SMA actuator diameters.

Nikel-titanyum Şekil Bellekli Alaşımlar Kullanılarak Geliştirilen İtü Robot El Ve Performans Analizleri

Joint Control Implementation of 4-DOF Robotic Arm Using Robot Operating System

Experimental and Numerical Analysis of Additive Manufactured Pneumatic Artificial Muscle Hand Rehabilitation Orthosis

2022 Innovations in Intelligent Systems and Applications Conference (ASYU), Sep 7, 2022

Stabilized actuation of a novel NiTi shape-memory-alloy-actuated flexible structure under thermal loading

Materiali in Tehnologije, Oct 2, 2018

Shape-memory-alloy (SMA) actuated flexible structures are used in a variety of configurations in ... more Shape-memory-alloy (SMA) actuated flexible structures are used in a variety of configurations in many aerospace, robotics and underwater applications. In this study, a pair of nickel-titanium (NiTi) shape-memory-alloy plates is embedded in a flexible structure. An antagonistic design with a plate geometry is selected for the NiTi SMA to achieve bidirectional flexibility. A three-point-bending test is conducted to reveal the bending strength of the NiTi plates in the martensite and austenite phases. The antagonistic NiTi SMA plates are geometrically adapted and embedded into the flexible structure, which is fabricated through additive manufacturing using thermoplastic-polyurethane (TPU) flexible filament. The stabilized actuation stages of the antagonistic NiTi SMA plates embedded in the flexible structure are examined through observation of an extended number of thermal cycles. A comparison is made by applying two different electrical-current values with a regulated high-current DC power supply. A cycling profile with a maximum, bidirectional, stabilized actuation stroke of 52 mm is obtained through 100 heating/cooling cycles for the NiTi SMA-plate-actuated flexible structure. The effects of the high and low heating/cooling cyclic periods on the stabilized actuation stroke are also investigated.

Development of Bioinspired Robotic Pectoral Fin Structure Using Radial Scissor Mechanism

2021 3rd International Congress on Human-Computer Interaction, Optimization and Robotic Applications (HORA), Jun 11, 2021

In this study, the flapping pectoral fin structure of the manta ray has been mimicked with radial... more In this study, the flapping pectoral fin structure of the manta ray has been mimicked with radial scissor mechanisms. The flapping behavior for swimming is configured via generative design using two different scissor mechanisms. The bioinspired four-cell and six-cell robotic fin structures are designed, analyzed and additively manufactured for comparison purpose. Experimental and numerical analysis are conducted to unveil the displacement, and stress distribution parameters for both structures. A comparison is made between the experimental and numerical analysis results.

The effect of employed loading mode on the mechanical cyclic stabilization of NiTi shape memory alloys

Intermetallics, Oct 1, 2017

One of the effective parameters on the characteristic response of the nickel-titanium (NiTi) shap... more One of the effective parameters on the characteristic response of the nickel-titanium (NiTi) shape memory alloy (SMA) is the employed loading mode during the uniaxial cycling. In this study, the uniaxial tensile tests are conducted under an extended number of mechanical cycles in order to investigate the effect of force control on the pseudoelastic response of the NiTi SMA. The results which are obtained under the force control are compared with the mixed (force/displacement) control counterpart. An evolutionary stress-strain pattern is observed during the 100 cycles of mechanical loading. Additionally, it is noticed that the residual strain and mechanical hysteresis area also show an evolutionary pattern. The observed evolutionary patterns are delineated in three regimes: (i) early evolution; (ii) approach to a nearly stable stage (transient); and (iii) stabilization stage. Furthermore, the in-situ digital image correlation (DIC) is applied to receive the meso-/micro-scale full-field strain measurements. Severe strain localization is observed under force-controlled tensile test during meso-,/ micro-scale DIC analysis.

Investigation of Nucleation and Growth of Detwinning Mechanism in Martensitic Single Crystal NiTi Using Digital Image Correlation

Metallography, Microstructure, and Analysis, Jul 23, 2013

In this study, the deformation of martensitic NiTi was investigated utilizing single crystal Ti-5... more In this study, the deformation of martensitic NiTi was investigated utilizing single crystal Ti-50.1 at.% Ni in [123], [111], and [001] orientations. The stress-strain response of the martensitic NiTi was resolved experimentally using incremental tensile loading. The nucleation and growth of the detwinning mechanism was investigated by means of in-situ digital image correlation (DIC) technique which enabled the precise determination of the onset of detwinning on the stress-strain curve. The mechanism of detwinning nucleation was observed before the stress plateau on the stress-strain curve. The use of DIC for the [123] orientation revealed that the intersection of twins causes more hardening through twinning-induced strains. Based on the stress-strain response of the [123], [111], and [001] orientations, it is obvious that detwinning is orientation independent. In contrast, the evolution of detwinning after nucleation is orientation dependent.

Development of IoMT Device for Mobile Eye Examination Via Cloud-based TeleOphthalmology

A periodic visit of an ophthalmologist is crucial for monitoring the eye health regularly. Howeve... more A periodic visit of an ophthalmologist is crucial for monitoring the eye health regularly. However, the periodic visit to the ophthalmologist may become difficult to handle in the cases of the patient's visual status varies; personal location is far away from the hospital or special cases; such as COVID-19 pandemic. In this study, a novel ophthalmologist-and-patient-in-the-loop telemedicine platform is built to remotely examine the corneal surface of the eye. An internet-of-medical-things (IoMT)-based biomedical device is developed with ophthalmologist dashboard and patient interface. The developed biomedical device, Mobile XMI, is validated by testing in the ophthalmologist-and-patient-in-the-loop telemedicine system. The preliminary results showed that the cloud-based teleophthalmology architecture provides a potential tool for the early detection and diagnosis of the corneal related symptoms and diseases. Additionally, the developed medical platform facilitates the remote eye examination of the patients with disability or patients who locate far away from the ophthalmologist or hospital.

Experimental Investigation on the EBM-Based Additively Manufactured Prismatic Nickel–Titanium SMA Components

Russian Journal of Non-ferrous Metals, May 1, 2021

Abstract Additive manufacturing (AM) of the nickel–titanium (NiTi) shape memory alloys (SMA) have... more Abstract Additive manufacturing (AM) of the nickel–titanium (NiTi) shape memory alloys (SMA) have provided novel component solutions with a variety of design configurations in the industry. Electron beam melting (EBM) is a trending metal additive manufacturing process for industrial applications in the field of biomedical and aerospace engineering. In this study, experimental investigations were conducted to reveal the effect of processing conditions on the microstructure and hardness properties of EBM-fabricated nickel-titanium components. Furthermore, detailed microstructural characterizations were performed with a scanning electron microscope, EDS, and XRD for unveiling of the microscopic structure and phase analysis during the layer by layer solidification. The experimental results were systematically evaluated for the powder and the bulk prismatic components, respectively.

Design and Production of Aluminum Alloy Heat Sinks Using the Direct Metal Laser Sintering Manufacturing Method for Thermoelectric Modules

International Journal of 3D Printing Technologies and Digital Industry, 2021

Doğru akım ile ısı kontrolüne olanak tanıyan yarı-iletken yapıdaki termoelektrik malzemeler, term... more Doğru akım ile ısı kontrolüne olanak tanıyan yarı-iletken yapıdaki termoelektrik malzemeler, termoelektrik modül yüzeyleri arasında bir ısı farkı oluşturur. Termoelektrik modüllerde teknolojik imkânlar arttıkça değişik malzemelerin birleştirilmesiyle verimlilikleri artmaktadır. Termoelektrik modüllerde farklı yöntemlerle verimlilik artışı sağlanabilmesine rağmen üretildiği malzemelerin yapılarından kaynaklı verimliliklerini sınırlayan önemli faktörler bulunmaktadır. Farklı geometrilerde soğutucuların temel amacı termoelektrik parça yüzeyinde oluşan ısının en hızlı şekilde ve malzemeye zarar vermeyecek şekilde soğutulmasını sağlamaktır. Soğutucu geometrisinde yapılacak değişikliklerle her bir yüzeyin ısı dengesini ayarlayarak, ısının eşit dağılımıyla sistemden hızlı ve güvenilir bir şekilde aktarılması sağlanmalıdır. Doğrudan (direkt) Metal Lazer Sinterleme (DMLS) eklemeli imalat yöntemi üç boyutlu model verilerinden belirlenen farklı geometrilerde komponentler üretmek için katmanlar...

Characterization of energy dissipative cushions made of Ni–Ti shape memory alloy

Smart Materials and Structures, 2021

Earthquake-resistant design of structures requires dissipating seismic energy by deformations of ... more Earthquake-resistant design of structures requires dissipating seismic energy by deformations of structural members or additional fuse elements. Owing to its easy-to-produce, plug-and-play, high equivalent damping ratio, and large displacement capacity characteristics, energy dissipative steel cushions (SCs) were found to be an efficient candidate for this purpose. However, similar to other conventional metallic dampers, residual displacement after a strong shaking is the most notable drawback of the SCs. In this work, cushions produced from Ni–Ti shape memory alloy (SMA) are evaluated numerically by experimentally verified finite element models to assess their impact on the performance of earthquake-resistant structures. Furthermore, a reinforced concrete testing frame is retrofitted with energy dissipative steel and Ni–Ti cushions. Performance of the frames (e.g. dissipated energy by the cushions, hysteretic energy to input energy ratio, maximum drift, and residual drift) with dif...

Shape memory alloy tube actuators inherently enable internal fluidic cooling for a robotic finger under force control

Smart Materials and Structures, Sep 22, 2020

This paper presents the design, control and evaluation of a novel robotic finger actuated by shap... more This paper presents the design, control and evaluation of a novel robotic finger actuated by shape memory alloy (SMA) tubes which intrinsically afford an internal conduit for fluidic cooling. The SMA tubes are thermomechanically programmed to flex the robotic finger when Joule heated. A superelastic SMA plate provides a spring return motion to extend the finger when cooling liquid is pumped through the internal channel of the SMA tube actuators. The mechanical design and nonlinear force controller are presented for this unique robotic finger. Sinusoidal and step response experiments demonstrate excellent error minimization when operated below the bandwidth which was empirically determined to be 6 rad s−1. Disturbance rejection experiments are also performed to demonstrate the potential to minimize externally applied forces. This method of internal liquid cooling of Joule heated SMA tubes simultaneously increases the system bandwidth and expands the potential uses of SMA actuators for robotic applications. The results show that this novel robotic finger is capable of precise force control and has a high strength to weight ratio. The finger can apply a force of 4.35 N and has a mass of 30 g. Implementing this design into wearable prosthetic devices could enable lightweight, high strength applications previously not achievable.

Manufacturing and Characterizaton of Waam-Based Bimetallic Cutting Tool

International journal of 3d printing technologies and digital industry, Dec 31, 2022

Wire-arc additive manufacturing (WAAM) is a promising method to produce many functional component... more Wire-arc additive manufacturing (WAAM) is a promising method to produce many functional components in different industries. In this method, the welding wires from the feedstock are melted by arc discharge and deposited layer by layer. Other welding wires having different chemical compositions can also be added to the top of the previously deposited layer by replacing the feed wire from the stock to produce bimetallic components. This study investigated the feasibility of using robotic wire arc additive manufacturing technology to produce a bimetallic cutting equipment. The bimetallic cutting equipment was produced by depositing MSG 6 GZ-60 hard-facing welding wire on top of the austenitic stainless-steel wall produced with ER 316LSi solid wire. The cutting-based equipment requires an increased abrasion resistance with the combination of ductility to provide adequate equipment life and performance. Thus, detailed microstructural analysis and hardness tests were conducted to understand the general microstructural characteristic of the manufactured cutting equipment, including interfaces between two different materials.

Experimental Investigation of Wire Arc Additively Manufactured Inconel 625 Superalloy

Transactions of the Indian Institute of Metals, Jan 7, 2023

Characterization of a low-alloy steel component produced with wire arc additive manufacturing process using metal-cored wire

MP MATERIALPRUEFUNG - MP MATERIALS TESTING, Jun 1, 2022

In this study, a low-alloy steel component was manufactured using specially produced E70C-6M clas... more In this study, a low-alloy steel component was manufactured using specially produced E70C-6M class of metal-cored welding wire according to AWS A5.18 standard for the WAAM process. The manufactured low-alloy steel component was first subjected to radiographic examination to detect any weld defect. Uniaxial tensile tests were conducted for the bottom, middle and upper regions. The micro-hardness tests were performed parallel to the deposition direction. The results show that microstructures varied from base metal to the face region of the WAAM component, including the bottom, middle and top sections. The bottom region showed lamellar structures; the middle and upper region presented equiaxed ferrite structure with a small amount of grain boundary pearlites and the face region displayed a mix of equiaxed and lamellar structures of ferrites. The yield and ultimate tensile strengths of the top, middle, and bottom regions exhibited similar results varying between 370 MPa and 490 MPa, respectively. In contrast, the top region showed an elongation value about 15% higher than other regions. Moreover, the yield and ultimate tensile strength for WAAM-produced component were found to be 14% and 24% lower than the multiple-pass all-weld metal of E70C-6M class of metal-cored wire.

Additively Manufactured Soft Pneumatic Gripper Integrated Remotely Operated Underwater Vehicle (ROV) for Grasping Archeological Remains

Effect of Wire Electrical Discharge Machining on the Surface of Ebm-Additive Manufactured Niti Alloys

International journal of 3d printing technologies and digital industry, Dec 30, 2021

Nickel-titanium (NiTi) shape memory alloys are used in varied engineering products, such as biome... more Nickel-titanium (NiTi) shape memory alloys are used in varied engineering products, such as biomedical device and mechatronic actuator applications. The conventional machining technology are utilized in the limited fields due to their effects on the hardness and brittleness of the machined alloys. However, the wire electrical discharge machining (WEDM) technology is one of the most preferred postprocessing tool to obtain a surface with high quality. The electrical current and voltage values with pulse on and pulse off time are the crucial parameters for WEDM. These parameters should be optimized before wire electrical discharge machining process. Electron beam melting (EBM)-based additive manufacturing of the nickel-titanium powders provides obtaining bulk NiTi shape memory alloys using high energy electron beams. In this study, the application of WEDM which is used as a post-processing tool is evaluated for the EBM-based additive manufactured NiTi samples. Additionally, the scanning electron microscopy, elemental analysis and microhardness characteristics results of the wire electrical discharge machined NiTi samples are carefully investigated.

Corrigendum to “On the volume change in Co–Ni–Al during pseudoelasticity” [Mater. Sci. Eng. A 528 (2011) 2875–2881]

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, May 1, 2011

CoNiAl alloys are a new class of shape memory alloys, which exhibit pseudoelastic strains as high... more CoNiAl alloys are a new class of shape memory alloys, which exhibit pseudoelastic strains as high 6% over a broad range of temperatures. Based on the crystallographic lattice constants, a substantial volume change upon transformation is expected at the mesoscopic level, yet it has not been measured previously. Transformation strains are established in three mutually orthogonal directions in the [0 0 1]-oriented CoNiAl single crystals under compression. Experiments reveal that the transformation volume change is approximately 2% based on determination of strains on transformed and untransformed locations. Despite the high volumetric strain, the pseudoelastic stress-strain response represents full recoverability with small stress hysteresis. Additional factors that influence pseudoelasticity behavior are discussed particularly the M d − A f interval and the flow resistance, which are both higher for CoNiAl compared to other shape memory alloys.

Nikel-Titanyum Şekil Bellekli Alaşımların Süperelastik Davranışına Isıl İşlemin Etkisi

Politeknik dergisi, Sep 15, 2017

Şekil bellekli alaşımlar (ŞBA), mikroyapıda östenit ve martenzit fazlar arasında tersinir termoel... more Şekil bellekli alaşımlar (ŞBA), mikroyapıda östenit ve martenzit fazlar arasında tersinir termoelastik faz dönüşümü ile makroyapıda şekil belleği ve süperelastik davranış gösterebilen intermetalik malzemelerdir. Nikel-titanyum (NiTi) ŞBA`lar süperelastik özelliği sebebiyle başta biyomedikal uygulamalar olmak üzere birçok alanda hızla yaygınlaşmaktadır. Bu çalışmada, atomik olarak % 50.8 nikel içeren NiTi numunelere uygulanan ısıl işlemin, alaşımın faz dönüşüm sıcaklığı ve süperelastik davranışına etkisi incelenmiştir. Yapılan diferansiyel taramalı kalorimetri (DSC) analizleri ve çekme testlerinde elde edilen sonuçlar karşılaştırılmıştır. Çözeltiye alma ve yaşlandırma ısıl işlemlerinin, NiTi numunelerin süperelastik davranış gösterme karakteristiğini artırdığı deneysel sonuçlarla gözlemlenmiştir.

Finger-like manipulator driven by antagonistic nickel-titanium shape memory alloy actuators

Shape memory alloy (SMA) actuators generally have a fast response time when heated. However, the ... more Shape memory alloy (SMA) actuators generally have a fast response time when heated. However, the return stroke during cooling can be slow and has been a hindrance to the application of SMA actuators in different areas such as robotic hands. Thus, a novel finger-like antagonistic SMA actuator design is presented in this paper. By using different thermal shape setting processes, one SMA actuator was designed to take a curved shape when heated. This actuator was antagonistically coupled to a different actuator that took a straight shape when heated. Thus, alternately heating each actuator caused the finger-like manipulator to flex and extend rapidly. A comparison study was performed between the novel antagonistic design and a single actuator which showed that the both designs applied approximately the same force with the same velocity when flexing. However, the antagonistic design was able to extend, or open, more rapidly with statistical significance. This was demonstrated for 1.5mm, 1.9mm, and 3.0mm SMA actuator diameters.

Nikel-titanyum Şekil Bellekli Alaşımlar Kullanılarak Geliştirilen İtü Robot El Ve Performans Analizleri

Joint Control Implementation of 4-DOF Robotic Arm Using Robot Operating System

Experimental and Numerical Analysis of Additive Manufactured Pneumatic Artificial Muscle Hand Rehabilitation Orthosis

2022 Innovations in Intelligent Systems and Applications Conference (ASYU), Sep 7, 2022

Stabilized actuation of a novel NiTi shape-memory-alloy-actuated flexible structure under thermal loading

Materiali in Tehnologije, Oct 2, 2018

Shape-memory-alloy (SMA) actuated flexible structures are used in a variety of configurations in ... more Shape-memory-alloy (SMA) actuated flexible structures are used in a variety of configurations in many aerospace, robotics and underwater applications. In this study, a pair of nickel-titanium (NiTi) shape-memory-alloy plates is embedded in a flexible structure. An antagonistic design with a plate geometry is selected for the NiTi SMA to achieve bidirectional flexibility. A three-point-bending test is conducted to reveal the bending strength of the NiTi plates in the martensite and austenite phases. The antagonistic NiTi SMA plates are geometrically adapted and embedded into the flexible structure, which is fabricated through additive manufacturing using thermoplastic-polyurethane (TPU) flexible filament. The stabilized actuation stages of the antagonistic NiTi SMA plates embedded in the flexible structure are examined through observation of an extended number of thermal cycles. A comparison is made by applying two different electrical-current values with a regulated high-current DC power supply. A cycling profile with a maximum, bidirectional, stabilized actuation stroke of 52 mm is obtained through 100 heating/cooling cycles for the NiTi SMA-plate-actuated flexible structure. The effects of the high and low heating/cooling cyclic periods on the stabilized actuation stroke are also investigated.

Development of Bioinspired Robotic Pectoral Fin Structure Using Radial Scissor Mechanism

2021 3rd International Congress on Human-Computer Interaction, Optimization and Robotic Applications (HORA), Jun 11, 2021

In this study, the flapping pectoral fin structure of the manta ray has been mimicked with radial... more In this study, the flapping pectoral fin structure of the manta ray has been mimicked with radial scissor mechanisms. The flapping behavior for swimming is configured via generative design using two different scissor mechanisms. The bioinspired four-cell and six-cell robotic fin structures are designed, analyzed and additively manufactured for comparison purpose. Experimental and numerical analysis are conducted to unveil the displacement, and stress distribution parameters for both structures. A comparison is made between the experimental and numerical analysis results.

The effect of employed loading mode on the mechanical cyclic stabilization of NiTi shape memory alloys

Intermetallics, Oct 1, 2017

One of the effective parameters on the characteristic response of the nickel-titanium (NiTi) shap... more One of the effective parameters on the characteristic response of the nickel-titanium (NiTi) shape memory alloy (SMA) is the employed loading mode during the uniaxial cycling. In this study, the uniaxial tensile tests are conducted under an extended number of mechanical cycles in order to investigate the effect of force control on the pseudoelastic response of the NiTi SMA. The results which are obtained under the force control are compared with the mixed (force/displacement) control counterpart. An evolutionary stress-strain pattern is observed during the 100 cycles of mechanical loading. Additionally, it is noticed that the residual strain and mechanical hysteresis area also show an evolutionary pattern. The observed evolutionary patterns are delineated in three regimes: (i) early evolution; (ii) approach to a nearly stable stage (transient); and (iii) stabilization stage. Furthermore, the in-situ digital image correlation (DIC) is applied to receive the meso-/micro-scale full-field strain measurements. Severe strain localization is observed under force-controlled tensile test during meso-,/ micro-scale DIC analysis.

Investigation of Nucleation and Growth of Detwinning Mechanism in Martensitic Single Crystal NiTi Using Digital Image Correlation

Metallography, Microstructure, and Analysis, Jul 23, 2013

In this study, the deformation of martensitic NiTi was investigated utilizing single crystal Ti-5... more In this study, the deformation of martensitic NiTi was investigated utilizing single crystal Ti-50.1 at.% Ni in [123], [111], and [001] orientations. The stress-strain response of the martensitic NiTi was resolved experimentally using incremental tensile loading. The nucleation and growth of the detwinning mechanism was investigated by means of in-situ digital image correlation (DIC) technique which enabled the precise determination of the onset of detwinning on the stress-strain curve. The mechanism of detwinning nucleation was observed before the stress plateau on the stress-strain curve. The use of DIC for the [123] orientation revealed that the intersection of twins causes more hardening through twinning-induced strains. Based on the stress-strain response of the [123], [111], and [001] orientations, it is obvious that detwinning is orientation independent. In contrast, the evolution of detwinning after nucleation is orientation dependent.

Development of IoMT Device for Mobile Eye Examination Via Cloud-based TeleOphthalmology

A periodic visit of an ophthalmologist is crucial for monitoring the eye health regularly. Howeve... more A periodic visit of an ophthalmologist is crucial for monitoring the eye health regularly. However, the periodic visit to the ophthalmologist may become difficult to handle in the cases of the patient's visual status varies; personal location is far away from the hospital or special cases; such as COVID-19 pandemic. In this study, a novel ophthalmologist-and-patient-in-the-loop telemedicine platform is built to remotely examine the corneal surface of the eye. An internet-of-medical-things (IoMT)-based biomedical device is developed with ophthalmologist dashboard and patient interface. The developed biomedical device, Mobile XMI, is validated by testing in the ophthalmologist-and-patient-in-the-loop telemedicine system. The preliminary results showed that the cloud-based teleophthalmology architecture provides a potential tool for the early detection and diagnosis of the corneal related symptoms and diseases. Additionally, the developed medical platform facilitates the remote eye examination of the patients with disability or patients who locate far away from the ophthalmologist or hospital.

Experimental Investigation on the EBM-Based Additively Manufactured Prismatic Nickel–Titanium SMA Components

Russian Journal of Non-ferrous Metals, May 1, 2021

Abstract Additive manufacturing (AM) of the nickel–titanium (NiTi) shape memory alloys (SMA) have... more Abstract Additive manufacturing (AM) of the nickel–titanium (NiTi) shape memory alloys (SMA) have provided novel component solutions with a variety of design configurations in the industry. Electron beam melting (EBM) is a trending metal additive manufacturing process for industrial applications in the field of biomedical and aerospace engineering. In this study, experimental investigations were conducted to reveal the effect of processing conditions on the microstructure and hardness properties of EBM-fabricated nickel-titanium components. Furthermore, detailed microstructural characterizations were performed with a scanning electron microscope, EDS, and XRD for unveiling of the microscopic structure and phase analysis during the layer by layer solidification. The experimental results were systematically evaluated for the powder and the bulk prismatic components, respectively.

Design and Production of Aluminum Alloy Heat Sinks Using the Direct Metal Laser Sintering Manufacturing Method for Thermoelectric Modules

International Journal of 3D Printing Technologies and Digital Industry, 2021

Doğru akım ile ısı kontrolüne olanak tanıyan yarı-iletken yapıdaki termoelektrik malzemeler, term... more Doğru akım ile ısı kontrolüne olanak tanıyan yarı-iletken yapıdaki termoelektrik malzemeler, termoelektrik modül yüzeyleri arasında bir ısı farkı oluşturur. Termoelektrik modüllerde teknolojik imkânlar arttıkça değişik malzemelerin birleştirilmesiyle verimlilikleri artmaktadır. Termoelektrik modüllerde farklı yöntemlerle verimlilik artışı sağlanabilmesine rağmen üretildiği malzemelerin yapılarından kaynaklı verimliliklerini sınırlayan önemli faktörler bulunmaktadır. Farklı geometrilerde soğutucuların temel amacı termoelektrik parça yüzeyinde oluşan ısının en hızlı şekilde ve malzemeye zarar vermeyecek şekilde soğutulmasını sağlamaktır. Soğutucu geometrisinde yapılacak değişikliklerle her bir yüzeyin ısı dengesini ayarlayarak, ısının eşit dağılımıyla sistemden hızlı ve güvenilir bir şekilde aktarılması sağlanmalıdır. Doğrudan (direkt) Metal Lazer Sinterleme (DMLS) eklemeli imalat yöntemi üç boyutlu model verilerinden belirlenen farklı geometrilerde komponentler üretmek için katmanlar...

Characterization of energy dissipative cushions made of Ni–Ti shape memory alloy

Smart Materials and Structures, 2021

Earthquake-resistant design of structures requires dissipating seismic energy by deformations of ... more Earthquake-resistant design of structures requires dissipating seismic energy by deformations of structural members or additional fuse elements. Owing to its easy-to-produce, plug-and-play, high equivalent damping ratio, and large displacement capacity characteristics, energy dissipative steel cushions (SCs) were found to be an efficient candidate for this purpose. However, similar to other conventional metallic dampers, residual displacement after a strong shaking is the most notable drawback of the SCs. In this work, cushions produced from Ni–Ti shape memory alloy (SMA) are evaluated numerically by experimentally verified finite element models to assess their impact on the performance of earthquake-resistant structures. Furthermore, a reinforced concrete testing frame is retrofitted with energy dissipative steel and Ni–Ti cushions. Performance of the frames (e.g. dissipated energy by the cushions, hysteretic energy to input energy ratio, maximum drift, and residual drift) with dif...

Shape memory alloy tube actuators inherently enable internal fluidic cooling for a robotic finger under force control

Smart Materials and Structures, Sep 22, 2020

This paper presents the design, control and evaluation of a novel robotic finger actuated by shap... more This paper presents the design, control and evaluation of a novel robotic finger actuated by shape memory alloy (SMA) tubes which intrinsically afford an internal conduit for fluidic cooling. The SMA tubes are thermomechanically programmed to flex the robotic finger when Joule heated. A superelastic SMA plate provides a spring return motion to extend the finger when cooling liquid is pumped through the internal channel of the SMA tube actuators. The mechanical design and nonlinear force controller are presented for this unique robotic finger. Sinusoidal and step response experiments demonstrate excellent error minimization when operated below the bandwidth which was empirically determined to be 6 rad s−1. Disturbance rejection experiments are also performed to demonstrate the potential to minimize externally applied forces. This method of internal liquid cooling of Joule heated SMA tubes simultaneously increases the system bandwidth and expands the potential uses of SMA actuators for robotic applications. The results show that this novel robotic finger is capable of precise force control and has a high strength to weight ratio. The finger can apply a force of 4.35 N and has a mass of 30 g. Implementing this design into wearable prosthetic devices could enable lightweight, high strength applications previously not achievable.

Manufacturing and Characterizaton of Waam-Based Bimetallic Cutting Tool

International journal of 3d printing technologies and digital industry, Dec 31, 2022

Wire-arc additive manufacturing (WAAM) is a promising method to produce many functional component... more Wire-arc additive manufacturing (WAAM) is a promising method to produce many functional components in different industries. In this method, the welding wires from the feedstock are melted by arc discharge and deposited layer by layer. Other welding wires having different chemical compositions can also be added to the top of the previously deposited layer by replacing the feed wire from the stock to produce bimetallic components. This study investigated the feasibility of using robotic wire arc additive manufacturing technology to produce a bimetallic cutting equipment. The bimetallic cutting equipment was produced by depositing MSG 6 GZ-60 hard-facing welding wire on top of the austenitic stainless-steel wall produced with ER 316LSi solid wire. The cutting-based equipment requires an increased abrasion resistance with the combination of ductility to provide adequate equipment life and performance. Thus, detailed microstructural analysis and hardness tests were conducted to understand the general microstructural characteristic of the manufactured cutting equipment, including interfaces between two different materials.

Experimental Investigation of Wire Arc Additively Manufactured Inconel 625 Superalloy

Transactions of the Indian Institute of Metals, Jan 7, 2023

Characterization of a low-alloy steel component produced with wire arc additive manufacturing process using metal-cored wire

MP MATERIALPRUEFUNG - MP MATERIALS TESTING, Jun 1, 2022

In this study, a low-alloy steel component was manufactured using specially produced E70C-6M clas... more In this study, a low-alloy steel component was manufactured using specially produced E70C-6M class of metal-cored welding wire according to AWS A5.18 standard for the WAAM process. The manufactured low-alloy steel component was first subjected to radiographic examination to detect any weld defect. Uniaxial tensile tests were conducted for the bottom, middle and upper regions. The micro-hardness tests were performed parallel to the deposition direction. The results show that microstructures varied from base metal to the face region of the WAAM component, including the bottom, middle and top sections. The bottom region showed lamellar structures; the middle and upper region presented equiaxed ferrite structure with a small amount of grain boundary pearlites and the face region displayed a mix of equiaxed and lamellar structures of ferrites. The yield and ultimate tensile strengths of the top, middle, and bottom regions exhibited similar results varying between 370 MPa and 490 MPa, respectively. In contrast, the top region showed an elongation value about 15% higher than other regions. Moreover, the yield and ultimate tensile strength for WAAM-produced component were found to be 14% and 24% lower than the multiple-pass all-weld metal of E70C-6M class of metal-cored wire.