Christopher J. Netwall, James P. Thomas, M. Kubista, Kerry A. Griffith, Christopher Kindle, Jordan Schlater, Joseph T. Hays, Phillip A. Feerst, N. Wereley
The U.S. Naval Research Laboratory (NRL) has been developing a space-rated 7 degree of freedom (DOF) robot arm with a high payload-to-mass ratio as an alternative design to motor-gear driven robotic manipulators. The robot arm employs antagonistic pairs of pneumatic artificial muscle (PAM) actuators to control each degree-of-freedom (DOF) to achieve large force outputs relative to the PAM component masses. A novel feature of the NRL PAM actuator was the integration of the pneumatic control components inside the pressure-bladder, which not only reduces the volume of the robotic arm hardware but also reduces the pressurized-gas actuation volume in the PAM enabling significant reductions in gas consumption during actuation. This multifunctional design enables reductions in launch-weight costs and increases in operational endurance for space applications. The integration of these PAMs into a well-designed robotic-arm structure, in tandem with a newly developed control algorithm, has the potential to exceed the performance metrics of traditional motor-driven robot arms. This paper describes the development of the improved efficiency PAM design that is advancing this technology towards space flight readiness.
{"title":"Pneumatic Artificial Muscle Actuators With Integrated Controls for Space Flight Applications","authors":"Christopher J. Netwall, James P. Thomas, M. Kubista, Kerry A. Griffith, Christopher Kindle, Jordan Schlater, Joseph T. Hays, Phillip A. Feerst, N. Wereley","doi":"10.1115/smasis2019-5630","DOIUrl":"https://doi.org/10.1115/smasis2019-5630","url":null,"abstract":"\u0000 The U.S. Naval Research Laboratory (NRL) has been developing a space-rated 7 degree of freedom (DOF) robot arm with a high payload-to-mass ratio as an alternative design to motor-gear driven robotic manipulators. The robot arm employs antagonistic pairs of pneumatic artificial muscle (PAM) actuators to control each degree-of-freedom (DOF) to achieve large force outputs relative to the PAM component masses. A novel feature of the NRL PAM actuator was the integration of the pneumatic control components inside the pressure-bladder, which not only reduces the volume of the robotic arm hardware but also reduces the pressurized-gas actuation volume in the PAM enabling significant reductions in gas consumption during actuation. This multifunctional design enables reductions in launch-weight costs and increases in operational endurance for space applications. The integration of these PAMs into a well-designed robotic-arm structure, in tandem with a newly developed control algorithm, has the potential to exceed the performance metrics of traditional motor-driven robot arms. This paper describes the development of the improved efficiency PAM design that is advancing this technology towards space flight readiness.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134492056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shape memory alloys (SMAs) are a class of metallic alloys that possess remarkable characteristics such as superelasticity and shape memory effect. Superelastic SMAs have been considered as fiber in polymer composites due to their ability to recover their deformation upon removal of load, good energy dissipation capacity and impact resistance. Graphene nanoplatelets (GNPs) consists of small stacks of graphene sheets that are two-dimensional. Both sides of atomic lattice of GNPs contact matrix of a composite system and can generate more sites for potential chemical and physical bonding with the host material. Most importantly, graphene sheets and their derivatives can be produced at large-scale for industrial demand at low-cost. This study explores the fabrication of multi-scale reinforced epoxy matrix composites in which GNPs and SMA strands are employed as nano- and micro-scale reinforcements, respectively. First, GNPs are dispersed into a ductile and brittle epoxy matrix to produce GNP/epoxy nanocomposites. To study the effect of GNP content on the behavior of the developed nanocomposite, GNPs are added to the epoxy-hardener mixture at different weight percentages (neat, 0.1%, 0.25%, 0.5%, 1%, and 2%). Uniaxial tensile tests of the developed nanocomposites are conducted under monotonic load up to failure. The optimum GNP content for GNP-reinforced epoxy matrix is determined and used in the fabrication of SMA fiber/epoxy composite. The developed multiscale reinforced epoxy composites are tested under tensile loading and their full-field strain and temperature behavior are monitored and evaluated using a digital image correlation system and an infrared thermal camera.
{"title":"Full-Field Deformation and Thermal Characterization of GNP/Epoxy and GNP/SMA Fiber/Epoxy Composites","authors":"Ugur Kilic, M. Sherif, S. Daghash, O. Ozbulut","doi":"10.1115/smasis2019-5640","DOIUrl":"https://doi.org/10.1115/smasis2019-5640","url":null,"abstract":"\u0000 Shape memory alloys (SMAs) are a class of metallic alloys that possess remarkable characteristics such as superelasticity and shape memory effect. Superelastic SMAs have been considered as fiber in polymer composites due to their ability to recover their deformation upon removal of load, good energy dissipation capacity and impact resistance. Graphene nanoplatelets (GNPs) consists of small stacks of graphene sheets that are two-dimensional. Both sides of atomic lattice of GNPs contact matrix of a composite system and can generate more sites for potential chemical and physical bonding with the host material. Most importantly, graphene sheets and their derivatives can be produced at large-scale for industrial demand at low-cost.\u0000 This study explores the fabrication of multi-scale reinforced epoxy matrix composites in which GNPs and SMA strands are employed as nano- and micro-scale reinforcements, respectively. First, GNPs are dispersed into a ductile and brittle epoxy matrix to produce GNP/epoxy nanocomposites. To study the effect of GNP content on the behavior of the developed nanocomposite, GNPs are added to the epoxy-hardener mixture at different weight percentages (neat, 0.1%, 0.25%, 0.5%, 1%, and 2%). Uniaxial tensile tests of the developed nanocomposites are conducted under monotonic load up to failure. The optimum GNP content for GNP-reinforced epoxy matrix is determined and used in the fabrication of SMA fiber/epoxy composite. The developed multiscale reinforced epoxy composites are tested under tensile loading and their full-field strain and temperature behavior are monitored and evaluated using a digital image correlation system and an infrared thermal camera.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122630706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mechanoluminescent-particulate filled composites have been gaining significant interest for light generation, stress visualization, health monitoring, damage sensing and pressure mapping applications. Previous works on stress-dependence of light emission have modeled emission intensity as a function of macroscopic composite stress. While this approach may suffice from an application point of view, the resulting model may not represent the mechanoluminescence phenomenon accurately. This is because in particulate filled elastomer composites, particulate stresses can be significantly different from matrix and macroscopic stresses, especially in composites with moderate and low filler volume fraction. Experimental difficulty in measuring stresses within micron-sized particles necessitate micromechanical models that can connect macroscale measurements to microscale parameters through material properties. Apart from the material properties of the matrix and the particles, the bonding between the two dissimilar materials at their interface influences the stress transfer significantly. Cohesive zone modeling (CZM) approach defines the interface between particles and matrix as a piecewise linear stiffness element with possible degradation of stiffness beyond a certain strain. CZM provides a convenient way to not only predict particulate stress from macroscopic stress, but also to track interface damage and debonding. In this paper, we demonstrate an experimental technique to obtain cohesive zone parameters for mechanoluminescent-particulate filled elastomer composites, utilizing optical microscopy and Digital Image Correlation (DIC). CZM thus obtained can help predict particulate stresses and aid better modeling of the mechanoluminescence phenomenon. The experimental technique can also be easily adopted for other particulate-filled composites.
{"title":"Experimental Technique to Estimate Interfacial Properties of Mechanoluminescent Particles in an Elastomer Matrix","authors":"S. Krishnan, N. Katsube, V. Sundaresan","doi":"10.1115/smasis2019-5691","DOIUrl":"https://doi.org/10.1115/smasis2019-5691","url":null,"abstract":"\u0000 Mechanoluminescent-particulate filled composites have been gaining significant interest for light generation, stress visualization, health monitoring, damage sensing and pressure mapping applications. Previous works on stress-dependence of light emission have modeled emission intensity as a function of macroscopic composite stress. While this approach may suffice from an application point of view, the resulting model may not represent the mechanoluminescence phenomenon accurately. This is because in particulate filled elastomer composites, particulate stresses can be significantly different from matrix and macroscopic stresses, especially in composites with moderate and low filler volume fraction. Experimental difficulty in measuring stresses within micron-sized particles necessitate micromechanical models that can connect macroscale measurements to microscale parameters through material properties. Apart from the material properties of the matrix and the particles, the bonding between the two dissimilar materials at their interface influences the stress transfer significantly. Cohesive zone modeling (CZM) approach defines the interface between particles and matrix as a piecewise linear stiffness element with possible degradation of stiffness beyond a certain strain. CZM provides a convenient way to not only predict particulate stress from macroscopic stress, but also to track interface damage and debonding. In this paper, we demonstrate an experimental technique to obtain cohesive zone parameters for mechanoluminescent-particulate filled elastomer composites, utilizing optical microscopy and Digital Image Correlation (DIC). CZM thus obtained can help predict particulate stresses and aid better modeling of the mechanoluminescence phenomenon. The experimental technique can also be easily adopted for other particulate-filled composites.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124800360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a three-row opposed gripping mechanism with radial configuration for wall-climbing robots inspired by the structure of the gripper of LEMUR IIB. The mechanism builds upon a kind of microspines for climbing robots. This work utilizes an opposed spoke configuration with 3 rows of 31 microspines on each linkage array, splayed around a central bracket. A single motor drives the 3 linkage arrays by a set of gears to achieve attachment and detachment procedures, and the trajectory of each linkage array tip makes the miniature spines easy to penetrate in and pull off the surfaces. The mechanism designed as a foot of climbing robots can vertically resist at least 1kg of load on rough surface. The findings provide a foundation for constructing a system for a rough-wall-climbing robot.
{"title":"A Three-Row Opposed Gripping Mechanism With Radial Configuration for Wall-Climbing Robots","authors":"Chao Xie, Xuan Wu, XiaojieĀ Wang","doi":"10.1115/smasis2019-5549","DOIUrl":"https://doi.org/10.1115/smasis2019-5549","url":null,"abstract":"\u0000 This paper presents a three-row opposed gripping mechanism with radial configuration for wall-climbing robots inspired by the structure of the gripper of LEMUR IIB. The mechanism builds upon a kind of microspines for climbing robots. This work utilizes an opposed spoke configuration with 3 rows of 31 microspines on each linkage array, splayed around a central bracket. A single motor drives the 3 linkage arrays by a set of gears to achieve attachment and detachment procedures, and the trajectory of each linkage array tip makes the miniature spines easy to penetrate in and pull off the surfaces. The mechanism designed as a foot of climbing robots can vertically resist at least 1kg of load on rough surface. The findings provide a foundation for constructing a system for a rough-wall-climbing robot.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132178306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dennis Otibar, Benedict Theren, Antonia Weirich, B. Kuhlenkötter, H. Tung
The properties of shape memory alloy wires (SMA wires) have still not been sufficiently investigated, which is the reason why shape memory-based actuators can hardly be found in serial or commercial applications in industry. The most important parameter for industrial applications is the fatigue strength of SMA wires under cyclic activation with mechanical stress. So far only isolated and application-specific investigations have been carried out. Thus there are no reliable statements on fatigue strength or reliable design calculations for design and application. Among other things, this circumstance is considered to be the reason why the majority of companies is still not ready or willing to use SMA technology in series production. This paper deals with a series of tests to determine the fatigue life of shape memory wires of different diameters by means of the design of experiments. Primarily the results aim at making more reliable predictions about the fatigue strength of shape memory wires, which are subject to statistical safety. Besides, the focus is on the influence of the wire diameter on the fatigue strength. The interdependency parameters are strain, stress and wire diameter. The fatigue strengths are shown in standardized Wohler diagrams, which should serve as a basis for future fatigue tests of shape memory wires. The main influence on the fatigue strength is the strain as expected. Another interesting tendency can be seen in the dependence on the wire diameter. Thus, this paper makes a contribution to the further application of this technology in both industrial and scientific environments.
{"title":"Investigation of the Fatigue Strength of Shape Memory Wires With Different Diameters","authors":"Dennis Otibar, Benedict Theren, Antonia Weirich, B. Kuhlenkötter, H. Tung","doi":"10.1115/smasis2019-5512","DOIUrl":"https://doi.org/10.1115/smasis2019-5512","url":null,"abstract":"\u0000 The properties of shape memory alloy wires (SMA wires) have still not been sufficiently investigated, which is the reason why shape memory-based actuators can hardly be found in serial or commercial applications in industry. The most important parameter for industrial applications is the fatigue strength of SMA wires under cyclic activation with mechanical stress. So far only isolated and application-specific investigations have been carried out. Thus there are no reliable statements on fatigue strength or reliable design calculations for design and application. Among other things, this circumstance is considered to be the reason why the majority of companies is still not ready or willing to use SMA technology in series production. This paper deals with a series of tests to determine the fatigue life of shape memory wires of different diameters by means of the design of experiments. Primarily the results aim at making more reliable predictions about the fatigue strength of shape memory wires, which are subject to statistical safety. Besides, the focus is on the influence of the wire diameter on the fatigue strength. The interdependency parameters are strain, stress and wire diameter. The fatigue strengths are shown in standardized Wohler diagrams, which should serve as a basis for future fatigue tests of shape memory wires. The main influence on the fatigue strength is the strain as expected. Another interesting tendency can be seen in the dependence on the wire diameter. Thus, this paper makes a contribution to the further application of this technology in both industrial and scientific environments.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130452657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Synchronized switch damping (SSD) technique utilizing piezoelectric elements is one of good methods of vibration control. This work develops numerical tools for dynamic analysis of structures with SSD dampers, and conducts experiments to verify the effectiveness. A cantilevered beam bonded with piezoelectric patches is considered as the host structure. Two types of SSD circuits are considered, one with no subsequent electric element (SSDS) and another with inductance (SSDI). Firstly, a lumped parameter electromechanical coupling model is employed, with parameters determined experimentally. Then, the frequency response curves of the nonlinear vibration systems are analyzed by the multi-harmonic balance method combined with alternating frequency-time techniques (MHBM/AFT). In order to verify the proposed method, an experimental study is performed. In the experiment SSD circuit is realized by an enhanced analog circuit which is more complex but also more stable than the original SSD circuits. The measured results are compared with those obtained by proposed numerical tools with good agreements. It is also shown that the modal frequencies and modal shapes of SSD systems are almost unchanged with the vibration amplitudes, which indicates that the nonlinear force generated by SSD has little influence on the characteristics of linear structure. It is verified both numerically and experimentally that SSDI damper can produce significant damping for multiple modes.
{"title":"Numerical Analysis and Experimental Verification of Synchronized Switching Damping Systems","authors":"Fengling Zhang, Lin Li, Yu Fan, Jiuzhou Liu","doi":"10.1115/smasis2019-5570","DOIUrl":"https://doi.org/10.1115/smasis2019-5570","url":null,"abstract":"\u0000 Synchronized switch damping (SSD) technique utilizing piezoelectric elements is one of good methods of vibration control. This work develops numerical tools for dynamic analysis of structures with SSD dampers, and conducts experiments to verify the effectiveness. A cantilevered beam bonded with piezoelectric patches is considered as the host structure. Two types of SSD circuits are considered, one with no subsequent electric element (SSDS) and another with inductance (SSDI). Firstly, a lumped parameter electromechanical coupling model is employed, with parameters determined experimentally. Then, the frequency response curves of the nonlinear vibration systems are analyzed by the multi-harmonic balance method combined with alternating frequency-time techniques (MHBM/AFT). In order to verify the proposed method, an experimental study is performed. In the experiment SSD circuit is realized by an enhanced analog circuit which is more complex but also more stable than the original SSD circuits. The measured results are compared with those obtained by proposed numerical tools with good agreements. It is also shown that the modal frequencies and modal shapes of SSD systems are almost unchanged with the vibration amplitudes, which indicates that the nonlinear force generated by SSD has little influence on the characteristics of linear structure. It is verified both numerically and experimentally that SSDI damper can produce significant damping for multiple modes.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129850480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Amanda Skalitzky, Caleb Petersen, A. Gurley, D. Beale
Nitinol in the form of wires, tubes, and plates have been explored extensively; however, the characteristics of Nitinol as a woven fabric have so far been little-studied analytically. It would be easier to design such a fabric if conventional fabric models were known to apply to Nitinol fabrics, potentially with modifications required by Nitinol’s unique properties. A 25 mm wide Nitinol narrow fabric has been manufactured using traditional weaving equipment using a proprietary process that achieves a uniform and tight weave. Heat-treatment and straight shape-set is applied to a single Nitinol wire and the woven Nitinol fabric at 600°C for 30 minutes. The 0.25 mm Nitinol wire constituent was tested using differential scanning calorimetry (DSC) to determine the transition temperatures (Mf, Ms, As, and Af), which were found on average to be 54.5°C, 66.9°C, 88.7°C, and 103.5°C respectively. Both the Nitinol wire and fabric were tested in a temperature-controlled chamber (testing temperatures ranged from room temperature to 200°C) in which the tensile stress-strain characteristics were observed. It was determined that existing analytical models can be employed to accurately estimate the overall tensile stiffness of woven Nitinol fabrics in a small-strain regime. Additionally, it was confirmed that the tensile loading of woven Nitinol fabric can be modeled in MSC.Adams with beam elements. In combination with the geometric model presented, woven Nitinol fabric behavior can be predicted from the experimental behavior of the constituent Nitinol wire.
{"title":"Woven Nitinol Fabric Strips Characterized in Tension via Finite Element Analysis and Geometric Modeling","authors":"Amanda Skalitzky, Caleb Petersen, A. Gurley, D. Beale","doi":"10.1115/smasis2019-5669","DOIUrl":"https://doi.org/10.1115/smasis2019-5669","url":null,"abstract":"\u0000 Nitinol in the form of wires, tubes, and plates have been explored extensively; however, the characteristics of Nitinol as a woven fabric have so far been little-studied analytically. It would be easier to design such a fabric if conventional fabric models were known to apply to Nitinol fabrics, potentially with modifications required by Nitinol’s unique properties. A 25 mm wide Nitinol narrow fabric has been manufactured using traditional weaving equipment using a proprietary process that achieves a uniform and tight weave. Heat-treatment and straight shape-set is applied to a single Nitinol wire and the woven Nitinol fabric at 600°C for 30 minutes. The 0.25 mm Nitinol wire constituent was tested using differential scanning calorimetry (DSC) to determine the transition temperatures (Mf, Ms, As, and Af), which were found on average to be 54.5°C, 66.9°C, 88.7°C, and 103.5°C respectively. Both the Nitinol wire and fabric were tested in a temperature-controlled chamber (testing temperatures ranged from room temperature to 200°C) in which the tensile stress-strain characteristics were observed. It was determined that existing analytical models can be employed to accurately estimate the overall tensile stiffness of woven Nitinol fabrics in a small-strain regime. Additionally, it was confirmed that the tensile loading of woven Nitinol fabric can be modeled in MSC.Adams with beam elements. In combination with the geometric model presented, woven Nitinol fabric behavior can be predicted from the experimental behavior of the constituent Nitinol wire.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123669861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The shape memory effect and the superelasticity of nickel titanium (NiTi) alloys are beneficial for design of compliant mechanisms. The superelastic behavior of NiTi can be tailored for optimal flexure design in the compliant mechanism, allowing large deformation and shape change. The shape memory effect can also be utilized to actuate the compliant mechanism flexures enabling programing of the material to take on variety of shapes at different temperatures over time. The compliant mechanism analyzed in this work is inspired from 3D multi leg spider-like locomotion, enabling movement in all directions by triggering different target shapes in time. The control of the material spatial distribution facilitated by additive manufacturing will enable tailored superelastic and shape memory behavior in the flexures of the multifunctional 3D compliant mechanism. Design optimization and analyses as well as overall shape change are explored in this work. Superelastic joints are introduced as flexures to enable segment flexibility. The temperature change is used for actuation taking in consideration different initial strain conditions.
{"title":"Target Shape Optimization of 3D Compliant Mechanism With Superelastic Joints and Shape Memory Actuation","authors":"J. Jovanova, Angela Nastevska, M. Frecker","doi":"10.1115/smasis2019-5639","DOIUrl":"https://doi.org/10.1115/smasis2019-5639","url":null,"abstract":"\u0000 The shape memory effect and the superelasticity of nickel titanium (NiTi) alloys are beneficial for design of compliant mechanisms. The superelastic behavior of NiTi can be tailored for optimal flexure design in the compliant mechanism, allowing large deformation and shape change. The shape memory effect can also be utilized to actuate the compliant mechanism flexures enabling programing of the material to take on variety of shapes at different temperatures over time.\u0000 The compliant mechanism analyzed in this work is inspired from 3D multi leg spider-like locomotion, enabling movement in all directions by triggering different target shapes in time. The control of the material spatial distribution facilitated by additive manufacturing will enable tailored superelastic and shape memory behavior in the flexures of the multifunctional 3D compliant mechanism.\u0000 Design optimization and analyses as well as overall shape change are explored in this work. Superelastic joints are introduced as flexures to enable segment flexibility. The temperature change is used for actuation taking in consideration different initial strain conditions.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126721263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
David Bombara, V. Mansurov, Revanth Konda, Steven Fowzer, Jun Zhang
The twisted string actuator (TSA), as a recently discovered artificial muscle, has attracted a lot of attention as a compliant and powerful actuation mechanism. A TSA consists of two strings attached to a motor on one end and a load on the other end. The motor’s rotation twists the strings and generates linear actuation. A common challenge is to obtain TSAs’ strains using compact approaches. Previous studies exclusively utilized external position sensors that not only increased system cost, size and complexity, but also lowered actuator compliance. In this paper, self-sensing strategies are presented to estimate TSAs’ strains without external sensors. By incorporating conductive and stretchable nylon strings, called super-coiled polymer (SCP) strings, into TSAs, their strains can be estimated from the resistance values of SCP strings. Two self-sensing configurations are realized: (1) TSA with one regular string and one SCP string, and (2) TSA with two SCP strings. Experiments are conducted to show the correlation between the length and resistance of TSA under different conditions. Polynomial and Preisach hysteresis models were successfully employed to capture the Length – Resistance correlation and to estimate TSA’s length using the resistance.
{"title":"Self-Sensing for Twisted String Actuators Using Conductive Supercoiled Polymers","authors":"David Bombara, V. Mansurov, Revanth Konda, Steven Fowzer, Jun Zhang","doi":"10.1115/smasis2019-5587","DOIUrl":"https://doi.org/10.1115/smasis2019-5587","url":null,"abstract":"\u0000 The twisted string actuator (TSA), as a recently discovered artificial muscle, has attracted a lot of attention as a compliant and powerful actuation mechanism. A TSA consists of two strings attached to a motor on one end and a load on the other end. The motor’s rotation twists the strings and generates linear actuation. A common challenge is to obtain TSAs’ strains using compact approaches. Previous studies exclusively utilized external position sensors that not only increased system cost, size and complexity, but also lowered actuator compliance. In this paper, self-sensing strategies are presented to estimate TSAs’ strains without external sensors. By incorporating conductive and stretchable nylon strings, called super-coiled polymer (SCP) strings, into TSAs, their strains can be estimated from the resistance values of SCP strings. Two self-sensing configurations are realized: (1) TSA with one regular string and one SCP string, and (2) TSA with two SCP strings. Experiments are conducted to show the correlation between the length and resistance of TSA under different conditions. Polynomial and Preisach hysteresis models were successfully employed to capture the Length – Resistance correlation and to estimate TSA’s length using the resistance.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127895593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Over the past decades, a number of structural health monitoring methods have been developed for condition assessment of concrete structures. Most of these methods require the installation of external sensors. Accelerometers are commonly used for vibration-based damage detection for the entire structure, while strain gauges are installed in order to detect cracking and damage at the component level. Conventional strain sensors, such as metal foil strain gauges, have been widely used to monitor local conditions in concrete structures. However, all of these sensors have certain shortcomings such as exhibiting limited durability and low gauge factor, and providing only pointwise strain measurements. Multifunctional cement-based composites that can determine their own strain and damage can overcome the limitations of these traditional sensors. This study explores the use of two different nanomaterials, namely graphene nanoplatelets (GNP) and carbon black (CB) for the development of self-sensing cementitious composites and the synergetic effects in their hybrid utilization. A simple fabrication method that does not require special treating procedures such as ultrasonication for dispersing nanomaterials is pursued. Twelve batches of mortar specimens reinforced with only GNP or CB at different concentrations, or with both GNP and CB fillers are prepared. A polycarboxylate-based superplasticizer is used to disperse nanomaterials and to increase the workability of the nano-reinforced mortar. Scanning electron microscope (SEM) is utilized to assess the distribution quality of nanomaterials. Standard cubic specimens are tested for compressive strength at 28 days. The bulk resistivity of the standard prismatic specimens is measured using the four-point probe method. The piezoresistive response of nano-reinforced cement composites is evaluated under the cyclic compressive loads.
{"title":"Self-Sensing Characterization of GNP and Carbon Black Filled Cementitious Composites","authors":"Zhangfan Jiang, O. Ozbulut, G. Xing","doi":"10.1115/smasis2019-5653","DOIUrl":"https://doi.org/10.1115/smasis2019-5653","url":null,"abstract":"\u0000 Over the past decades, a number of structural health monitoring methods have been developed for condition assessment of concrete structures. Most of these methods require the installation of external sensors. Accelerometers are commonly used for vibration-based damage detection for the entire structure, while strain gauges are installed in order to detect cracking and damage at the component level. Conventional strain sensors, such as metal foil strain gauges, have been widely used to monitor local conditions in concrete structures. However, all of these sensors have certain shortcomings such as exhibiting limited durability and low gauge factor, and providing only pointwise strain measurements. Multifunctional cement-based composites that can determine their own strain and damage can overcome the limitations of these traditional sensors.\u0000 This study explores the use of two different nanomaterials, namely graphene nanoplatelets (GNP) and carbon black (CB) for the development of self-sensing cementitious composites and the synergetic effects in their hybrid utilization. A simple fabrication method that does not require special treating procedures such as ultrasonication for dispersing nanomaterials is pursued. Twelve batches of mortar specimens reinforced with only GNP or CB at different concentrations, or with both GNP and CB fillers are prepared. A polycarboxylate-based superplasticizer is used to disperse nanomaterials and to increase the workability of the nano-reinforced mortar. Scanning electron microscope (SEM) is utilized to assess the distribution quality of nanomaterials. Standard cubic specimens are tested for compressive strength at 28 days. The bulk resistivity of the standard prismatic specimens is measured using the four-point probe method. The piezoresistive response of nano-reinforced cement composites is evaluated under the cyclic compressive loads.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128354664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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