Origami-inspired structures and material systems have been used in many engineering applications because of their unique kinematic and mechanical properties induced by folding. However, accurately modeling and analyzing origami folding and the associated mechanical properties are challenging, especially when large deformation and dynamic responses need to be considered. In this paper, we formulate a high-fidelity model — based on the iso-parametric Absolute Nodal Coordinate Formulation (ANCF) — for simulating the dynamic folding behaviors of origami involving large deformation. The center piece of this new model is the characterization of crease deformation. To this end, we model the crease using rotational spring at the nodes. The corresponding folding angle is calculated based on the local surface normal vectors. Compared to the currently popular analytical methods for analyzing origami, such as the rigid-facet and equivalent bar-hinge approach, this new model is more accurate in that it can describe the large crease and facet deformation without imposing many assumptions. Meanwhile, the ANCF based origami model can be more efficient computationally compared to the traditional finite element simulations. Therefore, this new model can lay down the foundation for high-fidelity origami analysis and design that involve mechanics and dynamics.
{"title":"A High-Fidelity Dynamic Model for Origami Based on Iso-Parametric Absolute Nodal Coordinate Formulation (Iso-ANCF)","authors":"Jiayu Tao, Suyi Li","doi":"10.1115/smasis2019-5534","DOIUrl":"https://doi.org/10.1115/smasis2019-5534","url":null,"abstract":"\u0000 Origami-inspired structures and material systems have been used in many engineering applications because of their unique kinematic and mechanical properties induced by folding. However, accurately modeling and analyzing origami folding and the associated mechanical properties are challenging, especially when large deformation and dynamic responses need to be considered. In this paper, we formulate a high-fidelity model — based on the iso-parametric Absolute Nodal Coordinate Formulation (ANCF) — for simulating the dynamic folding behaviors of origami involving large deformation. The center piece of this new model is the characterization of crease deformation. To this end, we model the crease using rotational spring at the nodes. The corresponding folding angle is calculated based on the local surface normal vectors. Compared to the currently popular analytical methods for analyzing origami, such as the rigid-facet and equivalent bar-hinge approach, this new model is more accurate in that it can describe the large crease and facet deformation without imposing many assumptions. Meanwhile, the ANCF based origami model can be more efficient computationally compared to the traditional finite element simulations. Therefore, this new model can lay down the foundation for high-fidelity origami analysis and design that involve mechanics and dynamics.","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":"129462899","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 discusses open-loop and closed-loop active control investigations of a full-scale Bo 105 helicopter rotor with active camber morphing. The potential of an active camber morphing concept to reduce non-rotating vibratory hub loads and rotor power using active control was investigated. The mechanism employed was a dynamically actuated airfoil camber morphing concept known as Fish Bone Active Camber (FishBAC) that smoothly deforms the camber over the aft section of the airfoil. A comprehensive rotorcraft aeromechanics analysis was used that modeled the blade elastic motion using one-dimensional finite beam elements combined with multibody dynamics. Aerodynamic forces were calculated with a free-vortex wake model together with lifting line theory for the blade aerodynamics. The open-loop investigation comprised of a parametric study of relevant control parameters that govern the active camber deflection cyclic actuation profile and their effects on rotor performance and hub vibration. It was found that active camber morphing using superimposed once-per-revolution (1P) and 2P control inputs was able to simultaneously reduce rotor power by 4.3% and overall vibratory hub loads by 27%. Additionally, a closed-loop adaptive multicyclic controller was used to identify the potential of this morphing concept for hub vibration reduction using multicyclic active control inputs. Active camber actuation using a sum of four control harmonic inputs, i.e. 1-4P, resulted in a maximum hub vibration reduction of 50%.
{"title":"Integrated Rotor Performance Improvement and Vibration Reduction Using Active Camber Morphing","authors":"Sumeet Kumar, Dominik Komp, M. Hajek, J. Rauleder","doi":"10.1115/smasis2019-5588","DOIUrl":"https://doi.org/10.1115/smasis2019-5588","url":null,"abstract":"\u0000 This paper discusses open-loop and closed-loop active control investigations of a full-scale Bo 105 helicopter rotor with active camber morphing. The potential of an active camber morphing concept to reduce non-rotating vibratory hub loads and rotor power using active control was investigated. The mechanism employed was a dynamically actuated airfoil camber morphing concept known as Fish Bone Active Camber (FishBAC) that smoothly deforms the camber over the aft section of the airfoil. A comprehensive rotorcraft aeromechanics analysis was used that modeled the blade elastic motion using one-dimensional finite beam elements combined with multibody dynamics. Aerodynamic forces were calculated with a free-vortex wake model together with lifting line theory for the blade aerodynamics. The open-loop investigation comprised of a parametric study of relevant control parameters that govern the active camber deflection cyclic actuation profile and their effects on rotor performance and hub vibration. It was found that active camber morphing using superimposed once-per-revolution (1P) and 2P control inputs was able to simultaneously reduce rotor power by 4.3% and overall vibratory hub loads by 27%. Additionally, a closed-loop adaptive multicyclic controller was used to identify the potential of this morphing concept for hub vibration reduction using multicyclic active control inputs. Active camber actuation using a sum of four control harmonic inputs, i.e. 1-4P, resulted in a maximum hub vibration reduction of 50%.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127280495","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}
In this paper, we demonstrate the application of the ionic redox transistor as a reversible shutdown membrane separator (RSMS) in a custom designed Li-ion battery (LIB). The oxidized state corresponds to the OFF state and reduced state corresponds to the ON state of the RSMS in the LIB. It is demonstrated that RSMS reversibly enables and disables the LIB from charging/discharging as it is switched between its reduced (ON) and oxidized (OFF) state, respectively. The operation of the LIB with RSMS is compared with a standard LIB fabricated from identical cathodes and anodes at various C-rates. The specific capacity of the standard LIB is 144, 132, and 50 mAh/g at C/12, C/4, and C/2 rates, respectively. The specific capacity of the LIB with RSMS in the reduced state is 134, 108, and 48 mAh/g at C/12, C/4, and C/2 rates, respectively, showing similar capacity to the standard LIB at all C-rates. The specific capacity of the LIB with RSMS in the oxidized state is 125, 11, and 5 mAh/g at C/12, C/4, and C/2 rates, respectively, demonstrating a capacity decrease compared to the reduced state at all C-rates.
{"title":"Controlled Operation of Lithium Ion Batteries Using Reversible Shutdown Membrane Separators","authors":"Travis M Hery, V. Sundaresan","doi":"10.1115/smasis2019-5650","DOIUrl":"https://doi.org/10.1115/smasis2019-5650","url":null,"abstract":"\u0000 In this paper, we demonstrate the application of the ionic redox transistor as a reversible shutdown membrane separator (RSMS) in a custom designed Li-ion battery (LIB). The oxidized state corresponds to the OFF state and reduced state corresponds to the ON state of the RSMS in the LIB. It is demonstrated that RSMS reversibly enables and disables the LIB from charging/discharging as it is switched between its reduced (ON) and oxidized (OFF) state, respectively. The operation of the LIB with RSMS is compared with a standard LIB fabricated from identical cathodes and anodes at various C-rates.\u0000 The specific capacity of the standard LIB is 144, 132, and 50 mAh/g at C/12, C/4, and C/2 rates, respectively. The specific capacity of the LIB with RSMS in the reduced state is 134, 108, and 48 mAh/g at C/12, C/4, and C/2 rates, respectively, showing similar capacity to the standard LIB at all C-rates. The specific capacity of the LIB with RSMS in the oxidized state is 125, 11, and 5 mAh/g at C/12, C/4, and C/2 rates, respectively, demonstrating a capacity decrease compared to the reduced state at all C-rates.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129351754","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 increasing electrification places great demands on the supply and storage of electrical energy. Beside batteries, supercapacitors are a second storage technology with clear advantages compared to batteries in terms of charging time, energy density and cycle stability. This publication deals with the structurally compliant integration of pouch supercapacitor cells which are developed for integration into fiber-reinforced composites. The energy storage components are designed to transmit mechanical stresses. The aim is to qualify a space structure with integrated supercapacitors for use under space conditions. For a special peak power application, 14 supercapacitors are integrated into the lay-up of a glass fiber-reinforced structure. This structure connects electronic components and is therefore designed load-bearingly. Thermal cycling under high vacuum between −22°C and +67°C shows temperature effects, as result of the temperature dependence of the ion mobility. During the other mechanical tests (sinus vibration, random vibration, pyroshock) and irradiation with a Co60 source the electrical performance keeps at the same level. The structure featuring 14 integrated supercapacitors exhibits a specific capacitance of 1.12 F/g compared to a specific capacitance of 0.35 F/g of a structure using 16 commercial supercapacitors (FastCap EE350). These results demonstrate the great weight- and volume-saving potential of this approach.
{"title":"Structure Integrated Supercapacitors for Space Applications","authors":"S. Geier, Jan Petersen, P. Wierach","doi":"10.1115/smasis2019-5687","DOIUrl":"https://doi.org/10.1115/smasis2019-5687","url":null,"abstract":"\u0000 The increasing electrification places great demands on the supply and storage of electrical energy. Beside batteries, supercapacitors are a second storage technology with clear advantages compared to batteries in terms of charging time, energy density and cycle stability.\u0000 This publication deals with the structurally compliant integration of pouch supercapacitor cells which are developed for integration into fiber-reinforced composites. The energy storage components are designed to transmit mechanical stresses. The aim is to qualify a space structure with integrated supercapacitors for use under space conditions. For a special peak power application, 14 supercapacitors are integrated into the lay-up of a glass fiber-reinforced structure. This structure connects electronic components and is therefore designed load-bearingly.\u0000 Thermal cycling under high vacuum between −22°C and +67°C shows temperature effects, as result of the temperature dependence of the ion mobility. During the other mechanical tests (sinus vibration, random vibration, pyroshock) and irradiation with a Co60 source the electrical performance keeps at the same level.\u0000 The structure featuring 14 integrated supercapacitors exhibits a specific capacitance of 1.12 F/g compared to a specific capacitance of 0.35 F/g of a structure using 16 commercial supercapacitors (FastCap EE350). These results demonstrate the great weight- and volume-saving potential of this approach.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129299563","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}
Carbon nanotubes (CNTs) show an active behavior when they are positioned within an electric field, immersed into an electrolyte and charged. Several explanations are given, ranging from nanoscopic to macroscopic effects. This paper presents experimental proven explanations of the paper actuation and results using continuous CNTs of a CNT-array. For the first test series specimens are cut off a paper manufactured of single-walled, μ-long CNTs working in series. The second test series uses specimens which are prepared of free standing multi-walled CNTs. Their CNT lengths reach macroscopic dimensions of almost 3 mm and they can be considered as connected in parallel. Both series are electromechanically tested. The paper tests reveal their strong condition-dependent microstructure. Generally, the observed effects can be explained by diffusion of ions into the flexible CNT microstructure. In contrast, the CNT-array based specimens show almost no condition dependency which can be explained by the strong carbon bonds. Due to specimen orientation and test set-up, macroscopic effects can be excluded. The found actuation can be attributed to an elongation of the carbon structure as result of ion-interaction. However, it must be assumed that there are further superimposing effects which might not be distinguished from each other down to the last detail.
{"title":"Experimental Studies of the Actuation of Carbon Nanotube-Based Materials","authors":"S. Geier, T. Mahrholz, P. Wierach, M. Sinapius","doi":"10.1115/smasis2019-5685","DOIUrl":"https://doi.org/10.1115/smasis2019-5685","url":null,"abstract":"\u0000 Carbon nanotubes (CNTs) show an active behavior when they are positioned within an electric field, immersed into an electrolyte and charged. Several explanations are given, ranging from nanoscopic to macroscopic effects. This paper presents experimental proven explanations of the paper actuation and results using continuous CNTs of a CNT-array.\u0000 For the first test series specimens are cut off a paper manufactured of single-walled, μ-long CNTs working in series. The second test series uses specimens which are prepared of free standing multi-walled CNTs. Their CNT lengths reach macroscopic dimensions of almost 3 mm and they can be considered as connected in parallel. Both series are electromechanically tested.\u0000 The paper tests reveal their strong condition-dependent microstructure. Generally, the observed effects can be explained by diffusion of ions into the flexible CNT microstructure.\u0000 In contrast, the CNT-array based specimens show almost no condition dependency which can be explained by the strong carbon bonds. Due to specimen orientation and test set-up, macroscopic effects can be excluded. The found actuation can be attributed to an elongation of the carbon structure as result of ion-interaction. However, it must be assumed that there are further superimposing effects which might not be distinguished from each other down to the last detail.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127712478","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}
Morphing wings and the adaptive systems they form have been developed significantly over recent decades. Increased efficiency and control performance can be achieved with their implementation, while advances in material technology, system integration and control, have allowed concepts to present a realistic alternative to fixed-wing and aft-tail aircraft. Set out in this paper is the preliminary design and development for a novel span-wise morphing concept which employs and heavily implements biomimetic design. Specifically, the skeletal structure of the bird wing by mimicking the humerus, ulna/radius, and carpometacarpus of birds of prey as they exhibit the most versatile wing shape enabling multiple manoeuvre and flight types. The concept comprises three sections corresponding to the skeletal structure, each consisting of a leading edge D-spar and an internal structural member onto which trailing edge plates are mounted. Pneumatic artificial muscle (PAM) actuators are presented as a drive for a biologically derived ‘drawing-parallels’ mechanism, through which a 75% semi-span length change and variable sweep angle, can be obtained. Analysis of initial CFD results is discussed in comparison with similar concepts in the field and a proposal for small scale wind tunnel verification put forward. While a rapid prototype is printed to confirm the viability of the concept.
{"title":"Initial Analysis of a Novel Biomimetic Span-Wise Morphing Wing Concept","authors":"Benjamin J. Stacey, Peter Thomas","doi":"10.1115/smasis2019-5567","DOIUrl":"https://doi.org/10.1115/smasis2019-5567","url":null,"abstract":"\u0000 Morphing wings and the adaptive systems they form have been developed significantly over recent decades. Increased efficiency and control performance can be achieved with their implementation, while advances in material technology, system integration and control, have allowed concepts to present a realistic alternative to fixed-wing and aft-tail aircraft. Set out in this paper is the preliminary design and development for a novel span-wise morphing concept which employs and heavily implements biomimetic design. Specifically, the skeletal structure of the bird wing by mimicking the humerus, ulna/radius, and carpometacarpus of birds of prey as they exhibit the most versatile wing shape enabling multiple manoeuvre and flight types. The concept comprises three sections corresponding to the skeletal structure, each consisting of a leading edge D-spar and an internal structural member onto which trailing edge plates are mounted. Pneumatic artificial muscle (PAM) actuators are presented as a drive for a biologically derived ‘drawing-parallels’ mechanism, through which a 75% semi-span length change and variable sweep angle, can be obtained. Analysis of initial CFD results is discussed in comparison with similar concepts in the field and a proposal for small scale wind tunnel verification put forward. While a rapid prototype is printed to confirm the viability of the concept.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116624148","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 paper introduces the design and testing of a tank-like modular wall-climbing robot (WCR). Firstly, a bioinspired dry adhesive patterned with papilla-like array is fabricated, and its quasi-static adhesive properties is tested and evaluated. Based on the material’s properties, a single tank-like module using timing adhesive belts is optimally designed for maximum adhesive force. An under-actuated four-bar compliant linkage is utilized to connect the two modules of the WCR. The lengths of the linkage are optimized in keeping both of the modules having constant preloading forces on surfaces with different inclinations. Experimental results show that the compliant link functions like the digital joint of the gecko that is able to maintain enough preloading force for each module on the surfaces of variable inclinations, making the robot adapted to surface transitioning easily.
{"title":"Design and Testing of a Wall-Climbing Robot With Under-Actuated Force Adjusting Mechanism","authors":"Xuan Wu, Hong Liu, XiaojieĀ Wang","doi":"10.1115/smasis2019-5553","DOIUrl":"https://doi.org/10.1115/smasis2019-5553","url":null,"abstract":"\u0000 The paper introduces the design and testing of a tank-like modular wall-climbing robot (WCR). Firstly, a bioinspired dry adhesive patterned with papilla-like array is fabricated, and its quasi-static adhesive properties is tested and evaluated. Based on the material’s properties, a single tank-like module using timing adhesive belts is optimally designed for maximum adhesive force. An under-actuated four-bar compliant linkage is utilized to connect the two modules of the WCR. The lengths of the linkage are optimized in keeping both of the modules having constant preloading forces on surfaces with different inclinations. Experimental results show that the compliant link functions like the digital joint of the gecko that is able to maintain enough preloading force for each module on the surfaces of variable inclinations, making the robot adapted to surface transitioning easily.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132184551","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 layering approach for the manufacturing of pneumatic soft actuators as a coalesced solution to the diverse array of existing fabrication methods. While most research groups have developed their own (often tedious) fabrication strategies for soft actuators, these methods are usually based on available equipment and project-specific design requirements, making them impractical for use in other laboratories. In contrast, the layered substrate approach enables repeatable production of highly-capable pneumatic actuators that can be easily customized to suit a variety of applications. Here we propose layering fiber-reinforced silicone on both sides of a thin pneumatic chamber to directionally constrain expansion. Similar in concept to the Venus flytrap, pressurization of the chamber causes the module to deform and expand where unrestrained. Strategic orientation and patterning of the fiber reinforcement layers results in multiple unique shear and bending capabilities upon pressurization. Combinations of multiple reinforced pneumatic units in series or parallel could match the capabilities of most soft pneumatic actuators, while requiring only simple, universal fabrication methods that may be replicated by other research groups.
{"title":"Versatile Layering Approach to Pneumatic Soft Actuator Manufacturing","authors":"Emily A. Allen, J. Swensen","doi":"10.1115/smasis2019-5561","DOIUrl":"https://doi.org/10.1115/smasis2019-5561","url":null,"abstract":"\u0000 This paper presents a layering approach for the manufacturing of pneumatic soft actuators as a coalesced solution to the diverse array of existing fabrication methods. While most research groups have developed their own (often tedious) fabrication strategies for soft actuators, these methods are usually based on available equipment and project-specific design requirements, making them impractical for use in other laboratories. In contrast, the layered substrate approach enables repeatable production of highly-capable pneumatic actuators that can be easily customized to suit a variety of applications. Here we propose layering fiber-reinforced silicone on both sides of a thin pneumatic chamber to directionally constrain expansion. Similar in concept to the Venus flytrap, pressurization of the chamber causes the module to deform and expand where unrestrained. Strategic orientation and patterning of the fiber reinforcement layers results in multiple unique shear and bending capabilities upon pressurization. Combinations of multiple reinforced pneumatic units in series or parallel could match the capabilities of most soft pneumatic actuators, while requiring only simple, universal fabrication methods that may be replicated by other research groups.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130124931","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}
M. Haider, A. Yazdi, Maysam Rezaee, Li-Chih Tsai, N. Salowitz
Recent research has revealed that Nickel Titanium (NiTi) shape memory alloys can produce residual stresses after undergoing constrained recovery and returning to their low temperature, martensitic state while still constrained. The nature and underlying mechanisms that cause this post constrained recovery residual stress (PCRRS) are not well understood. This paper presents experimental research and results seeking to further understand the PCRRS. Experiments were performed on multiple formulations of NiTi subjected to: 1) Cyclic loading and training before producing PCRRS, 2) Repeated thermomechanical loading with large strains followed by a thermal cycle to create and re-generated the PCRRS, and 3) Creation of the PCRRS followed by repeated cycles of small, 0.5% strains. Experiments found that the training in 1) did not significantly alter the ability to produce PCRRS or its magnitude. Straining samples from the PCRRS state could reduce the residual stress state to zero stress, but the PCRRS could be recreated by repeating thermal actuation with the only significant variation being a reduction in magnitude for the first to second cycle. Multiple small strain cycles applied from the PCRRS state caused an incremental reduction in residual stress. The full PCRRS could be re-created by repeating the initial thermomechanical cycle. The values of the residual stress varied across the first 3 sets of cycles, but from the third set onward the response stabilized. These results indicate that the primary mechanisms for generating a PCRRS are stable and recoverable with only minor and diminishing variations due to training or repeated regeneration of the PCRRS. Grain boundary stabilization and similar mechanisms may be responsible for the minor variation between the first few regenerations of the PCRRS. The incremental reduction in the residual stress after exposure to small 0.5% strains must be due to a recoverable process like partial and accumulating detwinning of the NiTi with each load cycle. Further work is underway to perform microstructural analysis of samples in the various states to further the theorized material states. The ability to generate and control PCRRS has the potential to find new application and advance capabilities in fields like self-healing and fatigue resistant materials by generating stresses without the continuous application of heat energy. New forms of actuation could also be developed based on the potential energy stored in a structure through PCRRS.
{"title":"Mechanics of Post Constrained Recovery Residual Stress Produced by NiTi","authors":"M. Haider, A. Yazdi, Maysam Rezaee, Li-Chih Tsai, N. Salowitz","doi":"10.1115/smasis2019-5619","DOIUrl":"https://doi.org/10.1115/smasis2019-5619","url":null,"abstract":"\u0000 Recent research has revealed that Nickel Titanium (NiTi) shape memory alloys can produce residual stresses after undergoing constrained recovery and returning to their low temperature, martensitic state while still constrained. The nature and underlying mechanisms that cause this post constrained recovery residual stress (PCRRS) are not well understood. This paper presents experimental research and results seeking to further understand the PCRRS. Experiments were performed on multiple formulations of NiTi subjected to: 1) Cyclic loading and training before producing PCRRS, 2) Repeated thermomechanical loading with large strains followed by a thermal cycle to create and re-generated the PCRRS, and 3) Creation of the PCRRS followed by repeated cycles of small, 0.5% strains.\u0000 Experiments found that the training in 1) did not significantly alter the ability to produce PCRRS or its magnitude. Straining samples from the PCRRS state could reduce the residual stress state to zero stress, but the PCRRS could be recreated by repeating thermal actuation with the only significant variation being a reduction in magnitude for the first to second cycle. Multiple small strain cycles applied from the PCRRS state caused an incremental reduction in residual stress. The full PCRRS could be re-created by repeating the initial thermomechanical cycle. The values of the residual stress varied across the first 3 sets of cycles, but from the third set onward the response stabilized.\u0000 These results indicate that the primary mechanisms for generating a PCRRS are stable and recoverable with only minor and diminishing variations due to training or repeated regeneration of the PCRRS. Grain boundary stabilization and similar mechanisms may be responsible for the minor variation between the first few regenerations of the PCRRS. The incremental reduction in the residual stress after exposure to small 0.5% strains must be due to a recoverable process like partial and accumulating detwinning of the NiTi with each load cycle.\u0000 Further work is underway to perform microstructural analysis of samples in the various states to further the theorized material states.\u0000 The ability to generate and control PCRRS has the potential to find new application and advance capabilities in fields like self-healing and fatigue resistant materials by generating stresses without the continuous application of heat energy. New forms of actuation could also be developed based on the potential energy stored in a structure through PCRRS.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130008817","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}
Morphing wings offer potential efficiency and performance benefits for aircraft fulfilling multiple mission requirements. However, the design of shape adaptable wings is limited by the inherent design trade-offs of weight, aerodynamic control authority, and load-carrying capacity. A potential solution to this trilemma is proposed by exploiting the stiffness adaptability of thin, curved structures which geometric instability results in two statically stable states. We design and manufacture a morphing wing section demonstrator composed of two compliant 3D printed ribs monolithically embedded with the proposed bi-stable elements. The demonstrator’s structural response is numerically modelled and compared with experimental results from a static loading test. A deflection field of the response under mechanical actuation is obtained through digital image correlation. Numerical and experimental results indicate the capability of the wing section to achieve four distinct stable configurations with varying global stiffness behavior.
{"title":"Design and Manufacturing of a Multi-Stable Selectively Stiff Morphing Section Demonstrator","authors":"D. M. Boston, José R Rivas-Padilla, A. F. Arrieta","doi":"10.1115/smasis2019-5706","DOIUrl":"https://doi.org/10.1115/smasis2019-5706","url":null,"abstract":"\u0000 Morphing wings offer potential efficiency and performance benefits for aircraft fulfilling multiple mission requirements. However, the design of shape adaptable wings is limited by the inherent design trade-offs of weight, aerodynamic control authority, and load-carrying capacity. A potential solution to this trilemma is proposed by exploiting the stiffness adaptability of thin, curved structures which geometric instability results in two statically stable states. We design and manufacture a morphing wing section demonstrator composed of two compliant 3D printed ribs monolithically embedded with the proposed bi-stable elements. The demonstrator’s structural response is numerically modelled and compared with experimental results from a static loading test. A deflection field of the response under mechanical actuation is obtained through digital image correlation. Numerical and experimental results indicate the capability of the wing section to achieve four distinct stable configurations with varying global stiffness behavior.","PeriodicalId":235262,"journal":{"name":"ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132538986","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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