Pub Date : 2024-09-18DOI: 10.1088/1361-665x/ad78cd
Abdullah Solayman, Baosong Li, Rashid Abu Al-Rub and Kin Liao
The behavior of two-dimensional (2D) materials constructed as three-dimensional structures is studied to bring such materials one step closer to the real-life application. Lattices structures of gyroid triply periodic minimal surface (TPMS) were fabricated out of 2D materials, namely, molybdenum disulfide (MoS2), and reduced graphene oxide (rGO), forming for the first time free-standing MoS2 (FSM) lattice and free-standing hetero-structural lattice of MoS2 and rGO (FSH) out of TPMS. These 2D materials were also integrated with polydimethylsiloxane (PDMS) elastomer, forming FSM/PDMS and FSH/PDMS composites. Mechanical characterization, including compression and cyclic tests, were conducted on FSM, FSH, and the composites. Additionally, electromechanical characterization was conducted to evaluate the sensing potential of these structures. It is worth noting that the elastic modulus of the 10 unit-cells with either FSM or FSH was higher than the other lattices of the same type. FSH tends to have a higher modulus at 1504.4 kPa in the 10 unit-cells. This modulus is even higher at 3 MPa when PDMS is added to the FSH lattice. Due to the brittle fracture, FSM or FSH lattices follow the layer-by-layer failure mechanism. Samples with PDMS are more stable towards such cyclic tests without noticeable failures or a decrease in elastic modulus. Finally, the 10 unit-cell lattices of FSH/PDMS composite have the highest conductivity at 2.5 mA, and a comparable sensitivity at 0.365 kPa−1 over the range of 0–100 kPa.
{"title":"Three-dimensional free-standing heterostructures out of MoS2 and rGO with infused PDMS towards electromechanical pressure sensing","authors":"Abdullah Solayman, Baosong Li, Rashid Abu Al-Rub and Kin Liao","doi":"10.1088/1361-665x/ad78cd","DOIUrl":"https://doi.org/10.1088/1361-665x/ad78cd","url":null,"abstract":"The behavior of two-dimensional (2D) materials constructed as three-dimensional structures is studied to bring such materials one step closer to the real-life application. Lattices structures of gyroid triply periodic minimal surface (TPMS) were fabricated out of 2D materials, namely, molybdenum disulfide (MoS2), and reduced graphene oxide (rGO), forming for the first time free-standing MoS2 (FSM) lattice and free-standing hetero-structural lattice of MoS2 and rGO (FSH) out of TPMS. These 2D materials were also integrated with polydimethylsiloxane (PDMS) elastomer, forming FSM/PDMS and FSH/PDMS composites. Mechanical characterization, including compression and cyclic tests, were conducted on FSM, FSH, and the composites. Additionally, electromechanical characterization was conducted to evaluate the sensing potential of these structures. It is worth noting that the elastic modulus of the 10 unit-cells with either FSM or FSH was higher than the other lattices of the same type. FSH tends to have a higher modulus at 1504.4 kPa in the 10 unit-cells. This modulus is even higher at 3 MPa when PDMS is added to the FSH lattice. Due to the brittle fracture, FSM or FSH lattices follow the layer-by-layer failure mechanism. Samples with PDMS are more stable towards such cyclic tests without noticeable failures or a decrease in elastic modulus. Finally, the 10 unit-cell lattices of FSH/PDMS composite have the highest conductivity at 2.5 mA, and a comparable sensitivity at 0.365 kPa−1 over the range of 0–100 kPa.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1088/1361-665x/ad7659
Shizhe Feng, Yicheng Guo, Weihua Li, Haiping Du, Grzegorz Krolczyk and Z Li
An effective approach is proposed to evaluate the service life reliability of a multi-physics coupling structure of an insulated gate bipolar transistor (IGBT) module. The node-based smoothed finite element method with stabilization terms is firstly employed to construct an electrical-thermal-mechanical (ETM) coupling structure of the IGBT module, based on which the multi-physics responses can be accurately calculated to predict the service life of the IGBT module. By using the high-quality sample data obtained through the ETM coupling model, a Monte Carlo based active learning Kriging metamodel (AK-MCS) is developed to assess the service life reliability of the IGBT module, which can greatly reduce the computational cost needed by the surrogate model construction and reliability analysis. Numerical results show that the proposed ETM coupling structure can produce high-quality sample data of the IGBT dynamics and the AK-MCS machine learning technique can accurately estimate the service life reliability of the IGBT module.
{"title":"An IGBT coupling structure with a smart service life reliability predictor using active learning","authors":"Shizhe Feng, Yicheng Guo, Weihua Li, Haiping Du, Grzegorz Krolczyk and Z Li","doi":"10.1088/1361-665x/ad7659","DOIUrl":"https://doi.org/10.1088/1361-665x/ad7659","url":null,"abstract":"An effective approach is proposed to evaluate the service life reliability of a multi-physics coupling structure of an insulated gate bipolar transistor (IGBT) module. The node-based smoothed finite element method with stabilization terms is firstly employed to construct an electrical-thermal-mechanical (ETM) coupling structure of the IGBT module, based on which the multi-physics responses can be accurately calculated to predict the service life of the IGBT module. By using the high-quality sample data obtained through the ETM coupling model, a Monte Carlo based active learning Kriging metamodel (AK-MCS) is developed to assess the service life reliability of the IGBT module, which can greatly reduce the computational cost needed by the surrogate model construction and reliability analysis. Numerical results show that the proposed ETM coupling structure can produce high-quality sample data of the IGBT dynamics and the AK-MCS machine learning technique can accurately estimate the service life reliability of the IGBT module.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1088/1361-665x/ad79cf
Tao Liu, Chaoyang Zhao, Yaowen Yang and Weifeng Yuan
Designing wideband energy harvesters using beam structures typically involves complexities, particularly in low-frequency and low-energy environments where the limitations of beam structures become more evident. To address these challenges, this study proposed a strategy for energy harvesting using a loaded-string system and established a theoretical model to investigate its performance. A parametric study was conducted for the string system, examining the effects of initial tension, mass location, material stiffness and excitation amplitude. The accuracy of the proposed model was verified through experimental validation. Both theoretical and experimental analyses observed a frequency shifting phenomenon, demonstrating the wideband characteristics of the system. Furthermore, the proposed string structure allows for convenient parameter adjustments, enabling the tuning of its natural frequency and operating bandwidth to meet more stringent practical requirements. The string system provides a new direction for designing energy harvesters to harness low-frequency energy from the ambient environment.
{"title":"Nonlinear vibration of a loaded string in energy harvesting","authors":"Tao Liu, Chaoyang Zhao, Yaowen Yang and Weifeng Yuan","doi":"10.1088/1361-665x/ad79cf","DOIUrl":"https://doi.org/10.1088/1361-665x/ad79cf","url":null,"abstract":"Designing wideband energy harvesters using beam structures typically involves complexities, particularly in low-frequency and low-energy environments where the limitations of beam structures become more evident. To address these challenges, this study proposed a strategy for energy harvesting using a loaded-string system and established a theoretical model to investigate its performance. A parametric study was conducted for the string system, examining the effects of initial tension, mass location, material stiffness and excitation amplitude. The accuracy of the proposed model was verified through experimental validation. Both theoretical and experimental analyses observed a frequency shifting phenomenon, demonstrating the wideband characteristics of the system. Furthermore, the proposed string structure allows for convenient parameter adjustments, enabling the tuning of its natural frequency and operating bandwidth to meet more stringent practical requirements. The string system provides a new direction for designing energy harvesters to harness low-frequency energy from the ambient environment.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-17DOI: 10.1088/1361-665x/ad78ce
Haisu Liao, Tsunho Wu, Gang Gao, Xinyu Wu and Fei Gao
Scavenging energy from the human body to provide a sustainable source for electronic devices has gained significant attention. Recently, scientists have focused on harnessing biomechanical energy from human motion. This study was dedicated to developing and optimizing a non-uniform piezoelectric bending beam-based human knee energy harvester. The bimorph non-uniform piezoelectric bending beam consisted of a non-uniform carbon fiber substrate and piezoelectric macro fiber composites. Compared to the uniform piezoelectric bending beam, the non-uniform piezoelectric beam can optimize the shape to improve the average strain, thus improving the energy harvesting efficiency. In this study, eight shape functions, including ellipse, sin, tanh, exponential function, parabola, trigonometric line, and bell curves, were investigated and optimized. The bell curve bending beam was selected and fabricated due to its good performance. Then, a benchmark platform was developed to test the deflection curve and reaction force when the nonuniform bending beam was compressed. Finally, to validate the design, experimental testing on three subjects was conducted when they were equipped with the harvester and walked on a treadmill. Testing results indicated that the non-uniform bending beam-based energy harvester can improve the energy harvesting efficiency by 28.57% compared to the uniform beam-based energy harvester. The output power can reach 18.94 mW when walking at 7.0 km h−1.
从人体中收集能量，为电子设备提供可持续的能量来源，已经引起了人们的极大关注。最近，科学家们开始关注从人体运动中利用生物机械能。本研究致力于开发和优化基于非均匀压电弯曲梁的人体膝关节能量收集器。双态非均匀压电弯曲梁由非均匀碳纤维基板和压电宏纤维复合材料组成。与均匀压电弯曲梁相比，非均匀压电梁可以通过优化形状来提高平均应变，从而提高能量收集效率。本研究对椭圆、sin、tanh、指数函数、抛物线、三角线和钟形曲线等八种形状函数进行了研究和优化。由于钟形曲线弯曲梁性能良好，因此选择并制作了钟形曲线弯曲梁。然后，开发了一个基准平台来测试非均匀弯曲梁受压时的挠度曲线和反作用力。最后，为了验证设计的有效性，我们对三名受试者进行了实验测试，测试时他们都配备了收割机并在跑步机上行走。测试结果表明，与基于均匀梁的能量收集器相比，基于非均匀弯曲梁的能量收集器可将能量收集效率提高 28.57%。当以 7.0 km h-1 的速度行走时，输出功率可达 18.94 mW。
{"title":"Shape optimization of a non-uniform piezoelectric bending beam for human knee energy harvester","authors":"Haisu Liao, Tsunho Wu, Gang Gao, Xinyu Wu and Fei Gao","doi":"10.1088/1361-665x/ad78ce","DOIUrl":"https://doi.org/10.1088/1361-665x/ad78ce","url":null,"abstract":"Scavenging energy from the human body to provide a sustainable source for electronic devices has gained significant attention. Recently, scientists have focused on harnessing biomechanical energy from human motion. This study was dedicated to developing and optimizing a non-uniform piezoelectric bending beam-based human knee energy harvester. The bimorph non-uniform piezoelectric bending beam consisted of a non-uniform carbon fiber substrate and piezoelectric macro fiber composites. Compared to the uniform piezoelectric bending beam, the non-uniform piezoelectric beam can optimize the shape to improve the average strain, thus improving the energy harvesting efficiency. In this study, eight shape functions, including ellipse, sin, tanh, exponential function, parabola, trigonometric line, and bell curves, were investigated and optimized. The bell curve bending beam was selected and fabricated due to its good performance. Then, a benchmark platform was developed to test the deflection curve and reaction force when the nonuniform bending beam was compressed. Finally, to validate the design, experimental testing on three subjects was conducted when they were equipped with the harvester and walked on a treadmill. Testing results indicated that the non-uniform bending beam-based energy harvester can improve the energy harvesting efficiency by 28.57% compared to the uniform beam-based energy harvester. The output power can reach 18.94 mW when walking at 7.0 km h−1.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-17DOI: 10.1088/1361-665x/ad78cf
Lucas M Martinho, Luca De Marchi and Alan C Kubrusly
Electromagnetic acoustic transducers (EMATs) are convenient for non-destructive evaluation of plate-like structures since they can generate, without the need for contact with the medium under test, different types of ultrasonic guided waves. Guided-wave EMATs usually generate waves omnidirectionally or in a principal propagation direction. Beam steering is desirable in several applications, such as in inspections of large-area structures. This is usually achieved with several independently controlled elements forming a phased array. Alternatively, mono-element transducers with directional-dependent spectral content can steer the generated wave beam by altering the frequency of the excitation signal. A piezoelectric transducer with this characteristic, namely a frequency steerable acoustic transducer, was previously proposed. Its design was addressed in the wavenumber domain, leading to unconventional transducer shapes, but still reproducible with a piezoelectric patch, albeit unfeasible to implement as an EMAT. Here, we propose a new kind of EMAT, namely, frequency steerable EMAT (FSEMAT), whose design is addressed in the spatial domain in order to ensure its physical realization with a coil-magnet arrangement whilst still effectively presenting steering capability. The novel EMAT was designed to generate the A0 Lamb wave mode in a frequency range from approximately 100 to 600 kHz. The FSEMAT was fabricated and experimentally evaluated in an aluminium plate at different frequencies within the designed frequency range, where each frequency corresponded to a specific propagating direction with high directivity, assessed by half-power beam widths of approximately 10 degrees. Furthermore, its theoretical directivity was computed by means of a wavenumber spectrum-based model, and showed good agreement with experimental results. The new transducer allows great flexibility effectively providing beam steering with a single EMAT.
{"title":"A frequency steerable electromagnetic acoustic transducer","authors":"Lucas M Martinho, Luca De Marchi and Alan C Kubrusly","doi":"10.1088/1361-665x/ad78cf","DOIUrl":"https://doi.org/10.1088/1361-665x/ad78cf","url":null,"abstract":"Electromagnetic acoustic transducers (EMATs) are convenient for non-destructive evaluation of plate-like structures since they can generate, without the need for contact with the medium under test, different types of ultrasonic guided waves. Guided-wave EMATs usually generate waves omnidirectionally or in a principal propagation direction. Beam steering is desirable in several applications, such as in inspections of large-area structures. This is usually achieved with several independently controlled elements forming a phased array. Alternatively, mono-element transducers with directional-dependent spectral content can steer the generated wave beam by altering the frequency of the excitation signal. A piezoelectric transducer with this characteristic, namely a frequency steerable acoustic transducer, was previously proposed. Its design was addressed in the wavenumber domain, leading to unconventional transducer shapes, but still reproducible with a piezoelectric patch, albeit unfeasible to implement as an EMAT. Here, we propose a new kind of EMAT, namely, frequency steerable EMAT (FSEMAT), whose design is addressed in the spatial domain in order to ensure its physical realization with a coil-magnet arrangement whilst still effectively presenting steering capability. The novel EMAT was designed to generate the A0 Lamb wave mode in a frequency range from approximately 100 to 600 kHz. The FSEMAT was fabricated and experimentally evaluated in an aluminium plate at different frequencies within the designed frequency range, where each frequency corresponded to a specific propagating direction with high directivity, assessed by half-power beam widths of approximately 10 degrees. Furthermore, its theoretical directivity was computed by means of a wavenumber spectrum-based model, and showed good agreement with experimental results. The new transducer allows great flexibility effectively providing beam steering with a single EMAT.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-17DOI: 10.1088/1361-665x/ad77ff
R S Kattimani, P V Malaji, S S Chappar and S Adhikari
Achieving higher power output across a broader frequency spectrum presents a significant challenge for vibration energy harvesters aimed at powering low-powered devices from ambient sources. This study introduces the novel concept of employing inertial amplifiers to couple mistuned pendulum electromagnetic harvesters for enhanced energy harvesting performance. A mathematical model elucidating the inertial amplifier mechanism is developed, and analytical results are compared against conventional uncoupled harvesters. Experimental studies demonstrated up to 1.8 times higher power output and a 2-fold increase in operational frequency bandwidth compared to uncoupled harvesters when employing inertial amplifier coupling. The proposed inertially coupled harvester design offers a powerful solution to significantly improve energy transduction levels and extend the viable frequency range, enabling efficient scavenging of ambient vibrations for powering wireless sensors and low-power electronics.
{"title":"Enhanced vibration energy harvesting from coupled pendulums through inertial amplifiers","authors":"R S Kattimani, P V Malaji, S S Chappar and S Adhikari","doi":"10.1088/1361-665x/ad77ff","DOIUrl":"https://doi.org/10.1088/1361-665x/ad77ff","url":null,"abstract":"Achieving higher power output across a broader frequency spectrum presents a significant challenge for vibration energy harvesters aimed at powering low-powered devices from ambient sources. This study introduces the novel concept of employing inertial amplifiers to couple mistuned pendulum electromagnetic harvesters for enhanced energy harvesting performance. A mathematical model elucidating the inertial amplifier mechanism is developed, and analytical results are compared against conventional uncoupled harvesters. Experimental studies demonstrated up to 1.8 times higher power output and a 2-fold increase in operational frequency bandwidth compared to uncoupled harvesters when employing inertial amplifier coupling. The proposed inertially coupled harvester design offers a powerful solution to significantly improve energy transduction levels and extend the viable frequency range, enabling efficient scavenging of ambient vibrations for powering wireless sensors and low-power electronics.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-15DOI: 10.1088/1361-665x/ad7801
Liulan Lin, Jiajie Yan and Shaolong Qiu
Achieving shape programming of 4D printed actuators by varying the manufacturing process parameters. In this study, the effect of different path combinations on structural deformation was investigated. By altering the driving layer, passive layer, and grid angle, the spiral deformation direction of the double-layer structure was precisely controlled. Additionally, a finite element analysis model was established to predict the deformation behavior of PLA-based spiral structures. Furthermore, the influence of printing speed, nozzle temperature, line width, layer height, and plate temperature on the spiral curvature of the structure was examined. The results show that increasing printing speed and plate temperature can improve the spiral behavior of the structure, whereas increasing line width, layer height, and nozzle temperature have opposite effects. A multiple linear regression analysis was conducted on the five printing parameters to predict their influence on the spiral curvature of the structure, and a predictive model for the spiral deformation was developed. The structure was partitioned for design purposes, aiming to achieve diverse deformations of the actuator under the same geometric configuration. A loop-shaped actuator was designed to capture objects. The results showed that the path combination determined the spiral direction of the actuator, while the forming parameters effectively controlled the spiral curvature of the actuator.
{"title":"Programming the deformation of the temperature driven spiral structure in 4D printing","authors":"Liulan Lin, Jiajie Yan and Shaolong Qiu","doi":"10.1088/1361-665x/ad7801","DOIUrl":"https://doi.org/10.1088/1361-665x/ad7801","url":null,"abstract":"Achieving shape programming of 4D printed actuators by varying the manufacturing process parameters. In this study, the effect of different path combinations on structural deformation was investigated. By altering the driving layer, passive layer, and grid angle, the spiral deformation direction of the double-layer structure was precisely controlled. Additionally, a finite element analysis model was established to predict the deformation behavior of PLA-based spiral structures. Furthermore, the influence of printing speed, nozzle temperature, line width, layer height, and plate temperature on the spiral curvature of the structure was examined. The results show that increasing printing speed and plate temperature can improve the spiral behavior of the structure, whereas increasing line width, layer height, and nozzle temperature have opposite effects. A multiple linear regression analysis was conducted on the five printing parameters to predict their influence on the spiral curvature of the structure, and a predictive model for the spiral deformation was developed. The structure was partitioned for design purposes, aiming to achieve diverse deformations of the actuator under the same geometric configuration. A loop-shaped actuator was designed to capture objects. The results showed that the path combination determined the spiral direction of the actuator, while the forming parameters effectively controlled the spiral curvature of the actuator.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-15DOI: 10.1088/1361-665x/ad765a
Manoj Prabhakar and Senthil Murugan
Morphing, adaptable or smart structures are being used in mechanical and aerospace applications in recent years. These structures often have the property of time-varying stiffness or inertial properties, which can cause parametric instability issues that are not well understood. This paper examines the dynamic stability and response of a morphing aircraft wing with periodically time-varying structural stiffness. The wing is modeled as a beam with coupled bending-torsion motion, and parametrically excited stiffness. Aerodynamic loads introduce aerodynamic damping and aerodynamic stiffness to the wing structure. The dynamic and aeroelastic equation of motion resembles a coupled, damped Mathieu-type equation but differs with asymmetric damping and stiffness matrices, and symmetric inertial matrix. Further, these equations are functions of airspeed, magnitude and frequency of parametric excitation. Initially, dynamic stability of the wing is analyzed using Floquet theory, and the instability regions are numerically quantified by stability charts. Subsequently, dynamic responses in the stable and unstable regions are investigated with a Floquet-based Harmonic balance method. The findings reveal that, at zero airspeed, the combination instabilities are eliminated by varying the bending and torsional stiffness with equal magnitudes and frequency. However, as airspeed increases, instability regions shift unevenly, leading to the emergence of new instabilities. Furthermore, the response analysis within stable regions uncovers several unfavorable zones for operating the variable stiffness, where response decay is slower. The results clearly show that parametric excitation can cause unusual phenomena that significantly impact the operation of morphing wings with variable stiffness, which needs to be thoroughly investigated for successful implementation.
{"title":"Dynamic stability and response of morphing wing structure with time-varying stiffness","authors":"Manoj Prabhakar and Senthil Murugan","doi":"10.1088/1361-665x/ad765a","DOIUrl":"https://doi.org/10.1088/1361-665x/ad765a","url":null,"abstract":"Morphing, adaptable or smart structures are being used in mechanical and aerospace applications in recent years. These structures often have the property of time-varying stiffness or inertial properties, which can cause parametric instability issues that are not well understood. This paper examines the dynamic stability and response of a morphing aircraft wing with periodically time-varying structural stiffness. The wing is modeled as a beam with coupled bending-torsion motion, and parametrically excited stiffness. Aerodynamic loads introduce aerodynamic damping and aerodynamic stiffness to the wing structure. The dynamic and aeroelastic equation of motion resembles a coupled, damped Mathieu-type equation but differs with asymmetric damping and stiffness matrices, and symmetric inertial matrix. Further, these equations are functions of airspeed, magnitude and frequency of parametric excitation. Initially, dynamic stability of the wing is analyzed using Floquet theory, and the instability regions are numerically quantified by stability charts. Subsequently, dynamic responses in the stable and unstable regions are investigated with a Floquet-based Harmonic balance method. The findings reveal that, at zero airspeed, the combination instabilities are eliminated by varying the bending and torsional stiffness with equal magnitudes and frequency. However, as airspeed increases, instability regions shift unevenly, leading to the emergence of new instabilities. Furthermore, the response analysis within stable regions uncovers several unfavorable zones for operating the variable stiffness, where response decay is slower. The results clearly show that parametric excitation can cause unusual phenomena that significantly impact the operation of morphing wings with variable stiffness, which needs to be thoroughly investigated for successful implementation.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-15DOI: 10.1088/1361-665x/ad7800
Stefano Pandini, Chiara Pasini, Davide Battini, Andrea Avanzini, Antonio Fiorentino, Ileana Bodini and Simone Pasinetti
4D textiles are a specific class of 4D printed materials obtained by printing flat patterns on elastically pre-tensioned textiles and being able to switch from planar systems to complex 3D objects after the textile pre-stretch is released. The mechanical balance between textile recovering strain and printed structure stiffness determines the final shape. This study is carried out by coupling pre-stretched Lycra to PLA and explores ways to control 4D textile shape transformations by varying pre-stretch (10% ÷ 60%), printed structure geometry (bar-shaped and star-shaped elements; star-shaped patterns), printed element thickness (0.3 ÷ 3 mm) and mutual distance (2 ÷ 15 mm). By adjusting these parameters, a wide set of out-of-plane curvatures are obtained, ranging from flat, to dome-like and highly curved, wrapped or coiled shapes. Digital optical methods, including digital image analysis, 3D scanning, and digital image correlation, are used to evaluate the complexity of the final shape and strain state evolution during shape transformation. The geometry variation is measured in terms of height increase (maximum 45 mm for a star-shaped system, 30 mm for a multiple star pattern) and of area decrease (maximum 80% for a star-shaped system, 60% for a multiple star pattern). While most shape transformations occur immediately after printing (‘direct 4D printing’), further shape evolutions may be triggered by heating above the PLA glass transition, allowing for the creation of dynamic structures whose shape changes upon external stimuli. The adhesion between the 3D printed element and the stretched textile is also examined, with a focus on determining the role of interfacial strength and the conditions that could enhance it. This study provides an overview of the primary design variables and valuable maps of their impacts on shape transformations in this broad scenario of influencing parameters.
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Pub Date : 2024-09-11DOI: 10.1088/1361-665x/ad754f
Lukesh Parida and Sumedha Moharana
The integration of 3D printed constructions into civil projects has created new opportunities for economically efficient construction. However, preserving the long-term structural integrity of 3D-printed structures poses considerable challenges. This study covers the importance of structural health monitoring (SHM) and deployment of sensors for condition monitoring of 3D-printed civil infrastructure. It explores a wide range of sensors that might be used for continual evaluation and assessment of structural efficiency and the challenges related to SHM in these components. The report provides cost benefit analysis and case studies describing effective sensor installations in 3D-printed structures, demonstrating the ability of the technology to enhance the safety and integrity of infrastructure systems. It also identifies potential challenges and issues that must be resolved before sensor-based SHM can be successfully used in 3D-printed civil structures. The research emphasizes the potential of maintenance planning and decision support systems for optimizing maintenance schedules, reducing downtime, and increasing cost-effectiveness. This research is critical for academics, engineers, and professionals using sensors for 3D-printed structural systems.
将三维打印建筑融入民用项目为经济高效的建筑工程创造了新机遇。然而，如何保持 3D 打印结构的长期结构完整性是一个相当大的挑战。本研究涵盖了结构健康监测（SHM）和部署传感器对 3D 打印民用基础设施进行状态监测的重要性。报告探讨了可用于持续评估和评价结构效率的各种传感器，以及与这些组件的结构健康监测相关的挑战。报告提供了成本效益分析和案例研究，介绍了在三维打印结构中有效安装传感器的情况，展示了该技术提高基础设施系统安全性和完整性的能力。报告还指出了在三维打印民用结构中成功使用基于传感器的 SHM 之前必须解决的潜在挑战和问题。研究强调了维护规划和决策支持系统在优化维护计划、减少停机时间和提高成本效益方面的潜力。这项研究对于将传感器用于三维打印结构系统的学者、工程师和专业人员来说至关重要。
{"title":"Structural health monitoring for 3D-printed civil infrastructures: a review of challenges, applications and future directions","authors":"Lukesh Parida and Sumedha Moharana","doi":"10.1088/1361-665x/ad754f","DOIUrl":"https://doi.org/10.1088/1361-665x/ad754f","url":null,"abstract":"The integration of 3D printed constructions into civil projects has created new opportunities for economically efficient construction. However, preserving the long-term structural integrity of 3D-printed structures poses considerable challenges. This study covers the importance of structural health monitoring (SHM) and deployment of sensors for condition monitoring of 3D-printed civil infrastructure. It explores a wide range of sensors that might be used for continual evaluation and assessment of structural efficiency and the challenges related to SHM in these components. The report provides cost benefit analysis and case studies describing effective sensor installations in 3D-printed structures, demonstrating the ability of the technology to enhance the safety and integrity of infrastructure systems. It also identifies potential challenges and issues that must be resolved before sensor-based SHM can be successfully used in 3D-printed civil structures. The research emphasizes the potential of maintenance planning and decision support systems for optimizing maintenance schedules, reducing downtime, and increasing cost-effectiveness. This research is critical for academics, engineers, and professionals using sensors for 3D-printed structural systems.","PeriodicalId":21656,"journal":{"name":"Smart Materials and Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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