scholarly journals Improving Robustness of Tuned Vibration Absorbers Using Shape Memory Alloys

2005 ◽  
Vol 12 (5) ◽  
pp. 349-361 ◽  
Author(s):  
Mohammad H. Elahinia ◽  
Jeong-Hoi Koo ◽  
Honghao Tan
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Natural Frequency ◽  
Constitutive Relations ◽  
Robustness Analysis ◽  
Variable Stiffness ◽  
Primary System ◽  
Tuned Vibration Absorbers ◽  
Spring Element ◽  
Frequency Changes

A conventional passive tuned vibration absorber (TVA) is effective when it is precisely tuned to the frequency of a vibration mode; otherwise, it may amplify the vibrations of the primary system. In many applications, the frequency often changes over time. For example, adding or subtracting external mass on the existing primary system results in changes in the system’s natural frequency. The frequency changes of the primary system can significantly degrade the performance of TVA. To cope with this problem, many alternative TVAs (such as semiactive, adaptive, and active TVAs) have been studied. As another alternative, this paper investigates the use of Shape Memory Alloys (SMAs) in passive TVAs in order to improve the robustness of the TVAs subject to mass change in the primary system. The proposed SMA-TVA employs SMA wires, which exhibit variable stiffness, as the spring element of the TVA. This allows us to tune effective stiffness of the TVA to adapt to the changes in the primary system's natural frequency. The simulation model, presented in this paper, contains the dynamics of the TVA along with the SMA wire model that includes phase transformation, heat transfer, and the constitutive relations. Additionally, a PID controller is included for regulating the applied voltage to the SMA wires in order to maintain the desired stiffness. The robustness analysis is then performed on both the SMA-TVA and the equivalent passive TVA. For our robustness analysis, the mass of the primary system is varied by ± 30% of its nominal mass. The simulation results show that the SMA-TVA is more robust than the equivalent passive TVA in reducing peak vibrations in the primary system subject to change of its mass.

Shape Memory Alloy Tuned Vibration Absorbers: Robustness Analysis

2004 ◽  
Author(s):  
Mohammad H. Elahinia ◽  
Jeong-Hoi Koo ◽  
Mehdi Ahmadian
Keyword(s):  
Shape Memory ◽  
Natural Frequency ◽  
Constitutive Relations ◽  
Robustness Analysis ◽  
Variable Stiffness ◽  
Primary System ◽  
Tuned Vibration Absorbers ◽  
Spring Element ◽  
Frequency Changes ◽  
Changes Over Time

A conventional passive tuned vibration absorber (TVA) is effective when it is precisely tuned to the frequency of a vibration mode; otherwise, it may amplify the vibrations of the primary system. In many applications, the frequency often changes over time. For example, adding or subtracting external mass on the existing primary system results in changes in the system’s natural frequency. The frequency changes of the primary system can significantly degrade the performance of TVA. To cope with this problem, many alternative TVAs (such as semiactive, adaptive, and active TVAs) have been studied. As another alternative, this paper investigates the use of Shape Memory Alloys (SMAs) in passive TVAs in order to improve the robustness of the TVAs subject to mass change in the primary system. The proposed SMA-TVA employs SMA wires, which exhibit variable stiffness, as the spring element of the TVA. This allows us to tune effective stiffness of the TVA to adapt to the changes in the primary system’s natural frequency. The stimulation model, presented in this paper, contains the dynamics of the TVA along with the SMA wire model that includes phase transformation, heat transfer, and the constitutive relations. The robustness analysis is then performed on both the SMA-TVA and the equivalent passive TVA. For our robustness analysis, the mass of the primary system is varied by 30% of its nominal mass. The simulation results show that the SMA-TVA is more robust than the equivalent passive TVA in reducing peak vibrations in the primary system subject to change of its mass.

Control of a Tuned Vibration Absorber Based on SMA Wires

2005 ◽  
Author(s):  
Eric Williams ◽  
Mohammad H. Elahinia ◽  
Jeong-Hoi Koo
Keyword(s):  
Shape Memory ◽  
Natural Frequency ◽  
Constitutive Relations ◽  
Robustness Analysis ◽  
Vibration Absorber ◽  
Primary System ◽  
Frequency Change ◽  
Simulation Results ◽  
Close Loop Control ◽  
Tuned Vibration Absorber

This paper presents the control simulation results of a tuned vibration absorber (TVA) that utilizes the properties of shape memory alloy (SMA) wires. A conventional passive TVA is effective when it is precisely tuned to the frequency of a vibration mode; otherwise, resonance may occur that could damage the system. Additionally, in many applications the frequency of the primary system often changes over time. For example, the mass of the primary system can change causing a change in its natural frequency. This frequency change of the primary system can significantly degrade the performance of the TVA. To cope with this problem, many alternative TVA’s (such as semiactive, adaptive, and active TVA’s) have been studied. As another alternative, this paper investigates the use of Shape Memory Alloys (SMA’s) in passive TVA’s in order to improve the robustness of the TVA’s subject to mass change in the primary system. This allows for effective tuning of the stiffness of the TVA to adapt to the changes in the primary system’s natural frequency. To this end, a close-loop control system adjusts the applied current to the SMA wires in order to maintain the desired stiffness. The model, presented in this paper, contains the dynamics of the TVA along with the SMA wire model that includes phase transformation, heat transfer, and the constitutive relations. The closed-loop robustness analysis is performed for the SMA-TVA and is compared with the equivalent passive TVA. For the robustness analysis, the mass of the primary system is varied by ± 30% of its nominal mass. The simulation results show that the SMA-TVA is more robust than the equivalent passive TVA in reducing peak vibrations in the primary system subject to change of its mass.

Self-Assembling Swimming Smart Boxes

2014 ◽  
Author(s):  
M. Amin Karami ◽  
Ehsan T. Esfahani ◽  
Mohsen Daghooghi ◽  
Iman Borazjani
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Natural Frequency ◽  
Slight Modification ◽  
The Body ◽  
Mode Shapes ◽  
Primary Mode ◽  
Final Destination ◽  
Self Assembling ◽  
Almost All

This paper presents vibration analysis and structural optimization of a self-assembled structure for swimming. The mode shapes of the structure resemble the body waveform of a swimming Mackerel fish. The lateral deformation waveform of the body of Mackerel is extracted from literature. At higher swimming speeds fish generate the waveform at a higher frequency. Their body waveform stays the same at almost all normal swimming speeds. At the final destination, the box self-assembles using shape memory alloys. The shape memory alloys used for configuration change of the box robot cannot be used for swimming since they fail to operate at high frequencies. MFCs are actuated at the fundamental natural frequency of the structure. This excites the primary mode of resonance. The primary mode of resonance involves rotations of the joints of the robot in the desired fashion. The MFCs are therefore used to indirectly generate the body waveform. We optimize the thickness of the panels and the stiffness of the joints to most efficiently generate the swimming waveforms. Unlike eel we change the speed of the robot by changing the amplitude of the body motions. This is because the frequency of the motion is fixed to the first natural frequency of the robot. The swimming box can swim over the surface and can also swim underwater. With slight modification the boxes can crawl or slither over the land.

Shape Memory Alloys for Classroom Demonstrations, Laboratories, and Student Projects

2004 ◽  
Vol 827 ◽  
Author(s):  
Katherine C. Chen ◽  
Wendy C. Crone ◽  
Eric J. Voss
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Phase Transformations ◽  
Smart Materials ◽  
Constitutive Relations ◽  
Web Based ◽  
Student Projects ◽  
Change Transformation ◽  
Niti Shape Memory Alloys ◽  
Different Levels

AbstractShape memory alloys (SMAs) are unique materials that effectively capture the attention of students due to their dramatic phase transformations that result from temperature or stress. The fascinating properties and intriguing applications of SMAs can entice students to learn about the materials field, as well as relatively complicated materials concepts. SMAs have been incorporated into a range of courses under a variety of topics, such as crystal structures, phase transformations, kinetics, constitutive relations, and smart materials. The concepts can be presented at different levels of knowledge, appropriate to the learning objectives for the particular audience. Several educational activities using NiTi shape memory alloys have been developed, such as web-based videos, shape setting of new designs, classroom demonstration of actuation, visualization of stress-induced transformations, and heat treatments to change transformation temperatures.

Analysis on Vibration Characteristics of Wind Turbine Blade to Improve the Effectiveness through CFD Developed by ANSYS

2018 ◽  
Vol 937 ◽  
pp. 43-50
Author(s):  
M. Rajaram Narayanan ◽  
S. Nallusamy
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Wind Turbine ◽  
Natural Frequency ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Vibration Characteristics ◽  
Wind Turbine Blade ◽  
Horizontal Axis Wind Turbine ◽  
Damping Material

In the current scenario, there is a continuous need for increasing the efficiency of the aerodynamics of wind turbine blades through research studies. Vibration in a wind turbine blade has lot to do on its performance. An effective approach is required by wind mill including to control the vibration to achieve better results. The objective of this research is to investigate the vibration characteristics of the prototype horizontal axis wind turbine blade developed by using 3D modelling software. Shape memory alloys with their variable material properties offer an alternative adaptive mechanism hence it is used as a damping material. A prototype blade with S1223 profile was manufactured and the natural frequency was found over the surface of the blade. Similarly, results were studied by increasing the number of alloys wires over the blade up to three. Results showed that the embedment of shape memory alloys over the blade’s surface increases the natural frequency and reduce the amplitude of vibration because of super elastic nature of alloys. Also it was observed that the natural frequency increased by 6% and reduced the amplitude by about 93% where three wires of 0.5mm diameter were kept for the length of 720mm.

scholarly journals Radiation Effect on Shape Memory Alloy

2018 ◽  
Author(s):  
Amine Riad ◽  
Amine Riad ◽  
Amine Riad ◽  
Mohamed Mansouri
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Natural Frequency ◽  
Mechanical Loading ◽  
Smart Materials ◽  
Mechanical Characteristics ◽  
Radiation Effect ◽  
Response To Stress

The shape memory alloys belong to the smart materials thanks to their thermomechanical proprieties' reply to thermal or to mechanical loading. These materials can change shape, stiffness, displacement, natural frequency, and many mechanical characteristics in response to stress or to heat such as conduction, convection or radiation. However, heating by convection or conduction are the most useful and studied methods unlike radiation. Therefore, this paper aims to study the radiation effect on the shape memory alloy behavior

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