International Journal of Machine Tools and Manufacture, 2000
A new analytical cutting force model is proposed for micro-end-milling operations. The model calc... more A new analytical cutting force model is proposed for micro-end-milling operations. The model calculates the chip thickness by considering the trajectory of the tool tip while the tool rotates and moves ahead continuously. The proposed approach allows the calculation of the cutting forces to be done accurately in typical micro-end-milling operations with very aggressively selected feed per tooth to tool radius (f t /r) ratio. The difference of the simulated cutting forces between the proposed and conventional models can be experienced when f t /r is larger than 0.1. The estimated cutting force profile of the proposed model had good agreement with the experimental data.
Testing, Reliability, and Application of Micro- and Nano-Material Systems, 2003
The detection and microscopic characterization of hidden corrosion has recently been a focus of s... more The detection and microscopic characterization of hidden corrosion has recently been a focus of several advanced NDE research efforts. A variety of approaches have been suggested, with laser ultrasonic (LU), scanning acoustic microscopy (SAM), thermography,and x-ray systems being four of the most promising NDE techniques. In this effort, a side-by-side comparison of each of these four techniques was conducted with
Servomotors are devices commonly utilized in motion generation and position control. Such devices... more Servomotors are devices commonly utilized in motion generation and position control. Such devices have become preferred by designers because they provide a reliable and inexpensive solution. One of the main problems associated with servomotors is that they tend to burnout if the system in overloaded. This research focuses on developing a low cost, highly reliable solution to this problem. A magnetic field sensor was employed to acquire information of the electric current flowing through a line powering a servomotor. The data was processed employing a fast Fourier transform in order to identify any possible trends that could assist identifying overload conditions. Two different states were tested and compared to judge whether they represent normal operation or overstress conditions. The characterized overstress frequency was utilized to conceptualize a design that will provide fault-tolerant alternatives for mechanical systems that employ servomotors.
Additive manufacturing (AM) applications have been steadily increasing in many industry sectors. ... more Additive manufacturing (AM) applications have been steadily increasing in many industry sectors. AM allows creating complex geometries inside of a part to leave some space empty, called infills. Lighter parts are manufactured in a shorter time with less warpage if the strength of the part meets the design requirements. While the benefits of structural health monitoring (SHM) have been proven in different structures, few studies have investigated SHM methods on AM parts. In this study, the relationship between wave propagation and infill density has been studied for the additively manufactured polymer parts. The propagation of surface waves is monitored by using piezoelectric elements. Four rectangular parts are manufactured by using the material extrusion method with 20%, 40%, 60%, and 100% rectilinear infill densities. Four piezoelectric elements were attached on the surface of each beam, one for excitation and three for monitoring the response of the part at equal distances on eac...
The use of CubeSat systems for low-orbit data collection has increased due to their low cost deve... more The use of CubeSat systems for low-orbit data collection has increased due to their low cost development and light weight designs. For efficient data collection to occur, it is imperative that the satellite’s internal components remain fully functional throughout its mission life. To ensure the components remain in their operational range, an internal thermal control subsystem must be developed to effectively combat the transfer of heat. The standard size and payload of a CubeSat eliminates the possibility of designing a conventional fluid flow piping system. Through the development of a phase change material (PCM) thermal control system, the internal components will experience smaller temperature variations, while remaining within their operational limits. The melting temperature for optimal PCM performance, with a component operational range from 0-40 , is currently desired to be 45 , and the selection between Organic and Inorganic materials can be found below. The calculations de...
SOFT ROBOTIC ACTUATORS WITH CUSTOMIZABLE INNER GEOMETRIES USING ADDITIVE MANUFACTURING Kumar Y. S... more SOFT ROBOTIC ACTUATORS WITH CUSTOMIZABLE INNER GEOMETRIES USING ADDITIVE MANUFACTURING Kumar Y. Shah*, Andrew Martinez, Gonzalo Seisdedos, Juan Salazar, and Ibrahim Tansel Mechanical and Materials Engineering Department Florida International University 10555 W. Flagler St. Miami, FL 33174 The world of Soft Robotics is a relatively new research field. Top universities are advancing this topic by incorporating external geometric changes and electrical components to further observe predicted actions [1]. Currently, one of the only industrial implementations of Soft Robotics are grippers [1][2]. These grippers are incorporated into industrial robotic arms to grab, lift, or move fragile items such as live animals, produce, or sharp items, as shown in figure 1 [2]. Using the methods of Mechanical Design and Additive Manufacturing (3-D Printing), we have created actuator designs that are highly customizable and replicable worldwide. The actuator shown in figure 2, shows the internal cavity...
2017 8th International Conference on Recent Advances in Space Technologies (RAST), 2017
Active structural health monitoring methods are becoming increasingly popular for defect detectio... more Active structural health monitoring methods are becoming increasingly popular for defect detection in hollow cylindrical structures utilized in aerospace applications. Electro mechanical impedance (EMI) based methods are commonly used to study the health of hollow cylinders in broad frequency ranges. However, the EMI analyzers are bulky and costly. In addition, EMI based methods require high quantity of sensors for monitoring a large area. The Surface Response to Excitation (SuRE) method was developed to eliminate the need for EMI analyzers in broad frequency range inspections and to decrease the number of sensors in monitoring of large structures. In this study, the performance of the SuRE method in detection of internal defects is evaluated theoretically and experimentally. Different internal damages were created in an aluminum pipe specimen. The data collected from four bonded piezoelectric elements were used for damage detection and quantification. The test results showed the hi...
A complete thermal analysis on picosatellites is of most importance because it helps in the devel... more A complete thermal analysis on picosatellites is of most importance because it helps in the development of thermal control system that can protect the satellite’s internal systems from the extreme condition of outer space. Lack of a properly designed thermal control system could potentially mean the failure of the mission. Budget constraints in the design of the NEESAT-1U picosatellite, lead the team to implement passive thermal control systems on their CubeSat. In this paper, various materials have been considered for implementation as a thermal insulator. These materials have been evaluated by numerical methods. Best performing material was then evaluated using one-dimensional heat conduction to find the appropriate thickness needed to maintain the internal components at a safe operating temperature.
The CubeSat program has facilitated space access for students for over a decade through the innov... more The CubeSat program has facilitated space access for students for over a decade through the innovative design of versatile, and inexpensive research platforms. However, what started as an initiative for academic institutions to be able to data gathering platforms that can be cheaply and rather quickly assembled and launched, has now revolutionized the way even more established agencies look at orbital and space exploration. The mission type determines the payload and capabilities a CubeSat must have. Standard size of a 1U CubeSat is 10 cm x 10 cm x 10 cm. Due to the small dimensions of the pico-satellite, new innovative subsystem designs must be used to accomplish similar mission parameters that larger platforms perform with ease. This paper presents the design and optimization of a payload originally designed for ROARSAT, a larger 3U satellite of dimensions 10 cm x 10 cm x 30 cm developed at Florida International University. This is accomplished by arranging a set of achromatic len...
Structural Health Monitoring-an International Journal, 2017
With daily increase of application composite materials in commercial and military aircrafts, long... more With daily increase of application composite materials in commercial and military aircrafts, longevity of composite bonds has become a substantial factor in aerospace industry. Although tremendous amount of research has been conducted on monitoring the integrity of composite bonds, developing new structural health monitoring (SHM) techniques for evaluating bond strength could be essential. In this study, heterodyning method is implemented for exploring bond strength and detecting delamination in composite materials. Heterodyne effect may be utilized for the evaluation of debonded area when the linear characteristics of the system changes to nonlinear. The light contact in the bonding zone can result in this conversion from linear to nonlinear behavior. The nonlinear system responds to two appropriate excitation frequencies with new frequencies. For some nonlinear systems, the output has these new frequencies at the subtraction and summation of excitation frequencies. This is called ...
Heterodyning effect has been used for many wireless communication, electronics and ultrasound app... more Heterodyning effect has been used for many wireless communication, electronics and ultrasound applications. When two different frequencies are applied to proper nonlinear systems, new frequency components develop at the predictable frequencies. In the experimental studies, the perfect plates without any defects behaved like linear systems. Only the applied frequencies existed when the surface vibrations were monitored. However, once a defect like a crack or debonding started to develop the structure behaved like a nonlinear system. New frequencies and their harmonics developed at the difference and addition of the applied frequencies. In this study, COMSOL Multiphysics software was used to simulate the heterodyning effect. The response of two aluminum plates were studied when the upper face of one plate was excited at two different frequencies and the response of the bottom face of the second plate at the opposite side was simulated. Similar to the experimental studies, the monitore...
Electromechanical impedance (EMI) method is one of the most widely used structural health monitor... more Electromechanical impedance (EMI) method is one of the most widely used structural health monitoring (SHM) methods. The low-cost alternative of the method, surface response to excitation (SuRE) method has the similar characteristics. Both methods require additional disks/sensors to estimate the location of defects or external loading. Additive manufacturing (AM) methods have been matured and started to be an alternative to the conventional manufacturing. Most of the parts made by the AM methods are hollow. The infill type and skin thickness are selected to manufacture the parts faster by using less material and to avoid warping of the part. In this paper, manufacture of the parts with two infill types and two surface skin thicknesses at their different locations are proposed to estimate the site of the applied external forces without using additional disks/sensors. SuRE method was used in the study. The experimental results indicated that the frequencies of the most changed spectrum sections were different depending on the infill types and surface skin thicknesses. The same approach could be used for the EMI applications.
International Journal of Prognostics and Health Management
Rapid screening and monitoring of hollow cylindrical structures using active guided-waves based s... more Rapid screening and monitoring of hollow cylindrical structures using active guided-waves based structural health monitoring (SHM) techniques are important in chemical, petro-chemical, oil and gas industries. Successful implementation of the majority of these techniques in the SHM of pipes depends on the identification of the appropriate guided-waves modes and their frequencies for each application. The highly dispersive nature of the guided-waves and presence of multi modes at each frequency makes the mode selection and the interpretation of signals a challenging task. The surface response to excitation (SuRE) method was developed to detect the defects and loading condition changes on plates with minimum dependence on the excitation of particular modes at certain frequencies. In the present study, the SuRE method is proposed for quantification of longitudinal and circumferential defects, with varying severities, as common examples of axisymmetric and nonaxisymmetric defects in pipe...
Additive manufacturing (AM) technology has been used for the creation of complex parts in differe... more Additive manufacturing (AM) technology has been used for the creation of complex parts in different industries. The addition of defect detection and load sensing capabilities to these products can highly increase their values. The application of structural health monitoring (SHM) methods on AM parts is proposed in this paper by implementing the internal design capabilities of the AM parts. First, the influence of the internal top surface layers on the surface wave propagation characteristics was studied. A round part with different top skin thicknesses in each quarter (10, 20, 30, and 40 layers) was designed and fabricated of polylactic acid (PLA). The height of each layer was 0.1 mm and different spectral characteristics were observed in each quarter. Then, the location of an external compression loading was estimated with the help of different skin thicknesses on a plate designed with five zones. Although estimation of the defect or loading on the structure has always been a challenge in SHM studies, the use of hidden geometries helps to effectively overcome this challenge. Surface response to excitation method was used in this study to estimate the loading location by using two piezoelectric elements. A simple algorithm was used to estimate the loading zones in all the test cases.
Abstract Electromechanical Impedance (EMI) approach is a widely used Structural Health Monitoring... more Abstract Electromechanical Impedance (EMI) approach is a widely used Structural Health Monitoring (SHM) method. The EMI of a piezoelectric disk is monitored with an impedance analyzer or impedance measurement chip. In addition to the cracks, EMI may monitor compressive forces and may be used for detection of loose bolts. Surface Response to Excitation (SuRE) method is a low-cost alternative to the EMI method. The SuRE method uses one piezoelectric disk for excitation and a sensor to monitor the surface wave propagation. Digitization and Fast Fourier Transformation (FFT) of the signal of the sensor, such as another piezoelectric disk, is satisfactory to monitor the characteristics of the system. The important weakness of both approaches is not being able to estimate the location of the defect at their minimal configuration. Recently, Additive Manufacturing (AM) has been used for the manufacturing of parts for various reasons. The layer by layer part building techniques of the AM methods allow for the hiding of geometric features behind the part’s exposed skin. Use of the hidden features of the additively manufactured parts is proposed in the paper to help the SuRE method for estimation of the location of defects. Experimental studies verified the validity of the proposed approach. In addition, the EMI methods may benefit from this same approach.
Abstract Array systems of transducers have found numerous applications in detection and localizat... more Abstract Array systems of transducers have found numerous applications in detection and localization of defects in structural health monitoring (SHM) of plate-like structures. Different types of array configurations and analysis algorithms have been used to improve the process of localization of defects. For accurate and reliable monitoring of large structures by array systems, a high number of actuator and sensor elements are often required. In this study, a compact phased array system consisting of only three piezoelectric elements is used in conjunction with an updated total focusing method (TFM) for localization of single and multiple defects in an aluminum plate. The accuracy of the localization process was greatly improved by including wave propagation information in TFM. Results indicated that the proposed CPA approach can locate single and multiple defects with high accuracy while decreasing the processing costs and the number of required transducers. This method can be utilized in critical applications such as aerospace structures where the use of a large number of transducers is not desirable.
With increasing utilization of the composite materials in commercial and military applications, t... more With increasing utilization of the composite materials in commercial and military applications, the longevity of composite bonds has become a crucial concern of the aerospace industry. In spite of the previous studies in the literature for characterization of bonding condition in composite materials, implementation of more advanced structural health monitoring (SHM) techniques are still required to ensure flight safety and quick inspections of structures. In this study, two different SHM methods were used to evaluate the strength of composite bonds by using two separate experimental setups. First, the heterodyne effect method was used for assessing the separation in the composite joint. Then, the surface response to excitation (SuRE) method was used for studying various simulated contamination levels. Results of the experimental studies showed that the proposed methods could be efficiently utilized for evaluating bonding strength of composite materials.
To date, sensors have been the inevitable component of structural health monitoring (SHM) systems... more To date, sensors have been the inevitable component of structural health monitoring (SHM) systems. Typically, sensory signals are digitized, processed by computers, and then the information is presented to the operator with plots or warnings depending on the sophistication of the system. This study proposes a novel nonlinear acoustic health monitoring (NAHM) approach for detection of loose bolts, which can work with and without any sensors. The structure is excited with bitonal excitations, which their difference is in the audible range. When the bolts are well tightened, the structure remains silent. But, the structure creates audible sound or verbal warnings in the presence of one or more loose bolts. There is no need for sensor(s), A/D converters or computers between the operator and the structure. However, it is also possible to attach a piezoelectric sensor or to use a microphone/sound level meter for further analysis of the structure's response. The feasibility of the concept was demonstrated by detecting the loose bolt in a bolted plate system. For demonstrating the industrial potential of the proposed NAHM system, the concept was implemented for two simple washers held with nuts and bolts. Additionally, the intensities of the audible alarms were studied at different torque levels. The proposed NAHM may be used as a low-cost sensor-free SHM or as a backup for conventional nonlinear SHM systems. Keywords Structural health monitoring • Loose bolt detection • Sensor-free • Heterodyning effect • Ultrasonic guided-waves 1 Introduction Structural health monitoring (SHM) techniques have been used for detection of structural defects in many applica-B Amin Baghalian
Abstract : This program was successful in producing a state-of-the art capability, resulting in t... more Abstract : This program was successful in producing a state-of-the art capability, resulting in the development and implementation of the following: A unique horizontal/vertical precision-ballistics gun system, multiple wave mechanics diagnostics, and two experimental configurations were developed and employed in this research. The diagnostics developed and implemented include a redundant induction-coil system, B-dot (rate change of magnetic field) sensor coils and analysis system for dynamic 5DOF state measurement, a network of flush-mounted surface pressure gages (initial size of phi 6.35 mm, final size phi 1.26 mm), fiber optic break wires, colored particulate mechanics layering method, chemical fixing/sectioning of target, and Scanning Electron Microscope (SEM) particle analysis techniques. This document captures details of the last year (of a three year effort) with an Executive Summary covering the early years and tying the efforts together.
Conference Proceedings of the Society for Experimental Mechanics Series, 2016
Surface response to excitation (SuRE) method is a low-cost alternative to the electromechanical i... more Surface response to excitation (SuRE) method is a low-cost alternative to the electromechanical impedance method developed for the structural health monitoring (SHM) applications. This method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave. One or more piezoelectric sensors or scanning laser vibrometer monitors the dynamic response of the surface to the excitation. The spectrum of the dynamic response is collected at the optimal operating conditions. Any significant change of the spectral characteristics may indicate defects, improper loading or loose fasteners.
International Journal of Machine Tools and Manufacture, 2000
A new analytical cutting force model is proposed for micro-end-milling operations. The model calc... more A new analytical cutting force model is proposed for micro-end-milling operations. The model calculates the chip thickness by considering the trajectory of the tool tip while the tool rotates and moves ahead continuously. The proposed approach allows the calculation of the cutting forces to be done accurately in typical micro-end-milling operations with very aggressively selected feed per tooth to tool radius (f t /r) ratio. The difference of the simulated cutting forces between the proposed and conventional models can be experienced when f t /r is larger than 0.1. The estimated cutting force profile of the proposed model had good agreement with the experimental data.
Testing, Reliability, and Application of Micro- and Nano-Material Systems, 2003
The detection and microscopic characterization of hidden corrosion has recently been a focus of s... more The detection and microscopic characterization of hidden corrosion has recently been a focus of several advanced NDE research efforts. A variety of approaches have been suggested, with laser ultrasonic (LU), scanning acoustic microscopy (SAM), thermography,and x-ray systems being four of the most promising NDE techniques. In this effort, a side-by-side comparison of each of these four techniques was conducted with
Servomotors are devices commonly utilized in motion generation and position control. Such devices... more Servomotors are devices commonly utilized in motion generation and position control. Such devices have become preferred by designers because they provide a reliable and inexpensive solution. One of the main problems associated with servomotors is that they tend to burnout if the system in overloaded. This research focuses on developing a low cost, highly reliable solution to this problem. A magnetic field sensor was employed to acquire information of the electric current flowing through a line powering a servomotor. The data was processed employing a fast Fourier transform in order to identify any possible trends that could assist identifying overload conditions. Two different states were tested and compared to judge whether they represent normal operation or overstress conditions. The characterized overstress frequency was utilized to conceptualize a design that will provide fault-tolerant alternatives for mechanical systems that employ servomotors.
Additive manufacturing (AM) applications have been steadily increasing in many industry sectors. ... more Additive manufacturing (AM) applications have been steadily increasing in many industry sectors. AM allows creating complex geometries inside of a part to leave some space empty, called infills. Lighter parts are manufactured in a shorter time with less warpage if the strength of the part meets the design requirements. While the benefits of structural health monitoring (SHM) have been proven in different structures, few studies have investigated SHM methods on AM parts. In this study, the relationship between wave propagation and infill density has been studied for the additively manufactured polymer parts. The propagation of surface waves is monitored by using piezoelectric elements. Four rectangular parts are manufactured by using the material extrusion method with 20%, 40%, 60%, and 100% rectilinear infill densities. Four piezoelectric elements were attached on the surface of each beam, one for excitation and three for monitoring the response of the part at equal distances on eac...
The use of CubeSat systems for low-orbit data collection has increased due to their low cost deve... more The use of CubeSat systems for low-orbit data collection has increased due to their low cost development and light weight designs. For efficient data collection to occur, it is imperative that the satellite’s internal components remain fully functional throughout its mission life. To ensure the components remain in their operational range, an internal thermal control subsystem must be developed to effectively combat the transfer of heat. The standard size and payload of a CubeSat eliminates the possibility of designing a conventional fluid flow piping system. Through the development of a phase change material (PCM) thermal control system, the internal components will experience smaller temperature variations, while remaining within their operational limits. The melting temperature for optimal PCM performance, with a component operational range from 0-40 , is currently desired to be 45 , and the selection between Organic and Inorganic materials can be found below. The calculations de...
SOFT ROBOTIC ACTUATORS WITH CUSTOMIZABLE INNER GEOMETRIES USING ADDITIVE MANUFACTURING Kumar Y. S... more SOFT ROBOTIC ACTUATORS WITH CUSTOMIZABLE INNER GEOMETRIES USING ADDITIVE MANUFACTURING Kumar Y. Shah*, Andrew Martinez, Gonzalo Seisdedos, Juan Salazar, and Ibrahim Tansel Mechanical and Materials Engineering Department Florida International University 10555 W. Flagler St. Miami, FL 33174 The world of Soft Robotics is a relatively new research field. Top universities are advancing this topic by incorporating external geometric changes and electrical components to further observe predicted actions [1]. Currently, one of the only industrial implementations of Soft Robotics are grippers [1][2]. These grippers are incorporated into industrial robotic arms to grab, lift, or move fragile items such as live animals, produce, or sharp items, as shown in figure 1 [2]. Using the methods of Mechanical Design and Additive Manufacturing (3-D Printing), we have created actuator designs that are highly customizable and replicable worldwide. The actuator shown in figure 2, shows the internal cavity...
2017 8th International Conference on Recent Advances in Space Technologies (RAST), 2017
Active structural health monitoring methods are becoming increasingly popular for defect detectio... more Active structural health monitoring methods are becoming increasingly popular for defect detection in hollow cylindrical structures utilized in aerospace applications. Electro mechanical impedance (EMI) based methods are commonly used to study the health of hollow cylinders in broad frequency ranges. However, the EMI analyzers are bulky and costly. In addition, EMI based methods require high quantity of sensors for monitoring a large area. The Surface Response to Excitation (SuRE) method was developed to eliminate the need for EMI analyzers in broad frequency range inspections and to decrease the number of sensors in monitoring of large structures. In this study, the performance of the SuRE method in detection of internal defects is evaluated theoretically and experimentally. Different internal damages were created in an aluminum pipe specimen. The data collected from four bonded piezoelectric elements were used for damage detection and quantification. The test results showed the hi...
A complete thermal analysis on picosatellites is of most importance because it helps in the devel... more A complete thermal analysis on picosatellites is of most importance because it helps in the development of thermal control system that can protect the satellite’s internal systems from the extreme condition of outer space. Lack of a properly designed thermal control system could potentially mean the failure of the mission. Budget constraints in the design of the NEESAT-1U picosatellite, lead the team to implement passive thermal control systems on their CubeSat. In this paper, various materials have been considered for implementation as a thermal insulator. These materials have been evaluated by numerical methods. Best performing material was then evaluated using one-dimensional heat conduction to find the appropriate thickness needed to maintain the internal components at a safe operating temperature.
The CubeSat program has facilitated space access for students for over a decade through the innov... more The CubeSat program has facilitated space access for students for over a decade through the innovative design of versatile, and inexpensive research platforms. However, what started as an initiative for academic institutions to be able to data gathering platforms that can be cheaply and rather quickly assembled and launched, has now revolutionized the way even more established agencies look at orbital and space exploration. The mission type determines the payload and capabilities a CubeSat must have. Standard size of a 1U CubeSat is 10 cm x 10 cm x 10 cm. Due to the small dimensions of the pico-satellite, new innovative subsystem designs must be used to accomplish similar mission parameters that larger platforms perform with ease. This paper presents the design and optimization of a payload originally designed for ROARSAT, a larger 3U satellite of dimensions 10 cm x 10 cm x 30 cm developed at Florida International University. This is accomplished by arranging a set of achromatic len...
Structural Health Monitoring-an International Journal, 2017
With daily increase of application composite materials in commercial and military aircrafts, long... more With daily increase of application composite materials in commercial and military aircrafts, longevity of composite bonds has become a substantial factor in aerospace industry. Although tremendous amount of research has been conducted on monitoring the integrity of composite bonds, developing new structural health monitoring (SHM) techniques for evaluating bond strength could be essential. In this study, heterodyning method is implemented for exploring bond strength and detecting delamination in composite materials. Heterodyne effect may be utilized for the evaluation of debonded area when the linear characteristics of the system changes to nonlinear. The light contact in the bonding zone can result in this conversion from linear to nonlinear behavior. The nonlinear system responds to two appropriate excitation frequencies with new frequencies. For some nonlinear systems, the output has these new frequencies at the subtraction and summation of excitation frequencies. This is called ...
Heterodyning effect has been used for many wireless communication, electronics and ultrasound app... more Heterodyning effect has been used for many wireless communication, electronics and ultrasound applications. When two different frequencies are applied to proper nonlinear systems, new frequency components develop at the predictable frequencies. In the experimental studies, the perfect plates without any defects behaved like linear systems. Only the applied frequencies existed when the surface vibrations were monitored. However, once a defect like a crack or debonding started to develop the structure behaved like a nonlinear system. New frequencies and their harmonics developed at the difference and addition of the applied frequencies. In this study, COMSOL Multiphysics software was used to simulate the heterodyning effect. The response of two aluminum plates were studied when the upper face of one plate was excited at two different frequencies and the response of the bottom face of the second plate at the opposite side was simulated. Similar to the experimental studies, the monitore...
Electromechanical impedance (EMI) method is one of the most widely used structural health monitor... more Electromechanical impedance (EMI) method is one of the most widely used structural health monitoring (SHM) methods. The low-cost alternative of the method, surface response to excitation (SuRE) method has the similar characteristics. Both methods require additional disks/sensors to estimate the location of defects or external loading. Additive manufacturing (AM) methods have been matured and started to be an alternative to the conventional manufacturing. Most of the parts made by the AM methods are hollow. The infill type and skin thickness are selected to manufacture the parts faster by using less material and to avoid warping of the part. In this paper, manufacture of the parts with two infill types and two surface skin thicknesses at their different locations are proposed to estimate the site of the applied external forces without using additional disks/sensors. SuRE method was used in the study. The experimental results indicated that the frequencies of the most changed spectrum sections were different depending on the infill types and surface skin thicknesses. The same approach could be used for the EMI applications.
International Journal of Prognostics and Health Management
Rapid screening and monitoring of hollow cylindrical structures using active guided-waves based s... more Rapid screening and monitoring of hollow cylindrical structures using active guided-waves based structural health monitoring (SHM) techniques are important in chemical, petro-chemical, oil and gas industries. Successful implementation of the majority of these techniques in the SHM of pipes depends on the identification of the appropriate guided-waves modes and their frequencies for each application. The highly dispersive nature of the guided-waves and presence of multi modes at each frequency makes the mode selection and the interpretation of signals a challenging task. The surface response to excitation (SuRE) method was developed to detect the defects and loading condition changes on plates with minimum dependence on the excitation of particular modes at certain frequencies. In the present study, the SuRE method is proposed for quantification of longitudinal and circumferential defects, with varying severities, as common examples of axisymmetric and nonaxisymmetric defects in pipe...
Additive manufacturing (AM) technology has been used for the creation of complex parts in differe... more Additive manufacturing (AM) technology has been used for the creation of complex parts in different industries. The addition of defect detection and load sensing capabilities to these products can highly increase their values. The application of structural health monitoring (SHM) methods on AM parts is proposed in this paper by implementing the internal design capabilities of the AM parts. First, the influence of the internal top surface layers on the surface wave propagation characteristics was studied. A round part with different top skin thicknesses in each quarter (10, 20, 30, and 40 layers) was designed and fabricated of polylactic acid (PLA). The height of each layer was 0.1 mm and different spectral characteristics were observed in each quarter. Then, the location of an external compression loading was estimated with the help of different skin thicknesses on a plate designed with five zones. Although estimation of the defect or loading on the structure has always been a challenge in SHM studies, the use of hidden geometries helps to effectively overcome this challenge. Surface response to excitation method was used in this study to estimate the loading location by using two piezoelectric elements. A simple algorithm was used to estimate the loading zones in all the test cases.
Abstract Electromechanical Impedance (EMI) approach is a widely used Structural Health Monitoring... more Abstract Electromechanical Impedance (EMI) approach is a widely used Structural Health Monitoring (SHM) method. The EMI of a piezoelectric disk is monitored with an impedance analyzer or impedance measurement chip. In addition to the cracks, EMI may monitor compressive forces and may be used for detection of loose bolts. Surface Response to Excitation (SuRE) method is a low-cost alternative to the EMI method. The SuRE method uses one piezoelectric disk for excitation and a sensor to monitor the surface wave propagation. Digitization and Fast Fourier Transformation (FFT) of the signal of the sensor, such as another piezoelectric disk, is satisfactory to monitor the characteristics of the system. The important weakness of both approaches is not being able to estimate the location of the defect at their minimal configuration. Recently, Additive Manufacturing (AM) has been used for the manufacturing of parts for various reasons. The layer by layer part building techniques of the AM methods allow for the hiding of geometric features behind the part’s exposed skin. Use of the hidden features of the additively manufactured parts is proposed in the paper to help the SuRE method for estimation of the location of defects. Experimental studies verified the validity of the proposed approach. In addition, the EMI methods may benefit from this same approach.
Abstract Array systems of transducers have found numerous applications in detection and localizat... more Abstract Array systems of transducers have found numerous applications in detection and localization of defects in structural health monitoring (SHM) of plate-like structures. Different types of array configurations and analysis algorithms have been used to improve the process of localization of defects. For accurate and reliable monitoring of large structures by array systems, a high number of actuator and sensor elements are often required. In this study, a compact phased array system consisting of only three piezoelectric elements is used in conjunction with an updated total focusing method (TFM) for localization of single and multiple defects in an aluminum plate. The accuracy of the localization process was greatly improved by including wave propagation information in TFM. Results indicated that the proposed CPA approach can locate single and multiple defects with high accuracy while decreasing the processing costs and the number of required transducers. This method can be utilized in critical applications such as aerospace structures where the use of a large number of transducers is not desirable.
With increasing utilization of the composite materials in commercial and military applications, t... more With increasing utilization of the composite materials in commercial and military applications, the longevity of composite bonds has become a crucial concern of the aerospace industry. In spite of the previous studies in the literature for characterization of bonding condition in composite materials, implementation of more advanced structural health monitoring (SHM) techniques are still required to ensure flight safety and quick inspections of structures. In this study, two different SHM methods were used to evaluate the strength of composite bonds by using two separate experimental setups. First, the heterodyne effect method was used for assessing the separation in the composite joint. Then, the surface response to excitation (SuRE) method was used for studying various simulated contamination levels. Results of the experimental studies showed that the proposed methods could be efficiently utilized for evaluating bonding strength of composite materials.
To date, sensors have been the inevitable component of structural health monitoring (SHM) systems... more To date, sensors have been the inevitable component of structural health monitoring (SHM) systems. Typically, sensory signals are digitized, processed by computers, and then the information is presented to the operator with plots or warnings depending on the sophistication of the system. This study proposes a novel nonlinear acoustic health monitoring (NAHM) approach for detection of loose bolts, which can work with and without any sensors. The structure is excited with bitonal excitations, which their difference is in the audible range. When the bolts are well tightened, the structure remains silent. But, the structure creates audible sound or verbal warnings in the presence of one or more loose bolts. There is no need for sensor(s), A/D converters or computers between the operator and the structure. However, it is also possible to attach a piezoelectric sensor or to use a microphone/sound level meter for further analysis of the structure's response. The feasibility of the concept was demonstrated by detecting the loose bolt in a bolted plate system. For demonstrating the industrial potential of the proposed NAHM system, the concept was implemented for two simple washers held with nuts and bolts. Additionally, the intensities of the audible alarms were studied at different torque levels. The proposed NAHM may be used as a low-cost sensor-free SHM or as a backup for conventional nonlinear SHM systems. Keywords Structural health monitoring • Loose bolt detection • Sensor-free • Heterodyning effect • Ultrasonic guided-waves 1 Introduction Structural health monitoring (SHM) techniques have been used for detection of structural defects in many applica-B Amin Baghalian
Abstract : This program was successful in producing a state-of-the art capability, resulting in t... more Abstract : This program was successful in producing a state-of-the art capability, resulting in the development and implementation of the following: A unique horizontal/vertical precision-ballistics gun system, multiple wave mechanics diagnostics, and two experimental configurations were developed and employed in this research. The diagnostics developed and implemented include a redundant induction-coil system, B-dot (rate change of magnetic field) sensor coils and analysis system for dynamic 5DOF state measurement, a network of flush-mounted surface pressure gages (initial size of phi 6.35 mm, final size phi 1.26 mm), fiber optic break wires, colored particulate mechanics layering method, chemical fixing/sectioning of target, and Scanning Electron Microscope (SEM) particle analysis techniques. This document captures details of the last year (of a three year effort) with an Executive Summary covering the early years and tying the efforts together.
Conference Proceedings of the Society for Experimental Mechanics Series, 2016
Surface response to excitation (SuRE) method is a low-cost alternative to the electromechanical i... more Surface response to excitation (SuRE) method is a low-cost alternative to the electromechanical impedance method developed for the structural health monitoring (SHM) applications. This method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave. One or more piezoelectric sensors or scanning laser vibrometer monitors the dynamic response of the surface to the excitation. The spectrum of the dynamic response is collected at the optimal operating conditions. Any significant change of the spectral characteristics may indicate defects, improper loading or loose fasteners.
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Papers by Ibrahim Tansel