A rheology model of soft elastomeric capacitor for Weigh-in-motion application

As a result of fast growing industry, there is an increase in traffic congestion and deterioration of transportation inventory. Real-time traffic characterisation could be used to amoliorate the efficiency of our transportation system. Weigh-In-Motion (WIM) systems offer the advantages of vehicle classification, speed measurement, in addition to weight measurement while vehicles are moving. In this thesis, state-of-the-art WIM systems are discussed and limitations of current technologies are identified. A Soft Elastomeric Capacitor (SEC) that works as a large scale surface strain gauge is introduced to address the limitations in existing techniques and investigated for its applicability as a WIM sensor. Though the novel SEC has potential advantages, the relationship axial strain -to-stress needs to be modeled to enable its utilization as a WIM sensor. A Zener model is selected and modified by the addition of a slider to characterize the polymer behavior. An overstress approach is used to study the resultant stress-strain response owing to its simplicity and computational benefits. Since the overstress approach is data-driven, an experimental testing scheme is used to identify the model parameters. The tests comprise three types of applied strain loading: multi step relaxation, simple relaxation and cyclic compression. Specimens with varying stiffness are employed for these tests.. Numerical simulations for the cyclic compression loading are presented to assess the model performance. The model is found to be capable of reproducing the experimental data with an absolute maximum error value of 0.085 MPa for slow loading rate tests and 0.175 MPa for high loading rate tests. Comparative studies are completed to investigate the impact of patch stiffness on the mechanical behavior of the soft elastomeric capacitor patches. It is observed that as stiffness decreases, the nonlinearity in stress-strain response increase

Large-scale surface strain gauge for health monitoring of civil structures

Health monitoring of civil structures is a process that aims at diagnosing and localizing structural damages. It is typically conducted by visual inspections, therefore relying vastly on the monitoring frequency and individual judgement of the inspectors. The automation of the monitoring process would be greatly beneficial by increasing life expectancy of civil structures via timely maintenance, thus improving their sustainability. In this paper, we present a sensing method for automatically localizing strain over large surfaces. The sensor consists of several soft capacitors arranged in a matrix form, which can be applied over large areas. Local strains are converted into changes in capacitance among a soft capacitors matrix, permitting damage localization. The proposed sensing method has the fundamental advantage of being inexpensive to apply over large-scale surfaces. which allows local monitoring over large regions, analogous to a biological skin. In addition, its installation is simple, necessitating only limited surface preparation and deployable utilizing off-the-shelf epoxy. Here, we demonstrate the performance of the sensor at measuring static and dynamic strain, and discuss preliminary results from an application on a bridge located in Ames, IA. Results show that the proposed sensor is a promising health monitoring method for diagnosing and localizing strain on a large-scale surface

A rheology model of soft elastomeric capacitor for Weigh-in-motion application

As a result of fast growing industry, there is an increase in traffic congestion and deterioration of transportation inventory. Real-time traffic characterisation could be used to amoliorate the efficiency of our transportation system. Weigh-In-Motion (WIM) systems offer the advantages of vehicle classification, speed measurement, in addition to weight measurement while vehicles are moving. In this thesis, state-of-the-art WIM systems are discussed and limitations of current technologies are identified. A Soft Elastomeric Capacitor (SEC) that works as a large scale surface strain gauge is introduced to address the limitations in existing techniques and investigated for its applicability as a WIM sensor. Though the novel SEC has potential advantages, the relationship axial strain -to-stress needs to be modeled to enable its utilization as a WIM sensor. A Zener model is selected and modified by the addition of a slider to characterize the polymer behavior. An overstress approach is used to study the resultant stress-strain response owing to its simplicity and computational benefits. Since the overstress approach is data-driven, an experimental testing scheme is used to identify the model parameters. The tests comprise three types of applied strain loading: multi step relaxation, simple relaxation and cyclic compression. Specimens with varying stiffness are employed for these tests.. Numerical simulations for the cyclic compression loading are presented to assess the model performance. The model is found to be capable of reproducing the experimental data with an absolute maximum error value of 0.085 MPa for slow loading rate tests and 0.175 MPa for high loading rate tests. Comparative studies are completed to investigate the impact of patch stiffness on the mechanical behavior of the soft elastomeric capacitor patches. It is observed that as stiffness decreases, the nonlinearity in stress-strain response increases</p

Large-scale surface strain gauge for health monitoring of civil structures

Health monitoring of civil structures is a process that aims at diagnosing and localizing structural damages. It is typically conducted by visual inspections, therefore relying vastly on the monitoring frequency and individual judgement of the inspectors. The automation of the monitoring process would be greatly beneficial by increasing life expectancy of civil structures via timely maintenance, thus improving their sustainability. In this paper, we present a sensing method for automatically localizing strain over large surfaces. The sensor consists of several soft capacitors arranged in a matrix form, which can be applied over large areas. Local strains are converted into changes in capacitance among a soft capacitors matrix, permitting damage localization. The proposed sensing method has the fundamental advantage of being inexpensive to apply over large-scale surfaces. which allows local monitoring over large regions, analogous to a biological skin. In addition, its installation is simple, necessitating only limited surface preparation and deployable utilizing off-the-shelf epoxy. Here, we demonstrate the performance of the sensor at measuring static and dynamic strain, and discuss preliminary results from an application on a bridge located in Ames, IA. Results show that the proposed sensor is a promising health monitoring method for diagnosing and localizing strain on a large-scale surface.This proceeding is published as Simon Laflamme, Matthais Kollosche, Venkata D. Kollipara, Hussam S. Saleem, Guggi Kofod, "Large-scale surface strain gauge for health monitoring of civil structures", Proc. SPIE 8347, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2012, 83471P (5 April 2012); doi: 10.1117/12.913187. Posted with permission.</p