Vladimir Torres

A Preliminary Magnetoinductive Sensor System for Real-Time Imaging of Steel Reinforcing Bars Embedded Within Concrete

This paper studies the feasibility of using solid-state magnetoinductive probes for detecting and imaging steel reinforcing bars embedded within prestressed and reinforced concrete. Changes in the inductance of the sensor material are directly proportional to the strength of the measured magnetic field parallel to the sensor. Using a square coil of 300 mm times 300 mm times 2.5 mm, 10-mm rebars can be imaged down up to a depth of 100 mm. Experimental results obtained by scanning steel bar specimens are presented. General performance characteristics and sensor limitations are also investigated.

Development of a solid-state multi-sensor array camera for real time imaging of magnetic fields

The development of a real-time magnetic field imaging camera based on solid-state sensors is described. The final laboratory comprises a 2D array of 33 x 33 solid state, tri-axial magneto-inductive sensors, and is located within a large current-carrying coil. This may be excited to produce either a steady or time-varying magnetic field. Outputs from several rows of sensors are routed to a sub-master controller and all sub-masters route to a master-controller responsible for data coordination and signal pre-processing. The data are finally streamed to a host computer via a USB interface and the image generated and displayed at a rate of several frames per second. Accurate image generation is predicated on a knowledge of the sensor response, magnetic field perturbations and the nature of the target respecting permeability and conductivity. To this end, the development of the instrumentation has been complemented by extensive numerical modelling of field distribution patterns using boundary element methods. Although it was originally intended for deployment in the nondestructive evaluation (NDE) of reinforced concrete, it was soon realised during the course of the work that the magnetic field imaging system had many potential applications, for example, in medicine, security screening, quality assurance (such as the food industry), other areas of nondestructive evaluation (NDE), designs associated with magnetic fields, teaching and research.

A 1-D Solid-State-Sensor-Based Array System for Magnetic Field Imaging of Steel Reinforcing Bars Embedded Within Reinforced Concrete

This paper describes a linear 1-D solid-state-based magneto-inductive sensor array for detecting and imaging steel-reinforcing bars embedded within prestressed and reinforced concrete. Using a square coil of 300 mm times 300 mm times 2.5 mm and by only measures of the vertical component of the magnetic flux density, pictorial representation of embedded rebars of different diameters and configurations can be imaged down up to a depth of 100 mm. The system is also capable of imaging metallic objects of different shapes. Experimental results obtained by scanning different steel bar specimens are presented.

Modeling Studies on the Development of a System for Real-Time Magnetic-Field Imaging of Steel Reinforcing Bars Embedded Within Reinforced Concrete

This paper addresses fundamental issues associated with the development of a real-time magnetic-field imaging system for nondestructive testing of prestressed and reinforced concrete. Modeling results have shown that with a square coil of 300 times300 times2.5 mm3, 10-mm rebars can be imaged down to a depth of 100 mm. Studies also indicate that the vertical component of the induced magnetic field is most favorable as it can readily be reconstructed to yield geometry and dimensional information pertaining to the rebar structure.

THE APPLICATION OF MAGNETO INDUCTIVE SENSORS FOR NON-DESTRUCTIVE TESTING OF STEEL REINFORCING BARS EMBEDDED WITHIN PRE-STRESSED AND REINFORCED CONCRETE

This paper demonstrates the feasibility of using solid‐state magneto‐inductive probes for detecting and imaging of steel reinforcing bars embedded within pre‐stressed and reinforced concrete. Changes in the inductance of the sensor material are directly proportional to the strength of the measured magnetic field parallel to the sensor. Experimental results obtained by scanning steel bars specimens are presented. General performance characteristics and sensor output limitations are investigated by using different orientations, sensing distance, excitation intensity, bar sizes and geometries.

The use of magnetoresistors for imaging steel bars in concrete

This paper reports on the design of a new system for the detection and imaging of steel bars in concrete. It is based on the magnetoresistive effect, whereby the resistance of a material changes due to the presence of a magnetic field. An innovative way of processing and separating the steel characteristics is presented. Here, the combination voltage, frequency and distance parameters generate a unique signature for each metal, profoundly enhancing the analysis.

Solid-state multi-sensor array system for real time imaging of magnetic fields and ferrous objects

In this paper the development of a solid‐state sensors based system for real‐time imaging of magnetic fields and ferrous objects is described. The system comprises 1089 magneto inductive solid state sensors arranged in a 2D array matrix of 33×33 files and columns, equally spaced in order to cover an approximate area of 300 by 300 mm. The sensor array is located within a large current‐carrying coil. Data is sampled from the sensors by several DSP controlling units and finally streamed to a host computer via a USB 2.0 interface and the image generated and displayed at a rate of 20 frames per minute. The development of the instrumentation has been complemented by extensive numerical modeling of field distribution patterns using boundary element methods. The system was originally intended for deployment in the non‐destructive evaluation (NDE) of reinforced concrete. Nevertheless, the system is not only capable of producing real‐time, live video images of the metal target embedded within any opaque medium, it ...

STUDY AND APPLICATION OF A MULTI MAGNETORESISTOR SENSOR SYSTEM TO DETECT CORROSION IN SUSPENSION CABLES

Aging and deterioration of the main functional parts in civil structures is one of the biggest problems that private and governmental institutions, dedicated to operate and maintain such structures, are facing now days. In the case of relatively old suspension bridges, problems emerge due to corrosion and break of wires in the main cables. Decisive information and a reliable monitoring and evaluation are factors of great relevance required to prevent significant or catastrophic damages caused to the structure, and more importantly, to people. The main challenge for the NDE methods of inspection arises in dealing with the steel wrapping barrier of the suspension cable, which main function is to shield, shape and hold the bundles. The following work, presents a study of a multi‐Magnetoresistive sensors system aiming to support the monitoring and evaluation of suspension cables at some of its stages. Modelling, signal acquisition, signal processing, experiments and the initial phases of implementation are pr...

Studies on Geometries for Inducing Homogeneous Magnetic Fields in the Application of Real Time Imaging of Steel Reinforcing Bars Embedded Within Pre‐Stressed and Reinforced Concrete

This paper addresses fundamental issues associated with the development of a real time inductive scanning system for non‐destructive testing of pre‐stressed and reinforced concrete. Simulated results has indicated that given a coil dimension of 300mm×300mm×2.5mm, 10mm rebars can be imaged down to a depth of 100 mm. Studies also indicate that the vertical component of the induced magnetic field is most favourable as it can be readily reconstructed to yield geometry and dimensional information pertaining to the rebar structure.

A Dual‐Function Inductive Sensor for Imaging Steel, Corrosion Products and Graphite Based Materials

An inductive sensor is described that combines both Q‐detection and heterodyne technology. By exploiting the change in amplitude and frequency of the received signals, it may be used for imaging steel reinforcement bars, surface corrosion and, generally, materials with different permeability and conductivity ratios. Real time digital signal processing is used to improve the signal to noise ratio of the sensor and to provide a feedback stabilization mechanism for the reduction of long‐term drift.