In order to estimate the amount of plane bending fatigue damage in an austenitic stainless steel (SUS304), we were investigating the relationship between plane bending fatigue damage and the perpendicular residual lea...
In order to estimate the amount of plane bending fatigue damage in an austenitic stainless steel (SUS304), we were investigating the relationship between plane bending fatigue damage and the perpendicular residual leakage magnetic flux density caused by martensitic structure induced by plane bending fatigue. A specimen such as SUS304 had been excited in a constant external magnetic field perpendicularly to measure dependence of the perpendicular residual leakage magnetic flux density on plane bending fatigue damage accurately. The Z component of the magnetic flux density at 1 mm above a specimen is measured by using a thin‐film flux‐gate (FG) magnetic sensor. Residual magnetization is caused by partial martensitic structure in an austenitic stainless steel induced by cyclic bending stress. From our experiments, we can evaluate dependence of the perpendicular residual leakage magnetic flux density on plane bending fatigue damage and know the relationship between growth of a crack and the perpendicular residual leakage magnetic flux density.
Fiber Reinforced Polymer (FRP) composite is rapidly emerging as an alternative material for the infrastructure industry, and as a supplement to the conventional material such as steel, concrete, and timber. However, t...
Fiber Reinforced Polymer (FRP) composite is rapidly emerging as an alternative material for the infrastructure industry, and as a supplement to the conventional material such as steel, concrete, and timber. However, the long‐term behavior of these materials has not been fully understood. In order to study the durability issues, it is important to develop a nondestructive evaluation (NDE) system for continuous monitoring of structural members built with FRP materials. This paper presents the results of an experimental study on delamination detection in FRP composite members using infrared thermography. Simulated delaminations of various sizes were inserted into several FRP box sections and deck sections during the pultrusion process to create subsurface defects. The defective specimens were then tested in the laboratory using infrared thermography to predict the location and planar extent of these subsurface delaminations. The infrared tests yielded good results, which indicate that the technique can be developed for long‐term in‐service monitoring of FRP structural members in the field environment.
This paper proposes a framework for quantifying logical and geometric inquiry through specific interpretations of Bayes’ Theorem and Information Theory. In logical inquiry there are a countable number of possible dis...
This paper proposes a framework for quantifying logical and geometric inquiry through specific interpretations of Bayes’ Theorem and Information Theory. In logical inquiry there are a countable number of possible discrete answers that define the inquiry, and Bayes’ Theorem serves to move the observer posing the question along a trajectory in a hyberbolic figure in a manner suggested by Rodriguez. For N=3, this plane is a hyperbolic triangle whose angles sum to zero — the smallest possible value in the hyperbolic plane where the sum of the angles of a triangle must sum to a positive number less than pi. In euclidean space, the hyberbolic figure becomes a multi‐dimensional simplex or polyhedron described by Shannon in his paper on a geometrical perspective of channel capacity. A theory of geometric inquiry requires that one consider an observer who conjointly possesses an objective reality space Θ and a physical or measurable space X. It is discussed how the matching of these spaces characterizes the ability of an observer to distinguish its posited objective reality. A simple functional form I is suggested as a measure of the degree of distinguishability for an observer. This form corresponds to the trace of the Fisher information matrix of p(x|θ) over θ∈ Θ. The origin and precise specification of the requirements that give rise to the specified functional form are unknown and represents an important area of future study with clues suggested in the work of Balasubramanian. At the same time, the question is asked regarding the nature of the metrics and probability distributions arising when an observer balances prior ignorance and prior knowledge through the extremizing of a functional J (p,∇p) = I + λH over probability densities p. The functional I is the a priori ability of the observer to distinguish pure space, H is the prior ignorance of the same observer over the same space, and λ is a scalar Lagrange multiplier ostensibly needed to balance units, but having add
Stress is one of the principal external factors affecting the magnetization of materials. A new and improved model equation for interpreting the magnetomechanical effect has been developed based on extension of the pr...
Stress is one of the principal external factors affecting the magnetization of materials. A new and improved model equation for interpreting the magnetomechanical effect has been developed based on extension of the previous equation to include the Rayleigh law. The previous theory “law of approach” has been refined by including a new linear term in the model equation in addition to the well‐known quadratic term. It was found that the modified theory provides a much better description of the magnetization changes under stress.
Repetitive processes are a distinct class of 2D systems of both systems theoretic and applications interest. They cannot be controlled by direct extension of existing techniques from either standard or 2D systems theo...
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Repetitive processes are a distinct class of 2D systems of both systems theoretic and applications interest. They cannot be controlled by direct extension of existing techniques from either standard or 2D systems theory. Here we give new results on the design of physically based feedback control laws. These results relate to design for performance and are illustrated on data for a model which arises in the modelling of a physical process.
This paper presents the results of an experimental study on the use of infrared thermography technique for detection of subsurface debonds in fiber reinforced polymer (FRP) wrapped timber railroad bridge components. S...
This paper presents the results of an experimental study on the use of infrared thermography technique for detection of subsurface debonds in fiber reinforced polymer (FRP) wrapped timber railroad bridge components. Simulated subsurface debonds were constructed in the laboratory in timber piles wrapped with FRP composite fabric. The debonds varied in size, thickness and severity. These debonds were placed between the 1/8″ thick FRP wrap and the timber surface. The thermal images from the delaminated specimens were compared with the thermal images from undamaged specimens to study the effect of subsurface debonds. In addition, several field tests were conducted using the infrared imaging system on three timber railroad bridges located in Moorefield, West Virginia that were rehabilitated with FRP composite fabric wraps. The field test data was used to detect any possible debond at the composite‐timber interface and study the effect of environmental parameters on the infrared images. This study showed that the infrared thermography technique can be effectively used to detect subsurface debonds in timber components wrapped with FRP composite fabric. The study also shows the effect of different parameters (environmental conditions, heat source, etc.) on the infrared images.
Data fusion techniques are based on the premise that two or more carefully designed NDE tests are potentially capable of offering additional information concerning the test object relative to what can be garnered from...
Data fusion techniques are based on the premise that two or more carefully designed NDE tests are potentially capable of offering additional information concerning the test object relative to what can be garnered from a single test. However, information from a heterogeneous set of transducers cannot be fused unless the data is mapped onto a common ‘format’. The eddy current method cannot, for example, provide time‐of‐flight information that can be combined from estimates derived from ultrasonic tests. This paper presents a simple solution to address the problem by employing the so‐called Q‐transform to relate diffusive fields, such as those generated by eddy current probes, and propagating wave fields generated by ultrasonic NDT sensors. The paper illustrates how the distance between a defect and a source can be extracted from eddy current data generated using carefully selected excitation signals. Numerical results and comparisons with analytical predictions are presented.
Differential linear repetitive processes are a class of continuous-discrete 2D linear systems of both systems theoretic and applications interest. The feature which makes them distinct from other classes of such syste...
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Differential linear repetitive processes are a class of continuous-discrete 2D linear systems of both systems theoretic and applications interest. The feature which makes them distinct from other classes of such systems is that information propagation in one of the two independent directions only occurs over a finite interval. Applications areas include iterative learning control and iterative solution algorithms for classes of dynamic nonlinear optimal control problems based on the maximum principle. In this paper, we investigate further the structural links between differential linear repetitive processes and a special class of time delay systems. This leads to some significant new controllability and optimal control results for these processes.
Bit errors and impulses introduced into cardiographic image sequences prohibit to process and evaluate the heart dynamics correctly. Thus, biomedical imaging such as vascular imaging and quantification of heart dynami...
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We describe recent developments in sonic infrared (IR) imaging. The sonic IR imaging NDE technique uses a single short pulse of sound to cause cracks to heat up and become visible in the infrared. Results of recent ex...
We describe recent developments in sonic infrared (IR) imaging. The sonic IR imaging NDE technique uses a single short pulse of sound to cause cracks to heat up and become visible in the infrared. Results of recent experiments on metal aircraft structures and composite test samples with natural and simulated defects are presented in this paper. Examples of defects in metals include cracks originating under fasteners and cracks in mechanical parts. Examples of defects in composites include fatigue cracks, pillow inserts, pull‐tab disbonds, skin‐to‐core disbonds, etc. Both 20kHz and 40kHz ultrasonic excitation sources were used for studying the frequency effect. Vibrational behavior of surfaces near the defects was monitored and correlated with the IR signals.
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