The application of Non-Destructive testing and Structural Health Monitoring systems in historical... more The application of Non-Destructive testing and Structural Health Monitoring systems in historical buildings is of great interest and actuality due to the need to guarantee safety and conservation. The present memory focuses on the case study of the historical wrought iron tie-rods of Duomo di Milano, Italy. In recent years, two of these elements presented critical failures, making necessary the replacement. Consequently, a monitoring methodology, based on acoustic emission, was defined. First, the fracture toughness of historical wrought iron was experimentally characterized by employing standard small scale specimens taken from one of the failed tie-rods. At the same time, acoustic emission was acquired to define a methodology for detecting and localizing the events due to damage in the material, separating those due to background noise by applying suitable pattern recognition algorithms. Subsequently, a tensile test was performed on a full scale section of the same tie-rod. Before...
Insight - Non-Destructive Testing and Condition Monitoring, 2020
Railway sleepers represent an essential element of the track; indeed, their structural integrity ... more Railway sleepers represent an essential element of the track; indeed, their structural integrity is closely related to important technical and safety issues. Today, periodical visual inspections are the only method applied to check the status of sleepers but are limited to visible surfaces, whereas the early detection of in-service cracks in the whole volume of sleepers would provide great advantages in terms of maintenance and management. The aim of the paper is to propose an acoustic emission (AE)-based structural health monitoring (SHM) approach that is able to detect the initiation and propagation of cracks in in-service pre-stressed concrete sleepers. The investigation is carried out in the laboratory, comparing the results obtained by acoustic emission monitoring and digital image correlation when subjecting pre-stressed concrete sleepers, taken from production, to both static and cyclic loads. The main points dealt with in the paper include the sensitivity of acoustic emissio...
The “plasticity-induced crack closure” phenomenon is the leading mechanism which controls the mai... more The “plasticity-induced crack closure” phenomenon is the leading mechanism which controls the main effects on fatigue crack growth (e.g. stress ratio and load interaction effects) in metallic materials. Experimental tests, consisting mainly in global and/or local compliance measurements of the considered specimen, are usually carried out to quantify the physical phenomenon, but some aspects concerning the elaboration of acquired local
Some typical fatigue failures of butt-welded rails consist in fractures ofthe web. In the early s... more Some typical fatigue failures of butt-welded rails consist in fractures ofthe web. In the early stage, crack propagates parallel to rail surface but, after a while,it tends to propagate with a slant surface. The aim of the present work is to analyse themechanisms involved in crack propagation in rail’s web in order to be able to predictthe crack path and, in a second step, the rail inspection intervals. From this point ofview, FEM analyses of an observed fracture were carried out in order to determinate K Iand KII history at different positions of crack tip during the passages of the typical loadsinduced by trains. The results have shown that the initial flaw tends to follow a pathwhere ∆KII is close to maximum values and a small superimposed KI traction is present.Fractographic analyses have confirmed that propagation is mainly controlled by modeII and that mode I is prevalent only after the final bifurcation of the cracks.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 2008
Corrosion fatigue is an important topic in the evaluation of the structural integrity of railway ... more Corrosion fatigue is an important topic in the evaluation of the structural integrity of railway axles. In fact, several recent axle failures have been attributed to the presence of corrosion pits and axle surface corrosion. Despite the importance of this issue, existing EN standards do not precisely quantify the effect that corrosion or corrosion-fatigue might have on the fatigue strength of a railway axle. Consequently, there is a need to have a better understanding of this problem. In this paper, two main lines of research have been adopted with a view to investigating the issues regarding the corrosion fatigue properties of AlN steel. The first line of research assesses the morphology and the statistical distribution of corrosion defects present on the surface of retired axles together with the detrimental effect of the defects detected on the in-air fatigue strength of AlN steel. The second line of research examines the fatigue properties of AlN steel in the presence of artific...
Sommario Il meccanismo guida dei principali effetti (rapporto di ciclo, interazione dei carichi, ... more Sommario Il meccanismo guida dei principali effetti (rapporto di ciclo, interazione dei carichi, ecc.) osservabili sulla velocità di propagazione di cricche in materiali metallici è stato dimostrato essere il fenomeno, dovuto agli effetti di plasticità all'apice, della chiusura anticipata delle cricche stesse durante il ciclo di carico. Test sperimentali, consistenti fondamentalmente in misure di cedevolezza globale e/o locale del provino
The application of Non-Destructive testing and Structural Health Monitoring systems in historical... more The application of Non-Destructive testing and Structural Health Monitoring systems in historical buildings is of great interest and actuality due to the need to guarantee safety and conservation. The present memory focuses on the case study of the historical wrought iron tie-rods of Duomo di Milano, Italy. In recent years, two of these elements presented critical failures, making necessary the replacement. Consequently, a monitoring methodology, based on acoustic emission, was defined. First, the fracture toughness of historical wrought iron was experimentally characterized by employing standard small scale specimens taken from one of the failed tie-rods. At the same time, acoustic emission was acquired to define a methodology for detecting and localizing the events due to damage in the material, separating those due to background noise by applying suitable pattern recognition algorithms. Subsequently, a tensile test was performed on a full scale section of the same tie-rod. Before...
Insight - Non-Destructive Testing and Condition Monitoring, 2020
Railway sleepers represent an essential element of the track; indeed, their structural integrity ... more Railway sleepers represent an essential element of the track; indeed, their structural integrity is closely related to important technical and safety issues. Today, periodical visual inspections are the only method applied to check the status of sleepers but are limited to visible surfaces, whereas the early detection of in-service cracks in the whole volume of sleepers would provide great advantages in terms of maintenance and management. The aim of the paper is to propose an acoustic emission (AE)-based structural health monitoring (SHM) approach that is able to detect the initiation and propagation of cracks in in-service pre-stressed concrete sleepers. The investigation is carried out in the laboratory, comparing the results obtained by acoustic emission monitoring and digital image correlation when subjecting pre-stressed concrete sleepers, taken from production, to both static and cyclic loads. The main points dealt with in the paper include the sensitivity of acoustic emissio...
The “plasticity-induced crack closure” phenomenon is the leading mechanism which controls the mai... more The “plasticity-induced crack closure” phenomenon is the leading mechanism which controls the main effects on fatigue crack growth (e.g. stress ratio and load interaction effects) in metallic materials. Experimental tests, consisting mainly in global and/or local compliance measurements of the considered specimen, are usually carried out to quantify the physical phenomenon, but some aspects concerning the elaboration of acquired local
Some typical fatigue failures of butt-welded rails consist in fractures ofthe web. In the early s... more Some typical fatigue failures of butt-welded rails consist in fractures ofthe web. In the early stage, crack propagates parallel to rail surface but, after a while,it tends to propagate with a slant surface. The aim of the present work is to analyse themechanisms involved in crack propagation in rail’s web in order to be able to predictthe crack path and, in a second step, the rail inspection intervals. From this point ofview, FEM analyses of an observed fracture were carried out in order to determinate K Iand KII history at different positions of crack tip during the passages of the typical loadsinduced by trains. The results have shown that the initial flaw tends to follow a pathwhere ∆KII is close to maximum values and a small superimposed KI traction is present.Fractographic analyses have confirmed that propagation is mainly controlled by modeII and that mode I is prevalent only after the final bifurcation of the cracks.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 2008
Corrosion fatigue is an important topic in the evaluation of the structural integrity of railway ... more Corrosion fatigue is an important topic in the evaluation of the structural integrity of railway axles. In fact, several recent axle failures have been attributed to the presence of corrosion pits and axle surface corrosion. Despite the importance of this issue, existing EN standards do not precisely quantify the effect that corrosion or corrosion-fatigue might have on the fatigue strength of a railway axle. Consequently, there is a need to have a better understanding of this problem. In this paper, two main lines of research have been adopted with a view to investigating the issues regarding the corrosion fatigue properties of AlN steel. The first line of research assesses the morphology and the statistical distribution of corrosion defects present on the surface of retired axles together with the detrimental effect of the defects detected on the in-air fatigue strength of AlN steel. The second line of research examines the fatigue properties of AlN steel in the presence of artific...
Sommario Il meccanismo guida dei principali effetti (rapporto di ciclo, interazione dei carichi, ... more Sommario Il meccanismo guida dei principali effetti (rapporto di ciclo, interazione dei carichi, ecc.) osservabili sulla velocità di propagazione di cricche in materiali metallici è stato dimostrato essere il fenomeno, dovuto agli effetti di plasticità all'apice, della chiusura anticipata delle cricche stesse durante il ciclo di carico. Test sperimentali, consistenti fondamentalmente in misure di cedevolezza globale e/o locale del provino
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Papers by Michele Carboni