Simulation-Based Investigation of a Probability of Detection (POD) Model Using Phased Array Ultrasonic Testing (PAUT) Technique

Probability of detection (POD) as a metric for quantifying the capability of inspection procedures in nondestructive evaluation (NDE), has been applied and evolved in industries since 1970s. Progress had been noted when certain statistical functions were brought up to model POD behavior, including log-normal model (also referred as Probit model). This model had been concluded to be the best fit and therefore has been widely used in many studies, while the involved assumptions and conditions were not carefully addressed and explored. To make flexible POD datasets available for specific inspection procedures and reduce the number of expensive experiments needed, model-assisted POD (MAPOD) is an alternative. This paper addresses a pure simulation-based POD procedure of an inspection scenario involving phased array ultrasonic testing (PAUT) on lack-of-fusion defects in additive manufactured (AM) components. The mathematical simulations are performed by an ultrasonic testing (UT) simulation software, simSUNDT, developed at Chalmers University of Technology in Sweden. Resulted inspection datasets with the proposed data processing steps are evaluated in terms of the assumptions and conditions of log-normal POD model, with the purpose of discussing the POD model validity under different circumstances. Simulation-based POD curves are finally compared with several discrete POD values at some defect sizes, calculated through massive computations from physics-model based metamodel. Comparisons and observations confirm satisfactory application of log-normal POD model despite some violations in model hypotheses

Experimental Validation of a Phased Array Probe Model in Ultrasonic Inspection

New manufacturing technologies such as additive manufacturing facilitate flexible and complex designs and production of components. However, these new techniques should not compromise the safety aspect, which imposes higher demands on the integrity insurance and inspection methods. Phased array ultrasonic testing (PAUT) provides advanced inspection and evaluation processes, whereas qualification is still needed when applied together with new manufacturing techniques. Numerical modeling, as one of the potential qualification methods, has been developed for decades and should be validated before practical applications. This paper presents an experimental validation work of the phased array probe model implemented in a software, simSUNDT, by comparing the maximum echo amplitudes between the physical experiments and simulations. Two test specimens with side-drilled holes (SDHs) and different materials are considered for validation and practical purposes. An experimental platform with a mechanized gantry system, which enables stabilized inspection procedure, is built and applied during the validation work. Good correlations can be seen from the comparisons and this model is concluded as an acceptable alternative to the corresponding experimental work. The relation between depth and beam angle is also noticed and investigated, which is essential to guarantee an accurate inspection

Experimental Validation and Application of a Phased Array Ultrasonic Testing Model on Sound Field Optimization

In safety dominant industries, nondestructive evaluation (NDE) is crucial in quality assurance and assessment. Phased array ultrasonic testing (PAUT) as one of the NDE methods is more promising compared with conventional ultrasonic testing (UT) method in terms of inspection speed and flexibility. To incorporate PAUT, the techniques should be qualified, which traditionally is performed by extensive physical experiments. However, with the development of numerical models simulating UT method, it is expected to complement or partly replace the experiments with the intention to reduce costs and operational uncertainties. The models should be validated to ensure its consistency to reality. This validation work can be done by comparing the model with other validated models or corresponding experiments. The purpose of current work focuses on the experimental validation of a numerical model, simSUNDT, developed by the Chalmers University of Technology. Validation is conducted by comparing different data presentations (A-, B- and C-scan) from experimental and simulated results with some well-defined artificial defects. Satisfactory correlations can be observed from the comparisons. After the validation, sound field optimization work aiming at retrieving maximized echo amplitude on a certain defect can be started using the model. This also reveals the flexibility of parametric studies using simulation models

Tracing postrepresentational visions of the city: representing the unrepresentable Skateworlds of Tyneside

In any visualisation of the city more is left unseen than made visible. Contemporary visualisations of the city are increasingly influenced by quantification, and thus anything which cannot be quantified is hidden. In contrast, we explore the use of ‘lo-fi’, doodled, participatory maps made by skateboarders in Tyneside, England, as a means to represent their cityscape. Drawing on established work an skateboarding and recent developments in cartography, we argue that skateboarders understand the city from a postrepresentational perspective. Such a framing presents a series of challenges to map their worlds which we explore through a processual account of our mapmaking practice. In this process we chart how skateboarders’ mappings became part of a more significant interplay of performance, identity, visualisation, and exhibition. The paper makes contributions to the emerging field of postrepresentational cartography and argues that its processual focus provides useful tools to understand how visions of the city are produced