A Unified Creep-Fatigue Equation with Application to Engineering Design

Background: Creep-fatigue damage occurs under cyclic loading at elevated temperature. The existing creep-fatigue models have limited ability to cover the full combination of creep and fatigue behaviours, except with extensive prior empirical testing. Consequently, they cannot effectively and efficiently be used for early engineering design

Motion of Particles at the Fundamental Level: NLHV Theory Predictions for a Spiral Gait Locus

Context: The existing literature on particle motion at the fundamental level is sparse. Particles, whether classical or quantum, are assumed to move with a continuous (even if uncertain) velocity. Purpose: The work prospects for a descriptive theory of particle motion from a non-local hidden-variable (NLHV) perspective. This is worth attempting for the potential to better understand fundamental dynamics and kinematics. Method: The new physics provided by the cordus theory was used to infer the mathematical representation of the energisation behaviour of the inner structures, specifically the reactive ends. From this, the motion function of the particle as a whole was determined. Findings: In three dimensional space, the motion of each reactive end is an irregular spiral displacement locus. The motion comprises a movement phase and a brief immobile phase. This is called a “gait” as it is reminiscent of biological locomotion. Originality: A novel theory of particle motion is offered. The theory predicts that motion comprises a complex spiral locus of the particle. This is unique among theories of physics. Further contributions are the provision of explanations for several physical phenomena: ponderomotive force, the nature of momentum, and bremsstrahlung radiation. Specifically, the theory explains why photon emission would be increasingly concentrated in the forward direction with increased electron energy. The theory provides a means to bridge quantum mechanics and special relativity, because it accommodates both particle uncertainty and field transmissions

Assessment of Aircraft Engine Blade Inspection Performance Using Attribute Agreement Analysis

Background—Visual inspection is an important element of aircraft engine maintenance to assure flight safety. Predominantly performed by human operators, those maintenance activities are prone to human error. While false negatives imply a risk to aviation safety, false positives can lead to increased maintenance cost. The aim of the present study was to evaluate the human performance in visual inspection of aero engine blades, specifically the operators’ consistency, accuracy, and reproducibility, as well as the system reliability. Methods—Photographs of 26 blades were presented to 50 industry practitioners of three skill levels to assess their performance. Each image was shown to each operator twice in random order, leading to N = 2600 observations. The data were statistically analysed using Attribute Agreement Analysis (AAA) and Kappa analysis. Results—The results show that operators were on average 82.5% consistent with their serviceability decision, while achieving an inspection accuracy of 67.7%. The operators’ reproducibility was 15.4%, as was the accuracy of all operators with the ground truth. Subsequently, the false-positive and false-negative rates were analysed separately to the overall inspection accuracy, showing that 20 operators (40%) achieved acceptable performances, thus meeting the required standard. Conclusions—In aviation maintenance the false-negative rate of <5% as per Aerospace Standard AS13100 is arguably the single most important metric since it determines the safety outcomes. The results of this study show acceptable false-negative performance in 60% of appraisers. Thus, there is the desirability to seek ways to improve the performance. Some suggestions are given in this regard

Comparative Analysis of Human Operators and Advanced Technologies in the Visual Inspection of Aero Engine Blades

Background—Aircraft inspection is crucial for safe flight operations and is predominantly performed by human operators, who are unreliable, inconsistent, subjective, and prone to err. Thus, advanced technologies offer the potential to overcome those limitations and improve inspection quality. Method—This paper compares the performance of human operators with image processing, artificial intelligence software and 3D scanning for different types of inspection. The results were statistically analysed in terms of inspection accuracy, consistency and time. Additionally, other factors relevant to operations were assessed using a SWOT and weighted factor analysis. Results—The results show that operators’ performance in screen‐based inspection tasks was superior to inspection software due to their strong cognitive abilities, decision‐making capabilities, versatility and adaptability to changing conditions. In part‐based inspection however, 3D scanning outperformed the operator while being significantly slower. Overall, the strength of technological systems lies in their consistency, availability and unbiasedness. Conclusions—The performance of inspection software should improve to be reliably used in blade inspection. While 3D scanning showed the best results, it is not always technically feasible (e.g., in a borescope inspection) nor economically viable. This work provides a list of evaluation criteria beyond solely inspection performance that could be considered when comparing different inspection systems

A Framework for Interactive Development of Simulation Models with Strategical–Tactical–Operational Layering Applied to the Logistics of Bulk Commodities

CONTEXT–Simulation modelling provides insight into hidden dynamics underlying business processes. However, an accurate understanding of operations is necessary for fidelity of the model. This is challenging because of the need to extract the tacit nature of operational knowledge and facilitate the representation of complex processes and decision-making patterns that do not depend on classes, objects, and instantiations. Commonly used industrial simulation, such as Arena®, does not natively support the object-oriented constructs available for software development. OBJECTIVE–This paper proposes a method for developing simulation models that allow process-owners and modellers to jointly build a series of evolutionary models that improve conceptual validity of the executable computer model. APPROACH-Software and Systems Engineering principles were adapted to develop a framework that allows a systematic transition from conceptual to executable model, which allows multiple perspectives to be simultaneously considered. The framework was applied to a logistics case study in a bulk commodities distribution context. FINDINGS–The method guided the development of a set of models that served as scaffolds to allow the natural flow of ideas from a natural language domain to Arena® code. In doing so, modeller and process-owners at strategic, tactical, and operational levels developed and validated the simulation model. ORIGINALITY—This work provides a framework for structuring the development of simulation models. The framework allows the use of non-object-oriented constructs, making it applicable to SIMAN-based simulation languages and packages as Arena®

The sustainability ballast framework for design of remote electrification

The UN sustainable development goal No 7 aims to achieve affordable and clean energy for all, but this is not yet achieved for approximately one billion people in remote communities. Small scale systems can provide benefits, but existing approaches are primarily top-down ap-proaches that are developed by experts, and focus on the electrical engineering, economics, and policy aspects. These are not always successful, because the sociological aspects are overlooked. A new approach to addressing remote energy development is required that better addresses the societal component. The objective was to develop a conceptual framework whereby the sociologi-cal values of indigenous communities were better included in electrification decision-making.A grounded theory approach was used to interview members of a rural indigenous community and identify key features of their world view. Several categories of values were identified, referred to as ’ballasts’. The idea of balance between these was a strong theme that emerged from the community discussion. A composite index was then constructed. Case study results are presented for a remote rural Amazonian community, Kabakaburi in Guyana. Nine sustainability ballasts were identified as part of the indigenous community’s world view: biological capacity, social capacity, autonomy, equity & equality, electric utility, health, education, communication, and products and services. This paper develops a new framework to include the values and world-view aspects of indigenous communities in electrification decision-making

Evaluation of Influence Factors on the Visual Inspection Performance of Aircraft Engine Blades

Background—There are various influence factors that affect visual inspection of aircraft engine blades including type of inspection, defect type, severity level, blade perspective and background colour. The effect of those factors on the inspection performance was assessed. Method—The inspection accuracy of fifty industry practitioners was measured for 137 blade images, leading to N = 6850 observations. The data were statistically analysed to identify the significant factors. Subsequent evaluation of the eye tracking data provided additional insights into the inspection process. Results—Inspection accuracies in borescope inspections were significantly lower compared to piece-part inspection at 63.8% and 82.6%, respectively. Airfoil dents (19.0%), cracks (11.0%), and blockage (8.0%) were the most difficult defects to detect, while nicks (100.0%), tears (95.5%), and tip curls (89.0%) had the highest detection rates. The classification accuracy was lowest for airfoil dents (5.3%), burns (38.4%), and tears (44.9%), while coating loss (98.1%), nicks (90.0%), and blockage (87.5%) were most accurately classified. Defects of severity level S1 (72.0%) were more difficult to detect than increased severity levels S2 (92.8%) and S3 (99.0%). Moreover, visual perspectives perpendicular to the airfoil led to better inspection rates (up to 87.5%) than edge perspectives (51.0% to 66.5%). Background colour was not a significant factor. The eye tracking results of novices showed an unstructured search path, characterised by numerous fixations, leading to longer inspection times. Experts in contrast applied a systematic search strategy with focus on the edges, and showed a better defect discrimination ability. This observation was consistent across all stimuli, thus independent of the influence factors. Conclusions—Eye tracking identified the challenges of the inspection process and errors made. A revised inspection framework was proposed based on insights gained, and support the idea of an underlying mental model

Freight Operations Modelling for Urban Delivery and Pickup with Flexible Routing: Cluster Transport Modelling Incorporating Discrete-Event Simulation and GIS

Urban pickup and delivery (PUD) activities are important for logistics operations. Real operations for general freight involve a high degree of complexity due to daily variability. Discrete-event simulation (DES) is a method that can mimic real operations and include stochastic parameters. However, realistic vehicle routing is difficult to build in DES models. The objective is to create a DES model for realistic freight routing, which considers the driver’s routing decisions. Realistic models need to predict the delivery route (including time and distance) for variable consignment address and backhaul pickup. Geographic information systems (GIS) and DES were combined to develop freight PUD models. GIS was used to process geographical data. Two DES models were developed and compared. The first was a simple suburb model, and the second an intersection-based model. Real industrial data were applied including one-year consignment data and global positioning system (GPS) data. A case study of one delivery tour is shown, with results validated with actual GPS data. The DES results were also compared with conventional GIS models. The result shows the intersection-based model is adequate to mimic actual PUD routing. This work provides a method for combining GIS and DES to build freight operation models for urban PUD. This has the potential to help industry logistics practitioners better understand their current operations and experiment with different scenarios

Minimum Viable Model (MVM) Methodology for Integration of Agile Methods into Operational Simulation of Logistics

Background: Logistics problems involve a large number of complexities, which makes the development of models challenging. While computer simulation models are developed for addressing complexities, it is essential to ensure that the necessary operational behaviours are captured, and that the architecture of the model is suitable to represent them. The early stage of simulation modelling, known as conceptual modelling (CM), is thus dependent on successfully extracting tacit operational knowledge and avoiding misunderstanding between the client (customer of the model) and simulation analyst. Objective: This paper developed a methodology for managing the knowledge-acquisition process needed to create a sufficient simulation model at the early or the CM stage to ensure the correctness of operation representation. Methods: A minimum viable model (MVM) methodology was proposed with five principles relevant to CM: iterative development, embedded communication, soliciting tacit knowledge, interactive face validity, and a sufficient model. The method was validated by a case study of freight operations, and the results were encouraging. Conclusions: The MVM method improved the architecture of the simulation model through eliciting tacit knowledge and clearing up communication misunderstandings. It also helped shape the architecture of the model towards the features most appreciated by the client, and features not needed in the model. Originality: The novel contribution of this work is the presentation of a method for eliciting tacit information from industrial clients, and building a minimally sufficient simulation model at the early modelling stage. The framework is demonstrated for logistics operations, though the principles may benefit simulation practitioners more generally.</jats:p

Multiscale Analogue Modelling of Clinching Process to Investigate Thickness Tolerance and Tool Misalignment

NEED—The effect of dimensional variability of sheet thickness (tolerance) and tool misalignment is poorly understood for the clinching process. Finite element analysis (FEA) is valuable but requires a lot of and is difficult to verify in this situation due to the asymmetrical geometry and nonlinear plasticity. OBJECTIVE—The objective of this work was to determine the effect of thickness tolerance, tool misalignment and sheet placement (top vs. bottom) in the clinching process, by use of analogue modelling with plasticine. METHOD—Experiments used a scaled-up punch and die, with plasticine as the analogue. Thickness tolerances were represented by sheet thicknesses of 11 and 7 mm, 12 and 8 mm, 8 and 12 mm and 13 and 9 mm for upper and lower sheets, respectively. Two types of lubricant were tested between sheets: glycerine and silicone oil. Angular variability was also introduced. Measured parameters were interlock (also called undercut) and neck thickness. Analogue results for deformation were compared with microscopy of metal clinching. FINDINGS—The results reveal that the multiscale analogue model is an efficient tool for studying the effect of dimensional deviation on a clinch joint. Thickness tolerance showed a critical relationship with interlock, namely a reduction to about half that of the nominal, for both maximum and least material conditions. Increased angular misalignment also reduced the interlock. Compared with glycerine, silicone oil tests showed reduced interlock, possibly the result of a lower coefficient of friction. ORIGINALITY—This work demonstrates the usefulness of analogue modelling for exploring process variability in clinching. The results also show that significant effects for sheet placement are ductility, lubricant (friction), thickness of samples and tool misalignment