Monitoring the mechanical performance of self-drilling, self-tapping fasteners after installation using impact-type tooling in Modern Methods of Construction (MMC)

The rapid adoption of Modern Methods of Construction (MMC) in the United Kingdom has introduced new challenges in ensuring structural rigidity, particular in light-gauge steel structures. This study investigates the impact of fastener installation methods on the mechanical performance of connections in MMC applications, addressing a critical knowledge gap in the industry.The research focused on comparing the performance of self-drilling, self-tapping fasteners installed using traditional electric screwdrivers and increasingly popular impact-type screwdrivers. Two standardised test series based on EAD 330046-01-0602 were conducted to determine the characteristic lap-shearing resistance and characteristic withdrawal resistance of fastener connections.Test specimens were prepared using stainless-steel fasteners (EN 1.4301) and cold-rolled mild structural steel (S350GD+Z) in various thicknesses, representing common MMC configurations. A total of 500 tests were performed using a calibrated universal testing machine, with rigorous quality control measures implemented throughout the experimental process.Results revealed significant reductions in fastener performance when impact screwdrivers were used for installation. Withdrawal resistance decreased by 34.71% to 59.71%, while lap-shearing resistance reduced by 47.85% to 70.65% compared to traditional installation methods. Statistical analysis confirmed the significance of these findings, with all tests falling within ± 3.0 standard deviations in Z-score analysis.These results have profound implications for the structural integrity of MMC units. Connections designed based on traditional installation assumptions may be significantly under strength when impact screwdrivers are used, potentially leading to premature structural failures. The research highlights the need for updated design guidelines, stricter quality control in MMC fabrication, and potential revisions to building codes and standards.The research also establishes a foundation for future studies, including investigations into the long-term effects of installation methods on fastener performance, coating integrity and overall structural health. The findings underscore the importance of proper installation techniques in ensuring the safety and reliability of MMC structures.This research contributes valuable insights to the field of fastener technology in MMC and calls for immediate action from industry stakeholders to address the identified issues. The results provide a basis for updating fastener selection and installation guidelines for MMC applications, ultimately enhancing the structural performance longevity of light-gauge steel structures in innovative construction techniques

ESSAYS ON DECEPTIVE COUNTERFEITS IN SUPPLY CHAINS: A BEHAVORIAL PERSPECTIVE

This dissertation is comprised of three essays intended to contribute to the operations management discipline, specifically within supply chain management. The first essay provides a research agenda for studying deceptive product counterfeits, which are products that have been manufactured and/or distributed and sold by an entity in violation of another’s intellectual property rights and intentionally misrepresented by the seller as the genuine article. The proliferation of counterfeits into legitimate supply chains presents quality, health and safety and cost concerns for nearly all industries. We identify antecedents of vulnerability to deceptive counterfeits for firms and their supply chain partners using Situational Crime Prevention Theory and Normal Accident Theory. Vulnerability to counterfeiting has negative performance impacts for the firm, its customers and society. We propose using the Six Ts of Supply Chain Quality Management (Roth, Tsay, Pullman and Gray, 2008) as an approach to select effective strategies to mitigate these impacts. Essay Two serves as an initial effort to understand how counterfeits can enter supply chains. In this essay, we test whether purchasing specialists can serve as effective guardians of the supply chain using a scenario based role playing experiment. We explore if buyers can detect signals of counterfeits in proposals and successfully avoid the counterfeit supplier in the decision process. We additionally examine whether time constraints and workload pressure detracts from the ability to successfully process signals and avoid the counterfeit. We find that the buyers can successfully detect counterfeit signals and avoid the counterfeit in the selection decision, but don’t find support for time constraints and workload pressure effects. The final contribution of this dissertation is a methodological essay that explores the effect of time pressure on decision making by using a combination of perceived time pressure and objective measures of time spent in the decision process to determine if time pressure affects the quality of the decision making in a supplier selection decision. We find that time constraints and perceived time pressure are related constructs that negatively affect decision quality in a supplier selection decision

A Study of the Effects of Manufacturing Complexity on Product Quality in Mixed-Model Automotive Assembly

The objective of this research is to test the hypothesis that manufacturing complexity can reliably predict product quality in mixed-model automotive assembly. Originally, assembly lines were developed for cost efficient mass-production of standardized products. Today, in order to respond to diversified customer needs, companies have to allow for an individualization of their products, leading to the development of the Flexible Manufacturing Systems (FMS). Assembly line balancing problems (ALBP) consist of assigning the total workload for manufacturing a product to stations of an assembly line as typically applied in the automotive industry. Precedence relationships among tasks are required to conduct partly or fully automated Assembly Line Balancing. Efforts associated with manual precedence graph generation at a major automotive manufacturer have highlighted a potential relationship between manufacturing complexity (driven by product design, assembly process, and human factors) and product quality, a potential link that is usually ignored during Assembly Line Balancing and one that has received very little research focus so far. The methodology used in this research will potentially help develop a new set of constraints for an optimization model that can be used to minimize manufacturing complexity and maximize product quality, while satisfying the precedence constraints. This research aims to validate the hypothesis that the contribution of design variables, process variables, and human-factors can be represented by a complexity metric that can be used to predict their contribution on product quality. The research will also identify how classes of defect prevention methods can be incorporated in the predictive model to prevent defects in applications that exhibit high level of complexity. The manufacturing complexity model is applied to mechanical fastening processes which are accountable for the top 28% of defects found in automotive assembly, according to statistical analysis of historical data collected over the course of one year of vehicle production at a major automotive assembly plant. The predictive model is validated using mechanical fastening processes at an independent automotive assembly plant. This complexity-based predictive model will be the first of its kind that will take into account design, process, and human factors to define complexity and validate it using a real-world automotive manufacturing process. The model will have the potential to be utilized by design and process engineers to evaluate the effect of manufacturing complexity on product quality before implementing the process in a real-world assembly environment

Aeronautical Engineering: A special bibliography with indexes, supplement 74

This special bibliography lists 295 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1976

Residual stress and fatigue crack growth life prediction in fastener holes cold-worked by uniform indentation in 2024-T351 aluminium alloy

This thesis concerns primarily the residual stress characterisation in fastener holes coldworked by a novel StressWave process, and the prediction of the fatigue crack growth under the influence of such residual stress. Aerospace 2024—T351 aluminium alloy plate of 6.35 mm thickness containing a nominal 06.35 mm hole was used. Using neutron and laboratory X-ray diffraction measurements, a large compressive residual stress was found in StressWave and split-sleeve cold-worked holes. Detailed stress mapping indicates that a StressWave hole contains a highly symmetric residual stress field with a wider compressive region. Conversely, the split-sleeve technique generates a complex asymmetric stress variation through the specimen thickness and around the hole. Independently, a comprehensive finite element study was conducted to reveal the residual stress development associated with the two distinct cold-working techniques at various stages. Favourable agreement was achieved between the experiment and simulations. The deformation mechanism associated with the cold-working process is decisive to the behaviour of the residual stress field created. The symmetric crack growth behaviour observed in StressWave specimens permits a through-thickness crack geometry to be considered. Accordingly, Green’s functions for a single crack and two symmetric cracks originating from the edge of a circular hole were developed. These solutions were verified using weight function and finite element analysis and are therefore appropriate for subsequent study of fatigue crack growth. A theoretical framework was proposed to explicate the interaction of residual stress with the superimposed loading at the crack tip, which was mathematically expounded as a function of stress intensity factor and stress ratio. This analytical framework provides a reasonable correlation between the mean stress and crack closure criteria. As a demonstration, a finite-width plate containing a centre hole with a single crack, with surface residual stress measured by X-Ray diffraction was analysed. It was revealed that for a predictive task, both the mean stress and crack closure definitions necessitate different requirements of material database and parametric definitions. Next, the fatigue testing suggested that the fatigue durability of fastener holes treated by the StressWave method generally outperformed those observed for split-sleeve samples. Prediction according to the unified theory produced encouraging results matching the experimental fatigue crack growth measurement. Detailed analysis showed that suitable parametric calibration and the appropriate use of crack models were imperative to achieve reliable prediction. Future efforts necessary for accuracy of prediction work for StressWave cold-worked holes are discussed

Active disassembly applied to end of life vehicles

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Active Disassembly is technology that has been developed to allow assemblies to readily separate for recycling when they are exposed to certain triggering conditions. It is based around fasteners that use `Smart' Materials, typically Shape Memory Alloys (SMA) or Shape Memory Polymers (SMP). This has led to research in the field to be known as Active Disassembly Using Smart Materials (ADSM). Particularly within the context of the EU End of Life Vehicle (ELV) legislation, ADSM has the potential to enable the achievement of the recycling levels required. In this thesis, active disassembly solutions have been developed which have focused on the disassembly of the Instrument Panel, and the glazing within a vehicle. To achieve this, a number of novel Smart fastening devices have been developed, two of which are triggered by integral heating elements. This investigation also led to the creation of a new releasable hook and loop fastening system, known as `Shape Memory Hook and Loop Fasteners' (SM-HALF). SM-HALF is a repositionable fastening system that can be released remotely under a thermal stimulus. Research into the residual energy content of ELV batteries has been a significant part of the investigation. It has been found that it is possible to use the energy from `dead' car batteries to power at least 16 shape-memory alloy devices constructed from 25-micron diameter wire, at End of Life. No external energy input is required for disassembly. This research is timely as it provides a means of reclaiming 10% of a vehicle that would otherwise be lost to the shredder. The technology can: increase the number of parts available for recycling and reuse, separate waste streams, decrease shredder residue otherwise destined for landfill and increase economic returns for either the vehicle dismantling yards or shredder operator

Life Cycle Impact of Different Joining Decisions on Vehicle Recycling

Stricter vehicle emission legislation has driven significant reduction in environmental impact of the vehicle use phase through increasing use of lightweight materials and multi-material concepts to reduce the vehicle mass. The joining techniques used for joining multi-material designs has led to reduction in efficiency of the current shredder-based recycling practices. This thesis quantifies this reduction in efficiency using data captured from industrial recycling trials. Life Cycle Assessment has been widely used to assess the environmental impact throughout the vehicle life cycle stages. Although there is significant research on material selection or substitution to improve the vehicle’s carbon footprint, the correlation between multi-material vehicle designs and the material separation through commonly used shredding process is not well captured in the current analysis. This thesis addresses this gap using data captured from industrial trials to measure the influence of different joining techniques on material recycling efficiencies. The effects of material degradation due to joining choices are examined using the life cycle analysis including exergy losses to account for a closed-loop system. The System Dynamics approach is then performed to demonstrate the dynamic life cycle impact of joining choices used for new multi-material vehicle designs. Observations from the case studies conducted in Australia and Europe showed that mechanical fasteners, particularly machine screws, are increasingly used to join different material types and are less likely to be perfectly liberated during the shredding process. The characteristics of joints, such as joint strength, material type, size, diameter, location, temperature resistance, protrusion level, and surface smoothness, have an influence on the material liberation in the current sorting practices. Additionally, the liberation of joints is also affected by the density and thickness of materials being joined. The life cycle analysis including exergy losses shows a significant environmental burden caused by the amount of impurities and valuable material losses due to unliberated joints. By measuring the influence of joints quantitatively, this work has looked at the potential of improving the quality of materials recycled from ELV to be reused in a closed-loop system. The dynamic behaviours between the joining choices and their delayed influence on material recycling efficiencies from the life cycle perspective are performed using the data from case studies. It shows that the short-term reduction in environmental impact through multi-material structures is offset over the long-term by the increasing impurities and valuable material losses due to unliberated joints. The different vehicle recycling systems can then be resembled using two widely known system archetypes: “Fixes that Fail” and “Shifting the Burden”. Despite the adoption of more rigorous recycling approaches, the life cycle impact of different joining techniques on vehicle recycling continue to exist. The enactment of strict regulations in current ELV recycling systems is unable to solve the underlying ELV waste problem, and only prolongs the delay in material degradation due to joining choices. This work shows that the choice of joining techniques used for multi-material vehicle designs has a significant impact on the environmental performance during the ELV recycling phase

Attachment methods for advanced spacecraft thermal control materials - An annotated bibliography, phase 1 Summary report supplement

Annotated bibliography on attachment methods for advanced spacecraft thermal control material