1,721,114 research outputs found
Charge weld evolution in hollow aluminum extrusion: Experiments and modeling
Full text linkCharge welds occur in billet-to-billet extrusion processes due to the transition between successive billets. The material in this transition zone is typically characterized by substandard mechanical properties. In industrial practice, a specified length of the extruded profile is cut away and recycled as in-process scrap. Therefore, understanding the extrusion mechanisms affecting the properties of the charge weld is crucial to controlling product quality, reducing non-conformities and improving the extrusion yield. This paper provides new insights into thermo-mechanical mechanisms associated with charge weld of circular aluminum tubes. A large number of carefully-controlled, full-scale extrusion experiments were conducted in an industrial environment to research charge weld evolution mechanisms and influential parameters. In addition, a finite element (FE) model was developed to predict the charge weld evolution across the cross section and along the profile. The experimental and numerical results show good agreement in terms of the location of the charge weld within the extruded profile. Moreover, a comparison with analytical models in the literature reveals that the FE model provides a significantly more accurate prediction of the length of the extruded profile affected by the charge weld (‘scrap length’). Based on the validated FE model, a sensitivity study was done to explore the effect of process parameters on charge weld evolution, particularly focusing on material flow and dead metal zone. The results show that the ram speed influences the charge weld evolution, while changes in billet temperature are insignificant. In conclusion, the findings presented in this study provide new insights that serve as practical guidance to the mechanism of charge weld evolution. They also highlight the applicability and limitations of numerical and analytical methods in assessing industrial extrusion problems.publishedVersio
Investigating Product Design and Development Capabilities for Transformation to Automated Assembly in a Low-Volume Industry Context
Full text linkThis thesis context has been the maritime low-volume manufacturing industry undergoing change and restructuring due to markets affected by a shift in energy sources and digitalization. More cost-effective production methods are needed to sustain competitiveness while ensuring sustainable and environmentally friendly products and manufacturing processes. Forwardlooking businesses increase in-house production by investing in advanced technology, reducing labour to a less significant portion of the production cost. Successful product development, including productivity improvement promised by new-to-the-company manufacturing technology, relies heavily on creating a strong interface between design and manufacturing, such that product- and process design considerations are collectively considered.
How to enhance product design and development capabilities needed to enable automated assembly of large and heavy marine low-volume products still need to be fully accounted for in existing theoretical frameworks. This thesis aims to contribute to and extend theory about the complex nature of product development to the low-volume industrial context. Through the lens of (Lean) product development theory, this thesis explores product design and development capabilities for transformation to automated assembly in the given context. As Lean is primarily a management approach, the present problem makes it necessary to include engineering strategies as a starting point for the study. The thesis has adopted Design for X strategies to supplement Lean in identifying necessary changes in product design.
The investigation is guided by three overarching research questions (RQ):
RQ1: What are the obstacles of the existing product development system and product design practices to enable the transformation to automated assembly in a low-volume industrial context?
RQ2: How can an industrial company operating in a low-volume context best combine people, processes and technology & tools in an LPD system to optimize product development to facilitate automated assembly?
RQ3: How can the combination of Industry 4.0 and precise product information (data accuracy) contribute to more sustainable choices and improved ways of working in product development?
The three research questions are investigated through the literature, retrospective and longitudinal case studies, and interviews with case company employees involved in recent and ongoing product development projects: four main and three supportive papers answer the thesis’s overall research objective. The individual research papers apply different perspectives. However, what they have in common is investigating product design and development capabilities for transformation to automated assembly in a low-volume (industrial) context. The research objective is answered by and contributes to the theoretical perspective of Lean PD and DfX, providing operational insights from product development in KM.
All four main papers have some overlapping contributions to the RQs in this thesis. The answer to the first research question (RQ1) is mainly based on data from semi-structured interviews with 18 KM respondents. These interviews and the initial LPD workshop helped identify obstacles to enabling automated assembly in the given context. The answer to the second research question (RQ2) is mainly based on the longitudinal study presented in main papers 2 and 3, assessing company PD practice against the 13 management principles presented by Morgan and Liker (2006) and how these capabilities can improve product design and development practice in KM. As a follow-up, the effect of introducing new PD practices outlined for the development stage of a new, optimized tunnel thruster (TTC) for closing observed capability gaps was analysed.
In answer to the third research question (RQ3), main paper 4 presents a participatory research study of two projects in KM, aiming to autogenerate process output based on adequate data input. Main paper 4 contributes to Design for X and Industry 4.0 literature investigating concerns related to product data and digital data flow when aiming to automate and improve working practices using tools in the context of Industry 4.0. A prerequisite for digital tools to support sustainable decision-making in PD is adequate data to be available early in the PD process and throughout the entire lifecycle.
The three supportive papers have overlapping findings based on product and process development case studies, including automated assembly in KM. These findings contribute to and support answering this thesis’s overarching RQs.
In total, this thesis makes nine contributions to answer the overarching research questions in this thesis. In answer to RQ1, this thesis identifies obstacles to address to transform toward more automated assembly in the given context. These obstacles include ‘project-like’ PD practices and heritage within existing design practices for manual assembly (C1). Moreover, it identifies obstacles in PD within the three categories of people, process, and technology & tools (C2). This thesis emphasizes making major trade-offs between Engineer-to-order (what the customer wants) and the standardization of products and components. When a prototype is sold to a customer, there is extensive work to prepare documentation and ensure quality. This can lead to point-based design focusing on the optimization of the chosen (customized) solution rather than exploring alternative solutions (C5). In answer to RQ2, main paper 1 argues that in the early design phase, company design practices must include leveraging automated assembly in terms of more conventional product and component engineering (DfX). Moreover, to carefully consider synergies within a product, product family, and product variants to facilitate standardized operations in production (C3). Main paper 2 & 3 identifies several areas that have the potential to strengthen the PD process once contextualized to the marine sector (C6). The reassessment based on new design practices in a PD benchmark project identifies six lean capability improvements and one new capability gap (C7). In answer to RQ3, this thesis identifies how product data must be made available early in the PD process and connected throughout the lifecycle through harmonization, integration, and automation to utilize digital tools efficiently and effectively (C8). The two case studies emphasize the digital thread in engineering and manufacturing as a promising start toward more data-driven and sustainable decision-making (C9).
This thesis can serve as a source for practitioners and the academic audience to understand better what product development capabilities within lean PD and engineering strategies within Design for X are relevant for the transformation towards more automated assembly in the low-volume industry context.Digital fulltext is not availabl
Managing unplanned design iterations in new product development: An approach using risk management, resilience, and organizational learning
Full text linkMost new-product development (NPD) engineering projects encounter uncertainties from rapidly shifting market demands and developing technologies resulting in requirements change and the organization's ability to implement state-of-the-art processes reliably. This complexity triggers unplanned design iterations in the engineering design phase of the NPD process. These unplanned design iterations can be assumed to be the occurrence of a specific class of NPD project risks. Unplanned design iterations ultimately cause failures in reaching cost, schedule, quality, and customer satisfaction targets.
Today's organizations utilize traditional risk management practices to mitigate risks in NPD projects. However, even with mitigation actions in place, projects still struggle to manage NPD project risks. Therefore, this PhD thesis explored the utilization of risk management, resilience, and organizational learning in managing unplanned design iterations risk in the design and development of new products. To achieve this aim, we used different research methods including literature review, case study, cross-sectional interviews and survey.
The empirical findings of this PhD thesis suggest that risk management processes must be tailored according to the contextual factors of the NPD projects to manage unplanned design iterations. The overlap of risk management-based and resilience-based approaches is required to treat known and unknown NPD project risks that may cause unplanned design iterations. The thesis's findings recommend developing a structured approach for selecting suitable learning methods for managing unplanned design iterations after their occurrence. Finally, the thesis's findings suggest establishing a systematic approach for capturing newly generated knowledge in the resolution of the unplanned design iterations employing organizational learning
On measuring, prediction and control of 3D profile bending towards Industry 4.0
Full text linkAluminum profile bending is one of the methods providing potential to reduce weight and improve fuel efficiency in automotive, aerospace, and other industries. Most of manufacturers make efforts to reduce the number of components and processing steps for manufacturing efficiency and to increase product quality. Two and three-dimensional shapes of products are also demanded to satisfy aesthetic perspectives.
To meet the industrial demands toward Industry 4.0, the current research mainly focuses on the development of the springback monitoring and control by non-contact measurement methods, analytic models and artificial neural networks. A new strategy for on-machine springback measurement in rotary draw bending was developed. The measurement strategy is to evaluate springback by integrating digital image processing and laser tracking, enabling the bending process and springback to be monitored in real time. As a non-contact measurement method, this affordable system eliminates an offline measurement process by integrative monitoring the springback angle in rotary draw bending.
Based on the digital image measurement strategy in rotary draw bending, an in-situ springback monitoring technique was also developed for stretch bending of large-size profiles. The measurement technique is to evaluate springback in real time. Using the so-called circular hough transform algorithm, the center of reference circles marked on the profile were detected, and springback was calculated. The applicability of computer vision-based springback monitoring in large-size profile bending was validated with experiments.
In advanced 3D stretch bending, a 5-axis machine was used to bend hollow aluminum alloy profiles. The method provides the capability of reduced springback for complex shapes. The configuration of the 3D bend die and its rotational mechanism were kinematically analyzed and an analytical springback model was proposed based on the Frenet-Serret theorem. While the kinematically controlled stretch bending imposes stretch through the configuration of the tool, super-imposed stretch applied prior to bending provides further springback reduction. Thus, the effect of the pre-stretch before bending was also explored in this work. The proposed model was validated with finite element simulations and experiments to demonstrate springback evaluation for product design and process control purposes.
To reduce springback variations and improve process control, an artificial neural network (ANN) model was developed. The ANN model was trained based on experimental and analytical data. This model provides compensated bending angles to achieve the desired dimensions of the product. The proposed strategy was validated with 2D and 3D stretch bending experiments and provided evidence to improve the dimensional quality of bent profiles.Fulltext not availabl
Local strain energy density to assess the multiaxial fatigue strength of titanium alloys
Full text linkThe present paper investigates the multiaxial fatigue strength of sharp V-notched components
made of titanium grade 5 alloy (Ti-6Al-4V). Axisymmetric notched specimens have been tested under combined
tension and torsion fatigue loadings, both proportional and non-proportional, taking into account different
nominal load ratios (R = -1 and 0). All tested samples have a notch root radius about equal to 0.1 mm, a notch
depth of 6 mm and an opening angle of 90 degrees. The fatigue results obtained by applying multiaxial loadings
are discussed together with those related to pure tension and pure torsion experimental fatigue tests, carried out
on both smooth and notched specimens at load ratios R ranging between -3 and 0.5.
Altogether, more than 250 fatigue results (19 S-N curves) are examined, first on the basis of nominal stress
amplitudes referred to the net area and secondly by means of the strain energy density averaged over a control
volume embracing the V-notch tip. The effect of the loading mode on the control volume size has been
analysed, highlighting a wide difference in the notch sensitivity of the considered material under tension and
torsion loadings. Accordingly, the control radius of the considered titanium alloy (Ti-6Al-4V) is found to be
strongly affected by the loading mode
On Solid-State Deposition of Metal Structures: Conceptualization of a New Additive Manufacturing Method based on Hybrid Metal Extrusion & Bonding
Full text linkThis thesis presents the conceptualization of a new solid-state process for additive manufacturing (AM) of extrudable metals and alloys. The process is based on the Hybrid Metal Extrusion & Bonding (HYB) technology and has been termed HYB-AM.
The main objective of this thesis has been to develop the HYB-AM process through concept evaluation and full-scale experimental testing, hence making it possible to assess the mechanical integrity of a deposited structure and understand the governing mechanisms of the process.
A novel set-based approach for concept evaluation has been developed and applied. The combination of rapid prototyping and physical modelling made it possible to test and evaluate multiple extruder and deposition concepts without having to build full-scale steel prototypes. Plastic models of the different extruder concepts were produced by rapid prototyping and attached to a small CNC-machine. To test the function of each design, plasticine was processed through the different extruders and deposited on the machine bed. Through the evaluation of all the modelled concepts the extruder design for full-scale testing was identified.
Full-scale experiments have been carried out for two different extruder designs. Through the fabrication of samples and the subsequent assessment of the layer bonding, the technical feasibility of the HYB-AM process has been conclusively demonstrated in producing mechanically sound 3D structures. The results from the mechanical testing display an ultimate tensile strength across the bonded layers approaching that of the substrate material, yet at lower elongation prior to fracture. Moreover, inspections of the fracture surfaces show evidence of extensive dimple formation. This indicates that metallic bonding is achieved between the layers. However, regions of kissing-bonds and lack of bonding are also present, thus calling for further process optimization.
A novel method for fabrication of tensile specimens for assessing the bond strength between the layers has been developed and applied. The miniature specimens are machined from the samples using a single thread milling tool. In this way, the specimens can be located such that the interface between separate layers crosses the reduced section of the specimens. This allows the bond strength between the layers to be
tested in pure tension. FEA has been used to study material flow in the extruder, as well as the conditions at the interfaces of the deposited extrudate and the substrate in order to identify and characterize the process parameters involved.
Analysis of the material flow, shows that the extrusion pressure is virtually independent of the deposition rate. Furthermore, from the simulations of the material deposition sequence it is visible how the contact pressure at the interface will drop below the bonding threshold if the feed speed becomes too high relative to the material flow through the die.
The results obtained in this work, will be useful in the further development towards industrialization of the process. Although this work has demonstrated the process in full scale and established an understanding of the process, further research is required prior to industrialization
On Digitally Capturing Prototypes from Early-Stage Product Development Projects- A Technology-Focused Approach to Enabling Research on Prototype-Driven Projects
No full textDenne avhandlingen er adressert til forskere innen produktutvikling. Den har som mål å styrke og forbedre produktutviklingsforskning ved å tilby bedre metoder og verktøy for å forske på prototyping i prosjekter innen tidligfase produktutvikling. Avhandlingen argumenterer for at det er et behov for en ny metode som muliggjør at forskere kan gjøre flere observasjoner fra utviklingsprosjekter, uten å bruke så mye ressurser som eksisterende forskningsmetoder krever, og at dette behovet kommer fra begrensningene til metodene, verktøyene og ressursene som er tilgjengelige for produktutviklingsforskeren. Hovedbidraget i avhandlingen er derfor å presentere enmetode for a samle fysiske prototyper fra aktive prosjekter innen tidligfase produktutvikling, hvilket muliggjør analyse av store datasett med prototyper. Avhandlingen hevder at å samle fysiske prototyper er en gjennomførbar løsning for å samle større datasett fra aktive produktutviklingsprosjekter, da dette krever betraktelig mindre arbeidsinnsats fra forskeren sammenlignet med eksisterende forskningsmetoder. For å teste og evaluere den foreslåtte metoden har et system for digital innsamling av fysiske prototyper blitt utviklet. Dette systemet har som mål å møte et sett med funksjonskrav som har blitt identifisert som viktige for å implementere den foreslåtte metoden. Systemet har blitt utplassert på to forskjellige lokasjoner; i produktutviklingsavdelingen til en større norsk bedrift og i forskningslaboratoriet TrollLABS på NTNU. Et datasett på over 950 fysiske prototyper har blitt samlet inn digitalt gjennom bilder og metadata i løpet av dette prosjektet—noe som demonstrerer at den foreslåtte metoden er gjennomførbar for å samle forskningsdata fra aktive tidligfase produktutviklingsprosjekter. Avhandlingen argumenterer for at den foreslåtte metoden kan brukes til både kvantitative og kvalitative undersøkelser av tidligfase produktutviklingsprosjekter, og viser hvordan dette kan gjøres ved innsamling av prototyper fra ett prosjekt. En utfordring som oppstår når man samler større datasett med fysiske prototyper er at det kreves store ressurser for å analysere datasettet. Denne avhandlingen viser flere mulige løsninger på dette problemet ved å automatisk klassifisere ulike egenskaper fra bilder av prototyper gjennom å trene om eksisterende modeller med spesialtilpassede datasett—noe som viser at slike løsninger kan redusere ressursene som kreves for å analysere prototyper betydelig
Multiaxial fatigue strength of titanium alloys
Full text linkThe present paper investigates the multiaxial fatigue strength of sharp V-notched components made of titanium grade 5 alloy (Ti-6Al-4V). Axisymmetric notched specimens have been tested under combined tension and torsion fatigue loadings, both proportional and non-proportional, taking into account different nominal load ratios (R = -1 and 0). All tested samples have a notch root radius about equal to 0.1 mm, a notch depth of 6 mm and an opening angle of 90 degrees. The fatigue results obtained by applying multiaxial loadings are discussed together with those related to pure tension and pure torsion experimental fatigue tests, carried out on both smooth and notched specimens at load ratios R ranging between -3 and 0.5. Altogether, more than 250 fatigue results (19 S-N curves) are examined, first on the basis of nominal stress amplitudes referred to the net area and secondly by means of the strain energy density averaged over a control volume embracing the V-notch tip. The effect of the loading mode on the control volume size has been analysed, highlighting a wide difference in the notch sensitivity of the considered material under tension and torsion loadings. Accordingly, the control radius of the considered titanium alloy (Ti-6Al-4V) is found to be strongly affected by the loading mode
Industry-Academia Collaboration in Research and Innovation Projects. A Knowledge Management Perspective
Full text linkIndustry-academia research and innovation projects often fail to transform research results into successful outcomes in industrial settings.
This thesis concerns the understanding of lack of transparency—the gap, or the so-called ‘valley of death’—in cases where collaborative projects between industry and academia fail to realise research results derived from collaborative projects.
The study proposes the conceptual knowledge management model for industry-academia research and innovation projects. The study shows that the use of the proposed conceptual knowledge management model and the agile principles can potentially be a practical tool for knowledge management of industry-academia research and innovation projects. This means that the proposed knowledge management model, together with the agile principles, can contribute to bridging the ‘valley of death’.
Industrial companies, academia, and society in general will benefit from a successful transformation of research outcomes into successful innovations and new value creation. The results from this study can also support national and federal research/innovation councils in decision making when assessing industrial research applications
Prototyping and testing of novel flood protection systems
Full text linkThis thesis describes the early development stages of novel consumer flood protection systems. The development process has emphasized prototyping and experimentation as a strategy to front-load the development, which is outlined by a literature study.
A framework for the development and a set of quantitative and qualitative measures for the systems being designed were established. The development has been based on rigid-flexible hybrid systems, combining desired aspects from each.
As consumer flood protection systems represent an immature market with little knowledge to base the development on, generating and capturing knowledge has been a priority. Furthermore, the thesis describes the development and application of a program for capturing and reusing the knowledge obtained during this project. Knowledge was primarily gained through prototyping and by designing and conducting experiments.
The feasibility of using PVC canvas in hybrid systems in terms of stability was investigated. The test setup used to investigate this also showed great potential for testing overall stability of systems. In addition, a new innovative way for testing gaskets, independent of system design, was designed and performed.
Lastly, the thesis describes two promising concepts for consumer flood protection systems and points out further work that needs to be completed in order to move the products towards industrialization
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