A criterion space decomposition approach to generalized tri-objective tactical resource allocation

We present a tri-objective mixed-integer linear programming model of the tactical resource allocation problem with inventories, called the\ua0generalized tactical resource allocation problem\ua0(GTRAP). We propose a specialized criterion space decomposition strategy, in which the projected two-dimensional criterion space is partitioned and the corresponding sub-problems are solved in parallel by application of the\ua0quadrant shrinking method\ua0(QSM) (Boland in Eur J Oper Res 260(3):873–885, 2017) for identifying non-dominated points. To obtain an efficient implementation of the parallel variant of the QSM we suggest some modifications to reduce redundancies. Our approach is tailored for the GTRAP and is shown to have superior computational performance as compared to using the QSM without parallelization when applied to industrial instances

Predicting Geometrical Variation in Fabricated Assemblies Using a Digital Twin Approach Including a Novel Non-Nominal Welding Simulation

The aerospace industry faces constantly increasing demands on performance and reliability, especially within the vital area of engine development. New technologies are needed in order to push the limits of high precision manufacturing processes for the next generation of aircraft engines. An increased use of in-line data collection in manufacturing is creating an opportunity to individualize each assembly operation rather than treating them identically. Welding is common in this context, and the interaction between welding distortion and variation in part geometries is difficult to predict and manage in products with tight tolerances. This paper proposes an approach based on the Digital Twin paradigm, aiming to increase geometrical quality by combining the novel SCV (Steady-state Convex hull Volumetric shrinkage) method for non-nominal welding simulation with geometrical data collected from 3D scanning of parts. A case study is presented where two parts are scanned and then welded together into an assembly. The scan data is used as input for a non-nominal welding simulation, and the result of the simulation is compared directly to scan data from the real welded assembly. Three different welding simulation methods are used and assessed based on simulation speed and ability to predict the real welding result. The segmented SCV method for welding simulation shows promising potential for this implementation, delivering good prediction accuracy and high simulation speed

The role of microstructural characteristics of additively manufactured Alloy 718 on tool wear in machining

This study aims to provide a fundamental understanding of the role of microstructural characteristics influencing tool wear when machining Alloy 718 fabricated using Powder Bed Fusion (PBF). The effects of preferred crystallographic orientation (texture), shape and distribution of grains, local misorientation, type and amount of precipitates as well as the type, size and amount of abrasive carbides, nitrides and oxides on tool wear are investigated in as-built condition and after the standard solutionising and double-aging treatment. The microstructures of workpiece materials and the surfaces of worn tools were examined using different material characterisation techniques, including Scanning Electron Microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). A dislocation-based approach was used to reveal the cumulative effects of the microstructural characteristics on deformation behaviour and the thermo-mechanical loads on the tools during cutting. The analyses suggest that texture and the extent of material work-hardening prior to the onset of crack formation markedly influence the amount of plastic work and thus heat generation when machining Electron Beam Powder Bed Fusion (EB-PBF) material. The higher heat generation in the cutting zones provokes thermally-induced wear mechanisms like diffusion-dissolution and oxidation. In addition, the larger amount of hard oxide inclusions present in EB-PBF material leads to higher wear by abrasion. In contrast to the prevailing experimental approaches in this field, the present investigation is built on a physics-based framework to understand the fundamental aspects that govern material deformation and heat generation in cutting and, consequently, tool wear mechanisms. This framework can be used for machinability assessment of any alloy manufactured by different additive manufacturing (AM) technologies and for optimising the process-chain, including printing strategies and thermal post-treatments, to improve the machinability of AM alloys by tailoring their microstructure

Challenges and Enablers to Integrate Land-Sea-Interactions in Cross-Border Marine and Coastal Planning:Experiences from the Pan Baltic Scope Collaboration

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Influence of Material Variations on Machinability - Machining Difficult-to-Machine Alloys

The aim of this study is to investigate the effect of work material variations on machinability. Improved knowledge in this respect supports the development of sustainable production both from resource and economical points of view.The properties of work materials vary greatly depending on how they were manufactured. Castings generally have coarse microstructure compared to wrought material, where the added thermo-mechanical processing steps in the latter produce finer microstructure. Local within-part variations in microstructure are found in both castings and wrought material. In cast material this varies due to factors such as undercooling and cooling rate. In wrought material local variations in process parameters, such as deformation and temperature produce different microstructures.Within-process variations during machining also exist, where surfaces deformed during cutting are left to subsequent cuts. The same occurs when machining sheet metal, where degree of deformation also may vary due to local variations in strain. In this work differences in both microstructure and deformation has been investigated for three work materials; nickel-iron based Alloy 718, titanium alloy Ti-6Al-4V and the stainless steel 316L. It was found that coarse microstructures result in anisotropic chip formation, where chips had a non-periodic serrated appearance in both Alloy 718 and Ti-6Al-4V. Both alloys are known to produce continuous chips at low feed rates and cutting speeds, with a transition to serrated chips as these parameters are increased, due to instability in the cutting process. The serrations due to this instability show a more periodic appearance, clearly distinguishable to the serrations due to anisotropy.In Alloy 718 coarse microstructure was also found to produce large burrs, that were continuously built-up during machining, as well as increase notch wear at the depth-of-cut on the cutting tool. In Ti-6Al-4V the anisotropic chip formation behavior found in coarse microstructure was connected to orientations of alpha colonies, i.e. where some orientations produce highly localized deformation and others were homogeneously deformed at all feed rates and speeds investigated. Chip breakability was found to increase with size of alpha colonies, aided by the colonies that had highly localized deformation. The influence of the less periodic serrations found in coarse microstructure was also found to produce vibrations over a wider cutting speed range compared to the periodic serrations in finer microstructures.In both Alloy 718 and stainless steel 316L cutting forces were reduced when the work material had been deformed prior to machining, compared to annealed material

Influence of Microstructure on Chip Formation - Machining Aero Engine Alloys

Aero engine materials such as nickel-iron and titanium based alloys are known to be very difficult to machine. They are also known to produce shear-localized chips; a type of chip which is associated with both an increase of the tool wear and the vibration levels during machining. Robust machining operations are crucial for maintaining high productivity in the machining shop and variations in the actual work material, e.g. between batches or when the material supplier is changed, are known causes for unwanted disturbances. It goes without saying that a deeper understanding of how the work material microstructure interacts with the machining operation will lead to more robust processes. The aim of this work was to increase the understanding of how the microstructure of work material influences shear-localized chip formation. This was studied through transverse and orthogonal turning in two alloys, the superalloy Alloy 718 and the titanium alloy Ti-6Al-4V, for both of which the microstructure was varied by means of heat treatment. It was found that if the microstructures were finer than the uncut chip thickness, the machining behaviour was isotropic with a gradual increase of the shear-localization in chips when the cutting speed was increased in Alloy 718, and when feed rate was increased in Ti-6Al-4V. However, when the size of the microstructural constituents was increased through heat treatments and to be in the same order of magnitude as the chip thickness, anisotropic effects were found. The result was serrated chips at all cutting speeds in the case of Alloy 718, due to anisotropic deformation of grains at low speeds and with an increased influence of shear localization at higher speeds. The amount of shear localization was found to vary with the crystallographic orientation. In Ti-6Al-4V the orientation of the lamellar structure in the coarse Widmanst\ue4tten microstructure type affected the shear localization and this anisotropy could explain the presence of large lamellae in chips even at low feed rate

Performance in Product Development - The Case of Complex Products

This research addresses the concept of performance in the development of complex products. More specifically, its aim is to study how performance is perceived and measured within large global companies, and how performance measurement systems can be designed in a systematic way. The exploratory results regard how performance is currently perceived and measured. It is argued that performance measurements are focused on the later stages of the development of complex products, thus making it difficult to perform changes during the development. The focus is on lagging rather than leading indicators of performance, hence it is concluded that focus is on reporting the result rather than the causes of the result. In line with these findings is the weak link between what managers perceive as success factors and what is measured, the perception of performance being influenced by what is measured, rather than the reverse. The prescriptive results focus on the development of models and frameworks to be used during the development of complex products. A general method for developing performance indicators is presented. The concept of Products in Development is proposed, this making it possible to monitor how value is created during the development of a product. Both these models aim at complementing the currently used performance measurement system in order to support effective and efficient development of complex products. The method used in this research is mainly focused around the collection of qualitative data through a focused group interview, multiple case studies,and industrial reference-group seminars. A survey has also been used to complement the qualitative with quantitative data. The use of various research methods has made it possible to triangulate the data, thus strengthening the validity of the findings

Improving Traceability by Focusing on Value during Development

ABSTRACT Product delivering companies invest resources in software development activities in order to create value. Still, when performance in software development is to be measured, focus easily turns to time, cost, and quality in the later stages of the development process. Time, cost, and quality are important dimensions of performance but they are not revealing the complete picture. Missing is the value perspective. This paper outlines a method for how customer value can be used to evaluate performance and improve traceability during the development of a new product. The first step in the method is to value each requirement in the development project according to their perceived customer value. Hence, the value propagation can be monitored as the activities related the requirements are completed during the development. This information can then be used in order to improve traceability by visualizing the value propagation and performance during the development. The paper is concluded with outlining four key needs for future research

Managing change in performance measures – An inter-company case study approach

The field of performance measurement and management (PMM) is well filled with frameworks, models and guidelines addressing what to measure and how to design a performance measurement system (PMS). However, what has been less examined so far is how to ensure that PM evolve in tandem with their environments. Further, the few approaches available today are prescriptive and outlines how or what practitioners should do in order to manage change in their PM. Thus, a gap exists in understanding how organisations manage change in their PM in practice. Thus, the purpose of this paper is to outline and compare the approaches of three case companies for managing PM change. In order to fulfil the purpose of the paper, the data presented has been collected through the deployment of case studies. The choice of case studies as means for data collection stems from the possibility of an in-depth and holistic examination of the formulated phenomenon. All three case companies belong to the same company-group that operates within the transportation industry. The industrial footprint of the company is global with operations and sales spread out over the world. The findings suggest that all three companies have processes in place for managing change in PM. However, the approaches differ in design and context. Even though the case companies had different approaches in place to manage change in PM, they shared several commonalities. Commonalities were shared in the way of execution, process input and challenges in IT and culture. Furthermore, employee involvement seemed to be the biggest challenge for all three companies. The findings put forward in this paper are limited as they are confined to three companies from the same company-group. More studies, both from within and outside the company-group, are needed in order to establish a solid base of empirical data for generalisation. However, this paper makes a contribution both through describing how three companies manage PM change and through elaborating on the underlying factors affecting functionality.xpre