Complexity in design of technical systems

This paper discusses the complexity of technical systems resulted from engineering design. We defined the “overall difficulty” of such a system as consisting of “inborn complication” due to customer needs and external constraints as well as “acquired complexity” associated with uncertainty in satisfying the functional requirements caused by design decisions. An ideal design should lead to the least difficult technical system by minimizing inborn complication and eliminating acquired complexity. To achieve this design ideality, strategies of using the Axiomatic Design theory and the Design-Centric Complexity theory are introduced to guide the creation and improvement of complex time-independent and time-dependent technical systems.     

A synthetic DNA based approach to design of adaptive systems

Development of large engineered systems involves large amount of investments. Yet the value of these systems decreases significantly as requirements and environments change. For mission critical systems the capability of adapting to unpredictable situations is the key for success. While the importance of system adaptability has been recognized, little research has been done for “design for adaptability”. We take a “naturalistic design” approach to developing adaptive “lifelike” systems by exploiting natural “design” processes and mimicking its DNA based way of capturing, representing and applying “design” information pertaining to needed functions and changing operational situations. The concepts and examples of this approach are discussed.     

An Axiomatic Approach for “Target Cascading” of Parametric Design of Engineering Systems

Complex engineering system realization involves finding out design specifications that simultaneously achieve performance objectives at different levels. A common practice in industry is to adopt “Target Cascading” to obtain proper settings of the performance objectives, and find out those design specifications, not necessarily optimal, but satisfying all the desirable component-level, subsystem-level and system-level performance objectives. In this paper, an Axiomatic Approach to “Target Cascading” (AATC) is presented to improve the current “Target Cascading” process. AATC uses axioms to guide the decompositions of performance objectives, and an integration of a hybrid meta-modeling tool and direct synthesis method to enhance both robustness and efficiency. The preliminary results of AATC's industrial applications demonstrate its advantage in improving productivity at the early stage parametric design, especially for complex engineering systems.     

Design knowledge extraction from scenario-based databases using associative search engine for FR-induced decisions

The authors set the functional requirement of “reduce your own risk” and ran sessions of associative search to extract useful knowledge from databases. Ninety engineers found the most analogous knowledge using the associative search engine “GETA/IMAGINE” on scenario-based databases “Failure Knowledge Database” and “100 Scenarios of Failure.” Above 60% of their risk concern cases successfully reached the most analogous accident cases or failure scenarios from either database in about 10 min. Associative search can aid the designer in selecting design solutions for the functional domain.     

Decoupling Executions in Navigating Manufacturing Processes for Shortening Lead Time and Its Implementation to an Unmanned Machine Shop

A new navigation method that decouples manufacturing processes of tailor-made products has been developed for shortening lead time. Axiomatic Design expresses manufacturing processes with two design equations; one with functional requirement (FR) of “defining process” and design parameter (DP) of “decisions in process,” and the other with FR of “predicting completion time of product” and DP of “priority of product.” Once formulated, decoupling the system with the rules of “No feedback” and “No moving up” effectively shortens lead time. Applying the navigation methodology to a real unmanned machine shop of molds, eventually shortened it from 44 to 7.7 days.     

The effect of partially cut-out blanks on geometric accuracy in incremental sheet forming

Industrial requirements for accuracy in metal sheet components are typically ±0.2 mm where current incremental sheet forming processes are capable of an accuracy of only ±3 mm. Several approaches based on process design modifications or control strategies are being developed to overcome this problem, but none has as yet been entirely successful. This paper proposes and examines a new approach in which the area to be formed within the blank is “partially cut-out” using a water jet or laser cutter. The aim of this partial cut-out is to localise deformation to the area over which the tool travels and thus reduce the difference between a part made by a “contour tool path” and the target product geometry. Several design options are considered, and the approach is evaluated with one simple and one complex part. The results indicate that partially cut-out blanks lead to slightly more accurate forming than conventional blanks when unsupported, but that the accuracy improvement is less than that which is achieved by use of a stiff cut-out supporting plate. The results include an experimental investigation of residual stresses and springback in incremental sheet forming.     

Decision-based process design for shortening the lead time for mold design and production

We propose “Decision-based process design” for reducing the process time of the design and production of molds. This method reviews the human processes of making decisions for setting unknown parameters, and reduces their process time by actively reducing the operations with such decisions. We applied decision-based process design to the design and production of injection molding cellular phone shells, together with 3D-CAD and high speed machining. The application reduced the number of decision operations to 77, 13% of the total number of operations, and drastically decreased the process time by 86% down to 50 hours.     

Design for Environment — Do We Get the Focus Right?

Sometimes, products resulting from design for environment (DFE) endeavours are sub-optimisations from an environmental perspective, because the tool determines the process and not vice versa. For a more systematic way of getting the focus right a hierarchy of focusing is introduced:1. What is the function provided and what is the optimal way of providing it while making a business out of it? Which product should the company then produce?2. Where are the “environmental hot spots” in the life cycle of this product?3. Which DFE tool supports optimisation of the product by reducing these hot spots?     

Rapid nitriding of pure iron by thermal plasma jet irradiation

Pure iron samples were exposed to thermal plasma jet and nitrided for 15 min at a temperature ranging from 545 °C to 742 °C. For comparison purposes, conventional ion nitriding was also performed using glow discharge plasma at 580 °C for 8 h. For conventional plasma nitriding, a top compound layer and a bottom diffusion zone are observed. In contrast, an additional “transition zone” is observed between the compound layer and the diffusion zone for the thermal plasma jet treatment when the process temperature is 667 °C or above. This “transition zone” is quite thick (a few tens of micrometers), determined by the treatment temperature, and has unique features in the phase formation and nitrogen distribution. At 706 °C, the content of γ′phase, as well as the content of nitrogen and the hardness, reaches the maximum. Compared with the traditional plasma nitriding process, the reaction speed of thermal plasma irradiation is much higher. A nitrided case depth over a few tens of micrometers is obtained in plasma jet nitriding for only 15 min versus a depth of only a few micrometers in conventional plasma nitriding for 8 h. The formation of the “transition zone” and the mechanism for the high nitriding speed are discussed in the paper. It is believed that this technology can be applied at atmospheric pressure in field without the requirement for a vacuum system. Hence, this technology may be advantageous for practical applications.     

Microstructure characterization of as-fabricated and 475 °C annealed U-7 wt.% Mo dispersion fuel in Al-Si alloy matrix

High-density uranium (U) alloys with an increased concentration of U are being examined for the development of research and test reactors with low enriched metallic fuels. The U-Mo fuel alloy dispersed in Al-Si alloy has attracted particular interest for this application. This paper reports our detailed characterization results of as-fabricated and annealed (475 °C for 4 h) U-Mo dispersion fuels in Al-Si matrix with a Si concentration of 2 and 5 wt.%, named as “As2Si”, “As5Si”, “An2Si”, “An5Si” accordingly. Techniques employed for the characterization include scanning electron microscopy and transmission electron microscopy with specimen prepared by focused ion beam in situ lift-out. Fuel plates with Al-5 wt.% Si matrix consistently yielded thicker interaction layers developed between U-Mo particles and Al-Si matrix, than those with Al-2 wt.% Si matrix, given the same processing parameters. A single layer of interaction zone was observed in as-fabricated samples (i.e., “As2Si”, “As5Si”), and this layer mainly consisted of U₃Si₃Al₂ phase. The annealed samples contained a two-layered interaction zone, with a Si-rich layer near the U-Mo side, and an Al-rich layer near the Al-Si matrix side. The U₃Si₅ appeared as the main phase in the Si-rich layer in “An2Si” sample, while both U₃Si₅ and U₃Si₃Al₂ were identified in sample “An5Si”. The Al-rich layer in sample “An2Si” was amorphous, whereas that in sample “An5Si” mostly consisted of crystalline U(Al,Si)₃, along with a small fraction of U(Al,Si)₄ and U₆Mo₄Al₄₃ phases. The influence of Si on the diffusion and reaction in the development of interaction layers in U(Mo)/Al(Si) is discussed in the light of growth-controlling mechanisms and irradiation performance.     

Chip Form Monitoring through Advanced Processing of Cutting Force Sensor Signals

This paper draws on the activities of the CIRP Collaborative Work on “Round Robin on Chip Form Monitoring” carried out within the Scientific-Technical Committee Cutting (STC-C). This collaborative work involved the following main round robin activities: (a) generation, detection, storage and exchange of cutting force sensor signals obtained at different Laboratories during sensor-based monitoring of machining processes with variable cutting conditions yielding diverse chip forms, and (b) cutting force signal (CFS) characterization and feature extraction through advanced processing methodologies, both aimed at comparing chip form monitoring results achieved on the basis of innovative analysis paradigms.     

Distortion minimization of disks for gear manufacture

In order to minimize shape deviations in hardening of gear wheels, all production steps in the manufacture of disks made of SAE 5120 prior to heat-treatment were analyzed by means of design of experiments (DoE). The influence of hardenability, pre-heat treatment, forging temperature, and feed rate and partition of material removal in cutting on the distortion of disks were investigated. Standard case hardening of the disks led to a characteristic shape change called “dishing”. The statistical analysis of the test results has proven that dishing of disks is mainly affected by the partition of the material removal in the considered case. In additional experiments dishing could be eliminated (on average) by an optimized partition of the material removal. However, results from experiments with spray-formed disks and with disks using a different forming strategy imply that the material flow combined with material inhomogeneities are the physical causes for dishing rather than the partition of material removal.     

Effect of molten pool boundaries on the mechanical properties of selective laser melting parts

Selective laser melting (SLM) manufactures components through the overlapping of multi-track and multi-layer molten pools of metal powders, resulting in two types of molten pool boundaries (MPBs), “layer–layer” and “track–track” MPBs, remaining in SLM parts. The microstructure of MPBs exhibits a complex and regular spatial topological structure. There is a coarse grain zone below the MPBs and nonmetallic elements (C, O, Si) near the MPBs are in an unstable state. Long and thin columnar grains with the same orientations distribute on two sides of the “layer–layer” MPBs, whereas the columnar grains on both sides of “track–track” MPBs have different orientations. The “track–track” MPBs are short and intersect with “layer–layer” MPBs at some points and form acute angles, where cracks are initiated when applied with external loads. The effect of the MPBs on microscopic slipping, macroscopic ductility and fracture mechanism of the SLM parts made along different directions, which were exerted a tensile loading in the as-built condition without heat treatment, was analyzed and evaluated using slip theory and experiments. The results reveal that the MPBs have a significant impact on the microscopic slipping at the loading, macroscopic plastic behavior and fracture mode, and are one of the main reasons for the obvious anisotropy and low ductility of SLM parts.     

Virtual environments for dynamically reconfigurable Concurrent/Collaborative Engineering “virtual” teams

The paper presents a hypothesis, and its experimental validation, on virtual environments, i.e. Virtual Reality based interfaces, which hide the real appearance of their interlocutors, as enablers, or facilitators, of performance of dynamically reconfigurable “virtual” teams in Concurrent/Collaborative Engineering. Design teams’ dynamic reconfiguration may either be a need for (1) their structural and functional optimization (e.g. for improving their productivity) or (2) to support dissipatedness of the design teams in Chaordic Manufacturing Systems. The effect that virtual environments have on reducing the “set-up” time when switching from one interlocutor to another during the communication process is evaluated. The proof of the hypothesis is presented through a statistical evaluation of the experiment.     

Role of Bayer solution concentration and temperature in stress corrosion cracking susceptibility of steel

To improve the efficiency of the Bayer process for the extraction of alumina from Bauxite ore, there is a push for increasing processing temperature and caustic concentrations, which has also led to an increased concern for caustic embrittlement. In this study, the caustic cracking behaviour of steel in Bayer solutions of 2.5, 5, 7.5 and 10 mol dm⁻³ “free caustic” concentrations have been studied at different temperatures using pre-cracked circumferential notch tensile specimens. It has been observed that at 100 °C, steel is susceptible to caustic cracking in each of the four Bayer solutions. Caustic cracking has also been observed at temperatures as low as 55 °C. Tests were also conducted using only the notched specimens (i.e., without pre-cracking) in a 7.5 mol dm⁻³ “free caustic” Bayer solution at 120 °C to study the stress corrosion crack formation and propagation behaviour in blunt notches.     

RFBS: A model for knowledge representation of conceptual design

Conceptual design has been broken down into sub-processes and elementary tasks in methodologies. These methodologies proposed suggest their systematic application. This paper assumes the possible execution of these tasks automatically. Nevertheless, it is necessary for computers to integrate the knowledge required during the conceptual design process. Knowledge models have been proposed, for instance Gero's Function-Behaviour-Structure (FBS) model for design. This paper presents the integration of methodologies with a model of knowledge for conceptual design in accordance with model-driven engineering. Our proposition extends the FBS model and presents its practical implementation through ontology and language such as SysML.     

Defects in axisymmetrically drawn bars caused by longitudinal superficial imperfections in the initial material

Metallic wires and bars are produced by axisymmetric drawing of hot rolled material and must not display surface defects that impair their service use or whose opening during subsequent cold forming is unacceptable. Experimental and numerical (Finite Element Analysis - FEA) analyses of the evolution of longitudinal superficial defects in copper bars during seven successive axisymmetric drawing passes are presented. The initial experimental defects displayed a rectangular cross-section, 1 mm wide and 0.3, 0.6 or 0.9 mm deep; the two latter evolved after drawing into the “inverted Y” defect already reported in the literature, but the former led to a newly reported “double V” defect. There was a good agreement between the results from experiments and FEA and further analyses were then carried only through FEA, covering two other materials (a carbon steel and aluminum), a decrease in the defect width (from 1.0 to 0.5 mm) and an inclination of 15° or 30° of the walls of the 1.0 mm wide rectangular defect. The defect evolution was similar for the three materials; the decrease in the defect width enhanced the incidence of “inverted Y” defects, and indicated the formation of newly reported “Radial” and “Inverted V” defects. The inclination of the defect walls led to the possibility of a change from the “inverted Y” defect to a “double V” one. Defects 0.3 mm deep and with walls at 30° were eliminated by the present drawing sequence. A novel approach for the prediction of the effect of the initial superficial imperfections on the final drawn stock, through the so called “defect evolution maps” is presented.     

Oxidation mechanism of an Fe-9Cr-1Mo steel by liquid Pb-Bi eutectic alloy at 470 °C (Part II)

This paper is the second part of a global study on the oxidation process of an Fe-9Cr-1Mo martensitic steel (T91) in static liquid Pb-Bi. It focuses on the growth mechanism of a duplex oxide scale. The oxide layer has a duplex structure composed of an internal Fe-Cr spinel layer and an external magnetite layer. The magnetite layer grows by iron diffusion until Pb-Bi/oxide interface whereas the Fe-Cr spinel layer grows, at the metal/oxide interface, inside the space kept “available” by the iron vacancies accumulation due to iron outwards diffusion for magnetite formation. This growth mechanism is close to the “available space model”. However, this model is completed by an auto-regulation process based on oxygen supply.     

Innovations in Abrasive Products for Precision Grinding

This paper is a review of recent developments in the design and manufacture of precision, fixed-abrasive tools. The role of each component within the “engineered composite” is also discussed, with examples showing how the components have been enhanced to achieve their current high levels of performance. The paper also looks at examples where innovations in the abrasive tool have enabled the development of innovative abrasive processes. A vision of future abrasive product developments is also presented by the authors.     

Sustainability of abrasive processes

This paper presents an overview of research on sustainability of abrasive processes. It incorporates results from a round robin study on “energy-efficiency of abrasive processes” which has been carried out within the scientific technical committee “abrasive processes” (STC G) of CIRP, the content of technical presentations in STC G, and the results of a comprehensive literature study. The approach to sustainability includes environmental, social, and economic sustainability in accordance with the definition proposed in the Brundtland Report of the United Nations [156]. The main focus is on environmental and social sustainability. Economic sustainability will be considered as manufacturing productivity.