Life cycle modeling for adaptive and variant design part 2: case study

Life cycle modeling for design (LCMD) facilitates the incorporation of life cycle modeling into product design by including consideration of uncertainty in a products final specifications. The methodology combines Life Cycle Assessment with probabilistic design methods in a way that reduces information needs. Part 1 of this article presents the basic LCMD methodology. Here, in Part 2, LCMD is used to evaluate material substitution opportunities to reduce resource consumption, reduce life cycle air emissions, and increase the recyclable mass for a Ford C-class sedan. In addition to further illustrating LCMD, the case study identifies vehicle design scenarios that offer modest improvements in environmental performance and related cost tradeoffs.

The synthesis and characterisation of grafted random styrene butadiene for biomedical applications

The work undertaken investigates the spectral, thermal and surface characteristics of a random styrene butadiene rubber (SBR) with monomeric graft(s) of acrylic acid (AA), N-vinyl-2-pyrrolidinone (NVP) or N-isopropylacrylamide (NIPAAm) synthesised using UV polymerisation. The grafted materials were characterised by differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC), attenuated total reflectance infrared Fourier transform spectrometry (ATR-FTIR) and atomic force microscopy (AFM). Thermograph analysis has shown an endothermic transition occurring at ~75 °C for all random SB-g-NVP copolymers, whereas the T _g value for random SB copolymer was found at 60 °C, thus suggesting that a chemical reaction between styrene and NVP had occurred. Similar thermal profiles to that of random SB-g-NVP copolymers were evident when random SB was UV polymerised with AA. When NIPAAm was grafted onto random SB, a notable exothermic transition was evident in all samples tested using DSC. It was established using MDSC that this exothermic transition was caused by the breakdown of crosslinks as a result of UV polymerisation.

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Self-assembled nanowires on semiconductor surfaces

A number of different families of nanowires which self-assemble on semiconductor surfaces have been identified in recent years. They are particularly interesting from the standpoint of nanoelectronics, which seeks non-lithographic ways of creating interconnects at the nm scale (though possibly for carrying signal rather than current), as well as from the standpoint of traditional materials science and surface science. We survey these families and consider their physical and electronic structure, as well as their formation and reactivity. Particular attention is paid to rare earth nanowires and the Bi nanoline, both of which self-assemble on Si(001).Further information within the topic of this review article, including an up-to-date list of relevant publications, can be found on our Website. The address is:

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Information hiding in product development: the design churn effect

Execution of a complex product development project is facilitated through its decomposition into an interrelated set of localized development tasks. When a local task is completed, its output is integrated through an iterative cycle of system-wide integration activities. Integration is often accompanied by inadvertent information hiding due to the asynchronous information exchanges. We show that information hiding leads to persistent recurrence of problems (termed the design churn effect) such that progress oscillates between being on schedule and falling behind. The oscillatory nature of the PD process confounds progress measurement and makes it difficult to judge whether the project is on schedule or slipping. We develop a dynamic model of work transformation to derive conditions under which churn is observed as an unintended consequence of information hiding due to local and system task decomposition. We illustrate these conditions with a case example from an automotive development project and discuss strategies to mitigate design churn.

Nitrogen absorption by Fe-1.04at.%Cr alloy: uptake of excess nitrogen

By dedicated pre-nitriding (at 580 °C in an ammonia/hydrogen gas atmosphere) and de-nitriding (at 470 °C in a hydrogen gas atmosphere) experiments, performed on Fe-1.04at.%Cr alloy, it could be demonstrated that the uptake of “excess” nitrogen by the nitrided ferritic matrix is not due to the presence of iron in chromium-nitride precipitates, as it was suggested previously. The determination of nitrogen-absorption isotherms for these pre-nitrided and de-nitrided Fe-1.04at.%Cr alloy specimens revealed that the total amount of excess nitrogen in the alloy is composed of two parts: (a) nitrogen adsorbed at the precipitate/matrix interface, and (b) nitrogen dissolved interstitially in the ferrite matrix strained by the misfit between (coherent) the CrN precipitates and the matrix.

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Morphology and constitution of the compound layer formed on nitrided Fe–4wt.%V alloy

The microstructure of the compound (“white”) layer formed on the surface of Fe–4wt.%V alloy, by nitriding in a gas mixture of ammonia and hydrogen at 580 °C, has been investigated by employing light and scanning electron microscopy, X-ray diffraction and electron probe microanalysis. The compound layer is dominantly composed of γ^|-Fe₄N nitride. Quantitative analysis of the composition data demonstrated that V is present in the compound layer as VN precipitates, i.e. V is not taken up significantly in (Fe, V) nitrides. A mechanism for compound-layer formation has been proposed.

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Optical switching of a photochromic bis-phenylazo compound in PMMA films

We present our results on a newly synthesized bis-phenylazo derivative, namely bisperfluoroalkylsulfonylamino- arylazomethylene-triphenyl-phosphorane (BAM-TPP). Thin films of BAM-TPP in polymethylmethacrylate (PMMA) matrix were prepared. The films (thickness, d < 60 μm) were exposed to UV-vis light with variable intensity in order to stimulate the photochromic reaction of BAM-TPP. The resulting absorption changes of the BAM-TPP/PMMA films were investigated by spectrophotometry. The absorption spectra reveal that BAM-TPP molecules in PMMA undergo photoisomerization with resulting decrease of absorbance in the range 500–700 nm. Finally, the time response of film transmittance at 514 nm under increasing CW light intensity was recorded, showing that the reverse photochromic process brings the absorbance back to its pristine value. The obtained films thus proved to be suitable for optical switching applications.

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Development and characterisation of error functions in design

As simulation is increasingly used in product development, there is a need to better characterise the errors inherent in simulation techniques by comparing such techniques with evidence from experiment, test and in-service. This is necessary to allow judgement of the adequacy of simulations in place of physical tests and to identify situations where further data collection and experimentation need to be expended. This paper discusses a framework for uncertainty characterisation based on the management of design knowledge leading to the development and characterisation of error functions. A classification is devised in the framework to identify the most appropriate method for the representation of error, including probability theory, interval analysis and Fuzzy set theory. The development is demonstrated with two case studies to justify rationale of the framework. Such formal knowledge management of design simulation processes can facilitate utilisation of cumulated design knowledge as companies migrate from testing to simulation-based design.

Infused design. I. Theory

The paper introduces infused design: an approach for establishing effective collaboration between designers from different engineering fields. In infused design, the design problem representation is brought up to a mathematical meta-level, which is common to all engineering disciplines. The reasoning about the problem is then done by using mathematical terminology and tools that, due to their generality, are the same for all engineers, disregarding their background. This gives engineers an opportunity to infuse their work with knowledge, methods, and solutions shared by specialists from other engineering fields. When these knowledge, methods, and solutions cross disciplinary boundaries, they are provably relevant to any problem in another domain to which it can be transformed. The suggested meta-level consists of general discrete mathematical models, called combinatorial representations (CR). Specific mathematical basis for the combinatorial representations chosen in this paper is graph theory although other representations are possible. We explain the theory of infused design and carefully contrast it with other approaches. This comparison clearly demonstrates the advantages of infused design and its potential. We conclude with several practical issues related to the introduction of infused design into practice and briefly discuss the role of information systems in infused design. A companion paper includes several examples that demonstrate the details of infused design.

Automatic conceptual design using experience-derived heuristics

Conceptual design is considered to be the most difficult phase of engineering design, with success dependent to a great extent on the expertise of the designer. Automation of some aspects of this phase would be of immense practical benefit. It is suggested that the generation of design solutions can be brought about through the application of heuristic knowledge. However, this sort of knowledge is in short supply and has proven difficult to acquire for computer systems. Nevertheless, actual examples of designers' work are more readily available, and the heuristics applied by designers may be considered to be implicit in these examples. The technique of Case-Informed Reasoning has been developed to try to exploit this potential source of knowledge, and applied to the task of fluid power circuit design, a configuration design task. This technique offers a practical approach to conceptual design automation in domains where design knowledge is lacking.

Composite bond inspection

After 50+ years of research to discover a way of determining the in situ strength of an adhesive bond, a method has been found to probe this key parameter. The initial testing on composite joints has shown it to be accurate and reliable. While effective, it is expensive to implement in a production environment and then during the final stages of assembly. A second method of probing the adherent surface prior to bonding is presented that offers the promise of determining adhesion potential before final bond consolidation. These new inspection methods should enable significant increases in structural performance for structures that utilize composite materials. Before examining these two new methods a brief review of past work on adhesive bond strength determination is presented.

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Amorphous and nano crystalline phase formation in Ni<Subscript>2</Subscript>MnGa ferromagnetic shape memory alloy synthesized by melt spinning

Melt spinning technique was used to synthesize Ni₂MnGa ferromagnetic shape memory alloy ribbons. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis of the ribbon synthesized at lower wheel speed (20 m/s) reveal the formation of very fine clusters of austenitic phase of Ni₂MnGa. However at higher wheel speed (30 m/s) the formation of martensite and nanoparticles of Ni₂MnGa with a size range of 10–20 nm in the amorphous matrix is observed. Also an amorphous phase was observed at higher wheel speed in some areas of the ribbon. Annealing (1000 °C, 1 h) of the ribbon synthesized at higher wheel speed resulted in martensite and γ (gamma) phases. Amorphous phase, Ni₂MnGa nanoparticles, and the martensite phase are analyzed in detail.

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Mechanics of the hysteretic large strain behavior of mussel byssus threads

Natural fibers are particularly interesting from a materials point of view since their morphology has been tailored to enable a wide range of macroscopic level functions and mechanical properties. In this paper, we focus on mussel byssal threads which possess a morphology specifically designed to provide a hysteretic yet resilient large strain deformation behavior. X-ray diffraction studies have shown that numerous natural fibers have a multi-domain architecture composed of folded modules which are linked together in series along a macromolecular chain. This microstructure leads to a strong rate and temperature dependent mechanical behavior and one which exhibits a stretch-induced softening of the mechanical response as a result of the underlying morphology evolving with imposed stretched. This paper addresses the development of a constitutive model for the stress–strain behavior of the distal portion of mussel byssal threads based on the underlying protein network structure and its morphology evolving with imposed stretched. The model will be shown to capture the major features of the stress–strain behavior, including the highly nonlinear stress–strain behavior, and its dependence on strain rate and stretch-induced softening.

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Are partwise comparisons reliable?

It is not unusual for decisions in engineering or customer surveys to compare pairs or subsets of alternatives. Surprisingly, this standard, natural approach can cause valued information to be lost: a loss so severe that it can cause demonstrably incorrect decisions. By understanding why these errors occur, we identify an alternative, closely related decision approach that eliminates these problems. Also, we identify the nature of the lost information, and we show how to compute the likelihood that an incorrect outcome will occur.

Towards an ontology of generic engineering design activities

This paper argues that there is no shared understanding (i.e. an ontology) of the design activities that designers perform in the design process. Hence the purpose of the paper was directed towards identifying and classifying a generic set of design activities from published literature into what are referred to as design definition activities, design evaluation activities and design management activities. In an attempt to achieve a shared understanding of these activities, a set of consistent and coherent definitions of these activities are deliberated and presented. A knowledge level representation based on Newells Knowledge Level hypothesis governed by the Principle of Rationality is used to represent a design activity that is motivated by a design goal of that activity through which input knowledge is changed into output knowledge by the design agents knowledge. The ontological completeness, clarity and coherence of activities are evaluated through a protocol analysis and the design process in the domain of electronic design (in particular System-on-a-Chip designs (SoC)).

Multidisciplinary grammars supporting design optimization of buildings

Optimization often focuses only on the variation of parameters while neglecting the consideration of alternative systems. However, the rearrangement of the components of a design offers important scope for improvement. To deal with such variations concerning the system structure of models for multidisciplinary design optimization (MDO), this paper proposes a framework for generating models dynamically using a design grammar with an underlying component-oriented analysis. Decomposition and modification rules support the derivation of alternative optimization model and the formalization of system changes. By linking qualitative characteristics with quantitative analyses, the components serve to assign architectural qualities to economic and environmental resources such as costs and energy consumption and thus to include non-numerical, qualitative characteristics within numerical optimization. The approach is developed with the help of a frame-based hall design and demonstrates system modifications of the optimization model by a specific rule set. The rule set focuses on the structural design but considers the effects for the other essential disciplines involved in the design case. The setup and the prototypical implementation of an optimization model for this design illustrate a way of including grammar-based system variations in MDO.

A quantitative characterization of the optical absorption spectrum associated with hydrogenated amorphous silicon

We propose a quantitative means of characterizing the optical absorption spectrum associated with an amorphous semiconductor. In particular, for a representative hydrogenated amorphous silicon optical absorption experimental data set, through a series of least-squares linear fits of an exponential function to this experimental data set, taken over a number of optical absorption ranges, we determine how the breadth of the optical absorption tail varies along the optical absorption spectrum of hydrogenated amorphous silicon. We find that the quantitative variations in the breadth of the optical absorption tail that are found provide for a clear delineation between the different regions of the optical absorption spectrum of hydrogenated amorphous silicon. We complete this analysis by theoretically determining the form of the optical absorption spectrum using a recently developed empirical model for the density of states functions corresponding to hydrogenated amorphous silicon, this analysis providing a theoretical basis for the interpretation of our results.

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