Mechanical Engineering Publications and Research

Evaluating Design Project Creativity in Engineering Design Courses

Ivey Chiu et al. — Thu, 09 May 2013 10:20:45 PDT

Creativity is integral to design success, yet creativity is not well-defined nor easily evaluated. A goal of engineering design courses is to teach creativity, or at least creativity methods, e.g., brainstorming, random stimuli, etc., that when applied, should increase design creativity. However, it is unclear how creativity outcomes can be evaluated, or even if creativity should be evaluated within an engineering design course, such as for a design project. In this paper, we discuss creativity and approaches to evaluating creativity using both the literature and our experiences with evaluating design project creativity. We also describe future work required to further understand and develop methods of evaluating design project creativity with the aim of encouraging students to consciously work towards creative designs.

Misfits, Balance, Requirements, and Systems: thoughts on Alexander's Notes on the Synthesis of Form.

Filippo A. Salustri — Mon, 06 Aug 2012 08:12:26 PDT

The author examines the notion of misfit as presented by Christopher Alexander in his book Notes on the Synthesis of Form. We argue that from the point of view of our current understanding of design, the approach is flawed, but not flawed beyond use. In fact, the core concept of misfit, and how misfits can be addressed, remain as important to design today as when Alexander wrote about them. In this paper, a number of flaws are identified and explored. Subsequently, a new approach, which the author calls a balanced systems approach, is sketched. This approach preserves the intent and core of Alexander’s work, while addressing the identified flaws. The main contribution of this paper is to indicate the shortcomings of Alexander’s approach, but only for the sake of refining it and ensuring it remains relevant and useful.

Understanding the Design Concept Identification Process

Ivey Chiu et al. — Mon, 09 Jul 2012 10:11:26 PDT

In the design literature, the term design concept is often used de facto, or with only a brief definition provided. Despite the cursory definition for concept, the design process rests heavily on concepts, e.g., brainstorming and generating multiple design concepts, and subsequently identifying design concepts for concept selection, evaluation and development, etc. Concepts and concept formation are of particular interest in psychology, as concepts play a central role in human cognition. Concepts and concept identification are also of interest in other fields such as archaeology, bioinformatics and education. In this paper, we explore the process of design concept identification and address the issue of identifying design concepts in free-form text. Our exploratory experiment uses text transcripts of verbal concept generation sessions to first investigate agreeability between human concept identifiers. Next, we perform a language analysis on the transcripts to uncover language patterns that may differentiate between text segments containing concepts and text segments not containing concepts. Our results show that humans are adept at identifying and agreeing upon concepts (average agreeability > 0.70), and that there are significant language differences that may distinguish concept segments from non-concept segments (i.e., non-concept segments have significantly more verbs and borderline significantly more self-references than concept segments). In general, automated concept identification may lead to better integration of early conceptual design with more detailed and computable downstream processes, resulting in a unified design workflow.

Representing CK theory with an action logic

Filippo A. Salustri — Mon, 09 Jul 2012 10:11:23 PDT

CK theory is an interesting and unique theory of engineering design. This paper introduces ALX3d, a formal descriptive version of CK based on the action logic ALX3, which is able to represent aspects of the actions, preferences, beliefs, and knowledge of collaborating, imperfect agents (such as human designers). It is shown that all the basic notions of CK can be rendered in the logic of ALX3d with only one relatively minor change in how the CK terms concept and knowledge are defined and related. A case study of CK is used to show how ALX3d can also be used to describe some “real-world” situations. The advantages of ALX3d are that they recast CK in a form more readily understood by those accustomed to expert, knowledge-based, and formal systems; provide a “scientific” vehicle for reasoning about the design activities it can describe; and define a possible basis for the development of new, computer-based designers’ aids.

An axiomatic theory of engineering design information

Filippo A. Salustri et al. — Fri, 05 Aug 2011 10:04:31 PDT

Recent research in design theory has sought to formalize the engineering design process without particular concern for the paradigm used to model design information. The authors propose that no correct formalization of the design process can be achieved without first formalizing the semantics of the information used in the process. To this end, the authors present a new formal theory of design information. The theory, called the Hybrid Model, is an extended form of axiomatic set theory, and relies on it for consistency and logical rigor. The theory is stated as a collection of axioms, using a standard logic notation. Design entities are modeled by formal units called objects. Generalized functions and relations are used to formalize important ordering schemes and abstraction mechanisms relevant to design, including classification by structure and by function, aggregation, specialization and generalization. The hybrid model is meant not only to aid in the study of the design process itself, but also to improve communications between designers, assist standardization of design specifications, and develop new, powerful software tools to aid the designer in his work.

A new programming paradigm for engineering design software

Filippo A. Salustri et al. — Wed, 06 Jul 2011 08:00:24 PDT

Currently available programming and database systems are insufﬁcient for engineering applications. The authors contend that a logical progression from a formal conceptual model of the engineering domain to a computational model will lead to new programming paradigms capable of directly supporting engineering applications in a rigorous,concise manner. A formal domain model devised by the authors, the Hybrid Model (HM) of design information, is brieﬂy introduced. It is an extension of axiomatic set theory and is discussed in detail elsewhere. HM forms the basis of Designer, a prototype-based object-oriented programming language supporting a signature-based canonical message passing mechanism and multiple inheritance. Designer is implemented using the Scheme programming language. Because Designer satisﬁes a formal conceptual model, and because it is based on a formally speciﬁed language, its robustness and logical validity is superior to that of other languages not founded on formal principles.Designer combines concepts of functional and object oriented programming to provide the formal rigor and ﬂexibility to capture the complex and strongly interrelated information that designers use. Examples demonstrate how Designer represents design information. The results of the authors’ research indicate that Designer can capture design information(including aspects of functional requirements and design intent) effectively and efﬁciently.

Defining the engine design process

J. C. Lockledge et al. — Tue, 07 Jun 2011 11:02:35 PDT

Shortening design lead times while maintaining product quality requires careful planning of the design process. This paper describes a technique used at a major automobile manufacturer to create a simple, flexible process to do just that for their engine design group. The design organization's communications infrastructure was tailored to assure that design information was reliably transmitted through the organization. The mechanism used to achieve this accounts for (a) both component and system perspectives, and (b) the unpredictable nature of the flow of design information by treating unpredictability as an acceptable, even desirable, state of affairs.

Simultaneous Tolerance Synthesis for Manufacturing and Quality

B. Ye et al. — Tue, 10 May 2011 08:13:49 PDT

Tolerance allocation aects product design, manufacturing, and quality. No existing technique has b een found by the authors that takes product design, manufacturing, and quality into account simultaneously. This paper introduces a new concurrent engineering method for tolerance allocation. A nonlinear optimization model has been constructed to implement the method. The model minimizes the combination of quality loss and manufacturing cost simultaneously in a single objective function by setting both process tolerances and design tolerances simultaneously. The purpose of the model is to balance manufacturing cost and quality loss to achieve near-optimal design and process tolerances simultaneously for minimum combined manufacturing cost and quality loss over the life of the product. Compared to other models, this model shows signicant improvements.

Mereotopology for product modeling

Filippo A. Salustri — Thu, 14 Apr 2011 06:23:03 PDT

Mereotopology is the branch of logic that treats the qualitative formalisation of parthood and connection relations between entities. Although it has apparently not yet found use in spatial reasoning for designed product modelling, the author proposes that it is well suited to the task. This paper introduces mereotopology and discusses some of the principles guiding the development of design mereotopology (DMT), a logic being developed by the author for product modelling. Typical MT logics cannot be applied directly to engineering applications because they assume a “common sense” approach, whereas design requires a more strict “engineering sense.” DMT can provide a framework for improved understanding of product modelling knowledge and will lead to better computer-based aids to manipulate that knowledge.

Visualising early engineering design information with diagrams

Filippo A. Salustri et al. — Wed, 16 Mar 2011 11:08:27 PDT

The authors report on their development of computer-based diagramming tools to support the early stages of engineering design and to improve the capacity to innovate. We believe that the human brain is currently the best available device to perform early designing. Thus, good tools will facilitate designers' abilities to “see” information patterns, reflect on them, and achieve insights they may not have achieved otherwise. Our work suggests that diagram layout and style are at least as important as the textual content for their rapid comprehension. These features can be easier to manage in software than in textual descriptions, leading to tools that are more robust and usable. We are working along several lines of inquiry intended to explore particular aspects of the matter, including using existent tools such as concept maps, and developing alternative tools to test ideas about supporting early design by diagramming. While we have not formally evaluated much of our work, anecdotal evidence is encouraging.

Wikis in Design Engineering Research

Filippo A. Salustri et al. — Mon, 17 Jan 2011 07:00:27 PST

Wiki technology has been successfully used for collaboration in various settings. Wikis are, however, rarely used in design engineering research. The authors’ research involved studying how design research occurs and how wikis can be used to support it. The authors observed, and report on, several instances of design research where wikis were used. We ﬁnd that successful application of wikis depends on the software exhibiting certain characteristics. Some of these character-istics include: both WYSIWYG and “raw” editing modes, the ability to edit page elements without editing the entire page, and the ability to comment on or annotate content. To validate these ﬁndings, we are developing a new wiki, the intended user community of which are design researchers. While that development is still ongoing, we report early ﬁndings here.

Improving time-dependent deformation measurement

Hua Lu Cuiru Sun et al. — Wed, 01 Dec 2010 12:33:54 PST

A new method for characterizing shape changes over time may improve nondestructive testing.

Airfoil Performance at Low Reynolds Numbers in the Presence of Periodic Disturbances

S Yarusevych et al. — Fri, 05 Nov 2010 09:11:44 PDT

The boundary-layer separation and wake structure of a NACA 0025 airfoil and the effect of external excitations in presence of structural vibrations on airfoil performance were studied experimentally. Wind tunnel experiments were carried out for three Reynolds numbers and three angles of attack, involving hot-wire measurements and complementary surface flow visualization. The results establish that external acoustic excitation at a particular frequency and appropriate amplitude suppresses or reduces the separation region and decreases the airfoil wake, i.e., produces an increase of the lift and/or decrease of the drag. The acoustic excitation also alters characteristics of the vortical structures in the wake, decreasing the vortex length scale and coherency. Optimum excitation frequencies were found to correlate with the fundamental frequencies of the naturally amplified disturbances in the separated shear layer. The results suggest that acoustic waves play a dominant role in exciting the separated shear layer of the airfoil. Moreover, low-frequency structural vibrations are found to have a significant effect on airfoil performance, as they enhance the sound pressure levels within the test section.

The biomechanical analysis of three plating fixation systems for periprosthetic femoral fracture near the tip of a total hip arthroplasty

James O. Lever et al. — Wed, 27 Oct 2010 08:08:07 PDT

Background A variety of techniques are available for fixation of femoral shaft fractures following total hip arthroplasty. The optimal surgical repair method still remains a point of controversy in the literature. However, few studies have quantified the performance of such repair constructs. This study biomechanically examined 3 different screw-plate and cable-plate systems for fixation of periprosthetic femoral fractures near the tip of a total hip arthroplasty.

Methods Twelve pairs of human cadaveric femurs were utilized. Each left femur was prepared for the cemented insertion of the femoral component of a total hip implant. Femoral fractures were created in the femurs and subsequently repaired with Construct A (Zimmer Cable Ready System), Construct B (AO Cable-Plate System), or Construct C (Dall-Miles Cable Grip System). Right femora served as matched intact controls. Axial, torsional, and four-point bending tests were performed to obtain stiffness values.

Results All repair systems showed 3.08 to 5.33 times greater axial stiffness over intact control specimens. Four-point normalized bending (0.69 to 0.85) and normalized torsional (0.55 to 0.69) stiffnesses were lower than intact controls for most comparisons. Screw-plates provided either greater or equal stiffness compared to cable-plates in almost all cases. There were no statistical differences between plating systems A, B, or C when compared to each other (p > 0.05).

Conclusions Screw-plate systems provide more optimal mechanical stability than cable-plate systems for periprosthetic femur fractures near the tip of a total hip arthroplasty.

A biomechanical assessment of modular and monoblock revision hip implants using FE analysis and strain gage measurements

Habiba Bougherara et al. — Wed, 27 Oct 2010 08:08:06 PDT

Background The bone loss associated with revision surgery or pathology has been the impetus for developing modular revision total hip prostheses. Few studies have assessed these modular implants quantitatively from a mechanical standpoint.

Methods Three-dimensional finite element (FE) models were developed to mimic a hip implant alone (Construct A) and a hip implant-femur configuration (Construct B). Bonded contact was assumed for all interfaces to simulate long-term bony ongrowth and stability. The hip implants modeled were a Modular stem having two interlocking parts (Zimmer Modular Revision Hip System, Zimmer, Warsaw, IN, USA) and a Monoblock stem made from a single piece of material (Stryker Restoration HA Hip System, Stryker, Mahwah, NJ, USA). Axial loads of 700 and 2000 N were applied to Construct A and 2000 N to Construct B models. Stiffness, strain, and stress were computed. Mechanical tests using axial loads were used for Construct A to validate the FE model. Strain gages were placed along the medial and lateral side of the hip implants at 8 locations to measure axial strain distribution.

Results There was approximately a 3% average difference between FE and experimental strains for Construct A at all locations for the Modular implant and in the proximal region for the Monoblock implant. FE results for Construct B showed that both implants carried the majority (Modular, 76%; Monoblock, 66%) of the 2000 N load relative to the femur. FE analysis and experiments demonstrated that the Modular implant was 3 to 4.5 times mechanically stiffer than the Monoblock due primarily to geometric differences.

Conclusions This study provides mechanical characteristics of revision hip implants at sub-clinical axial loads as an initial predictor of potential failure.

Design as...: Thinking of What Design Might Be

Filippo A. Salustri et al. — Thu, 10 Jun 2010 10:29:54 PDT

In this speculative paper, we will consider the question "What is Design?" Instead of a compositional perspective (defining design by its constituents), we will take a qualitative comparative approach, of designing with respect to other phenomena, to illuminate their boundaries. Obviously, these boundaries are not crisp; they ought never be so. Still, learning more about them can help us understand design without requiring their crisp prescription. One may draw the analogy to a jigsaw puzzle: design is the missing piece; to understand its shape (and thus find the piece), we look at the hole in the puzzle, the boundary with other phenomena (jigsaw pieces). For each phenomenon considered, we will use typical, "common sense" dictionary definitions, to help keep the arguments broadly relevant. We will then consider how designing is like and unlike the phenomenon, thereby illuminating the nature of the boundary between it and design. The specific phenomena we will consider include: problem solving, planning, creativity, synthesis, and naturally evolved human ability. In exploring the boundaries between designing and these other phenomena, we seek to illuminate where design stops and those other phenomena begin thereby helping to "define" design. While no clearcut answers result in this paper, we hope that by stimulating further thought and discussion, a more sophisticated and richer understanding of design will eventually result.

Visualizing Information in the Early Stages of Engineering Design

Filippo A. Salustri et al. — Mon, 08 Mar 2010 08:35:15 PST

The early stages of engineering design are the most crucial for successful product development, yet they are not well supported with computer tools compared to other, downstream stages. This paper will discuss recent efforts by the authors to create visual representations of, and tools for, the non- geometric, qualitative information typical in the early stages of engineering design. It appears evident that there is tremendous opportunity to improve the capacity of designers to think both critically and creatively through diagramming in early design, but the field is still embryonic and much work remains to be done.

Designing as Balance-Seeking Instead of Problem-Solving

Filippo A. Salustri et al. — Mon, 01 Mar 2010 10:02:54 PST