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Editorial

J. Mech. Des. 2014;136(5):050201-050201-1. doi:10.1115/1.4027308.

Last year, I appointed an Ad-hoc committee that consisted of Professor Jon Cagan (CMU), Professor Panos Papalambros (University of Michigan), Professor Jim Schmiedeler (University of Notre Dame), and Professor Janis Terpenny (Iowa State University). Professor Papalambros, the last Editor of Journal of Mechanical Design (JMD), served as the chair of the committee. The charge to the committee was to devise guidelines for the selection of the JMD’s Annual Best Paper Award. The goal of the award is to promote JMD submissions that are of the highest quality and impact.

Commentary by Dr. Valentin Fuster

Research Papers

J. Mech. Des. 2014;136(5):051001-051001-12. doi:10.1115/1.4026495.

Seat style designers transform their ideas into 3-D forms using creative, iterative modeling processes to quickly evolve their designs from concept to reality, while refining the design details of the seat shape. Although the recent introduction of computer-aided styling systems to the design process has greatly enhanced designers' productivity, they still prefer to ideate using “pen and paper.” Here, we propose a sketch-based 3-D modeling system that enables designers to rapidly and intuitively create a seat shape by applying a 2-D sketch to a normalized seat reference model and then evaluating the newly designed model. For this purpose, we describe three modeling techniques that support interactive shape editing: curve manipulation using pen strokes, vertex point manipulation, and tangent vector manipulation. In addition, we propose three methods for the design and functional evaluation of an automotive seat, checking for interference between a seat skin and its frame, checking for foldability among seat components with regard to their positioning, and checking for coupling between a seat model and a digital human body.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051002-051002-11. doi:10.1115/1.4026648.

An important factor in system longevity is service-phase evolvability, which is defined as the ability of a system to physically transform from one configuration to a more desirable configuration while in service. These transformations may or may not be known during the design process, and may or may not be reversible. In a different study, we examined 210 engineered systems and found that system excess and modularity allow a system to evolve while in service. Building on this observation, the present paper introduces mathematical relationships that map a system's excess to that system's ability to evolve. As introduced in this paper, this relationship is derived from elastic potential-energy theories. The use of the evolvability measure, and other related measures presented herein, are illustrated with simple examples and applied to the design of U.S. Navy nuclear aircraft carriers. Using these relationships, we show that the Navy's new Ford-class aircraft carrier is measurably more evolvable than the Nimitz-class carriers. While the ability for systems to evolve is based on excess and modularity, this paper is focused only on excess. The mapping between modularity and evolvability is the focus of another work by the authors.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051003-051003-13. doi:10.1115/1.4025821.

This paper presents two integrated planar-spherical overconstrained mechanisms that are inspired and evolved from origami cartons with a crash-lock base. Investigating the crash-lock base of the origami cartons, the first overconstrained mechanism is evolved by integrating a planar four-bar linkage with two spherical linkages in the diagonal corners. The mechanism has mobility one and the overconstraint was exerted by the two spherical linkages. This mechanism is then evolved into another integrated planar-spherical overconstrained mechanism with two double-spherical linkages at the diagonal corners. The evolved mechanism has mobility one. It is interesting to find that the double-spherical linkage at the corner of this new mechanism is an overconstrained 6R linkage. The geometry evolution is presented and the constraint matrices of the mechanisms are formulated using screw-loop equations verifying mobility of the mechanisms. The paper further reveals the assembly conditions and geometric constraint of the two overconstrained mechanisms. Further, with mechanism decomposition, geometry and kinematics of the mechanisms are investigated with closed-form equations, leading to comparison of these two mechanisms with numerical simulation. The paper further proposes that the evolved overconstrained mechanism can in reverse lead to new origami folds and crease patterns. The paper hence not only lays the groundwork for kinematic investigation of origami-inspired mechanisms but also sheds light on the investigation of integrated overconstrained mechanisms.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051004-051004-7. doi:10.1115/1.4026867.

Rotary engines require seals inserted into each rotor apex to maintain contact with the housing and prevent leaks during internal combustion. These seals are called apex seals and their effectiveness directly influences the engine operation and efficiency. The deviation function (DF) method of rotary engine design has several advantages over the conventional design method with regard to the apex seals, and also finds many more possibilities. The DF method can be used to incorporate the profile of the apex seal into the design process and the rotor profile itself. In the DF method, the seal profile is used as a generating curve and the housing bore profile is a generated curve. The housing is conjugate to the apex seal, and therefore conforms to the seal profile, unlike the conventional rotary engine. Another advantage the DF method has over the conventional method is that different apex seal profiles can be used, resulting in a larger variety of rotary engine designs. This paper introduces the DF method of rotary engine design and selection by the geometric parameters rotor radius, R, and eccentricity, l. In conventional rotary (Wankel) engine design, these parameters are used as a ratio called the K factor. The K factor uniquely identifies a conventional rotary engine profile and is therefore used to associate performance criteria such as displacement, compression ratio, and apex sealing. The DF method can be used to employ the same ratio as a selection tool. Instead of a single profile for each K factor, there is a range of possible DF-designed engine profiles associated with each R/l ratio. The resulting design flexibility is shown using two example deviation functions and the design criteria swept area and maximum theoretical compression ratio. Furthermore, the R/l ratio is not an indication of apex sealing effectiveness because the DF method of rotary engine design and selection separates the engine profile geometry from the apex seal geometry. An apex sealing index is presented to show how the DF method can be used to quantify, analyze, and improve apex sealing.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051005-051005-12. doi:10.1115/1.4026869.

This paper presents case-based reasoning methods for cost estimation and cost uncertainty modeling that may help designers select a new product concept at the early stage of product development. The case-based reasoning methods without cost adjustment (CBR) and with cost adjustment (CBR-A) are compared with analogy-based cost estimation (ABCE) and multivariate linear regression analysis (RA). Under the conditions studied in the illustrative example of this paper (i.e., a single knowledge base, sport utility vehicle (SUV) concepts, and up to five concept attributes), leave-one-out cross-validation results indicate that both CBR-A and RA accurately estimate cost and reliably model cost uncertainty; and optimum attribute sets for the most accurate cost estimation and the most reliable cost uncertainty modeling are different in all methods. The results of this paper indicate that designers may need to carefully select attribute sets by analyzing trade-offs between the accuracy of cost estimation and the reliability of cost uncertainty modeling when product cost is used as a criterion to select concepts.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051006-051006-5. doi:10.1115/1.4026870.

The wear of star-wheel teeth is an important problem in single screw compressors. In order to prolong the service life of star wheels, a new curved flank of the tooth is proposed. Section profile of the tooth flank is a curve, which could be elliptical, hyperbolic, involute, or new defined. The screw groove flank is the envelope surface corresponding to the surface of the tooth flank. During the tooth meshing with the groove, the contact line moves in the tooth flank area.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051007-051007-12. doi:10.1115/1.4026649.
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In designing a microstructural materials system, there are several key questions associated with design representation, design evaluation, and design synthesis: how to quantitatively represent the design space of a heterogeneous microstructure system using a small set of design variables, how to efficiently reconstruct statistically equivalent microstructures for design evaluation, and how to quickly search for the optimal microstructure design to achieve the desired material properties. This paper proposes a new descriptor-based methodology for designing microstructural materials systems. It is proposed to use a small set of microstructure descriptors to represent material morphology features quantitatively. The descriptor set should be able to cover microstructure features at different levels, including composition, dispersion status, and phase geometry. A descriptor-based multiphase microstructure reconstruction algorithm is developed accordingly that allows efficient stochastic reconstructions of microstructures in both 2D and 3D spaces for finite element analysis (FEA) of material behavior. Finally, the descriptor-based representation allows the use of parametric optimization approach to search the optimal microstructure design that meets the target material properties. To improve the search efficiency, this paper integrates state-of-the-art computational design methods such as design of experiment (DOE), metamodeling, statistical sensitivity analysis, and multi-objective optimization, into one design optimization framework to automate the microstructure design process. The proposed methodology is demonstrated using the design of a polymer nanocomposites system. The choice of descriptors for polymer nanocomposites is verified by establishing a mapping between the finite set of descriptors and the infinite dimensional correlation function.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051008-051008-11. doi:10.1115/1.4026650.

This paper presents an efficient uncertainty analysis for estimating the possibility distribution of structural reliability in presence of mixed uncertain variables. The proposed method involves high dimensional model representation for the limit state function approximation, transformation technique to obtain the contribution of the fuzzy variables to the convolution integral and fast Fourier transform for solving the convolution integral. In this methodology, efforts are required in evaluating conditional responses at a selected input determined by sample points, as compared to full scale simulation methods, thus the computational efficiency is accomplished. The proposed method is applicable for structural reliability estimation involving any number of fuzzy and random variables with any kind of distribution.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051009-051009-12. doi:10.1115/1.4026951.

An important part of designing successful products is building empathy for the people for whom the product is intended. Despite recent interest in empathic design techniques, they remain confined primarily to customer needs analysis and design problem definition activities, and much of the evidence for their impact on engineering designs is anecdotal. In this paper, empathic design techniques are formally integrated into the conceptual design process, and their effectiveness is investigated with a controlled idea generation experiment. Empathic experience design (EED) is a structured conceptual design method focused on stimulating creative, user-centered concept generation by engaging designers in empathic experiences as part of concept generation. Empathic experiences are demanding product interaction tasks that are intended to help a design engineer empathize with customers who use a product under a variety of sometimes challenging conditions. Empathic experiences can represent either actual disabilities or situational disabilities, which are experienced by lead users who push a product to its extremes and experience needs prior to the general population. In some cases, these empathic experiences amplify the situational disability as a means of highlighting the challenges of interacting with a particular product or system. A representative example is the use of thick gloves to limit a designer's dexterity and thereby highlight the challenges associated with either actual disabilities, such as arthritis, or situational disabilities, such as extreme cold or fatigue that make it difficult to move one's fingers freely. The EED method precedes concept generation activities with a series of these empathic experiences involving a baseline product to be redesigned. Many professional designers incorporate empathy and empathic experiences into their design practices, but evidence of their impact on resulting designs has been largely anecdotal. In this paper, their effectiveness is investigated formally with strategically designed experiments. The research hypothesis is that empathic experiences, when coupled with concept generation activities, lead to designs that are more original, especially with respect to features that enhance product-user interactions. To test this hypothesis, experiments were conducted on two example problems in which participants were asked to develop concepts for a next-generation product. Experimental groups completed a controlled concept generation task after engaging in empathic experiences with a prototype product to be redesigned. Control groups completed an identical concept generation task after interacting with the prototype products freely. Resulting concepts were analyzed for their originality, technical feasibility, and embodiment of a specific set of innovation characteristics. Results indicate that the experimental participants who were exposed to empathic experiences prior to concept generation produced concepts with significantly higher rates of original product-user interaction features without any sacrifice in technical feasibility. The overall originality of the concepts is also higher for redesign problems with an abundance of existing solutions, indicating that the EED method also helps alleviate design fixation.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051010-051010-9. doi:10.1115/1.4026949.

The rigid-body replacement method is often used when designing a compliant mechanism. The stiffness of the compliant mechanism, one of its main properties, is then highly dependent on the initial choice of a rigid-body architecture. In this paper, we propose to enhance the efficiency of the synthesis method by focusing on the architecture selection. This selection is done by considering the required mobilities and parallel manipulators in singularity to achieve them. Kinematic singularities of parallel structures are indeed advantageously used to propose compliant mechanisms with interesting stiffness properties. The approach is first illustrated by an example, the design of a one degree of freedom compliant architecture. Then, the method is used to design a medical device where a compliant mechanism with three degrees of freedom is needed. The interest of the approach is outlined after application of the method.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2014;136(5):051011-051011-9. doi:10.1115/1.4026824.

As observed in the design of antenna reflectors and rocket bodies, both flat and 3D-shaped honeycomb cores are used in the field of aerospace engineering. This study illustrates a new strategy to fabricate arbitrary cross-section honeycombs with applications of advanced composite materials by using the concept of the kirigami honeycomb, which is made from single flat sheets and has periodical slits resembling origami. The authors also describe a method of applying this technique to advanced composite materials. Applying the partially soft composite techniques, 3D shaped composite honeycombs are manufactured, and some typical samples are shown with their folding line diagrams.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Mech. Des. 2014;136(5):054501-054501-8. doi:10.1115/1.4026991.

Product design success depends on the engineering performance of the product and also on the reaction of external stakeholders such as customers, retailers, and policymakers. This article illustrates how an early-stage engineering design performance model can be incorporated into a decision framework representing customers, retailers, and policymakers to assess the revenue potential for different technologies. Sensitivity analysis is performed for revenue and other stakeholder decision criteria with respect to the design performance measures. We illustrate our approach for photovoltaic panels in the context of the residential solar electricity generation system market in New South Wales, Australia that experienced a variety of federal and state government incentive programs between 2010 and 2012. The analysis is based on engineering performance modeling, discrete choice demand modeling, and cost modeling all with simplifying assumptions.

Commentary by Dr. Valentin Fuster

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