Newest Issue

Research Papers: Design Theory and Methodology

J. Mech. Des. 2017;140(3):031101-031101-13. doi:10.1115/1.4038565.

This study examines how the quantity of ideas and analog transfer in design-by-analogy (DbA) are affected by multiple analogs and extraneous information, or noise, using a between-subjects, factorial experiment. To evaluate the effects of multiple analogs and noise on ideation, the study uses two metrics in conjunction with one another; namely, number of ideas (most typical in engineering design) and recognition of high-level principle (more common in psychology). The quantity analysis included three components: number of ideas generated, number of ideas that use example products (analogs and noise stimuli), and number of ideas that use analogs. The results indicate two important findings: (1) providing multiple analogs during ideation had a positive impact on ideation quantity and analog transfer. Specifically, the number of analog-based ideas increased with increasing number of analogs but eventually reached a “saturation point”; (2) introducing extraneous information (noise) diminished the successful mapping of analogs to design solutions. The presence of extraneous information did not significantly affect student designers' ability to identify high-level principles in analogs. The study demonstrated that some extraneous information was perceived as surface similar analogs. Any design analog retrieval method or automated tool will produce extraneous information, and more work is needed to understand and minimize its impact.

Topics: Noise (Sound) , Design
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2018;140(3):031102-031102-9. doi:10.1115/1.4038264.

Functional fixedness refers to a cognitive bias that prevents people from using objects in new ways and more abstractly from perceiving problems in new ways. Supporting people in overcoming functional fixedness could improve creative problem solving and capacities for creative design. A study was conducted to detect whether a relationship exists between participants' tendency to reorient objects presented as stimuli in an alternative uses test (AUT) and their creativity, also measured using the Wallach Kogan (WaKo) pattern meanings test. The AUT measures creativity as a function of identifying alternative uses for traditional objects. The WaKo pattern meanings test detects the ability to see an abstract pattern as different possible objects or scenes. Also studied is whether Kruglanski's need for closure (NFC) scale, a psychological measure, can predict the ability to incorporate reorientation cues when identifying uses. This study revealed highly significant, high correlations between reorientation and several creativity measures, and a correlation between reorientation and the predictability subscale of the NFC scale. A qualitative exploration of participants' responses reveals further metrics that may be relevant to assessing creativity in the AUT.

Commentary by Dr. Valentin Fuster

Research Papers: Design Automation

J. Mech. Des. 2017;140(3):031401-031401-11. doi:10.1115/1.4038566.

In probabilistic approaches to engineering design, including robust design, mean and variance are commonly used as the optimization objectives. This method, however, has significant limitations. For one, some mean–variance Pareto efficient designs may be stochastically dominated and should not be considered. Stochastic dominance is a mathematically rigorous concept commonly used in risk and decision analysis, based on the cumulative distribution function (CDFs), which establishes that one uncertain prospect is superior to another, while requiring minimal assumptions about the utility function of the outcome. This property makes it applicable to a wide range of engineering problems that ordinarily do not utilize techniques from normative decision analysis. In this work, we present a method to perform optimizations consistent with stochastic dominance: the Mean–Gini method. In macroeconomics, the Gini Index is the de facto metric for economic inequality, but statisticians have also proven a variant of it can be used to establish two conditions that are necessary and sufficient for both first and second-order stochastic dominance . These conditions can be used to reduce the Pareto frontier, eliminating stochastically dominated options. Remarkably, one of the conditions combines both mean and Gini, allowing for both expected outcome and uncertainty to be expressed in a single objective which, when maximized, produces a result that is not stochastically dominated given the Pareto front meets a convexity condition. We also find that, in a multi-objective optimization, the Mean–Gini optimization converges slightly faster than the mean–variance optimization.

Commentary by Dr. Valentin Fuster

Research Papers: Design of Direct Contact Systems

J. Mech. Des. 2017;140(3):033301-033301-9. doi:10.1115/1.4038646.

With the advantages of high torque and low noise, traction drive continuously variable transmissions (TDCVTs) have a promising application in future vehicles. However, their efficiency is limited by spin losses caused by the different speed distributions between the contact areas of the traction. To overcome this shortcoming, this paper proposes a novel zero-spin design methodology applicable to any type of TDCVTs. The methodology analyzes the features of TDCVTs in terms of the variation of contact position and the shifting motion of traction components. It also establishes a mathematical model resulting in differential equations, whose general solution is the substitute for the equation of traction components generatrix. After applications of the methodology to two original TDCVTs, two zero-spin TDCVTs are proposed. A computational method of spin ratios, which are in direct proportion to spin losses, of four TDCVTs is introduced. The results of comparisons demonstrate that the proposed methodology can dramatically reduce the spin losses.

Commentary by Dr. Valentin Fuster

Design Innovation Papers

J. Mech. Des. 2017;140(3):035001-035001-7. doi:10.1115/1.4038211.

This study presents the design and validation of on-line pressure-compensating (PC) drip irrigation emitters with a substantially lower minimum compensating inlet pressure (MCIP) than commercially available products. A reduced MCIP, or activation pressure, results in a drip irrigation system that can operate at a reduced pumping pressure, has lower power and energy requirements, requires a lower initial capital cost, and facilitates solar-powered irrigation systems. The technology presented herein can help spread drip irrigation to remote regions and contribute to reducing poverty, particularly in developing countries. The activation pressures of drip emitters at three flow rates were minimized using a genetic algorithm (GA)-based optimization method coupled with a recently published fluid–structure interaction analytical model of on-line PC drip emitter performance. The optimization took into account manufacturing constraints and the need to economically retrofit existing machines to manufacture new emitters. Optimized PC drip emitter designs with flow rates of 3.3, 4.2, and 8.2 lph were validated using precision machined prototype emitters. The activation pressure for all was ≤0.2 bar, which is as low as 16.7% that of commercial products. A limited production run of injection molded 8.2 lph dripper prototypes demonstrated they could be made with conventional manufacturing techniques. These drippers had an activation pressure of 0.15 bar. A cost analysis showed that low MCIP drip emitters can reduce the cost of solar-powered drip irrigation systems by up to 40%.

Commentary by Dr. Valentin Fuster

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