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Editorial

J. Mech. Des. 2012;134(3):030201-030201-1. doi:10.1115/1.4006105.
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You can recognize the many faces of design by looking at the many different professional societies that promote design around the world. These societies may have roots in engineering or architecture or industrial design but they all share the view of design as the vanguard of innovation and as the creative front end of the production of goods and services.

Topics: Design
Commentary by Dr. Valentin Fuster

Guest Editorial

J. Mech. Des. 2012;134(3):030301-030301-2. doi:10.1115/1.4006185.
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There has been significant European interest in design research and education over many years, with particularly strong research traditions especially in the ‘design science/theory of technical systems’ movement in Germany, Switzerland, Denmark, and the Czech Republic in the second half of the 20th century and in the “design methods” movement that started in the UK in the 1960s. This interest led to the first International Conference on Engineering Design (ICED) being held in Rome in 1981, and in the early eighties to the Workshop Design Konstruktion (WDK) organization being established under the inspiration of Vladimir Hubka of Swiss Federal Technical University (ETH) in Zürich, supported by Mogens Andreasen of the Technical University of Denmark and Umberto Pighini of the University of Rome. WDK and ICED were instrumental in contributing to a flourishing in design research in the last two decades of the 20th century, with conferences held in different European locations every 2 years (with one foray across the Atlantic to Boston in 1987), culminating in more than 600 people meeting in Munich in August 1999 and with active programmes of design research in many European countries.

Commentary by Dr. Valentin Fuster

Research Papers

J. Mech. Des. 2012;134(3):031001-031001-11. doi:10.1115/1.4005595.

Traditional reliability analysis generally uses probability approach to quantify the uncertainty, while it needs a great amount of information to construct precise distributions of the uncertain parameters. In this paper, a new reliability analysis technique is developed based on a hybrid uncertain model, which can deal with problems with limited information. All uncertain parameters are treated as random variables, while some of their distribution parameters are not given precise values but variation intervals. Due to the existence of the interval parameters, a limit-state strip enclosed by two bounding hyper-surfaces will be resulted in the transformed normal space, instead of a single hyper-surface as we usually obtain in conventional reliability analysis. All the limit-state strips are then summarized into two different classes and corresponding reliability analysis models are proposed for them. A monotonicity analysis is carried out for probability transformations of the random variables, through which effects of the interval distribution parameters on the limit state can be well revealed. Based on the monotonicity analysis, two algorithms are then formulated to solve the proposed hybrid reliability models. Three numerical examples are investigated to demonstrate the effectiveness of the present method.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):031002-031002-10. doi:10.1115/1.4005620.

This paper presents a backwards design method for mechanical conceptual design. The method involves starting with a very idealistic semiworking solution and then systematically solving the unworkable parts of the solution until a complete solution is found. The method can work in conjunction with other methods such as Theory of Inventive Problem Solving (TRIZ) or brainstorming. The method tries to exploit the principle that it is easier to critique and modify a design than it is to create a fully working solution in one go. The visual nature of the method means that it is suited to design problems where geometry is important such as mechanism design and machine design. Three case studies of conceptual design are presented. The case studies involve a novel clutch, a novel rotary damping mechanism and a novel worm gearbox. Each of these designs won at least one national design competition in the UK. A simple design experiment has been carried out which indicated that the backwards design method was at least as effective as the morphological chart method for a simple machine design exercise.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):031003-031003-11. doi:10.1115/1.4005601.

Origami and paperfolding techniques may inspire the design of structures that have the ability to be folded and unfolded: their geometry can be changed from an extended, servicing state to a compact one, and back-forth. In traditional origami, folds are introduced in a sheet of paper (a developable surface) for transforming its shape, with artistic, or decorative intent; in recent times the ideas behind origami techniques were transferred in various design disciplines to build developable foldable/unfoldable structures, mostly in aerospace industry (Miura, 1985, “Method of Packaging and Deployment of Large Membranes in Space,” Inst. Space Astronaut. Sci. Rep., 618 , pp. 1–9; Ikema , 2009, “Deformation Analysis of a Joint Structure Designed for Space Suit With the Aid of an Origami Technology,” 27th International Symposium on Space Technology and Science (ISTS)). The geometrical arrangement of folds allows a folding mechanism of great efficiency and is often derived from the buckling patterns of simple geometries, like a plane or a cylinder (e.g., Miura-ori and Yoshimura folding pattern) (Wu , 2007, “Optimization of Crush Characteristics of the Cylindrical Origami Structure,” Int. J. Veh. Des., 43 , pp. 66–81; Hunt and Ario, 2005, “Twist Buckling and the Foldable Cylinder: An Exercise in Origami,” Int. J. Non-Linear Mech., 40 (6), pp. 833–843). Here, we interest ourselves to the conception of foldable/unfoldable structures for civil engineering and architecture. In those disciplines, the need for folding efficiency comes along with the need for structural efficiency (stiffness); for this purpose, we will explore nondevelopable foldable/unfoldable structures: those structures exhibit potential stiffness because, when unfolded, they cannot be flattened to a plane (nondevelopability). In this paper, we propose a classification for foldable/unfoldable surfaces that comprehend non fully developable (and also non fully foldable) surfaces and a method for the description of folding motion. Then, we propose innovative geometrical configurations for those structures by generalizing the Miura-ori folding pattern to nondevelopable surfaces that, once unfolded, exhibit curvature.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):031004-031004-14. doi:10.1115/1.4005600.

Many structures in the real world show nonlinear responses. The nonlinearity may be due to some reasons, such as nonlinear material (material nonlinearity), large deformation of the structures (geometric nonlinearity), or contact between the parts (contact nonlinearity). Conventional optimization algorithms considering the nonlinearities are fairly difficult and expensive because many nonlinear analyses are required. It is quite difficult to perform topology optimization considering nonlinear static behavior because of the many design variables. In the current element density based topology optimization considering nonlinear behavior, low-density finite elements cause serious numerical problems due to excessive mesh distortion. Updating the material of the finite elements based on the density is considerably complicated because of the relationship between the element density and structural material. The equivalent static loads method for nonlinear static response structural optimization (ESLSO) has been proposed for size and shape optimization. The equivalent static loads (ESLs) are defined as the linear static load sets which generate the same displacement field from nonlinear static analysis. In this research, a new algorithm is proposed for topology optimization considering all kinds of nonlinearities by modifying the existing ESLSO. The new ESLSO can overcome the difficulties which may occur in topology optimization with nonlinear static behavior. A nonlinear static response optimization problem is converted to cyclic use of linear static response optimization with ESLs. Therefore, the new ESLSO can generate results of nonlinear static response topology optimization by using well established nonlinear static analysis and linear static response topology optimization methods. Four structural examples are demonstrated using the finite element method. Different kinds of nonlinearities are involved in each example.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):031005-031005-9. doi:10.1115/1.4005865.

Force regulation is a challenging problem for robot end-effectors when interacting with an unknown environment. It often requires sophisticated sensors with computerized control. This paper presents an adjustable constant-force mechanism (ACFM) to passively regulate the contact force of a robot end-effector. The proposed ACFM combines the negative stiffness of a bistable mechanism and positive stiffness of a linear spring to generate a constant-force output. Through prestressing the linear spring, the constant-force magnitude can be adjusted to adapt to different working environments. The ACFM is a monolithic compliant mechanism that has no frictional wear and is capable of miniaturization. We propose a design formulation to find optimal mechanism configurations that produce the most constant-force. A resulting force to displacement curve and maximal stress curve can be easily manipulated to fit a different application requirement. Illustrated experiments show that an end-effector equipped with the ACFM can adapt to a surface of variable height, without additional motion programming. Since sensors and control effort are minimized, we expect this mechanism can provide a reliable alternative for robot end-effectors to interact friendly with an environment.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):031006-031006-10. doi:10.1115/1.4005866.

The creation of novel kinematic structures of mechanisms still represents a major challenge in the quest for developing new, innovative devices. In this setting, computer models that can automatically generate and visualize all possible independent structures in an intuitive manner prove to be valuable as a support in the creative process of the designer. This paper proposes an automatic approach for establishing the complete atlas database of 2-DOF kinematic chains and a systematic approach for the creative design of mechanisms based on such an atlas. First, the transformation of the kinematic structure into a graph-based representation is addressed. Then, an approach for the generation of all nonfractionated topological graphs of 2-DOF (degrees of freedom) kinematic chains using contracted graphs as well as a method for synthesizing all the fractionated topological graphs through the combination of corresponding 1-DOF kinematic chains are addressed. Based on these methods, the complete atlas database of 2-DOF kinematic chains up to 15 links is established in this paper for the first time. Using this complete database, a systematic approach for the creative design of mechanisms can be derived, as illustrated for the example of an 11-link 2-DOF rode tractor.

Topics: Chain , Design , Databases
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):031007-031007-11. doi:10.1115/1.4005860.

Usage context-based design (UCBD) is an emerging design paradigm where usage context is considered as a critical part of driving factors behind customers’ choices. Here, usage context is defined as all aspects describing the context of product use that vary under different use conditions and affect product performance and/or consumer preferences for the product attributes. In this paper, we propose a choice modeling framework for UCBD to quantify the impact of usage context on customer choices. We start with defining a taxonomy for UCBD. By explicitly modeling usage context’s influence on both product performances and customer preferences, a step-by-step choice modeling procedure is proposed to support UCBD. Two case studies, a jigsaw example with stated preference data and a hybrid electric vehicle example with revealed preference data, demonstrate the needs and benefits of incorporating usage context in choice modeling.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):031008-031008-12. doi:10.1115/1.4005619.

This paper proposes a new methodology for uncertainty quantification in systems that require multidisciplinary iterative analysis between two or more coupled component models. This methodology is based on computing the probability of satisfying the interdisciplinary compatibility equations, conditioned on specific values of the coupling (or feedback) variables, and this information is used to estimate the probability distributions of the coupling variables. The estimation of the coupling variables is analogous to likelihood-based parameter estimation in statistics and thus leads to the proposed likelihood approach for multidisciplinary analysis (LAMDA). Using the distributions of the feedback variables, the coupling can be removed in any one direction without loss of generality, while still preserving the mathematical relationship between the coupling variables. The calculation of the probability distributions of the coupling variables is theoretically exact and does not require a fully coupled system analysis. The proposed method is illustrated using a mathematical example and an aerospace system application—a fire detection satellite.

Commentary by Dr. Valentin Fuster

Design Education

J. Mech. Des. 2012;134(3):032001-032001-11. doi:10.1115/1.4005858.

Second-hand market value is important for manufacturers in that it affects the profitability of both new product sales and end-of-life recovery. To gain a better understanding of second-hand market value, this paper presents an empirical study of buy-back price using laptop computers and mobile phones as examples. A thousand items that were on the market in recent years were examined, and their current buy-back prices were estimated using the pricing engine of a real buy-back company. The statistical analysis provided a model that could assess the value of used products. The model links a product’s specifications to its second-hand market value. It also incorporates the impacts of product age and cosmetic and hardware conditions. Based on the results of the analysis, the design implications for improving the value of used products were discussed.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Mech. Des. 2012;134(3):034501-034501-4. doi:10.1115/1.4005618.

In this paper, involute profiles are used for the design of screw driver and screw heads instead of traditional straight line profiles to increase their load capacity and durability. New screw driver profiles have lower contact stress than traditional screw drivers due to the surface contact between screw driver and screw head. This enables the involute screw drivers to sustain higher load capacity than traditional screw drivers and reduce the material failure at the tip portions for both screw drivers and screw heads. Four different designs of screw driver profiles are provided for illustration.

Topics: Screws , Stress , Design
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2012;134(3):034502-034502-7. doi:10.1115/1.4005863.

Validation of computational models with multiple, repeated, and correlated functional responses for a dynamic system requires the consideration of uncertainty quantification and propagation, multivariate data correlation, and objective robust metrics. This paper presents a new method of model validation under uncertainty to address these critical issues. Three key technologies of this new method are uncertainty quantification and propagation using statistical data analysis, probabilistic principal component analysis (PPCA), and interval-based Bayesian hypothesis testing. Statistical data analysis is used to quantify the variabilities of the repeated tests and computer-aided engineering (CAE) model results. The differences between the mean values of test and CAE data are extracted as validation features, and the PPCA is employed to handle multivariate correlation and to reduce the dimension of the multivariate difference curves. The variabilities of the repeated test and CAE data are propagated through the data transformation to the PPCA space. In addition, physics-based thresholds are defined and transformed to the PPCA space. Finally, interval-based Bayesian hypothesis testing is conducted on the reduced difference data to assess the model validity under uncertainty. A real-world dynamic system example which has one set of the repeated test data and two stochastic CAE models is used to demonstrate this new approach.

Commentary by Dr. Valentin Fuster

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