Cityplot is a new visualization technique for engineering design that uses a dimensionally-reduced representation of the design decisions to represent the mapping from the decisions to the criteria upon which a design is judged. The shown Cityplot depicts possible CubeSat constellations to support the 2007 Earth Science Decadal Survey. Each constellation is comprised of up to 4 CubeSats and each CubeSat can select from a list of 7 instruments. Possible CubeSat constellations are “cities” and are placed in a 2d space to be visualized. An individual constellation can also be seen as a table of instruments (rows) being present (black) on a given CubeSat (columns). The benefits, costs and risks of each possible constellation are represented as color-coded “buildings” in each “city”. The criteria in this example are: a tiered count of satisfied Decadal objectives (blue), the average CubeSat Technology Readiness Level (red), lifecycle cost (green), maximum number of lost instruments upon loss of a single satellite (black). A taller building indicates the possible constellation performs better in that criteria. Dark purple “roads” between two designs indicate that only one instrument is either added to or removed from one CubeSat to make one constellation identical to the other. Cityplot simultaneously shows sensitivity of criteria to decisions, criteria tradeoffs and design families via a quick intuitive view of the design space.
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The synthesis of functional molecular mechanisms is constrained by the notorious difficulties in fabricating nano-links of prescribed shapes and sizes. Thus, the classical mechanism synthesis methods, which assume the ability to manufacture any designed links, cannot provide a systematic process for designing molecular mechanisms. We propose a new approach to build functional mechanisms with prescribed mobility by only using elements from a predefined "link soup". The resulting synthesis procedure is the first of its kind that is capable of systematically synthesizing functional linkages with prescribed mobility constructed from a soup of primitive entities. Furthermore, the proposed systematic approach outputs the ATLAS of candidate mechanisms, which can be further processed for downstream applications. Although the scope of this technique is rather general, its immediate application is the design of molecular machines assembled from nano-links that either exist in nature or can be fabricated.
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Darren J. Hartl, Edgar Galvan, Richard J. Malak and Jeffrey W. Baur
J. Mech. Des 138(3), 031402; doi: 10.1115/1.4032268
This work is the first demonstration of the use of a parameterized approach to design optimization on a complex engineering problem. Parameterized optimization solves a family of optimization problems as a function of exogenous parameters. When applied to a subsystem of interest, it results in general knowledge about the capabilities of the subsystem rather than a restrictive point solution. The motivation is that it often is necessary to advance the development of a subsystem independent of system-level specifics. This is true during initial research and development efforts or in sensitive military and competitive industrial design environments in which compartmentalization of information is common and necessary. It also is important in systems development projects when the need for concurrency often requires subsystem designers to make progress in the absence of full information about other interfacing subsystems. We solve this specialized design problem using the predictive parameterized Pareto genetic algorithm (P3GA). The approach is demonstrated for the multifunctional design of a structurally-integrated liquid metal circuit intended to provide integrated cooling functionality. A family of optimal design solutions associated with values of external parameters (bounded real numbers) is computed efficiently using P3GA. The demonstration employs both high- and low-fidelity multi-physical engineering models seamlessly and results in general knowledge about the subsystem as a function of parameters associated with other interfacing subsystems.
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Kurt Maute, Anton Tkachuk, Jiangtao Wu, H. Jerry Qi, Zhen Ding and Martin L. Dunn
J. Mech. Des 137(11), 111402; doi: 10.1115/1.4030994
Multi-material polymer printers allow the placement of different materials within a composite. The individual material phases can be spatially arranged and shaped in an almost arbitrary fashion. Utilizing the shape memory behavior of at least one of the material phases, active composites can be 3D printed such that they deform from an initially flat plate into a curved structure. To navigate this vast design space, systematically and efficiently explorer design options, and find an optimum layout of the composite this paper presents a novel design optimization approach. The optimization approach combines a level set method for describing the material layout and a generalized formulation of the extended finite element method (XFEM) for predicting the response of the printed active composite (PAC). This combination of methods yields optimization results that can be directly printed without the need for additional post-processing steps. The proposed optimization method is studied with examples where the target shapes correspond to a plate-bending type deformation and to a localized deformation. The optimized designs are 3D printed and the XFEM predictions are compared against the experimental measurements. The design studies demonstrate the ability of the proposed optimization method to yield a crisp and highly resolved description of the optimized material layout that can be realized by 3D printing.
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Toward a Unified Design Approach for Both Compliant Mechanisms and Rigid-Body Mechanisms: Module Optimization
Lin Cao, Allan T. Dolovich, Arend L. Schwab, Just L. Herder and Wenjun (Chris) ZhangJ. Mech. Des 137(12), 122301; doi: 10.1115/1.4031294
Rigid-body mechanisms (RBMs) and compliant mechanisms (CMs) are traditionally treated in significantly different ways. In this paper, we present an approach to the synthesis of both RBMs and CMs. In this approach, RBMs and CMs are generalized into mechanisms that consist of five basic modules, including Compliant Link (CL), Rigid Link (RL), Pin Joint (PJ), Compliant Joint (CJ), and Rigid Joint (RJ). The link modules and joint modules are modeled with beam and hinge elements, respectively, in a geometrically nonlinear finite element solver, and subsequently a discrete beam-hinge ground structure model is established. Based on this discrete beam-hinge model, a procedure that follows topology optimization is developed, called module optimization. Particularly, in the module optimization approach, the states (both presence or absence and sizes) of joints and links are all design variables, and one may obtain a RBM, a partially CM, or a fully CM for a given mechanical task. The proposed approach has thus successfully addressed the challenge in the type and dimensional synthesis of RBMs and CMs. Three design examples of the path generator are discussed to demonstrate the effectiveness of the proposed approach.
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Redundancy Allocation Optimization for Multistate Systems With Failure Interactions Using Semi-Markov Process
Adding redundancy is a widely used method in engineering to improve the system reliability. How to add redundancy, (i.e., to meet the reliability requirement with the minimum cost), is an interesting topic in system design. Traditionally, the optimal redundancy allocation scheme is obtained under two simplified assumptions, i.e., binary states of each component and no failure dependency between components. The binary-state assumption assumes that each component and the entire system can only have two states: fully operational and completely failed. The failure independency assumption assumes no failure interaction between components, i.e., one component failure will not affect the failure process of other components. Although those two assumptions can simplify the analysis, they may lead to inaccurate reliability predictions and thus results in doubtful and misleading redundancy allocation scheme which in fact may not meet the reliability requirement. This work proposes a method to obtain the optimal redundancy allocation scheme by using the Semi-Markov process and optimization techniques without those two simplified assumptions. The target system is a type of commonly-seen system having multiple states and failure interactions. The target system contains a main subsystem providing the required output and an auxiliary subsystem helping the main subsystem function normally, such as the rotating subsystem and the lubricating subsystem, the computer mother board and the fan, and so on. A case study of a shipboard power electronic cabinet demonstrates the applicability of the proposed approach.
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Kazuko Fuchi, Philip R. Buskohl, Giorgio Bazzan, Michael F. Durstock, Gregory W. Reich, Richard A. Vaia and James J. Joo
J. Mech. Des 137(9), 091401; doi: 10.1115/1.4030876
Origami structures morph between 2D and 3D configurations, and their efficient shape reconfigurations show potential for many engineering applications. However, the enormity of the design space and the complex relationship between origami-based geometries and engineering metrics place a severe limitation on design strategies based on intuition. This work proposes a physics-based origami design method using topology optimization that determines an optimal crease pattern for a folding by adding or removing folds based on a design metric. Optimization techniques and mechanical analysis are also co-utilized to identify an action origami building block and determine the optimal network connectivity between multiple actuators.
Sen Lin Longyu Zhao James K. Guest Timothy P. Weihs Zhenyu Liu
J. Mech. Des 137(8), 081402 (Aug 01, 2015); doi: 10.1115/1.4030297
Fixed geometry fluid diodes are devices that allow fluid to flow in one direction but inhibit flow in the reverse direction. Unlike valves, which have moving parts, fixed geometry fluid diodes achieve this effect by using the inertia of the fluid to guide flow into tortuous paths in the reverse flow case. Topology optimization is used in this paper to design diodes of various aspect ratios, including an example to reproduce the Tesla valve, a fixed geometry diode originally designed and patented by Nicola Tesla. The objective function is to maximize diodicity, measured as the ratio of pressure drop in the reverse flow case to the forward flow case, and a gradient-based optimizer is used to solve the topology optimization formulation. An optimized design was 3D printed and experimentally tested to verify diode-like behavior.
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Systematic Design Optimization of the Metamaterial Shear Beam of a Nonpneumatic Wheel for Low Rolling Resistance
Authors: Christopher Czech, Paolo Guarneri, Niranjan Thyagaraja, Georges Fadel
J. Mech. Des.. 2015;137(4):041404-041404-9. doi:10.1115/1.4029518
Design requirements for engineered components are growing more complex and specific, with heavier emphases on efficiencies like weight and energy considerations. Often times, these considerations require the component to be constructed from materials that do not occur naturally. Instead, a metamaterial, one with properties not exhibited naturally by any known material, may be tailored to achieve the design requirements. Some examples include metamaterials with large strength to weight ratios, low energy loss moduli, or specified optical properties. However, designing these materials in a systematic manner has remained an engineering challenge, as linking the overall design requirements to the material requirements (a multiscale design problem) is not an elementary task. In this research, a method to design a shear layer metamaterial for a non-pneumatic wheel using a two-level optimization approach is presented. The design requirements for the shear layer metamaterial are determined in a top-level optimization, and mesostructures with the desired properties are designed using novel topology optimization methods at the material structure level. Inspired by honeycomb structures, a half-period staggered unit cell connectivity was utilized to change the inherent symmetry between unit cell layers. One geometry found using this staggered connectivity, the auxetic honeycomb (pictured below), is shown to be an optimum to the minimum volume topology optimization problem for materials subjected to pure shear boundary conditions. This is the first evidence supporting this structure as an optimum of a structural problem in shear deformation.
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In joint replacement surgery, Patient Specific Surgical Guides (PSSGs) are used for accurate alignment of implant components. PSSGs are designed preoperatively to have a geometric fit with the patient’s bone such that the incorporated guidance for drilling or cutting is instantly aligned (a). It is essential that the position of the PSSG is maintained, and hence, the influence of the location and direction of the pushing force should be minimal. The extent that the pushing force may vary is what we refer to as docking robustness. In this article, we present a docking robustness framework comprising quantitative measures and graphical tool. The contact efficiency and guide efficiency measures can successively be used to find appropriate contact locations and an appropriate location for the application surface. Robustness maps (b) graphically depict for a chosen contact set the allowed variation in the surgeons pushing force. An optimization of the PSSG dimensions for the distal femur shows that twelve contacts already result in a relatively high contact efficiency. The re-located application surface S2 (b) increases the guide efficiency as it is located in brighter parts of the robustness map.
This section includes brief descriptions of articles soon to be or recently published by the Journal of Mechanical Design. These featured articles highlight recent research developments and emerging trends in mechanical design. For Abstracts and Full Articles please see ASME's Digital Collection.