Accepted Manuscripts

Xiaojun Fu, Geng Liu, Shangjun Ma, Ruiting Tong and Teik C. Lim
J. Mech. Des   doi: 10.1115/1.4039005
A kinematic model of the Planetary Roller Screw Mechanism (PRSM) is proposed, which accounts for the run-out errors of the screw, roller, nut, ring gear and carrier, and the position errors of the nut and the pinhole in the carrier. The roller floating region, which contains all the possible positions of the roller inside the pinhole, is obtained by analyzing the axial clearances between mating thread surfaces and the radial clearance between the roller and carrier. The proposed model is based on the constraint that the set of roller floating region is not empty. Then, the additional rigid-body movement on the nut is derived and the path of motion transfer from the screw to the nut is obtained. According to the fundamental property of rigid-body kinematics, the axial velocity of the nut is derived and the transmission error of the PRSM is calculated. The proposed model is verified by comparing the calculated transmission error with experimental one. The results show that the transmission error of the PRSM with run-out and position errors is cyclic with a period corresponding to the rotation period of the screw and the magnitude of the transmission error can be much larger than the lead error of the screw. Besides, due to the run-out and position errors, the roller can move radially or transversally inside the pinhole of the carrier when the elements in the PRSM are regarded as rigid-bodies.
TOPICS: Screws, Kinematics, Errors, Rollers, Rotation, Thread, Clearances (Engineering), Gears
Josh Coburn, John Salmon and Ian Freeman
J. Mech. Des   doi: 10.1115/1.4039006
Since the advent of modern computer-aided design software, engineers have been divorced from the highly collaborative environment previously enjoyed. Today's highly complex designs require modern software tools and the realities of a global economy often constrain engineers to remote collaboration. These conditions often make it impractical to collaborate locally around physical models. Various approaches to creating new collaboration tools and software which alleviate these issues have been tried previously. However, past solutions either used expensive hardware, which is not widely available, or used standard 2D monitors to share 3D information. Recently, new low-cost virtual reality hardware has been introduced which creates a highly immersive 3D experience at a tiny fraction of the cost of previous hardware. This work demonstrates an immersive collaborative environment built using this cost effective system which allows users to view, gesture, and collaborate around virtual models as if collaborating locally around a physical model. A study of the virtual environment compared to traditional video conferencing software is also presented which shows time savings of up to 45% while also increasing communication accuracy. It is expected that as this VR hardware proliferates, immersive collaborative environments, such as the one presented here, will provide significant benefits over current systems.
TOPICS: Hardware, Virtual reality, Collaboration, Computer software, Engineers, Computer-aided design, Economics
Esraa Abdelall, Matthew C. Frank and Richard Stone
J. Mech. Des   doi: 10.1115/1.4039007
This study aims to understand the effect of additive manufacturing (AM) on designer fixation. Whereas previous research illustrates the positive aspects of additive manufacturing, the overarching hypothesis of this work is that it might also have negative effects with respect to conventional manufacturability. In this work, participants from two groups, a Design for Conventional Manufacturing (DfCM) group, and a Design for Additive Manufacturing (DfAM) group were asked to design a basic product. Then, a second iteration of design asked both groups to design for conventional processes; to include subtractive and formative methods like machining and casting, respectively. In the study, the DfAM group showed evidence of fixation on non-producible features and consequently had harder to conventionally manufacture designs in the second iteration, even when told specifically to design for conventional manufacturing. There was also evidence that the complex designs of the DfAM group limited their modeling success and seemed to encourage them to violate more design constraints. This study draws attention toward the effect of the knowledge and use of additive manufacturing technologies on designers and provides motivation for treatment methods. This is important if additive manufacturing is used in prototyping or short run production of parts that are slated for conventional manufacturing later. The issue of design fixation is not a problem, of course, if Additive Manufacturing is the final manufacturing method; a more common practice every day. This work suggests that one should consider possibility of fixation in design environments where AM precedes larger volume conventional manufacturing.
TOPICS: Design, Additive manufacturing, Manufacturing, Modeling, Machining, Casting
Alexandru-Ciprian Zavoianu, Susanne Saminger-Platz, Doris Entner, Thorsten Prante, Michael Hellwig, Martin Schwarz and Klara Fink
J. Mech. Des   doi: 10.1115/1.4039009
We present an effective optimization strategy that is capable of discovering high-quality cost-optimal solution for 2D path network layouts that, among other applications, can serve as templates for complete ascent assembly structures. The main innovative aspect of our approach is that our aim is not restricted to simply synthesizing optimal assembly designs with regard to a given goal, but we also strive to discover the best trade-offs between geometric and domain-dependent optimal designs. As such, the proposed approach is centered on a variably constrained multi-objective formulation of the optimal design task and on an efficient coevolutionary solver. The results we obtained on both artificial problems and realistic design scenarios based on an industrial test case empirically support the value of our contribution to the field of design automation.
TOPICS: Manufacturing, Design, Design automation, Optimization, Tradeoffs
Rulong Tan, Bingkui Chen, Dongyun Xiang and Dong Liang
J. Mech. Des   doi: 10.1115/1.4039008
To avoid the negative influence of sliding contact, this paper tries to investigate the spiral bevels of pure-rolling contact which can be manufactured by existing manufacture technology. In this process, spatial conjugate curve meshing theory and conjugate surface theory are both introduced to investigate the geometric principles and face hobbing process of pure-rolling contact epicycloid bevels (PCEB for short in this paper). the tooth surface models of PCEB by face hobbing process are obtained. Besides, a sample is represented to show an application of this model. Then, finite element analysis(FEA) is applied to investigate the contact mechanical characteristics of these gears. At last, the performance experiment of a prototype is completed to evaluate the deviations between theoretical expectations and practical results. From the FEA and experimental results, it is concluded that, the PCEB can mesh correctly and achieve a higher transmission efficiency.
TOPICS: Engineering prototypes, Mechanical properties, Design, Finite element analysis, Gears
Sheng Yang and Yaoyao Fiona Zhao
J. Mech. Des   doi: 10.1115/1.4038922
Part count reduction (PCR) is one of the typical motivations for using additive manufacturing (AM) processes. However, the implications and trade-offs of employing AM for PCR are not well understood. The deficits are mainly reflected in two aspects: 1) lifecycle-effect analysis of PCR is rare and scattered; 2) current PCR rules lack full consideration of AM capabilities and constraints. To fill these gaps, this paper first summarizes the main effect of general PCR (G-PCR) on lifecycle activities to make designers aware of potential benefits and risks, and discusses in a point-to-point fashion the new opportunities and challenges presented by AM-enabled PCR (AM-PCR). Second, a new set of design rules and principles are proposed to support potential candidate detection for AM-PCR. Third, a dual-level screening and refinement design framework is presented aiming at finding the optimal combination of AM-PCR candidates. In this framework, the first level down-samples combinatory space based on the proposed new rules while the second one exhausts and refines each feasible solution via design optimization. A case study of a motorcycle steering assembly is considered to demonstrate the effectiveness of the proposed design rules and framework. In the end, possible challenges and limitations of the presented design framework are discussed.
TOPICS: Manufacturing, Design, Optimization, Motorcycles, Additive manufacturing, Tradeoffs
Sheng Yang, Florian Santoro and Yaoyao Fiona Zhao
J. Mech. Des   doi: 10.1115/1.4038923
Part consolidation (PC) is one of the typical design freedoms enabled by AM processes. However, how to select potential candidates for PC is rarely discussed. This deficiency has hindered AM from wider applications in industry. Currently available design guidelines are based on obsolete heuristic rules provided for conventional manufacturing processes. This paper firstly revises these rules to take account of AM constraints and lifecycle factors so that efforts can be saved and used at the downstream detailed design stage. To automate the implementation of these revised rules, a numerical approach named part consolidation candidate detection (PCCD) framework is proposed. This framework is comprised of two steps: construct functional and physical interaction (FPI) network and PCCD algorithm. FPI network is to abstractly represent the interaction relations between components as a graph whose nodes and edges have defined physical attributes. These attributes are taken as inputs for the PCCD algorithm to verify conformance to the revised rules. In this PCCD algorithm, verification sequence of rules, conflict handling, and the optimum grouping approach with the minimum part count are studied. Compared to manual ad-hoc design practices, the proposed PCCD method shows promise in repeatability, retrievability, and efficiency. Two case studies of a throttle pedal and a tripod are presented to show the application and effectiveness of the proposed methods.
TOPICS: Manufacturing, Algorithms, Design, Engineering design processes
Ettore Pennestri and Pier Paolo Valentini
J. Mech. Des   doi: 10.1115/1.4038924
Planar motion coordination of a line passing through a point or tangent to a conic is a well known problem in kinematics. In the analytical treatments the line is usually considered unoriented. In this paper, for the first time, it is explored the use of Yaglom algebraic geometry to deduce the equations of circles tangent to three and four homologous planar positions of oriented lines. The analytical developments are based on the dual number representation of oriented lines in a plane. The paper proposes the application of findings to the kinematic synthesis of planar linkages. It is also demonstrated that, for a general planar motion, there is not any line whose five finitely separated positions share the same concurrency point.
TOPICS: Kinematics, Linkages, Algebra, Geometry
Phillip Stevenson, Christopher Mattson, Dr. Kenneth Mark Bryden and Nordica MacCarty
J. Mech. Des   doi: 10.1115/1.4038925
One of the purposes creating products for developing countries is to improve the consumer's quality of life. Currently, there is no standard method for measuring the social impact of these types of products. As a result, engineers have used their own metrics, if at all. Some of the common metrics used include products sold and revenue, which measure the financial success of a product without recognizing the social successes or failures it might have. In this paper we introduce a potential universal metric, the Product Impact Metric (PIM), which quantifies the impact a product has on impoverished individuals -- especially those living in developing countries. It measures social impact broadly in five dimensions: health, education, standard of living, employment quality, and security. By measuring impact multidimensionally, it captures impacts both directly and indirectly related to the product, thereby providing a broader assessment of the product's total impact than with other more specific metrics. The PIM is calculated based on 18 simple field measurements of the consumer. It is inspired by the UN's Multidimensional Poverty Index (UNMPI) created by the United Nations Development Programme. The UNMPI measures how the depth of poverty within a nation changes year after year, and the PIM measures how an individual's quality of life changes after being affected by an engineered product. The Product Impact Metric can be used to measure social impact (using specific data from products introduced into the market) or predict social impact (using personas that represent real individuals).
TOPICS: Engineers, Dimensions, Failure, Education, Developing nations, Security
Mohamed Zanaty, Ilan Vardi and Simon Henein
J. Mech. Des   doi: 10.1115/1.4038926
Compliant mechanisms can be classified according to the number of their stable states and are called multistable mechanisms if they have more than one stable state. We introduce a new family of mechanisms for which the number of stable states is modified by programming inputs, we call such mechanisms programmable multistable mechanisms (PMM). A complete qualitative analysis of a PMM, the T-mechanism, is provided including a description of its multistability as a function of the programming inputs. We give an exhaustive set of diagrams illustrating equilibrium states and their stiffness as one programming input varies while the other is fixed. Constant force behavior is also characterized. Our results use polynomial expressions for the reaction force derived from Euler-Bernoulli beam theory. Qualitative behavior follows from the evaluation of the zeros of the polynomial and its discriminant. These analytical results are validated by numerical FEM simulations.
TOPICS: Simulation, Equilibrium (Physics), Finite element methods, Engineering simulation, Modeling, Finite element model, Polynomials, Stiffness, Computer programming, Compliant mechanisms, Euler-Bernoulli beam theory
Federico Ballo, Giorgio Previati, Massimiliano Gobbi and Giampiero Mastinu
J. Mech. Des   doi: 10.1115/1.4038927
his paper deals with the development and validation of a semi-analytical tire model able to compute the forces at the interface between tire and rim. The knowledge of the forces acting on the rim is of crucial importance for the lightweight design of wheels. The proposed model requires a limited set of data to be calibrated. The model is compared with complete FE models of the tire and rim. Despite its simplicity, the semi-analytical model is able to predict the forces acting on the rim, in agreement with the forces computed by complete FE models. The stress state in the wheel rim, computed by the developed semi-analytical model matches fairly well the corresponding stress state coming from experimental tests.
TOPICS: Tires, Wheels, Stress, Finite element model, Design
yi-pei Shih and Yun-Jun Li
J. Mech. Des   doi: 10.1115/1.4038567
Power skiving for internal gears has drawn increased industry attention in recent years because it has higher precision and productivity than gear shaping or broaching. Yet even though the commonly adopted conical skiving tool has better wear resistance than the cylindrical one, when known design methods are used, the tool geometry is still subject to profile errors. This paper therefore proposes a novel design method for the conical skiving tool and establishes a mathematical model of error-free flank faces. These faces are formed by conjugating the cutting edges on the rake faces - derived from a group of generating gears with progressively decreasing profile shifted coefficients - with the work gear. A mathematical model of the work gear tooth surfaces produced by the cutting edges (over flank faces) of tool at different resharpened depths is then adopted to examine the tooth surface deviations produced with their theoretical equivalents. The results verify the correctness of the mathematical models.
TOPICS: Errors, Gears, Cutting, Design methodology, Gear teeth, Geometry, Wear resistance
Design Innovation Paper  
Rami Alfattani and Craig Lusk
J. Mech. Des   doi: 10.1115/1.4037621
This paper presents a new Bistable Collapsible Compliant Mechanism (BCCM) that is utilized in a Lamina- Emergent Frustum. The mechanism is based on transforming a polygon spiral into spatial frustum shape using a mechanism composed of compliant links and joints that exhibits bistable behavior. A number of mechanism types (graphs) were considered to implement the shape-morphing spiral, including 4-bar, 6-bar, and 8-bar chains. Our design requirements permitted the selection of a particular 8-bar chain as the basis for the BCCM. Bistable behavior was added to the mechanism by introducing snap-through bistability as the mechanism morphs. Parametric CAD was used to perform the dimensional synthesis. The design was successfully prototyped. We anticipate that the mechanism may be useful in commercial small animal enclosures or as a frame for a solar still.
TOPICS: Compliant mechanisms, Chain, Design, Shapes, Computer-aided design, Solar stills
Amy Suski
J. Mech. Des   doi: 10.1115/1.4025965
TOPICS: Design

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