Research Papers: Design Automation

J. Mech. Des. 2018;140(4):041401-041401-12. doi:10.1115/1.4038927.

This 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 finite element (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.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2018;140(4):041402-041402-9. doi:10.1115/1.4039128.

Hybrid or ensemble surrogate models developed in recent years have shown a better accuracy compared to individual surrogate models. However, it is still challenging for hybrid surrogate models to always meet the accuracy, robustness, and efficiency requirements for many specific problems. In this paper, an advanced hybrid surrogate model, namely, extended adaptive hybrid functions (E-AHF), is developed, which consists of two major components. The first part automatically filters out the poorly performing individual models and remains the appropriate ones based on the leave-one-out (LOO) cross-validation (CV) error. The second part calculates the adaptive weight factors for each individual surrogate model based on the baseline model and the estimated mean square error in a Gaussian process prediction. A large set of numerical experiments consisting of up to 40 test problems from one dimension to 16 dimensions are used to verify the accuracy and robustness of the proposed model. The results show that both the accuracy and the robustness of E-AHF have been remarkably improved compared with the individual surrogate models and multiple benchmark hybrid surrogate models. The computational time of E-AHF has also been considerately reduced compared with other hybrid models.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2018;140(4):041403-041403-13. doi:10.1115/1.4039200.

Design documents and design project footprints accumulated by corporate information technology systems have increasingly become valuable sources of evidence for design information and knowledge management. Identification and extraction of such embedded information and knowledge into a clear and usable format will greatly accelerate continuous learning from past design efforts for competitive product innovation and efficient design process management in future design projects. Most of the existing design information extraction systems focus on either organizing design documents for efficient retrieval or extracting relevant product information for product optimization. Different from traditional systems, this paper proposes a methodology of learning and extracting useful knowledge using past design project documents from design process perspective based on process mining techniques. Particularly different from conventional techniques that deal with timestamps or event logs only, a new process mining approach that is able to directly process textual data is proposed at the first stage of the proposed methodology. The outcome is a hierarchical process model that reveals the actual design process hidden behind a large amount of design documents and enables the connection of various design information from different perspectives. At the second stage, the discovered process model is analyzed to extract multifaceted knowledge patterns by applying a number of statistical analysis methods. The outcomes range from task dependency study from workflow analysis, identification of irregular task execution from performance analysis, cooperation pattern discovery from social net analysis to evaluation of personal contribution based on role analysis. Relying on the knowledge patterns extracted, lessons and best practices can be uncovered which offer great support to decision makers in managing any future design initiatives. The proposed methodology was tested using an email dataset from a university-hosted multiyear multidisciplinary design project.

Topics: Mining , Design , Workflow
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2018;140(4):041404-041404-10. doi:10.1115/1.4038925.

One of the purposes of 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 anticipated and unanticipated, 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 (UNDP). The UNMPI measures how level of poverty within a nation changes year after year, and the PIM measures how an individual's poverty level changes after being affected by an engineered product. The PIM 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).

Commentary by Dr. Valentin Fuster

Research Papers: Design for Manufacture and the Life Cycle

J. Mech. Des. 2018;140(4):041701-041701-13. doi:10.1115/1.4038923.

Part consolidation (PC) is one of the typical design freedoms enabled by additive manufacturing (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 first 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 PC 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.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2018;140(4):041702-041702-10. doi:10.1115/1.4039007.

This study aims to understand the effect of additive manufacturing (AM) on design fixation. Whereas previous research illustrates the positive aspects of AM, 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 the design asked both groups to design for conventional processes, and to include subtractive and formative methods like machining and casting, respectively. Findings showed that the DfAM fixated on nonproducible manufacturing features and produced harder to conventionally manufacture designs, even when told specifically to DfCM. 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 to the negative effect of AM knowledge on designers and provides motivation for treatment methods. This is important if AM 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 if AM is the final manufacturing method—a more common practice nowadays. This work suggests that one should consider the possibility of fixation in design environments where AM precedes larger volume conventional manufacturing.

Commentary by Dr. Valentin Fuster

Research Papers: Design Education

J. Mech. Des. 2018;140(4):042001-042001-9. 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 make it highly 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 two-dimensional (2D) monitors to share three-dimensional (3D) information. Recently, new low-cost virtual reality (VR) 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 a network of this hardware, which allows users to interact with gestures virtually and conducts a study to show its advantages over traditional video conferencing software.

Commentary by Dr. Valentin Fuster

Research Papers: Design of Mechanisms and Robotic Systems

J. Mech. Des. 2018;140(4):042301-042301-13. 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 finite element method simulations.

Commentary by Dr. Valentin Fuster

Research Papers: Design of Direct Contact Systems

J. Mech. Des. 2018;140(4):043301-043301-11. 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 that 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 the pure-rolling contact epicycloid bevel (PCEB for short in this paper). The tooth surface models of PCEBs by face hobbing process are obtained. Next, a sample is represented to show an application of this model. Then, finite element analysis (FEA) is applied to investigate the contact mechanics characteristics of these gears. Finally, 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 PCEBs can mesh correctly and achieve a higher transmission efficiency.

Topics: Gears , Design
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2018;140(4):043302-043302-9. 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: Gears , Cutting , Errors , Gear teeth
Commentary by Dr. Valentin Fuster

Technical Briefs

J. Mech. Des. 2018;140(4):044501-044501-4. doi:10.1115/1.4039202.

In this technical brief, the authors compare the torque capacity of a magnetorheological (MR) fluid brake with a conventional frictional disk brake. In the development of the torque models for both brakes, a mathematical expression for the compared torque ratio is presented. For the frictional disk brake, constant pressure and constant wear theories are considered, while static torque of the MR fluid brake is considered for comparison purpose only. Throughout the analysis, the outer radius of the compared brakes is assumed to be the same to ensure similarity of size, while the inner radius is selected to achieve maximum values of braking torque for both brake designs. Reasonable values of design variables for each brake are obtained from references and adopted in this study for making comparisons between the two designs. In conclusion, it is shown that the torque capacity for a frictional disk brake is 10–18 times greater than the torque capacity for a MR fluid brake of similar size.

Topics: Torque , Fluids , Disks , Brakes , Pressure
Commentary by Dr. Valentin Fuster

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