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Accepted Manuscripts

BASIC VIEW  |  EXPANDED VIEW
research-article  
Hongzhe Zhao, Dong Han and Shusheng Bi
J. Mech. Des   doi: 10.1115/1.4036836
The center shift, a common problem existing in the rotating flexural pivots, is diminished in a multi-beam flexural pivot by the internal interaction among these beams. The objectives of this paper are to develop a model for this flexural pivot and to analyze the interaction. Firstly, the calculus of variations with a Lagrange multiplier is exploited to develop the model based on energy approach. Then the properties of a conservative system are utilized to analyze the constraint characteristics of these beams, and two different load sequences are taken into account to formulate the rotating stiffness of the flexural pivot. The three methods that are used to develop the same model are compared to show their respective advantages, and the analysis of the internal constraints offers several significant qualitative and quantitative design insights. Furthermore, the circular arc motion is expanded to the elliptic arc motion, and an approximate replacement is therefore presented. Finally, the validation of the model and analysis is verified by finite element analysis (FEA).
TOPICS: Stress, Design, Finite element analysis, Modeling, Stiffness, Variational techniques
research-article  
Mostafa Sabbaghi and Sara Behdad
J. Mech. Des   doi: 10.1115/1.4036777
Consumers might be willing to repair their broken devices as long as the associated repair costs do not exceed an undesirable threshold. However, in many cases the technological obsolescence actuates consumers to retire old devices and replace them with new ones rather than extending the product lifecycle through repair. In this paper, we aim to investigate the impact of components’ deterioration profiles and consumers’ repair decisions on the lifespan of devices, and then assesse the anticipated life cycle environmental impacts. A Monte Carlo simulation is developed to estimate the life cycle characteristics such as the average lifespan, the number of failed components’ replacement, and the total repair cost per cycle for a laptop computer. The lifecycle characteristics estimated from simulation model further have been used in a Life Cycle Assessment (LCA) study to quantify the environmental impact associated with different design scenarios. The results reveal the impact of product design as well as consumers’ repair decisions on the product lifespan and the corresponding environmental impacts.
TOPICS: Maintenance, Product design, Cycles, Laptop computers, Simulation models, Simulation, Life cycle assessment, Design
research-article  
Ibrahim Chamseddine and Michael Kokkolaras
J. Mech. Des   doi: 10.1115/1.4036778
Previous work in air transportation system-of-systems design optimization considered integrated aircraft sizing, fleet allocation and route network configuration. The associated nested multidisciplinary formulation posed a numerically challenging optimization problem; therefore, direct search methods with convergence properties were used to solve it. However, the complexity of the blackbox is such that it impedes greatly the solution of larger-scale problems, where the number of considered nodes in the route network is high. The research presented here adopts a rule-based route network design inspired by biological transfer principles. This bio-inspired approach decouples the network configuration problem from the optimization loop, leading to significant numerical simplifications. The usefulness of the bio-inspired approach is demonstrated by comparing its results to those obtained using the nested formulation for a 15-city network. We then consider introduction of new aircraft as well as a larger problem with 20 cities.
TOPICS: Design, Optimization, Transportation systems, Biomimetics, Aircraft
Design Innovation Paper  
Nogill Park
J. Mech. Des   doi: 10.1115/1.4036779
A new hypoid gearing using a common crown rack is introduced. The proposed hypoid gear has no unloaded gear transmission errors. The common crown rack is located at a neutral position between the pinion and gear blanks. An arbitrary generating surface inclined by a pressure angle is prescribed. The proposed hypoid gearing is in point-contact with fulfilling the constant speed ratio along the curved line of action. The synthesis feasibility is numerically verified on the full range of hypoid gears including parallel-, intersect- and crossed- axis gear systems. The marking test on a generated hypoid gearing is in good agreement with the simulation results. From that the unloaded gear transmission error is measured less than the notified commercial CNC machine error, it is shown experimentally that the speed ratio of the proposed hypoid gearing keeps constant.
TOPICS: Gears, Blanks, Spiral bevel gears, Errors, Simulation results, Computer numerical control machine tools, Pressure, Machinery
research-article  
Dipanjan Ghosh, Andrew Olewnik, Kemper Lewis, Junghan Kim and Arun Lakshmanan
J. Mech. Des   doi: 10.1115/1.4036780
Background: A critical task in product design is mapping information from consumer to design space. Currently, this process largely depends on designers identifying and mapping psychological and consumer level factors to engineered attributes. In this way, current methodologies lack provision to test a designer's cognitive reasoning and could introduce bias when mapping from consumer to design space. In addition, current dominant frameworks do not include user-product interaction data in design decision making, nor do they assist designers in understanding why a consumer has a particular perception about a product. Method of approach: This paper proposes a new framework - Cyber-Empathic Design - where user-product interaction data is acquired via embedded sensors. To understand the motivations behind consumer perceptions, a network of latent constructs forms a causal model framework. Structural Equation Modeling (SEM) is used as the parameter estimation and hypothesis testing technique, making the framework falsifiable in nature. Results: To demonstrate the framework, a case study of sensor-integrated shoes is presented, where two models are compared - one Survey-based and one using the Cyber-Empathic framework model. Two methods are used to estimate the parameters and the fit indices - Covariance based SEM and Partial Least Square SEM. It is shown that the Cyber-Empathic framework results in improved fit using both estimation techniques over survey-only SEM. Conclusion: This work demonstrates how low level user-product interaction data can be used to understand and model user perceptions in a way that can support falsifiable design inference.
TOPICS: Design, Product design, Sensors, Modeling, Testing, Decision making, Parameter estimation
research-article  
Wenjian Yang, Huafeng Ding, Yong He and Min Wu
J. Mech. Des   doi: 10.1115/1.4036781
The sketching of kinematic chains is important in the conceptual design of mechanisms. In general, the process of sketching kinematic chains can be divided into two steps, namely sketching topological graphs and converting them into the corresponding kinematic chains. This paper proposes a new method to automatically sketch topological graphs including both planar and non-planar graphs. First, two parameters called Moving Sign (MS) and Moving Sign String (MSS) are defined, based on which a new algorithm is proposed to acquire all feasible layouts of the contracted graph by moving inner edges. All topological graphs synthesized from the same contracted graph are identified to have the shared feasible layouts, and another algorithm is proposed to determine the optimal layout for each topological graph. Then, topological graphs are sketched automatically by determining the location of vertices. The method has low complexity and is easy to be programmed using computer language.
TOPICS: Kinematic chains, Algorithms, Computers, Conceptual design, String
research-article  
Venkata Kamesh Vinjamuri, Mallikarjuna Rao Kuchibhotla and Balaji Srinivasa Rao Annambhotla
J. Mech. Des   doi: 10.1115/1.4036782
Graph theory is a powerful tool in structural synthesis and analysis of planetary gear trains. In this paper, a new algorithm has been developed for detecting degenerate structure in planetary gear trains. The proposed algorithm is based on the concept of fundamental circuits’ rotation graphs. Detection of degeneracy is entirely based on finding one key element. The key element or link that makes planetary gear train into two groups is found in this work. The main advantage of the proposed method lies in the drastic reduction in the required combinatorial analysis compared to other methods available. Algorithm is implemented on 4, 5, 6, 7, 8 ,9-link 1-degree of freedom (dof) planetary gear trains in Appendix I. Results are presented in the Appendix II.
TOPICS: Planetary gears, Degrees of freedom, Trains, Algorithms, Circuits, Rotation
Announcements  
Amy Suski
J. Mech. Des   doi: 10.1115/1.4025965
TOPICS: Design

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