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Research Papers: Design Automation

J. Mech. Des. 2017;140(2):021401-021401-13. doi:10.1115/1.4038333.

Multidisciplinary systems with transient behavior under time-varying inputs and coupling variables pose significant computational challenges in reliability analysis. Surrogate models of individual disciplinary analyses could be used to mitigate the computational effort; however, the accuracy of the surrogate models is of concern, since the errors introduced by the surrogate models accumulate at each time-step of the simulation. This paper develops a framework for adaptive surrogate-based multidisciplinary analysis (MDA) of reliability over time (A-SMART). The proposed framework consists of three modules, namely, initialization, uncertainty propagation, and three-level global sensitivity analysis (GSA). The first two modules check the quality of the surrogate models and determine when and where we should refine the surrogate models from the reliability analysis perspective. Approaches are proposed to estimate the potential error of the failure probability estimate and to determine the locations of new training points. The three-level GSA method identifies the individual surrogate model for refinement. The combination of the three modules facilitates adaptive and efficient allocation of computational resources, and enables high accuracy in the reliability analysis result. The proposed framework is illustrated with two numerical examples.

Commentary by Dr. Valentin Fuster

Research Papers: Design for Manufacture and the Life Cycle

J. Mech. Des. 2017;140(2):021701-021701-15. doi:10.1115/1.4038069.

Manufacturing systems need to be designed to cope with products’ variety and frequent changes in market requirements. Switching between product families in different production periods often requires reconfiguration of the manufacturing system with associated additional cost and interruption of production. A mixed integer linear programing (MILP) model is proposed to synthesize manufacturing systems based on the co-platforming methodology taking into consideration machine level changes including addition or removal of machine axes and changing setup as well as system level changes such as addition or removal of machines. The objective is to minimize the cost of change needed for transition between product families and production periods. An illustrative numerical example and an industrial case study from tier I automotive supplier are used for verification. Finally, the effect of maintaining a common core of machines in the manufacturing system on the total capital and change cost is investigated. It has been demonstrated that synthesizing manufacturing systems designed using the co-platforming strategy reduces the total investment cost including initial cost of machines and cost of reconfiguration.

Commentary by Dr. Valentin Fuster

Research Papers: Design of Direct Contact Systems

J. Mech. Des. 2017;140(2):023301-023301-13. doi:10.1115/1.4038301.

A new finite element model for stress analysis of gear drives is proposed. Tie-surface constraints are applied at each tooth of the gear model to obtain meshes that can be independently defined: a finer mesh at contact surfaces and fillet and a coarser mesh in the remaining part of the tooth. Tie-surface constraints are also applied for the connection of several teeth in the model. The model is validated by application of the Hertz's theory in a spiral bevel gear drive with localized bearing contact and by observation of convergency of contact and bending stresses. Maximum contact pressure, maximum Mises stress, maximum Tresca stress, maximum major principal stress, and loaded transmission errors are evaluated along two cycles of meshing. The effects of the boundary conditions that models with three, five, seven, and all the teeth of the gear drive provide on the above-mentioned variables are discussed. Several numerical examples are presented.

Commentary by Dr. Valentin Fuster

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