Mark J. Jakiela

Continuum structural topology design with genetic algorithms

The genetic algorithm (GA), an optimization technique based on the theory of natural selection, is applied to structural topology design problems. After reviewing the GA and previous research in structural topology optimization, we describe a binary material/void design representation that is encoded in GA chromosome data structures. This representation is intended to approximate a material continuum as opposed to discrete truss structures. Four examples, showing the broad utility of the approach and representation, are then presented. A fifth example suggests an alternate representation that allows continuously-variable material density. Concluding discussion suggests recommended uses of the technique and describes ongoing and possible future work.

Mechanics of vibration-assisted entrapment with application to design

The phenomenon of vibration-assisted entrapment is analyzed in the context of a vibratory parts feeder - the SONY automated parts orienting system (APOS). Entrapment is treated as an energy minimization process. Mechanisms of energy increase and decrease are described. Conditions that lead to failure of entrapment are discussed for a planar part-relief system.

A cost model for optimizing the take back phase of used product recovery

Taking back the end-of-life products from customers can be made profitable by optimizing the combination of advertising, financial benefits for the customer, and ease of delivery (product transport). In this paper we present a detailed modeling framework developed for the cost benefit analysis of the take back process. This model includes many aspects that have not been modeled before, including financial incentives in the form of discounts, as well as transportation and advertisement costs. In this model customers are motivated to return their used products with financial incentives in the forms of cash and discounts for the purchase of new products. Cost and revenue allocation between take back and new product sale is discussed and modeled. The frequency, method and cost of advertisement are also addressed. The convenience of transportation method and the transportation costs are included in the model as well. The effects of the type and amount of financial incentives, frequency and method of advertisement, and method of transportation on the product return rate and the net profit of take back were formulated and studied. The application of the model for determining the optimum strategies (operational levels) and predicting the maximum net profit of the take back process was demonstrated through a practical, but hypothetical, example.

A method to resolve ambiguities in corner‐corner interactions between polygons in the context of motion simulations

The motion of systems of polygonal objects is characterized by discontinuities due to changes in the set of contacts between polygons. Effective simulations of such a motion requires a simulation scheme that can automatically update the set of contacts during the simulation. This article focuses on a contact updating problem that arises when a penalty based contact model is used. A penalty based model requires a finite overlap of contacting polygons. This overlap results in ambiguities in characterizing corner‐corner contact between polygons. A simple yet effective scheme to overcome such ambiguities is presented.

An Investigation of the Productivity Difference in Mechanical Embodiment Design Between Face-to-Face and Threaded Online Collaboration

The threaded online, also known as “forum,” collaboration method is widely used by open source software projects. As open source and Crowdsourcing [3] design approaches gain attention, there is a need to explore whether the threaded online method would compete with the more traditional method, face to face, in mechanical engineering design in terms of productivity. Our experiment shows that with a suitably sized challenge, the threaded online method does generate about equal productivity as the face-to-face method. However, the participation rates are lower in the threaded online method and the participants’ satisfaction with the experience was also less. This suggests that additional communication mechanisms are needed to facilitate the threaded online method, and management mechanisms should be imposed. We also identified two phenomena that warrant further investigation. The first is what we call “inertia loafing.” Enthusiasm among online community members is fragile. A small drop in satisfaction level can cause many to become unwilling to participate. The second is that an online community tends to have two kinds of members: “players” who are responsible for most content creation; and “cheer leaders” who provide feedback or provide an assisting function.Copyright

WeDesign: A Forum-Based Tool for Managing User-Generated Content in Engineering Design and Product Development

A web forum-based tool for managing user-generated content in engineering design and product development is described. The system is intended to allow a “crowdsourcing” approach, in which large groups perform the work more commonly by individuals. User tests are conducted with an initial implementation, with the system configured in control and “parliamentary” modes. This experiment is done in the setting of a mechanical engineering senior capstone design course. The parliamentary mode is intended to encourage discussion and negotiation among participants, and allows them to design their own work processes. Review of the designs produced together with responses to a survey indicate the system was favorably received, and allowed a group to generate and select concept designs. Future research directions are suggested.Copyright

Fastener Pattern Optimization of an Eccentrically Loaded Multi-Fastener Connection

This paper presents the use of a genetic algorithm in conjunction with geometric nonlinear finite element analysis to optimize the fastener pattern and lug location in an eccentrically loaded multi-fastener connection. No frictional resistance to shear was included in the model, as the connection transmitted shear loads into four dowel fasteners through bearing-type contact without fastener preload. With the goal of reducing the maximum von Mises stress in the connection to improve fatigue life, the location of the lug hole and four fastener holes were optimized to achieve 55% less maximum stress than a similar optimization using the traditional instantaneous center of rotation method. Since the maximum stress concentration was located at the edge of a fastener hole where fatigue cracks could be a concern, reduction of this quantity lowers the probability of crack growth for both bearing-type and slip-resistant connections. It was also found that the location of the maximum von Mises stress concentration jumped from the fastener region to the lug as the applied force angle was decreased below 45 degrees, thus the fastener pattern could not be optimized for lower angles.Copyright

Resonance-Induced Failure of Entrapment: Application to Industrial Parts Feeding

Parts feeders are devices used in automated assembly lines to present component parts to the assembly machinery in a consistent and predetermined orientation. The process of converting a randomly oriented set of parts (as obtained from a vendor) into an ordered array is called parts feeding. There are many different types of feeders and feeding techniques used in the industry. This paper deals with a particular feeding process referred to here as vibratory entrapment. It describes a particular cause of failure of vibratory entrapment, namely, resonance. Failure due to resonance was first observed in high-speed video images of the entrapment phenomenon. This paper provides a description of the mechanics of failure of entrapment due to resonance. The mechanics is introduced with the simple example of a ping-pong ball in a cup and extended to real parts in a parts feeder. Conditions for resonance are derived and experimentally verified for a simple part shape and vibration pattern.