Nonlinear Modeling of a Rigid Rotor Supported on Rolling Element Bearings With Localized Defects

In this paper a nonlinear model for defects in rolling element bearings is developed. Detailed nonlinear models are useful to detect, estimate and predict failure in rotating machines. Also, accurate modeling of the defect provides parameters that can be estimated to determine the health of the machine. In this paper the rotor-bearing system is modeled as a rigid rotor and the defects are modeled as pits in the bearing race. Unlike the previous models, the motion of the rolling element thorough the defect is not modeled as a predetermined function; instead, it is dynamically determined since it depends on the clearance and the position of the shaft. Using this nonlinear model, the motion of the shaft is simulated and the effect of the rolling element passing through the defect is studied. The effect of shaft parameters and the defect parameters on the precision of the shaft and the overall performance of the system is studied. Finally, suitable measures for health monitoring and defect tracking are suggested.

Exploring the Meaning of Success in Outsourced Product Development

Research on outsourced product development has focused primarily on the motives behind firms’ decisions to outsource, with less attention paid to the outcomes of those decisions. The few existing academic studies have reported high failure rates, but there is little consensus as to what is meant by “project success” and “failure” and some do not define success at all. Such ambiguity makes comparisons difficult and hinders explanation of observed variation in project outcomes. This paper explores the many meanings of project success in outsourced product development, based on in-depth interviews of thirty design consultants and clients. After reviewing the merits and limitations of each metric, we propose that the client’s willingness to recommend the consultant may be a suitable outcome variable for assessing project outcomes and comparing success rates across diverse projects, companies, and industries. We present preliminary data that suggests client willingness to recommend varies widely and is multimodal in distribution. Finally, we identify several commonly encountered failure modes, i.e., sequences of events that generate discrepancies between client expectations and project deliverables, thereby producing client dissatisfaction.

Dynamic Responses of Beam With Sloping Support Traversed by a Moving Mass

This paper contributes to investigation on vibration analysis for cradle subjected to the moving barrel. The tipping part of the gun is simplified by a beam with sloping support traversed by a moving mass. The cradle structure is modeled by Euler-Bernoulli variable cross-section beam and the elevating strut is modeled by elastic supporting rod. The beam and supporting rod are discretized into finite elements, and then the main mass matrix, stiffness matrix, and damping matrix can be formulated. Gravity and inertial force are described by external nodal load vectors. The time-varying additional mass matrix, stiffness matrix, and damping matrix are derived. Numerical computation is conducted to analyze the effect of the barrel velocity on dynamic response of system, which can provide theoretical foundation to structural design of such system.

Physical Models in Idea Generation: Hindrance or Help?

Engineering idea generation is a critical part of new product development and physical models are one tool used in this phase of design. Unfortunately, few guidelines about the effective use of physical models to support idea generation exist. The advantages and disadvantages of physical models need to be clarified so that engineers know when and where to implement them effectively. Previous literature indicates there is potential for design fixation on physical prototypes. This limits the solutions considered. In contrast, other recommendations encourage the extensive use of physical models and the psychological literature indicates that physical representations have the potential to lead to more feasible design by supporting designers’ mental models of physical phenomena. This study evaluates these questions with a between-subjects experiment with four conditions, sketching only, building, building & testing, and constrained sketching. No evidence for design fixation is observed. The results show that physical models supplement designers’ mental models, thereby leading to higher quality ideas (fraction of functional ideas). This result shows a potential way of improving designer’s innovation by strategically implementing fast and cheap prototyping methods.

Targeted Energy Transfer to a Rotary Nonlinear Energy Sink

We study computationally the passive, nonlinear targeted energy transfers induced by resonant interactions between a single-degree-of-freedom nonlinear energy sink and a uniform-plate model of a flexible, swept aircraft wing. We show that the nonlinear energy sink can be designed to quickly and efficiently absorb energy from one or more wing modes in a completely passive manner. Results indicate that it is feasible to use such a device to suppress or prevent aeroelastic instabilities like limit-cycle oscillations. The design of a compact nonlinear energy sink is introduced and the parameters of the device are examined. Simulations performed using a finite-element model of the wing coupled to discrete equations governing the energy sink indicate that targeted energy transfer is achievable, resulting, for example, in a rapid and significant reduction in the second bending mode response of the wing. Finally, the finite element model is used to simulate the effects of increased nonlinear energy sink stiffness, and to show the conditions under which the nonlinear energy sink will resonantly interact with higher-frequency wing modes.

On the Modeling of Open and Breathing Cracks of a Cracked Rotor System

The modeling of a cracked rotor system with an open or breathing transverse crack is addressed here. The cracked rotor with an open crack model behaves as an asymmetric shaft. Hence, the time-varying area moments of inertia of the cracked section are employed in formulating the periodic finite element stiffness matrix for both crack models which yields a linear time-periodic system. The harmonic balance method (HB) is used in solving the finite element (FE) equations of motions for studying the dynamic behavior of the cracked rotor system. The unique behavior of the whirl orbits during the passage through the subcritical rotational speeds and the sensitivity of these orbits to the unbalance force direction can be used for early crack detection of the cracked rotor for both crack models. These whirl orbits were verified experimentally for the open crack model in the neighborhood of 1/2 of the first critical rotational speed where a good match with the theoretical whirl orbits was observed.

The Multi-Relationship Evaluation Design Framework: Designing Testing Plans to Comprehensively Assess Advanced and Intelligent Technologies

As new technologies develop and mature, it becomes critical to provide both formative and summative assessments on their performance. Performance assessment events range in form from a few simple tests of key elements of the technology to highly complex and extensive evaluation exercises targeting specific levels and capabilities of the system under scrutiny. Typically the more advanced the system, the more often performance evaluations are warranted, and the more complex the evaluation planning becomes. Numerous evaluation frameworks have been developed to generate evaluation designs intent on characterizing the performance of intelligent systems. Many of these frameworks enable the design of extensive evaluations, but each has its own focused objectives within an inherent set of known boundaries. This paper introduces the Multi-Relationship Evaluation Design (MRED) framework whose ultimate goal is to automatically generate an evaluation design based upon multiple inputs. The MRED framework takes input goal data and outputs an evaluation blueprint complete with specific evaluation elements including level of technology to be tested, metric type, user type, and, evaluation environment. Some of MRED’s unique features are that it characterizes these relationships and manages their uncertainties along with those associated with evaluation input. The authors will introduce MRED by first presenting relationships between four main evaluation design elements. These evaluation elements are defined and the relationships between them are established including the connections between evaluation personnel (not just the users), their level of knowledge, and decision-making authority. This will be further supported through the definition of key terms. An example will be presented in which these terms and relationships are applied to the evaluation design of an automobile technology. An initial validation step follows where MRED is applied to the speech translation technology whose evaluation design was inspired by the successful use of a pre-existing evaluation framework. It is important to note that MRED is still in its early stages of development where this paper presents numerous MRED outputs. Future publications will present the remaining outputs, the uncertain inputs, and MRED’s implementation steps that produce the detailed evaluation blueprints.

Biologically Inspired Design: A Macrocognitive Account

Biologically inspired engineering design is an approach to design that espouses the adaptation of functions and mechanisms in biological sciences to solve engineering design problems. We have conducted an in situ study of designers engaged in biologically inspired design. Based on this study we develop here a macrocognitive information-processing model of biologically inspired design. We also compare and contrast the model with other information-processing models of analogical design such as TRIZ, case-based design, and design patterns.

Parametric Instability in Metallic Bellows Subjected to Seismic Excitation

This paper investigates the parametric instability of a metallic bellows filled with fluid and subjected to the variance of dynamic internal pressure due to an earthquake. The axial stiffness of the bellows varies due to the variation in internal static fluid pressure, and this stiffness variation induces a parametric instability in the bellows. A finite element model describing a bellows connected to a pipe is developed to examine the question of whether parametric instability is excited in such bellows by earthquake motion, which is not the harmonic vibration. Numerical simulations and experiments were carried out using the acceleration recorded by past recorded actual earthquakes. We find that indeed parametric instability may appear in the bellows when the natural frequency of the pipe is close to the predominant frequency component of the earthquake, though the earthquake motion is not harmonic.

Study of Existing Metrics Used in Measurement of Ideation Effectiveness

In recent years, many new idea generation methods have been developed to generate innovative concepts. The effectiveness of those methods is evaluated by applying a set of metrics to the resulting concepts. Several metrics have been proposed for this purpose, including quality, novelty, and variety metrics, but the inter-rater reliability of those metrics has not been investigated extensively. In this paper, the inter-rater reliability of three existing metrics is analyzed by applying them to the results of a representative idea generation study. The effects on inter-rater agreement of analyzing concepts at the overall concept level versus the feature level are investigated, along with the impacts of alternative scales for specific metrics. In general, the inter-rater reliability of the metrics is found to be relatively low, with the most reliable results obtained at the feature level. The use of different scales also affects inter-rater reliability, but the effect is less significant. In addition to their low levels of repeatability, the metrics differ in how novelty is appraised.