A bifurcation study to guide the design of a landing gear with a combined uplock/downlock mechanism

This paper discusses the insights that a bifurcation analysis can provide when designing mechanisms. A model, in the form of a set of coupled steady-state equations, can be derived to describe the mechanism. Solutions to this model can be traced through the mechanism's state versus parameter space via numerical continuation, under the simultaneous variation of one or more parameters. With this approach, crucial features in the response surface, such as bifurcation points, can be identified. By numerically continuing these points in the appropriate parameter space, the resulting bifurcation diagram can be used to guide parameter selection and optimization. In this paper, we demonstrate the potential of this technique by considering an aircraft nose landing gear, with a novel locking strategy that uses a combined uplock/downlock mechanism. The landing gear is locked when in the retracted or deployed states. Transitions between these locked states and the unlocked state (where the landing gear is a mechanism) are shown to depend upon the positions of two fold point bifurcations. By performing a two-parameter continuation, the critical points are traced to identify operational boundaries. Following the variation of the fold points through parameter space, a minimum spring stiffness is identified that enables the landing gear to be locked in the retracted state. The bifurcation analysis also shows that the unlocking of a retracted landing gear should use an unlock force measure, rather than a position indicator, to de-couple the effects of the retraction and locking actuators. Overall, the study demonstrates that bifurcation analysis can enhance the understanding of the influence of design choices over a wide operating range where nonlinearity is significant

Development of welding techniques and filler metals for high strength aluminum alloys Annual summary report, 27 Jun. 1964 - 27 Jun. 1965

Welding techniques and filler metals for high strength aluminum alloy

Do insect and mold damage affect maize prices in Africa? Evidence from Malawi

Economic losses to stored grain can potentially come from both quantity losses and quality losses in the form of price discounts for damage from insects and mold. This article uses choice experiments conducted with physical samples of maize to estimate discounts for damaged grain among maize traders in Malawi. Using the Equality Constrained Latent Class method to correct for non-attendance to the price attribute, we find that traders place a statistically and economically significant discount on insect-damaged maize. We estimate that a 1% increase in maize damage reduces the price of maize by 2.8% to 3.6%, depending on damage level. We discuss the implications of these results for farmers’ incentives to adopt improved storage technologies that can reduce post-harvest losses