The effect of thickness on fatigue crack propagation in 7475-T731 aluminum alloy sheet

Tests were conducted on three thicknesses of 7475-T731 aluminum alloy sheet to investigate the effect of thickness on fatigue crack propagation under constant amplitude loading conditions and on retardation following a single peak overload. Constant amplitude loading tests were performed at stress ratios of 0.05 and 0.75 to obtain data for conditions with crack closure and without crack closure, respectively. At both stress ratios a thickness effect was clearly evident, with thicker specimens exhibiting higher growth rates in the transition from plane strain to plane stress region. The effect of thickness for a stress ratio of 0.05 corresponded well with the fracturing mode transitions observed on the specimens. A model based on the strain energy release rate which accounted for the fracture mode transition was found to correlate the thickness effects well. The specimens tested at the stress ratio of 0.75 did not make the transition from tensile mode to shear mode, indicating that another mechanism besides crack closure or fracture mode transition was active

‘Fair trade’ coffee and the mitigation of local oligopsony power

In recent years, there has been considerable growth in ‘fair trade’ markets for several commodities, most notably coffee. We argue that coffee is grown under conditions that might well subject growers to the market power of downstream intermediaries (processors). Using an approach designed to evaluate the effects of state trading enterprises on trade and welfare, we develop an oligopsony model of intermediaries. In this model, fair-trade processors optimise a welfare function that includes the producer surplus of coffee growers. This concern for growers' welfare among some processing firms helps to alleviate the market power distortion. We calibrate the model to price data reported by a fair-trade organisation and consider the counterfactual removal of fair-trade behaviour by processors. As expected, the income of coffee growers (in aggregate) is reduced, though the effects are quite small

Production Networks in Asia: A Case Study from the Hard Disk Drive Industry

Production networks have been extensively developed in East Asia. Previous studies on production networks used international trade data or input-output tables, but such aggregate data cannot explain how the networks actually operate. With the aim of understanding the features and characteristics of East Asian production networks, this paper examines the procurement system of a HDD assembler operating in Thailand. This micro-level case study found that this particular production network consists mostly of arm's-length suppliers, who are independent and on an equal footing with the assembler. These arm's-length suppliers are mostly located in the assembling country, but some are located in neighboring countries. This proximity is necessary to establish good relationships between customer and suppliers and allows problems to be solved as soon as they occur. The arm's-length suppliers engaged in each country's leading industries, such as the electronics industry in Malaysia and Singapore and the automobile industry in Thailand, have extended their business to supply the HDD industry. These suppliers have formed an industrial cluster in each country within a two- or three-hour drive area. Each cluster that spans different countries is linked by a well-developed logistic network that employs the just-in-time production method that prevails in East Asia. On a regional level, these separate clusters tend to form international production networks that connect to each other across neighboring countries within a distance that provides a quick response time for problem solving. This study also found that American HDD assemblers outsourced indigenous suppliers in Malaysia and Singapore because American suppliers did not follow the assemblers' move to the region. However, since Japanese suppliers did follow the Japanese HDD assemblers to the Philippines and Thailand, indigenous suppliers were not outsourced

A Coasian model of international production chains

International supply chains require coordination of numerous activities across multiple countries and firms. We adapt a model of supply chains and apply it to an international trade setting. In each chain, the measure of tasks completed within a firm is determined by a tradeoff between transaction costs and diseconomies of scope linked to management of a larger measure of tasks within the firm. The structural parameters that determine firm scope explain variation in supply-chain length and gross-output-to-value-added ratios, and determine countries' comparative advantage along and across supply chains. We calibrate the model to match key observables in East Asia, and evaluate implications of changes in model parameters for trade, welfare, the length of supply chains and countries' relative position within them

Trade responses to geographic frictions: A decomposition using micro-data

C1 - Refereed Journal Articl