Creep Life Prediction of Alloy 718 for Automotive Engine Materials

This study was carried out to investigate the creep life at the high temperature of the Alloy 718 for automotive engine components using the initial strain parameter method (ISPM). Creep tests have performed at elevated temperatures in the range of 550 oC to 700 oC in this work. We also carried out constant stress creep tests. The initial strains were measured during 1 minute after loading. Both the creep stress and rupture time depend on the initial strain. We calculated the creep life of Alloy 718 by using the creep life prediction equations obtained from the ISPM. Then, we compared the creep life predicted by the ISPM to the Larson-Miller parameter (LMP). The experimental rupture time and the calculated rupture time by using the ISPM agreed with a confidence level of 95 %. The creep life predicted by using the ISPM was in very good agreement with the creep life predicted using the LMP method.     

Choice of parking: Stated preference approach

Over recent years, parking policy has become a key element of transport policy in many countries. Parking policy measures can affect many different dimensions of travel behaviour but are likely to be most significant in terms of travellers' choice of parking type and location. This dimension of travel choice has, to date, received comparatively little attention, yet is of vital importance if we are to properly understand and predict the effects of parking policy measures.This paper presents two studies addressing this issue carried out in the United Kingdom and Germany. Both studies used a stated preference approach in order to collect disaggregate data on travellers responses to changes in parking attributes and used these data to build simple logit models of parking type choice. The studies were designed in order to allow comparable choice models to be estimated from the two datasets. The results obtained strongly indicate the need to separately identify the costs associated with different components of the parking activity (e.g., general in-vehicle time, parking search time, egress time) and also point to the existence of significant differences in the relative valuation of these components across different journey purposes. Where possible, the results of the choice modelling exercises are also compared with existing revealed and stated preference results and are found to be generally in line with prior expectations.     

Primary productivity and export fluxes on the Canadian shelf of the Beaufort Sea: A modelling study

We present a coupled sea ice–ocean-biological (including ice algae) model in the Arctic Ocean. The 1D model was developed and implemented on the Canadian Beaufort Sea shelf to examine the importance of different physical processes in controlling the timing and magnitude of primary production and biogenic particle export over an annual cycle (1987). Our results show that the snow and sea ice cover melt and/or break-up controls the timing of the phytoplankton bloom but primary producers (ice algae and phytoplankton) on the outer shelf are essentially nutrient limited. The total annual primary production (22.7 to 27.7 g-C m^? 2) is thus controlled by nutrient “pre-conditioning” in the previous fall and winter and by the depth of wind mixing that is controlled in part by the supply of fresh water at the end of spring (ice melt or runoff). The spring bloom represents about 40% of the total annual primary production and occurs in a period of the year when sampling is often lacking. Time interpolation of observed values to obtain total annual primary production, as done in many studies, was shown to lead to an underestimation of the actual production. Our simulated ratios of export to primary production vary between 0.42 and 0.44.     

Equilibria of bilateral taxi–customer searching and meeting on networks

This paper proposes an equilibrium model to characterize the bilateral searching and meeting between customers and taxis on road networks. A taxi driver searches or waits for a customer by considering both the expected searching or waiting time cost and ride revenue, and a customer seeks a taxi ride to minimize full trip price. We suppose that the bilateral taxi–customer searching and meeting occurs anywhere in residential and commercial zones or at prescribed taxi stands, such as an airport or a railway station. We propose a meeting function to spell out the search and meeting frictions that arise endogenously as a result of the distinct spatial feature of the area and the taxi–customer moving decisions. With the proposed meeting function and the assumptions underlying taxi–customer search behaviors, the stationary competitive equilibrium achieved at fixed fare prices is determined when the demand of the customers matches the supply of taxis or there is market clearing at the prevailing searching and waiting times in every meeting location. We establish the existence of such an equilibrium by virtue of Brouwer’s fixed-point theorem and demonstrate its principal operational characteristics with a numerical example.     

Changing ownership structures in the Dutch fleet

The new Dutch shipping policy has given rise to high expectation and curiosity in the world of shipping. This, together with the obvious difficulties of an ex-post study of the effectiveness of such innovative policy, has prompted the authors to take an interest in attempting to investigate changes in ownership of the Dutch fleet 2 years after the new policy has been introduced. To do this, a rather new concept of ‘flagging out’ has been adopted, which is interpreted as a process leading to different degrees of ‘foreignness’ in a shipping operation. In this paper, a method to structure is presented, and ownership information, and changes in it are presented, that are essentially based on the theory of stochastic processes. The data used is the Dutch fleet data, which includes information on the nationality of the flag, parent ownership and management over the period 1994–1998. The results yield interesting insights in the shifts in the ownership and operational structure of shipping companies induced by the new policy. In particular, they allow one to establish the origin of new vessels, in which stage of ownership/operation it is most likely that shifts occur, and to determine the relationship between the different stages of the ‘flagging out’ process. These results, thus, enable an evaluation of the areas in which the policy can be expected to yield results.     

Red-light cameras at intersections: Estimating preferences using a stated choice model

Red-light cameras placed at intersections have the potential to increase safety, but they are often viewed as an invasion of privacy. Preferences for these cameras were explored using a stated choice model that presents key attributes of camera placements. Stated choice models involve careful experimental design, akin to experimental control in laboratory settings. A variety of design approaches were used, settling on a composition of the choice sets people face in the survey. To illustrate the approach, an internet survey was used with a convenience sample containing a high percentage of college students. The results show that while not the case independently, as the number of cameras and fines for violators are simultaneously increased, the preferences for one particular red light cameras program are likely to improve.     

Development of a low-noise cooling fan for an alternator using numerical and doe methods

An alternator, which converts mechanical rotational energy into electrical energy, is an important component of a vehicle. Alternators operate over a broad range of rotational speeds, typically from 3,000 RPM to 18,000 RPM, which demands a cooling fan producing sufficient airflow, ideally with a minimum of noise. In the current study, an optimized alternator-cooling fan was developed through a linked DOE(Design OF Experiment) process and numerical analysis. The SC/Tetra and FlowNoise S/W programs were used to calculate flow rates and noise levels, respectively, for the newly developed fan. Compared with original model, the numerical results predicted a 3 dBA noise reduction; the measured reduction was 4 dBA.     

Piston-temperature measuring system using electromagnetic induction with verification by a telemetry system

The development of an inner-piston-chamber temperature measurement system is a necessary step in engine development or when solving other fundamental problems related to automotive engines. There are various pre-existing measurement methods available, e.g., the linkage method, piston telemetry, templog, and the electromagnetic induction method. In this study, we first redesigned the coil sensor used in the electromagnetic induction method using PEEK and then used Taguchi methods to reduce the number of experiments in the development process and finally utilized piston telemetry via Bluetooth to verify the precision and accuracy of the redesigned PEEK coil sensor and electromagnetic induction method. The results displayed a reproducibility within 0.5 degrees and an accuracy within 2 degrees Celsius.