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Long A.,Queens University of Belfast | Thornhill D.,Queens University of Belfast | Armstrong C.,Queens University of Belfast | Watson D.,Ryobi Aluminium Castings UK Ltd
Applied Thermal Engineering | Year: 2012

The objective of this research was to determine the surface temperature of a high pressure die casting die during casting conditions. This was achieved by instrumentation of an insert which was placed in the shotplate region of the die. This research overcame the challenge of directly measuring the die surface temperature during a HPDC production casting cycle and shows that this is an effective method to determine the die surface temperature during the casting cycle. The instrumentation results gave a peak and minimum temperature of 500 °C and 240°C respectively during steady state running conditions with a molten aluminium casting temperature of 660°C. Stress analysis from the steady state measured temperature of the die surface was calculated through a simple FEA model and the resulting stress fluctuation was applied to a fatigue equation for the die material, the predicted number of cycles for cracking to start was found to correlate well with observed die damage. © 2012 Elsevier Ltd. All rights reserved. Source


Long A.,Queens University of Belfast | Thornhill D.,Queens University of Belfast | Armstrong C.,Queens University of Belfast | Watson D.,Ryobi Aluminium Castings UK Ltd
Applied Thermal Engineering | Year: 2011

When simulating the High Pressure Die Casting 'HPDC' process, the heat transfer coefficient 'HTC' between the casting and the die is critical to accurately predict the quality of the casting. To determine the HTC at the metal-die interface a production die for an automotive engine bearing beam, Die 1, was instrumented with type K thermocouples. A Magmasoft® simulation model was generated with virtual thermocouple points placed in the same location as the production die. The temperature traces from the simulation model were compared to the instrumentation results. Using the default simulation HTC for the metal-die interface, a poor correlation was seen, with the temperature response being much less for the simulation model. Because of this, the HTC at the metal-die interface was modified in order to get a better fit. After many simulation iterations, a good fit was established using a peak HTC of 42,000 W/m2 K, this modified HTC was further validated by a second instrumented production die, proving that the modified HTC gives good correlation to the instrumentation trials. The updated HTC properties for the simulation model will improve the predictive capabilities of the casting simulation software and better predict casting defects. © 2011 Elsevier Ltd. All rights reserved. Source


Long A.,Queens University of Belfast | Thornhill D.,Queens University of Belfast | Armstrong C.,Queens University of Belfast | Watson D.,Ryobi Aluminium Castings UK Ltd
SAE Technical Papers | Year: 2013

Die pre-heating has a beneficial effect on die life, by reducing thermal shock and stress fluctuations on the die surface. The findings from this paper indicate that the die surface stress decreased by 44% when the die is pre-heated to 150°C, and decreases by 57% when the die is pre-heated to 200°C, in comparison to when the die is started cold with an initial temperature of 20°C. Changes to the die start-up procedure, by switching off the die internal water cooling for the first four casting cycles, results in the die heating to operating temperature in fewer casting cycles, resulting in fewer castings being scrapped before the die achieves steady state operating temperature. From this, a saving of four castings per start-up can be made, reducing scrap by 4.5%, leading to lower manufacturing costs, reduced energy usage and increased useful die life. The modified die start-up procedure had a negligible effect on the die surface stress fluctuation, with a beneficial reduction in scrap. The process improvements which were run to improve die life, show that by modifying the die start-up procedure, the scrap rate can be reduced making the process more profitable. Copyright © 2013 SAE International. Source


Long A.,Queens University of Belfast | Thornhill D.,Queens University of Belfast | Armstrong C.,Queens University of Belfast | Watson D.,Ryobi Aluminium Castings UK Ltd
International Journal of Metalcasting | Year: 2013

A strain gauge instrumentation trial on a high-pressure die casting (HPDC) die was compared to a corresponding simulation model using Magmasoft® casting simulation software at two strain gauge rosette locations. The strains were measured during the casting cycle, from which the von Mises stress was determined and then compared to the simulation model. The von Mises stress from the simulation model correlated well with the findings from the instrumentation trial, showing a difference of 5.5%, ∼ 10 MPa for one strain gauge rosette located in an area of low stress gradient. The second rosette was in a region of steep stress gradient, which resulted in a difference of up to 40%, ∼40 MPa between the simulation and instrumentation results. Factors such as additional loading from die closure force or metal injection pressure which are not modelled were shown to have very little influence on the stress in the die, less than 7%. Copyright © 2013 American Foundry Society. Source

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