Thesis (M.S.)--Ohio University, March, 1990. / Title from PDF t.p.

No description available.

published_or_final_version / abstract / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

In this study, mixing is identified to be the most crucial step during the pre-processing process of extruded food and feed stocks. This study therefore aimed to investigate different mixing techniques in an effort to identify the most effective method and its feasibility to pilot plant application for food extrusion processing. The study furthermore considered the methods of mixing with the view to incorporating the identified method in a standard portable cargo container. The research included an investigation and the design of an inexpensive pre-processing control system that would also save space in such applications where storing facilities for ingredients are housed. After investigating different mixing solutions, a V-blender was identified to be a feasible option. It is suggested that by adding a third leg to the V-blender, to obtain what is dubbed as a “Y”-blender, the effectiveness of mixing would be improved upon - not only in the specified application but with respect to mixing in general. In order to evaluate and compare the effectiveness of the mixers, rapid prototyping models of a V- and a Y- blender, with capacities of about 7.6 litres each, were produced from medium density fibreboard (MDF) with the aid of a laser cutter. It was found that, for a recipe consisting of 87% fine yellow maize, 12.75% fine sugar and 0.25% colorant, the effectiveness of mixing within the V-blender was greatly influenced by the level to which it was filled. This was not the case for the Y-blender. This therefore suggested that a Y-blender is the ideal solution for the given application. A layout of a pre-processing system that fits in a standard shipping container and can accommodate six funnel-shaped raw material storage bins with a feed conveyor leading to a Y-blender is designed and a rapid prototyping model of the most vital components of the system is produced. A novel control system using the IOIO USB controller coupled to an Andriod device is developed and this sub-system, with dedicated software, is coupled to the prototyped pre-processing set-up and operated successfully. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

No description available.

No description available.

In this study, mixing is identified to be the most crucial step during the pre-processing process of extruded food and feed stocks. This study therefore aimed to investigate different mixing techniques in an effort to identify the most effective method and its feasibility to pilot plant application for food extrusion processing. The study furthermore considered the methods of mixing with the view to incorporating the identified method in a standard portable cargo container. The research included an investigation and the design of an inexpensive pre-processing control system that would also save space in such applications where storing facilities for ingredients are housed. After investigating different mixing solutions, a V-blender was identified to be a feasible option. It is suggested that by adding a third leg to the V-blender, to obtain what is dubbed as a “Y”-blender, the effectiveness of mixing would be improved upon - not only in the specified application but with respect to mixing in general. In order to evaluate and compare the effectiveness of the mixers, rapid prototyping models of a V- and a Y- blender, with capacities of about 7.6 litres each, were produced from medium density fibreboard (MDF) with the aid of a laser cutter. It was found that, for a recipe consisting of 87% fine yellow maize, 12.75% fine sugar and 0.25% colorant, the effectiveness of mixing within the V-blender was greatly influenced by the level to which it was filled. This was not the case for the Y-blender. This therefore suggested that a Y-blender is the ideal solution for the given application. A layout of a pre-processing system that fits in a standard shipping container and can accommodate six funnel-shaped raw material storage bins with a feed conveyor leading to a Y-blender is designed and a rapid prototyping model of the most vital components of the system is produced. A novel control system using the IOIO USB controller coupled to an Andriod device is developed and this sub-system, with dedicated software, is coupled to the prototyped pre-processing set-up and operated successfully. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

Sheet metal surfaces with pin-fin features have potential fluid and thermal applications. Extrusion forging process and extrusion rolling process can be used to create such surface features on sheet metals. Extrusion forging process is a metal forming process that combines extrusion and forging into one operation. In extrusion forging, the pin-fin surface feature is created by compressing the work-piece using a punch with designed cavities. Experiments and numerical analysis were conducted to investigate the effects of tooling geometries, material properties, work-piece thickness, thickness reduction ratio and friction on the deformation behavior of sheet metals. It was found that increasing fillet radius of the orifice results in decrease in compressive force and boss height. As the negative draft angle increases, the compressive force and boss height decrease. Higher yield strength and higher friction lead to higher compressive force. The boss height is not significantly affected by the friction between the tooling and the work-piece. Due to limitation in force capacity, it may not be feasible to apply extrusion forging technique to generate surface features on large surface area. As such, the extrusion rolling process is proposed. In extrusion rolling, the pin-fin feature is created by compressing the strip using a pair of rolls. The upper roll is manufactured with surface cavities. Finite element method are employed to investigate the effects of rolling speed, thickness reduction ratio, roll diameter and front tension force on the deformation behavior of metal strip. It was found that the rolling speed has little influence on the roll force and boss height. The front tension force has little effect on the average pressure and boss height. Increase the roll diameter results in in roll force increase. This research investigated the effect of parameters on the deformation behavior during the extrusion forging and extrusion rolling processes. The research generated the knowledge needed for design and manufacture of micro/meso surface features on thin metal sheet. Moreover, this thesis presents a novel bulk forming process on metal sheets, which can have significant impacts in industrial practice.

Fletcher Aluminium is a New Zealand company that manufactures aluminium extrusions for the building market. Their extrusion process involves using a hydraulic ram to force heated raw supplied material, in the form of large diameter cylindrical logs, through a die land that is the desired product shape. The final quality of the extruded product is influenced by the extrusion temperature, ram pressure and extrusion speed. The speed of extrusion at Fletcher Aluminium is limited by the extrusion ram pressure because the extrusion machine is operating at the pressure limit of the compressor. Currently the company requires an increase in the extrusion speed, while maintaining quality requirements where these improvements are desired without upgrading the compressor. The press pressure is required to overcome friction and the flow stress of the billet, which is dependent on the precipitates and solutes conditions and their strengthening effects in the billet. However, the preheating temperature and extrusion speeds need to be sufficiently low enough to avoid hot tearing. This research starts to increase the ram speed by decreasing the Mg2Si content for precipitation strengthening. Heat treatment may be used to dissolve Mg2Si content by billet preheat to a temperature at or exceeds solvus temperature (TSolvus). However, a higher (than TSolvus) billet temperature may have two conflicting effects. First, a higher temperature in general reduces the flow stress thus lowering the required pressure. On the other hand, at temperature higher than Tsolvus, Mg2Si should completely dissolve, resulting in solid solution strengthening thus increasing the flow stress. The objective of the study is to quantify the strengthening contributions from solute atoms (Mg / Si) and precipitates (Mg2Si) on the as-received and heat treated test samples using room temperature mechanical testing and phase diagram analysis. The selected heat treatment conditions fully enclose the preheating temperature and time range currently used in Fletcher Aluminium production. Simulations of the extrusion were conducted by hot compression testing (Gleeble test), to measure the combination of strengthening effects during deformation at elevated temperatures. The room temperature tests have shown that hardness, yield strength (YS) and ultimate tensile strength (UTS) are minimised at approximately 405°C. The minimum point is shown to be caused by the combination of strengthening and softening due to solid solution and precipitation strengthening. The higher values of hardness, YS and UTS at lower and higher preheating temperatures are mainly due to precipitation and solution strengthening respectively. The findings show that, the solution of Mg2Si gradually increases as the temperature increases at temperatures exceeding 405°C. Hardness, YS and UTS were compared in order to determine the correlation between each mechanical property. A correlation exists, but it is not simple to translate between each mechanical property. The relationship between hardness and stress observed for 8% permanent strain was also investigated; there was no improvement in correlation. The elevated temperature tests show that initial flow stress and peak flow stress reduces linearly with temperature increases, which means higher testing temperature results lower precipitation and solid solution strengthening effects. Additionally, the constants of the Gleeble – Holomon equation were numerically calculated and are similar to published values. The Gleeble – Holomon equation was combined with Felthams equation in order to provide a relationship between extrusion velocity and extrusion temperature.

Fletcher Aluminium is a New Zealand company that manufactures aluminium extrusions for the building market. Their extrusion process involves using a hydraulic ram to force heated raw supplied material, in the form of large diameter cylindrical logs, through a die land that is the desired product shape. The final quality of the extruded product is influenced by the extrusion temperature, ram pressure and extrusion speed. The speed of extrusion at Fletcher Aluminium is limited by the extrusion ram pressure because the extrusion machine is operating at the pressure limit of the compressor. Currently the company requires an increase in the extrusion speed, while maintaining quality requirements where these improvements are desired without upgrading the compressor. The press pressure is required to overcome friction and the flow stress of the billet, which is dependent on the precipitates and solutes conditions and their strengthening effects in the billet. However, the preheating temperature and extrusion speeds need to be sufficiently low enough to avoid hot tearing. This research starts to increase the ram speed by decreasing the Mg2Si content for precipitation strengthening. Heat treatment may be used to dissolve Mg2Si content by billet preheat to a temperature at or exceeds solvus temperature (TSolvus). However, a higher (than TSolvus) billet temperature may have two conflicting effects. First, a higher temperature in general reduces the flow stress thus lowering the required pressure. On the other hand, at temperature higher than Tsolvus, Mg2Si should completely dissolve, resulting in solid solution strengthening thus increasing the flow stress. The objective of the study is to quantify the strengthening contributions from solute atoms (Mg / Si) and precipitates (Mg2Si) on the as-received and heat treated test samples using room temperature mechanical testing and phase diagram analysis. The selected heat treatment conditions fully enclose the preheating temperature and time range currently used in Fletcher Aluminium production. Simulations of the extrusion were conducted by hot compression testing (Gleeble test), to measure the combination of strengthening effects during deformation at elevated temperatures. The room temperature tests have shown that hardness, yield strength (YS) and ultimate tensile strength (UTS) are minimised at approximately 405°C. The minimum point is shown to be caused by the combination of strengthening and softening due to solid solution and precipitation strengthening. The higher values of hardness, YS and UTS at lower and higher preheating temperatures are mainly due to precipitation and solution strengthening respectively. The findings show that, the solution of Mg2Si gradually increases as the temperature increases at temperatures exceeding 405°C. Hardness, YS and UTS were compared in order to determine the correlation between each mechanical property. A correlation exists, but it is not simple to translate between each mechanical property. The relationship between hardness and stress observed for 8% permanent strain was also investigated; there was no improvement in correlation. The elevated temperature tests show that initial flow stress and peak flow stress reduces linearly with temperature increases, which means higher testing temperature results lower precipitation and solid solution strengthening effects. Additionally, the constants of the Gleeble – Holomon equation were numerically calculated and are similar to published values. The Gleeble – Holomon equation was combined with Felthams equation in order to provide a relationship between extrusion velocity and extrusion temperature.