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Extrusion. The aim of this experiment was to examine the effects of different cross sections on the extrusion process. The cross sections used were five different angles circular, one square and one hexagonal. To compare theoretical values for extrusion w

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Introduction

3MEMS1 Extrusion Experiments Lab By Eoin Kearney 07383002 Abstract The aim of this experiment was to examine the effects of different cross sections on the extrusion process. The cross sections used were five different angles circular, one square and one hexagonal. To compare theoretical values for extrusion with experimental. The data was then plotted and the differences in die angles were compared. Contents Introduction Pg 3 Metal Flow and Deformation Pg 6 Extrusion Defects Pg 6 Theory Pg 7 Experimental Rig Pg 9 Calculations Pg 10 Graphs Pg14 Results Pg 15 Errors Pg 16 Discussion Pg 16 Conclusion Pg 17 Reference Pg 18 Introduction Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section. Extrusion may be continuous in theory or semi-continuous. The extrusion process can be done with the material hot or cold. In this case lead is extruded at room temperature; this is hot working as the recrystallisation temperature for lead is room temperature. Commonly extruded materials include metals, polymers, ceramics, concrete and foodstuffs. Advantages The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections and work materials that are brittle, because the material only encounters compressive and shear stresses. ...read more.

Middle

* The outer layers are deformed to a greater degree than the core. * The leading end of the extrude is almost undeformed. * The metal adjacent to the die does not flow easily, leading to the initiation of zones where little deformation occurs. These zones are called Dead-Metal-Zones. Extrusion Defects Defects in extruded parts usually fall under one of three main categories: * Surface or internal cracking * Sinking in * Skin-inclusion defects. Cracking is caused by secondary tensile stresses acting within a material having low plasticity. Cracks can occur in the form of a "fir-tree" or "central burst" when extruding materials such as steel and brittle aluminum alloys Piping involves sinking of the material at the rear end of the billet. This defect is usually encountered toward the end of the extrusion stroke, especially when the initial billet length is short. Skin inclusions depend on the degree of lubrication and the hardness of the surface layer of the initial stock material. With some materials, such as high copper alloys, the surface skin slides over the container wall and penetrates the billet. Theory An element of the deforming metal is subject to a state of stress involving triaxial compression, during an extrusion process. ...read more.

Conclusion

Section 3 From graph 3 it is clear that the square die required the highest load to extrude the metal most likely caused by the square die having largest circumference therefore the highest friction. The circular and hexagonal dies appear to have much the same slope, with the circular die requiring slightly more load, this was not expected as in theory the circular die should require the least. I will account why this mite of happened in the errors section of the report. The results above comparing the theoretical and the experimental values show that the experimental values found, though were in the general region were not what was expected from the theoretical values, these can be explained from the errors, expanded on in the errors section above. Conclusion That redundant work has a greater impact on load than friction Backward extrusion definitely requires far less load than forward That a 90 degree die angle requires the least force when using a circular die That if redundant work and friction can be minimized, less loads is required for extrusion That the slab analysis equation is an approximation and doesn't take likely errors into account That there were errors in this experiment Reference Ashby and Jones Engineering Materials Volume 1 third edition Lab handout Bauser, Martin; Sauer, G´┐Żnther; Siegert, Klaus (2006), Extrusion ?? ?? ?? ?? ...read more.

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