Various empirical formulas for predicting the maximum load in practical forgings are reviewed. Assuming a constant friction shear stress at the material-tool interface, the slab method of analysis is applied to the general upsetting operation under inclined surfaces. The stress and load equations are derived for plane strain and axisymmetric deformation. A method for determining flow models in practical forgings is presented. This method gives better approximations of forging loads than the fictitious disk model. The theory presented in this work is applied to a lead forging at room temperature and to a 1043 steel forging at 1180 C. The agreement with predictions and experimental results are within useful engineering accuracy.

SynopsisA process has been developed by which very high-modulus semicrystalline polymer films can be extruded continuously from a melt. This is accomplished by controlled cooling of the melt in a two-stage flow channel. A temperature gradient along the flow channel quenches the melt prior to an area reduction in which the polymer undergoes solid-state orientation. Analysis of high-density polyethylene tapes extruded by this process shows that they have properties similar to samples hydrostatically extruded a t 120°C. Infrared analysis was used to determine both the degree of crystallinity and degree of orientation in these tapes as well as previously prepared hydrostatically extruded samples.

Solid state rolling of semi‐crystalline polymers is shown to be an effective method of producing high strength, high modulus tape at acceptable production rates. High density polyethylene tape was produced having a tensile strength exceeding 300 MPa and a tensile modulus of 8.7 GPa at production rates exceeding 8 m/min. A significant factor in producing highly oriented tape by the rolling process is roll temperature. Increasing the roll temperature from 25°C to 125°C not only increases the maximum extent of orientation achievable, but increases the mechanical properties at a given degree of thickness reduction. Internal frictional heat development limited the maximum thickness reduction ratio of polypropylene to 6.6:1. This reduction was reached by rolling at 150°C. The resultant tape had a tensile modulus of 5.1 GPa and a tensile strength of 300 MPa.

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Hydrostatic extrusion of high density polyethylene at an extrusion ratio of 15:1 was investigated in the temperature range between 100 and 134°C. A thin‐walled tube was extruded having a tensile strength of 370 MPa and a tensile modulus of 10 GPa. The extrusion rate was limited by severe extrudate distortion which occurs at a limiting shear stress under stick‐slip conditions. Even during steady extrusion wall slip was evident. At a constant extrusion speed, the extrusion pressure was found to be very sensitive to the extrusion temperature. An increase from 120 to 125°C reduced the extrusion pressure by half. Various thermal pretreatments of the starting billets were found to have little effect on the extrusion behavior and physical properties of the extrudate.