Upsetting Of Cylindrical Specimens Research Articles

Effects of Rocking Motion Induced by Multiple Linear Actuators in Upsetting of Cylindrical Specimen into Rectangular Shape

Effects of Rocking Motion Induced by Multiple Linear Actuators in Upsetting of Cylindrical Specimen into Rectangular Shape

Strain induced damage of ductile materials under compression

AbstractThe problem of ductile damage and failure prediction at the upsetting of cylindrical specimens with artificial voids is solved by taking a change in stress triaxiality into account. It is shown that such a more accurate assessment leads to a greater shift of stress triaxialities into a range of negative values as compared to their averaged values. At such values of stress triaxiality the material can be subjected to compression without failure under arbitrarily large deformations due to healing of micro‐defects. The constitutive equations of a recently developed tensorial framework for ductile damage [5] are applied to modelling. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Modelling Texturised Cast Structures in the Forging of Superalloys

The main objective of remelting processes commonly used in the production of super¬alloys is to obtain a columnar dendritic solidification structure throughout the whole ingot. Besides reduced microsegregation, this cast structure features a preferred orientation, which is depending on the primary dendrites’ growth direction and therefore closely related to the ingot’s pool shape. As a result, non-isotropic material behaviour can be observed during initial forging operations. Since the correct prediction of material flow is a prerequisite for the further analysis of forging processes by means of numerical simulation, the solidification texture’s influence on plastic flow was accounted for by the application of an anisotropic material model. The model according to Barlat was used to scale the flow stress with respect to the crystal orientations observed in the examination of vacuum arc remelted alloy 718, thereby considering the flow stress’ dependency on strain, strain rate and temperature. The parameters defining the material's anisotropy could be determined by the upsetting of cylindrical specimen from a remelted ingot.

Effect of aspect ratio on barreling contour and variation of total surface area during upsetting of cylindrical specimen

The barreling phenomenon that occurs at the upsetting of a cylindrical specimen and the effect of aspect ratio ( h/ d) on varying of a barrel contour were the main subject of this study. Aluminum 7075 (AlZnMgCu1.5) specimens were used as test specimens in the experiments. Specimens were upset between flat faced dies. Measurement data of upset specimens, which were obtained from experiments, are presented graphically. Progression of barreling contour and variation of total surface area according to the increase of barreling was investigated for different aspect ratios and a determined friction value and surface roughness.

Theoretical-experimental examination of the up setting of cylindrical specimens

Theoretical-experimental examination of the up setting of cylindrical specimens

Acoustic Emission From Simple Upsetting of Solid Cylinders

Acoustic emission (AE) generated during simple upsetting (forging) of solid cylinders contains information that could potentially be used to separate the upsetting process into a range of zones of plastic deformation and a zone of both plastic deformation and cracking. This investigation monitored the AE signals during the upsetting of cylindrical specimens of 7075-T6 Aluminum from the start of plastic deformation through eventual cracking. The count rate (N˙) and cumulative count (N) as a function of effective strain were determined. The count rate data are characterized by three distinct regions, an initial peak during yielding of the material, a period of gradual increase during the progression of plastic deformation and the accompanying changes in specimen geometry, and finally a region of rapid increase in N˙ as cracking begins. The cumulative count and rms data follow similar patterns. An analysis of the amplitude distribution of the cumulative count data over a range of strain was made, and in the region of higher amplitude emissions, changes in the distribution of up to two orders of magnitude are observed for data obtained during plastic deformation and surface cracking compared to that from the region of pure deformation only. If plotted as log count (N) versus signal amplitude, the resulting data can be fit with a line using least squares methods yielding a power law relationship sensitive to the degree of deformation.