Plasma-Jet Forming of Sheet Metal Shapes

Plasma-jet forming is a newly proposed flexible sheet metal forming process. A non-transferred arc plasma torch is used as a controllable heat source to produce internal stress in sheet metals, causing plastic deformation without the necessity of hard tooling. This method has potential for rapid prototyping of sheet metal parts by reducing development costs and lead times. A robotic system has been used to perform simple linear bends in several different alloys. In order to develop a controllable process and to improve the forming accuracy, the effects of various process parameters on the obtained shape changes and on the resulting structure and properties have been studied. The overall goal is to understand the roles of the forming parameters and their inter-relationship in optimizing the forming procedure-a high forming speed without damage to the material structure or properties.

Modeling of the Shape Forming of Composite Roll

A shape modeling of spray formed composite roll, which is utilized to predict the shape and dimension of roll during spray forming process, is developed in this paper. The influences of the principal spray forming parameters, such as the spatial distribution of melt mass flux, spray distance, rotating and translating speeds of substrate bar etc. , on the geometry and dimension of spray formed product were investigated.

An approach to form the dome shape by 3D laser forming

Application of a thermal source in non-contact forming of sheet metal is known for some time. Replacement of this thermal source with a laser beam promises the much greater controllability of the process. To date, research focuses on dealing with rectangular plates, and only a few studies are presented for axis-symmetric geometries like circular plates. This study presents the work to get the dish or bowl shape by an initially flat circular plate. Two different scanning strategies circular and radial are attempted to get the desired dish shape. Following the unexpected distortion throughout the plate, a second series of experiments are conducted on a wide range of specimen geometries. An interesting phenomenon is observed. It is suggested that homogeneous dissemination of heat along with combined form of both of the scanning strategies, could have more potential to form dome shape.

Three-dimensional multiple optical cages formed by focusing double-ring shaped radially and azimuthally polarized beams

We propose and simulate a method for generating a three-dimensional （3D） optical cage in the vicinity of focus by focusing a double-ring shaped radially and azimuthally polarized beam. Our study shows that the combination of an inner ring with an azimuthally polarized field and an outer ring with a radially polarized field and a phase factor can produce an optical cage with a dark region enclosed by higher intensity. The shape of the cage can be tailored by appropriately adjusting the parameters of double-mode beams. Furthermore, multiple 3D optical cages can be realized by applying the shift theorem of the Fourier transform and macro-pixel sampling algorithm to a double-ring shaped radially and azimuthally polarized beam.

Characterization of Prealloyed Ti–6Al–4V Powders from EIGA and PREP Process and Mechanical Properties of HIPed Powder Compacts

Prealloyed Ti-6Al-4V powders were prepared by electrode induction melting gas atomization （EIGA） and plasma rotating electrode process （PREP） in this work. A comparative study of EIGA and PREP powders for hot isostatic pressing （HIPing） compaction was conducted. Characterization of important technological parameters such as particle size distribution, powder surface morphology and flowability was carried out. Microstructure and mechanical properties of Ti- 6Al-4V powder compacts HIPed from EIGA and PREP powders were also investigated. The results showed that the EIGA powder has a finer average particle size and higher tap density, while the PREP powder has better flowability and less pores. Micropores can be observed in heat-treated EIGA powder compacts by X-ray tomography and the porosity was found to be about 0.02%. There are no micropores （≥4 μm） to be detected in heat-treated PREP powder compacts. Transgranular fracture mode as well as micropores contributes to the scatter in fatigue property of heat-treated PREP powder compacts. The respective advantages and disadvantages of both EIGA and PREP powders for producing Ti-based complex parts through HIPing were also discussed.

Promotion mechanism of the pulse current on the superplastic deformation of AZ31 magnesium alloy

The effects of pulse current on the superplastic deformation of AZ31 magnesium alloy with different microstructures were examined. The results of TEM analysis showed that the dislocation movement was mainly glide, and the dislocation lines were approximate parallel with few dislocation tangles observed, which indicated that the dislocation movementwas promoted during the deformation, and therefore the formability of the coarse-grained AZ31 magnesium alloy was enhanced by the pulse current. This effect was also indicated by the asymmetrical contour of the free bulging sample, which was observed in the unidirectional pulses auxiliary equi-biaxial tensile test of coarse-grained alloy. In addition, the phenomenon of the restrained cavity growth caused by the thermoelectrical effect of the pulse current was discovered and studied.