An Optimization Design for Coefficient of Weld Reinforcement in Rapid Prototyping Based on Robotic Pulse MAG Forming

During the process of rapid prototyping based on robotic pulse MAG forming, the coefficient of weld reinforcement is crucial to the geometric accuracy and mechanical property of metallic parts. The orthogonal design method, as well as the range analysis and variance analysis, were applied in this article to study the effects of wire feed rate, welding speed, pulse correction and arc length correction on coefficient of weld reinforcement, finding out the factors which were significant to the coefficient of weld reinforcement and optimizing the process parameters. The experimental results show that the order of the significance of parameters is as following: the welding speed, the arc length correction, the wire feed rate, and the pulse correction. Among them, the welding speed and arc length correction have the greatest influence on the coefficient of weld reinforcement, as is 0.025. The optimal process parameters are: arc length correction 8%, welding speed 14mm/s, wire feed rate 7.2m/min and pulse correction 0. At the same time, the coefficient of weld reinforcement is between 2.94 and 3.00, as the degree of confidence is 97.5%.

Simulated and Associated Experimental Results of CdZnTe Radiation Detector Response for Gamma-Ray Imaging Applications

Simulated and associated experimental results of a high efficiency CdZnTe (CZT) radiation detector response for gamma-ray imaging applications are presented. The model of a high efficiency semiconductor gamma ray detector takes into account several different physical phenomena involved in the detection and correction processes, namely the geometry of the irradiation, the gamma-ray's interaction with the crystal, the physics of the semiconductor's charge collection, the electric field distribution and the pulse height correction method. A few important decoupling assumptions allow us to use a one dimensional charge collection simulation with a two-dimensional field model and a full three dimensional Monte-Carlo calculation of the gamma ray interactions. The model allows calculation of charge collection and gamma ray spectra for non uniform electric field distribution in either planar, striped or pixellated detector.The model takes also into account the new CZT fast pulse correction method and its associated noise by considering the pulse height and the rise time of electron signals (Bi-Parametric spectrum) for all gamma ray interactions. Specific simulated and experimental spectra at 122 keV are presented for CZT. First, basic spectral changes are calculated for variations in crystal and detector properties like mobility, trapping lifetime and electric field profilesSecond, new experimental results of the fast pulse correction method applied to different CZT detector grades are presented. This method allows to achieve a high detection efficiency (> 80 %) with a good energy resolution (< 6 % FWHM) at 122 keV for a 4×4×6 mm3 CZT detector. No specific contact geometry is needed and the unusual low applied bias voltage allows to limit the ageing and break voltage effects and also the dark current and its associated noise. This fast correction method is expected to be useful for medical imaging and other applications.Finally, simulated Bi-Parametric (BP) spectra expected with the fast pulse correction method according to the detector properties (electric field profiles, electron lifetime) are simulated and a qualitative comparison is provided.