1,721,315 research outputs found
Influence of process parameters in electrostatic fluidized bed coating
Full text linkExperimental analysis of the electrostatic fluidized bed coating process of carbon steel thin sheets was performed using two different mesh-sized epoxy-polyester powders. In particular, systematic analysis of the influence of the operative variables oil coating and process variability in the field of low film thickness (below 100 mu m), was carried out, which for electrostatic fluidized beds has previously not been considered feasible. In this context, the effect of varying both the electrostatic and fluidized bed setting oil the amount of the powder layer coating the workpiece surface was studied. In particular, exposure time, applied corona voltage, and airflow rate were found to influence the performance of the coating process significantly. Experimental results produced coating thickness trends consistent with theoretic expectations. In particular, effects on the coating process of both electric and aerodynamic forces, which in turn affect the powder particles drawn up to the work-piece surface could largely be predicted by examining experimental data. A set of 3D maps of the coating thickness achieved are also reported as they provide a useful tool to monitor the process in a 5 - 15 s time range, applied voltage from 45 to 90 kV, and flow rate from 3 to 11 m(3)/h. (c) 2005 Elsevier B.V. All rights reserved
Electrostatic fluidized bed deposition of a high performance polymeric powder on metallic substrates
Full text linkThe electrostatic fluidized bed deposition of a single-layer PPA 571 coating onto low carbon steel rods is reported. A full factorial experimental design was developed in order to study the influence of several operative variables on the effectiveness of the coating process and on the coating thickness and uniformity. The operative variables included exposure time, air flow, the applied voltage, attitude, and the radial and vertical location of the work-piece in the fluid bed. After the experimentation, several process maps were developed as a support to identify the best way to lead the coating process. Finally, by using a statistical approach, the reliability and repeatability of the coating process was also established. Experimental trends were consistent with theoretical expectation. A significant growth in achievable coating thickness was obtained by increasing voltage and air flow. Furthermore, at higher values of exposure time and applied voltage, relevant back ionization phenomena occurred, which simultaneously caused a top limit in coating thickness and a worsening of surface finishing. Process characteristics, leading mechanisms, and some practical aspects are also discussed in detail. (c) 2005 Elsevier B.V. All rights reserved
Development of an abrasive jet machining system assisted by two fluidized beds for internal polishing of circular tubes
No full textThis paper deals with the definition of a relatively novel machining technology to finish the internal part of narrow and long tubular parts made from high resistance stainless steel. A hybrid technology, namely, fluidized bed assisted abrasive jet machining (FB-AJM), was developed and a thorough experimental investigation was concurrently performed. First, a systematic approach, based upon design of experiments, was used to examine the influence of leading operative variables on process. Surface roughness and material removal trends consistent with theoretical expectations were found. Subsequently, the machining mechanisms were analyzed in terms of the evolution of roughness and waviness profile. FB-AJM was found to be a not pressure-copying machining technology. Lastly, the uniformity and the precision of machining all around the internal circumferences of the workpieces were checked out to assure the applicability of FB-AJM to process an ever-growing variety of complex shaped components. © 2005 Elsevier Ltd. All rights reserved
Laser cutting of reinforced materials
No full textThe work is a review of the laser cutting of Fibre Reinforced Plastics: the major parameters determining the cutting results, especially with respect to quality, are discussed and explained
Characterization of laser beam transmission through a High Density Polyethylene (HDPE) plate
No full textInfrared (IR) light propagation in semicrystalline polymers involves mechanisms such as reflection, transmission, absorption and internal scattering. These different rates determine either the interaction mechanism, either the temperatures reached in the IR heating processes. Consequently, the knowledge of these rates is fundamental in the development of IR heating processes in order to avoid the polymer's damage and to increase the process energy efficiency. Aim of this work is to assess a simple procedure to determine the rates of absorbed, reflected, transmitted and scattered energy in the case of an unfilled High Density Polyethylene (HDPE) plate. Experimental tests were performed by exposing a HDPE plate, 3 mm in thickness, to a diode laser source, working at the fundamental wavelength of 975 nm. The transmitted power was measured by power meter, the reflected one by applying the Beer–Lambert law to sample of different thickness. IR thermal images were adopted to measure the absorbed ratio. The scattered ratio was measured by energetic balance, as difference between the incoming power and the other ratios. Finally, IR thermal images were adopted to measure the scattered ratio and to validate the procedure
ADVANCE IN ADAPTABLE AND RECONFIGURABLE SYSTEMS: THE APPLICATION OF A DIODE LASER SOURCE TO METALS PROCESSING
No full textHeat affected zone induced by laser forming
No full textLaser forming induces mechanical and structural modifications around the Laser Scanning Path. Various conventional methods are currently available to estimate properties of materials like X-ray and neutron diffraction, strain/curvature measurement, hole drilling, layer removal, chemical etching, etc. but their use is severely restricted due to measurement accuracy, applicability to different materials and geometrical configurations. An application of an experimental method to estimate mechanical properties associated with laser forming of metallic sheets is proposed. This method is based on an instrumented indentation technique which offers a more flexible tool to measure mechanical properties of Heat Affected Zone. The main advantage of this technique consists of testing complex geometric forms with a cheap system able to be used for on-line implementation. The experimental validation of the method was performed calibrating the procedure by using several indentation tests in standard condition. A full map of mechanical properties was subsequently traced employing systematic investigations focused on specimens zone closer to the laser heated scanning path
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