Heat-affected Area Research Articles

Nutritional, immunological and microbiological profiles of burn patients

A burn is a lesion on an organic tissue resultant from direct or indirect action of heat on the organism. The present study aimed to evaluate the nutritional, immunological and microbiological status of burn patients at the Bauru State Hospital, São Paulo state, Brazil, in 2007. Eight patients, aged more than 18 years and injured up to 24 hours, were evaluated at the moment of hospitalization and seven days later. All victims were males with a mean age of 38 years. On average, 17.5% of their body surfaces were burned and 50% of the patients were eutrophic. There were significant alterations in levels of erythrocytes, hemoglobin, hematocrit, total protein and albumin due to increased endothelial permeability, direct destruction of proteins in the heat-affected area and blood loss from lesions or debridement. At a second moment, cytokines IL-6 and TNF-α had augmented significantly, with IL-6 presenting elevated levels in relation to controls at the first moment. Microbiological analysis showed that 100% of the samples collected at hospital admission were negative and after one week Staphylococcus aureus was found in all cultures. Therefore, a burn patient may be considered immunosuppressed and these results indicate significant nutritional, immunological and microbiological alterations that can interfere in his recovery.

Finite element analysis and verification of laser marking on eggshell

The first aim of the study was to establish the temperature model of the eggshell by the finite element analysis software ANSYS and realize the eggshell temperature field based on the laser marking processing. The eggshell surface which created the meshing model, set the parameters with the ANSYS Parameter Design Language and simulated that the Gaussian distributed laser beam acted on the surface were established. In addition, marking characters made use of the CO 2 laser processing system on the brittle eggshell to analyze whether laser beams caused damage to the inner of the eggshell. According to the results of the comparison between the simulation by ANSYS and the experiment of laser marking, it is revealed that the heat-affected area by laser marking is similar to that of the simulation.

마이크로 열소자 제작을 위한 고세장비 금속채널의 레이저 가공

A fabrication method fur high-aspect-ratio microchannels in stainless steel using laser-assisted thermochemical wet etching is reported in this paper. The fabrication of deep microchannels with an aspect ratio over ten is realized by applying a multiple etching process with an optimization of process conditions. The cross-sectional profile of the microchannels can be adjusted between rectangular and triangular shapes by properly controlling laser power and etchant concentration. Excellent dimensional uniformity is achieved among the channels with little heat-affected area. Microchannels with a width ranging from 15 to can be fabricated with an aspect ratio of ten and a pitch of 150 m or smaller. The effects of process variables such as laser power, scan speed, and etchant concentration on the fabrication results, including etch width, depth, and cross-sectional profile are closely examined.

Water droplet erosion and microstructure of laser-nitrided Ti6A14V

The ability of laser nitriding to improve water droplet erosion resistance of Ti6Al4V alloy was studied. Using a CO 2 continuous laser, a layer of about 400 μm thickness was nitrided and another layer of 400–500 μm was only heat affected. Electron microscopy observations showed that the microstructure of nitrided layers consists essentially of TiN compounds which are embedded in Ti(α) matrix. Depending on the nitrogen concentrations within the feeding gas, the titanium nitrides exhibited plate-like shape or dendritic morphologies. Below the nitrided layer a thickness of 50–100 μm of samples underwent martensitic structure which in its turn gives rise progressively to bimodal (α + β) base material. Laser nitriding increased microhardness from 370–400 to 650–800kgf mm −2, and enhanced erosion resistance significantly compared with untreated Ti6A14V and hardened 12% Cr stainless steel. The mechanism of material removal by erosion was changed from work hardening and platelets detachment in untreated samples to brittle fracture by formation of large flakes and spalling in nitrided layers. Advanced stages of erosion are accompanied by the appearance of macrocracks of ten in the nitrided zone, but some of them propagate even into heat-affected area. The annealing at 650 and 700°C of the laser-nitrided samples results in precipitation of β phase rich in vanadium.

Real-time imaging for thermal spray process development and control

Thermal spray and other high-temperature industrial processes are quite difficult to monitor with the human eye, because the luminous volume of the plasma or flame obscures the behavior of the solid or molten material in the heat-affected area. When a photographic or video camera is used, viewing is further degraded by the extreme contrast variation across the image area, making it impossible to achieve proper exposure throughout the image—except possibly for small areas of comparable brightness. Optical filtering with neutral density filters, such as those used in a welder’s helmet, are of no practical benefit. With thermal spray processes, the injection and flow of particles within the plasma flame is almost totally concealed by the extreme brightness of the plasma, flame, or arc. In addition, the particles quickly accelerate to very high speeds, making their detection even more difficult. This article discusses the development of integrated thermal spray process monitoring and analysis techniques based on two principles. The first is a unique vision sensing system that suppresses the flame, plasma, arc, or other high-luminosity phenomena in the video image. A further improvement is the use of dedicated image and analysis processing to enhance the sensor images and extract features of interest or dimensional measurements. These experimental techniques can be used as feedback for automated process monitoring and control.

Welding of Titanium using Normal Pulse Nd-YAG Laser

Soldering has been chiefly used for jointing prosthetic materials. Titanium is very difficult to solder because it is highly susceptible to oxidation. The recent development of an infrared heater soldering system is expected to make titanium soldering easier. However, because this soldering system uses a solder different from the conventional solder, it may cause problems in the oral cavity such as low resistance to corrosion. Titanium soldering requires prior fixation with the investment material. Therefore, the authors recently attempted laser welding of titanium.In this attempt, normal pulse Nd-YAG laser (ML-2310A, Miyachi Technos Co.) was used. Laser welding was first used to join 2 titanium cast crowns together and then 2 round tita nium rods (2mm in diameter) together under the following settings: voltage, 300V; pulse width, 6ms (for crowns) or 5ms (for round rods); output, 7J (for crowns) or 6J (for rods). The round rods were rotated during welding. The focus spot diameter was 0.6mm. Laser was applied to the materials while spraying argon gas onto them.In both cases, laser welding resulted in glossy and strong union. Because the spot diameter was small, the heat-affected area was very narrow. Therefore, direct welding on a working model was possible, without necessitating fixation with an investment material. In case of round rods, it was possible to hold one end of both rods between fingers during laser welding. Because laser welding is a kind of sweating, it is expected to involve no risk for reduction of anti-corrosion resistance inthe welded area.The weld strengths of titanium plate specimens obtained by two different welding techniques were compared. With a laser beam (70mm in focal distance, 0.8mm in diameter), two titanium plates (40×10×3mm), superimposed each other 2mm at the end, were welded either by lap seam welding or by spot welding. The load required to tear off the joint by pulling for the spot-welded specimen was 56kgf in average, while that for the lap-seam-welded specimen was more than 106kgf in average, where the breakage of the base metal often arose in the proximity of the weld.A major factor hampering the utilization of titanium for prosthesis is the difficutly in processing. If laser welding is introduced to titanium, the dental application of titanium will widen.