Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “WELDING”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMed1991

The three dimensional distribution of chromium and nickel alloy welding fumes.

In the present study, the fumes generated from manual metal arc (MMA) and submerged metal arc (SMA) welding of low temperature service steel, and the chromium and nickel percentages in these fumes, were measured at various horizontal distances and vertical heights from the arc in order to obtain a three dimensional distribution. The MMA welding fume concentrations were significantly higher than the SMA welding fume concentrations. The highest fume concentration on the horizontal was shown in the fumes collected directly above the arc. The fume concentration vertically was highest at 50 cm height and reduced by half at 150 cm height. The fume concentration at 250 cm height was scarcely different from that at 150 cm height. The distribution of the chromium concentration vertically was analogous to the fume concentration, and a statistically significant difference in the chromium percentages was not found at the different heights. The nickel concentrations were not statistically significant within the welding processes, but the nickel percentages in the SMA welding fumes were statistically higher than in the MMA welding fumes. The highest nickel concentration on the horizontal was found in the fumes collected directly above the arc. The highest nickel concentration vertically showed in the fume samples collected at 50 cm height, but the greater the height the larger the nickel percentage in the fumes.

Air Pollutants, Occupational↗
PubMed1983

Comparison of the behavior of stainless and mild steel manual metal arc welding fumes in rat lung.

The lung retention and clearance of manual metal arc (MMA) stainless steel and mild steel welding fumes were determined in the rat. The exposure simulated the actual welding situation. The duration of exposure in the "nose-only" exposure chamber was 1 h/workday for one, two, three, or four weeks in the retention study and for four weeks in the clearance study. The concentration of exogenous iron was determined by the magnetic measuring method. Instrumental neutron activation analysis was applied to determine the concentration of total iron, chromium, and nickel in the lungs. The results indicated that the lung retention and clearance patterns for the two types of welding fumes were different. A linear relationship was observed between the amount of stainless steel MMA welding fume retained in the lungs and the duration of exposure, whereas the retention of mild steel MMA welding fume in the lung was saturated as a function of the cumulative exposure time rates. The maximum amount of lung-retained contaminants was 880 micrograms for stainless steel MMA welding fume and 220 micrograms for mild steel MMA fume.

Alloys↗
PubMed2000

[K-ras gene mutations of asbestos and welding-fumes related human lung cancer].

UNLABELLED: To investigate the K-ras gene mutations in asbestos and welding-fumes related human lung cancer (hLC), comparing with the mutational spectrum of K-ras gene in non-occupational hLC, 8 cases of non-occupational hLC, 9 cases of asbestos-related hLC and 4 cases of welding-fumes related hLC were collected. The techniques of genomic DNA extraction, nested-polymerase chain reaction (PCR), polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and DNA direct sequencing were employed. THE RESULTS: showed the mutation frequencies of K-ras gene were 25% in non-occupational hLC and welding-fumes related hLC, whereas 44.4% in asbestos-related hLC. Mutations mainly occurred in codons 12 and 15. A mutation of codon 13 was detected in welding-fumes related hLC. The type of base substitution was principally G-->T transversion in non-occupational hLC, whereas mainly G-->A transition in asbestos and welding-fumes related hLC. THE RESULTS suggested there were obvious differences of K-ras gene mutations among non-occupational hLC, asbestos and silica related hLC. Therefore, different mechanisms of carcinogenesis were implicated among them. However, no speific spectrum of K-ras gene mutation can be derived from welding-fumes related hLC because of the limitation of samples.

Asbestos↗
PubMed1990

Subfertility in relation to welding. A case referent study among male welders.

A recent report indicates that welding work is associated with increased risk of reduced semen quality. The purpose of this study was to investigate a possible association between welding exposure and male subfertility. A cross-sectional population of 673 metal workers and electricians employed at six major Danish work places in the same geographic area constituted the study population. Data on reproductive and occupational experience was obtained by means of a self-administered postal questionnaire. The response rate was 79 percent among welders and 83 percent among the other workers. A significantly increased rate of delayed conception in relation to welding work at the time of this event was observed when self-reported welding exposure among cases of delayed conception was compared to welding exposure both among age-matched referents and among referents with a child born without delay in conception. However, in the first approach the risk dropped to insignificant levels when adjustments were made for potential confounding factors. This preliminary study has methodological drawbacks, and the association between welding exposure and male fertility should be investigated further.

Adult↗
PubMed1986

Comparison of laser-welded and sutured arteriotomies.

We compared the histologic features, tensile strength, and collagen synthesis of laser-welded and sutured arteriotomies. Four bilateral canine femoral or carotid arteries, 2 cm long, were studied at one through four weeks postoperatively, with one vessel (control) closed with interrupted 6-0 polypropylene sutures and the contralateral vessel (experimental) welded with an argon laser (0.5 W [1417 J/cm2], four-minute exposure per 1-cm length of incision). Histologic examination revealed that laser-welded arteriotomies had less inflammatory reaction, more normal collagen and elastin reorientation, and similar endothelial continuity when compared with the control, sutured wounds. The tensile strength of the one- and two-week laser-welded specimens was less than that of sutured wounds and became approximately equal to sutured repairs at three and four weeks. There were no significant differences in the rate of collagen synthesis. There was no evidence of abnormal healing in the laser-welded specimens, suggesting that argon laser welding may be an alternative to suture repair of arteriotomies.

Animals↗
PubMed1996

Tendon repair by laser welding: a histologic and biomechanical comparison and suture repair with CO2 and argon lasers.

BACKGROUND AND OBJECTIVE: The purpose of this study was to determine whether welding of tendinous tissue is possible with the application of thermal lasers. STUDY DESIGN MATERIALS AND METHODS: After sharp transection of a unilateral achilles tendon, 40 male outbred Spraque Dawley rats were divided equally between four treatment groups. Ten animals underwent repair using the modified Kessler suture technique. The remaining animals underwent application of laser after the tendon edges were reapproximated and held in place with a vascular clamp. CO2 and Nd:YAG lasers were applied using 25% human albumin as a solder. Fluorescein dye was added to albumin and used as solder for the Argon laser. Biomechanical and histologic testing were performed immediately and 14 days postoperatively. RESULTS: Argon and CO2 lasers successfully fused the tendon ends together. However, immediately postoperative, the resultant tissue weld was tenuous and conventional tensile strength testing was not possible. At 14 days postoperatively, all modes of tendon repair resulted in tensile failure at consistently lower levels of tension than those required for the normal uninjured tendons. The ultimate tensile strength for the suture-repaired, CO2 laser welded, and Argon laser welded tendons were 74%, 59%, and 64% of the strength of the control tendons respectively. No statistically significant difference was found in the tensile strength among the three repair groups. Histologic evaluation at 14 days revealed the greatest degree of inflammatory response in those tendons repaired with the Argon laser. Those tendons repaired with suture demonstrated the least amount of inflammatory change. CONCLUSION: Our study demonstrates that welding of a tendon is possible with the application of laser energy. However, we were unable to produce a weld sufficient to withstand significant tensile loads in the immediate postoperative period.

Achilles Tendon↗
PubMed2006

Joint properties of cast Fe-Pt magnetic alloy laser welded to gold alloys.

This study investigated the joint properties of a cast Fe-Pt magnetic alloy (Fe-36 at % Pt) laser welded to three gold alloys. The gold alloys used were ADA Type II and Type IV gold alloys, and an Ag-based (Ag-Au) gold alloy. Cast plates (0.5 x 3.0 x 10 mm) were prepared for each alloy. After the cast Fe-Pt plates were heat treated, they were butted against each of the three alloys and then laser welded with Nd:YAG laser at 200 V. Homogeneously welded specimens were also prepared for each alloy. Tensile testing was conducted at a crosshead speed of 1 mm/min. Failure load (N) and elongation (%) were recorded. After tensile testing, the fractured surfaces were examined with the use of SEM. The failure-load values of the group of alloys welded homogeneously were ranked in the order of: Ag-Au alloy > Type IV alloy > Type II alloy > Fe-Pt alloy. The Type IV alloy welded to Fe-Pt alloy had the highest failure-load value among the three alloys tested. The elongation results tended to follow a similar pattern. The results of this study indicated that Type IV gold alloy is a suitable alloy for metal frameworks to which cast Fe-Pt magnetic alloy is laser welded.

Alloys↗
PubMed1988

Laser balloon angioplasty: effect of tissue temperature on weld strength of human postmortem intima-media separations.

Dehiscence of portions of atheromatous plaques fractured during percutaneous transluminal coronary angioplasty may contribute to both abrupt reclosure and gradual restenosis. Laser balloon angioplasty has been shown to be effective in welding human plaque-arterial wall separations in vitro by heating tissues with a Nd:YAG laser during balloon inflation. To define the potentially useful therapeutic range of tissue temperature required to achieve thermal welds, 220 1-cm diameter discs of human postmortem atheromatous aortic tissue, the intimal plaque of which had been separated from the media, were exposed to 3-25 watts of Nd:YAG laser radiation delivered over a 12-mm2 nominal spot size for 20 seconds via a 400-micron core optical fiber. As measured with a thermistor, adventitial temperature reflected the temperature at the plaque-media junction to within 10 degrees C. The degree of tissue temperature elevation was related to delivered energy, while effective tissue penetration increased to maximum depth of 3 mm at the highest power density. Strength of tissue welds was defined as the force required to shear opposing layers of welded segments. Adventitial tissue temperatures below 80 degrees C were not associated with appreciable welds, while equilibrium temperatures between 95 degrees C and 140 degrees C were consistently associated with effective mean weld strengths, which increased linearly from 25 to 110 g, respectively. Temperatures greater than 150 degrees C were associated with rapid tissue dehydration and charring. These data suggest that the therapeutic range of tissue temperature that provides effective thermal fusion of intima-media separations is broad and that the depth and degree of thermal coagulation can be controlled by manipulation of laser energy delivery.

Angioplasty, Balloon↗
PubMed1989

In vitro comparison of thulium-holmium-chromium: YAG and argon ion lasers for welding of biliary tissue.

Laser welding offers several potential advantages over suture closure, including improved healing, lack of a nidus for stone formation, and greater speed and ease. We examined in vitro gallbladder cystic duct welds created by two different systems, the thulmium-holmium-chromium (THC):YAG (2,150 nm) and argon ion (488-514 nm) lasers, in an effort to define suitable parameters for tissue fusion. Mean bursting pressures for argon welds were 95 mm Hg at 1.5 W CW and 26 mm Hg at 1.5 W, 50 msec chopped delivery. For the THC:YAG laser, the mean bursting pressure for welds created with 300 mJ pulses was 45 mm Hg. Full-thickness tissue fusion and limited collateral thermal damage were observed histologically for both the CW argon and pulsed THC:YAG welds. Examination of the suggested mechanisms of tissue fusion for these photothermal lasers suggests that increased duration of tissue heating at the appropriate temperature results in more extensive collagen crosslinking and a stronger weld.

Animals↗
PubMed1995

Laser patch welding: experimental study for application to endoscopic closure of bronchopleural fistula, a preliminary report.

BACKGROUND AND OBJECTIVE: Postoperative bronchopleural fistula is a serious complication following pulmonary resection. To close the bronchopleural fistula, we developed a new method of endoscopic patch welding using laser tissue welding between bronchial tissue and a patch. STUDY DESIGN/MATERIALS AND METHODS: The feasibility of the laser patch welding was examined by in vitro and in vivo animal experiments. A newly developed carbon monoxide (CO) laser and an Argon ion laser were evaluated. Various tissue membranes and artificial membranes were evaluated as patch materials. RESULTS: We found that the combination of expanded polytetrafluoroethylene (e-PTFE; 200 microns in thickness) and the CO laser with contact irradiation method offered the strongest laser patch welding. Using this combination, the irradiation at 400 W/cm2 for 10 seconds resulted in 16-18 g of measured traction strength at the welding spot (2 mm in diameter). The welded e-PTFE patch at bronchial stump remained for 5 weeks. CONCLUSION: Our results encourage use of this novel laser patch technique for clinical applications.

Animals↗
PubMed2005

Near infrared laser-tissue welding using nanoshells as an exogenous absorber.

BACKGROUND AND OBJECTIVE: Gold nanoshells are a new class of nanoparticles that can be designed to strongly absorb light in the near infrared (NIR). These particles provide much larger absorption cross-sections and efficiency than can be achieved with currently used chemical chromophores without photobleaching. In these studies, we have investigated the use of gold nanoshells as exogenous NIR absorbers to facilitate NIR laser-tissue welding. STUDY DESIGN/MATERIALS AND METHODS: Gold nanoshells with peak extinction matching the NIR wavelength of the laser being used were manufactured and suspended in an albumin solder. Optimization work was performed on ex vivo muscle samples and then translated into testing in an in vivo rat skin wound-healing model. Mechanical testing of the muscle samples was immediately performed and compared to intact tissue mechanical properties. In the in vivo study, full thickness incisions in the dorsal skin of rats were welded, and samples of skin were excised at 0, 5, 10, 21, and 32 days for analysis of strength and wound healing response. RESULTS: Mechanical testing of nanoshell-solder welds in muscle revealed successful fusion of tissues with tensile strengths of the weld site equal to the uncut tissue. No welding was accomplished with this light source when using solder formulations without nanoshells. Mechanical testing of the skin wounds showed sufficient strength for closure and strength increased over time. Histological examination showed good wound-healing response in the soldered skin. CONCLUSIONS: The use of nanoshells as an exogenous absorber allows the usage of light sources that are minimally absorbed by tissue components, thereby, minimizing damage to surrounding tissue and allowing welding of thicker tissues.

Animals↗
PubMed2001

Determination of Cr(VI) in welding fumes by anion-exchange fast protein liquid chromatography with electrothermal atomic absorption spectrometric detection.

The applicability of an anion-exchange fast protein liquid chromatographic-electrothermal atomic absorption spectrometric procedure (FPLC-ETAAS) was investigated for the determination of Cr(VI) in welding fumes after alkaline extraction of aerosols loaded on filters. Gas tungsten arc welding (GTAW) of stainless steel was applied. Samples of welding fumes were collected during regular welding on polycarbonate membrane filters of 8 microm and 0.4 microm pore size (inhalable and respirable aerosols). Alkaline extraction (2% NaOH-3% Na2CO3) of filters in a heated ultrasonic bath was applied to leach Cr from the airborne particulate matter. 0.5 cm3 of sample extract was then injected onto an anion-exchange FPLC column. Tris-HCl buffer (0.005 mol dm(-3), pH 8.0) and the same buffer with NaCl (0.5 mol dm(-3)) were employed in gradient elution (15 min, flow rate 1 cm3 min(-1)). The separated Cr species were determined "off line" by ETAAS in 0.5 cm3 fractions. Cr(VI) was reproducibly and quantitatively eluted from 12.0 to 13.0 min with a maximum peak at 12.5 min. Good repeatability of measurement (+/-3.0%) of alkaline extracts was obtained for Cr(VI). The LOD (3s) was found to be 0.035 microg m(-3) Cr(VI), when 2 m3 of aerosols were collected on the filter. Validation of the procedure was performed by spiking alkaline extracts and by the analysis of standard reference material CRM 545, Cr(VI) in welding dust loaded on a filter. The technique was successfully applied for the determination of Cr(VI) in welding fumes.

Journal Article↗
PubMed1986

Laser welding: an alternative method of venous repair.

This study compared the histology, biochemistry, tensile strength, and extensibility of Nd:YAG laser-welded and sutured venotomies. Two-centimeter-length bilateral canine femoral or jugular venotomies were evaluated with one vessel (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral vessel (experimental) welded with the Nd:YAG laser (1 W power and 30- to 40-sec exposure). Specimens were removed and examined immediately after fashioning (t0) and at 1, 4, or 5 weeks post-operatively to compare the progression of healing. Histologic examination of the 4- and 5-week sutured wounds had granulomatous reaction around the sutures with areas of excessive collagen accumulation. In contrast, the laser-welded wounds had minimal inflammatory response, near normal collagen content, and minimal residual disorientation and break in the elastic fiber continuity. The rate of collagen synthesis in laser-welded wounds was approximately twice that of sutured wounds at 1, 4, and 5 weeks, and correlated with increased tensile strengths of lasered wounds. The extensibility of the 5-week specimens was 0.19 for sutured and 0.29 for laser-welded wounds as compared to 0.29 for normal vein. These preliminary data suggest that laser welding of venotomies may have several advantages over conventional suture techniques.

Animals↗
PubMed1997

Mechanical and elemental characterization of solder joints and welds using a gold-palladium alloy.

PURPOSE: This study was conducted to determine whether newer infrared or laser welding technologies created joints superior to traditional furnace or torch soldering methods of joining metals. It was designed to assess the mechanical resistance, the characteristics of the fractured surfaces, and the elemental diffusion of joints obtained by four different techniques: (1) preceramic soldering with a propane-oxygen torch, (2) postceramic soldering with a porcelain furnace, (3) preceramic and (4) postceramic soldering with an infrared heat source, and (5) laser welding. MATERIAL AND METHODS: Mechanical resistance was determined by measuring the ultimate tensile strength of the joint and by determining their resistance to fatigue loading. Elemental diffusion to and from the joint was assessed with microprobe tracings. Scanning electron microscopy micrographs of the fractured surface were also obtained and evaluated. RESULTS: Under monotonic tensile stress, three groups emerged: The laser welds were the strongest, the preceramic joints ranged second, and the postceramic joints were the weakest. Under fatigue stress, the order was as follows: first, the preceramic joints, and second, a group that comprised both postceramic joints and the laser welds. Inspection of the fractographs revealed several fracture modes but no consistent pattern emerged. Microprobe analyses demonstrated minor diffusion processes in the preceramic joints, whereas significant diffusion was observed in the postceramic joints. CLINICAL IMPLICATIONS: The mechanical resistance data conflicted as to the strength that could be expected of laser welded joints. On the basis of fatigue resistance of the joints, neither infrared solder joints nor laser welds were stronger than torch or furnace soldered joints.

Ceramics↗
PubMed1998

Mechanical properties of laser-welded cast titanium joints under different conditions.

STATEMENT OF THE PROBLEM: Data on optimal conditions for laser welding commercial pure cast titanium used in dental restorations are sparse and not well established. PURPOSE: The mechanical properties of laser-welded cast commercially pure titanium under different laser welding conditions were evaluated to find the optimal parameters in terms of duration and voltage (energy level). MATERIAL AND METHODS: Fifty-seven cast pure titanium specimens according to ISO specification 6871 were divided into nine experimental groups and one control group. The sectioned titanium bars were laser-welded under different duration (8, 10, and 12 ms) and energy (290, 300, and 310 V) levels and evaluated for ranges of ultimate tensile strength (374 to 562 MPa), 0.2% yield strength (206 to 338 MPa), and percentage elongation (2.49% to 10.58%). RESULTS: Under a suitable laser-welding setting parameter the ultimate tensile strength and 0.2% yield strength of experimental groups were weaker than the unsectioned control specimens (control group ultimate tensile strength 540 +/- 11 MPa, 0.2% yield strength 258 +/- 49 MPa) or too brittle (control group percentage elongation 12.41% +/- 1.83%). Two-way ANOVA, nonparametric tests showed that voltage was the only significant factor for all parameters studied (p < 0.01). Optimal conditions were determined with three-dimensional response curves (305 V, 12 ms ultimate tensile strength; 310 V, 10 ms 0.2% yield strength; 300 V, 12 ms percentage elongation). CONCLUSION: Optimal duration and voltage (energy level) used in laser welding for cast CP grade I titanium bar was superior to or comparable with and produced properties that were superior to or comparable with the unsectioned control specimens.

Analysis of Variance↗
PubMed1994

Development and initial application of a real time thermal control system for laser tissue welding.

The ability to sense and control continuously surface temperatures of a tissue being exposed to laser radiation could standardize parameters and eliminate subjective interpretation of results during laser tissue repair. We describe the development and testing of a control system that enables the operator to maintain relatively specific tissue temperatures for the purpose of laser welding. After initial development, the infrared thermal control system combined with an argon laser was used to repair urethral defects in 45 adult male rats. Repairs were completed using various predetermined temperatures of 50, 60, 70, 80 or 90C. The integrity of each weld was quantitatively determined by measuring intraluminal bursting pressure immediately after repair. In all temperature groups bursting pressures were in excess of 85 mm. Hg. Those performed at 80C produced the strongest weld (analysis of variance p = 0.0001). However, welding temperatures above 70C sacrificed the integrity of the underlying urothelium producing obvious damage when viewed microscopically. We were able to demonstrate that temperature is an objective parameter of tissue welding that can be continuously assessed and controlled during the laser repair of tissue defects to produce effective, predictable welds.

Animals↗
PubMed1992

Arterial laser welding with a 1.9 micrometer Raman-shifted laser.

A new 1.9 micron Raman-shifted neodymium:yttrium aluminum garnet (Nd:YAG) laser was used for small vessel welding. Bursting pressures and stresses of sutured and laser-welded arteriotomies created in the rat femoral artery and aorta were measured. Sutured arteriotomies had a significantly higher burst stress than laser-welded arteriotomies. Although there were no significant differences in burst stress at the various laser powers tested, an optimal power was identified. The laser was also used to weld transected rat aortas. The average power delivered was 200 mW for 30 seconds per anastomosis. The average time for completing an anastomosis was 6 minutes compared with 18 minutes when sutures were used. In relation to proximal aortic diameter, there was a 7.9% decrease at the anastomosis immediately (n = 4), and a 6.6% and 4.9% increase occurred at 24 hours (n = 4) and 10 weeks (n = 5), respectively. Acute anastomotic compliance, and compliance at 24 hours and 10 weeks were decreased by 47.2%, 39.5%, and 47.8%, respectively, and were similar to sutured anastomoses. Histology showed little thermal denaturation of the aorta within 0.6 mm of the anastomosis, approximately 1 mm of medial cell death, and nearly normal elastic fiber alignment. One focal false aneurysm was noted at 10 weeks. Although the sutured and laser-welded anastomoses share similar compliance changes, the laser-welded anastomoses are more isodiametric. This preliminary experience with the 1.9 micron laser shows the distinct advantages of a handheld fiber, no requirement for cooling irrigation, speed, and no difference in compliance from sutured anastomoses.

Analysis of Variance↗
PubMedDate not supplied

Exposures from thorium contained in thoriated tungsten welding electrodes.

Information provided in this article can be used for estimating the radiation dose associated with the use of thoriated tungsten electrodes in tungsten inert gas welding. Area and breathing zone concentrations of 232Th generated by welding and electrode sharpening along with particle size information; isotopic composition of electrodes from two domestic manufacturers and one European manufacturer; and process variables and estimates on the number of thoriated tungsten electrodes manufactured are presented. Past literature is reviewed and compared with the results of this study. Isotopic analysis of a nominal 2% thoriated electrode found 0.6 ppm +/- 0.4 ppm 230Th and less than 0.1 ppm 228Th. Analysis of a ceriated tungsten electrode and a lanthanated tungsten electrode for 232Th found 124 ppm and 177 ppm, respectively. Electrode consumption during welding was primarily the result of tip sharpening. Less than 3% of the weight loss was attributable to the welding process. The in-mask concentration of respirable thorium particulate in the welder's breathing zone was 0.002 x 10(-12) microCi 232Th/mL. The concentration of respirable thorium particulate from electrode sharpening was 1.3 x 10(-12) microCi 232Th/mL. The measured sharpening time was 20 sec per electrode. Estimates of the activity median aerodynamic diameters for the respirable fraction of the welding and electrode sharpening aerosols were 3.5 and 5 microns, respectively, when measured in the breathing zone at 0.3 m (12 inches) from the point of operation. The respirable fraction of the total welding and sharpening aerosols was 45 and 60%.

Air Pollutants, Occupational↗