Mathematical Modeling of Optical Radiation Emission as a Function of Welding Power during Gas Shielded Metal Arc Welding
Abstract Arc welding is accompanied by intense optical radiation emission that can be detrimental not only for the welder himself but also for people working nearby or for passersby. Technological progress advances continuously in the field of joining, so an up-to-date radiation database is necessary. Additionally, many literature irradiance data have been measured for a few welding currents or for parts of the optical spectral region only. Within this paper, a comprehensive study of contemporary metal active gas, metal inert gas, and cold metal transfer welding is presented covering optical radiation emission from 200 up to 2,700 nm by means of (spectro-) radiometric measurements. The investigated welding currents range from 70 to 350 A, reflecting values usually applied in industry. Based upon these new irradiance data, three mathematical models were derived in order to describe optical radiation emission as a function of welding power. The linear, exponential, and sigmoidal emission models depend on the process variant (standard or pulsed) as well as on the welding material (mild and stainless steel, aluminum). In conjunction with the corresponding exposure limit values for incoherent optical radiation maximum permissible exposure durations were calculated as a function of welding power. Typical times are shorter than 1 s for the ultraviolet spectral region and range from 1 to 10 s for visible radiation. For the infrared regime, exposure durations are of the order of minutes to hours. Finally, a validation of the metal active gas emission models was carried out with manual arc welding.
Ultraviolet spectral irradiance measurements: an intercomparison of spectroradiometers in laboratory combined with a workplace field test
Ultraviolet (UV) irradiance measurements are usually associated with large inaccuracies and uncertainties complicating the comparability of corresponding measurement equipment and its data. For supervisors or safety experts, though, it is mandatory to measure reliable UV irradiances with regard to occupational safety regulations. The following work aims at an intercomparison of five different types of spectroradiometers regarding their wavelength alignment and irradiance accuracy in the UV spectral region that provides the reader with information on how to determine and compare the measurement accuracies of their own devices. In a first step, measurements of two UV irradiance standards, a deuterium and a halogen lamp, were carried out. The percentage deviations of the measured total UV irradiances from their calibrated ones are smaller than ±10% for all spectroradiometers. The quality of wavelength accuracy as well as of the spectral bandwidth, both investigated by means of a low pressure mercury argon lamp are consistent with those stated by the manufacturers. In a second step, UV radiation from a metal active gas welding arc was examined at three distances in combination with a variation of welding current and arc length to check the behaviour of UV irradiance accuracy in field. The overall averaged standard deviation of these field measurements for all CCD array detectors is given by ±8%. For high welding currents this accuracy decreases to ±21%.
Ultraviolet Radiation
another in the animal body. The full demonstration of the importance of transmethylation and of its relationship to the metabolism of choline, betaine, creatine, sarcosine, and a number of other methylated substances involved research that extended over a number of years. The discussion forms the subject matter of three of the chapters and requires considerably more than one-half of the book. In the last chapter, the author describes briefly the most recent investigations of the complex polypeptide pressor hormones of the posterior pituitary, studies in which modern techniques are applied to the problem of the determination of amino acids and in which the trail of research has led in full circle back to a problem similar to that with which it started, the determination of cystine in insulin. Taken together, this discussion of the work of the author and his numerous collaborators is an outstanding example of what is best in American biochemistry. It illustrates the application of rigid and relentless chemical logic to the solution of biological problems, some of which were relatively simple but most of which were extremely complex. Inevitably the book will become required reading for all graduate students in biochemistry and it will indeed serve as an encouragement to them, for it shows how the wellplanned experimental attack in which nothing is left to chance and no loose ends remain for others to toy with leads in the end to unequivocal advance in knowledge.