Portable instrument for in-vivo infrared oxymetry using spread-spectrum modulation

Near Infrared Spectroscopy (NIRS) can be employed to monitor noninvasively and continuously local changes in hemodynamics and oxygenation of human tissues. A portable NIRS research-grade acquisition system, dedicated to measurements during muscular exercise, is presented. The instrument is able to control up to eight LED sources and two detectors. A digital correlation technique, implemented on a single-chip RISC microcontroller, performs source-to-detector multiplexing. Such algorithm is highly optimized for computational efficiency and ambient noise rejection. Software-configurable input stages allow for flexibility in instrument setup. As a result of the specific correlation technique employed, the instrument is compact, lightweight and efficient. Clinical tests on oxygen consumption show excellent performance

Portable instrument for in-vivo infrared oxymetry using spread-spectrum modulation

Near Infrared Spectroscopy (NIRS) can be employed to monitor noninvasively and continuously local changes in hemodynamics and oxygenation of human tissues. A portable NIRS research-grade acquisition system, dedicated to measurements during muscular exercise, is presented. The instrument is able to control up to eight LED sources and two detectors. A digital correlation technique, implemented on a single-chip RISC microcontroller, performs source-to-detector multiplexing. Such algorithm is highly optimized for computational efficiency and ambient noise rejection. Software-configurable input stages allow for flexibility in instrument setup. As a result of the specific correlation technique employed, the instrument is compact, lightweight and efficient. Clinical tests on oxygen consumption show excellent performance

Implant Test And Acoustic Emission Technique Used To Investigate Hydrogen Assisted Cracking In The Melted Zone Of A Welded Hsla-80 Steel [uso Del Ensayo De Implante Y La Tecnica De Emision Acustica Para Estudiar El Agrietamiento Asistido Por Hidrogeno En La Zona Fundida En La Soldadura De Un Acero Hsla-80]

Weld metal hydrogen assisted cracking was studied using two flux cored wire (AWS E 70T-5 and AWS E 120 T5-K4) and a mixture gas of CO2 + 5% H2 to induce high values of diffusible hydrogen in high strength low alloy steel (HSLA-80) weldments. An Acoustical Emission Measurement System (AEMS) RMS voltmeter was coupled to the implant test (NF 89-100) apparatus to determine energy, amplitude and event numbers of signal. All cracks were initiated in the partially melted zone and propagated into the coarse-grained region of the heat affected zone when E 70 T5 consumable was used, and the quasi-cleavage fracture mode was predominant. When E 120 T5 K4 consumable was used the cracks propagated vertically across the fusion zone, and a mixed fracture mode was the most important. A significant relationship between acoustic emission parameters and fracture modes was found.354233241Vuick, J., (1992) Weld. World, V31 (5), pp. 308-321Svensson, L.E., (1994) Control of Microestrutures and Properties in Steel Arc Welds, pp. 39-44. , The ESAB Group. Esab AB. Gotherburg (Suecia). CRC Pres, IncBeachem, C.D., (1972) Metall. Trans., 3 (2), pp. 437-451Yurioka, N., Suzuki, H., (1990) Int. Mater. Rev., 35 (4), pp. 217-249Gedeon, S.A., Eagar, T.W., (1990) Weld. J., pp. 213s. , junioFang, C.K., Kannatey-Asibu E., Jr., Barber, J.R., (1995) Weld. J., pp. 177-184. , junioTrevisan, R.E., Ferraresi, A.V., Abstracts of Papers (1998) 79th Am. Weld. Soc. Annual Meeting (EE.UU.), p. 151. , 26-30 abrilCarpenter, S.H., Smith D.R., Jr., (1990) Metall. Trans. A, 21 A, pp. 1933-1938. , julioFals, H.C., Trevisan, R.E., (1998) Proceedings. 17th Int. Offshore & Arctic Engineering Conference, , Lisboa (Portugal), 5-9 julio(1986) Standard Methods for Determination of the Diffusible Hydrogen Content of Martensitic, Bainitic, and Ferritic Steel Weld Metal Produced by Arc Welding, , 17 p(1982) Cold Cracking Test Methods Using Implants, , Abril 10 pMota, J.M.F., Apps, R.L., (1982) Weld. J., pp. 222s. , juli

Effects Of Nitrogen And Pulsed Mean Welding Current In Aisi 316 Austenitic Stainless Steel Solidification Cracks [efecto Del Nitrógeno Y La Corriente Media Pulsada De Soldadura En La Formación De Grietas De Solidificación En Aceros Inoxidables Aisi 316l]

An analysis of the influence of nitrogen concentration in the weld zone and the pulsed mean welding current in the solidification crack formation is presented in this paper. The AISI 316L austenitic stainless steel was employed as the metal base. The welding was done using CC+ pulsed flux cored arc welding process and AWS E316LT-1 wire type. The tests were conducted using CO2 shielding gas with four different nitrogen levels (0, 5, 10 and 15 %) in order to induce different nitrogen weld metal concentrations. The pulsed mean welding current was varied in three levels and the Transvarestraint tangential strain test was fixed of 5 %. The results showed that the solidification cracking decreased as the pulsed mean welding current increase. It was also verified that an increase of the weld zone nitrogen level was associated with a decrease in both the total length of solidification crack and the amount of δ ferrite.384256262Fredriksson, H., (1972) Metall. Trans., 3, pp. 2989-2997Padilha, A.F., Guedes, L.C., (1994) Aços Inoxidáveis Austeníticos. Microestrutura e Propriedades, , Hemus Editora Ltda, São Paulo, BrasilFolkhard, E., (1988) Welding Metallurgy of Stainless Steels, , Springer-Verlag Wien, New York, EE.UUSuutala, N., Takalo, T., Moisio, T., (1980) Metall. Trans., 11 (A), pp. 717-725Suutala, N., Takalo, T., Moisio, T., (1979) Metall. Trans., 10 (A), pp. 1183-1190Lothongkum, G., Viyanit, E., Bhandhubanyong, (2001) J. Mater. Process. Technol., 110, pp. 233-238Backman, A., Lundqvist, B., (1977) Weld. J., JANUARY, pp. 23s-28sKearns, J.R., (1985) J. Mater. Energy Syst., 7, pp. 16-26Rabensteiner, G., (1985) Weld. World., 23, pp. 26-34Baeslack W.A. III, Savage, W.F., Duquete, D.J., (1979) Weld. J., MARCH, pp. 83s-90sOgawa, W., Murata, K.A.S., Tsunetone, E., (1980) J. Jpn. Weld. Soc., 49, pp. 564-571Klimpel, A., Mazur, W., Szymanki, A., (1979) Przegl. Spawalnictwa., 31 (6), pp. 9-12Zhitnikov, N.P., (1981) Weld. Prod., 28 (3), pp. 15-17Vitek, J.M., Dasgupta, A., David, S.A., (1983) Metall. Trans., 14, p. 1833Lundin, C.D., Chou, C.P.D., Sullivan, C.J.H., (1980) Weld. J., AUGUST, pp. 226s-232sBernstein, A., Areskoug, M., (1971) Aust. Weld. J., SEPTEMBER, pp. 84-87Arata, Y., Matsuda, F., Saruwatari, S., (1974) Trans. JWRI., 3 (1), pp. 79-88Kotecki, D.J., (1978) Weld. J., pp. 109s-117sHammar, O., Svensson, U., (1979) Solidification and Casting of Metals, pp. 401-410. , The Metals SocietyVarol, I., Baeslack, W.A., Lippold, J.C., (1997) Mater. Characterization, 39, pp. 555-57

Homopolar Pulsed Welding for Offshore Applications

Center for Electromechanic

Homopolar Pulsed Welding: Interface Properties of High Strength Steel Pipe, a Technical Note

This note discusses the microstructure, hardness, and toughness of a homopolar weld (HPW) performed on API 5L grade X-52 line pipe (90 mm diameter and 10 mm wall thickness). Homopolar welding is a solid state welding process made possible by a large pulse of direct current from a homopolar generator (HPG) The heat generated by electrical resistance leads to complex phase transformations resulting in different structures with different characteristics. The results show the weld properties are affected by the pipe materials and that HPW is a promising process for joining high strength steel pipe.Center for Electromechanic

Homopolar Pulsed Welding of Steel Pipe: Effects of Controlled Parameters on Weld Properties

This paper reports on recent and continuing research into the optimization of the homopolar pulsed weld (HPW) process for welding 89-mm diameter, ASTM 1035 steel pipe. Present study characterizes the typical macro- and microstructure found in HPW and seeks to identify causes of low toughness. Metallurgical and mechanical evaluation indicated nonuniform heating around the circumference of the pipe. New electrodes were fabricated and shown to reduce circumferential nonuniformity in the weld specimens, and improve the weld repeatability. Several experiments were performed that varied process control parameters, one at a time, and identified the effects on weld properties. However, the process control parameters investigated did not improve the weld toughness. The reduced toughness at the weld line of the HPW process is attributed to the large grain size present on this region.Center for Electromechanic