Development of Robotized Laser Welding Applications for Joining Thin Sheets

Laser Welding (LW) is more often used in manufacturing due to its advantages, such as accurate control, good repeatability, less heat input, opportunities for joining of special materials, high speed, capability to join small dimension parts etc. LW is dedicated to robotized manufacturing, and the fabrication cells are using various level of flexibility, from specialized robots to very flexible setups. This paper features several LW applications using two industrially-scaled manufacturing cells at UPM Laser Centre (CLUPM) of Polytechnical University of Madrid (Universidad Politécnica de Madrid). The one dedicated to Remote Laser Welding (RLW) of thin sheets for automotive and other sectors uses a CO2 laser of 3500 W. The second has a high flexibility, is based on a 6-axis ABB robot and a Nd:YAG laser of 3300 W, and is meant for various laser processing methods, including welding. After a short description of each cell, several LW applications experimented at CLUPM and recently implemented in industry are briefly presented: RLW of automotive coated sheets, LW of high strength automotive sheets, LW vs. laser hybrid welding (LHW) of Double Phase steel thin sheets, and LHW of thin sheets of stainless steel and carbon steel (dissimilar joints). The main technological issues overcame and the critical process parameters are pointed out. Conclusions about achievements and trends are provided.

Dynamic analysis using finite elements to calculate the critical wear section of the contact wire in suburban railway overhead conductor rails

The purpose of this study is to determine the critical wear levels of the contact wire of the catenary on metropolitan lines. The study has focussed on the zones of contact wire where localised wear is produced, normally associated with the appearance of electric arcs. To this end, a finite element model has been developed to study the dynamics of pantograph-catenary interaction. The model includes a zone of localised wear and a singularity in the contact wire in order to simulate the worst case scenario from the point of view of stresses. In order to consider the different stages in the wire wear process, different depths and widths of the localised wear zone were defined. The results of the dynamic simulations performed for each stage of wear let the area of the minimum resistant section of the contact wire be determined for which stresses are greater than the allowable stress. The maximum tensile stress reached in the contact wire shows a clear sensitivity to the size of the local wear zone, defined by its width and depth. In this way, if the wear measurements taken with an overhead line recording vehicle are analysed, it will be possible to calculate the potential breakage risk of the wire. A strong dependence of the tensile forces of the contact wire has also been observed. These results will allow priorities to be set for replacing the most critical sections of wire, thereby making maintenance much more efficient. The results obtained show that the wire replacement criteria currently borne in mind have turned out to be appropriate, although in some wear scenarios these criteria could be adjusted even more, and so prolong the life cycle of the contact wire.

In hoc volumine beati Bonaue[n]ture subiecta comprehenduntur : Oratio Octauiani in vitam beati Bonauenture ; Libellus de reductione artium ad theologiam ; Tractatus de paup[eri]tate [Christi] [con]tra mag[ist]r[u]m, vvilhelmum ; Tractatulus de quinq[ue] f

Impresor y año tomados del colofón

In hoc volumine beati Bonaue[n]ture subiecta comprehenduntur : Oratio Octauiani in vitam beati Bonauenture ; Libellus de reductione artium ad theologiam ; Tractatus de paup[eri]tate [Christi] [con]tra mag[ist]r[u]m, vvilhelmum ; Tractatulus de quinq[ue] f

Impresor y año tomados del colofón

Quaestiones eruditissimae in libros physicorum / Reuer. P.F. Francisci Syluestri Ferrariensis totius ordinis Pr[a]edicatorum Generalis Mag. ... ; cum quibusdam aliis quaestionibus, [et] additionibus R.P.F. Mathiae Aquarij ...

Marca tip. en port. (Vaccaro, 196) y en 3F4r (Zapella, 130)

Quaestiones eruditissimae in libros physicorum / Reuer. P.F. Francisci Syluestri Ferrariensis totius ordinis Pr[a]edicatorum Generalis Mag. ... ; cum quibusdam aliis quaestionibus, [et] additionibus R.P.F. Mathiae Aquarij ...

Marca tip. en port. (Vaccaro, 196) y en 3F4r (Zapella, 130)

Cohesive-frictional modelling of bond and splitting action of prestressing wire

This work shows a numerical procedure for bond between indented wires and concrete, and the coupled splitting of the concrete. The bond model is an interface, non-associative, plasticity model. It is coupled with a cohesive fracture model for concrete to take into account the splitting of such concrete. The radial component of the prestressing force, increased by Poisson’s effect, may split the surrounding concrete, decreasing the wire confinement and diminishing the bonding. The combined action of the bond and the splitting is studied with the proposed model. The results of the numerical model are compared with the results of a series of tests, such as those which showed splitting induced by the bond between wire and concrete. Tests with different steel indentation depths were performed. The numerical procedure accurately reproduces the experimental records and improves knowledge of this complex process.

Bare wire anodes for electrodynamic tethers

The collection of electrons from the ionosphere is the major problem facing high-power electrodynamic tethers. This article discusses a simple electron-collection concept which is free of most of the physical uncertainties associated with plasma contactors in the rarefied, magnetized environment of an orbiting tether. The idea is to leave exposed a fraction of the tether length near its anodic end, such that, when a positive bias develops locally with respect to the ambient plasma, and for a tether radius small compared with both thermal gyroradius and Debye length, electrons are collected in an orbital-motion-limited regime. It is shown that large currents can be drawn in this way with only moderate voltage drops. The concept is illustrated through a discussion of performance characteristics for generators and thrusters.

Mechanical and thermal behaviour of isotactic polypropylene reinforced with inorganic fullerene-like WS2 nanoparticles: Effect of filler loading and temperature

The thermal and mechanical behaviour of isotactic polypropylene (iPP) nanocomposites reinforced with different loadings of inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles was investigated. The IF-WS2 noticeably enhanced the polymer stiffness and strength, ascribed to their uniform dispersion, the formation of a large nanoparticle?matrix interface combined with a nucleating effect on iPP crystallization. Their reinforcement effect was more pronounced at high temperatures. However, a drop in ductility and toughness was found at higher IF-WS2 concentrations. The tensile behaviour of the nanocomposites was extremely sensitive to the strain rate and temperature, and their yield strength was properly described by the Eyring s equation. The activation energy increased while the activation volume decreased with increasing nanoparticle loading, indicating a reduction in polymer chain motion. The nanoparticles improved the thermomechanical properties of iPP: raised the glass transition and heat deflection temperatures while decreased the coefficient of thermal expansion. The nanocomposites also displayed superior flame retardancy with longer ignition time and reduced peak heat release rate. Further, a gradual rise in thermal conductivity was found with increasing IF-WS2 loading both in the glassy and rubbery states. The results presented herein highlight the benefits and high potential of using IF-nanoparticles for enhancing the thermomechanical properties of thermoplastic polymers compared to other nanoscale fillers.

Residual stress distribution in ferritic-austenitic steel joints made by laser welding

The present investigation addresse the influence of laser welding process-ing parameters used for joining dis-similar metals (ferritic to austenitic steel), on the induced residual stress field. Welding was performed on a Nd:YAG laser DY033 (3300 W) in a continuous wave (CW), keyhole mode. The base metals (BM) employed in this study are AISI 1010 carbon steel (CS) and AISI 304L austenitic stainless steel (SS). Pairs of dissimilar plates of 200 mm x 45 mm x 3 mm were butt joined by laser welding. Different sets of parameters were used to engineer the base metals apportionment at joint formation, namely distinct dilution rates. Residual strain scanning, carried out by neutron diffraction was used to assess the joints. Through-thickness residual stress maps were determined for the laser welded samples of dis-similar steels using high spatial reso-lution. As a result, an appropriate set of processing parameters, able to mi-nimize the local tensile residual stress associated to the welding process, was found.

Residual stress distribution in ferritic to austenitic steel joints made by laser welding,

In this study, autogenous laser welding was used to join thin plates of low carbon ferritic and austenitic stainless steel. Due to the differences in the thermo-physical properties of base metals, this kind of weld exhibits a complex microstructure, which frequently leads to an overall loss of joint quality. Four welded samples were prepared by using different sets of processing parameters, with the aim of minimizing the induced residual stress field. The dissimilar austenitic-ferritic joints obtained under all welding conditions were uniform and free of defects. Variations in beam position did not influence the weld geometiy, which is a typical keyhole welding. Microstructural characterization and residual strain scanning (by neutron diffraction) were used to assess the features of the joints. By varying laser beam power density and by displacing the laser beam towards the carbon steel side, an optimum combination of processing parameters was found.

Relacion del seru[icio] que Adrian Bay[arte] ... ha hecho a su Mag[estad] en la Comiss[i]on que lleuo al Reyno de Val[enci]a y de lo que queda por hacer [Manuscrito]

Alcance y contenido: Copia ms. con la relación sumaria de la Comisión/nes encargadas a D. Adrián Bayarte, caballero aragonés, nombrado Comisario General en Valencia por el rey Felipe III, para que en dicho reino tasase y vendiese "las haziendas que los moriscos dexaron en las ciudades y villas reales", pagando todas las deudas y censales justificados sobre dichos bienes. El número de comisiones encargadas por el rey a Adrián Bayarte ascendieron a 4, realizadas entre 1614 y 1617. Al final del texto aparece "Vto. Dr. Ambrosio Alos"

Señor, el seguro conocimiento de que muy facilmente pueden equivocarse con los fervores de un verdadero zelo ... determina al Cabildo de la Santa Metropolitana Iglesia de Valencia, à poner ... a los ... pies de V. Mag. esta rendida suplica ... porque la noticia de estàr solicitando ... la Colegial de la ciudad de San Felipe, que es de su Arzobispado ... de V. Mag. para que la Sede Apostolica conceda ... la "Cathedralidad" ... mueve al de la Metropolitana a que solicite, que se examine ... este zelo ..

Título tomado de comienzo de texto

Reales ordenanzas comedidas por su Mag... en Sevilla à 9 de Mayo de 1732 en favor del Colegio de Torcedores de Seda de la Ciudad de Valencia vistas por la Real Junta de Comercio y Moneda

Sign. : A-I 2

Ordenanzas concedidas al gremio de pelaires de la Ciudad de Valencia en virtud de Real Cedula de Su Mag... y Señores de su Real Junta de Comercio, y de Moneda, expedida en 15 de Febrero de 1734... : con la explicación de diferentes capitulos...

Texto fechado en Valencia a 17 de abril de 1734