The conjecture which explains the humping phenomenon in terms of Marangoni convection is discussed and rejected. Instead, Rayleigh's theory instability a free liquid cylinder due to surface tension applied. width-to-length ratio weld pool has exceed 1/2 pi avoid humping. growth time disturbance found be approximately same as hump. analysis bounded provides new stability criterion allows introduction bounding function distinguish between arc laser welding. dimensions are estimated simple heat...

The keyhole formed during penetration welding with a laser is modelled so far as its thermal absorption characteristics are concerned by the combination of point and line source. In this way representation broader surface section weld obtained in addition to lower section. A simple analytical form for temperature distribution possible profiles found numerically from this. These compared examples actual welds; it estimate proportion power absorbed each weld. Graphs some approximations given...

Discusses the interaction of conditions in liquid metal surrounding keyhole which is formed when a laser used as source power for welding, with vapor itself. The transfer and matter across interface considered, simple model set up energy interchange flow principal processes are identified. then to calculate shapes, variation depth related quantities found.

An integrated mathematical model for laser welding of thin metal sheets under a variety material processing conditions has been developed and tested against the results experiments. Full account is taken in interaction laser-generated keyhole with weld pool. Results calculated from are found to agree well experiment appropriate values radius. The analysis yields power absorption metal. In complementary calculation total energy determined detailed consideration inverse Bremsstrahlung plasma...

In penetration welding with a laser, plasma is formed in the keyhole. energy exchange process it to be expected that substantial part of power absorbed directly at walls keyhole, but another mechanism interaction laser beam plasma. A simple model this described and its properties are investigated. It found consistent, estimates obtained for parameters. The existence linking intensity deduced. This relates by workpiece per unit thickness available each cross section

A mathematical model for the laser drilling of metals is given cases constant and pulsed sources. Attenuation beam within vapour considered through an averaged absorption coefficient . The experimentally observed logarithmic dependence hole depth on energy predicted theoretically. singular perturbation technique used in order to find solutions valid different regimes time, namely pre-vaporization post-vaporization times. Uniformly are found one-dimensional analysis drilling-front position...

The hardening of steel by means a rapidly scanning laser is investigated from theoretical viewpoint based on the equation heat conduction. criteria for are considered and related to parameters laser. With aid approximations simple formula obtained depth in terms these parameters. predictions this model were compared with results set experiments En8 steel, found be good agreement.

Vascular aging is characterized by a tandem increase in pulse pressure and large elastic artery stiffness. Greater stiffness of the arteries leads to elevated transmitted into cerebral circulation, causing dysfunction. However, little known females about age-related stiffening impacts high on vasculature. To examine effects sex age response pressure, we studied collected from young old female male C57BL/6 mice. Isolated were exposed ex vivo static low pressure. Exposure impaired...

In penetration welding with a laser, ripple pattern is frozen into the weld bead. The causes of this are not clear but frequencies most readily observed likely to be related natural oscillation pool when in its molten state. These investigated by combination analytical and numerical methods which allow for presence inner outer boundaries pool, finite depth dependence surface tension on temperature. effect oscillations forced pulsations keyhole also studied.

The characteristics of thermal absorption by the workpiece during penetration welding with a laser can be represented combination point and line sources on axis keyhole. This gives an insight into way in which beam interacts material being welded. analysis is worked out for finite thickness, then applied to series lap welds galvanised steel plates. shows that many these very substantial near surface workpiece, but some cases it falls rapidly before increasing again depth. In examples, there...

Continuous CO2 lasers have been used for many years to weld a variety of materials. A problem importance is the question what thickest work piece that can be reliably welded with complete penetration occurring at all times. Empirical results indicate size keyhole radius top almost exactly three times bottom in case maximum penetration. mechanism based on instability inherent variable absorption capabilities when absorbing energy from laser beam an interference pattern which itself result...

In most applications of lasers for material processing a plasma is detected above the hot surface workpiece. Since in certain ranges temperature and density plasmas are able to absorb significant part incident laser power, physical processes which supply this energy into workpiece special interest. paper collisional with low degree ionisation considered steady state one-dimensional geometry. The dominant transport process found be release kinetic charged particles being absorbed then...

The three-dimensional, time-dependent temperature distribution in a moving solid of finite thickness due to laser beam with Gaussian power on its surface is investigated. effects latent heat and the keyhole are neglected. model determined by Peclet number Pe=r0U/2 kappa , non-dimensional melting Theta m= lambda r0 pi 32/(Tm-T0)/P xi 0=h/r0. An upper limit for time needed establish steady state 0.1 s case iron all travel speeds. Accounting specimen essential thin metal sheets used high-speed...

In penetration welding with a laser, the pressure in keyhole is excess at atmospheric pressure. A gradient related to this produced liquid region surrounding it, result that there flow parallel axis of laser. The velocity found as function material constants, and volume rate calculated. From it possible construct an estimate elevation or depression surface weld. shape cross section discussed, some deductions made about distribution metal.

The weld bead formed when a laser is used for penetration welding usually exhibits ripple pattern superimposed on the surface. reasons this are not clear but frequencies most likely to be observed will related natural of oscillation pool it molten. Postacioglu et al. (see ibid., vol.22, p.1050, 1989) have already studied these in case almost circular and deep. When speed higher however, nearer being ellipsoidal shape. frequency first asymmetric mode calculated, found depend shape pool.

A number of models plasma arc welding have been constructed, including some that describe the itself. Relatively few rely solely on physics a and associated fluid dynamics for construction mathematical models; most part they use mixture empirical results basic physical principles. Models depend principles only advantage produce kind insight makes them flexible enough to be applicable situations which were not originally envisaged. Such an approach reduces development time revised increases...

A thermal model has been developed for laser welding which describes the heat input in terms of point and line sources. The was used to generate weld profiles closely matched those found by experiment. Outputs (the gradient G L growth rate R) were describe macroscopic grain structure along centreline. Columnar structures predicted at low speeds (high /R ratio) equiaxed high (low GL/R ratio). Using model, cooling rates ∼1500 K s –1 estimated lowest speed, increased an order magnitude highest...

The keyhole formed when a laser is used as the power source for weld between two pieces of metal contains partially ionized vapour well other material. This flow linked with fluid motion and thermal conduction taking place in liquid solid regions surrounding it. A simple model presented which describes parallel to axis welding speed medium range. It shown that shock waves may be present at its ends. formulation time dependent. Investigation blind keyholes shows there no solutions consistent...

Surface tension variations on the surface of weld pool produced by a laser during process welding, can produce very strong currents. A linearized description is constructed, as well non-linear boundary layer model that takes account thermal conduction and fluid convection. It found there considerable difference between predictions two approaches. The produces results are compatible with what believed to occur in practice.

In the process of penetration welding with a laser an intense beam is focused on workpiece and partially ionised plasma forms around focal point light. The weld assumed to be assisted by inert argon shielding gas jet directed specimen. As result absorption light electrons in over inverse bremsstrahlung, high temperatures will occur gas. presence modifies refractive index neighbourhood focus so defocuses laser. performing calculation full account taken variation relevant properties...

Two thin elastic plates in the form of infinite half planes are joined together as a butt weld by moving general heat source travelling at constant speed. The stresses along direction and distortion unwelded open end resulting from welding process evaluated using Mellin-transform technique. final result for an plate is expressed terms convolution integral illustrated numerical calculations point Rosenthal approximation to source. section case compared with that finite size computed...

In transferred arc plasma welding, the is not electrically neutral. Some simple mathematical models are constructed to demonstrate this fact and orders of magnitude obtained. The relevance these welding cutting considered; quite long arcs can be achieved if flow rate sufficiently high, an from a consumed tubular field emitting cathode 75 mm length described. keyhole it found that current earths at surface workpiece, or close top keyhole.

In the welding of metal sheets by lasers or electric arcs, a problem considerable interest and importance is formation stresses strains in material undergoing process. This paper investigates process making use linear theory elasticity. The non-uniform heating allowed for presence an appropriate term stress tensor representing temperature field. weld pool approximated elliptic region which constant cross sectional shape with depth. calculates outside molten frame laser using mainly...

An integrated mathematical model for the laser welding of thin sheets under a variety material processing conditions is presented. Full account taken interaction generated keyhole with weldpool. analytical solution to heat conduction equation obtained in metal, subject appropriate boundary conditions, and used calculate weldpool shapes. These results are found agree well experiment values radius. The analysis also yields power absorption metal that ultimately conditioned by experiment. In...