Journal Article•
Temperature fields produced by traveling distributed heat sources
TL;DR: The solution of a traveling distributed heat source on a semi-infinite plate provides information about both the size and the shape of arc weld pools as mentioned in this paper, and the results indicate that both welding process variables (current, arc length and travel speed) and material parameters (thermal diffusivity) have significant effects on weld shape.
Abstract: The solution of a traveling distributed heat source on a semi-infinite plate provides information about both the size and the shape of arc weld pools. The results indicate that both welding process variables (current, arc length and travel speed) and material parameters (thermal diffusivity) have significant effects on weld shape. The theoretical predictions are compared with experimental results on carbon steels, stainless steel, titanium and aluminum with good agreement. 25 references, 23 figures, 1 table.
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TL;DR: A review of the emerging research on additive manufacturing of metallic materials is provided in this article, which provides a comprehensive overview of the physical processes and the underlying science of metallurgical structure and properties of the deposited parts.
4,192 citations
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...There are many analytic, numeric and experimental studies of this effect, including the influence of welding heat input and different materials on weld pool geometry and cooling rate [616,617]....
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TL;DR: In this article, the experimental observation of keyhole-mode laser melting in a laser powder-bed fusion additive manufacturing setting for 316L stainless steel is presented, and the conditions required to transition from conduction controlled melting to keyholemode melting are identified.
981 citations
TL;DR: A detailed overview of the thermal/fluid properties inherent in the direct laser deposition (DLD) process can be found in this article, with a focus on the mechanical properties and microstructure of parts manufactured via DLD.
Abstract: Laser-based additive manufacturing (LBAM) processes can be utilized to generate functional parts (or prototypes) from the ground-up via layer-wise cladding – providing an opportunity to generate complex-shaped, functionally graded or custom-tailored parts that can be utilized for a variety of engineering applications. Directed Energy Deposition (DED), utilizes a concentrated heat source, which may be a laser or electron beam, with in situ delivery of powder- or wire-shaped material for subsequent melting to accomplish layer-by-layer part fabrication or single-to-multi layer cladding/repair. Direct Laser Deposition (DLD), a form of DED, has been investigated heavily in the last several years as it provides the potential to (i) rapidly prototype metallic parts, (ii) produce complex and customized parts, (iii) clad/repair precious metallic components and (iv) manufacture/repair in remote or logistically weak locations. DLD and Powder Bed Fusion-Laser (PBF-L) are two common LBAM processes for additive metal part fabrication and are currently demonstrating their ability to revolutionize the manufacturing industry; breaking barriers imposed via traditional, ‘subtractive’ metalworking processes. This article provides an overview of the major advancements, challenges and physical attributes related to DLD, and is one of two Parts focused specifically on DLD. Part I (this article) focuses on describing the thermal/fluidic phenomena during the powder-fed DLD process, while Part II focuses on the mechanical properties and microstructure of parts manufactured via DLD. In this current article, a selection of recent research efforts – including methodology, models and experimental results – will be provided in order to educate the reader of the thermal/fluidic processes that occur during DLD, as well as providing important background information relevant to DLD as a whole. The thermal/fluid phenomena inherent to DLD directly influence the solidification heat transfer which thus impacts the part's microstructure and associated thermo-mechanical properties. A thorough understanding of the thermal/fluid aspects inherent to DLD is vital for optimizing the DLD process and ensuring consistent, high-quality parts.
781 citations
TL;DR: In this paper, a review of the current literature on additive manufacturing of 316L stainless steel (SS) related to input parameter scaling relations is presented, where the authors identify a range of Volumetric Energy Density (VED) values that should lead to fully dense parts.
464 citations
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.
369 citations
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...[277], which predicts this type of geometry when conduction mode is observed and was experimentally validated for fusion-based additive manufacturing in [149]....
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TL;DR: In this paper, a thermal analysis for laser heating and melting materials is derived for a Gaussian source moving at a constant velocity, where the resulting temperature distribution, cooling rate distribution, and depth of melting are related to the laser spot size, velocity, and power level.
Abstract: A thermal analysis for laser heating and melting materials is derived for a Gaussian source moving at a constant velocity. The resulting temperature distribution, cooling rate distribution, and depth of melting are related to the laser spot size, velocity, and power level. As the power is increased to heat the liquid above the boiling point, a transition to deep penetration welding is described. Calculations are presented for 304‐stainless steel which are in agreement with experiment.
520 citations
TL;DR: In this article, heat and current distributions at the anode of high current arcs in inert gas atmospheres were determined experimentally, and the experimental method consisted of splitting anode, measuring the heat flux and the current to one of the sections as a function of arc position relative to the splitting plane, and calculating therefrom the distribution functions.
Abstract: Heat transfer intensity and current density distributions at the anode of high current arcs in predominantly inert gas atmospheres were determined experimentally. Measurements were made for stable, axially symmetric arcs having a small diameter refractory metal cathode and a plane, cooled copper anode. The experimental method consisted of splitting the anode, measuring the heat flux and the current to one of the sections as a function of arc position relative to the splitting plane, and calculating therefrom the distribution functions. The work encompassed the effects of gas pressure (195–790 mm Hg), cathode geometry and material (tungsten and W‐1% ThO2), electrode separation (1.6–12.7 mm), arc current (100–300 amp), gas composition (argon, helium, and diatomic gas‐argon mixtures), and localized constriction of the plasma column. Peak heat transfer intensities ranged from 1.0 to 20 kw/cm2 and peak current densities from 100 to 2500 amp/cm2. The heat and current distribution curves were of similar shape an...
184 citations
TL;DR: In this article, the authors made an analysis of the phenomena at the electrodes of a high-current short-time arc and showed that the input power density to the anode spot is in the range 5×104 to 1×106 watts/cm2.
Abstract: An analysis is made of the phenomena at the electrodes of a high‐current short‐time arc. It is shown that the input power density to the anode spot is in the range 5×104 to 1×106 watts/cm2. To a first‐order approximation, all this power can be carried off by evaporation. Power conducted into the metal and lost by radiation is negligible in the probable operating range. For most materials, the anode spot is probably considerably above the boiling temperature. The process of evaporation holds the spot temperature constant at a value such that the input power and evaporation power are equal. Experimental data indicate that for any given metal the anode spot temperature is that for which the evaporation power density is at least 3×105 watts/cm2. As an example, for copper the theoretical limits of temperature are 2490 to 3040°K, while experimental data indicate a temperature of 2920°K. Other metals considered are: Ag, Al, C, Fe, Mo, Sn, Ti, W, Zn, Zr. It is also shown that for the maximum power input that can ...
175 citations
01 Nov 1982
TL;DR: In this paper, a mathematical model was developed to account for convection and temperature distributions in stationary arc weld pools driven by buoyancy, electromagnetic and surface tension forces, and it was shown that these forces dominate the flow behavior.
Abstract: A mathematical model was developed to account for convection and temperature distributions in stationary arc weld pools driven by buoyancy, electromagnetic and surface tension forces. It is shown that the electromagnetic and surface tension forces dominate the flow behavior. In some cases, these forces produce double circulation loops, which are indirectly confirmed by experimental measurements of segregation in the weld pool. It is also shown that the surface tension driven flows are very effective in dissipating the incident energy flux on the pool surface which, in turn, reduces the vaporization from the weld pool.
83 citations
01 Aug 1981
TL;DR: In this article, small additions of selenium to 21-6-9 stainless steel dramatically increase the depth/width ratio of bead-on-plate welds, which is consistent with a model for control of weld fusion zone geometry.
Abstract: Small additions of selenium to 21-6-9 stainless steel dramatically increase the depth/width ratio of bead-on-plate welds. The depth/width ratio increased by over 160% with the addition of 140 ppm selenium to the base metal. The change depth/width ratio is consistent with, and was predicted by, a model for control of weld fusion zone geometry by fluid flow in the weld pool driven by surface tension gradients on the weld pool.
68 citations