Effect Of Energy Parameters Research Articles

Effect of energy parameters on droplet transfer behavior and weld formation in laser-arc hybrid welding with cable-type welding wire

This paper describes the droplet transfer behavior and weld formation of laser-arc hybrid welding with cable-type welding wire (CWW). The droplet transfer behavior was photographed in real time by using a high-speed camera. The effects of energy parameters on arc morphology, droplet transfer behavior and weld formation were studied through experimental and theoretical analyses. The results show that the arc is deflected toward the laser direction, and the deflection degree increases with increasing laser power. The interaction between the laser and arc is enhanced by rotating the arc. The rotating arc enhances the interaction between plasma, the arc is more compressed and the arc volume is smaller as the welding current increases. The droplet transfer frequency increased with increasing laser power and decreased after reaching the critical value. The reaction force of metal vapor and electromagnetic force affect the droplet transfer frequency, and the maximum frequency of droplet transfer is 180.8 Hz under a laser power of 2.5 kW. The rotational force promotes molten droplet transfer and maintains the axial transition, and the welding current has a strong effect on increasing the droplet transfer frequency. The influence of laser power on weld penetration is greater than that of welding current, the weld penetration increases significantly with increasing laser power, and the cross section of the weld seam exhibits laser-arc hybrid welding characteristics.

Effects of Energy Parameters on Dimensional Accuracy When Joining Stainless-Steel Powders with Heterogeneous Metal Substrates

This work presents some breakthroughs for obtaining high dimensional accuracy and reliable geometrical tolerance in the joining of stainless-steel powders with heterogeneous substrates. In the laser melting process, the interfacial energy fractions and forces acting at the solid–liquid surface of the melting powders can effectively vary their geometrical shapes and positions before they turn into the liquid phase. When the interfacial free energy is low, the melting powders are near molten, thus the successive volumetric changes can alter the layered geometry and positions. This assumption was validated by a powder-bedding additive manufacturing process to consolidate stainless-steel 316L powders (SLM 316L) on a thin heterogeneous stainless-steel substrate. Experiments were carried out to reveal the effects of the process parameters, such as laser power (100–200 W), exposure duration (50–100 µs) and point distance (35–70 µm) on the resulting material density and porosity and the corresponding dimensional variations. A fractional factorial design of experiment was proposed and the results of which were analyzed statistically using analysis of variances (ANOVA) to identify the influence of each operating factor. High energy densities are required to achieve materials of high density (7.71 g/cm3) or low porosity (3.15%), whereas low energy densities are preferable when the objective is dimensional accuracy (0.016 mm). Thermally induced deflections (~0.108 mm) in the heterogeneous metal substrate were analyzed using curvature plots. Thermally induced deformations can be attributed to volumetric energy density, scanning strategy, and the lay-up orientation. The parametric optimizations for increasing in dimensional accuracy (Z1: ~0.105 mm), or in material density (~7.71 g/cm3) were proven with high conversion rates of 88.2% and 96.4%, respectively, in validation runs.

A Husimi rhombus lattice with random angles to present the configurational stochasticity in exact thermodynamic calculation

Abstract The square unit in Husimi lattice is generalized to be rhombus with random angles. The independence feature of unit cells in recursive lattice makes the random conformation possible, which is unfeasible in conventional lattices. Since the randomness of conformations in real system is naturally introduced into the model, this new lattice can describe the off-crystal metastable states without artificial randomness. With reasonable simplification, a coefficient A ( θ ) is formulated to present the effect of angle in the rhombus unit. A “visit and count” recursive calculation is developed to numerically approach the thermodynamics. The critical temperature T c of spontaneous magnetization is lowered with the presence of angle randomness, implying a less stable system. Besides consistent results to the regular lattice, the random-angled model features a distribution of solutions and thermal fluctuation with exact calculation. The Kauzmann paradox and ideal glass transition due to the off-crystal metastable portion are identified by the appearance of negative entropy. The effects of energy parameters on thermodynamics and the ground states are investigated.

Effect of electrical parameters on the efficiency of the process of microarc oxidation of D69 aluminium alloy

Results of investigations of the effect of energy parameters on the process of micro-oxidation and the quality of produced oxidised coatings on the D16 aluminium alloy are presented. The coatings formed in oxidation in different working conditions of the power source with the capacitance regulation of power are compared. The microstructure of the surface of the specimens with the coatings produced in microarc oxidation in three sets of conditions is shown.

A Phase Transition in Energy-Filtered RNA Secondary Structures

In this article we study the effect of energy parameters on minimum free energy (mfe) RNA secondary structures. Employing a simplified combinatorial energy model that is only dependent on the diagram representation and is not sequence-specific, we prove the following dichotomy result. Mfe structures derived via the Turner energy parameters contain only finitely many complex irreducible substructures, and just minor parameter changes produce a class of mfe structures that contain a large number of small irreducibles. We localize the exact point at which the distribution of irreducibles experiences this phase transition from a discrete limit to a central limit distribution and, subsequently, put our result into the context of quantifying the effect of sparsification of the folding of these respective mfe structures. We show that the sparsification of realistic mfe structures leads to a constant time and space reduction, and that the sparsification of the folding of structures with modified parameters leads to a linear time and space reduction. We, furthermore, identify the limit distribution at the phase transition as a Rayleigh distribution.