Laser welding of tailored blanks made of Al-Si-coated 22MnB5 steel using a filler wire and a variable energy distribution laser optics

Laser welding of Al-Si-coated steels for hot stamping in automotive applications is problematic due to the mixing of the coating layers inside the molten pool that weakens the resulting weld seam. In this case, the most common welding procedure to overcome this issue consists in removing the Al-Si layer through laser ablation prior to the joining. This method continues to be the most widely used by major producers of tailor welded blanks, although in situ ablation of the Al-Si coating can be costly and time consuming. In this work, a novel approach consisting in joining as-received (i.e., not decoated) materials using a filler wire and an innovative variable energy distribution laser optics is introduced and tested on tailor welded blanks made of 22MnB5. Tensile tests of specimens obtained from a 3(3) full factorial design of experiment have shown an average value of ultimate tensile strength of 1523 MPa, which is much higher than the one usually observed in as-received welded then hot-stamped conditions and aligned with hot-stamped base material values. Hardness test results (494-543 HV0.5) were in the typical hot-stamped base material range of values as well, while SEM-EDS analyses detected no ferrite inclusions inside the fusion zone. Variations of the main process parameters have been considered on an iso-thickness and iso-material configuration, empirically demonstrating the stability and reliability of the proposed methodology as well as its suitability for production purposes

EquilTheTA: Thermodynamic and Transport Properties of Complex Equilibrium Plasmas

EquilTheTA (EQUILibrium for plasma THErmodynamics and Transport Applications) is a web-based software which calculates chemical equilibrium product concentrations from any set of reactants and determines thermodynamic and transport properties for the product mixture in wide temperature and pressure ranges. The program calculates chemical equilibrium by using a hierarchical approach, thermodynamic properties and transport coefficients starting from recent and accurate databases of atomic and molecular energy levels and collision integrals. In the calculations, Debye length and cut-off are consistently updated and virial corrections (up to third order) can be considered. Transport coefficients are calculated by using high order approximations of the Chapman-Enskog method

PIC/Monte Carlo simulation of dielectric barrier discharge in Argon

The present work deals with the study of an atmospheric pressure Argon plasma in a parallel-plate dielectric barrier discharge (DBD) by a one-dimensional particle-in-cell/Monte Carlo code, supposing that the reactor gap is much smaller than the plate area of electrodes. Electron-neutral collisions, both elastic and inelastic, have been considered, including superelastic collisions and electron impact ionizations. The kinetic model has been coupled self-consistently with a proper electric circuit model

Analytical solutions for the energy distribution of charged particles in a weak electric field

The paper deals with the stationary distribution of charged particles moving in a material medium, having scattering and absorption properties, in which a uniform electric field is present. The purpose of the work is finding analytical solutions in simplified but physically significant situations and comparing different approximations based on a spherical-harmonics expansion of the velocity distribution

The two-term Boltzmann equation

Plasma Modeling: Methods and Applications presents and discusses the different approaches that can be adopted for plasma modeling, giving details about theoretical and numerical methods. The book is intended to assist and direct students and researchers, who want to develop research activity in the field of plasma physics, in the choice of the best model for the problem of interest. The book is organised in three parts. The first describes kinetic models used in plasma investigations, consisting of the solution of the Boltzmann equation using different approaches. The second part develops the theory of fluid equations and of hybrid models, and the third part is devoted to applications, considering some practical problems of interest in different fields