Amin S. Azar

A heat source model for cold metal transfer (CMT) welding

A heat source model is proposed to simulate the effect of periodic and recurrent arcing and metal deposition phenomena in the cold metal transfer type of welding. This model will facilitate studying of weld pool behavior and resultant mechanical properties in detail for this type of welding. The proposed model utilizes a double-ellipsoidal heat source model as the basis and makes the geometrical and heat input parameters dependent on time.

Reference data set of volcanic ash physicochemical and optical properties

Uncertainty in the physicochemical and optical properties of volcanic ash particles creates errors in the detection and modeling of volcanic ash clouds and in quantification of their potential impacts. In this study, we provide a dataset that describes the physicochemical and optical properties of a representative selection of volcanic ash samples from nine different volcanic eruptions covering a wide range of silica contents (50 - 80 wt. % SiO2). We measured and calculated parameters describing the physical (size distribution, complex shape, and dense-rock equivalent mass density), chemical (bulk and surface composition) and optical (complex refractive index from ultra-violet to near-infrared wavelengths) properties of the volcanic ash and classified the samples according to their SiO2 and total alkali contents into the common igneous rock types Basalt to Rhyolite. We found that the mass density ranges between ρ = 2.49 and 2.98 g/cm3 for rhyolitic to basaltic ash types, and that the particle shape varies with changing particle size (d < 100 μm). The complex refractive indices in the wavelength range between λ = 300 nm and 1500 nm depends systematically on the composition of the samples. The real part values vary from n = 1.38 to 1.66 depending on ash type and wavelength and the imaginary part values from k = 0.00027 to 0.00268. We place our results into the context of existing data, and thus provide a comprehensive dataset that can be used for future and historic eruptions, when only basic information about the magma type producing the ash is known.

Tensile Properties and Hot-Tearing Tendencies of 3xxx Alloys

A set-up for tensile testing in the mushy zone allowing for studies of semi-solid mechanical behavior is available at SINTEF. A hot-tearing experimental set-up has recently been developed allowing for investigation of the hot-tearing susceptibility of industrial aluminium alloys and effects of e.g. alloying composition and grain-refiner. Load and temperature are registered during constrained solidification giving information on the mechanical behavior of the alloy during solidification. Two crack-prone alloys in the 3xxx-series (A and B) have been investigated using both techniques and the results analyzed using information about solidification path from a thermo-physical model. Alloy B is found to be mechanically weaker in the interval most susceptible to hot-tearing in agreement with cast-house experience. This study shows that the experimental techniques combined with thermo-physical modeling and characterization allow for a better understanding of the hot-tearing sensitivity of the alloys.

Orientation Relationships and Texture of the Iron-Nitride Phase Constituents in Pulsed Plasma Nitriding

Electron backscattered diffraction study was used to determine the preferred orientations of the crystals and texture evolution as a consequence of nitrogen diffusion. In the current study, the nitrided layer on a steel substrate was selected as a model material to investigate the distribution of different phases as well as their crystallographic relationships. Possible phase orientation relationships between the constituents were found based on which a phase transformation mechanism was proposed. The investigation of coincidence site lattice revealed that Σ9 and Σ25 types of grain boundaries are separating the elongated ε-phase grains. It was also presented how the phase constituents’ distribution affects the mechanical properties using nanomechanical indentation technique. Moreover, it was found that the ε-phase exists in three distinguished orientations across the matrix each of which representing a definite phase transformation phenomenon.

Advances in robotics for additive/hybrid manufacturing: robot control, speech interface and path planning

Purpose This paper aims to introduce the ideas of practical implications of using industrial robots to implement additive/hybrid manufacturing. The process is discussed and briefly demonstrated. This paper also introduces recent developments on human–machine interface for robotic manufacturing cells, namely the ones used for additive/hybrid manufacturing, as well as interoperability methods between the computer-aided design (CAD) data and material modeling systems. It is presented – using a few solutions developed by the authors – as a set of conceptual guidelines discussed throughout the paper and as a way to demonstrate how they can be applied and their practical implications. Design/methodology/approach The possibility to program the system from CAD information, which is argued to be crucial, is explored, and the methods necessary for connecting the CAD data to material modeling systems are introduced. This paper also discusses in detail the main requirements (also from a system point-of-view) needed for a full implementation of the presented ideas and methods. A few simulations to better characterize the interactions from heat conduction and physical metallurgy were conducted in an effort to better tune the additive manufacturing process. The results demonstrate how the toolpath planning and deposition strategies can be extracted and studied from a CAD model. Findings The paper fully demonstrates the possibility to use a robotic setup for additive manufacturing applications and shows the first steps of an innovative system designed with that objective. Originality/value Using the aimed platform, unsupervised net-shaping of complex components will substitute the cumbersome processes, and it is expected that such a visionary concept brings about a significant reduction in cost, energy consumption, lead time and production waste through the introduction of optimized and interactive processes. This can be considered as a breakthrough in the field of manufacturing and metal processing as the performance is indicated to increase significantly compared to the current instruction-dependent methods.