Konstantinos Salonitis

Simulation of metallic powder bed additive manufacturing processes with the finite element method: A critical review:

This article provides a literature review of finite element simulation studies for metallic powder bed additive manufacturing processes. The various approaches in the numerical modeling of the processes and the selection of materials properties are presented in detail. Simulation results are categorized according to three major findings’ groups (i.e. temperature field, residual stresses and melt pool characteristics). Moreover, the means used for the experimental validation of the simulation findings are described. Looking deeper into the studies reviewed, a number of future directions are identified in the context of transforming simulation into a powerful tool for the industrial application of additive manufacturing. Smart modeling approaches should be developed, materials and their properties should be further characterized and standardized, commercial packages specialized in additive manufacturing simulation have to be developed and simulation needs to become part of the modern digital production chains. Finally, the reviewed studies are organized in a table and characterized according to the process and material studied, the modeling methodology and the experimental validation method used in each of them. The key findings of the reviewed studies are also summarized.

Nanomanufacturing processes: a critical review

Nanomanufacturing encompasses processes aimed at building nanoscale structures, devices and systems in one, two or three dimensions. Nanomanufacturing involves both bottom-up and top-down approaches. This paper reviews and discusses some critical issues of nanomanufacturing from the cost, production rate, quality and flexibility point of view.

An analytical, numerical, and experimental approach to grind hardening

Abstract In grind hardening, the heat dissipated in the cutting area during grinding is used for the heat treatment of the workpiece. Analytical and numerical techniques have been employed to understand the grind-hardening mechanisms as well as the working conditions during the process. Parameters considered include workpiece speed and depth of cut at a constant cutting speed. The hardness penetration depth has been calculated, for a given set of process parameters, and compared with experimental data from a cylindrical dry grindhardening process.

Thermal analysis of grind-hardening process

Grind hardening process is a novel alternative surface hardening method. The heat generation rate and partition and the temperature field within the workpiece are modelled for the prediction of the Hardness Penetration Depth (HPD). A maximum HPD is indicated that exists for specific sets of process parameters.

Multi-criteria decision analysis of offshore wind turbines support structures under stochastic inputs

Selection of the optimum support structural configuration for offshore wind turbines is a decision that should take into account a variety of both technical and non-technical criteria in order to aggregate cumulatively the performance of several concepts such as jackets, tripods, monopiles, spars, semi-subs, tri-floaters and others with varying suitability and relevance to offshore wind applications. In the preliminary phases of a project, consideration of qualitative attributes based on experts’ opinions is a common practice due to the limited availability of quantitative data for attribute scores and relevant weights, which are mainly based on past experience. This practice can introduce a bias in the considered scores reducing the confidence of the qualifying solution. This paper documents the extension of the widely used TOPSIS method (Technique for Order of Preference by Similarity to Ideal Solution) to explicitly consider stochastic inputs (statistical distributions) following a systematic gathering of data through surveys and questionnaires. The methodology proposed has been efficiently implemented in a numerical tool and the case study that is presented on the decision analysis of an offshore wind turbine supports structure under given deployment conditions, illustrates its applicability and allows for a sensitivity analysis of the effect of the resolution of simulation, selection of statistical distributions and weighting of experts’ opinions based on their perceived level of expertise.

Experimental and theoretical investigation of the ablation mechanisms during femptosecond laser machining

In this work, a theoretical model based on molecular dynamics (MD) simulations and experimentation results of the femptosecond laser (FS) ablation, are applied for the description of ultrashort laser ablation of metals, with emphasis being given to the understanding of the material removal. The ablation of Fe with the use of 100 fs laser pulses, at a wavelength of 775 nm, is studied. Computational and experimental results have revealed that within the investigated laser fluences range (0.01 to 30 J/cm²), four different ablation areas accompanied by different ablation mechanisms, are distinguished. The threshold of the actual ablation has been determined to be at 0.1 J/cm². The ablation depth as a function of the laser fluence and the ablation threshold value have been evaluated and compared with the experimental data available.

Multifunctional Materials Used in Automotive Industry: A Critical Review

Nowadays, advanced materials and related processes in the automotive industry, are more widely used, leading to an effort towards reducing weight and fuel consumption. The use of such advanced materials and technologies tends to increase the cost. Multifunctional materials (MFMs) and related processing technologies aim at overcoming this increase of cost by exploiting the high level of functional integration. MFMs are designed so as to meet specific requirements through tailored properties. The use of such materials, in the automotive body construction, can help reduce produced parts, lightweight design, high level of integration of functionalities, advancements in mechanical properties of structures etc. In the current study, there is a clear definition of MFMs, and a critical view of such materials used both in the automotive body construction and in other industrial applications.

Overview of 3D laser materials processing concepts

The term of 3D laser processing has been used so far to describe a group of different three-dimensional laser processing concepts. At each of these concepts the 3D aspect refers to a different manipulation of one or more laser beams, as to process and/or produce three-dimensional geometries by performing material removal, welding or heat treating. The most important concepts are focused mainly in laser machining and laser welding processes by incorporating one or two laser beams simultaneously. This paper overviews a number of these concepts that have been developed in research or industrial level, along with their advantages, drawbacks and fields of application.

Energy efficiency of laser based manufacturing processes

This paper describes an analytical approach for estimating the energy efficiency of laser machining processes such as laser drilling and grooving. The results of the analysis are used for developing processing strategies.This paper describes an analytical approach for estimating the energy efficiency of laser machining processes such as laser drilling and grooving. The results of the analysis are used for developing processing strategies.

Roll Forming of AHSS: Numerical Simulation and Investigation of Effects of Main Process Parameters on Quality

The roll forming process is one of the main processes of producing straight profiles in many industrial sectors. The introduction of Advanced High Strength Steels (AHSS), such as the DP and TRIP-series, into the production of roll-formed profiles has emerged new challenges. The combination of a higher yield strength with a lower total elongation of AHSS, brings new challenges to the roll forming process. In the current study, the numerical simulation of a V-section profile has been implemented. The effect of the main process parameters, such as the roll forming line velocity, rolls inter-distance, roll gap and rolls diameter on quality characteristics is investigated.