Thermoelectric magnetohydrodynamic control of melt pool dynamics and microstructure evolution in additive manufacturing

A rational approach to beam path planning in additive manufacturing: the inverse heat placement problem

High demand for components with complex geometries at macro and micro levels drives the development of additive manufacturing (AM). However, the scientific basis for designing energy beam scanning strategies (e.g. beam scanning speed, beam path, beam power) still relies on trial and error approaches (i.e. experimental/simulation of predefined beam trajectories) followed by the evaluation of process outcomes (e.g. structural/metallurgical properties of the built parts); this is the Direct Problem. To address such drawbacks, this paper reports, for the first time, a mathematical model for selecting key parameters related to beam exposure time in AM processes as an attempt to improve the build part's uniform properties, i.e. the Inverse Heat Placement Problem. Our algorithm yields variable beam scanning speeds and optimized beam paths for achieving a desired maximum temperature distribution (uniform or target pattern) and is suitable for different circumstances and scanning strategies dependent on the print part configuration. Here, raster and spiral predefined beam paths are chosen as examples. Variable beam scanning speeds and optimized beam paths obtained from our algorithm are able to induce a desirable uniform maximum temperature distribution compared with the conventional approach of constant beam scanning speeds and a predefined beam path.

Patterns in soft and biological matters

The issue is devoted to theoretical, computer and experimental studies of internal heterogeneous patterns, their morphology and evolution in various soft physical systems-organic and inorganic materials (e.g. alloys, polymers, cell cultures, biological tissues as well as metastable and composite materials). The importance of these studies is determined by the significant role of internal structures on the macroscopic properties and behaviour of natural and manufactured tissues and materials. Modern methods of computer modelling, statistical physics, heat and mass transfer, statistical hydrodynamics, nonlinear dynamics and experimental methods are presented and discussed. Non-equilibrium patterns which appear during macroscopic transport and hydrodynamic flow, chemical reactions, external physical fields (magnetic, electrical, thermal and hydrodynamic) and the impact of external noise on pattern evolution are the foci of this issue. Special attention is paid to pattern formation in biological systems (such as drug transport, hydrodynamic patterns in blood and pattern dynamics in protein and insulin crystals) and to the development of a scientific background for progressive methods of cancer and insult therapy (magnetic hyperthermia for cancer therapy; magnetically induced drug delivery in thrombosed blood vessels). The present issue includes works on pattern growth and their evolution in systems with complex internal structures, including stochastic dynamics, and the influence of internal structures on the external static, dynamic magnetic and mechanical properties of these systems. This article is part of the theme issue 'Patterns in soft and biological matters'.