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•An automated python script to slice a macro-scale part into micro-scale layers and assign boundary conditions steps for each layer is presented.•Key parameter interdependencies of resolution, energy and time are investigated in a series of layer-scaling thermomechanical process models.•Guidelines for simulation the thermal and stress results of higher resolution by lower resolution for the LPBF modelling are proposed.•A novel efficient method for simulating powder-solid heat conduction by interface surface convection is presented.

The repeated localised heating-melting-cooling-solidification processes during laser beam powder bed fusion (PBF-LB) additive manufacturing (AM) induce intricate thermal residual stress (RS) in manufactured parts. Non-destructive characterisation using X-ray diffraction was used to measure the RS of Ti-6Al-4V square plates that were manufactured by using six different scanning strategies. Computational modelling was used to interpret the experimental stress measurement results. It was revealed that an inclined scanning strategy is beneficial for reducing the average through-thickness RS because the inclined scanning strategy can mitigate the non-uniform thermal profile and corresponding residual thermal stresses in successive layers of material. Among all the different scanning strategies that were analysed in this work, the 45° inclined 90° rotation scanning resulted in the lowest RS. The thicker parts have a greater gradient of RS than the thinner parts, after base plate removal. This research outcome can help the AM industry to design or optimise the process parameters of the PBF-LB aiming to minimise the RS of metal parts.

Additively manufactured components by laser powder bed fusion (LPBF) often suffer from stress-induced cracks (e.g. delamination), especially at the build-substrate interfaces where stiff mechanical constraints and large thermal gradients coexist. To reduce the probability of cracking, this work proposes an innovative strategy to optimize the geometry of the substrate by reducing its mechanical stiffness and, consequently, the stress accumulation during LPBF. To assess the feasibility of the strategy, a coupled thermo-mechanical finite element model, calibrated with the experimental evidence obtained from the LPBF metal deposition of a bridge-type structure, is used to predict the thermo-mechanical behavior of two T-shape AM parts built on (i) a typical solid substrate and (ii) a groove patterned substrate, respectively. The results show that several visible cracks appear at the interface between the build and the typical solid substrate due to stress concentration (up to 1600 MPa), while a crack-free component can be manufactured by adding grooves through the thickness of the substrate, without compromising the resulting microstructure and microhardness of the metallic materials with high crack sensitivity. The difference between the groove patterned substrate design with respect to the use of support structures used for printing cantilever structures is clarified to further justify the novelty of the proposed approach.

From a geomechanical point of view, qualitative experimental analysis with models shows that overthrusting and underthrusting are two components of one relative shearing displacement of a thrusting due to horizontal compression. Obduction and subduction are thought to be comparable to overthrusting and underthrusting respectively in tectonic movements. Continental creep often occurs as obduction whilst oceanic spreading occurs as subduction. It is more reasonable to consider both the processes together in tectonic analysis.

•A custom FORTRAN subroutine to simulate thermal-mechanical process modelling of dual laser beam PBF is presented.•The influence of scanning strategy on temperature, residual stress and deflection in dual laser beam PBF is investigated.•The ‘following but time delayed’ dual laser beam scanning strategy is beneficial for minimising final part residual stress.•This research work serves as a guideline for part designers and PBF machine operators of dual laser beam PBF machines.