In the implantation of porous bone scaffolds, good mechanical properties of the scaffold are a prerequisite for the long-term functionality of the implanted scaffolds, which varies according to the structure and the forming process. In this study, the influence of the forming parameters and structure of the Selective Laser Melting (SLM) process on the mechanical properties of 316L stainless steel bone scaffolds was investigated using finite element simulation combined with experimental methods. The mechanism of the influence of the process parameters and structure on the mechanical properties of bone scaffolds was summarized using static compression finite element numerical simulations, compression experiments, hydrodynamic simulations, forming numerical simulations and SLM forming experiments. The results show that the magnitude of residual stress and the distribution of defects under different process parameters had a strong influence on the microstructure and properties of the scaffold, and the residual stress of the Body-Centered Cube (BCC) structure formed at an energy density of 41.7 J/mm³ was significantly reduced, with less surface spheroidization and fewer cracks on the melt pool surface. The smallest grain size of 321 nm was obtained at an energy density of 77.4 J/mm³, while in terms of mechanical properties, the optimization of the structure resulted in an 8.3% increase in yield strength and a reduction in stress concentration. The predictions of stress, deformation, and forming quality during construction with different process parameters, achieved using finite element analysis, are basically in agreement with the experimental results, indicating that the best process parameters for forming BCC structural supports were determined by using finite element simulation combined with experiments; moreover, the distribution and evolution of residual stresses and defects under different process parameters for constructing BCC structures were obtained.

To investigate the effect of selective laser melting (SLM) energy densities on the performance of porous 316L stainless steel bone scaffolds, the porous bone scaffolds with a face-centered cubic (FCC) structure were prepared using SLM technology, and a comprehensive study combining finite element analysis (FEA) and experiments was conducted on the SLM-formed 316L porous bone scaffolds. The mechanism of how various energy densities affect bone scaffolds were identified, and the effects of different energy densities on the primary dendrite spacing, grain orientation, residual stress, and transient melt pool variation in the scaffolds were discussed and summarized. It was found that the change in the energy densities had a more serious effect on the primary dendrite spacing, with the primary dendrite spacing increasing from 320 to 501 nm when the energy densities were increased from 41.7 to 111.1 J/mm³. In addition, analysis of the residual stress in the formed scaffolds showed that when an energy density of 41.7 J/mm³ was chosen for construction, the internal residual stress in the scaffolds reached a minimum value of 195.78 MPa, a reduction of approximately 36.6% compared to that of 111.1 J/mm³ for the porous scaffold. For the other properties of the scaffolds, the choice of low energy densities for the construction of FCC-structured porous bone scaffolds allowed for a maximum 10% reduction in the controlled deformation and a maximum 17% increase in the compressive properties. At the same time, it was found that the analysis results of the SLM-forming process by the FEA method were consistent with the experimental results. The main innovation of this paper is the proposal of the best construction parameters for porous bone scaffolds with an FCC structure formed by SLM and verification of the rationality of the best parameters through macro and micro experimental analysis, which guides the construction of porous bone scaffolds with an FCC structure formed by additive manufacturing. In addition, this study used finite element simulation to analyze the SLM process. This provides early prediction, optimization, and improvement for SLM-forming FCC porous bone scaffolds. The most important thing is that FEA can be used to more rapidly and economically analyze SLM. In the future, FEA can be used to provide a reference for porous bone scaffolds with different structures, different construction energy densities, different materials, and additive manufacturing in other industries.

Aiming at the problems of large elastic deformation and low machining accuracy in cutting titanium alloy thin-walled parts, this paper establishes the finite element model of milling titanium alloy thin-walled parts, and simulates and analyses the milling process of titanium alloy thin-walled parts by the statics analysis module of ANSYS 15.0 software. The maximum deformation point of the workpiece in the milling process is determined. Then the combination of cutting parameters that can minimize the deformation is determined by the orthogonal experiments of four factors and four levels. This paper designs the single factor experiments, which study the distribution of the milling force and the deformation law of the parts in the milling process. Moreover, this paper carries out the optimal design of the cutting parameters by orthogonal experiments, which provides a reference for the selection of the cutting parameters for the bending thin-walled parts of titanium alloy.

The primary purpose of this paper is to study the size effect of surface roughness and realize the quantitative description of the surface roughness in micro-forming process. This work is a continuation of the previous work by the authors. The effects of the initial surface roughness of the specimen, the grain size, and grain orientations on the surface roughness of micro-upsetting products were investigated. The ratio of the number of grains of the surface layer to the total number of grains was adopted to characterize the size effect. The variation of the size effect on the contact normal pressure during the compression process was also analyzed. And the quantitative description of the evolution law of surface roughness for micro-formed parts was realized. The corresponding micro compression experiment was done in order to testify the prediction model.