An Innovative Finite Element Geometric Modeling of Single-Layer Multi-Bead WAAMed Part

Finite element (FE) coupled thermal-mechanical analysis is widely used to predict the deformation and residualstress of wire arc additive manufacturing (WAAM) parts. In this study, an innovative single-layermulti-bead profilegeometric modeling method through the isosceles trapezoid function is proposed to build the FE model of theWAAMprocess. Firstly, a straight-line model for overlapping beads based on the parabola function was establishedto calculate the optimal center distance. Then, the isosceles trapezoid-based profile was employed to replace theparabola profiles of the parabola-based overlapping model to establish an innovative isosceles trapezoid-basedmulti-bead overlapping geometric model. The rationality of the isosceles trapezoid-based overlapping model wasconfirmed by comparing the geometric deviation and the heat dissipation performance index of the two overlappingmodels. In addition, the FE-coupled thermal-mechanical analysis, as well as a comparative experiment of thesingle-layer eight-bead deposition process show that the simulation results of the above two models agree with theexperimental results. At the same time, the proposed isosceles trapezoid-based overlappingmodels are all straightlineprofiles, which can be divided into high-quality FE elements. It can improve the modeling efficiency andshorten the simulation calculation time. The innovative modeling method proposed in this study can provide anefficient and high-precision geometricmodelingmethod forWAAMpart FE coupled thermal-mechanical analysis.

Design and Mechanical Characterization of an S-Based TPMS Hollow Isotropic Cellular Structure

Cellular structures are regarded as excellent candidates for lightweight-design,load-bearing,and energy-absorbing applications.In this paper,a novel S-based TPMS hollow isotropic cellular structure is proposed with both superior load-bearing and energy-absorbing performances.The hollow cellular structure is designed with Boolean operation based on the Fischer-Koch(S)implicit triply periodic minimal surfaces(TPMS)with different level parameters.The anisotropy and effective elasticity properties of cellular structures are evaluated with the numerical homogenization method.The finite element method is further conducted to analyze the static mechanical performance of hollow cellular structure considering the size effect.The compression experiments are finally carried out to reveal the compression properties and energy-absorption characteristics.Numerical results of the Zener ratio proved that the S-based hollow cellular structure tends to be isotropic,even better than the sheet-based Gyroid TPMS.Compared with the solid counterpart,the S-based hollow cellular structure has a higher elastic modulus,better load-bearing and energy absorption characteristics.

Printing ionic polymer metal composite actuators by fused deposition modeling technology

In this work,we printed a Nafion precursor membrane by fused deposition modeling(FDM)rapid prototyping technology and further fabricated IPMCs by electroless plating.The ion-exchange capacity of the Nafion membrane was tested,and the morphology of IPMCs was observed.The electro-mechanical properties of IPMCs under AC voltage inputs were studied,and grasping experiments were performed.The results show that the Nafion membrane after hydrolysis has a good ion-exchange ability and water-holding capacity.SEM observed that the thickness of the IPMC’s electrode layer was about 400 nm,and the platinum layer was tightly combined with the substrate membrane.When using a square wave input of 3.5 V and 0.1 Hz,the maximum current of IPMCs reached 0.30 A,and the displacement and blocking force were 7.57 mm and 10.5 mN,respectively.The new fabrication process ensures the good driving performance of the printed IPMC.And two pieces of IPMCs can capture the irregular objects successfully,indicating the feasibility of printing IPMCs by FDM technology.This paper provides a new and simple method for the fabrication of three-dimensional IPMCs,which can be further applied in flexible grippers and soft robotics.