A novel approach of jet polishing for interior surface of small-grooved components using three developed setups

It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken.

Mechanical design and analysis of bio-inspired reentrant negative Poisson’s ratio metamaterials with rigid-flexible distinction

Aiming at achieving tunable reentrant structures with rigidity and uniformity,respectively,the C-shaped and S-shaped reentrant metamaterials were proposed by the bionic design of animal structures.Utilizing beam theory and energy methodology,the analytical expressions of the equivalent elastic modulus of the metamaterials were derived.Differences in deformation modes,mechanical properties,and energy absorption capacities were characterized by using experiments and the finite element analysis method.The effects of ligament angle and thickness on the mechanical characteristics of two novel metamaterials were investigated by using a parametric analysis.The results show that the stiffness,deformation mode,stress-strain curve,and energy absorption effects of three metamaterials are significantly different.This design philosophy can be extended from 2D to 3D and is applicable at multiple dimensions.

Compressive Mechanical and Heat Conduction Properties of AlSi10Mg Gradient Metamaterials Fabricated via Laser Powder Bed Fusion

Metamaterials are defined as artificially designed micro-architectures with unusual physical properties,including optical,electromagnetic,mechanical,and thermal characteristics.This study investigates the compressive mechanical and heat transfer properties of AlSi10Mg gradient metamaterials fabricated by Laser Powder Bed Fusion(LPBF).The morphology of the AlSi10Mg metamaterials was examined using an ultrahigh-resolution microscope.Quasi-static uniaxial compression tests were conducted at room temperature,with deformation behavior captured through camera recordings.The findings indicate that the proposed gradient metamaterial exhibits superior compressive strength properties and energy absorption capacity.The Gradient-SplitP structure demonstrated better compressive performance compared to other strut-based structures,including Gradient-Gyroid and Gradient-Lidinoid structures.With an apparent density of 0.796,the Gradient-SplitP structure exhibited an outstanding energy absorption capacity,reaching an impressive 23.57 MJ/m^(3).In addition,heat conductivity tests were performed to assess the thermal resistance of these structures with different cell configurations.The gradient metamaterials exhibited higher thermal resistance and lower thermal conductivity.Consequently,the designed gradient metamaterials can be considered valuable in various applications,such as thermal management,load-bearing,and energy absorption components.

Research on the Surface Subsidence Monitoring Technology Based on Fiber Bragg Grating Sensing

In order to monitor the process of surface subsidence caused by mining in real time, we reported two types of fiber Bragg grating （FBG） based sensors. The principles of the FBG-based displacement sensor and the FBG-based micro-seismic sensor were described. The surface subsidence monitoring system based on the FBG sensing technology was designed. Some factual application of using these FBG-based sensors for subsidence monitoring in iron mines was presented.

A novel hybrid design method of lattice structure based on failure mode

Adjusting the mechanical properties of lattice structures is important for many modern application fields. In this paper, a new design method for hybrid multi-layer lattice structures was developed to improve the mechanical properties and energy absorption, by altering and suppressing the formation of the shear band. In these hybrids, all unit cells were divided into two parts:(i) diagonal unit cells and(ii) matrix unit cells. Four categories of unit cells were selected to construct the hybrid multi-layer structures. The compressive moduli, ultimate strengths, and energy absorption properties of the laser powder bed fusion(L-PBF)fabricated structures were assessed by experiments and finite element analysis(FEA). The results revealed the great impact of diagonal unit cells on the mechanical properties of the structures. Stronger diagonal unit cells than matrix unit cells led to hybrid structures with enhanced mechanical properties. Compared with a uniform body-centered cubic(BCC) lattice structure, the relative density of the lattice structure consisting of the weakest BCC matrix unit cells and strongest BFVC diagonal unit cells(coupling of BCC, FCC, and VC) exhibited an increase of 20%. The compressive modulus and ultimate strength of this structure rose by more than 200% and 90%, respectively. Two types of structures with specific properties were generated by hybrid design.The first displayed higher modulus, superior strength, and elevated specific energy absorption(SEA) but lower crash load efficiency(CLE). The second illustrated simultaneously higher SEA and elevated CLE. The present results provide a new insight for improving the load-bearing and energy absorption capacities of lattice structures.