基于SLA和FDM的3D打印发动机风扇工艺与性能分析

在新产品样件开发中,导入3D打印技术,以一款微型汽车发动机风扇快速成型制造为研究对象,简述了SLA和FDM2种3D打印快速成型方法的概念和原理,介绍了SLA和FDM2种不同的3D打印设备。探讨了基于SLA和FDM的发动机风扇3D打印过程及工艺方法,对比分析了SLA和FDM快速成型制造方法的特点和差异,并通过力学实验和高低温交变试验,对比验证SLA和FDM快速成型的发动机风扇产品的力学性能,总结了SLA和FDM的工艺特点,提出了新产品开发如何选择恰当的3D打印设备与工艺的建议。

Dense ceramics with complex shape fabricated by 3D printing:A review

Three-dimensional(3D)printing technology is becoming a promising method for fabricating highly complex ceramics owing to the arbitrary design and the infinite combination of materials.Insufficient density is one of the main problems with 3D printed ceramics,but concentrated descriptions of making dense ceramics are scarce.This review specifically introduces the principles of the four 3D printing technologies and focuses on the parameters of each technology that affect the densification of 3D printed ceramics,such as the performance of raw materials and the interaction between energy and materials.The technical challenges and suggestions about how to achieve higher ceramic density are presented subsequently.The goal of the presented work is to comprehend the roles of critical parameters in the subsequent 3D printing process to prepare dense ceramics that can meet the practical applications.

Influence of curing conditions on the shrinkage behavior of three-dimensional printed concrete formwork

The use of three-dimensional(3D)printed concrete as formwork is becoming more widely applied within the industry.However,the technology is still not optimized and there are many reports of preliminary cracking during the curing of cast concrete.This is believed to result from differential shrinkage between the printed and cast concrete.These cracks(in the printed concrete or at the interface between the infill and printed concrete)form a preferential path for aggressive substances and can reduce the durability of the combined concrete element.To ensure the desired service life of the structure,it is important that the differential shrinkage between cast and printed concrete is understood.This study investigated the effect of curing conditions on the differential shrinkage behavior of 3D and cast concrete.The influence of prewetting of the dry-cured 3D printed formwork was also determined.In the experimental program,a vibrated and self-compacting concrete were used as cast material.Linear 3D printed formwork was produced and combined with cast concrete to simulate a concrete structure.Printed formwork was cured for 1,7,or 28 d exposed to the air(relative humidity:60%or 95%)or submerged in water.The length change of the combined elements was observed over 56 d after concrete casting and throughout the thickness of the materials.Results show that increasing the curing period in dry conditions of the printed concrete leads to an expansion of the formwork on the first day after casting.The expansion leads to a non-uniform strain evolution throughout the curing period of the combined element.Printed concrete formwork stored in wet conditions does not expand after the casting process but tends to show a decreasing linear deformation within the whole elements.

Experimental investigation on the deformation characteristics of locking-steel-pipe(LSP)pile retaining structure during excavation in sand

Locking-steel-pipe(LSP)piles connect with adjacent joints to form a pile row enclosure structure.Due to the advantages of quick construction,efficiency in installation,and recycle utilization,the connected LSP piles are frequently used as retaining structure in deep excavation.However,systematic studies of the deformation mechanism of the LSP pile retaining structure are rarely reported,and it still lack of experimental evidence to optimize the design.In this study,a braced supported excavation experimental model test in sand was designed and conducted to investigate the deformation characteristics of LSP pile retaining structure.Three dimensional(3D)printing technique was creatively applied to manufacture LSP model piles.The experimental results show that,a“S”shaped distribution of bending moments is observed along pile shaft when excavation is executed;the deflection of pile shaft develops deep-seated movements toward the excavation side as excavation went deeper,resulting in a“bowl”ground settlement.With the deflection of LSP piles,a rotating trend was occurred between pairs of locking joint,and the severe open deformation of locking joint arose on excavation side.There was a gradual reduction in earth pressure behind the LSP pile retaining wall with excavation depth.The earth pressure between two struts level had no obvious changing,owing to the supported effect of inner struts.

Energy Absorption Characteristics of a Novel Asymmetric and Rotatable Re-entrant Honeycomb Structure

Based on the symmetric re-entrant honeycomb(S-RH)structure with negative Poisson’s ratios,a novel asymmetric and rotatable re-entrant honeycomb(AR-RH)structure was proposed.Both the S-RH structure and AR-RH structure were produced by the 3D printing technology.Through experimental test and finite element simulation,the deformation mechanism and energy absorption characteristics of the AR-RH structure and the S-RH structure with negative Poisson’s ratios at different impact velocities were compared.The experimental test and finite element simulation results show that the novel AR-RH structure with negative Poisson’s ratios has stronger energy absorption capacity than the S-RH structure,and it has been verified that the rotatability of AR-RH can indeed absorb energy.Furthermore,the degree of asymmetry of the AR-RH structure was discussed.