Blast response of continuous-density graded cellular material based on the 3D Voronoi model

One-dimensional blast response of continuous-density graded cellular rods was investigated theoretically and numerically. Analytical model based on the rigid-plastic hardening(R-PH) model was used to predict the blast response of density-graded cellular rods. Finite element(FE) analysis was performed using a new model based on the 3 D Voronoi technique. The FE results have a good agreement with the analytical predictions. The blast response and energy absorption of cellular rods with the same mass but different density distributions were examined under different blast loading. As a blast resistance structure, cellular materials with high energy absorption and low impulse transmit is attractive. However, high energy absorption and low impulse transmit cannot be achieved at the same time by changing the density distribution. The energy absorption capacity increases with the initial blast pressure and characteristic time of the exponentially decaying blast loading. By contract, when the blast loading exceeds the resistance capacity of cellular material, the transmitted stress will be enhanced which is detrimental to the structure being protected.

Finite Element Simulation of Flexible Roll Forming with Supplemented Material Data and the Experimental Verification

Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

Co-continuous Composite Material Design Using the Volumetric Distance Field Based on Analytic Shape Functions

An effective and simple design method for co-continuous composite material construction is proposed by using a hybrid methodology with triply periodic minimal surface( TPMS) cellular topology and the volumetric distance field( VDF). After generating a set of VDF-based features for the given exterior shape and desired internal core structure,a series of simple modifications in distance fields enabled us to obtain an arbitrarily-shaped complex co-continuous composite material computational model. Design results and manufactured prototypes through 3 D printing technology show that the proposed methodology has the potential to open a new paradigm for producing multifunctional next generation co-continuous composite materials which are impossible to design and manufacture using traditional CAD and CAM.

An extended numerical model of the first exothermic peak for three dimensional printed cement-based materials

The first exothermic peak of cement-based material occurs a few minutes after mixing,and the properties of three dimensional(3D)printed concrete,such as setting time,are very sensitive to this.Against this background,based on the classical Park cement exothermic model of hydration,we propose and construct a numerical model of the first exothermic peak,taking into account the proportions of C_(3)S,C_(3)A and quicklime in particular.The calculated parameters are calibrated by means of relevant published exothermic test data.It is found that this developed model offers a good simulation of the first exothermic peak of hydration for C_(3)S and C_(3)A proportions from 0 to 100% of cement clinker and reflects the effect of quicklime content at 8%-10%.The unique value of this research is provision of an important computational tool for applications that are sensitive to the first exothermic peak of hydration,such as 3D printing.

Auspicious Patterns and 3D Models Applied in the Creation of Personalized Products

Auspicious patterns are an important manifestation of traditional crafts aesthetics for Chinese culture, and it not only exhibits the clever tricks of folk art, showing more personality and characteristics of Chinese culture in the humanities and arts aesthetic concerns. It shows the traditional aesthetics, based on the harmonious and success, constructed by intelligence and humbleness, shaped by symmetry and balance. This thesis contains two topics: they are the 2D image materialization and the 3D model flattening. First is analyzing the image of the auspicious pattern, and transformed the 2D image into a solid model. The second is through the mathematical operation skills of the geometric model, the existing auspicious 3D model of the triangular mesh is scaled, appropriately rotated and divided to form a flattening model of different visual effects. Finally, these models by means of other modeling software were combined into a new 3D model, then through the 3D printer to quickly print out part of the unique personalized products, to promote the natural beauty of traditional Chinese culture.

3D printing of tissue engineering scaffolds:a focus on vascular regeneration

Tissue engineering is an emerging means for resolving the problems of tissue repair and organ replacement in regenerative medicine.Insufficient supply of nutrients and oxygen to cells in large-scale tissues has led to the demand to prepare blood vessels.Scaffold-based tissue engineering approaches are effective methods to form new blood vessel tissues.The demand for blood vessels prompts systematic research on fabrication strategies of vascular scaffolds for tissue engineering.Recent advances in 3D printing have facilitated fabrication of vascular scaffolds,contributing to broad prospects for tissue vascularization.This review presents state of the art on modeling methods,print materials and preparation processes for fabrication of vascular scaffolds,and discusses the advantages and application fields of each method.Specially,significance and importance of scaffold-based tissue engineering for vascular regeneration are emphasized.Print materials and preparation processes are discussed in detail.And a focus is placed on preparation processes based on 3D printing technologies and traditional manufacturing technologies including casting,electrospinning,and Lego-like construction.And related studies are exemplified.Transformation of vascular scaffolds to clinical application is discussed.Also,four trends of 3D printing of tissue engineering vascular scaffolds are presented,including machine learning,near-infrared photopolymerization,4D printing,and combination of self-assembly and 3D printing-based methods.

工业级熔融沉积式3D打印材料研究

工业级熔融沉积式3D打印技术是应用于大型塑料产品制造的新型技术,该技术熔融沉积式3D打印由创意制作、教学科普推广到工业生产领域。现有打印材料在进行大型产品打印时会出现强度不足、翘曲开裂等问题,因此为满足产品的打印需求,针对打印需要开发出两款适用于大型产品打印的改性打印材料——ABS、PLA,以实现最佳的打印效果。

Experimental study on the movement law of overlying rock non-pillar coal overhead mining

Pillarless coal mining technology is a new practical technology.Based on the compensating mechanical behavior of the Negative Poisson’s Ratio(NPR)anchor cable on the roof,the roadway was successfully retained by the top cutting and pressure relief technology.This study utilizes the Digital Speckle Monitoring(DIC monitoring),stress-strain monitoring,and infrared thermal imaging systems to conduct physical model experiment of similar materials from the displacement,stress-strain,and temperature fields to investigate in depth the fracture change law of the overlying rock.In addition,it uses FLAC3D numerical simulation to invert the surface displacement settlement.The results show that the non-pillar overhead mining under the 110 mining method has little influence on the rock crack in the middle of the coal seam,and the crack development area is mainly concentrated in the overlying rock mass of the upward coal seam.The compensatory mechanical behavior of NPR anchor cable and the dilatation characteristics of rock mass have a good effect of retaining roadway along goaf,and can also reduce surface settlement.The 110 mining method provides a scientific basis for ecological environment protection and the development of other kilometer deep soft rock high ground stress underground projects.

基于FDM工艺的多材料建模方法及应用研究

在三维打印成型中,多材料的应用不仅可以增强模型的表达效果,还能够制造出多功能复合材料零件,所以近年取得越来越广泛的应用。针对困扰多材料三维打印成型的基本问题,研究了建模方法,在综合比较的基础上,提出采用多色距离场方法解决多材料CAD建模的问题,这样的模型不仅能表达模型传统的结构信息,同时也能准确的用不同颜色表达不同的材料信息;此外,变形是制约成型质量的重要因素,因此针对FDM工艺中的变形,进行了理论分析,建立了数学模型,在此基础上得出减少变形的办法。并成功应用在多材料的三维打印中,取得了良好的效果。

Material,design,and fabrication of custom prosthetic liners for lower-extremity amputees:A review

As a physical interface,a prosthetic liner is commonly used as a transition material between the residual limb and the stiff socket.Typically made from a compliant material such as silicone,the main function of a prosthetic liner is to protect the residual limb from injuries induced by load-bearing normal and shear stresses.Compared to conventional liners,custom prosthetic lower-extremity(LE)liners have been shown to better relieve stress concentrations in painful and sensitive regions of the residual limb.Although custom LE liners have been shown to offer clinical benefits,no review article on their design and efficacy has yet been written.To address this shortcoming in the literature,this paper provides a comprehensive survey of custom LE liner materials,design,and fabrication methods.First,custom LE liner materials and components are summarized,including a description of commercial liners and their efficacy.Subsequently,digital methods used to design and fabricate custom LE liners are addressed,including residual limb biomechanical modeling,finite element-based design methods,and 3-D printing techniques.Finally,current evaluation methods of custom/commercial LE liners are presented and discussed.We hope that this review article will inspire further research and development into the design and manufacture of custom LE liners.

Numerical Study of the Influence of Grain Size and Loading Conditions on the Deformation of a Polycrystalline Aluminum Alloy

This work is concerned with numerical simulations of surface roughening in a polycrystalline aluminum alloy. Using 3D finite difference model, high-resolution simulations are conducted. Effects of loading conditions and grain size on surface roughening and mesoscale deformation processes in AL6061-T3 aluminum alloy under quasistatic uniaxial tension are investigated.

镁合金ZK60的三维加工图及失稳分析

在PRASAD提出的二维加工图的基础上，建立包含应变的三维加工图，经分析得到适合镁合金ZK60的失稳判据，讨论并解决了三维力睁工图绘制中的关键技术。在Gleeble-1500热模拟机上对镁合金ZK60进行了热压缩实验，研究了200-360℃和0．01～5／s条件下的热变形行为。该加工图的结果显示一个非失稳、功率耗散峰值区：温度为300～360℃、应变速率为0．01-0．1／s，功率耗散平均值为35％，此区为适合的加工区。

CATIA V5环境下水电工程三维可视化仿真场景中的应用研究

在水电工程三维可视化仿真场景实现过程中,针对水电工程的设计特点与视觉特征,提出CG知识库的概念,并以CATIA与3DS MAX软件为应用平台,从环节分解、要素分类、建立方法、关键问题等方面探讨了水电工程三维参数化模型库与三维网格模型库、材质库等CG知识库的实现思路及采用的主要技术,并阐述了通过CG知识库的运用,可快速搭建三维可视化仿真场景,缩短同类项目的制作周期,提高应用自动化的程度。

三维机织复合材料纱线观测与细观几何模型

通过对三维机织复合材料细观切片拍照,追踪材料内部纱线各个截面的形状和形心坐标,从而确定三维机织复合材料纱线真实细观形态和轨迹。并据此建立了一个新的三维机织复合材料几何模型,计算了三维机织复合材料的纤维体积含量。结果表明:该模型能够较好地反映三维机织复合材料内部的真实结构,为建立更精确的力学模型打下基础。

地震物理模型中三维地质模型材料特性研究

实际地质构造具有复杂和岩层速度变化大等特点,制作相应的三维地质模型,需要有各种性质的模型材料,以满足模型与实际情况相接近的要求。为此,对几种模型材料的性质和适用范围进行了分析。一般工业材料的速度,虽然有些能与岩石速度相匹配,但却难以加工成各种各样的构造形态,而且不能满足对层与层之间胶合质量的要求。环氧树脂和合成橡胶是工业上常用的2种材料,具有液态固化特性,将两者混合在一起可得到速度连续可变的混合材料。实验表明,混合材料中硅橡胶与环氧树脂的量之比(配比ε)不同,速度可在2600～950 m/s之间变化。变化规律呈现出3种方式：配比ε在0～50%之间,混合材料的速度随硅橡胶量的增加线性降低；配比ε在60%～100%之间,速度下降的趋势变缓,速度的变化主要取决于硅橡胶的速度；配比ε在50%～60%之间,混合材料的速度范围为1350～1800 m/s,在此范围,速度受温度的影响较大,出现了不稳定现象,用柔性环氧树脂可以消除这种现象。此外,硅橡胶量多的混合材料,对横波的传播不利。利用混合材料的液态固化特性,可以根据需要,利用模具技术制作各种形态的地质构造模型,且层与层之间的胶合性质与实际地层沉积特性相似。

三维五向矩形编织复合材料的细观结构模型

分析了三维五向矩形编织工艺携纱器的运动规律,基于映射思想研究了纱线的空间走向及规律。经分析内部区域编织纱及轴纱的空间挤压交织关系,建立了能有效反映其纱线空间构型特征的三维实体细观结构模型。根据3单胞划分思想,提出了平行于材料边界方向的单胞几何模型,建立了编织工艺参数和模型宏细观结构参数的关系。模型数值结果与试件实测数据基本吻合,证明了该模型合理、有效。

纱线真实感的计算机仿真

通过摄取不同材质的纱线图片,利用RGB颜色空间和HLS颜色空间的相互转换提取纱线的亮度值,并以纱线上像素点的位置坐标为X、Y轴,提取的亮度为Z轴作亮度分布图来分析纱线表面的反射特征。从亮度分布图中获得不同材质的纱线图片亮度分布的差异,用Shepard插值法拟合纱线表面的光反射分布,用拟合得到的函数来仿真纱线,得到的纱线效果较自然,并能反映出不同材质纱线的光泽和构成纱线的纤维聚集形态的差异,真实感强。

基于Python的Abaqus二次开发在层压板修理模拟中的应用

为加快复合材料层压板单面贴补参数设计的效率,利用基于Python的Abaqus二次开发技术,开发针对复合材料层压板单面贴补修理的快速建模及后处理程序.结果表明,程序能够通过输入单面贴补设计参数便捷地创建模型,并且计算结束后能通过快速后处理程序自动提取所需的数据和信息.该程序能够针对单面贴补修理母板的长度、宽度、单层厚度、层数和铺层顺序,补片的层数、直径和铺层顺序,以及复合材料单向预浸料和胶膜的性能等参数进行设计分析.用该程序计算得到的易破坏位置和破坏模式与试验结果的误差小于10%,证明该程序可行.

激光感生等离子体特性的三维数值模拟

在激光焊接过程中,作用于金属工件表面的高强度激光会引起材料的强烈蒸发,金属蒸汽与入射激光相互怍用,又会引起金属蒸汽部分电离,形成激光感生等离子体。本文采用三维模拟方法,考虑保护气和侧吹气的影响,对激光感生等离子体中的温度与速度分布进行了研究。

管道材料统计文件的控制点

结合广东LNG项目的实例,提出料表文件中的几个重要的控制点,并进行了相关的分析,为同类型工程项目的材料控制工作提供参考。