熔融沉积(FDM) 3D打印成形件的力学性能实验研究

为提高不同填充率的制品力学性能,采用打印精度更高的类Delta并联式打印机,以较优固定参量实施应用广泛的熔融沉积(FDM)3D打印工艺,制备了不同填充率PLA耗材实验试件,并分别做了拉伸、弯曲和压缩实验,得到了较优的拉伸、压缩应力-应变曲线和弯曲载荷-位移曲线。同时开展了3D打印试件的抗拉强度、断裂伸长率、抗拉刚度、所承受的最大弯曲载荷和抗压强度研究。结果显示,填充率是影响3D打印试件变形失效和力学性能的关键因素,随着填充率的增加,试件的强度和刚度明显提高,而且同心线填充试件抗拉强度和断裂伸长率最大,直线形填充的刚度要优于同心线填充和格子形填充的刚度。     

Ag/TiO_2纳米复合材料的制备及结构研究

首先采用化学氧化在块体Ti表面制备出多孔纳米TiO2,随后通过高能离子束轰击实现Ag纳米粒子在TiO2表面的有效固定,最终在Ti表面制备出Ag/TiO2纳米复合材料。采用XRD、SEM及TEM手段对其进行了结构表征。结果表明,化学氧化法可制备出多孔纳米TiO2,其晶粒尺寸为10 nm左右;通过调节高能Ar离子束轰击的时间,可对TiO2晶粒尺寸进行小范围有效控制。     

铸造砂型3D打印技术应用及选型分析

研究了当前铸造砂型3D打印机的应用原理、工艺流程及主要性能,并对选型参考、应用等方面进行分析。结果表明,砂型3D打印技术相比传统树脂砂铸造技术有其先进性及优势,企业用户在选择砂型3D打印设备时,需根据自身企业产品的特点综合考虑,砂型3D打印在铸造上的应用工艺已相对成熟。     

3D网状结构TiBw/Ti60复合材料高温力学性能

利用反应热压技术制备了3D网状结构Ti Bw/Ti60复合材料,对复合材料在600~750℃范围内的高温力学性能进行了测试。结果表明,与Ti60合金相比,3D网状结构Ti Bw的原位形成显著提高了复合材料高温强度。在600、650、700和750℃,5.1%(体积分数)Ti Bw/Ti60复合材料的抗拉强度相比Ti60合金分别提高了42.5%、39.9%、35%和13.2%,而延伸率在各温度下均低于基体合金。网状结构复合材料断裂时形成的主裂纹沿网状界面处扩展,且断裂机制随实验温度增加而改变。     

溶液共混法制备TiO_2/PBO纳米复合材料

以甲基磺酸(MSA)作为溶剂,采用溶液共混法制备二氧化钛/聚亚苯基苯并二噁唑(TiO2/PBO)纳米复合材料;研究超声功率和超声时间对纳米TiO2/MSA悬浮液分散性的影响;并通过傅立叶红外光谱(FTIR)、热重分析(TGA)、扫描电镜(SEM)和紫外吸收光谱(UV)方法表征复合材料的结构特性。结果表明:当超声功率为250 W和超声时间为15 min时,纳米粒子在MSA中的分散性最佳;在红外图谱中,当TiO2的质量分数达到5%时,TiO2/PBO纳米复合材料与纯PBO的红外光谱无明显差别,说明纳米TiO2和PBO基体是通过物理作用连接起来的;与纯PBO相比,复合材料具有更优异的耐热性能,表现为热分解温度从PBO的689℃依次增高到690℃(1%TiO2)、694℃(5%TiO2)和698℃(10%TiO2)。由于纳米TiO2优异的紫外屏蔽性能,复合材料的吸光度在200~400 nm波段显著增大,因此,复合材料的抗老化性能也得到了极大的提高。     

3D打印技术应用

以某工业产品为例,应用3D打印技术加工铸造蜡型,并用熔模铸造制造出不锈钢产品。重点介绍了该打印材料的性能和设备参数、以及熔模铸造的工艺过程,实现了3D打印技术与铸造的完美结合,所用材料符合污染小、节约能源的绿色环保制造理念,符合现代制造业的最新发展趋势和市场经济的发展要求。     

3D打印速度的影响因素及改善措施研究

3D打印作为一项先进制造技术,近年来在全世界得到了广泛的重视和发展,打印速度是限制3D打印技术发展的重要瓶颈之一。介绍了限制3D打印速度的主要因素,从打印设备、控制策略、成型工艺方法等方面论述了提高3D打印速度的方法和措施,为今后提高3D打印速度的研究提供了方向和思路。     

3D打印大尺寸CF/PC复合材料框架式模具温度分布

为提高热压罐成型过程模具温度分布的均匀性和固化结束后制件的成形质量,采用与复合材料构件热膨胀系数差值较小的短切CF/PC复合材料为模具材料,3D打印大尺寸框架式模具。通过数值模拟、方差分析和实验研究了模具结构及工艺参数对3D打印模具型面温度分布的均匀性的影响规律。结果表明,3D打印模具型面厚度越小和热压罐入口风速越大,越有利于提高模具型面温度均匀性。模具型面温度模拟值和实验值的相对误差最大值为6.7%,验证了利用有限元方法模拟热压罐成型过程模具型面温度场分布的高可靠性。升温结束时,3D打印成型模具型面温度呈阶梯状分布,在支撑晶格与模具型面接触处易出现低温区。     

Ti3SiC2/HAp陶瓷复合材料力学性能研究

以Ti3SiC2(10%～50%,体积分数)和HAp粉为原料,采用等离子体放电烧结(SPS)方法,在外加应力60 MPa,烧结温度1200℃条件下,制备了Ti3SiC2/HAp陶瓷复合材料.研究了Ti3SiC2含量对复合材料的硬度、抗弯强度、断裂韧性等力学性能的影响.实验结果表明,随Ti3SiC2含量的变化,复合材料的强度和韧性均得到了提高和改善.分析认为,Ti3SiC2材料的微观结构特征和增韧机制起到了重要作用.     

3D打印技术在装备维修保障的应用及展望

介绍3D打印技术的概念、原理,归纳该技术的特点,阐述该技术在国内外的发展现状,重点对该技术在装备维修保障方面的应用进行了展望,同时指出该技术发展面临的挑战,为未来3D打印技术在装备维修保障方面的应用提供参考。     

Microstructure and mechanical properties of 2D woven Grf/Al composite

A 2D woven graphite fibers reinforced aluminum matrix composite with 50%Grf （volume fraction） was fabricated by the squeeze-casting technology, and its microstructure and mechanical properties were investigated. The results show that the composite is dense, the graphite fibers are distributed uniformly in the composite. TEM observation indicates the bonding between fiber and matrix is good and little interfacial reaction is found in the Grf/Al composite. This is attributed to the better stability of graphite fiber and the fabrication process minimizing the contact time between fiber with matrix at high temperatures. The 2D woven Grf/Al composite exhibites better mechanical properties with tensile strength, bending strength and elastic modulus of 366.2, 519.7 and 110.7 GPa, respectively.＂ SEM images suggeste that the fracture is irregular and some pulled-out fibers are found, which indicats that the high strength of fiber is not degraded.     

3D打印轻质高强钨材的力学性能研究

采用选择性激光熔化（SLM）3D打印方式成功设计和制造了具有点阵结构的钨材,结合有限元分析、扫描电镜、准静态单轴压缩试验探究了不同点阵结构下钨材力学性能的变化规律,分析了微观组织对力学性能的影响。结果表明圆弧型点阵结构可有效降低节点处的应力集中,保持点阵结构轻质、低孔隙率特性同时还维持着钨材的高强度力学性能,平均抗压强度达到535MPa,平均质量仅为1.25g,激光打印后圆弧点阵较立方点阵平均抗压强度提升93%,其中体心圆弧点阵（BCA）显示出更优抗压性能,极限抗压强度达到721MPa,结构致密度为理论值12.8%;力学性能指标接近于变形态。与立方点阵相比,圆弧点阵具有良好的能力吸收特性,后者相较前者总能量吸收值提升223%,圆弧点阵平均能量吸收达到1664J/cm3。此外,SEM图像显示圆弧点阵因其弧形特性,减少了打印中斜支柱的悬挂距离,成型效果优于立方点阵。     

Microstrucmre and mechanical properties of Al2O3/TiAl composite

Al2O3/TiAl composites were fabricated by PAXD （pressure-assisted exothermic dispersion） method. The effects of Nb205 content on the microstructure and mechanical properties of the composites were investigated. The results show that the ultimate phases of the composite consist of TiAl, Ti3Al, Al2O3 and a small amount of NbA13. SEM reveals that a submicron γ＋（α2/γ） dual phases structure can be presented after sintered at 1 200 ℃, Furthermore, with the increase of Nb205 content, the ratio of TiAl to Ti3Al phase decreases correspondingly, the grains of the corflposites are remarkably refined, and the produced Al2O3 particles are uniformly dispersed. When 6% Nb205 is added, the composite has the best comprehensive properties. It exhibits a Vickers hardness of 4.77 GPa and a bending strength of 642 MPa. Grain-refinement and dispersion-strengthening are the main strengthening mechanisms.     

Fabrication of carbon nanotube reinforced AZ91D composite with superior mechanical properties

AZ91D alloy composites with 1.0% CNTs have been fabricated by a method combined ball milling with stirring casting. The composite was investigated using optical microscopy(OM), X-ray diffraction(XRD), Fourier transform infrared spectroscope (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and room temperature (RT) tensile test. The results show that CNTs were homogeneously distributed in the matrix and maintained integrated structure. The yield strength and ductility of AZ91D/CNTs composite were improved by 47.2% and 112.2%, respectively, when compared with the AZ91 alloy. The uniform distribution of CNTs and the strong interfacial bonds between CNT and the matrix are dominated to the simultaneous improvement of yield strength and ductility of the composite. In addition, the grain refinement as well as the finer β phase (Mg₁₇Al₁₂) with homogenous distribution in the matrix can also slightly assist to the enhancement of the mechanical properties of the composite.     

NiCoCrAlY/Al2O3复合涂层的组织与性能

采用离子喷涂和超音速火焰喷涂技术分别制备了NiCoCrAlY/Al₂O₃耐磨复合涂层,通过SEM、显微硬度计和万能材料测试机研究了粉体和涂层的显微结构、显微硬度和结合强度。结果表明,Al₂O₃颗粒表面包覆着一层致密的NiCoCrAlY合金,涂层与基体结合良好,超音速火焰喷涂涂层的孔隙率仅为等离子喷涂涂层的1/7。超音速火焰喷涂涂层的显微硬度和结合强度均高于等离子喷涂涂层。两种方法制备的涂层的破坏属脆性断裂机理。     

Fabrication and mechanical properties of TiB2/ZrO2 functionally graded ceramics

Five layers were considered for the present TiB₂/ZrO₂ functionally graded ceramics and TiB₂/ZrO₂ functionally graded ceramics were prepared by hot-pressing. The first layer, marked as L₁, was composed of TiB₂–15vol%SiC. The L₂ layer was composed of TiB₂–15vol%SiC–10vol%ZrO₂. The L₃ layer was composed of TiB₂–25vol%ZrO₂ without addition of SiC, because 25vol%ZrO₂ was enough to densify TiB₂. The last two layers, L₄ and L₅, were composed of TiB₂–35vol%ZrO₂ and TiB₂–45vol%ZrO₂, respectively. Denser graded microstructures as well as the stronger interfaces were achieved for TiB₂/ZrO₂ functionally graded ceramics hot-pressed at 1900 °C. Due to the phase transformation of ZrO₂, the toughness of TiB₂/ZrO₂ functionally graded ceramics increased from ~ 4.3 MPa m^1/2 for the TiB₂-rich layer to ~ 8.9 MPa m^1/2 for the ZrO₂-rich layer. The effect of hot-pressing temperature on the toughness of TiB₂/ZrO₂ functionally graded ceramics was further investigated in detail.     

XFEM计算3D打印PLA材料拉伸试样的裂纹扩展

以PLA型3D打印材料为研究对象,通过3D成型的方式制备出拉伸和扭转试验样本,测定了该材料的弹性力学性能。并通过扩展有限元法(XFEM)进行了样本的拉伸断裂性能计算。为评估PLA材料在3D打印件的应用领域提供了相应的断裂参数,同时也为改善3D打印材料力学特性提供了依据。研究结果表明,PLA型3D打印件弹性本构为横贯各向异性;最大拉伸应力为20MPa,拉伸过程中出现的两条裂纹都是以I型和III型裂纹为主,裂纹尖端应力奇异最大值为1.9GPa。     

Micro mechanical properties of n-Al2O3/Ni composite coating by nanoindentation

A new type of nano test system was introduced, the test principle and the indentation data analysis method were described. It was used to test the micro mechanical properties, such as hardness, elastic modulus and indentation creep property of n-Al2O3/Ni composite coating on steel prepared by brush plating, and the variety of mechanical properties with coating thickness was researched. The results show that the mechanical properties are basically identical within the whole coating, the hardness and modulus decrease in the defect fields, especially within the dendritic crystals, whereas the mechanical properties are not influenced greatly at the interspaces among dendritic crystals. The average hardness and elastic modulus of n-Al2O3/Ni coating are 6.34 GPa and 154 GPa respectively, and the hardness is 2.4 times higher than that of steel and the indentation creep curve of n-Al2O3/Ni coating is similar to that of the uniaxial compression creep, and the creep rate of steady-state is about 0. 104 nm/s. These results will supply useful data for process improvement, new type material development and application expansion.     

Effect of printing parameters on properties of 3D printing sand samples

Three-dimensional sand printing(3DSP) is widely applied in sand mold fabrication.In this study,the effects of printing parameters including the resolution of printehead holes,activator content,layer thickness,and recoating speed on the tensile and bending strengths,gas evolution,and loss-on-ignition(LOI) of 3DSP samples were investigated by changing single parameter,and the dimension deviation was also measured.As the resolution increases,the tensile strength,bending strength,gas evolution,LOI,a...