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1.
基于响应面法和支持向量回归模型对熔丝制造3D打印能效进行预测与优化。首先,利用田口方法设计六因素三水平正交试验,通过响应面法分析得出对加工能效影响较为显著的3个因素即层高、打印速度和热床温度;然后,通过支持向量回归方法建立加工能效预测模型,并与BP神经网络方法进行对比,结果表明支持向量回归方法建模预测性能更优;最后,建立以加工时间和能效为目标的优化模型,利用NSGA-Ⅱ、MOEA/D、SPEA2和MOPSO 4种算法分别对模型进行求解,分析比较4种算法的Pareto前沿,结果表明NSGA-Ⅱ算法在求解此问题时综合表现最佳,对比NGSA-Ⅱ算法求得的优化结果与试验结果可知,NSGA-Ⅱ算法具有有效性和合理性。 相似文献
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Taper grinding experiments were conducted in this paper to investigate the continuous and complete ductile-brittle transition process of two kinds of amorphous glass: high purity fused silica (HPFS) which is silica rich glass and soda-lime silica glass (SLSG) which is low silica glass. The grinding force, ground surface morphology, surface roughness, and subsurface damage depth induced during different stages of taper grinding were all analyzed. A mathematical model describing the cutting force of a grit and micro-crack length was established to clarify the ductile-brittle transition mechanisms of isotropic material. The model revealed that material removal mechanisms and grinding force were mainly determined by the crack equivalent length in front of the grit and its equivalent cutting force. The ground surface roughness and subsurface damage depth were mainly affected by the cutting force of the grit and length of cracks behind it. The ductile machinability of SLSG was better than that of HPFS due to the bonding of metallic atoms in SLSG with nonbridging oxygens, as well as their packing into free volume in SiO2 network. 相似文献
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对市售聚对苯二甲酸乙二醇酯-1,4-环己烷二甲醇酯(PETG)丝材及原材料进行研究,选用PETG 2012作为制备熔融堆积成型技术(FDM)用PETG丝材的基体树脂。选用聚碳酸酯(PC)对基体PETG进行增韧增强改性,并制成3D打印高分子丝材进行打印测试,探讨了PC含量对PETG耗材及制件性能的影响。结果表明,在低PC含量下,PETG与PC的相容性较好,PETG与PC制件未出现明显的分层,分布比较均匀;共混物的流动性随着PC含量的增加而降低,且打印件的维卡软化温度和热变形温度随着PC用量的增加而增加;此外,PC材料的加入使得PETG打印件的力学性能得到较大改善:打印件的拉伸强度随着PC用量的增加而增大,缺口冲击强度却随着PC用量的增加呈现先增加后减小的趋势; PETG/PC的配比为1∶1时,可制得力学性能优异的3D打印耗材。 相似文献
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以聚乳酸(PLA)和聚己二酸/对苯二甲酸丁二酯(PBAT)为基体,杨木粉(WF)为填充增强材料,使用混炼机熔融共混制备PLA/PBAT/WF复合材料,采用熔融沉积成型(FDM)技术制备标准实验试样,通过扫描电子显微镜、红外光谱分析、旋转流变测试以及力学试验等方法,研究不同含量的硅烷偶联剂KH550对PLA/PBAT共混物以及PLA/PBAT/WF的相容性、流变性及力学性能的影响。结果表明,在偶联剂用量为3 %(质量分数,下同)时,拉伸强度提高了136 %;偶联剂KH550与 PLA和PBAT共价键偶联生成接枝聚合物,二者相容性得到提高;同时偶联剂与WF表面羟基发生缩聚反应有效的改善了其与PLA/PBAT的基体相容性,PLA/PBAT/WF复合材料的FDM的制件力学性能得到较大提升;复合材料的黏度随偶联剂含量的增加呈下降的趋势,含量为3 %时线材的综合打印性能及制品质量最佳。 相似文献
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《Journal of the European Ceramic Society》2020,40(4):1728-1737
To investigate the fracture behavior of cement-bonded corundum castables, various cement contents and pre-treating temperatures have been comparatively studied using the wedge splitting method and the digital image correlation technique. The results show that the microstructure enhances the mechanical properties, so the fracture energy and the maximum load as well as the fracture modes are affected correspondingly. The castables demonstrate the highest fracture energy and maximum load at 1600 °C with cement content of 10 wt% due to an appropriate amount of CA6. At the temperatures of 110 and 1100 °C, the crack propagation within the matrix and along the interface are dominated whereas within the aggregates significantly increased at 1600 °C, leading to the brittleness of materials. However, increasing the cement content can reduce their brittleness, caused by the maximum strain in thex-direction, largest length of the main crack, and high ratio of crack propagation in the matrix. 相似文献
8.
《Ceramics International》2020,46(3):2654-2660
Brown fused alumina is a cost-effective alumina material, and the state of Ti in alumina has a great influence on its high-temperature performance. In this paper, the Ti-containing phases in brown fused alumina particles and Al-brown fused alumina refractory were successfully transformed into Ti(C,N) at 1973 K in flowing N2. The evolution of the Ti-containing phases in brown fused alumina under high temperature and nitrogen conditions was investigated by XRD, SEM and EDS. The results show that the Ti-containing phases in brown fused alumina include Ti2O3, Ti(C,N,O), TiFeSi2, Ca0·95Mg0·9Al10·1(Ti)O17 and a low-melting point Ca3Al2Si3(Mg,Ti)O12 phase. Under high temperature and nitrogen conditions, the TiO2[liquid], MgO[liquid] and SiO2[liquid] in the low-melting point phase are transformed into Ti(C,N), Mg(g) and SiO(g), while they are supplemented from Ti2O3, Ti(C,N,O) and Ca0·95Mg0·9Al10·1(Ti)O17. After heat treatment at 1973 K for 3 h, Ti2O3 and Ti(C,N,O) disappear, Ca0·95Mg0·9Al10·1(Ti)O17 is transformed into plate-like Ca0·55Al11O17.05, and Ti(C,N) is formed on the surface of the corundum particles. The formation of Ti(C,N) reduces the porosity of the brown fused alumina particles and increases their strength. 相似文献
9.
Preparation of calcium aluminate cement by combustion synthesis and application for corundum‐based castables 下载免费PDF全文
Shoulei Yang Guoqing Xiao Donghai Ding Yun Ren Lihua Lv Pan Yang 《International Journal of Applied Ceramic Technology》2018,15(3):678-688
Calcium aluminate cement was prepared by combustion synthesis with CaO2, Al, and Al2O3 as raw materials. The effects of CaO/Al2O3 (C/A) molar ratios in raw materials on the phase compositions and morphologies of calcium aluminate were investigated in detail. It was found that when the C/A reduced from 1.1 to 0.74, the content of CaO·2Al2O3 (CA2) in products increased, whereas contents of CaO·Al2O3 (CA) and 12CaO·7Al2O3 (C12A7) decreased; when the C/A was 0.8, the phase composition of product (CS71) was equal to that of Secar71. Additionally, the crystallines of CA and CA2 in the product were reduced when the C/A molar ratio was decreased. And then, the bulk density, apparent porosity, permanent linear change, cold crushing strength (CCS), and cold modulus of rupture (CMOR) of the corundum‐based castables bonded with CS71, Secar7 were compared. The castables bonded with CS71 demonstrate obviously improved CCS, CMOR, and volume stability. 相似文献
10.
考虑人眼主观评价在彩色融合图像质量评价中的重要作用,设计了52人的彩色融合图像质量主观评价实验。采用"目标背景的感知对比度","清晰度","颜色协调性","颜色自然感"4个单一评价指标以及"基于目标探测的图像感知质量","基于场景理解的图像感知质量"2个综合评价指标对绿地、海天和城镇3类典型场景、8种融合算法获得的240幅彩色融合图像进行了主观评价,并依此进行指标分值归整及相关性分析,建立了2个综合指标的预测模型。实验结果表明:彩色融合图像的"颜色协调性"和"颜色自然感"有较高的相关性;基于目标探测的图像感知质量可用"目标背景的感知对比度"和"清晰度"来描述,基于场景理解的图像感知质量可用"颜色协调性"和"清晰度"来描述。但是对于不同的场景,每个指标的影响效果不同,所以预测模型中的权重系数不同。 相似文献