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桉木纤维 1

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Modeling limit force capacities of high force to volume lead extrusion dampers

《结构与土木工程前沿（英文）》 2021年第15卷第3期页码 609-622 doi: 10.1007/s11709-021-0724-x

摘要： Lead extrusion dampers are supplemental energy-dissipation devices that are used to mitigate seismic structural damage. Small volumetric sizes and high force capacities define high-force-to-volume (HF2V) devices, which can absorb significant response energy without sacrificial damage. However, the design of such devices for specific force capacities has proven difficult based on the complexities of their internal reaction mechanisms, leading to the adoption of empirical approaches. This study developed upper- and lower-bound force capacity estimates from analytical mechanics based on direct and indirect metal extrusion for guiding design. The derived equations are strictly functions of HF2V device geometric parameters, lead material properties, and extrusion mechanics. The upper-bound estimates from direct and indirect extrusion are denoted as (F_UB,1, F_UB,2) and (F_UB,3, F_UB,4), respectively, and the lower-bound estimates are denoted as (F_LB, F_LB,1) based on the combination of extrusion and friction forces. The proposed models were validated by comparing the predicted bounds to experimental force capacity data from 15 experimental HF2V device tests. The experimental device forces all lie above the lower-bound estimates (F_LB, F_LB,1) and below the upper-bound estimates (F_UB,1, F_UB,2, F_UB,4). Overall, the (F_LB, F_UB,2) pair provides wider bounds and the (F_LB,1, F_UB,4/F_UB,1) pair provides narrower bounds. The (F_LB,1, F_UB,1) pair has a mean lower-bound gap of 36%, meaning the lower bound was 74% of the actual device force on average. The mean upper-bound gap was 33%. The bulge area and cylinder diameter of HF2V devices are key parameters affecting device forces. These relatively tight bounds provide useful mechanics-based predictive design guides for ensuring that device forces are within the targeted design range after manufacturing.

关键词： extrusion lead dampers upper and lower bound analytical modelling limit force

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Development of lunar regolith-based composite for - 3D printing via high-pressure extrusion system

《机械工程前沿（英文）》 2023年第18卷第2期 doi: 10.1007/s11465-022-0745-8

摘要： To fully utilize the in-situ resources on the moon to facilitate the establishment of a lunar habitat is significant to realize the long-term residence of mankind on the moon and the deep space exploration in the future. Thus, intensive research works have been conducted to develop types of 3D printing approach to adapt to the extreme environment and utilize the lunar regolith for in-situ construction. However, the in-situ 3D printing using raw lunar regolith consumes extremely high energy and time. In this work, we proposed a cost-effective melting extrusion system for lunar regolith-based composite printing, and engineering thermoplastic powders are employed as a bonding agent for lunar regolith composite. The high-performance nylon and lunar regolith are uniformly pre-mixed in powder form with different weight fractions. The high-pressure extrusion system is helpful to enhance the interface affinity of polymer binders with lunar regolith as well as maximize the loading ratio of in-situ resources of lunar regolith. Mechanical properties such as tensile strength, elastic modulus, and Poisson’s ratio of the printed specimens were evaluated systematically. Especially, the impact performance was emphasized to improve the resistance of the meteorite impact on the moon. The maximum tensile strength and impact toughness reach 36.2 MPa and 5.15 kJ/m², respectively. High-pressure melt extrusion for lunar regolith composite can increase the effective loading fraction up to 80 wt.% and relatively easily adapt to extreme conditions for in-situ manufacturing.

关键词： in-situ resource utilization melt extrusion molding lunar regolith-based composites mechanical properties additive manufacturing

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Effect of extrusion temperature on the physical properties of high-silicon aluminum alloy

YANG Fuliang, GAN Weiping, CHEN Zhaoke

《机械工程前沿（英文）》 2007年第2卷第1期页码 120-124 doi: 10.1007/s11465-007-0021-y

摘要： Light-weight high-silicon aluminum alloys are used for electronic packaging in the aviation and space-flight industry. Al-30Si and Al-40Si are fabricated with air-atomization and vacuum-canning hot-extrusion process. The density, thermal conductivity, hermeticity and thermal expansion coefficients of the material are measured, and the relationship between extrusion temperature and properties is obtained. Experimental results show that the density of high-silicon aluminum alloys prepared with this method is as high as 99.64% of the theory density, and increases with elevating extrusion temperature. At the same time, thermal conductivity varies between 104-140 W/(m " K); with the extrusion temperature, thermal expansion coefficient also increases but within 13?10 (at 100?C) and hermeticity of the material is high to 10 order of magnitude.

关键词： coefficient hermeticity temperature relationship air-atomization

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New technique of precision necking for long tubes with variable wall thickness

Yongqiang GUO, Chunguo XU, Jingtao HAN, Zhengyu WANG

《机械工程前沿（英文）》 2020年第15卷第4期页码 622-630 doi: 10.1007/s11465-019-0565-7

摘要： This study analyzed the deformation law of rear axles with variable wall thickness under bidirectional horizontal extrusion and found that necking was accompanied by upsetting deformation through theoretical calculation, numerical simulation, and experimental research. The sequence and occurrence of necking and upsetting deformations were obtained. A theory of deformation was proposed by controlling the distribution of temperature field. Effective processes to control the wall thickness of rear axle at different positions were also proposed. The ultimate limit deformation with a necking coefficient of 0.68 could be achieved using the temperature gradient coefficient. A new technology of two-step heating and two-step extrusion for a 13 t rear axle was developed, qualified test samples were obtained, and suggestions for further industrial application were put forward.

关键词： extrusion rear axle necking coefficient temperature gradient

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反应性挤出——利用化学和工程学方法解决海洋塑料污染问题

Philippe Dubois

《工程（英文）》 2022年第14卷第7期页码 15-18 doi: 10.1016/j.eng.2021.12.009

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Development of oxide dispersion strengthened ferritic steels with and without aluminum

Jae Hoon LEE

《能源前沿（英文）》 2012年第6卷第1期页码 29-34 doi: 10.1007/s11708-012-0178-x

摘要： Pure Fe, Cr, Al, Ti elemental powders and pre-alloyed Y O powder were processed by high energy mechanical milling. The compositions of the mixed powders are designed as Fe-18Cr-0.2Ti-0.35Y O and Fe-18Cr-5Al-0.2Ti-0.35Y O in weight percent. The as-milled powders were consolidated by hot extrusion at 1423 K. The dispersed oxide particles were identified to be titania+ yttria for Al-free oxide dispersion strengthened (ODS) steel and alumina+ yttria for Al-added ODS steel, respectively. The ultimate tensile strength of Al-free ODS steel was higher than that of Al-added ODS steel over the temperature range of 298–973 K, because of the difference in number density and size of thermally stable oxide particles dispersed in both steel matrices. The strength in the longitudinal direction was lower than that in the transverse direction, probably due to anisotropy of the microstructure with elongated grains in the hot-extrusion direction for the 18%Cr-ODS steels with and without 5%Al.

关键词： oxide dispersion strengthened (ODS) steel milling extrusion aluminum yttria

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Effect of temperature in the conversion of methanol to olefins (MTO) using an extruded SAPO-34 catalyst

Ignacio Jorge Castellanos-Beltran, Gnouyaro Palla Assima, Jean-Michel Lavoie

《化学科学与工程前沿（英文）》 2018年第12卷第2期页码 226-238 doi: 10.1007/s11705-018-1709-8

摘要： The methanol-to-olefin (MTO) reaction was investigated in a bench-scale, fixed-bed reactor using an extruded catalyst composed of a commercial SAPO-34 (65 weight percentage, wt-%) embedded in an amorphous SiO matrix (35 wt-%). The texture properties, acidity and crystal structure of the pure SAPO-34 and its extruded form (E-SAPO-34) were analyzed and results indicated that the extrusion step did not affect the properties of the catalyst. Subsequently, E-SAPO-34 was tested in a temperature range between 300 and 500 °C, using an aqueous methanol mixture (80 wt-% water content) fed at a weight hour space velocity (WHSV) of 1.21 h . At 300 °C, a low conversion was observed combined with catalyst deactivation, which was ascribed to oligomerization and condensation reactions. The coke analysis showed the presence of diamandoid hydrocarbons, which are known to be inactive molecules in the MTO process. At higher temperatures, a quasi-steady state was reached during a 6 h reaction where the optimal temperature was identified at 450 °C, which incidentally led to the lowest coke deposition combined with the highest H/C ratio. Above 450 °C, surges of ethylene and methane were associated to a combination of H-transfer and protolytic cracking reactions. Finally, the present work underscored the convenience of the extrusion technique for testing catalysts at simulated scale-up conditions.

关键词： MTO SAPO-34 temperature extrusion coke light alkanes

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碱处理对桉木纤维挤压结合机理的影响

彭万喜,林芝,李年存

《中国工程科学》 2014年第16卷第4期页码 64-68

摘要：

采用桉木纤维为原料，探讨碱处理对板材挤压结合机理的影响。结果表明：碱处理对木质素、半纤维素都有不同程度的降解作用；在热压制板过程中，经过降解作用的木材成分经适当的热压工艺能够发生聚合反应从而粘合成板；强碱（NaOH）对桉木纤维的影响大于弱碱溶液（Na2CO3），且处理时间为10 h 较适宜；碱处理过程产生的活性羟基，热压后可以缔合形成氢键，增加了纤维之间的结合力，有利于桉木纤维自身粘合成板。

关键词：桉木纤维碱处理傅立叶红外光谱扫描电子显微镜（SEM）

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轴向零泊松比结构心血管支架的设计、3D打印与表征 Article

王程锦, 张磊, 方永聪, 孙伟

《工程（英文）》 2021年第7卷第7期页码 979-990 doi: 10.1016/j.eng.2020.02.013

摘要：

药物洗脱支架固有的缺陷促进了生物可吸收心血管支架的研究与发展。近年来，增材制造技术（也称3D打印技术）在医疗器械领域得到了广泛的应用。本文提出了一种新型的微螺杆挤出式3D打印系统，并利用该系统制备了一种具有零泊松比（ZPR）结构的支架。首先进行了初步的单丝挤出试验来研究合适的制造参数；随后，制备了具有不同几何结构的3D打印支架，并通过扫描电子显微镜（SEM）观察分析支架表面形貌；最后，对不同参数的3D打印支架进行了力学性能评价和初步的生物学评价。总之，基于微螺杆挤出式3D打印系统具有制备个性化支架的潜力。

关键词：增材制造 3D打印螺杆挤出心血管支架零泊松比