Advances of physics-based precision modeling and simulation for manufacturing processes     

Gang Wang  Yi-Ming Rong 《上海大学学报(英文版)》2013,(1):75-81

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A nano to macroscale study on structure-mechanics relationships of archaeological oak     

Thomas K. Bader  Karin de Borst  Karin Fackler  Thomas Ters  Susan Braovac 《Journal of Cultural Heritage》2013,14(5):377-388

Mechanical properties of wood at different length scales of its hierarchical structure are governed by structural and compositional properties on smaller length scales. This opens up the possibility to use microstructural data for estimating mechanical properties, which are difficult to assess by conventional, destructive testing but are nevertheless of high relevance for conservation practice. Herein, we investigate such microstructure-mechanics relationships for a particular example, namely the load bearing archaeological oak of the Oseberg Viking ship, displayed at the Viking Ship Museum in Oslo, Norway. In order to identify the effects of degradation on the mechanical behavior and their relations to the microstructure, recent oak specimens of different geographical origin (Norway and Austria) are investigated as well. Wood exhibits a cellular structure. Its cell walls are composed of an amorphous polymer matrix consisting of lignin and hemicelluloses and embedded, stiff cellulose fibers. At the cell level, experimental studies comprised microscopic investigations of the cellular structure, chemical analyses of the composition of the cell walls, as well as nanoindentation tests on single cell walls. The same samples were also analyzed on the macroscopic level, where additionally mass density and annual ring data were measured together with ultrasonic stiffnesses. The chemical data clearly indicate deterioration in the archaeological oak, affecting mainly hemicelluloses and amorphous cellulose. At the cell wall scale, however, this does not necessarily lead to a weaker material behavior. The nanoindentation modulus, as a measure of the cell wall stiffness, was found to even increase. This is counterintuitive to our understanding of the effects of chemical degradation. It might be due to possible modification of lignin in the Oseberg oak, and thus have a stronger effect on the indentation modulus than the concurrent weakening of the interfaces between the load-carrying cellulose fibers and the connecting cell wall matrix when analyzing wood at the microscopic level. A similar effect is also observed for the transversal stiffness of macroscopic samples, which increases. In tension-dominated loading modes, however, the degradation of the interfaces is the dominant effect, resulting for example in a considerable reduction of the macroscopic stiffness in longitudinal direction. This underlines the utmost relevance of the loading condition on the remaining load-carrying capacity of degraded wood. On the macroscale, effects of the geographical origin (i.e. growth conditions) on ring characteristics of the oak tissues override the effects of degradation on the mechanical behavior. They have to be carefully extracted in order to come up with conclusions on the effect of degradation from macroscopic test results. The identified microstructure-mechanics relationships provide the basis for–in further research steps–building mathematical models describing the relations between microstructural characteristics and macroscopic mechanical properties and, thereon, for structural analyses of historical wooden objects.  相似文献   

图像捕获设备测量与分析数字印刷质量的可行性   总被引：4，自引：0，他引：4  

姚海根 《出版与印刷》2008,(3):2-5

本文讨论以图像捕获设备组建数字印刷质量检测与分析系统的可能性。工业界的成功应用经验表明,只要经过了正确的密度标定,则这种系统完全适用于数字印刷质量检验与评价。  相似文献   

试论期刊的特征与作用——兼评当前期刊出版的某些不良现象     

常勤毅 《宁波教育学院学报》2002,4(4):72-75

期刊是一种有固定的出版形式和统一固定名称的连续的定期出版物。而当前有的期刊 ,忽略或无视期刊的独特属性与功能。无论是何种类型的期刊都应该坚持期刊的本质特征与作用 ,自觉抵制、防止和消除不良现象的发生。  相似文献   

M-ZSM-5分子筛的结构及催化性能研究进展   总被引：3，自引：0，他引：3  

薛英  吴宇  万家义 《绵阳师范学院学报》2005,24(5):1-4

探究了ZSM-5分子筛的晶体结构、孔结构及酸性质：对通过离子变换对其表面进行优化以提高催化活性方面的研究工作进行了阐述；对Cu-ZSM-5分子筛上NO直接催化分解反应提出了：4CuO=2Cu20＋02，2Cu2O＋4NO=4CuO＋2N2＋O2的反应机理。  相似文献   

6061-T5铝合金搅拌摩擦焊接头组织和力学性能     

吕煜  郭国林  徐子骞  王杰  王乐  吴柯寒  高安慧 《常熟理工学院学报》2020,(2):66-69

采用搅拌摩擦焊技术对6061-T5铝合金进行焊接,分析了焊接速度对接头成形、微观结构及力学性能的影响.结果表明:随着焊接速度的增加,沉淀相固溶度下降,晶粒细化;焊接速度过大时,热输入不足,呈现原始态组织.当转速为800 r/min,焊接速度为60 mm/min时,接头成形良好,抗拉强度达到最大值.采用合适的搅拌摩擦焊工艺参数,6061-T5铝合金能实现可靠的连接.  相似文献   

细长轴车削动特性的研究   总被引：9，自引：0，他引：9  

黄跃华  张景勘  李德滋 《科技通报》2001,17(4):41-45,49

对细长轴车削的动特性进行了分析、试验和研究，为保证细长轴车削的稳定性以提高加工质量，提出了转速与进量的合理计算公式，计算与实验结果基本一致。  相似文献   

核物质环境中的非拓扑孤粒子     

张建玮  夏克定  邱锡钓 《中国科学院研究生院学报》1991,(2)

本文利用非拓扑粒子模型计算了核物质环境中的核子(孤粒子)的尺度增量等物理量。这些结果可被认为是由核物质中真空性质的变化引起的。相对论性核平均场论可以用来研究核介质中与夸克相互作用的标量场。计算结果能够合理地符合与质量数相关的轻子与核的深度非弹散射的测量。  相似文献   

硅土充填高聚物的性能研究   总被引：1，自引：0，他引：1  

潘建强  李长江 《科技通报》1996,12(3):139-142

探讨了硅土的矿物学特性及其对充填高聚合物的影响，研究表明，天然超细粒度（０．０１－０．００１ｍｍ）复合矿物的及独特的粒－片叠置结构是导致硅土在高聚合物中具有良好增强性能的主要原因。  相似文献   

热处理时间对IT0薄膜显微组织及光电性能的影响     

王敏  蒙继龙 《广东技术师范学院学报》2007,(7)

采用溶胶一凝胶法在玻璃基体上制备了ITO薄膜,研究了后续热处理时间对ITO薄膜显微组织及光电性能的影响。研究结果表明:随着热处理时间的延长,ITO薄膜的微观形貌发生了很大的变化,出现了小丘生长并伴随着回复与再结晶过程,严重影响了ITO薄膜的光电性能。  相似文献