考虑脱空缺陷影响的钢管混凝土压弯剪力学性能分析与实用设计方法

完成了12根带脱空缺陷的钢管混凝土试件在压弯剪复合作用下的滞回试验,考察了脱空缺陷对试件破坏模态、滞回曲线、极限承载力、耗能和延性的影响。建立了带脱空缺陷的钢管混凝土压弯剪试件的有限元分析模型,采用试验数据验证了有限元模型的可靠性。利用有限元模型分析了带脱空缺陷的钢管混凝土试件在压弯剪复杂受力作用下的工作机理,揭示了缺陷对钢管与混凝土之间相互作用的影响规律,并系统分析了含钢率、钢材屈服强度、剪跨比、轴压比和混凝土强度等参数对带缺陷试件抗剪承载力的影响规律。在参数分析的基础上,提出了用于区分试件剪切破坏和弯曲破坏的界限剪跨比,回归了考虑脱空缺陷影响的钢管混凝土压弯剪承载力实用计算公式,可为相关规范的制定或修订提供依据。

论人生的三个维度

人生分为三个层次,即自然之人生、社会之人生和历史之人生。自然之人生指人维持自然生命的整个过程;社会之人生指人在各种社会活动中形成的天人、人与人、个人与社会以及人与自然的关系;历史之人生是指人的历史责任与历史评价。

Drilling Force and Temperature of Bone under Dry and Physiological Drilling Conditions

Many researches on drilling force and temperature have been done with the aim to reduce the labour intensiveness of surgery, avoid unnecessary damage and improve drilling quality. However, there has not been a systematic study of mid- and high-speed drilling under dry and physiological conditions（injection of saline）. Furthermore, there is no consensus on optimal drilling parameters. To study these parameters under dry and physiological drilling conditions, pig humerus bones are drilled with medical twist drills operated using a wide range of drilling speeds and feed rates. Drilling force and temperature are measured using a YDZ-II01W dynamometer and a NEC TVS-500EX thermal infrared imager, respectively, to evaluate internal bone damage. To evaluate drilling quality, bone debris and hole morphology are observed by SEM（scanning electron microscopy）. Changes in drilling force and temperature give similar results during drilling such that the value of each parameter peaks just before the drill penetrates through the osteon of the compact bone into the trabeculae of the spongy bone. Drilling temperatures under physiological conditions are much lower than those observed under dry conditions, while a larger drilling force occurs under physiological conditions than dry conditions. Drilling speed and feed rate have a significant influence on drilling force, temperature, bone debris and hole morphology. The investigation of the effect of drilling force and temperature on internal bone damage reveals that a drilling speed of 4500 r/min and a feed rate of 50 mm/min are recommended for bone drilling under physiological conditions. Drilling quality peaks under these optimal parameter conditions. This paper proposes the optimal drilling parameters under mid- and high-speed surgical drilling, considering internal bone damage and drilling quality, which can be looked as a reference for surgeons performing orthopedic operations.

半厚度Z-pin植入对层合板弯曲性能的影响研究

通过三点弯曲试验研究了Z-pin在半厚度植入条件下其材质、直径和加捻状态对Z-pin增强复合材料层合板弯曲性能的影响。结果表明,采用Z-pin半厚度植入工艺相比于未增强对照组试件,增强组试件的弯曲强度、弯曲模量及弯曲应变能都有所提升。Z-pin材质、直径和加捻状态对试件弯曲强度、模量和弯曲应变能的影响甚微,究其原因为增强组试件界面X、Y处潜在的分层缺陷扩展严重,分层损伤主导了弯曲过程中试件的破坏。但Z-pin直径对层合板的失效模式有着重要影响,表现为小直径Z-pin增强试件分层裂纹扩展较为严重,但萌生裂纹数量较少,试件损伤多表现为受单一裂纹控制;大直径Z-pin增强试件裂纹扩展相对一般,但萌生裂纹数量较多,试件多表现为多重裂纹的损伤。