中应变率加载下云杉各向异性力学行为研究

发布时间：2018-01-21 01:55

本文关键词： 云杉冲击失效应变率空间屈服面各向异性　出处：《工程力学》2016年05期 　论文类型：期刊论文

【摘要】：采用高速加载INSTRON设备对云杉开展10~0s~(-1)~10~2s~(-1)中应变率压缩实验,研究了材料沿顺纹、横纹径向、弦向、以及径(弦)切面内与顺纹呈15°、30°、45°、60°和75°夹角方向的力学性能。实验表明随着加载方向由顺纹向横纹径(弦)向变化,材料屈服强度逐渐减小,应力-应变曲线塑性流动段由"塑性软化"向"塑性硬化"转变;试件沿不同方向压缩屈服强度表现出较强应变率敏感性。冲击压缩下云杉宏观破坏模式与加载方向相关,沿顺纹方向加载时,试件中部向外膨胀,产生褶皱、纤维屈曲折断;当载荷方向与顺纹夹角逐渐增大时,材料失效模式体现为木材纤维分层滑移、撕裂。采用简化Hill强度理论对中低应变率下云杉空间屈服行为进行了理论描述,不同应变率下云杉空间屈服面为椭圆柱曲面,屈服曲面半径长度随应变率提高而增加。实验与理论分析表明,云杉沿空间不同方向具有各向异性力学特性,屈服强度受应变率和加载方向影响较大,而破坏模式则主要依赖于载荷方向。
[Abstract]:Strain rate compression experiments were carried out on Picea spruce by using a high-speed loading INSTRON equipment. The strain rate compression experiments were carried out on the spruce along the longitudinal, transverse, radial and chord directions. The mechanical properties of the diameters (chords) in the tangent plane are at an angle of 15 掳/ 30 掳/ 45 掳(60 掳) and 75 掳(n = 75). The experimental results show that the diameters (chords) vary with the direction of loading from the direction of the parallel striation to the direction of the transverse striation (chord). The yield strength of the material decreases gradually, and the plastic flow section of the stress-strain curve changes from "plastic softening" to "plastic hardening". The compressive yield strength of the specimens along different directions showed a strong strain rate sensitivity. The macroscopic failure mode of spruce under impact compression was related to the loading direction. When loaded along the direction of the grain, the central part of the specimen expanded outward, resulting in folds. Fiber buckling fracture; When the loading direction and the angle along the grain gradually increase, the failure mode of the material is reflected in the laminated slip of wood fiber. Tear. The spatial yield behavior of spruce under low and low strain rate is described theoretically by simplified Hill strength theory. The spatial yield surface of spruce is elliptic cylindrical surface under different strain rates. The experimental and theoretical analysis shows that spruce has anisotropic mechanical properties along different directions of space, and the yield strength is greatly affected by strain rate and loading direction. The failure mode mainly depends on the direction of load.
【作者单位】：中国工程物理研究院总体工程研究所;
【基金】：国家自然科学基金项目(11302211,11390361,11472257) 中国工程物理研究院学科909项目
【分类号】：O344.3
【正文快照】： 云杉作为比强度(强度与密度之比)较高的木材种类,其纤维长、纹理直、质地软,具有良好的韧性恢复弹性,能够承受突加的荷载,压缩平台值可保持到60%变形,且干燥后尺寸稳定,不易翘曲或扭曲,已被广泛应用于欧美国家抗事故包装箱缓冲结构设计[1 3]。目前针对云杉宏细观力学性能和胞

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