今日更新:International Journal of Solids and Structures 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇
Cracks in tensile-contracting and tensile-dilating poroelastic materials
Garyfallogiannis Konstantinos, Purohit Prashant K., Bassani John L.
doi:10.1016/j.ijsolstr.2023.112563
拉伸收缩和拉伸膨胀孔弹性材料中的裂纹
Fibrous gels such as cartilage, blood clots, and carbon-nanotube-based sponges with absorbed oils suffer a reduction in volume by the expulsion of liquid under uniaxial tension, and this directly affects crack-tip fields and energy release rates. A continuum model is formulated for isotropic fibrous gels that exhibit a range of behaviors from volume increasing to volume decreasing in uniaxial tension by changing the ratio of two material parameters. The motion of liquid in the pores of such gels is modeled using poroelasticity. The direction of liquid fluxes around cracks is shown to depend on whether the gel locally increases or decreases in volume. The energy release rate for cracks is computed using a surface-independent integral and it is shown to have two contributions - one from the stresses in the solid network, and another from the flow of liquid. The contribution to the integral from liquid permeation tends to be negative when the gel exhibits volume decrease, which effectively is a crack shielding mechanism.
纤维凝胶,如软骨、血凝块和碳纳米管海绵,在单轴拉伸下,由于液体的排出,其体积会减少,这直接影响到裂纹尖端的场和能量释放率。对于各向同性纤维凝胶,通过改变两种材料参数的比例,在单轴拉伸下表现出从体积增加到体积减少的一系列行为,建立了连续介质模型。液体在这种凝胶的孔隙中的运动是用孔隙弹性来模拟的。裂缝周围液体通量的方向取决于凝胶的局部体积是增加还是减少。裂缝的能量释放率是用与表面无关的积分来计算的,它有两个贡献——一个来自固体网络中的应力,另一个来自液体的流动。当凝胶体积减小时,液体渗透对积分的贡献趋于负,这是一种有效的裂缝屏蔽机制。
Strain delocalization in a gradient-structured high entropy alloy under uniaxial tensile loading
Fu Wujing, Sun Yonggang, Fan Guohua, Huang Yongjiang, Ning Zhiliang, Li Xuewen, Wang Keyan, Sun Jianfei, Jiang Shan
doi:10.1016/j.ijplas.2023.103808
梯度结构高熵合金在单轴拉伸载荷下的应变离域
Suppressing strain localization in hard layers was crucial for making gradient alloys ductile. Here, a typical structure in CrFeCoNiMn0.75Cu0.25 high entropy alloy (HEA), which combines gradient distributions along the depth for grain width and twin density, was fabricated using the laser shock peening treatment. In situ digital image correlation methods elucidated the mechanisms of the excellent mechanical properties in HEAs treated by LSP for 4 cycles from the perspective of local strain. Dense shear bands were nucleated at the low-strain stage, and remained stable evolution during the entire plastic deformation, thus, leading to an excellent tensile ductility (∼40%). The plastic deformation incompatibility results in two-dimensional stress states and lateral strain gradient near the plastic-elastic interfaces, which stimulates the interaction and accumulation of micro-defects, thus, improving the strain hardening capacity of alloys. These observations will reveal the mechanistic origin of the gradient structured alloys with superior strength-ductility from a new perspective, which also provide a guidance for optimized mechanical performances of HEAs.
抑制硬层应变局部化是提高梯度合金延展性的关键。采用激光冲击强化处理,制备了CrFeCoNiMn0.75Cu0.25高熵合金(HEA)中晶粒宽度和孪晶密度沿深度梯度分布的典型组织。原位数字图像相关方法从局部应变的角度阐明了4次LSP处理后HEAs优异力学性能的机理。密集的剪切带在低应变阶段成核,并在整个塑性变形过程中保持稳定演变,从而导致优异的拉伸延展性(约40%)。塑性变形不相容导致在弹塑性界面附近产生二维应力状态和侧向应变梯度,刺 激微缺陷的相互作用和积累,从而提高合金的应变硬化能力。这些观察结果将从新的角度揭示具有优异强度-延展性的梯度结构合金的机理根源,并为优化HEAs的力学性能提供指导。
Nonlinear Vibrations of FG-GRLCC Rectangular Variable Cross-Section Plate Subjected to Transverse and Parametric Excitations in Thermal Environment
Jiang Y., Zhang W., Zhang Y.F.
doi:10.1016/j.tws.2023.111354
热环境下FG-GRLCC变截面矩形板在横向和参数激励下的非线性振动
This paper investigates the linear and nonlinear vibration responses for the functionally graded graphene-reinforced laminated composite cantilever (FG-GRLCC) rectangular variable cross-section plate subjected to the transverse and parametric excitations under the thermal environment. Halpin-Tsai model is used to calculate the material properties of the graphene-reinforced structure. Using the classical laminated plate theory, von Karman large deformation theory, Hamilton principle and Galerkin method, the dynamic model is given for the FG-GRLCC rectangular variable cross-section plate. The natural frequencies and mode shapes are analyzed for the FG-GRLCC rectangular variable cross-section plate under the thermal environment through using Rayleigh-Ritz method. The averaged equations of the system are obtained based on the multiple scale perturbation (MSP) under the primary, 1/2 sub-harmonic and 1:1 internal resonances. The comparisons between the theoretical algorithm and finite element method are proposed to illustrate the accuracy of the present model. The results about the frequency veering phenomenon and mode shape interaction have been illustrated. The amplitude-frequency response curves and force-amplitude response curves are depicted for the FG-GRLCC rectangular variable cross-section plate. The nonlinear and chaotic vibrations for the FG-GRLCC rectangular variable cross-section plate is studied by using the bifurcation diagrams and max Lyapunov exponents.
研究了热环境下梯度石墨烯增强层合复合材料悬臂梁(FG-GRLCC)变截面矩形板在横向和参数激励下的线性和非线性振动响应。采用Halpin-Tsai模型计算石墨烯增强结构的材料性能。利用经典叠合板理论、von Karman大变形理论、Hamilton原理和Galerkin方法,建立了FG-GRLCC变截面矩形板的动力学模型。采用瑞利-里兹法分析了FG-GRLCC变截面矩形板在热环境下的固有频率和振型。在主谐振、1/2次谐振和1:1内谐振的情况下,得到了系统的平均方程。将理论算法与有限元法进行了比较,说明了模型的准确性。给出了频率转向现象和模态振型相互作用的研究结果。给出了FG-GRLCC矩形变截面板的幅频响应曲线和力幅响应曲线。利用分岔图和最大李雅普诺夫指数研究了FG-GRLCC矩形变截面板的非线性和混沌振动。