今日更新:International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇
Micro-mechanisms of anisotropic deformation in the presence of notch in commercially pure titanium: an in-situ study with CPFEM simulations
Vivek Kumar Sahu, Pritam Chakraborty, Manasij Yadava, Nilesh P. Gurao
doi:10.1016/j.ijplas.2024.103985
工业纯钛中存在缺口时各向异性变形的微观机制:用CPFEM模拟的原位研究
This study investigates the impact of notch severity and initial texture on the micro-mechanisms during low strain deformation in commercially pure titanium, exploiting in-situ electron back scatter diffraction (EBSD) experiments and crystal plasticity finite element model (CPFEM). In-situ tests were performed at different strain steps of un-notched and notched samples of transverse direction (TD) and rolling direction (RD) orientations. CPFEM, based on initial EBSD microstructures, predicted profuse prismatic slip traces and early activation of prismatic slip in notched sample, with RD orientation exhibiting higher activity. Further, CPFEM results revealed early activation of high CRSS slip systems as well as evidence of early twin activity at notch tip due to severely localized plastic deformation and steep strain gradient, as observed by GND maps causing higher stress at grain boundaries. At the notch tip, digital images correlation (DIC) at microscale indicated strain localization at 45° nd 90° to the tensile axis for TD and RD orientations, respectively. Furthermore, 2.5D and 3D CPFEM confirmed distinct strain patterns at notch tip: TD orientation exhibited combined basal and prismatic slip influences, while RD orientation displayed dominant prismatic slip systems at localized strain. The model also successfully predicted anisotropic surface roughness, contributing to early necking in RD orientation.
本研究利用原位电子背散射衍射(EBSD)实验和晶体塑性有限元模型(CPFEM),研究了缺口严重程度和初始纹理对商业纯钛低应变变形过程中的微观机制的影响。对横向(TD)和滚动方向(RD)的未缺口和缺口样品进行了不同应变阶跃的原位测试。CPFEM 根据最初的 EBSD 显微结构预测了缺口样品中大量的棱柱滑移痕迹和棱柱滑移的早期激活,其中 RD 方向表现出更高的活动性。此外,CPFEM 结果还显示了高 CRSS 滑移系统的早期激活,以及缺口顶端早期孪晶活动的证据,这是由于严重的局部塑性变形和陡峭的应变梯度造成的,正如 GND 图所观察到的那样,这些应变梯度在晶界处造成了较高的应力。在缺口顶端,微尺度数字图像相关(DIC)显示,TD 和 RD 方向的应变定位分别与拉伸轴成 45° 和 90°。此外,2.5D 和 3D CPFEM 证实了缺口顶端不同的应变模式:TD 方向表现出基底和棱柱滑移的综合影响,而 RD 方向则在局部应变时表现出主要的棱柱滑移系统。该模型还成功预测了各向异性的表面粗糙度,从而导致 RD 方向的早期颈缩。
Research on hexagonal concrete-filled steel tubular transition pieces for wind turbine hybrid towers under axial compression
Kai-Yuan Jin, Xu-Hong Zhou, Wei Ren, Yu-Hang Wang, Wei Luo
doi:10.1016/j.tws.2024.111956
轴压作用下风电混合塔六角钢管混凝土过渡件研究
With the escalating height of wind turbine structures, wind turbine steel-concrete hybrid towers have gradually become a new type of structure to replace pure steel towers. As a component connecting the upper steel tower with the lower concrete tower, the transition piece assumes an indispensable role in the overall structure of the hybrid tower. The traditional reinforced concrete-type transition piece has necessitated enhancements owing to the complicated construction and concrete cracking problems. A hexagonal concrete-filled double skin steel tubular (CFDST) transition piece is proposed to fit the hexagonal steel-concrete hybrid tower. Studies that investigate the hexagonal CFDST structures are currently few. Based on this, three hexagonal CFDST stub columns were tested, with the variables in stiffened measures. The experimental portion included a thorough investigation of local buckling behaviors and failure modes in addition to the analysis of typical mechanical indexes. Further, the validated finite element (FE) model was then utilized for mechanism analysis about the contact stress between different interfaces, the stress distributions, and so on. Besides, a parametric study was done to identify the sensitive parameters affecting this kind of structure's peak loads. Ultimately, the peak load prediction formulas found in published studies and specifications were modified by incorporating the findings from this investigation.
随着风力机结构高度的不断提升,风力机钢-混凝土混合塔逐渐成为取代纯钢塔的一种新型结构。过渡件作为连接上部钢塔和下部混凝土塔的构件,在混合塔的整体结构中起着不可缺少的作用。传统的钢筋混凝土型过渡件由于施工复杂和混凝土开裂问题,需要对其进行改进。为适应六角形钢-混凝土混合塔结构,提出了一种六角形双皮钢管混凝土过渡件。目前对六方CFDST结构的研究很少。在此基础上,对3根CFDST短柱进行了加筋试验。除典型力学指标分析外,实验部分还包括对局部屈曲行为和破坏模式的深入研究。在此基础上,利用验证的有限元模型对不同界面间的接触应力、应力分布等进行了机理分析。此外,对影响该类结构峰值荷载的敏感参数进行了参数化研究。最终,在已发表的研究和规范中发现的峰值负荷预测公式通过纳入本调查的结果进行了修改。