This paper proposes a novel in-vacuo adaptive beam element for vibration control, which, in this study, is employed as an adaptive tuneable vibration absorber. The element is formed by a composite beam with a core of structured fabrics wrapped in a deflated plastic bag skin. The fabrics consist of 3D-printed chain mails of hollowed truss-like particles. A base post is connected at the middle section of the composite beam, such that its flexural vibration is controlled by a flapping fundamental natural mode whose natural frequency can be varied by changing the vacuum level in the bag. The dynamics of this arrangement replicates that of a suspended mass-spring-damper system and, thus, can be suitably used as a tuneable vibration absorber. The study considers in-vacuo composite beams with one or two overlapping chain mails made with cubic, spherical-octahedral, octahedral hollowed truss-like particles. To start with, the dynamic response of these structures is analysed with respect to dynamic stiffness frequency response functions measured with a six-point bending setup. The dynamic response of the centrally pinned in-vacuo adaptive beam element is then investigated considering the vibration transmissibility and base impedance frequency response functions. Finally, the tuning features and vibration control effects of the adaptive beam element are assessed by fitting it at the free termination of a clamped beam in order to control the resonant response of a target flexural mode. Overall, the experimental results have shown that the fundamental natural frequency of the proposed in-vacuo adaptive beam element can be swiftly lifted or lowered by modulating the vacuum level in the bag encasing the structured fabrics. Indicatively, the working centre frequency of the resulting absorber depends on the number of strips piled in the vacuum bag, which defines the thickness, and thus the reference bending stiffness, of the in-vacuo composite beam. Also, the working frequency bandwidth of the in-vacuo adaptive beam element mostly depends on the geometry, the material and the finishing of the chain mail particles. In fact, these properties infer on the number, the type (between convex or non-convex surfaces), the area and the friction coefficient of the contacts that develop between neighbouring particles of the mails and thus determine the range of bending stiffness that can be achieved by a given vacuum range in the deflated bag.

中文翻译：

---

用于振动控制的真空自适应梁元件


本文提出了一种用于振动控制的新型真空内自适应梁元件，在本研究中，该元件被用作自适应可调减振器。该元件由复合梁形成，其核心是结构化织物，包裹在放气的塑料袋皮中。这些织物由 3D 打印的空心桁架状颗粒锁子甲组成。在复合梁的中间部分连接了一个基柱，因此其弯曲振动由拍打的基本固有模式控制，其固有频率可以通过改变袋子中的真空度来改变。这种布置的动力学复制了悬挂质量弹簧阻尼器系统的动力学，因此可以适当地用作可调节的减振器。该研究考虑了由立方体、球形八面体、八面体空心桁架状颗粒制成的具有一个或两个重叠锁子甲的真空内复合梁。首先，根据六点弯曲装置测量的动态刚度频率响应函数来分析这些结构的动态响应。然后，考虑了振动传递率和基极阻抗频率响应函数，研究了中心固定真空内自适应梁单元的动态响应。最后，通过将自适应梁元件安装在夹紧梁的自由端接处来评估自适应梁元件的调谐特性和振动控制效果，以控制目标弯曲模式的谐振响应。总体而言，实验结果表明，通过调制包裹结构化织物的袋子中的真空度，可以迅速升高或降低所提出的真空内自适应梁元件的基本固有频率。 指示性地，所得减振器的工作中心频率取决于真空袋中堆积的条带数量，该数量决定了真空内复合梁的厚度，从而决定了参考弯曲刚度。此外，真空内自适应梁元件的工作频率带宽主要取决于锁子甲粒子的几何形状、材料和表面处理。事实上，这些特性根据邮件的相邻颗粒之间形成的触点的数量、类型（凸面或非凸面之间）、面积和摩擦系数进行推断，从而决定了在放气袋中给定真空范围可以达到的弯曲刚度范围。