Elsevier

Mechanics of Materials 材料力学

Volume 165, February 2022, 104205
第 165 卷,2022 年 2 月,104205
Mechanics of Materials

Crushing behavior on the cylindrical tube based on lotus leaf vein branched structure
基于荷叶脉分枝结构的圆柱形管上的破碎行为

https://doi.org/10.1016/j.mechmat.2021.104205Get rights and content 获取权利和内容

Highlights 突出

  • A new leaf vein branched circular tubes (LVBCT) was established.
    建立了一种新的叶脉分支圆管 (LVBCT)。

  • The mechanical properties of LVBCTs are revealed by analyzing the deformation mechanism and crashworthiness indicators.
    通过分析变形机制和耐撞性指标来揭示 LVBCT 的机械性能。

  • The energy absorption capacity of the LVBCTs was improved greatly.
    LVBCTs 的能量吸收能力大大提高。

  • The SEAm of LVBCT could be further increased by 11.3% through the thickness matching.
    SEAm 通过厚度匹配,LVBCT 可进一步提高 11.3%。

Abstract 抽象

By imitating the structural characteristics of the lotus leaf, a new excellent energy absorption structure named as the leaf vein branched circular tube (LVBCT) is proposed by referring to lotus leaf vein branched structure. The evolution of its cross-section may be controlled by the number of main veins distributed along the circumference (N) and the ratio of radius of inner circle Rinner to radius of outer circle Router (γ). To study the crushing behavior of LVBCTs under axial dynamic crushing, the finite element simulation model established by LS-DYNA is first verified by comparing with the experimental results. Following that, a systematic parametric study on geometric parameters N and γ is carried out with three different wall thicknesses. The mechanical properties of LVBCTs are revealed by analyzing the deformation mechanism and crashworthiness indicators (specific energy absorption per unit mass SEAm and peak crushing force PCF). The numerical results show that the LVBCTs may absorb more impact energy and its energy absorption characteristics are closely related to geometric parameters N, γ and wall thickness t. The LVBCTs with N = 6 and γ of0.50.7 have better crashworthiness. Furthermore, the numerical results show that the thickness matching between main vein and branch vein has influence on the energy absorption ability. The SEAm of LVBCT is improved by 11.3% when the thickness matching between the main vein and the branch vein is 0.92 mm. The results of this study will be helpful to design novel thin-walled structure with better energy absorption ability.
通过模仿荷叶的结构特征,参照荷叶脉分枝结构,提出了一种新的优良能量吸收结构,称为叶脉分枝圆管(LVBCT)。其横截面的演变可能由沿圆周分布的主脉数量 (N) 和内圆半径与外圆 Rinner Router 半径的比值 ( γ ) 控制。为研究轴向动碎作用下LVBCTs的破碎行为, 首先通过与实验结果对比,验证了LS-DYNA建立的有限元仿真模型。之后,几何参数 N 和 γ 进行了系统的参数化研究,并对三种不同的壁厚进行了研究。通过分析变形机制和耐撞性指标(每单位质量 SEAm 的比能量吸收和峰值破碎力 PCF)来揭示 LVBCT 的机械性能。数值结果表明,LVBCTs可以吸收更多的冲击能量,其能量吸收特性与几何参数Nγ 壁厚t密切相关。N = 6 的 LVBCT γ of0.50.7 具有更好的耐撞性。此外,数值结果表明,主脉和支脉之间的厚度匹配对能量吸收能力有影响。 SEAm 当主静脉和分支静脉之间的厚度匹配为 11.3 mm 时,LVBCT 提高了 0.92%。 本研究结果将有助于设计具有更好能量吸收能力的新型薄壁结构。

Introduction 介绍

Thin-walled structures are of great importance to the fields of aviation, vehicles and industry due to its extraordinary mechanical behavior. In the past decades, the static and dynamic mechanical properties of conventional single-walled structures have been extensively studied, including circular (Karagiozova and Jones, 2001), square (Jensen et al., 2004; Zhang et al., 2009) and triangular tubes (Krolak et al., 2007; Wu and JinZhou, 2013). The results show that the mechanical properties of thin-walled tubes are closely related to their cross-section characteristics.
薄壁结构由于其非凡的机械性能,对航空、车辆和工业领域非常重要。在过去的几十年里,传统单壁结构的静态和动态机械性能得到了广泛的研究,包括圆形(Karagiozova 和 Jones,2001 年)、方形(Jensen 等人,2004 年;Zhang等人,2009 年)和三角管(Krolak等人,2007 年;Wu 和 JinZhou,2013 年)。结果表明,薄壁管的力学性能与其截面特性密切相关。

In recent years, thin-walled tubes have been widely used in many fields, and scholars have carried out extensive research on their mechanical properties. Yamashita et al. (2003) pointed out that the increase of the number of corner elements can enhance the energy absorption capacity of tubes. Zhang et al. (Zhang and Zhang, 2013) and Wu et al. (2016) further confirmed that multi-cell tubes have superior energy absorption ability through experimental and simulation research. Nia (Nia and Parsapour, 2014) found that the multi-cell thin-walled tubes with hexagonal and octagonal sections have the best energy absorption characteristics. After studying the dynamic response of multi-cell tubes under impact loads in different directions, Fang et al. (2015) carried out optimization design in crashworthiness. Tran et al., 2014a, 2014b, 2015 theoretically deduced the axial impact force of several multi-cell tubes based on the analysis of the deformation mechanism. Xiang et al. (2016) introduced the key performance indicators to analyze and evaluate the mechanical behavior of polygonal tubes, multi-cell tubes and honeycombs. Mahmoodi et al. (2016) studied the energy-absorption properties of tapered multi-cell tubes by means of theory and simulation. Tabacu et al. (Tabacu, 2015) numerically simulated and analyzed the mechanical behavior of circular tubes with rectangular multi-cell insert.
近年来,薄壁管已广泛应用于许多领域,学者们对其机械性能进行了广泛的研究。Yamashita et al. (2003) 指出,角元件数量的增加可以提高管材的能量吸收能力。Zhang et al. (Zhang and Zhang, 2013) 和 Wu et al. (2016) 通过实验和模拟研究进一步证实了多细胞管具有优越的能量吸收能力。Nia (Nia and Parsapour, 2014) 发现具有六边形和八边形截面的多孔薄壁管具有最佳的能量吸收特性。在研究了多单元管在不同方向冲击载荷下的动态响应后,Fang et al. (2015) 进行了耐撞性的优化设计。Tran et al., 2014a, 2014b, 2015 基于变形机理的分析,理论推导出了几种多胞管的轴向冲击力。Xiang et al. (2016) 介绍了分析和评估多边形管、多单元管和蜂窝的机械行为的关键性能指标。Mahmoodi 等人(2016 年)通过理论和模拟研究了锥形多细胞管的能量吸收特性。Tabacu 等人 (Tabacu, 2015) 对带有矩形多孔嵌件的圆管的机械行为进行了数值模拟和分析。

In recent years, many researchers further sought inspiration from nature and proposed thin-walled tubes with self-similar hierarchical characteristics to improve its mechanical performances (Gibson et al., 2010; Zhang et al., 2015). Sun et al., 2016a, 2016b analyzed the energy absorbing ability of self-similar triangular lattice tubes and found that the incorporation of hierarchy greatly improved its energy absorption capacity. Luo et al. (Luo and Fan, 2018; Fan et al., 2018) investigated the dynamic behavior of rectangular self-similar multi-cell structures and theoretically calculated its mean crushing force. He et al. (2021) proposed Sierpinski hierarchical triangular (SHT) tube and studied its mechanical properties.
近年来,许多研究人员进一步从大自然中寻求灵感,并提出了具有自相似分层特征的薄壁管,以改善其机械性能(Gibson et al., 2010;Zhang et al., 2015)。Sun et al., 2016a, 2016b 分析了自相似三角晶格管的能量吸收能力,发现层次结构的加入大大提高了其能量吸收能力。Luo 等人(Luo 和 Fan,2018 年;Fan et al., 2018)研究了矩形自相似多细胞结构的动力学行为,并从理论上计算了其平均破碎力。他等人(2021 年)提出了 Sierpinski 分层三角形 (SHT) 管并研究了其机械性能。

Some experts also proposed to introduce mathematical functions or curves into the section design of thin-walled structures. Wu (Wu et al., 2017) studied the deformation mechanism of the Fourier-varying sectional tubes and carried out the optimization of crashworthiness. Liu et al. (LiuWenqian et al., 2015) introduced the sinusoidal patterns into the corrugated tubes and investigated its dynamic response under axial impact. Sun (Sun et al., 2017) parametrically modeled a wide range of criss-cross sections with spline curves and studied the influence of structural parameters on its mechanical properties. Deng et al. (2018) put forward a new type of lateral corrugated tube (LCTs) with a sinusoidal cross-section and the crashworthiness was studied systematically. Wang et al. (2018) focused on the Koch fractal structure and found that the 2nd order hybrid Koch structure had better energy absorption performance. Li et al. (2019) numerically analyzed the mechanical performance of a new corrugated square tube controlled by a cosine expression.

The inspiration from bionics has opened up a new idea for the design of thin-walled structure to improve their mechanical properties (San HaLu, 2020). Chen et al. (Chen et al., 2018; Song et al., 2018; Liu et al., 2017; Fu et al., 2019) proposed some new thin-walled structures inspired by bamboo and found that the bionic-bamboo tubes exhibit superior crashworthiness characteristics. The crashworthiness of a group of bionic multi-cell tubes based on the microstructure of beetle forewings had also been widely studied (Hao and Du, 2018; Chen et al., 2012, 2014; Xiang and Du, 2017). Ding et al. (2018) designed new square multi-cell tubes with lateral variable thickness based on the stem of a plant and bones structure of animals. Mousanezhad et al. (2015) proposed the spider-web hierarchical structure which displayed high stiffness and toughness. Zhang et al. (2018) and He et al. (2020) further analyzed the effect of hierarchical structural parameters on the crashworthiness of this structure. It is widely known that the leaf vein veins not only carry nutrients, but also support the weight and external load of the whole blade in structure to ensure the overall stiffness and plane ductility of the blade. Therefore, the rationality and size of the vein distribution play a decisive role in the blade bearing capacity and maintaining the shape of the blade. However, up to now, there is still no relevant research introducing such structural features into thin-walled energy absorbing structures.

In order to further improve the energy absorption characteristics of thin-walled tube, a new excellent energy absorption structure named as the leaf vein branched circular tubes (LVBCT) is proposed. The crushing behavior of LVBCT subjected to axial impact load is studied systematically by numerical simulation method. Section 2 describes the configurations of the LVBCT. In Section 3, the computational models are established and further verified by comparing with the experimental results. Finally, systematic parametric study on the influences of geometric parameters (the number of main veins N, the structural parameter γ, which is defined as the ratio of radius of inner circle Rinner to radius of outer circle Routerγ and thickness of all the cell-walls t) on the crushing behavior of LVBCTs is carried out to enhance the understanding of the clear correlation of vein branching characteristics and energy absorption performance in Section 4.

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Section snippets

Design based on lotus leaf vein branched structure

In order to study the vein distribution, the leaf vein structure of lotus leaves is selected as the analysis object in Fig. 1. By imitating the structural characteristics of the lotus leaf, a novel circular thin-walled structure with leaf vein branched ribs is proposed and the crushing behavior of the leaf vein branched circular tube (LVBCT) is further analyzed in this study. Fig. 2 shows the geometrical characteristic and cross-section evolution of LVBCT. The geometry of the LVBCTs may be

Crashworthiness indicators

There are many different indicators available to evaluate the energy absorption capabilities of different structures (Yin et al., 2011). Several creditworthiness indicators can be obtained from the numerical simulation. EA is the total energy absorbed by the thin-walled structure during the effective compression process, which may be equal to the area under the impact force-compression distance curve at the impact end (Hu et al., 2019):EA=0δF(δ)dδwhere δ is the axial compression distance, F(δ)

Parametric analysis of crushing behavior

A systematic parametric study is carried out to study the influences of geometric parameters N, γ and t on the energy absorption of LVBCTs. The number of N is chosen as 4, 5, 6 and 7; γ varies with an increment of 0.05 from 0 to a certain range to avoid the overlapping of the branch veins; t is set to three levels ranging from 0.5, 1 and 1.5 mm. These levels are orthogonal to each other, producing a full factorial design matrix. The levels of the three parameters are summarized in Table 1.

Conclusion

A new type of thin-walled structure named leaf vein branched circular tube (LVBCT) is proposed inspired by the structural characteristics of the lotus leaf. The finite element simulation model established by LS-DYNA is first verified by comparing with the experimental results. Then the energy absorption properties of the LVBCTs subjected to axial impact are studied numerically.

The mechanical properties of LVBCTs are revealed by analyzing the deformation mechanism and crashworthiness indicators

Declaration of competing interest

The authors declared that they have no conflicts of interest to this work.

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

Acknowledgement

This work was financially supported by The National Natural Science Foundation of China (No. 51705215), The Graduate Student Scientific Research Innovation Projects in Jiangsu Province (NO. KYCX21_3444). The authors would like to express their thanks.

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