Pub Date : 2024-10-12DOI: 10.1016/j.tws.2024.112549
Enbo Zhao , Qiheng Xia , Lulu Liu , Feng Jin , Gang Luo , Zhenhua Zhao , Wei Chen
Fiber-reinforced thermoset polymers are widely used in aerospace as a material with excellent performance. However, for the low-velocity impact damage to which they are most susceptible, existing repair methods are difficult to maintain the aerodynamic performance of the components (back to its pre-damage shape) after repair. In this study, the multiple impact deformation recovery, internal damage healing, and post-repair impact properties of epoxy-PCL (ε-caprolactone) 2D carbon fiber fabric-reinforced polymers with shape memory and self-healing properties were investigated. The material is manufactured using a hot press tank-prepreg process, curing at 160 °C for 3.5 h at 6 atmospheres. The results show that the incorporation of thermoplastic PCL into the composite matrix can enhance the self-healing ability and impact resistance of the material. Composites after lower energy impacts retain their structural integrity and mechanical properties after healing. Materials can recover effectively from a single impact, but repeated impacts can lead to more extensive damage, which makes healing more difficult and causes a decrease in Healing efficiency. The shape memory effect of composites can restore plastic deformation caused by impact, which highlights the potential of shape memory smart composites for aerospace applications.
纤维增强热固性聚合物作为一种性能优异的材料被广泛应用于航空航天领域。然而，对于它们最容易受到的低速冲击损伤，现有的修复方法很难在修复后保持部件的气动性能（恢复到损伤前的形状）。在本研究中，研究了具有形状记忆和自修复特性的环氧树脂-PCL（ε-己内酯）二维碳纤维织物增强聚合物的多次冲击变形恢复、内部损伤愈合以及修复后的冲击性能。该材料采用热压罐-预浸工艺制造，在 6 个大气压下于 160 °C 固化 3.5 小时。结果表明，在复合材料基体中加入热塑性 PCL 可增强材料的自愈合能力和抗冲击性。受到较低能量冲击的复合材料在愈合后仍能保持其结构完整性和机械性能。材料可以从单次撞击中有效恢复，但反复撞击会导致更大范围的损伤，从而增加愈合难度并降低愈合效率。复合材料的形状记忆效应可以恢复撞击造成的塑性变形，这凸显了形状记忆智能复合材料在航空航天应用中的潜力。
{"title":"Experimental study on multiple self-healing and impact properties of 2D carbon fiber fabric-reinforced epoxy composites with shape memory properties","authors":"Enbo Zhao , Qiheng Xia , Lulu Liu , Feng Jin , Gang Luo , Zhenhua Zhao , Wei Chen","doi":"10.1016/j.tws.2024.112549","DOIUrl":"10.1016/j.tws.2024.112549","url":null,"abstract":"<div><div>Fiber-reinforced thermoset polymers are widely used in aerospace as a material with excellent performance. However, for the low-velocity impact damage to which they are most susceptible, existing repair methods are difficult to maintain the aerodynamic performance of the components (back to its pre-damage shape) after repair. In this study, the multiple impact deformation recovery, internal damage healing, and post-repair impact properties of epoxy-PCL (ε-caprolactone) 2D carbon fiber fabric-reinforced polymers with shape memory and self-healing properties were investigated. The material is manufactured using a hot press tank-prepreg process, curing at 160 °C for 3.5 h at 6 atmospheres. The results show that the incorporation of thermoplastic PCL into the composite matrix can enhance the self-healing ability and impact resistance of the material. Composites after lower energy impacts retain their structural integrity and mechanical properties after healing. Materials can recover effectively from a single impact, but repeated impacts can lead to more extensive damage, which makes healing more difficult and causes a decrease in Healing efficiency. The shape memory effect of composites can restore plastic deformation caused by impact, which highlights the potential of shape memory smart composites for aerospace applications.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112549"},"PeriodicalIF":5.7,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-12DOI: 10.1016/j.tws.2024.112581
Lichao Zhang , Hongshan Zhou , Jingyuan Chen , Hongyang Wang , Weiwei Liu , Zhaodong Zhang , Gang Song , Liming Liu , Zhao Zhang
The difference of cooling rates on the surface and the interior of thin-walled structures leads to significant differences of microstructures in additive manufacturing (AM). To reveal the microstructure control in wire arc additive manufacturing of thin-walled structures, a gas-heat coupling model with experimental validation is proposed. The computational accuracy can reach 96 % in prediction of temperatures and microstructures. Increasing the preheating or scanning speed leads to a higher probability of heterogeneous nucleation on the surface of thin-walled structures. When the pre-heating is increased from 550 K to 750 K, the proportion of equiaxed grains increases by 20.8 %. When the gas flow rate of super cooling is increased from 20 L/min to 30 L/min, the size of equiaxed grains is decreased from 0.33 mm to 0.23 mm on the surface, and the width of columnar grains is decreased from 0.53 mm to 0.42 mm in the interior. This is due to the significant differences in cooling rates in thin-walled structures.
薄壁结构表面和内部的冷却速率不同，导致增材制造（AM）中的微观结构存在显著差异。为了揭示线弧线弧增材制造薄壁结构中的微观结构控制，我们提出了一个经过实验验证的气热耦合模型。在预测温度和微观结构方面，计算精度可达 96%。提高预热或扫描速度会导致薄壁结构表面异质成核的概率增加。当预热从 550 K 增加到 750 K 时，等轴晶粒的比例增加了 20.8%。当过冷气体流速从 20 L/min 增加到 30 L/min 时，表面等轴晶粒的尺寸从 0.33 mm 减小到 0.23 mm，内部柱状晶粒的宽度从 0.53 mm 减小到 0.42 mm。这是由于薄壁结构的冷却速率存在显著差异。
{"title":"Numerical simulation for microstructure control in wire arc additive manufacturing of thin-walled structures","authors":"Lichao Zhang , Hongshan Zhou , Jingyuan Chen , Hongyang Wang , Weiwei Liu , Zhaodong Zhang , Gang Song , Liming Liu , Zhao Zhang","doi":"10.1016/j.tws.2024.112581","DOIUrl":"10.1016/j.tws.2024.112581","url":null,"abstract":"<div><div>The difference of cooling rates on the surface and the interior of thin-walled structures leads to significant differences of microstructures in additive manufacturing (AM). To reveal the microstructure control in wire arc additive manufacturing of thin-walled structures, a gas-heat coupling model with experimental validation is proposed. The computational accuracy can reach 96 % in prediction of temperatures and microstructures. Increasing the preheating or scanning speed leads to a higher probability of heterogeneous nucleation on the surface of thin-walled structures. When the pre-heating is increased from 550 K to 750 K, the proportion of equiaxed grains increases by 20.8 %. When the gas flow rate of super cooling is increased from 20 L/min to 30 L/min, the size of equiaxed grains is decreased from 0.33 mm to 0.23 mm on the surface, and the width of columnar grains is decreased from 0.53 mm to 0.42 mm in the interior. This is due to the significant differences in cooling rates in thin-walled structures.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112581"},"PeriodicalIF":5.7,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.tws.2024.112539
Daniel Martins , Mahmoud Karimi , Laurent Maxit
Stiffened structures are widely used in aeronautics, marine and rail industries. When stiffeners are integrated into host structures, so-called Bloch–Floquet waves are generated due to interactions between the host’s flexural waves and the stiffeners’ flexural and torsional waves. It is reported in the literature that these waves are often the source of undesirable noise and vibrations when the stiffened structure is excited by a force. To mitigate unwanted noise and vibrations from the stiffened structures, this study proposes to replace common rectangular stiffeners with acoustic black hole (ABH) stiffeners. To do this, a semi-analytical model is initially developed in the wavenumber domain to predict the forced vibroacoustic response of a 2D fluid-loaded infinite plate with stiffeners on one side. In the proposed model, the stiffeners are characterised by their translational and rotational dynamic stiffnesses which can be estimated by a finite element method (FEM). These dynamic stiffnesses are then coupled with the analytical formulation of the fluid-loaded plate to obtain the expressions of the spectral displacement and radiated pressure. Comparisons of the results in terms of the plate’s mean quadratic velocity and radiated sound power for the rectangular and ABH stiffeners show that by using the ABH stiffeners instead of the conventional stiffeners, one can significantly reduce the vibroacoustic response of light/heavy fluid-loaded plates.
{"title":"Semi-analytical formulation to predict the vibroacoustic response of a fluid-loaded plate with ABH stiffeners","authors":"Daniel Martins , Mahmoud Karimi , Laurent Maxit","doi":"10.1016/j.tws.2024.112539","DOIUrl":"10.1016/j.tws.2024.112539","url":null,"abstract":"<div><div>Stiffened structures are widely used in aeronautics, marine and rail industries. When stiffeners are integrated into host structures, so-called Bloch–Floquet waves are generated due to interactions between the host’s flexural waves and the stiffeners’ flexural and torsional waves. It is reported in the literature that these waves are often the source of undesirable noise and vibrations when the stiffened structure is excited by a force. To mitigate unwanted noise and vibrations from the stiffened structures, this study proposes to replace common rectangular stiffeners with acoustic black hole (ABH) stiffeners. To do this, a semi-analytical model is initially developed in the wavenumber domain to predict the forced vibroacoustic response of a 2D fluid-loaded infinite plate with stiffeners on one side. In the proposed model, the stiffeners are characterised by their translational and rotational dynamic stiffnesses which can be estimated by a finite element method (FEM). These dynamic stiffnesses are then coupled with the analytical formulation of the fluid-loaded plate to obtain the expressions of the spectral displacement and radiated pressure. Comparisons of the results in terms of the plate’s mean quadratic velocity and radiated sound power for the rectangular and ABH stiffeners show that by using the ABH stiffeners instead of the conventional stiffeners, one can significantly reduce the vibroacoustic response of light/heavy fluid-loaded plates.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112539"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.tws.2024.112578
Gang Wei, Chenyu Hao, Hongwei Jin, Yunfei Deng
In order to meet the urgent needs for the application of thermoplastic composite structures in aircraft manufacturing and other fields, the impact resistance and damage tolerance of continuous carbon fiber reinforced thermoplastic composite laminates (CCFRTP) are investigated by high-velocity impact (HVI) and compression after impact (CAI) experiments in this paper. The impact experiment results show that the ballistic response of laminates under small-angle conventional impact is similar, and the impact resistance of laminates under large-angle oblique impact is significantly improved. The failure mechanism of laminates under high-velocity impact is revealed by analyzing the impact process of the projectile, the energy absorption level, the failure morphology and internal damage degree of laminates comprehensively. It is clear that the impact angle and velocity of the projectile will significantly affect the coupling form of the failure mechanism and lead to differentiated results. The results of in-plane compression experiment of laminates with impact damage show that the bearing capacity of laminates is significantly weakened by high velocity impact damage, and the residual strength of laminates is directly determined by the mode and degree of impact damage. In particular, through the analysis of the energy absorption mechanism, a trend prediction model of ballistic limit value with impact angle is established, and the influence of high-velocity impact damage on the residual strength of laminates is revealed. This study provides a better understanding of the mechanical response of thermoplastic composite structures to high-velocity impact loads.
{"title":"Experimental investigation of high-velocity impact response and compression after impact behavior of continuous carbon fiber thermoplastic composites","authors":"Gang Wei, Chenyu Hao, Hongwei Jin, Yunfei Deng","doi":"10.1016/j.tws.2024.112578","DOIUrl":"10.1016/j.tws.2024.112578","url":null,"abstract":"<div><div>In order to meet the urgent needs for the application of thermoplastic composite structures in aircraft manufacturing and other fields, the impact resistance and damage tolerance of continuous carbon fiber reinforced thermoplastic composite laminates (CCFRTP) are investigated by high-velocity impact (HVI) and compression after impact (CAI) experiments in this paper. The impact experiment results show that the ballistic response of laminates under small-angle conventional impact is similar, and the impact resistance of laminates under large-angle oblique impact is significantly improved. The failure mechanism of laminates under high-velocity impact is revealed by analyzing the impact process of the projectile, the energy absorption level, the failure morphology and internal damage degree of laminates comprehensively. It is clear that the impact angle and velocity of the projectile will significantly affect the coupling form of the failure mechanism and lead to differentiated results. The results of in-plane compression experiment of laminates with impact damage show that the bearing capacity of laminates is significantly weakened by high velocity impact damage, and the residual strength of laminates is directly determined by the mode and degree of impact damage. In particular, through the analysis of the energy absorption mechanism, a trend prediction model of ballistic limit value with impact angle is established, and the influence of high-velocity impact damage on the residual strength of laminates is revealed. This study provides a better understanding of the mechanical response of thermoplastic composite structures to high-velocity impact loads.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112578"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An experimental investigation into the structural response of cold-formed steel-timber composite flooring systems with innovative and irregularly spaced shear connectors is presented in this paper. Five composite beam tests and a series of supporting material and push-out tests were carried out. The obtained results showed that the innovative shear connectors enabled the generation of considerable composite action, resulting in up to about 45 % increases in load-carrying capacity and 15 % and 20 % increases in the initial and mid-range stiffnesses respectively over the non-composite system. Methods for predicting the effective flexural stiffness and moment capacity of the examined cold-formed steel-timber composite beams are presented and validated against the derived physical test data. It is shown that accurate predictions for both the flexural stiffness and moment capacity can be obtained, with mean prediction-to-test ratios of 0.93 and 0.91 respectively.
{"title":"Experimental study of composite cold-formed steel and timber flooring systems with innovative shear connectors","authors":"Nathan Vella , Pinelopi Kyvelou , Spiridione Buhagiar , Leroy Gardner","doi":"10.1016/j.tws.2024.112571","DOIUrl":"10.1016/j.tws.2024.112571","url":null,"abstract":"<div><div>An experimental investigation into the structural response of cold-formed steel-timber composite flooring systems with innovative and irregularly spaced shear connectors is presented in this paper. Five composite beam tests and a series of supporting material and push-out tests were carried out. The obtained results showed that the innovative shear connectors enabled the generation of considerable composite action, resulting in up to about 45 % increases in load-carrying capacity and 15 % and 20 % increases in the initial and mid-range stiffnesses respectively over the non-composite system. Methods for predicting the effective flexural stiffness and moment capacity of the examined cold-formed steel-timber composite beams are presented and validated against the derived physical test data. It is shown that accurate predictions for both the flexural stiffness and moment capacity can be obtained, with mean prediction-to-test ratios of 0.93 and 0.91 respectively.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112571"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.tws.2024.112553
Jiaxuan Li , Chao Sui , Yuna Sang , Yichen Zhou , Zifu Zang , Yushun Zhao , Xiaodong He , Chao Wang
Thin-walled tubes are widely used in the field of cushioning energy absorption as an ideal structural unit. However, the performance of the thin-walled tube system is greatly limited by the presence of redundant connection structures. To address these issues, a multi-bionic design strategy for high-performance modular system was developed in this work, which innovatively combines the robust joint structure of the interlocking suture with the efficient deformation mode of the Bouligand structures. In the design process, the suture-inspired system was studied separately, and its mechanical behaviors were investigated by FEM simulations and experiments. The results showed that the modular system has good structural scalability and tunable deformation mode, and can be adjusted on demand to accommodate different loads and geometric features. Furthermore, in order to reduce the weight and improve the deformation degree of the system, an optimization strategy inspired by the efficient deformation mode of the Bouligand structure was proposed by perforating a sequence of helix-arranged guide holes in the sidewalls of the tubes. The results showed that the double-helix perforated system can reduce the weight by 10% while increasing the specific energy absorption by 58% compared with the unperforated system. In addition, the specific energy absorption and energy absorption efficiency of the system are as high as 48.25 J/g and 56.17%, which is comparable to traditional honeycomb sandwich panels while retaining structural stability and adjustable performance. Therefore, this multi-bionic strategy can integrate the advantages of various natural structures and provide new insights for the design of high-performance protective systems.
{"title":"A multi-bionic design strategy for modular energy absorption system based on interlocking suture integrated with Bouligand-like arranged perforations","authors":"Jiaxuan Li , Chao Sui , Yuna Sang , Yichen Zhou , Zifu Zang , Yushun Zhao , Xiaodong He , Chao Wang","doi":"10.1016/j.tws.2024.112553","DOIUrl":"10.1016/j.tws.2024.112553","url":null,"abstract":"<div><div>Thin-walled tubes are widely used in the field of cushioning energy absorption as an ideal structural unit. However, the performance of the thin-walled tube system is greatly limited by the presence of redundant connection structures. To address these issues, a multi-bionic design strategy for high-performance modular system was developed in this work, which innovatively combines the robust joint structure of the interlocking suture with the efficient deformation mode of the Bouligand structures. In the design process, the suture-inspired system was studied separately, and its mechanical behaviors were investigated by FEM simulations and experiments. The results showed that the modular system has good structural scalability and tunable deformation mode, and can be adjusted on demand to accommodate different loads and geometric features. Furthermore, in order to reduce the weight and improve the deformation degree of the system, an optimization strategy inspired by the efficient deformation mode of the Bouligand structure was proposed by perforating a sequence of helix-arranged guide holes in the sidewalls of the tubes. The results showed that the double-helix perforated system can reduce the weight by 10% while increasing the specific energy absorption by 58% compared with the unperforated system. In addition, the specific energy absorption and energy absorption efficiency of the system are as high as 48.25 <em>J</em>/g and 56.17%, which is comparable to traditional honeycomb sandwich panels while retaining structural stability and adjustable performance. Therefore, this multi-bionic strategy can integrate the advantages of various natural structures and provide new insights for the design of high-performance protective systems.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112553"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.tws.2024.112570
Fan Dong , Yazhi Li , Xin Qi , Weijie Ma , Chunping Zhou , Biao Li
Composite sandwich panels present a variety of damage modes due to their diverse components and variable structural parameters. This work conducted three-point bending static and fatigue tests on composite sandwich panels using specially designed fixtures to investigate their bending-shear characteristics and failure behaviors. The effects of core orientations, i.e., L-direction and W-direction, on the static strength, fatigue life, and fatigue crack initiation and propagation were compared. A stiffness-degradation-based fatigue damage model was constructed for the sandwich panels to describe the entire failure process from core cracking to core/plates debonding, achieving accurate modeling under the full load ratios. A differential evolution algorithm incorporating a penalty function was employed to optimize the model parameters under varying stresses. It was found that the designed fixture enables bi-directional fatigue loading and effectively avoids additional axial forces. Fatigue damage in sandwich panels resembles static but spans a wider area. While damage modes are similar in W-direction and L-direction, L-direction cores have higher stiffness and strength, and lower fatigue resistance in W-direction. Furthermore, the proposed fatigue damage model demonstrates excellent agreement with experimental results, achieving R2 = 0.968.
复合材料夹层板由于其成分和结构参数的多样性而呈现出多种破坏模式。这项研究利用专门设计的夹具对复合材料夹芯板进行了三点弯曲静态和疲劳试验，以研究其弯曲剪切特性和破坏行为。比较了芯材方向（即 L 方向和 W 方向）对静态强度、疲劳寿命以及疲劳裂纹萌发和扩展的影响。为夹芯板构建了基于刚度降解的疲劳损伤模型，以描述从夹芯开裂到夹芯/夹板脱粘的整个失效过程，实现了全载荷比下的精确建模。采用了一种包含惩罚函数的微分进化算法，以优化不同应力下的模型参数。研究发现，所设计的夹具可实现双向疲劳加载，并有效避免了额外的轴向力。夹芯板的疲劳损伤类似于静态损伤，但范围更广。虽然 W 方向和 L 方向的损伤模式相似，但 L 方向的夹芯具有更高的刚度和强度，而 W 方向的抗疲劳性能较低。此外，所提出的疲劳损伤模型与实验结果非常吻合，R2 = 0.968。
{"title":"Failure behavior and damage model of composite sandwich panels under three-point bending fatigue load","authors":"Fan Dong , Yazhi Li , Xin Qi , Weijie Ma , Chunping Zhou , Biao Li","doi":"10.1016/j.tws.2024.112570","DOIUrl":"10.1016/j.tws.2024.112570","url":null,"abstract":"<div><div>Composite sandwich panels present a variety of damage modes due to their diverse components and variable structural parameters. This work conducted three-point bending static and fatigue tests on composite sandwich panels using specially designed fixtures to investigate their bending-shear characteristics and failure behaviors. The effects of core orientations, i.e., <span>L</span>-direction and W-direction, on the static strength, fatigue life, and fatigue crack initiation and propagation were compared. A stiffness-degradation-based fatigue damage model was constructed for the sandwich panels to describe the entire failure process from core cracking to core/plates debonding, achieving accurate modeling under the full load ratios. A differential evolution algorithm incorporating a penalty function was employed to optimize the model parameters under varying stresses. It was found that the designed fixture enables bi-directional fatigue loading and effectively avoids additional axial forces. Fatigue damage in sandwich panels resembles static but spans a wider area. While damage modes are similar in W-direction and <span>L</span>-direction, <span>L</span>-direction cores have higher stiffness and strength, and lower fatigue resistance in W-direction. Furthermore, the proposed fatigue damage model demonstrates excellent agreement with experimental results, achieving <em>R<sup>2</sup></em> = 0.968.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112570"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.tws.2024.112537
Xiao Wang , Guangming Fu , Huilin Jiao , Boying Wang , Baojiang Sun , Jian Su
This study investigates the vibration behavior of a vertical cantilever pipe conveying gas–liquid two-phase flow, focusing on the influence of lumped masses attached to the vertical cantilevered pipe. The governing motion equation based on small deflection Euler–Bernoulli beam theory is solved by using the generalized integral transforms technique. The proposed solution approach was first validated against available numerical and experimental results in the literature. The effects of the mass ratios, number and position of lumped masses on the stability of the pipe are investigated. Numerical results show that the parameters of the lumped masses affect significantly the stability of the pipe conveying two-phase flow, by altering the fluid–structure interaction dynamics and impacting natural frequencies and vibration modes of the pipe. Specifically, as the position of a single lumped mass moves downward from the fixed end to the free end, the critical flow velocity initially increases and subsequently decreases, thereby reducing the stability of pipe. Moreover, increasing the number of lumped masses significantly impacts the critical flow velocity due to the mass ratios and locations. Notably, modal “jumping” phenomena are observed, which demonstrate continuous shifts between equilibrium and non-equilibrium states in the cantilever pipes. These findings are crucial for ensuring the safe operation of pipes with discrete masses across various engineering applications.
{"title":"Stability analysis of a vertical cantilever pipe with lumped masses conveying two-phase flow","authors":"Xiao Wang , Guangming Fu , Huilin Jiao , Boying Wang , Baojiang Sun , Jian Su","doi":"10.1016/j.tws.2024.112537","DOIUrl":"10.1016/j.tws.2024.112537","url":null,"abstract":"<div><div>This study investigates the vibration behavior of a vertical cantilever pipe conveying gas–liquid two-phase flow, focusing on the influence of lumped masses attached to the vertical cantilevered pipe. The governing motion equation based on small deflection Euler–Bernoulli beam theory is solved by using the generalized integral transforms technique. The proposed solution approach was first validated against available numerical and experimental results in the literature. The effects of the mass ratios, number and position of lumped masses on the stability of the pipe are investigated. Numerical results show that the parameters of the lumped masses affect significantly the stability of the pipe conveying two-phase flow, by altering the fluid–structure interaction dynamics and impacting natural frequencies and vibration modes of the pipe. Specifically, as the position of a single lumped mass moves downward from the fixed end to the free end, the critical flow velocity initially increases and subsequently decreases, thereby reducing the stability of pipe. Moreover, increasing the number of lumped masses significantly impacts the critical flow velocity due to the mass ratios and locations. Notably, modal “jumping” phenomena are observed, which demonstrate continuous shifts between equilibrium and non-equilibrium states in the cantilever pipes. These findings are crucial for ensuring the safe operation of pipes with discrete masses across various engineering applications.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112537"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.tws.2024.112573
Ihyun Ryu , Seon-Hu Kim , Cheol-Ho Lee
Applying high strength steels to tubular joints can increase the propensity to fracture failure due to their lower ductility. However, to simulate the fracture behavior in the finite element (FE) analysis, sophisticated material damage model with rigorous fracture criteria should be incorporated. Recently, the latest draft of ISO 14346 has advocated the use of 5 % strain limit in FE analysis of tubular joints. The strain limit concept has been further developed by the authors’ previous work, for its use as a practical alternative to the complicated material damage model. Specifically, a lowered limit of 2.5 % was recommended for longitudinal plate to circular hollow section (CHS) joints subjected to in-plane bending. This study extends the strain limit investigation to longitudinal plate to tubular X joints subjected to tensile loads. An experimental program is first presented which included both CHS and rectangular hollow section (RHS) chord members fabricated from two high strength steels with nominal yield stresses of 460 MPa and 700 MPa. Based on test-validated supplemental numerical analyses, it is suggested that the joint load corresponding to 2.5 % strain limit can be taken as the load-bearing capacity to suppress occurrence of a fracture failure for the tubular joint configurations considered in this study.
{"title":"Experimental testing and plastic strain analysis of high strength steel longitudinal plate to tubular X joints","authors":"Ihyun Ryu , Seon-Hu Kim , Cheol-Ho Lee","doi":"10.1016/j.tws.2024.112573","DOIUrl":"10.1016/j.tws.2024.112573","url":null,"abstract":"<div><div>Applying high strength steels to tubular joints can increase the propensity to fracture failure due to their lower ductility. However, to simulate the fracture behavior in the finite element (FE) analysis, sophisticated material damage model with rigorous fracture criteria should be incorporated. Recently, the latest draft of ISO 14346 has advocated the use of 5 % strain limit in FE analysis of tubular joints. The strain limit concept has been further developed by the authors’ previous work, for its use as a practical alternative to the complicated material damage model. Specifically, a lowered limit of 2.5 % was recommended for longitudinal plate to circular hollow section (CHS) joints subjected to in-plane bending. This study extends the strain limit investigation to longitudinal plate to tubular X joints subjected to tensile loads. An experimental program is first presented which included both CHS and rectangular hollow section (RHS) chord members fabricated from two high strength steels with nominal yield stresses of 460 MPa and 700 MPa. Based on test-validated supplemental numerical analyses, it is suggested that the joint load corresponding to 2.5 % strain limit can be taken as the load-bearing capacity to suppress occurrence of a fracture failure for the tubular joint configurations considered in this study.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"206 ","pages":"Article 112573"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.tws.2024.112579
Boshan Chen , Yecheng Dai , Wei Wang , Youtian Wang , Lisheng Luo , Peng Dai , James Lim
Cold-formed steel (CFS) sigma-shaped sections used as flooring joists and bearers are commonly fabricated with web holes to accommodate building services. These sections featuring web stiffeners and curved lips exhibit lower web-bearing resistance than traditional lipped channel sections. However, the web-bearing resistance of CFS sigma-shaped sections with web holes has not been thoroughly investigated. To address this gap, a detailed experimental investigation was conducted, testing 29 CFS sigma-shaped sections with web holes under an interior-two-flange (ITF) loading case. For comparison, specimens without web holes were also tested. Variables such as hole diameter ratio, hole location, bearing length, and flange condition were examined. A finite element (FE) model was developed and validated against the test results. The results indicated that the web-bearing resistance for specimens with web holes was reduced by 24.0 % on average. To assess the accuracy of existing design specifications, the test results were compared against the design strengths predicted by the American Iron and Steel Institute (AISI) (2016), Australian and New Zealand Standards (AS/NZS) (2018), European Standard (EC3) (2006), and Uzzaman et al. (2012). The comparison revealed that the design strength predicted by Uzzaman et al. (2012) agreed well with the test results.
{"title":"An experimental study on web-bearing resistance of cold-formed steel sigma-shaped sections with web holes under interior-two-flange loading case","authors":"Boshan Chen , Yecheng Dai , Wei Wang , Youtian Wang , Lisheng Luo , Peng Dai , James Lim","doi":"10.1016/j.tws.2024.112579","DOIUrl":"10.1016/j.tws.2024.112579","url":null,"abstract":"<div><div>Cold-formed steel (CFS) sigma-shaped sections used as flooring joists and bearers are commonly fabricated with web holes to accommodate building services. These sections featuring web stiffeners and curved lips exhibit lower web-bearing resistance than traditional lipped channel sections. However, the web-bearing resistance of CFS sigma-shaped sections with web holes has not been thoroughly investigated. To address this gap, a detailed experimental investigation was conducted, testing 29 CFS sigma-shaped sections with web holes under an interior-two-flange (ITF) loading case. For comparison, specimens without web holes were also tested. Variables such as hole diameter ratio, hole location, bearing length, and flange condition were examined. A finite element (FE) model was developed and validated against the test results. The results indicated that the web-bearing resistance for specimens with web holes was reduced by 24.0 % on average. To assess the accuracy of existing design specifications, the test results were compared against the design strengths predicted by the American Iron and Steel Institute (AISI) (2016), Australian and New Zealand Standards (AS/NZS) (2018), European Standard (EC3) (2006), and Uzzaman et al. (2012). The comparison revealed that the design strength predicted by Uzzaman et al. (2012) agreed well with the test results.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112579"},"PeriodicalIF":5.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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