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Exploring Humerus Bone’s Fracture Patterns and Fixation Systems Via Laser Vibrometry 用激光振动仪研究肱骨骨折模式和固定系统
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-06-02 DOI: 10.1007/s11340-025-01198-7
B. Carboni, S. K. Guruva, S. Gumina, V. Candela, J. Tirilló, C. Sergi, T. Valente, W. Lacarbonara

Background

The mechanical performance assessment of orthopedic fixation systems is computationally and experimentally challenging due to the complex geometrical and mechanical features of bones. Non-contact experimental techniques, widely adopted in several engineering fields, is shown to overcome these issues.

Objective

This work discusses a comparative experimental investigation into specimens mimicking healthy humerus bones and fractured bones subject to an innovative surgery procedure and to a classical technique referred to as the gold standard surgery. The new surgery consists in the installation of an external fixation mechanism that constrains, according to different spatial patterns, a certain number of titanium slender bars inserted and clamped into the fractured bones.

Methods

The mechanical properties of artificial bones are characterized through compressive tests, while the morphology of the fracture surface is analyzed using a scanning electron microscope. A three-dimensional laser vibrometer is used to measure the resonance frequencies, mode shapes, damping ratios, and mechanical waves propagating from the actuators across the surface of the bones.

Results

The results provide insights into which configuration of the fixator performs better for a fast recovery. Based on the observed dynamic behaviors, the optimal configuration of the fixator offers performance that is comparable to, or potentially better than, the gold standard surgical procedure.

Conclusions

The novelty and feasibility of the adopted experimental approach paves the way towards the adoption of advanced non-contact techniques for the mechanical characterization of complex, non-homegenous and anisotropic materials and structures in biomedical applications enabling also data-driven models of the systems.

由于骨骼复杂的几何和力学特征,骨科固定系统的力学性能评估在计算和实验上都具有挑战性。非接触式实验技术被广泛应用于多个工程领域,克服了这些问题。目的本研究讨论了一项比较实验研究,通过一种创新的手术程序和一种被称为金标准手术的经典技术来模拟健康的肱骨和骨折的骨头。新的手术包括安装一个外固定装置,根据不同的空间模式,将一定数量的钛细长棒插入并夹入骨折的骨头中。方法通过压缩试验对人工骨的力学性能进行表征,同时用扫描电镜对断口形貌进行分析。三维激光测振仪用于测量谐振频率、模态振型、阻尼比和从驱动器穿过骨骼表面传播的机械波。结果说明了哪种固定架配置对快速恢复效果更好。根据观察到的动态行为,固定架的最佳配置提供了与金标准手术程序相当或可能更好的性能。所采用的实验方法的新颖性和可行性为采用先进的非接触技术来表征生物医学应用中复杂、非均质和各向异性材料和结构的力学特性铺平了道路,也使系统的数据驱动模型成为可能。
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引用次数: 0
On the Cover: Overcoming Dynamic Stiffness Damping Trade Off with Structural Gradients in 3D Printed Elastomeric Gyroid Lattices 封面:克服动态刚度阻尼权衡与结构梯度在3D打印弹性体陀螺晶格
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-06-02 DOI: 10.1007/s11340-025-01202-0
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引用次数: 0
A Method to Perform an Experimental Modal Analysis of a Medium Head Francis Runner in Operation 一种运行中水头混流式转轮试验模态分析方法
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-28 DOI: 10.1007/s11340-025-01185-y
A. Tessier, M. Coulaud, D. Thibault, S. Houde, Y. St-Amant

Background

Hydraulic turbines are increasingly used outside the range of operation for which they were designed due to the growth of electricity produced by wind and solar power sources, which are intermittent. The new operating ranges cause high level of vibrations that reduce significantly the lifespan of the turbine runner. Modal parameters of the runner are influenced by the operating condition, but the extent of this influence remains unknown. Closely spaced modes, which are typical in turbine runners, also remain challenging to identify.

Objective

This paper presents a methodology for conducting an experimental modal analysis of a medium head model Francis turbine runner during operation, with the objective of identifying its natural frequencies and damping ratios while minimizing the impact on the hydraulic surface.

Methods

The runner of a medium head model Francis turbine is instrumented with piezoelectric actuators located on the outer side of the band and semiconductor strain gauges on the blades and the inner side of the band. Classical strain gauges and accelerometers are installed as reference measurements. Piezoelectric actuators are driven by sine sweep signals to generate standing and travelling waves matching the mode shapes of band dominant modes. Natural frequencies and damping ratios are then identified from the frequency response functions.

Results

The energy injected by the piezoelectric actuators is sufficiently high to excite band-dominant natural modes of the runner in operation. The high sensitivity of semiconductor strain gauges allows for low-noise measurements compared to classical strain gauges. The quality of the obtained frequency response functions is high, enabling the identification of natural frequencies and damping ratios and resulting in strong agreement between measured and model-predicted responses. With eight piezoelectric actuators located on the band, the use of traveling wave excitation pattern allows for the individual excitation of the forward and backward components of the first two pairs of band-dominant natural modes.

Conclusion

The proposed method for conducting experimental modal analysis enables the identification of modal parameters of a model Francis turbine runner in operation. By using a traveling wave excitation pattern, the method allows for the individual excitation of the forward and backward components of band-dominant natural modes—provided the number of actuators is sufficiently large—which is particularly beneficial for identifying closely spaced modes when such modes are present.

水力涡轮机越来越多地在其设计的运行范围之外使用,这是由于风能和太阳能发电的增长,这是间歇性的。新的操作范围引起高水平的振动,大大减少了涡轮转轮的寿命。转轮的模态参数受工况的影响,但影响的程度尚不清楚。紧密间隔模式,这是典型的涡轮转轮,也仍然具有挑战性的识别。本文提出了一种对中型水头型混流式水轮机转轮在运行过程中进行试验模态分析的方法,目的是确定其固有频率和阻尼比,同时最大限度地减少对液压表面的影响。方法在中水头型混流式水轮机转轮的传动带外侧安装了压电作动器,叶片和传动带内侧安装了半导体应变片。安装经典应变计和加速度计作为参考测量。压电驱动器由正弦扫描信号驱动,产生与带优势模态振型相匹配的驻波和行波。然后从频率响应函数中确定固有频率和阻尼比。结果压电致动器注入的能量足够高,可以激发转轮运行时的带状优势自然模态。与经典应变片相比,半导体应变片的高灵敏度允许进行低噪声测量。所获得的频率响应函数的质量很高,能够识别固有频率和阻尼比,并在测量和模型预测响应之间产生强烈的一致性。带上有八个压电致动器,使用行波激励模式可以单独激励前两对带主导自然模态的前向和后向分量。结论本文提出的试验模态分析方法能够识别运行中的水轮机混流式转轮模型模态参数。通过使用行波激励模式,该方法允许单独激励带优势自然模式的前向和后向分量——只要执行器的数量足够大——当这种模式存在时,这对识别紧密间隔的模式特别有益。
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引用次数: 0
Effects of Drilling Induced Heating During IHD of FRP Laminates 钻致加热对玻璃钢层合板IHD的影响
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-22 DOI: 10.1007/s11340-025-01196-9
M. Horan, T. C. Smit, R.G. Reid

Background

Incremental hole-drilling has been used extensively in composite laminates, however, the low thermal conductivity of GFRP laminates results in drilling induced heat build-up near the hole. This can lead to measurement errors due to post-cure shrinkage of the matrix, and additional thermal drift errors arising from the necessary data acquisition delay after each drilling increment to allow adequate heat dissipation before taking strain measurements.

Objective

Investigate the significance of drilling induced post-cure shrinkage and the effects of different bottom-surface thermal boundary conditions on the drilling induced heat dissipation in GFRP laminates during IHD.

Methods

IHD is performed on GFRP laminates, specifically an annealed ([0_{8}]) laminate and a ([0_{2}/90_{2}]_{s}) laminate with different support configurations. The through-thickness residual stress distribution is determined using the integral computational method. The magnitude of drilling induced post-cure shrinkage effects and those of the different thermal boundary conditions are investigated.

Results

IHD on the annealed ([0_{8}]) specimens demonstrated that drilling induced post-cure shrinkage effects are not significant. The use of different thermal boundary conditions for the ([0_{2}/90_{2}]_{s}) specimens demonstrated the necessity for good heat transfer out of the laminate to achieve accurate results.

Conclusions

Carefully performed IHD does not cause sufficient drilling induced heating to result in post-cure shrinkage of GFRP laminates. Experimental parameters and the thermal boundary conditions of the bottom surface must be carefully considered to ensure a successful measurement. A lack of good heat transfer out of the bottom surface of the specimen increases the required testing time and can produce unreliable results.

背景:渐进式钻孔已广泛应用于复合材料层压板,然而,GFRP层压板的低导热性导致钻孔引起的热积聚在孔附近。这可能会导致由于基体固化后收缩而产生的测量误差,以及由于每次钻井增量后必要的数据采集延迟而产生的额外热漂移误差,以便在进行应变测量之前充分散热。目的探讨钻孔致固化后收缩的意义,以及不同底表面热边界条件对GFRP复合材料在IHD过程中钻孔致散热的影响。方法在GFRP层压板上进行sihd,特别是退火([0_{8}])层压板和具有不同支撑配置的([0_{2}/90_{2}]_{s})层压板。采用积分计算法确定了整个厚度的残余应力分布。研究了钻孔引起的固化后收缩效应的大小以及不同热边界条件下的收缩效应。结果对([0_{8}])退火试样进行的hd实验表明,钻孔引起的固化后收缩效应不显著。对([0_{2}/90_{2}]_{s})试样使用不同的热边界条件表明,为了获得准确的结果,层压板必须有良好的传热。结论仔细进行的IHD不会引起足够的钻孔引起的加热导致GFRP层合板的固化后收缩。为了保证测量的成功,必须仔细考虑实验参数和底表面的热边界条件。试样底表面缺乏良好的热传递会增加所需的测试时间,并可能产生不可靠的结果。
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引用次数: 0
Tuning Energy Absorption of Metallic TPMS Cellular Structures via Wall Thickness Gradient Design 基于壁厚梯度设计的金属TPMS细胞结构的能量吸收调谐
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-15 DOI: 10.1007/s11340-025-01190-1
M. Zhong, W. Zhou, Z. Wu, J. Deng, Y. Du

Background

In the study of laser melting fabricated 316L stainless steel triply periodic minimal surface (TPMS) structures, a knowledge gap persists. The understanding of optimizing deformation mechanisms and energy absorption, especially via gradient wall thickness design, remains inadequate.

Objective

The main aim of this research is to explore the deformation and energy absorption features of particular 316L stainless steel TPMS structures made by laser melting, emphasizing the use of gradient wall thickness design to improve overall energy absorption.

Methods

An integrated experimental and computational approach was developed. TPMS structures with diverse wall thicknesses were fabricated through laser melting. Then, detailed analyses were performed to examine stress and deformation under compression. The novelty was the local strategies in gradient wall thickness design for enhanced stress redistribution.

Results

Quantitatively, compared to uniform ones, the specific energy absorption (SEA) of gradient structures rose by 18.3% along the loading direction and 26.8% perpendicular to diagonal shearing. Qualitatively, the gradient design reduced early densification and improved stress redistribution, yielding new insights for future designs.

Conclusions

Overall, the strategic use of gradient design and wall thickness control significantly boosts the SEA of laser melting fabricated 316L stainless steel TPMS structures, showing great potential for future applications.

在激光熔化制备316L不锈钢三周期最小表面(TPMS)结构的研究中,知识差距仍然存在。对优化变形机制和能量吸收的理解,特别是通过梯度壁厚设计,仍然不足。目的探讨激光熔化316L不锈钢TPMS结构的变形和吸能特性,强调采用梯度壁厚设计来提高整体吸能。方法建立了一种实验与计算相结合的方法。采用激光熔化法制备了不同壁厚的TPMS结构。然后,进行了详细的分析,以检查应力和变形下的压缩。新颖之处在于梯度壁厚设计中的局部策略,以增强应力重分布。结果与均匀结构相比,梯度结构的比能吸收(SEA)沿加载方向和垂直于斜剪方向分别提高了18.3%和26.8%。从质量上讲,梯度设计减少了早期致密化,改善了应力再分布,为未来的设计提供了新的见解。综上所述,梯度设计和壁厚控制的策略应用显著提高了激光熔制316L不锈钢TPMS结构的SEA,具有广阔的应用前景。
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引用次数: 0
Study on the Long-Term Monitoring of Contact Deformation Field of Periodic Rotating Gears Using DIC Combined with SURF Algorithm 基于DIC与SURF算法的周期旋转齿轮接触变形场长期监测研究
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-15 DOI: 10.1007/s11340-025-01189-8
X. Hou, D. Zeng, X. Huang, H. Zhang, Z. Liu, X. Huang

Background

Digital image correlation (DIC) is a widely adopted non-contact method for precise motion and deformation measurement, valued for its high accuracy. However, standard 2D DIC struggles to track relative displacements in materials with significant rigid rotations or out-of-plane displacement interference, such as in monitoring rotating gears. Additionally, the extensive data generated during in-situ monitoring makes DIC-based image matching impractical.

Objective

This study proposes a method for rapidly identifying identical images from large datasets. The proposed method can also effectively eliminate the impact of rigid rotation and out-of-plane displacement.

Methods

This study proposes a dynamic period digital image correlation (DP-DIC) method. The technique utilizes the speeded-up robust features (SURF) algorithm to match and select feature points efficiently, addressing the issue of image decorrelation caused by large-angle rotations. Furthermore, a rigid-body matrix restoration algorithm is incorporated to reduce the effects of rigid rotation and out-of-plane displacement partially.

Results

Validation tests for measuring the dynamic deformation field of rotating gears provide essential data. This data supports gear design optimization, performance evaluation, and lifetime prediction.

Conclusion

This study proposes a DP-DIC method based on DIC. Validation tests demonstrate that the DP-DIC method is suitable for long-term monitoring of the contact deformation field in periodically rotating gears.

数字图像相关(DIC)是一种被广泛采用的用于精确运动和变形测量的非接触方法,其精度高。然而,标准的2D DIC难以跟踪具有明显刚性旋转或面外位移干扰的材料中的相对位移,例如监测旋转齿轮。此外,现场监测过程中产生的大量数据使得基于dic的图像匹配不切实际。目的提出一种从大数据集中快速识别相同图像的方法。该方法还可以有效地消除刚性旋转和面外位移的影响。方法提出一种动态周期数字图像相关(DP-DIC)方法。该技术利用加速鲁棒特征(SURF)算法有效匹配和选择特征点,解决了大角度旋转引起的图像去相关问题。在此基础上,引入刚体矩阵恢复算法,部分降低了刚体旋转和面外位移的影响。结果验证试验为测量旋转齿轮动态变形场提供了必要的数据。这些数据支持齿轮设计优化,性能评估和寿命预测。结论本研究提出了一种基于DIC的DP-DIC方法。验证试验表明,DP-DIC方法适用于周期旋转齿轮接触变形场的长期监测。
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引用次数: 0
Quantifying the Optimal Two-Step Photocuring Protocol for Maximally Reduced Shrinkage Stress during Photopolymerization 量化光聚合过程中最大限度减少收缩应力的最佳两步光固化方案
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-13 DOI: 10.1007/s11340-025-01193-y
L. Bao, K. Wang, Z. Wang

Background

Shrinkage stress accumulated during photopolymerization significantly impairs the quality and lifespan of photopolymerized materials. Soft-start photocuring protocols like ramp, two-step, and pulse-delay have been proposed to mitigate this issue, among which the two-step protocol has been proved to be the most effective. However, the accuracy and underlying mechanisms of the previously proposed strategy for quantifying the optimal two-step protocol have not been validated.

Objective

In this study, the universality of the strategy for quantifying the optimal two-step photocuring protocol was validated experimentally under varying working conditions, and the mechanism was systematically investigated to correct previous conjectures.

Methods

Shrinkage stress and reaction temperature of typical methacrylate resins during photopolymerization were measured under various working conditions (irradiation intensity, stiffness of constraint, and particle filling content of the testing material) using a standardized cantilever beam instrument.

Results

The optimal first irradiation time and delay time were identified based on the initiation of the stress evolution and the inflection point where shrinkage stress stabilized under the standard protocol, respectively. This optimal protocol resulted in a 20%-40% reduction in the shrinkage stress across all the working conditions tested with the shortest total curing duration. The stress reduction can be attributed to delayed gelation and a lower peak temperature change after gelation.

Conclusions

The present study not only validates the broad applicability of the optimal two-step curing protocol for maximally-reduced shrinkage stress, it also uncovers the underlying mechanism that should guide the manufacturing and application of photopolymers for improved service quality and longevity.

光聚合过程中积累的收缩应力会严重影响光聚合材料的质量和使用寿命。为了缓解这一问题,人们提出了一些软启动光固化协议,如斜坡、两步和脉冲延迟,其中两步协议已被证明是最有效的。然而,先前提出的量化最优两步协议的策略的准确性和潜在机制尚未得到验证。目的在不同的工作条件下,通过实验验证两步光固化最佳方案量化策略的通用性,并对其机理进行系统的探讨,以纠正以往的猜想。方法采用标准悬臂梁式测量仪,测量了典型甲基丙烯酸酯树脂在不同工作条件下(辐照强度、约束刚度和测试材料颗粒填充量)光聚合过程中的收缩应力和反应温度。结果根据应力演化起始点和标准方案下收缩应力稳定拐点确定了最佳的首次辐照时间和延迟时间。在最短的总固化时间内,在所有测试的工作条件下,这种最佳方案使收缩应力降低了20%-40%。应力的减小可归因于胶凝延迟和胶凝后温度变化峰值的降低。结论本研究不仅验证了最佳两步固化方案在最大限度地降低收缩应力方面的广泛适用性,而且揭示了指导光聚合物制造和应用以提高使用质量和寿命的潜在机制。
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引用次数: 0
Characterization of Polymerization Shrinkage Behavior in Photocurable Resins Using Digital Image Correlation 利用数字图像相关技术表征光固化树脂的聚合收缩行为
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-13 DOI: 10.1007/s11340-025-01191-0
Q. Lin, X. Zhang, X. Sun, B. Zhang, W. Liu, Y. Wu, Y. Huang, J. Zhu, N. Zhao, Q. Li

Background

Photocurable resins are widely used in industrial production, but the polymerization shrinkage that occurs during their curing process generates adverse polymerization shrinkage stresses within the material and at the interface between the material and the substrate, which can affect the performance of the photocurable resin material.

Objective

Measuring the polymerization shrinkage and the associated shrinkage stress not only allows for the evaluation of the material’s performance but also helps to research and develop the photocurable resin. Furthermore, it could help to analyze the failure mechanisms of the service process of the resin and enables the active control of polymerization shrinkage stress.

Methods

We employ Digital Image Correlation to actively measure the polymerization shrinkage of photocurable resins. Basing on the experimental results, multi-physics simulation analysis was conducted, successfully establishing a curing model for photocurable resins.

Results

The measurement results indicate that increasing the amount of photoinitiator reduces polymerization shrinkage stress, changes in ultraviolet light incident energy do not significantly affect the polymerization shrinkage stress. For simulation’s results, the maximum error in stress–strain comparison between the simulation model and the experimental model is no more than 10%, with the minimum error being 2.7%, confirming the accuracy of the simulation model.

Conclusion

The contactless characterization technique successfully measures polymer shrinkage strain and the simulation’s curing model for photocurable resins shows high agreement of experiment, which provides insights for the experimental design and theoretical study of shrinkage stress in photocurable resins. It offers some reference for the design of photocurable resin used in electronic packaging.

背景光固化树脂广泛应用于工业生产,但其固化过程中发生的聚合收缩会在材料内部和材料与基材界面处产生不良的聚合收缩应力,从而影响光固化树脂材料的性能。目的测定聚合收缩率及其相关的收缩应力,不仅可以评价材料的性能,而且有助于光固化树脂的研究和开发。进一步分析了树脂在使用过程中的失效机理,实现了对聚合收缩应力的主动控制。方法采用数字图像相关技术主动测量光固化树脂的聚合收缩率。在实验结果的基础上,进行了多物理场模拟分析,成功建立了光固化树脂的固化模型。结果光引发剂用量的增加可降低聚合收缩应力,紫外光入射能量的变化对聚合收缩应力影响不显著。仿真结果表明,仿真模型与实验模型的应力应变对比最大误差不大于10%,最小误差为2.7%,验证了仿真模型的准确性。结论采用非接触式表征技术成功地测量了聚合物的收缩应变,所建立的光固化树脂的模拟固化模型具有较高的实验一致性,为光固化树脂收缩应力的实验设计和理论研究提供了参考。为电子封装用光固化树脂的设计提供参考。
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引用次数: 0
Acoustic Emission Behavior of Carbon Fiber Bundle Under Tensile Load 拉伸载荷下碳纤维束的声发射特性
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-13 DOI: 10.1007/s11340-025-01192-z
Z. Yang, G. Fang

Background

Acoustic emission (AE) is widely used to study the progressive damage of composite materials. Traditionally, the AE method focuses on assessing structural damage by experimentally testing AE signals. However, the application of mechanical methods to theoretically predict AE signals during the progressive damage process of dry fiber bundles has been limited.

Objective

The primary objective of this study is to establish a theoretical method for predicting AE signals during the tensile fracture process of dry fiber bundles.

Methods

This model comprises three key components: (1) Single Fiber Fracture Dynamics Model: This component analyzes the motion of the fracture cross-section at the moment of fiber breakage. (2) Point Sound Source Model: Utilizing the motion of fiber cross-sections as a source, this model analyzes the acoustic signals generated during one single fiber fractures. (3) Monte Carlo Model: This model simulates the progressive fracture of the dry fiber bundle by aggregating the AE signals from individual fiber fractures. It generates a comprehensive time-domain signal profile by summing the contributions from each fracture event.

Results

To validate the model's effectiveness and accuracy, a comparison was made with existing prediction models and available experimental data. The experimental results were found to be in good agreement with the theoretical predictions.

Conclusion

This theoretical model has been thoroughly validated and can be applied to analyze AE signals in other brittle dry fiber bundles, providing valuable insights into their fracture behaviors.

背景声发射(AE)被广泛用于研究复合材料的渐进损伤。传统的声发射方法侧重于通过实验测试声发射信号来评估结构损伤。然而,利用力学方法对干纤维束渐进损伤过程中的声发射信号进行理论预测还存在一定的局限性。目的建立一种预测干纤维束拉伸断裂过程声发射信号的理论方法。方法该模型由三个关键部分组成:(1)单纤维断裂动力学模型:该模型分析纤维断裂时刻断裂截面的运动。(2)点声源模型:该模型以纤维截面运动为源,分析单个纤维断裂时产生的声信号。(3)蒙特卡罗模型(Monte Carlo Model):该模型通过汇总来自单个纤维断裂的声发射信号来模拟干纤维束的渐进断裂。它通过汇总每个裂缝事件的贡献来生成一个全面的时域信号剖面。结果为了验证模型的有效性和准确性,将模型与已有的预测模型和实验数据进行了比较。实验结果与理论预测相吻合。结论该理论模型已得到充分验证,可用于分析其他脆性干纤维束的声发射信号,为其断裂行为提供有价值的见解。
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引用次数: 0
Thermal Expansion Coefficient Measurement of Stack Structure of REBCO Coated Conductors By Strain Gages At Cryogenic Temperatures 低温下应变片测量REBCO涂层导体堆叠结构的热膨胀系数
IF 2.4 3区 工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING Pub Date : 2025-05-09 DOI: 10.1007/s11340-025-01187-w
C. Liu, C. Ma, Y. Shi, J. Zhou

Background

The structures of stack REBa2Cu3O7-x (RE: rare earth elements) coated conductors (CCs), with epoxy impregnated, are commonly involved in superconducting cables and pancake magnet coils. Thermal stresses are inevitable in the stack structures because of the mismatch of coefficient of thermal expansion (CTE) between the CCs and epoxy at cryogenic temperatures.

Objective

It is essential to precisely measure the thermal deformation of the stack structure such that to determine the corresponding CTE. Here, a protocol for determine the CTE by strain gages was reported.

Methods

Copper was used as a standard reference material, and its cryogenic thermal expansion curve was determined by the digital image correlation method. This curve was then used to correct the thermal deformation curves of the testing samples, eliminating the heat output of the strain gage itself.

Results

Thermal deformation of an aluminum beam has been measured with a relative error of less than 5% compared to that from the National Institute of Standards and Technology of the United States. The maximum thermal deformation of the stack sample along the thickness direction was almost 4.5 times of those along other two orthogonal directions.

Conclusions

The approach presented was validated by the aluminum test, CTE for stack structure along the thickness direction was found to be larger than those along other two orthogonal directions.

REBa2Cu3O7-x (REBa2Cu3O7-x, RE: rare earth elements)涂层导体(CCs)是一种环氧浸渍的叠层结构,通常用于超导电缆和烙饼磁体线圈中。低温下,碳纤维与环氧树脂之间的热膨胀系数(CTE)不匹配,导致叠层结构不可避免地存在热应力。目的精确测量叠层结构的热变形,以确定相应的CTE。本文报道了一种用应变片测定CTE的方法。方法以scopper为标准对照品,采用数字图像相关法测定其低温热膨胀曲线。然后使用该曲线来校正测试样品的热变形曲线,消除应变片本身的热输出。结果铝梁的热变形测量结果与美国国家标准与技术研究院的测量结果相对误差小于5%。叠层试样沿厚度方向的最大热变形几乎是沿其他两个正交方向的4.5倍。结论该方法得到了铝材试验的验证,叠层结构沿厚度方向的CTE值大于其他两个正交方向。
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引用次数: 0
期刊
Experimental Mechanics
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