Experimental Mechanics最新文献

A Note of Gratitude from the Editor-in-Chief 主编的感谢信

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-10-10 DOI: 10.1007/s11340-024-01121-6

A. Zehnder

引用次数: 0

On the Cover: Accounting for Localized Deformation: A Simple Computation of True Stress in Micropillar Compression Experiments 封面考虑局部变形：微柱压缩实验中真实应力的简单计算

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-10-08 DOI: 10.1007/s11340-024-01120-7

引用次数: 0

Dynamic Magneto-Mechanical Analysis of Isotropic and Anisotropic Magneto-Active Elastomers 各向同性和各向异性磁活性弹性体的动态磁力学分析

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-26 DOI: 10.1007/s11340-024-01115-4

C.D. Pierce, N.J. Salim, K.H. Matlack

Background

Magneto-active elastomers (MAEs) are soft composite materials comprising ferromagnetic particles in an elastomer matrix which exhibit a magnetically-induced effective modulus change. The change in modulus has been experimentally studied in many MAE formulations using several techniques; however, this makes comparisons between studies difficult, and there lacks a comprehensive study on the dynamic magneto-mechanical properties of MAEs.

Objective

In this article, we seek to understand the effect of mechanical loading direction and magnetic field orientation on the dynamic magneto-mechanical response of isotropic and anisotropic MAEs.

Methods

We develop a new apparatus to perform dynamic mechanical analysis of MAEs at frequencies up to 600Hz subject to magnetic fields of varying strength. We measure the magnetically-induced modulus change in MAEs prepared from a single elastomer-particle combination and specimen geometry, systematically varying the anisotropy direction relative to the magnetic field.

Results

Our results show that isotropic MAEs are up to three times stiffer and anisotropic MAEs up to 65 times stiffer than pure elastomer. Of all configurations studied, the longitudinal modulus of anisotropic MAEs exhibits the largest absolute magnetically-induced change while the transverse modulus exhibits the largest relative change. The magnetically-induced change in loss factor depends on anisotropy and loading condition: isotropic MAEs have no change in loss factor while anisotropic MAEs become less lossy at low strain amplitudes but more lossy at high strain amplitudes.

Conclusions

These results provide new insights into the fundamental mechanisms by which microstructure and magnetic field interact to affect the MAE effective properties.

背景磁活性弹性体（MAE）是一种软复合材料，由弹性体基体中的铁磁性颗粒组成，表现出磁诱导的有效模量变化。本文试图了解机械加载方向和磁场方向对各向同性和各向异性 MAE 动态磁力学响应的影响。方法我们开发了一种新仪器，可在频率高达 600Hz 的不同强度磁场中对 MAE 进行动态力学分析。我们测量了由单一弹性体-粒子组合和试样几何形状制备而成的 MAE 在磁力作用下的模量变化，系统地改变了相对于磁场的各向异性方向。结果我们的结果表明，各向同性 MAE 的刚度是纯弹性体的 3 倍，各向异性 MAE 的刚度是纯弹性体的 65 倍。在研究的所有结构中，各向异性 MAE 的纵向模量表现出最大的绝对磁诱导变化，而横向模量则表现出最大的相对变化。磁引起的损耗因子变化取决于各向异性和加载条件：各向同性 MAE 的损耗因子没有变化，而各向异性 MAE 在低应变振幅时损耗较小，但在高应变振幅时损耗较大。

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引用次数: 0

Measurement of the Tension Loss in a Cable Traveling Over a Pulley, for Low-Speed Applications 测量电缆在滑轮上移动时的张力损失，用于低速应用

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-20 DOI: 10.1007/s11340-024-01097-3

P. Máté, A. Szekrényes

Background

Wire ropes or cables are widely used solutions for force transmission in several industrial applications. Their hysteretic behavior may significantly influence control accuracy or the force transmission’s efficiency. Cables traveling through sheaves can suffer a relatively high tension loss, which this article addresses.

Objective

This paper aims to present a simple measurement method for the tension loss in cables traveling over sheaves on bearings.

Methods

The presented measurement method uses a cable-pulley system with a spring installed at one cable end. The pulley is moved in a zig-zag pattern. The force is measured on both cable ends; this way, the tension loss can be determined as a function of the cable tension. The force was measured with S-type load cells, which are highly sensitive to off-axis loads; this problem can be overcome by proving that the force measurement has a proportional error, which can be eliminated from the frictional coefficient. The measurements are compared to two models from the literature; one approximates the power loss of a cable drive by calculating the work of the cable’s inner friction, and the other is a cable bending model, which is used to determine the hysteretic energy of the cyclic bending.

Results

The result of the measurement evaluation is a coefficient of tension loss that contains the loss coming from the cable bending and the bearing friction. Four cable types and a steel strip with negligible bending hysteresis were measured, the latter for control measurement. It is demonstrated that a significant part of the tension loss originates from the inner friction of the cable and that it is equal to the hysteretic energy of the cyclic bending.

Conclusion

The presented method provides a robust measurement for the tension loss factor in cables traveling over pulleys. It is proven that the off-axis loads cause a proportional error in the force measured by S-type load cells, and this measurement error can be eliminated from the tension loss factor. The results demonstrated that the presented models can be used to predict the tension loss in cables traveling over sheaves.

背景钢丝绳或电缆是多种工业应用中广泛使用的力传递解决方案。它们的滞后行为可能会严重影响控制精度或力传输效率。本文旨在介绍一种简单的测量方法，用于测量通过轴承上的滑轮的电缆的张力损失。滑轮以之字形模式移动。测量电缆两端的力；这样就可以根据电缆张力的函数确定张力损失。力是用 S 型称重传感器测量的，这种传感器对偏轴载荷非常敏感；通过证明力的测量有一个比例误差，就可以克服这个问题，这个误差可以从摩擦系数中消除。测量结果与文献中的两个模型进行了比较：一个是通过计算电缆内部摩擦力的功来近似计算电缆驱动的功率损耗，另一个是电缆弯曲模型，用于确定循环弯曲的滞后能量。测量了四种类型的电缆和弯曲滞后可忽略不计的钢带，后者用于控制测量。结果表明，拉力损失的很大一部分来自于电缆内部摩擦，并且与循环弯曲的滞后能量相等。事实证明，离轴载荷会导致 S 型称重传感器测量的力出现比例误差，而这种测量误差可以从张力损失因子中消除。结果表明，所提出的模型可用于预测滑轮上电缆的张力损失。

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引用次数: 0

Biomechanical Hand Model: Modeling and Simulating the Lateral Pinch Movement 手部生物力学模型：建模和模拟侧捏运动

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-19 DOI: 10.1007/s11340-024-01109-2

A.F. Lemos, L. A. Rodrigues da Silva, B. V. Nagy, P. N. Barroso, C. B. S. Vimieiro

Background

Hand movements are crucial in daily activities, sparking extensive interest and research in biomechanical models. While existing models offer valuable insights, their complexity and processing costs may limit their suitability for all applications, sometimes impeding research efficiency.

Objectives

This study aimed to develop a biomechanical model of the human hand for analyzing the physiology of lateral pinch movement. Unlike conventional methodologies, this approach focuses on delivering a computationally efficient model while incorporating the trapeziometacarpal joint into the analysis.

Methods

The model, which operates in a multibody environment, simulates lateral pinching movement by applying external time-varying torques to digit joints, emulating musculature, tendons, and ligaments. Torque estimation was achieved through the Euler-Lagrange approach. The model generates animated representations of the movement, aiding pathology identification and outputting dynamic variables. The model’s was validated through data acquired from asymptomatic subjects via an OptiTrack system.

Results

The average disparity between the expected and obtained joint angular displacements was (varvec{6.06~%}) and (varvec{1.90~%}) during validation and verification stages, suggesting high fidelity in the model performance. Correlation analysis revealed strong positive linear relationships and robust correlations between the obtained and expected configuration data. Model-generated pinch postures closely resembled expected physiological patterns, with results falling within the range for asymptomatic individuals documented in the scientific literature.

Conclusion

The system efficiently analyzes dynamic variables at a low computational cost, offering animated representations for pathology identification. The model’s potential for rehabilitation solutions and adaptability, coupled with its accuracy and versatility, make it an asset for advancing hand biomechanics research.

背景手部运动在日常活动中至关重要，因此引发了对生物力学模型的广泛兴趣和研究。虽然现有模型能提供有价值的见解，但其复杂性和处理成本可能会限制其在所有应用中的适用性，有时还会妨碍研究效率。方法该模型在多体环境中运行，通过向数字关节施加外部时变扭矩来模拟侧捏运动，同时模拟肌肉组织、肌腱和韧带。扭矩估计通过欧拉-拉格朗日方法实现。该模型可生成运动的动画表示，帮助病理识别并输出动态变量。结果在验证和确认阶段，预期关节角位移与获得关节角位移之间的平均差距为（varvec{6.06~%}）和（varvec{1.90~%}），这表明模型的性能具有很高的保真度。相关性分析表明，获得的配置数据与预期的配置数据之间具有很强的正线性关系和稳健的相关性。模型生成的捏合姿势与预期的生理模式非常相似，其结果在科学文献记载的无症状个体范围内。该模型具有潜在的康复解决方案和适应性，再加上其准确性和多功能性，使其成为推动手部生物力学研究的重要资产。

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引用次数: 0

Size Effects in Strength and Strain Hardening Behavior of Single-Crystal 7075 Aluminum Alloy Micropillars 单晶 7075 铝合金微柱强度和应变硬化行为的尺寸效应

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-18 DOI: 10.1007/s11340-024-01112-7

H. Li, D. Zhao, Y. Cui, C. Dan, S. Ma, L. Wang, J. Liu, Y. Li, Z. Chen, H. Wang

Background

The size effect and deformation instability exhibited by materials at the micro- and nano-scale constrain the development and application of miniaturized devices. Introducing different defects in materials through different technical means to improve the deformation stability of materials has been the main research point of micro- and nano mechanics.

Objective

This paper presents a novel strategy to completely eliminate the instability of microscopic deformations by the introduction of high-density precipitates in aluminum alloys by means of suitable heat treatment.

Methods

A suitable heat treatment is used to introduce a high density of precipitates in the 7075 aluminum alloy. Using the Focused Ion Beam technique and in situ micropillar compression tests, micron-sized single-crystal micropillars were fabricated and the size dependence of the strength and strain-hardening behavior of 7075 aluminum alloy was systematically analyzed.

Results

Compared with precipitate-free Al–Mg alloy micropillars, the micropillars fabricated from 7075 aluminum alloy exhibited more stable deformation behavior, predominantly due to the impediment of dislocation motion by precipitates. The power-law exponent for yield strength relative to pillar size was determined to approach a near-zero value, indicating a negligible dependency of yield strength on specimen size. Similarly, the smaller the size of micropillar, the higher the hardening rate, which can be rationalized by exhaustion hardening.

Conclusions

The proposed method can eliminate the size effect of materials with pillar size above 0.5 μm and leads to a stabilization in deformation behavior. These are advantageous for the application of micro- and nano-sized components in advanced engineering systems.

背景材料在微米和纳米尺度上表现出的尺寸效应和变形不稳定性制约着微型器件的开发和应用。通过不同的技术手段在材料中引入不同的缺陷以提高材料的变形稳定性一直是微米和纳米力学的研究重点。本文提出了一种新颖的策略，即通过合适的热处理在铝合金中引入高密度析出物来彻底消除微观变形的不稳定性。结果与不含析出物的铝镁合金微柱相比，用 7075 铝合金制造的微柱表现出更稳定的变形行为，这主要是由于析出物阻碍了位错运动。屈服强度与微柱尺寸的幂律指数接近零值，表明屈服强度与试样尺寸的关系可以忽略不计。同样，微柱尺寸越小，硬化率越高，这可以用衰竭硬化来解释。结论所提出的方法可以消除柱尺寸大于 0.5 μm 的材料的尺寸效应，并使变形行为趋于稳定。这些都有利于在先进工程系统中应用微米级和纳米级部件。

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引用次数: 0

Validation of Hole-Drilling Residual Stress Measurements in Workpieces of Various Thickness 不同厚度工件的钻孔残余应力测量验证

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-17 DOI: 10.1007/s11340-024-01107-4

M. C. Lakey, M. R. Hill

Background

A recent revision to the ASTM E837 standard for near-surface residual stress measurement by the hole-drilling method describes a new thickness-dependent stress calculation procedure applicable to “thin” and “intermediate” workpieces for which strain versus depth response depends on workpiece thickness. This new calculation procedure differs from that of the prior standard, which applies only to thick workpieces with strain versus depth response independent of thickness.

Objective

Herein we assess the new calculation procedures by performing hole-drilling residual stress measurements in samples with a range of thickness.

Methods

Near-surface residual stress is measured in a thick aluminum plate containing near-surface residual stress from a uniform shot peening treatment, and in samples of different thickness removed from the plate at the peened surface. A finite element (FE) model is used to assess consistency between measured residual stress across the range of sample thickness.

Results

Measured residual stress varies with sample thickness, with thinner samples exhibiting smaller near-surface compressive stress and a larger gradient of subsurface stress. These trends are consistent with both observed bending (curvature) of the removed samples and the trend in FE-calculated expected residual stress. The measured and expected residual stresses are in good agreement for samples of intermediate thickness, but the agreement decreases with sample thickness. Measured residual stress is invariant with gage circle diameter.

Conclusion

The new thickness-dependent stress calculation procedure for hole-drilling provides meaningful improvement compared to thick-workpiece calculations.

背景最近对 ASTM E837 钻孔法近表面残余应力测量标准进行了修订，新的厚度应力计算程序适用于 "薄 "和 "中等 "工件，其应变与深度响应取决于工件厚度。这种新的计算程序不同于先前的标准，后者仅适用于应变与深度响应与厚度无关的厚工件。方法在一块厚铝板上测量近表面残余应力，该铝板含有均匀喷丸强化处理产生的近表面残余应力，并在强化表面测量从铝板上取下的不同厚度的样品。结果测量到的残余应力随样品厚度的变化而变化，较薄的样品表现出较小的近表面压应力和较大的次表面应力梯度。这些趋势与观察到的被移除样品的弯曲（曲率）和 FE 计算的预期残余应力趋势一致。对于中等厚度的样品，测量的残余应力和预期的残余应力非常一致，但随着样品厚度的增加，两者的一致程度降低。测量的残余应力与量具圆直径无关。

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引用次数: 0

Simultaneous Measurement of Fiber-Matrix Interface Debonding and Tunneling Using a Dual-Vision Experimental Setup 使用双视角实验装置同时测量光纤-基质界面脱粘和隧道效应

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-16 DOI: 10.1007/s11340-024-01111-8

K. Z. Uddin, H. Girard, N. B. Mennie, A. Doitrand, B. Koohbor

Background

Fiber-matrix debonding is a precursor for transverse cracking and several other types of damage in fiber composites. However, to date, there are limited experiment-based reports that study the fundamental mechanisms of fiber-matrix debonding.

Objective

This work aims to uncover the governing mechanisms of fiber-matrix interface debonding by full-field measurements supplemented by numerical simulations. In particular, the application of a dual-vision image-based characterization approach on single glass macro fiber samples is discussed and proven useful in understanding the in-plane and out-of-plane debonding characteristics at the fiber-matrix interface.

Methods

Full-field strain and displacement measurements based on digital image correlation are performed on model single-fiber composites. The use of a dual-vision system allows strain measurements in the vicinity of the fiber-matrix interface, also allowing for the identification of critical strain and stress values corresponding to the initiation and propagation of debonding damage. The experimental data are used to calibrate an inverse identification approach that outputs the shape of the debonded interface along the fiber length.

Results

Full-field measurements allow for establishing correlations between local and global strain fields. Observation of debonding propagation along the fiber axis seems to be representative of the crack tunneling during the early stages of the failure process, i.e., when the crack tip is subjected to opening mode only.

Conclusions

Side view measurements are useful as a first-order approximation of the debonding propagation velocity along the fiber axis but fail to provide accurate measurements for the debonding shape, esp. in areas where the crack is under a dominantly shear stress state. This issue can be resolved by full-field measurements coupled with computational simulations.

背景纤维-基体脱粘是纤维复合材料横向开裂和其他几种类型损伤的前兆。然而，迄今为止，基于实验研究纤维-基体脱粘基本机制的报告还很有限。这项工作旨在通过全场测量并辅以数值模拟，揭示纤维-基体界面脱粘的支配机制。特别是讨论了基于双视觉图像的表征方法在单根玻璃纤维样品上的应用，该方法被证明有助于了解纤维-基体界面的面内和面外脱粘特征。方法基于数字图像相关技术对模型单纤维复合材料进行全场应变和位移测量。使用双视觉系统可以测量纤维-基体界面附近的应变，还可以确定与脱粘损伤的开始和传播相对应的临界应变和应力值。实验数据用于校准逆识别方法，该方法可沿纤维长度输出脱粘界面的形状。结果全场测量可建立局部应变场和全局应变场之间的相关性。沿纤维轴线观察到的脱粘传播似乎代表了失效过程早期阶段的裂纹隧道，即裂纹尖端仅受到开裂模式的影响。结论侧视测量可作为沿纤维轴线脱粘传播速度的一阶近似值，但无法提供脱粘形状的精确测量，尤其是在裂纹主要处于剪应力状态的区域。这个问题可以通过全场测量和计算模拟来解决。

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引用次数: 0

An Accurate Strain Gauge Positioning Approach Based on Geometry and Color Features 基于几何和颜色特征的应变计精确定位方法

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-12 DOI: 10.1007/s11340-024-01114-5

C. Zhou, H. Sun, Y. Li, Z. Song, X. Bi, B. Wang

Background

Strain gauges commonly used in structural testing are manually pasted, usually with a 1–4 mm deviation between the actual pasted position and the theoretical position. The deviation leads to measurement errors, which are more pronounced in high strain gradient regions with stiffness discontinuities such as openings, reinforcements, and notches.

Objective

This study aims to obtain the actual pasted position of strain gauges and thus improving the testing measurement accuracy.

Methods

A non-contact strain gauge positioning method is proposed. Firstly, considering that the strain gauges have a regular shape, the irregular borderlines are filtered out based on the geometric features of a borderline image. Secondly, considering that the color of the strain gauge is significantly different from the test piece, and the color features within the borderline are extracted by clustering and compared with the strain gauges to complete the recognition. Finally, based on the epipolar geometry, the matching relationship of the strain gauges in different images is obtained, and the positioning is completed based on binocular vision according to the strain gauge recognition results.

Results

For a simple plate, the average positional error of strain gauges is reduced by 71%. For a small square tube, the average error is reduced by 44%. For a large cylinder, the average error is reduced by 32.4%.

Conclusion

The proposed non-contact strain gauge positioning method can obtain high precision strain gauge positions, which effectively improves the test measurement accuracy.

背景结构测试中常用的应变片都是人工粘贴的，通常实际粘贴位置与理论位置有 1-4 毫米的偏差。本研究旨在获取应变片的实际粘贴位置，从而提高测试测量精度。方法提出了一种非接触式应变片定位方法。首先，考虑到应变片具有规则的形状，根据边界线图像的几何特征过滤掉不规则的边界线。其次，考虑到应变片的颜色与测试片有明显差异，通过聚类提取边界线内的颜色特征，并与应变片进行比对，完成识别。最后，根据外极几何图形，得到不同图像中应变片的匹配关系，并根据应变片识别结果，基于双目视觉完成定位。对于小型方管，平均误差减少了 44%。结论所提出的非接触式应变片定位方法可获得高精度的应变片位置，从而有效提高测试测量精度。

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引用次数: 0

Size Effect on the Ductile Fracture of the Aluminium Alloy 2024-T351 尺寸对铝合金 2024-T351 韧性断裂的影响

IF 2 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-09-10 DOI: 10.1007/s11340-024-01108-3

F. Šebek, P. Salvet, P. Boháč, R. Adámek, S. Věchet, T. Návrat, J. Zapletal, M. Ganjiani

Background

Reliably calibrated criteria are needed for an accurate prediction of fracture of various components. However, there is not always a sufficient amount of material available. Therefore, miniature testing provides an alternative that is researched together with the following calibration of the ductile fracture criteria and investigating the size effect.

Objective

The aim is to design miniature testing equipment and specimens for tensile testing, which covers various stress states. This is supplemented by the small punch test, which has the same specimen thickness, taken from the literature to broaden the portfolio for calibration. The second part deals with conducting the finite element analysis, which provided a basis for the calibration of the phenomenological ductile fracture criterion applicable to crack-free bodies to indicate the crack initiation.

Methods

The steel frame to test thin specimens is designed with optical measurement of deformations. The finite element method is used, within Abaqus and user subroutines, to simulate the tests to obtain the variables needed for the calibration. In addition, the calibration of the criterion using machine learning is explored.

Results

The feasibility of the proposed experimental program is tested on the aluminium alloy 2024-T351. Moreover, the numerical simulations, which showed a good match with experiments in terms of force responses, adds to the knowledge of modelling in the scope of continuum damage mechanics.

Conclusions

The presented results provide a material basis for the aluminium alloy studied on a lower scale, while they broaden the testing possibilities and analyses the calibration strategies for the best failure predictability possible.

背景为了准确预测各种部件的断裂情况，需要有可靠的校准标准。然而，并不总是有足够数量的材料可用。因此，微型试验提供了一种替代方法，我们将在校准韧性断裂标准和研究尺寸效应的同时对其进行研究。目的设计用于拉伸试验的微型试验设备和试样，涵盖各种应力状态。此外，还从文献中提取了具有相同试样厚度的小型冲压试验作为补充，以扩大校准组合。第二部分是进行有限元分析，为校准适用于无裂纹体的现象学韧性断裂准则提供依据，以指示裂纹的起始。在 Abaqus 和用户子程序中使用有限元法模拟试验，以获得校准所需的变量。此外，还探讨了使用机器学习对标准进行校准的问题。结果在铝合金 2024-T351 上测试了拟议实验程序的可行性。此外，数值模拟在力响应方面与实验显示出良好的匹配性，为连续损伤力学范围内的建模知识提供了补充。

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引用次数: 0