Experimental Mechanics最新文献

X-Ray Digital Image Correlation: A Reliable Method for Deformation Measurement at 1000 °C X 射线数字图像相关性：1000 °C 下变形测量的可靠方法

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-07-02 DOI: 10.1007/s11340-024-01094-6

G. Niu, R. Zhu, Y. Li, Z. Qu, H. Lei, P. Wang, H. Yang

Background

Digital image correlation (DIC) is widely used as a noncontact optical deformation measurement method. However, optical DIC encounters difficulties when measuring displacement and strain at high temperatures, including false deformation caused by heat haze and image overexposure caused by intense thermal radiation. X-ray imaging is not affected by these factors, so the combination of X-ray imaging and the DIC algorithm (X-DIC) holds the potential for measuring deformation during high-temperature tests.

Objective

This study investigated the ability of X-DIC to measure deformation in high-temperature experiments, expand the applicable temperature range of X-DIC, and provide a reliable method for obtaining deformation measurements in high-temperature experiments.

Methods

A combination of X-ray digital radiography (DR) images and the DIC algorithm was used to measure deformation. Numerical experiments based on synthetic images were used to evaluate the measurement accuracy of X-DIC, and the influence of different DIC parameters on the measurement error was discussed. Ductile iron and C/SiC composites were subjected to tensile tests at different temperatures from ambient temperature to 1000 °C, and different deformation measurement methods were used to simultaneously measure the deformation of the samples to verify the accuracy of the X-DIC results.

Results

In the numerical experiments, the displacement measurement error of X-DIC is less than 0.02 px. The relative error between the X-DIC and blue-light DIC measurements of the tensile deformation of ductile iron at 500 °C is 0.65%. When the deformation of the C/SiC composite materials was measured at 1000 °C, the root mean square error (RMSE) of the strain data obtained by X-DIC and optical DIC was 1.12 × 10^–4.

Conclusions

These results prove that X-DIC has high measurement accuracy. Compared with optical DIC, X-DIC is insensitive to high-temperature environments and provides alternative experimental methods for high-temperature deformation measurements.

背景数字图像相关（DIC）作为一种非接触式光学变形测量方法被广泛使用。然而，光学 DIC 在测量高温下的位移和应变时会遇到一些困难，包括热雾造成的假变形和强热辐射造成的图像过度曝光。X 射线成像不受这些因素的影响，因此 X 射线成像和 DIC 算法（X-DIC）的结合有望测量高温试验中的变形。基于合成图像的数值实验用于评估 X-DIC 的测量精度，并讨论了不同 DIC 参数对测量误差的影响。对球墨铸铁和 C/SiC 复合材料进行了从环境温度到 1000 ℃ 的不同温度下的拉伸试验，并采用不同的形变测量方法同时测量样品的形变，以验证 X-DIC 结果的准确性。X-DIC 和蓝光 DIC 测量 500 °C 下球墨铸铁拉伸变形的相对误差为 0.65%。在 1000 ℃ 下测量 C/SiC 复合材料的变形时，X-DIC 和光学 DIC 获得的应变数据的均方根误差为 1.12 × 10-4。与光学 DIC 相比，X-DIC 对高温环境不敏感，为高温变形测量提供了替代实验方法。

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引用次数: 0

Strain Determination Using a Global Interpolation Concept Based on Coherence Scanning Interferometry Measurements 利用基于相干扫描干涉测量的全局插值概念进行应变测定

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-07-02 DOI: 10.1007/s11340-024-01084-8

L. Müller-Lohse, S. Hartmann, A. Richter, C. Rembe

Background

The experimental detection of small and large strains requires special approaches of full-field measurement techniques and their evaluation on 3D curved surfaces of components.

Objectives

Since classical digital image correlation methods have difficulties with the application of paints in some applications, one aim is to use a method in which the surface roughness is used to apply the strain calculation.

Methods

In this paper, 2D digital image correlation is applied to 2D intensity maps extracted from a coherence scanning interferometer together with height information. Height information are used to reconstruct the 3D motion of tracked material points. Surface interpolation and strain calculation are performed using globally formulated radial basis functions.

Results

The entire procedure leads to an appropriate technique for determining the in-plane strains in curved surfaces of parts, whereas the expected accuracy for various levels of the radial basis functions are discussed in detail.

Conclusions

Particularly, coherence scanning interferometry yields highly accurate height information. To smooth the surface motion, it turns out that in particular a regression analysis is required, where we apply radial basis functions with various approximation levels. This is an alternative procedure for surface strain determination.

背景小应变和大应变的实验检测需要全场测量技术的特殊方法，以及在部件的三维曲面上对其进行评估。方法本文将二维数字图像相关技术应用于从相干扫描干涉仪提取的二维强度图以及高度信息。高度信息用于重建被跟踪材料点的三维运动。结果整个过程为确定零件曲面的面内应变提供了一种适当的技术，同时详细讨论了不同径向基函数水平的预期精度。为了平滑表面运动，我们特别需要进行回归分析，在回归分析中，我们应用了具有不同近似等级的径向基函数。这是确定表面应变的另一种方法。

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引用次数: 0

Oil-Pressure Based Apparatus for In-Situ High-Energy Synchrotron X-Ray Diffraction Studies During Biaxial Deformation 基于油压的双轴变形过程中原位高能同步辐射 X 射线衍射研究装置

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-07-02 DOI: 10.1007/s11340-024-01092-8

R.R. Kamath, J. Thomas, A.C. Chuang, B. Barua, J.-S. Park, L. Xiong, T.R. Watkins, S.S. Babu, G. Cola, D. Singh

Background

Understanding biaxial loading response at the microstructural level is crucial in helping better design sheet manufacturing processes and calibrate/validate material deformation models.

Objective

The objective of this work was to develop a low-cost testing apparatus to probe, with sufficient spatial resolution, the micro-mechanical response of a sheet material in-situ under biaxial loading conditions.

Methods

The testing apparatus fabricated as a part of this study operates in a similar fashion to a standard bulge test and uses oil pressure to generate biaxial loading conditions. This biaxial testing apparatus was operated within a synchrotron beamline to characterize the mechanical response of a flash-processed steel sheet using in-situ high-energy X-ray diffraction (XRD) measurements. The GSAS-II package was utilized to develop a workflow for the analysis of the large volume of diffraction data acquired. The workflow was then used to extract the peak position, width, and integrated intensity of the XRD peaks corresponding to the major body-centered cubic phase.

Results

The equi-biaxial nature of the loading in the measured area was independently corroborated using experimental (XRD) and simulation (finite element analysis) methods. Furthermore, we discuss the evolution of elastic strain in the major body-centered cubic phase as a function of applied oil pressure and location on the steel sheet.

Conclusions

A key advantage of the biaxial apparatus fabricated in this synchrotron study is demonstrated using the results obtained for the flash-processed steel sheet – i.e., mapping the lattice plane-dependent response to biaxial loading for a relatively large sample area in a spatially resolved manner.

背景了解微观结构层面的双轴加载响应对于帮助更好地设计钢板制造工艺和校准/验证材料变形模型至关重要。方法作为本研究一部分而制造的测试设备的操作方式与标准隆起测试类似，使用油压产生双轴加载条件。该双轴测试设备在同步辐射光束线内运行，利用原位高能 X 射线衍射 (XRD) 测量表征闪速加工钢板的机械响应。利用 GSAS-II 软件包开发了一个工作流程，用于分析获取的大量衍射数据。然后利用该工作流程提取了与主要体心立方相相对应的 XRD 峰的峰位、宽度和综合强度。此外，我们还讨论了主要体心立方相的弹性应变随施加的油压和钢板上的位置而变化的情况。结论同步辐射研究中制造的双轴仪器的一个关键优势是利用闪速加工钢板获得的结果来证明的，即以空间分辨的方式绘制出相对较大的样品面积上与晶格平面相关的双轴加载响应图。

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引用次数: 0

Determining Residual Stress Using Indentation and Surface Displacement Measurement 利用压痕和表面位移测量确定残余应力

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-06-27 DOI: 10.1007/s11340-024-01090-w

S. Vaidyanathan, G. S. Schajer

Background

Residual stresses exist in many manufactured materials and must be measured and taken into account for safe structural design. Established residual stress measurement methods are either destructive or require substantial material-dependent calibration.

Objective

The present work is aimed at developing an indentation-based method for measuring residual stress that causes minimal specimen damage, does not require a stress-free reference specimen, and has the capability to identify both the size and direction of the surface residual stresses. In this initial study, the simpler case of equi-biaxial stresses is addressed in preparation for subsequent general stress evaluations.

Methods

The surface displacements around an indentation made by a conical indenter are measured using digital image correlation. The residual stresses are then identified by comparison to the results of a finite model of the indentation process.

Results

The proposed method is shown to 2–5 times more sensitive to the presence of residual stresses than other commonly used indentation methods, particularly for materials with low Hollomon exponent n. In example measurements, axi-symmetric residual stresses were determined within 8% of the material yield stress.

Conclusions

The initial study presented here successfully considered the equal-biaxial stress case. The proposed method is attractive for future development because it gives directional information and therefore can be extended to the general non-equal-biaxial case.

背景许多人造材料中都存在残余应力，必须对其进行测量并将其纳入安全结构设计的考虑范围。本研究旨在开发一种基于压痕的残余应力测量方法，该方法对试样的破坏极小，不需要无应力参考试样，并且能够识别表面残余应力的大小和方向。在这项初步研究中，我们将处理较简单的等轴向应力情况，为后续的一般应力评估做准备。方法使用数字图像相关技术测量锥形压头压痕周围的表面位移。结果表明，与其他常用的压痕方法相比，所提出的方法对残余应力的敏感性提高了 2-5 倍，特别是对于霍洛蒙指数 n 较低的材料。在实例测量中，确定的轴对称残余应力在材料屈服应力的 8% 以内。所提出的方法提供了方向信息，因此可以扩展到一般的非等轴情况，因此对未来的发展很有吸引力。

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引用次数: 0

Thermal Stress Analysis for Functionally Graded Plates with Modulus Gradation, Part II 模量分级功能分级板的热应力分析，第二部分

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-06-27 DOI: 10.1007/s11340-024-01091-9

T. Baytak, M. Tosun, C. Ipek, C. Mollamahmutoglu, O. Bulut

Background

The gradation of thermal expansion coefficient was analyzed in the earlier study. The analytical formulation derived here, which is quite different, should be validated to understand the thermal stress distribution in a laminated composite and functionally graded material. Besides this solution, a validated numerical model can also be used to optimize the material gradation of plates in terms of sustainability.

Objective

To validate the analytical formulation derived here, an experimental model is presented to understand the thermal stress concentration for functionally graded and laminated composite plates. A numerical model is also validated to extend to understand the effects of the number of layers, the thickness of a layer, the gradation function, the ratio of elastic moduli, and the coating.

Methods

The experimental problems in the production of the experimental models with layers of different elastic moduli are discussed here. In the experimental analysis, a three-dimensional photoelastic stress analysis of two- and four-layer composite plate was used to mechanically model the thermal expansion. The analytical solution for the thermal stress in a free plate was derived by the strain suppression method based on the principle of superposition. The numerical models were analyzed using finite element software. The step variation in the experiment was used as a reference point for a continuous or multi-layer (> 2) step variation of material coefficients in the models.

Results

The variation of stress concentration is shown for various cases of laminated and continuous gradations of elastic modulus. The four-layer experimental model provides the difference in thermal stress distribution as a result of a layered coating. The validated analytical and numerical models provide reasonable results. An empirical formula to optimize the material gradation in terms of elastic modulus is derived.

Conclusions

The experimental model can be used to analyze thermal stress in functionally graded materials. The gradations of the material in the plate or the coating of the plates can be optimized by the validated analytical and numerical models. The empirical formula can be used to determine the elastic modulus of the coating to minimize the stress concentration.

背景早先的研究分析了热膨胀系数的分级。本文得出的分析公式与之大相径庭，应加以验证，以了解层压复合材料和功能分级材料中的热应力分布。为了验证本文得出的分析公式，本文提出了一个实验模型，以了解功能分级和层压复合板的热应力集中情况。同时还验证了一个数值模型，以扩展了解层数、层厚、分级函数、弹性模量比和涂层的影响。方法这里讨论了在制作具有不同弹性模量层的实验模型时遇到的实验问题。在实验分析中，使用了二层和四层复合板的三维光弹性应力分析来建立热膨胀的力学模型。自由板中热应力的解析解是通过基于叠加原理的应变抑制法得出的。数值模型使用有限元软件进行分析。实验中的阶跃变化被用作模型中材料系数连续或多层（> 2）阶跃变化的参考点。四层实验模型提供了分层涂层导致的热应力分布差异。经过验证的分析和数值模型提供了合理的结果。结论实验模型可用于分析功能分级材料中的热应力。通过验证分析和数值模型，可以优化板材或板材涂层中的材料级配。经验公式可用于确定涂层的弹性模量，以尽量减少应力集中。

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引用次数: 0

User-Independent, Accurate and Pixel-Wise DIC Measurements with a Task-Optimized Neural Network 利用任务优化神经网络进行与用户无关、精确且像素化的 DIC 测量

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-06-26 DOI: 10.1007/s11340-024-01088-4

B. Pan, Y. Liu

Background

Being an image-based optical technique for full-field deformation measurements, the ultimate purpose of digital image correlation (DIC) is to realize accurate, precise and pixel-wise displacement/strain measurements in a full-automatic manner without users’ inputs.

Objective

In this work, we propose a task-optimized neural network, called RAFT-DIC, to achieve user-independent, accurate and pixel-wise displacement field measurements.

Methods

RAFT-DIC is based on the state-of-the-art optical flow architecture: Recurrent All-Pairs Field Transforms (RAFT). We make two targeted improvements that fundamentally enhanced its measurement accuracy and generalization performance. Firstly, we remove all the down-sampling operations in the encode module to improve the perception of spatial information, and reduce the number of pyramid levels of the correlation layer to increase the small displacement accuracy. By building the correlation layer to compute the similarity of pixel pairs, and iteratively updating the displacement field through a recurrent unit, RAFT-DIC introduces the prior information of DIC measurement to guide the displacement estimation with high accuracy. Secondly, we develop a novel dataset generation method to synthesize customized speckle patterns and diverse displacement fields, which facilitate the construction of a robust and adaptable dataset to improve the network generalization.

Results

Both simulated and real experimental results demonstrate that the accuracy of the proposed method is approximately an order of magnitude higher than pervious deep learning-based DIC (DL-DIC).

Conclusions

The proposed RAFT-DIC shows higher accuracy as well as stronger practicality and cross-dataset generalization performance over existing DL-DIC methods, and is expected to be a new standard architecture for DL-DIC.

背景作为一种基于图像的全场形变测量光学技术，数字图像相关（DIC）的最终目的是在不需要用户输入的情况下，以全自动的方式实现准确、精确和像素级的位移/应变测量：RAFT-DIC基于最先进的光流架构：递归全对场变换（RAFT）。我们进行了两项有针对性的改进，从根本上提高了测量精度和泛化性能。首先，我们取消了编码模块中的所有下采样操作，以提高空间信息的感知能力；同时减少了相关层的金字塔层数，以提高小位移精度。通过建立相关层来计算像素对的相似度，并通过递归单元迭代更新位移场，RAFT-DIC 引入了 DIC 测量的先验信息来指导高精度的位移估计。其次，我们开发了一种新颖的数据集生成方法，以合成定制的斑点模式和多样化的位移场，从而有助于构建稳健且适应性强的数据集，提高网络的泛化能力。结论与现有的 DL-DIC 方法相比，所提出的 RAFT-DIC 具有更高的精度、更强的实用性和跨数据集泛化性能，有望成为 DL-DIC 的新标准架构。

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引用次数: 0

Research on the Mechanical Properties of Single-Lap Rivet-Bonded Hybrid Joint Considering the Rivet Forming Process 考虑铆钉成型工艺的单圈铆接混合接头力学性能研究

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-06-26 DOI: 10.1007/s11340-024-01093-7

X. Han, L. Z. Ren, X. Xu, L. Ying, C. W. Wu, W. B. Hou

Background

This paper investigates the mechanical properties and failure behaviours of rivet-bonded hybrid joints composed of aluminium adherends and steel rivets under quasi-static tensile loading.

Objective

The damage law of hybrid joints is studied to provide a reference for the design and manufacture of hybrid joints.

Methods

Tensile tests were conducted on aluminium and steel specimens at various triaxial stress levels. The corresponding finite element model (FEM) was developed to verify the Johnson–Cook damage parameters of the studied metals. The hybrid joint considering the rivet forming process was constructed through FE modelling using the Johnson–Cook failure criterion and Cohesive Zone Model (CZM), which was then validated with the experimental results.

Results

Experimental results of the hybrid joint showed that a typical two-stage failure: 1) the adhesive layer bears the majority of the load during the initial loading stage, and 2) the adhesive layer completely fails after reaching the peak load and the rivet solely bears the load subsequently.

Conclusions

The riveting process did not cause damage to the adhesive layer, which ensured the reliability of the manufacturing techniques of the hybrid joint. And the yielding of rivets may buffer the immediate failure of hybrid joints.

背景本文研究了由铝粘合剂和钢铆钉组成的铆接混合接头在准静态拉伸载荷下的机械性能和破坏行为。目的研究混合接头的破坏规律，为混合接头的设计和制造提供参考。开发了相应的有限元模型（FEM），以验证所研究金属的约翰逊-库克损伤参数。通过使用约翰逊-库克破坏准则和内聚区模型（CZM）进行有限元建模，构建了考虑铆钉成型过程的混合接头，并与实验结果进行了验证。结果混合接头的实验结果表明，典型的两阶段失效：1）在初始加载阶段，粘合剂层承受了大部分载荷；2）在达到峰值载荷后，粘合剂层完全失效，铆钉独自承受随后的载荷。铆钉的屈服可缓冲混合接头的直接失效。

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引用次数: 0

Operando Characterizations of Lithium Penetration-Induced Fracture in Solid Electrolytes 固体电解质中锂离子穿透诱发断裂的操作特性分析

IF 2.4 3区工程技术 Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Experimental Mechanics

Pub Date : 2024-06-26 DOI: 10.1007/s11340-024-01085-7

M. Lu, S. Xia

Background

Lithium penetration-induced fracture within solid electrolytes (SEs) is a major issue hindering the commercialization of solid-state lithium-ion batteries (SS-LIBs). Such fracture has been frequently observed during electrochemical plating of lithium (Li)-metal anodes, but its mechanistic origin is still largely unclear.

Objective

We present the first quantitative operando analysis of the fracture characteristics of a model SE material under battery-relevant electrochemical cycling conditions.

Methods

Full-field deformation during Li deposition-induced cracking of garnet-type LLZTO was measured using the digital image correlation (DIC) method. The obtained displacement data were denoised via equilibrium smoothing, and then fitted to the linear elastic asymptotic crack-tip field to extract the electrochemical fracture toughness values under different current densities.

Results

The physics-based equilibrium smoothing method demonstrated effectiveness in enhancing the accuracy of DIC measurements. The electrochemical fracture toughness obtained was substantially lower than the mechanical fracture toughness of the same material determined through indentation, attributed to combined effects of electrochemical embrittlement and a transition in fracture mode from intergranular to transgranular.

Conclusion

The discrepancy between the two types of fracture toughness suggests that electrochemical cycling could have a significant impact on the fracture mode and resistance of a solid electrolyte.

背景固态电解质（SE）中锂渗透引起的断裂是阻碍固态锂离子电池（SS-LIB）商业化的一个主要问题。在锂（Li）金属阳极的电化学电镀过程中，经常会观察到这种断裂，但其机理起源在很大程度上仍不清楚。通过平衡平滑法对获得的位移数据进行去噪处理，然后与线性弹性渐近裂纹尖端场进行拟合，以提取不同电流密度下的电化学断裂韧性值。获得的电化学断裂韧性大大低于通过压痕法测定的同种材料的机械断裂韧性，这归因于电化学脆化和断裂模式从晶间过渡到晶间的综合影响。

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引用次数: 0

Effect of Speckle Edge Characteristics on DIC Calculation Error 斑点边缘特性对 DIC 计算误差的影响

IF 2.4 3区工程技术 Q2 Engineering

Experimental Mechanics

Pub Date : 2024-06-07 DOI: 10.1007/s11340-024-01078-6

H. Cui, Z. Zeng, H. Zhang, F. Yang

引用次数: 0

Stereo-DIC Challenge 1.0 – Rigid Body Motion of a Complex Shape Stereo-DIC Challenge 1.0 - 复杂形状的刚体运动

IF 2.4 3区工程技术 Q2 Engineering

Experimental Mechanics

Pub Date : 2024-05-31 DOI: 10.1007/s11340-024-01077-7

W. Ahmad, J. Helm, S. Bossuyt, P. Reu, D. Turner, L.K. Luan, P. Lava, T. Siebert, M. Simonsen

Background

Stereo-DIC is a widely used optical measurement technique that provides a dense full-field 3D measurement of the shape, displacement, and strain of a solid sample. When compared with 2D-DIC, Stereo-DIC provides greater flexibility and expands its use beyond flat, planar specimens. Furthermore, the widespread availability of commercial systems has led to the adoption of the technique throughout industry, academia, and government research labs.

Objective

Even though some research has been done to understand the effects of different experimental and stereo-DIC parameters, no reference is available to benchmark and compare the performance of current stereo-DIC algorithms to each other.

Methods

This paper provides the description and analysis of a carefully controlled 3D experiment and associated images used to compare the results from five subset based DIC software packages. Both the images and analysis codes used in this paper to compare the results are described here and are available for download and use for continued research.

Results

We show that over a very large range of motion, the 3D errors are very small, less than 80(mu)m over a travel of ±20 mm out-of-plane and ±20 mm in-plane. While all codes performed similarly, there are important differences noted in the paper.

Conclusion

The image sets and results comparison software are hosted by the International DIC Society (www.iDICs.org) and are freely available for download and analysis for comparison with results in this paper. Furthermore, it is hoped that this set of images can be used for future research in improving stereo-DIC by future authors.

背景立体-DIC 是一种广泛使用的光学测量技术，可对固体样品的形状、位移和应变进行密集的全场三维测量。与 2D-DIC 相比，立体-DIC 提供了更大的灵活性，并将其应用扩展到平面试样之外。此外，商业系统的普及也促使该技术在工业界、学术界和政府研究实验室得到广泛应用。方法本文描述并分析了一个精心控制的三维实验和相关图像，用于比较基于子集的五个 DIC 软件包的结果。结果我们发现，在很大的运动范围内，三维误差非常小，在平面外±20 毫米和平面内±20 毫米的行程中，误差小于 80 （mu）米。虽然所有代码的性能相似，但本文中指出了一些重要的差异。结论图像集和结果比较软件由国际 DIC 协会 (www.iDICs.org) 托管，可免费下载和分析，以便与本文中的结果进行比较。此外，我们还希望这组图像可用于未来作者改进立体 DIC 的研究。

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引用次数: 0