Pub Date : 2024-10-10DOI: 10.1007/s11340-024-01121-6
A. Zehnder
{"title":"A Note of Gratitude from the Editor-in-Chief","authors":"A. Zehnder","doi":"10.1007/s11340-024-01121-6","DOIUrl":"10.1007/s11340-024-01121-6","url":null,"abstract":"","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"64 9","pages":"1383 - 1383"},"PeriodicalIF":2.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-10-08DOI: 10.1007/s11340-024-01120-7
{"title":"On the Cover: Accounting for Localized Deformation: A Simple Computation of True Stress in Micropillar Compression Experiments","authors":"","doi":"10.1007/s11340-024-01120-7","DOIUrl":"10.1007/s11340-024-01120-7","url":null,"abstract":"","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"64 9","pages":"1381 - 1381"},"PeriodicalIF":2.0,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-10-03DOI: 10.1007/s11340-024-01113-6
C. Geng, Q. Zhong, H. Luo, W. Shi, H. Xie, W. He
Background
Nickel-based superalloys are key materials for aero-engine hot-end components, and fatigue is one of their most typical failure forms. In the field of fatigue research, in-situ characterization of crack growth behavior is crucial, and more intuitive and accurate characterization methods need to be developed.
Objective
In this work, to better understand their fatigue crack growth behavior, we have developed new methods for in-situ characterization of crack growth behavior using laser thermography detection technique.
Methods
According to the thermal images of sample surfaces captured during the fatigue process, a method for positioning crack tip based on Prewitt edge detection is proposed, and a novel parameter, i.e., the crack opening temperature gradient (COTG), is defined to evaluate the crack closure effect.
Results
Based on the variation characteristics of COTG with load rate, the crack initial opening load rate (CIOLR) and crack opening load ratio (COLR) can be determined under different fatigue cycles. The results show that CIOTG and COTG tend to decrease with increasing fatigue cycles.
Conclusion
This work provides a visual and quantitative in-situ method for crack detection and characterization of the crack closure effect in fatigue testing.
{"title":"A Novel Method to In-Situ Characterize Fatigue Crack Growth Behavior of Nickel-Based Superalloys By Laser Thermography","authors":"C. Geng, Q. Zhong, H. Luo, W. Shi, H. Xie, W. He","doi":"10.1007/s11340-024-01113-6","DOIUrl":"10.1007/s11340-024-01113-6","url":null,"abstract":"<div><h3>Background</h3><p>Nickel-based superalloys are key materials for aero-engine hot-end components, and fatigue is one of their most typical failure forms. In the field of fatigue research, in-situ characterization of crack growth behavior is crucial, and more intuitive and accurate characterization methods need to be developed.</p><h3>Objective</h3><p>In this work, to better understand their fatigue crack growth behavior, we have developed new methods for in-situ characterization of crack growth behavior using laser thermography detection technique.</p><h3>Methods</h3><p>According to the thermal images of sample surfaces captured during the fatigue process, a method for positioning crack tip based on Prewitt edge detection is proposed, and a novel parameter, i.e., the crack opening temperature gradient (COTG), is defined to evaluate the crack closure effect.</p><h3>Results</h3><p>Based on the variation characteristics of COTG with load rate, the crack initial opening load rate (CIOLR) and crack opening load ratio (COLR) can be determined under different fatigue cycles. The results show that CIOTG and COTG tend to decrease with increasing fatigue cycles.</p><h3>Conclusion</h3><p>This work provides a visual and quantitative in-situ method for crack detection and characterization of the crack closure effect in fatigue testing.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"65 1","pages":"5 - 23"},"PeriodicalIF":2.0,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-10-03DOI: 10.1007/s11340-024-01117-2
M. Benzarti, P. Henry
Background
Varnish is used in many domains to enhance wear resistance, mechanical behaviour or chemical resistance. To characterize varnish cohesion or adhesion on plane surface, a scratch-test is predominantly used. In order to investigate coating properties on fibres, the common method uses tensile tests.
Objective
The aim of this paper was to investigate the adhesion of varnish on a monofibre of polyamide using an out of the box procedure based on scratch tests. To do so, a specific device was conceived to enable a scratch test on a single fibre.
Methods
Adhesion between varnish and a monofibre of nylon was investigated using several series of scratch tests on fibres coated by two types of varnish. Coating toughness and adhesion were investigated according to the coating composition and thermal treatment. A comparison between the different prints was discussed to characterize the effect of varnish type on the scratch resistance and to determine the parameters that influence this adhesion using scratch-test.
Results
The obtained results highlighted the influence of the thermal treatment imposed to the fibres on the mechanical behaviour. Tensile tests were conducted on the three types of samples in order to establish a link in terms of classification between a well-known characterization experiment and the presented scratch test.
Conclusion
Beyond the investigation of varnish/nylon fibre adhesion, this paper mostly aims at validating an innovative process for the characterization of coatings deposited on curved surfaces like fibres.
{"title":"An INNOVative Approach for Mechanical Characterization of Coatings on Fibres","authors":"M. Benzarti, P. Henry","doi":"10.1007/s11340-024-01117-2","DOIUrl":"10.1007/s11340-024-01117-2","url":null,"abstract":"<div><h3>Background</h3><p>Varnish is used in many domains to enhance wear resistance, mechanical behaviour or chemical resistance. To characterize varnish cohesion or adhesion on plane surface, a scratch-test is predominantly used. In order to investigate coating properties on fibres, the common method uses tensile tests.</p><h3>Objective</h3><p>The aim of this paper was to investigate the adhesion of varnish on a monofibre of polyamide using an out of the box procedure based on scratch tests. To do so, a specific device was conceived to enable a scratch test on a single fibre.</p><h3>Methods</h3><p>Adhesion between varnish and a monofibre of nylon was investigated using several series of scratch tests on fibres coated by two types of varnish. Coating toughness and adhesion were investigated according to the coating composition and thermal treatment. A comparison between the different prints was discussed to characterize the effect of varnish type on the scratch resistance and to determine the parameters that influence this adhesion using scratch-test.</p><h3>Results</h3><p>The obtained results highlighted the influence of the thermal treatment imposed to the fibres on the mechanical behaviour. Tensile tests were conducted on the three types of samples in order to establish a link in terms of classification between a well-known characterization experiment and the presented scratch test.</p><h3>Conclusion</h3><p>Beyond the investigation of varnish/nylon fibre adhesion, this paper mostly aims at validating an innovative process for the characterization of coatings deposited on curved surfaces like fibres.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"65 1","pages":"25 - 34"},"PeriodicalIF":2.0,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-26DOI: 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。
{"title":"Dynamic Magneto-Mechanical Analysis of Isotropic and Anisotropic Magneto-Active Elastomers","authors":"C.D. Pierce, N.J. Salim, K.H. Matlack","doi":"10.1007/s11340-024-01115-4","DOIUrl":"10.1007/s11340-024-01115-4","url":null,"abstract":"<div><h3>Background</h3><p>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.</p><h3>Objective</h3><p>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.</p><h3>Methods</h3><p>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.</p><h3>Results</h3><p>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.</p><h3>Conclusions</h3><p>These results provide new insights into the fundamental mechanisms by which microstructure and magnetic field interact to affect the MAE effective properties.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"64 9","pages":"1601 - 1618"},"PeriodicalIF":2.0,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-20DOI: 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。
{"title":"Measurement of the Tension Loss in a Cable Traveling Over a Pulley, for Low-Speed Applications","authors":"P. Máté, A. Szekrényes","doi":"10.1007/s11340-024-01097-3","DOIUrl":"10.1007/s11340-024-01097-3","url":null,"abstract":"<div><h3>Background</h3><p>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.</p><h3>Objective</h3><p>This paper aims to present a simple measurement method for the tension loss in cables traveling over sheaves on bearings.</p><h3>Methods</h3><p>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.</p><h3>Results</h3><p>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.</p><h3>Conclusion</h3><p>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.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"64 9","pages":"1579 - 1599"},"PeriodicalIF":2.0,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11340-024-01097-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-19DOI: 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.
{"title":"Biomechanical Hand Model: Modeling and Simulating the Lateral Pinch Movement","authors":"A.F. Lemos, L. A. Rodrigues da Silva, B. V. Nagy, P. N. Barroso, C. B. S. Vimieiro","doi":"10.1007/s11340-024-01109-2","DOIUrl":"10.1007/s11340-024-01109-2","url":null,"abstract":"<div><h3>Background</h3><p>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.</p><h3>Objectives</h3><p>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.</p><h3>Methods</h3><p>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.</p><h3>Results</h3><p>The average disparity between the expected and obtained joint angular displacements was <span>(varvec{6.06~%})</span> and <span>(varvec{1.90~%})</span> 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.</p><h3>Conclusion</h3><p>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.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"64 9","pages":"1557 - 1578"},"PeriodicalIF":2.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11340-024-01109-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-18DOI: 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.
{"title":"Size Effects in Strength and Strain Hardening Behavior of Single-Crystal 7075 Aluminum Alloy Micropillars","authors":"H. Li, D. Zhao, Y. Cui, C. Dan, S. Ma, L. Wang, J. Liu, Y. Li, Z. Chen, H. Wang","doi":"10.1007/s11340-024-01112-7","DOIUrl":"10.1007/s11340-024-01112-7","url":null,"abstract":"<div><h3>Background</h3><p>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.</p><h3>Objective</h3><p>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.</p><h3>Methods</h3><p>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.</p><h3>Results</h3><p>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.</p><h3>Conclusions</h3><p>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.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"64 9","pages":"1545 - 1555"},"PeriodicalIF":2.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-17DOI: 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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Pub Date : 2024-09-16DOI: 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.
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