The presence of residual stresses in materials or engineering structures can significantly influence their mechanical per-formance.Accurate measurement of residual stresses is of great importance to ensure their in-se...The presence of residual stresses in materials or engineering structures can significantly influence their mechanical per-formance.Accurate measurement of residual stresses is of great importance to ensure their in-service reliability.Although numerous instrumented indentation methods have been proposed to evaluate residual stresses,the majority of them require a stress-free reference sample as a comparison benchmark,thereby limiting their applicability in scenarios where obtaining stress-free reference samples is challenging.In this work,through a number of finite element simulations,it was found that the loading exponent of the loading load-depth curve and the recovered depth during unloading are insensitive to residual stresses.The loading curve of the stress-free specimen was virtually reconstructed using such stress-insensitive parameters extracted from the load-depth curves of the stressed state,thus eliminating the requirement for stress-free reference samples.The residual stress was then correlated with the fractional change in loading work between stressed and stress-free loading curves through dimensional analysis and finite element simulations.Based on this correlation,an instrumented sharp indentation method for measuring equibiaxial residual stress without requiring a stress-free specimen was established.Both numerical and experimental verifications were carried out to demonstrate the accuracy and reliability of the newly proposed method.The maximum relative error and absolute error in measured residual stresses are typically within±20%and±20 MPa,respectively.展开更多
The machining process remains relevant for manufacturing high-quality and high-precision parts,which can be found in industries such as aerospace and aeronautical,with many produced by turning,drilling,and milling pro...The machining process remains relevant for manufacturing high-quality and high-precision parts,which can be found in industries such as aerospace and aeronautical,with many produced by turning,drilling,and milling processes.Monitoring and analyzing tool wear during these processes is crucial to assess the tool’s life and optimize the tool’s performance under study;as such,standards detail procedures to measure and assess tool wear for various tools.Measuring wear in machining tools can be time-consuming,as the process is usually manual,requiring human interaction and judgment.In the present work,an automated offline flank wear measurement algorithm was developed in Python.The algorithm measures the flank wear of coated end-mills and slot drills from Scanning Electron Microscopy(SEM)images,according to the ISO 8688 standard,following the same wear measurement procedure.SEM images acquired with different magnifications and tools with varying machining parameters were analyzed using the developed algorithm.The flank wear measurements were then compared to the manually obtained,achieving relative errors for the most common magnifications of around 2.5%.Higher magnifications were also tested,yielding a maximum relative error of 13.4%.The algorithm can measure batches of images quickly on an ordinary personal computer,analyzing and measuring a 10-image batch in around 30 s,a process that would require around 30 min when performed manually by a skilled operator.Therefore,it can be a reliable alternative to measuring flank wear on many tools from SEM images,with the possibility of being adjusted for other wear measurements on different kinds of tools and different image types,for example,on images obtained by optical microscopy.展开更多
Traditional automated guided vehicle(AGV)primarily relies on scheduling systems to manage warehouse locations and execute picking or placing tasks on fixedheight pallets.However,these conventional systems are illsuite...Traditional automated guided vehicle(AGV)primarily relies on scheduling systems to manage warehouse locations and execute picking or placing tasks on fixedheight pallets.However,these conventional systems are illsuited for scenarios involving variable heights,such as vehicle loading and unloading or the complex stacking of soft packages.To address the challenges of AGV endeffector operations in nonfixed height scenarios,this paper proposes an innovative solution leveraging lowcost depth camera sensors.By capturing image and depth data,and integrating deep learning,image processing,and spatial attitude calculation techniques,the method accurately determines the position of the endeffector center point relative to the upper plane of the fork.The approach effectively resolves a key issue in AGV operations within intelligent logistics scenarios that lack fixed heights.The proposed algorithm is deployed on a domestic embedded,lowcost ARM chip controller,and extensive experiments are conducted on a real AGV equipped with multiple stacked vehicles and nonstandard vehicles.The experimental results demonstrate that for diverse vehicles with different heights,the measurement error can be maintained within±10 mm,satisfying the requirements for highprecision measurement.The height measurement method developed in the paper not only enhances the AGV’s adaptability in nonfixed height scenarios but also significantly broadens its application potential across various industries.展开更多
Rapid technological advancements drive miniaturization and high energy density in devices,thereby increasing nanoscale thermal management demands and urging development of higher spatial resolution technologies for th...Rapid technological advancements drive miniaturization and high energy density in devices,thereby increasing nanoscale thermal management demands and urging development of higher spatial resolution technologies for thermal imaging and transport research.Here,we introduce an approach to measure nanoscale thermal resistance using in situ inelastic scanning transmission electron microscopy.By constructing unidirectional heating flux with controlled temperature gradients and analyzing electron energy-loss/gain signals under optimized acquisition conditions,nanometer-resolution in mapping phonon apparent temperature is achieved.Thus,interfacial thermal resistance is determined by calculating the ratio of interfacial temperature difference to bulk temperature gradient.This methodology enables direct measurement of thermal transport properties for atomic-scale structural features(e.g.,defects and heterointerfaces),resolving critical structure-performance relationships,providing a useful tool for investigating thermal phenomena at the(sub-)nanoscale.展开更多
结局测量工具(OMI)是评估患者感受或健康状况的重要工具,但其质量参差不齐。选择健康测量工具的共识标准(COSMIN)为遴选高质量的OMI提供了方法学指导,得到广泛认可。近年来,基于COSMIN开展的OMI系统评价数量激增,然而许多已发表的相关...结局测量工具(OMI)是评估患者感受或健康状况的重要工具,但其质量参差不齐。选择健康测量工具的共识标准(COSMIN)为遴选高质量的OMI提供了方法学指导,得到广泛认可。近年来,基于COSMIN开展的OMI系统评价数量激增,然而许多已发表的相关系统评价常未能充分报告关键信息,严重影响了OMI系统评价的可重复性和可解释性,从而影响其结果的推广应用。鉴于PRISMA 2020未包含报告此类系统评价的所有必要信息,有关学者在前者基础上制订了新的报告规范“PRISMA-COSMIN for OMIs 2024”,以帮助研究人员以清晰、详细和透明的方式撰写和报告OMI系统评价。本文结合实例对该规范进行了介绍和解读,旨在帮助国内学者深入理解并有效应用该指南,提高国内OMI系统评价进行全面地的整体质量。展开更多
A high precision, high antijamming multipoint infrared telemetry system was developed to measure the piston temperature in internal combustion engine. The temperature at the measuring point is converted into correspon...A high precision, high antijamming multipoint infrared telemetry system was developed to measure the piston temperature in internal combustion engine. The temperature at the measuring point is converted into corresponding voltage signal by the thermo-couple first. Then after the V/F stage, the voltage signal is converted into the frequency signal to drive the infrared light-emitting diode to transmit infrared pulses. At the receiver end, a photosensitive audion receives the infrared pulses. After conversion, the voltage recorded by the receiver stands for the magnitude of temperature at the measuring point. Test results of the system indicate that the system is practical and the system can perform multipoint looping temperature measurements for the piston.展开更多
水下爆炸气泡的膨胀-收缩运动会持续多次,在此过程中将发生能量的相互转换。在爆炸水池内分别开展了20、40和60 g RS211装药的气泡运动光测试验,采用高速相机拍摄气泡多次脉动的演化过程,对图像进行智能化识别处理,得到气泡的脉动周期...水下爆炸气泡的膨胀-收缩运动会持续多次,在此过程中将发生能量的相互转换。在爆炸水池内分别开展了20、40和60 g RS211装药的气泡运动光测试验,采用高速相机拍摄气泡多次脉动的演化过程,对图像进行智能化识别处理,得到气泡的脉动周期和最大半径。在此基础上,理论分析了气泡多次脉动过程中势能、内能的转换机制。结果表明:第2次气泡脉动相对于第1次气泡脉动的余能率为0.31;气泡内能占总能的比例为5.4%~6.6%;工程计算时,可忽略气泡内能,采用气泡势能表征气泡能。展开更多
基金support from the National Natural Science Foundation of China(Grant Nos.12172332,11727803 and 12072009)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LZ23A020007)the Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.RF-C2022003).
文摘The presence of residual stresses in materials or engineering structures can significantly influence their mechanical per-formance.Accurate measurement of residual stresses is of great importance to ensure their in-service reliability.Although numerous instrumented indentation methods have been proposed to evaluate residual stresses,the majority of them require a stress-free reference sample as a comparison benchmark,thereby limiting their applicability in scenarios where obtaining stress-free reference samples is challenging.In this work,through a number of finite element simulations,it was found that the loading exponent of the loading load-depth curve and the recovered depth during unloading are insensitive to residual stresses.The loading curve of the stress-free specimen was virtually reconstructed using such stress-insensitive parameters extracted from the load-depth curves of the stressed state,thus eliminating the requirement for stress-free reference samples.The residual stress was then correlated with the fractional change in loading work between stressed and stress-free loading curves through dimensional analysis and finite element simulations.Based on this correlation,an instrumented sharp indentation method for measuring equibiaxial residual stress without requiring a stress-free specimen was established.Both numerical and experimental verifications were carried out to demonstrate the accuracy and reliability of the newly proposed method.The maximum relative error and absolute error in measured residual stresses are typically within±20%and±20 MPa,respectively.
文摘The machining process remains relevant for manufacturing high-quality and high-precision parts,which can be found in industries such as aerospace and aeronautical,with many produced by turning,drilling,and milling processes.Monitoring and analyzing tool wear during these processes is crucial to assess the tool’s life and optimize the tool’s performance under study;as such,standards detail procedures to measure and assess tool wear for various tools.Measuring wear in machining tools can be time-consuming,as the process is usually manual,requiring human interaction and judgment.In the present work,an automated offline flank wear measurement algorithm was developed in Python.The algorithm measures the flank wear of coated end-mills and slot drills from Scanning Electron Microscopy(SEM)images,according to the ISO 8688 standard,following the same wear measurement procedure.SEM images acquired with different magnifications and tools with varying machining parameters were analyzed using the developed algorithm.The flank wear measurements were then compared to the manually obtained,achieving relative errors for the most common magnifications of around 2.5%.Higher magnifications were also tested,yielding a maximum relative error of 13.4%.The algorithm can measure batches of images quickly on an ordinary personal computer,analyzing and measuring a 10-image batch in around 30 s,a process that would require around 30 min when performed manually by a skilled operator.Therefore,it can be a reliable alternative to measuring flank wear on many tools from SEM images,with the possibility of being adjusted for other wear measurements on different kinds of tools and different image types,for example,on images obtained by optical microscopy.
基金Supported by the Key Research and Development Program of Anhui Province(No.201904a05020035)the Postdoctoral Research Initiative of Anhui Province(No.2024B804)the Hefei City Key Technology Research and Development‘Ranking’(No.2023SGJ017).
文摘Traditional automated guided vehicle(AGV)primarily relies on scheduling systems to manage warehouse locations and execute picking or placing tasks on fixedheight pallets.However,these conventional systems are illsuited for scenarios involving variable heights,such as vehicle loading and unloading or the complex stacking of soft packages.To address the challenges of AGV endeffector operations in nonfixed height scenarios,this paper proposes an innovative solution leveraging lowcost depth camera sensors.By capturing image and depth data,and integrating deep learning,image processing,and spatial attitude calculation techniques,the method accurately determines the position of the endeffector center point relative to the upper plane of the fork.The approach effectively resolves a key issue in AGV operations within intelligent logistics scenarios that lack fixed heights.The proposed algorithm is deployed on a domestic embedded,lowcost ARM chip controller,and extensive experiments are conducted on a real AGV equipped with multiple stacked vehicles and nonstandard vehicles.The experimental results demonstrate that for diverse vehicles with different heights,the measurement error can be maintained within±10 mm,satisfying the requirements for highprecision measurement.The height measurement method developed in the paper not only enhances the AGV’s adaptability in nonfixed height scenarios but also significantly broadens its application potential across various industries.
基金supported by the National Natural Science Foundation of China(Grant No.52125307)the National Key R&D Program of China(Grant No.2021YFB3501500)the support from the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘Rapid technological advancements drive miniaturization and high energy density in devices,thereby increasing nanoscale thermal management demands and urging development of higher spatial resolution technologies for thermal imaging and transport research.Here,we introduce an approach to measure nanoscale thermal resistance using in situ inelastic scanning transmission electron microscopy.By constructing unidirectional heating flux with controlled temperature gradients and analyzing electron energy-loss/gain signals under optimized acquisition conditions,nanometer-resolution in mapping phonon apparent temperature is achieved.Thus,interfacial thermal resistance is determined by calculating the ratio of interfacial temperature difference to bulk temperature gradient.This methodology enables direct measurement of thermal transport properties for atomic-scale structural features(e.g.,defects and heterointerfaces),resolving critical structure-performance relationships,providing a useful tool for investigating thermal phenomena at the(sub-)nanoscale.
文摘结局测量工具(OMI)是评估患者感受或健康状况的重要工具,但其质量参差不齐。选择健康测量工具的共识标准(COSMIN)为遴选高质量的OMI提供了方法学指导,得到广泛认可。近年来,基于COSMIN开展的OMI系统评价数量激增,然而许多已发表的相关系统评价常未能充分报告关键信息,严重影响了OMI系统评价的可重复性和可解释性,从而影响其结果的推广应用。鉴于PRISMA 2020未包含报告此类系统评价的所有必要信息,有关学者在前者基础上制订了新的报告规范“PRISMA-COSMIN for OMIs 2024”,以帮助研究人员以清晰、详细和透明的方式撰写和报告OMI系统评价。本文结合实例对该规范进行了介绍和解读,旨在帮助国内学者深入理解并有效应用该指南,提高国内OMI系统评价进行全面地的整体质量。
文摘A high precision, high antijamming multipoint infrared telemetry system was developed to measure the piston temperature in internal combustion engine. The temperature at the measuring point is converted into corresponding voltage signal by the thermo-couple first. Then after the V/F stage, the voltage signal is converted into the frequency signal to drive the infrared light-emitting diode to transmit infrared pulses. At the receiver end, a photosensitive audion receives the infrared pulses. After conversion, the voltage recorded by the receiver stands for the magnitude of temperature at the measuring point. Test results of the system indicate that the system is practical and the system can perform multipoint looping temperature measurements for the piston.
文摘水下爆炸气泡的膨胀-收缩运动会持续多次,在此过程中将发生能量的相互转换。在爆炸水池内分别开展了20、40和60 g RS211装药的气泡运动光测试验,采用高速相机拍摄气泡多次脉动的演化过程,对图像进行智能化识别处理,得到气泡的脉动周期和最大半径。在此基础上,理论分析了气泡多次脉动过程中势能、内能的转换机制。结果表明:第2次气泡脉动相对于第1次气泡脉动的余能率为0.31;气泡内能占总能的比例为5.4%~6.6%;工程计算时,可忽略气泡内能,采用气泡势能表征气泡能。
