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Effect of Surface Adhesion on the Rough Contact Response Near Complete Contact 接近完全接触时表面附着对粗接触响应的影响
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.28978
Siyuan Zhang, Yanwei Liu
The adhesion phenomena between interfaces is widely investigated in engineering and scientific research. Due to the complexity of loading condition and surface topography, the traditional adhesive theory has many limitations. To better understand the adhesive properties of rough surfaces, we release the restrictions of JKR theory and propose a new adhesive model for single asperity. Initiated by this, a discrete rough surface contact model is presented, which extends the application scope of the traditional theory. First, we establish an elastic model by describing the gap between the interfaces accurately, so analytical solutions which are still valid for high contact pressure are proposed. Then, based on this, the exact adhesive solutions for different shapes of indenters are derived, which greatly improves the predicting accuracy of contact relationship and adhesion force. Finally, we use the results in the analysis of rough surface. The effect of both surface roughness and surface energy on the adhesive response of rough contact are studied in detail. The results show that adhesion is more easily to happen for smooth and geometrically continuous surfaces. The overall adhesion effect will be reduced in rough surface analysis with the increasing of surface roughness and the decreasing of surface energy. Our research sheds light on the understanding of the adhesion between solids and provides a theoretical guidance for the design of adhesion biomimetic materials and MEMS systems.
界面之间的粘附现象在工程和科学研究中得到了广泛的研究。由于加载条件和表面形貌的复杂性,传统的粘接理论存在许多局限性。为了更好地理解粗糙表面的粘附特性,我们释放了JKR理论的限制,提出了一个新的单粗糙表面粘附模型。由此提出了一种离散粗糙面接触模型,扩展了传统理论的应用范围。首先,我们通过准确描述界面之间的间隙来建立弹性模型,从而提出了对高接触压力仍然有效的解析解。在此基础上,推导出了不同形状压头的精确粘着力解,大大提高了接触关系和粘着力的预测精度。最后,我们将这些结果用于粗糙表面的分析。详细研究了表面粗糙度和表面能对粗糙接触粘附响应的影响。结果表明,对于光滑且几何连续的表面,粘附更容易发生。在粗糙表面分析中,随着表面粗糙度的增加和表面能的降低,整体粘附效应会降低。我们的研究揭示了对固体之间粘附的理解,并为粘附仿生材料和MEMS系统的设计提供了理论指导。
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引用次数: 0
Multiscale Analysis of the Performance of Micro/nano Porous Filtration Membranes with Double Concentric Cylindrical Pores: Part II-Optimization Results 双同心圆柱孔微纳多孔过滤膜性能的多尺度分析:第二部分-优化结果
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.30509
Zhipeng Tang, Yongbin Zhang
The multiscale calculation results for the values of the optimized parameters are presented for the micro/nano porous filtration membranes with double concentric cylindrical pores where multiscale flows occur. For a weak liquid-pore wall interaction, the optimum ratio of the radius of the bigger pore to the radius of the smaller pore (i.e. the filtration pore) can be calculated from the classical equation, however the corresponding lowest flow resistance of the membrane should still be calculated from the multiscale analysis owing to the adsorbed layer effect when the ratio Landax of the thickness of the adsorbed layer to the radius of the smaller pore is greater than 0.1. For medium and strong liquid-pore wall interactions, the optimum ratios of the pore radii should be calculated from the multiscale analysis, and the corresponding lowest flow resistances of the membrane are much higher than the classical calculation showing the significant effect of the adsorbed layer when Landax>=0.1.
给出了发生多尺度流动的具有双同心圆柱孔的微/纳米多孔过滤膜的优化参数值的多尺度计算结果。对于较弱的液体-孔壁相互作用,较大孔隙的半径与较小孔隙(即过滤孔隙)的半径的最佳比率可以根据经典方程计算,然而,当吸附层的厚度与较小孔隙的半径的比值Landax大于0.1时,由于吸附层效应,膜的相应最低流动阻力仍然应该根据多尺度分析来计算。对于中等和强烈的液体-孔壁相互作用,应通过多尺度分析计算孔径的最佳比率,并且膜的相应最低流动阻力远高于经典计算,表明当Landax>=0.1时吸附层的显著影响。
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引用次数: 0
Numerical Modelling of Emission Characteristic for a Single Cylinder Spark Ignition Engine 单缸火花点火发动机排放特性的数值模拟
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.31064
Brahim Menacer, Naima Khatir, M. Bouchetara
The main objective of this study is to elaborate an engine cycle simulation program using GT-Suite software to analyze the influence of equivalence ration and compression ratio on the main emissions of a four-stroke direct injection spark ignition engine. The experimental result is used to compare the cylinder pressure result obtained with the developed model. The present article is a study of the effect of compression ratio and equivalence ratio on the main emissions of the direct injection spark engine for a two-zone combustion analytical model and by using of the GT-Suite simulation software. The developed analytical model is validated by the use of experimental data. The analytical curve of the pressure in the combustion chamber is experimentally validated with a difference of the order of 6%.
本研究的主要目的是利用GT Suite软件开发一个发动机循环模拟程序,分析当量比和压缩比对四冲程直喷火花点火式发动机主要排放的影响。实验结果用于将所获得的气缸压力结果与所开发的模型进行比较。本文采用两区燃烧分析模型,利用GT Suite仿真软件,研究了压缩比和当量比对直喷火花发动机主要排放的影响。利用实验数据对所建立的分析模型进行了验证。通过实验验证了燃烧室中压力的分析曲线,其差值约为6%。
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引用次数: 0
Computational Evaluation of the Effect of Plunger Spring Stiffness On Opening and Closing Times of the Low-Pressure Gas-Phase Injector 柱塞弹簧刚度对低压气相喷射器启闭次数影响的计算评价
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.31230
D. Szpica, Michal Kusznier
In the paper, an attempt was made to computationally demonstrate the effect of the plunger pressure stiffness on the opening and closing times of the low-pressure gas-phase injector as a filling of the research gap in this subject.  Based on the presented mathematical model describing the operation of the injector, firstly the results were related to the manufacturer's technical data showing a shorter time to full opening by 2.77% and a longer time to full closing by 0.50%. On this basis, it was considered that the proposed model can be used for comparison purposes. In the assumed range of compression spring stiffness (100... 2000) N/m, it was shown that as the stiffness increases, the time to fully open decreases by 18.85%, while the time to fully closed decreases by 80.17%. Additionally, it is shown that the time-cross section as the stiffness of the compression spring increases can decrease up to 35.21% from the initial value. The obtained results can be useful in modeling the operation of an internal combustion engine or in the operational assessment of the gas injector condition.
本文试图通过计算来证明柱塞压力刚度对低压气相喷射器启闭次数的影响,以填补本课题的研究空白。根据所建立的喷油器运行数学模型,首先将结果与制造商的技术数据相关联,表明完全开启时间缩短了2.77%,完全关闭时间延长了0.50%。在此基础上,有人认为提议的模型可用于比较目的。在假定的压缩弹簧刚度范围内(100…2000) N/m,结果表明,随着刚度的增加,完全打开时间减少18.85%,完全关闭时间减少80.17%。随着压缩弹簧刚度的增大,压缩弹簧的时间截面比初始值减小了35.21%。所得结果可用于内燃机的运行建模或气体喷射器状态的运行评估。
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引用次数: 2
A Battery-free Pressure Sensing System Based on Soft Piezoelectric Device for Tennis Training 基于软压电装置的无电池网球训练压力传感系统
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.30459
K. Yu, Yingxiang Gong, Zhifang Fan
In this work, a battery-free position and pressure monitoring system based on soft polyvinylidene fluoride (PVDF) piezoelectric thin film with helical coils circuit design is designed and used for tennis training. The racket surface is firstly divided into block areas and the sensing transducers are placed in each of them to detect the hitting position and force in these areas. To modify the extensibility of the system for tennis training, all the devices are connected by the S-shape helical line, which has two states: curled at usual and straight at work. Four piezoelectric patches form a series system to power the energy harvest system and wireless communication module, which help to realize the battery-free and wearable functions. A linear relation between the hitting force and induced electric voltage is experiment verified with the slope of 0.05 V/N. The system is also verified in the real tennis ball game monitoring for the hitting time and hitting position, benefiting the future application of wearable devices in artificial intelligence and the Internet of Things (IoT).
本文设计了一种基于柔性聚偏氟乙烯(PVDF)压电薄膜和螺旋线圈电路设计的无电池位置和压力监测系统,并用于网球训练。球拍表面首先被划分为块区域,在每个块区域放置传感传感器,以检测这些区域的击球位置和力度。为了提高网球训练系统的可扩展性,所有的设备都通过s形螺旋线连接,该螺旋线有两种状态:平时卷曲和工作时直。四个压电片组成串联系统,为能量采集系统和无线通信模块供电,实现无电池可穿戴功能。实验验证了撞击力与感应电压呈线性关系,斜率为0.05 V/N。该系统还在真实的网球比赛中进行了击球时间和击球位置的监控验证,有利于未来可穿戴设备在人工智能和物联网(IoT)中的应用。
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引用次数: 1
Multiscale Analysis of the Performance of Micro/nano Porous Filtration Membranes with Double Concentric Cylindrical Pores: Part I-Analysis Development 双同心圆柱孔微纳多孔过滤膜性能的多尺度分析:第一部分-分析进展
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.30507
Zhipeng Tang, Yongbin Zhang
In nanoporous filtration membranes, when the radius of the filtration pore is so big that the flow of the adsorbed layer on the pore wall is comparable with the flow of the continuum fluid in the central region of the pore, the multiscale analysis is required for estimating the performance of the membranes. The present paper presents such a multiscale analysis for the performance of nanoporous filtration membranes with double concentric cylindrical pores. The dimensionless flow resistance of the membrane was calculated for a weak fluid-pore wall interaction for varying operational parameter values. It was found that there is the optimum ratio of the radius of the filtration pore to the radius of the other bigger pore for the highest flux of the membrane.
在纳米孔过滤膜中,当过滤孔半径较大,吸附层在孔壁上的流动与孔中心区域连续流体的流动相当时,需要对膜的性能进行多尺度分析。本文对具有双同心圆柱孔的纳米孔过滤膜的性能进行了多尺度分析。在不同的操作参数值下,计算了弱流体-孔壁相互作用下膜的无因次流动阻力。结果表明,滤孔半径与另一个较大孔半径的最佳比值可使膜通量达到最高。
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引用次数: 1
Investigation of the Effect of Cutting Directions On the Improvement of Mechanical Parameters of Treated Cork by THT: Experimental Measurement, Modelling and Optimization of Mass Transfer 切割方向对THT处理后软木材料力学参数改善的影响研究:传质实验测量、建模与优化
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.26956
Abdelkrim Zemirline, T. Kermezli, M. Announ, M. Douani
This work aims to investigate the impact of the cutting direction on the transfer properties of both the native cork and the treated by an optimized cycle at high temperature and boiling for the purpose to improve its mechanical characteristics in all three orthotropic directions. The study of the insulation performance is based on tracking the apparent mass diffusion coefficient (Dapp) variation in order to evolve a new material with the thermal, mass, acoustic and vibratory properties needed for various applications. TGA, IR and SEM analyzes are used to confirm the enhancement of the treated cork. The Dapp of the diffusing chemical species, NaCl (0.7M), is determined by conductimetric method. In transient mode, a mathematical model of mass transfer, which includes the diffusion parameters of the chemical species, is developed. Through the calibration of the model with the experimental measurements the Dapp values ​​were determined and then refined numerically by optimization using the Bat-Algorithm. The obtained results showed that the treatment improves the diffusion property of the native (DN) compared to the treaty (DA) with the values in the order of 10-12 and 10-13 m2.s-1 respectively with a relative uncertainty of 10-7. In addition, this investigation reveals that the radial diffusion coefficient (DR) is significantly higher than the tangential diffusion (DT) and longitudinal (DL) diffusion coefficients which both are almost of the same.
这项工作旨在研究切割方向对天然软木和经过高温沸腾优化循环处理的软木的传递特性的影响,以改善其在所有三个正交异性方向上的机械特性。研究绝缘性能是基于跟踪表观质量扩散系数(Dapp)的变化,以发展一种具有各种应用所需的热、质量、声学和振动性能的新材料。用热重分析仪、红外光谱和扫描电镜分析证实了处理后软木的增强作用。采用电导法测定了扩散化学物质NaCl (0.7M)的Dapp。在瞬态模式下,建立了包含化学物质扩散参数的传质数学模型。通过对模型与实验测量值的标定,确定了Dapp值,并利用蝙蝠算法进行了数值优化。结果表明,与条约(DA)相比,该处理改善了原生(DN)的扩散性能,其数值分别为10-12和10-13 m2。S-1,相对不确定度为10-7。此外,研究发现径向扩散系数(DR)明显高于切向扩散系数(DT)和纵向扩散系数(DL),两者几乎相同。
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引用次数: 1
Impacts of Length Scale Parameter on Material Dependent Thermoelastic Damping in Micro/nanoplates Applying Modified Coupled Stress Theory 基于修正耦合应力理论的长度尺度参数对微纳板材料热弹性阻尼的影响
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.25841
R. R., V. Babu, M. Baiju
Among the different energy dissipation mechanisms, thermoelastic damping plays a vital role and need tobe alleviated in resonators inorder to enhance its performance parameters by improving its thermoelastic dampinglimited qualityfactor, QTED. The maximum energy dissipation is also interrelated with critical length (???????? ) of theplates and by optimizing the dimensions the peaking of energy dissipation can be diminished. As the size of thedevices is scaled down, classical continuum theories are not able to explain the size effect related mechanicalbehavior at micron or submicron levels and as a result non-classical continuum theories are pioneered with theinception of internal length scale parameters. In this paper, analysis of isotropic rectangular micro-plates based onKirchhoff model applying Modified Coupled Stress Theory is used toanalyzethe size-dependent thermoelasticdamping and its impact on quality factor and critical dimensions.Hamilton principle is adapted to derive thegoverning equations of motion and the coupled heat conduction equation is employed to formulate the thermoelasticdamping limited quality factor of the plates. Five different structural materials (PolySi, Diamond,Si, GaAs andSiC)are used for optimizing QTED which depends on the materialperformance index parameters. ThermoelasticDamping Index [TDI] and thermal diffusion length, lT. According to this work, the maximum QTED is attained forPolySi with the lowest TDI and Lcmax is obtained for SiC which is having the lowest lT. The impact of lengthscaleparameters (l), vibration modes, boundary conditions (Clamped–Clamped and Simply Supported), and operatingtemperatures on QTED and Lcare also investigated. It is concluded that QTED is further maximized by selecting lowtemperatures and higher internal length scale parameters (l).The prior knowledge of QTED and Lchelp the designers tocome out with high performance low loss resonators.
在不同的能量耗散机制中,热弹性阻尼在谐振器中起着至关重要的作用,需要通过改善其热弹性阻尼有限质量因子(QTED)来改善其性能参数。最大能量耗散也与临界长度相关(????????)。通过优化板的尺寸,可以减少能量耗散的峰值。随着器件尺寸的缩小,经典连续统理论无法解释微米或亚微米水平上与尺寸效应相关的力学行为,因此非经典连续统理论开创了内部长度尺度参数的开始。本文应用修正耦合应力理论,基于kirchhoff模型对各向同性矩形微板进行分析,分析了尺寸相关的热弹性阻尼及其对质量因子和临界尺寸的影响。采用Hamilton原理推导运动控制方程,采用耦合热传导方程推导板的热弹性阻尼限制品质因子。五种不同的结构材料(多晶硅、金刚石、硅、砷化镓和sic)被用于优化QTED,这取决于材料的性能指标参数。热弹性阻尼指数[TDI]和热扩散长度,lT.根据这项工作,获得了具有最低TDI的多晶硅的最大QTED和具有最低ltc的SiC的最大Lcmax。还研究了长度尺度参数(l),振动模式,边界条件(夹紧-夹紧和简支撑)和工作温度对QTED和Lcare的影响。结果表明,选择低温和较高的内部长度尺度参数可以进一步最大化QTED。QTED和Lchelp的先验知识有助于设计出高性能低损耗谐振器。
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引用次数: 0
Ballistic and Aerodynamic Characteristics Simulation for Trajectory Correction Projectile 弹道修正弹的弹道和气动特性仿真
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.31431
F. Dong, Yongjie Xu, Nana Zheng
Conventional ammunition easily deviates from the intended target. Its hit probability is reduced by such disturbance factors as fabrication errors, initial muzzle disturbance, initial velocity probable error, and stochastic wind effect. The effect of the above interference factors can be reduced by improving the shooting dispersion, ammunition, and gun or rocket engine structure. However, such improvements may fail to meet the operational requirements for modern warfare. Ballistic correction technique is a proposed trajectory control technique for precision strike with effective damage. Taking a 57mm calibre projectile as research object, trajectory correction projectile with different aerodynamic layouts were designed. The aerodynamic characteristic, static stability, exterior ballistic characteristic and firing density of each projectile has been studied through research method of theoretical analysis and numerical calculation. These findings are considered instrumental in the trajectory correction technology research and engineering application.
常规弹药很容易偏离预定目标。考虑了制造误差、初始炮口扰动、初始速度概率误差和随机风效应等干扰因素,降低了其命中概率。上述干扰因素的影响可以通过改善射击弥散、弹药和火炮或火箭发动机结构来减小。然而,这种改进可能无法满足现代战争的作战要求。弹道修正技术是一种针对有效杀伤精确打击而提出的弹道控制技术。以某57mm口径弹丸为研究对象,设计了不同气动布局的弹道修正弹。采用理论分析和数值计算相结合的研究方法,对各弹的气动特性、静稳定性、外弹道特性和发射密度进行了研究。这些发现对弹道修正技术的研究和工程应用具有重要意义。
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引用次数: 0
Vibration Energy Harvester (VEH) for a Free Body Moving in Space at Vibro Shock Mode 振动冲击模式下自由体空间运动的振动能量采集器
IF 0.7 4区 工程技术 Q4 MECHANICS Pub Date : 2022-06-21 DOI: 10.5755/j02.mech.31034
R. Gaidys, Egidijus Stasytis, V. Daniulaitis, B. Narijauskaite
The type of the generator was chosen to be piezoelectric because it is most widely used to capture the energy of mechanical vibrations and convert it into electricity. A 2D generator model was chosen for the analysis of the dynamics of the energy harvester (VEH) for a free body moving in space at vibro shock mode. The computational schemes of the model are presented. A mathematical model describing the dynamics is developed: generator casing, inertial mass, nonlinear contact/impact. The mathematical model is implemented by the Runge-Kutta numerical method in the Matlab system. Analysis of experimental and modeling results is performed: comparison of generator eigen frequencies, the logarithmic decrement and the damping coefficient – the error is in range of 5%. This generator can be used to collect mechanical energy of water waves, wind, human movements, and other environmental factors in the presence of the body's free movement trajectory in space.
发电机的类型被选择为压电,因为它最广泛地用于捕获机械振动的能量并将其转化为电能。选取二维发电机模型,对空间运动自由体在振动冲击模式下的能量采集器(VEH)进行动力学分析。给出了模型的计算格式。建立了发电机机壳、惯性质量、非线性接触/冲击的动力学数学模型。数学模型在Matlab系统中采用龙格-库塔数值法实现。对实验结果和建模结果进行了分析:比较了发电机本征频率、对数衰减量和阻尼系数,误差在5%范围内。该发电机可用于收集人体在空间中自由运动轨迹存在的水波、风、人体运动等环境因素的机械能。
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引用次数: 2
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Mechanika
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