Comptes Rendus Mecanique最新文献_第6页

Prediction of the uniaxial compressive strength of rocks from simple index tests using a random forest predictive model 用随机森林预测模型从简单指数试验中预测岩石的单轴抗压强度

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2020-01-01 DOI: 10.5802/crmeca.3

Min Wang, W. Wan, Yanlin Zhao

{"title":"Prediction of the uniaxial compressive strength of rocks from simple index tests using a random forest predictive model","authors":"Min Wang, W. Wan, Yanlin Zhao","doi":"10.5802/crmeca.3","DOIUrl":"https://doi.org/10.5802/crmeca.3","url":null,"abstract":"Uniaxial compressive strength (UCS) is an important mechanical parameter for stability assessments in rock mass engineering. In practice, obtaining the UCS simply, accurately and economically has attracted substantial attention. In this paper, studies related to UCS estimation using indirect tests were reviewed, it was found that regression techniques and soft computing techniques were mainly used to evaluate the UCS value, and theses soft computing techniques can accurately and effectively predict the UCS. To select the proper indirect parameters to predict the UCS, statistical analysis was performed on the relationships between UCS and indirect parameters, and based on the analysis, two indirect parameters (the Schmidt hammer rebound value (L-type) and ultrasonic P-wave velocity) were deemed adequate to predict UCS. To establish the UCS predictive model, the random forest algorithm was employed, the predictive model was verified by data collected from references. To further verify the validity of the predictive model, laboratory tests were performed, and the predictive results were consistent with the measured results, thus the UCS value predictive model can be applied to the fields of rock mechanics and engineering geology.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76281230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 26

Implementation and experimental tests of an impedance control of pneumatic artificial muscles for isokinetic rehabilitation 等速康复用气动人工肌肉阻抗控制的实现与实验测试

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2020-01-01 DOI: 10.5802/crmeca.16

Mahdi Chavoshian, M. Taghizadeh, Nima Zamani Meymian

{"title":"Implementation and experimental tests of an impedance control of pneumatic artificial muscles for isokinetic rehabilitation","authors":"Mahdi Chavoshian, M. Taghizadeh, Nima Zamani Meymian","doi":"10.5802/crmeca.16","DOIUrl":"https://doi.org/10.5802/crmeca.16","url":null,"abstract":"The impedance control of an pneumatic artificial muscle for isokinetic rehabilitation applications was investigated. Due to the direct contact of rehabilitation robots with the human body, the safety and reliability of these robots are of significant importance. For such applications, position and force must be introduced simultaneously. In this regard, there are two scenarios in which the controller should compromise between the position commands and the resultant force or vice versa. To achieve these goals and considering the safety requirements, a novel control algorithm was proposed, which was identified as a reliable strategy that can be utilized for rehabilitation purposes. The fuzzy sliding mode controller was implemented to control the actuator’s velocity (time-varying position signal) to eliminate/reduce chattering and improve the settling time. The performance of the controller using the position-based impedance algorithm was investigated through lab experiments. For experiments, a mechanism consisting of a pneumatic muscle and a pneumatic proportional valve was used, and the control of vertical reciprocating motion of a mass attached to the end of the muscle was investigated. Three different reference signals were used in tests, and the maximum tracking error was measured to be less than 6%. Using the measured error criteria, a parametric study was performed to identify the effects of three impedance parameters on the outputs. The results of the parametric study were reported through response surfaces and sensitivity charts. The presented methods have not been implemented in prior research for controlling a pneumatic muscle, and the results of the experiments were satisfactory.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74866741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Cracking behavior and local stress characteristics around the opening surrounded by two intermittent joints: experiment and numerical simulation 两个间歇节理围合孔口的开裂行为及局部应力特征:实验与数值模拟

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2020-01-01 DOI: 10.5802/crmeca.4

Yuanchao Zhang, Yu-jing Jiang, Xiao Tang, Miao Chen, Xinshuai Shi

{"title":"Cracking behavior and local stress characteristics around the opening surrounded by two intermittent joints: experiment and numerical simulation","authors":"Yuanchao Zhang, Yu-jing Jiang, Xiao Tang, Miao Chen, Xinshuai Shi","doi":"10.5802/crmeca.4","DOIUrl":"https://doi.org/10.5802/crmeca.4","url":null,"abstract":"In this research, the Strength and deformation behaviors, cracking process, and local stress evolution of sandstone specimens containing a circular opening and two joints (called H-J sandstone specimens in this study) were researched by experiment and numerical simulation (two-dimension particle flow code). The effect of different joint positions around the opening has been specifically studied by changing the ligament angle (β). The test results show that peak strength and peak strain firstly decrease then increase with the increasing β, while the peak strain presents an overall upward trend. Three types of coalescence failure patterns between the opening and joints formed, and the corresponding cracking process and acoustic emission (AE) characteristics are highly related to the ligament angle. Based on the micro-parameters calibration, a good agreement was achieved between experimental and numerical simulation. The numerical results show that the local stress evolution around the opening is highly corresponding to the cracking process. The microcracks initiation and propagation cause obvious stress fluctuations, drops or increasements of minimum principal stress, while the cracks coalescence results in obvious reduction of maximum principal stress and drops of stress-strain curve. It also be found that the stress distribution and magnitude around the opening tend to be closely related to both coalescence failure and strength characteristics of H-J specimens. Finally, the cracking mechanism between the opening and joints was revealed based on particle displacement fields. The results show that different cracking mechanism may cause different local stress changes, which finally determines the overall mechanical behavior of specimens.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77606678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Influence of geometry on stress state in bulk characterization tests 几何形状对体特性试验中应力状态的影响

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2019-12-01 DOI: 10.1016/j.crme.2019.10.003

S. Moakhar, H. Hentati, M. Barkallah, J. Louati, M. Haddar

引用次数: 4

A screw dislocation near a non-parabolic open inhomogeneity with internal uniform stresses 内应力均匀的非抛物状开不均匀附近的螺位错

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2019-12-01 DOI: 10.1016/j.crme.2019.10.006

Xu Wang , Peter Schiavone

引用次数: 3

Measurement of the relative air permeability of compacted earth in the hygroscopic regime of saturation 饱和吸湿状态下压实土相对透气性的测量

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2019-12-01 DOI: 10.1016/j.crme.2019.11.017

A. Fabbri, Noha Al Haffar, F. McGregor

引用次数: 10

Nonlinear vibration analysis of piezoelectric bending actuators: Theoretical and experimental studies 压电弯曲作动器的非线性振动分析:理论与实验研究

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2019-12-01 DOI: 10.1016/j.crme.2019.10.007

Pouyan Shahabi, Hamed Ghafarirad, Afshin Taghvaeipour

{"title":"Nonlinear vibration analysis of piezoelectric bending actuators: Theoretical and experimental studies","authors":"Pouyan Shahabi, Hamed Ghafarirad, Afshin Taghvaeipour","doi":"10.1016/j.crme.2019.10.007","DOIUrl":"https://doi.org/10.1016/j.crme.2019.10.007","url":null,"abstract":"<div><p>Piezoelectric bimorph actuators are used in a variety of applications, including micro positioning, vibration control, and micro robotics. The nature of the aforementioned applications calls for the dynamic characteristics identification of actuator at the embodiment design stage. For decades, many linear models have been presented to describe the dynamic behavior of this type of actuators; however, in many situations, such as resonant actuation, the piezoelectric actuators exhibit a softening nonlinear behavior; hence, an accurate dynamic model is demanded to properly predict the nonlinearity. In this study, first, the nonlinear stress–strain relationship of a piezoelectric material at high frequencies is modified. Then, based on the obtained constitutive equations and Euler–Bernoulli beam theory, a continuous nonlinear dynamic model for a piezoelectric bending actuator is presented. Next, the method of multiple scales is used to solve the discretized nonlinear differential equations. Finally, the results are compared with the ones obtained experimentally and nonlinear parameters are identified considering frequency response and phase response simultaneously. Also, in order to evaluate the accuracy of the proposed model, it is tested out of the identification range as well.</p></div>","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.crme.2019.10.007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91738330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 9

Passive vibration absorber effect on the machining surface quality of a flexible workpiece 被动吸振器对柔性工件加工表面质量的影响

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2019-12-01 DOI: 10.1016/j.crme.2019.11.014

Riadh Chaari, Marwa Haddar, Fathi Djemal, Fakher Chaari, Mohamed Haddar

引用次数: 5

Nonisothermal immiscible compressible thermodynamically consistent two-phase flow in porous media 多孔介质中非等温非混溶可压缩热一致两相流

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2019-12-01 DOI: 10.1016/j.crme.2019.11.015

Mladen Jurak , Alexandre Koldoba , Andrey Konyukhov , Leonid Pankratov

引用次数: 2

Measurement of the relative air permeability of compacted earth in the hygroscopic regime of saturation 饱和吸湿状态下压实土相对透气性的测量

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2019-12-01 DOI: 10.1016/j.crme.2019.11.017

Antonin Fabbri, Noha Al Haffar, Fionn McGregor

{"title":"Measurement of the relative air permeability of compacted earth in the hygroscopic regime of saturation","authors":"Antonin Fabbri, Noha Al Haffar, Fionn McGregor","doi":"10.1016/j.crme.2019.11.017","DOIUrl":"https://doi.org/10.1016/j.crme.2019.11.017","url":null,"abstract":"<div><p>The hygroscopic behavior of earthen materials has been extensively studied in the past decades. However, while the air flow within their porous network may significantly affect the kinetics of vapor transfer and thus their hygroscopic performances, few studies have focused on its assessment. For that purpose, a key parameter would be the gas permeability of the material, and its evolution with the relative humidity of the air. Indeed, due to the sorption properties of earthen material, an evolution of the water content, and thus of relative permeability, are foreseeable if the humidity of in-pore air changes. To fill this gap, this paper presents the measurement of relative permeabilities of a compacted earth sample with a new experimental set-up. The air flow through the sample is induced with an air generator at controlled flow rate, temperature, and humidity. The sample geometry was chosen in order to reduce, as much as possible, its heterogeneity in water content, and the tests were realized for several flow rates. The results, which show the evolution of gas permeability with the relative humidity of the injected air and with the water content of the material, either in adsorption or in desorption, were eventually successfully compared to predictions of the well-known Corey's law.</p></div>","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.crme.2019.11.017","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91652425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 9