Article
Mechanics
Wujiu Pan, Changxuan Song, Liangyu Ling, Haoyong Qu, Minghai Wang
Summary: This paper establishes an unloading fractal prediction model between rough contact surfaces based on a three-dimensional fractal loading model and previous research results, revealing that the unloading process depends on the final loading state of the surface, and both the friction factor and fractal dimension of the contact surface have significant effects on the unloading model.
ARCHIVE OF APPLIED MECHANICS
(2021)
Article
Engineering, Chemical
Anle Wang, Martin H. Mueser
Summary: In this work, the elastic contact between isotropic and anisotropic, rigid, randomly rough surfaces and linearly elastic counterfaces, as well as the subsequent Reynolds flow through the gap between them, is numerically studied. The percolation threshold is found to be dependent on fluid flow direction in anisotropic systems, and a critical contact area near 0.415 is confirmed. Effective-medium treatments provide accurate expressions for Reynolds fluid flow conductances.
Article
Engineering, Mechanical
Jian Chen, Wangyang Zhang, Di Liu, Chenglong Wang, Linbo Zhu
Summary: The contact behavior between elastic-perfectly plastic ellipsoidal asperity and rigid planes under different ellipticities during loading and unloading was investigated using the finite element method. The study found that the changing trend of the contact load, residual displacement, contact area, and plastic work with displacement was similar for different ellipticities, but the magnitude varied. The contact area during unloading was not always smaller than that during loading with the same displacement, and the initial unloading stage contact area was larger than that of the loading stage. Analytical dimensionless expressions were proposed for the residual displacement, plastic work, contact area, and contact load after fully unloading the ellipsoids with different ellipticities for a wide range of displacements, and their effectiveness and correctness were verified through prediction results from previous models. These empirical relations can be combined with statistical or fractal methods to study the contact behavior of macroscopic rough surfaces.
JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Jian Chen, Wangyang Zhang, Di Liu, Chenglong Wang, Linbo Zhu
Summary: Understanding the elastoplastic contact loading-unloading behavior between a sphere and a rigid plane, this study used a bilinear strain-hardening material model to analyze the effects of the tangent modulus (E-t) and the ratio of the reduced elastic modulus to the yield strength (E/Y). The results showed that the effects of E-t and E/Y were amplified with increasing interference, while an increase in E-t diminished the effect of E/Y. A new constitutive model for elastoplastic contact loading-unloading was proposed and validated against previous models. The findings can be applied to particle and contact mechanics.
JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME
(2023)
Article
Engineering, Chemical
B. N. J. Persson
Summary: This article discusses the impact of interfacial surface roughness on seal leakage and presents results for static rubber seals. The influence of fluid pressure on interfacial surface separation and leak rate is also studied.
Article
Engineering, Geological
Pengfei Li, Qiang Sun, Lei Xue, Jishi Geng, Hailiang Jia, Tao Luo, Xinchao Zheng
Summary: Load damage during rock failure leads to changes in radon exhalation characteristics, which can be used to predict rock instability. This study investigates the characteristics and influence mechanism of radon exhalation in sandstone under different stresses using nuclear magnetic resonance and radon measurement. The results show that the radon exhalation rate of sandstone decreases first and then increases with increasing stress level, with the fastest rate occurring at the peak intensity of stress. The changes in pore structure inside sandstone and the volume of micropores play important roles in radon exhalation ability.
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
(2023)
Article
Mechanics
B. Gurrutxaga-Lerma
Summary: This article provides mathematical solutions to the elastodynamic fields of a semi-infinite interface lying along two dissimilar media under sudden loading. The solutions for slipping and welded interfaces are obtained utilizing Wiener-Hopf and Cagniard-de Hoop techniques, showing no oscillatory singularity at the crack tip for the slipping boundary. The solution for the welded interface crack involves a matricial Wiener-Hopf problem that is achieved through successive Abrahams approximations, leading to a quickly convergent solution with asymptotic character.
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
(2021)
Article
Engineering, Mechanical
Wangyang Zhang, Jian Chen, Chenglong Wang, Di Liu, Linbo Zhu
Summary: The loading and unloading contact behavior between an elastic-plastic ellipsoid and a rigid body is analyzed using the finite element method in this study. A new empirical formula is proposed to describe the residual plastic interference of the ellipsoid after elastic-plastic unloading. The correctness and validity of the study are evaluated through comparison with previous models and experiments.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Xingya Ni, Chenbo Ma, Jianjun Sun, Yuyan Zhang, Qiuping Yu
Summary: A theoretical model based on the fractal theory of porous media was established for calculating the leakage rate of contact mechanical seals, considering the real seal contact interface and providing calculation methods for interface characteristic parameters. Numerical simulation results showed that as contact pressure increased, interface porosity and maximum pore diameter decreased gradually, leading to a decrease in leakage rate.
Article
Chemistry, Physical
Shuguang Zhang, Yanmo Li, Juefeng Yang, Yu Song, Li Yang, Jiahao Guo
Summary: Reinforcement is essential in underground engineering to ensure the stability of surrounding rock. This study simulated the rock reinforcement effect of bolt and shotcrete support using pasted circular CFRP. Triaxial cyclic loading and unloading tests were conducted on reinforced sandstone to analyze the impact of different reinforcement schemes on mechanical properties. The results showed that CFRP can improve peak and residual strength, enhance energy absorption efficiency, and reduce dissipation efficiency of the rock mass.
Article
Chemistry, Multidisciplinary
Dunwen Liu, Shulin Jiang, Yu Tang
Summary: The acoustic emission and wave velocity characteristics of metasandstone under graded cyclic loading and unloading were studied, revealing that the acoustic emission signals are mainly generated during loading and the wave velocity rapidly decreases when the stress exceeds a threshold. These findings can be used to predict the instability and damage of rock masses in engineering.
APPLIED SCIENCES-BASEL
(2022)
Article
Materials Science, Ceramics
Longbiao Li
Summary: Under monotonic and cyclic tensile loading, stochastic brittle fragmentations significantly influence the mechanical behavior of fiber-reinforced ceramic-matrix composites (CMCs). Experimental and theoretical models were used to study the synergistic effects of matrix and fiber fragmentations on loading/unloading hysteresis behavior. The study also analyzed the impacts of fiber volume fraction and strength on the hysteresis loops of CMCs, providing valuable insights for composite material design optimization.
CERAMICS INTERNATIONAL
(2021)
Article
Computer Science, Interdisciplinary Applications
Mingchun Lin, Wei Zhou, Jiaying Liu, Gang Ma, Xuexing Cao
Summary: In this study, biaxial tests of dense and loose granular assemblies are conducted using the discrete element method. The multiscale behaviors of granular materials under loading-unloading-reloading path are investigated. The dense and loose granular assemblies exhibit different hysteresis behaviors and mesostructural evolutions.
COMPUTERS AND GEOTECHNICS
(2022)
Article
Chemistry, Physical
Wei Zheng, Linlin Gu, Zhen Wang, Junnan Ma, Hujun Li, Hang Zhou
Summary: The energy evolution of rock discontinuities under cyclic loading and unloading was studied through experiments, with results showing that samples harden with an increase in cycles, dissipated energy exceeds elastic energy, and the energy dissipation ratio can characterize internal damage.
Article
Engineering, Mechanical
Oliver Feuchtmueller, Nino Dakov, Lothar Hoerl, Frank Bauer
Summary: The generation and thickness of the oil film in U-cup rod seals were studied through analytical, numerical, and experimental methods. The analysis showed that the film thickness follows a square-root function with respect to the product of dynamic viscosity and rod speed. Discrepancies between theory and experiments were discussed, and a potential remedy for the modeling gap was proposed.
Article
Engineering, Mechanical
Francesc Perez-Rafols, Andreas Almqvist
TRIBOLOGY INTERNATIONAL
(2019)
Article
Engineering, Multidisciplinary
Andreas Almqvist, Evgeniya Burtseva, Francesc Perez-Rafols, Peter Wall
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2019)
Article
Engineering, Mechanical
Kalle Kalliorinne, Francesc Peez-Rafols, John Fabricius, Andreas Almqvist
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY
(2020)
Article
Engineering, Chemical
Francesc Perez-Rafols, Fredrik Forsberg, Gunnar Hellstrom, Andreas Almqvist
TRANSPORT IN POROUS MEDIA
(2020)
Article
Multidisciplinary Sciences
Francesc Perez-Rafols, Andreas Almqvist
Summary: This study investigates the relationship between stiffness and load for self-affine fractal surfaces with non-Gaussian height distribution. Unlike Gaussian surfaces, a linear relation between stiffness and load is not found, while a power law relationship is a better descriptor. The stiffness curve is also dependent on the Hurst exponent in this case, unlike for Gaussian surfaces. The study carefully assesses possible convergence errors to ensure the conclusions are reliable.
SCIENTIFIC REPORTS
(2021)
Article
Engineering, Mechanical
Jan Steven Van Dokkum, Francesc Perez-Rafols, Leonid Dorogin, Lucia Nicola
Summary: The retraction of a cylindrical rigid indenter from a viscoelastic substrate was studied using an efficient Green's function method. Hysteresis was observed in the load to area relationship, falling between predicted limits at high and low retraction velocities. Adhesion work changed during retraction, and a non-dimensional parameter was proposed to estimate the effect of viscoelasticity in adhesive hysteresis.
TRIBOLOGY INTERNATIONAL
(2021)
Article
Engineering, Mechanical
Francesc Perez-Rafols, Lucia Nicola
Summary: A model is proposed to study the incipient sliding of contacts in the presence of friction and adhesion, showcasing different contact pressure profiles under varying parameters. Experimental investigation is conducted on the contact between a smooth cylinder and a flat body under strong adhesion-friction interactions.
Article
Engineering, Mechanical
Mohammad Aramfard, Francisco Perez-Rafols, Lucia Nicola
Summary: A seamless 2D dual-scale computational scheme has been developed to study contact problems, combining an atomistic domain for contact interaction description and an elastic continuum domain. The innovative scheme is validated against full atomistic simulations and used to investigate the effect of adhesion on scratching processes.
TRIBOLOGY INTERNATIONAL
(2022)
Article
Materials Science, Multidisciplinary
Francesc Perez-Rafols, Jan Steven Van Dokkum, Lucia Nicola
Summary: Viscoelasticity and roughness are the main causes of adhesive hysteresis in soft contacts. When the viscoelasticity is confined to the edges of the contact, the contributions of viscoelasticity and roughness to adhesive hysteresis are nearly independent and additive. At low retraction rates, the instabilities typical of rough elastic contacts are suppressed by viscoelasticity, while at high retraction rates mechanical instabilities appear.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Materials Science, Multidisciplinary
R. Civiero, F. Perez-Rafols, L. Nicola
Summary: The effect of a passivation layer on a rough metal surface during contact loading is studied using dislocation dynamics simulations. The metal body is modeled as an FCC single crystal with a self-affine rough surface, which can be either bare or covered by a thin coating that is impenetrable to dislocations. The simulation allows for analyzing the influence of surface roughening caused by dislocation motion, where bare surfaces result in crystallographic steps due to dislocation glide, while passivated surfaces stop dislocations at the interface.
MECHANICS OF MATERIALS
(2023)
Article
Engineering, Mechanical
Francesc Perez-Rafols
Summary: Two-scale models are effective for studying mechanical problems with a wide range of length scales. However, they cannot be directly applied in contact mechanics due to a lack of scale separation, which results in inadequate representation of local-scale results. This work proposes a model that incorporates stochastic variability of local scale results into the global-scale problem to overcome this issue. Several test cases are conducted to demonstrate the model's performance.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Engineering, Mechanical
Kalle Kalliorinne, Roland Larsson, Francesc Perez-Rafols, Marcus Liwicki, Andreas Almqvist
Summary: Predicting the contact mechanical response for various types of surfaces is a challenging task that has been researched by many scholars. The impact of surface topography on tribological performance is significant, and different methods can be used to solve the contact mechanics problem. ANN-based models offer a fast and accurate solution for predicting the contact mechanical response based on surface topography.
FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND
(2021)
Article
Engineering, Petroleum
Dennis Ernens, Francesc Perez-Rafols, Dennis Van Hoecke, Roel F. H. Roijmans, Egbert J. van Riet, John B. E. Vande Voorde, Andreas Almqvist, Matthijn Bas de Rooij, Serge Mathieu Roggeband, Willem Maarten van Haaften, Marc Vanderschueren, Phiilipe Thibaux, Henry Rihard Pasaribu
SPE DRILLING & COMPLETION
(2019)
Article
Engineering, Mechanical
Francesc Perez-Rafols, Andreas Almqvist