Effect Of Interface Roughness Research Articles

Mesoscale modeling of new-to-old concrete interface under combined shear and compressive loads

A mesoscale model of new-to-old concrete interface under combined shear and compressive loads is established, and a parameter study is conducted to evaluate the influence of interface roughness, bond strength, and fracture energy. The mesoscale model is numerically generated using a random aggregate technique, in which the number of aggregates is calculated using the Fuller grading curve and Walraven formula and the aggregates are randomly placed using the Monte Carlo simulation. The concrete damaged plasticity model is employed to simulate the mechanical behaviors of new and old mortars, as well as the interfacial transition zone between the mortar and aggregate. The linear elastic model is utilized to simulate the behavior of aggregates, while the cohesive-friction model is employed to represent the behavior of new-to-old concrete interface. The effect of interface roughness, bond strength, and fracture energy on the interface shear strength and post-peak shear strength using the double-shear test specimens is investigated. The results indicate that increasing the roughness of old concrete surface leads to significant increases in both the interface shear strength and post-peak shear strength, but the larger interface roughness is not necessarily better. As the interface bond strength increases, the interface shear strength remains the same, whereas the post-peak shear strength shows a large increase with the lower interface roughness. Moreover, the interface fracture energy imparts the minimal influence on the interface shear strength and post-peak shear strength, but the higher interface fracture energy can improve the overall constitutive behavior of new-to-old concrete interface if the roughness of old concrete surface is low. The numerical mesoscale model presented can provide the theoretical guidance and technical support for effective design and construction of new-to-old concrete interface and structures.

Analysis of the Sand-Concrete Interface Shear Behaviors Considering the Soil Unloading and Interface Roughness Effects

Analysis of the Sand-Concrete Interface Shear Behaviors Considering the Soil Unloading and Interface Roughness Effects

Discrete element modeling of effect of interfacial roughness and pre-crack on crack propagation in thermal barrier coatings

Discrete element modeling of effect of interfacial roughness and pre-crack on crack propagation in thermal barrier coatings

Advancing Rock-Socketed Pile Design with a Unified Interface Shear Strength Framework for Soft Rocks

AbstractThe shaft resistance of rock-socketed piles (RSPs) is primarily influenced by the interactions between the pile, rock and any soft interface materials. This study presents a fundamental experimental and numerical investigation to predict the shaft resistance of model RSPs in soft rocks through a comprehensive shear strength framework incorporating the major variables such as roughness and smear fabric. By calibrating the Discrete Element Method (DEM) results with the experimental outcomes, this study evaluates the load-resistance attributes of RSPs in three different soft rocks for a wide range of roughness and smear configurations. The interface roughness effect of the RSPs in terms of the friction coefficient was correlated with the ultimate shaft resistances, uniaxial compressive strength and Young’s modulus of the rock. The study then incorporated the effect of smear fabric (placement, thickness and area proportion) in the shear strength framework of clean shafts. Comprehensive review of the DEM results revealed that the socket roughness effect diminishes at a critical roughness factor $$({\text{RF}})$$ ( RF ) of 0.4, beyond which the smear predominantly influences the shaft capacity. Following this, the effects of roughness and smear fabric were incorporated into a single equation representing the interface shear strength of RSPs, where the existence of smear results in a maximum reduction of up to 75% of the ultimate shaft resistance. The distinctive feature of this unified interface shear strength framework lies in its integration of the new smear fabric parameter and the linkage to the mechanical properties of soft rocks, which is the limitation of the earlier studies. It thereby sets a strong base for future studies aimed at advancing the pile-rock interface models.

Shear rate and roughness effect on clay-steel interface strength properties in CU and CPD drainage conditions

Based on the concept of the preformed failure plane, this paper conducted a series of clay-interface tests using a modified triaxial apparatus that can directly measure the interface pore pressure, to investigate the shear rate and interface roughness effect on the deviator stress, interface excess pore pressure, interface stress path, and interface friction angle in both consolidated undrained (CU) and consolidated partially drained (CPD) interface drainage conditions. In general, the specimen with the clay-steel interface had a lower shear strength than the pure clay specimen under the same testing conditions. In CU tests, the total and effective interface friction angles increase approximately linearly with the shear rate in the semi-logarithmic scale, while in CPD tests, both the total and effective interface friction angles decrease with increasing shear rate. Moreover, the increased surface roughness is found to enhance the interface shear strength and the maximum interface pore pressure at a given shear rate and confining pressure. In CU tests, both the normalized efficiency parameter E and the corresponding interface friction angle increase with the average roughness (Ra) in a logarithmic relationship, but it is difficult to describe the positive correlation perfectly in CPD tests.

Effect of interface roughness on the elastic properties of 3D layered media

In our work, we numerically investigated how the roughness of interfaces between different layers in 3D layered models affects the upscaled and downscaled elastic properties. We considered layered models with random rough interfaces and fixed elastic properties in the background and the middle layer, upscaled them to compute the effective stiffness tensor and then downscaled them to obtain new elastic parameters of the middle layer in the statistically equivalent models with smooth interfaces. Afterward, we investigated the dependence of the obtained results on four input varied parameters (the correlation length, standard deviation of the roughness and two physical elastic parameters of the middle layer). Next, we proposed an algorithm for recovering the covariance matrix of such stiffness tensors for arbitrary values from the four-parameter space, applying bilinear regression to the parameters of the interface and the linear component-by-component interpolation by two nearest points to the material parameters. Verification of this algorithm showed that for limited standard deviation values the errors in restoring the covariance matrix do not exceed 0.07. Thus, smooth interface models with random material parameters in the middle layer can be statistically simulated with arbitrary values of the input parameters with high accuracy.

Effect of interface roughness on mechanical properties of layered cemented tailings backfill

Research on the roughness parameters of the layered interface of the layered cemented tailings backfill (LCTB) is of great significance to improve the cementation quality of layered layers and reduce the strength reduction rate caused by layering for the safety and stability of the mine structure. Using the sedimentation mechanism of tailing sand particles, different roughness interfaces with different solid densities (SDs) and number of layered layers were designed, and the influence mechanism of interface roughness on the cementation quality of layered layers was studied by using uniaxial compression test, surface roughness detection and particle size detection. The results show that the existence of stratified surfaces can significantly reduce the uniaxial compressive strength (UCS) of the LCTB, which is defined here as the Stratified reduction rate (SRR).When the number of stratified layers is constant, the strength reduction rate caused by stratified layers decreases with the increase of SD, and the increase of SD will increase the shear resistance of the coarse particles in the slurry, making it less prone to segregation and subsidence. As a result, the larger the proportion of coarse particle size distribution on the layered surface, the macroscopic surface roughness increases. The SRR has a good linear fitting relationship with surface roughness Ra, and the SRR decreases with the increase of Ra, indicating that to a certain extent, the greater the surface roughness of the stratified plane, the better the cementation quality of the delamination surface, and the weaker the reduction effect of the delamination on the strength of the LCTB.

A-C/GeTe superlattices: Effect of interfacial impedance adaptation modeling on the thermal properties

Recently, nanostructuration has been proposed to improve the performance of phase change memories. This is the case of superlattices composed of amorphous carbon and crystalline germanium telluride, which we have investigated by molecular dynamics. For this, a modified Stillinger–Weber potential is adapted to reproduce their stiffness contrast/impedance ratio. In order to study the effect of the interface interaction, two sets of parameters are used to model the interfaces with different interactions between the two materials using the properties of the softer material or the average properties between the two creating an adaptation of impedance across the layers. The effects of interface roughness and carbon diffusion at grain boundaries are studied. Using equilibrium molecular dynamics as well as the propagation of wave-packets, we show first that without impedance adaptation, the anisotropy is high, and the roughness has a marked impact on the properties. However, the introduction of impedance adaptation destroys those effects on the thermal conductivity. Finally, we show that the periodic texturing of the interface increases the transmission of in-plane transverse phonons.

Interface-Roughness Effect on Polarization Switching and Reliability Performance of Doped-HfO2 Capacitors

Interface-Roughness Effect on Polarization Switching and Reliability Performance of Doped-HfO₂ Capacitors

Experimental study of shear behavior of rock–shotcrete interface under dynamic shearing: insights from interface roughness and strain rate

Rock–shotcrete structures are often suffered from dynamic shearing. However, the understanding of the dynamic shear response of rock–shotcrete structures is still at its infancy. To investigate the effects of strain rate and interface roughness on the dynamic shear response of rock–shotcrete structure, laboratory tests were carried out on the modified double notched sandstone–concrete specimen. Testing results show that the dynamic shear strength and dynamic peak strain of sandstone–concrete specimens are both far less than those of sandstone and concrete specimens. With increasing strain rate, the dynamic shear strength of sandstone–concrete specimen increases and the failure mode changes from interfacial shear failure to the mixed failure, i.e., the interfacial, concrete and sandstone shear failure. With the increase in interface roughness, the failure mode changes from sliding fracture to shear-off fracture, leading to an increase in dynamic shear strength and shear peak strain of sandstone–concrete specimens. In addition, it is the smallest sawtooth angle at the sandstone–concrete interface that dominates the dynamic shear strength of sandstone–concrete specimens. The findings in the present study could facilitate understanding the shear behavior and failure mechanism of the rock–shotcrete structure subjected to dynamic loading and be helpful in the efficient design, reinforcement and stability of rock–shotcrete engineering.

Examination of interface roughness and particle morphology on granular soil–structure shearing behavior using DEM and 3D printing

Understanding the mechanical behavior of soil-structure interaction (SSI) is crucial for the safety and stability of infrastructures. From mesoscale to macroscale, the coupled effects of particle morphology and structural surface roughness on SSI has received little attention. Herein, a series of interface shear tests and simulations were carried out by combining 3D printing and discrete element method (DEM). To quantitatively characterize particle shape and structural surface roughness, modified particle shape parameter Sh and interface morphology factor λ are introduced. The results indicate that increasing the inclination of asperities 1/λ promotes lateral slip displacement of particles and results in significant delamination at the interface. In the vertical shear direction, particle displacement exhibits two patterns: backward falling and maximum displacement at the top of the shear zone, and continuous forward displacement decrease along the height of the specimen. Thus, a new index (i.e., maximum backward falling displacement of particles) is proposed to define the shear zone thickness. Particle shapes and interface roughness have different effects on the particle displacement in the vertical shear direction. An increase in Sh reduces relative displacement, while an increase in 1/λ can increase the magnitude of the relative displacement of particle lateral sliding. The overall strength of particles depends on the coupling effect of particle shapes and interface roughness, both of which have corresponding thresholds. As the interface roughness or Sh increases, three parameters used to describe the contact state of clusters first increase until reaching a turning point and then remain stable or slightly decrease. This paper aims to broaden the understanding of the coupling effects of interfaces with various roughness and particles with different shapes on SSI, with the ultimate goal of contributing to the design of structural interfaces more effective and safety in sandy soil area.

Analytical model of skin friction for bored pile socketed into weak rocks in ice-rich permafrost regions

Bored piles constructed in permafrost regions often need to be socketed into weak and weathered rock strata, such as marl stratum. When these strata are ice-rich, the meltwater caused by construction will form an ice film at the pile-rock interface during refreezing, leading to a reduction in pile bearing capacity. By analyzing the shear mechanism of pile-rock interface with ice film, an interface shear model was proposed in this paper. Based on this model, the load transfer analytical method of rock-socketed bored piles was improved. Finally, the effects of pile-rock interface roughness, ice filling degree, and residual friction angle on skin friction were analyzed. The results show that the shear stress-displacement curve of the ice-containing interface unit exhibits two peaks and can be divided into four stages: ice film shear stage, ice film extrusion stage, concrete-rock relative sliding stage, and interface residual sliding stage. Increasing either the dilation angle or half-wavelength can improve the interface's shear resistance when only one variable is altered. Furthermore, the peak shear strength of the interface decreases as the filling degree increases. The interface residual shear stress is positively correlated with both the residual friction angle of weak rock (ϕu−r) and ice (ϕi−r), and increasing the proportion of ice in the residual sliding surface will lead to the reduction of residual shear stress.

The Effects of Interface Roughness on the Pull-Out Performance and Failure Characteristics of Tunnel-Type Anchorages in Soft Rock

The Effects of Interface Roughness on the Pull-Out Performance and Failure Characteristics of Tunnel-Type Anchorages in Soft Rock

Regulated Thermal Boundary Conductance between Copper and Diamond through Nanoscale Interfacial Rough Structures.

Interfacial structure optimization is important to enhance the thermal boundary conductance (TBC) as well as the overall performance of thermal conductive composites. In this work, the effect of interfacial roughness on the TBC between copper and diamond is investigated with molecular dynamics (MD) simulations and time-domain thermoreflectance (TDTR) experiments. It is found from MD simulations that the thermal transport efficiency across a rough interface is higher, and the TBC can be improved 5.5 times to 133 MW/m2·K compared with that of the flat interface. Also, the TBC is only dominated by the actual contact area at the interface for larger roughness cases; thus, we conclude that the phonon scattering probability increases with the increase of roughness and becomes stable gradually. Finally, the TBC of the copper/diamond interface with different roughness is characterized by TDTR experiments, and the results also confirm the trend of MD simulations. This study demonstrates the feasibility of the roughness modification for interfacial thermal management from both theoretical analysis and experimental measurements and provides a new idea for enhancing the thermal conductivity of composites.

Visualizing the Effect of Oxidation on Magnetic Domain Behavior of Nanoscale Fe3GeTe2 for Applications in Spintronics

Magnetic van der Waals (vdW) materials offer an opportunity to design heterostructures that will lead to exotic functionalities that arise from interfacial interaction. In addition to coupling to different vdW materials, the naturally oxidized surface layer of a vdW material also forms a heterostructure with its bulk film, giving rise to intriguing phenomena. Here, we directly observe the impact of oxidation on the magnetic domains, namely, magnetic stripe domain and skyrmions, in a nanoscale Fe3GeTe2 flake using cryo Lorentz transmission electron microscopy. After the Fe3GeTe2 is exposed to ambient conditions, partial oxidation leads to an increase in the density of skyrmions even under zero magnetic field. Complete oxidation leads to a loss of the magnetic domain structure. We observe a gradual change in Fe3GeTe2 from single crystal to amorphous as the oxidation increases. The oxidized Fe3GeTe2 primarily consists of iron oxide, which could be antiferromagnetic in nature. We hypothesize that the interfacial interaction between these surface antiferromagnetic oxides and the bulk ferromagnetic Fe3GeTe2, as well as the effect of interfacial roughness, leads to the increase in Néel skyrmion creation. This work opens a path to harness controlled oxidation as a build block to create dense skyrmion lattices without the need for an external magnetic field, leading to potential future applications in spintronic devices.

Effects of the substrate state beneath the coating-substrate interface on fatigue properties of micro-arc oxidation coated 6082-T6 aluminum alloy

Low, medium and high-intensity (0.19, 0.26 and 0.34 mmA) shot peening treatments and 0.34 mmA high-intensity shot peening combined with slight and severe polishing treatments were used as the pre-treatments to improve the fatigue property of micro-arc oxidation (MAO) coated 6082-T6 aluminum alloy, respectively. In consideration of the significance of substrate residual stress beneath the coating-substrate interface on MAO coated specimens' fatigue property, the substrate residual stress of various coated specimens was analyzed by the X-ray's powerful penetrability. Results indicate that the substrate residual stress state of MAO coated specimens is changed from tensile (+93 MPa) to compressive (−65 to −93 MPa) by the above pre-treatments, which is beneficial for inhibiting the crack initiation at the substrate or resisting the crack's further propagation from the coating into the substrate. Whereas, similar to the compressive residual stress induced by shot peening, the compressive substrate residual stress for prior shot peening + MAO composite coated specimens will also relax during the fatigue tests. In addition, the gradient compressive residual stress beneath the interface induced by prior shot peening reduce the crack propagating rate, thus improving the fatigue property of coated specimens; after the 0.26 mmA shot peening pre-treatment, the fatigue strength at 2 × 107 cycles of MAO coated specimens increases by 59.1 %. Finally, the effects of surface and interface roughness, substrate residual stress and in-depth compressive residual stress on the fatigue life of MAO coated specimens are further discussed.

Load transfer analysis of vertically loaded bored piles in sea reclamation areas considering the effect of the pile-gravel interface roughness

A load transfer model for vertically loaded bored piles in sea reclamation areas with gravel is proposed in this paper. The focus is on quantifying the mobilization of pile-side friction, which is closely related to the shear behaviors of the pile-gravel interface. The surface profile of the gravel particles and the concrete piles are assumed to be circle and wave curves, respectively. The shear displacement and dilatancy calculation are based on the macro and micro geometry relationship between gravel particles and pile surface. The shear stress calculation of the pile-gravel interface is dealt with by empirical elastoplastic equations. A simple slip-line field is also built to identify the critical shear displacement. The finite difference equations are used to derive the load-displacement curves for vertically loaded bored piles in sea reclamation areas with gravel. The model predictions are compared with field observations and particle flow numerical simulation to validate the performance of the proposed method, and the results prove to be reasonable. Moreover, parameter studies are conducted and the results prove that the pile can bear more load when the particle diameter is similar to the pile's rough surface, and both the increases of wave angle and the relative friction coefficient can promote the bearing capacity.

Correlation of interfacial stress with the surface roughness of carbon fiber in composites by the improved shear-lag theory

ABSTRACT An improved shear-lag model is proposed in this article to study the effects of interface roughness and interfacial stiffness on the mechanical properties of a representative volume element (RVE). The surface roughness of the fiber is represented by grooves distributed around the fiber. The interfacial stiffness is introduced by the cohesive zone modeling (CZM) to study the nonideal adhesion interface. This paper also considered the influence of fiber length on stress transfer. The theoretical model was validated through numerical simulation considering both regularly and irregularly distributed grooves. The results show that the improved shear-lag model can describe the interfacial stress properties accurately. Furthermore, it is found that the influence of surface roughness varies for different interfacial stiffness. The proposed method and results can guide the design and analysis of interfacial modifications in carbon fiber composites.

Interface roughness effects and relaxation dynamics of an amorphous semiconductor oxide-based analog resistance switching memory.

The analog resistive switching properties of amorphous InGaZnOx (a-IGZO)-based devices with Al as the top and bottom electrodes and an Al-Ox interface layer inserted on the bottom electrode are presented here. The influence of the electrode deposition rate on the surface roughness was established and proposed as the cause of the observed unusual anomalous switching effects. The DC electrical characterization of the optimized Al/a-IGZO/AlOx/Al devices revealed an analog resistive switching with a satisfactory value for retention levels, but the endurance was found to decrease after 200 cycles. The predominant conduction mechanism in these devices was found to be thermionic emission. An in-depth analysis was performed to explore the relaxation kinetics of the device and it was found that the current has a lower decay rate. The current level stability was tested and found reliable even after 5 h. The cost-effective and precious metal-free nature of the a-IGZO memristor investigated in this study makes it a highly desirable candidate for neuromorphic computing applications.

The effect of seafloor roughness on passive estimates of the seabed reflection coefficient.

In this work, a model is developed for the effect of seafloor interface roughness on passive estimates of the reflection coefficient. The main result is an expression for the total intensity reflection coefficient, with separate coherent and incoherent contributions. Assumptions of this model include constant sound speed in the ocean, stationary and Gaussian seafloor roughness, and ambient noise. Numerical examples for the coherent, incoherent, and total contributions to the intensity reflection coefficient are presented for halfspace and layered environments-all using the small slope approximation. To illustrate the potential parameter errors that results from using a flat interface wave model when roughness is present, a geoacoustic inversion is performed using the proposed model as input data. A joint roughness-geoacoustic inversion of simulated data using the proposed model was also performed. It was found that the true roughness and geoacoustic parameters can be inverted using this model, but the sensitivity to the outer scale of the rough surface has the highest error compared to the other parameters.