Mechanism Of Surface Deformation Research Articles

Enhanced fretting fatigue strength of TC11 titanium alloy using laser-assisted ultrasonic surface rolling process

In this paper, ultrasonic surface rolling (USRP) and laser heating-assisted USRP (Laser-USRP) techniques are employed to enhance the fretting fatigue strength of TC11 titanium alloy. Furthermore, the surface deformation mechanism and fretting fatigue behavior are investigated. The properties of the reinforced surfaces were observed using transmission electron microscope (TEM), microhardness test, residual stress test and fretting fatigue experiments. The results showed that laser-USRP led to a remarkable enhancement in the fretting fatigue life of TC11 titanium alloy compared to traditional USRP. This was mainly due to the fact that laser heating improved the plasticity of TC11 titanium alloy, contributed to the formation of a smoother surface and increased the degree of surface oxidation, which could improve surface lubrication. Under high temperature, more slip systems were activated and more stable dislocations were formed, which resulted in larger compressive residual stress (CRS) with higher stability. The superposition of the elevated temperature field and the kinetic energy of the ultrasonic vibration produced an annealing effect in localized regions, resulting in the formation of more stable gradient nanograins. This study demonstrated the immense potential of laser-assisted plastic deformation in improving the surface properties of titanium alloys.

Analytical method for laterally loaded short piles near clay slopes considering the soil-pile-slope surface deformation mechanism

Piles are inevitably installed on sloping coastlines or inclined seabeds to support offshore wind turbines, offshore bridges, and other structures. The objective of this paper is to develop an analytical method for investigating the lateral response of short piles near clay slopes. The soil-pile interaction is modelled by a two-spring model which is used to describe the soil resistance around the pile and the horizontal shear force at the pile base. Considering the combined effect of slope angle and near-slope distance, the ultimate soil resistance along the pile is divided into three cases based on the nearby soil flow mechanism. The soil-pile-slope surface deformation mechanism is established according to the rotational deformation characteristics of short piles. In contrast to the modification of the initial stiffness, the p-y curve around the pile is constructed by considering the deformation mechanism. The accuracy of the analytical method is verified by comparing its results with two piles on level ground and five piles near slopes. Considering the soil-pile-slope deformation mechanism, the secant stiffness of the p-y curve is automatically adjusted and reduced without the need for additional numerical simulations or pile tests to determine the reduction factor of the initial stiffness.

Friction anisotropy and associated surface deformation mechanisms in heterogeneous copper/bronze laminates

Heterogeneous laminates have demonstrated an extraordinary combination of strength and ductility. However, their response to tribological loading remains elusive. Here, a series of bulk heterogeneous Cu/CuZn laminates with layer spacings from 20 to 200 μm were prepared, to systematically investigate the role of layer spacing and sliding direction on friction and wear. We find that below a critical spacing value or above a tribological stress threshold, the friction coefficient and wear rate during sliding perpendicular to the laminate interface are much lower than the parallel one. When sliding parallel to the interfaces, the formation of a brittle nanostructured tribolayer dominates in the CuZn layers for all sliding cycles. While sliding perpendicular to the interfaces in the early stage, many deformation twins and dislocations form close to the interfaces in the CuZn layer, producing strain gradients and thus alleviating the strain localization. In the late stage of the sliding contact, friction-induced chemical mixing perpendicular to the interfaces is significantly stimulated below the critical layer spacing, mitigating the formation of a delaminating tribolayer. The observed friction anisotropy is intimately related to interface-induced strain delocalization, providing guidelines in designing the heterogeneous laminates with outstanding tribological properties.

Investigating Surface Deformation and Its Intrinsic Mechanism in Shenzhen, China Using Sentinel‐1A SAR Imagery

AbstractTo avoid disasters caused by surface deformation in urban areas, monitoring and analyzing the mechanism of surface deformation in urban areas on a large scale and in long‐term series is mandatory. Based on PS‐InSAR technology and using 157 Sentinel‐1A images, the surface deformation in Shenzhen was monitored from 2015 to 2022, and the obtained deformation rate ranged from −22.8 to +23.2 mm/year. In this paper, analysis is presented by integrating urbanization, climate, and geology data from Shenzhen. The analysis indicates that surface deformation caused by natural factors is typically observed in regions with unique geological characteristics, such as seasonal deformation in sedimentary areas and uplift along reverse fault zones. Human factors chiefly cause subsidence, and the areas with greater subsidence are generally urbanized areas (∼10 mm/year), industrial areas (∼20 mm/year), and reclamation areas (∼15 mm/year). The deformation of the reservoir dam is subject to multiple factors. The differential subsidence of 2–8 mm/year at both ends is due to the engineering geological conditions. In comparison, the weak rotation with a linear velocity of 18 mm/year is due to hydrostatic pressure and its structural characteristics. The research results of this paper systematically explore the phenomena and the intrinsic mechanism of surface deformation in Shenzhen, providing a safety basis for urban development and emergency disaster prevention in Shenzhen.

An exceptionally wear-resistant CoFeNi2 medium entropy alloy via tribo-induced nanocrystallites with amorphous boundaries

Single-phase face centered cubic (FCC) high entropy alloys (HEAs) usually display high coefficients of friction and poor wear resistance at ambient temperature, especially for CoCrFeMnNi HEA and its derived CoCrFeNi and CoCrNi medium entropy alloys (MEAs). Here, we reported a novel CoFeNi2 MEA exhibiting relatively low COFs (0.37–0.40); in particular, the wear rates (7.04 × 10−7 - 3 × 10−6 mm3 N−1 m−1) are two orders of magnitude lower than the other derivatives. This is primarily due to the unexpected occurrence of topmost micrometer-thick layer consisting of sub-10 nm nanocrystallites surrounded by the amorphous boundaries during steady-stage sliding. This study ignites some insights into designing exceptional friction and wear resistant MEAs/HEAs by linking to tribo-induced surface deformation mechanisms.

Extended terramechanics model for machine–soil interaction: Representation of change in the ground shape and property via cellular automata

Terramechanics, as an interdisciplinary field, focuses on the interaction between the ground and vehicles. Terramechanics concepts can be used to realize the design of underbodies and pass-planning of off-road vehicles, among other applications. However, conventional semi-empirical terramechanics models cannot accurately evaluate the terrain surface deformation associated with the interaction between the solid object and ground. Therefore, this article proposes an extended terramechanics model, which incorporates the terrain surface deformation mechanism based on cellular automata. First, to examine the effectiveness of the proposed model to capture variations in the terrain surface deformation and draft force, an analysis of a vertical plate drag test was conducted based on the proposed model. Next, a single-wheel traveling analysis was performed. The experimentally obtained drawbar-pull and sinkage could be reasonably simulated, which cannot be easily realized using conventional methods.

Tribo-induced surface deformation mechanisms govern friction and wear in ultra-light HCP and duplex Mg–Li alloys

Adding lithium into Mg can activate more deformation modes in both hexagonal close packed (hcp) and body centered cubic (bcc) Mg–Li alloys. In this work, friction and wear tests were performed on coarse-grained Mg-xLi-3Al–3Zn (x = 4 and 10 wt %) alloys and detailed surface deformation mechanisms were uncovered. Compared with the duplex Mg–10Li alloy, the hcp Mg–4Li shows a 40% lower friction coefficient and a significantly smaller wear rate by nearly one order of magnitude. The low wear rate stems from formation of hard and stable nanograined surface layer through rapid grain refinement of the hcp grains upon sliding. While for the dual-phase alloy, dynamic recrystallization (DRX) dominates the deformation of bcc grains, unavoidably causing its cracking and delamination within the ultra-fine grained DRX layer. Our results are suggestive in designing wear resistant ultra-light Mg–Li alloys through in-depth understanding of tribo-induced surface deformation mechanisms.

Time-Series Analysis and Prediction of Surface Deformation in the Jinchuan Mining Area, Gansu Province, by Using InSAR and CNN–PhLSTM Network

Surface deformation poses a great threat to the safety of Jinchuan mining area production activities. At present, the spatio-temporal evolution law and mechanism of surface deformation in the Jinchuan mining area are unclear, and it is difficult to obtain reliable prediction results using the existing spatio-temporal prediction methods due to the lack of model parameters or relevant data. To solve these problems, this study proposes a new unified convolutional neural network with peephole long short-term memory (CNN-PhLSTM). Small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technology was used to obtain the spatio-temporal evolution characteristics of surface deformation in the period of 2014–2021. Time series InSAR deformation data are merged into a unified network model in series with a time-distributed CNN segmentation and stacked PhLSTM. The InSAR measurement results are shown to be reliable by comparison and verification with the benchmark and InSAR results of different orbits. The proposed CNN-PhLSTM model was evaluated by mean absolute error and structural similarity (SSIM) evaluation indexes, and was compared with support vector regression (SVR), multilayer perceptron (MLP) and CNN-LSTM models. The results show three continuous subsidence areas, namely the Longshou, second western and third eastern mining areas. The cumulative surface deformation continued to increase from 2014 to 2021. Faults and lithology control the spatial distribution of surface deformation in the Jinchuan mining area. The prediction results demonstrate that the surface deformation range will continue to expand and that time-series surface deformation will show a slow deceleration trend in the next two years.

Tribo-Induced Surface Deformation Mechanisms Govern Friction and Wear in Ultralight HCP and Duplex Mg-Li Alloys

Tribo-Induced Surface Deformation Mechanisms Govern Friction and Wear in Ultralight HCP and Duplex Mg-Li Alloys

Friction of stable gradient nano-grained metals

In this paper, a novel strategy for lowering the coefficients of friction (COFs) of metals during dry sliding is introduced by producing a gradient nano-grained (GNG) surface layer without changing chemical compositions or phase constitution. Surface morphology variation, subsurface structural evolution and stress field analysis unfold that sliding-induced strain localization and microstructural instabilities are significantly mitigated through dislocation activity and grain boundary activities in the GNG surface layers. In addition, design guidelines for GNG materials with unprecedented low COFs are discussed based on interlinking tribological stress, surface deformation mechanisms and friction behavior.

Transient numerical simulation on the surface deformation for GAE forming of plastic micro-pipe

To ascertain the mechanism of gas-assisted extrusion (GAE) deformation for the plastic micro-pipe (PMP), the transient simulation was done. The geometric model based on three phase fluids and finite element mesh were established. To get the converge solutions, the Crank-Nicolson integration, the interpolation method of elastic-viscous split-stress finite element method combined with streamline-upwind scheme were used. At the reasonable boundary and material conditions, the GAE forming of PMP for different gases flow rates were numerically studied. Moreover, the extrusion profiles of PMP under different transient times were also obtained. To explain the reason of surface deformation for the GAE forming of PMP, the radial and axial velocity, and stress difference of melt under larger gases flow rates at different transient times were all obtained. The transient numerical results can better interpret the mechanism of surface deformation of PMP.

Numerical investigation on overburden migration behaviors in stope under thick magmatic rocks

Quantification of the influence of the fracture of thick magmatic rock (TMR) on the behavior of its overlying strata is a prerequisite to the understanding of the deformation behavior of the earth\'s surface in deep mining. A three-dimensional numerical model of a special geological mining condition of overlying TMR was developed to investigate the overburden movement and fracture law, and compare the influence of the occurrence horizon of TMR. The research results show that the movement of overlying rock was greatly affected by the TMR. Before the fracture of TMR, the TMR had shielding and controlling effects on the overlying strata, the maximum vertical and horizontal displacement values of overlying strata were 0.68 m and 0.062 m. After the fracture, the vertical and horizontal displacements suddenly increased to 3.06 m and 0.105 m, with an increase of 350% and 69.4%, respectively, and the higher the occurrence of TMR, the smaller the settlement of the overlying strata, but the wider the settlement span, the smaller the corresponding deformation value of the basin edge (the more difficult the surface to crack). These results are of tremendous importance for the control of rock strata and the revealing of surface deformation mechanism under TMR mining conditions in mines.

Measurement and analysis of surface deformation after the sixth nuclear explosion in the Democratic People’s Republic of Korea using InSAR

We use the small baseline subset (SBAS) method and Sentinel-1B synthetic aperture radar data to obtain the cumulative surface deformation at highly coherent points and different times (12-d intervals from September 10, 2017 to June 1, 2018) following the sixth nuclear explosion conducted by the Democratic People’s Republic of Korea (DPRK). The study is conducted for a 17 km ×22 km area centered on the explosion. Measurement points are aggregated into 14 sets according to their spatial neighborhood. According to the average coherence of each point in the set, the point deformation is weighted and averaged to obtain the cumulative deformation of each set. The location of each set is also weighted and averaged according to the average coherence of each point in standing for all points in the set. The analysis and discussion in this paper are based on these 14 sets for 14 different regions. Results show that the deformation process in the thermal radiation aftereffect stage of the sixth nuclear test can be effectively observed using interferometric synthetic aperture radar. There was still surface uplift near the epicenter for ~10 d after the explosion, after which the surface began to sink. The sinking rate and total sinking amount varied by location. Meanwhile, the phenomenon of subsidence slowing or even the surface uplifting possibly due to the freeze–thaw cycle of water in underground rock in winter was observed. After May 24, 2018, deformation began to rise because the government of the DPRK bombed the entrance of the nuclear facilities. We indirectly demonstrate the reasonableness and consistency of the observation results via the coherence of high-resolution optical images, meteorological data, and interferograms for the area of the nuclear explosion. The spatial and temporal distributions of surface deformation and their causes are then modeled. The results of modeling analysis are as follows. (1) In the thermal radiation aftereffect stage of the DPRK’s sixth nuclear explosion, the surrounding rock softened under high temperature and high pressure, and the surrounding metamorphic rock then compressed under the action of its own gravity and began to sink. This time-varying process is fitted by a deformation prediction model based on the Weibull function, and four parameters—namely the acceleration factor of deformation, comprehensive influence factor of deformation, initial surface deformation, and prediction value of maximum deformation—are obtained. The average correlation coefficient of the fitting curve is about 0.97. Model fitting results show that the sinking deformation tended to stop around May 20. (2) A function model was proposed to analyze the genetic mechanism of surface deformation, where the thickness of the layer of metamorphic rock is taken as the independent variable and the maximum deformation is taken as the dependent variable. The thickness of the layer of metamorphic rock was calculated for explosion burial depths of 450 and 770 m. The vertical impact distance of the explosion from the epicenter was about 1800–2300 m while the deformation coefficient of the metamorphic rock was about 7×10−5–8×10−5. The statistical fitting degree R 2 is about 0.8 and the P value is close to zero. In conclusion, the scope of the impact of the explosion metamorphism is the intrinsic condition of deformation, and gravity is the driving force of surface subsidence in the explosion area. Differences in the deformation rate and amount in different geomorphological locations are due to different thicknesses of the compressible layer relating to the rock thickness and metamorphism. Such differences have directionality, possibly because the attenuation of high-temperature and high-pressure propagation in the direction of tunnel works is less than that in the direction of surrounding rock.

Using Linear and Nonlinear Inversion Algorithm Combined with Simple Dislocation Model Inversion of Coal Mine Subsidence Mechanism

The long-term exploiting activity of coal mine threats the local ecological environment. Combined with surface level monitoring data of a mine in Jiangxi province, discussed the simplified dislocation model suited for coal mine, through the least squares method and Monte Carlo method to invert the Tensile component of mining area faulting. Comparing forward calculation data with level data, the accuracy of the inversion method has been analysis. The research results have realistic meanings for reducing the surface deformation mechanism due to the excavation in coal mine. It can provided theoretical basis for early warning of our country coal mining surface deformation.

Heliostat Surface Deformation Mechanism Design and Shape Optimization

Heliostat Surface Deformation Mechanism Design and Shape Optimization

On the modeling and shape optimization of hydrodynamic flexible-pad thrust bearings

A theoretical analysis of a hydrodynamic thrust bearing with a flexible-pad design is presented. The flexibility of pads improves the load-carrying capacity (LCC) of the bearing for a wide range of loading conditions by providing an adaptive surface deformation mechanism. To accurately predict the behavior of flexible-pad thrust bearings, an appropriate multi-physics model that considers the coupled mechanism between the lubricant pressure and the pad deformation is developed. An optimization study is carried out that uses hybrid harmony search algorithm and sequential quadratic programming to find the optimum geometrical parameters of the pad for maximum LCC. In addition, an approximate analytical method for optimum bearing design is presented. The results of simulations reveal that the flexible-pad bearings provide up to 30% more LCC in comparison with conventional inclined pad thrust bearings.

MD simulations of near surface void in copper under thermal compression

ABSTRACTDislocation mediated mechanism of surface deformation due to localized stress and strain concentration near a void could give an explanation of field enhancement in conditions relevant to the design of rf accelerating structures of the Compact Linear Collider (CLIC). We have performed molecular dynamics simulations of a near surface void in copper under thermal stressing conditions. The von Mises strain was observed to be concentrated near the void surface with the maximum strain concentration factor of 1.9. To observe the activated slip-planes, we exaggerated the compressive stress to the extent that the dislocations were nucleated on the void surface at sites where von Mises strain was largest. Void depth and size were found to affect the dislocation nucleation. The nucleation was easier for larger voids and for voids which were closer to the surface.

Dynamic subsidence basins in coal mines based on rock mass rheological theory

In order to investigate the surface deformation caused by coal mining and to reduce environmental damage, more accurate information of dynamic subsidence basins, caused by coal mining, is needed. Based on rheological theory, we discuss surface deformation mechanism of dynamic subsidence on the assumption that both the roof and the coal seam are visco-elastic media, put forward the idea that the principle of surface deformation is similar to that of roofs, except for their parameters. Therefore, a surface deformation equation can be obtained, given the equation of the roof deformation derived from using a H|M rheological model. In the end, we apply the equation of surface deformation as a practical subsidence prediction in a coal mine. Given the rheologic properties of a rock mass, the results of our research of a dynamic subsidence basin can predict the development of surface deformation as a function of time, which is more important than the ultimate subsidence itself. The results indicate that using rheological theory to calculate the deformation of a dynamic subsidence basin is suitable and provides some reference for surface deformation of dynamic subsidence basins.

Surface-Deformation Characteristics of Uniaxially Oriented Poly(ethylene terephthalate) Film as Evaluated from Nanoscratch Tests with Scanning Probe Microscopy

The surface-deformation characteristics of uniaxially drawn poly(ethylene terephthalate) (PET) film were successfully evaluated with multiline scratch tests using scanning probe microscopy (SPM) on a nanometer scale. The PET film was prepared by compression molding from the melt, followed by quenching in ice water. The obtained amorphous film was drawn uniaxially below its glass-transition temperature, and the resultant surface roughness could be reduced to within 5 nm. A multiline scratch with the Si(3)N(4) tip of an SPM on the oriented PET surface was made parallel and perpendicular to the drawing axis under applied loads of 5-30 nN. The perpendicular scratching generated a characteristic periodic pattern on the film surface, but the parallel scratching induced a tearing of the surface. These results suggest that surface-deformation mechanisms were dominated by molecular anisotropy. The surface-deformation properties, as evaluated from scratch-angle dependences on morphological changes on a nanometer scale, were similar to the mechanical properties of the bulk.

On stress whitening during surface deformation in clay-containing polymer nanocomposites: A microstructural approach

The study describes the surface deformation behavior and susceptibility to surface damage in two clay-reinforced intercalated polymer nanocomposite systems that have significant differences in ductility. Neat polybutene (PB) experiences a severe and distinct ‘quasi-periodic psiloma-type’ deformation process that was absent on reinforcement with clay. In clay-PB nanocomposite system, ‘ironing,’ a less severe surface damage mechanism is dominant. While in the less ductile polymethylpentene (PMP) polymer system, ploughing–tearing and micro-voiding constitute the surface deformation mechanism. Both the clay-reinforced polymer nanocomposite systems experience significantly reduced stress whitening and is characterized by a lower change in gray level. The optical transparency of the polymeric systems is governed by the micromechanism of deformation and is greater for the ductile PB system. The difference in the susceptibility to surface deformation behavior is discussed in terms of mechanical properties and clay-induced structural changes. The reinforcement of polymers with nanoclay has a positive overriding positive influence on the modulus and yield strength that increases the resistance to surface deformation.