Deformation Of Components Research Articles

Texture transition in friction stir processed Al powder compact

Green Al powder compacts of commercial purity with random orientation were subjected to single pass friction stir processing (FSP) with different tool rotational and traverse speeds. The evolution of crystallographic texture obtained from large area electron back scattered diffraction were compared with the bulk texture of the nugget zone characterized using synchrotron diffraction. Evolution of different deformation and recrystallization texture components were discussed. While the grain size distributions were found to be independent of process parameters, the texture components and their strength of the FSPed samples were strongly influenced by the process parameters. Continuous dynamic recrystallization (CDRx) was found to be the primary restoration mechanism for most of the processing conditions leading to a bi-modal misorientation distribution. The possible relations between different texture components and the appearance or suppression of bimodal misorientation distributions were discussed. Restoration mechanism changed to discontinuous dynamic recrystallization (DDRx) with the evolution of cube component at the stir zone along with random misorientation distribution. Dominance of a particular restoration mechanism depends on strain, strain rate and temperature attained during the processing.

Effect of density on skin friction response of piles embedded in sand by simple shear interface tests

This study focuses on a particular phenomenon related to the reduction in sand–pile skin friction with initial relative density increment from medium to dense. Frictional behaviour of a sand–pile interface is simulated using a simple shear-type device capable of inducing a constant normal stiffness condition. Sand–pile interface sliding and soil deformation components are distinguished quantitatively. The effects of initial relative density of sand, initial normal load, and constant normal stiffness on the magnitude of the pile skin friction and shear displacement at failure are examined. Results indicate that the magnitude of the mobilized shear stress at failure relies significantly on the shear stress state with respect to the inflexion point on the volume change graph, which is equivalent to the position of the peak stress ratio. Good correlations exist between results of this study and field data of several heavily instrumented piles embedded in dense to very dense sands. The presented procedure is a useful framework for establishing more accurate skin friction calculation methodologies and “t-z” curve developments of axially loaded piles.

3D multi-source model of elastic volcanic ground deformation

Developments in Interferometric Synthetic Aperture Radar (InSAR) and GNSS (Global Navigation Satellite System) during the past decades have promoted significant advances in geosciences, providing high-resolution ground deformation data with dense spatio-temporal coverage. This large dataset can be exploited to produce accurate assessments of the primary processes occurring in geologically active areas. We present a new, original methodology to carry out a multi-source inversion of ground deformation data to better understand the subsurface causative processes. A nonlinear approach permits the determination of location, size and three-dimensional configuration, without any a priori assumption as to the number, nature or shape of the potential sources. The proposed method identifies a combination of pressure bodies and different types of dislocation sources (dip-slip, strike-slip and tensile) that represent magmatic sources and other processes such as earthquakes, landslides or groundwater-induced subsidence through the aggregation of elemental cells. This approach has the following features: (1) simultaneous inversion of the deformation components and/or line-of-sight (LOS) data; (2) simultaneous determination of diverse structures such as pressure bodies or dislocation sources, representing local and regional effects; (3) a fully 3D context; and (4) no initial hypothesis about the number, geometry or types of the causative sources is necessary. This methodology is applied to Mt. Etna (Southern Italy). We analyze the ground deformation field derived from a large InSAR dataset acquired during the January 2009 – June 2013 time period. The application of the inversion approach models several interesting buried structures as well as processes related to the volcano magmatic plumbing system, local subsidence within the Valle del Bove and seaward motion of eastern flank of the volcano.

Wear Kinetics of Steels with Diffusion Coatings in Rolling Friction

It is shown that the wear kinetics of steels with diffusion coatings under the conditions of rolling friction strongly depends on the physicomechanical properties and phase compositions of the coatings, hardness of the base, and the modes of thermal and thermochemical treatments. The dependence of the degree of wear on the number of loading cycles is always parabolic. The contact fatigue strength in rolling is strongly affected by the ratio of slip and deformation components of wear. The deformation component is predominant for low hardnesses of the surface and the base and results in the minimum contact fatigue strength. At the same time, the slip component prevails for high hardnesses of the base and corresponds to the highest contact fatigue strength under the conditions of rolling friction.

Deformations of reinforced-concrete beam–column joint assemblies

Beam–column joints are generally recognised as critical regions in the analysis and design of moment-resisting reinforced-concrete (RC) frames subjected to both lateral and vertical loads. Such joints should be designed and detailed to ensure that they have adequate overstrength and allow adjacent beams to reach their full ductile capacities. To develop an improved method for predicting the deformation capacity of RC beam–column joint assemblies, the deformation contributions of structural members connecting the joint should be considered. A method is proposed to predict the deformation component ratios of RC beam–column joint assemblies that fail in shear after the adjacent beams have reached their full plastic capacities. The proposed method takes into account the effect of the longitudinal axial strain in the plastic hinge region of beams on the joint longitudinal strain and the strength deterioration of the joint. To verify the deformations of typical RC beam–column joint assemblies estimated using the proposed method, six specimens were tested. Furthermore, 35 experimental results of joints reported in the technical literature were compared with the deformations predicted by the proposed method. Comparisons between the observed and calculated deformations of the considered RC beam–column joint assemblies showed reasonable agreement.

Subsurface characterization of quaternary scarps and their possible connection to main structures of the western margin of Precordillera, San Juan, Argentina

The El Tigre fault provides a significant example of Pliocene-Quaternary tectonic activity at the West of Precordillera, receiving considerable attention in the last years. However, longitudinal thrusts of the nearest Sierra del Tigre and a minor piedmont deformation belt identified in its western piedmont are still poorly understood. The present work comprised a detailed map of the geomorphological features of tectonic origin and Quaternary alluvial fan terraces located between the Sierra del Tigre and the El Tigre fault. Several topographic and geoelectrical profiles across minor fault and fold scarps were surveyed to define the displacement scarps, the geological structure geometries at subsurface and their relationship with main structures. Geoelectrical models allowed us to recognize three geoelectrical levels: A (> 200–300 Ω.m) correlated to Pleistocene alluvial fan terraces Q4 and Q3; B (ranging from 50 to 300/450 Ω.m), under level A and correlated to the Neogene substratum (Rodeo Formation); C (< 30–40 Ω.m) intercalated in level B, conforming aquifers (20 and 40 m deep) within the Neogene substratum. Subvertical conductive zones (10–40 Ω.m) were correlated to high angle (~60°-80°) reverse faults, which are associated with open anticlines and synclines that affect the Quaternary levels and the Neogene substratum. The structural style interpreted here allows us to conclude that the main piedmont thrust is a frontal splay of the backthrust of the Sierra del Tigre with western vergence. A better connection to the compressive deformation component, which uplifts the range, instead of to the strike-slip deformation component of the El Tigre Fault is demonstrated. This tectonic propagation probably happens during Middle-Upper Pleistocene to Holocene. The observations show that minor deformation belt is subjected to piedmont compressive movements while the El Tigre Fault absorbs the strike-slip movements, so a local partition of the deformation in the western margin of Precordillera probably happens during Quaternary.

Multiresolution analysis relying on Beta wavelet transform and multi-mother wavelet network for a novel 3D mesh alignment and deformation technique

In this paper, we propose a new 3D high mesh deformation technique to extract intuitive and interpretable deformation and alignment components. Our framework is based on a fast Beta wavelet transform for a multi-resolution analysis relying on multi-library wavelet neural network architecture. The main drawback of 3D high mesh deformation is the large number of triangles necessary to characterize a smooth surface; the majority of these techniques impose a very high computational cost. Our approach is based on the idea of combining the decomposition technique of multi-resolution analysis by Beta wavelet transform for each level of deformation process and a multi-mother wavelet network structure to construct an effective 3D alignment algorithm. We use, in our experiment, only the approximation coefficients at a chosen decomposition level to reduce the complexity of the mesh and to facilitate the alignment until reaching the target mesh, for the purpose of improving various executions and obtaining an optimal solution while reducing the error between the original and the reconstructed object to create a well-formed object. Then, to enhance the performance of wavelet networks, a novel learning algorithm based on multi-mother wavelet neural network architecture using trust region spherical is employed as an approximation tool for feature alignment between the source and the target models. This network architecture ensures the use of several mother wavelets to solve the problem of high mesh deformation utilizing the best wavelet mother that well models the object. Extensive experimental results demonstrate that the progressive deformation processes aim at avoiding the weaknesses of traditional approaches such as the slowness and the difficulty of finding an exact reconstruction.

Experimental investigation and simplified stiffness degradation model of precast concrete shear wall with steel connectors

Premature damage of the post-cast concrete joints of precast concrete shear walls (PSWs) was observed in the past earthquakes due to the poor connection details and stress concentration of the wall-beam-slab joints. To avoid the potential failure, a new connection method featuring steel connectors, applied in the PSWs, is firstly proposed based on the plastic damage relocation design concept. Five 1/3 scaled specimens, including one monolithic concrete shear wall (MSW) and four PSWs, were constructed and tested under quasi-static cyclic loading. Seismic performances in terms of damage modes, drift ratio versus shear force behaviors, equivalent viscous damping ratio, deformation components, and stiffness degradation characteristics of PSWs were investigated. It shows that concrete cracks are developed at the bottom of the precast shear wall panel initially and its crack widths are decreased. The connection method can provide efficient stiffness and strength for the precast concrete shear wall system as no significant degradation of shear force occurs before a drift ratio of 1/50. Precast concrete shear wall having T-shaped with non-full length type connectors (TPSW-N) has the lowest cracking shear force and one having H-shaped connectors (HPSW) possesses a more stable lateral force-resisting capacity. The equivalent viscous damping ratios of the PSWs are higher than that of the MSW up to a drift ratio of 1/100. Among the PSWs, the HPSW shows the best seismic performance by comprehensively considering the damage mode, shear force characteristics and energy dissipation capacity. The flexural deformation at the middle of the precast shear wall panel is decreased compared with that of the wall panel of the MSW. The proposed connection method moves the critical region outside the week connection zones, which could be an alternative for the conventional post-cast concrete connection scheme. A simplified five-line stiffness degradation model of PSWs, controlled by elastic, cracking, yield, peak and ultimate points, is established and verified. The simplified model can be used to estimate the stiffness degradation properties of the proposed PSWs.

ВЛАСТИВОСТІ ЕЛАСТИЧНИХ ОСНОВОВ'ЯЗАНИХ БИНТІВ

The market analysis of knitted elastic bandages in Ukraine, the investigation of the parameters and properties of the most common products and their comparison as well as determination of compliance to requirements are the main purposes of this study. Methodology. Standard test methods were used to experimental study the raw material composition, type of interlooping, structure parameters and relaxation characteristics of elastic bandages. Results. As a result of the study of the elastic bandage structure, it is found that all tested bandages are produced on Crochet knitting machine using four yarn systems. chain stitch with closed loop from is a ground interlooping. The ground guide bar is partially threaded with polyester yarn depending on the manufacturer. The requested level of elasticity is provided by elastomeric threads, which are used as longitudinal in-lay yarn with incomplete threaded of the guide bar and a diff erent repeat of its shifting behind the needles. The other two yarns systems are cotton yarn in several ends, which is laid across the bandage's entire width at both sides of the elastomeric yarn, ensuring its overlap and the combination of individual chain wales into the fabric. Obtained experimental data of the parameters and elongation of elastic bandages of diff erent manufactures allowed to establish their compliance with standardized values. It ensures the products functionality during usage. It is indicated that the yarn composition specifi ed by the manufacturers correlated with experimental results. The percentage of the elastomeric thread content is not a determining characteristic of the bandage's stretchability since the elastic component of full deformation for all tested bandages exceeds 0.95. The residual component is less than 0.02. It is indicating high elastic properties and functionality. The practical signifi cance of the work is confi rmed by the possibility of evaluating a bandage of a particular manufacturer based on the resulting array of their properties data. The results of the work expand the knowledge about the infl uence of the knitted structure on the parameters and deformation properties of elastic bandage.

Simplified numerical approach for the lateral load analysis of light-frame wood shear wall structures

Increasing global demand for a sustainable society is driving the development of multi-storey light-frame wood structures, yet their complex structural components make detailed finite element modelling (FEM) impractical. The structural response of these buildings cannot typically be accurately captured with traditional simplified computational methods that rely on the use of parameter-based spring hysteretic properties or mathematical derivation. This paper proposes a powerful simplified nonlinear FEM procedure capable of accurately and efficiently capturing the responses of single-storey and multi-storey light-frame wood shear wall structures with respect to lateral displacement against base shear. The proposed procedure involves the separation of flexural and shear deformations from the total deformation resulting from the detailed model pushover analysis. The nonlinear curves of these deformation components against base shear are used to develop the properties of simplified axial and shear link models based on an approach equating external and internal work. To demonstrate the accuracy of the simplified FEM in conducting pushover analysis for structures with different structural details, 6 single-storey shear walls and 4 four-storey shear walls were modelled using this nonlinear simplified FEM analysis procedure. Compared with detailed FEM procedure, the developed simplified FEM method accurately captured the pushover analysis results with acceptable discrepancies and significantly less computational time. This proposed simplified procedure has the potential for wide applicability in structural design and analysis through the establishment of a simplified model database and the embedment of this database into any commonly used commercial FEM software.

Numerical study on seismic behavior of precast bridge columns with large-diameter bars and UHPC grout considering the bar-slip effect

A novel connection adopting lap-spliced large-diameter bars and ultra-high performance concrete (UHPC) grout was developed to accelerate the assemble progress of precast bridge columns. The precast bridge column adopting the connections was testified to be on a par with the monolithic concrete counterpart in terms of seismic performance in previous research. This paper aims to develop a numerical model to further investigate the seismic behavior of the proposed bridge column considering the bar-slip effect. A finite element model was established for the bridge columns considering deformation components of flexure, shear, and bar-slip. The bond behavior between the deformed bar and UHPC was defined using a new practical model, which was developed based on a pullout test including five specimens in this research. The established finite element model was verified by the cyclic loading test in literature in terms of the overall hysteretic curve and local responses. The validated model was used to conduct parametric analysis to study the contributions of the different deformation components to lateral deformation as well as the effects of large-diameter bars on seismic performance. Results show that all the pullout specimens have the tensile fracture of bars, which indicates that the development length of 5 times bar diameter is sufficient for deformed bars in UHPC when the bar diameter is no more than 32 mm. The practical model is effective to consider the effects of the slip between the deformed bar and UHPC. The finite element model can predict the overall hysteretic curve and local responses at different drift ratios. The bar-slip has a considerable even dominative contribution to the lateral deformation of the proposed bridge column. Larger bar diameter can enhance deformation capacity as well as reduce energy dissipation and residual drift ratio.

Algorithm of applying the energy conservation law to study the thermal stress-strain state of a rod of variable cross section with the simultaneous presence of local temperatures, heat exchanges and thermal insulations

The bearing elements of power plants, internal combustion engines of jet engines, nuclear thermal power plants, gas-generating power plants, processing lines, and spacecraft antennas are rods of variable cross-section. They work in a difficult temperature environment. In this paper, we propose an algorithm for applying the fundamental law of energy conservation for a deep study of the resulting thermal-stress-strain state of a rod of limited length and variable cross-section in the simultaneous presence of local temperatures, heat exchange and thermal insulation. At the same time, the obtained solutions in the form of determining the temperature field, displacement, all the components of deformations and stresses, as well as the calculated values of the rod elongation and the resulting axial force are highly accurate at the level of satisfying the energy conservation law.

Transient Vibro-Thermography and Nonlinear Resonant Modes

Abstract Transient vibro-thermography for nondestructive evaluation and super-resolution imaging of material defects invariably employs nonlinear contact dynamics involving the ultrasonic actuator (horn) and the surface of the target structure. It produces nonlinear resonant modes of vibration in the target structural component. Vibration-induced heat generation is one phenomenon involved here. However, the contribution of nonlinear vibration on the thermal signature is poorly understood. In this study, we consider a metallic component with a thin-walled cavity as a representative sharp feature tuned to the main excitation frequency of the ultrasonic actuator. We have developed a mathematical model to simulate transient thermal signature of structural discontinuity/cavity/defect. The model incorporates a coupled thermo-viscoelastic heat generation process in the bulk material based on the Helmholtz free energy formulation. To capture the source of nonlinear resonant modes, we incorporate the stick-separation contact dynamics due to the ultrasonic horn and the target structural component. Commercial finite element simulation (comsol multiphysics) is used to quantitatively understand the nonlinear vibration response and the thermal transport behavior of the target structure with the cavity. The proposed model accounts for the effects of both the normal and the shear components of deformation contributing on heat generation and captures the nonlinear modal contribution on the heat flux map. The study shows how the geometric feature and material parameters produce an evolution of the nonlinear subsuper harmonics along with the primary harmonics tuned to the excitation frequency. Results obtained from numerical simulations are compared with the experimental results.

Reduced ice mass loss and three-dimensional viscoelastic deformation in northern Antarctic Peninsula inferred from GPS

SUMMARY We consider the viscoelastic rheology of the solid Earth under the Antarctic Peninsula due to ice mass loss that commenced after the breakup of the Larsen-B ice shelf. We extend the previous analysis of nearby continuous GPS time-series to include five additional years and the additional consideration of the horizontal components of deformation. They show strong uplift from ∼2002 to 2011 followed by reduced uplift rates to 2018. Modelling the GPS-derived uplift as a viscoelastic response to ongoing regional ice unloading from a new ice model confirms earlier estimates of low upper-mantle viscosities of ∼0.3–3 × 1018 Pa s in this region but allows a wide range of elastic lithosphere thickness. The observed and modelled north coordinate component shows little nonlinear variation due to the location of ice mass change to the east of the GPS sites. However, comparison of the observed and modelled east coordinate component constrains the upper-mantle viscosity to be less than ∼9 × 1018 Pa s, consistent with the viscosity range suggested by the uplift rates alone and providing important, largely independent, confirmation of that result. Our horizontal analysis showed only marginal sensitivity to modelled lithospheric thickness. The results for the horizontal components are sensitive to the adopted plate rotation model, with the estimate based on ITRF2014 suggesting that the sum of residual plate motion and pre-2002 glacial isostatic adjustment is likely less than ∼±0.5 mm yr−1 in the east component.

Monitoring mining-induced subsidence by integrating differential radar interferometry and persistent scatterer techniques

ABSTRACT Surface subsidence is a dominant component of the displacement vector triggered by underground mining. Over the last few decades, Differential Interferometry Synthetic Aperture Radar (DInSAR) has been used to efficiently monitor this phenomenon with great spatial and temporal coverage. More advanced multi-temporal DInSAR (MTInSAR) algorithms have been proposed to overcome some of the limitations of conventional DInSAR. However, advanced MTInSAR approaches are also not perfect in terms of measuring mining subsidence (e.g., temporal decorrelation, ambiguity, nonlinearity). For this reason, we propose a fusion of the Persistent Scatterer Interferometry (PSInSAR) and DInSAR results. By combining these complementary techniques, the atmospheric errors in PSInSAR data are reduced and larger deformation rates could have been detected more accurately (thanks to DInSAR) than by an approach solely based on PS-InSAR. This allows to measure areas with fast-moving subsidence (1 m/year) due to ongoing underground coal exploitation. Data from ascending and descending orbits of Sentinel-1A\\B were used to obtain the vertical deformation component. The resulting integrated vertical deformation map was compared with the results from levelling benchmarks. The Root Mean Square Error (RMSE) calculated based on this comparison was 22 mm. Moreover, the maximal vertical cumulative subsidence detected in the study area was 1.05 m/year.

Improvement of Stamping by Rolling Processes of Pipe and Cylindrical Blades on Experimental Research

During the experimental study, a pronounced beating and sealing of the side surface of the tubular, cylindrical blanks was recorded. It is established that cracks appear and develop in the central part of the lateral surface, i.e., it are destroyed. This fact confirms the claim that the destruction of tubular, cylindrical blanks of some materials begins on the side surface. It is established that the bases of analytical dependencies between the components of deformations describe the obtained results of the experimental study of SR tubular, cylindrical blanks within the error of the experimental data, which made it possible to construct a number of mathematical models for the purpose of further study of the SDS and the method of their determination.

Sliding of a Smooth Indenter over a Viscoelastic Half-Space Covered with an Elastic Layer

A solution method is proposed for a 3-D contact problem that considers an indenter sliding over a viscoelastic half-space covered with a Winkler layer. Analysis of the contact pressure distribution, deformation component of the friction force, and internal stresses depending on the properties of elastic layer and other input parameters was carried out. It is shown that the presence of an elastic layer decreases the deformation component of the friction force and also leads to a significant decrease in the internal stresses of the substrate.

Curve severity and apical vertebral rotation and their association with curve flexibility in adolescent idiopathic scoliosis

PurposeTo determine the association between coronal Cobb’s angle and Nash–Moe index in patients with adolescent idiopathic scoliosis. We also attempted to determine whether apical vertebral derotation depended upon the curve flexibility.Overview of literatureThe three-dimensional nature of adolescent idiopathic scoliosis (AIS) is well established. Knowledge of all components of this complex deformity is essential to formulate effective treatment strategies. Though the importance of quantifying all the components of the deformity, in AIS, has been analysed in detail, very few studies have been done to ascertain the relationship between the coronal plane deformity and apical vertebral rotation.MethodsDigitalised standing and supine stretch anteroposterior (AP) radiographs of 158 patients with AIS were analysed. The standing and supine stretch AP radiographs were compared to calculate the percentage reduction of Cobb’s angle to determine curve flexibility. The derotation of the apical vertebra on application of traction was also noted. The one-way repeated ANOVA was used to determine the association between Cobb’s angle and Nash–Moe index. The independent sample t test was used to determine whether a statistically significant difference was present, in the age of the patient, severity of the curve and percentage reduction of Cobb’s angle between those curves that derotated and those that did not, when stretched.ResultsThe one-way repeated ANOVA revealed an association between Cobb’s angle and Nash–Moe index on the standing and supine AP stretch radiographs (P < 0.01). The Independent sample t-test showed a statistically significant difference in percentage reduction of Cobb’s angle between those curves that derotated compared to those that did not, on stretch (P < 0.01).ConclusionsThis study demonstrates that there is an association between apical vertebral rotation and the coronal plane deformity. It also demonstrates that flexible curves derotate to a greater extent compared to rigid curves, when stretched.

Hydrologic control on natural land subsidence in the shallow coastal aquifer of the Ravenna coast, Italy

Abstract. Multiple processes contributing to natural land subsidence in a shallow coastal aquifer near Ravenna (Italy) were identified by analysing the relationships among different data set time series (water table level, rainfall, land reclamation drainage, sea level, etc.) and establishing the correlations with vertical ground motion observed at a high-resolution settlement gauge. Our study highlights the presence of three deformation components related to different processes controlling land subsidence: elastic, delayed-elastic, and irreversible (plastic) components. The elastic and delayed-elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily (in the sandy unconfined portion) and seasonal time scales (in the layered clay-rich semi-confined prodelta portion), respectively. The irreversible component represents the trend in the land subsidence time series and is due to primary consolidation (pore pressure dissipation) of the fine-grained prodelta levels above where the settlement gauge is located. The amplitudes of the elastic component can be up to 0.2–0.3 mm whereas the amplitude of the delayed-elastic component reaches 0.89 mm. The primary consolidation rate of deformation is 0.9 mm yr−1 and constrains the likely age of prodelta sediments deposition to 1300–2800 years before present. The delayed-elastic subsidence rate has similar magnitude to that due to primary consolidation and is connected to poroelastic effects in the prodelta sequence following seasonal variations in water table. Our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings. The natural land subsidence rate in the Holocene sediments of the shallow coastal aquifer of Ravenna (North eastern Italy) that we measured in this study accounts for 10 %–20 % of the total current land subsidence rate observed in this portion of Ravenna coastal area (10–20 mm yr−1).

Modeling the Contribution of Poroelastic Deformation to Postseismic Geodetic Signals

AbstractTo constrain the poroelastic component of postseismic deformation, we model the subsurface hydrologic response to the Mw 7.6 subduction zone earthquake that occurred on the plate interface beneath the Nicoya peninsula in Costa Rica on 5 September 2012. The model shows that poroelastic relaxation occurs on multiple time scales and the associated deformation can be up to 2 cm for the trench‐perpendicular component. By modeling the time‐dependent deformation associated with poroelastic relaxation, we can begin to remove its contribution from the observed geodetic signal. Inversions for after slip that ignore poroelastic deformation have errors of 10–20% overall and up to 50% locally. Poroelastic effects can both mute and amplify the inferred afterslip.