Deformation Of Components Research Articles

Long-term deformation safety evaluation method of concrete dams based on the time-varying stability of concrete material

A concrete dam is a kind of large-volume hydraulic structure made of concrete materials. The deformation of the concrete material of the dam body has an obvious time effect. The time-effect component of deformation comprehensively reflects the trend change of the dam deformation and its stability is an important index for evaluating the long-term safety state of concrete dams. Dam safety monitoring theory is generally applied to obtain the time-effect component based on statistical models. The regression parameters of traditional concrete dam deformation statistical models are fixed values, which cannot effectively reflect the dynamic changes in concrete dam deformation characteristics. The variable parameter statistical model is more applicable to practical deformation law of concrete dam based on time-varying parameter. This paper constructs a novel variable parameter statistical model based on the recursive least squares with forgetting factor (FFRLS) method to derive a more precisely concrete dam time-effect component. FFRLS method assigns different weights to the modeling historical data and enhances the impact of new data on the statistical model. To analyze the long-term stability of the time-effect component of concrete deformation, the stability evaluation criterion of the time-effect component is established by its long-term variation characteristics and cusp catastrophe theory. The engineering example shows that the prediction effect of the variable parameter statistical model is better than that of the fixed parameter statistical model and traditional variable parameter statistical model, the mean absolute percentage error of FFRLS model are decreased by 97.39% and 54.63% on average compared with least squares (LS) and recursive least squares (RLS) model. By fusing FFRLS variable parameter statistical model and cusp point mutation model, the safety state of concrete dam after long-term operation can be rapidly and effectively evaluated. The proposed evaluation method has significant engineering application value in concrete dam statistical modeling and safety evaluation.

Towards a wavefront-preservation X-ray crystal monochromator for high-repetition-rate FELs.

The wavefront preservation of coherent X-ray free-electron laser beams is pushing the requirement on the quality and performance of X-ray optics to an unprecedented level. The Strehl ratio can be used to quantify this requirement. In this paper, the criteria for thermal deformation of the X-ray optics are formulated, especially for crystal monochromators. To preserve the X-ray wavefront, the standard deviation of the height error should be sub-nm for mirrors and less than 25 pm for crystal monochromators. Cryocooled silicon crystals combined with two techniques can be used to achieve this level of performance for monochromator crystals: (1) using a focusing element to compensate the second-order component of the thermal deformation; (2)introducing a cooling pad between the cooling block and silicon crystal and optimizing the effective cooling temperature. Each of these techniques allows the thermal deformation in standard deviation of the height error to be reduced by an order of magnitude. As an example, for the LCLS-II-HE Dynamic X-ray Scattering instrument, the criteria on thermal deformation of a high-heat-load monochromator crystal can be achieved for a 100 W SASE FEL beam. Wavefront propagation simulations confirm that the reflected beam intensity profile is satisfactory on both the peak power density and focused beam size.

A numerical framework for the simulation of coupled electromechanical growth

Electro-mechanical response exists in growing materials such as biological tissues and hydrogels, influencing the growth process, pattern formation and geometry remodelling. To gain a better understanding of the mechanism of the coupled effects of growth and electric fields on the deformation behaviour, a finite element framework for coupled electro-elastic growth is established. Based on the extended volume growth theory, the governing equations of the growing electro-elastic solid are obtained. A coupled three-field mixed displacement-pressure-potential finite element formulation using inf–sup stable combinations is adapted. The finite element formulation is implemented in ABAQUS via a user element subroutine. The implementation is validated first by comparing the deformation and stress components of a growing tubular structure under axial strain and radial voltage. Using the example of a bi-layer beam actuator, it is illustrated that growth parameters and the external voltage can precisely control the bending angle. The framework is then applied to simulate pattern formation and transition behaviour, such as doubling and tripling of wrinkles, by specifying growth parameters and external voltage in a 3D stiff film/soft substrate structure. Furthermore, the suppression of wrinkles by applying external voltage is demonstrated. It is observed that the electric field plays a significant role in stress redistribution and guiding growth, resulting in the promotion or suppression of wrinkles, which is demonstrated by the numerical simulation of a long tubular structure. The proposed finite element scheme provides an accurate, efficient and stable tool for numerical simulation of electro-elastic solids incorporating growth effect, which can be used for understanding coupled growth phenomenon in biological soft matter and developing smart devices for medical treatment.

Rheological properties and group chemical composition of oxidized bitumen in the presence of fibrous materials of various structures

The rheological properties of oxidized bitumen in the presence of fibrous materials based on cellulose and chrysotile asbestos used as stabilizing additives in the production of crushed stone-mastic asphalt concrete mixtures have been studied. It has been established that the supramolecular structure of fibers characterizing the interaction between macromolecules largely determines the effectiveness of their structuring action for oxidized bitumen. Thus, the introduction of cellulose fiber leads to an increase in the ability of the bitumen colloidal structure to the simultaneous occurrence of elastic and plastic components of deformation. This is due to the uniform distribution of the fiber in the dispersion medium of bitumen due to the penetration of hydrocarbon components of bitumen into the interfibrillary space of cellulose and the rupture of hydrogen bonds between hydroxyl groups. Тhe presence of strong structural bonds between chrysotile-asbestos macromolecules prevents the formation of strong reinforcing mesh in bitumen oils. As a result, the values of the structural and rheological parameters Pk1, Pk2 and Pm of the bitumen/chrysotile-asbestos composition are 1.5–2 times lower compared to the values for the bitumen/cellulose composition. The results of the study of the group composition and structural-rheological properties of bitumen compositions after heating at T = 163 °C indicate a higher stability of the bitumen-cellulose structure to the processes of thermal oxidative degradation compared to the structure formed in the bitumen/chrysotile-asbestos composition. By the method of thin-layer chromatography, it was found that the concentration of oils in the bitumen/chrysotile-asbestos composition is higher as compared to the bitumen/cellulose composition, indicating that the weakening of rheological properties and thermal stability in the presence of chrysotile-asbestos is not related to the microstructure of its fibers, which, according to some researchers, is prone to selective diffusion of oils into the capillaries of fibrils.

An Investigation of Volcanic Ground Deformation Using InSAR Observations at Tendürek Volcano (Turkey)

Although approximately one-tenth of the world’s population lives near volcanoes, most of the 1500 active volcanoes are not monitored by ground-based instruments because of the cost and difficulty of access. Since the development of interferometric synthetic aperture radar (InSAR) in the 1990s, recent advances have allowed the near-real-time detection of surface deformations, one of the earliest markers of volcanic activity. According to the Global Volcanism Program, Turkey’s most recent eruption (involving gas and ash) occurred in the Tendürek volcano in 1885. An explosion in the Tendürek volcano, which continues to actively output gas and steam, would be a critical issue for the life and property of the people living nearby. In this context, we processed the Sentinel-1 data collected by the European Space Agency using the Stanford Method for Persistent Scatterers, and the surface deformations of the Tendürek volcano were investigated. In addition, we applied two different atmospheric correction approaches (linear phase-based tropospheric correction and the Generic Atmospheric Correction Online Service for InSAR) to reduce atmospheric effects and found that the linear phase-based tropospheric correction model produced lower standard deviation values. Subsequently, the mean deformation velocity maps, displacement time series, and deformation components in the line-of-sight direction were calculated. The results showed that the most severe subsidence was −11 mm/yr on the upper slopes of the Tendürek volcano. Although the lower slopes of the subsidence region have a lower settlement rate, the subsidence has a peak-caldera-centered location.

Fastening solutions on composite structures: model and verifications of contact with friction, progressive composite damage, and ductile metal damage

In this study, the fundamental steps required for the mechanical analysis of bolted laminated composite structures were revealed. Advanced methods were developed in Fortran and Python to implement nonlinearity to the composite material model using MARC/MENTAT finite element software. Friction and damage parameters for HTA/6376 CFRP material are verified using experimental data sources in the literature. The critical Cockroft–Latham ductile damage parameter of AISI 304L sheet material with its anisotropic properties, which is required for the design of plastically deformable metal components in the composite joint, is computed. Good agreement was obtained between the friction and progressive damage of CFRP composite, ductile damage of AISI 304L, and the external experimental references.

Geometry and Kinematics of strike-slip faults in the Dibrugarh field of the Upper Assam foreland basin, NE India

Sedimentary basins within fold-and-thrust belts preserve the structural record of complex deformations and are essential to many orogenic systems worldwide. One of the component of such deformations is strike-slip tectonics. This research uses high-quality, three-dimensional seismic reflection data to investigate the geometry and kinematics of strike-slip faults developed within a geologically complex region in the Upper Assam foreland basin, NE India. Faults in the basin have a dominant NE-SW trend, with most faults in the SE and SW parts exhibiting sinistral strike-slip. These lateral movements are evidenced by extensional horsetail splay faults, negative flower structures, and minor transfer faults. The displacement profiles of the strike-slip faults also reveal complex segmentation, linkage, and mechanical interactions at different structural levels, indicating their prolonged histories and development. Tectonic tilts of the basin, along with sediment loading from the bordering fold-and-thrust belts over the geologic time, structurally changed the basin configuration giving rise to strike-slip deformations in the study region. These findings contribute to our knowledge of sedimentary basins within fold-and-thrust belts and their structural records of complex deformations.

Research for the Process of Forming the Metal during its Cyclic Deformation

Use the devices for the implementation of the combined casting process and deformation of non-ferrous alloys is a relatively new direction in the technology of materials processing by pressure. For an adequate description of the shaping processes implemented in such devices on the basis of certain mathematical models, experimental data on the energy-force parameters of deformation are required, as well as data for the nature of the distribution and intensity of deformations arising in the process during cyclic deformation of a metal product. The cyclical nature of the process of forming a metal product, coupled with large plastic deformations, does not allow directly using the traditional methods of experimental research of its stress-strain state adopted in the theory of metalworking by pressure. This gap is partly intended to fill by this study. The paper proposes a complex technique based on the registration (according to the electrical characteristics of the drive motor) of the instantaneous power of irreversible deformation for the material of a metal product. Prone to strain hardening in a cold state, a method for directly establishing the components of plastic deformation of the workpiece based on the method of rolled dividing grids with subsequent calculations according to Siebel's method. Analysis of the experimental results allows us to establish a qualitative picture of the deformation mechanism. The obtained experimental values are necessary for the verification of mathematical models and software systems for calculating the stress-strain state of materials under complex loading and finite deformations.

Force of cutting by a single abrasive grain

This paper investigates the cutting forces arising when using a single abrasive grain. Analytical studies were carried out using a model of a single abrasive grain in the form of a rod with a radiused apex acting on the workpiece material. The slip-line method (method of characteristics) was used to calculate the deformation intensity of a plastically edged workpiece material under the action of a single grain. Mathematical models were developed for the following factors: plastic deformation of the material, edging of the stagnated zone and its friction against the grain surface when moved upwards in the form of chippings, grain friction against the plastically deformed material, and the action of the dynamic component of plastic deformation. The significance of the dynamic component in the overall balance of forces related to plastic deformation was established by determining the ratio of dynamic stress on the break line and shear yield point. This dependence calculated for D16T and 30HGSA materials showed the feasibility of accounting for the dynamic component of the cutting force under the velocity of a single grain impacting the workpiece surface of above 50 m/s. Graphs depicting the relative grain force and the relative depth of grain penetration are given. The proposed calculation method for cutting forces using a single grain can be used to determine the total force of interaction between the single grain and the work-piece material. In order to adopt the defined processing method and the workpiece material, the number of grains in contact, the contact duration, and the cutting speed should be found. On this basis, the process performance and the quality of the workpiece surface can be calculated.

Joint Estimation of Ground Displacement and Atmospheric Model Parameters in Ground-Based Radar

Atmospheric delay is the primary error in ground-based synthetic aperture radar (GBSAR). The existing compensation methods include the external meteorological data correction method, the polynomial fitting method, and the persistent scatterers SAR interferometry (PSInSAR) calibration method. Combining the polynomial fitting and the persistent scatterers targets is the most popular method of GBSAR atmospheric delay compensation. However, the displacement component of the coherent target is always ignored in the atmospheric delay compensation, which is unpractical. A joint estimation method of ground displacement and atmospheric model parameters is developed in this paper. The displacement component is determined by the spatial and temporal features of the objects. The atmospheric delay component is regarded as a systematic error represented by a quadratic polynomial related to distance. The result is resolved by the least-square method. Compared to the existing method, the root-mean-square error (RMSE) of the proposed method had a significant improvement in the validation experiment. In the real in situ experiment, the time series obtained by the GBSAR had a similar trend to that acquired by the Global Positioning System (GPS) receiver. It is indicated that the proposed method can lead to a better deformation estimation by taking the deformation component into account in the atmospheric compensation.

Electro‐Reconfigurable Adaptive Microlens with Simultaneous Multidirectional Focal Adjustment and Zooming

AbstractElectrically reconfigurable lenses capable of focal adjustment and zooming require deformable adaptive optical components. However, existing electroactive optical devices that perform these functions are limited by fluid leakage or require complex mechanical parts. Although polyvinyl chloride (PVC) gel‐based lenses with variable focal lengths and zooming have recently been developed, focal adjustment can only be made in the horizontal axis. Herein, a PVC gel‐based adaptive microlens capable of controlling the focal length and focal point simultaneously in the vertical, horizontal, and diagonal directions without mechanical gears or liquid leakage is presented. By optimizing the characteristics of PVC gels plasticized with three different structured plasticizers, a PVC gel‐based adaptive microlens is fabricated. The produced microlens demonstrates the properties of multidirectional focal adjustment, variable focal length (+33.7 to −15.1 mm) at low input voltages (<300 V), excellent transparency (>90%), fast response (0.10 s at 100 V), silent operation, low power consumption (0.39 mW), and excellent potential for further miniaturization.

ANALYSIS OF THE INFLUENCE OF THE SPECIFIC PRESSURE ON THE MOVEMENT RESISTANCE OF SELF-PROPELLED TRACKED MACHINES WITH SMOOTH TRACKS

The paper analyzes the influence of the design parameters of the crawler motor on the operational and environmental parameters of general-purpose tractors. A mathematical model of the dynamics of the crawler motor and its influence on the support surface is developed. Analysis of research results shows that an increase in specific pressure leads to an increase in the coefficient of movement resistance. The intensity of changes in the forces of movement resistance increases with an increase in specific pressure due to an increase in the soil deformation component

Methods for determining the critical deformations of wood with various moisture content

During construction of bridges, the possibility of flooding periods should be considered. Therefore, it is necessary to understand the degree of possible deformation of wooden structures and calculate the limit of their plasticity and elasticity at different values of moisture content. Thus, the purpose of study is to find the method for determining the relative critical deformations of wood with different moisture content and analyse the dynamics of their change. Problems of a deformable solid material were investigated by the analysis of a model of complete deformation diagram “stress σс – deformation uс ”, methods of mathematical statistics, and systematic analysis of experimental results. This study allowed formulating the method for determining the relative critical deformations of solid wood at different moisture levels by axial compression along the fibres of experimental samples. Based on the experiment results, the formula for determining the relative critical deformations of solid wood with different moisture was proposed. The dynamics of changes in critical relative deformations at different moisture, and its elastic and plastic components were presented. It was found that in case of drying wood from 30 to 12%, the plastic component of relative critical deformations decreases and the elastic one, on the contrary, increases. The findings can be used in the deformation calculation methodology for wooden elements and structures of bridges, hydraulic structures, buildings, taking into account the changes in the moisture content of the material

Experimental investigation of the seismic performance of precast post-tensioned segmental bridge piers with stainless energy-dissipating bars

The seismic performance of seven precast post-tensioned segmental (PPS) bridge piers is investigated by quasi-static tests in this work. Five piers are reinforced by stainless energy-dissipating bars. Two piers are reinforced by conventional carbon energy-dissipating bars as control specimens. Different reinforcement ratios of energy-dissipating bars are considered. The specimens are tested under different axial loads and prestressing levels. The experimental results are analysed in terms of hysteresis characteristics, damping (energy dissipation), residual displacement, the opening width of the bottom joint and variation of prestressing tendons. With optically measured strain data based on digital image correlation (DIC) theory, the deformation components of the segmental bridge pier are calculated to evaluate the contribution ratios of deformation components to the total top displacement of the pier. It is found that the PPS piers with stainless reinforcement have the comparable seismic capacity, larger deformation capacity and smaller residual displacement compared to the control specimen. The top displacement of the column obtained by deformation component analysis is in agreement with the directly measured displacement. The bottom joint opening contributes the most of the total top displacement (about 70%).

Effect of assembly pressure on the performance of proton exchange membrane fuel cell

The assembly force is a crucial factor in the process of proton exchange membrane fuel cell (PEMFC) stacking, and has significant effects on the fluid flow, mass transfer, and water and thermal management, which affect the fuel cell performance. In this study, from the most deformable component, the gas diffusion layer (GDL), combining with a finite-element analysis, and computational fluid dynamic method, the impact of the assembly force on a single-channel PEMFC is analyzed. A nonlinear stress–strain curve obtained from a microanalysis is creatively introduced into the two-dimensional compression model. The gas diffusion coefficient in the three-dimensional model is also obtained from the microscopic simulation. The simulated effective oxygen diffusion coefficient of the compressed GDL is approximately 0.86 times the Bruggemann estimated value. When the contact resistance is ignored, the output voltage at 2.5 MPa is decreased by approximately 15.4% at 1.7 A·cm−2 compared with that at 0.5 MPa. After the contact resistance is considered, the effects of the assembly pressure on the cell performance (V–I curve) are qualitatively different. The pressure drop of the 2.5 MPa case is 20% higher than that of the 1.4 MPa case at 1.7 A cm−2. O2 is hard to flow into the region under the rib where the porosity and permeability are lower. The results indicate that both liquid water and membrane water contents increase when the assembly force increases. The effect of the assembly force on the temperature is also analyzed.

A micromechanics‐based approach to damage propagation criterion in viscoelastic fractured materials regarded as homogenized media

AbstractThis paper aims to formulate a damage propagation criterion in microfractured viscoelastic materials, relying upon a micromechanics reasoning together with thermodynamics concepts. The fracture density is regarded as damage parameter at macroscopic scale. The equivalent behavior of the heterogeneous material (solid matrix + fractures) is first formulated within the framework of viscoelastic homogenization theory. In this context, relevant relationships relating local fields to macroscopic fields are derived, thus allowing a clear micromechanical interpretation of quantities involved in the upscaling process, such as the residual or viscous strains. Based on thermodynamic concepts, the energy dissipation and the free energy of the homogenized viscoelastic material are deduced at the macroscopic scale. The formulation of an energetic‐based criterion for damage propagation in viscoelastic fractured materials is then achieved by viewing the macroscopic energy release rate as the thermodynamic force responsible for propagation. Due to the delayed deformation component, the formulation is time‐dependent. Since it is formulated directly at the homogenized material level, the main advantage of the approach developed in this work is the rigorous determination of the energy release rate expression, without neglecting any residual term. In the last part of the paper, several numerical applications are performed to illustrate the main features of the modeling and to provide comparison with available simplified formulations. Finally, the proposed damage propagation criterion is applied to give qualitative insights on fracturing process of sedimentary layered rocks at geological times scale viewed as a long‐term mechanical damage problem, emphasizing the viscosity effects in preventing fracture propagation.

Monitoring nonlinear and fast deformation caused by underground mining exploitation using multi-temporal Sentinel-1 radar interferometry and corner reflectors: application, validation and processing obstacles

ABSTRACT In this study, Differential Interferometric Synthetic Aperture Radar Interferometry (DInSAR) of artificial Corner Reflectors (CRs) were validated in the area of fast and nonlinear deformation gradient caused by active coal longwall exploitation. Three Sentinel-1 datasets were processed using conventional DInSAR, Persistent Scatterer Interferometry (PSI), and Small BAseline Subset methods implemented in ENVI SARscape™. For evaluation, leveling and Global Navigation Satellite System (GNSS) measurements were used. Considering the challenge of snow cover, the removal of all winter images was not a successful strategy due to the long temporal baseline and strong movement, which cause phase unwrapping problems and underestimate the real deformation. The results indicate that only conventional DInSAR and SBAS with low network redundancy allow us to capture maximal deformation gradient and the root mean square error calculated between the CRs and the ground truth is on the level of 2–3 cm for the vertical and easting deformation component, respectively. For the small deformation gradient represented by the permanent GNSS station (4 cm/year), all SBAS techniques appeared to be more accurate than DInSAR, which corresponds to higher redundancy and better removal of the atmospheric signal. In contrast, DInSAR results allowed to capture information about two subsidence basins, which was not possible with SBAS and PSI approaches.

Virtual Restoration of Ancient Wooden Ships Through Non-rigid 3D Shape Assembly with Ruled-Surface FFD

In recent years, 3D data has been widely used in archaeology and in the field of conservation and restoration of cultural properties. Virtual restoration, which reconstructs the original state in virtual space, is one of the promising applications utilizing 3D scanning data. Though many studies of virtual restoration have been conducted, it is still challenging to restore the cultural properties that consist of multiple deformable components because it is not feasible to identify the original shape uniquely. As a solution to such a problem, we proposed a non-rigid 3D shape assembly method for virtually restoring wooden ships that are composed of multiple timbers. The deformed timber can be well represented by ruled surface. We proposed a free-form deformation method with a ruled surface and an assembly method to align the deformable components mutually. The method employs a bottom-up approach that does not require reference data for target objects. The proposed framework narrows down the searching space for optimization using the physical constraints of wooden materials, and it can also obtain optimal solutions. We also showed an experimental result, where we virtually restored King Khufu’s first solar boat. The boat was originally constructed by assembling several timbers. The boat was reconstructed as a real object and is currently exhibited at a museum. However, unfortunately, the entire shape of the boat is slightly distorted. We applied the proposed method using archaeological knowledge and then showed the virtual restoration results using the acquired 3D data of the boat’s components.

Experimental study on in-plane behavior of composite frame slabs and the influence of out-of-plane effect

This paper experimentally investigated the in-plane behavior of a steel–concrete composite frame slab under cyclic loading by considering the influence of the out-of-plane effect. A pure in-plane loading test and two in-plane loading tests of frame slabs with different out-of-plane loads were designed and conducted. Subsequently, the test observations, load–displacement relationships, and shear and flexural deformation components were discussed to investigate the in-plane load resistance behaviors and failure mechanisms of the composite frame slabs with different out-of-plane loads. The experimental results of the pure in-plane loading test demonstrated an evident shear cracking concentration behavior and a pinching hysteretic curve associated with a typical shear-tension failure mode of the composite frame slab. Further, the in-plane loading test of the composite frame slab with small out-of-plane loads also exhibited a typical shear-tension failure mode, and thus had a load–displacement relationship similar to that of the pure in-plane loading test. In contrast, the in-plane loading test with large out-of-plane loads exhibited a horizontal shear failure mode, and thus exhibited a load–displacement curve with a more obvious pinching effect and significantly decreased ultimate load capacity. In addition, the influence of the out-of-plane loads on the in-plane stiffness of the composite frame slab was analyzed.

Multiple factors contributing to the metatarsal head eversion in hallux valgus deformity. A prospective study using weight-bearing CT

PurposeRecently first tarsometatarsal arthrodesis for hallux abducto valgus (HAV) has been advocated as the sole procedure to correct the multiplanar components of the deformity. However, recent debate suggests other factors such as rearfoot pronation and metatarsal torsion affect frontal plane metatarsal eversion and sesamoid positioning. Using weight-bearing CT, 12 feet (12 subjects) with HAV deformities were placed in positions of maximum rearfoot pronation and supination in order to study the effects on metatarsal eversion, sesamoid rotation/displacement, and secondarily the influence of first metatarsal torsion. Sesamoid displacement was quantified by the novel use of the sesamoid displacement angle. Principle resultsAlthough first metatarsal eversion was nearly double in the pronated versus supinated foot, the difference was not statistically significant. Therefore, the bulk of first metatarsal eversion was not secondary to rearfoot eversion. Conversely, a significant positive correlation was found between metatarsal torsion and metatarsal head eversion angles in both supinated and pronated foot positions, with the strongest correlation with rearfoot pronation. Finally, significant increases in sesamoid displacement angles were noted with pronation. Major conclusionsThe findings of the present study support the contention that multiple factors are associated with frontal plane first metatarsal eversion and sesamoid displacement. Weight-bearing CT scanning can be used to effectively evaluate the frontal plane components in HAV deformities. The sesamoid displacement angle appears to be a useful adjunct to evaluating the hallucal sesamoids. For surgical correction of the deformity, consideration should be given to pre-operative weight-bearing CT evaluation of the foot. This can illuminate the effects of rearfoot/medial column pronation and the potential influence of metatarsal torsion on the frontal plane components of this triplane deformity. In this way the potential for post-operative HAV recurrence can be minimized.