Deformation Tracking Research Articles

FEATURES OF STRESS-STRAIN STATE OF THE DUAL RAILWAY GAUGE

Purpose. The possibilities of railway transport for organizing transportation between the countries of the European Union and Ukraine are not fully utilized, since there are a number of technical differences in transport systems, namely: wheel gauge, characteristics of rolling stock, voltage in the contact network, dimensions, etc. One of the options in the organization of goods transportation in international traffic is the use of 1.435/1.520 mm dual gauge. The purpose of this study is to analyze the features of the stress-strain state of the combined construction of the track, first of all the changes in the operation of the under-sleeper base due to the use of a special design of reinforced concrete sleepers with simultaneous fastening of four rails. Methodology. To determine the stresses in the under-sleeper base, a spatial model of dynamic deformations of the railway track was chosen based on the elasticity theory. The movement on a railway track of a conventional construction (with sleepers Ш-1-1), accepted as a reference one, and along the track for combined movement, which differs from a standard using sleepers of type Ш2С-1, was considered. The main results of the calculations were the matrix of stresses in the under-sleeper base. Findings. The analysis of the results of the stresses simulation in the under-sleeper base of the dual gauge did not show their increase in absolute values, but revealed cyclical changes in the possible directions in deviation of ballast particles if there is a propensity for the occurrence of inelastic deformations in the ballast layer. Such a stress-strain state of the under-sleeper base, in turn, can lead to the appearance of deformations in the sleepers and the deterioration of the overall track geometry. Originality. The tasks of simulation got the further development of the track and rolling stock interaction, in particular to determine the stress-strain state of the under-sleeper base of the dual gauge. Practical value. The obtained results can be used to determine the timing of repair work on the sections with a combined track construction, justify the necessary degree of ballast consolidation, the feasibility of using the geogrids or special bonding materials.

Surface deformation tracking and modelling of soft materials

Many computer vision algorithms have been presented to track surface deformations, but few have provided a direct comparison of measurements with other stereoscopic approaches and physics-based models. We have previously developed a phase-based cross-correlation algorithm to track dense distributions of displacements over three-dimensional surfaces. In the present work, we compare this algorithm with one that uses an independent tracking system, derived from an array of fluorescent microspheres. A smooth bicubic Hermite mesh was fitted to deformations obtained from the phase-based cross-correlation data. This mesh was then used to estimate the microsphere locations, which were compared to stereo reconstructions of the microsphere positions. The method was applied to a 35mm × 35mm × 35mm soft silicone gel cube under indentation, with three square bands of microspheres placed around the indenter tip. At an indentation depth of 4.5mm, the root-mean-square (RMS) differences between the reconstructed positions of the microspheres and their identified positions for the inner, middle, and outer bands were 60µm, 20µm, and 19µm, respectively. The usefulness of the strain-tracking data for physics-based finite element modelling of large deformation mechanics was then demonstrated by estimating a neo-Hookean stiffness parameter for the gel. At the optimal constitutive parameter estimate, the RMS difference between the measured microsphere positions and their finite element model-predicted locations was 143µm.

Automated Tracking of Biopolymer Growth and Network Deformation with TSOAX

Studies of how individual semi-flexible biopolymers and their network assemblies change over time reveal dynamical and mechanical properties important to the understanding of their function in tissues and living cells. Automatic tracking of biopolymer networks from fluorescence microscopy time-lapse sequences facilitates such quantitative studies. We present an open source software tool that combines a global and local correspondence algorithm to track biopolymer networks in 2D and 3D, using stretching open active contours. We demonstrate its application in fully automated tracking of elongating and intersecting actin filaments, detection of loop formation and constriction of tilted contractile rings in live cells, and tracking of network deformation under shear deformation.

Fracture toughness measurement without force data – Application to high rate DCB on CFRP

The measurement of the fracture toughness of fiber reinforced composites at high rates of loading is still, despite years of research, not well established. This can be related to challenges in applying appropriate high rate loading on the specimen, accurately measuring the load, and in-situ determination of the crack length. In this work these challenges are addressed by using a direct wedge-on-specimen type loading of a double cantilever beam (DCB) specimen, high resolution optical deformation tracking, and a beam theory based analysis of the specimen deflection and crack length. This approach results in symmetric mode I opening of the crack and a robust analytical determination of the fracture toughness without the need to measure the external forces acting on the specimen nor to visually estimate the crack length. Tests carried out on carbon fiber reinforced epoxy composite at quasi-static and high rates (relative velocity up to 15 m/s) show the validity of the approach.

Use of Geogrids and Recycled Rubber in Railroad Infrastructure for Enhanced Performance

Railway tracks are conventionally built on compacted ballast and structural fill layers placed above the natural (subgrade) foundation. However, during train operations, track deteriorations occur progressively due to ballast degradation. The associated track deformation is usually accompanied by a reduction in both load bearing capacity and drainage, apart from imposing frequent track maintenance. Suitable ground improvement techniques involving plastic inclusions (e.g., geogrids) and energy absorbing materials (e.g., rubber products) to enhance the stability and longevity of tracks have become increasingly popular. This paper presents the outcomes from innovative research and development measures into the use of plastic and rubber elements in rail tracks undertaken at the University of Wollongong, Australia, over the past twenty years. The results obtained from laboratory tests, mathematical modelling and numerical modelling reveal that track performance can be improved significantly by using geogrid and energy absorbing rubber products (e.g., rubber crumbs, waste tire-cell and rubber mats). Test results show that the addition of rubber materials can efficiently improve the energy absorption of the structural layer and also reduce ballast breakage. Furthermore, by incorporating the work input parameters, the energy absorbing property of the newly developed synthetic capping layer is captured by correct modelling of dilatancy. In addition, the laboratory behavior of tire cells and geogrids has been validated by numerical modelling (i.e., Finite Element Modelling-FEM, Discrete Element—DEM), and a coupled DEM-FEM modelling approach is also introduced to simulate ballast deformation.

Track Irregularity Disturbance Rejection for Maglev Train Based on Online Optimization of PnP Control Architecture

Track irregularities, caused by reasons such as track deformation and installation error, are common in real maglev line. These disturbances brought by tracks exert an adverse influence on the performance of a maglev train levitation system. It takes a lot of maintenance costs and time to keep the tracks in a good condition. In another way, a disturbance rejection through a controller optimization method is proposed in this paper. First, the influences of the track irregularity disturbances on levitation performance are illustrated in detail. Then, an online optimization of the PnP control architecture method is adopted to reject the disturbances caused by track irregularities. The effectiveness of this method is verified through the MATLAB simulation. This method makes the levitation system adaptive to known and unknown time-varying track irregularities, saving time, and human resources.

Soil Deformation Tracking in Model Chamber by Targetless Close-Range Photogrammetry

Soil Deformation Tracking in Model Chamber by Targetless Close-Range Photogrammetry

Effects of initial up-warp deformation on the stability of the CRTS II slab track at high temperatures

Initial up-warp deformation is one of the key factors that affect the stability of the China Railway Track System type II (CRTS II) slab track. Through modeling analysis, we studied the effects of different initial up-warp conditions on the deformation and stability of a slab track at high temperatures. Based on the theory of ‘variable span length’ in continuous welded rail (CWR), a vertical stability analysis model of the CRTS II slab track was established using the finite element method (FEM), and a scale model test was conducted. The effects of initial up-warp deformation features, such as rise displacement, span length, and line type on the stability of track slabs at high temperatures were studied through simulation. Results showed that the trends of vertical displacement were almost the same based on the FEM, analytical method, and on-site testing, but there was a better agreement between results from the FEM and the analytical method. When the span length was 6.5 m and the rise displacement of the initial up-warp reached 15 mm, compressional destruction was most likely to occur on the concrete at the bottom of the apex. The rise-span ratio of the slab up-warp reached its maximum when the initial up-warp span was 6.5 m at high temperatures. It is easier for track slabs to maintain their original form at a high temperature when there is an angle at the apex or a smooth boundary. However, with a smooth boundary, the concrete at the bottom of the apex is more likely to suffer compressional destruction. Therefore, to ensure the stability of the CRTS II slab track, an initial up-warp with a span of 6.5 m and a rise of 15 mm should be avoided, and the effects of different line types of the initial up-warp also need to be considered.

Simulation of Sheet Metal Forming Processes Using a Fully Rheological-Damage Constitutive Model Coupling and a Specific 3D Remeshing Method

Automatic process modeling has become an effective tool in reducing the lead-time and the cost for designing forming processes. The numerical modeling process is performed on a fully coupled damage constitutive equations and the advanced 3D adaptive remeshing procedure. Based on continuum damage mechanics, an isotropic damage model coupled with the Johnson–Cook flow law is proposed to satisfy the thermodynamic and damage requirements in metals. The Lemaitre damage potential was chosen to control the damage evolution process and the effective configuration. These fully coupled constitutive equations have been implemented into a Dynamic Explicit finite element code Abaqus using user subroutine. On the other hand, an adaptive remeshing scheme in three dimensions is established to constantly update the deformed mesh to enable tracking of the large plastic deformations. The quantitative effects of coupled ductile damage and adaptive remeshing on the sheet metal forming are studied, and qualitative comparison with some available experimental data are given. As illustrated in the presented examples this overall strategy ensures a robust and efficient remeshing scheme for finite element simulation of sheet metal-forming processes.

Centrifuge modelling of traffic simulation on a construction waste layer

This paper describes a set of physical modelling laboratory tests on recycled construction and demolition waste (RCDW) in Paraná, Brazil. The physical modelling tests were conducted in the geotechnical beam centrifuge at the Federal University of Rio de Janeiro. The main idea of the tests was to run a wheel cyclically forward and backward on a strip over the RCDW layer applying a constant force corresponding to approximately 1 and 2 t in prototype scale. The force was kept constant through a specially designed control system that moves the actuator up and down in order to compensate for force variations due to horizontal movements. A total cell placed at the bottom of the RCDW layer, just above the middle of the track where the wheel runs, measured the increase in vertical stress. Comparison with a simplified analytical solution results in a slight underestimation of the total stress in the RCDW layer, whereas comparison with a classical elastic solution results in overestimation of the total stress. The permanent wheel track deformation due to the applied load was also measured during the cycles. The deformations observed in the centrifuge tests were higher than those obtained in the cyclic triaxial test.

Structured polarized light microscopy for collagen fiber structure and orientation quantification in thick ocular tissues.

Collagen is a major constituent of the eye and understanding its architecture and biomechanics is critical to preserve and restore vision. We, recently, demonstrated polarized light microscopy (PLM) as a powerful technique for measuring properties of the collagen fibers of the eye, such as spatial distribution and orientation. Our implementation of PLM, however, required sectioning the tissues for imaging using transmitted light. This is problematic because it limits analysis to thin sections. This is not only slow, but precludes study of dynamic events such as pressure-induced deformations, which are central to the role of collagen. We introduce structured polarized light microscopy (SPLM), an imaging technique that combines structured light illumination with PLM to allow imaging and measurement of collagen fiber properties in thick ocular tissues. Using pig and sheep eyes, we show that SPLM rejects diffuse background light effectively in thick tissues, significantly enhancing visualization of optic nerve head (ONH) structures, such as the lamina cribrosa, and improving the accuracy of the collagen fiber orientation measurements. Further, we demonstrate the integration of SPLM with an inflation device to enable direct visualization, deformation tracking, and quantification of collagen fibers in ONHs while under controlled pressure.

Effect of daily changing temperature on the curling behavior and interface stress of slab track in construction stage

Interface damage, which even happens in construction phase, has become a major problem for China Railway Track System (CRTS-II) slab track. The slab track in construction stage is a block structure and sensitive to daily changing temperature. In order to reveal the temperature behavior of the slab track and provide meaningful information to the control of early interface damage, a three-dimensional finite element model of slab track was developed to study the deformation and interface stress of the slab track under daily changing temperature in this paper. The daily changing temperature was measured on a testing platform constructed in open field, and imported to the model using user-defined subroutines UTEMP. Based on the developed model, the effect of initial temperature and construction seasons were then investigated. The analysis indicates that the slab deformation and stress change with time obviously and the positions of maximum interface stresses are near the slab corner, which is consistent with the location of interface disease. Initial temperature has significant influence on the slab temperature behavior. The initial temperature at 14:00 induces the largest interface tensile stress exceeding the interface bonding strength, while the interface stresses are relatively small from 19:00 to 24:00. Therefore, it is suggested that CA mortar injection should be finished before midnight. Additionally, as the overall temperature variation and temperature gradient are very obvious in summer, spring and autumn, the grouting operation of CA mortar in these three seasons is required to pay equal attention.

Using Time Domain Reflectometry to Determine Depth of Fouling and Fouling Type in Railway Track Substructure

Abstract This study documents the development of a procedure for the identification of the depth and type of ballast fouling using the time domain reflectometry (TDR) technique. Ballast fouling leads to a reduction in the bearing capacity of the railway substructure, a decrease in the drainage capacity, and an increase in track deformation. As a consequence of these detrimental effects, rail tracks lose load capacity, ride comfort deteriorates, and trains may ultimately derail. The determination of type and extent of ballast fouling may be used to assess the expected life of rail track and to plan maintenance operations. TDR waveforms of variably fouled ballast and subballast layers were evaluated in the lab to yield relative dielectric permittivity and electrical conductivity and to thus characterize the effect of ballast gradation, mineralogy, and water content on electromagnetic response. Strong relationships between depth of fouling, volumetric water content, and relative dielectric permittivity were developed. These results were then expanded to the interpretation of ground penetrating radar (GPR) inspection and to quantify the level of fouling in larger-scale maintenance operations. The proposed technique can be complementary to GPR as it reduces the uncertainty in determining the depth and type of fouling when using GPR alone.

Analytical derivation of elasticity in breast phantoms for deformation tracking

PurposePatient-specific biomedical modeling of the breast is of interest for medical applications such as image registration, image guided procedures and the alignment for biopsy or surgery purposes. The computation of elastic properties is essential to simulate deformations in a realistic way. This study presents an innovative analytical method to compute the elastic modulus and evaluate the elasticity of a breast using magnetic resonance (MRI) images of breast phantoms.MethodsAn analytical method for elasticity computation was developed and subsequently validated on a series of geometric shapes, and on four physical breast phantoms that are supported by a planar frame. This method can compute the elasticity of a shape directly from a set of MRI scans. For comparison, elasticity values were also computed numerically using two different simulation software packages.ResultsApplication of the different methods on the geometric shapes shows that the analytically derived elongation differs from simulated elongation by less than 9% for cylindrical shapes, and up to 18% for other shapes that are also substantially vertically supported by a planar base. For the four physical breast phantoms, the analytically derived elasticity differs from numeric elasticity by 18% on average, which is in accordance with the difference in elongation estimation for the geometric shapes. The analytic method has shown to be multiple orders of magnitude faster than the numerical methods.ConclusionIt can be concluded that the analytical elasticity computation method has good potential to supplement or replace numerical elasticity simulations in gravity-induced deformations, for shapes that are substantially supported by a planar base perpendicular to the gravitational field. The error is manageable, while the calculation procedure takes less than one second as opposed to multiple minutes with numerical methods. The results will be used in the MRI and Ultrasound Robotic Assisted Biopsy (MURAB) project.

Mouse Keratinocytes Without Keratin Intermediate Filaments Demonstrate Substrate Stiffness Dependent Behaviors.

Traditionally thought to serve active vs. passive mechanical functions, respectively, a growing body of evidence suggests that actin microfilament and keratin intermediate filament (IF) networks, together with their associated cell-cell and cell-matrix anchoring junctions, may have a large degree of functional interdependence. Therefore, we hypothesized that the loss of keratin IFs in a knockout mouse keratinocyte model would affect the kinematics of colony formation, i.e., the spatiotemporal process by which individual cells join to form colonies and eventually a nascent epithelial sheet. Time-lapse imaging and deformation tracking microscopy was used to observe colony formation for both wild type (WT) and keratin-deficient knockout (KO) mouse keratinocytes over 24h. Cells were cultured under high calcium conditions on collagen-coated substrates with nominal stiffnesses of ~ 1.2kPa (soft) and 24kPa (stiff). Immunofluorescent staining of actin and selected adhesion proteins was also performed. The absence of keratin IFs markedly affected cell morphology, spread area, and cytoskeleton and adhesion protein organization on both soft and stiff substrates. Strikingly, an absence of keratin IFs also significantly reduced the ability of mouse keratinocytes to mechanically deform the soft substrate. Furthermore, KO cells formed colonies more efficiently on stiff vs. soft substrates, a behavior opposite to that observed for WT keratinocytes. Collectively, these data are strongly supportive of the idea that an interdependence between actin microfilaments and keratin IFs does exist, while further suggesting that keratin IFs may represent an important and under-recognized component of keratinocyte mechanosensation and the force generation apparatus.

궤도의 변형에 따른 열차운행에 소요되는 전력비용 평가

궤도의 변형에 따른 열차운행에 소요되는 전력비용 평가

Experimental study of a tracked mobile robot’s mobility performance

This paper proposes an experimental method of predicting the traction performance of a small tracked mobile robot. Firstly, a track-terrain interaction model based on terramechanics is built. Then, an experimental platform of the tracked robot is established, on which the measurement methods of the parameters that influencing the accuracy of the prediction model are introduced and the data post-processing are improved, including drawbar pull, slip ratio, sinkage, track deformation and so on. Based on the experimental data, several key terrain parameters are identified. With the tracked robot platform, the drawbar pull-slip ratio relationship is tested, and the effects on drawbar pull considering different kinds of terrain and the influence of the grousers are analyzed as well. The research results provide a reference for the experimental study on the traction performance of small tracked robots.

Chronic oxycodone induces axonal degeneration in rat brain

BackgroundChronic opioid therapy for non-malignant pain conditions has significantly increased over the last 15 years. Recently, the correlation between opioid analgesics and alternations in brain structure, such as leukoencephalopathy, axon demyelination, and white matter lesions, has been demonstrated in patients with a history of long-term use of prescription opioids. The exact mechanisms underlying the neurotoxic effect of opioids on the central nervous system are still not fully understood. We investigated the effect of chronic opioids using an animal model in which female rats were orally gavaged with 15 mg/kg of oxycodone every 24 h for 30 days. In addition we tested oxycodone, morphine and DAMGO in breast adenocarcinoma MCF7 cells, which are known to express the μ-opioid receptor.ResultsWe observed several changes in the white matter of animals treated with oxycodone: deformation of axonal tracks, reduction in size of axonal fascicles, loss of myelin basic protein and accumulation of amyloid precursor protein beta (β-APP), suggesting axonal damages by chronic oxycodone. Moreover, we demonstrated activation of pro-apoptotic machinery amid suppression of anti-apoptotic signaling in axonal tracks that correlated with activation of biomarkers of the integrated stress response (ISR) in these structures after oxycodone exposure. Using MCF7 cells, we observed induction of the ISR and pro-apoptotic signaling after opioid treatment. We showed that the ISR inhibitor, ISRIB, suppresses opioid-induced Bax and CHOP expression in MCF7 cells.ConclusionsAltogether, our data suggest that chronic opioid administration may cause neuronal degeneration by activation of the integrated stress response leading to induction of apoptotic signaling in neurons and also by promoting demyelination in CNS.

Automated three-dimensional tracking of the left ventricular myocardium in time-resolved and dose-modulated cardiac CT images using deformable image registration

BackgroundAssessment of myocardial deformation from time-resolved cardiac computed tomography (4D CT) would augment the already available functional information from such an examination without incurring any additional costs. A deformable image registration (DIR) based approach is proposed to allow fast and automatic myocardial tracking in clinical 4D CT images. MethodsLeft ventricular myocardial tissue displacement through a cardiac cycle was tracked using a B-spline transformation based DIR. Gradient of such displacements allowed Lagrangian strain estimation with respect to end-diastole in clinical 4D CT data from ten subjects with suspected coronary artery disease. Dice similarity coefficient (DSC), point-to-curve error (PTC), and tracking error were used to assess the tracking accuracy. Wilcoxon signed rank test provided significance of tracking errors. Topology preservation was verified using Jacobian of the deformation. Reliability of estimated strains and torsion (normalized twist angle) was tested in subjects with normal function by comparing them with normal strain in the literature. ResultsComparison with manual tracking showed high accuracy (DSC: 0.99±0.05; PTC: 0.56mm±0.47 mm) and resulted in determinant(Jacobian)>0 for all subjects, indicating preservation of topology. Average radial (0.13 mm), angular (0.64) and longitudinal (0.10 mm) tracking errors for the entire cohort were not significant (p > 0.9). For patients with normal function, average strain [circumferential, radial, longitudinal] and peak torsion estimates were: [-23.5%, 31.1%, −17.2%] and 7.22°, respectively. These estimates were in conformity with the reported normal ranges in the existing literature. ConclusionsAccurate wall deformation tracking and subsequent strain estimation are feasible with the proposed method using only routine time-resolved 3D cardiac CT.

Adaptive Shape Control for Thermal Deformation of Membrane Mirror with In-plane PVDF Actuators

Optical membrane mirrors are promising key components for future space telescopes. Due to their ultra-thin and high flexible properties, the surfaces of these membrane mirrors are susceptible to temperature variations. Therefore adaptive shape control of the mirror is essential to maintain the surface precision and to ensure its working performance. However, researches on modeling and control of membrane mirrors under thermal loads are sparse in open literatures. A 0.2 m diameter scale model of a polyimide membrane mirror is developed in this study. Three Polyvinylidene fluoride (PVDF) patches are laminated on the non-reflective side of the membrane mirror to serve as in-plane actuators. A new mathematical model of the piezoelectric actuated membrane mirror in multiple fields, (i.e., thermal, mechanical, and electrical field) is established, with which dynamic and static behaviors of the mirror can be analyzed. A closed-loop membrane mirror shape control system is set up and a surface shape control method based on an influence function matrix of the mirror is then investigated. Several experiments including surface displacement tracking and thermal deformation alleviation are performed. The deviations range from 15 μm to 20 μm are eliminated within 0.1 s and the residual deformation is controlled to micron level, which demonstrates the effectiveness of the proposed membrane shape control strategy and shows a satisfactory real-time performance. The proposed research provides a technological support and instruction for shape control of optical membrane mirrors.