Local Elastic Deformation Research Articles

MSIreg: an R package for unsupervised coregistration of mass spectrometry and H&E images.

Joint analysis of mass spectrometry images (MS images) and microscopy images of hematoxylin and eosin (H&E) stained tissues assists pathologists in characterizing the morphological structure of the tissues, and in performing diagnosis. Unfortunately, the analysis is undermined by substantial differences between these modalities in terms of aspect ratios, spatial resolution, number of channels in each image, as well as by large global or small local elastic spatial deformations of one image with respect to the other. Therefore, accurate coregistration of the images is a critical pre-requisite for their joint interpretation. We introduce MSIreg, an open-source R package for coregistration of MSI and H&E images. MSIreg is designed for high-dimensional MSI experiments where each spatial location is represented by thousands of mass features. Unlike most existing coregistration methods, MSIreg implements a landmark free workflow, and quantitative metrics for performance evaluation. We evaluate the performance of MSIreg on six case studies, including coregistration of contiguous tissues with large deformations, as well as simultaneous coregistration of 29 tissue microarray cores. The R package, installation instructions, and fully reproducible vignettes describing methods and Case Studies are are available open-source under the GPL-3.0 license at https://github.com/sslakkimsetty/msireg/.

First-principles approach to x-ray active optics: design and verification.

This paper presents the first-principles design approach for x-ray active optics. The feature of deterministic modulation enables the simulation-modulation cycle in place of the measurement-modulation feedback loops used in traditional active optics. We apply an x-ray mirror with localized thermal elastic deformation to validate the idea. Our experiments have demonstrated that the new active optics have the potential to outperform the accuracy of surface shape metrology instruments.

Strain in Hybrid Organic-Inorganic Metal Halide Perovskites Microstructures by Numerical Simulations.

Hybrid organic-inorganic metal halide perovskites (HOIPs) are promising materials for optoelectronics applications. Their optical and electrical properties can be controlled by strain engineering, that results from application of local elastic deformation or deposition on pre-patterned substrates acquiring a conformal 3D shape. Most interesting, their mechanical properties depend on their crystal structure, composition and dimensionality. We explore by numerical simulations the deformation of a selection of HOIPs comprising a broad range of elastic properties. We consider an axial symmetry with the formation of microdomes on flakes. Radial and vertical forces are considered, finding that the radial force is more effective to obtain large deformation. Large vertical displacement and strain is obtained for HOIPs with low stiffness. The layered nature of HOIPs, that are formed by inorganic layers of different thickness and organic spacers, is also investigated, revealing a non-monotonous trend with the proportion of inorganic to organic part.

Ballistic perforation of aramid laminates: Projectile nose shape sensitivity

The influence of projectile shape on the ballistic properties and mechanism of aramid laminates is investigated through experiments and simulations. Three types of projectiles (blunt, hemispherical, and ogival) are used to obtain ballistic curves. The dynamic penetration process, deformation and damage characteristics of the targets are analyzed. A three-dimensional finite element model is established, and good agreement is observed between the simulation and test results. The findings demonstrate that projectile shape significantly impacts the ballistic response of aramid laminates. As the projectile transitions from blunt and hemispherical to ogival, the ballistic limiting velocity decreases continuously, the area of target plate deformation and damage decreases, and the occurrence of delamination becomes less pronounced. And the energy dissipation through local damage, elastic deformation and overall motion of the aramid material is decreasing and the energy dissipation through friction is increasing.

Failure analysis of slurry TBM discharge pipe in complex strata combined with wear and vibration characteristics

The slurry TBM circulation system plays a crucial role in supplying the slurry to the excavation face and conveying the cut rock particles to the ground. Rock particles in excavated materials will cause damage and failure of slurry discharge pipelines, which seriously restricts the efficiency of slurry TBM tunneling. In this paper, the two major behaviors of wear and vibration that induce slurry discharge pipelines failure are systematically investigated based on a water delivery tunnel located in Beijing. The wear morphology of typical pipes is studied combining the measured wear data and CFD-DEM coupling simulation. The time–frequency characteristics of slurry discharge pipe in different strata are measured and analyzed. Furthermore, the variation of time–frequency characteristics with the decrease of pipe wall thickness is investigated, a multi-parameters early warning methods based on vibration characteristics is proposed for detecting pipe wear. The results show that The CFD-DEM coupling method and Archard wear model can accurately determine the location of the maximum wear point of various pipes conducive to local thickening of pipes. The elbow pipe joints are prone to fatigue damage and have a high risk of slurry leakage during transport of large-sized particles. When the pipeline is severely worn, the interaction between the rock particles and the worn wall causes local elastic deformation, resulting in a high frequency response of 50–150 Hz and a rapid increase in the kurtosis K.

Solute-solute interactions and their impacts on solute co-segregation and interfacial cohesion of {101¯2} twin boundary in zinc

• Zn-based biodegradable alloys are receiving increasing attention in recent years. Alloying is an effective approach to increase mechanical properties of such alloys for load bearing biodegradable applications, but it is unclear how solute atoms of the added alloying elements interact with each other and how these solute-solute interactions affect the mechanical properties of these alloys. In this work, the interactions between solutes (Li, Mg, Mn, Cu, and Ag) commonly used in biodegradable Zn alloys are investigated using first-principles calculations. The segregation ability of these solutes and the effects of the segregations of these solutes on { 10 1 ¯ 2 } twin boundary cohesion are also examined. This work uncovers the effect of solute-solute interactions on solute co-segregation and interfacial cohesion of twin boundaries along which fracture occurs. The findings of the present work are extendable to other hexagonal alloys such as Mg that often contain multiple alloying elements. Interactions of solute atoms in biodegradable zinc alloys and their effect on alloy mechanical properties have been less investigated. In this work, the interactions between the common solutes (Li, Mg, Mn, Cu, and Ag) used in the biodegradable Zn alloys, including a solute-solute pair with the same element or with two different elements, are investigated based on first-principles calculations. It is found that the energetically favorable configuration is the third nearest-neighboring for most solute-solute pairs in the bulk lattice because of the relatively strong electronic interaction between solute and Zn atoms or the relatively small local elastic deformation associated with the configuration. Considering that interfacial cleavage is a key fracture mode of zinc, the segregation ability of these solutes and their effect on the { 10 1 ¯ 2 } twin boundary cohesion are also examined. The result shows that Li tends to fully occupy its preferred site in the twin boundary, while Mg, Mn, Cu, or Ag has a concentration limitation in the twin boundary. The twin boundary cohesion can be significantly enhanced by the segregation of Mn, followed by Cu and Ag, because of the contribution of their d states close to the Fermi level. Furthermore, the co-segregation ability of two solute atoms in the twin boundary increases with increasing the binding tendency of these two solute atoms in the boundary. Mn and Li or Mg show a relatively strong co-segregation ability in the twin boundary. Adding Mn to Zn-Li or Zn-Mg alloys can significantly enhance the resistance to fracture of twin boundaries.

The enhancement of exciton-like luminescence in KCl single crystals under local and uniaxial elastic lattice deformation

Radiative annihilation of exciton-like formations (bound excitons) in KCl single crystals doped with various impurity cations (Li, Na, Sr) has been studied using highly sensitive luminescence methods. In KCl:Na with different sodium concentration, X-ray luminescence bands with the maxima at 2.8 and 3.1 eV, which and attributed to exciton-like formations in the region of local lattice deformation by single Na+ and pair Na+-Na+ centers, become significantly more intense with sodium impurity concentration. The luminescence efficiency of such bound anion excitons also increases in the KCl:Na crystals exposed to a uniaxial elastic stress along the 〈100〉 and 〈110〉 crystallographic directions. The influence of temperature as well as lattice symmetry lowering due to applied elastic deformation (external action) or local deformation in the vicinity of impurity ions (internal action) on the efficiency of the recombination formation of bound excitons has been analyzed.

Stress-Induced Self-Magnetic Flux Leakage at Stress Concentration Zone

The residual magnetization technique is a new method for detecting stress concentration zones (SCZs) in ferromagnetic materials. Local rising of stress at SCZs, such as cracks, results in the development of local elastic and plastic deformation. The two deformation regimes produce different magnetic characteristics, which have competing effects on self-magnetic-flux-leakage signals. In the present research, samples with three different groove depths were subjected to different tensile stress levels. A surface scanning system was used to record the variation of magnetic signals at grooves of varying depth under steadily increasing stress conditions. The results show that elastic deformation increases peak-to-peak values of normal magnetic components and a maximum gradient of the normal magnetic component in the direction of applied stress, while the development of local plastic deformation reduces signal intensity at groove locations. The magnetic object (MO) model is used to explain the mechanism for excess flux leakage field at SCZs as being due to the conversion of magnetoelastic energy—introduced by the application of tensile stress up to the local yield point—into magnetostatic surface poles that are sensed as an increase in the normal component of leakage.

Numerical Simulation of the Effects of Strain Hardening Exponent with and without Strain Rate Sensitivity of Material on Normal Elastic Plastic Impact

The material behavior selection is an important factor governing the structural response analysis of transverse impact problems, such as impact force, indentation and local elastic plastic deformation. In the present paper, the effects of strain hardening exponent (n) and strain rate sensitivity (m) on the transient response were investigated for low impact velocity by the aid of finite element simulation using the Abaqus Software. Investigated parameters are impact force histories, indentation and plastic strain (PEEQ). Results showed that the effect of n values on required parameters is more pronounced, unlike strain rate sensitivity which has not a significant influence. As well, material behavior selection is essential for an accurate local plastic strain analysis.

Evolution of high-pressure metastable phase Si-XIII during silicon nanoindentation: A molecular dynamics study

Berkovich indenters are widely employed in nanoindentation experiments of single-crystal silicon, in molecular dynamic simulations of silicon nanoindentation, however, spherical indenters are generally employed. To close this gap, in this paper, a series of molecular dynamic simulations are conducted on (001), (101), and (111) silicon surfaces to explore the evolution of high-pressure phases. Several possible silicon phases are tracked by coordination number (CN), radial distribution function (RDF), and angular distribution function (ADF). Results show that the metastable phases and the high-pressure phases present different symmetrical patterns along different crystallographic orientations. A large amount of high-pressure phase Si-XIII, which is seldomly observed in nanoindentation using a spherical indenter, is first discovered under the Berkovich indenter, and the evolution mechanism is characterized by tracking the position transition of labeled silicon atoms. As a transition phase for high-pressure phase Si-II and Si-XIII, bct5 phase is found in the {111} [110] slip systems, which is related with slipping flatten lattice structures. Different from the phase transformation criterion for Si-II, the transformation from Si-I to Si-XIII companies with the local elastic deformation of (001) surface. The atoms in the three neighboring unit cells are compressed into a uniform long-distance ordered crystal structure. Upon indenter extraction and rapid stress releasing, the elastic deformation of the crystal surface resumes incompletely. A part of Si-XIII recovers to pristine Si-I and the rest changes into amorphous phase. The distribution of local hydrostatic pressure and von Mises stress in the phase transformation regions indicates that the concentrated hydrostatic pressure and specific stress induce this high-pressure silicon phase. This research clarifies the evolutionary process of Si-XIII phase generation and enriches fundamental understanding on the mechanisms of silicon phase transformations in nanoindentation.

The shapes of physical trefoil knots

We perform a compare-and-contrast investigation between the equilibrium shapes of physical and ideal trefoil knots, both in closed and open configurations. Ideal knots are purely geometric abstractions for the tightest configuration tied in a perfectly flexible, self-avoiding tube with an inextensible centerline and undeformable cross-sections. Here, we construct physical realizations of tight trefoil knots tied in an elastomeric rod, and use X-ray tomography and 3D finite element simulation for detailed characterization. Specifically, we evaluate the role of elasticity in dictating the physical knot’s overall shape, self-contact regions, curvature profile, and cross-section deformation. We compare the shape of our elastic knots to prior computations of the corresponding ideal configurations. Our results on tight physical knots exhibit many similarities to their purely geometric counterparts, but also some striking dissimilarities that we examine in detail. These observations raise the hypothesis that regions of localized elastic deformation, not captured by the geometric models, could act as precursors for the weak spots that compromise the strength of knotted filaments.

Evaluation of the sensitivity of springback to various process parameters of aluminum alloy sheet with different heat treatment conditions

The forming steps by permanent deformation controlled by the tools generate a distribution of stresses inside the material which directly depends on the work hardening properties of the latter. The change in boundary conditions following the removal of the tools imposes the material to redistribute the stresses in the sections in a manner compatible with the new boundary conditions. This new distribution necessarily operates by local elastic deformations that result globally in a general change of shape called springback. This geometrical deviation can be minimized by the meticulous focus of the tools, but it cannot generally be completely annihilated due to the influence of several parameters. For this reason, the study of the influence of the different technological factors and physico-metallurgical parameters on the springback for the different metals is very important to design and properly realize forming tools. The main objective of this work is to find solutions to problems encountered in sheet metal forming such as the problem of springback. Our work has two essential purposes: the first is summarized in an experimental study based on theoretical analyses. To this end, much effort is made to add a new design of parts for a U-type stretch-bending device and adapt it to a tensile testing machine. This design has the advantage of modifying and assembling all parameters affecting springback at the same time and also of carrying out several forming processes on the same device. The second goal is the experimental and numerical prediction of springback, and the study of the effect of various stretch-bending process parameters such as punch velocity, the orientation of the sheet (anisotropy), hold time and punch-die clearance on springback behavior under heat treatment of aluminum alloy sheets with three different rolling directions (0°,45°,90°). A finite element (FE) model of stretch-bending has been established by utilizing ABAQUS/CAE software. From this analysis, it can be concluded that the springback is affected by the anisotropy of the sheet and the heat treatment in the stretch-bending process. The obtained experimental results were compared with the numerical simulations found in good agreement.

Peridynamics boundary condition treatments via the pseudo-layer enrichment method and variable horizon approach

Peridynamics is a nonlocal theory that applies an integral term to represent the material response. Without a spatial differential term involved, peridynamics possesses certain advantages for solving discontinuity-involved problems. However, due to the reduction of stiffness, the deformation near the boundary region by peridynamics has a low accuracy compared to the local elastic deformation. Previous peridynamics boundary condition treatment enriches the stiffness on the boundary region by adding an artificial layer outside the domain boundary. However, this requires the deformation of the pseudo-layer to be pre-determined. In addition, the accuracy of the response on the physical domain depends largely on the accuracy of the pre-determined deformation on the pseudo-layer. Considering the fact that peridynamics reduces to local elasticity as the horizon size goes to zero, and previous researches indicate the potential advantage of boundary enrichment via the horizon varying approach, in this paper, peridynamics with a variable horizon is utilized as an efficient way to reduce the boundary-induced inaccuracy. Firstly, the pseudo-layer boundary condition treatments are discussed by using the symmetrical enrichment function and other extrapolation functions. Then, the variable horizon boundary condition treatment is introduced and a robust improvement of deformation accuracy on the boundary region is observed compared to other boundary condition treatments for both one- and two-dimensional examples. The variable horizon approach requires no additional pseudo-layer and the boundary conditions are applied directly on the physical boundary. Thus, the variable horizon approach is easy to implement and its computational cost is reduced.

Modeling of micro-grinding forces considering dressing parameters and tool deflection

The prediction of cutting forces is critical for the control and optimization of machining processes. This paper is concerned with developing prediction model for cutting forces in micro-grinding. The approach is based on the probabilistic distribution of undeformed chip thickness. This distribution is a function of the process kinematics, properties of the workpiece, and micro-topography of the grinding tool. A Rayleigh probability density function is used to determine the distribution of the maximum chip thickness as an independent parameter. The prediction model further includes the effect of dressing parameters. The integration of the dressing model enables the prediction of static grain density of the grinding tool at various radial dressing depths. The tool deflection is also considered in order to account for the actual depth of cut in the modeling process. The dynamic cutting-edge density as a function of the static grain density, the local tool deflection, elastic deformation, and process kinematics can hence be calculated. Once the chip thickness is calculated, the single-grain forces for individual abrasive grains are predicted and the specific tangential and normal grinding forces simulated. The simulation results are experimentally validated via cutting-force measurements in micro-grinding of Ti6Al4V. The results show that the model can predict the tangential and normal grinding forces with a mean accuracy of 10% and 30%, respectively. The observed cutting forces further imply that the flow stress of the material did not change with changing the cutting speed and the cutting strain rate. Moreover, it was observed that the depth of cut and grinding feed rate had the same neutral effect on the resultant grinding forces.

Mechanics model and optimum design of PE pellet shell for anti-water-seepage with ease in open

Polyethylene capsule shells are a kind of container for pills with low cost and long-term preservation, after paraffin-sealed. This kind of pellet shell is composed of two hemispheric shells with the seal convex and concave allowances, at which they connect, locate and unify together as a whole by local elastic deformation. However, the water seepage occurs in certain percentage of the pills during paraffin-seal operation. In order to solve the problem of water seepage and further improve the process, the current study presents the tension model under the action of ideal gas in paraffin-sealing, the enhanced cantilever beam model under water cooling, and the simply supported beam model for investigation of the cause of the water seepage. The criterion of impervious water was put forward and developed with anti-inference method. The case analysis shows that the seepage is caused by the unreasonable structure of the seal of PE pellet. On the basis of this, the seal allowance of the shell is improved and optimized in the current design. And the overlap amount of the half shells was increased from 0.15mm to 0.30mm, at least, with protruding and half shot shell with concave is increased and the small Angle of the double V structure is adopted. The results of calculation and test show that the new design is of rational and reliability, and it met the requirements of small force and ease in opening the shell.

Numerical Analysis Based on a Multi-Body Simulation for a Plunging Type Constant Velocity Joint

In early design phases of ball typed constant velocity joints (CVJ), which are widely used for the uniform transmission of rotational movement in driveshafts, the knowledge of the interactions between the components is essential. Therefore, a simulation model for a multi-body analysis is developed to consider general, transient operating conditions of the joint in the development process. The model is derived using the example of a plunging joint of the rear prop shaft, which has a straight track geometry and two track angles. On this basis, a two-dimensional, analytical contact determination between balls and tracks can be carried out, which reduces the required computation times compared to a general contact determination. Although rigid bodies are used for numerical analysis, local elastic deformations between the contact bodies are possible on the basis of Hertzian contact theory. For a higher level of detail, frictional forces are also taken into account via the Coulomb friction law, which is adapted for numerical use. To validate the simulation model, the influences of the numerical parameters are discussed and the numerical results are compared with the analytical results of the statically undeflected joint condition. Finally, the created simulation model is utilised to present the numerical joint analysis using two examples of joint kinematics analysis.

Finite Element Analysis and Parameter Influence of Non-developable Ruled Surface Impeller Blade in Flank Milling

Through the cutting simulation of titanium alloy impeller blade, the effect of the actual milling processing path on the elastic part deflection to of complicated thin-walled workpiece with low rigidity and high precision is studied. Use the principle of impeller modeling to model the spline of the impeller, and the spline curve of the impeller generated in MABLEB is imported into UG for digital modeling. The spline curve is used to generate the neutral surface, and the suction surface and pressure surface are obtained by the method of non-equidistant offset. The model of the non-stretchable straight surface blade is imported into ABAQUS for static simulation. Using MATLAB to fit the experimental data in the reference literature that fits the milling process range, the side milling experience formula is fitted. Calculate the equivalent milling force corresponding to different axial cutting depths, import into ABAQUS and use Python for secondary development. By simulating the milling process through the life-and-death element method, the local elastic deformation law of the milled thin-walled parts when multi-layer milling the impeller blades is explored. The influence of different machining paths on the deformation of the tool is studied. Simulation results show that the part deflection of workpiece can be reduced by rationally planning the machining path.

The tangent stiffness matrix for an absolute interface coordinates floating frame of reference formulation

In this work, a full and complete development of the tangent stiffness matrix is presented, suitable for the use in an absolute interface coordinates floating frame of reference formulation. For simulation of flexible multibody systems, the floating frame formulation is used for its advantage to describe local elastic deformation by means of a body’s linear finite element model. Consequently, the powerful Craig–Bampton method can be applied for model order reduction. By establishing a coordinate transformation from the absolute floating frame coordinates and local interface coordinates corresponding to the Craig–Bampton modes to absolute interface coordinates, it is possible to satisfy kinematic constraints without the use of Lagrange multipliers. In this way, the floating frame does not need to be located at an interface point and can be positioned close to the body’s center of mass, without requiring an interface point at the center of mass. This improves simulation accuracy. In this work, the expression for the new method’s tangent stiffness matrix is obtained by taking the variation of the equation of equilibrium. The global tangent stiffness matrix is expressed as a local tangent stiffness matrix, consisting of both material stiffness and geometric stiffness terms, transformed to the global frame by the rotation matrix of the floating frame. Simulations of static and dynamic validation problems are performed. These simulations show the importance of including the tangent stiffness matrix for both convergence and simulation efficiency.

Human action recognition based on spatio-temporal three-dimensional scattering transform descriptor and an improved VLAD feature encoding algorithm

The local spatio-temporal descriptor and feature encoding algorithm are two crucial key steps for human action recognition based on spatio-temporal interest points (STIP). Since the local descriptors for STIP are essentially a type of motion information based on the texture, the key point of local feature description is to extract invariable, robust and distinguishable local texture features and motion information in reference spatio-temporal volume. Scattering transform is an image transform method based on directional wavelet transform and scale convolution, which has local translation invariance, rotation invariance and elastic deformation stability for local texture features. A novel local descriptor for STIP based on spatio-temporal three-dimensional scattering transform is proposed in this paper, which extends the original scattering transform to spatio-temporal three-dimensional space. Compared to the traditional descriptors, such as HOG, HOF and so on, the proposed scattering transform coefficients based histogram of oriented gradients (STC-HOG) descriptor can capture more robust and distinguishable motion information of local texture for STIP. In order to incorporate the local descriptors into action video representation, the feature encoding algorithm is indispensable. For the problem that vector of locally aggregated descriptors (VLAD) loses feature distribution location information during feature encoding, a histogram of distribution vector of locally aggregated descriptors (HOD-VALD) based on Gaussian kernel is proposed. We validated the proposed algorithm for human action recognition on multiple public available datasets, such as KTH, UCF Sports, HMDB51 and so on. The evaluation experiment results indicate that the proposed descriptor and encoding method can improve the efficiency of human action recognition and the recognition accuracy.

Nonlinear dynamic behaviour of joint effects on a 2(3PUS+S) parallel manipulator

Clearance, friction, and local elastic and plastic deformation of joint, which can be called joint effects, may cause nonlinear dynamic behaviour of mechanisms. In the paper, nonlinear dynamic behaviour of joint effects on a 2(3PUS+S) parallel manipulator was studied. There are 10 spherical joints in the 2(3PUS+S) parallel manipulator, and the dynamic characteristics of the spherical joints directly affect the overall output performance since they are connected to the moving platforms. Therefore, the joint effects of spherical joint and its effect are studied. To study the effect of the irregular clearance (size of the clearance varies with the attitude) of spherical joint due to manufacturing tolerance and wear, the spherical surface is approximated as an ellipsoid. In addition, the contact force models of spherical joint with variable contact stiffness were established under dry friction and lubrication condition, respectively. And then considering the contact forces of the spherical joints, the overall dynamic model of the 2(3PUS+S) parallel manipulator was established. Based on the overall dynamic model, the influence of joint effects on the dynamic characteristics of the 2(3PUS+S) parallel manipulator was studied, and the correctness of theoretical models was verified through experiments. The results from the simulation and experiments indicate that joint effects can cause nonlinear dynamic characteristics and have important influence on the dynamic performance of the 2(3PUS+S) parallel manipulator.