Magnitude Of Local Deformation Research Articles

Spatiotemporal characteristics of upper-crust seasonal velocity changes in North–South Seismic Belt and South China block in China

Investigating mechanisms and characteristics of the non-tectonic deformation has crucial implications for evaluating the subsurface stress evolution. In this study, we continuously tracked the seasonal velocity changes of Rayleigh wave at 2–10 s with the ambient noise interferometry and discrete wavelet decomposition, in different regions along the actively deforming North–South Seismic Belt (NSSB) and the stable Guangdong region in the South China block in China. The seasonal velocity changes exhibit strong lateral variations across different regions, with much larger seasonality (annual periodicity) and amplitude along the NSSB than those in the stable Guangdong region. There are also small-scale lateral variations inside of each region and generally larger amplitudes of the seasonal velocity changes at greater depth, but the phases (peaks, mostly in winter or summer) at different depths are consistent. The mechanism of the seasonal changes is most likely the direct loading effect of the precipitation, as indicated by consistency in their phases. However, the amplitudes of the seasonal velocity changes seem not controlled by the amount of precipitation, but are more dependent on the tectonic deformation at the different scales, from the correlation between the amplitude of the velocity change and the absolute strain rate. We demonstrate that the crustal media in the regions with larger tectonic background stress are more sensitive to the seasonal loadings. The new finding also highlights the role of the external seasonal loadings in the modulation of seismic activities and risk evaluations. Keypoints•Seasonal seismic velocity variations are found in different regions in China, likely from direct hydrological loadings of precipitation.•The spatial pattern of the seasonal velocity changes is consistent with the distribution of tectonic deformation at multi-scales.•The amplitude of the seasonal velocity changes is more dependent on the magnitude of local deformation than the amount of precipitation.

High-resolution mapping of the strain heterogeneity in heterogeneous and homogeneous structured Mg 13Gd alloy

The hetero-deformation induced (HDI) stress can effectively promote extra strengthening and strain hardening behavior, which originates from the heterogenous deformation between soft and hard domains. How to quantitatively evaluate the strain heterogeneity at the micron and sub-micron scales remains a great challenge during deformation incompatibility. In this study, the strain evolution at grain level of heterogeneous (HES) and homogeneous-structured (HOS) Mg 13Gd (wt%) alloy was characterized by high-resolution digital image correlation. Both HES and HOS samples show strain heterogeneity related to the physical slip bands inside grains, and the magnitude of local deformation in grain level is much higher than the macroscopic strain, especially at grain boundaries. The HOS sample can also generate HDI stress due to the remarkable difference in Schmid factor and lower geometrical compatibility factor between adjacent grains. The formation of dispersed strain bands in the coarse grains with hard orientation of the HES sample contributes to strain delocalization behavior and the improvement of strain hardening capacity. These results provide us with a new insight for heterostructured design of Mg alloys on a more microscopic scale. • The strain evolution at grain level of heterogeneous and homogeneous-structured Mg 13Gd (wt%) alloy was characterized by high-resolution digital image correlation. • The heterogeneous and homogeneous-structured sample showed strain heterogeneity, and the magnitude of local deformation in grain level was much higher than the macroscopic strain, especially at grain boundaries. • The homogeneous-structured sample can also generate the hetero-deformation induced stress due to the remarkable difference in Schmid factor and lower geometrical compatibility factor between adjacent grains. • The formation of dispersed strain bands in the coarse grains of the heterogeneous-structured sample contributed to strain delocalization behavior as well as the improvement of strain hardening capacity.

Buckling Behavior of Compression-loaded Advanced Grid Stiffened Composite Cylindrical Shells with Reinforced Cutouts

In this paper, the buckling behavior of an advanced grid stiffened (AGS) composite cylindrical shell with a rectangular cutout is systematically investigated using the finite element method. The effects of reinforcement dimension of cutout on the non-linear response of the AGS composite cylindrical shell are described. The simulational results illustrate the complex non-linear response of a compression-loaded AGS composite cylindrical shell with an unreinforced cutout. In particular, a local buckling response occurs on the shell near the cutout which is caused by local skin deformations near the cutout. In general, reinforcement around a cutout in a compression-loaded AGS composite cylindrical shell can eliminate the local buckling response near the cutout and increase the global collapse load of the shell. However, simulational results illustrate that which reinforcement configurations can cause an unexpected increase in the magnitude of local deformations in the shell and cause a reduction in the global collapse load. A parameter study, including the orientation, thickness and size of cutout reinforcement in the AGS composite cylindrical shells, was conducted to improve the buckling response characteristics by determining a set of appropriate parameters.

A method for assessing voxel correspondence in longitudinal tumor imaginga)

Tumor characterization employing a voxel-wise analysis of image signal facilitates the determination of the spatial distribution of tumor attributes, and when employed for therapy response assessment offers the promise of greater sensitivity to change than conventional approaches. However, the accuracy of a voxel-wise analysis of change is limited by local registration uncertainties that can disrupt the spatiotemporal correspondence between assessed voxels. We present a method for assessing voxel correspondence strength using a multiresolution local histogram-based measure of image structure similarity. When employed in a longitudinal tumor imaging context, a voxel similarity measure must be robust to intensity variations that can arise from the image acquisition, treatment effects, or changes in underlying disease processes. Consequently, the local histogram-based similarity measure is evaluated for sensitivity to structural change and robustness to intensity variation and is compared against normalized mutual information and normalized cross-correlation. T1-weighted (T1W) magnetic resonance (MR) images of glioblastoma acquired as part of a longitudinal response assessment study are first rigidly registered, and then similarity between spatially corresponding voxels is evaluated using multiresolution local histograms. Region-based and nonuniform intensity changes of varying magnitude as well as deformations to image structure are applied individually and in combination to the test images. Statistical analysis is used to test for interaction effects between the applied perturbations and the value of the local histogram similarity function. Pair-wise voxel similarity maps are computed for pairs of longitudinal clinical MR image volumes and compared with observed patterns of change on conventional imaging. The simulations demonstrated that the local histogram measure was robust to intensity modulations applied to increasing region sizes and exhibited a strong negative correlation with the magnitude of local deformation. No statistically significant interaction effects were observed upon the value of the local histogram similarity function when deformation was applied in conjunction with a nonuniform intensity change. Pair-wise voxel similarity maps were consistent with image change observed on T1W MR imaging and revealed patterns of change not apparent in conventional image sequences. A measure of local histogram image structure similarity can be used to assess the strength of voxel to voxel correspondences independently of intensity nonuniformities. The metric can provide a local estimate of the limits of achievable correspondence underlying the registration and voxel-wise comparison of signal in longitudinal imaging used for assessing tumor response to treatment.

ProcDef: Local-to-global Deformation for Skeleton-free Character Animation

Animations of characters with flexible bodies such as jellyfish, snails, and, hearts are difficult to design using traditional skeleton-based approaches. A standard approach is keyframing, but adjusting the shape of the flexible body for each key frame is tedious. In addition, the character cannot dynamically adjust its motion to respond to the environment or user input. This paper introduces a new procedural deformation framework (ProcDef) for designing and driving animations of such flexible objects. Our approach is to synthesize global motions procedurally by integrating local deformations. ProcDef provides an efficient design scheme for local deformation patterns; the user can control the orientation and magnitude of local deformations as well as the propagation of deformation signals by specifying line charts and volumetric fields. We also present a fast and robust deformation algorithm based on shape-matching dynamics and show some example animations to illustrate the feasibility of our framework.

Buckling behavior of compression-loaded composite cylindrical shells with reinforced cutouts

Results from a numerical study of the response of thin-walled compression-loaded quasi-isotropic laminated composite cylindrical shells with unreinforced and reinforced square cutouts are presented. The effects of cutout reinforcement orthotropy, size, and thickness on the non-linear response of the shells are described. A high-fidelity non-linear analysis procedure has been used to predict the non-linear response of the shells. The analysis procedure includes a non-linear static analysis that predicts stable response characteristics of the shells and a non-linear transient analysis that predicts unstable dynamic buckling response characteristics. The results illustrate the complex non-linear response of a compression-loaded shell with an unreinforced cutout. In particular, a local buckling response occurs in the shell near the cutout and is caused by a complex non-linear coupling between local shell-wall deformations and in-plane destabilizing compression stresses near the cutout. In general, reinforcement around a cutout in a compression-loaded shell can retard or eliminate the local buckling response near the cutout and increase the buckling load of the shell. However, results are presented that show how certain reinforcement configurations can cause an unexpected increase in the magnitude of local deformations and stresses in the shell and cause a reduction in the buckling load. Specific cases are presented that suggest that the orthotropy, thickness, and size of a cutout reinforcement in a shell can be tailored to achieve improved buckling response characteristics.

A design method for prediction of dimensions of rectangular hollow sections formed in stretch bending

Local deformation of individual cross-sectional members is of great interest in bending of aluminium alloy extrusions for tight tolerance production such as automotive components. The primary concern is the impact of such distortions on manufacturability as well as the dimensional tolerances of the component. This paper presents analytical models for the determination of local post-buckling and suck-in deformations in stretch bending. The models are based on the deformation theory of plasticity combined with an energy method using appropriate shape functions. The analytical predictions are being verified with experimental results. Based on the present findings, a simplified design method for evaluation of bendability of sections in industrial forming operations is being proposed. The results show that the slenderness ( b/ t) and the width of the flange are the main parameters related to the bending radius at the onset of plastic buckling and the magnitude of local deformations, respectively. Material parameters have proven to be relatively more important to the former than to the latter. Although there is some discrepancy at tight nominal bend radii, the overall correlation between the experimental and theoretical results is surprisingly good. It is therefore concluded that the present method provides to be an efficient means to the evaluation of bendability of rectangular hollow sections.

Flexural Strength and Ductility of Extended Pile-Shafts. II: Experimental Study

Results of an experimental program investigating the lateral strength and ductility capacity of reinforced concrete piles are presented. Four full-scale reinforced concrete piles with details representative of the current California design were tested under combined axial compression and reversed cyclic lateral displacement. Test parameters include confining steel ratio, aboveground height, and soil density. Of particular interests are the lateral strength and stiffness of the soil-pile system, depth-to-maximum-moment, and magnitude of local deformation upon formation of a plastic hinge in the pile. Equivalent plastic hinge lengths were determined using curvatures measured along the length of the pile. Test results indicated that the equivalent plastic hinge length of piles is generally longer than that of an equivalent base-restrained column. The equivalent plastic hinge length of the pile depends primarily on the aboveground height of the pile, but is not overly sensitive to the soil density. Test results also provided the basis for an analytical model presented in a companion paper for assessing the local ductility demand of a yielding pile-shaft.

A design method for rectangular hollow sections in bending

Local deformation of individual cross-sectional members is of great interest in the bending of aluminium alloy extrusions for automotive applications. The primary concern is the impact of such distortions on the manufacturability of components as well as the dimensional tolerances of the final build. This paper presents analytical models for the determination of local post-buckling and suck-in deformations in bending. The models are based on the deformation theory of plasticity combined with an energy method using appropriate shape functions. The analytical predictions are verified with experimental results. Based on the present findings, an approximate design method for evaluation of the bendability of sections in industrial forming operations is proposed. The results show that the slenderness ratio ( b/ t) and the width of the flange are the main parameters related to the bending radius at the onset of plastic buckling and the magnitude of local deformations, respectively. Material parameters have proven to be relatively more important to buckling radius than to deformation of individual cross-sectional members. Although there is some discrepancy between the experimental and theoretical results at tight nominal bend radii, the overall correlation is surprisingly good. It is, therefore, concluded that the present approach provides an efficient method for the evaluation of the bendability of rectangular hollow sections.