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1
Stefanelli, Ulisse. "Existence for dislocation-free finite plasticity." ESAIM: Control, Optimisation and Calculus of Variations 25 (2019): 21. http://dx.doi.org/10.1051/cocv/2018014.
Анотація:
This note addresses finite plasticity under the constraint that plastic deformations are compatible. In this case, the total elastoplastic deformation of the medium is decomposed as y = ye ○ yp, where the plastic deformation yp is defined on the fixed reference configuration and the elastic deformation ye is a mapping from the varying intermediate configuration yp(Ω). Correspondingly, the energy of the medium features both Lagrangian (plastic, loads) and not Lagrangian contributions (elastic). We present a variational formulation of the static elastoplastic problem in this setting and show that a solution is attained in a suitable class of admissible deformations. Possible extensions of the result, especially in the direction of quasistatic evolutions, are also discussed.
2
Dai, Ming, and Jian Hua. "Discussion on the conformal mapping of a half-plane onto a unit disk in anisotropic elasticity and related applications." Mathematics and Mechanics of Solids 26, no. 1 (August 8, 2020): 110–17. http://dx.doi.org/10.1177/1081286520948928.
Анотація:
The conformal mapping, which transforms a half-plane into a unit disk, has been used widely in studies involving an isotropic elastic half-plane under anti-plane shear or plane deformation. However, very little attention has been paid to the possibility of utilizing this mapping in the study of an anisotropic elastic half-plane under the same deformation. In this paper, we discuss a general case of an arbitrarily located anisotropic elastic half-plane that corresponds to several affine counterparts (resulting from corresponding complex variable formalism). We show that this mapping is indeed applicable to each of the affine half-planes if and only if the key parameters in the mapping satisfy simple geometrical conditions. In addition, we introduce the application of this mapping with the corresponding geometrical conditions to the related study of anisotropic thin films under two-dimensional deformation.
3
Guo, Peng, Xiang Wu, and Liangbi Wang. "New Solutions of Elastic Waves in an Elastic Rod under Finite Deformation." Journal of Applied Mathematics 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/495125.
Анотація:
The nonlinear wave equation of an elastic rod under finite deformation is solved by the extended mapping method. Abundant new exact traveling wave solutions for this equation are obtained, which contain trigonometric function solutions, solitary wave solutions, Jacobian elliptic function solutions, and Weierstrass elliptic function solutions. The method can be used in further works to establish more entirely new solutions for other kinds of nonlinear evolution equations arising in physics.
4
Fan, Rui Jun, Hong Chao Gao, and Zhou Zhou. "Parallelized Aeroelastic Investigation Based on Delaunay Graph Mapping." Applied Mechanics and Materials 444-445 (October 2013): 227–32. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.227.
Анотація:
In this paper, an effective and well robust dynamic grid deformation method based on Delaunay graph mapping is developed to solve the deformation of the 3-D hybrid multiblocks grids which is combined by near-wall viscosity grids and unstructured grids. Further more, the static aeroelastics problems of the standard model M6 elastic wing is investigated altogether by coupled with structure dynamic equation. The comparison, analysis and investigation were done as well. The CFD grids domain is subdivided into subdomains for parallel computation. And the program is carried out by MPI parallel computation standards.
5
Kuo, Chang Hung, Siew Fern Lim, and Hung Ru Ho. "Cyclic Deformation Caused by Repeatedly Contact Loading." Applied Mechanics and Materials 883 (July 2018): 8–15. http://dx.doi.org/10.4028/www.scientific.net/amm.883.8.
Анотація:
An elastic-plastic contact stress analysis is presented to study cyclic plastic deformation of rolling elements under repeatedly contact loadings. The rolling contact is simulated by a Hertzian line contact loading translating over the surface of an elastic-plastic half-space, and the Chaboche nonlinear hardening rule is used to model the cyclic plastic behavior of contact components. A finite element procedure based on the return mapping algorithm is implemented to analyze the evolution plastic strains and residual stresses versus contact cycles. For the contact loading below the shakedown limit, p0/k=4, the plastic deformation occur only at first few contact cycles and become pure elastic in the subsequent cycles due to the existing residual stresses and material hardening. For the contact loading exceeding the shakedown limit, p0/k=7, the plastic strains increase progressively with each pass of contact cycles and result in plastic ratchetting. The normal residual stresses, however, quickly reach a steady state after few contact cycles.
6
Zantopulos, H. "An Alternate Solution of the Deformation of a Cylinder Between Two Flat Plates." Journal of Tribology 110, no. 4 (October 1, 1988): 727–29. http://dx.doi.org/10.1115/1.3261720.
Анотація:
Using the method of conformal mapping, an alternate solution is obtained for the line contact deformation of a cylinder loaded between two flat plates. In this method, the elastic deformation of two half spaces, assuming an elliptical pressure distribution across the width of contact, does not have to be calculated relative to an arbitrarily selected stationary reference point.
7
Ting, T. C. T., Y. Hu, and H. O. K. Kirchner. "Anisotropic Elastic Materials With a Parabolic or Hyperbolic Boundary: A Classical Problem Revisited." Journal of Applied Mechanics 68, no. 4 (January 2, 2001): 537–42. http://dx.doi.org/10.1115/1.1381393.
Анотація:
When an anisotropic elastic material is under a two-dimensional deformation that has a hole of given geometry Γ subjected to a prescribed boundary condition, the problem can be solved by mapping Γ to a circle of unit radius. It is important that (i) each point on Γ is mapped to the same point for the three Stroh eigenvalues p1,p2,p3 and (ii) the mapping is one-to-one for the region outside Γ. In an earlier paper it was shown that conditions (i) and (ii) are satisfied when Γ is an ellipse. The paper did not address to the case when Γ is an open boundary, such as a parabola or hyperbola that was studied by Lekhnitskii. We examine the mappings employed by Lekhnitskii for a parabola and hyperbola, and show that while the mapping for a parabola satisfies conditions (i) and (ii), the mapping for a hyperbola does not satisfy condition (i). Nevertheless, a valid solution can be obtained for the problem with a hyperbolic boundary, although the prescription of the boundary condition is restricted. We generalize Lekhnitskii’s solutions for general anisotropic elastic materials and for more general boundary conditions. Using known identities and new identities presented here, real form expressions are given for the displacement and hoop stress vector at the parabolic and hyperbolic boundary.
8
Wang, Shuangbu, Nan Xiang, Yu Xia, Lihua You, and Jianjun Zhang. "Real-time surface manipulation with $$C^{1}$$ continuity through simple and efficient physics-based deformations." Visual Computer 37, no. 9-11 (June 17, 2021): 2741–53. http://dx.doi.org/10.1007/s00371-021-02169-4.
Анотація:
AbstractWe present a novel but simple physics-based method to interactively manipulate surface shapes of 3D models with $$ C^1 $$ C 1 continuity in real time. A fourth-order partial differential equation involving a sculpting force originating from elastic bending of thin plates is proposed to define physics-based deformations and achieve $$ C^1 $$ C 1 continuity at the boundary of deformation regions. In order to obtain real-time physics-based surface manipulation, we construct a mapping relationship between a deformation region in a 3D coordinate space and a unit circle on a 2D parametric plane, formulate corresponding $$ C^1 $$ C 1 continuous boundary conditions for the unit circle, and obtain a simple analytical solution to describe the physics-based deformation in the unit circle caused by a sculpting force. After that, the obtained physics-based deformation is mapped back to the 3D coordinate space, and added to the original surface to create a new surface shape with $$ C^1 $$ C 1 continuity at the boundary of the deformation region. We also develop an interactive user interface as a plug-in of the 3D modelling software package Maya to achieve real-time surface manipulation. The effectiveness, easiness, real-time performance, and better realism of our proposed method is demonstrated by testing surface deformations on several 3D models and comparing with other methods and ground-truth deformations.
9
Iwase, Kenji, Hirotaka Sato, Stefanus Harjo, Takashi Kamiyama, Takayoshi Ito, Shinichi Takata, Kazuya Aizawa, and Yoshiaki Kiyanagi. "In situlattice strain mapping during tensile loading using the neutron transmission and diffraction methods." Journal of Applied Crystallography 45, no. 1 (January 14, 2012): 113–18. http://dx.doi.org/10.1107/s0021889812000076.
Анотація:
In this study, the change in internal lattice strain in an iron plate during tensile deformation was investigated by performingin situmeasurements under applied force. The lattice strain was evaluated by neutron diffraction and Bragg-edge transmission. The neutron diffraction results showed that the averaged 110 lattice strain along the direction perpendicular to the applied force was between −422 and −109 × 10−6. The position dependence of the lattice strain and the change in the distribution of elastic strain in an iron plate with notches during tensile deformation was obtained by Bragg-edge transmission. It was also observed that, when the load increased over 30 kN, the area of plastic deformation increased around the positions of the notches.
10
Hoshino, Kiyoshi, Daisuke Mori, and Motomasa Tomida. "An Optical Tactile Sensor Assuming Cubic Polynomial Deformation of Elastic Body." Journal of Robotics and Mechatronics 21, no. 6 (December 20, 2009): 780–88. http://dx.doi.org/10.20965/jrm.2009.p0780.
Анотація:
Assuming that the elastic body makes cubic polynomial deformation, we propose a compact three-dimensional (3D) optical tactile sensor for high-speed detection of three-axial directional force components. We constructed a 3D tactile sensor using thin, soft elastic and without pattern delineation or pigment injection such as that used in light-section measurement but having wider dynamic ranges and higher resolution. Conventional light-section measurement irradiating light onto sheets to measure objects requires a huge construction of the optical tactile sensor. Light-emitting diode (LED) sources are arranged around thin, deformable elastic membrane to obtain 3D force components from two-dimensional (2D) camera images taken using light sources of a minimum number of depth layers. Using two LED light sources - red and blue - around an elastic body, we estimate an object contact point pressing the elastic body and force magnitude and force incidence angle based on a mapping relationship predetermined through neural network learning from four ellipsoids formed by light irradiation and major and minor axis intersection points. To confirm that the elastic body forms cubic polynomial concavities at the point to rubber edges where force is applied based on X-, Y-, and Z-axes force components, we photographed elastic deformation and fitted curves into cubic polynomial expressions to investigate fitting accuracy. Fitting accuracy confirmed that cubic polynomials may reasonably approximate elastic deformation. We found that fitting curves onto cubic polynomials required two intersection points in addition to each edge of contact point and each of rubber edge point. Two is the minimum number of light sources required for irradiation. Experiments with this optical tactile sensor confirmed it to be effective in accurately estimating 3D elastic deformation, the object contact point, force magnitude, and force incidence angle.
11
Ting, T. C. T. "Common Errors on Mapping of Nonelliptic Curves in Anisotropic Elasticity." Journal of Applied Mechanics 67, no. 4 (December 15, 1999): 655–57. http://dx.doi.org/10.1115/1.1311961.
Анотація:
For an isotropic elastic material under a two-dimensional plane-stress or plane-strain deformation that involves a closed boundary of a given geometry Γ, it is a common practice to use a conformal mapping to map Γ to a circle of unit radius. For an anisotropic elastic material, the mapping produces the correct solution to the physical problem when Γ is an ellipse. There are published (and unpublished) papers that report solutions to anisotropic elasticity problems with a nonelliptic curve Γ. They all fail to solve the physical problem correctly. The purpose of this paper is to show the common errors made by many researchers, and to alert newcomers on the subject so that they do not fall into the same trap. [S0021-8936(00)02403-X]
12
Park, Taehyo, and G. Z. Voyiadjis. "Kinematic Description of Damage." Journal of Applied Mechanics 65, no. 1 (March 1, 1998): 93–98. http://dx.doi.org/10.1115/1.2789052.
Анотація:
In this paper the kinematics of damage for finite elastic deformations is introduced using the fourth-order damage effect tensor through the concept of the effective stress within the framework of continuum damage mechanics. However, the absence of the kinematic description of damage deformation leads one to adopt one of the following two different hypotheses. One uses either the hypothesis of strain equivalence or the hypothesis of energy equivalence in order to characterize the damage of the material. The proposed approach in this work provides a relation between the effective strain and the damage elastic strain that is also applicable to finite strains. This is accomplished in this work by directly considering the kinematics of the deformation field and furthermore it is not confined to small strains as in the case of the strain equivalence or the strain energy equivalence approaches. The proposed approach shows that it is equivalent to the hypothesis of energy equivalence for finite strains. In this work, the damage is described kinematically in the elastic domain using the fourth-order damage effect tensor which is a function of the second-order damage tensor. The damage effect tensor is explicitly characterized in terms of a kinematic measure of damage through a second-order damage tensor. The constitutive equations of the elastic-damage behavior are derived through the kinematics of damage using the simple mapping instead of the other two hypotheses.
13
Shahidi, A. R., M. Mahzoon, M. M. Saadatpour, and M. Azhari. "Very Large Deformation but Small Strain Analysis of Plates and Folded Plates by Finite Strip Method." Advances in Structural Engineering 8, no. 6 (December 2005): 547–60. http://dx.doi.org/10.1260/136943305776318347.
Анотація:
In this paper a Finite strip method is developed to analyze very large deformations of thin plates and folded plates by use of the elastic Cosserat theory. The principle of virtual work is exploited to present the weak form of the governing differential equations. Through a linear mapping, a rectangular strip is transformed into a standard square computational domain in which the deformation and director fields are developed together with the general forms of the uncoupled nonlinear equations. The geometric and material tangential stiffness matrices are formed through linearization, and a step by step procedure is presented to complete the scheme. The validity and the accuracy of the method are illustrated through certain numerical examples and comparison of the results with other researches. The method is shown to be capable of handling numerical analysis of plates experiencing very large deformations.
14
Cai, Kun. "Mechanical Properties of Single-Walled Carbon Nanotubes under Large Axial Deformation." Advanced Materials Research 97-101 (March 2010): 3910–15. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.3910.
Анотація:
The deformation of single-walled carbon nanotubes (SWCNTs) under large axial strain is studied by a geometrical mapping method. The interactions between atoms in carbon nanotubes (CNTs) are described by Tersoff-Brenner potential. Results show the strain energy depends on chirality but hardly on tubes’ radii. For graphitic sheet under large axial deformation, the elastic moduli decrease with the increase of engineering strain under tension. The modulus reaches the peak value as the axial engineering strain reaches -0.08 for armchair pattern and -0.15 for zigzag pattern under compression.
15
Koumoulos, Elias, and Costas Charitidis. "Integrity of Carbon-Fibre Epoxy Composites through a Nanomechanical Mapping Protocol towards Quality Assurance." Fibers 6, no. 4 (October 11, 2018): 78. http://dx.doi.org/10.3390/fib6040078.
Анотація:
The purpose of this study is to assess the integrity of carbon-fibre reinforced plastics (CFRP) comprising of commercial and surface modified CFs through nanomechanical mapping protocol, towards the feasibility of nanoindentation tool as a quality assurance means in a composite manufacturing process. Carbon fibre surface modification was selected for enhancement of the wetting properties of carbon fibres in order to improve the adhesion force between the fibre and the polymer matrix. In all cases, epoxy resin was used as a matrix for the manufacturing of composite samples. Plastic deformation/elastic recovery were recorded (together with viscoelasticity and adhesion-discontinuities and fluctuations during measurement), while elastic modulus values are also mapped. Moreover, the resistance to applied load is assessed and compared for all cases.
16
Dai, Ming, Cun-Fa Gao, and C. Q. Ru. "Uniform stress fields inside multiple inclusions in an elastic infinite plane under plane deformation." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2177 (May 2015): 20140933. http://dx.doi.org/10.1098/rspa.2014.0933.
Анотація:
Multiple elastic inclusions with uniform internal stress fields in an infinite elastic matrix are constructed under given uniform remote in-plane loadings. The method is based on the sufficient and necessary condition imposed on the boundary value of a holomorphic function that guarantees the existence of the holomorphic function in a multiply connected region. The unknown shape of each of the multiple inclusions is characterized by a conformal mapping. This work focuses on a major large class of multiple inclusions characterized by a simple condition that covers and is much beyond the known related results reported in previous works. Extensive examples of multiple inclusions with or without geometrical symmetry are shown. Our results showed that the inclusion shapes obtained for the uniformity of internal stress fields are independent of the remote loading only when all of the multiple inclusions have the same shear modulus as that of the matrix. Moreover, specific conditions are derived on remote loading, elastic constants of the inclusions and uniform internal stress fields, which guarantee the existence of multiple symmetric inclusions or multiple rotationally symmetrical inclusions with uniform internal stress fields.
17
Guo, Liqiu, Hao Lu, D. Y. Li, Q. X. Huang, Xu Wang, and J. A. Szpunar. "Crystallographic anisotropy in surface properties of brass and its dependence on the electron work function." Journal of Applied Crystallography 51, no. 6 (November 28, 2018): 1715–20. http://dx.doi.org/10.1107/s160057671801573x.
Анотація:
The crystallographic anisotropy of the electric current or conductance, adhesive force, elastic modulus, and deformation magnitude of alpha brass were investigated through property mapping using an atomic force microscope. Surface electron work functions of differently oriented grains in the brass were also analyzed using atomic force microscopy. The mapped surface properties are closely related to the electron work function; the work function reflects the surface activity, which is itself dependent on the surface energy. The anisotropy of the properties is closely correlated to the in situ measured surface electron work function. It is demonstrated that crystallographic planes with higher electron work functions exhibit lower current, smaller adhesive forces, larger elastic moduli and smaller deformation magnitudes. Efforts are made to understand the relationships by connecting the properties with surface energy and electron work function. The dependence of the properties on crystallographic orientation can be elucidated by considering the surface electron behavior using electron work function as a novel probing parameter.
18
Tang, M. X., J. W. Huang, J. C. E, Y. Y. Zhang, and S. N. Luo. "Full strain tensor measurements with X-ray diffraction and strain field mapping: a simulation study." Journal of Synchrotron Radiation 27, no. 3 (April 15, 2020): 646–52. http://dx.doi.org/10.1107/s1600577520003926.
Анотація:
Strain tensor measurements are important for understanding elastic and plastic deformation, but full bulk strain tensor measurement techniques are still lacking, in particular for dynamic loading. Here, such a methodology is reported, combining imaging-based strain field mapping and simultaneous X-ray diffraction for four typical loading modes: one-dimensional strain/stress compression/tension. Strain field mapping resolves two in-plane principal strains, and X-ray diffraction analysis yields volumetric strain, and thus the out-of-plane principal strain. This methodology is validated against direct molecular dynamics simulations on nanocrystalline tantalum. This methodology can be implemented with simultaneous X-ray diffraction and digital image correlation in synchrotron radiation or free-electron laser experiments.
19
Jing, Shi, and Yan Xin-li. "Analytical Solutions for the Elastic Circular Rod Nonlinear Wave, Boussinesq, and Dispersive Long Wave Equations." Journal of Applied Mathematics 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/487571.
Анотація:
The solving processes of the homogeneous balance method, Jacobi elliptic function expansion method, fixed point method, and modified mapping method are introduced in this paper. By using four different methods, the exact solutions of nonlinear wave equation of a finite deformation elastic circular rod, Boussinesq equations and dispersive long wave equations are studied. In the discussion, the more physical specifications of these nonlinear equations, have been identified and the results indicated that these methods (especially the fixed point method) can be used to solve other similar nonlinear wave equations.
20
Utsunomiya, H., P. Hartley, and I. Pillinger. "Three-Dimensional Elastic-Plastic Finite-Element Analysis of the Flattening of Wire Between Plain Rolls*." Journal of Manufacturing Science and Engineering 123, no. 3 (June 1, 2000): 397–404. http://dx.doi.org/10.1115/1.1365158.
Анотація:
It is normal industrial practice to roll round edged flat wires from round circular wires using plain rolls. Although this is not a complex type of metal forming process, the internal deformation is highly three-dimensional. It is important to be able to determine the lateral spread, elongation and final profile precisely. In this paper, this process has been analyzed using an elastic-plastic finite element program. Firstly, algorithms for integrating the constitutive equations, i.e., return mapping algorithms, are evaluated to determine the most accurate technique. Then, the influences of friction and reduction in thickness on the deformation characteristics are investigated. The lateral spread and the radius of curvature of the free surface are quantitatively in reasonable agreement with those obtained from empirical formulas. The lateral spread increases with friction and with reduction. The variation of elongation in the roll bite is investigated in detail. It is found that the elongation is not uniformly distributed across the cross section. After passing the roll gap, the distribution is compensated by the elastic recovery of wire, otherwise it may cause edge waves.
21
Yoganathan, Murugesu, Ejiro Emorhokpor, Thomas Kerr, A. Gupta, C. D. Tanner, and Ilya Zwieback. "Characterization of SiC Substrates Using X-Ray Rocking Curve Mapping." Materials Science Forum 527-529 (October 2006): 729–32. http://dx.doi.org/10.4028/www.scientific.net/msf.527-529.729.
Анотація:
SiC substrates produced at II-VI, Inc. have been characterized using x-ray rocking curve mapping (topography). The rocking curves have been measured in the -scan mode for the (0006) Bragg reflection of 6H and the (0004) reflection of 4H SiC substrates. The maps contain information extracted from the rocking curves, such as the peak angle () and the rocking curve broadening (FWHM). In the case when lattice distortion is present due to the elastic or plastic deformation, the peak angle () changes gradually upon scanning, with the d/dx gradient proportional to the lattice curvature in the plane of diffraction. Multi-peak reflections and/or sharp change in the value of indicate the presence of misoriented grains. X-ray rocking curve mapping of SiC substrates yields excellent measures of crystalline quality that contain important information on the lattice strain and sub-grain misorientation.
22
Yang, Hai-Bing, and Shuang Wang. "Interface tension-induced stress field around periodic nano-inclusions of arbitrary shape." Mathematics and Mechanics of Solids 24, no. 9 (December 29, 2018): 2844–57. http://dx.doi.org/10.1177/1081286518820084.
Анотація:
This paper investigates the plane deformation of periodic nano-inclusions of arbitrary shape embedded in a homogeneous isotropic material. A representative unit cell (RUC) with periodic boundary conditions imposed on its edges is used to represent the periodicity of the structure. Residual interface tension is incorporated into the deformation model so that the normal and tangential stresses have to jump across the matrix–inclusion interface, despite that the displacement can generally be treated as continuous across that interface. The stress field in the entire RUC is obtained by using the complex variable methods with the assistance of conformal mapping, series expansion, and collocation techniques. Numerical examples are presented for three different inclusion shapes. The results show that the interface tension-induced stress field can be greatly influenced by the shape, elastic modulus, and volume fraction of the inclusions.
23
CUI, X. Y., G. Y. LI, and G. R. LIU. "AN EXPLICIT SMOOTHED FINITE ELEMENT METHOD (SFEM) FOR ELASTIC DYNAMIC PROBLEMS." International Journal of Computational Methods 10, no. 01 (February 2013): 1340002. http://dx.doi.org/10.1142/s0219876213400021.
Анотація:
This paper presents an explicit smoothed finite element method (SFEM) for elastic dynamic problems. The central difference method for time integration will be used in presented formulations. A simple but general contact searching algorithm is used to treat the contact interface and an algorithm for the contact force is presented. In present method, the problem domain is first divided into elements as in the finite element method (FEM), and the elements are further subdivided into several smoothing cells. Cell-wise strain smoothing operations are used to obtain the stresses, which are constants in each smoothing cells. Area integration over the smoothing cell becomes line integration along its edges, and no gradient of shape functions is involved in computing the field gradients nor in forming the internal force. No mapping or coordinate transformation is necessary so that the element can be used effectively for large deformation problems. Through several examples, the simplicity, efficiency and reliability of the smoothed finite element method are demonstrated.
24
Sun, Yu Ping, Wei Li Zhou, Hui Li, and Jin Mei Li. "Numerical Simulation of Bending Performance of Laser-Welded I-Core Sandwich Plates Considering Weld Material Properties." Advanced Materials Research 742 (August 2013): 24–29. http://dx.doi.org/10.4028/www.scientific.net/amr.742.24.
Анотація:
The properties of the base metal, weld and joint of CCS-B material for sandwich plate used in ship structurewasconfirmedthrough the tensile test,which provided the data parameters for the finite element simulation;The three points bending test for laser-weldedI-coresandwich plate was simulated by ABAQUS,and two kinds of models were establishedby considering and without considering weld material properties, which load-displacement curve shows that the influence of the weld material properties is larger to plates stiffness, but less to bearing capacity; For the model whichwas considered the weld material property, the development of plastic zone and the measurement of stress state show:In the elastic stage, the localposition yield in the junction zone between the web and upper and lower weld; In the plastic stage,the large areayield in the panel and the web of T-joint zone; The mapping relationship from the stress state to macroscopic deformation shows that both of the panel and the web occur S shape deformation and the whole web plate occur inclination deformation.
25
Bubendorf, Alexandre, Stefan Walheim, Thomas Schimmel, and Ernst Meyer. "A robust AFM-based method for locally measuring the elasticity of samples." Beilstein Journal of Nanotechnology 9 (January 2, 2018): 1–10. http://dx.doi.org/10.3762/bjnano.9.1.
Анотація:
Investigation of the local sample elasticity is of high importance in many scientific domains. In 2014, Herruzo et al. published a new method based on frequency-modulation atomic force microscopy to locally determine the elasticity of samples (Nat. Commun. 2014, 5, 3126). This method gives evidence for the linearity of the relation between the frequency shift of the cantilever first flexural mode Δf 1 and the square of the frequency shift of the second flexural mode Δf 2 2. In the present work, we showed that a similar linear relation exists when measuring in contact mode with a certain load F N and propose a new method for determining the elastic modulus of samples from this relation. The measurements were performed in non-dry air at ambient temperature on three different polymers (polystyrene, polypropylene and linear low-density polyethylene) and a self-assembled monolayer of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) on a silicon oxide substrate perforated with circular holes prepared by polymer blend lithography. For all samples the relation was evidenced by recording Δf 1, Δf 2 and F N as a function of the Z-displacement curves of the piezoelectric scanner. The occurence of a plastic deformation followed by an elastic deformation is shown and explained. The necessary load F N for measuring in the elastic domain was assessed for each sample, used for mapping the frequency shifts Δf 1 and Δf 2 and for determining the elastic modulus from Δf 2 2/Δf 1. The method was used to give an estimate of the Young’s modulus of the FDTS thin film.
26
Potjananapasiri, Kobsak, Sutthisak Phongthanapanich, Paritud Bhandhubanyong, and Pramote Dechaumphai. "Combined Adaptive Finite Element Method and J-Domain Integral Technique for Crack Problems." Key Engineering Materials 340-341 (June 2007): 459–64. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.459.
Анотація:
An adaptive finite element method for analyzing two-dimensional and axisymmetric nonlinear elastic fracture mechanics problems with cracks is presented. The J-integral is used as a parameter to characterize the severity of stresses and deformation near a crack tip. The domain integral technique is utilized as the J-integral solution scheme with the 9-node degenerated crack tip elements. The solution accuracy is further improved by incorporating an error estimation procedure to a remeshing algorithm with a solution mapping scheme to resume the analysis at a particular load level after the adaptive remeshing technique has been applied. Two benchmark problems are analyzed to evaluate the efficiency of the combined procedure.
27
Blouin, Stéphane, Stephan Puchegger, Andreas Roschger, Andrea Berzlanovich, Peter Fratzl, Klaus Klaushofer, and Paul Roschger. "Mapping Dynamical Mechanical Properties of Osteonal Bone by Scanning Acoustic Microscopy in Time-of-Flight Mode." Microscopy and Microanalysis 20, no. 3 (April 11, 2014): 924–36. http://dx.doi.org/10.1017/s1431927614000646.
Анотація:
AbstractAn important determinant of mechanical properties of bone is Young’s modulus and its variation in individual osteons of cortical bone tissue. Its mechanical behavior also depends on deformation rate owing to its visco- or poroelastic properties. We developed a method to measure dynamical mechanical properties of bulk bone tissue at osteonal level based on scanning acoustic microscopy (SAM) using time-of-flight (TOF) measurements in combination with quantitative backscattered electron imaging (qBEI). SAM-TOF yields local sound velocities and qBEI corresponding material densities together providing elastic properties. Osteons (n=55) were measured in three human femoral diaphyseal ground bone sections (∼30µm in thickness). In addition, subchondral bone and mineralized articular cartilage were investigated. The mean mineral contents, the mean sound velocities, and the mean elastic modulus of the osteons ranged from 20 to 26 wt%, from 3,819 to 5,260 m/s, and from 21 to 44 GPa, respectively. There was a strong positive correlation between material density and sound velocity (Pearson’sr=0.701;p<0.0001) of the osteons. Sound velocities between cartilage and bone was similar, though material density was higher in cartilage (+4.46%,p<0.0001). These results demonstrate the power of SAM-TOF to estimate dynamic mechanical properties of the bone materials at the osteonal level.
28
Weissmann, Sigmund. "Characterization of Lattice Defects and Concomitant Strain Distribution." Advances in X-ray Analysis 35, A (1991): 221–37. http://dx.doi.org/10.1154/s0376030800008879.
Анотація:
AbstractA number of X-ray methods characterizing lattice defects are described. They were developed in response to a variety of challenging problems in materials science, A method based on a computer-aided rocking curve analysis, CARCA, was developed which offers a rapid mapping of the dislocation structure in an epitaxial film, as well as a tensor analysis of nonuniform elastic strains. Characterization methods were developed in an attempt at bridging, systematically, the gap between micro and macromechanics when the problem arose to clarify the distribution of elastic strains emanating from stress concentrators such as notches, cracks, holes and to elucidate strain interactions. Gradients of elastic strains were characterized by a method of local intensity measurements. For crystal with homogeneous elastic strain distribution a tensor analysis is described, based on precision measurements obtained by the backreflection divergent beam method. A direct linkage between the imaging of the micro structure by TEM and the macro-response of deformation and recovery of commercial alloys was achieved by a version of the CARCA method, designed to characterize the lattice defects in polycrystalline materials. Example applications of the methods are presented with the hope that their usefulness may find adaptations in other areas of investigation.
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Spolenak, R., W. Ludwig, J. Y. Buffiere, and J. Michler. "In SituElastic Strain Measurements—Diffraction and Spectroscopy." MRS Bulletin 35, no. 5 (May 2010): 368–74. http://dx.doi.org/10.1557/mrs2010.569.
Анотація:
AbstractUnderstanding the mechanical properties of materials is crucial for their reliable application as bulk materials as well as in a miniaturized form. The deformation of materials is usually non-uniform and, hence, needs to be characterized on a local level. The following article focuses on thein-Situdetermination of mechanical stresses in crystalline materials during deformation. This can be achieved by both diffraction as well as spectroscopical methods, where the elastic strain is the parameter measured, which is subsequently converted into stresses by the application of Hooke's law. Asin Situmeasurements require rapid data acquisition in conjunction with reasonable penetration depths, we will focus on x-rays. However, the different techniques described can be applied to any other diffraction probe as well. The description of diffraction techniques, which span the range from averaging techniques to 2D and 3D strain mapping, is complemented by a section on Raman spectroscopy as an alternative method for stress determination for non-metallic materials. Local stresses also can be correlated to local defect densities.
30
Mostafavi, Mahmoud, Yelena Vertyagina, Christina Reinhard, Robert Bradley, Xia Jiang, Marina Galano, and James Marrow. "3D Studies of Indentation by Combined X-Ray Tomography and Digital Volume Correlation." Key Engineering Materials 592-593 (November 2013): 14–21. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.14.
Анотація:
Hardness testing obtains material properties from small specimens via measurement of load-displacement response to an imposed indentation; it is a surface characterisation technique so, except in optically transparent materials, there is no direct observation of the assumed damage and deformation processes within the material. Three-dimensional digital image correlation (digital volume correlation) is applied to study deformation beneath indentations, mapping the relative displacements between high-resolution synchrotron X-ray computed tomographs (0.9 μm voxel size). Two classes of material are examined: ductile aluminium-silicon carbide composite (Al-SiC) and brittle alumina (Al2O3). The measured displacements for Hertzian indentation in Al-SiC are in good agreement with an elastic-plastic finite element simulation. In alumina, radial cracking is observed beneath a Vickers indentation and the crack opening displacements are measured, in situ under load, for the first time. Potential applications are discussed of this characterization technique, which does not require resolution of microstructural features.
31
Sharma, Hemant Kumar, Raghvendra Sahai Saxena, Aditya Gokhale, Ashok Kapoor, Rajesh Prasad, and Rajesh Kumar Sharma. "Cathodoluminescence Studies of Nanoindented CdZnTe Single Crystal Substrates for Analysis of Residual Stresses and Deformation Behaviour." Defence Science Journal 70, no. 6 (October 12, 2020): 650–55. http://dx.doi.org/10.14429/dsj.70.16383.
Анотація:
Nanoindentation-induced residual stresses were analysed on (111) Te face CdZnTe single-crystal substrates in this study. CdZnTe substrates were subjected to nanoindentation using cube corner indenter geometry with a peak load of 10 mN. Loading rates of 1 mN/s and 5 mN/s were used in the experiments, with a holding time of 10 s at peak load. Residual stresses on the indented region were analysed from load-displacement curves and explained using dislocation generation and elastic recovery mechanisms. Residual stresses were found to be of compressive type, just on the indented surface. The slip lines along the slip directions of this material were clearly visible in the FE-SEM images of the indents. Indents and surrounding surfaces were characterized using the Cathodoluminescence (CL) technique. CL mapping of the indented surface revealed the dislocation generation and their propagation behaviour just beneath the indenter as well as in the surrounding surfaces. The dislocations act as non-radiative recombination centres and quench the CL intensity locally. Dark lines were explained as the presence of dislocations in the material. CL mapping analysis shows that both the rosette glide and tetrahedral glide of dislocations are the primary deformation mechanisms present in CdZnTe. A rosette structure was observed in the CL mapping. CL spectra at 300 K of un-deformed CdZnTe show a peak at 810 nm wavelength, which corresponds to near-band-edge emission. After indentation, the CL spectra show the peak intensity at 814 nm and 823 nm wavelengths at the edge of the indents created with a loading rate of 1 mN/s and 5 mN/s, respectively. These peak shifts from 810 nm were attributed to the tensile residual stresses present in the indented material.
32
Dai, Ming, Peter Schiavone, and Cun-Fa Gao. "Harmonic holes with surface tension in an elastic plane under uniform remote loading." Mathematics and Mechanics of Solids 22, no. 9 (May 17, 2016): 1806–12. http://dx.doi.org/10.1177/1081286516647205.
Анотація:
Harmonic holes are designed to leave undisturbed the mean stress in an uncut body subjected to a system of prescribed remote loadings. The role of residual surface tension in the design of harmonic holes is an important consideration, which is usually neglected at the macroscale but remains a significant factor in the design of such holes at the nanoscale. We consider the identification of the geometry of a single harmonic hole in an elastic plane subjected to uniform remote loading when residual surface tension is incorporated into the model of deformation. The geometry of the hole is defined by a conformal mapping with certain unknown coefficients determined from a system of non-linear equations. We illustrate our results with several examples. In particular, we show that for a given remote loading and surface tension, the shapes obtained exhibit strong size-dependency. Moreover, we find that the incorporation of the effect of surface tension greatly extends the range of admissible uniform remote loadings that guarantee the existence of harmonic holes.
33
Varghese, T., J. Ophir, E. Konofagou, F. Kallel, and R. Righetti. "Tradeoffs in Elastographic Imaging." Ultrasonic Imaging 23, no. 4 (October 2001): 216–48. http://dx.doi.org/10.1177/016173460102300402.
Анотація:
This paper presents the tradeoffs in elastographic imaging. Elastography is viewed as a new imaging modality and presented in terms of three fundamental concepts that constitute the basis for the elastographic imaging process. These are the tissue elastic deformation process, the statistical analysis of strain estimation and the image characterization. The first concept involves the use of the contrast transfer efficiency ( CTE) that describes the mapping of a distribution of local tissue elastic moduli into a distribution of local longitudinal tissue strains. The second concept defines the elastographic system and the relationship between ultrasonic and signal processing parameters. This process is described in terms of a stochastic framework (the strain filter) that provides upper and practical performance bounds and their dependence on the various system parameters. Finally, the output image, the elastogram, is characterized by its image parameters, such as signal-to-noise ratio, contrast-to-noise ratio, dynamic range and resolution. Finite-element simulations are used to generate examples of elastograms that are confirmed by the theoretical prediction tools.
34
Li, Y. M., B. Abbès, and Y. Q. Guo. "Two Efficient Algorithms of Plastic Integration for Sheet Forming Modeling." Journal of Manufacturing Science and Engineering 129, no. 4 (February 13, 2007): 698–704. http://dx.doi.org/10.1115/1.2738125.
Анотація:
A fast method called the “inverse approach” for sheet forming modeling is based on the assumptions of the proportional loading and simplified tool actions. To improve the stress estimation, the pseudo-inverse approach was recently developed: some realistic intermediate configurations are geometrically determined to consider the deformation paths; two new efficient algorithms of plastic integration are proposed to consider the loading history. In the direct scalar algorithm (DSA), an elastic unloading-reloading factor γ is introduced to deal with the bending-unbending effects; the equation in unknown stress vectors is transformed into a scalar equation using the notion of the equivalent stress, thus the plastic multiplier Δλ can be directly obtained without iterative resolution scheme. In the γ-return mapping algorithm, the equivalent plastic strain increment estimated by DSA is taken as the initial solution in Simo’s return mapping algorithm, leading to a stable, efficient, and accurate plastic integration scheme. The numerical experience has shown that these two algorithms give a considerable reduction of CPU time in the plastic integration.
35
Zhou, Liming, Ming Li, Bingkun Chen, Feng Li, and Xiaolin Li. "An inhomogeneous cell-based smoothed finite element method for the nonlinear transient response of functionally graded magneto-electro-elastic structures with damping factors." Journal of Intelligent Material Systems and Structures 30, no. 3 (November 29, 2018): 416–37. http://dx.doi.org/10.1177/1045389x18812712.
Анотація:
In this article, an inhomogeneous cell-based smoothed finite element method (ICS-FEM) was proposed to overcome the over-stiffness of finite element method in calculating transient responses of functionally graded magneto-electro-elastic structures. The ICS-FEM equations were derived by introducing gradient smoothing technique into the standard finite element model; a close-to-exact system stiffness was also obtained. In addition, ICS-FEM could be carried out with user-defined sub-routines in the business software now available conveniently. In ICS-FEM, the parameters at Gaussian integration point were adopted directly in the creation of shape functions; the computation process is simplified, for the mapping procedure in standard finite element method is not required; this also gives permission to utilize poor quality elements and few mesh distortions during large deformation. Combining with the improved Newmark scheme, several numerical examples were used to prove the accuracy, convergence, and efficiency of ICS-FEM. Results showed that ICS-FEM could provide solutions with higher accuracy and reliability than finite element method in analyzing models with Rayleigh damping. Such method is also applied to complex structures such as typical micro-electro-mechanical system–based functionally graded magneto-electro-elastic energy harvester. Hence, ICS-FEM can be a powerful tool for transient problems of functionally graded magneto-electro-elastic models with damping which is of great value in designing intelligence structures.
36
Pei, Yongjie, and Xiangyang Cui. "A Novel Triangular Prism Element Based on Smoothed Finite Element Method." International Journal of Computational Methods 15, no. 07 (October 12, 2018): 1850058. http://dx.doi.org/10.1142/s0219876218500585.
Анотація:
In this paper, a novel triangular prism element based on smoothed finite element method (SFEM) is proposed for three-dimensional static and dynamic mechanics problems. The accuracy of the proposed element is comparable to that of the hexahedral element while keeping good adaptability as the tetrahedral element on a surface dimension. In the process of constructing the proposed element, one triangular prism element is further divided into two smoothing cells. Very simple shape functions and a constant smoothing function are used in the construction of the smoothed strains and the smoothed nominal stresses. The divergence theorem is applied to convert the volume integral to the integrals of all the surrounding surfaces of a smoothing cell. Thus, no gradient of shape function and no mapping or coordinate transformation are involved in the process of creating the discretized system equations. Afterwards, several numerical examples include elastic-static and free vibration problems are provided to demonstrate the accuracy and efficiency of the proposed element. Meanwhile, an explicit scheme of the proposed element is given for dynamic large-deformation analysis of elastic-plastic materials, and the numerical results show good agreement with the experimental data.
37
Jiang, An Nan, Jun Xiang Wang, and De Hai Yu. "Intelligent Simulation and Recognition of Metro Station Excavation Based on Differential Evolution and Finite Element." Advanced Materials Research 168-170 (December 2010): 2641–47. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.2641.
Анотація:
Differential Evolution (DE) is a new algorithm. Displacement back analysis method based on the algorithm can effectively solve the problems of rock mechanics parameters which are not accurate. Constitutive integration algorithm divided into explicit and implicit integration is the key points of finite element analysis, which affect the convergence and accuracy of the results. Return mapping algorithm avoiding directly solving the equivalent plastic strain is a kind of implicit integration algorithm, which would achieve rapid and accurate for the solution of constitutive equations. This article describes the theoretical framework based on elastic-plastic, von Mises yield criterion conditions, using C + + language to carry out plastic simulation of Dalian metro station CRD excavation and parameter identification based on differential evolution algorithm. The calculated stress, displacement and deformation can determine the surface subsidence and the development of plastic zone, the stability analysis to provide a reference for the construction.
38
Russell, Phillip E., and A. D. Batchelor. "AFM and Other Scanned Probe Microscopies Tutorial." Microscopy and Microanalysis 4, S2 (July 1998): 878–79. http://dx.doi.org/10.1017/s143192760002451x.
Анотація:
While the techniques offer high spatial resolution in some cases down to the atomic scale and three dimensional mapping of surface topography, there still remain issues related to quantitative interpretation of scanned probe data, particularly in the recently developed phase contrast imaging modes. In this talk, the various modes of force microscopy will be introduced, along with examples. New techniques are starting to emerge which allow us to use the scanned probe microscope to measure properties such as local adhesion and local elastic and plastic deformation of samples.Each scanned probe technique relies on a very sharp probe positioned within a few nanometers of the surface of interest. Some combination of probe and/or substrate positioning is required to provide sub-nm-resolution, three-dimensional motion of the probe relative to the substrate. When the probe translates laterally (horizontally) relative to the sample, any change in the height of the surface causes the detected probe signal to change.
39
Gupta, Nabanita, Supratik Sarkar, and Kurt J. Marfurt. "Seismic attribute driven integrated characterization of the Woodford Shale in west-central Oklahoma." Interpretation 1, no. 2 (November 1, 2013): SB85—SB96. http://dx.doi.org/10.1190/int-2013-0033.1.
Анотація:
The organic-rich, silty Woodford Shale in west-central Oklahoma is a prolific resource play producing gas and liquid hydrocarbons. We calibrated seismic attributes and prestack inversion using well logs and core information within a seismic geomorphologic framework to define the overall basin architecture, major stratigraphic changes, and related variations in lithologies. Core measurements of elastic moduli and total organic content (TOC) indicated that the Woodford Shale can be broken into three elastic petrotypes important to well completion and hydrocarbon enrichment. Upscaling these measurements facilitates regional mapping of petrotypes from prestack seismic inversion of surface data. Seismic attributes highlight rugged topography of the basin floor of the Paleo Woodford Sea, which controls the lateral and vertical distribution of different lithofacies containing variable quantity of TOC as well as quartz, which controls brittleness. Depressions on the basin floor contain TOC-lean cherty lithofacies alternating with TOC-rich lithofacies, resulting in brittle-ductile rock couplets. In contrast, basin floor highs are characterized by overall TOC-rich ductile lithofacies. Seismic attributes illuminate complex post-Woodford tectonic deformation. The Woodford Shale is known to be naturally fractured on outcrop. Image log analysis in other shale plays showed a good correlation between such tectonic features and natural fractures. These features need to be correlated with well trajectories and production data to determine which hypothesized “fracture sets,” if any, improve well performance.
40
Zhou, Xin, Yundou Xu, Jiantao Yao, Kuijing Zheng, and Yongsheng Zhao. "Stiffness modelling and comparison of the 5-UPS/PRPU parallel machine tool with its non-redundant counterpart." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 231, no. 9 (January 28, 2016): 1646–57. http://dx.doi.org/10.1177/0954405415600014.
Анотація:
This article presents a derivation of the stiffness matrix of a general redundantly actuated parallel mechanism based on the overall Jacobian. The Jacobian of the constraints and actuations is derived using reciprocal screw theory. Based on the mapping relationship between constraint, actuated and external forces combined with the principle of virtual work, a compatibility equation for the deformation of all of the limbs is achieved, and the stiffness model of the general redundantly actuated parallel mechanism is derived. The 5-UPS/PRPU redundantly actuated parallel machine tool is used to illustrate this method. The parallel machine tool comprehensively reveals the effect of the elastic deformation of active–passive joints and some basic transmission parts. The stiffness model is further validated by experimental data. Moreover, the global stiffness matrix of the general redundantly actuated parallel mechanism can be separated into two parts via matrix decomposition. The first part is the stiffness matrix of the corresponding non-redundant parallel mechanism, and the second part is the stiffness matrix of the redundantly actuated limbs (actuators). The redundantly actuated 5-UPS/PRPU parallel machine tool is also investigated for further analysis. The different stiffness characteristics of the machine tool and its corresponding non-redundant 5-UPS/PRPU parallel machine tool are compared. Actuation redundancy is found to improve the stiffness performance of the machine tool efficiently.
41
Boullier, Anne-Marie, Odile Robach, Benoît Ildefonse, Fabrice Barou, David Mainprice, Tomoyuki Ohtani, and Koichiro Fujimoto. "High stresses stored in fault zones: example of the Nojima fault (Japan)." Solid Earth 9, no. 2 (April 26, 2018): 505–29. http://dx.doi.org/10.5194/se-9-505-2018.
Анотація:
Abstract. During the last decade pulverized rocks have been described on outcrops along large active faults and attributed to damage related to a propagating seismic rupture front. Questions remain concerning the maximal lateral distance from the fault plane and maximal depth for dynamic damage to be imprinted in rocks. In order to document these questions, a representative core sample of granodiorite located 51.3 m from the Nojima fault (Japan) that was drilled after the Hyogo-ken Nanbu (Kobe) earthquake is studied by using electron backscattered diffraction (EBSD) and high-resolution X-ray Laue microdiffraction. Although located outside of the Nojima damage fault zone and macroscopically undeformed, the sample shows pervasive microfractures and local fragmentation. These features are attributed to the first stage of seismic activity along the Nojima fault characterized by laumontite as the main sealing mineral. EBSD mapping was used in order to characterize the crystallographic orientation and deformation microstructures in the sample, and X-ray microdiffraction was used to measure elastic strain and residual stresses on each point of the mapped quartz grain. Both methods give consistent results on the crystallographic orientation and show small and short wavelength misorientations associated with laumontite-sealed microfractures and alignments of tiny fluid inclusions. Deformation microstructures in quartz are symptomatic of the semi-brittle faulting regime, in which low-temperature brittle plastic deformation and stress-driven dissolution-deposition processes occur conjointly. This deformation occurred at a 3.7–11.1 km depth interval as indicated by the laumontite stability domain. Residual stresses are calculated from deviatoric elastic strain tensor measured using X-ray Laue microdiffraction using the Hooke's law. The modal value of the von Mises stress distribution is at 100 MPa and the mean at 141 MPa. Such stress values are comparable to the peak strength of a deformed granodiorite from the damage zone of the Nojima fault. This indicates that, although apparently and macroscopically undeformed, the sample is actually damaged. The homogeneously distributed microfracturing of quartz is the microscopically visible imprint of this damage and suggests that high stresses were stored in the whole sample and not only concentrated on some crystal defects. It is proposed that the high residual stresses are the sum of the stress fields associated with individual dislocations and dislocation microstructures. These stresses are interpreted to be originated from the dynamic damage related to the propagation of rupture fronts or seismic waves at a depth where confining pressure prevented pulverization. Actually, M6 to M7 earthquakes occurred during the Paleocene on the Nojima fault and are good candidates for inducing this dynamic damage. The high residual stresses and the deformation microstructures would have contributed to the widening of the damaged fault zone with additional large earthquakes occurring on the Nojima fault.
42
Osechinskiy, Sergey, and Frithjof Kruggel. "Slice-to-Volume Nonrigid Registration of Histological Sections to MR Images of the Human Brain." Anatomy Research International 2011 (December 12, 2011): 1–17. http://dx.doi.org/10.1155/2011/287860.
Анотація:
Registration of histological images to three-dimensional imaging modalities is an important step in quantitative analysis of brain structure, in architectonic mapping of the brain, and in investigation of the pathology of a brain disease. Reconstruction of histology volume from serial sections is a well-established procedure, but it does not address registration of individual slices from sparse sections, which is the aim of the slice-to-volume approach. This study presents a flexible framework for intensity-based slice-to-volume nonrigid registration algorithms with a geometric transformation deformation field parametrized by various classes of spline functions: thin-plate splines (TPS), Gaussian elastic body splines (GEBS), or cubic B-splines. Algorithms are applied to cross-modality registration of histological and magnetic resonance images of the human brain. Registration performance is evaluated across a range of optimization algorithms and intensity-based cost functions. For a particular case of histological data, best results are obtained with a TPS three-dimensional (3D) warp, a new unconstrained optimization algorithm (NEWUOA), and a correlation-coefficient-based cost function.
43
Murray, Conal E., H. Yan, and I. C. Noyan. "Mechanics of microelectronics structures as revealed by X-ray diffraction." Powder Diffraction 22, no. 2 (June 2007): 98–102. http://dx.doi.org/10.1154/1.2737460.
Анотація:
The presence of strain distributions within semiconductor features influences many aspects of their behavior. For example, microelectronic technology that incorporates strained silicon improves device performance by increasing carrier mobility in the Si channels. Because current semiconductor fabrication contains multiple levels of metallic and dielectric structures, an understanding of the mechanical response of the constituent elements is critical to the prediction of the overall device performance. In addition, the interaction of strain fields between adjacent structures becomes greater as feature sizes decrease and the corresponding feature density increases. The use of synchrotron-based X-ray methods allows one to determine the interaction between strained features and their environment at a submicron resolution. Real-space mapping of strain distributions in pseudomorphically strained, raised SiGe structures revealed that elastic relaxation extends approximately 20 times the feature thickness from their edges. X-ray topographic methods were also applied to map the substrate deformation induced by overlying SiGe features. A formulation based on the classical Ewald-von Laue theory of dynamical diffraction was derived to match the measured diffraction profiles.
44
Sendrowicz, Aleksander, Aleksander Omholt Myhre, Seweryn Witold Wierdak, and Alexei Vinogradov. "Challenges and Accomplishments in Mechanical Testing Instrumented by In Situ Techniques: Infrared Thermography, Digital Image Correlation, and Acoustic Emission." Applied Sciences 11, no. 15 (July 22, 2021): 6718. http://dx.doi.org/10.3390/app11156718.
Анотація:
A current trend in mechanical testing technologies is to equip researchers and industrial practitioners with the facilities for non-destructive characterisation of the deformation and fracture processes occurring on different scales. The synergistic effect of such a combination of destructive and non-destructive techniques both widens and deepens existing knowledge in the field of plasticity and fracture of materials and provides the feedback sought to develop new non-destructive testing approaches and in situ monitoring techniques with enhanced reliability, accuracy and a wider scope of applications. The macroscopic standardised mechanical testing is still dominant in the research laboratories and industrial sector worldwide. The present paper reviews multiple challenges commonly faced by experimentalists, aiming at enhancing the capability of conventional mechanical testing by a combination of contemporary infrared thermography (IRT), rapid video imaging (RVI) with non-contact strain mapping possibilities enabled by the digital image correlation (DIC) method, and the acoustic emission (AE) technique providing unbeatable temporal resolution of the stochastic defect dynamics under load. Practical recommendations to address these challenges are outlined. A versatile experimental setup uniting the unique competencies of all named techniques is described alone with the fascinating possibilities it offers for the comprehensive characterisation of damage accumulation during plastic deformation and fracture of materials. The developed toolbox comprising practical hardware and software solutions brings together measuring technologies, data, and processing in a single place. The proposed methodology focuses on the characterisation of the thermodynamics, kinematics and dynamics of the deformation and fracture processes occurring on different spatial and temporal scales. The capacity of the proposed combination is illustrated using preliminary results on the tensile and fatigue behaviour of the fcc Inconel-625 alloy used as a representative example. Dissipative processes occurring in this alloy are assessed through the complex interplay between the released heat, acoustic emission waves, and expended and stored elastic energy.
45
Yang, Zewen, Hong Xu, Yao Huang, Jingyao Sun, Daming Wu, Xiaolong Gao, and Yajun Zhang. "Measuring Mechanism and Applications of Polymer-Based Flexible Sensors." Sensors 19, no. 6 (March 21, 2019): 1403. http://dx.doi.org/10.3390/s19061403.
Анотація:
A new type of flexible sensor, which could maintain the deformation consistency and achieve the real-time detection of the variation in load of the measured object, was proposed in this work. According to the principle of forced assembly, PDMS was used as the substrate of sensitive components and electrodes, while carbon fiber was added as a conductive medium to prepare a polymer-based flexible sensor, which effectively overcame the deformation limitation and output instability of conventional flexible sensors due to different substrates of sensitive components and the electrode. Combined with the sensor structure and the forced assembly method, a theoretical analysis of its conductive measurement mechanism was carried out. Meanwhile, an experimental test device was designed to test and analyze the output characteristics of the flexible sensor under a static and dynamic alternating load. The results show that the flexible sensor exhibited linear output under the dynamic alternating load of 10 kN to 60 kN and frequency of 3 Hz. Peak and valley value had the same phase with the load extremes. The dynamic and static experiments show that the resistance output signal and the sensitivity was in the range of 310~624.15 Ω and 171–183 N/Ω respectively. However, due to the hysteresis of the elastic recovery of the polymer, the output repeatability of the flexible sensor under the dynamic alternating load was 5.03% and 0.78% lower than that of the static load, respectively. Combined with the static and dynamic experiments, it was verified that the polymer-based flexible sensor can maintain the same deformation characteristics with the measured object, and at the same time outputted a resistance signal with a certain mapping relationship with the applied load. The repeatability of the output signal under dynamic and static experiments was within ±7%, which can meet the measurement requirements of the fatigue life of the measured body during periodic load.
46
Bodaghi, M., M. Shakeri, and MM Aghdam. "Passive vibration control of plate structures using shape memory alloy ribbons." Journal of Vibration and Control 23, no. 1 (August 9, 2016): 69–88. http://dx.doi.org/10.1177/1077546315575676.
Анотація:
Problems associated with the modeling and vibration control of rectangular plates under dynamic loads with integrated polycrystalline NiTi shape memory alloy (SMA) ribbons are developed. In order to simulate the thermo-mechanical behavior of SMA ribbons under dominant axial and transverse shear stresses, a robust macroscopic constitutive model is introduced. The model is able to accurately predict martensite transformation/orientation, shape memory effect, pseudo-elasticity and in particular reorientation of martensite variants and ferro-elasticity features. The structural model is based on the adoption of the first-order shear deformation theory and on the geometrical non-linearity in the von Kármán sense. Towards obtaining the governing equations of motion, the Hamilton principle is used. Finite element and Newmark methods along with an iterative incremental process based on the elastic-predictor inelastic-corrector return mapping algorithm are implemented to solve the non-linear governing equations in spatial and time domains. Numerical simulations highlighting the implications of pre-strain state and temperature of the SMA ribbons, as well as those related to the respective dynamic loads, are presented and discussed in detail. It is found that the modeling of ferro-elasticity in the dynamic analysis of SMA composite structures could lead to significant conclusions concerning the passive vibration control capability of low-temperature SMA ribbons.
47
Kaboli, Shirin, та Pamela C. Burnley. "ECCI, EBSD and EPSC characterization of rhombohedral twinning in polycrystalline α-alumina deformed in a D-DIA apparatus". Journal of Applied Crystallography 50, № 6 (3 листопада 2017): 1691–704. http://dx.doi.org/10.1107/s1600576717013991.
Анотація:
Rhombohedral twinning in alumina (aluminium oxide, α-Al2O3) is an important mechanism for plastic deformation under high-temperature–pressure conditions. Rhombohedral twins in a polycrystalline alumina sample deformed in a D-DIA apparatus at 965 K and 4.48 GPa have been characterized. Three classes of grains were imaged, containing single, double and mosaic twins, using electron channeling contrast imaging (ECCI) in a field emission scanning electron microscope. These twinned grains were analyzed using electron backscatter diffraction (EBSD). The methodology for twin identification presented here is based on comparison of theoretical pole figures for a rhombohedral twin with experimental pole figures obtained with EBSD crystal orientation mapping. An 85°〈02{\overline 2}1〉 angle–axis pair of misorientation was identified for rhombohedral twin boundaries in alumina, which can be readily used in EBSD post-processing software to identify the twin boundaries in EBSD maps and distinguish the rhombohedral twins from basal twins. Elastic plastic self-consistent (EPSC) modeling was then used to model the synchrotron X-ray diffraction data from the D-DIA experiments utilizing the rhombohedral twinning law. From these EPSC models, a critical resolved shear stress of 0.25 GPa was obtained for rhombohedral twinning under the above experimental conditions, which is internally consistent with the value estimated from the applied load and Schmid factors determined by EBSD analysis.
48
Zajkani, Asghar, Abolfazl Darvizeh, and Mansour Darvizeh. "A computational investigation for propagation of elasto-viscoplastic zones in the shock loaded circular plates." Engineering Computations 31, no. 7 (September 30, 2014): 1401–43. http://dx.doi.org/10.1108/ec-11-2012-0303.
Анотація:
Purpose – The purpose of this paper is to introduce a computational time dependent modeling to investigate propagation of elastic-viscoplastic zones in the shock wave loaded circular plates. Design/methodology/approach – Constitutive equations are implemented incrementally by the Von-Kármán finite deflection system which is coupled with a mixed strain hardening rule and physical-base viscoplastic models. Time integrations of the equations are done by the return mapping technique through the cutting-plane algorithm. An integrated solution is established by pseudo-spectral collocation methodology. The Chebyshev basis functions are utilized to evaluate the coefficients of displacement fields. Temporal terms are discretized by the Houbolt marching method. Spatial linearizations are accomplished by the quadratic extrapolation technique. Findings – Results of the center point deflections, effective plastic strain and stress (dynamic flow stress) and temperature rise are compared for three features of the Von-Kármán system. Identifying time history of resultant stresses, propagations of the viscoplastic plastic zones are illustrated for two circumstances; with considering strain rate and hardening effects, and without them. Some of modeling and computation aspects are discussed, carefully. When the results are compared with experimental data of shock wave loadings and finite element simulations, good agreements between them are observed. Originality/value – This computational approach makes coupling the structural equations with the physical descriptions of the high rate deformation through step-by-step spectral solution of the constitutive equations.
49
Wang, Zhiqiang, Chao Wu, Jianqiao Luo, Wenyu Lv, Lei Shi, and Peng Wang. "Research on Stress Analysis and Control of Surrounding Rock of Trapezoidal Roadways Based on Complex Variable Theory." Shock and Vibration 2021 (August 3, 2021): 1–14. http://dx.doi.org/10.1155/2021/6381785.
Анотація:
Aiming at the problem of the serious deformation of the mining roadways in the trapezoidal section of the coal mine, the method of combining theoretical analysis and field application is used to study the surrounding rock control method of the trapezoidal roadways. The conformal mapping function of the trapezoidal roadways is calculated by the theory of complex change, and then from the analytical solution of the tangential stress distributed in the surrounding rock of trapezoidal roadways which is under the influence of the bidirectional unequal pressure, homogeneous, isotropic, and elastic rock mass is obtained. Research studies show that the roof-stress distribution of the trapezoidal roadways is uniform and the confining pressure is small, while the two sidewalls and the floor are opposite. The stress distribution of the two sidewalls and the floor varies greatly, and the stress concentration factor is large. The top corner of the trapezoidal roadways is basically not affected by stress concentration, but the stress concentration coefficient at the bottom corner is relatively large, and reinforcement measures are required in the roadway support. Based on the aforementioned research results, the multisupport scheme of “bolting with wire mesh and anchor cable + W-type steel belt + joist steel shed support + anchor cable grouting” was proposed to the surrounding rock of trapezoidal roadways with large stress caused by mining influence, thus solving the actual mining problem.
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Ye, Jin Duo, Zhe Li, and Yu Ting Xi. "The Analysis to the Forming Process of Welded Pipe by Non-Linear Finite Element Method." Advanced Materials Research 291-294 (July 2011): 585–89. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.585.
Анотація:
Understanding the mechanism of the forming of the welded pipe may help the engineer to design the shape of forming rollers and forming technology. It is hard to study the forming process of the welded pipe by both the method of experiment and numerical modeling because of too much nonlinear factors included in the forming process such as elastic-plastic large deformation and non linear contact. Although many research works have been conducted in this field by the method of experiment or numerical modeling, but few of the works deal with the whole forming process of the welded pipe. The main difficulties in the numerical modeling are of huge computational labor time, witch has been over the ability of the hardware and software of the computer. The whole process of roll forming of welded pipe has been simulated by nonlinear finite element method with ANSYS and LS-DYNA solver, the distribution of both stresses and strains have been got successfully. Mapping meshes and the rigid models for rollers have been used in the analysis in order to decrease the number of the elements. Numerical results and parameter study have shown that the forming rollers of both the level and vertical are the key factors to the forming process. It is believe that the method used in the paper can also be used to study the forming process of both cage roll forming and flexible forming.