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Analytical modeling of the squeezing force for aircraft wings and fuselage panels in the existing literature usually assumes uniform deformation of the rivets, while in reality, the deformation of the rivets is non-uniform. To achieve high-quality squeezing force modeling, this paper introduces Coulomb's friction and four critical adjustments to the original equation: the non-uniform rivet/sheet interference along the sheet's hole axial ordinate; the barreling effect when calculating the driven head's volume; the spring-back of the driven head's dimensions; the modified height of the driven head; and the modified sheet-hole expanded diameter considering the convex structure of the driven head. The calculated values of the proposed new model demonstrate an improved level of accuracy, particularly under squeeze ratios commonly encountered in the aerospace industry. [ABSTRACT FROM AUTHOR]

The study of interfacial transition zone characteristics in manufactured sand mortar is of great significance in enhancing the strength and durability of manufactured sand mortar. The interface microstructure, microzone mechanical strength, and non-uniform deformation of mortar composed of river sand and manufactured sand were examined through scanning electron microscopy (SEM), nanoindentation, and three-dimensional digital image correlation (3D-DIC) techniques. The results indicate that the width of the interfacial transition zone in manufactured sand mortar exceeds that in river sand mortar. Nevertheless, the interface cracks between fine aggregate particles and mortar matrix are smaller in manufactured sand mortar. Notably, microcracks are prone to occurring at the edges of manufactured sand particles. The elastic modulus of the interfacial transition zone in manufactured sand is slightly higher than that in river sand, suggesting that manufactured sand can mitigate the edge effect of aggregates to a certain extent. The non-uniformity of shrinkage deformation is most conspicuous in sandstone manufactured sand mortar, displaying larger internal tensile strains, ultimately leading to a more severe distribution of damage. This implies that an excessive proportion of blade-shaped particles in fine aggregates may heighten the risk of cracking in mortar. [ABSTRACT FROM AUTHOR]

In order to solve the problem that the dynamic measurement of non-uniform deformation of aircraft door gap is difficult and requires high accuracy under complex test environment, a measurement method of aircraft door gap was proposed based on surface structured light, and the measurement method of fringe projection structural surface was studied, including searching the stereo correspondence and absolute fringe order of each effective pixel in the wrapped phase image without spatial phase unwrapping process or any prior information, generate initial disparity map and absolute phase map and optimize disparity. The 3D structured light model was established, and the 3D coordinates were calculated using the parallax map and the absolute phase map. Process the obtained data, including establishing the physical coordinate system of the tested object, capturing the surface, and extracting the gap displacement. Two standard gaps were designed to verify the rationality and effectiveness of the proposed method. It can quickly and accurately measure gaps and step difference on any surface and dynamic scene. This method is applied to measure the deformation of a certain aircraft cabin door gap, and the actual deformation displacement was obtained. [ABSTRACT FROM AUTHOR]

Analytical modeling of the squeezing force for aircraft wings and fuselage panels in the existing literature usually assumes uniform deformation of the rivets, while in reality, the deformation of the rivets is non-uniform. To achieve high-quality squeezing force modeling, this paper introduces Coulomb’s friction and four critical adjustments to the original equation: the non-uniform rivet/sheet interference along the sheet’s hole axial ordinate; the barreling effect when calculating the driven head’s volume; the spring-back of the driven head’s dimensions; the modified height of the driven head; and the modified sheet-hole expanded diameter considering the convex structure of the driven head. The calculated values of the proposed new model demonstrate an improved level of accuracy, particularly under squeeze ratios commonly encountered in the aerospace industry.

Numerical methods, such as finite element or finite difference, have been widely used in the past decades for modeling solid mechanics problems by solving partial differential equations (PDEs). Differently from the traditional computational paradigm employed in numerical methods, physics-informed deep learning approximates the physics domains using a neural network and embeds physics laws to regularize the network. In this work, a physics-informed neural network (PINN) is extended for application to linear elasticity problems that arise in modeling non-uniform deformation for a typical open-holed plate specimen. The main focus will be on investigating the performance of a conventional PINN approach to modeling non-uniform deformation with high stress concentration in relation to solid mechanics involving forward and inverse problems. Compared to the conventional finite element method, our results show the promise of using PINN in modeling the non-uniform deformation of materials with the occurrence of both forward and inverse problems. [ABSTRACT FROM AUTHOR]

To safely store wheat in silos considering filling and discharging process, the stress–strain behaviour of wheat plays a key role for silos design. A series of triaxial tests of wheat were performed using a digital imaging triaxial apparatus, which can capture local deformation across the entire surface of the specimen. By comparing the global and local stress–strain behaviour of wheat, the non-uniform deformation affected by the end restraints of triaxial apparatus were identified during the pre-failure and failure processes. The radial strain contour corresponding with non-uniformity coefficient values was presented. It was concluded that local stress–strain of the 40 mm-high specimens from the central regions of the specimen was less affected by the end restraints, indicating that they better characterise the stress–strain behaviour of wheat. A constitutive model of wheat was then deduced based on local measurements, from which strength and deformation characteristics were quantificationally analysed. It was concluded that the mechanical parameters from the local data of wheat specimen were greater than the global ones identified from the whole data. • Local stress–strain from specimen centre better characterised behaviour. • Tests were conducted on wheat using a modified digital imaging triaxial apparatus. • Entire surface deformation across the specimen was investigated. • This reduced the effects of end restraints by the triaxial apparatus. • A constitutive model of wheat was deduced from local data from experiments. [ABSTRACT FROM AUTHOR]

• We proposed the mechanical model predicting microstructure-induced non-uniform deformation (micro-NUD). • Parameters quantifying micro-NUD are determined using experimentally measured strain field. • Nonlocal finite element model established could predict the strain field of the fine and coarse grain specimens. Engineering materials have a heterogeneous microstructure that induces non-uniform deformations (NUDs) even under uniform stress. Therefore, the development of NUDs in heterogeneous materials under a macroscopically non-uniform stress is characterized by the interactions between micro- and macroscopic NUDs. In this study, we attempt to directly describe microscopic NUDs by introducing a constitutive equation for the strain field. Using polycrystalline metal, which is a well-known heterogeneous material, we performed the uniaxial tensile tests on specimens with curved gauge sections. During modeling, the constitutive equation without nonlocal effect was first fitted based on the distribution of the local equivalent stress and strain. The strain calculated using the fitted equation was regarded as the strain for the homogeneous material, whereas the strain deviating from the fitted equation was assumed to be induced by the microscopic heterogeneity of the material. The respective strains were represented using different constitutive models, and the parameters employed in the models were fitted separately using the experimentally measured strain field. The plastic compliance gradient was employed as a material parameter quantifying the microscopic NUDs. Subsequently, a multiaxial elastoplastic nonlocal constitutive equation was formulated based on the nonlocally extended J 2 flow theory. Finite element method simulations introducing the proposed nonlocal effect indicated that a scale-dependent NUD characterized by the interactions between micro- and macro-NUDs could be represented using the proposed model. Furthermore, the proposed model could predict the experimentally observed strain field characterized by a polycrystalline microstructure, such as the dispersion of the strain concentration at the curved gauge section and the appearance of NUDs even under uniform stress. [Display omitted] [ABSTRACT FROM AUTHOR]

In room-and-pillar mining (RPM), the roof of a coal seam is supported by coal pillars; however, the roof is non-uniformly deformed with time. Moreover, coal pillars at different positions are subjected to different stresses and some coal pillars are prone to the effects of eccentric load, thus influencing their stability. Therefore, by taking Bandingliang Coal Mine, Shaanxi Province, China, as the engineering background, the non-uniform deformation characteristics of the roof of a room-and-pillar mining goaf (RPMG) were first analysed by using numerical simulation and theoretical analysis. The residual pillars in the RPMG were partitioned into a uniform deformation zone, a transition zone, and a sub-uniform deformation zone; thereafter, the stress distribution in coal pillars under non-uniform deformation was revealed to show that coal pillars were subjected to non-uniform stresses; subsequently, the distributed force under the eccentric load was concentrated to attain the changes in stress state of coal pillars under eccentric load, including behaviour such as a non-uniformly compressed state, critical state, and a tensile stress state; finally, the pillar stability under the eccentric load was judged by taking the No. 19 coal pillar as an example. The result showed that the shear stress generated by the coal pillar was 0.58 MPa, which was lower than the allowable shear stress (1.51 MPa). As a result, the pillar did not collapse, consistent with actual conditions on site. The result is expected to provide a theoretical basis for controlling pillar stability in the RPMG. The theory of the stability of the residual pillars in the RPMG provided in this paper provides a new direction for determining the stability of pillars, and the study findings have been applied in specific mines and verified.

In this study, both the "softening" behavior and the effect of the partial rolling on characteristics of welded joints of 7075-T6 aluminum (Al) alloy with a laser-tungsten inert gas (TIG) hybrid welding process were studied. Partial rolling of welded joints is a kind of non-uniform deformation that is different from conventional rolling. In addition, the microstructure and properties of different welding zones are also different. It is found in this study that the microstructure and mechanical properties of different welding zones have undergone diversified evolution during the partial rolling process. Reduction of microhardness occurs in the fusion zone (FZ) and heat-affected zone (HAZ) of welded joints. The application of partial rolling makes the microhardness of FZ and thermal "softening" zone increase by 43.5% and 17.8%, respectively. The tensile strength of partially rolled joints reaches up to 87% of the base metal (BM), which is 18% higher than that of hybrid welded joints. By partial rolling process, the elongations of joints increase from 3.3 to 6.6%, and the fracture position transforms from FZ to HAZ. The dislocation density of partially rolled joints increases by 58.1% and 32.5% in FZ and HAZ, respectively. [ABSTRACT FROM AUTHOR]

Numerical methods, such as finite element or finite difference, have been widely used in the past decades for modeling solid mechanics problems by solving partial differential equations (PDEs). Differently from the traditional computational paradigm employed in numerical methods, physics-informed deep learning approximates the physics domains using a neural network and embeds physics laws to regularize the network. In this work, a physics-informed neural network (PINN) is extended for application to linear elasticity problems that arise in modeling non-uniform deformation for a typical open-holed plate specimen. The main focus will be on investigating the performance of a conventional PINN approach to modeling non-uniform deformation with high stress concentration in relation to solid mechanics involving forward and inverse problems. Compared to the conventional finite element method, our results show the promise of using PINN in modeling the non-uniform deformation of materials with the occurrence of both forward and inverse problems.

Digital image correlation (DIC) techniques were used to evaluate strain distributions along tensile gage lengths immediately after yielding of a medium manganese steel (7 wt% Mn) in samples cold rolled in the range of 1–6 pct. With an increase in cold work, DIC confirmed that the yielding behavior transitioned from nucleation and propagation of a single localized deformation zone (Lüders band) to uniform deformation, that is, no evidence of strain localization. At intermediate amounts of cold work, a unique yielding behavior was evident where the initially-low positive strain hardening rate increased with tensile strain until conventional strain hardening (i.e., decrease in strain hardening rate with strain). The intermediate yielding behavior was associated with the development of multiple non‑propagating regions of strain localization, an observation not previously evident without the use of DIC.

Triaxial test on both saturated and unsaturated soils is associated with non-uniform deformation, especially during shearing. This non-uniform deformation plays an important role in the soil strength and constitutive behavior. In the past, several image-based methods have been proposed to measure non-uniform soil deformation. However, accurate non-uniform soil deformation measurement during triaxial testing is still a great challenge for researchers. This study documented a new technique for the visualization of a deforming specimen during triaxial testing based on a full-field deformation measurement system with help of a self-developed software package GeoTri3D. A dot matrix (i.e., 13,320 dots in 90 rows × 148 columns) at a density of 57 dots/cm2 is directly printed to a latex membrane which covers a 61.8 × 123.2 mm specimen during triaxial testing. With the deformation measurement system, three-dimensional (3D) coordinates of each dot on membrane surface are accurately measured at different axial displacements during loading. Point clouds, which represent the specimen surface at these displacement levels, are then generated and further utilized for the generation of triangular meshes and reconstruction of specimen 3D surfaces. The full-field deformations (i.e., axial displacement, radial and axial strain) during testing are then derived based on the triangular meshes. These 3D surfaces and full-field deformations facilitated a 3D visualization of the specimen deforming process at an unprecedented high resolution. Accurate reconstruction of specimen surface and the associated 3D visualization of the deforming process offer a great potential for advanced soil behavior characterization. [ABSTRACT FROM AUTHOR]

Boundary constraint induced inhomogeneous effects are important for mechanical responses of nano/micro-devices. For microcantilever sensors, the clamped-end constraint induced inhomogeneous effect of static deformation, so called the clamped-end effect, has great influence on the detection signals. This paper is devoted to developing an alternative mechanical model to characterize the clamped-end effect on the static detection signals of the DNA-microcantilever. Different from the previous concentrated load models, the DNA adsorption is taken as an equivalent uniformly distributed tangential load on the substrate upper surface, which exactly satisfies the zero force boundary condition at the free-end. Thereout, a variable coefficient differential governing equation describing the non-uniform deformation of the DNA-microcantilever induced by the clamped-end constraint is established by using the principle of minimum potential energy. By reducing the order of the governing equation, the analytical solutions of the curvature distribution and static bending deflection are obtained. By comparing with the previous approximate surface stress models, the clamped-end effect on the static deflection signals is discussed, and the importance of the neutral axis shift effect is also illustrated for the asymmetric laminated microcantilever. [ABSTRACT FROM AUTHOR]

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• Three kinds of indexes quantify the degrees of non-uniform deformations of coal. • Non-uniform deformations are induced by gas adsorption and mechanical action. • Bulk modulus ratio and Langmuir constants control the MNDI and ANDI, respectively. • Solution of modified effective stress-model is consistent with traditional solution. This article is the second part of the series: modelling study. Physical properties of the coal fractures are not equal to those of coal bulk, which lead to non-uniform deformation between coal bulk and fractures in response to gas adsorption and pressure change. In this study, we defined three kinds of non-uniform deformation indexes: adsorptive non-uniform deformation index (ANDI), mechanistic non-uniform deformation index (MNDI), and comprehensive non-uniform deformation index (CNDI) to quantify the degrees of the non-uniform deformations between coal bulk and fractures, and we established a new multi-physical field coupling model based on these non-uniform deformation indexes. The theoretical solutions of the new permeability model agree well with the experimental solutions. The non-uniform deformation is contributed by the gas adsorption and mechanical action, and closely related to the type of boundary conditions. The ratio of the coal bulk modulus to the fracture modulus and the Langmuir pressure constant of matrix controls the MNDI and ANDI, respectively. In addition, in order to explain the fact that part of the theoretical solution of permeability is inconsistent with the experimental solution under constant effective stress condition, we proposed the concept of modified effective stress, which is obtained by adding an additional effective stress based on the traditional effective stress. The additional effective stress reflects the contribution of other factors to effective stress except confining pressure and pore pressure, such as gas adsorption, temperature change, biological decomposition etc. The modified effective stress is the only variable in the new permeability model. The definitions of the additional effective stress and modified effective stress solve the problem that the theoretical solution of permeability is inconsistent with the experimental solution. [ABSTRACT FROM AUTHOR]

Surface roughening (SR) is one of the most common defects in deformation-based processing worsening surface quality and service performance of forming components, and in-depth understanding of SR is still a non-trivial and challenging issue for defect free processes since this phenomenon is interactively influenced by so many intrinsic and extrinsic factors. This paper aims to provide a panoramic discussion on the origination and evolution mechanisms of SR considering both intrinsic and extrinsic factors. A macro‑meso scale modeling framework, including Voronoi tessellation based geometrical model and crystal plasticity finite element (CPFE) based constitutive model, is established to explore non-uniform plastic deformation at grain-scale, and then the above framework is numerically implemented and applied into the 5052-O Al-alloy tube bending. The coupling effects of intrinsic factors (i.e., grain size, grain orientation and abnormal large grain) and extrinsic factors (i.e., deformation conditions, strain accumulation and strain rate) on SR are investigated. The results show that SR in plastic deformation stems from the accumulated intergranular non-uniform deformation through thickness direction, indicating that SR is an inherent characteristic and cannot be eradicated. SR is controlled by several factors: grain size, intergranular misorientation, the abnormal large grain, strain accumulation and deformation conditions. In a practical view, these are two effective ways to improve the surface quality by reducing grain size and removing abnormal large grains. From the extrinsic factor, it also makes sense to design the processing parameters reasonably and reduce friction in order to avoid local large deformation. [ABSTRACT FROM AUTHOR]

In order to solve the problem of non-uniform large deformation control of narrow pillar roadway, the narrow coal pillar roadway in Fenghui Coal Mine was used as the engineering background. The field survey, laboratory experiments, numerical simulation and theoretical analysis were used to study the stress and plastic zone distribution characteristics of surrounding rock of mining roadway under the influence of different coal pillar sizes. The deformation and failure laws of narrow coal pillar roadway and the movement characteristics of overlying strata structure were analyzed, and the mechanism of non-uniform deformation of narrow coal pillar roadway was revealed. Mining stress fields are superimposed, and results in a large abutment pressure; the structure of overlying strata is asymmetric, and causes a significant partial load effect; due to the small size and low strength of coal pillar, it is difficult to provide an effective support for the roof; and the supporting scheme is symmetrically arranged, and poorly targeted, which are the main reasons for the non-uniform deformation of narrow pillar roadway. Based on the difficult control characteristics of surrounding rock in narrow coal pillar roadway, the differential support technology with "the change of roadway support mode, the enhanced support density and grouting modification of broken surrounding rock" is proposed to strengthen the control of local large deformation of surrounding rock to give a full play to the carrying capacity of surrounding rocks. On-site monitoring results show that the non-uniform deformation of narrow coal pillar roadway during the service is effectively controlled, the surrounding rock is very stable. The differentiated support technology has a high reference value for the same type of roadway surrounding rock control. [ABSTRACT FROM AUTHOR]

Non-rigid models are needed to correct the non-uniform deformation between two images; dense, uniformly distributed control points is the premise of constructing such non-rigid models. This paper puts forward an affine invariant-based match propagation method for quasi-dense image registration. Interest points are extracted from the input image and reference image, respectively; and sparsely matched. According to the sparsely matched points, the global offset between the two images is estimated and corrected. A corresponding adjacent triangle is established using the interest points in the two images interactively; and an affine invariant, the ratio of the triangle area, is employed to determine whether the vertices in the two triangles match or not. Through this method, the spare initial seed matching points propagate to other points of interest to obtain quasi-dense match. The HJ-Landsat image and ETM+ data of Antarctic data are taken in an experiment, the results show that our method can extract dense and uniformly distributed matching points while outperforming other state of art methods in true positive ratio. [ABSTRACT FROM AUTHOR]

In order to study the mechanic responding mechanism of rock materials under cyclic loading and unloading,uniaxial cyclic loading and unloading tests were carried out to investigate the non-uniform deformation evolution processes of granite specimens.The deformation images of specimens during the tests were collected by CCD camera and based on the digital speckle correlation method,the non-uniform deformation,the evolution laws of the characteristic parameters of the localization during cyclic loading and unloading were analyzed.The research results show that:With the increase of cycle numbers,the non-uniform deformation is more and more obvious.The statistical index Sw of non-uniform deformation increases with the increase of loading stress,and increases with the increase of cycle numbers.After the localization of a specimen appears,the extrusion displacement and the influence width of the localization band all increase with the increase of stress and cycle numbers in the subsequent cycles. [ABSTRACT FROM AUTHOR]

Non-uniform deformation in the thickness of tubular spun parts is a common problem in the flow forming process and has a significant impact on the performance of spun parts. In this paper, the plastic strain distribution in the wall thickness of tubular spun parts made of Haynes230 superalloy was obtained by the finite element method and microindentation hardness measurements. Moreover, the causes of the non-uniformity in plastic strain distribution were analysed, particularly the effect of main processing factors such as thickness reduction, feed rate and forming passes on plastic strain distribution in the thickness direction. The results indicate that the factors that have significant impacts on uniformity of deformation are thickness reduction and forming passes; deformation in the material is mainly concentrated in the outer layer of the spun part and less so in the inner layer. Furthermore, the plastic strain increases with an increase in thickness reduction, and the number of forming passes with the former process more favourably increasing the plastic strain in the inner layer than the latter. Therefore, in order to improve deformation uniformity in the spun parts, thickness reduction should be increased and the number of forming passes should be decreased when determining the total thickness reduction. This study is equally applicable to other materials. [ABSTRACT FROM AUTHOR]

Inhomogeneity of microstructure evolution in cold-rolled austenitic stainless steel after surface mechanical attrition treatment (SMAT) was investigated. A characteristic deformation pattern was obtained for all studied specimens. Selected areas were examined through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Estimation of the α′-martensite volume fraction below the treated surfaces showed, that some of the studied areas are characterised by significant different amount of this phase (from 10 to 22% - BB, from 19 to 31% - GIXD). The performed finite element (FE) numerical analysis showed, that the reason for this may be the presence of an air gap between the impacted material and fixation and also relatively short high stress time duration due to surface inclination during the surface treatment. Annealing at 550 and 650 °C greatly increased the volume fraction of α′-martensite (up to 47% - BB) and formed Fe 2 O 3 as well as Fe 3 O 4 , whereas annealing at 700 °C resulted in both disappearance of α′-martensite and in reduction of oxides. [ABSTRACT FROM AUTHOR]

Macroscopic non-uniform deformation is usually found in deformed joints of friction sir welded (FSW) wrought Mg alloys, detrimental to the joint performance. In the present work, two kinds of FSW joints with different stirred zone (SZ) structures were generated for extruded AZ31 plates. Comparative studies were conducted aiming to unravel the underline mechanism of the non-uniform deformation and their effect on tensile properties. It was found that the occurrence of non-uniform deformation was associated with the special texture distribution and twinning behavior in the SZ. The shape of concave sub-regions in the SZ coincided with the distribution area of extension twins. Texture evolution showed that consistent lattice rotation occurred across the SZ during tensile process. Schmid factor analysis revealed the role acted by basal slip and extension twinning in sub-regions at various deformation stages. In addition, the non-uniform deformation behavior could be suppressed by modifying the texture distribution through increasing the tool rotation rate, which meanwhile could improve both the tensile strength and ductility of the joints. Digital image correlation measurements provided detailed examination of the actual strain distribution evolved in the joints and demonstrated the dominant contribution of strain localization to the tensile properties. [ABSTRACT FROM AUTHOR]

• Coal sample used in the experiments under three boundary conditions is the same one. • Non-uniform deformations are closely related to the type of boundary conditions. • Non-uniform deformation of US group is greater than that of CCP and CES groups. Permeability is a key parameter to evaluate the ability of coal reservoir for transmitting coalbed methane (CBM). Deformations of internal components of coal caused by the variations of physical fields control the evolution of coal permeability. And there is obvious non-uniform in the deformations of coal bulk and fracture due to the heterogeneity of coal. However, at present, the evolution of non-uniform deformation and its relationship with coal permeability are unclear. In this study, first of a two-part series, we completed a series of experiments to measure the permeability, axial strain, radial strain, overall strain and fracture strain of a coal sample under different boundary conditions (constant confining pressure, constant effective stress and uniaxial strain) at different injection pressures of carbon dioxide (0.2 MPa, 1.0 MPa, 2.0 MPa, 3.0 MPa, 4.0 MPa and 5.0 MPa). And we defined the comprehensive non-uniform deformation index (CNDI) as the ratio of the fracture strain to the overall strain to quantify the degree of the non-uniform deformation between coal bulk and fracture. The experimental results show that the deformation of the coal sample in the longitudinal joint direction is smaller than that in the transverse joint direction, which indicates that the mechanical properties of the coal sample is anisotropic in different directions. And there are obvious differences between the deformations of coal bulk and fractures. When the gas pressure is in the range of 0.2 ∼ 5.0 MPa, the non-uniform deformations are vaguely related to the change of gas pressure, but closely related to the type of boundary conditions. The influence of gas pressure under displacement-controlled boundary condition (uniaxial strain) on the CNDI is greater than that under stress-controlled boundary conditions (constant confining pressure, constant effective stress). In addition, we also observed the phenomenon by the experimental results of the constant effective stress group: the permeability decreases gradually with the gas pressure even after removing the influence of gas slip effect, which is inconsistent with the traditional theoretical solution under the constant effective stress condition. Based on the fact that coal sample is a heterogeneous body, we tentatively believe that one of the reasons for this inconsistency may be that the traditional definition of effective stress does not include the effect of gas adsorption. [ABSTRACT FROM AUTHOR]

We examined the stress concentration that would occur at grain boundary triple lines during deformation in two copper tricrystals with [011] tilt boundaries; one was a symmetrical tricrystal with respect to the loading axis and the other was an anti-symmetrical one. In principle, the finite element method can provide solutions with prescribed amount of precision for the anisotropic elasticity problem. It was shown that a close approximation was possible by means of a disclination model in elastically homogeneous material. This disclination model was numerically solved with the finite element method proposed in a previous paper (Hosoya, Kato, Sasaki, Trans. JSME, Vol.80, No.819 (2014 ). It was concluded that the disclination model is appropriate for estimating the stress concentration at the grain boundary triple lines in deformed polycrystals.

Deformation behaviors of polycrystalline metals are quite complex, and we are not easy to directly investigate them; thus, analyses employing simple models such as bicrystals are required. In this study, we conducted crystal plasticity analysis of unidirectional tensile tests, using compatible-symmetric-type bicrystal models with the not-inclined grain boundary and incompatible-type bicrystal model with the inclined grain boundary; we investigated changes in patterns of geometrically necessary dislocation (GND) bans and the density of GNDs in the initial deformation. In the condition where the grain boundary contacted with the constrained faces, GND bans were formed and the distribution was changed with changing the inclination angle α of the grain boundary. In contrast, GNDs were not localized in high density in the condition where the grain boundary contacted with the free surfaces; the changes were caused by two-reasons: one was changes of compatibility of the bicrystal model with changing the inclination angle α, and the other was that deformation shapes of the bicrystal model under tensile loading were changed with changing the inclination angle α and the deformation was constrained by the constrained faces. The compatibility of and average density of GNDs in the bicrystal model could be estimated using differences of components of Schmid tensors between the crystal grains.

Highlights: [•] Construction of initial yield surface of 2D beams lattice by means of discrete asymptotic homogenization. [•] Construction of the elastoplastic homogenized response of 2D lattices subjected to multiaxial loadings. [•] General methodology, can deal with internal nodes and no assumption of uniform deformation is needed. [•] Applications to conceived 2D lattices (Octagon-Mixed, asymmetric and star-square lattices). [•] Good agreement with FE simulations. [ABSTRACT FROM AUTHOR]

Highlights: [•] DDRX of IMI834 alloy is modeled by combining a CA method with CPFEM. [•] Non-uniform deformation at the grain level is considered in the model. [•] The predicted recrystallization kinetics displays nonlinear behavior. [•] The nucleation mode appears heterogeneous and non-random. [•] Average re-grain size increases with temperature or decreasing strain rate. [ABSTRACT FROM AUTHOR]

Abstract: On the basis of high temperature ductility tests in single-phase cupronickel CuNi25 sample has been found a relation between microstructure, grain size and effect of ductility minimum temperature (DMT). Metallographic tests confirmed literature studies that cracks nucleate at points of two or three grain joints and cross-cut of twined grain with border of the grains. The non-homogeneous character of chemical composition concentrating in areas of grain joints and cracks at high temperature has been investigated by linear and point Cu and Ni analysis (EDS). This analysis shows that local areas of non-equilibrium formation concentrate at this places. This fact can be accepted as one of the reasons of non-homogeneous deformation, cracking and its location at DMT. Experimental results were compared with two-dimensional finite element method (FEM) simulation results of proposed hypothesis of non-uniform deformation. [Copyright &y& Elsevier]

From full 3-D FVM simulation, the chronologically contoured effective strain behavior, and more detailed effective strain and stress distributions during ECAE process were obtained at each locally distributed particle. Additionally, load–stroke curve and meshes’ grid distortion displayed the non-uniform deformation in ECAE by 3-D symmetric FVM simulation. [Copyright &y& Elsevier]

Concrete generally deforms and cracks in a non-uniform manner under drying-induced stress. This study used the lattice fracture model to simulate the drying-induced non-uniform deformations, stresses, and micro-crack propagation in concrete. Experiments were designed to validate the lattice fracture model, wherein the drying-induced non-uniform deformations and micro-crack patterns in concrete were measured using a digital image correlation technique and a fluorescent epoxy impregnation method, respectively. It was found that the simulated non-uniform deformations and micro-crack patterns were close to the experimental observations. The interaction mechanism between drying-induced non-uniform stresses and micro-cracks was analysed based on the validated lattice fracture model. The micro-cracks were found to cause stress concentration both in coarse aggregate and the mortar that covered coarse aggregate, which could lead to high micro-cracking risk as drying continues. [ABSTRACT FROM AUTHOR]

Due to the deformation ability over a wide frequency range, dielectric elastomer actuators (DEAs) under an alternating electric load have received increasing attention. In the theoretical analysis of an in-plane oscillating DEA (edge clamped membrane without a pressure load), the assumption of homogeneous deformation is applied, which conflicts with the observed non-uniform deformation under a combination of pressure and voltage load. To validate the simplification, experimental and theoretical studies of a circular DEA under alternating voltage are reported here. A laser Doppler vibrometer is used to acquire the full-field oscillating response of the DEA fabricated by commercial VHB4905 with hydrogel electrodes. The measured amplitude and phase illustrate that the assumption of homogeneous deformation only works at low frequencies, whereas the non-uniform deformation dominates the oscillation with the increase of excitation frequency. In addition, the in-plane oscillating DEA behaves as a complex mode system. Accordingly, the motion equation is proposed by considering the general viscous damping effect. The experimentally observed transition (from uniform to non-uniform deformation) is analyzed numerically. The normalized upper frequency, under which the deformation field can be treated as uniform, is also obtained based on full-wave simulations. [ABSTRACT FROM AUTHOR]