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The paper aims to develop a finite element methodology to deal with vibrations and buckling of laminated thin plates subjected to thermal and hygroscopic effects, once a second-order strain gradient theory is included to overcome the limitations of conventional elasticity and to capture nonlocal phenomena. The numerical scheme takes advantage of Hermite approximation for both membrane and bending primary variables, since the strain gradient introduces higher-order derivatives of the nodal displacements. Its versatility is proven by dealing with general lamination schemes and arbitrary boundary conditions. The analyzed configurations cannot be solved analytically. [ABSTRACT FROM AUTHOR]

The paper presents a numerical model based on the finite element method (FEM) to predict deformations and residual stresses in socket welding of different diameter stainless steel pipes made of X5CrNi18-10 steel. The next part of the paper concerns the determination of strength properties of a welded joint in terms of a shear test. A thermo-elastic–plastic numerical model is developed using Abaqus FEA software in order to determine the thermal and mechanical phenomena of the welded joint. This approach requires the implementation of moveable heat source power intensity distribution based on circumferentially moving Goldak's heat source model. This model is implemented in the additional DFLUX subroutine, written in Fortran programming language. The correctness of the assumed model of thermal phenomena is confirmed by examinations of the shape and size of the melted zone. The strength of the welded joint subjected to shear is verified by performing a compression test of welded pipes as well as computer simulations with validation of the computational model using the Dantec 3D image correlation system. [ABSTRACT FROM AUTHOR]

Summary: The paper considers errors that occur during strain measurement by fiber‐optic sensors based on Bragg gratings, which are mounted on the surface of the controlled object with a connecting material. Errors due to the use of the assumption of a uniaxial stress state in the Bragg grating zone in the strains calculation based on the measured physical quantities are considered. The errors associated with the strain gradient along the Bragg grating and the strain gradient from the measurement zone to the measuring element are analyzed. To answer the question of what strain is measured, the change in the measured strain as a result of mounting the sensor on the material surface is estimated. Models and algorithms for numerical simulation of errors arising in the strain measurement are presented. Numerical results are given for estimating the considered types of errors when sensor is mounted with epoxy adhesives on the surface of isotropic and anisotropic (fiberglass, carbon fiber) materials. Variants of experiments are presented in which various options of nonuniform distribution of strains and a complex stress state are provided in the zones of strain measurement. The experimental results are compared with the results of numerical simulation based on the finite element method. The results of the analysis of the choice of the resonant wavelength from the reflected optical spectrum, which is used to calculate the strains under the assumption of a uniaxial stress state in the Bragg grating, are presented. [ABSTRACT FROM AUTHOR]

Introduction/purpose: The paper presents a numerical simulation of an impact of a 12.7 mm projectile on an armored metal plate with a velocity of 500 m/s at a distance of 900 m. Numerical simulations offer the possibility of drastically reducing the time required to obtain results in comparison to the time required for planning, organization and execution of experiments. The numerical simulation is done by variations in the thickness of the armor metal plate, specifically an armor metal plate of a thickness of 10 mm, 17 mm, 18 mm, and 23 mm. The mentioned armored plate thicknesses were chosen based on the results in order to determine the limit thickness of the armored plate for the projectile perforation limit, as well as for complete ballistic protection. Methods: Finite element modeling is used for analyzing stresses and deformations of the armored plates. The mentioned method calculates the impact of the projectile on the obstacle, precisely the collision of the projectile and the armor plate. Results: For the comparative analysis, the parameters used are the values of the stress and the displacement. For each of the above-mentioned thicknesses of the armored metal plate, the values of stress and displacement during projectile impact were determined. The results of this study show how the thickness of the armor plate affects the interaction of the projectile and the armor plate. Conclusion: If the physical and chemical characteristics of the armored plate remain unchanged, as the thickness of the armored plate increases, the possibility of projectile penetration decreases, and vice versa. This research is of essential importance because it analyzes the stresses and deformation of armor plates whose basic role is the protection of personnel and equipment from the projectile impact. In this regard, the thickness of the armored plate for semi-penetration of the projectile is determined. [ABSTRACT FROM AUTHOR]

The Xinbaishiyan tunnel in the reconstruction Chengdu–Kunming railway Ermeishan-Mipan section mainly runs through dolomite with dolomitic limestone, with an excavation area of 260 m2, a maximum span of 22.3 m, a maximum height of 14.4 m, a vector height of 7 m, and a rise-span ratio of 0.31. The tunnel has an extra-large cross section, and it is a low flat-ration railway tunnel. This paper mainly describes the finite element analysis for this tunnel excavation that was used to guide the construction. Finite element software was used to model the tunnel according to the engineering geological conditions of the tunnel. These engineering geological conditions included the rock mass, system bolts, middle pipe shed, steel arch and shotcrete, grouting layer, second lining and so on. Nonlinear construction phase analysis was adopted. The results showed that the maximum vertical deformation of the tunnel vault and the middle of the invert was about 34 mm. The vertical deformation of the tunnel could be divided into an acceleration deformation section, linear deformation section, deceleration deformation section, and stable deformation section. The maximum horizontal deformation in the middle of the side wall was about 12.3 mm. Under the effect of the initial support, the equivalent stress of the side wall gradually increased with the excavation of the steps and the increase in the support structure. The axial force of the bolt in the middle of the side wall was larger than that in other places and the axial force of the middle pipe shed went along with the excavation of the tunnel in waves. The steel arch and the shotcrete had the maximum effective stress at the arch shoulder, which played the role of the deformation and pressure for the surrounding rock. During the construction, the length and height of the three-step method had to be set reasonably. The middle pipe shed and the system bolt supported the rock mass together. In the construction of the extra-large cross section and the flat tunnel, there was no need to set up temporary support, which was convenient for mechanical excavation. [ABSTRACT FROM AUTHOR]

• Developed a FEA model for six-phase MRCAC. • Studied the influence of MRCA replacement rate and residual mortar thickness on compressive performance of recycled concrete. • Clarified coverage and adhesion amount of old cement mortar by statistical methods and analysis results. Based on the typical morphology of recycled coarse aggregate in reality and the ontological relationship of the existing recycled aggregate concrete (RAC) mesoscopic constituent materials, a finite element analysis model of recycled coarse aggregate that can take into account the factors of the amount and location of attachment of the residual mortar was developed to establish the Modeled Recycled Coarse Aggregate Concrete (MRCAC). Combined with the mesoscopic mechanical properties of MRCAC, a plastic damage intrinsic model was used in the numerical analysis of MRCAC under uniaxial compressive loading to study the damage characteristics and stress–strain relationships of MRCAC. In this paper, the Modeled Recycled Coarse Aggregate (MRCA) is established in the ABAQUS numerical analysis software by self-compiled Python script, and the uniaxial compression simulation of MRCAC is carried out. Compared with the existing idealized model recycled concrete and other forms of digital recycled concrete model, The results show that, on the premise of meeting the general law of existing research results, the development of cracks in MRCAC under load is directly related to the shape of residual mortar wrapping. The strength of MRCAC is minimally influenced by residual mortar adhesion amount; however, the coverage of residual mortar has a significant impact on its strength. The arrangement of MRCA may also play a role in the stress–strain relationship of MRCAC. Additionally, it should be noted that residual mortar adhesion amount and coverage are distinct concepts that affect the strength and strain of MRCAC independently. These findings highlight the need to differentiate between these two factors in further research. [ABSTRACT FROM AUTHOR]

Fast-growing forests are widespread distribution, but the relevant timber products are limited by insufficient strength and low reliability in the architectural structure. In recent years, the combination of rapidly growing timber and thin-walled steel to enhance structural performance has attracted attention, and connection performance is critical in ensuring a compelling combination. In addition, adhesive technology has potential applications due to its high efficiency and lightweight. Nevertheless, in light construction, the adhesion behavior between thin-walled steel and largethickness timber with relatively low mechanical properties has yet to be effectively studied and revealed. This study investigates the bonding properties of thin-walled steel and fast-growing timber single-strap joints by numerical and experimental methods. The SS joints' shear strength and failure modes were obtained by tensile tests, considering different adhesive and overlap lengths. In addition, stress analysis was performed using the finite element method (FEM) combined with the cohesive zone model (CZM) to explore critical issues such as damage variables, peak stresses, etc. Furthermore, the parameters such as overlap, the thickness of adherends, and edge distance were investigated. As a result, it is concluded that the bond of thin-walled steel-fast-growing timber is a special non-balanced connection. The study indicates that shear stress distribution is steeper than other strap joints. The other difference is that the right end in overlapping areas may experience higher peel stress than the left ends, which might delaminate the timber. Yielding phenomena may also occur at such weak timber ends along the normal direction. The bearing capacity of these joints is susceptible to the difference in stiffness between timber and steel. Joint performance can be enhanced by increasing the timber thickness and overlap length appropriately. The summary obtained from this paper can be a reference for applying adhesive in thin-walled steel-fast-growing timber composite structure systems. • Bond failure between thin-steel and fast-growing natural timber. • Unbalanced performance of steel-timber single strap joints under tensile. • Influence of the plastic behavior and material defect of natural timber on the tensile properties of joints. • Failure mechanism of steel-timber bonded joints by detailed finite element modeling. [ABSTRACT FROM AUTHOR]

This paper proposes a new estimation formulation for CTOD fracture parameter for clamped SE(T) geometry. Based upon the plastic-hinge model, CTOD is defined using the crack opening displacements (COD) measured at two locations along the crack flanks of the specimen. One measurement point is fixed at the CMOD and the second point z 3 is chosen close to the crack tip such that the CTOD based on geometrical relationship is equal to the CTOD converted from the J -integral. The opening displacement close to the crack tip is defined by a proportionality factor, named λ , which is a function of the crack size ratio a ∕ W and the strain hardening property of the material. Expressions for both z 3 and λ are obtained through detailed finite element analyses under plane strain condition. Experimental fracture R-curves from the literature are used to check the validity of the current proposal. Good agreement is obtained between the CTOD based on the J -integral conversion and the current CTOD approach for three steels with different hardening properties and initial crack size ratios. To apply the proposed method, only CMOD measurements from a single clip gauge are needed during a fracture toughness tests. Thus, the double clip gauge CTOD test method is simplified facilitating the test protocol for measuring the fracture toughness of pipelines. • The double clip gauge method is used to obtain the CTOD by FEM analyses. • A new CTOD formulation is proposed based on only CMOD values. • CTOD converted from J-integral agrees with the new CTOD proposal. • Experimental fracture tests are simplified for clamped SE(T) specimens. • Experimental fracture toughness data from three different materials validate the current proposal. [ABSTRACT FROM AUTHOR]