DEFORMATION TRANSVERSE SHEAR BENDING STATE OF A THIN PLATE LAYER OF AN ANISOTROPIC GEOLOGICAL MEDIUM FROM THE ACTION OF CONCENTRATED ENERGY IMPULSES

A method is proposed for study the structural stability of the deformation state of structural blocks of the earth's crust, approximated in the form of plate layers of the geological medium when transverse shear bending from the action of concentrated energy impulses. Advances here are carried out in the two directions. First, in contrast to the previous article, the physical and mechanical model of the geological medium is endowed with anisotropic properties, which makes it possible to increase the adequacy of the obtained numerical results to the specifics of the real problem. Secondly, instead of the simplest bilinear 4-node finite elements, the special spectral non-algebraic 8-node finite iso-parametric finite elements are used, the use of which significantly increases both the accuracy of calculations and their reliability in the sense of ensuring the robustness of calculations for relatively small values of the plate thickness. It should be noted that the Finite Element Method uses exclusively only algebraic finite elements (power polynomials in the h-version and orthogonal polynomials in the p-version). It is known from approximation theory that the use of spectral non-algebraic approximations improves the quality of approximations. Therefore, their introduction into the structure of finite element calculations can improve the quality of modeling in the study of the strain-stress-state (SSS) of the geological medium. A structural block (SB) is understood as a plate layer with plan dimensions exceeding the thickness by more than 10 times. The identification of hazardous zones in the rock massive due to stress concentration is complemented by the development of mechanical, mathematical and computational tools for modeling the curvature of the earth's crust during bending based on the classical theory of Kirchhoff and refined Reissner-Mindlin theory. Test calculations have shown that the accuracy of the calculation and the quality of geometric modeling of fragments of an anisotropic geological environment based on the refined 8-node spectral finite element is significantly better than for the 8-node algebraic finite

Development of an experimental approach to study preforming mesoscopic defects of woven fabrics

Composite materials can be produced by several technologies, such as Liquid Composite Manufacturing (LCM). In this technology, a fabric can be formed by highly double curved punch geometries. During its forming, the fabric is submitted to several deformations and mechanical stresses, like biaxial tensile stress, shear, bending, compaction and friction. The cumulative effect of these stresses leads to the appearance of different types of defects such as wrinkles, buckles, sliding, etc. These defects may have a significant influence on the mechanical properties of the final composite materials. In order to understand the forming mechanisms of these defects, as well as their effect on the behavior of composite materials, an experimental machine was designed and built. The aim of this machine is to generate different types of defects with controlled and adjusted amplitudes (calibrated defects), in samples of a fabric. These samples are then used to manufacture composite samples with calibrated defects, by an LCM process. The defected composite samples are then tested and compared with composite samples without defects. The obtained results have identified the experimental parameters corresponding to the appearance of different types of defects.

Experimental study of wind-induced shear, bending, and torsional loads on rectangular tall buildings

To investigate wind-induced torsional loads on rectangular tall buildings, five rigid scale models were tested in an atmospheric boundary layer wind tunnel. Each model was built with identical plan dimensions but different aspect ratios. Two terrain categories were experimentally simulated in the wind tunnel to evaluate each model under different wind directions. From synchronized wind pressure measurements, the values for the shear wind force, bending moment, and torsion moment at the base of each model were calculated. The results were normalized in terms of mean shear, bending, and torque coefficients. Variations of the coefficients obtained with respect to the aspect ratio of the models tested were analyzed. Based on the experimental results, a new parametric equation to estimate the torque coefficients at the base of rectangular tall buildings as a function of aspect ratio and wind direction was proposed. The base torque coefficients obtained with the proposed equation are in good agreement with the experimental results.

Efficient Deep Learning for Gradient-Enhanced Stress Dependent Damage Model

This manuscript introduces a computational approach to micro-damage problems using deep learning for the prediction of loading deflection curves. The location of applied forces, dimensions of the specimen and material parameters are used as inputs of the process. The micro-damage is modelled with a gradient-enhanced damage model which ensures the well-posedness of the boundary value and yields mesh-independent results in computational methods such as FEM. We employ the Adam optimizer and Rectified linear unit activation function for training processes and research into the deep neural network architecture. The performance of our approach is demonstrated through some numerical examples including the three-point bending specimen, shear bending on L-shaped specimen and different failure mechanisms.

Effects of moisture content on lap-shear, bending, and tensile strength of lap-jointed and finger-jointed southern pine using phenol resorcinol formaldehyde and melamine urea formaldehyde

The bonding performance of the phenol-resorcinol-formaldehyde adhesive (PRF) and melamine-urea-formaldehyde adhesive (MUF) with southern pine as substrates at various moisture contents (MC) was evaluated. The results showed that bonding shear strength with MUF and PRF was negatively related to wood MC, and bonding shear strength with MUF was higher than that of the PRF. The bending and tensile strengths of finger-jointed lumber decreased with wood MC. The bending strength of finger-jointed lumber was affected more by wood than adhesive. However, both wood and adhesive exhibited the same important contribution to the tensile strength.