AUTOMATED SENSORY MONITORING SYSTEM PROTOTYPE FOR CONTINUOUS MONITORING OF MATERIAL AND STRUCTURE STATE

The goal of this article is to solve problems of automated monitoring systems of industrial and aviation constructions. Based on the latest research results, the most cost-effective solutions are covered, and a practical solution is offered. This article is part of the scientific project “Development of an integrated sensor system for material and structure monitoring”. The article describes the problem and suggests a practical solution for an integrated sensor system for material and structure monitoring prototype.

Optimization of the Structural Parameters of a Wing

The substantiation of the optimum design decisions providing the minimal weight of a structure, is one of the basic preconditions of successful realization of the project ultra light UAV. Therefore at definition of key structural parameters of a wing there was a task in view of optimization which in connection with the big complexity was solved at enough rigid restrictions and in some stages. At the first stage the choice of the basic structural scheme, potentially capable to provide the requirement of static strength in all limiting cases loading, and also requirements of dynamic strength was carried out. As a result the thin-walled structure with a twice-closed contour of the cross-section section, made of composite materials, mainly type a sandwich has been chosen. Together with the theoretical geometrical sizes of a wing which are growing out previous aerodynamic researches, the choice of the structural scheme defined the basic restrictions in a problem of optimization. At the second stage parametrical researches of dependence of the intense condition and bearing ability of simple elements of a design of a wing (type of flat panels or cylindrical shell of small curvature) from a kind of external loading were carried out. Optimum parameters of panels (thickness and structure of face layers, type and the sizes of a core) were defined at various variants of external loading: tension, compression, bending, shift and their various combinations. The problem of buckling of panels and post-buckling behavior as advantages of the thin-walled composite panel are substantially lost in conditions of compression has special value. The problem of an optimum choice was put as follows. Let overall dimensions of the rectangular panel fixed on all four parties (Figure1) are given. Rigidity of a material of an internal layer of the panel is fixed, and external running load for single length 2T is set. It is required to define an optimum combination of thickness of face layers and a core. For definition of critical loading 2Tc the formula from [1] was used. where B is tensile rigidity of a face layer and δ its thickness, ar is reduced length of a panel, H is its thickness, G is shear rigidity of a core. On the third stage a settlement schematization of a wing in the form of a thin-walled cylindrical shell of twice-closed cross-section section at the bending and torsion is used for stress and strain state analysis. The post-buckling behavior of compressed panel is performed by energy approach. Optimization of parameters of a design (thickness of the walls and layers) is performed by a method of iteration

Cross-Ply BendingaAnd Stability of Compressed Bar with Crack

The analysis of rod cross-ply bending and stability of rod systems in the presence of cracks is the aim of this paper. Using Maxwell's theorem about the reciprosity of displacements and the linear fracture mechanics methods for research of mechanical properties of rod systems in presence of cracks, there were obtained the main equation of the cross-ply bending, its common solution, the expression of relation between the rod deflection and the distributing cross-force and transcendental equation for determination of interior boundary of critical fotrce of rod with a crack

Fatigue Crack Growth in Aircraft Structural Elements at Real

The analytical and experimental researches concerning predicting of fatigue crack growth in the operating conditions are presented. Theory offatigue crack growthindicationis developed. There is planned and executed a flight experiment using the crack growth indicator (CGI) located on two aircraft An-24 and An-26. Results of crack growth in CGI at operational load allowed evaluating the parameters of generalized Paris- Erdogan law and statistical properties of crack increment per fligh

The Regularities of Fatigue Crack Growth in Airframes Elements at Real Operation Conditions

The results of analytical and experimental researches concerning predicting of fatigue crack growth in the operating conditions are presented. First of all the main factors causing a fatigue damage initiation and growth are analyzed and divided to two groups. Common conditions of fatigue damage precise predicting are established. The problem of fatigue crack growth at the stresses of variable amplitude was analyzed and an approach of description of this process is performed. Two examples present the efficiency of this approach. Theory of fatigue crack growth indication and the crack growth indicator (CGI) are developed. There is planned and executed a flight experiment using CGI located on two aircraft An-24 and An-26. Results of crack growth in CGI at operational load allowed to evaluate the parameters of generalized Paris-Erdogan law and statistical properties of crack increment per flight

Post-Bucling Behavior of a Layered Composite Beam with Delamination

Post-Bucling Behavior of a Layered Composite Beam with Delaminatio

Behavior of Thin-Film-Type Delamination of Layered Composite in Post-Buckling

A revision of the basic assumptions those are usually used in the analysis of stability of thin delaminated layer and delamination propagation in a compressed composite is presented in this paper. For this purpose, the theory of flexible elastic plates with large displacements was used. As a result the compressive force and the total longitudinal strain of sub-laminate are expressed in terms of complete elliptic integrals, which uniquely identify the buckled shape of sub-laminate, the effect of buckling on the compression strain and increment of the compressive force in the buckled state. Stress and strain, as well as the strength of the buckled sub-laminate in the dangerous cross-section were also analyzed. The results of the general analysis of delamination propagation and its compression-bending destruction in the buckled state allow to define the basic regularities of the damage behavior of compressed layered composite

Application of the Nonlinear Model of a Beam for Investigation of Interlaminar Fracture Toughness of Layered Composite

Earlier presented the geometrically nonlinear model of a flexible beam (cylindrical bending of a plate) was used for analysis of post-buckling behavior of the layered composite with delamination at compression. In this paper the model is used for more details nonlinear analysis of double cantilever beam (DCB) that used in standard test for determination of the interlaminar fracture toughness composites with delamination-type damage. The main advantage of the model is a precise description of the curved axis of the beam (plate) without linearization or other higher order approximations. The exact solution of bending differential equation finally can be expressed in terms of the incomplete elliptic integrals of the first and second kind. The model describes only geometrically nonlinear effect of DCB arms bending (global effect) and should be combined with the procedure of effective delamination extension to correct DCB arms rotation at delamination front (local effect). First of all the nonlinear model can serve as a tool to estimate the possible error due the geometrical nonlinearity in comparison with linear solution. On the other hand, this model can be effectively used to determine interlaminar fracture toughness using DCB samples at large deflections. Validation of the model is made using data of standard tests of glass/epoxy DCB samples

Analytical 1D Model of Delamination Development and Strength of Layered Composite Beam in Post-Buckling

1D nonlinear model of a thin plate (or beam) with delamination was developed earlier. Large deflections and membrane strains of a plate in buckled state, as well as the strain energy described using elliptic integrals. The Griffith-type energy condition was used as a criteria of delamination propagation. The analysis of the destruction of the plate was performed depending on the geometrical dimensionless parameters of a plate and the material strength performance. Here the mentioned model is extended to the general mode of delamination and it allows to describe the post-buckling stage and damage propagation. Model application as a base for the alternative determination of the interlaminar fracture toughness of the layered composites is indicated