Wave fronts via Fourier series coefficients

Motivated by the product of periodic distributions, we give a new description of the wave front and the Sobolev-type wave front of a distribution $f\in\mathscr{D}'(\mathbb{R}^d)$ in terms of Fourier series coefficients.Comment: 10 page

Fatigue failure analysis of pin-loaded lugs

In the present paper, mathematical models are proposed in order to analyze the strength of pinloaded lugs with semi-elliptical crack and through-the-thickness crack. The crack growth investigation of considered crack configurations tackles the fatigue life evaluation and the crack path simulation of semi-elliptical crack. The residual strength is estimated by applying the two-parameter driving force model. The numerical and analytical approaches are employed for the stress intensity factor calculation. Experimental fatigue crack growth data are used in order to verify efficiency of the developed models. A good correlation between fatigue crack growth estimations and experimental observations is obtained

Determination of Stress Intensity Factors in Low Pressure Turbine Rotor Discs

An attention in this paper is focused on the stress analysis and the determination of fracture mechanics parameters in low pressure (LP) turbine rotor discs and on developing analytic expressions for stress intensity factors at the critical location of LP steam turbine disc. Critical locations such as keyway and dovetail area experienced stress concentration leading to crack initiation. Major concerns for the power industry are determining the critical locations with one side and fracture mechanics parameters with the other side. For determination of the critical locations in LP turbine rotor disc conventional finite elements are used here. For this initial crack length and during crack growth it is necessary to determine SIFs. In fatigue crack growth process it is necessary to have analytic formulas for the stress intensity factor. To determine analytic formula for stress intensity factor (SIF) of cracked turbine rotor disc special singular finite elements are used. Using discrete values of SIFs which correspond to various crack lengths analytic formula of SIF in polynomial forms is derived here. For determination of SIF in this paper, combined J-integral approach and singular finite elements are used. The interaction of mechanical and thermal effects was correlated in terms of the fracture toughness

Improved computation method in residual life estimation of structural components

This work considers the numerical computation methods and procedures for the fatigue crack growth predicting of cracked notched structural components. Computation method is based on fatigue life prediction using the strain energy density approach. Based on the strain energy density (SED) theory, a fatigue crack growth model is developed to predict the lifetime of fatigue crack growth for single or mixed mode cracks. The model is based on an equation expressed in terms of low cycle fatigue parameters. Attention is focused on crack growth analysis of structural components under variable amplitude loads. Crack growth is largely influenced by the effect of the plastic zone at the front of the crack. To obtain efficient computation model plasticity-induced crack closure phenomenon is considered during fatigue crack growth. The use of the strain energy density method is efficient for fatigue crack growth prediction under cyclic loading in damaged structural components. Strain energy density method is easy for engineering applications since it does not require any additional determination of fatigue parameters (those would need to be separately determined for fatigue crack propagation phase), and low cyclic fatigue parameters are used instead. Accurate determination of fatigue crack closure has been a complex task for years. The influence of this phenomenon can be considered by means of experimental and numerical methods. Both of these models are considered. Finite element analysis (FEA) has been shown to be a powerful and useful tool1,6 to analyze crack growth and crack closure effects. Computation results are compared with available experimental results. [Projekat Ministarstva nauke Republike Srbije, br. OI 174001

Strength Analysis of Helicopter Tail Rotor Blades Made from Composite Materials

This work considers fatigue strength behavior of construction made from composite materials. Primary attention in this work is focused to fatigue strength behaviors of helicopter tail rotor blade made from composite materials. In this investigation some aspects of design and experimental verification of composite structural elements are considered. Special attention in this consideration is focused on strength analysis of composite structures with application to helicopter tail rotor blades HT-40. To analyze fatigue strength behavior of composite blade here the blade tested under static and fatigue load spectrum. For precise definition of load spectrum of helicopter tail rotor blades here computation fluid dynamic (CFD) numerical simulation is used. In this consideration for determination aerodynamic loads of helicopter tail rotor blades two computation models are used. In first model isolated tail rotor blade is considered. In the second computation model the complete helicopter is modeled including fuselage together with main and tail rotor blades. To determine stresses in blades here finite element method (FEM) is used. To verify fatigue strength of the tail rotor composite blade here is tested with respect to fatigue for one critical load case. In addition to experimental verification of tail rotor blade here is illustrated computation procedure for optimal design of the layered composite panel

NUMERICAL SIMULATION OF AIRCRAFT WINDSHIELD SUBJECTED TO BIRD IMPACT

Mirko Maksimovic, Ivana Vasovic Maksimovic, Katarina Maksimovic, Dragi Stamenkovic, Stevan Maksimovic; NUMERICAL SIMULATION OF AIRCRAFT WINDSHIELD SUBJECTED TO BIRD IMPACT; International Conference of Experimental and Numerical Investigations and New Technologies“ Zlatibor, June 29- July 02, 202

STABILITY AND FAILURE ANALYSIS OF LAYERED COMPRESSED COMPOSITE PANELS USING FEM

STABILITY AND FAILURE ANALYSIS OF LAYERED COMPRESSED COMPOSITE PANELS USING FEM; International Conference of Experimental and Numerical Investigations and New Technologie

Residual life estimation of a thermal power plant component: The high-pressure turbine housing case

This study focuses on the estimation of residual life of damaged thermal power plant components. The high-pressure turbine housing was chosen as an example of thermal power plant component where, during the years of exploitation, damage appeared in the form of dominant crack. Residual life estimation procedure, based upon experimental and numerical methods has been introduced and applied. Material properties were determined experimentally both at room and operating temperature, while all necessary calculations were performed by the special finite element method, so-called X-FEM. The residual life estimation of the damaged high-pressure turbine housing was performed by applying the Paris's law for crack growth analysis

Complexity and flexibility of production structures

101-105This paper presents procedure developments for design of effective production structures of an enterprise. It considers possibilities of making production structures more manageable by means of lowering degree of complexity and enabling production structures to adapt flexibility. Case study was conducted in the company with machine tools production structures