Stiffness estimation and equivalence of boundary conditions in FEM models

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.Web of Science114art. no. 148

Q-STRESS v.1.0–a Tool for Determination of Stress Fields Using Digital Image Correlation Systems

AbstractThe contribution deals with a description of noncommercial program, created for digital image correlation systems Dantec Dynamics. Described version of this product called Q-STRESS v.1.0 processes data exported from the software delivered together with correlation systems and allows fast and simply visualize displacement or strain fields and calculate the further to the stress fields. Moreover in chosen points the program allows depict the courses of displacements, strains as well as stresses during the loading process. In this contribution the description of the program is supplemented by its practical application in investigation of stress fields in the surroundings of small hole. Version 1.0 is created only for the analyses in elastic domain

Structural Design and Impact Test of a Suspension Mountain Bicycle Frame by Using FEM Analysis

Abstract The paper deals with numerical strength analysis of a prototype of full suspension mountain bicycle frame. Frame and its suspension were specially designed to meet predetermined requirements establishing the final properties of bicycle. In the design, also other aspects such as the driving style, characteristic of lines and the figure of driver were taken into account. In this regard, the final design is completely unique. In the paper there are described two impact tests: drop mass and frame drop, which are defined in standard EN ISO 14 766. Both tests were carried out using Finite Element Method

Geometric Optimization of a Tuning Fork in NX Nastran

Abstract A tuning fork is a simple tool used by musicians to tune their instruments or by medical practitioners to assess a patient's hearing. It produces a very pure and fixed tone, with most of the vibrational energy at the fundamental frequency, and little at its harmonic frequencies. To achieve a required tone it is needed to determine the exact dimensions of a tuning fork with regard to the material used for its manufacturing. Geometric optimization is an ideal design tool for this purpose. Paper deals with the process of proposal and design optimization of a common tuning fork by using NX Nastran software. Paper is divided into two parts. The first part deals with the experimental and numerical modal analysis of an existing tuning fork with the prongs of circular section. The second part describes the proposal and optimization of a new tuning fork with the prongs of square section

The Possibilities in Use of ESPI Method by Investigation of Strain Fields of Specimen with Stress Concentrator

Abstract The analysis of sheets deformation and corresponding knowledge of their elastic and plastic properties has a great meaning by their following processing. The aim of this contribution is to focus on the description of use an optical ESPI system Q-300 Dantec Dynamics by investigation of elastic deformations of sheets with stress concentrators in a form of notch. The results obtained experimentally using mentioned measuring device were verified numerically in program Ansys Workbench. The paper briefly describes the methodologies of both, experimental and numerical, types of modeling. Keyword

Design and strength analysis of C-hook for load using the finite element method

The special type of C-hook is investigated in this paper. The C-hook is designed to carry a special load, where is not possible to use classical hooks or chain slings. The designed hook is consisted of two arms that ensure the stability of the load being carried. The finite element analysis is performed for the control of the stress and deformation state in the whole hook. The fatigue analysis is performed for the check of a lifetime of C-hook

Using High-speed Digital Image Correlation to Determine the Damping Ratio

AbstractThe article deals with the possibility of using digital image correlation method in experimental determining of damping ratio. The essence of the article is a proposal of algorithm for the processing of a time responses measured by correlation system Q-450 Dantec Dynamics. The algorithm uses a Fast Fourier Transformation and bandwidth method to calculate a damping ratio. The output is a graphical representation of the value of damping ratio for given natural frequency of the test object. The article presents the method of verification by testing algorithm on numerical models and its practical application in determining the value of damping ratio of a specimen material

Design and strength analysis of C-hook for load using the finite element method

The special type of C-hook is investigated in this paper. The C-hook is designed to carry a special load, where is not possible to use classical hooks or chain slings. The designed hook is consisted of two arms that ensure the stability of the load being carried. The finite element analysis is performed for the control of the stress and deformation state in the whole hook. The fatigue analysis is performed for the check of a lifetime of C-hook

Influence of PSD Estimation Parameters on Fatigue Life Prediction in Spectral Method

The paper analyzes in detail the influence of the Welch method on the estimation of fatigue life in the frequency domain. The aim is to examine how the setting of parameters, such as window size, weighting and overlap, affects the calculation of power spectral density (PSD) and thus lifetime. The paper uses knowledge from the theory of signal processing, statistics and fatigue life estimation in the frequency domain. In order to demonstrate the general validity of the conclusions, four different reference PSD spectra are generated and examined. The spectra are converted to time histories using an inverse fast Fourier transform and then used as input (measured) data for the Welch method. The PSD thus obtained are subsequently subjected to lifetime estimation using the Dirlik and Tovo–Benasciutti models. Based on the obtained results, it was found that the best configuration of the parameters of the Welch method for fatigue calculations is the selection of the smallest possible time window (maximum 60% of the observation length) and the largest possible overlap (minimum 70% of the window size)