The Pitfalls of Reverse Engineering Topology Optimised Load-Carrying Structural Parts into Parametric Models

In this paper, we will show the topological optimization of a load-carrying structural parts and the errors that can occur when the topological solution in the form of a triangulated mesh of the surface of the optimized part is reconstructed into a parametric CAD form. Such a reconstruction always introduces geometric errors in the resulting optimal structure of the structural element. A numerical example will be used to show how quickly stress concentrations are reproduced on surfaces where they should not be. The numerical results are also supported by experiment. In the conclusion, it is suggested how, with a specific topological model, the obtained stress concentrations at the edges of the structure can be reduced

Determination of Stresses in the Axle Pin Based on the Wind Model in the Wind Turbine

Even when all the details are provided, the design of wind turbines is a big challenge. The detailed knowledge of the deformation of vital wind turbine components caused by a wind with extreme operating gusts and other type of winds can be obtained only by performing measurements on the wind turbine. The vital component of the wind turbine is axle pin. This article presents the results of the measured changes in wind speed at the height at which strains were measured. The measured strains are used for calculating the stress. It is also shown that on the basis of the calculations on the wind model obtained with the GH Bladed software, the input data are obtained for the SolidWorks software, by which stress on the axle pin can be calculated. The final confirmation of the proper approach and the calculation is achieved by comparison between the calculated and the measured strains on the axle pin during exploitation of a wind turbine of nominal power output of 1 MW

Measurement of strain using stereometry

This paper presents measurement of strain using stereometry method. It describes the use of digital stereometry to measure microstrains on the surface. This can be achieved by comparison of the images of point distribution on faced surface at different load levels. The examples present the possibility to measure strain concentration in the vicinity of crack tip on metallic sample. Applying two video cameras and corresponding software the image of strain distribution can be obtained in different forms, in 2D and 3D formats

A Fracture-Mechanics-Based Approach to the Analysis of the Structural Integrity of a Howitzer Cannon Barrel

This study explores the determination of the critical crack depth in howitzer cannon barrels, which is essential for ensuring operational safety, particularly under high-pressure conditions during firing. The fracture-mechanics-based approach, emphasizing the stress intensity factor KI, is employed to evaluate crack propagation. Specifically, the R6 procedure is applied to assess the failure assessment diagram (FAD), crucial for identifying critical pressures concerning varying crack shapes and depths. The study examines the utilization of high-strength steel 35NiCrMoV12-5 in two distinct heat treatments (materials A and B). Experimental tensile tests and measurements of the critical stress intensity factor KIC were conducted on both materials. The Finite Element Method (FEM) using Abaqus/CAE software was used in combination with experimental results. The FEM model was used to analyses semi-elliptical cracks of different depths and two different shapes. Stress intensity factor distributions along the crack tip were derived, indicating the material resistance to crack propagation

Experimental Investigation of the Effect of Temperature on the Structures in the Measurement of Displacements

Measurement of displacement and deformation of structures is a very demanding engineering task and is carried out on all existing and newly built bridges and other demanding structures. The results of the measured displacements are thus influenced by several atmospheric parameters, among which the temperature is exposed, since the measurements are usually carried out over the whole day at different seasons and conditions, where the temperature differences are significant. In this paper the influence of temperature on the geodetic measurements of the displacements of the steel structure in the unburdened state is presented. To this end, measurements of the steel bridge during the summer time were performed. The temperature and thermal imaging at various locations every half hour were investigated. To calculate the influence of the temperature on the position of the observed point some statistical methods were used. It is evident from the results that in this kind of geodetic measurements, temperature measurements are indispensable. By taking into account the temperature correction results that are very comparable with the predicted values of displacements which can be obtained. Not observing the temperature can result in misleading values of displacement which can lead to misinterpretation and consideration of the obtained value

DESIGN AND TUNING OF THE LYAPUNOV BASED NONLINEAR POSITION CONTROL OF ELECTROHYDRAULIC SERVO SYSTEMS

A complete study of the development of a nonlinear backstepping controller for an electrohydraulic servo system is shown in this paper. The authors present an optimized nonlinear mathematical model used as fundamental for computer simulation. A proposed nonlinear controller is suitable for research of behavior of the complete system in control. Special attention is paid to the selection of tuning parameters. Using the experience of earlier studies of the state-space controller where the additional feedback signals such as velocity and acceleration signal increase the frequency and damping factor of the system, the results were proved by computer simulation. The results show that by appropriate selection of tuning parameters the system can achieve the best reference signal tracking performance with a small tracking error. The proposed approach seems to be adequate not only for step reference signals but also for ramp and sinusoidal reference signals. However, the parameters of the backstepping controller can be optimized manually to achieve the best results required

Measurement of strain using stereometry

This paper presents measurement of strain using stereometry method. It describes the use of digital stereometry to measure microstrains on the surface. This can be achieved by comparison of the images of point distribution on faced surface at different load levels. The examples present the possibility to measure strain concentration in the vicinity of crack tip on metallic sample. Applying two video cameras and corresponding software the image of strain distribution can be obtained in different forms, in 2D and 3D formats

Determination of Characteristics of a Laminated Torsion Bar Spring by Using Correction Coefficients in Respect to Clamping Conditions

The laminated torsion bar is used for many mechanical purposes where a large angle with decreasing or increasing torque is necessary. The design of laminated torsion bar relates to dissipation of energy by friction between laminae, number of laminae and clamp conditions at the end of bar. The paper presents theoretical, experimental and numerical analysis of a laminated torsion bar with different numbers of laminae. Results show that in the design of a laminated torsion bar it is necessary to consider correction coefficients with respect to the geometry of laminae and the clamping conditions on both sides of the laminated torsion bar. In this paper the correction coefficients are experimentally determined. We present the procedure for determination of correction parameters for the calculation of the laminated torsion spring characteristics with a relatively large ratio of width and thickness, (h/b > 7) for low rigidity of the individual lamella

Experimental and numerical cross-correlated modal analysis of the floor structure dynamics in a thermal power plant

This article presents search methodology after the cause of excessive floor vibrations in a thermal power plant control room. The floor structure is a composition of a steel grillage and concrete slabs at 12 m level above soil. It was detected that floor vibration severity exceeds the threshold of the permitted rate. After full scale measurements are conducted on site, the results are arranged versus time and frequency domain. In parallel to site measurements a 3D modal analysis is performed in ANSYS. The outcome is a set of modal frequencies and modal shapes. Cross-correlated analytical and experimental analysis formed a true picture of the excitation, response and their mutual interaction. The obtained results and appropriate conclusions had profiled a remedy strategy to mitigate the severity of the floor vibration