This paper describes a problem related to a casting bridge crane with a combined load of 200/50/12.5 t and a span of 18.6 m, working in a heavy metallurgical operation. Due to the specific stress of the structure after its long-term operation, longitudinal fillet welds between the upper flange and the web of the main box beam on the rail side of the 200 t trolley were irreparably damaged. As a result, the cross-section of the main beam had opened, thereby substantially reducing its strength and stiffness. This resulted in a disproportionate increase and undesirable redistribution of stresses in the beam and, at the same time, an increase in the probability of acute fatigue or the loss of stability of the elastic beam shape. Therefore, the rectification of the damaged load-bearing structure was carried out by specific structural modifications. Critical load-bearing elements were subjected to complicated strength and fatigue life analyses before and after rectification. These analyses were supported by experimental measurements. The applied modifications resulted in a partial strengthening of the lifting device with the possibility of its further operation, but only in a limited mode, with a limited period of operation with a time limit of 2 years and a reduced total load capacity of 150 t. The applied methods are also applicable for the fatigue analysis of load-bearing elements and equipment for bridge, gantry and tower cranes, crane tracks, road and railway bridges and support structures under machinery and other devices with a dominant transverse and rotating effect.
Genetic algorithms are a robust method for a solution of wide variety optimization problems. It explores a big space of design variables in order to find the best solution. From the point of view of a user, the algorithm requires the encoding of design variables into the form of strings and the procedure of optimization uses them for optimization. Here, for the structural engineer, it is crucial to find the form of objective function including the constraints of the task and also to avoid critical states during the solution of structural responses. This paper presents the use of genetic algorithm for solving truss structures. The use of genetic algorithm approach is shown on three cases of truss structures.
In technical practice, problems associated with material fatigue often arise. These problems can be caused by errors in the stages of design, production or use of the structure, e.g., by incorrect determination of service life, incorrect dimensioning of construction details, incorrect welds, etc. In the case of welds, such issues may be caused due to the fact that the base material is not welded through or due to the presence of a fistula inside the weld, the presence of slags or cracks inside the weld, etc. The task of the designer is to design a technological unit that meets all the requirements of future users. Components have to be designed for fatigue so that there is an acceptable level of probability that their operation will be satisfactory during their operation life. One of the most common causes of failure of welded joints is fatigue. Fatigue design life is understood to be the reference period of time during which the structure is required to serve safely and not to fail with an acceptable probability. This article deals with the assessment of service life of a welded supporting structure of technological equipment. The structure was subjected to strength analysis. The obtained FEA results were needed to plot the extreme amplitudes of the stresses. Based on the obtained stress vibrations and the welds used, the service life of the structure was assessed by means of the standard.
This paper deals with kinematic analysis of a six-member mechanism. The analytical solution is based on the fundamental kinematic relations derived for this mechanism. The program MSC ADAMS was selected for the simulation modeling of mechanism. That program allows comprehensive analysis of this system using a simple modeling.
The present paper discusses a new approach for the experimental determination of modal parameters (resonant frequencies, modal shapes and damping coefficients) based on measured displacement values, using the non-contact optical method of digital image correlation (DIC). The output is a newly developed application module that, based on a three-dimensional displacement matrix from the experimental measurement results, can construct a frequency response function (FRF) for the purpose of experimental and operational modal analysis. From this frequency response function, the modal parameters of interest are able to be determined. The application module has been designed for practical use in Scilab 6.1.0, and its code interfaces directly with the ISTRA4D high-speed camera software. The module was built on measurements of a steel plate excited by an impact hammer to simulate experimental modal analysis. Verification of the correctness of the computational algorithm or the obtained modal parameters of the excited sheet metal plate was performed by simulation in the numerical software Abaqus, whose modal shapes and resonant frequencies showed high agreement with the results of the newly developed application.
Failure of pipeline system can endanger human lives and cause serious damage; therefore it is necessary to check it in terms of strength and life reliability. Inspection was performed on compressor station pipeline, where in terms of resistance to brittle failure it was discovered, that the weakest point of the pipeline is the weld. At lower temperatures danger of brittle failure of weld joint can arise. To assess the strength of the pipeline in investigated cross-section, with respect to state of plane stress, strength theories were applied. Values of reduced stresses were assigned based on main normal stresses resulting from experimentally set components of state of plane stress. Fatigue assessment was done, based on currently valid standards.
The aim of the paper is to present the application of MSC Adams/View for kinematic analysis of a press mechanism. The press mechanism is simulated in MSC Adams/View software. MSC Adams and its modules Adams/View work with this module and its basic operation is dedicated to the solution of kinematics by means of numerical methods. Press mechanism works on the principle of converting rotational motion of a crank to translational motion of a slider block. This paper deals with model press mechanism in Adams/View, simulation running, plotting of the mechanisms points trajectory and kinematic parameters of mechanism members. The computer program shows displacement, velocity and acceleration, and angular velocity and angular acceleration. The paper presents the results with graphic display of parameters such as displacement, velocity, and acceleration.
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