The paper is devoted to a simply supported rectangular plate subjected to two types of compressive edge loads. The first load is applied uniformly along a part of two opposite edges, the second one has a non-uniform distribution (defined by a half wave of the sink function). The critical load value of the plate is located between the values for uniformly distributed and concentrated load. Critical value of thickness of the plate is determined. The problem is solved by the orthogonalization method, and the results are compared with those of numerical analysis done by means of the finite element method.
The paper presents experimental investigations of pressure fluctuations near the tip clearance region of the rotor blades of the axial-flow low-speed compressor stage in stable and unstable parts of the overall performance characteristic. In this investigation, unsteady pressure was measured with the use of high frequency pressure transducers mounted on the casing wall of rotor passage. The pressure signals and their frequency characteristics were analyzed during the steady-state processes, before the rotating stall, during the transition from the steady-state process to the rotating stall, and during a stabilized phenomenon of low-frequency rotating stall. As the operating point moves to the unstable region of flow characteristic, an inception of the rotating stall can be observed, which rotates with a speed of about 41.4% of the rotor speed. The results of this study confirm that in the low-speed axial compressor stage operating in a rotating stall regime there appears one stall cell that spreads over to adjacent rotor blade channels. As the flow rate is reduced further, the frequency of the rotating stall decreased to 34.8% of the rotor speed and the number of blade channels with the stall cell increases.
The paper presents the methodology that makes it possible to evaluate computational model and introduce current corrections to it. The methodology ensures proper interpretation of nonlinear results of numerical analyses of thin-walled structures. The suggested methodology is based on carrying out, in parallel to nonlinear numerical analysis, experimental research on some selected crucial zones of loadcarrying structures. Attention is drawn to the determinants concerning the performance of an adequate experiment. The author points out on indicating the role of model tests as a fast and economically justified research instruments practicable when designing thin-walled load-carrying structures.
The presented considerations are illustrated by an example of a structure whose geometrical complexity and ranges of deformation are characteristic for modern solutions applied in the load-carrying structures of airframes. As the representative example, one selected the area of the load-carrying structure that contains an extensive cut-out, in which the highest levels and stress gradients occur in the conditions of torsion evoking the post-buckling states within the permissible loads. The stress distributions within these ranges of deformations were used as the basis for determining the fatigue life of the structure.
The paper is concerned with an analysis of behaviour of the cableway. On the basis of design data and results of adequate experiments, a physical model of cableway was formulated. The static of cableway was developed assuming a full nonlinear model based on elastic catenary curve. The tension of the rope and the reactive forces between the rope and the supports were calculated. Assuming various loadings of the rope, the relation between the tension in bottom and upper stations and the length of the rope was determined. The model describing the motion of the system is linear. Finite elements were used to formulate the model. Two methods of accelerating the system were investigated.
For riveted joints with eccentricities of the load path, bending moments referred to as secondary bending are induced under nominally tensile loading conditions. Two simple theoretical models proposed in the literature to estimate the associated bending stresses are evaluated in the paper. Both approaches have been implemented in computer programs and applied to estimate the effect of several variables on the calculated bending stresses in the lap joint. Possibilities of the experimental and numerical verification of the models are also considered. Finally, a correlation between the secondary bending computed by one of the simple models and the observed fatigue properties of riveted specimens, as reported in the literature, is investigated. It is shown that deviations of the experimental results from the theoretical expectations stem from additional to secondary bending factors, like the inhomogeneous load transmission through the joint and the residual stresses induced by riveting process. These phenomena are known to be relevant to the fatigue behaviour of riveted joints, but they are not accounted for by the simple models. A conclusion from the present study is that despite the limitations and approximations inherent in the simple models, they provide reliable estimates of nominal bending stresses at the critical rivet rows and can be utilized in currently used semi-empirical concepts for predictions on the fatigue life of riveted joints.
The small artificial surface defects in the coarse-grain steel are studied. The size of the used defects is smaller than the most relevant microstructural unit of steel, i.e. the average grain size. The samples of coarse-grain steel are prepared using a welding thermal-cycle simulator and a laboratory furnace. The defects are made by indenting with a Vickers pyramid. One of the final results of the defect making is the existence of local residual stresses. The influence of residual stresses on the crack initiation from those artificial defects is discussed in the article.
About the Journal
Archive of Mechanical Engineering is an international journal publishing works of wide significance, originality and relevance in most branches of mechanical engineering. The journal is peer-reviewed and is published in electronic form. Archive of Mechanical Engineering publishes original papers which have not been previously published in other journal, and are not being prepared for publication elsewhere. The publisher will not be held legally responsible should there be any claims for compensation. The journal accepts papers in English.
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