Mechanics and Control
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ISSN 2083-6759
e-ISSN: 2300-7079
Issue Date
2012
Volume
Vol. 31
Number
No. 3
Description
Journal Volume
Mechanics and Control
Vol. 31 (2012)
Projects
Pages
Articles
Prediction of elastic properties of polyurethane-infiltrated carbon foams
(2012) Janus-Michalska, Małgorzata Beata
This paper presents micromechanical approach to assessment of elastic properties of composite polyurethane-carbon foams. Analysis is based on specific choice of RVE combined with micro-macro transition. It leads to evaluation of strength and elastic constants of a composite. Foam behaviour is investigated numerically. Solid skeleton part shape is based on the tetrahedron cut out with spheres. 3D unit cell model is FE discetized. Calculations are performed for foams of selected densities using ABAQUS system. The comparison shows good agreement between the theoretical approach and experimental data. The presented method may be applied to design novel materials such as graphitized foam and nano composites and tailoring these materials for desired elastic properties.
Strength analysis of a gantry crane of a coating structure
(2012) Ładecki, Bogusław; Badura, Sławomir; Matachowski, Filip
Gantry cranes with coating construction are used in Polish steel industry much less than truss bridges. For several bridges, which span and the supports have coating construction, there were made series of non-destructive testing, which revealed the presence of numerous fatigue cracks: in the area of a beam pad, the coating, as well as other elements of their supporting structure. Periodically carried out repairs and strengthening of bridges have not eliminated the problem of the emergence of more fatigue cracks. The analysis of FEM, verified by extensometer measurements of strains, gave the basis to designate the most strenuous areas of the construction. Gathered results of periodic non-destructive testing, combined with obtained results of FEM analysis, were the basis for designing appropriate reinforcements and indication the scope of conducting non-destructive testing of considered construction of bridges with coating.
Observations on fatigue crack growth and fatigue life of riveted lap joints
(2012) Skorupa, Andrzej; Skorupa, Małgorzata; Machniewicz, Tomasz; Korbel, Adam
Effects of variables related to design and production of riveted lap joints representative of longitudinal sheet connections for a pressurized transport aircraft fuselage were experimentally investigated. The specimens from an aircraft Al alloy D16 Alclad sheets of three different thicknesses (1.9, 1.2 and 0.8 mm) were assembled under load control using round head rivets and rivets with the compensator from a P24 Al alloy. For the joints from 1.9 mm thick sheets fatigue tests indicated a dependency of the crack initiation site and crack path on the squeeze force level and on the rivet type. At the same time, increasing the squeeze force led to improved fatigue properties of the joints, specimens assembled using the rivets with the compensator showing fatigue lives consistently longer than joints with the round head rivets. All observed trends have been explained based on hole expansion and load transfer measurements. For thin sheets connected using the round head rivets, local deformations and indentations under the driven rivet head promoted crack initiation and failure in the adjacent sheet. Fatigue test results indicated that the detrimental effect of this type imperfections could outweigh the benefits associated with a decrease in secondary bending due to thinning the sheets. The rivets with the compensator were observed to cause significant local imperfections beneath the manufactured head, which adversely affected the joint fatigue performance.
The possibility of using pseudo-phase space methods in the analysis of the positive displacement pump wear
(2012) Stojek, Jerzy
In this paper the possibility of tracking the evolution of reconstructed pseudo-phase portraits in the diagnosis of positive-displacement pump wear has been presented. The reconstructed pseudo-phase portraits were obtained from vibration signals measured in characteristic places on the pump casing and from the dynamic pressure graphs recorded in the output port of the pump during the passive test experiment. The recorded measurement concerned to tree state of pump condition: in full working order, in part working order and pump with wear out elements.
Directions of extreme stiffness and strength in linear elastic anisotropic solids
(2012) Szeptyński, Paweł
An investigation for directions of extreme - maximum or minimum - values of the longitudinal and transverse stiffness moduli as well as of the limit uniaxial and limit shear stresses in anisotropic linear elastic solids is performed in the paper. The cases of cubic symmetry (regular crystal system) and of volumetrically isotropic cylindrical symmetry (hexagonal crystal system with additional constraints) are considered. The systems of non-linear equations for the components of the versors of investigated directions are derived with use of the spectral decomposition of the elasticity (stiffness and compliance) tensors.