Tytuł Data publikacji Autor
Large deformations and stress analyses in two types of space structures that are intended for people to live in space have been studied in this research. The structure under analysis is assumed to rotate around the central axis to create artificial gravitational acceleration equal to the gravity on the Earth's surface. The analysis is fully dynamic, which is formulated based on the energy method by using the first-order shear deformation shell theory in two systems, cylindrical and torus. Also, the nonlinear von Kármán strain field has been assumed. The obtained set of partial differential equations has been solved using the semi-analytical polynomial solution method (SAPM). The main purpose of this paper is to study the effects of unusual conditions in the space outside the Earth's atmosphere (which is a complete vacuum environment without pressure) on the strength of the analyzed structure. The numerical results of the governing equations have been evaluated using those of other studies and the simulation efficiency performed in this research has been proven. Finally, the effect of important parameters on the numerical results, including the angular velocity of the structure (which causes artificial gravity), the amount of imposed mechanical and hygro-thermal loads, the structure size and material specifications have been investigated in more detail.
2021
Shahriar Dastjerdi,
Mohammad Malikan,
Victor Eremeev,
Bekir Akgöz,
Ömer Civalek
The performance of novel Layered Two Stage Fibrous Composite slabs (LTSFC) was pioneered under falling mass collisions using a combined experimental and numerical study. Such LTSFC slabs consist of three layers with and without the insertion of glass fibre mesh between the layers. LTSFC techniques were used to fabricate the composite slabs with three layers including 3%, 1.5%, and 3% of fibre content for the top, middle, and bottom layers respectively. Sixteen MLPAFC square slabs were cast with only short hooked end fibres and tested under falling mass collisions by amending two parameters namely the type of support (fixed and hinge) and support layout. Two distinct support layouts on two types of support were considered and tested with and without the glass fibre mesh between layers of LTSFC. A glass fibre mesh was introduced between the three layers to block crack growth propagation and absorb additional collision energy. The glass fibre mesh insertion between the layers and the LTSFC production technique were considered as novel modifications. A numerical study using Auto desk Fusion 360 was conducted and compared with experimental results. The numerical results showed fair agreement with the experimental test results. Based on the validated numerical models, collision energy and cracking pattern evolution were studied. The findings indicated that the glass fibre mesh insertion between the layers combined with steel fibres disrupted crack proliferation, thus exhibiting superior engrossed collision energy and postponing crack growth. Additionally, the engrossed collision energy at crack initiation and ultimate crack for the slabs with four sides fixed and hinged support were greater with respect to two opposite sides fixed and hinged support. Numerical values were in reasonable agreement with the experimental values in terms of collision energy and cracking patterns.
2021
R. Rithanyaa,
G. Murali,
M.P. Salaimanimagudam,
Roman Fediuk,
Hakim Abdelgader,
A. Siva
Monitoring the stiffness of adhesives is a crucial issue when considering the durability andstrength of adhesive joints. While there are many studies conducted on specimens madeonly from adhesive, the problem of curing of an adhesive film in real joints is moderatelyconsidered. This paper presents the monitoring of stiffening of epoxy adhesive using ultra-sound. Ultrasonic pulse velocity method was firstly applied for monitoring of adhesivespecimens. Then, a new procedure using dispersion relations and scanning laser vibrome-try was proposed for monitoring the curing process of an adhesive joint of steel plates. Bothapproaches gave comparable results showing the increase of the dynamic elastic modulusof adhesive in time. The study presented that the proposed procedure was capable of real-time monitoring the curing process of an adhesive layer in multi-layer systems.
2021
Erwin Wojtczak,
Magdalena Rucka
We discuss the propagation of localized surface waves in the framework of the linear Gurtin–Murdoch surface elasticity and taking into account a roughness of a free boundary. We derive a boundary-value problem for anti-plane motions with curvilinear boundary and surface stresses. Using the asymptotic technique developed earlier, we obtain the form of a localized wave and analyze its amplitude evolution. As the main result we present the dependence of the wave amplitude on the roughness magnitude. The presented results could be used for non-destructive evaluation of the surface microstructure using surface waves-based devices. In particular, measuring the decay rate with the depth one can estimate roughness of a surface and appearance of new surface defects.
2021
Gennadi Mikhasev,
Marina Botogova,
Victor Eremeev
This research aimed to determine the durability and strength of an old concrete built-in arch bridge based on selected mechanical, physical, and chemical properties of the concrete. The bridge was erected in 1925 and is located in Jagodnik (northern Poland). Cylindrical specimens were taken from the side ribs connected to the top plate using a concrete core borehole diamond drill machine. The properties of the old concrete were compared with the present and previous standard requirements and guidelines. The laboratory testing program consisted of the following set of tests: measurements of the depth of carbonated zone and dry density, water absorption tests, determination of concrete compressive strength and frost resistance, determination of modulus of elasticity, measurement of the pH value, determination of water-soluble chloride salt and sulfate ion content, and X-ray diffraction analyses. Large variations in the cylindrical compressive strength (14.9 to 22.0 MPa), modulus of elasticity (17,900 to 26,483 MPa), density (2064 to 2231 kg/m3), and water absorption (3.88 to 6.58%) were observed. In addition to the experiments, a brief literature survey relating to old concrete properties was also conducted. This paper can provide scientists, engineers, and designers an experimental basis in the field of old concrete built-in bridge construction.
2021
Andrzej Ambroziak,
Elżbieta Haustein,
Maciej Niedostatkiewicz
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