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Open access

Michat Grendaa

Abstract

Demand for thin-walled structures has been increasing for many years. Cold- formed, thin-walled channel beams are the subject of presented research. The local elastic buckling and limit load of these beams subjected to pure bending are investigated. This study includes numerical investigation called the Finite Strip Method (FSM). The presented results give a deep insight into behaviour of such beams and may be used to validate analytical models. The number of works devoted to the theory of thin-walled structures has been steadily growing in recent years. It means that is an increasing interest in practical methods of manufacturing cold-formed thin-walled beams with complicated cross-sections, including also beams with web stiffeners. The ratio of transverse dimensions of beam to its wall-thickness is high, therefore, thin-walled beams are prone to local buckling that may interact with other buckling modes. The stability constraints should be always considered when using cold-formed thin-walled beams.

Open access

Marton Czikkely and Csaba Fogarassy

Abstract

In our study, we focused on urban wastewater management, with special regard to the problems caused by heavy metal contaminations. Heavy metals function at low concentrations as a biogenic element, but at the same time in higher amounts (especially above the limit value) are considered as pollutants. We determined the basic wastewater treatment problem: which is the main problem of heavy metal contaminated urban wastewaters and how could eliminate heavy metals. We focused on wastewater origin heavy metal mobility in environment and effect (risk) on human health. In the following, we undertook to analyse urban wastewater in this direction.

Open access

Aurél Benárd

Abstract

Reykjavík’s largest church, Hallgrímskirkja has become a symbol and an important part of Icelandic national identity. This edifice result of conscious planning process with its location and form reinforce its national significance. Its impact derives from several elements. Buildings symbolizing the identity of communities are usually quite conservative in form. Hallgrímskirkja, however, has distinct individual features that stem from architect Guðjón Samúelsson’s aspiration to express the nation’s identity in a specific architectural form.

Open access

Krzysztof Jarosz, Piotr Niesłony and Piotr Löschner

Abstract

In this article, a novel approach to computer optimization of CNC toolpaths by adjustment of cutting speed vcand depth of cut apis presented. Available software works by the principle of adjusting feed rate on the basis of calculations and numerical simulation of the machining process. The authors wish to expand upon this approach by proposing toolpath optimization by altering two other basic process parameters. Intricacies and problems related totheadjustment of apand vcwere explained in the introductory part. Simulation of different variant of the same turning process with different parameter values were conducted to evaluate the effect of changes in depth of cut and cutting speed on process performance. Obtained results were investigated on the account of cutting force and tool life. The authors have found that depth of cut substantially affects cutting force, while the effect of cutting speed on it is minimal. An increase in both depth of cut and cutting speed affects tool life negatively, although the impact of cutting speed is much more severe. An increase in depth of cut allows for a more significant reduction of machining time, while affecting tool life less negatively. On the other hand, the adjustment of cutting speed helpsto reduce machining time without increasing cutting force component values and spindle load.

Open access

Nikodem Wróbel, Michał Rejek and Grzegorz Królczyk

Abstract

The purpose of this study is to form and test inseparable tight joints, commonly used in the construction of heat exchangers, by crimping operation on designed prototype stand. Crimped joints are made by tools in form of cones with two types of shapes, each of the designed tools have got identical forming angle. This study uses two types of connecting blocks and plates, differing in diameters of hole and flange. Elaboration contains a case study of joints being made by the stand, which in addition to the crimping operations for some cases were glued or brazed. The article presents the features of the formed joints, by examining them by destructive testing: Micrography, tensile strength test, and non-destructive testing: Leakage test. The examined elements have been made of aluminum 6060, which is well suited to indirect or direct operations of forming joints for all kinds of coolers or condensers. Elaborated tests and studies in this study allowed to state, that joining the connection block to plate with the small diameter, was more energy-consuming than in sample sets with bigger diameter, use of glue increasing the strength of the joints by 20%, significant strength increase can be obtained after mechanical clinching with brazing operation or modification of geometrical shape of the jaws

Open access

Christopher Fapohunda, Bolatito Akinbile and Akintoye Oyelade

Abstract

There is a growing concern that the sustainability of our built environment is being endangered, due to the uncontrolled and massive use of non-renewable natural resources in the production of structural concrete that is used for the construction of her infrastructure. Alternative material resources are being discovered through myriads of research efforts to address this concern. One of such alternative materials is the wood waste material. This paper presents a comprehensive review of properties, structural behaviour and application potentials of concrete containing wood waste, either in form of saw dust ash (SDA) as partial replacement of cement, or saw dust as partial replacement of fine aggregates, or wood aggregates as partial replacement of coarse aggregates. The results of the review showed that, (i) with appropriate mix design, wood waste, either in the form of saw dust ash, or wood aggregate, or saw dust; can be incorporated into the concrete mix to develop structural concrete that satisfies codes requirements, provided the replacement is not above 20%,.and (ii) concrete incorporating SDA has good durability properties against most of the process of deterioration encountered by concrete in service life. Thus, the use of saw dust waste in concrete will enhance sustainable structural and constructional practices.

Open access

Frederik Stefanski and Bartosz Minorowicz

Abstract

This paper is focused on the open loop control of a piezoelectric tube actuator, hindered by a strong hysteresis. The actuator was distinguished with 22 % hysteresis, which hinders the positioning of piezoelectric actuator. One of the possible ways to solve this problem is application of an accurate analytical inversed model of the hysteresis in the control loop. In this paper generalized Prandtl-Ishlinskii model was used for both modeling and open loop control of the piezoelectric actuator. Achieved modeling error does not exceed max. 2.34 % of the whole range of tube deflection. Finally, the inverse hysteresis model was applied to the control line of the tube. For the same input signal (damped sine 0.2 Hz) as for the model estimation the positioning error was max. 4.6 % of the tube deflection. Additionally, for a verification reason three different complex harmonic functions were applied. For the verification functions, still a good positioning was obtained with positioning error of max.4.56 %, 6.75 %and5.6%of the tube deflection.

Open access

Konrad Łyduch and Wojciech Gęstwa

Abstract

The paper presents the influences of nanofluids, which are used in hardening process, to dimension changes, hardness and microstructure of hardened construction of steel samples. An analysis was also carried out with the use of English methods of cooling abilities of nanofluids environments based on water, solid nanoparticles of Al2O3 and ammoniac water. The results of this experiment show, that only one of specific dimensions of cooled samples, in the distilled water, changed for about 9%, but when using nanofluids this change was smaller. The hardness of alloy materials got a few percent more when nanofluids were used in comparasion to using the distilled water. The gained results allow to conclude the positive influence of nanofluids on parameters of the hardened materials.

Open access

Vladislav Kaverinsky

Abstract

Using an originally-developed computer model and appropriate software the impact of deformation on austenite phase transformation in low carbon alloyed steel was carried out. The computer simulation takes into account an impact of the deformation degree and takes into account non-constant cooling rate. That makes it useful for the development of thermal and deformation technological processes development. Based on the simulation results a technology of controlled rolling of low carbon steel alloyed by carbide forming elements (Nb, V, Ti) was developed. The proposed technique allows production of rolled steel sheets with high strength and plastic properties, as well as high impact strength in normal and low temperatures.

Open access

Krisztina Fehér, Brigitta Szilágyi and Balázs Halmos

Abstract

The construction of the regular pentagon has always meant a difficult geometrical exercise for architects during the Middle Ages. As the correct drafting was forgotten after the Antiquity, several methods for its approximation had been invented in medieval times. As Golden Ratio appears between several parts of the regular pentagon, the role of the Fibonacci sequence in these approximate constructions is to be examined. The pentagonal drawing in the sketchbook of Villard de Honnecourt calls our attention to a possible way how medieval architects could have applied simple numerical ratios for getting angles they needed. The approximation of 72°, for instance, is likely to have been crucial for this pentagonal construction, as well as the approximation of Golden Ratio that could have been achieved by neighbouring pairs from Fibonacci’s sequence.