Papers by Keyword: Mechanical Tests

Abstract: Fires can affect both civil and industrial buildings. Following a fire affecting a building or industrial structure, inspections are normally carried out to assess how the materials used in the construction have deteriorated and the severity of this phenomena. Emphasis is put on assessing the material damage, which involves understanding the mode of degradation, the mechanical and physical characteristics of these building materials and their behaviour in the presence of a thermal source. Understanding how heat affects building materials is very useful in assessing the extent of damage to various building components. Paper presents the results of an in-depth investigation of the effect of fire on an industrial building that has suffered a fire. Conclusions are drawn on the degree of material degradation of various elements of the hall structure.

Abstract: The results of a study of carbon fiber-filled samples with an epoxy amine-cured matrix are presented. Independent quasi-periodic oscillations of the density and Young's modulus were recorded for the first time, against the backdrop of a monotonic increase in the strength of the samples. The probable causes of the appearance of the vibrational kinetics of the physico-mechanical parameters of the composite are determined depending on the content of the filler in the reaction volume of constant magnitude.

Abstract: Nowadays, FRCM (Fibre Reinforced Cementitious Matrix) systems are highly attractive for the building materials market; thus, their optimization and development cover an essential role. This work points out the chemical and physical parameters influencing the carbon-FRCM mechanical behaviour. Three different FRCMs composed of commercially available carbon fabric and different inorganic matrices are involved. Matrices are specifically developed to enhance the adhesion with the fabric and differ in organic additive used. Moreover, different fabric geometry (twisted and untwisted) and fibre coatings are considered: micro-silica, fine silica aggregate and medium-size silica aggregate. A new shear test setup is designed to obtain an inexpensive characterization method and employs traditional mechanical tests. Morphological and compositional analyses were performed on the surface fractures. On equal reinforcement typology, significant improvements in shear strength are promoted by organic additives and fabric coatings. Also, pull-out test displays that the twisted bundle promoted the fibre-to-matrix adhesion and remarkably modified the sample failure mechanism compared to the untwisted one. Finally, the FRCM mechanical performance is primarily influenced by mechanical adhesion contribution that might be increased by adopting simple geometrical choices or fabric surface treatments.

Abstract: Over the last few years, the effectiveness of textile-reinforced mortar (TRM) composite systems for structural retrofitting has led to the widespread adoption of these materials in the practice and to the issue of up-to-date design guidelines. Nonetheless, the weak interfacial bonding that is frequently observed between matrix and fibres is likely to cause inconsistent failure modes and, generally speaking, to severely limit the reinforcing potential of the textile. A promising solution to tackle this issue consists in treating the surface of the reinforcing fibres with a functional coating to improve the adhesion at the interphase. In this paper, a pilot study is presented to assess the effectiveness of a fully sustainable polymer coating, consisting in polyvinyl alcohol (PVA) loaded with with rice husk ash (RHA) or with a 50/50 mixture of RHA and silica fume (SF). The coating was applied on basalt fabrics to reinforce TRM coupons that were mechanically tested under uni-axial tensile loads. The mechanical properties of the TRM samples were significantly increased by up to 20%, and the peak load was attained at a higher deformability level, which is a clue of the enhanced ductility of the reinforced elements.

Abstract: Welded flexible compensating elements made of austenitic stainless steels, such as metal hoses and bellows expansion joints, operate in a complex stress state; therefore, almost all corrosion damage of these products occurs in a stressed state. In addition, in welded joints, defects are possible associated with elastic-plastic deformations and stresses arising in the manufacturing process. Paper considers the defects of welded joints of multilayer bellows expansion joints made of stainless steels AISI 304 and AISI 316 types. The influence of the parameters of the argon tungsten electrode welding mode, with or without filler wire, on the mechanical characteristics of welded joints was studied. Mechanical tests of samples of welded joints were carried out on a tensile testing machine. The optimal range of variation of the parameters of the welding mode has been established, in which the plastic characteristics of the welded joints have maximum values. A metallographic study of the microstructure of welded joints of metal hoses and bellows expansion joints was carried out. The influence of the content of nonmetallic inclusions in the material of products on the conditions of melting and crystallization of the weld pool, contributing to the appearance of pores and hot cracks in the metal of the weld and the heat affected zone, has been established. To reduce the influence of the content of non-metallic inclusions in the weld metal and the heat-affected zone on the conditions of melting and crystallization of the weld pool, it is recommended to carry out preliminary heat treatment of the austenitic steel strip.

Abstract: In this paper the methods of mechanical testing of metal and the possibility of their implementation, using mathematical modeling by the finite element method in Deform software package, are considered. As the studied parameters, both the strength indicators (yield strength, tensile strength, Brinel micro-hardness), and the plasticity indicator (the number of kinks before the crack is formed), were studied. The values obtained in the simulation have a very high convergence with the real data.

Abstract: Hydro-energetic equipment and installations are part of a national energy system. Age and their wear, lack of implementation of the risk-based inspections on the structural integrity of components and a proper risk management system can lead to unexpected in-service failure, which causes temporary disturbances in electricity distribution networks and financial losses. Paper presents the structural integrity analysis of the cause of failure of a spindle from a hydro-aggregate. For the material characterization, tensile tests, notch impact tests, hardness tests and non-destructive visual and magnetic particle tests (NDT) were performed. The experimental program also includes complementary investigation for chemical and structural analysis using Energy-Dispersive X-ray spectroscopy (EDX) and Scanning Electron Microscopy (SEM) techniques to assess the quantity and dispersion of elements in different areas of the fractured surface to highlight the particularities of material degradation. Connecting the inspections results leads to an in-depth understanding of the components failure mechanisms, which allows increasing the safety level in operation of the installations by adopting specific measures for avoidance of similar failure. From analysis and experimental results of this study, overload by shock in operation, particularly low steel toughness and non-metallic aligned or clustered inclusions are shown to be the main reason of spindle failure.

Abstract: The necessity and urgency of studying plastic deformation of metals is determined by both scientific significance of the problem and requirements of practice. So the objective of this work is investigation of aluminum alloy creep under action of static magnetic fields. This subject matter is of practical importance for engineering since the parts of engineering constructions are subject to various loads which may lead to their damage or even creep rupture. Based on the experiments performed by us, it is found that creeping increases under stable magnetic field; the main features appear at the first creep stage. Investigation of these processes will help to predict time dependence of creep strain and its rate as well as durability and plasticity at destruction.

Abstract: Compositions with different pipe segments for constructing structural columns were investigated. In this article there is shown a column type composed of five parallel bamboo bars, connected by screws 16 mm and 13 mm in diameter. Compression tests instrumented with displacement transducers are associated with numerical modeling analysis to describe the column load capacity, from the general criteria of dimensioning. The chosen Bamboos are from the species Phyllostachys pubescens due to its favorable characteristics to produce structures and their common use in China, Brazil and other countries of temperate zones. In this proposal, the load capacity is considerably increased and lateral displacements are insignificant compared to the bamboo tested separately. More usual columns 3 and 4 meters long were modeled and presented the load limits of use for these types of structures. Other dimensions of columns can be calculated by the same system, presenting great design opportunities in the construction of the architecture and built spaces. This article shows a great advantage in using columns with bamboo bars compared to other materials used in the architecture, with guarantee and good indexes of security.

Abstract: In this article the technology “high-speed direct laser deposition” is performed. Influence of process parameters on product properties and material structure was defined for Ni-based alloy Inconel 625. Developed technology provided the mechanic properties of products on the bottom level of rolled metal and allows avoid heat treatment and HIP in production process. Economic efficiency of this technology is demonstrated for main areas of industry.