Investigation of Structure and Physical-Mechanical Properties of Metal in Different Zones of Welded Trunk Pipelines Made of X80 Strength Grade Steel

The development of trunk pipelines network, taking into accont their operation in difficult climatic conditions, leads to the creation and the development of non-destructive testing methods to control the stress-strain state of the pipe itself, as well as welded joints. This work presents the results of studies of the microstructure, as well as the mechanical and magnetic characteristics of the metal cut from different zones of the welded joint of X80 strength class pipe steel.

Influence of Concrete Strength Class on the Long-Term Static and Dynamic Elastic Moduli of Concrete

Construction materials, among which concrete is by far the most used, have followed a trend of continuously increasing demand in real estate. A relatively small number of research works have been published on the long-term material properties of concrete in comparison to studies reporting their findings at standard curing ages of 28 days. This is due, in part, to the length of time one must wait until the intended age of concrete is reached. The present paper contributes to filling this gap of information in terms of the strength and dynamic elastic properties of concrete. The dynamic modulus of elasticity may be used to assess the static modulus of elasticity (Young’s modulus), a key property used during the design stage of a structure, in a non-destructive manner. This paper presents the results obtained from laboratory tests on the long-term (6 years) characterization of concrete from the point of view of dynamic shear and longitudinal moduli of elasticity, dynamic Poisson’s ratio, static modulus of elasticity, compressive and tensile splitting strengths, and their change depending on the concrete strength class.

Physical and mechanical properties of four wood species from community forests in Binjai Regency, North Sumatra

The fundamental properties of wood are significant to determine the purposes of wood used. This study aims to determine the physical and mechanical properties of four wood species namely terap (Artocarpus odoratissimus ), durian (Durio zibethinus), mindi (Melia azedarach L.), and karet or rubber wood (Hevea brasiliensis Muell. Arg) from community forests in the Binjai Regency, North Sumatra. The physical properties were determined as described in ASTM D4442 and ASTM D2395 while the mechanical properties were conducted according to ASTM D143 and BS 373. The results showed the moisture contents of four wood species ranged 12.66– 15.28%, densities 0.35–0.59 gcm-3, and specific gravities (SG) 0.33–0.55. The compression, tensile and shear strengths parallel to the grain, hardness, modulus of elasticity (MOE), and modulus of rupture (MOR) ranged 20–35 MPa, 36–80 MPa, 6.5–9.7 MPa, 1713–3226 N, 5463– 7497 MPa and 43–71 MPa, respectively. Based on the SG and MOR values, the terap wood is included in strength class IV, while the other woods are in strength class III. Meanwhile, based on the compression strength values, the terap wood is included in strength class V, durian and mindi wood are in strength class IV, while karet wood is in strength class III.

Engineered bamboo: The promising material for building and construction application in Indonesia

There is a rising gap between supply and demand of wood as building and construction materials. The search of alternative materials to fill in the gap is an urgent concern. Bamboo is one of locally abundant resources; 88 out of 135 species growth in Indonesia is an endemic. It is a renewably material and has comparable characteristics to wood. Notable efforts to reduce the variability of raw bamboo have led to the improved physical and mechanical properties of the engineered bamboo. Laminated bamboo and hybrid laminated bamboo-wood had superior wood strength in comparison to the raw materials. Laminated bamboo produced from andong (Gigantochloa pseudoarundinacea (Steud.) Widjaja), mayan (Gigantochloa robusta Kurz), vertically laminated andong bamboo comparable to wood strength class I, I-II and II, respectively. Furthermore, hybrid laminated bamboo-wood andong-manii (Maesopsis eminii Engl.), andong-mayan-jabon (Anthocephalus cadamba (Roxb.) Miq.) comparable to wood strength class II and III, respectively. The properties improvement of engineered bamboo demonstrates the potential application of laminated bamboo as a substitution for building and construction material.

Efficiency of Visual and Machine Strength Grading of Sawn Timber with Respect to Log Type

A batch of pine timber sawn from butt, middle and top logs was strength graded with the visual method (classification into grading classes KW—best quality, KS—medium quality, KG—inferior quality and Reject) and with the machine strength grading method—performed with the use of a mobile timber grader (classification into C strength classes). We compared the efficiency of grading classes and strength classes, depending on the type of log from which the material was obtained (butt, middle, top). Next, a strength grading machine was used to measure the modulus of elasticity in bending (MOE) and static bending strength (MOR). The ANOVA confirmed the influence of both the log type (butt, middle, top), the C strength class, and the visual strength grading class on the values of density (DEN) and MOR. Timber density and MOR decreased from the butt log section to the top log section. The ANOVA confirmed the influence of log type on MOE values, but only to a limited extent.

ABOUT TECHNOLOGICAL FEATURES OF PRODUCTION OF REINFORSING BARS FROM PEARLITE GRADE STEELS

Formulation of the problem. In the production of coiled rolled products from perlite grade steels, metallurgical enterprises encounter with the sorting of some batches of continuously cast billets or commercial products due to non-compliance with regulatory requirements. One of the alternative ways of using such blanks can be their reassignment for the production of thermally hardened reinforcing bars. In accordance with the edition of GOST 5781-82, it was possible to produce hot rolled reinforcing bars from steel grade 80C (carbon content 0,74…0,82 %), and according to TU 14-15-339-94 – thermally hardened with a carbon content of 0,50…0,85 % C. In world practice, reinforcing bars of a strength class similar to classes A800…A1000 (DSTU 3760:2019) are made mainly of high-carbon steels. The main type of stressed reinforcement in the EU, USA, Canada and Great Britain are rods with a nominal diameter of 26…40 mm of strength class 835…1030 MPa and 26…36 mm of strength class 1080…1230 MPa. An analysis of the requirements for reinforcing bars according to various regulatory documents shows that in the standards of Canada, the USA and the UK, the carbon content is not standardized, but according to the standards of Japan and Ukraine it is 0,45…0,80 % and 0,13…0,37 % respectively. According to the requirements of international standards, the minimum values of the yield strength and strength correspond to the reinforcing bar A800 (DSTU 3760:2019). Therefore, for the possibility of producing reinforcing bars from high-carbon steels, it is necessary to establish rational temperature-time conditions for heat hardening modes, which will ensure that the finished metal products comply with the requirements of DSTU 3760:2019. Purpose. Determine the influence of the parameters of the technology of thermal hardening on the features of the formation of the structure and mechanical properties of reinforcing bars made of steels with a carbon content of 0,50…0,90 %. Results. The possibility of producing reinforcing bars of strength classes А800 and А1000 from steels С56DВ, C70DВ, C80DВ and C82DВ (EN 16120-2:2017) using intermittent and interrupted quenching methods has been scientifically proven. In accordance with the results obtained, the industrial production of reinforcing bars of strength classes A800 and A1000 from these steels is expedient, since it will contribute to the improvement of technical and economic indicators in the production of coiled steel from perlite grade steels intended for high-strength products (cold-worked rebar, metal cord, bead wire, spring wire, reinforcing ropes, etc.). Based on the results of industrial experiments, a technical agreement was developed and approved for the production of pilot batches of thermally hardened reinforcing bars of strength classes A800 and A1000 from steels containing 0.50...0.90 % carbon.

INFLUENCE OF STIFFNESS RELATED TO THE C40 STRENGTH CLASS OF THE HARDWOOD GROUP ESTABLISHED BY THE BRAZILIAN STANDARD IN THE DESIGN OF TIMBER STRUCTURES

The Brazilian standard ABNT 7190 (1997) establishes the strength classes C20, C30, C40 and C60 for the proper framework of the different wood types in the group of hardwoods. Associated with the strength class, which is based on the compressive strength characteristic value parallel to the fibers (fc0,k), the standard stipulates the respective values representing the stiffness (Ec0), with 19500 MPa being the reference value for the class C40, essential variables in structural design. For being the C40 class is the one with the greatest amplitude (20 MPa), it is possible that the value 19500 MPa is not the best representation of stiffness. This work aimed to verify the representativeness the stiffness value established by the Brazilian standard for C40 wood. The result obtained from the average confidence interval indicates the value of 14110 MPa as being the most representative, which may imply structures that are supposedly more rigid than they really are.

Effect of Chemical Composition and Network of Fly Ash Glass on the Hydration Process and Properties of Portland-Fly Ash Cement

In the experiment, the aluminosilicate glasses with aluminum saturation index (ASI), defined as the Al2O3/(Na2O+K2O+2CaO), equal to 0.74, 1.72. 2.52, or 4.05 were synthesized. The spectroscopy tests (MIR and 27Al MAS-NMR) confirm that in glass with ASI < 1, the aluminum ions occur in the [AlO4]5- only. In glasses with ASI > 1, the aluminum ions create mainly [AlO4]5-, but part of them occurs in the form of [AlO6]9-. The content of [AlO6]9- octahedrons increases successively for ASI from 1.72 to 4.05. Glass with ASI equal to 4.05 demonstrates the highest content of pozzolanic active Al2O3. Model ashes were prepared by mixing 70 wt.% of glass, 20 wt.% of synthetic mullite and 10 wt.% of SiO2 as an equivalent of quartz. Then Portland cement CEM I 42.5R was milled together with 20 wt.% of each of model ashes to Blaine’s specific surface area of 4,200±50 cm2 g-1. It was found that the addition of ash with higher content of [AlO6]9- octahedrons in the structure of glass accelerates the hydration process of cement blend, which, in turn, positively affects its usable features (heat of hydration, initial setting time and compressive strength). According to the requirements of PN-EN 197-1:2012 standard, the introduction of ash with ASI coefficient equal to 4.05 gives cement blend of strength class of 52.5N. Cement blends with the ash of ASI value equal to 1.72 and 2.52 correspond to strength class of 32.5R, whereas the cement blend with the ash of ASI value equal to 0.74 does not achieve the minimum value of strength for any cement strength class. Results show that the change in chemical composition of fly ash glass and resulting from this diversified structure are essential from the point of view of hydration and properties of cement containing fly ashes in its composition.