Improvement of methods for monitoring mechanical properties and reliability of steel rod fasteners

The analysis of testing methods for steel rod fasteners in accordance with GOST ISO 898-1-2014 has been performed. It is shown that the control of mechanical properties according to this standard is sometimes ineffective, which leads to the destruction of products during the installation of metal structures. This can be explained by the imperfection of existing control methods, as well as by the fact that when testing fasteners, the technology of their manufacture and preparation for use is not taken into account. Other methods of monitoring the mechanical properties of rod fasteners, both delivery at the manufacturer and input at the consumer, have been proposed and tested, which should be carried out on the basis of new developments in product testing, taking into account the technology from manufacture and use, as well as taking into account the phenomena of deformation aging. The new methods imply the assessment of the plastic properties of full-size products, control of the impact work using special semi-natural samples, control of the tendency to brittle fracture taking into account the structural state of the threaded section of the product, and control of the tendency to deformation aging. All the proposed methods simplify the testing process and increase the reliability of the control of the mechanical properties and reliability of steel rod fasteners.

Deformation Aging in Low Carbon Steels

The results of mechanical spectroscopy are shown when studying the processes of strain age-hardening in mild steel with a ferrite-bainitic structure.

Investigation of the Pipe Weld for Brittle Metal Fracture

The article presents the results of studies of artificial strain aging of pipe steels. The effect of deformation aging on the mechanical properties of steel during tensile tests has been determined.

INVESTIGATION OF THE FEATURES OF THE DECOMPOSITION OF A SOLID SOLUTION DURING AGING OF ALLOYS OF THE Al–Mg–Si–Cu SYSTEM

In this work, the samples of alloy 6013 of the Al–Mg–Si–Cu system after low-temperature thermomechanical treatment (LTMT) according to the scheme: quenching → aging → deformation → aging were studied by dark-field methods of transmission electron microscopy. The analysis of the structure of precipitates of hardening phases and dislocation structure in the volume of grains after different degrees of cold hardening of LHMT is carried out. It is shown that LHMT affects the formation of the structure of hardening precipitates, contributing to both heterogeneous nucleation at dislocations and homogeneous nucleation in the bulk of grains, due to the intensification of diffusion processes.

The mechanical behavior of two warm-mix asphalts

This paper presents results stemming from a comparative experimental analysis of two warm-mix asphalts (WMA) and a dense-graded hot-mix asphalt (HMA). In order to evaluate asphalt mixture behavior, physical and rheological tests were conducted, including tests on resilient modulus, resistance to moisture-induced damage, resistance to fatigue and resistance to permanent deformation. Samples studied were subjected to short (STOA) and long-term (LTOA) aging. As far as asphalt mixture composition is concerned, the same particle size distribution and coarse aggregate were employed for both mixture types. The control HMA mixture was produced with AC 60-70, and the WMAs used the same asphalt cement modified with two chemical additives (Rediset WMX® and Cecabase RT®). The modified mixtures exhibited better resistance to permanent deformation, aging and moisture-induced damage (versus the control mixture). Likewise, WMAs generally saw increased fatigue resistance under controlled-stress loading, which rheological characterization showed is mainly attributable to binder additives and their concomitant modifications.

Application of Orthogonal Experiments Design to Optimize Process Parameters in the Alloy Heat Treatment

The heat treatment process parameters are designed by orthogonal test method. Choosing the most important three parameters of the deformation aging parameters, deformation at room temperature, aging temperature and aging time as 3 factors and each factor uses 4 levels. 16 sets of experiments are organized in accordance with orthogonal table to get each factor in order of priority in effecting on the experimental results and the optimal process combination. Through experiments, the optimal process combination agrees with the actual.