Papers by Keyword: Ultimate Strength

Abstract: The issues of determining the Mayer index depending on the parameters of strain hardening of an elastoplastic body described by the Hollomon equation are considered. The analysis of expressions connecting the engineering uniform deformation with the Mayer index is carried out. A new expression is obtained, a particular case of which is the result obtained by V.M. Matyunin et al. Applying the ratio of the maximum Mayer hardness to the Brinell hardness, the relationship of the ultimate strength to the Brinell hardness, and the Hollomon equation, a new expression of the Mayer law is obtained. The description of the radius of the contact area by a power function of the depth of the indenter insertion allowed us to represent the Mayer index as a ratio of known parameters obtained by finite element modeling for other purposes. The graphical dependences of the results obtained are presented.

Abstract: This paper explores the ultimate strength of the composite floor system of structural steel concrete. ABAQUS, used to research non-linear competencies and ultimate load-carrying capability of such floor systems, developed the Finite Element Model (FEM) in 3-D. A comparison of computed values with experimental results has validated the proposed finite element model. The measured and experimental findings show a good match with an average variation of 10%. In parametric study effects of different sizes of shear studs on the ultimate strength of the floor system have been explored on full size specimens. Results show that an increase in height of the shear stud with the same diameter increases the ultimate strength of the floor system. An Increase in the diameter of the shear stud also increases the ultimate capacity of the floor system.

Abstract: During operation many metal structures are under conditions of combined impact of aggressive media (natural and/or technological) and mechanical loads. At the same time, the damage caused by the combined effect of corrosion and stress is often more significant than with simple "superimposing" of damage caused by mechanical load and influence of aggressive medium acting separately. When carrying out destructive tensile tests of equipment materials, there is a possibility of inaccuracy of results for determination of mechanical characteristics of this material due to actual operation of the material under conditions of aggressive environment. This, in turn, can lead to an erroneous calculation of the strength and life of the equipment. In this regard, it is particularly relevant to study the behavior of materials under the influence of various mechanical loads in aggressive media, as well as to determine the limit state of the metal based on the results of measurement of its electrode potential.

Abstract: A steadily rising interest which specialists in various fields show towards the problem of hydrogen affecting metallic materials and causing their failure is connected to all-increasing requirements set on the durability of machines and equipment in operation. Metallic structures are most often surrounded by such environment which contains hydrogenous components or hydrogen itself (in chemical industry, power engineering, etc). And it leads to various types of degradation in metals (hydrogen embrittlement, hydrogen corrosion, and so on), which, in its turn, could cause catastrophic results. Ultimate strength is considered to be a representative parameter of the process of hydrogen degradation in steels. The authors cite the results of testing conducted on hydrogen-saturated specimens made of A516-55 steel which register a significant decrease in the ultimate strength. It is proposed to use a diagram which describes a fall in metal strength and transition of structural materials into their brittle states following an increase in hydrogen concentration. Discussion is made on criteria for hydrogen-saturated materials of metallic structures failing when a momentary overload occurs under default working conditions.

Abstract: The paper is primarily focused on the determination of the ultimate strength of pressed materials in the form of steel sheets. The breaking strength of homogeneous materials such as e.g. steel sheet is not a relevant indication for pressed steel sheet waste material. The ultimate strength serves as a main parameter in the design of sheet metal cutting machines. For the design and technological design of machines and equipment for shearing steel waste in the form of pressed sheets, it is necessary to know the limit strength of the material. The paper describes in detail the experimental procedure and the principle of determining the ultimate strength of the steel waste sheet. Several dozen experimental samples of pressed metal waste were used. The very principle of the experiment consisted of sheared samples, while monitoring the shear force and the thickness of the pressed material. The ultimate strength of the shear material was calculated from the measured data. The measured and calculated data were statistically processed to increase the objectivity of the determination of the already mentioned ultimate strength parameter of the pressed waste sheets.

Abstract: On the basis of approach to primary structure of gray cast iron as to an analog of the composite material, reinforced by discrete fibers, the quantitative contribution of dendritic crystals and the eutectic matrix to ultimate strength in tension is defined.

Abstract: Aiming at the damage and failure problem of copper alloy netting structure, the ultimate strength and fatigue performance of the net structure were studied by test method. Based on the research on the ultimate strength of copper wire, through a series of fatigue tests on copper wire and net structure, the fatigue life and failure modes of copper wire and net structure under different loads are analyzed, and their fatigue life curves are also drawn. The results show that the fatigue strength of copper wire and net structure considering corner processing is lower than that of copper wire not considering corner processing, which indicates that corner processing has a great influence on the fatigue strength of actual copper net structure. Compared with the fatigue strength value of 32.8 MPa of the copper net, the fatigue strength value of the net structure decreases to a certain extent (about 14.3%), which indicates that the assembly process of the copper net has certain influence on the fatigue life of the net structure.

Abstract: One of the most important features of a material to know before using it is the maximum limit of the load at which it fails. This paper presents a micromechanical strength theory to estimate the tensile strength of the unidirectional fiber reinforced composite. The fibers used can be considered transversely isotropic and elastic till failure, but the matrix material is considered to be Elastic-plastic. The mathematical formulation used is the Variational-Asymptotic Method (VAM), which is used to construct the asymptotically-correct a reduced-dimensional model that is free of a priori assumption regarding the kinematics. The 3-D strain generated in each constituent material is explicitly expressed in 1-D strains and initial curvatures. The advantage of using VAM is that the stress state correlation of constituent materials is taken care of while applying warping constraints. Prandtl-Reuss plasticity theory has been implemented for the plastic region constitutive relationship. The other advantage of this work is that the load-bearing capacity of the composite beyond the elastic region has been considered. Good agreement has been found between experimental data and VAM analysis.

Abstract: The corrosion of concrete structures is serious in sulfuric acid environments. Corrosion damage of reinforcements caused sulfuric acid corrosion is very serious. The rapid experiments of sulfuric acid corrosion steel bars were carried out, and the apparent morphology and mechanical properties of sulfuric acid corrosion steel bars were studied. The results show that the corrosion of steel bars is uniform corrosion. With the increase of corrosion rate, the yield platforms and the yield strengths and ultimate strengths are reduced. Based on the experimental datas, the relationship models between yield strengths and ultimate strengths and corrosion rates were obtained. The constitutive models of corrosion steel bars were established. The stress - strain relationship model is in good agreement with the experimental data.

Abstract: This paper describes a Monte Carlo simulation of the correlated steel characteristics of yield stress and ultimate strength of steel S235 grade from Northern Moravia region in the Czech Republic. Their joint distribution is described by a correlation index and frequency histograms. The paper step-by-step describes simulation process of the transformation of a correlated Gaussian joint distribution to a general joint distribution, because the yield stress as well as ultimate steel strength random parameters do not follow a Gaussian distribution. Their marginal distribution can be easily described by a suitable parametric distribution or frequency histogram suitable for use with the Simulation-based Reliability Assessment method (SBRA). Describing joint distributions of non-Gaussian processes is overcome by application of fractile correlation.