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In this paper, we propose an algorithm for predicting the residual life of structures made of polymer composite materials (PCM) using a structured phenomenological model. In the developed algorithm for estimating the residual life of PCM structures under cyclic loading, it is proposed to use the explicit description of the process of destruction of adhesive layers. The implementation of the algorithm is accomplished in the APDL language in ANSYS Mechanical. The algorithm and the program are tested on a flange type design. Based on the results of numerical experiments, the area of damage is identified. The service life is determined, as well as the allowable value of the PCM flange stiffness drop under cyclic loading. [ABSTRACT FROM AUTHOR]

The paper focuses on the destruction specifics of main gas pipelines (MG) on welded joints and their relation to the technology of construction welding of non-rotating joints of pipes at temperatures of down to −35 ... −50 °С in field environment. It is demonstrated that the metal of the heat-affected zone (HAZ) significantly softens under welding with specified values of qh (heat input), kJ/m, of the pipe joints of a gas pipeline in the conditions of the North. Herewith, in-service defects and cracks tend to appear in welded joints of pipes. [ABSTRACT FROM AUTHOR]

One of the main problems in control is that the overwhelming number of physical quantities cannot be measured directly. Hence, there arise so-called inverse problems on the determination of physical quantities from the results of their manifestations. In the mechanics of a deformable solid there is a problem of obtaining material properties at all stages of deformation and especially at the overcritical stage. In this paper, we formulate and solve the inverse problem of finding the tensile diagram of a material element from the diagram of the dependence of the bending moment on the curvature of a rectangular beam under pure bending. [ABSTRACT FROM AUTHOR]

In this paper, the structures of structural steel for railway transport 1566 and tool steel w1-7 are investigated. For the analysis of the structures of these steels, two techniques are used: traditional optical microscopy (Neophot-21) and ASM (Solver PH47-PRO) with use of a contact method. The microstructure of the steels is studied after complete annealing. The temperature of complete annealing for structural steel 1566 is 770–790 °С. The annealing temperature for tool steel w1-7 is 760–780 °C. The atomic force analysis of the structure of the steels is carried out using different modes. The prospects of using atomic force microscopy in solving theoretical and applied problems of modern metallurgy are demonstrated. [ABSTRACT FROM AUTHOR]

The paper presents a shear strength model used to evaluate information of interest from shock experiments aimed at studying the properties of the hardened 30KhGSA steel and the MA14 magnesium alloy subjected to low- and high-intensity loadings. The model parameters are adjusted by experimental deformation curves obtained from static and dynamic tests at different temperatures and the data from shock experiments to account for strength variation at high strain rates. The simulation of low-intensity loading tests helped to improve the description of elastic-plastic properties and to adjust our failure model. The data from the shock experiments with high-intensity loading of 30KhGSA steel samples and unloading of the shocked samples in window materials were used to verify the phase diagram and the kinetics of direct and inverse phase transitions, and to determine more exactly how the changed phase state influences the strength. The model presented here has allowed us to reproduce the complicated strength behavior of the MA14 alloy at different loading intensities. [ABSTRACT FROM AUTHOR]

This paper deals with the development and approbation of a computational model of damage accumulation in a vertical steel tank at the non-uniform foundation subsidence. The object of research is structure behavior at the survivability stage, namely, the character and sequence of damage initiation and accumulation (elastic-plastic strain, bottom and wall buckling) in the tank structure. [ABSTRACT FROM AUTHOR]

In contrast with neat polymers, filled polymeric composites of ultrahigh molecular weight polyethylene (UHMWPE) are certainly more efficient in manufacturing industrial products (for instance, when reinforcing fibers are loaded). An experimental-theoretical technique for designing a polymer composite with specified properties is discussed in the paper. An approach to determine control parameters (phase composition, physical and mechanical properties, etc.) in order to design a composite with prescribed effective properties or providing them within a predetermined range is proposed. With the use of the approach based on the experimental data analysis in concern of effective characteristics versus the values of the control parameters, corresponding response surfaces of the physical-mechanical characteristics are constructed in the space of states. This allows one to determine the correct and reachable values of the control parameters. The calculated response surfaces make it possible to reveal the range of values of control parameters for specified characteristics of multicomponent reinforced extrudable UHMWPE polymer composites. [ABSTRACT FROM AUTHOR]

This paper studies the applicability of magnetic parameters for testing residual stresses in ferromagnetic structural steels. A unique correlation of the coercive force, initial magnetic permeability, reversible magnetic permeability in the remanent state, and the ratio of initial to reversible permeability with the level of microstresses for Armco iron is established. Thus, the prospects of using these parameters for the evaluation of residual stresses in ferromagnetic structural materials are demonstrated. It is shown that the ratio of reversible magnetic permeability in the remanent state to initial magnetic permeability is the most sensitive to the variation of microstresses. [ABSTRACT FROM AUTHOR]

The paper presents an automated system for monitoring the deformation state of a building complex. The measurement unit of the system records the vertical displacements of a number of bearing columns using the hydroleveling method. In the analytical block, numerical modeling of deformation processes in the subsoil–foundation– building system is performed. The information on the foundation settling obtained during monitoring is used to specify the boundary conditions for modeling the stress-strain state of the structure. Thus, the deformation response of all structural elements to uneven vertical settling of supporting columns is evaluated. The monitoring system has been working since 2010 and it has demonstrated high efficiency. [ABSTRACT FROM AUTHOR]

The present work focuses on methods for investigating the strength of the material of the weld produced by the currently most widely used methods of welding polymer pipes – butt welding with a heated tool, welding with an embedded heating element, and fusion welding with a heated tool. The methods under consideration have been developed due to the absence of simple methods of the quantitative evaluation of the strength of the weld material in the normative documents and scientific papers devoted to the investigation of welded joints of polymer pipes, which are necessary for studying the efficiency of the developed technologies for welding polymer pipes at low temperatures in open areas. The proposed methods for determining the strength of the weld can be used to assess the influence of changing welding parameters on the strength of the joint, as well as to assess the strength of the perimeter of welding and the strength in zones of welded joints in case of fusion welding. The same methods can be used for qualification tests of welders. [ABSTRACT FROM AUTHOR]

This paper presents an approach of direct die shape compensation implemented in a forging optimization system in order to achieve net-shape forging production for aeroengine blade components. This approach is based on the modification of die shape in relation to the dimensional errors of forged aerofoil shape due to the die and press deflections during forging and the thermal distortion upon cooling. In hot forging of a Ni-based alloy, the forging errors due to die elastic deformation, thermal distortion and press elasticity were quantified and further minimized by up to 95% of the original errors prior to the die shape compensation. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Spatial and temporal limitations of atomistic simulations necessitate the development of multiscale methodologies that link atomic and continuum scales. In this paper, a hierarchical multiscale model is presented to study the thermomechanical behavior of carbon nanotube (CNT) based composites. The method explicitly accounts for the behavior of nanoscale interfaces existing between the matrix and CNT. Molecular dynamics simulations based on Tersoff-Brenner potential are employed to study the interfaces in CNT based composites, while finite element method simulates macro behavior with the link provided by cohesive zone model parameters. The multiscale model is used to study the effect of interface strength on stiffness of the composite. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Numerical codes based on the ideal flow theory have been mainly developed for nonsteady sheet (membrane) metal forming processes. To account for thickness effects in sheet metal forming processes, two- and three- dimensional theories should be adopted. The simplest theory of this class is the theory of plane strain deformation. In particular, it can be applied to design sheet bending. It is known that pure bending under the plane strain condition produces redundant work in a layer near the center of the material. To exclude such redundant work, appropriate loading conditions should be chosen. One way to determine such loading conditions is to apply the ideal flow theory. In general, the ideal flow theory is restricted to perfectly plastic materials. However, in the case under consideration, viscoplastic hardening materials can be treated as well. In the present paper, a semi-analytical solution for such materials is found. An optimal initial shape is determined by adopting the criterion that the work required to transform the initial shape into the final shape attains a minimum among a class of initial shapes. The solution also gives tractions for obtaining the final shape of given geometry with no redundant work. Comparison with pure bending is made. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

With advances in computer capabilities, cost of sheet metal forming has being reducing mainly due to the reduction of trial and error approaches. At the moment, a complete process can be simulated on computer and appropriate forming conditions optimized before actual industrial forming process is carried out. While formability predictions have improved, the problem of springback exhibited by most metal, including aluminum alloy AA6111-T4, after forming persist and often leads to significant part fit-up problems during assembly. There are a number of factors that affect springback and perhaps the most significant one is constitutive equation. In this paper springback predicted by six advanced kinematic models are evaluated. In addition an improved constitutive kinematic model is presented. It is shown that by adding stress correction term (SCT) to Armstrong-Frederick model a relatively simple and yet accurate stress prediction could be obtained. The SCT was developed with the assumption that the yield surface remains convex, yield center depends on translation, size and shape variations of the yield surface. The model is implemented in a commercial finite element code (ABAQUS/Standard) via its user material interface (UMAT). Numerical simulations of U-bending were performed using automotive aluminum sheet material (AA6111-T4). It was noted that springback has inverse relationship with residual stress. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The paper describes a model and an inverse identification procedure for the material behaviour of new austenitic stainless steels used for car body panels, exhibiting transformation induced plasticity effects. The modelling is based on a phenomenological macroscopic approach and describes well the evolution of martensitic phase during deformation. The identification is based on a combination of experiment simulations by FEM and optimization. The resulting model and parameters are then used to illustrate in typical sheet metal forming cases the main effects associated to these new materials exhibiting martensitic transformation. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Analytical models of the penetration process focus on estimating depth of penetration based on target density, target strength (sometimes associated with the unconfined compressive strength of the target for geological targets), the areal density of the penetrator (W/A), and the impact velocity. In this paper, an expression for work is used in conjunction with thermodynamic considerations to devise a simple estimate for mass lost by a high velocity projectile during the penetration process. The result shows that the mass loss is directly proportional to the tunnel length and the target shear strength. The constant of proportionality is not easy to deduce, however, in that it contains an unusual factor from the work analysis. A method for estimating target shear under high pressure from penetration experiments is introduced. [ABSTRACT FROM AUTHOR]

The 1TW HELEN laser at AWE has been used to obtain data on material properties at high pressures and strain-rates. This paper presents recent results from experiments in some of these areas. These studies include measurements of the Principal shock Hugoniot from (relative) impedance match experiments using aluminium as the standard. Shock transit times are measured using optical streak cameras to record the times of shock breakout on stepped targets. Attention to target fabrication, step height measurement and streak camera calibration have enabled us to achieve an accuracy of ~1% in shock velocity. The techniques developed in this programme have applications to other experiments such as hohlraum drive characterisation. Designs for off-Hugoniot EOS experiments, including adiabatic compression, by shaping the hohlraum X-ray drive are being studied The feasibility of this has already been tested by using a shaped laser pulse to generate an increased duration steady single shock. A Michelson interferometer has been developed to assess the effects of preheat on EOS targets by measuring surface motion before shock arrival. This instrument has also been used to measure spall strengths and thicknesses in bulk aluminium at the very high strain rates associated with such laser experiments. [ABSTRACT FROM AUTHOR]

In the paper is presented energy method that determines the electric field pressure on a conductor. This method is more understandable for mechanical faculty students, which is way for them it is easier to comprehend the material. It is shown that molecular electric fields of the order of 1011 V/m create huge tension (∼1010∼Pa) and they are responsible for the strength of the solids. In this way we introduce electrical picture in determining the strength of the solid and show one of the application of physics in material science and strength of material classes. [ABSTRACT FROM AUTHOR]