Development of a macro-element model for rockfall steel wires using

This paper aims to present a few aspects of the development of a plastic-hardening macro-element model for steel wires in flexible protection systems. First, the material behaviour is obtained using uniaxial tensile tests. Successively, the evolution of the elastic and plastic domain is obtained using a combination of physical tests, analytical models, and numerical simulations. Finally, the results obtained with the macro-element model are compared to those obtained using other approaches found in literature.

Two-Intervals Hardening Function in a Phase-Field Damage Model for the Simulation of Aluminum Alloy Ductile Behavior

The aluminum alloys (AA) are among the most utilized materials in engineering structures, which induces the need for careful investigation, testing, and possibilities for accurate simulation of the structure’s response. AA 5083-H111 specimens were used to investigate the possibility of employing a Phase-Field Damage Model (PFDM) for the simulation of AA structures’ behavior. The specimens were mechanically tested by uniaxial tensile loading tests. Based on the obtained results, the PFDM was employed with a von Mises plasticity model, implemented in the Finite Element Method software. The plasticity model was extended by modification of the hardening function defined in two-intervals: a linear hardening and a Simo-type hardening. An excellent superposition of the simulation and experimental force-displacement response was recorded. These findings suggest that the AA structures’ response can be successfully simulated in the elastic-plastic domain, as well as its failure by damage being controlled.

Hydrogen diffusion in low alloy steels under cyclic loading

The aim of this work is to analyze hydrogen transport in a low alloy steel by applying the electrochemical permeation technique to matrices subject to cyclic loading conditions, up to the yield strength and beyond this limit. The results indicate that, with an increase in the applied maximum stress, a decrease in the apparent diffusivity takes place, along with a marked and instantaneous reduction of diffusing hydrogen in the lattice and an increase in hydrogen solubility. An effect on the permeation current was observed, together with a variation of hydrogen diffusion kinetics ascribable to the activation on new trapping sites, with an appreciable effect under cyclic loading already at 55% of the yield limit, which becomes more relevant in the plastic domain.

The Effect of Internal Pressure on Radial Strain of Steel Pipe Subjected to Monotonic and Cyclic Loading

Steel pipes in different engineering applications may fail, leading to numerous environmental disasters. During loading, certain mechanical and chemical phenomena develop inside the pipes and cause them to burst. In this study, the influence of internal pressure on the elastic and plastic behaviour of E355 steel pipes was investigated on small specimens with different wall thicknesses. First, the failure modes of pipes subjected to monotonic loading were assessed, and then the behaviour of specimens subjected to cyclic internal pressure was analysed in terms of variation of radial strain. The strain and stress states of pipes were analysed using the finite element method. The results revealed that the hardening of materials inside the pipes increases the risk of cracking and bursting because of elasticity limits being exceeded, causing entry into the plastic domain. The transition of mechanical behaviour can be observed in the microstructure of steel in cracked areas from the inside to the outside of the pipe.

On-Coupling Mechanical, Electrical and Thermal Behavior of Submarine Power Phases

Floating offshore renewable energies (OREs), such as offshore floating wind turbines (wind energy) or wave power (wave and wave energy), are increasingly in demand. Submarine cables that transmit the energy produced from offshore farms all the way to onshore stations are critical structures that must be able to work perfectly over 20 years without any maintenance. In order to reduce the significant costs associated with electrical cables, it is important to optimize the dimensioning of the components of these cables, or to develop structural monitoring techniques that target zero and/or minimum maintenance over their lifespan. In this paper, we FEM of the impact of damage mechanisms of the conductor part of a submarine power phase on its mechanical, electrical, and thermal behavior. The main damage mechanisms are local plasticity and wire failure. The first mechanical study made it possible to obtain the elasto-plastic behavior of the conductor. The electrical study took into consideration the deformed geometry of the conductor in the elasto-plastic domain, as well as the non-homogeneous distribution of the electrical conductivity of the conductor. Their influence on the electrical resistance of the conductor was then analyzed. Finally, we studied the impact of plasticity and conductor failure on the thermal behavior of the phase. The temperature differences obtained in the numerical analysis of this work may be used further to help preventive and curative maintenance of the cables, for example, by using an optical fiber as sensor for structural health monitoring.

A Study on the Dynamic Transmission Law of Spiral Drum Cutting Coal Rock Based on ANSYS/LS-DYNA Simulation

The ANSYS/LS-DYNA software has been used in this paper to establish the coal rock coupling model. A dynamic simulation of the cutting process was used to analyze the variation of the load. Based on the dynamic analysis of the coal and rock that were cut by the spiral drum, the stress cloud diagram of the coupled model of the spiral drum and the coal and the plastic domain evolution law of the coal and the rock were obtained from the coal to the rock. The time history curves of the parameters, such as the stress and strain of the drum and the pick, were obtained, and the stress distribution of the spiral drum during the working process was ascertained. The results showed that when the spiral drum cuts the interface between the coal and the rock, the coal and the rock collapsed and the working load fluctuated. Changing the traction speed in order to change the rotational speed of the drum had a more obvious effect on the load and the stress on the drum. Through the use of simulation, the stress distribution cloud diagram of the drum was obtained. The study has shown that the stress on the end plate was significantly higher than that on the cutting blade. The maximum stress acting on the alloy head was 1209.26 MPa. This study has provided a basis for the design and optimization of the drum with regard to reliability.

Generation of Constant Life Diagram under Elevated Temperature Ratcheting of 316LN Stainless Steel

Combined influence of mean stress and stress amplitude on the cyclic life under elevated temperature (823–923 K) ratcheting of 316LN austenitic stainless steel is discussed. Constant life Haigh diagrams have been generated, using different combinations of stress amplitude and mean stress. In the plastic domain, the allowable stress was found to increase or decrease with mean stress depending on the temperature and combination of mean stress – stress amplitude employed. Strong influence of dynamic strain aging (DSA) was found at 823 K which affected the mode of deformation of the material in comparison with 923 K. Failure mode expressed through a fracture mechanism map was found to change from fatigue to necking depending on the test temperature as well as combinations of mean stress and stress amplitude. Occurrence of DSA at 823 K proved to be beneficial by way of extending the safe zone of operation to higherR-ratios in comparison with 923 K.

Elastoplastic and Damage Analysis of Trusses Subjected to Cyclic Loading

In the present paper, the Preisach model of hysteresis is extended to structural analysis of trusses damaged under cyclic loading in plastic range. Parameters for the Preisach model of cyclic plasticity are obtained from uniaxial loading experiment. Damage, as a consequence of micro cracks appearance due to alternating loading in plastic domain, is modeled using brittle elements according to Preisach procedure. Results of this research are compared with the already existing in the literature. In the paper examples of trusses under various cyclic loadings are presented.

Elasto-Plastic Stability Analysis of the Frame Structures Using the Tangent Modulus Approach

This paper presents the procedure for stability analysis of frames in elastic-plastic domain using the concept of the tangent modulus. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. Formulation of the corresponding stiffness matrices is based upon the solution of the equation of bending of the beam according to the second order theory. Numerical analysis was performed using the code ALIN, developed in the C++ programming language