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  • Author: M. Miśkiewicz x
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Structure and Properties of the Glow Discharge Nitrided Layers Produced on Austenitic Steel

The study is concerned with the nitrided layers produced on ‘medical’ steel of the 316L (00H17N14M2) grade at a temperature of 450°C. The results of the microstructural observations performed by TEM and of the phase analysis of the layers are presented and discussed. The examinations were conducted in the regions extending from the surface down to a depth of about 25 um. The near-surface zone appeared to contain nitrogen austenite and fine precipitates. There were also certain phases in the lamellar form. Because of the applicative aspect of the glow discharge nitriding of 316 steel, the examinations also included its mechanical strength, in particular the static tensile strength and the low-cycle fatigue strength. The static tensile tests showed no significant differences in the yield stress between the samples in the starting state and those subjected to the low-temperature glow discharge assisted nitriding. The low-cycle fatigue tests (which, in view of the differences between the properties of the untreated material and the nitrided layers, can be classified among the most severe mechanical tests) either, indicated no essential differences in the fatigue properties of the samples subjected to the surface treatments conducted under various conditions.

Abstract

This paper presents the study of the impact of vibration induced by the movement of the railway rolling stock on the Forum Gdańsk structure. This object is currently under construction and is located over the railway tracks in the vicinity of the Gdańsk Głowny and Gdańsk Środmieście railway stations. The analysis covers the influence of vibrations on the structure itself and on the people within. The in situ measurements on existing parts of the structure allow us to determine environmental excitations used for validation and verification of the derived FEM model. The numerical calculations made the estimates of the vibration amplitudes propagating throughout the whole structure possible.

Abstract

Numerical analysis of the tensioning cables anchorage zone of a bridge superstructure is presented in this paper. It aims to identify why severe concrete cracking occurs during the tensioning process in the vicinity of anchor heads. In order to simulate the tensioning, among others, a so-called local numerical model of a section of the bridge superstructure was created in the Abaqus Finite Element Method (FEM) environment. The model contains all the important elements of the analyzed section of the concrete bridge superstructure, namely concrete, reinforcement and the anchoring system. FEM analyses are performed with the inclusion of both material and geometric nonlinearities. Concrete Damage Plasticity (CDP) constitutive relation from Abaqus is used to describe nonlinear concrete behaviour, which enables analysis of concrete damage and crack propagation. These numerical FEM results are then compared with actual crack patterns, which have been spotted and inventoried at the bridge construction site.