Papers by Keyword: Welds

Abstract: In real conditions, bearing elements of metal structures are often subjected to the effect, both external loads, and various aggressive medium, under the influence of which corrosion processes are developed. Corrosive processes with prolonged action lead to a decrease the working area of ​​the welds and accordingly connected elements. During the examination of the technical condition of existing metal structures operating in aggressive medium, it is often necessary to perform calculations to define the reserve of strength. In case of exhaustion of material strength it is necessary to develop measures to strengthen certain weakened elements. Herewith, the quantitative assessment of the reduction of the reliability of welds remains a matter that requires additional research. To study the change in the ratio of squares of metal elements under the influence of the prolonged action of various aggressive medium, specially directed experimental studies were carried out. The results of studies allowed to determine the reserves of the strength of the welded elements in relation to the welds themselves. The ability to determine the reliability of welds depending on the reduction of the area of ​​the welded metal elements increases the operational reliability of metal structures, which for a long time are exploited in aggressive medium.

Abstract: In 2011, a new chapter was added to the Canadian Highway Bridge Design Code (CAN/CSA S6) [1] enabling the design of aluminum bridge components and structures in Canada. In 2016, activities are well underway, which will result in significant modifications to the Canadian aluminum structures code: “Strength Design in Aluminum” (CAN/CSA S157) [2] and the Canadian code for welding of aluminum structures: “Welded Aluminum Construction” (CAN/CSA W59.2) [3]. This paper discusses the philosophies employed in the development and modernization of these design codes and highlights some of the major changes to these codes. In the case of CAN/CSA S6, the new aluminum chapter was basically written from scratch. However, a practical approach was employed of using material from existing codes, where appropriate (including CAN/CSA S157, the AASHTO Bridge Design Specification [4], the U.S. Aluminum Design Manual [5], and the Eurocode [6]), and organizing the chapter to resemble as closely as possible the chapter for steel bridge structures, so that designers would be relatively comfortable with the new material. In the case of CAN/CSA S157, a significant reorganization of the code contents will be occurring in the latest edition, in order to bring it closer to the Canadian steel structures code (CAN/CSA S16) [7] where possible, again to make the code more user friendly. In the case of the aluminum welding code (CAN/CSA W59.2), changes are being considered to allow the use of technologies such as friction stir welding (FSW) and post-weld treatments (e.g. peening, grinding) for improving fatigue performance. This work is being done with input from Canadian industry experts and academics, in consultation with international experts from the U.S. and Europe. It is expected that this work will lead to substantially improved design codes, resulting in significant benefits in terms of the economics and safety implications of designing aluminum structures in Canada.

Abstract: The purpose of this study is to investigate the thermal aging of dissimilar metal welds for reactor pressurized vessels in the primary system of nuclear power plants. The influences of long-term aging of dissimilar-metal welds on microstructural and mechanical characteristics have been studied qualitatively and quantitatively. The dissimilar-metal welds composed of SA 508 Cl.3 low alloy steel and AISI 316L stainless steel are prepared after buttering alloy 82 on the SA 508 side by the gas tungsten arc welding process using Inconel 82 welding consumable. The test specimens are heat-treated at 600°C for 10000 hours at each predetermined aging time to simulate the degraded microstructure of dissimilar-metal welds subjected to high temperature and pressure. The long-term aging tests are interrupted at various stages to obtain the different level of degraded specimens. The microstructural changes in base metals and weld metal have been evaluated by the optical and electron microscope in relation with twins, grains, precipitates, and phase transformation. The residual stress and mechanical softening were also discussed in terms of microstructural changes during long-term aging.

Abstract: In this paper we considered changing the structure of the metal near the weld joint. The samples were tested under cyclic load with the asymmetry of the cycle of R=0.8 - 0.9. Influence of the weld on the cyclic strength is assessed. A methodology for determining residual life at any operation periods is developed.

Abstract: Two types of cast steel rail bogies have been affected by cracking and defects. The cast steel design was from a period when bogie loads were lower than the endurance limit. However, the bogies as manufactured included a large number of casting defects and 60 years of operations has resulted in many repairs being applied. Thus like all ageing structure, the original basis for safe operations may be invalid. Structural assurance instructions were developed based on the following work. A condition data survey was undertaken to obtain configurations and defects within the fleet. This was used to assist in identifying critical areas, types and shapes of defects. Two bogies were instrumented to obtain operational loads that were compared to modern standards to provide both a spectrum for future operations and loads for Finite Element Analysis (FEA), Fatigue and Damage Tolerance Assessment (DTA). Finite Element Models (FEM) were developed to provide internal bogie loads and stresses for use in the fatigue and DTA and identify additional critical locations not identified in the condition data survey. DTA were undertaken to determine maximum flaw sizes and to verify the safe period of operation; given the loads, usage and stress data of the previous tasks. Based on the work undertaken, instructions for continued management documenting acceptable flaw criteria, life limits, and ongoing inspections were provided.

Abstract: The failure Prediction for thick wall CrMoV steel pipes circumferentially welded was studied using the Finite Element Method (FEM) under close-ended, open-ended and axial compression conditions, respectively. The life span of failure, redistribution of stress on the welds and damage variations were obtained using damage modeling. Since there is a distinct mismatch of mechanical properties in parent material, weld material and heat affect zone, variations of damage with time, stress redistribution and failure life in each zone are different. The FEM results show that the weakness of the welds is the heat-affected zone (HAZ) where the hoop stresses increase sharply in the tertiary stage of creep. The maximum of damage of the welds lies on the inner surface of in the weld zone when failure occurs. The information is useful for assessing the performance of practical service welds in power plants pipe work.

Abstract: The detailed analysis of the tensile properties of the 1/2Y welded joint made of ultra-high strength steel S 960 QC was carried out. The analysis concerned various parts of welded joint and has been carried out with the help of both experiment and numerical simulation. Results were compared with the data measured using the ARAMIS system. The purpose of the analysis was to provide the constitutive relations for detailed analysis of the welded joint by finite element method.

Abstract: Aim of the work is to investigate different strategies in balancing material flow during direct extrusion through porthole dies. Two AA6082 hollow profiles were simultaneously extruded by a single die with different portholes extrusion ratio, dissimilar welding chambers and different bearing lengths. A strict process control was realized by measuring thermal conditions in the die by means of 6 thermocouples and on the profiles by a self calibrating pyrometer for aluminum alloy applications. Several billets were extruded at different ram speeds (2 to 7 mm/sec) and the effect of die design on surface quality, profile lengths and thermal field was recorded. The profiles were then sectioned and the position of the seam welds in the profiles identified and compared also with the profiles tip.

Abstract: The failure assessment for thick wall CrMoV steel pipes circumferentially welded at 640°C was studied using the Finite Element (FE) method under close-ended, open-ended and axial compression conditions, respectively. The life and position of failure, redistribution of stress on the welds and damage variations were obtained using damage modeling. Since there is a distinct mismatch of mechanical properties in parent material, weld material and heat affect zone, variations of damage with time, stress redistribution and failure life in each zone are different. The FEM results show that the weakness of the welds is the heat-affected zone (HAZ) where the hoop stresses increase sharply in the tertiary stage of creep. The maximum of damage of the welds lies on the inner surface of in the weld zone when failure occurs. The information is useful for assessing the performance of practical service welds in power plants pipe work.

Abstract: The goal of this research is to choose the proper method of car body welding. Properties of weld metal deposits depend on many conditions. First of all, this paper attempts to study the role of oxide inclusion sites on the transformation of austenite to acicular ferrite in steel weld metal deposits and their toughness. Safety and exploitation conditions of welded steel structure depend on many factors. The most significant of those factors are connected with materials, welding technology, state of stress and temperature. Because of that a good selection of steel and welding method is crucial to obtain proper steel structure. Car body elements of higher durability are made of low carbon and low alloy steel, very often with small amount of carbon and the amount of alloy elements such as Ni, Mn, Mo, Cr and V in low alloy steel and their welds. In the terms of the kind of steel it is used a proper welding method and adequate filler materials. In the present paper the influence of Mn, Ni, Mo, in WMD on the behaviour of steel structure for low temperature service was tested.