Papers by Keyword: Thermal Fatigue

Abstract: Magnetic abrasive finishing (MAF) is an advanced surface finishing technology that utilizes magnetic fields to control abrasive particles, enabling precise material removal and superior surface integrity. This review paper comprehensively analyzes MAF research from 2015 to 2024, focusing on key developments, process optimizations, and industrial applications. The study looks at how MAF affects different materials like titanium alloys, stainless steels, and 3D-printed parts, showing how it improves surface smoothness, leftover stress, and resistance to wear and tear. This review paper expands on the experimental investigation of MAF’s efficacy in removing crack fatigue layers for a high-cost product to give it a high performance and longer life, a critical aspect in enhancing the functional performance of components. It is synthesizing various studies that explore the principles of MAF, the preparation of magnetic abrasives, tool design, and the process’s modeling and simulation. It also examines the force measurement and material removal mechanisms, providing a comprehensive understanding of the process parameters and their optimization. It is highlighting the challenges faced ‎in the field and suggests future directions for research, aiming to contribute to the development of more efficient and precise finishing techniques in manufacturing industries. The findings of this study are expected to benefit researchers and practitioners in MAF-related fields, paving the way for innovations in surface finishing technologies.

Abstract: In this paper present the effects of 316L steel in the environment of repeated heat load, and the impact of the thermal load on fatigue life. Using thermal fatigue experiments and ABAQUS software, rain flow counting method is used to simplify the strain cycle spectrum of stress load. The Coffin-Manson nonlinear empirical equation was established based on thermal fatigue experiments, and the fatigue life estimation was completed in accordance with the Miner damage accumulation rule and FE-SAFE fatigue software. The test rods were respectively placed at room temperature and heated at 250°C for water cooling for tensile testing. Fatigue tests were performed with 5 strain parameters (0.8%, 0.7%, 0.6%, 0.5% and 0.4%). ABAQUS and FE-SAFE software used to study 316L testing rod fatigue life verification analysis. A composite heat exchange system model made of 316L was designed for the case study. It is found that the fatigue life after heating is reduced by 35% to 12% from the experimental results and numerical simulation calculation. Therefore, when the 316L steel is subjected to thermal fatigue, the fatigue life will be reduced. The research results can provide a reference for the design of heat exchangers using 316 steel in various fields.

Abstract: A significant number of high-performance engineering structures are repeatedly subjected to both thermal and mechanical loads, often in a combined fashion. However, because of the increase in the plasticity of metallic structures when they are loaded at high temperatures, the analysis become very complex. This presents a significant obstacle for the comprehension of both the growth of cracks and the thermo-mechanical fatigue performance of the material. Thermomechanical fatigue and thermal fatigue are characterized by external and internal constraining forces, respectively. The beginning and spread of thermal fatigue cracks are controlled by a variety of factors, including the modes of heating and cooling, the temperature range, the maximum temperature rates, and the holding times. The process of a crack beginning and the rate at which it spreads are both sped up when the temperature is raised. However, because of the development of powerful statistical learning algorithms as well as rapid advancements in computational power, there has been an increased adoption of machine learning approaches as well as other advanced computational analyses and numerical software for crack damage detection and damage severity. This has led to an increase in the use of these methods.

Abstract: — Corrosion is prevalent throughout the world, none less so than in the oil and gas industry. Managing and mitigating corrosion in refining complexes is of paramount importance in order to prevent undesirable consequences such as major fires, explosions and Boiling Liquid Expanding Vapor Explosion (BLEVE) due to Loss of Primary Containment caused by the thinning and ultimate failure of pipelines and vessel walls. Analysis of a platformer unit at a Malaysian refinery has identified the occurrence of thermal fatigue and erosion corrosion on the Vent Gas Tower (VGT) Caustic Circulation line, which in turn has led to the excessive degradation of the walls of a venturi scrubber and the 8’’ caustic circulation line with initial thickness of 12.70mm. The rate of corrosion (0.88 mm/year) of the 8’’ caustic circulation line exceeds the standard allowable carbon steel corrosion rate (0.1 mm/year) as stated in API 571 Damage Mechanisms Affecting Fixed Equipment in the Refining Industry. This indicates that the circulation line has significant potential to fail which would lead to a major HSE incident. Based on these findings it is recommended that the refinery in question modifies the line by increasing the thickness of the line and include a cooling system to reduce temperature swing (ΔT) to below 93°C. Besides that, it is suggested that the implementation of Corrosion-Resistant Alloys (CRA) is conducted on the line. According to ASME B31.3 and supported by ASTM A 193, the line can be replaced with nickel-based alloy, alloy 800H and killed carbon steel which have high resistivity to corrosion than carbon steel. However, more comprehensive studies need to be conducted to identify the viable mitigation methods that are suitable to be implemented on the Vent Gas Tower (VGT) Caustic Circulation line.

Abstract: This contribution presents a methodology for the structural analysis of the exhaust manifold of an internal combustion engine. In particular, the thermal loading and the related thermal fatigue damage mechanism are addressed. The component investigated is a melted exhaust manifold which includes the turbine involute. The complex geometry of the component derives from the project constrains in terms of engine performance and sound targets. Finite Element simulations are performed to obtain a virtual approval of the component geometry, in advance with respect to the component manufacturing. The Finite Element analysis accurately follow the experimental approval procedure which considers different warming and rapid cooling cycles to mimic typical engine operating conditions. Two particular aspects of the developed numerical methodology are described in details: a) the elasto-plastic behaviour of the material at high temperatures; b) a damage criterion for thermal fatigue. Following the Ferrari expertise derived by previous experimental and numerical analysis of other exhaust manifolds, the increase of the equivalent plastic strain registered for a single thermal cycle (delta PEEQ) is firstly adopted as a damage criterion. The methodology reveals itself to be well correlated with the experimental evidences thus limiting the number of tests necessary for the component approval.

Abstract: The bimetallic weld joints are widely utilized in the pressurized water reactors, boiling water reactors, heat exchangers in process industries, heat transport piping system utilized in nuclear plants, etc. The present study is aimed at analyzing the bimetallic weld strength degradation due to thermal fatigue. For generating thermal fatigue like conditions, an experimental test rig has been developed. The bimetallic weld between low alloy steel SA 516 grade 70 and stainless steel 304 L was prepared. The experimental results show that, heating time, notch radius and number of cycles have the effect on tensile properties of bimetallic welds.

Abstract: In this paper the effect of thermal fatigue on mechanical behaviour of the heat affected zone on ferritic side of bimetallic weld was investigated. The bimetallic weld coupons between ferritic steel SA516 Grade 70 and stainless steel 304L were fabricated using TIG (Tungsten Inert Gas) welding process. In this investigation, an experimental test rig was developed and used to simulate the thermal fatigue conditions at laboratory scale. The thermal fatigue factors selected were heating time, notch radius and number of cycles.

Abstract: Thermal fatigue tests of superalloy GH536 were carried out at different maximum temperature. Three-dimensional numerical finite element computations were performed to simulate thermal fatigue test process. The crack initiation, propagation and thermal fatigue failure mechanism of GH536 plate at different maximum temperatures were obtained by experiments and numerical methods. Result shows that the crack initiation life is shortened and the crack growth rate is accelerated with the increase of the maximum temperature of thermal fatigue test. The numbers of appearing 1 mm length cracks are 180, 74 and 37, respectively, when the maximum temperature is 800°C, 850°C and 900°C respectively. So the thermal fatigue performance decreases with the increase of the maximum temperature. But in the thermal fatigue tests of different maximum temperature, the thermal fatigue crack initiation is all caused by a single crack initiation source, and the thermal fatigue cracks initiate transgranularly, develop and propagate intergranularly.

Abstract: An experimental and numerical study on interlaminar thermal fatigue induced delamination in unidirectional carbon fiber reinforced laminate is presented in this work. The studied material consists of a unidirectional prepreg carbon fiber/epoxy (AS4/8552), which has the anti-symmetrical [90₂/0₂]_T X-ply lay-up. A Teflon^® film insert was introduced into the material between the third and fourth outer layers to simulate pre-existing crack. The samples were tested under thermal cycle condition within a temperature range of 130°C and -70°C. The curvature variation with the number of cycles was measured during the tests and presented along with the crack growth rate or delamination rate (da/dN) as a function of energy release rate amplitude (), which is the arithmetic difference between G_H and G_L that occur at lowest and highest temperatures respectively. The experimental results were compared with numerical results obtained using ABAQUS Finite Element code. A good correlation in terms of crack growth rate (da/dN) as a function of the energy release rate range () was obtained between experimental and numerical results. Furthermore, the results show that the experimental curvature decrease with increasing number of cycles, and its behavior varies with the range of thermal load imposed on the specimen.

Abstract: The difficulties and issues associated with the economics of the process and die life in casting aluminium alloys, as experienced by the high pressure die casting industry, were reasons behind undertaking this research project. The use of a tungsten alloy able to withstand high temperature process conditions without the welding problems experienced by standard die construction materials, such as H13, was examined in an extensive series of casting trials. The importance of operating dies at elevated temperatures to minimize heat checking has been demonstrated previously, both through theoretical thermal modelling and experimentation. This paper describes both aspects of die life extension and possibilities to reduce the amount of alloy material used in the cast part feed system, including overflows. CSIR intends using the results of this research for further development and application of high temperature die construction materials in high pressure die casting processes of light metal alloys.