Steel Casing Research Articles

하청업체 노동조합의 단체교섭 상대방으로서의 원청사업주의 사용자성 —제조업에서의 최근 하급심판결과 중앙노동위원회 판정을 중심으로—

Recently, the Busan High Court ruled in the Hyundai Heavy Industries case and the National Labor Relations Commission(NLRC) ruled in the Hyundai Steel case. Both cases are cases in which labor unions of in-house subcontractors demanded collective bargaining from users of the contractor. The court denied the status of the original company

Analysis of thermocouple-based finger contact temperature measurements

The understanding of heat conduction during finger contact with cooler or hotter objects is important for designing many electronic devices and for setting safety standards in a variety of occupational settings. In the most common experimental approach to study this process, a micro-thermocouple is placed at the finger-object interface. However, the interpretation of what this measurement corresponds to is not clear. To this end, we develop a three-dimensional thermal simulation of the finger-thermocouple-substrate configuration. The model predictions match finger cooling measurements in eight distinct cases available in prior literature (finger pressed with 1 N or 9.8 N against a steel or an aluminum substrate held at −2 °C or −10 °C). We demonstrate that the thermocouple can be represented accurately as a truncated sphere with emerging cylindrical wires while a multilayer block model of the finger provides similar results to an anatomically representative model. Our simulations show that in the eight previously studied cooling cases, the average surface temperature of skin that is in contact with the substrate follows nearly the same but offset cooling trend as the thermocouple tip temperature. The value of the offset is predominantly determined by the substrate material, with the thermocouple tip temperature being lower than the average skin surface temperature by 1–5 °C and 3–10 °C for steel and aluminum substrate cases, respectively. This temperature difference results in a moderate to an extreme thermocouple underprediction of the time necessary for the skin surface to reach the experimental safety threshold of 1 °C. Consequently, from the perspective of the safety related applications the thermocouple measurement provides a conservative limit on the contact duration and thereby is suitable for such purposes, but for applications requiring accurate skin temperature measurements alternative experimental approaches should be used.

Investigation of the ultrasonic welded stainless steel corrosion resistance

This article will present the ultrasonic welding technology of the stainless steel sheets, the joining with agreeing of the material science theory and metal-working rules-based executed experiments. Fusion welding is well understood and investigated in the case of steel. The ultrasonic welding in the case of metals causes different changes in the metals structure. The ultrasonic welding cause complex effect during the welding process. These effects are plastic deformation, heat, and ultrasound vibration. The goal of this research is to show the case of the experimented welded stainless steel (X5CrNi18-10) to determine the corrosion behaviour by non-destructive (visual test and microscopy) inspections. The stainless steel is sensible for all processes even that the cold working, heating and ultrasound effect. These effects can cause a decrease in the corrosion resistance of stainless steel.

The effect of combined loading on the behavior of micropiled rafts installed with inclined condition

One of the major disadvantages of micropiles is their low lateral stiffness and flexural rigidity due to the small diameter. This limitation can be handled in current practice, by installing the micropile with inclined condition or providing a steel casing. Additional steel casings will increase the lateral load capacity of micropiles but increase the project cost as well. Thus, inclination of micropile which is relatively simple and cheap is recommended. In this paper, a comprehensive numerical analysis is conducted on the behavior of micropiled rafts installed with inclined condition under combined vertical and lateral loading. A FEM calibrated against full-scale axial and lateral field tests is used to conduct the analysis. The soil profile is soft clay soil underlain by a layer of dense sand. The study investigates the impact of several parameters which are as follows: magnitude of vertical loading, reinforcement type, inclination angle of micropiles, and number of inclined micropiles. The study reveals that increasing vertical loads causes continuous decrease in the lateral load capacity of micropiled rafts. When all micropiles installed are inclined, the positively inclined micropiles carry 79–86% of the total lateral load carried by micropiles, whereas the negatively inclined ones carry 14–21%. Inclined micropiles offer greater lateral load sharing ratio (αh) than that of vertical ones, largest at θ = 45°. The effect of micropile reinforcement on improving the lateral performance is low compared to the effect of micropile inclination angle.

Thermal modelling of cylindrical Lithium‐Ion batteries to study the impact of structural components

AbstractTemperature has a profound impact on the performance of lithium‐ion batteries. The temperature distribution in the cylindrical cell during charging and discharging cycles is governed by physical features of materials such as thermal conductivity and specific heat capacity. The cells must operate at their optimal temperature. The eight thermal models were build by finite element analysis on the COMSOL Multiphysics 5.6 software. With inputs and average characteristics such as open‐circuit voltage (OCV), state of charge (SOC), thermal conductivities, specific heat capacities, and density of the materials employed, the software develops a two‐dimensional thermal model. The thermal model is designed to work with a cylindrical 18 650 lithium‐ion battery. The cell's initial temperature is 298.15 K. After the simulation, the results are interpolated to the 1500s. The thermal distribution in the axial and radial directions is investigated, with the conclusion that certain elements have a greater impact on the cell temperature distribution. The results show that the temperature distributions of the cell are greatly influenced by the steel case around the cylindrical structure, steel needle, electrolyte filled in between the cavities, and relief valve.

Sustainable service oriented equipment maintenance management of steel enterprises using a two-stage optimization approach

Equipment maintenance management is essential for steel enterprises to provide sustainable production services. However, few studies have considered the equipment maintenance scheduling of steel enterprises due to the characteristics of large-scale and complex constraints. This study analyses the characteristics of equipment maintenance scheduling in the steel industry and incorporates multiple complex constraints into a mathematical model. To find an optimal or near optimal solution, a two-stage optimization approach is developed that introduces the rule-based prescheduling method to quickly obtain a reasonable maintenance plan in the first stage and employs a modified genetic algorithm to further optimize the prescheduling maintenance plan in the second stage. The case of Baowu Steel is used for verification and the experimental results demonstrate the superiority and effectiveness of the proposed optimization approach, which improves the comprehensive performance by 40.3% on the basis of prescheduling.

Understanding Material Selection Challenges in Geothermal Well and Systematic Qualification Approach

Geothermal wells are usually operated under High Temperature High Pressure (HTHP) conditions where corrosion is the major threat to the well integrity. As a result, high operation cost and production time loss due to a short life span of steel casing reported in less than two years. This paper describes a study of the casing problems and failures observed in geothermal wells and a possible approach to optimize material selection and qualification of geothermal wellhead system materials.

Responses of steel casing composite piles of bridges under impact loads

Impact-induced damage to piles threatens bridge safety. Hence, the impact behaviour of a widely employed type of steel casing composite (SCC) pile needs to be investigated. To improve the understanding of the impact behaviours of SCC piles, pendulum impact tests were conducted on 21 specimens. The effects of the steel casing length, impact mass and velocity, and superstructure mass on the impact responses and failure mode of the piles were systematically investigated. In the absence of the upper mass (during the construction stage of bridges), piles with the optimum steel casing length sustained flexural failure within the wrapped region, whereas the short steel casing led to a more concentrated and brittle failure of the uncased concrete near the casing bottom. Furthermore, with an increase in the impact velocity, failures of piles with short steel casings transferred from bending to bending-shear. However, in the presence of the upper mass (during the service stage), piles with the optimum casing length failed in the cap-pile joint owing to high inertia. By revealing the failure behaviour of SCC piles under different impact conditions, the present study provides insight into the impact design and damage evaluation of SCC piles in practice.

Editor's Introduction

Editor's Introduction

Numerical Investigation of Outflow of Non-Metallic Inclusions during Steel Refining in the Ladle.

The article presents the results of numerical simulations of liquid steel flow in the main steelmaking ladle. The paper analyses the mechanism of the outflow of non-metallic Al2O3 and MnS inclusions with diameters in the range of 4–27 µm. The simulations were performed with ANSYS Fluent software. In order to determine the shape and size of non-metallic inclusions formed in the main ladle during steel refining, the collected samples of liquid metal were analysed using a scanning microscope with SEM/EDS and LM (light microscopy). Simulation tests and calculations were carried out for the case of steel refining under the conditions of the Cognor SA HSJ Department in Stalowa Wola (Poland). The presented method of using simulation tests to optimize the technology of steel refining in the ladle is an example. The analysis of the results shows that the gas flow in the metal volume has the greatest impact on the outflow of non-metallic inclusions in the steelmaking ladle.

High-Precision Probabilistic Imaging for Interface Debonding Monitoring Based on Electromechanical Impedance

Solid rocket motors (SRMs) are widely used in the aerospace and missile industries. The interface debonding between propellant/insulator/case determines the life of an SRM. Therefore, monitoring and further locating interface debonding are crucial to prevent catastrophic structural failures of an SRM. The electromechanical impedance (EMI) technique based on piezoelectric wafer transducers is a simple and sensitive structural health monitoring (SHM) method. In this study, a high-precision probabilistic imaging method of EMI for the debonding monitoring of the SRM case–insulator interface is proposed. In this method, the Gaussian window function is used to describe the variation of debonding damage index with the position. In addition, an experimental procedure based on simulated damage is presented to determine the parameter in the Gaussian window function. Finite element models of the steel case–insulator structure based on Rayleigh damping are established to analyze the effects of debonding and simulated damage on EMI signals. An experiment is conducted to verify the proposed probabilistic imaging method and the finite element analysis results. It is proved that the proposed probability method can achieve high-precision imaging of debonding of SRM case–insulator, even after several months of storage.

3D Correlative Imaging of Lithium Ion Concentration in a Vertically Oriented Electrode Microstructure with a Density Gradient.

The performance of Li+ ion batteries (LIBs) is hindered by steep Li+ ion concentration gradients in the electrodes. Although thick electrodes (≥300 µm) have the potential for reducing the proportion of inactive components inside LIBs and increasing battery energy density, the Li+ ion concentration gradient problem is exacerbated. Most understanding of Li+ ion diffusion in the electrodes is based on computational modeling because of the low atomic number (Z) of Li. There are few experimental methods to visualize Li+ ion concentration distribution of the electrode within a battery of typical configurations, for example, coin cells with stainless steel casing. Here, for the first time, an interrupted in situ correlative imaging technique is developed, combining novel, full‐field X‐ray Compton scattering imaging with X‐ray computed tomography that allows 3D pixel‐by‐pixel mapping of both Li+ stoichiometry and electrode microstructure of a LiNi0.8Mn0.1Co0.1O2 cathode to correlate the chemical and physical properties of the electrode inside a working coin cell battery. An electrode microstructure containing vertically oriented pore arrays and a density gradient is fabricated. It is shown how the designed electrode microstructure improves Li+ ion diffusivity, homogenizes Li+ ion concentration through the ultra‐thick electrode (1 mm), and improves utilization of electrode active materials.

Miniaturized Casing Collar Locator for Small Downhole Robots

Despite advances in robotics for many harsh environments, the downhole environment is rarely accessed by robots. Small, autonomous robots for logging oil and gas wells potentially offer significant cost savings over conventional wireline logging tools, but there are some major technical challenges to overcome. Among these is navigation or how the robot can know its own position along the well. Oil and gas wells are lined with steel casing, made up of 40-ft-long pipe joints held together by threaded collars. The collar locations could potentially be used as features for navigation, but conventional magnetic casing collar locator (CCL) sensors are large and must be mechanically stabilized within the casing. This letter investigates the design of CCLs for small, untethered robots with limited energy resources.

Optimization of axial load carrying capacity of CFST stub columns

Concrete filled steel tubular (CFST) columns are widely used due to their enhanced mechanical properties. The interaction between the concrete core and the steel casing increases structural stability and magnifies the compressive strength of concrete. Besides the structural performance, in alignment with the commitment of the concrete industry to reduce its environmental impact, lowering the carbon emissions caused by the production of concrete structures is gaining importance in recent years. The current paper gives an overview of the equations available in the literature that predict the axial load carrying capacity of rectangular CFST columns. A modified version of the Jaya metaheuristic algorithm is being proposed and the outcome of this algorithm is being presented. The algorithm is used in order to maximize the axial load-carrying capacity of a stub column. As an optimization constraint the CO2 emission associated with the production of the CFST column is being kept below a predefined level throughout the optimization process. The optimization process as well as the cross-sectional dimensions associated with the optimum solution are presented.

Microscopic mechanical simulation and experimental demonstration of deformed-induced failure for Li-ion battery package in electric vehicle

A microscopic finite element model validated by the quasi-static mechanical test on lithium ion battery cell is presented in this study. The investigated condition involves three-point bending and cell discharge test, which include the mechanical response and thermal response of lithium ion battery cell. The cell is investigated through computational simulation. Results show great correlation between the experiment and finite element simulation. A microscopic model requires a greater effort during simulation. Investigating the fracture on steel casing and cell core is possible by considering the fracture mechanism in steel shell and jelly roll. The classic von-Mises criterion is applied to predict the failure of carbon steel shell, and the maximum von-Mises strain criterion is used to investigate the jelly roll region. On the basis of the verified battery cell model, battery package with microscopic model, including cell core (cathode, anode, and separator) is constructed to analyze the mechanical response of battery pack. The von-Mises criterion is used to predict the fracture point location of the battery pack with various packing modes and packing densities.

Experimental and Numerical Study on Fatigue Behavior of RC Beams Strengthened with U-Shaped Steel Casing

Experimental and Numerical Study on Fatigue Behavior of RC Beams Strengthened with U-Shaped Steel Casing

A study on optimization of anode groundbeds for cathodic protection of deep well casings based on the boundary element method

AbstractAs a kind of basic facility in oil and gas exploitation, the deep well casing is often subjected to corrosion. Cathodic protection (CP) is an important technology to mitigate the corrosion of the deep well casing. However, the casing works in a deep well thousands of meters deep underground and passes through different stratigraphic structures with various soil environments. Besides this, in a casing well group including multiple casings, there are interactions between different casings. These problems make it difficult to design the anode groundbeds for the CP of the deep well casings and evaluate the effectiveness of CP system. Therefore, the optimization of anode groundbeds for CP of deep well casings was studied based on the boundary element method in this paper. The polarization behaviors of steel casing in different depths were measured in the field. And then the mathematical model for the CP of the deep well casing was built based on the geometric structure of casing, stratified soil resistivity, and polarization characteristics. The optimum design parameters of anode groundbeds for casing CP were explored by a numerical simulation with the boundary element method to provide a reference for the design and evaluation of CP systems for deep well casings.

Residual stress relaxation in the carburized case of austenitic stainless steel under alternating loading

Low-temperature gaseous carburization is an effective thermochemical surface modification process for austenitic stainless steels. The treatment results in the development of a carbon-enriched case with high hardness, improved localized corrosion performance and high compressive residual stress, that in principle improves the fatigue performance. Residual stress relaxation occurs during cyclic loading and the residual stress relaxation in carburized case on 316L austenitic stainless steel under cyclic loading was investigated with rotating bending fatigue testing. Two stages of residual stress relaxation in the surface region were identified: an instantaneous and large relaxation in the first cycle followed by gradual relaxation with the number of fatigue cycles. Depth-resolved analysis of residual stress showed that relaxation mainly occurs in the surface-near region of the carburized case. The rate of stress relaxations depends on the amplitude of the alternating load. The occurrence of plastic accommodation provoked by lattice expansion and the additional plastic deformation imposed during loading is decisive for stress relaxation. A model of surface residual stress evolution for carburized case under cyclic loading was established, which could accurately describe the relaxation.

Modeling carbonation and chloride ingress in well cements

The long-term durability of the wellbore system has become an important topic in recent decades. Specifically in a CO2 underground storage system, both the ingress of chloride and the leaking of carbon dioxide (CO2) can lead to severe degradation of the system, including corrosion of steel casing, and carbonation of the cement annulus. In this paper, a model was developed to consider the coupling effect of the carbonation reaction and chloride diffusion in well cement. The stoichiometric model was first applied to calculate the chemical compositions change of the well cement during the hydration process and the carbonation process. The chloride diffusion coefficient of carbonated well cement was calculated based on the general self-consistent (GSC) model and pore tortuosity. After that, the concentration of free chloride ions was predicted based on Fick's law, which takes into consideration released bonded chloride in the carbonated cement. The proposed model was validated based on available experimental data, and a comparison was made between the proposed model and other previously published models. The model has great significance for the safe and reliable geological storage of CO2. As described in this paper, the model can be used to predict the durability of a CO2 wellbore system and to inform the design of future systems.

Failure Cases of Stainless Steel 316/316L Pipe Welds in Moist Hydrogen Sulfide Environment

Failure Cases of Stainless Steel 316/316L Pipe Welds in Moist Hydrogen Sulfide Environment