The surface of railway wheels running on rails is subject to damage due to rail and frictional wear, damage from wheel tread and flange wear caused by curved track operations, and damage from flats and concave wear due to braking friction heat from brake shoes. Although the surface of wheels is regularly reprofiled through periodic grinding cycles, damage occurring to the wheel surface during operation can lead to deteriorated ride quality and potential failure due to crack propagation. In domestic railway components technical standards, wheel integrity is mandated to be demonstrated through non-destructive testing. To prevent and detect failures caused by damage occurring on railway wheels, it is necessary to develop methods that could detect and evaluate surface damage. The present study investigated a method for detecting and evaluating surface damage on railway wheels using electromagnetic imaging. Results demonstrated that defects with a length of 10 mm, a width of 0.8 to 1.0 mm, and a depth of 0.2 to 1.0 mm could be adequately detected using electromagnetic scan images.

A Continuous Ship Unloader (CSU) is a facility in which multiple buckets rotate to excavate cargo from a ship to land. It is typically designed to have a lifespan of 20 years. However, fatigue damage is likely to occur before the end of its designated lifespan. This study aims to examine the possibility of extending the component"s lifespan by evaluating the remaining useful life of L-holder, a part of CSU, that has been in use for 20 years. Fatigue load history was predicted by measuring the strain with or without strain at the L-holder part requiring periodic replacement. Through tensile and fatigue tests, the remaining life was evaluated when cracks were not present. In addition, the remaining life in the presence of cracks was evaluated through destructive toughness test and fatigue crack propagation test. Life prediction results based on test cycles were obtained. The proposed guidelines are expected to be helpful for preventing CSU accidents.

Majority of deformation and ruptures as a result of severe deformation of mechanical structures are due to the existence of cracks or cracks generated through specific situations. These cracks causes stress concentration and eventually ruptures under lower load conditions than they are designed to withstand. In this study, simulation tensile analysis was done by designing compact tension specimen models with the number of holes that existed inside and the materials of the test specimens by focusing on the effects of the cracks. The study results from all the analysis (deformations, equivalent stress and strain energy) confirmed that the specimen models having two holes had better strength characteristics than those with only one hole. Additionally, the durability and strength characteristics of specific mechanical structures against the load improved through appropriate arrangement of holes thereby reducing stress generation. As such the results of this study could be utilized as the basic data for future researches on composite materials and sandwich type homogenous materials. Furthermore, the study results can assist in designing more durable products.

Transportation machine manufacturers are putting in efforts on research based on weight reduction. One of the representative materials for weight reduction is Fiber Reinforced Plastic (FRP). Increased used of FRP, glass fiber and carbon fiber could be a way of weight reduction. It is almost unavoidable to generate holes or notches during structural design. Little research have been carried out based on cracks with respect to materials used for design. The utilization of finite element analysis and the reliability of the analysis methods are increasing in order to promptly cope with the damages in materials. In this study, Compact Tension (CT) model based on ASTM E647 was designed using SM45C, steel for structural use, short fiber Glass Fiber Reinforced Plastic (GFRP), and woven type Carbon Fiber Reinforced Plastic (CFRP). In addition, J-Integral, which is a factor for determination of growth of crack that appears in cracks, was applied to general structure analysis. J-Integral is an equation of the body force of the material and strain energy in accordance with the loading force, and illustrates the crack growth using energy release rate. J-Integral values of SM45C, short fiber GFRP and woven type CFRP were found to be approximately 74,978 mJ/mm², 7492.3 mJ/mm² and 6222.4 mJ/mm², respectively.

The CSU (continuous ship uploader) is one of the most advanced and high-tech machines among the logistics facilities. It is giant heavy equipment and has a number of driving systems compared to a general crane. In general, CSU is designed to have a life of 20 years, but recently it has been increased up to 30-50 years or is being used as a semi-permanent facility. In this study, based on the structural analysis and the elasto-plastic fracture mechanics, fracture toughness test was performed on the front tension bar, which is the main load bar of the CSU machine. The J-integral analysis was performed on the front tension bar. Based on the results of the J-integral analysis and fracture resistance test, the critical crack length without instantaneous fracture was calculated and analyzed for each operating load.

Fluid Catalytic Cracking (FCC) Unit is a large-pressure vessel that converts heavy crude oil, which cannot be distilled, into light crude oil. With the growing interest in renewable energy sources due to environmental regulations, various studies investigating FCC Units are ongoing. The catalytic reactor in FCC Unit is a large structure that generates prolonged high pressure, leading to changes in the properties of the material during operation. Therefore, stress analysis must be conducted based on the application of the actual mechanical properties. In cylindrical thin structures such as the FCC reactor, a tensile test is difficult to perform, warranting the need for Shear Punch (SP) test that uses a small specimen. The properties were utilized in finite element analysis. To determine the boundary and load conditions needed for stress analysis, the operational conditions of the reactor and the conditions for internal pressure of ASME Code regulation were used to evaluate the stress.

Rolling contact fatigue (RCF) and wear caused by rolling contact between the wheel and rail are inevitable problems in railway systems. An increase in axle load or the slip ratio causes excessive wear. However, RCF and wear do not act independently, but one influences the other. Wheel and rail materials and manufacturing quality have a considerable influence on the formation of RCF and the ensuing wear. Therefore, the mechanical properties of the wheel and rail are important factors for reducing RCF and wear on the contact surface. This paper presents a comparative evaluation of the wheel and rail used in the Korean industry for high speed trains and conventional rails with respect to their fatigue and fracture behavior. A series of tests such as uniaxial tensile tests, fracture toughness tests, and fatigue crack growth tests were carried out at both room temperature and low temperatures.

The repeated thermal load on the railway wheel for tread brakes has been remarkably tightened due to increase in speed of trains and increase of operation frequency. As overheating and cooling between the wheel and brake block are continuously repeated, the railway wheel is damaged. To understand the process, thermal cracks for wheel tread can be experimentally reproduced under the condition of cyclic frictional heat from brake blocks, through bench experiments using a railway wheel. Thermal cracks generated in the wheel were investigated to observe the cracks’ initiation processes using full-scale brake dynamometer. Results show that as braking energy and braking temperature continued to accumulate, a hot spot appeared on the wheel surface and 2 mm of thermal crack occurred in the wheel rim.