Papers by Author: Heung Seob Kim

Abstract: Structural analysis of automotive engine cover under vibration excitation is performed by finite element analysis (FEA) in order to identify the critical area of the structure. Assembly load due to the tightening of the bolts as well as the vibration excitation were considered to describe the actual loading condition. Natural frequencies of the system were extracted considering the damping effect of the structure. Dynamic analysis was performed based on the extracted natural frequency of the system. Experimental modal analysis (EMA) and measurement of strains were performed to verify the results of the analysis. Analysis results correlated closely with the experimental results. Analysis and experiments showed that contribution of the assembly load should not be ignored to predict the structural failure of the engine cover.

Abstract: This paper deals with the fatigue behavior and its statistical properties of SM490A steel at various temperatures, which is utilized in the railway vehicle. For these goals, the tensile ad fatigue tests were performed by using a servo-hydraulic fatigue testing machine at three temperatures: +20°C, -10°C and -40°C. The static strength and fatigue limits of SM490A steel were increased with decreasing of test temperature. The probabilistic properties of fatigue behavior are investigated by means of probabilistic stress-life (P-S-N) curve and they are well in conformance with the experimental results regardless of temperature. Also, based on P-S-N curves, the variation of fatigue life is investigated and as the temperature decreases, the variation of fatigue life increases moderately.

Abstract: This paper deals with the damage resistance of glass/epoxy laminates with embedded shape memory alloy (SMA) subjected to low-velocity impact at various temperatures. For this goal, the impact tests were performed by using an instrumented impact-testing machine at three temperatures: +20°C, -10°C and -40°C. And the resultant damages were inspected through the scanning acoustic microscope (SAM). Also, based on the impact force history and the damage configuration, the impact resistance parameters were employed to evaluate damage resistance of laminates with embedded SMA wires. As results, it was found that the damage resistance of glass/epoxy laminates with embedded SMA wires is dependent on the service temperature.

Abstract: This paper deals with the damage behavior of glass/epoxy composite laminates subjected to low-velocity impact at various temperatures. For this goal, the impact tests were performed by using an instrumented impact-testing machine at three temperatures: +20°C, -10°C and -40°C. And the resultant damages were inspected through the scanning acoustic microscope (SAM). Also, based on the impact force history and the damage configuration of the laminates, the impact resistance parameters were employed to evaluate damage resistance of glass/epoxy laminates. As results, it was found that the temperature changes affect the damage resistance capacity of glass/epoxy laminates.

Abstract: An automotive transmission (TM) rubber mount is a device that is used in automotive systems to cushion the loads transmitted from the vehicle body structure. A TM rubber mount is used to support the engine in the vertical direction. However, the dynamic behavior of loaded rubber mount is not yet known to a reasonable degree of accuracy. The relationship between the force applied to a TM rubber mount and the resulting deformation exhibits features of viscoelasticity. Therefore, in this study, viscoelastic properties were measured during ramp-toconstant displacement control tests. A force-displacement relationship for a TM rubber mount is important for multi-body dynamic numerical simulations. Hence, an explicit force-displacement relationship was developed and expressed in terms of a force relaxation function. A method that can be used to determine the force-displacement relationship from experimental data for a TM rubber mount was also developed. Solutions were obtained and the results were compared with experimentally measured force-displacement behavior. The predictions of the proposed forcedisplacement relationship were in very good agreement with the experimental results.

Abstract: In automotive applications, a particular area of concern is the relation between thermoelastically induced hot spots and noise and vibration in brake system. The finite element methods have been extensively used for thermal analysis applied to brake components. The two-dimensional model has been extended to an annular three-dimensional disc model in order to consider more realistic braking condition. In a conventional braking analysis, the interface pressure is assumed either constant or inversely proportional to radius. However, under the dynamic braking conditions, the frictional heat generated during braking causes thermoelastic distortion that modifies the contact pressure distribution. This paper describes the thermo-elastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation under single braking and repeated braking mode.

Abstract: The connecting rod is one of the most important parts of an engine system. It fits in between the crosshead and the crankshaft and converts the piston’s reciprocating motion to rotary motion with the crankshaft. The connecting rod is subjected to a complex state of loading. High compressive loads and high tensile loads are due to combustion and connecting rod’s mass of inertia, respectively. This is why the connecting rod is the most stressed part of an engine system. If the engine is operating, connecting rod fails, this could cause a critical situation. Therefore, the connecting rod should be able to withstand tremendous load and transmit a great deal of power smoothly. In general, the failure occurs at the big end of connecting rod. Hence, the connecting rod’s big end corner radius was taken as a design variable. Also, three dimensional finite element analyses were performed. From these results, the stress distribution was estimated and the value of the corner radius was optimized.

Abstract: The goals of the paper are to identify the impact damage and strength reduction behavior of sandwich structure, composed of carbon/epoxy laminates skin and Nomex core with two kinds of thickness (10 and 20mm). For these, low velocity impact tests were conducted using the instrumented impact-testing machine and damages are inspected by SAM. And then, subsequent static tests are conducted under flexural loading to identify the strength reduction behavior of the impacted sandwich structures. The impact damages are mainly delamination in carbon/epoxy skin and their behavior is mostly independent of core thickness. Also, their energy absorbing behavior is identified through calculating the energy absorbed by impact damage. Finally, the strength reduction behavior is evaluated through Caprino’s model, which was proposed on the unidirectional laminates.

Abstract: The goals of this paper are to identify the impact damage behavior of plain-weave E-glass/epoxy composites and predict the fatigue life of the composites with impact-induced damage under constant amplitude loading. To identify these behaviors, the low velocity impact and fatigue after impact tests are performed for glass/epoxy composites having two types of fiber orientations. The impact damage behavior is dependent on the fiber orientation of the composites. The fatigue life of the impacted composites can be identified through the prediction model, which was proposed on the carbon/epoxy laminates by authors regardless of fiber orientations.

Abstract: As the automobile industry develops, the demand for automobiles that provide more comfortable ride and safety is also increasing. In the conventional braking analysis, frictional heat generation is only related to wheel speed, friction material, and the interface pressure. However, under the dynamic braking conditions, the frictional heat causes the thermo-elastic distortion that leads to more concentrated distribution of contact pressure and hence more and more non-uniform temperature. This paper describes the thermo-elastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation.