• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.3
• /
• pp.283-289
• /
• 2015

In this study, the lightweight design of a brake bracket for a composite bogie was studied by considering two brake bracket models with thicknesses of 12t and 9t, respectively. For achieving this goal, finite element analysis and topology optimization were conducted. Firstly, the largest cross-sectional areas of the vertical and horizontal plates of the brake bracket were selected as the design variables. As the constraint, the Z-axis displacement of the brake bracket was increased by 2.5 units from the initial displacement value. The minimum volume fraction of the design regions was chosen as the objective function. The full model comprised a composite bogie frame and brackets attached together. However, to reduce the analysis time, 1D beam elements were used instead of the composite bogie frame by ensuring its equivalence with the full model. The result revealed that the weights of the 12t and 9t models of the brake bracket were reduced to 60 kg and 31 kg, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.5
• /
• pp.94-100
• /
• 2002

This paper is concerned with the development, and performance test of LIPCA (Lightweight Piezo-composite Curved Actuator) that is lighter than other conventional piezo-composite type actuators. LIPCA is composed of top fiber composite layers with a high modulus and low CTE (Coefficient of Thermal Expansion), a middle PZT cermaic wafer, and base layers with a high modulus and high CTE. The performance of each actuator was evaluated using an actuator test system consisting of an actuator supporting jig, a high voltage actuating power supplier, and a non-contact laser measuring system. The simply supported condition actuator was excited by the power supplier with 1.0Hz cycle and up to $100\sim400V_{pp}$. The displacement at the center point of actuator was measured with non-contact laser displacement measuring system, It has been shown that the LIPCA-C2 can 34% decrease in mass and 13% increase in displacement compared to THUNDER.

• Advanced Composite Materials
• /
• v.18 no.4
• /
• pp.327-338
• /
• 2009

In this paper, through an evaluation process conducted on several designs of mini-LIPCA (Lightweight Piezo-Composite curved Actuator), an optimal design of a mini-LIPCA has been proposed. Comparing with the LIPCA-C2, the design of the mini-LIPCA comes with reduced overall size and a thinner active layer. Since a variation in the number and lay-up of fiber composite layers may strongly affect the performance of the device, one is able to configure several designs of mini-LIPCA. The evaluation process is then followed in order to determine a configuration which characterizes the possibly optimal performance. That is, a design of a mini-LIPCA is said to be optimal if it is capable of producing a maximum out-of-plane displacement. The size of the LIPCA to be investigated was selected to be $10\;mm\;{\times}\;20\;mm$ in which the thickness of PZT plate is about 0.1 mm. The thickness of glass/epoxy and carbon/epoxy are about 0.09 mm and 0.1 mm, respectively. The evaluation process has been conducted thoroughly, i.e., analytical estimation, numerical approximation and the experimental measurement are all involved. Firstly, the design equation was used to calculate essential parameters of proposed lay-up configurations. Secondly, ANSYS, a commercial FEA package, was utilized to estimate displacement outputs of the actuators upon being excited. Finally, experimental measurements were able to verify the predicted results.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.4
• /
• pp.7-13
• /
• 2010

Linear motors are efficient mechanism that offers high speed and positioning accuracy. By eliminating mechanical transmission mechanisms, much higher speeds and greater acceleration can be achieved without backlash or excessive friction. However, an important disadvantage of linear motor system is its high power loss and heating up of motor and neighboring machine components on operation. Therefore, it is necessary to design moving table with high stiffness, high efficiency and light weight construction. This paper presents the development of moving table using composite material. In order to develop light weight construction of moving table, finite element analysis is performed to find best moving table construction and composite stacking sequence. NASTRAN and MINITAB were used as the optimizer. A prototype for the moving table using composite material was created.

• Composites Research
• /
• v.23 no.4
• /
• pp.35-43
• /
• 2010

The purpose of this paper is to develop a Hybrid Fiber-reinforced High Strength Lightweight Cementitious Composite (HFSLCC) incorporated with lightweight filler and hybrid fibers for lightness and high ductility. Optimal ingredients and mixture proportion were determined on the basis of the micromechanical analysis and the steady-state cracking theory considering the fracture characteristics of matrix and the interfacial properties between fibers and matrix. Then 4 mixture proportions were determined according to the type and amount of fibers and the experiment was performed to evaluate the mechanical performance of those. The HFSLCC showed 3% of tensile strain, 4.2MPa of ultimate tensile stress, 57MPa of compressive strength and $1,660kg/m^3$ of bulk density. The mechanical performance of HFSLCC incorporated with PVA fibers of 1.0 Vol.% and PE fibers of 0.5 Vol.% is similar to those of the HFSLCC incorporated with fibers of 2.0 Vol.%.

• Structural Engineering and Mechanics
• /
• v.50 no.5
• /
• pp.635-652
• /
• 2014

Creep and shrinkage behaviour of an ultra lightweight cement composite (ULCC) up to 450 days was evaluated in comparison with those of a normal weight aggregate concrete (NWAC) and a lightweight aggregate concrete (LWAC) with similar 28-day compressive strength. The ULCC is characterized by low density < 1500 $kg/m^3$ and high compressive strength about 60 MPa. Autogenous shrinkage increased rapidly in the ULCC at early-age and almost 95% occurred prior to the start of creep test at 28 days. Hence, majority of shrinkage of the ULCC during creep test was drying shrinkage. Total shrinkage of the ULCC during the 450-day creep test was the lowest compared to the NWAC and LWAC. However, corresponding total creep in the ULCC was the highest with high proportion attributed to basic creep (${\geq}$ ~90%) and limited drying creep. The high creep of the ULCC is likely due to its low elastic modulus. Specific creep of the ULCC was similar to that of the NWAC, but more than 80% higher than the LWAC. Creep coefficient of the ULCC was about 47% lower than that of the NWAC but about 18% higher than that of the LWAC. Among five creep models evaluated which tend to over-estimate the creep coefficient of the ULCC, EC2 model gives acceptable prediction within +25% deviations. The EC2 model may be used as a first approximate for the creep of ULCC in the designs of steel-concrete composites or sandwich structures in the absence of other relevant creep data.

• Steel and Composite Structures
• /
• v.39 no.5
• /
• pp.583-598
• /
• 2021

The composite steel reinforced concrete (SRC) columns have been widely used in Structural Engineering due to their good performances. Many studies have been done on the SRC columns' performances, but they focused on the ordinary types with conventional configurations and materials. In this study, nine new types of steel reinforced lightweight aggregate concrete (SRLAC) short columns with cross-shaped (+shaped and X-shaped) steel section were tested under monotonically axial compressive load; the studied parameters included steel section ratio, steel section configuration, ties spacing, lightweight aggregate concrete (LWAC) strength, and longitudinal bars ratio. From the results, it could be found that the specimens with larger ties ratio, concrete strength, longitudinal bars ratio, and steel section ratio achieved great strength and stiffness due to the excellent interaction between the concrete and steel. The well-confined concrete core could strengthen the steel section. The ductility and toughness of the specimens were influenced by the LWAC strength, steel section ratio, and longitudinal bars ratio; in addition, larger ties ratio with smaller LWAC strength led to better ductility and toughness. The load transfer between concrete and steel section largely depends on the LWAC strength, and the ultimate strength of the new types of SRLAC short columns could be approximately predicted, referring to the codes' formulas of ordinary types of steel reinforced concrete (SRC) columns. Among the used codes, the BS-5400-05 led to the most conservative results.

• Steel and Composite Structures
• /
• v.22 no.5
• /
• pp.1085-1114
• /
• 2016

This paper investigates the transverse impact response for ultra lightweight cement composite (ULCC) filled pipe-in-pipe structures through a parametric study using both a validated finite element procedure and a validated theoretical model. The parametric study explores the effect of the impact loading conditions (including the impact velocity and the indenter shape), the geometric properties (including the pipe length and the dimensions of the three material layers) as well as the material properties (including the material properties of the steel pipes and the filler materials) on the impact response of the pipe-in-pipe composite structures. The global impact responses predicted by the FE procedure and by the theoretical model agree with each other closely. The parametric study using the theoretical approach indicates the close relationships among the global impact responses (including the maximum impact force and the maximum global displacement) in specimens with the equivalent thicknesses, proposed in the theoretical model, for the pipe-in-pipe composite structures. In the pipe-in-pipe composite structure, the inner steel pipe, together with the outer steel pipe, imposes a strong confinement on the infilled cement composite and enhances significantly the composite action, leading to improved impact resistance, small global and local deformations.

• Proceedings of the KSR Conference
• /
• 1999.11a
• /
• pp.437-446
• /
• 1999

The structural behavior of the composite material light rail vehicle body are investigated. Composite material is very useful for light rail vehicle structure due to its high specific strength and lightweight characteristics. The main carbody is made of aluminum alloy. The side wall and roof with composite panels can reduce total vehicle weight about 2000kg. In addition, with the lower density of the foam, enhances lightness in the panel and to save the operation expenses. The finite element analysis code, ANSYS is used to evaluate the stability of the body structure under the various load conditions.

• Composites Research
• /
• v.32 no.1
• /
• pp.21-28
• /
• 2019

Recently, according to environmental regulations, the automobile industry has been conducting various research on the use of composite materials to increase fuel efficiency. However, there has not been much research on lightweight chassis components. Therefore, in this research, the purpose of this study is to apply composite materials to the sub-frame of chassis components to achieve equivalent levels of stiffness, strength, NVH performance and 50% lightweight compared to the steel sub-frame. First, the Natural frequency of steel and composite specimens was compared to the damping characteristics of composite materials. Then, in this study, the Lay-up Sequence was derived to maximize the stiffness and strength of the sub-frame by applying composite materials. And this lay-up Sequence is proposed to avoid heat shrinkage due to curing during manufacturing. This process was designed based on a FEM structural analysis, and a Natural frequency and frequency response function graph was confirmed based on a modal analysis. The prototype type composite sub-frame was manufactured based on the design and the F.E.M analysis was verified through a modal experiment. Furthermore, it was fitted to the actual vehicle to verify the natural frequency and the indoor noise vibration response, including idling and road noise. This result was confirmed to be equivalent to the steel sub-frame. Finally, the composite sub-frame weight was confirmed to be about 50% of the steel sub-frame.