• Journal of Biosystems Engineering
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• v.33 no.4
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• pp.224-229
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• 2008

This study was aimed to minimize the impact force and vibration transmitted to the transporting materials from the trailer and wheel shaft by installing the leaf spring suspension device at the space between the wheel shaft and frame of power tiller trailer. The developed trailer equipped with leaf spring suspension device was compared to the existing trailer without suspension device, in order to identify the vibration absorption effect of the leaf spring. The results of this study could be summarized as follows; (1) The length and the maximum bending amount of the leaf spring were designed as 1,000 mm and 42 mm, respectively, considering the possible space for installing at below the trailer. When 4 leaf springs were installed on both wheel shafts, the allowable maximum load was identified as 9,418 N. (2) The average vibration accelerations for the frequency less than 20 Hz, where the severe transporting loss could be represented, were $0.017\;m/s^2$ and $0.133\;m/s^2$ for the developed and the existing trailer, respectively, showing the vibration absorption effect of about 87%. And the average vibration accelerations on the driver's seat for the frequency less than 20 Hz were $0.01\;m/s^2$ and $0.20\;m/s^2$ for the developed and the existing trailer, respectively, which showed the similar vibration absorption effect. (3) The change of the average vibration accelerations for the frequency from 20 Hz to 80 Hz showed the similar tendency with the result for the frequency less than 20 Hz, but the effect for developed trailer was reduced slightly. And the effect of vibration absorption for the above 80 Hz was reduced highly. However, by installing the leaf spring suspension device at the trailer, the low frequency below 40 Hz, which could affect on transporting loss severely, could be reduced highly. (4) The maximum vibration acceleration for the frequency less than 20 Hz were $0.027\;m/s^2$ and $1.267\;m/s^2$ for the developed and the existing trailer, respectively. And the change of maximum acceleration between 20 Hz and 120 Hz was showed similar tendency with the result for the frequency less than 20 Hz, but the width of change was reduced highly.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.294-298
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• 2015

According to the results of "Highway Bridges Long Life Repair Plan." The most serious damage to RC slabs is caused by fatigue deterioration, which results from the driving loads of large-sized vehicles, and aging of materials. In response to this, adhesion reinforcement using carbon fiber sheet is being adopted. In addition, carbon fiber strand sheet that holds the same material characteristics as CFS, but has superior workability, has been developed as a new reinforcement material. However, almost no studies have been conducted on CFSS in relation to fatigue resistance evaluation through fatigue tests under running wheel loads, with the exception of a few by some organizations. Therefore, in this study, specimens with front CFS adhesion reinforcement on the bottom surface of the RC slab and specimens with grid-type CFSS reinforcement were manufactured. Then, fatigue tests under running wheel loads were conducted, and thus fatigue resistance was evaluated using the specimens.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.163-166
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• 2005

A hole expansion process is an important process in producing a hub-hole in a wheel disc of a vehicle. In this process, the main parameter is the formability of a material that is expressed as the hole expansion ratio. The hub-hole expansion process is different from conventional forming processes or hole flanging processes from the view-point of its deformation mode and forming of a thick plate. In the process, a crack is occurred in the upper edge of a hole as the hole is expanded. Since prediction of the forming limit by hole expansion experiment needs tremendous time and effort, an appropriate fracture criterion has to be developed fur finite element analysis to define forming limit of the material. In this paper, the hole expansion process of a hub-hole is studied by finite element analysis with ABAQUS/standard considering several ductile fracture criteria. The fracture mode and hole expansion ratio is compared with respect to the various fracture criteria. These criteria do not predict its fracture mode or hole expansion ratio adequately and show deviation from experimental results of hole expansion. A modified ductile fracture criterion is newly proposed to consider the deformation characteristics of a material accurately in a hole expansion process. A fracture propagation analysis at the hub-hole edge is also performed for high accuracy of prediction using the new fracture criterion proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.119-127
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• 2014

The application of sulfur polymer emulsion (SPE) as an acrylate substitute for semi-rigid pavement grout was evaluated, and the performance improvement by employing PVA fibers were also evaluated. The result indicated that the filling ratio of semi-rigid pavement material decreased as the fiber content increased, but it was measured to be 92~94% in every mixing condition, which satisfies the target performance, 90%. The maximum Marshall stability value of semi-rigid pavement material was measured to be 25.4 kN, which is about 4.7 times higher than the Korean Standard required for semi-rigid pavement material, 5.0 kN. The dynamic stability evaluation of semi-rigid pavement material indicated that the resistance to deformation from the wheel tracking test was improved by an SPE substitution, and in every mixing condition, the deformation converged to a constant value after 45 minutes with the same dynamic stability of 31,500 times/mm. The strain at the flexural failure was about 0.53%, which shows superior rigidity to asphalt pavements. The examination of abrasion resistance and impact resistance showed that the loss ratio was 9.8~6.0% in every mixing condition, which indicates a good abrasion resistance. Also, when fiber content ratio was 0.3%, the impact resistance was 2.82 times higher compared to plain (i.e., when fibers were not added). In the limited range of this study, an SPE substitution ratio of 30% was found to be an optimal level considering the mechanical and durability performance. In addition, it is thought that semi-rigid pavement material with superior performance could be manufactured if fiber content ratio up to 0.3% is applied depending on the purpose of use.

• International Journal of Railway
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• v.2 no.2
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• pp.43-49
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• 2009

Wear and rolling contact fatigue (RCF) defects are most important causes of rail damage, and often interaction competitive at present railway track. Head check is one of rolling contact fatigue (RCF) defects, and generally occurs in mild circular curves and transition curves that are set at both ends of sharp circular curves. Wear tends to limit the crack growth of head checks by removing the material from the RCF surface. In order to clarify the conditions of the occurrence and growth of head checks, the authors measured the interacting forces between wheels and rails and the angle of attack of wheelset, and carried out contact analyses using the actual profile data of wheels and rails. The effects of the lateral force, the contact geometry, and the wear rate at rail gauge comer on the formation of head checks were also analyzed by using the worn profiles of actual wheels and rails and the data obtained by a track inspection car. Some specific range of wear rate at the gauge comer was identified as having close relation with occurrence of head checks.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.172-181
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• 1999

The brakes employed on commercial vehicles must be able to withstand three types of demanding services which are use-emergency stops from high speed, many repeated stops as in a delivery or bus route, and speed control in mountain descents. Two type of friction brakes are in use ; drum breaks and disc brakes. Drum brakes are of the internally expanding type in which two shoes fitted externally with friction material are forced outward against the inside of a rotating drum on the wheel unit. In this case, the Braking power is produced by the friction force between a drum and a lining, and is converted into heat. In this research an unsteady state heat transfer analysis for drum brake system of heavy truck has been performed by ABAQUS/standard code in the case of single-braking and the repeated braking condition. The temperature histories obtained by the finite Element analysis have been compared with the result calculated by the simplified formulation and the result obtained by the experiment of real vehicle conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1011-1017
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• 1999

Electrolytic in-process dressing grinding technique which enables application of metal bond wheels with fine superabrasives in mirror surface grinding operations has developed. It is possible to make efficient precision machining of hard and brittle material such as ceramic and hard metal by the employment of this technique. However, in order to ensure the success of performances such as efficient machining, surface finish, and surface quality, it is important to sustain the insulating layer that has sharply exposed abrasives in wheel surface. Using AE(Acoustic Emission) sensor, this paper will show whether the insulating layer sustains stably or not in real grinding time. And by comparing AErms value and surface roughness their thresholds for stable electrolytic in-process dressing grinding will be determined.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.109-116
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• 2007

The present study examined mechanical properties according to the change of outer circumference in the friction welding of A2024-T4 stock, which is used much as aircraft structure, truck wheel, stainless materials and A2024-T4 stock with 10 hollow at the center. Welding conditions were fixed at RPM 2,000rpm, friction pressure of 50MPa, friction time of 1.5sec, upset pressure of 120MPa and upset time of 2.0 seconds. From the result of this study were drawn conclusions as follows : According to the result of a tensile strength test, the solid shaft showed linear increase of tensile strength with the change of outer circumference, the hollow shaft showed maximum tensile stength when the length (L) was 2mm and decrease of tensile strength with the change of outer circumference, hardness appeared to increase and then decrease for welding interface, and it showed maximum hardness 155Hv at L=5mm of the solid shaft. Bending strength increased linearly far change of the distance (L) of outer circumference in the solid shaft and then decreased linearly in the hollow shaft. the result of examining tissue, the tissue grew finer around the welding interface and divided the basic material and the welding surface.

• Journal of Power System Engineering
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• v.15 no.4
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• pp.19-24
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• 2011

The operational efficiency of domestic gas turbine is about 25% and it is now in the trend of the gradual growth in spite of the severe temperature, frequent starting and shutdown according to the environmental management and the energy-efficient use. Rotor bolts of gas turbine in power plants have been the cause of defects because these gas turbines have been operated for a long time under the high pressure and temperature environment experiencing the aging change and stress concentration of the bonded part. The connection parts of the bolt revealed various failure shape and these parts were elongated under very low pressure when operated in the relaxed condition. The cause is in the lack of the metal distribution in the bottle lack area and the cap screw of the bolt is broken totally in case that the nut is fastened in most cases. Gas turbine rotor bolts are connected to the rotor wheel and these bolts caused the vibration, the bulk accident of the rotor in the event that the coupling power among these bolts was relaxed. Therefore, we would like to evaluate the soundness of the main part of the gas turbine rotor bolt through the measurement of the inner condition change along with the mechanic deterioration and temperature, stress in the gas turbine rotor material.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.113-122
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• 1990

In case of repeated wheel-loads are acted on subbase course material, field test is generally executed to get the design standard, but the study shows dynamic properties of soils especially under repeated loads, which have not been well known to us. We try not only to obtain yield stress and elastic modulus of soil in terms of rheological model interpretation but also to investigate the influence of the repeated loads. Yield stress of soil induces hardening until approaching critical value along with the increase in number of cycle, whereas the change in modulus of elasticity with respect to the number of cycle greatly depends on the strength of repeated stress, if weak in strength of repeated stress, the modulus of elasticity increases along with the number of cycle, while if strong, it tends to decrease.