A popular approach to optimize the performance of a gear transmission system is the modification of the gear tooth microgeometry, which includes the intentional removal of material from the gear teeth flanks, so that the shape is no longer a perfect involute. Such modifications compensate teeth deflections under load, and the resulting transmission error is minimized under a specific torque. Therefore, micro-geometry modifications can be applied on the involute (or profile) and lead of the gear teeth. In order to study the tooth micro-geometry optimization, this research selected a mass produced planetary gear type drive reducer as a prototype. The original design was modeled by a commercial software named Romax Designer, which analyzes and optimizes different types of gear power transmission systems. The series analysis results obtained reveal some anomalies that require modification. Based on the result, optimization and gear tooth modification were done to deal with the load distributions on gear tooth, gear durability problem, safety factor and bearing life problem. This thesis presents the outstanding performance improvement obtained after such optimization.
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The planetary geartrain can be reduced in size and weight, and has excellent durability since the input torque is divided by the number of planet gears when the power is transmitted. In order to improve its durability, the load sharing among planet gears must be even. However, of the various manufacturing errors possible, the carrier pinhole position error has the greatest influence on load sharing. This study compared and analyzed the load sharing and the gear safety of planetary gears, according to the phase of the carrier pinhole position error. We confirmed that load sharing among the planet gears varied, depending on the phase of the carrier pinhole position error. The mesh load factor is inversely related to the gear safety factor for bending and contact, and affects the durability of the planetary geartrain. Also, in the design of the planetary geartrain, the load sharing among planet gears is directly affected by the carrier pinhole position error and its phase. Therefore, the geometric tolerance must be managed efficiently, which needs to be reflected in the production drawings.
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This study determined the equivalent moment of inertia of the upper rotating body of an excavator, for the inertial endurance test of an excavator slewing system. The input speed and torque of the slewing reducer were measured by an excavator slewing test, and the equivalent moment of inertia of the upper rotating body of the excavator was calculated using iterative calculation. We developed a dynamic simulation model of the excavator slewing system, and validated the model by comparing it with the slewing test results. Using the validated model, we further developed a simulation model for the inertial endurance test, that considers the moment of inertia of the upper rotating body of an excavator. We concluded that the new dynamic model for the inertial endurance test of an excavator slewing system well exemplified the actual slewing test results.
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A differential is a mechanical device that supports smooth driving, by allowing each of the two wheels, to rotate at differential speeds during a turn. This is particularly crucial for tractors, as they mainly work on the ground, often becoming stuck off-highway, or falling into pits. When the tractor wheel is stuck off-highway, it is difficult to get the wheel out, as the differential of the tractor reduces friction between the wheel and the ground surface. In order to prevent this wheel slip situation, the differential locking device, which restricts the two wheels on the axle to the same rotational speed, has been used in the axle of the tractor. In this study, analysis models of the hydraulic system and the dog clutch were developed to predict the performance of the differential locking device. Using the LMS imagine. AMEsim software, the analysis models were verified by comparing the simulation results with the experimental data. Using the models developed, the influence of the release time of the differential locking device on selected design parameters was analyzed, to determine the effect on the release time of the differential locking device. As a result, design values that will improve the performance of the differential locking device were derived.
Recently, technologies related to green cars are gaining attention. A variable valve-timing system (VVT) is widely used in internal-combustion engines to improve fuel efficiency and engine performance by controlling the valve open-close timing. Since conventional hydraulically controlled VVT has problems, such as slow response and low efficiency, an electrically controlled variable valve timing (ECVVT) system was developed as an alternative the conventional VVT. This paper presents a performance test rig for an ECVVT system using servo motors. The performance test rig consists of an ECVVT module with a cycloid reducer, an engine cylinder block, a driving part, and a motion controller. A small servo motor drives the ECVVT module through the cycloid gear, while a large servo motor drives the camshafts by means of a timing belt. We carried out simulations using a mathematical model of the ECVVT module, cam shaft, valve, and motion control. We then built a performance test rig for the ECVVT system, and did experiment of cam phase variations of the ECVVT system to confirm its performance.
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A Review of Recent Advances in Design Optimization of Gearbox Zhen Qin, Yu-Ting Wu, Sung-Ki Lyu International Journal of Precision Engineering and Manufacturing.2018; 19(11): 1753. CrossRef
An essential mechanical element in an industrial machine is a reducer, which transfers the rotation of an electrical motor or engine to another part with amplified torque. Some reducers, such as planetary reduction gears, a harmonic reducer, or a cycloid reducer, have been applied in various industries. Given the increase of demand for reducers with high precision, compact size, and high load capacity for use in industrial robots, the cycloid reducer has stood out. The cycloid reducer, compared with planetary reduction gears, has some merits, which include a larger reduction gear ratio at only one stage, higher durability, improved efficiency, and a larger torque because of its high tooth-contact ratio despite its being small. This paper presents a design technique for a cycloid reducer intended, because of those merits, for use in remote weapons systems of armed vehicles. In order to verify the performance of the cycloid reducer, we carried out experiments and analyzed the results systematically.
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Trochoid Gear Transmission Synchronized to Backward Driving Prevention Brake of Manual Wheelchair for Improved Driving Capability on Ramps Bu-Lyoung Ahn, Seok Hyeon Jo, Hyun Duk Moon, Kyung Sun, Du-Jin Bach Journal of the Korean Society for Precision Engineering.2020; 37(1): 67. CrossRef
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This paper aims to verify the reliability of the creep-life assessment regarding the STS304H-Type tube for which the hardness method of H. Tanaka is used. For this purpose, the creep-rupture test and the hardness test were conducted with a new tube and used tubes that were exposed to 96,000 hr under a 650oC condition. The hardness value of the used tubes is higher than that of the new tube by approximately 12 Hv to 15 Hv. This test result was applied to the creep-life assessment of the STS304H-Type for which the H. Tanaka hardness method was used, and the life consumption of the used tubes was evaluated as 13%. The rupture times of the new and used tubes are 802 hr and 707 hr, respectively. The use of the test results as a substitution of the results of the Larson Miller Parameter for a life-assessment tool produced a life-consumption calculation of approximately 12%. Similar results can be confirmed between the Larson Miller Parameter method and the hardness method.
In this study, a numerical analysis on the impact response of HHA (High Hardness Armor Plate) sequences under a 7.62 mm projectile impact was performed to obtain the fundamental design data for a combat-vehicle platform. Recently, the ballistic-protection levels for combat vehicles have increased, and ballistic-protection designs should now be able to deflect multi-hit projectiles. To study the ballistic-impact characteristics, armor-plate sequences of one or two layers with a gap of 0 mm to 2 mm between the front and rear plate were defined under the same weight and thickness. For the certification of the reliability of the numerical model, ballistic tests and an analysis of the single plate under the 7.62 mm projectile impact were performed and analyzed. On the basis of a valid numerical model, a numerical analysis was performed and analyzed. Lastly, it was proved that the performances of the two-layer sequence with the 2 mm gap regarding the impact-response acceleration, deflection efficiency, and penetration depth are the highest.
Seismic load induces a reverse cyclic load that alternately applies a tensile and a compressive load to a structure. For nuclear piping material, safety is assessed in terms of fracture toughness. However, test results using a quasi-static load can’t guarantee safety if there is a seismic load. In this paper, the fracture toughness of SA312 TP304 stainless steel, which is used as the safety injection pipe of a nuclear power plant, was estimated by using reverse cyclic loads with different ratios of tensile load to compressive load. The test results using a load ratio of -1 (compressive load / tensile load) show that fracture toughness decreases to approximately 10% against a load ratio of zero. These test results show that the reverse cyclic load must be considered in planning for the safety of nuclear power plants under seismic loads.
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Recently, Laser Direct Imaging (LDI) has been used to replace lithography in Flexible Printed Circuit Board (FPCB) manufacturing. However, repeated motion of a linear motor caused residual vibration in the granite on which the workpiece was placed when the motor either accelerated or decelerated. Because the residual vibration made positioning less accurate, there were more defective products and worse productivity. This paper proposes a way to reduce vibration in the granite during the precision stage. First, the frequency domain of the vibrations of a pneumatic vibration isolator is identified. Second, we present the design of the mechanism using a voice coil actuator and a capacitive displacement sensor. Third, we apply a feedback control algorithm based on PID to cancel displacement. Consequently, we are able to propose an optimal way to reduce vibration for the laser direct imaging equipment. The amount of vibration reduction is evaluated in terms of amplitude and settling time.
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Reaction Force Compensator for High‐Speed Precision Stage of Laser Direct Imaging Process Chang-hoon Seo, Yong ho Jeon, Hyung-ku Lee, Hyo-young Kim, Moon G. Lee, Francesco Franco Shock and Vibration.2018;[Epub] CrossRef
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