Yuji Ohue

Diagnosis of tooth surface failure by wavelet transform of dynamic characteristics

This paper deals with a diagnosis of the tooth surface failure by the wavelet transform. A gear fatigue test was performed and the dynamic characteristics were analysed in a time-frequency domain using the wavelet transform. The vibration acceleration of the gear box and the tooth root strain were measured and the tooth surfaces were observed during the fatigue test. The test gear had some tooth profile error due to the pressure angle before the fatigue test. At the initial stage of the fatigue test, this profile error closed to zero by moderate wear. Therefore, the wavelet intensity at each harmonic frequency of the tooth mesh frequency was considerably decreased at the initial stage of the fatigue test. A tooth surface of the gear was damaged by spalling failure with the progress of the fatigue test. The wavelet intensity at each harmonic frequency showed a high value when the spalled gear tooth meshed. It could be understood that a failed tooth can be diagnosed by this analysis when one tooth failed. However, in the case of adjoining plural failed teeth, it was difficult to diagnose each failed tooth.

New Evaluation Method on Gear Dynamics Using Continuous and Discrete Wavelet Transforms

The aim of this study is to propose a new evaluation method of gear dynamics using the continuous and discrete wavelet transforms. The wavelet transform (WT) is a method for the time-frequency analysis of signals. In order to evaluate the difference in the gear dynamics due to the gear materials, which are sintered and steel ones, the dynamic characteristics of gears were measured using a power circulating gear testing machine. The gear dynamics were analyzed in a time-frequency domain by the continuous and discrete WTs. The new evaluation method using the WTs proposed in this paper was more useful compared with the conventional one to investigate the damping characteristic and the dynamic condition of the gear equipment.

Influence of Shot Peening on Surface Durability of Plasma Case-Hardened Sintered Powder Metal Gears

In order to investigate the influence of shot peening on the surface durability of sintered powder metal gears, the plasma case-hardened sintered powder metal rollers and gears shotpeened with different condition were fatigue-tested under a sliding-rolling contact condition. The hardness, the compressive residual stress and the surface roughness of the rollers and gears increased by the shot peening. The failure mode of the rollers and gears was mainly spalling. The main crack of the failed rollers and gears propagated through the pores below the roller and the tooth surfaces. The surface durabilities of the lightly shot-peened rollers and gears were higher than those of the other rollers and gears. While, the surface durabilities of the strongly shot-peened rollers are lower than that of the unpeened roller because of the increase of the surface roughness and the deformed sharp pore by the strong shot peening.Copyright

Spalling Fatigue Life Assessment of Surface Hardened Sintered Gears Based on Fracture Mechanics

In order to evaluate the surface durability of surface-hardened sintered gears, the fatigue lives of 5 kinds of sintered gears and 28 kinds of sintered rollers under sliding-rolling contact conditions were examined and estimated based on the fracture mechanics. The sintered gears and rollers were surface-hardened by induction-hardening and ion-nitriding. The fatigue tests were conducted using a power circulating gear testing machine and two cylinder testing machines. The pore distributions included in the sintered materials were observed and were analyzed statistically. The failure mode of the sintered gears and roller was mainly spalling. The stress intensity factor obtained by FEM analysis for the mode II under a condition of Hertzian contact became larger as the crack length became longer. The estimation of fatigue life of the sintered gears and rollers was attempted using the pore distributions and the fracture mechanics. The estimated fatigue lives were almost the same as the tested fatigue ones. Therefore, it could be said that the crack propagation of the sintered gears and rollers depended on the pore size and hardness.Copyright

A Study on Detection of Small Fault in Cast Thin Plate Using Hitting Sound

The cast wood has the thin face with shallow grooves. The strength of the face was deteriorated, since the faults in the face cause the stress concentration. In order to investigate the possibility of the fault detection for the cast thin plate, seven kinds of thin plates with holes having a diameter of 0.3 to 1.0 mm and a depth of 0.7 mm were prepared and the hitting inspection were carried out using a swing robot. The signals were analyzed using FFT analysis and wavelet transform. The wavelet transform was better than the FFT analysis for the detection of the fault. It was possible to detect the existence of the fault in the plate using the hitting sound using the wavelet transform. It was clear that the fault detection in the thin plate depends on the relation between the vibration mode of the thin plate and the position of the fault in the plate.Copyright

Diagnosis of Tooth Surface Failure by Change in Dynamic Performance of Gear Using Wavelet Transform. Usefulness of Wavelet Transform to Diagnosis of Tooth Surface Failure.

This paper deals with a diagnosis of tooth surface failure by change in dynamic performance of a gear using the wavelet transform. The dynamic performances of the gear, which are tooth root strain and vibration acceleration of gear box, were mearsured during the fatigue process of the gear using a power circulating type gear testing machime. These dynamic performances were analyzed at a time-frequency domain using the wavelet transform. As the result of the time-frequency analysis of the vibration, it became clear that each failed tooth can be detected by this analysis when one tooth was failed. However, in the case of adjoining plural failed teeth, it was difficult to detect the all failed teeth. The result of the time- frequency analysis of the tooth root strain suggested that it is possible to detect the failed location on the tooth surface by this analysis.

Discussion on Diagnosis of Surface Failure of Roller Using Wavelet Transform. Observation of Dynamic Behavior due to Pitting and Spalling Failures.

In this paper, the wavelet transform was applied to diagnose the surface failures of rollers. The loading strain during a rotation of roller was analyzed using the wavelet transform. For pitting failure, the fatigue test was conducted using a two-cylinders testing machine. The occurring position of a large pit could be detected by the wavelet map of the loading strain, while it was difficult to detect the occurring position of a small pit. The roller with a groove was used to investigate the dynamic behavior due to spailing failure. The position of the groove could not be detected, but the intensity of the wavelet map was stronger after the groove contacted with the mating roller. From these results, it could be considered that the surface failure mode can be distinguished by the wavelet map, since the patterns on the wavelet maps between pitting failure and spalling failure were different from each other.

Influence of Particle Diameter of Steel Powder on Fatigue Strength of Induction-Hardened Sintered Powder Metal Gears.

In order to elucidate the influences of particle size of steel powder on the surface durability of induction-hardened sintered powder metal gears, the gears with three kinds of particle sizes were fatigue-tested using a power circulating gear testing machine. The three kinds of particle diameters were under 45μm, 75μm∼106μm and 150μm∼250μm, respectively. The surface durability of the gear with the smallest particle size was almost equal to that of the gear with the intermediate particle size. While the surface durability of the gear with the largest particle size was inferior to those of the other gears. The smaller the particle size became, the smaller the pore size became and the lager the pore cluster factor by fractal dimension became. The failure mode of all gears was spalling with pitting. It was understood that the pore size and the pore cluster factor were important parameters to evaluate the surface durability of the sintered powder metal gears.

Fatigue Strength and Dynamic Performance of Induction-Hardened Sintered Powder Metal Gears. Comparison with Steel Gear and Influence of Hardened Depth.

Int this paper, induction-hardened sintered powder metal spur gears were compared with an induction-hardened melted steel spur gear in terms of fatigue strength and dynamic performance, and the influence of hardened depth on the fatigue strength of the sintered gears was also investigated, using a power circulating gear testing machine. The damping characteristic of the sintered gear was superior to that of the steel gear, but the fatigue strength of the sintered gears was inferior to that of the steel gear, since many pores existed in the sintered gears. The failure mode of the sintered gears was pitting with spalling, and that of the steel gear was tooth breakage due to pitting. We consider the origin of pitting of the sintered gears was pores, while the origin of the pitting of the steel gear was defects on the tooth surface. The fatigue strength and the failure mode of the sintered gears were not influenced by hardened depth. During the fatigue processes of both the sintered gears and the steel gear, the changes in dynamic performance were almost the same since the tooth surface deteriorations of both types of gears were similar in shape. Both dynamic performances became worse due to the tooth surface deterioration.

Surface Durability of Induction-Hardened Powder Metal Rollers Sintered with and without HIP.

The purpose of this report is to elucidate the influences of sintering method and type of steel powder on surface durability of induction-hardened sintered powder metal rollers. Six kinds of induction-hardened sintered powder metal rollers with a diameter of 60 mm, which were produced by hot isostatic pressing process (HIP), and by single-pressing and single-sintering process (1P1S), using three types of steel powders-pure steel powder, prealloyed steel powder and partially prealloyed steel power, were fatigue-tested under a sliding-rolling contact condition. The failure mode of all rollers was spalling due to subsurface cracks. The surface durability of HIPed rollers was higher than that of 1P1Sed rollers. In the case of HIPed rolles, the surface durability of the roller made from the prealloyed steel powder was the highest. In the case of 1P1Sed rollers, the surface durability of the roller made from the partially prealloyed steel powder was the highest. The pores played an important role in the surface durability of the sintered rollers.