Change Of Tooth Profile Research Articles

Vibration-based monitoring and prediction of surface profile change and pitting density in a spur gear wear process

Gear wear often results in both tooth profile changes caused by abrasive wear, and fatigue pitting. Being able to accurately monitor and predict the profile change (i.e., the wear depth in the direction normal to the gear surface) and surface pitting propagation can bring enormous benefits to industrial practice. However, there is a lack of efficient, reliable, and effective tools to do so. To address this, this paper proposes a gear wear monitoring and prediction approach through the integration of: (i) a dynamic model, to simulate the dynamic responses of the gear system; (ii) two tribological models, to estimate wear depth (in the direction normal to the gear surface) and pitting density (on the gear surface); and (iii), model updating, by comparing simulated and measured vibration signals.More specifically, a 21-degree-of-freedom dynamic model is used to simulate a spur gearbox setup and produce simulated vibrations and contact forces between the meshing gear teeth. Using the contact pressure (calculated from the force) as an input, the wear depth and pitting density are then predicted by the tribological models and used to modify the gear geometry profile and contact area in the dynamic model. The developed approach allows the dynamic model and the wear models to communicate so that both the gear tooth profile change and pitting density can be simulated continuously. To guarantee accurate prediction results from the models, novel approaches are developed to update the wear coefficients in the tribological models by comparing simulated and measured vibrations. The paper demonstrates the ability and effectiveness of the proposed vibration-based methodology in monitoring and predicting gear wear, specifically the tooth profile change and surface pitting propagation, using measurements from both a lubricated test, dominated by surface pitting propagation with mild tooth profile change, and a dry test dominated by tooth profile change.

Linear correlation between tooth movement and facial profile change in patients with class Ⅱ division 1 malocclusion

Objective: To investigate the correlation between tooth movement and profile change in patients with class Ⅱ division 1 malocclusion. Methods: Pre- and post-treatment lateral cephalograms of 42 patients [10 males and 32 females, (23.8±6.3) years old, mean treatment time: 1.9 years] with class Ⅱ division 1 malocclusion were collected in Department of Oral & Cranio-Maxillofacial Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from June 2012 to November 2017. The patients were treated with extraction of four first premolars or two maxillary first premolars. Cephalometric analysis was carried out before and after treatment. Thirty parameters were measured. The changes of soft and hard tissue after orthodontic treatment and their correlations were analyzed using bivariate linear regression. Related factors affecting the upper and lower lip, nasolabial angle (NLA) and mentolabial angle (MLA) were analyzed according to the standardized regression coefficient (Beta). Results: Among all the 30 parameters, 18 parameters were statistically different before and after treatment. After treatment, upper central incisor sagittal distance [(63.87±7.14) mm] and upper lip sagittal distance [(77.73±7.60) mm] were significantly decreased (P<0.05). The changes in 14 parameters after treatment showed linear relationship including strong positive correlation between upper lip sagittal retraction and upper central incisor sagittal retraction (r=0.649, P<0.01). There were moderate positive correlations between upper lip and upper central incisor vertical movement (r=0.544, P<0.01). While the sagittal change of gnathion and the Y-axis angle showed moderate negative correlations (r=0.537, P<0.01). The stepwise multiple linear regression showed that the retraction of upper lip process was correlated with the retraction of upper central incisor, the increase of occlusal plane angle and the increase of upper central incisor angle, which was most correlated with the retraction of upper central incisor (Beta=0.79). The downward displacement of upper lip process was correlated with the downward displacement of upper incisor, the decrease of upper central incisor angle, the decrease of the distance between maxillary first molar and palatal plane, and the increase of occlusal plane angle, which was more correlated with the downward displacement of upper incisor and the increase of occlusal plane angle (Beta=0.59). The downward displacement of lower lip process was correlated with the downward displacement of upper incisor and lower incisor, which was more correlated with the upper incisor (Beta=0.36). Conclusions: The relationship among nose, lips and chin was more coordinated. Incisor retraction had significant influence on lip prominence, and the lower lip position was highly related to the movement of upper incisor in sagittal and vertical dimension after orthodontic treatment in patients with class Ⅱ division 1 malocclusion. However, tooth movement had limited impact on the chin position.

Influence of gear surface roughness on the pitting and micropitting life

Pitting and micropitting are the two main gear rolling contact fatigue modes. It is widely accepted that micropitting will lead to pitting; however, the relationship between pitting and micropitting life needs further investigation. In this work, micropitting and pitting tests were performed on an FZG back-to-back test rig using standard FZG PT-C and GF-C gears. The gear tooth profile change due to micropitting and pitting damage was measured in situ in the gearbox using a profilometer after each test. The gear surface roughness parameters were calculated from the measured tooth profile. A Gaussian low pass filter with cut off length [Formula: see text] mm was applied to the measured tooth profile to obtain the waviness. The calculated roughness parameters and the obtained tooth profile with waviness for each test were imported into the KISSsoft software to calculate the contact stress and specific film thickness at the corresponding load stage. Experimental results show that smooth gear surface can reduce or even avoid micropitting damage, but could lead to a reduction in pitting life.

In situ measurement of gear tooth profile during FZG gear micropitting test

According to the GFKT-C/8.3/90 FZG gear micropitting test procedure, the average value of gear tooth profile deviation is used as the failure criterion. Typically, gear tooth profile deviation is measured using a gear measuring machine. In order to do that during the FZG gear test, the gears tested have to be disassembled from, and assembled to the test rig. This process is tedious, time-consuming and is likely to add uncertainty to the testing results. An in situ gear tooth profile measurement method has been developed and applied in FZG gear micropitting tests. The tooth profile of the tested gear was measured in-situ in the gearbox before, during and after each load stage of the gear micropitting test. An algorithm was developed to fit the measured profile to its theoretical shape. Furthermore, a tooth profile change evaluation algorithm was developed for monitoring the evolution of the tooth profile during the duration of the test. The whole methodology was exemplified with a wrought gear test case run to pitting damage.

Dimensional Changes by Heat Treatment of Helical Gear

The dimensional change of tooth profile by heat treatment of helical gear was investigated by experimental and numerical approaches. Especially, the three-dimensional elasto-plastic finite element (FE) simulation was adopted to analyze the elastic deformation during load, unloading, ejecting of workpiece. Quenching simulation was also carried out to investigate the change of tooth profile on the forged gear. In experiments, the amount of elastic deformation of the forged gear was quantitatively determined by comparing the tooth profiles on the forged gear and die. The dimensional change of the forged gear tooth after quenching was also evaluated from the comparision of the cold forged and quenched gear teeth. From experimental works, it was found that the amounts of dimensional changes after forging and quenching of helical gear are 10 and 10 μm, respectively.

S111023 特殊歯形歯車とインボリュート歯車の摩耗特性の比較([S11102]伝動装置の基礎と応用(2))

In this study, we investigated the wear characteristics of four kinds of tooth profile spur gears; Involute-cycloid composite tooth profile gear, modified cycloid gear, cycloid gear, and involute gear. We carried out the wear test for those gears using power circulating-type gear testing machine, and measured the change of tooth profile. From a result of the wear test, it was found that there are some differences in wear characteristics among those four tooth profile gears. Moreover, we developed a wear calculation program to simulate the wear depth of tooth surface. We calculated the wear depth of involute spur gear and compared its result with the result of wear test. The calculation result almost agreed with the experimental result.

Polymer Alloy Gears. Polymer Alloy Gears Consisting of Polyacetal and Polyurethane.

Based on the fabrication of polymer alloys, a new plastic consisting of 50% polyacetal and 50% polyurethane (called FU polymer alloy) has been developed as a material for gears. For the FU polymer alloy gear, it has been predicted that its noise level becomes lower than that of polyacetal gear ; however, since the FU polymer alloy is weaker than polyacetal, problems arise in terms of the load capacity when it is used as a gear and some doubt still remains regarding its practical application. Because of these findings, in this study, operation tests of FU polymer alloy gears have been carried out under various conditions, and the operating characteristics such as noise level, wear and tooth profile change were investigated. Then these results were compared with those for polyacetal gears, and applicability of FU polymer alloy as a plastic gear material was evaluated.

Effect of Hardened Depth on Fatigue Strength of Carbonitrided Gears

To elucidate the effect of hardened depth on the fatigue strength of carbonitrided gears, gears with three kinds of hardened depths were fatigue-tested using a power circulating gear testing machine. In the case of gears with the shallowest and intermediate hardened depths, the failure mode was spalling. In the case of the gear with the greatest hardened depth, the failure modes were spalling and tooth breakage due to bending at the tooth fillet. The surface durability was higher with greater hardened depth. The bending strength of the gear with the greatest hardened depth was lower than that of the gear with intermediate hardened depth under the same loading condition. Therefore, when carbonitrided gears are designed, it is important to determine the optimum hardened depth of those gears. The change in dynamic performance of every gear was slight during the fatigue processes, since the change of tooth profile of every gear was slight.

Biodegradable Plastic Gears.

Presently, we often hear the phrase "plastics friendly to the global environment", and that a biodegradable plastic is being developed. However, no case has been reported up to now of mechanical parts being made of such plastics. Therefore, focusing the characteristics of this plastic, we have carried out a study to utilize this plastic for gears. In the study, first, biodegradable plastic gears were formed by injection molding similarly to commercial plastic gears, and their operation tests were carried out to investigate operating life, wear of teeth, tooth profile change, and tooth surface roughness. The results were compared with those of commonly used polyacetal gears, and the practicability of biodegradable plastic gears was examined.

Development of Polyacetal Gears Emitting Low Noise. 2nd Report. Polyacetal Gears Filled with Polyolefin and Synthetic Oil.

In the previous study, in order to reduce the noise of polyacetal gears, a composite polyacetal (called FO) made by filling several percent of low-molecular-weight polyolefin and mineral oil to polyacetal was developed. In these FO gears, noise was reduced as compared with polyacetal gears, but recently, gears with greater noise reduction than FO gears have been demanded. As a result, the authors developed a composite polyacetal (called FX) made by filling several percent of low-molecular-weight polyolefin and synthetic oil to polyacetal. In this study, the noise reduction in these FX gears was confirmed, and the wear of teeth, the change of tooth profile, the temperature on tooth surfaces and other characteristics were examined.

Estimate of Antistatic Plastic used as Gear Material.

Antistatic plastic is one of the functional plastics which have been developed recently, but their characteristics when they are used as machine parts have not yet been elucidated. Consequently, various problems have occurred in their practical use. Therefore, in this study, gears were made of two kinds of antistatic plastics which were compounded by filling a conductible agent into matrixes of nylon (MC nylon) and polyacetal (copolymer), which are typical engineering plastics, and operation tests were conducted. The characteristics of the wear of teeth, the change of tooth profile and so on were examined, and the practicality of these plastics as gear materials was evaluated.

Research on the operational characteristics of a plastic gear and an aluminum alloy gear pair.

Recently due to increased usage, there are many instances where plastic gears are used in combination with aluminum alloy gears. In these cases, since aluminum alloy gears are considerably softer than steel gears, the tooth surfaces become extremely worn and rough, and it is feared that the phenomenon of multiplied effect promoting the wear of plastic gears by such rough tooth surfaces may occur. Thus, in this study, an operating test was carried out by combining an MC nylon gear and an aluminum alloy gear, and the actual conditions of the wear of teeth, the roughness of tooth surfaces, the temperature of teeth, the change of tooth profile and so on were investigated.

An examination of body thickness of plastic gears.

In the case of cast gears, the dimensions of various parts of gear bodies are mostly designed on the basis of empirical data. However, for plastic gears, such empirical design data are few: accordingly, even though the indicated transmitting power is the same, large difference is observed in the thickness of gear bodies and others among different to manufacturers. Therefore, in this study, as one procedure of examining the effect of the difference in the thickness of gear bodies such as these on the operation of the plastic gears for transmitting power, operation tests were carried out by using various thicknesses of disks and of rims in disk type plastic gears, and the relationships of the change of these thickness with the life, wear, change of tooth profile and the other characteristics of plastic gears were examined.

Fatigue and dynamic performance of a carbonitrided SCr420 steel gear.

In order to elucidate the failure mode, the load carrying capacity and the relation between tooth profile change and dynamic performance in the fatigue process of carbonitrided steel gears, a carbonitrided chromium steel gear with a shallow hardened depth was fatigue-tested using a power circulating gear testing machine here. The failure modes of this carbonitrided gear were spalling on the tooth surface and tooth breakage due to spalling near the pitch point. The fatigue strength of this carbonitrided gear agreed almost with the lower limit of that of case-hardened gears and the upper limit of that of nitrided gears. The changes in the tooth profile and the dynamic characteristics during the fatigue process of this gear were slight.

A study on fatigue and dynamic performance of induction-hardened sintered powder metal gears. (Case of module 2, standard pressure angle 14.5.DEG. and contact ratio 2.172).

A conventional skew gear pair does not change its relative position of gear axes. On the contrary, one of the axes of the gear pair offered in this paper is able to be displaced one-parametrically on the space fixed to the other gear axis. At any relative position of the gear axes, the gears rotate at a constant speed ratio. The displaceable axis gear pair has three backgrounds as follows. (i) The gear pair is potentially a power transmission element. (ii) The motion of these gears can be applied to the generating motion of gear manufacturing. (iii) The gear tooth bearing problem is based on a deflection or displacement of the gear axis in loading. This paper discusses the relative curvature of gear tooth surfaces and the motion of the tooth bearing pattern.2145Three kinds of induction-hardened sintered powder metal gears were fatigue-tested using a power circulating gear testing machine in order to elucidate the fatigue strength and failure mode. The relation between the tooth profile change and the dynamic performance in the fatigue tests of the gears were also investigated. The fatigue strengths of three kinds of gears were almost the same. The failure modes in these gears were tooth breakage at the tooth fillet, tooth breakage due to pitting near the pitch point, and destructive tooth surface failure. Except for one case of the destructive tooth surface failure, the dynamic performace changed slightly during the fatigue test since the tooth profile deterioration was small. The occurrence of the destructive tooth surface failure influenced the dynamic performance of the gear.

Term of life and wear of plastic intermediate gears.

The plastic gears used for driving paper-drying drums in paper-making machines and others are used at a gear ratio of 1:1 by putting several gears in a row. Accordingly, the intermediate gears undergo loading on both tooth surfaces, but at present, the operational characteristics of the plastic gears being used in this way have not been elucidated at all. Therefore, in this study, the operation test applying alternating loads was carried out using MC nylon gears and such things as the operational term of life, the wear of teeth, and the state of change of tooth profile were examined.

Effect of standard pressure angle on the fatigue strength of nitrided gears.

Nitrided steel gears having three kinds of standard pressure angles were fatigue-tested using a power circulating gear testing machine, in order to elucidate the effect of standard pressure angle on the load carrying capacity and the failure mode of the nitrided gears. The relation between the tooth profile change and the dynamic performance of the gear in the fatigue process was also investigated. The failure modes were tooth breakage at the fillet or grinding notch under a lower pressure angle and higher load and spalling or tooth breakage due to spalling under a higher pressure angle and 10wer load. The fatigue strength for a normal load increased with an increasing pressure angle. The changes in the tooth profile and the dynamic characteristics during the fatigue process were slight.

Effect of standard pressure angle on the fatigue strength of nitrided gears.

Nitrided steel gears having three kinds of standard pressure angles were fatigue-tested using a power circulating gear testing machine, in order to elucidate the effect of standard pressure angle on the load carrying capacity and the failure mode of the nitrided gears. The relation between the tooth profile change and the dynamic performance of the gear in the fatigue process was also investigated. The failure modes were tooth breakage at the fillet or grinding notch under a lower pressure angle and higher load and spalling or tooth breakage due to spalling under a higher pressure angle and lower load. The fatigue strength for a nomal load increased with increasing pressure angle. The changes in the tooth profile and the dynamic characteristics during the fatigue process were slight.

Effect of hardened depth on the fatigue strength of nitrided gears.

Nitrided aluminium chromium molybdenum steel gears were fatigue-tested using a power circulating gear testing machine. The effect of hardened depth on the load carrying capacity and failure mode of the nitrided gears and the relation between tooth profile change and dynamic performance in the fatigue process were experimentally elucidated. Three failure modes were recognized in these experiments ; one was tooth breakage due to bending fatigue at the tooth fillet, and the others were spalling on the tooth surface and tooth breakage due to spalling near the pitch point. Fatigue strength of the nitrided gears tended to increase with the increase of hardened depth. The changes of tooth root strain, noise and vibration profiles during the fatigue process were slight, since the change of tooth profile deterioration was insignificant.

Investigation about the Prevention of Tooth Profile Change of Nylon Gears : 3rd Report, Wear and Tooth Profile Change in Profile Shifted Nylon Gears

Two prevention methods are proposed in the previous report as the prevention methods of tooth profile change in the course of operation of a nylon gear which transmits the power. And their effect is confirmed by experiments. In this report as a method simpler than those methods, a plus profile shifting of nylon gear is proposed. In the plus profile shifted gear, the tooth thickness of tooth flank increases and the tooth is less liable to deflect. Meanwhile the sliding of tooth is large. In this report the abrasion of tooth of nylon gear is investigated under several profile modification coefficients and this method is examined to see how useful it is as the prevention method of tooth profile change.