Parallel-Axis Gear Design Methodology for Minimization of Power Loss and Its Effect on Vibration Characteristics

Gear tooth strength is mainly considered in gear design to ensure the ability to transmit power. With the design process, various sets of gear parameters are probably selected to meet the tooth strength. However the efficiencies of various designed gears are different. Improper gear parameter selection probably makes the gear power loss increase significantly. In this paper, the design methodology to minimize gear power loss is presented. A spur gear selected from a catalogue is used as the reference gear. Then several gears with various parameters but having the ability to transmit the same load are designed. The power losses of the designed and the reference gears are estimated by the sliding loss model, hence the minimum power loss gear is able to choose from the various designed gear set.s Both analytical and experimental results show that to minimize gear power loss along with keeping loading capacity, pressure angle should be increased and module should be reduced. The effect of this design methodology on vibration characteristics is also investigated by measuring the vibration attributed to the sample gear sets. It is found that the helical gear having large pressure angle, wide face width and having helix angle about 10° to 20° is favorable, since it has more capability to transmit load, lower power loss and also lower vibration than the reference spur gear

Spur and Helical Gear Sliding Loss Model with Load Distribution Pattern on Gear Tooth Surface

The model for estimation of spur and helical gear sliding loss with load distribution pattern on gear tooth surface is presented in this paper. The load distribution for the spur gear is considered to distribute uniformly along the line of contact. During double teeth meshing, load sharing ratio between meshing teeth is considered to be 33:67 percent or 45:55 percent. For the helical gear the load distribution can be calculated by the method proposed by Niemann and Richter. The contour plots of load distribution conform to the tooth contact patterns obtained experimentally. The sliding losses estimated from the presented method are compared with the estimations done by the former model and also the experimental results. It is found that the sliding losses calculated from the presented method are closer to the experimental results than the estimations from the former model. The effects of the helix angle and pressure angle on the sliding loss can also be estimated correctly by the presented method.The model for estimation of spur and helical gear sliding loss with load distribution pattern on gear tooth surface is presented in this paper. The load distribution for the spur gear is considered to distribute uniformly along the line of contact. During double teeth meshing, load sharing ratio between meshing teeth is considered to be 33 : 67 percent or 45 : 55 percent. For the helical gear the load distribution can be calculated by the method proposed by Niemann and Richter. The contour plots of load distribution on gear tooth surface conform to the tooth contact patterns obtained experimentally. The sliding losses estimated from the presented method are compared with the estimations done by the former model and also the experimental results. It is found that the sliding losses calculated from the presented method are closer to the experimental results than the estimations from the former model. The effects of the helix angle and pressure angle on the sliding loss can also be estimated correctly by the presented method

Analytical and Experimental Investigation of Parameters Affecting Sliding Loss in a Spur Gear Pair

The effects of gear module, pressure angle and gear ratio on the sliding losses of a spur gear pair have been investigated analytically and experimentally in this paper. The analytical investigations were done by using the gear meshing model proposed in the authors' former work. The various empirical formulas of friction coefficient are used in the calculation process. The estimated results are compared with the experimental results done by using back-to-back gear test rig. The analytical results agree well with the experimental results. The sliding losses of gears having larger module are higher than the gears having smaller module. The larger pressure angle gears have lower sliding losses, and increasing the gear ratio causes the increase in sliding loss. The estimated results calculated by using the friction coefficient formula proposed by ISO TC60 are the most accurate comparing with the experimental results

The Empirical Formula for the Stiffness of a Spur Gear Pair Based on Finite Element Solutions

Gear meshing stiffness is commonly determined by the analytical method or the finite element method (FEM). Both methods can be used to determine the meshing stiffness but the calculation for the analytical method is more complicated, while the FEM is impacted by the tooth contact setting and large computation time. Thus, both methods have limitations for practical use. Here, an empirical formula was proposed to calculate meshing stiffness of a spur gear pair with gear ratio 1:1 in moderate to large load conditions. The formula was divided into two parts as 1) an equation used to calculate the stiffness of the gear cylinder derived from the elasticity equations, and 2) an empirical formula to determine the meshing stiffness of the tooth pair based on FEM solutions. The second part of the formula was constructed by selecting the related parameters, finding the appropriate formula pattern, and determining the relation between these parameters and tooth stiffness at any meshing position. Meshing stiffness of the gear pair was determined by combining the stiffness of two parts connected in series.  Accuracy of the empirical formula was verified by comparing the calculated meshing stiffness with previous research and indicated that the calculated meshing stiffness conformed well with other studies. Our proposed empirical formula can be applied to any spur gear pair with gear ratio 1:1 to accurately determine gear meshing stiffness

Average systolic blood pressure and clinical outcomes in patients with atrial fibrillation:Prospective data from COOL-AF registry

PurposeHypertension is associated with incident atrial fibrillation (AF) and AF-related complications. We investigated the associations between average systolic blood pressure (SBP) and outcomes in a nationwide cohort of Asian patients with non-valvular atrial fibrillation (NVAF).Patients and methodsA multicenter nationwide registry of patients with NVAF in Thailand was conducted during 2014-2017. Clinical data, including blood pressure, were recorded at baseline and then every 6 months. Average SBP was calculated from the average of SBP from every visit. Cox regression models were used to calculate the rate of clinical outcomes of interest, ie ischemic stroke or transient ischemic attack (TIA), intracerebral hemorrhage (ICH), and all-cause death. Average SBP was categorized into three groups: ResultsA total of 3402 patients were included, and the mean age was 67.4±11.3 years. The mean (±SD) baseline and average SBPs were 128.5±18.5 and 128.0±13.4 mmHg, respectively. The mean follow-up duration was 25.7±10.6 months. The median rate of ischemic stroke/TIA, ICH, and all-cause death was 1.43 (1.17-1.74), 0.70 (0.52-0.92), and 3.77 (3.33-4.24) per 100 person-years, respectively. The rate of ischemic stroke/TIA and ICH was lowest in patients with average SBP ConclusionSustained control of SBP was significantly associated with a reduction in adverse clinical outcomes in patients with NVAF

Volume estimation of cassava using consumer-grade RGB-D camera

Mismanagement during postharvest handling of cassava can degrade the quality of the product and depreciate its selling price considerably. This study proposed the feasibility of using RGB-depth camera to measure the quality of cassava roots in a non-destructive, fast and cost-effective manner. Methodology to estimate the volume of cassavas Kasetsart 50 variety was the focus of this study. Using RGB-D images collected from 60 cassava samples with each one being photographed from 6 different orientations. Image Processing model and Point Cloud image model were used to find the volume from depth images, and then disk method and box method were used to estimate the volume of cassava under ellipsoidal shape. Both estimation methods provided usable values for the volumes in the range of 100 - 500 ml with RMSE values of 5.91% and 4.02%, respectively. The estimated volume can be applied to find density to predict the rotten cassava for improving quality and efficiency of cassava industry