Load Sharing of Worm Gear With a Plastic Wheel

2006 ◽  
Vol 129 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Yann Hiltcher ◽  
Michèle Guingand ◽  
Jean-Pierre de Vaujany
Keyword(s):  
Experimental Tests ◽  
Load Sharing ◽  
Transmission Error ◽  
Original Method ◽  
Worm Gear ◽  
Structural Damping ◽  
Meshing Stiffness ◽  
History Of ◽  
Driving Torque ◽  
Very High

The material of the wheel in a worm gear has to be nonrigid due to very high sliding velocity. Such gears are currently made of plastic in the case of a small module. The present paper describes an original method for studying the quasi-static loaded behavior of a worm gear, with a steel worm and a nylon wheel. Plastics are viscoelastic materials and do not obey Hooke’s law. This paper describes an elaborated method that is a generalization of Kelvin’s model. The computation also uses experimental tests to obtain data relating to the plastic. The computation of the load sharing is described and uses the equation of displacement compatibility. The history of previous deformation and the effect of the nylon’s structural damping are taken into account. At a given constant temperature, the load sharing, meshing stiffness, and loaded transmission error depend on the driving torque and time, that is to say speed of rotation.

Numerical and Experimental Study of the Loaded Transmission Error of a Worm Gear With a Plastic Wheel

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Jean-Pierre de Vaujany ◽  
Michèle Guingand ◽  
Didier Remond
Keyword(s):  
Experimental Study ◽  
Transmission Error ◽  
Original Method ◽  
Worm Gear ◽  
Experimental Measurements ◽  
Structural Damping ◽  
Kelvin Model ◽  
Worm Gears ◽  
History Of ◽  
Generalized Kelvin Model

Nowadays, the wheels of worm gears with a low module can be made of plastic; thus, classical modeling can no longer be used satisfactorily. The present paper describes an original method for studying the quasistatic loaded behavior of a worm gear, with a steel worm and a nylon wheel. A generalized Kelvin model is proposed, and the computation of load sharing is described by using an equation of displacement compatibility. The history of previous deformation and the effect of the nylon’s structural damping are also taken into account. Experimental measurements of the loaded transmission error are performed with the help of optical encoders rigidly connected to the worm and gear shafts, giving access to their instantaneous angular positions. The numerical simulations fit quite well with the experimental results.

Numerical and Experimental Study of Loaded Transmission Error of Worm Gear With a Plastic Wheel

2007 ◽  
Author(s):  
Jean-Pierre de Vaujany ◽  
Miche`le Guingand ◽  
Didier Remond
Keyword(s):  
Experimental Study ◽  
Transmission Error ◽  
Original Method ◽  
Worm Gear ◽  
Experimental Measurements ◽  
Structural Damping ◽  
Kelvin Model ◽  
Worm Gears ◽  
History Of ◽  
Generalized Kelvin Model

Nowadays, the wheels of worm gears with a low module can be made of plastic, thus classical modeling can no longer be used satisfactorily. The present paper describes an original method for studying the quasi-static loaded behavior of a worm gear, with a steel worm and a nylon wheel. A generalized Kelvin model is proposed and the computation of load sharing is described by using an equation of displacement compatibility. The history of previous deformation and the effect of the nylon’s structural damping are also taken into account. Experimental measurements of the Loaded Transmission Error are performed with the help of optical encoders rigidly connected to the worm and gear shafts, giving access to their instantaneous angular positions. The numerical simulations fit quite well with the experimental results.

A wear model for worm gear

2015 ◽  
Vol 230 (7-8) ◽  
pp. 1290-1302 ◽  
Author(s):  
Dalia Jbily ◽  
Michèle Guingand ◽  
Jean-Pierre de Vaujany
Keyword(s):  
Surface Profile ◽  
Load Sharing ◽  
Transmission Error ◽  
Worm Gear ◽  
Influence Coefficient ◽  
Wear Model ◽  
Local Contact ◽  
Influence Coefficient Method ◽  
Contact Pressures ◽  
Coefficient Method

This paper presents a numerical model to predict the wear of worm gear. This last is based on well-known Archard’s wear formulation. The influence of lubrication is taken into account with a local wear coefficient, depending on the ratio between the minimum lubricant film thickness and the amplitude of the surface roughness. When material on a wheel flank is worn, it is then necessary to update the surface profile, consequently the contact pressure calculations. To compute the quasi-static load sharing and thus the contact pressures required for the wear model, the equation of displacement compatibility is solved, using the influence coefficient method, which allows a fast and accurate computing. The bending deflections of the worm and wheel, and the local contact deformations of mating surfaces are included. The Boussinesq theory is applied for calculating the local contact deformations. The bending is determined by the combination of only one standard finite element method computation and interpolation functions. This method allows taking into account the environment of the gear meshing, such as the actual shafts, rim, web, bearing locations, which affect the quasi-static results and thus the wear. In addition, the model allows to obtain numerous results, such as load sharing, contact pressures distribution, transmission error, stiffness, wear distribution, etc. A comparison between theoretical wear predictions and experimental results, issued from the literature, are also presented.

Predictions of Wear and Transmission Errors of Cylindrical Worm Gears

2003 ◽  
Author(s):  
X. Wang ◽  
L. Morrish
Keyword(s):  
Transmission Error ◽  
Wear Intensity ◽  
Worm Gear ◽  
Tooth Surface ◽  
Initial Shape ◽  
Gear Design ◽  
Transmission Errors ◽  
Meshing Stiffness ◽  
Contact Patterns ◽  
Worm Gears

Transmission error (TE) is an important transmission parameter for precision worm gears. Modern cutting methods in conjunction with modern software allow manufacturers to deliver worm gear products of high accuracy to the highly competitive market. However, the initial shape of a bronze wheel tooth changes dramatically due to bedding-in and wear when gears mesh under load, and hence transmission characteristics change. A computer program is being developed to predict wear during bedding-in and constant wear rate stages for involute worm gears. A progressive wear over given number of tooth engagements is estimated using both the available experimental wear data and theoretical considerations. Being subtracted from an “as-cut” geometry, a new shape of worm wheel tooth surface can be predicted. The calculations can be executed iteratively for as many wear steps as necessary. The model takes load sharing and contact stress distribution into account to estimate the lubrication oil film thickness and wear intensity. Contact patterns, TE, load cycles and meshing stiffness are also modeled. A comparison between theoretical wear predictions and experimental wear data is made. Predictions of wear and transmission errors are useful for optimization of existing worm gear design and for development of worm gears of new designs.

Finite Element Modelling and Analysis for Involute Worm Gears With Localised Tooth Contact

2000 ◽  
Author(s):  
D. Su ◽  
F. Yang ◽  
C. R. Gentle
Keyword(s):  
Finite Element ◽  
Finite Element Modelling ◽  
Transmission Error ◽  
Worm Gear ◽  
Tooth Contact ◽  
Element Modelling ◽  
Meshing Stiffness ◽  
Modelling Method ◽  
Worm Gears ◽  
Root Stress

Abstract A general approach is reported in this paper for finite element modelling and analysis of involute worm gear with localised tooth contact. The process of finite element modelling is based on the modified tooth geometry which was presented in a previous paper. The finite element analyses were conducted using commercially available software. The following topics have been investigated in this study: (1) geometric modelling method for involute worm gears, (2) tooth elastic deformation and tooth root stress of worm gear under different loads, and (3) instantaneous tooth meshing stiffness and loaded transmission error of the involute worm gear. Although this study is aimed at involute worm gears, the method developed is applicable for other worm gear types.

scholarly journals Antihypertensive Efficacy of Fixed Combination of Amlodipine and Ramipril in Patients with Arterial Hypertension and Very High Cardiovascular Risk

2019 ◽  
Vol 14 (6) ◽  
pp. 840-845
Author(s):  
O. Yu. Korennova ◽  
S. P. Podolnaya ◽  
E. P. Prihodko ◽  
E. A. Turusheva ◽  
S. N. Starinskaya ◽  
...  
Keyword(s):  
Cardiovascular Risk ◽  
Coronary Artery ◽  
Fixed Combination ◽  
Antihypertensive Drugs ◽  
Antihypertensive Efficacy ◽  
High Cardiovascular Risk ◽  
Hypertensive Patients ◽  
Coronary Artery Stenting ◽  
History Of ◽  
Very High

Aim. To evaluate the antihypertensive efficacy and tolerability of a fixed combination of amlodipine and ramipril in hypertensive patients with very high cardiovascular risk. Material and methods. A retrospective cohort study of real clinical practice of prescribing antihypertensive drugs according to 255 medical records of outpatient hypertensive patients with a history of acute coronary syndrome (ACS) and coronary artery stenting was performed in the first part. An open observational study was performed in the second part. 69 people older than 18 years with a history of ACS and coronary artery stenting, without reaching the target blood pressure (BP) level while using free combinations of antihypertensive drugs and with indications for a fixed combination of ramipril and amlodipine were included into the study. Analysis of self-monitoring of BP, office BP, daily BP monitoring (ABPM) and patients’ adherence to treatment (Morisky-Green test) initially, after 4 and after 12 weeks of taking the fixed combination of ramipril and amlodipine was performed to assess the clinical efficacy of the studied drug. Results. It was found that 42.0% of patients did not follow the recommendations for regular intake of antihypertensive drugs. So, hypertension of all patients regarded as false-refractory, which was the basis for the prescription of the fixed combination of ramipril and amlodipine in accordance with clinical guidelines for the diagnosis and treatment of hypertension. After 4 weeks of therapy, there was significant decrease in office BP with the achievement and preservation of the target level by the 12th week, normalization to the 12th week of day and night BP variability in 54.9% of patients. 78.0% of patients followed medical recommendations for regular administration of antihypertensive drugs, none of the patients had adverse events. Conclusion. The use of fixed combinations of drugs, in particular, amlodipine and ramipril as a part of multicomponent therapy in hypertensive patients with very high cardiovascular risk, led to the achievement of target BP by the 4th week of therapy and stable preservation of antihypertensive effect in 12 weeks of treatment as well as gradual normalization of day and night BP variability in more than half of patients. Fixed combination of ramipril and amlodipine allowed to improve adherence of patients to cardiovascular diseases.

Effects of the Gear Tooth Modification on the Nonlinear Dynamics of Gear Transmission System

2010 ◽  
Vol 97-101 ◽  
pp. 2764-2769
Author(s):  
Si Yu Chen ◽  
Jin Yuan Tang ◽  
C.W. Luo
Keyword(s):  
Nonlinear Dynamics ◽  
Gear Tooth ◽  
Simulation Method ◽  
Transmission Error ◽  
Dynamic Responses ◽  
Meshing Stiffness ◽  
Gear Transmission System ◽  
Tooth Modification ◽  
Static Transmission Error ◽  
Misalignment Error

The effects of tooth modification on the nonlinear dynamic behaviors are studied in this paper. Firstly, the static transmission error under load combined with misalignment error and modification are deduced. These effects can be introduced directly in the meshing stiffness and static transmission error models. Then the effect of two different type of tooth modification combined with misalignment error on the dynamic responses are investigated by using numerical simulation method. The numerical results show that the misalignment error has a significant effect on the static transmission error. The tooth crowning modification is generally preferred for absorbing the misalignment error by comparing with the tip and root relief. The tip and root relief can not resolve the vibration problem induced by misalignment error but the crowning modification can reduce the vibration significantly.

scholarly journals AB0420 RISK OF DEVELOPING TYPE 2 DIABETES MELLITUS IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1510.2-1510
Author(s):  
L. Kondrateva ◽  
T. Popkova ◽  
E. Nasonov ◽  
A. Lila
Keyword(s):  
Abdominal Obesity ◽  
Lupus Erythematosus ◽  
Antihypertensive Drugs ◽  
Control Group ◽  
Systemic Lupus ◽  
Type 2 Dm ◽  
History Of ◽  
Systemic Rheumatic Diseases ◽  
Very High

Background:Patients with systemic lupus erythematosus (SLE) have higher than in general population prevalence of diabetes mellitus (DM). Hyperinsulinemia is a predictor of developing type 2 DM, however routine measurement of insulin levels for DM risk assessment is uncomfortable in daily clinical practice. International Diabetes Federation recommends the use of patient questionnaires to quickly identify people who may be at a higher risk of DM development.Objectives:To determine the 10-years risk of developing type 2 DM in SLE patients using dedicated questionnaire - Finnish Type 2 Diabetes Risk Assessment Form (FINDRISK) data.Methods:The study included 92 SLE patients without DM (83 women, 9 men, 39 [34; 47] years old). The median disease duration was 6 [2,14] years, SLEDAI-2K was 4[2;8]. SLE pts were treated with glucocorticoids (GC) (89%) and hydroxychloroquine (78%), immunosuppressive drugs (28%) and biological agents (10%). The control group consisted of 88 subjects without systemic rheumatic diseases, inflammatory arthritis or DM, matched by age and sex with SLE patients. Eight items of FINDRISK questionnaire (age, overweight, abdominal obesity, family history of diabetes, physical inactivity, eating habits, history of antihypertensive drugs treatment, history of hyperglycemia) were taken into account to calculate the total risk score (TS). The risk of developing DM within following 10 years is regarded as low (1%) or slightly elevated (4%) with TS ≤11 points, as moderate (17%), high (33%) or very high (50%) with TS ≥12 points.Results:The risk of developing DM was low or slightly elevated in 65 (71%) SLE pts and moderate, high or very high in 27 (29%) pts. The difference was significant compared with the control group, in which 76 (86%) subjects had a low or slightly elevated risk and 12 (14%) had a moderate, high or very high risk (p=0,01). The number of risk factors (4[2;5]) and the median TS of SLE pts (9[5;12] points) were higher than values in control subjects (3[2,4] factors and 6[3;9] points, respectively) (p<0,01 for both). DM risk factors profiles were similar in two groups, except for higher prevalence of abdominal obesity (66% vs 41%, p<0,01) and history of antihypertensive drugs treatment (57% vs 17%, p<0,01) in SLE. There were positive correlations between TS and CRP levels (r=0,25, p=0,02), SLICC (r=0,36, p<0,01), HAQ (r=0,29, p<0,01), and negative correlations between TS and SLEDAI-2K (r= -0,32, p<0,01), glomerular filtration rate by CKD-EPI (r=-0,23, p=0,03). Current GC use had no influence on TS values in SLE.Conclusion:Patients with SLE were more likely than individuals without systemic rheumatic diseases to have a moderate, high and very high risk of developing DM, and therefore, required interventions to prevent the metabolic disease. Increased risk of developing DM was associated with most common traditional factors, especially by abdominal obesity and regular use of antihypertensive drugs that can be considered a kind of equivalent to the presence of hypertension. Curtain contribution of inflammation, lupus activity and irreversible damage index can’t be ignored. Clarification of SLE-specific phenomena in DM pathogenesis requires further research.Disclosure of Interests: :None declared

scholarly journals Multi-Locus Selection and the Structure of Variation at the white Gene of Drosophila melanogaster

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 635-645 ◽  
Author(s):  
David A Kirby ◽  
Wolfgang Stephan
Keyword(s):  
Drosophila Melanogaster ◽  
White Gene ◽  
Transcriptional Unit ◽  
North American Population ◽  
Evolutionary Mechanisms ◽  
Locus Selection ◽  
Neutral Equilibrium ◽  
History Of ◽  
High Degree ◽  
Very High

Abstract We surveyed sequence variation and divergence for the entire 5972-bp transcriptional unit of the white gene in 15 lines of Drosophila melanogaster and one line of D. simulans. We found a very high degree of haplotypic structuring for the polymorphisms in the 3′ half of the gene, as opposed to the polymorphisms in the 5′ half. To determine the evolutionary mechanisms responsible for this pattern, we sequenced a 1612-bp segment of the white gene from an additional 33 lines of D. melanogaster from a European and a North American population. This 1612-bp segment encompasses an 834bp region of the white gene in which the polymorphisms form high frequency haplotypes that cannot be explained by a neutral equilibrium model of molecular evolution. The small number of recombinants in the 834bp region suggests epistatic selection as the cause of the haplotypic structuring, while an investigation of nucleotide diversity supports a directional selection hypothesis. A multi-locus selection model that combines features from both-hypotheses and takes the recent history of D. melanogaster into account may be the best explanation for these data.

Sign in / Sign up

Export Citation Format

Share Document