Contact Damping and Stiffness Calculation Model for Rough Surface Considering Lubrication in Involute Spur Gear

The contact properties of an interface are crucial to the performance of equipment, and it is necessary to study the contact damping and contact stiffness, especially in the case of mixed lubrication. A calculation model for contact damping and contact stiffness considering lubrication was proposed on the basis of the KE contact model and mixed elastohydrodynamic lubrication theory. Both the damping and the stiffness were composed of the oil film portion and the asperity contact portion. Since the damping and the stiffness of oil film mainly depended on the film thickness and the pressure, which can be obtained with the mixed lubrication model, another crucial point was to figure out the contribution of asperity contact. Ignoring the effect of the tangential deformation, the stiffness and the load determined with the normal deformation of the asperity were obtained. Then, the contact damping and the contact stiffness considering lubrication could be derived. Finally, the model was applied to the study of contact damping and stiffness of the involute spur gear.

Behavioral Study of Bajulmati Dam Deformation Through Dam History Database-based Assessment

Dam will experience pressure from its own load up to the effect of loading reservoir water. As a result of this pressure force, the dam body will be deformed. The behavior of dam deformation needs to be monitored to know the vertical and horizontal deformation that occurs. This paper discusses the deformation behavior of bajulmati dam during the construction stage, first filling, and post-construction. The purpose of this analysis is to determine "normal" deformation behavior so that case studies showing "abnormal" deformation can be identified early and can then be further analyzed. Evaluation results of Bajulmati Dam deformation behavior based on the acceptance criteria from a similar dam history database showed that most instruments meet the criteria of deformation acceptance so that it is considered normal. Only a small percentage do not meet the acceptance criteria because the value is outside of the requirements. These results may be a concern and initial recommendation for further analysis of abnormal deformation behaviors occurring.

Towards a comprehensive delineation of white matter tract-related deformation

Finite element (FE) models of the human head are valuable instruments to explore the mechanobiological pathway from external loading, localized brain response, and resultant injury risks. The injury predictability of these models depends on the use of effective criteria as injury predictors. The FE-derived normal deformation along white matter (WM) fiber tracts (i.e., tract-oriented strain) has recently been suggested as an appropriate predictor for axonal injury. However, the tract-oriented strain only represents a partial depiction of the WM fiber tract deformation. A comprehensive delineation of tract-related deformation may improve the injury predictability of the FE head model by delivering new tract-related criteria as injury predictors. Thus, the present study performed a theoretical strain analysis to comprehensively characterize the WM fiber tract deformation by relating the strain tensor of the WM element to its embedded fiber tracts. Three new tract-related strains were proposed, measuring the normal deformation vertical to the fiber tracts (i.e., tract-vertical strain), and shear deformation along and vertical to the fiber tracts (i.e., axial-shear strain and lateral-shear strain, respectively). The injury predictability of these three newly-proposed strain peaks along with the previously-used tract-oriented strain peak and maximum principal strain (MPS) were evaluated by simulating 151 impacts with known outcome (concussion or no-concussion). The results showed that four tract-related strain peaks exhibit superior performance compared to MPS in discriminating concussion and non-concussion cases. This study presents a comprehensive quantification of WM tract-related deformation and advocates the use of orientation-dependent strains as criteria for injury prediction, which may ultimately contribute to an advanced mechanobiological understanding and enhanced computational predictability of brain injury.HighlightDeformation of white matte fiber tracts is directly related to brain injury, but only partially analyzed thus far.A theoretical derivation that comprehensively characterizes white matter tract-related deformation is conducted.Analytical formulas of three novel tract-related strains are presented.Tract-related strain peaks are better predictors for concussion than the maximum principal strain.

Tooth contact analysis of the effect of the addendum modification coefficient of helical gears having modified teeth

The helical gear pair is widely used in different mechanical constructions such as vehicle industry and working machine industry. The main property of them is the skew tooth direction with which better tooth connections could be available than in case of straight tooth direction. The analysis of the effect of the addendum modification coefficient for the normal stress and the normal deformation is the aim of the research which could be determined by finite element analysis. Five helical gear types are designed and modelled. The difference among them is only the different addendum modification coefficients. All of the other initial parameters are constant. After the result we determine the conclusions based on the diagram's results which are received by the mechanical parameters and the addendum modification coefficients.