Shaft Surface Roughness Research Articles

Measurement and prediction of thermal performance of automotive transmission radial lip seals

The paper reports on the use of a developed novel and specific test-rig for the assessment of performance of radial lip seals of automotive transmissions, with particular emphasis on determination of thermal performance. The test-rig can accommodate original components from a donor vehicle, thus accurately represents vehicular conditions. The specific aim is to experimentally determine the effect of shaft surface roughness parameters on the generated contact temperature. Excessive exposure to high temperatures can accelerate degradation and aging of elastomeric seals, resulting in increased wear. Corundum and CBN (Cubic Boron Nitride) ground shafts are used to ascertain the effect of surface roughness parameters in the shaft seal conjunction. An analytical thermal model is also developed in combination with temperature measurements to determine the exact temperature in the lip seal-shaft contact. It is shown that depending on the type of shaft surface grinding process some potential correlation exists between roughness parameters and generated contact temperatures. It is also shown that the contact temperature can be several degrees Celsius higher than those measured in the proximity of the seal contact.

Laboratory Investigation of Hollow and Solid Shaft Helical Soil Nail by Displacement Controlled Pullout Testing

A sequence of laboratory pullout tests was conducted to examine the installation and pullout behavior of hollow and solid shaft helical soil nails. The methodology involves installation and corresponding pullout testing of 12 mm, 14 mm, 16 mm and 18 mm hollow and solid shaft helical soil nails with varying number of helical plates between single to triple and shaft surface roughness from smooth to rough using a displacement-controlled apparatus. A total of 18 different helical soil nail combinations were investigated under surcharge pressures 5 kPa, 12.5 kPa, 25 kPa, and 50 kPa to examine the influence of shaft dimeter, shaft roughness, number of helices, pitch, interaction friction angle, embedment depth ratio on both installation and pullout capacity. Using the pullout capacities and corresponding installation torque, capacity-to-torque ratio (Kt) relationship was also established which yielded ranges of 19 m−1 to 61 m−1 and 23 m−1 to 58 m−1 for hollow and solid shafts, respectively. Moreover, interaction friction angles depicted that with similar number of helices, an increase of 25% in diameter of hollow shaft helical soil nail renders equivalent reinforcing action to a corresponding solid shaft. Also, for both hollow and solid shafts, double helical soil nails were observed to show the maximum efficiency, while the effect of number of helices was found to diminish beyond the embedment ratio of 11. Within the pitch range of 30–35.5 mm, pullout response for both hollow and solid shafts were found to be linearly dependent on its installation.

Effect of Shaft Surface Roughness on the Performance of Radial Lip Seals

Reduction of leakage from the shaft–radial lip seal conjunction is critical in ensuring enduring performance of entire lubrication system. This paper investigates leakage from three types of shaft surfaces, finished using different manufacturing processes. The measurement of surface topography is conducted in order to determine the pertinent roughness parameters which correspond to the observed sealing performance in real practical applications. It is found that the skewness of the surface topography correlates well with the anecdotal leakage failure rate. To quantify this association, a hydrodynamic model, accounting for shaft roughness in a deterministic manner is developed. The results from the numerical analyses confirm that the lubricant mass flow rate is reduced in the case of negatively skewed surface height distributions, when compared with the positively skewed profiles.

Numerical Investigation of the Effect of Radial Lip Seal Geometry on Sealing Performance

Sealing elements are often needed in industry and especially in machine design. With the change and development of machine technology from day to day, sealing elements show continuous development and change in parallel with these developments. Many factors influence the performance of the sealing elements such as shaft surface roughness, radial force, lip geometry etc. In addition, the radial lip seals must have a certain pre-load and interference in order to provide a good sealing. This also affects the friction torque. Researchers are developing new seal designs to reduce friction losses in mechanical systems. In the presented study, the effect of the lip seal geometry on sealing performance will be examined numerically. The numerical model created for this purpose will be verified with experimental data firstly. In the numerical model, shaft and seal will be modeled as hyper-elastic in 2D and 3D. NBR (Nitrile Butadiene Rubber) as seal material will be analyzed for the rotating shaft state at constant speed by applying a uniform radial force.

Effect of shaft roughness and pressure on friction of polymer bearings in water

In this study, the frictional behavior of selected commercially available unfilled polymers, namely, polyether ether ketone, polytetrafluoroethylene, polyethylene terephthalate, and ultra-high molecular weight polyethylene against an Inconel shaft was investigated using a journal bearing test configuration in water-lubricated sliding contact. Dynamic friction curves were obtained for various shaft roughness values and polymer combinations. The results showed a significant influence of shaft surface roughness on running-in and steady state friction in water-lubricated conditions. Contact angle measurements revealed a significant increase in wettability of Inconel counterfaces. The X-ray photoelectron spectroscopy (XPS) analysis of the surfaces suggests formation of a reaction layer on worn Inconel surfaces when sliding against the polymers. The influences of counter surface roughness and load on frictional response of polymers were studied through intermittent tests by obtaining dynamic and breakaway friction maps for different polymer materials, shaft roughness values, and pressure combinations. In general, a trend of decreasing friction was obtained with increasing contact pressure; however, the materials’ frictional responses to variations in counter surface roughness were different. These results indicate that although a reduced counter surface roughness may be beneficial for dynamic friction of polymers in all lubrication regimes, it can adversely affect the materials’ breakaway friction response.

Study on the Characteristics of the Hull Vibration Caused by the Shaft Surface Roughness

Nowadays vibration of hull caused by the shaft surface roughness has caught attentions all over the world. In this paper we conducted a brief analysis on this project based on the contact theory and FEM. Firstly, we calculated the contact force based on numerical simulation and contact theory. Then we analyzed the effects of speed and shaft surface roughness on the hull vibration. Results show that the effect of shaft surface roughness on the hull vibration is greater than that of speed. But when the frequency of contact force gets close to the natural frequency of hull, the effect of speed becomes obvious. These conclusions have large significance on the selection of shaft and the design of hull.

Basic Research on Ultrasonic Extrusion for 45 Steel Shaft

Research on ultrasonic extrusion under different process parameters for 45 steel shaft based on orthogonal test is carried out. The influences of various process parameters on shaft surface roughness and micro hardness are analyzed. The experimental results show that the influences of tool radius, pre-pressure, feed rate and rotating speed in the ultrasonic extrusion on surface roughness and micro hardness are different, but there are optimal values in the given experimental conditions. Compared with conventional extrusion, it can reduce the part surface roughness and improve surface micro hardness significantly in the process of ultrasonic extrusion.

Experimental Study on Optimizing Process Parameters in Two-Dimensional Ultrasonic Rolled Extrusion

Two-dimensional ultrasonic vibration was introduced into common rolled extrusion, effect of the process parameters including tool head radius, feed speed, preload and spindle speed on the 45 steel shaft surface roughness were analyzed through orthogonal experiments. Experimental results show that lower value of surface roughness may be obtained in the process of two-dimensional ultrasonic rolled extrusion than that of common rolled extrusion, and the influence order of process parameters on surface roughness is feed speed, spindle speed, preload and tool head radius; the influence curves of tool head radius and spindle speed on surface roughness are concave curves, and influence curves of feed speed and preload on surface roughness are convex curves, or optimizing process parameters exist. The empirical formula for surface roughness is given using multiple regression analysis based on the experimental results. This study will provide a new technique for finishing precision parts.

A Transient Mixed Lubrication Model of a Rotary Lip Seal with a Rough Shaft

A rotary lip seal, widely used in machines containing rotating shafts, is usually protected from mechanical and thermal damage by a thin film of lubricant under the lip, separating the lip and the shaft surfaces. However, under some transient conditions such as those during startup and shutdown, the fluid film is not fully established or it breaks down, and the seal operates in the mixed lubrication regime. To simulate such cases, a transient mixed lubrication analysis has been developed. It generates predictions of such seal operating characteristics as load support sharing between hydrodynamic and contact pressure, contact and cavitation area ratio, the reverse pumping rate, and the average film thickness. In most previous numerical simulations of the rotary lip seal, the shaft surface is modeled as perfectly smooth. In the present study, a more realistic shaft surface with asperities is used, and the effect of the shaft surface roughness on the behavior of the seal is investigated. Presented at the STLE Annual Meeting in Calgary, Alberta, Canada May 7-11, 2006 Review led by Luis San Andres

Hydrodynamic effects of shaft surface roughness on rotary lip seal behaviour

Richard F. Salant and Dawei Shen, Georgia Institute of Technology, Atlanta, Georgia, USA The early pioneer of research on elastomeric rotary shaft lip seals was the late Dr Ernest Jagger. During the 1960s, he demonstrated the existence of the lubricating film under the seal and proposed methods of load support and film control. Modern computing power has permitted a detailed theoretical study, much of which helps to confirm many of Jagger’s ideas. Research has now progressed to a stage where the shaft surface roughness can also be considered. This feature article, based on a paper originally presented at the International Sealing Conference, Stuttgart in September 2002, describes some of these studies.

Scuffing Failure of Hydrodynamic Bearings Due to an Abrasive Contaminant Partially Penetrated in the Bearing Over-Layer

Scuffing Failure of Hydrodynamic Bearings Due to an Abrasive Contaminant Partially Penetrated in the Bearing Over-Layer

Laboratory simulation to select oil seal and surface treatment

Reliability of rotary oil seals depends on many parameters related to seal design and material, shaft material, hardness and surface texture, medium; operating conditions, etc. This presentation will describe the accelerated testing methodology development as well as the results of shaft surface roughness and hardness analyses to decrease wear in rotary oil seal lips. Seals went through 200 h of accelerated testing which not only reproduced operating conditions but duplicated field service mode or seal lip and shaft wear mechanisms during accelerated testing. Dana's new oil seal accelerated tester has many unique features: (1) reproduction of several extreme operating conditions including oil temperature cycling and superposition of reciprocal motion; (2) devices to easily change shaft-to-bore misalignment and shaft eccentricity, and (3) measurement equipment for torque evaluation and photo-optical oil leak detection. The methodology consists of establishing simple engineering parameters including the number of tested cycles before the leak, oil seal lip wear path, shaft surface groove depth under oil lip, varieties of shaft surface roughness, and friction forces between seal lip and shaft surface. An important part of this methodology is detailed metallurgical and metrological examination of the field and lab test usage of the oil seal lips and shaft surfaces including SEM and EDX analysis. The shaft surface hardness and roughness characteristics, including core roughness depth, reduced peak height and valley depth, their ratios, and their influence on seal lip wear will be presented.

Optimized Design of Vibration Controllers for Steady and Transient Excitation of Flexible Rotors

Controller designs for the attenuation of rotor vibration are investigated. Disturbance inputs leading to vibration are classified and related to control forces and defined control states. Optimization based on the H∞ norm is then used to minimize the influence of forcing disturbances, modelling error and measurement error. The practicalities of applying the method to an experimental rotor-bearing system, with hardware constraints on controller order, are stated. The controller was implemented experimentally to conduct steady state and mass loss tests. Steady synchronous, non-synchronous and transient vibration attenuation was demonstrated. It was also shown that measurement error, caused by shaft surface roughness, can be incorporated into the controller design without the need to remove the roughness component from the measured displacement signals. If the roughness influence is not included in the design and the uncontrolled vibration is small, unnecessary control forces may result, causing an increase in vibration.

A Study of Characteristics of the Controlled Oil Leakage of Valve-Stem Seals for Automotive Engines

It is well known that the valve-stem seal has been used for the valve-stem application of automotive engines, and influences the lubricating status between the valve stem and a valve guide. The valve-stem seals are important in controlling consumption of lubricating oil for engines and in preventing air pollution. It is necessary that valve-stem seals have stable controlled oil leakage characteristics, Q (cm3/s), relative to variables such as oil viscosity, shaft speed and shaft-surface roughness. In this paper, characteristics of the controlled oil leakage on valve-stem seals have been discussed by applying an inverse problem of hydrodynamic lubrication.

Facts about fluid sealing

A rotary shaft lip seal operates with a lubricant film separating the seal from the shaft. In this paper the authors present experimental measurements of under‐lip temperatures which show that there is an optimum shaft surface roughness, and present thermal solutions for various convective heat transfer conditions which illustrate that the shaft conductivity is the predominant factor which affects the under‐lip temperature.