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Shaft surface manufacturing methods for rotary shaft lip seals
Abstract
Manufacturing methods such as hard turning are of interest to produce the counter face for rotary shaft lip seals to provide an economical replacement for plunge grinding. Currently applications are restricted due to lack of experience with such shaft surfaces. This article describes research work to investigate the suitability of several manufacturing processes by studying the pumping rate of the seals. The work shows that several surface finishing methods – including axial, plunge and tangential turning – can be used.
... Grinding is one of the most commonly used methods for finish machining of countersurfaces for radial shaft seals as it allows for the generation of twist-free surfaces, which impede significant conveying during rotation [3]. Nevertheless, from an economic and environmental point of view, this process entails numerous disadvantages, such as high Surfaces 2022, 5 396 investment costs, strongly limited flexibility, low predictability of the achieved surface, and poor energy efficiency [4,5]. ...
... As an alternative, hard turning offers advantages such as greater flexibility, the opportunity for complete and dry machining, and the elimination of spark-out times [4,6]. However, it generates surfaces with a twist structure that could lead to a rotation-dependent conveying effect of the sealed lubricant [7]. ...
... The disadvantages are the very high demands on the quality and the alignment of the cutting edge parallel to the workpiece axis [6]. In tangential turning, a wide cutting edge is used, which is inclined by a defined angle over the workpiece [4,10]. The point of contact moves along the cutting edge of the tool, and a twist-free surface is created. ...
Counter-surfaces for radial shaft seals are usually finished by infeed grinding to avoid macro twist structures on the surface since they can impose a conveying action on the lubricant. This can lead to either leakage or starved lubrication and subsequent thermal damage depending on the direction of said conveying action. Turning processes can offer a more cost-effective surface finish, but conventional methods cause twist structures, which can impair the leakage prevention of the sealing system. An approach for the production of twist-free surfaces was developed based on new kinematics for turning. However, the surfaces produced with this approach using case hardened specimens made from the steel 16MnCr5 show deviating structural characteristics compared to the kinematic simulation. The causes of this and the resulting influence on the conveying value are the subjects of the research work. For this purpose, in addition to hardened steel, two other materials are considered: the steel 16MnCr5 in the unhardened hot rolled delivery condition and brass as a material with good machinability. The results clearly show that there is a deviation in the machining behavior of the steel materials compared to the kinematic surface simulations, especially in the repeatedly turned areas. This is mainly due to elastic–plastic deformation effects. Despite the actually twist-free surface profile, certain characteristics result in an anisotropic structure, which partially has an influence on the conveying value.
... This functional property concerns often the counter face for rotary shaft lip seals produced by plunge grinding and hard turning operations (axial, plunge and tangential ones) [14]. The required roughness parameters are the maximum roughness height (SL) Rz between 1 and 5 m or equivalently the roughness average Ra between 0.2 and 0.8 m and the maximum roughness height (EL) Rt<0.63 m. ...
... The required roughness parameters are the maximum roughness height (SL) Rz between 1 and 5 m or equivalently the roughness average Ra between 0.2 and 0.8 m and the maximum roughness height (EL) Rt<0.63 m. Because these parameters are not sufficient to characterize the shaft surfaces for sealing applications, some additional bearing parameters such as the upper material ratio Mr1 between 50 and 70% at the cut of 0.25 Rz and two ratios Spk/St (0.40 after turning and 0.55 after plunge grinding) and Sk/St (0.40 after turning and 0.48 after plunge grinding) are proposed [14], [15], [16]. Moreover, the skew parameter Rsk (Ssk) has been shown to be a useful measure for seals and peak curvature Ssc to define elastic contact which characterizes lip seal performance [6]. ...
This literature survey highlights the possible influences of surface roughness parameters on functional properties of surfaces produced by different finishing operations. The prediction of such functional properties as fatigue, sealing capacity, adhesion, friction, wear and corrosion resistance based on five groups of spatial (S) roughness parameters is overviewed. In contrast, traditional approach based on 2D roughness parameters is provided. Some real 3D surface topographies produced with desired functional properties by finishing cutting and abrasive operations are characterized. This survey confirms the vital role of machined surfaces in the functionality of machine components. © 2016, Editorial Institution of Wrocaw Board of Scientific. All rights reserved.
... In vehicular differentials and transmissions, as in many other applications, leaking seals can lead to environmental pollution, also resulting in excessive warranty claims. 1,2 The performance of a sealing system, comprising a gearbox, rotary shaft seals and a driveshaft is significantly influenced by several internal and external factors during various vehicle manoeuvres. 3 These influential factors/conditions are shown in Figure 1. ...
There is an ever-increasing stringent directive for environmental protection, even for the previously rather negligible lubricant leakage from vehicular drivetrains. Leakage from transmissions and differential units are no longer permitted and can lead to excessive warranty costs. Additionally, the trend in component downsizing, including for sealing systems has indirectly altered the leakage behaviour of transmissions. To guarantee leakage-free operation, it is important to establish standardised methods of manufacturing processes, particularly for surface topography of shafts. The paper investigates the leakage from two different shaft machining processes: corundum and cubic boron nitride (CBN) grinding. The performance of passenger car transmission sealing system is ascertained with the development and use of a novel detailed representative fully instrumented test rig. A test protocol is set up to assess the performance of shafts during break-in period and correlate shaft topographic data with its measured performance. The results show that the measured oil leakage correlates well with the shaft surface skewness whilst no particular trend is observed with Ra, Rz and shaft lead angle values, which form the basis of most current standards used in industry. Overall, it was observed that shafts with negative skewness in their roughness profile produced lesser leakage. A basic analytical predictive method is also developed which corroborates with the measured data.
... Plunge grinding is shown to minimize the shaft lead and, consequently, the liquid pump rates. 31 Studies on pressurized rotary lip seals are scarce. Jagger 1 studied at what maximum pressure difference a rotary seal could operate without leaking, given a specific shaft velocity and loading of the contact. ...
Stern tube seals are a key component of the propulsion system of a ship. The purpose of these sealing rings is to ensure a reliable sealing condition, preventing the spillage of lubricant to the environment. The research on these large rotary seals is limited due to their complex accessibility: stern tube seals are located below the seawater level on a moving ship. A dynamic setup replicating the operating conditions of a stern tube seal is presented together with a novel arrangement for monitoring the flow rate across the seal. The frictional torque, the operating temperature, and the lubricant migration across the seal are measured under various shaft velocities and pressure differences. The existing theory for rotary lip seals is reviewed for the stern tube seal application. From the results it is deduced that the stern tube seals tested operate within the elastohydrodynamic regime with film thicknesses in the sub-micrometer range.
... W rzeczywistości wiele czynników ma wpływ na występowanie zjawiska uszczelniania w wargowych pierścieniach uszczelniających. Również geometria wału w skali mikro, ślady po obróbce powierzchni decydują o skuteczności procesu uszczelniania [6,7]. Jakość wykonania i montażu decydująca o współosiowości pierścienia względem wału jak i odchyłek kształtu samego wału to kolejne czynniki decydujące o skuteczności uszczelniania. ...
The article discusses the cooperation of the elastomeric sealing ring with the shaft in terms of wear and losses to overcome friction forces, the construction of a classic seal and a seal with reduced resistance to movement. Because the lip-shaft system is a specific friction pair, the focus has been on local micro contact conditions as a parameter that determines global motion resistances on a macro scale. Since the occurrence of premature sealing failure in spite of small costs of the element itself generates serious costs of repair and downtime of the transport fleet, the problem of durability and reliability of the described type of seals remains valid.
... The shaft was fabricated from stainless steel (SUS304-JIS), and had a diameter of 8 mm. The 0.02-µm surface roughness (Ra) of the rotating shaft was prepared by implementing a conventional lapping method (Thomas et al., 2005). The LLC was diluted to a concentration of 50% using distilled water, heated to 75 °C, and then pressurized to 0.3 MPa. ...
Power devices used for power control in electric vehicles have the drawback of high heat-generation, which can be effectively addressed by water-cooling. Their durability is affected by the performance of the seal lip in the coolant pump. The seal lip, in which a rotating shaft passes between liquid and gas phases, plays an important role in the separation of the two phases. To cool power devices, a specifically designed seal lip is required, as the seal lip is subjected to high pressure and temperatures of the water-based coolant and high-speed shaft rotation. A new type of seal lip has been developed by employing a biomimetic mechanism in which the hydrated lubrication mechanism found in natural articular cartilage is adopted. A fiber-reinforced PVF (polyvinyl formal) was employed as the hydrated and biomimetic seal lip material. The bio-inspired seal lip was attached to the shaft. Shaft rotation was controlled by a servomotor, which generated a speed of 5,000 rpm (revolutions per minute). An LLC (long-life coolant) was used as the coolant, which was diluted with distilled water at a concentration of 50%, heated to 75 °C, and pressurized to 0.3 MPa. Although the continuous leakage of LLC was observed, it was estimated that the bio-inspired seal lip might prevent the abrupt function failure in air-LLC separation. The frictional torque of the bio-inspired seal lip was lower than that of the conventional oil seal. These results suggest that the bio-inspired seal lip is a useful component in the water-cooling systems of high-power devices.
... The axial accuracy was guaranteed by the installation of a shaft seal and two bearings into the same body. The rotating shaft was made of stainless steel (SUS304, JIS) and its surface roughness was approximately 0.02 µm as shown in Fig. 3 ( Thomas and Werner, 2005). From a tribological viewpoint, the seal ring had a direct contact face against the rotating shaft in boundary lubrication mode. ...
The lips of a shaft seal need to be lubricated to ensure its performance. Such seals are subjected to difficult conditions inside water pumps or underwater mechanical systems. Poor lubrication can cause high friction and wear of seal lips. A new shaft seal was designed to prevent water ingress with low friction and high wear resistance by adopting hydrophilic materials to seal rings. Hydrated composites for seal rings were developed with fibers to avoid excessive deformation. In experiments, cellulose nanofibers were most appropriate for reinforcement of the matrix material and the shaft seal exhibited its sealing performance at the speed of 5000 rpm under pressure of 0.8 MPa. This shaft seal will be useful not only for industrial pumps but also for generation systems driven by water flow, such as ocean current or streamflow.
... Its surface was polished to a mirror finish of approximately 0.02 mm (Ra) 12 because the surface topography of the rotating shaft can influence the pumping ability of the seal lips. 13 Figure 5 presents the details of the seal holder for two seal rings. This holder was attached to the water chamber, as shown in Figure 4. Any leakage from the sealing system was collected in a pan covering the seal holder. ...
Shaft seals with a seal lip are used in various applications to separate gases and fluids, but their sealing function and durability are affected by the extent of lubrication at the dynamic seal faces between a rotating shaft and the seal lip. A new sealing system consisting of two hydrated seal rings and non-Newtonian lubricants was designed by a biomimetic approach to minimise frictional loss and provide high waterproof function when separating air and water. This system demonstrates significant superiority in low-speed rotation, conditions under which the lubrication mechanism of an oil seal or mechanical seal does not generally work well. Fibre reinforcement of the seal ring material was performed to prevent the deformation of the soft seal rings because of the frictional force in the tangential direction of the shaft and water pressure. This reinforcement enabled the new sealing system to obtain both high waterproof performance and low frictional characteristics in the speed range of 20–100 r/min.
... Steel balls (AISI 52100) of 25.4 mm diameter were used as sliding counterface after etching in 20% Nital solution for 20s, such that a fine pitting surface with a uniform roughness of 0.3 mm Ra was achieved, as suggested by Rutherford and Hutchings [17,18]. The roughness corresponds to the roughness value used in actual rotary shafts [23]. The roughness of the elastomeric samples was measured by using an optical profilometer (Contour GT-K, Bruker) while the roughness of the spheres was obtained by using a Dektak 150 stylus (contact) profilometer. ...
Elastomeric dynamic seals are components to prevent or to limit lubricant leakage in machinery. Nevertheless, they wear away under certain working conditions. Mostly, wear exists by starvation of lubricant film (two-body abrasion) and interaction with hard debris (three-body abrasion). This work aims to propose a suitable test methodology toward determining two-body and three-body abrasive wear rates of elastomers by using a TE66 Micro-Scale Abrasion Tester. In the tests, sections of silicone rubber were used. The experiments were divided in two parts. Firstly, dry runs were carried out replicating the two–body abrasion mechanism. Secondly, trials were run using two different media (contaminated oil and slurry) to reproduce three-body abrasive wear. Large viscoelastic deformations were generated in the samples and then they were considered for the wear estimation. In conclusion, the method shows advantages which make it suitable as an alternative test to obtain the wear behavior of sealing elastomers.
... The research included: the effect of cutting speed v c =100-200 m/min, feed f=0.1-0.3 mm/rev, depth of cut a p =0.1-0.2 mm, and length of cutting distance L on: unit production cost K j , time per unit t j , resultant cutting force F and selected parameters of the surface roughness: R a , R z and R max [24]. The research was carried out with respect to the machined surface mating with sealing rings (Radial shaft seal), where the following parameters are recommended: R a =0.2-0.8 µm, R z =1-4 µm i R max ≤6.3 µm [12]. On the basis of experimental research results formulas [24] were developed for: unit production cost - ...
In this paper a Modified Particle Swarm Optimization (PSO) method for multi-objective (MO) problems with a discrete decision space is proposed. In the PSO method the procedure to determine inertia weight, learning factor and social factor is modified. In addition, both an elitism strategy and innovative deceleration mechanism preventing the particles from going beyond the limits of decision space are introduced. The proposed approach has been applied to a series of currently used test functions as well as to optimization problems connected with finish hard turning operation, where the obtained results have been compared with those obtained by means of Genetic Algorithms (GA). The results indicate that the proposed approach is relatively quick, and thus it is highly competitive with other optimization methods. The authors have obtained a very good diversity, convergence and a maximum range of the Pareto front in the criteria space. In order to assess the quality of the generated Pareto set for each of presented examples, a rating has been determined based on the entropy measurement and inverted generational distance (IGD).
... The problem of finishing operations of a surfaces mating with radial shaft seals (Simmerring ring) is known for a long time and was discussed in the [1][2][3]. Especially, it concerns the shafts made from 18CrMo4 alloy steel with low contents of carbon, often used as a material for toothed elements in Poland. The surfaces mating with the radial shaft seals should fulfill suitable requirements in relation to dimensional accuracy and properties of surface layer [4][5][6]. ...
S u m m a r y A research results of surface texture after finish turning operation with plunge feed of hardened 18CrMo4 steel with use of cubical boron nitride (CBN) inserts having Wiper geometry are presented in this paper. The research was conducted according to Taguchi methodology, especially for mating of the machined surface with radial shaft seals. Next, the surface after finish turning with plunge feed was compared with the surface after plunge grinding, while assessment indicators used to this purpose testify a substantial similarity of the two surfaces.
Conventional turning results in surfaces with a twisted surface structure. However, for some applications of machine parts, twist-free surfaces are recommended. These surfaces can be obtained by grinding or turning with special one-purpose machine tools. Alternatively, a proprietary start-stop turning method can be used and applied on multi-purpose turning machine tools. In order to manufacture twist-free surfaces with start-stop turning, a conventional lathe is equipped with an additional short-stroke air bearing drive system. A series of experiments with specimens of hardened steel is performed and the effects of the process parameters nv (number of workpiece revolutions in the stop-phase) and vHub,v (short-stroke velocity in the positive direction of the machine tool feed motion) on the surface properties are investigated. The results show that the surface structure and the so called transition area lengths can be influenced by the settings of process parameters nv and vHub,v. The findings can be used to predetermine surface structures for machine parts and applications such as surfaces with demanding requirements regarding tribology.
Stern tube seals are a type of rotary lip seals used in the propulsion
system of ships. These large-sized elastomeric components are placed
at both ends of the stern tube of a ship preventing the lubricant
spillage to the environment while, at the same time, avoiding the
entrainment of seawater to the stern tube. The ideal leakless situation
does not occur and, in reality, a continuous amount of lubricant is
discharged to the ocean. The continuous spillage of lubricant is
normalized in the marine industry and it is typically referred as the
stern tube consumption. To limit the environmental impact of the oil,
new legislations replaced the traditionally-used mineral oil-based
lubricants for less environmentally harmful products, i.e. the
Environmentally Acceptable Lubricants (EALs). However, these
lubricants have brought all sorts of issues with the already existing
stern tube system of a ship, especially the stern tube seals. The
investigation conducted aimed to shed some light on the operation of
the stern tube seals in combination with these greener lubricants. This
project was divided in three parts: the data collection, the modelling
and the validation.
The first part consisted in obtaining the necessary information for
developing the computational models. The characteristics of the tribosystem
and the window of operation were investigated. The knowledge
on Environmentally Acceptable Lubricants is limited and hence
especial attention was paid to comparing the common mineral oilbased
lubricants to the EALs. Additionally, the seal and shaft
materials, the garter spring and the surface roughness were analysed.
The modelling part began by building a robust axisymmetric static
model of the stern tube seal, i.e. when the shaft is not rotating. This
thermomechanical model served as base on which to build more
complex models of the seal. Next, the dynamic operation of the seal
was modelled. Due to the complex alignment between the propulsion
shaft and the stern tube seals, it is likely that the seals operate under
non-concentric conditions. The focus of the research is placed on the
lubrication mechanisms that develop as a consequence of such a
misalignment. Two misalignment-induced hydrodynamic pressure
build-up mechanisms are presented complementing the primary
lubrication mechanism theory governing the operation of rotary lip
seals.
Validation has been done on many aspects of the models developed.
The unavailability of data on stern tube seals required from
specialized setups for the validation of the models. Three specialized
setups has been developed and used in this research: a split-shaft
setup, a static glass shaft setup and a dynamic setup. The radial force
between the shaft and the seal was measured via a large-sized splitshaft
setup. The width of the contact and the percolation threshold of
the seal was measured using the glass shaft test rig. Ultimately, the
third setup made it possible to study the behaviour of stern tube seals
under real operating conditions.
With the knowledge gained on the EALs, the models developed can be
used to significantly shorten the effort required to develop a EALsuitable
seal design. On the longer term, the work presented will give
the seals and lubricants manufacturers the opportunity to redesign
their products resulting in a less contaminant sailing while extending
the service time of stern tube seals.
This paper aims to investigate the degradation of physical and tribological properties (friction coefficients and wear resistance) of a dynamic sealing material (silicone rubber (VMQ)) exposed to Jatropha oil (JO), engine mineral oil (EMO) and a blend (B20) (80% EMO – 20% JO), separately. JO has demonstrated better lubricating properties than EMO´s in various mechanical applications; however, the degradation of elastomers by using this oil has not studied yet, and even less its effect on their tribological properties. The physical degradation was evaluated by conducting static immersion tests (670 h at 25°C) based on the ASTM-D471 and ASTM-D7216 methods. Hence, the changes in mass, volume, tensile and tear strengths, and hardness of VMQ were measured. Also, creep compliance tests were conducted to determine the changes in viscoelastic property, as well as, the changes in morphology and topography were measured by SEM and optical profilometry, respectively. In addition, the compositional changes were determined by FT-IR analyses to complement the degradation examination. On the other hand, the changes in friction coefficients were determined by ball-on-disk tests while the changes in wear resistance were obtained by accelerated wear tests (micro-abrasion tests). Finally, VMQ exhibited no significant physical and compositional degradation by the immersion in the three lubricants. However, considerable changes in the friction coefficients and wear resistances were observed, being the changes in friction coefficients minimal by using JO. Also, the coefficients by using JO were 50% lower than EMO and the wear resistance changes were the lowest after immersion in JO.
On the basis of elastohydrodynamic model established by the present authors in advance, the present study numerically analyzes the influence of the axial position of contact zone on the sealing performances of lip seals with different micro-dimple texture shapes (circle, square and triangle) on the shaft surface, assuming a smooth elastomer and that the contact zone spans only a few rows of texture. It is found that the triangle micro-dimple texture shape that can always produce positive pumping rate no matter where the contact zone locates on the shaft surface. According to the determined texture shape, parameter analysis is conducted to select the optimal shape parameter that is less sensitive to the axial position of contact zone and produces more pumping rate and less friction torque.
In order to study the influence of surface topography of shaft on pumping action and frictional properties of lip seals, the surface textures on rotary shaft are textured with a solid-state pluse Nd: YAG laser, and a series of comparison experiments under different rotational speeds, different surface topographies are conducted on an oil seal tester, some parameters such as pumping rate, friction force and temperature increment of seals during the experimental process are measured. Some lip surfaces after experiment are analyzed using scanning electron microscopy. The results show that the surface with triangular micro cavity toward oil side could enhance the pumping action, and the rotational speed plays an important role on pumping rate. The rest textured surfaces don't have positive effect on pumping action. In contrast with the surface without laser texturing, the surfaces with circle micro cavity having area densities of 7% and 21% show better friction reduction, and with triangular micro cavity lagging and leading can reduce the friction.
Rotary shaft lip seals are very frequently used dynamic seals. Large numbers of them are in use in many different applications. The sealing ring, the shaft and the sealed fluid form a complex sealing system. For a successfully operating sealing system an adequate combination of the components is required. Between the sealing lip and the rotating shaft there must be a thin lubricating film of oil. The "reverse pumping" process in the sealing zone prevents leakage through the film. This sealing mechanism is caused by microasperities on the lip surface and also affected by the shaft surface. In the sealing area most shafts are manufactured by plunge grinding. With rotary shaft lip seals they form a well operating sealing system, as the experiences of the last years show. However, this machining process takes long and is expensive. There is need at more economical processes for the machining of the sealing area on shafts. In some applications hard turned shafts are already used successfully. At Institute of Machine Components sealing systems with differently machined surfaces were examined. Ground, hard turned, rolled and shot-blasted shafts were used. The pumping effect and the friction torque were investigated in short-term tests. Leakage and wear of the sealing system were examined in 240h tests. The test results and their meaning for practice are explained.
Seals and Sealing Handbook, 6th Edition provides comprehensive coverage of sealing technology, bringing together information on all aspects of this area to enable you to make the right sealing choice. This includes detailed coverage on the seals applicable to static, rotary and reciprocating applications, the best materials to use in your sealing systems, and the legislature and regulations that may impact your sealing choices. Updated in line with current trends this updated reference provides the theory necessary for you to select the most appropriate seals for the job and with its Failure Guide, the factors to consider should anything go wrong. Building on the practical, stepped approach of its predecessor, Seals and Sealing Handbook, 6th Edition remains an essential reference for any engineer or designer who uses seals in their work.
Für ein zuverlässig funktionierendes Dichtsystem Radial-Wellendichtung ist die Wellenoberfläche von entscheidender Bedeutung. Als tribologischer Partner des Dichtrings ist die Wellenoberfläche direkt durch die gegebenenfalls vorhandene Eigenförderung und indirekt durch die Beeinflussung der Dichtringförderung für die Gesamtfunktion ausschlaggebend. Dieser Bedeutung wird durch strenge Vorgaben hinsichtlich der Herstellung und Ausprägung der Wellenoberfläche in den gültigen Normen Rechnung getragen.
Kostenreduktion und Prozessoptimierung erfordern Alternativen zu dem Jahrzehnte alte Fertigungsverfahren für Wellenoberflächen härten und im Einstich schleifen. Im Rahmen dieser Arbeit sollten einerseits in Frage kommende alternative Wellenoberflächen untersucht werden, und andererseits eine Vorgehensweise entwickelt werden, mit der entsprechende Wellenoberflächen hinsichtlich ihrer Eignung als Gegenlauffläche für Radial-Wellendichtringe erprobt und beurteilt werden können.
Dazu wurde im Rahmen dieser Arbeit eine vierstufige Vorgehensweise entwickelt. Ausgehend von der berührungslos optisch vermessenen 3D-Oberflächentopografie werden dabei für die vorliegende Wellenoberfläche anhand eines auf der Bildverarbeitung beruhenden Verfahrens charakteristische Kennkurven ermittelt. Anhand dieser Kennkurven kann die Oberflächenstruktur beurteilt, und durch typische Merkmale klassifiziert werden.
Im zweiten Schritt wird der Förderwert der Wellenoberflächen in beiden Drehrichtungen gemessen. Gilt die untersuchte Wellenoberfläche weiterhin als geeignet, wird im dritten Schritt ein erster Funktionstest im Dichtsystem durchgeführt.
Im vierten und letzten Schritt wird die Funktionalität des Dichtsystems über einen längeren Zeitraum beobachtet, um die Langzeiteigenschaften abzusichern. Dazu wird die vom Autor entwickelte modifizierte Zweikammermethode eingesetzt. Durch die Messung des Systemförderwerts in regelmäßigen Abständen, kann dessen Veränderung und somit die Veränderung der Dichtfunktion im Betrieb vermessen werden. Die eingesetzte Wellenoberfläche, aber auch alle übrigen Systemkomponenten können so hinsichtlich der Auswirkung auf die Dichtfunktion und Langzeiteigenschaften beurteilt werden. Dadurch sind künftig weitreichende Untersuchungen am Dichtsystem mit der Option, in das Dichtsystem hineinzublicken, möglich.
Der Schwerpunkt der so untersuchten alternativen Fertigungsverfahren lag im Bereich der Drehverfahren. Es wurden Parameterstudien für längsgedrehte Wellenoberflächen unter Verwendung von ungehärteten und gehärteten Werkstoffen durchgeführt. Variiert wurde: Vorschub, Schneidenradius, Einfluss von Maschinen- bzw. Werkzeugschwingungen und Schneidenverschleiß. Zusätzlich wurden Nachbearbeitungsverfahren und Drehverfahren ohne axialen Vorschub, wie das Tangentialdrehen und das Drehen im Einstich untersucht.
Grundsätzlich sind die längsgedrehten Wellenoberflächen, hart oder weich, als Gegenlauffläche für Radial-Wellendichtringe geeignet. Speziell die längs-hartgedrehten Wellenoberflächen zeigen kein drehrichtungsabhängiges Förderverhalten und geringe Förderwerte. Die längs-weichgedrehten Wellenoberflächen zeigen ein teilweise von der Drehrichtung abhängiges Förderverhalten, welches jedoch keine negativen Auswirkungen auf das Dichtverhalten hatte.
Auch die ohne axialen Vorschub hartgedrehten Wellenoberflächen sind geeignet, wobei die sehr glatten Oberflächen zu geringen Förderwerten der Wellenoberfläche und des Dichtrings führen. Die durch Bandfinishen oder Kurzhubhonen hervorgerufenen, sehr feinen und meist schräg zur Wellenachse gerichteten, Riefenstrukturen sind äußerst förderintensiv. Sie können zu großer Leckage oder ungünstigen Schmierungsbedingungen im Dichtsystem führen. Diese Verfahren sind damit keine taugliche Alternative.
Die makroskopische Drehwendel hat offensichtlich keinen Einfluss auf die Fördereigenschaft der Wellenoberfläche, eingebrachte Mikrostrukturen jedoch zeigen einen erheblichen Einfluss. Daraus kann abgeleitet werden, dass die Fördereigenschaften der Wellenoberfläche fast ausschließlich von deren Mikrostruktur bestimmt werden, die größenordnungsmäßig deutlich unterhalb z.B. einer Drehwendel (Steigung ca. 0,05 bis 0,3 mm) liegt.
Anhand der hier vorgestellten Vorgehensweise können beliebige Wellenoberflächen dichtungstechnisch geprüft und beurteilt werden. Künftig ist eine direkte Kennwertbildung aus den vorliegenden charakteristischen Kennkurven denkbar. Zur Verbesserung der Aussagemöglichkeiten sind weitere Erfahrungswerte hinsichtlich der Auswirkungen bestimmter Oberflächenstrukturen, Ausprägungen (z.B. Breiten-Längenverhältnis) etc. nötig. Dazu bietet unter anderem die Beobachtung des Systemförderwerts im Betrieb weit reichende Untersuchungsmöglichkeiten.
The purpose of this study is to investigate the effects of shaft surface roughness, speed, seal inner diameter, and lip geometry on the rotary lip seal’s performance. For this reason, a test system was developed. In this test system, a cylinder block is placed on four load cells to monitor the friction torque generated between seal and counter face. Radial lip geometry was taken as the prior criteria to group the seals for experiments. Two different profiles (with and without dust lip) and three different inner diameters (30-35-40 mm) were selected for the tests. Three shaft surface roughness values for each diameter were also tested. One shaft surface roughness value is between the limits that are recommended in standards, and two others are greater and less than that limits. At the end of the systematical experiments, variations of friction torque with respect to shaft surface roughness, lip profile and shaft diameter have been determined.
On the basis of elastohydrodynamic model, the present study numerically analyzes the effect of various microdimple texture shapes, namely, circular, square, oriented isosceles triangular, on the pumping rate and the friction torque of radial lip seals, and determines the microdimple texture shape that can produce positive pumping rate. The area ratio, depth and shape dimension of a single texture are the most important geometric parameters which influence the tribological performance. According to the selected texture shape, parameter analysis is conducted to determine the optimal combination for the above three parameters. Simultaneously, the simulated performances of radial lip seal with texture on the shaft surface are compared with those of the conventional lip seal without any texture on the shaft surface.
Starting from the fact that the experimental data are real data, and that the assessment of their values is of great importance in a design of the structure, this article seeks to draw attention to the designers of experimental data related to steel 20MnCr5 (1.7147, AISI 5120). In this sense, this paper presents the experimental results involving material ultimate tensile strength, yield strength, creep behavior, total fracture strain, reduction in the area as well as Charpy impact energy. All of the mentioned tests were conducted at room temperature and at elevated temperatures. Considerable tensile testing referring to determination of ultimate tensile strength as well as 0.2 offset yield strength resulted in engineering stress–strain diagrams, while those tensile testing regarding creep behavior resulted in creep curves. Also, modeling of material creep behavior using rheological models and an equation proposed by the authors can be found in this paper. Using Charpy impact energy tests, an assessment of fracture toughness was made. In addition to this, the paper presents a comparison of the material properties of 20MnCr5 steel with material properties of other similar (structural/constructional) steels.
A detailed numerical understanding of elastomer and plastic seals for dynamic applications is limited compared with current knowledge covering seals that use ‘hard’ materials, such as clearance and rotary mechanical face seals. Some of the key testing and research that has provided a thorough understanding of elastomer seals – enabling their empirical development over the last 50 years – is reviewed. The numerical analysis of rotary shaft lip seals is now well established and this is compared with practical experience.
The feature articles in Sealing Technology over the last year have included a wide variety of rotary seal designs, reciprocating seals and static seals. In addition elastomer material developments, emissions legislation and research work have been discussed. Contributions have varied from updates on standards to detailed numerical analysis. This feature is intended to provide an overview of the topics covered during the year.
A simulation model to predict pumping by shafts with various surface finishes, in combination with a rotary lip seal, has been developed and validated by experiment. The model consists of a fluid mechanics analysis of the flow in the sealing zone coupled with a deformation analysis of the seal. The experimental validation consists of pumping rate measurements with shafts whose surface structures contain laser generated oblique grooves. Plots of pumping rate vs. various parameters show good agreement between the model and experiment. Plots of torque vs. speed, as well, show good agreement between the model and experiment.Research highlights► Simulation model to predict pumping by shafts with various surface finishes, in combination with a rotary lip seal, has been developed. ► Experimental validation by means of pumping and torque measurements with shafts whose surfaces contain laser generated oblique grooves. ► Simulations also used to reveal details of physical processes occurring in the sealing zone.
The research results on multicriteria optimization of hard finish turning operation of hardened 18HGT steel are presented. The steel was machined with the use of cubical boron nitride (CBN) inserts of Wiper geometry. The following cutting parameters were subjected to optimization: cutting speed v
c, feed f, and depth of cut a
p
. Unit production cost K
j
, time per unit t
j
, and resultant cutting force F were assumed as optimization criteria. The equations describing the effect of cutting parameters upon particular optimization criteria were elaborated on the basis of some empirical research. The multicriteria optimization was carried out with the application of traditional method of weights, as well as the modified distance method (MDM) based on evolutionary computations (EC). From the obtained optimal sets of Pareto solutions, the best solution was selected with the aid of the hierarchical optimization method.
Gegenlaufflächen für Radial-dichtungen
- H K Müller
- W Haas
- G Wüstenhagen