•This paper finds the special problem in the use of texture technology for lip seals.•Influence of axial position of contact zone has been investigated.•A parameter analysis is conducted to find the optimal texture shape and layout form.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.

•A method is developed to study how aging in oil affects the lip seal performance.•There is good agreement between simulation and experimental results.•This method lays a solid foundation for the prediction of lip seal life.•This method can be also used for other forms of seal.The effect of aging in oil on the seal performance of a radial lip seal is investigated in the present study by conducting a constant temperature oil bath test to obtain aged rubber samples and seals, and measuring the changes of material properties and seal performance with the aging time. The change of lip surface micro-morphology with the aging time is also measured by using a 3D white light optical interferometer. The leakage and friction torque are computed in a numerical simulation, utilizing a mixed elastohydrodynamic lubrication (EHL) model, to determine how aging in oil affects the lip seal performance. Finally, the simulation results of the EHL model are verified by a bench test on aged lip seals.

The radial force is a critical factor to determine the sealing performance of radial lip seals. The effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and experiments. Finite-element analysis and mixed elastohydrodynamic lubrication simulation are used. Radial force, contact width, temperature in the sealing zone, the reverse pumping rate and friction torque are measured. A critical value of interference for a cost-effectively designed radial lip seal is found. Spring force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing performance. The quantitative results gotten in this study could provide guide for the seal design and improvement.

Since aging is an inevitable phenomenon during storage of a radial lip seal, this study aims to investigate the effect of aging on the seal performance. An air oven aging test is conducted to produce aged rubber samples and seal products. An aging life prediction model is constructed to predict the equivalent material properties at any storage temperature. The material property parameters of aged rubber samples are measured in a uniaxial compression experiment. The pumping rate and friction torque of the seal are calculated through numerical simulation by using a mixed elastohydrodynamic lubrication (EHL) model. A bench test is used to verify the aging life prediction model and the simulation results of the EHL model. Finally, the verified EHL model is used to study how aging during storage affects the lip seal performance, as characterized by the leakage and friction torque.

A mixed lubrication model of a rotary lip seal using flow factors has been developed. The model consists of coupled fluid mechanics, contact mechanics and deformation mechanics analyses. The fluid mechanics analysis is described by a Reynolds equation that takes into account the surface roughness effect using flow factors. The contact mechanics analysis uses the Greenwood and Williamson model to compute contact pressure. The deformation mechanics analysis utilizes the influence coefficient approach to compute deformation of the seal. Results for a typical seal show how the operation parameters and the surface roughness affect seal behavior.Highlights► Predicts performance: minimum film thickness, contact area, pumping rate, friction torque. ► Analyzes fluid mechanics, asperity contact, and elastic deformation of the lip. ► More computationally efficient than deterministic approach. ► Provides effective tool for designer to predict and optimize performance of a seal design.

A computational model that will predict the pumping rate, from the air-side to the liquid-side of rotary lip seals, produced by shafts that are manufactured by various techniques has been developed. Plots of computed pumping rate versus shaft speed, for plain plunge ground shafts and for ground shafts with various laser generated groove patterns, agree well with experimental measurements, providing validation of the model. This validated model is then used to investigate the effects of groove angle, groove density, and groove depth on the pumping rate.Highlights► Simulation model to predict pumping by plunge ground shafts with a rotary lip seal was developed. ► Experimental measurements agree well with the simulation results. ► The pumping rate produced by the shaft without grooves is of the same order as that produced by the seal. ► Ground shafts with oblique grooves behave like polished shafts but with higher pumping rates.

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.

This study relates the gait asymmetry, residual limb comfort, and energy cost during walking and identifies a compensating pattern for the trans-tibial amputees when the prostheses are misaligned. One male subject with a trans-tibial amputation volunteered for the study. The knee joint moments at the prosthetic side, the phase symmetry index, and the interface pressures were discussed under three sagittal alignment settings. The results show that the subject changes the knee joint moment, gait symmetry, and interface pressure with a misaligned prosthesis to improve his comfort and movement during walking. A high-quality liner reduces the gait sensitivity to misalignment and enhances the amputee's ability to compensate for misalignment. Since different people have different compensation patterns, more cases will be studied in future work.

This study accesses the effects of shoe heel heights on loading, muscle activity, and plantar foot pressure of trans-tibial amputees during standing. Five male subjects with unilateral trans-tibial amputation volunteered to participate in this study. Three pairs of shoes with zero, 20 mm, and 40 mm heel heights were used. The loading line of the prosthetic side, the plantar foot pressure, and the surface electromyography (EMG) of 10 muscles were simultaneously recorded. With increasing shoe heel heights during standing, the loading line of the prosthetic side shifted from the anterior to the posterior side of the knee center, the peak pressure was increased in the medial forefoot region, and the peak pressure was reduced in the heel region. The EMG of the medial and lateral gastrocnemius of the sound leg almost doubled and that of the rectus fomris, vastus lateralis, and vastus medialis of the prosthetic side increased to different extents with increasing heel heights from zero to 40 mm. These results show a high correlation with human physical behavior. Changing of the heel heights for trans-tibial amputees during standing actually had similar effects to altering the prosthetic sagittal alignment. The results suggest that an alignment change is necessary to accommodate heel height changes and that prosthesis users should be cautious when choosing shoes.