Thermal insulation effect on EHL of coated cam/tappet contact during start up

Meng, Xianghui; Yu, Changya; Xie, Youbai; Mei, Benfu

doi:10.1108/ilt-03-2016-0065

Cited by 6 publications

(5 citation statements)

References 20 publications

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“…Furthermore, using transient full-film TEHL simulations, Meng et al [46] concluded that amorphous carbon coating induced thermal insulation effects that are particularly beneficial in start-up processes of the cam/tappet-contact, leading to significantly reduced frictional losses. Gangopadhyay and Watt [47] used a motored valve train test-rig to determine a friction reduction of up to 35% from shallow V-shaped grooves fabricated by a diamond cutting tool.…”

Section: Introductionmentioning

confidence: 99%

On Friction Reduction by Surface Modifications in the TEHL Cam/Tappet-Contact-Experimental and Numerical Studies

2019

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The overall energy efficiency of machine elements and engine components could be improved by using new technologies such as surface modifications. In the literature, surface engineering approaches like micro-texturing and the application of diamond-like carbon (DLC) coatings were frequently studied separately, with focus on a specific model contact and lubrication conditions. The contribution of the current study is to elucidate and compare the underlying friction reduction mechanisms of the aforementioned surface modifications in an application-orientated manner. The study applied the operating conditions of the thermo-elastohydrodynamically lubricated (TEHL) cam/tappet-contact of the valve train. Therefore, tribological cam/bucket tappet component Stribeck tests were used to determine the friction behavior of ultrashort pulse laser fabricated microtextures and PVD/PECVD deposited silicon-doped amorphous carbon coatings. Moreover, advanced surface characterization methods, as well as numerical TEHL tribo-simulations, were utilized to explore the mechanisms responsible for the observed tribological effects. The results showed that the DLC-coating could reduce the solid and fluid friction force in a wide range of lubrication regimes. Conversely, micro-texturing may reduce solid friction while increasing the fraction of fluid friction.

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Section: Introductionmentioning

confidence: 99%

On Friction Reduction by Surface Modifications in the TEHL Cam/Tappet-Contact-Experimental and Numerical Studies

2019

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Section: Introductionmentioning

confidence: 99%

“…5 Guo et al identified the temperature-viscosity-wedge effect and explained the abnormal surface-dimple phenomena observed by Kaneta et al 6,7 Meng et al presented a numerical model for the analysis of thermal elastohydrodynamic lubrication of coated cam/tappet contact. 8 Liu et al proposed a numerical method to calculate the surface thermal stresses of solids in thermal elastohydrodynamic lubrication of line contact. 9 Although these studies have examined the effect of temperature on lubrication performance, they have failed to consider how temperature affects the deformation and subsurface stress of the contact bodies.…”

Section: Introductionmentioning

confidence: 99%

Modeling the effects of solid thermal expansion and thermal stress on elastohydrodynamic lubrication

Wang

Jiang

2022

Proceedings of the Institution of Mechanical Engineers, Part J:

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Temperature has a significant effect on the performance of elastohydrodynamic lubrication (EHL), and this topic has been extensively covered in many studies. These studies are focused on how temperature affects lubrication performance, without considering the effect of temperature on the deformation and the subsurface stress of the contact bodies. However, there will be a significant rise in temperature in the contact area under such conditions as high speeds, heavy loads, and high slide-roll ratios. This will generate significant thermal stress inside the solid, thus inhibiting the elastic deformation of the contact surface and impairing the lubrication performance in the contact area. In such cases, it is essential to consider the effects of solid thermal stress and thermal expansion on thermal elastohydrodynamic lubrication (TEHL). In this paper, a TEHL model that consider solid thermal expansion and thermal stress to solve point contact problems is developed. The effects of solid thermal expansion and thermal stress on pressure, film thickness, temperature, and subsurface stress are investigated. The results show that solid thermal expansion partially inhibits the elastic deformation of the contact surface, resulting in a decrease in film thickness and an increase in pressure. It is also found that solid thermal stress causes the subsurface von Mises stress of the upper contact body to increase and that of the lower contact body to decrease.

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“…For example, YU [30] investigated the influence of different coatings on tribological contact behavior. MENG [31] analyzed the significance of the thermal insulation effect during start-up from the hot and cold states for the initial cam cycles. The author described that the friction losses during a cold start-up are significantly higher than the losses during a warm startup, and that a coating generally reduces the friction losses due to thermal insulation.…”

Section: Introductionmentioning

confidence: 99%

Understanding Friction in Cam–Tappet Contacts—An Application-Oriented Time-Dependent Simulation Approach Considering Surface Asperities and Edge Effects

Orgeldinger

Tremmel

2021

Lubricants

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With the increasing challenges of climate change and scarce resources, the development of sustainable and energy-efficient technical systems is becoming increasingly important. In many applications, the friction losses occurring in contacts have a decisive influence on the overall efficiency. At this point, tribological contact optimization can make an important contribution to increasing the efficiency of technical systems. However, improvements are often associated with a considerable experimental effort. To reduce the development time, additional simulation models can be applied to predict the tribological behavior. This requires the closest possible approximation of the real contact within a numerical model. This paper presents a simulation approach for the time-dependent simulation of a cam–tappet contact. The simulation uses realistic operating conditions as they arise in the valve train of internal combustion engines. The influence of edge effects on the friction behavior is considered by a scaled calculation area and the influence of the surface roughness is investigated using stochastic asperity models. It is shown that the tribological behavior within the contact strongly depends on the surface properties and the load spectrum used. In addition, edge effects on the sides of the contact area have a clear influence on the pressure and film thickness distribution.

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Thermal insulation effect on EHL of coated cam/tappet contact during start up

Cited by 6 publications

References 20 publications

On Friction Reduction by Surface Modifications in the TEHL Cam/Tappet-Contact-Experimental and Numerical Studies

On Friction Reduction by Surface Modifications in the TEHL Cam/Tappet-Contact-Experimental and Numerical Studies

Modeling the effects of solid thermal expansion and thermal stress on elastohydrodynamic lubrication

Understanding Friction in Cam–Tappet Contacts—An Application-Oriented Time-Dependent Simulation Approach Considering Surface Asperities and Edge Effects

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