| 1. |
- Li, M., et al.
(author)
-
Model validation and uncertainty analysis in the wear prediction of a wet clutch
- 2016
-
In: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 364-365, s. 112-121
-
Journal article (peer-reviewed)abstract
- An uncertainty quantification analysis is performed to further investigate the nature of the “two-stage” wear process of the paper-based friction lining in a wet clutch. In this approach, the results of a computerized wear prediction model are examined through sensitivity analysis and a model validation that utilizes the Monte Carlo (MC) method. Extensive computational results that take into account the uncertainty and variability in the input data are presented to gain insight into the evolution of temperature and wear during the engagement process.
|
|
| 2. |
- Lingesten, Niklas, et al.
(author)
-
Apparatus for continuous wear measurements during wet clutch durability tests
- 2012
-
In: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 288, s. 54-61
-
Journal article (peer-reviewed)abstract
- Wet clutches are used in many applications today such as automatic transmissions and limited slip differentials in cars as well as in heavy duty equipment such as wheel loaders. The present study is concerned with the wear and engagement behavior of wet clutches in the latter type of application. A test rig is developed in which the wet clutch engagement is monitored during an arbitrary number of test cycles.This rig has many similarities with the SAE #2 test rig in that they are both inertia type test rigs. However, the test rig presented here has several original parts from heavy duty equipment in production incorporated into it. The data collection includes a continuous measurement of the position of the piston used to apply force on the clutch pack in addition to the separator disc temperatures, hydraulic actuating pressure and torque transfer characteristics. The measurements of the piston position can then be related to the clutch wear during a long test series.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Lingesten, Niklas, et al.
(author)
-
Studies on wear phenomena in wet clutches
- 2012
-
Conference paper (other academic/artistic)abstract
- Wet clutches are critical components in many automatic transmissions in the automotive industry. These components handle large amounts of energy through sliding friction as they engage during machine operation, resulting in clutch disc wear. Wear experiments at high clutch engagement energies has revealed that a change in the friction material wear rate can occur at some point during the test, i.e. transitioning from a low to a high wear rate. This brings into question the conventional way of performing wear tests i.e. measuring a specimen before and after testing and the usual way of viewing wear i.e. as a constant wear rate after running in. The authors propose a two step wear model to describe the wear that can occur under some conditions exemplified in this paper.
|
|
| 6. |
- Lingesten, Niklas, et al.
(author)
-
The influence of repeated high-energy engagements on the permeability of a paper-based wet clutch friction material
- 2017
-
In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : Sage Publications. - 1350-6501 .- 2041-305X. ; 231:12, s. 1574-1582
-
Journal article (peer-reviewed)abstract
- The behavior of a wet clutch during engagement is of great importance to the durability of the clutch and the drivability of a vehicle. While many different factors influence the engagement behavior, the focus of this paper is to investigate only one factor, the permeability of the wet clutch friction material. Two test cells for measuring the permeability of friction material mounted on clutch discs have been developed. The test cells were then used to examine the effect of clutch material ageing through clutch engagement on the permeability of the material. The tests were performed on full size friction discs including the steel core prior and subsequent to testing in a wet clutch engagement test rig. The ability of the friction material to allow for oil flow both through the sliding surface layer and the bulk of the material was measured. The results indicate that repeated clutch engagements will increase the bulk permeability. However, the repeated engagements will decrease the ability to pass fluid through the friction material sliding surface. This contradictory behavior could be explained by a combination of an increase in pore size through repeated compression and the surface glaze clogging of the friction interface surface pores.
|
|
| 7. |
- Lingesten, Niklas
(author)
-
Wear behavior of wet clutches
- 2012
-
Licentiate thesis (other academic/artistic)abstract
- Human civilization is largely based on the transformation of stored chemical energy in the form of fossil fuels into usable work through the use of the combustion engine. In recent years, the awareness of problems such as global warming due to emissions of greenhouse gases and the depletion of fossil fuel reserves has increased. New regulations have been put into place in order to limit these effects and as a result, the efforts made by the automotive industry to limit the emissions and fuel consumption of their products has taken a higher priority. Attempting to minimize power losses is one approach taken, where the knowledge of Tribology is often made use of to lower the fuel consumption. In heavy duty equipment such as wheel loaders and articulated haulers, a large portion of the mechanical power is lost in the transmission. One of the largest contributors to the transmission power losses is the viscous drag in disengaged wet clutches. While the method of reducing these losses are quite clear (e.g. a reduction in clutch size will yield lower losses), the effects of the subsequent increase in power and energy density in clutch engagements are less clear.In this thesis, the effects of increasing the load, i.e. increasing energy input density and power absorption density, on the clutch are investigated. The main concern with increased load on the clutch is the durability of the clutch. In particular, wear of the paper-based friction material lining of the friction discs has been evaluated, as well as the influence of friction material wear on the clutch performance. A new type of test rig has been developed to quantitatively measure the clutch wear throughout a durability test. The wear measured continuously in the test rig correlates well with verification measurements performed while the engagement behavior could be clearly distinguished through the measured torque transfer.At high energy densities and high power levels, a wear phenomenon was observed where the wear rate suddenly changed. During and after the change there was no significant change in engagement characteristics. However, if a clutch which experiences two different wear rates are to be used in a transmission, it is necessary to accurately model the wear so that a compensation can be implemented in the clutch control system. The model was derived in the form of a wear equation where the clutch pack thickness is described in terms of the number of clutch engagements, employing two different wear constants. Total clutch failure due to wear occurs once most of the friction lining has been removed from the friction discs. Up to that point, the clutch is still able to deliver the required torque transfer granted that the increased distance between discs can be compensated for by smart control of the clutch. Heavy duty wet clutches need to be designed in such a way that maximum power and energy density is achieved without reaching the point where the friction lining is totally removed within the required clutch life. The use of the proposed wear model can aid in the design of new wet clutch systems to minimize the clutch's size without compromising the length of its service life.
|
|
