Clutch Temperature Research Articles

A quantitative method of calculating transient nonlinear heat partition coefficient between clutch friction discs with deep learning

In the current clutch temperature field study, the generally used constant heat partition coefficient tends to overestimate the separator disc temperature and underestimate the friction disc temperature. Although some researchers have found the characteristics of the time-varying heat partition coefficient, a suitable method is still needed to apply it to temperature calculations. This study provides a quantitative method for the application of the transient nonlinear heat partition coefficient to temperature calculations. The finite difference method is adopted to figure out the time-varying curve of the heat partition coefficient by coupling the contact temperature of the friction components. The numerical results show that the heat partition coefficient is independent of rotation speed with three stages: initial value, rapid time-varying, and steady-state. Different from the analytical method, we apply a deep learning method to train the quantisation function to characterise these three stages, avoiding complex formula derivation. As a result, the quantitative function can characterise the time-varying heat partition coefficient accurately, with an average error of 0.19%, 3.05% and 0.62% for the inert, time-varying, and steady-state stages, respectively. In addition, the accuracy of applying the quantisation function in temperature simulation is verified by friction experiments, and the error is less than 8%. This is superior to the results of solving the temperature field by a constant heat partition coefficient.

Open-cup nesters in the Kalahari: Incubation and egg-shading behaviour in passerines cannot be detected with temperature dataloggers during hot periods

Birds that build open-cup nests in semi-arid or arid habitats have difficulty in maintaining clutch temperatures during incubation in a suitable incubation range due to high air temperatures and solar radiation, resulting in either embryo death or behavioural responses to preserve clutch viability. We investigated how Southern Fiscals (Lanius collaris), open-cup nesting passerines with female-only incubation in the Kalahari basin, allocated time for self-care (off-bouts) and incubation (on-bouts) and whether egg shading, a previously described behaviour in this species, is a widespread response during hot periods. We used a dual approach combining temperature dataloggers in the nest and behavioural observations during the hottest hours of the day. We found that in the early morning and late evening, Southern Fiscals behaved similarly to species incubating in temperate habitats by alternating off- and on-bouts, but during the hottest hours of the day, shading became the main activity. Behavioural observations were key to describing this behaviour indicating that it is necessary to combine different data collection strategies to successfully assess the behaviour of open-cup nesters in hot environments.

Research on temperature field of dry clutch assembly based on inverse analysis of thermal boundary conditions

The clutch temperature field is critical for the clutch design and lifetime analysis. In this paper, a new approach for reconstructing the temperature field of the clutch assembly based on the inverse analysis of thermal boundary conditions is present. Three typical types of thermal boundary conditions during the clutch operation were analyzed and integrated into a numerical model with several coefficients assumed. The optimal coefficients are obtained by optimizing the derivation between temperature simulation and rig test based on the reverse problem analysis. The NLPQL optimization algorithm, coupled with the Kriging response surface model, is utilized to improve the computation efficiency. Finally, the optimum parameter combination is conducted and the effectiveness of the proposed method is validated by the rig test data under the continuous engagement and disengagement condition. The results indicate that the clutch temperature distribution and the dynamic mechanism of the clutch contact status using the approach proposed agrees very well with the test data of the rig test. The temperature deviations between the model corrected and the rig test data are within 10 °C, with over 80% of the temperature deviations being less than 5 °C. This study establishes a new clutch temperature field simulation method based on reverse problem analysis and gives a significant insight and foundation for improving the prediction of the temperature distribution of the clutch.

Tribo-thermal simulation study of AMT dry clutch assembly under the continuous sliding grinding condition

Electronic Mechanical Transmission (AMT) is an automatic transmission device that combines hydraulic automatic transmission (AT) with manual transmission (MT). AMT has the advantages of automatic transmission as well as high efficiency, low cost, simple structure, and easy manufacture in the traditional manual transmission system. In dry clutch engagement, the wear of the engagement surface should be minimized to achieve good performance. It is necessary to control some influencing factors during its use. When the car starts, the flywheel and driven disc in the clutch change from a separation state to a full engagement state. When joining, due to the increase in speed of the driven disc, relative sliding occurs between the drive and driven parts, which causes the temperature of the friction surface to rise. If the temperature is too high, the wear of friction plates will be increased, which will reduce the service life and working stability of the clutch. In this study, the coupling field transient analysis of the clutch under continuous sliding wear conditions is carried out, and the clutch temperature change and heat generated by friction are obtained by simulation calculation under the use of simulated clutch holding for 1s. Based on the results of the simulation, the factors that may affect the friction heat generation of the clutch are analyzed.

The egg-thief architect: experimental oviraptorosaur nesting physiology, the possibility of adult-mediated incubation, and the feasibility of indirect contact incubation

AbstractNumerous, high-quality reproduction-related oviraptorosaur fossils have been described. However, oviraptorosaur-style nests are unknown among extant animals, and their curious construction makes nesting behavior difficult to interpret. Experiments were undertaken to better understand oviraptorosaur nesting strategies. A surrogate was constructed and placed atop mock-oviraptorosaur nests built from sand and 36 infertile emu eggs (as Macroolithus approximations) arranged according to the most current nest reconstructions. Thermometers, placed within each egg and throughout the experimental area, recorded energy flow from the surrogate dinosaur into the nesting microenvironment. One experiment examined a basic open nest warmed from above; the second, a fully buried clutch warmed from above; and the third, a nest open like the first but with heating elements (representing hindlimbs) extending down into the nest. It was found that egg temperatures in each scenario surpassed ambient temperatures without requiring excessive energy input. Final clutch temperatures were below most avian values, closer to crocodilian incubation, but are likely conservative, considering experimental parameters. These results may support the idea that an oviraptorosaur could use adult-generated energy to warm a clutch above ambient conditions. Additionally, egg tiers would be warmer and more uniform in temperature if heated by elements within the nest, such as hindlimbs, instead of solely from above. Results from the second experiment indicate that an endothermic adult could possibly warm a clutch fully buried beneath itself despite a barrier. Although not likely a behavior exhibited by oviraptorosaurs, such results suggest an important evolutionary step bridging guarded subterranean eggs and contact-incubated subaerial eggs.

Temperature field model of limited slip clutch based on dynamic heat flux partition characteristics

The interaxle torque distribution of off-road vehicle is interfered with temperature field variation of limited slip clutch during long-time sliding, which is controlled by actual heat flux input. The equivalent heat dissipation model is created based on the suggested calculation method of convective heat transfer equivalent coefficient in various lubrication phases. Further, thermal equilibrium equations of friction pair nodes are solved to produce the temperature field calculation model of dynamic heat flux partition. A clutch sliding bench is set up to verify and analyze the effect of heat flux partition on temperature field by organizing different operating conditions. The results demonstrate that the temperature difference of contact surface calculated by the constant heat flux partition model increases significantly along with sliding time and heat flux. In addition, the deviations of temperature rising rate at stage A and average temperature at stage B of separator plate higher than the experimental result also increases. On the contrary, the decrease value of actual input heat flux of separator plate from initial to steady state gradually increases with the increase of relative speed difference in dynamic heat flux partition model. The calculation deviations of temperature rising rate and average temperature are less than 0.1°C/s and 3°C, respectively. This model offers a novel approach for calculating clutch temperature field.

Extreme conditions reduce hatching success of green turtles (Chelonia mydas L.) at Karan Island, the major nesting site in the Arabian Gulf

Survival in the early life stages is a major factor determining the growth and stability of wildlife populations. For sea turtles, nest location must provide favorable conditions to support embryonic development. Hatching success and incubation environment of green turtle eggs were examined in July 2019 at Karan Island, a major nesting site for the species in the Arabian Gulf. Mean hatching success averaged at 38.8 % (range = 2.5–75.0 %, n = 14). Eggs that suffered early embryonic death (EED) and late embryonic death (LED) represented 19.8 % (range: 3.3–64.2 %) and 41.4 % (range: 4.8–92.6 %) of the clutch on average, respectively. Nest sand was either coarse (0.5–1 mm: mean 44.8 %, range = 30.4–56.9 % by dry weight, n = 14) or medium (0.25–0.5 mm: mean 33.6 %, range = 12.0–45.5 % by dry weight, n = 14). Mean sand moisture (4.0 %, range = 3.2–4.9 %, n = 14) was at the lower margin for successful development. Hatching success was significantly higher in clutches with sand salinity <1500 EC.uS/cm (n = 5) than those above 2500 EC.uS/cm (n = 5). Mean clutch temperatures at 1200 h increased by an average of 5.4 °C during the 50-d post-oviposition from 31.2 °C to 36.6 °C. Embryos experienced lethally high temperatures in addition to impacts of other environmental factors (salinity, moisture, sand grain size), which was related to reduced hatching success. Conservation initiatives must consider the synergistic influence of the above parameters in formulating strategies to improve the overall resilience of the green turtle population in the Arabian Gulf to anthropogenic and climate change-related stressors.

Thermal-Fluid-Solid Coupling Simulation and Oil Groove Structure Optimization of Wet Friction Clutch for High-Speed Helicopter

Wet friction clutch is the key functional component of the high-speed helicopter variable-speed transmission system, which is used to change the power transmission path. In the engagement process of wet friction clutch, the driving/driven disc will produce drag torque under the shearing of lubricating oil, which reduces the transmission efficiency. This unnecessary drag torque reduces efficiency and increases clutch temperature. The temperature increase promotes the wear of gears and bearings and the aging deformation of friction plates, which leads to local wear and reduces the service life of the clutch. From the principle of wet friction clutch, the oil groove structure is directly related to the drag torque and the temperature rise of friction disc. It is very important for the long-distance flight and service life of high-speed helicopters to obtain the groove structure with low drag torque and low temperature rise. In order to solve this problem, taking the wet friction clutch of a high-speed helicopter as the research object, based on the radial and annular compound groove, the thermal-fluid-solid coupling simulation model of the wet friction clutch is established to obtained the flow characteristics and temperature field distribution of the lubricating oil in the friction disc oil groove, and to analyze the influence law of the oil groove structure parameters on the drag torque and temperature field. In order to improve the transmission efficiency and the service life of friction disc, Taguchi experiment and non-dominated neighborhood immune algorithm were used to optimize the structural parameters of the oil grooves. The comparison results show that the optimized structural can effectively reduce the drag torque and the temperature rise. This work can provide a theoretical reference for the structure design of a wet friction clutch.

Machine Learning Based Surrogate Models for the Thermal Behavior of Multi-Plate Clutches

Multi-plate clutches play safety-critical roles in many applications. For this reason, correct functioning and safe operation are essential. Spontaneous damages are particularly critical because the failure of the clutch can lead to a failure of the system. Such damage mainly occurs due to very high loads and ultimately very high temperatures. Finite Element Analysis (FEA) enables simulation and prediction of these temperatures, but it is very time-consuming and costly. In order to reduce this computational effort, surrogate models can be created using machine learning (ML) methods, which reproduce the input and output behavior. In this study, various ML methods (polynomial regression, decision tree, support vector regressor, Gaussian process and neural networks) are evaluated with respect to their ability to predict the maximum clutch temperature based on the loads of a slip cycle. The models are examined based on two use cases. In the first use case, the axial force and the speed are varied. In the second use case, the lining thickness is additionally modified. We show that ML approaches fundamentally achieve good results for both use cases. Furthermore, we show that Gaussian process and backpropagation neural network provide the best results in both cases and that the requirement to generate predictions during operation is fulfilled.

Study on the Temperature Rise Characteristics of Successive Clutch Shifting Considering the Disengaged Friction Pair Gaps

The clutch temperature rise characteristics in successive shifting conditions are crucial to its thermal stability and thermal safety. In the present paper, a comprehensive numerical model is proposed to investigate the temperature change of separator discs during successive shifting with the consideration of convection heat transfer in disengaged friction pair gaps, which is validated by repeated shifting experiments on the SAE#2 test bench. Since the second separator disc near the piston has the widest disengaged gaps and double-sided heat input, its temperature rise and temperature drop are the highest. The temperature rise gradually equals the temperature drop with the increasing working cycle, then the maximum clutch temperature no longer increases. The longer the shifting interval, the better the heat dissipation is, thus the lower the accumulated temperature rise. Moreover, the increasing lubrication oil temperature reduces the convection heat transfer and increases the temperature rise in an engaging process, but the accumulated temperature rise does not increase due to the widened friction pair gaps. This paper can obtain the temperature rise characteristics of a wet multi-disc clutch concerning its disengaged gaps during successive shifting, which is a promising candidate for investigating its overall performance.

Real-time temperature calculation and temperature prediction of wet multi-plate clutches

Many applications of wet multi-plate clutches are within safety-critical areas since malfunction or failure of the clutch is often equivalent to “loss of drive”.The main criterion for the estimation of damage and endurance of wet multi-plate clutches is the temperature on the friction interface. Owing to the thin, rotating geometry of the plates, determination of relevant temperatures in operation mode is almost impossible. State of the art is that there is no general applicable model for real-time estimation of clutch temperatures during operation.This contribution presents a validated parametric real-time temperature model that is applicable to various use cases and operating conditions. The model enables the calculation of the actual clutch temperature during operation and the prediction of temperature for future shifting operations.The model is validated by comparing temperature measurements from a component test rig and from the KUPSIM thermal clutch design tool with the developed real-time temperature calculation. The validity of the model for serial parts from industry and automotive applications under various load cases (clutch mode, continuous slip, non-steady slip) is demonstrated. The deviation between measurement and calculation are typically very small (< 5 K). The temperature prediction allows a highly accurate (deviations typically < 5 K) conservative prediction of the thermal load for future shifting operations.The model can thus contribute to the increase of operational safety of wet multi-plate clutches while at the same time facilitating optimal component design by reducing thermal over-dimensioning of clutches.

Numerical and Experimental Investigation of Temperature Distribution for Dry-Clutches

The temperature rise of the engaging clutch during shifting depends heavily on the transmitted torque. Precisely estimating the clutch temperature not only improves clutch control but also the optimal design of the clutch. However, the contact surface of the friction lining is closed, and the surface temperature is often difficult to measure accurately. In this study, a theoretical model of a two-dimensional transient temperature field for the friction disc has been established. In the radial and axial directions under different launching conditions, the temperature field of a friction disc is investigated. Four stages of clutch engagement have been determined, and finite-element analysis has been used to study the temperature field of a single clutch and to determine its duration.Then, the latest internationally developed distributed optical fiber sensing technology is used to perform measurement tests on the designed dry clutch friction characteristic test rig. The distributed fiber-optic temperature measurement technology can accomplish accurate temperature measurement with fast response speed and can acquire temperature value on different radii of friction discs with high spatial resolution. Such temperature sensing technology is very suitable for clutch working conditions. By analyzing the simulation and experimental results of temperature variation of different radii, different working conditions and different components, an important reference is provided for the establishment of the clutch temperature model and the optimization of the clutch heat dissipation structure design.

A multibody dynamic model for predicting operational load spectra of dual clutch transmissions

In this paper, a generalized nonlinear time-varying multibody dynamic model of dual clutch transmissions (DCT) is presented. The model consists of clutches, shafts, gears and synchronizers, and can be used to model any DCT architecture. A nonlinear clutch model is used to determine the transmitted power to the transmission at any speed and clutch temperature. The clutch can be a single- or multi-plate clutch and can operate in a wet or dry-clutch configuration. A combined kinematic and powerflow simulation enables calculation of gear, shaft, bearing and clutch quasi-static loads as well as gear mesh frequencies following a duty cycle as the input. For the corresponding Linear-Time-Invariant (LTI) system model, natural frequencies and mode shapes are obtained by solving the eigenvalue problem. The modal summation technique is used to determine the steady state forced vibration response of the system. For the corresponding NTV system, Newmark's time-step marching based integration is used to determine both the steady state and transient forced vibration response of the system. The DCT model is exercised using a common transmission architecture operating at several different operating conditions. The resulting impact of changing operational conditions on gear and bearing loads as well as dynamic transmission error spectra are demonstrated.

E-Clutch Torque Control Including Compensation of Thermal Expansion Effects

The E-clutch considered is a dry clutch automated by means of a hydrostatic actuator, whose master cylinder is driven by an electric servomotor through a spindle drive. The paper deals with design of E-clutch open-loop torque control strategy which includes compensation of clutch thermal expansion effects. A series of experiments have been conducted by using a custom-designed E-clutch test rig, in order to characterize influence of thermal effects on clutch control performance. A comprehensive analysis of test data reveal a strong correlation of clutch torque reduction and E-clutch slave cylinder (CSC) position increase caused by clutch pack thermal expansion. The determined dependence, where CSC position measurement serves for quantification of thermal effects, is incorporated within the clutch torque control strategy for the sake of thermal effects compensation. Furthermore, it is found out that the CSC position can be effectively estimated based on clutch temperature inputs, thus implying that the CSC position sensor can be omitted, while still keeping the possibility of effective thermal expansion compensation. The proposed clutch control strategy is examined based on experimental data acquired for two clutch friction plates/materials.

Integrated Thermal and Dynamic Analysis of Dry Automotive Clutch Linings

Optimum operation of clutch systems is dictated by their dynamic as well as thermal performance. Both of these aspects are closely related to the interfacial frictional characteristics of the clutch lining material, which also affects the noise, vibration and harshness response of the entire vehicular powertrain system. Severe operating conditions such as interfacial clutch slip and increased contact pressures occur during clutch engagement, leading to generation of contact heat, and higher clutch system temperature. Therefore, any undesired oscillatory responses, generated during clutch engagement, such as take-up judder phenomenon can exacerbate generated heat due to stick-slip motion. The paper presents an integrated thermal, and 9-DOF dynamic model of a rear wheel drive light truck powertrain system. The model also includes experimentally measured clutch lining frictional variations with interfacial slip speed, non-linear contact pressure profile and generated surface flash temperature. It is shown that severe torsional oscillations known as take-up judder lead to an increased overall clutch temperature. It also shows that ageing of clutch lining material alters its dynamic and thermal performance.

Thermal Compensation Control Strategy in Automated Dry Clutch Engagement Dynamics and Launch Manoeuvre

Repeated engagements in dry clutch systems could yield remarkable increase of clutch disk temperature. In dry clutch based transmissions like Automated Manual Transmissions and Dual Clutch Transmissions the overheating leads to poor control of gearshift quality due to unpredictable and fast change of frictional characteristic. Even permanent damage of clutch facings may occur. Under this light, this paper focusing on thermal effects to improve control performances and prevent uncomfortable engagements. To this aim, detailed analyses of dry clutch architecture have been carried out to understand the main phenomena which affect the clutch torque transmissibility. Moreover, a lumped thermal model has been developed to predict both the disk surface and cushion spring temperature in real-time environment. To validate the proposed thermal model, a non-linear least squares method has been used by comparing simulations with finite element results. A control strategy based on model predictive control and thermal compensation effects has been proposed to simulate vehicle launch manoeuvres in flat and up-hill road conditions with low and high initial clutch temperature as well. Finally, the proposed control approach has been compared with classic PI control strategy to prove its effectiveness.

Numerical and experimental studies on the thermal characteristics of the clutch hydraulic system with provision for oil flow

PurposeThis paper aims to investigate the thermal characteristics of the clutch hydraulic system under various oil flow conditions. Increasing the oil flow is one of the most important approaches to reduce the clutch temperature. However, the effect of the oil flow on the clutch temperature remains to be explored.Design/methodology/approachThe thermal resistance network model and the lumped parameter method are used to study the thermal characteristics of the clutch hydraulic system. The predicted temperature variations of the clutch and the oil are compared with experimental data.FindingsResults demonstrate that the larger the friction power is, the higher the temperatures of the clutch and the oil are. However, the temperature growth rates of the clutch and oil present different trends: the former decreases gradually and the latter increases constantly. Additionally, increasing the oil flow within a certain range gives rise to the decrease of clutch temperature and the increase of oil temperature; nevertheless, their variation trends are gradually weakening. When the oil flow is large enough, it brings a slight effect on the clutch temperature rise.Originality/valueThis paper extends the knowledge into the oil flow supply of the clutch hydraulic system. The conclusions can provide a theoretical guidance for the oil management of the transmission system. Additionally, the thermal resistance network model is also effective and efficient for other hydraulic equipment to predict the temperature variation.

Analytical model and material equivalent methods for steady state heat partition coefficient between two contact discs in multi-disc clutch

The heat partition coefficient between two finite thickness contact discs during long-time sliding is studied with a coupled finite element method. Results show that the heat partition coefficient varies from its initial value to another steady state value rapidly instead of being a constant all the time. An analytical solution of the temperature field under invariant heat flux input is deduced, which tells that there exists a unique critical thickness ratio between the contact discs that keeps the heat partition coefficient a constant. An equivalent method for single-material contact bodies is proposed that is capable of calculating the steady state heat partition coefficient for any thickness ratio. It reveals that the steady state heat partition coefficient only has relationship with the mass density and the heat capacity of the materials and the thickness ratio. Based on this method, a two-step material equivalent method is further proposed for the contact discs that have friction linings on them. The solution shows that the steady state heat partition coefficient in this situation is also only determined by the material properties and the layer thicknesses. A test bench of multi-disc clutch is set up and a series of sliding experiments are conducted to validate the proposed equivalent methods and solutions of steady state heat partition coefficient. The measured experimental temperature variations show that the temperature level of the separator disc in the clutch is overestimated with the constant heat partition coefficient of semi-infinite model, while it is close to those calculated results with steady state heat partition coefficient. Therefore, the temperature fields of the contact discs during long-time sliding with constant speed can be figured out efficiently using the steady state heat partition coefficient with only small error, and these equivalent methods benefit the multi-disc clutch design and temperature estimation in practical applications.

Creeping control strategy for Direct Shift Gearbox based on the investigation of temperature variation of the wet multi-plate clutch

Proposing an appropriate control strategy is an effective and practical way to address the overheat problems of the wet multi-plate clutches in Direct Shift Gearbox under the long-time creeping condition. To do so, the temperature variation of the wet multi-plate clutch is investigated first by establishing a thermal resistance model for the gearbox cooling system. To calculate the generated heat flux and predict the clutch temperature precisely, the friction torque model is optimized by introducing an improved friction coefficient, which is related to the pressure, the relative speed and the temperature, before being demonstrated experimentally using a full scale powertrain test. After that, the verified heat transfer model and the reasonable friction torque model are employed by the vehicle powertrain model to construct a comprehensive co-simulation model for the Direct Shift Gearbox vehicle, capable of simulating the dynamic responses and predicting the temperature variations of two clutches. A creeping control strategy is then proposed and, to evaluate the vehicle performance, the safety temperature (250°C) is particularly adopted as an important metric. From the variations in torque and speed obtained from the simulation results, the vehicle can track the desired speed (1.5 km/h) satisfactorily, with only 3% fluctuation, and have good longitudinal dynamic performance (8.5 m/s3). But above all, during the entire 174 s creeping process, the temperature of two clutches is always under the safety value (250°C), which demonstrates the effectiveness of the proposed control strategy in avoiding the thermal failures of clutches.

The Nile Softshell Turtle (Trionyx triunguis): Nest Parameters and A New Nesting Site

There are no studies carried out on nest parameters of the Nile softshell turtle (Trionyx triunguis) in Turkey except for few studies on the Western Mediterranean coast of Turkey. In this study, 12 nests of the Nile softshell turtle were examined in terms of nest parameters during 2016 and 2017 nesting seasons on Belek, Göksu, and Burnaz beaches located on the Central and Eastern Mediterranean coast of Turkey. Nesting period started in May (17%) but intensified in June (83%). The distance of nests to the shore, depth of nests, clutch temperature, clutch size, and hatching success in the nests were recorded and calculated. Among three beaches, the lowest hatching success rate was on Göksu Beach (0.18 ± 0.26), whereas the values were similar on Belek (0.75 ± 0.22) and Burnaz (0.72 ± 0.36) beaches. Although clutch temperatures were measured in a range (29.5–33.0 °C) that is optimal for embryo development, most of the eggs inside nests were dead at the late embryonic period (5.1 ± 9.6) which was followed by early (1.8 ± 3.1) and middle stage embryos (0.3 ± 0,6). The highest number of unfertilized eggs was recorded on Burnaz Beach (14.5 ± 19.1) and the lowest was on Belek Beach (1.0 ± 1.5). Regarding the relationship between the nest parameters, it was detected that only the clutch temperature has a significant relationship with the clutch size. In this study, a new nesting site for the softshell Nile turtle on Burnaz Beach was discovered and nest parameters in this species were indicated on three beaches.