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Government’s focus on road safety requirements is resulting in faster adoption of stringent automobile safety regulations in India. In addition, due to changing customer preference, automobile companies are also working to provide safer vehicles in the market. Due to the complexity and high cost of the vehicle safety testing, more focus is given to development of CAE simulation technologies to validate the design for meeting regulatory norms, reducing design cycle time and number of physical tests. Safety requirement in vehicle safety regulations is to minimize the impact transfer to the occupants in case of vehicle crash. During vehicle crash condition, there is possibility that driver head may hit the gear shift lever assembly (GSLA) knob as it falls in the hitting area with respect to driver seat reference point (SRP). There is a regulatory requirement for the maximum acceleration level that is to be experienced by the driver during impact to prevent serious head injury.

Control Cables are used in automobiles to transfer loads and motions as intended and required by the driver. These cables are supported at multiple points by clamps, which are mounted at suitable locations. The Clutch-cable is one of the cables routed through clamps mounted on the engine and the vehicle-chassis. During the vehicle’s travel on the rough road, the powertrain, supported by flexible mounts, tends to swivel, generating relative motion with respect to the chassis. As one end of the clutch-cable is mounted on the chassis and other on the vibrating engine, this relative movement contributes to the additional forces on the clamps. These forces, sometimes, lead to the clamp’s failure. Thus, the knowledge of load behavior is important for failure investigation and further optimization of the clamp design. The failure of the engine-mounted clutch-cable-clamp was observed in the vehicle testing on the rough road.

Gearbox power transfer efficiency is a major factor in overall powertrain efficiency of a passenger vehicle. With rapidly changing emission and fuel efficiency regulations, there is a push to increase the gearbox efficiency to improve the overall fuel economy of the vehicle. In case of an existing gearbox, efficiency can be improved by using the low viscosity lubrication oil. Despite a benefit in increasing the gearbox efficiency, lowering down the viscosity of lubrication oil gives rise to few challenges with respect to its performance. One of these challenges is breather performance which defines that transmission oil should not come out of breather pipe in some pre-defined conditions during gearbox operation. As this validation is being carried out on proto parts when the complete system is ready, failure to satisfy the defined criteria for breather performance can lead to multiple trials.

Rapidly changing emission and fuel efficiency regulations are pushing the design optimization boundaries further in the Indian car market which is already a very cost conscious. Fuel economy can be improved by reducing moving parts friction and weight optimization. Driveline or Transmission power losses are major factor in overall efficiency of rotating parts in a vehicle. Transmission efficiency can be improved by using low viscosity oil, reducing oil quantity and reducing churning losses in car transmission. Changes like low viscosity and reduced oil volume give rise to challenges like compromised lubrication and durability of rotating parts. This further leads to extended design cycles for launching new cars with better transmission efficiency and fuel economy into the market. Design cycle time can be reduced by using CFD simulation for oil flow validation in the early design stage.

As the automotive market is very dynamic and vehicle manufactures try to reduce the vehicle development cycle time, more focus is being given to CAE simulation technologies to reduce the design cycle time and number of physical tests. CAE engineers are continuously working on improving the accuracy of CAE simulation, such as using flexible body dynamic simulation in place of linear static analysis. Strength calculation under dynamic condition is more accurate as compared to static condition as it gives more clear understanding of stress variation with motion, contacts and mass inertia. Failure has been observed in new development of valve train pivot screw under test conditions. As per linear static analysis, design was judged OK. Normal linear static analysis is a two stage process. In first stage loads are calculated by hand or peak loads are taken from multibody dynamics (MBD) rigid body analysis.

In a car with a Manual Transmission, Gear Knob is the main touch point for the driver to interact with vehicle control system. Therefore, Gear Shift Quality of vehicle is very important from customer point of view. With growing competition, even in a cost sensitive market like India, importance of the gearshift quality of manual transmissions has increased significantly over the past few years. In Manual Transmission, shift tower is a system to assist the driver during selecting and shifting of gears. Diagonal Shift Assist (DSA) is a part of shift tower, which guides the gear shift from 5th gear to 4th gear and act as a safety device to prevent 5th to reverse gear engagement. The dynamic interaction of DSA system in shift tower is difficult to interpret by traditional test methods and virtually impossible at concept stage.

Clutch actuation system in manual transmission is one of the key systems of power-train with which driver interacts frequently. Therefore its load and travel feeling are important to customer. Clutch actuation system consists of clutch pedal assembly, flexible cable mounted on body panel, and clutch release arm/ shaft assembly inside transmission unit assembly. Clutch pedal load, travel and engagement point are important parameters to specify the actuation feeling while designing the clutch actuation system. Validation of actual values is being done at proto vehicle testing stage, as final output calculation may not be accurate due to dependency on variables difficult to estimate. To overcome these difficulties a virtual dynamic model of the entire clutch actuation mechanism has been created in MBD software. Model input factors are based on actual testing results to improve the accuracy. The model predicts the clutch pedal load and travel values for a given set of vehicle inputs.

Manual transmission is one of the key system of power-train to which driver directly interacts, so its shift feeling is important for the merchantability. The importance of the gear shift quality of manual transmissions has increased significantly over the past few years as the refinement of other vehicle systems has increased and also due to rise in customer expectations. Shift Tower is a system to assist the driver during selecting and shifting of Gears. The dynamic interaction of shift Tower at a component level is difficult to interpret by traditional test methods and virtually impossible at concept stage. To overcome these difficulties a dynamic model of the entire Shift Tower mechanism i.e. Shift select lever, 3D Ramp, Detent Pin, Spring, Interlock mechanism has been created. The model predicts the gearshift quality i.e. Shift and Select force values for a given set of input parameters, which can be correlated against test data.