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Self-soiling or surface contamination is usual phenomenon observed during rainy season wherein dirt on road are picked by rotating wheel and later released in air as fine particles. These released dirt particles are further carried by airflow around vehicle and as a result stick on vehicle exterior surfaces leading to surface contamination. Surface dirt contamination is one of critical issues that need consideration during early phase of vehicle development as vehicle styling plays a critical role for airflow around vehicle and therefore settling of dirt on vehicle exterior surfaces. Non consideration of such aspects in design can lead to safety issues with likely non-functioning of parking sensors, camera and visibility issues through ORVM, tailgate glass etc. Hence it is important to understand physical as well as digital techniques for assessment of vehicle for surface dirt contamination.

Nowadays, E- commerce and logistics business model is booming in India with road transport as a major mode of delivery system using containers. As competition in such business are on rise, different ways of improving profit margins are being continuously evolved. One such scenario is to look at reducing transportation cost while reducing fuel consumption. Traditionally, aero dynamics of commercial vehicles have never been in focus during their product development although literature shows major part of total fuel energy is consumed in overcoming aerodynamic drag at and above 60 kmph in case of large commercial vehicle. Hence improving vehicle exterior aerodynamic performance gives opportunity to reduce fuel consumption and thereby business profitability. Also byproduct of this improvement is reduced emissions and meeting regulatory requirements.

Aerodynamics performance evaluation of passenger cars is important during early vehicle development phase as it influences fuel economy, vehicle stability and drivability. Usually during initial styling phase, scale model is prepared and tested in wind tunnel to check aerodynamic performance like drag coefficient and these are used to predict aerodynamic performance of full scale model as testing on full scale model is costly and time consuming. To ensure its correctness, it is important to understand difference in physics from scale model to full scale model. In predicting full vehicle aerodynamics performance from scale model assessment; importance of Reynolds number, effect of geometric scaling on flow i.e. flow separation and wake zone change needs to be understood and addressed. This paper discusses about effect of scaling on aerodynamic flow behavior and drag.

Vehicle crashworthiness is an important aspect of vehicle development. Vehicle structural performance plays a critical role during crash for controlling the occupant injuries. During a crash event, vehicle energy management governs the structural performance and passenger compartment integrity. However, these parameters are dependent on material properties such as yield/ultimate tensile strength, work hardening effects, strain rate dependency, material elongations and material fracture strains. Appropriate representation of these material properties in CAE (Computer Aided Engineering) environment is very critical for reliable prediction of vehicle structural performance during development phase. Among all material properties, material fracture strain is the most complex one and needs detailed material characterization approach for failure definitions.

Vehicle aerodynamic design has a critical impact on fuel efficiency of the vehicle. Reducing aerodynamic wind resistance of the vehicle's exterior shape and reducing losses associated with requirements for engine compartment cooling through vehicle front openings plays key role in achieving desired aerodynamic efficiency. Today fairly large number of computational fluid dynamics (CFD) simulations are being performed during the vehicle aerodynamic design and development process and it is rapidly increasing day by day. Vehicle aerodynamic design and development process involves mainly aerodynamic shape development, aerodynamic optimizations of vehicle external components (side view mirror, spoilers, underbody shield etc.) and number of” what if studies during preliminary design process. Licensing costs of the available commercial CFD simulation solver has significant impact on product development cost when numbers of aerodynamic simulations expand.

Tire plays an important role in frontal impacts as it acts as a load path to transfer loads from barrier to side sill or rocker panels of passenger vehicles. In order to achieve better correlation and more reliable predictions of vehicle crash performance in CAE simulations, modeling techniques are continuously getting refined with detailed representation of vehicle components in full vehicle crash simulations. In this study, detailed tire modeling process is explored to represent tire dynamic stiffness more accurately in frontal impact crash simulations. Detailed representation of tire internal components such as steel belts, body plies, steel beads along with rubber tread and sidewall portion have been done. Passenger car tubeless radial tire was chosen for this study. Initially, quasi-static tensile coupon tests were carried out in both longitudinal and lateral direction of tread portion of tire.

Accident statistics shows pedestrian accident fatalities as one of the important concerns globally. In view of this, new test protocols for pedestrian safety have been drafted in regulation as well as in consumer group. Also as per new ENCAP requirements, pedestrian safety assessment is used as one of the four assessment criteria's (Adult protection, child safety, pedestrian safety, safety assist) in deciding the overall vehicle safety. Hence today importance of pedestrian safety is perceived as never before in vehicle development program. Basically pedestrian safety evaluation involves subsystem level (head form, upper leg form and lower leg form) impact tests representing human body parts, at specific region on test vehicle with injury limits to decide the severity of impact. In general these injuries are governed by vehicle styling, vehicle stiffness, hard points clearances from vehicle exterior like bonnet, bumper etc.

Passive safety regulations specify minimum safety performance requirements of vehicle in terms of protecting its occupants and other road users in accident scenarios. Currently for majority cases, the compliance of vehicle design to passive safety regulations is assessed through physical testing. With increased number of products and more comprehensive passive safety requirements, the complexity of certification is getting challenged due to high cost involved in prototype parts and the market pressures for early product introduction through reduced product development timelines. One of the ways for addressing this challenge is to promote CAE based certification of vehicle designs for regulatory compliance. Since accuracy of CAE predictions have improved over a period of time, such an approach is accepted for few regulations like ECE-R 66/01, AIS069 etc which involves only loadings of the structures.

During the frontal pendulum impact on commercial vehicles as per AIS029, flat front end vehicles usually show severe cabin deformations. In most of these cases the impact load directly acts on the cabin structure resulting in severe loading of front part of the cabin. This is likely to result in failure of cab mounts causing cabin separation, undesirable cab movement and high intrusion inside the cabin structure. This unpredictable cabin behavior exposes cabin occupants to high risk of injuries. The possible way of reducing occupant injuries in pendulum impact test is to limit the undesirable displacement of the cabin structure during the test and maintain its structural integrity. This can be achieved by having multiple load paths to transfer loads from firewall structure to cabin underbody structure, chassis frame structure and controlling cabin displacement in case of cab mount failure preventing excessive rotation of cabin structure.

Pedestrian protection is becoming an increasingly important aspect in vehicle safety development across the globe. The two primary focus areas are protection to the head and the lower leg of the pedestrian in impacts with motor vehicles. This paper discusses the protection aspects for lower leg in pedestrian impacts. The pedestrian lower leg injuries are measured in the form of deceleration; bend angle and knee shear as stated in regulations. Careful study indicates that a minimum of two load paths namely the upper load path (to support the femur) and the lower load path (to support tibia) are required to control the above stated injuries. Careful optimization is required to balance the stiffness on both the load paths. This paper further focuses on the component optimization to achieve necessary stiffness along the lower load path for injury control. One of the lower load path usually consists of the bumper, “lower stiffener” and its fixing system.

In vehicular crashes, one of the main causes for occupant injuries is uncontrolled hard contact with the vehicle interiors. Typically in frontal crashes, injuries are mainly caused due to contact with the steering wheel and dashboard. In frontal crashes, upper leg injuries are caused due to forces applied on the knee and lower leg (tibia). This injury is a function of occupant forward movement, dashboard intrusion, dashboard stiffness and hard components behind the dashboard in the knee contact location. While trying to control the above design parameters is possible, provision of knee bolsters to limit the femur and knee injury is a more cost-effective, modular and a relatively simple countermeasure which can be used even for an existing vehicle. Knee bolster is a mechanical energy absorbing member packaged behind the dashboard. This member crushes or folds at a predetermined load due to contact forces from the upper leg, thus controlling the resulting injuries.

There is a continuous effort in enhancing the automobile crashworthiness while also trying to reduce weight. This up-gradation is even more difficult if the vehicle is in production due to additional constraints of production feasibility. Higher strength steels and add-on reinforcements are typical measures taken in such circumstances. Even these modifications require manufacturing setup changes and may lead to increase in product weight. One of the critical issues in automotive safety is to ensure passenger compartment integrity which is sometimes compromised due to section shape failure of a critical member. New concepts using structural foams have been introduced for increased strength. These materials work by avoiding collapse of critical sections and have the potential to provide adequate section strength with minimum mass penalty.