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Leaf Springs are commonly used as a suspension in heavy commercial vehicles for higher load carrying capacity. The leaf springs connect the vehicle body with road profile through the axle & tire assembly. It provides the relative motion between the vehicle body and road profile to improve the ride & handling performance. The leaf springs are designed to provide linear stiffness and uniform strength characteristics throughout its travel. Leaf springs are generally subjected to dynamic loads which are induced due to different road profiles & driving patterns. Leaf spring design should be robust as any failure in leaf springs will put vehicle safety at risk and cost the vehicle manufacturer their reputation. The design of a leaf spring based on conventional methods predicts the higher stress levels at the leaf spring center clamp location and stress levels gradually reduce from the center to free ends of the leaf spring.

In recent years, the push for reduced product development timelines has been more than ever with significant changes in the automotive market. High electrification, intelligent vehicle systems and increased number for car manufacturers are a few key drivers to the same. The front loading of development activities is now a key focus area for achieving faster product development. From vehicle dynamics point of view availability of subjective evaluation feedback plays a key role in optimization various system specifications. This paper discusses an approach for front loading through parallel development of the tire and vehicle chassis system, using advanced simulation and driving simulator technology. The proposed methodology uses virtual tire models which in combination with real-time vehicle model enables subjective evaluation of vehicle performance in driver-in-loop simulators.

The focus on driver and occupant safety as well as comfort is increasing rapidly while designing commercial vehicles in India. Improvements in the road network have enhanced road transport for commercial vehicles. Apart from the cost of operation and fuel economy, the commercial vehicles must deliver goods within stipulated time. These factors resulted in higher speed of operation for commercial vehicles. The design should not compromise the safety of the vehicle at these higher speeds of operation. The vehicle should obey the driver’s intended direction at all speeds and the response of the vehicle to driver input must be predictable without much larger surprises which can lead to accidents. The commercial vehicles are designed with rigid axle and RCB type steering system. This suspension and steering design combination introduce steering errors when vehicle travel over bump, braked and while cornering.

Customer expectations for cabin tractors from comfort perspective has grown multifold in the recent years. Cabin noise and vibration is one of the crucial parameters which drives comfort feel for the customer. This would enable customer to remain comfortable during long working hours. Moreover, Cabin Tractors with lesser noise levels found to have better acceptance by Customers all over the world. The Nebraska reports studied for US based tractor shows evolution of trend of cabin noise in 80-100HP tractors in last couple of decades. Undoubtedly, tractor manufacturers have put lot of efforts towards meeting legislation demand & stringent customer requirements for European and US market. This paper presents the work carried out for investigating major contributing factors affecting tractor cabin Noise & Vibration for a Noisy cabin tractor.

In farm tractors, the available drawbar power, and Power Take-Off (PTO) power are generally lower than the engine power due to parasitic losses. These losses are caused by engine-driven auxiliary loads such as cooling fans, hydraulic pumps for power steering, alternators, etc. Minimizing these parasitic losses can increase the available drawbar power and PTO power, resulting in direct fuel savings by reducing fuel consumption. The continuous increase in fuel costs and the environmental impact of emitted gases from burned fuel into the atmosphere have necessitated the replacement of hydraulic power steering and mechanical fans with Electric Power Steering (EPS) and electric fans, respectively, to improve efficiency. The existing battery has been replaced with a higher capacity battery to provide power to the electric fan, electric power steering, and other electrical components.

As a car OEM, we continuously strive to set the bar for competitors with every product. Consumer travel experiences are enhanced by increasing passenger cabin silence. There is only one steering system opening in the firewall panel, which is used for allowing intermediate shaft's fitment on the pinion shaft of the steering gear. The steering grommet is the sole component that covers the firewall cut-out without disrupting steering operations, which has a substantial impact on the NVH performance of the vehicle. It is typically used in cars to eliminate engine noise and dust entering to passenger compartment. The part is assembled inside the vehicle where the steering intermediate shaft passing through BIW firewall panel. We use a bearing, plastic bush, or direct rubber interference design in the steering grommet to accommodate the rotational input the driver provides to turn the automobile.

Restraint systems in automotives are inevitable for the safety of passengers. Seat belts are one such restraint system in automotives that prevent drivers and passengers from being injured during a crash by restraining them back. Seatbelt on automotives has interface with Body-in-white (henceforth called as BIW) and Trim parts in-order to serve its purpose at vehicle level. One such interface part of seat belt is the web guide, which assists and ensures the nylon web’s smooth motion at different seat track positions. Web-guides on automotives ensure the flawless motion of seat belt web at pillar trim areas. In this paper, we are discussing alternate ways of assisting the seat belt web without the web-guide as a separate part. In-order to assist and ensure the motion of nylon web in its trajectory, we have extended the flange of the pillar trim involved.

This paper focuses on reducing abnormal noise originating from suspension when driving on rough road at the speed of 20 kmph. The test vehicle is a front wheel driven monocoque SUV powered by four cylinder engine. Cabin noise levels are higher between 100 to 800 Hz when driven on rough road at 20 kmph. Vibration levels are measured on front and rear suspension components, front and rear subframe, subframe connections on body to identify the noise source locations. Since the noise levels are dominant only in certain rough patches at very narrow band of time, wavelet analysis is used for identification of frequency at which the problem exist. Based on wavelet analysis, it is identified that the vibration levels are dominant on front lower control arm (LCA). The dynamic stiffness of LCA bushes is reduced by ~ 40% to improve the isolator performance which reduced the noise levels by ~ 9 dB (A) at the problematic frequency band.

As customers are inching towards adoption of electric vehicles as an alternative to internal combustion engines, automotive OEM’s will have to embrace this change and equip with new product development process. When it comes to Electric Vehicle (EV) in comparison with Internal Combustion Engine (ICE), NVH plays a major differentiator for vehicle refinement. Squeak and rattles will account for 20-25% of overall in-cabin noise source in an electric vehicle, most of which is observed from interior trims. Trims are mounted using small plastic clips which function as attachments and play a significant role in part retention and part integrity during normal operation and in case of any transient events. The engineering specifications for selecting a clip is force in newtons and it is mostly driven by ease of assembly, serviceability, and durability. A single DOF system with a specimen mass is developed and stiffness and damping are calculated based on transmissibility.

This paper examines one of the approaches used to identify the root causes of sound quality issues in vehicles, including the direct impact of psychoacoustics on the human experience. Specifically, the absence of masking effects provided by traditional combustion engines has made noise and vibration from electric drives significant factors in decision-making processes, with high-pitched tonal noise from electric motors causing annoyance and sound quality concerns for electrified propulsion systems. During vehicle testing at different speeds, a whining noise was observed, leading to an NVH test to locate the noise source. The noise is traced to the transmission by the dominating order of input reduction along with the contribution from the casing resonance. A multi-physics-based e-NVH analysis was performed, and the test data were correlated.

In automotive manual transmission gearboxes, the synchronizer rings play a vital role in gear shift operations. The efficiency of the synchronizer ring depends upon the frictional surface geometry. The critical parameter is the synchronizer ring frictional surface circularity. The circularity deviation causes higher synchronizer ring wear and poor cone torque generation. With the current manufacturing methods and the thickness of the synchronizer ring, circularity improvement is a challenge. The synchronizer ring thread turned part is lapped to improve the circularity. Reduction in circularity can be improved by optimizing the lapping operation. In this work, an optimal lapping condition was developed using statistical methods. Taguchi DOE was used to analyze the different parameter combinations along with the noise parameter – different ranges of circularity variation in turning operation. This helps to find the best lapping parameter settings to improve the reduction in circularity.

In manual transmission, the vital function of synchronizer pack is to synchronize the speed of the target gear for smooth gear shifting. The synchronizer pack consists of various elements and each of these elements has specific function. These elements are baulk rings, shifter sleeve, hub, synchro key, synchro springs etc. The function of synchronizer can be affected due to failure of any one of these elements. This work focuses on the failure of synchronizer pack due to synchro spring failure. The function of synchronizer spring is to exert the required force, to index the synchronizer ring before the movement of shifter sleeve over synchronizer ring. During the shifting of shifter sleeve from one gear to another gear, the springs deflect in both shifting directions. This causes fatigue failure of synchronizer springs. The manufacturing variations, and part quality issues results in very early fatigue failure of synchronizer springs.

Tensile Testing is one of the most used and highly reliable method of mechanical testing to evaluate the tensile properties of the material. However, there is a large scope for discussing the behavior of the metals based on the direction of rolling and the tensile specimen size used for testing. This paper discusses the variation observed in the tensile values along the direction of rolling and traverse to the direction of rolling for S460MC. It also evaluates the variation observed in the values based on the various gauge lengths (GL) commonly used in testing as per international standards (80mm, 50mm and 25mm GL). It is observed that perpendicular to the direction of rolling, the Yield and Tensile strength of the material increase marginally while the Elongation percentage (%E) decreases by a small margin irrespective of the gauge length taken into consideration.

In most cases, the properties of a metal are evaluated in their as rolled condition, prior to any work hardening or bake hardening. But in the Automotive World, these steels get work hardened during the forming process and bake hardened in the paint shop. The goal of this paper is to evaluate the variations in the performance of Dual Phase (DP) steels and understand the most optimized method of testing and property generation. This method can then be used to extrapolate to real automotive components. Dual Phase Steels or DP Steels contain a mixture of Ferrite & Martensite from which they derive their name. They are a part of the advanced high strength and ultra-high strength steels steel family according to World Auto Steels. The Ferrite phase, with its iron content contributes to the material displaying an increased level of ductility whilst, the martensitic phase provides the steel with increased mechanical strength.

Original Equipment Manufacturers (OEMs) should innovate ways to delight customers by creating affordable products with improved drive experience and occupant comfort. Vehicle refinement is an important initiative that is often take-up by the project teams to ensure that the product meets the customer’s expectations. A few important aspects of vehicle refinement include improving the Noise Vibration Harshness (NVH), ride and handling performance pertaining to the Functional Image (FI) of the product. Optimizing the suspension design variables to meet both ride and handling performance is often challenging as improving the ride will have a deteriorating effect on handling and vice-versa. The present work involves Multi-Objective Design Optimization (MDO) of the suspension system of an automotive Sports Utility Vehicle (SUV) platform considering both ride and handling requirements, simultaneously.

For decades, customer complaints on Squeak & Rattle issues have come as a question of quality for the automotive industry. Squeak and rattle sounds are customer irritants due to their non-patterned and transient nature. Squeak is a friction induced noise that generally occurs because of rubbing of the two materials that are incompatible with each other. While rattle is a phenomenon that occurs due to the impact between the two parts having unintended gap. They are no more secondary noises and avoiding or elimination of these become significant for brand building and warranty cost reduction. Chucking is a form of squeak noise that occurs due to the interaction between uncoated seal to seal. In Swing gate, this phenomenon is seen when seal bulb inner layers are completely compressed. Swing gate have fore-aft modes that are excited due to dynamic responses from different road profiles.

The bolted joints in suspension systems are subjected to severe external service loads during vehicle operation. To prevent the loaded joint from loosening and allowing it to retain its potential energy stored during assembly, a holistic design approach is needed. This paper explains the methodology to design and optimize bolted joints for the suspension systems of a modern 7-seater sports utility vehicle.

PVC (polyvinylchloride) synthetic leather or called leatherette is being widely used for automotive interior applications for seat cover, gear boot, gap hider, steering wheel and roof liner due to their leather like feel and texture, flexibility, sewability, affordability, and wide design freedom. However, the leatherette construction such as top coating, backing fabric and fabric weaving pattern plays a critical role in the finished leatherette performance for the specific application. This study provides the influence of different coating material and different backing fabric in squeak behavior of gear boot PVC leatherette. The squeak behavior was studied by stick slip test as per automotive engineering requirements, and the response of these coating and fabric surface was measured in the form of Risk Priority Number (RPN).

Accurate ride and handling prediction is an important requirement in today's automobile industry. To achieve the same, it is imperative to have a good estimation of damper model. Conventional methods used for modelling complex vehicle components (like bushings and dampers) are often inadequate to represent behaviour over wide frequency ranges and/or different amplitudes. This is difficult in the part of OEMs to model the physics-based model as the damper’s geometry, material and characteristics property is proprietary to part manufacturer. This is also usually difficult to obtain as a typical data acquisition exercise takes lots of time, cost, and effort. This paper aims to address this problem by predicting the damper force accurately at different velocity/ frequency and amplitude of measured data using Artificial Neural Networks (ANN).

Vehicle pull during braking can be defined as the deviation of vehicle travel from intended path of the vehicle by a margin of half a wheel track or more. It is a dynamic phenomenon with very complex inter-dependencies among the combined functioning of various aggregates such as steering system, suspension system, axles, and brakes. The problem is aggravated with shorter wheelbase & higher CG (Centre of Gravity) height, where the instantaneous load transfers are sudden and of relatively high magnitude which can lead to a combination of forces that are responsible for vehicle drifting or pulling to anyone side of centre-line travel. Vehicle with shorter wheelbases, high GVW and high CG heights are more prone to this unstable behaviour due to sudden change in dynamic forces acting on the tires while turning and braking.