The transient dynamic behavior of the Valvetrain is very important to understand the design of Valvetrain for both durability and noise generation in the Valvetrain. The current simulation is carried out at constant engine speed with an implicit time-integration method. Dynamic implicit Valvetrain simulation usage for the prediction of Valvetrain durability has been discussed in detail by V Prasanth et. al.. The present paper is an extension to that previous work and this methodology has been used to identify the critical contact regions that have a major contribution to the Valvetrain noise. Comparing the PSD of the contact forces calculated from the dynamic simulation with the experimental noise measurement helped to identify the critical region. A separate modal analysis has been carried out in parallel. This is because in dynamic implicit simulation the PSD of the contact force will be highest at certain frequencies.
Over the past several decades, the automotive industry is more focused on reducing engine, wind, and road noise to improve comfort. However, as background noise levels continue to decrease, the squeaks and rattles created by the many components inside and outside the vehicle become gradually noticeable, and annoying. In electric vehicles the squeaks and rattles noise becomes more dominant than other type of noise as a result of absence of dominant noise source of engine from conventional petrol/diesel vehicle. In this paper, we are proposing a simulation methodology to develop a systematic approach to identify and solve squeak and rattle problems in vehicle components/sub-assemblies at primary stage of product development. This work will present a unique approach in understanding varied methods and Design of Experiments (DOE) techniques used to identify root-cause of squeak and rattle problems and to find a solution by using numerical methods.
The success of modern-day vehicles not only depends on good power train or fine aesthetics, but also on acceptable levels of NVH (Noise Vibration and Harshness). Moreover, the advent of electric vehicles has led to a quieter powertrain owing to lesser moving parts in the electric powertrain. Hence, the exterior tire noise becomes prominent. Consequently, the accurate measurement of tire noise is imperative to maintaining optimum noise level of the vehicle. Finite Element Analysis (FEA) is an important tool in the measurement of exterior tire noise. The reasons attributed to the use of FEA are: less cost, time saving and a near reproduction of the real time conditions. The present work focuses on the parametric acoustic mesh development for the simulation of external tire noise using FEA approach. The proposed project provides an alternative to licensed commercial software while improving meshing time and performance vis-à-vis said commercial software.
NVH has gained importance in the field of earth moving equipment due to the demand of quieter machines and stringent in-cab as well as exterior noise emission norms. Several parts of the world have adopted strict legislation on noise emission by earth moving equipment, but many countries have not adopted any regulations till date. This paper mainly focusses on helping governing bodies as well as machine manufacturers in adopting simple yet accurate testing method for compaction machine. The study consists of directivity analysis, noise source identification & noise source ranking and 4-point microphone position sound power evaluation method applied to compactors with wide range of engine power ratings. All the tests in 4-point method and directivity analysis were performed under stationary as well as dynamic conditions.
One of the main objective of manufacturer is to achieve high productivity with low cost while increasing the customer satisfaction. With increased competition in the automotive sector the product quality is defined not only from fuel economy and durability perspective but also Noise, Vibration and Harshness (NVH), which plays a vital role in attracting the customers. In two wheeler, engine is dominant noise source and its quality improvement is utmost priority. Now a days, several signal processing and sensing techniques are developed for noise source identification of an engine but precise source identification can be achieved only by advanced analysis technique. This paper focuses on a procedure for noise source identification from engine sub-system viz. valve operation and its generation mechanism using crank angle domain analysis in two wheeler engine. Baseline noise measurements were carried out for critical frequency identification.
The exhaust system design and development needs to be more flexible and easily adaptable for the dynamic changes with the introduction of new emission and noise regulations. Conventionally, bending moment testing is used to validate significant components like inlet and outlet pipe/cone joints and bend pipes through Bi-Ax test rig. Road load re-production test is an improvement of the conventional approach to predict component durability. However, it is more time consuming and involves the sequential process of acquiring road load data such as sensor instrumentation, strain measurement at the test track, data processing and input to Bi-Ax testing. S/N Curve testing is introduced recently as an alternate method to minimize the use of RLDA. It can be done upfront during vehicle unavailability and other challenging conditions and also as a parallel activity along with RLDA.
Short development cycles, less packaging space and stringent noise emission rules have increased the need of CAE usage and first time right design approach. Engine exhaust noise is the main contributor of automotive noise when vehicle speed is low to moderate. Exhaust noise contains tailpipe noise and shell radiation noise. As vehicle speed increases, contribution of flow noise and tire noise is comparatively at higher side. The cold end development engineer is responsible to design a muffler to meet tailpipe and shell radiation noise targets. Muffler shell stiffness is a key characteristic for deciding shell radiation noise. High intensity pulses of exhaust gas passes through the exhaust pipe and hits cold end from inside which causes shell vibration and respectively shell noise. There are several conventional methods available to improve shell stiffness, but all of them are not applicable for ‘double layered critically shaped mufflers’ and all of them are not cost-effective.
Due to recent advancements in interior noise level and the excessive use of different grade leathers and plastics in automotive interiors, squeak noise is one of the top customer complaints. Squeak is caused by friction induced vibration due to material incompatibility. To improve costumer perception, interior designs are following zero gap philosophy with little control on tolerances leading to squeak issues. Often manufacturers are left with costly passive treatments like coatings and felts. The best option is to select a compatible material with color and finish; however, this will reduce the design freedom. Material compatibility or stick-slip behavior can be analyzed with a tribology test stand. However, this test is performed on a specimen rather than actual geometry. There were instances, when a material pair was found incompatible when tested on a specimen, but never showed any issue in actual part and vice versa.
This paper deals with specific NVH related issues attributed due to LCA bush stiffness and Brake rotor DTV. While the focus is on the cause of such vibration (judder while braking at 120 kmph), the presentation goes to the root-cause of judder and how various suspension/tire/brake components contribute to the generation/amplification of such vibration. Results are presented for twist blade types of vehicle suspensions, along with procedures that were developed specifically for this study and some of the actual case study. DTV-Disk thickness variation
Predicting Vehicle Pass–by noise using simulation enables efficient development of adequate countermeasures to meet legislative targets while reducing development time and the number of physical trial-and-error prototypes and tests. It has already been shown that deterministic simulation methods such as the Boundary Element Method (BEM), which may also include directivity of sources, can support the trim package optimization process for Pass-by noise, especially for low to mid frequencies. At higher frequencies, the Ray Tracing technique, can represent an efficient alternate providing options to trade off speed versus accuracy compared to wave based technique such as FE/BEM. This paper presents a Ray Tracing approach with high order diffraction effect. Moreover, source directivity and sound package effect are accounted for.
Till recently supercharging was the most accepted technique for boost solution in gasoline engines. Recent advents in turbochargers introduced turbocharging technology into gasoline engines. Turbocharging of gasoline engines has helped in powertrains with higher power density and less overall weight. Along with the advantages in performance, new challenges arise, both in terms of thermal management as well as overall acoustic performance of powertrains. The study focuses mainly on NVH aspects of turbocharging of gasoline engines. Compressor surge is a common phenomenon in turbochargers. As the operating point on the compressor map moves closer to the surge line, the compressor starts to generate noise. The amplitude and frequency of the noise depends on the proximity of the operating point to the surge line. The severity of noise can be reduced by selecting a turbocharger with enough compressor surge margin.
Squeak and rattle concerns accounts for approximately 10% of overall vehicle Things Gone Wrong (TGW) and are major quality concern for automotive OEM's. Objectionable door noises such as squeak and rattle are among the top 10 IQS concerns under any OEM nameplate. Customers perceive Squeak and rattle noise inside a cabin as a major negative indicator of vehicle build quality and durability. Door squeak and rattle issues not only affects customer satisfaction index, but also increase warranty cost to OEM significantly. Specifically, door squeak issues which irritates customer generally occur due to incompatibility of materials used in different interface of door trim. Squeaks are friction-induced noises generated by stick-slip phenomenon between interfacing surfaces. Several factors, such as material property, friction coefficient, relative velocity, temperature, and humidity, are involved in squeak noise causes.
Traction motor is one of the most important system in the powertrain of an electric vehicle. Motor whine is a major source of concern in EV design and integration. Though not as loud as IC engines, this high-pitched noise, on a continuous basis can be annoying for the driver, especially at a frequency above 1 kHz. The main contributors for motor whine include radial electromagnetic (EM) forces and rotor eccentricity. Evaluation of these noise sources through simulation enables earlier intervention and correction in development process. The major challenge in NVH prediction of traction motors is incorporating multiple physical behaviour and integrating them. This becomes extremely necessary especially in noise optimization as it could adversely affect the motor performance. The developed method should include accurate EM analysis for performance estimation and force extraction as well as a detailed vibro – acoustic approach for noise prediction.
Groan is a low frequency noise generated when moderate brake pressure is applied between the surfaces of the brake disc and the brake pad at a low-speed condition. Brake groan is often very intense and can cause large numbers of customer complaints. During a groan noise event, vehicle structure and suspension components are excited by the brake system and result in a violent event that can be heard and felt during brake application. The cause of noise is friction variation of stick-slip phenomenon between friction material and disc. This paper discusses the approach for prediction and mitigation of brake groan noise for passenger vehicles having disc brakes. To identify the brake groan noise frequency, vehicle testing with operating condition for reproducing the groan noise is carried out and also impact frequency response analysis is performed to identify natural frequency of each chassis component like brake, suspension stud, lower control arm, knuckle etc.
From last few years, many Auto OEMs are started shifting towards Electric Vehicle development from their regular conventional vehicle development As the main conventional power source engine is changed to an electric motor, many research and developments going on design and validating the E-Motor performance through test and simulation approaches by the majority of Auto OEMs and electric motor manufacturers The design approach of motors for electric vehicle (EV) application satisfying the high torque, high power, Less weight and less torque ripples are important aspects, but also the efficiency for full driving cycle, temperature, noise, and vibrations are very critical for suitability of the vehicle This paper is focused on calculating the power requirement for an electric vehicle using empirical formulas. Permanent magnet synchronous motor topology designed based on the duty cycle requirements and validate the Electromagnetic & Thermal performance by simulation tools.
Last decade has been era of environmental awareness. Various programs have launched for making devices and appliances eco-friendly. This initiative has lead automobile industry toward hybridization and now total electrification of vehicles. As electric motor is being added to automobile as a prime mover, due to high frequency vibrations along with higher torque electric motor needs to be isolated properly & carefully as this vibration can damage other automobile parts. Dynamic response of electric motor is different from response of IC engines, so use of engine mounting design method may not be suitable for designing mounting system for electric motor. First, both 4- point and 3- point mounting system are considered for analytical and experimental investigation of force and displacement transmissibility. Position and orientation of elastomeric mounts plays important role in design of mounting system for electric motor.