Browse Topic: Noise, vibration, and harshness standards and regulations
This study focuses on the numerical analysis of weather-strip contact sealing performance with a variable cross-sectional design, addressing both static and dynamic behaviors, including the critical issue of stick-slip phenomena. By employing finite element modeling (FEM), the research simulates contact pressures and deformations under varying compression loads, DCE (Door Closing Efforts) requirements, typical in automotive applications. The analysis evaluates how changes in the cross-sectional shape of the weather-strip affect its ability to maintain a consistent sealing performance, especially under dynamic vehicle operations. The study also delves into stick-slip behavior, a known cause of noise and vibration issues, particularly improper/ loosened door-seal contact during dynamic driving condition. This study identifies key parameters influencing stick-slip events, such as friction coefficients, material stiffness, surface interactions, sliding velocity, wet/dry condition
ABSTRACT When we assess compliance of crew exposure to vibration within a military tracked vehicle we use international standards, these are ISO 2631 and BS 6841. Within these standards, weighting factors based on research carried out 40 years ago are applied to the measured vibration. These weighing filters attenuate and remove vibration above 80Hz. After conducting tests for over 30 years, it is the author’s intention to prove that these filters are no longer fit for purpose and the standards need revisiting.
Exhaust system of an automobile is primarily employed in automobile to purify exhaust gases and reduce noise due to combustion. However, a side-effect of the above function is the increase in backpressure. As specified in various literatures, an increase in backpressure can lead to a deterioration on engine performance (Power & torque). Benefit of backpressure reduction can be further taken in terms improving the power & torque of engine or improving the fuel economy. With growing concerns related to global warming and CO2 emissions, reducing exhaust back pressure is one of the promising areas in engine design in order to improve the fuel economy of the automobile and achieving carbon neutrality targets. However, reducing the back pressure generally tends to deteriorate the noise attenuation performance of the Exhaust system. Hence, it is imperative to reduce backpressure of an Exhaust system while at the same time ensuring adequate noise attenuation, for passenger comfort and noise
Reducing the emitted noise from vehicles is a primary issue for automotive OEMs due to the constant evolution of the noise regulations. In the context of electric powertrains, virtual prototyping has proven to be a cost-efficient alternative to the build-test process, especially in early design stage and/or if optimization is targeted. Due to the multiphysics nature of the model, the full simulation chain involves multiple components, each having its own specific modelling attributes. The difficulty then resides in the parts assembly, solving issues like mesh-to-mesh projections, time to frequency-domain transformation, 2d-axisymmetric to 3d mapping, data formatting and management, unit and local coordinate systems… This paper presents an environment that allows for the prediction and analysis of the noise radiated by electric automotive powertrains. The stator-rotor electro-magnetic behavior is represented by time-dependent forces applied on stator teeth. Transfer functions from
In recent times there has been rising demand for noise level reduction in commercial vehicles. Vehicle engine exhaust system is one of the key sources of noise at driver ear, especially in smaller wheel base vehicles, as well as critical for meeting pass by noise regulations. Several techniques are used to reduce the noise level of an exhaust system such as resonators, dissipative mufflers for low & high frequencies respectively. In this paper sound transmission loss (STL) measurement for a LMD bus exhaust system was carried out at rig level. It has been found from the measured data that noise attenuation of current exhaust system is poor in low frequency zone & therefore lower STL frequencies were identified. To attenuate the noises at identified frequencies Helmholtz resonator was introduced, which is particularly effective for low frequency noise attenuation. A design is conceptualized and developed based on Helmholtz resonator calculation for target frequencies and duty cycle gas
The exhaust system design and development need to be more flexible and easily adaptable for the requirement of dynamic changes to meet the upcoming emission and noise regulations. Durability of exhaust system components are evaluated through conventional bending moment testing using specified standard load conditions. Road load re-production test is an improvement of the conventional approach to predict component weld durability. It involves the systematic and 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 road load reproduction testing. It involves prediction of rough force using transient response analysis followed by Bi-Ax testing for the derived high and low load forces to meet the target number of cycles to failure. Targeted fatigue damage factor (< 1.0) is evaluated by comparing S/N
This SAE Standard sets forth measurement procedures and instrumentation to be used for determining a “representative” sound level during a representative time period at selected measurement locations on a construction site boundary. The document is not intended for use in determining occupational hearing damage risk. Determination of a representative time period is left to the judgment of the user.
Along with the global trend for electrification, also motorcycle industry is entering new spheres of highly advanced products and is increasing customer demands for electric mobility. Beside hard facts such as performance, driving range, durability and ease of use, also the brand specific attributes such as styling, driveability and even sound for electrified 2-wheeler are very emotional, unique selling prepositions. To determine the subjective parameters for driveability and acoustics, AVL has developed dedicated tools and methods to quantify these attributes with high maturity. In terms of acoustics and NVH there are several crucial noise sources within electrified powertrains, which have to be treated with high attention from the initial development phase to avoid any kind of unforeseen annoyances: E-motor with inverter, transmission and secondary drive are most relevant. This issue becomes even more important with the ongoing market trend of products featuring increased power
Vehicles with lower noise levels and better levels of vibratory comfort for passengers made the area of noise, vibration and harshness (NVH) one of the main areas related to the perception of vehicle quality. Several approaches on the contribution of transfer paths have been studied to define the propagation energy in vehicular structures. Transfer Path Analysis (TPA) is a tool to improve NVH performance with the primary goal of reducing and improving perceived vibrations and noise in the cabin vehicle by occupants. Indirect methods are especially important in cases where the force signals are immeasurable in practice in terms of cost and space for sensor couplings, in the measurement configuration, and particularly in the case of distributed forces. The matrix inversion method, perhaps the most popular classic TPA, identifies operational forces using passive body acceleration. However, removal of the source can change the dynamic characteristics of the assembled structure and increase
It is well known the difference between development levels and engineering investment applied to passenger car brake pads when compared to Original Equipment Manufacturer (OEM) and items sold in the Independent Aftermarket (IAM). Based on these differences, the objective of this paper is to propose a simple evaluation for the IAM that can provide at least some level of the understanding of frictional material behavior. Based on a tripod of variables, or three Dimensions Development, described in this work as Performance, Comfort (NVH) and Durability; and using internationally and established testing procedures to measure these dimensions in order to meet the IAM demands for the cost-benefit engineering investment. An important part of the proposed tool is to position friction material against competition for market known issues, and, more importantly, to ensure end product safety and reliability.
With fast pacing development of automobile industry and growing needs for better driving experience, NVH performance has become an important aspect of analysis in new driveline product development especially in hybrid and electric powered vehicles. Differential bevel gear has significant role in the final drive. Unlike parallel axis gears such as spur or helical gear, bevel gear mesh shows more complicated characteristics and its mesh parameters are mostly time-varying which calls for more extensive design and analysis. The purpose of this paper is to conduct design study on a differential bevel gear unit under light torque condition and evaluate its NVH characteristics. Unloaded tooth contact analysis (UTCA) of those designs are conducted and compared for several design cases with different micro geometry to investigate their pattern position and size variation effects on NVH response. Loaded tooth contact analysis (LTCA) that is based on semi-analytical and semi-FE method is used to
A major challenge in automotive NVH engineering is to approach complex structure-borne sound and vibration problems with sufficient accuracy but reasonable experimental effort. Typical issues encountered are poor correlation between objective component performance criteria tested for during bench validation and corresponding subjective targets evaluated during system validation in the actual vehicle. Additional challenges arise from the need to impose assumptions on sophisticated physical vibration problems to reduce the complexity to a level feasible for conventional experimental test methods. This paper addresses all mentioned issues by elaborating on a system NVH engineering approach employing Virtual Acoustic Prototyping (VAP) (related to what is now often called component Transfer Path Analysis) to synthesize time domain sound and vibration responses of vibrating machinery operated in a virtual vehicle environment. One crucial step of VAP is to characterize the strength of
The paper will present an integrated approach to system NVH analysis, which gives an insight into the system response in an EV driveline due to electrical and mechanical excitations; namely rotor mechanical imbalance, electrical machine torque ripple, and stator radial force shapes. The paper will address the fact that, as part of a practical design exercise, different subsystems and components may achieve design maturity at different times. It is therefore important to understand to what extent various drivetrain components may be considered in isolation, and at what point it becomes necessary to consider the interactions present in the full system. The paper will compare predicted NVH performance of a representative EV traction motor when different boundary conditions are considered; for example, when considering the motor being bested in isolation as part of a typical test setup, and when included in a representative drivetrain. For each configuration, the response to mechanical and
Items per page:
50
1 – 50 of 672