Search Results

Individuals responsible for quality management system, implementation, and auditing to the AS9100:2016 series of standards for Aviation, Space, and Defense will require an understanding of the requirements for the preparation and execution of the audit process as defined in these revised standards. Management and implementers of AS9100:2016 Rev. D within these organizations must also be aware of what these requirements mean for their company.

Part 21 is the FAA regulation that provides the regulatory framework to conduct certification of products and parts. This includes the engineering, airworthiness, production and quality systems. The aerospace industry is hinged around compliance with Part 21; however, comprehension of Part 21 and its role in civil certification is challenging. This course is designed to provide participants with an understanding of the processes that encompass aircraft certification, including compliance with FARs, certification procedures and post certification responsibilities.

Foaming materials such as 2C-PUR or expandable baffles are increasingly used in the acoustic package of modern passenger vehicles. Over the last decades the primary function of foaming materials was the moisture sealing and airborne noise absorption / insulation in various areas of the car body such as pillars, door sills or other cavities. Recent developments also show an increasing application of expandable foams, functioning as structural dampers and reducing structure borne noise transmission through frames and pillars. This paper summarizes the results of a study that deals with the impact of expandable baffle materials on structure-borne noise in car bodies. Structural vibrations are evaluated experimentally on foamed generic frames under free-free boundary conditions and the most promising foaming material from the Sika product portfolio is afterwards introduced into a C-Segment car body.

For liquid fueled engine, the fuel atomization affects fuel’s evaporation, combustion, noise and vibration characteristics eventually. In this study, the effects of fuel species on the internal flow and near field primary breakup characteristics of a nozzle "Spray C" are investigated. Based on the framework of OpenFOAM, the newly developed solver which coupled cavitation model and the multifluid-quasi-VOF (Volume-of-Fluid) model, and combines the LES (large eddy simulation) are applied to simulate the nozzle inner flow and near field jet breakup when using diesel and biodiesel respectively. The transient characteristics of nozzle inner flow and near field spray of two different fuels were analyzed, and the variation of axial pressure and velocity of nozzle was obtained. The simulation results show that the cavitation of biodiesel with high viscosity and low saturated vapor pressure develops slower and weaker.

The fast-growing automotive industry and rapid development of new E-drive technology nowadays brings about higher gear design requirements. E-motor applications challenge gear performance due to their higher load and speed levels compared to traditional internal combustion engines (ICE). The advantages of using asymmetric gears include lower stress, higher efficiency, better bending and contact strength, increased durability, etc. However, asymmetric gear dynamics are not well understood or analyzed, and this paper performs extensive study on the effect of asymmetric gears on NVH performance of compound gear transmissions. The parametric study covers different combinations of pressure angle and root fillet settings on the drive and coast sides of the gear. The analysis is focused on the sensitivity of gear transmission error (TE) and mesh stiffness towards different asymmetric gear designs.

The Automotive acoustics arena is rich with application opportunities for carbon neutral or climate positive parts. Designing possible “green” NVH solutions however must never compromise the intended acoustical performance of the vehicles. This paper investigates the acoustical needs of OEM vehicles with an emphasis on applying green solutions. These acoustic solutions proposed will compare and contrast barrier densities, flex modulus, weldability, flammability, sealing characteristics as well as Mass Law calculations between traditional and carbon neutral acoustical barriers. Furthermore, these measures will demonstrate that vehicular acoustic performance need not be compromised as the industry moves down the road towards more climate friendly initiatives. We intend to provide actual OEM vehicular test results measured using traditional and carbon neutral barrier solutions.

The tooth surface error will affect the contact pattern and transmission error of the hypoid gear, which may result in an unfavorable dynamic response. The tooth surface error can be generated by machine tool errors, such as blade wear. The most common forms of blade wear are the positive cutter radius and the positive blade angle error. In addition, in the cutting process of face-hobbed hypoid gear, the continuous indexing motion will aggravate the blade wear due to the alternating cutting force. Most previous studies on the influence of hypoid gear tool errors only focus on the contact pattern and static transmission error. However, there are very few studies about the effect of tool errors on hypoid gear dynamic responses. In this paper, a hypoid gear tooth surface, mesh, and linear dynamic model with tool errors were established.

An Inline 4-cylinder engine is equipped with second-order balance shafts. When the engine is running under a low load acceleration condition, the gear system of the balance shaft generated whine noise. In this paper, an analysis method for reducing the whine noise is presented. First, a flexible multi-body dynamic model of the engine is established, which includes shaft and casing deformation, micro-modification of the balance shaft gears. Taking the measured cylinder pressure as the input, the influence of the micro-modification of the gears’ tooth surface at the balance shaft on the meshed noise was calculated and analyzed. The torsional vibration at the crankshaft nose was measured during no-load conditions, and the measured data was compared with the estimated data, which validate the established multi-flexible body dynamic model of the engine. Secondly, a quasi-static model of the balance shaft gear transmission was established.

Data-driven modeling can help improve understanding of the governing equations for systems that are challenging to model. In the current work, the Sparse Identification of Nonlinear Dynamical systems (SINDy) is used to predict the dynamic behavior of dynamic problems for NVH applications. To show the merit of the approach, the paper demonstrates how the equations of motions for linear and nonlinear multi-degree of freedom systems can be obtained. First, the SINDy method is utilized to capture the dynamic behavior of linear systems. Second, the accuracy of the SINDy algorithm is investigated with nonlinear dynamic systems. SINDy can output differential equations that correspond to the data. This method can be used to find equations for dynamical systems that have not yet been discovered or to study current systems to compare with our current understanding of the dynamical system.

Conventional silencers have extensively been used to attenuate airborne pressure pulsations in the breathing system of internal combustion engines, typically at low frequencies as dictated by the crankshaft speed. With the introduction of turbocharger compressors, however, particularly those with the ported shroud recirculating casing treatment, high-frequency tones on the order of 10 kHz have become a significant contributor to noise in the induction system. The elevated frequencies promote multi-dimensional wave propagation, rendering traditional silencing design methods invalid, as well as the standard techniques to assess silencer performance. The present study features a novel high-frequency silencer designed to target blade-pass frequency (BPF) noise at the inlet of turbocharger compressors. The concept uses an acoustic straightener to promote planar wave propagation across arrays of quarter-wave resonators, achieving a broadband attenuation.

Abstract: As an important vibration damping element in automobile industries, the rubber mount can effectively reduce the vibration transmitted from the engine to the frame. The influence of preload on the static characteristics of rubber mounts and the identification of hyper-elastic material model coefficients were studied. Firstly, a test rig for stiffness test of a mount with preload was designed, and the influence of preload on the static force versus displacement of mounts was studied. Then, the model for estimating force versus displacement of rubber mounts was established, the response surface model for identifying coefficients was established, and the identification method for estimating constitute parameter of rubber materials was proposed the crow search algorithm.

Currently the world’s transportation sector is experiencing a paradigm shift towards electric mobility where electric and electronic components form an integral part of the vehicle. The heavy usage of electronic systems needs large size PCB boards with multiple subcomponents connected to it. Such a complex electronic system when excited by dynamic loads, would lead to generation of uncomfortable transient rattle events between the parts. As a result of this, there is an increasing requirement to analyze these subsystems to eliminate any unpleasant noise generation mechanisms. In this study, a printed circuit board (PCB) has been considered for such an analysis. A linear transient analysis was carried out for a sine-sweep excitation. Risk and root cause analysis was performed, and critical locations were identified. Variation in parameters like material incompatibility, connection stiffness, tolerances were considered and analyzed for the same.

NVH (Noise, Vibration and Harshness) of the electric drive axle (EDA) is a key attribute in electric-vehicle development. The NVH level of the EDA directly determines the driving comfort and customer feeling of the vehicle. Especially in pure electric models, the EDA noise is more prominent without the engine noise masking. The paper aimed at the problem of the 380±50Hz resonance band on the commercial EDA and caused abnormal noise inside the vehicle. Adopted modal analysis, MASTA simulation, modulation noise analysis and exchange parts DOE, gradually refined the source of the problem to a single part, and finally locked to the source of gear parameters Rs and Fr. By adjusting the production process of gear and the second shaft, the assembly process error was avoided, and the gear parameter targets are formulated.

This paper describes a simulation methodology developed for gear rattle severity evaluation and drivetrain architecture optimization . The noise generated by gear rattle is one of the main contributors towards customer's overall NVH perception. This study adopts a model-based design approach towards gear rattle phenomenon to simulate the tendency of gear rattle in neutral and drive conditions . Gear rattle simulation model for Tractor driveline developed in 1-D environment and correlated with test data acquired on tractor drivelines for multiple field applications. This analytical physics-based model includes engine torsional signature, clutch damper torsional characteristic and dynamics of traction and PTO driveline. This dynamic simulation model helps to understand and predict the gear rattle severity of various drivetrain architecture early in the product development cycle and assess & Optimize driveline NVH performance.

The technology of active sound generation (ASG) for automobiles is one of the most effective methods to flexibly achieve the sound design that meets the expectations of different user groups, and the active sound synthesis algorithms are crucial for the implementation of ASG. In this paper, the Kaiser window function-based the harmonic synthesis algorithm of automobile sound is proposed to achieve the extraction of the order sounds of target automobile. And, the suitable fitting functions are utilized to construct the mathematical model between the engine speed information and the amplitude of the different order sound. Then, a random phase correction algorithm is proposed to ensure the coherence of the synthesized sounds. Finally, the analysis of simulation results verifies that the established method of the extraction and synthesis of order sound can meet the requirements of target sound quality.

Piezoelectric Synthetic Jet Actuators (PSJAs) are a class of pulsatile flow generation devices that promises to improve upon steady forced cooling methods in air flow generation, surface cleaning and heat transfer applications. Their acoustic emissions and vibrations, an intrinsic by-product of their operation, needs to be mitigated for applications in noise-sensitive contexts. Already used for in aerodynamic control [1], thrust vectoring [2], spray control [3], and heat transfer [4, 5], they are being considered for sensor lens cleaning in automobiles. In this study, the sound generation mechanisms of PSJAs were investigated. Driven with a single frequency sinusoidal input, PSJAs produce undesirable emissions at harmonic frequencies within the frequency range of speech communication. The sound pressure levels of these emissions may exceed allowable levels standard in industry.

As more and more electric vehicles (EVs) on dedicated platforms are being developed and launched, powertrain (PT) mounting systems evolve to focus on the specific requirements of the electric drive units (EDUs) – especially the partially opposing targets of controlling powertrain motion under torque and enhancing high frequency isolation. Vibracoustic has faced this challenge by adapting its motor mount system simulation methodology as well as by extending and enhancing its subsystem and e-axle test capabilities. In modern battery electric light vehicles, the electric drive unit (EDU) in the front or the rear axle is typically suspended on the vehicle body on three or four bushing. An isolated subframe may be added between the EDU and the vehicle body for improved NVH via double isolation.

In the mounting of vibration sources and receivers, it is typically desirable to have low stiffness for isolation. On the other hand, durability may demand a high stiffness to handle large inputs without excessive motion, which seems like a contradictory requirement. Both may be achieved using nonlinear stiffness mounts which make use of elastomer deformation to exhibit softening through geometric nonlinearity. This paper discusses a physical proof of concept for a quasi-zero stiffness (QZS) mount design with a three-regime stiffness curve including a preload, isolation, and motion control regions. Building on a design concept proposed in prior literature, new experimental validation is obtained for the prior nonlinear static stiffness property, which is then fit into a more stable mount topology. Fabrication and material issues are also discussed.