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The most time-consuming step in an external aerodynamics or underhood CFD process is that of generating a usable mesh from CAD data. Conventional mesh generators require a water-tight surface mesh before they can generate the volume mesh. Typical CAD surface data available for mesh generation is far from satisfactory for volume mesh creation: no node-to-node matching between mating parts, minute gaps, overlapping surfaces, overlapping parts, etc. To clean up this kind of data to a level that can be used for volume mesh creation requires a lot of manual work that could take a couple of weeks or more to accomplish. This paper presents a fast and fully automated, Cartesian cell dominated projected mesh generation algorithm used in CFD-VisCART that eliminates the need for CAD data cleaning, thus shaving off weeks worth of time off the design cycle.

Since Statistical Energy Analysis (SEA) is based on lumped parameters, acoustic responses predicted by SEA are spatially discontinuous. However, in many practical applications, the ability to predict spatially continuous energy flow is useful for guiding the design of systems with improved acoustical characteristics. A new approach, utilizing integral equations derived from energy flow concepts, is developed to predict the continuous variation of acoustic field such as sound pressure level in the interior of acoustic domains using structural response predicted by SEA. The computer code developed based on energy flow boundary integral equations is initially validated by analyzing sound propagation in a duct.

Optimizing noise control treatments in the early design phase is crucial to meet new strict regulations for exterior vehicle noise. Contribution analysis of the different sources to the exterior acoustic performance plays an important role in prioritizing design changes. A method to predict Pass-by noise performance of a car, based on source-path-receiver approach, combining data coming from simulation and experimental campaigns, is presented along with its validation. With this method the effect of trim and sound package on exterior noise can be predicted and optimized.

Designing an effective AVAS system, not only to meet safety regulations, but also to create the expected perception for the vulnerable road user, relies on knowledge of the acoustic transfer function between the sound actuator and the receiver. It is preferable that the acoustic transfer function be as constant as possible to allow transferring the sound designed by the car OEM to ensure the safety of vulnerable road users while conveying the proper brand image. In this paper three different methodologies for the acoustic transfer function calculations are presented and compared in terms of accuracy and calculation time: classic Boundary Element method, H-Matrix BEM accelerated method and Ray tracing method. An example of binaural listening experience at different certification positions in the modeled simulated space is also presented.

In this paper, the distortion analysis in spot welded area of car body - front side member, it is found out that the optimum condition for panel assembly is closely related to the welding sequence, location of clamping system, number, shape and welding force. The distortion resulting from welding sequence is minimized starting from the surroundings of the clamping system and in the way that the value of the welding force is from large to small. The MCP is determined from the positions inducing the minimum distortion in panel through calculating the deformation and reacting force of the panel. The welding force originating from the manufacturing tolerance of assembly is a critical design factor determining the welding sequence and the clamping system that yield minimum distortion in spot welding of body panel.

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.

Wind noise is a major contributor to vehicle noise and a very common consumer complaint for overall vehicle quality [1]. The reduction of wind noise is becoming even more important as powertrain noise is reduced or eliminated (by conversion to hybrid and electric vehicles) and as the importance of quiet interior environment for hands-free device use and voice activation systems becomes more pronounced. In contrast to other noise sources such as tires, engine, intake, exhaust or other component noise whose acoustic loads may be measured in a direct and standardized way with the proper equipment, wind noise is very difficult to predict because the acoustic part of wind noise is a small component of overall fluctuating pressures. It is very challenging to either directly measure or to simulate the acoustic component of fluctuating exterior pressures using CFD (Computational Fluid Dynamics) without a great deal of specialized experience in this area.

One of the major concerns in the vehicle trim part design is the acoustic targets, which are generally defined by absorption area or coefficients, and sound transmission loss (STL) or sound insertion loss (SIL). The breaking down of acoustic targets in vehicle design, which is generally referred to as cascading, is the process of determining the trim part acoustic targets so as to satisfy full vehicle acoustic performance. In many cases, these targets are determined by experience or by subjective evaluation. Simulation based transfer path analysis (TPA), which traces the energy flow from source, through a set of paths to a given receiver, provides a systematic solution of this problem. Guided by TPA, this paper proposes a component level target setting approach that is based on the statistical energy analysis (SEA), an efficient method for vehicle NVH analysis in mid and high frequencies.

Recent developments in the prediction of the contribution of wind noise to the interior SPL have opened a realm of new possibilities. The main physical mechanisms related to noise generation within a turbulent flow and the vibro-acoustic transmission through the vehicle greenhouse is nowadays better understood. Several simulation methods such as CFD, FEM, BEM, FE/SEA Coupled and SEA can be coupled together to represent the physical phenomena involved. The main objective being to properly represent the convective and acoustic component within the turbulent flow to ensure proper computation of the wind noise contribution to the interior SPL of a vehicle.

To meet vehicle interior noise targets and expectations, components including those related to electric vehicles (EVs) can effectively be treated at the source with an encapsulation approach, preventing acoustic and vibration sources from propagating through multiple paths into the vehicle interior. Encapsulation can be especially useful when dealing with tonal noise sources in EVs which are common for electrical components. These treatments involve materials that block noise and vibration at its source but add weight and cost to vehicles – optimization and ensuring the material used is minimized but efficient in reducing noise everywhere where it is applied is critically important. Testing is important to confirm source levels and verify performance of some proposed configurations, but ideal encapsulation treatments are complex and cannot be efficiently achieved by trial-and-error testing.

The present contribution will present how local micromechanical properties can be used in an industrial way to assess the crash performance of parts made of short fiber reinforced polymers. To this end, local information about the material structure, predicted by a Manufacturing Process Simulation (MPS), is transferred and mapped automatically on the performance composite part model. The homogenization and mapping techniques will be presented for elastic and nonlinear application fields. Short fiber reinforced injected thermoplastics are widely used in the automotive industry in mass production. Reliable prediction of the performance of short fiber reinforced thermoplastics by simulation for statics and crash simulation can be achieved only by accounting for the full manufacturing process coming from process simulation software.

Electric vehicle makers have largely relied on aluminum to make their cars lighter in hopes of offsetting the weight of the battery pack and reducing overall weight. Distortion of Aluminum welding is a big issue due to Aluminum’s high coefficient of expansion ratios. This paper presents an effective numerical approach to minimize weld-induced distortion in Electrical Vehicle Aluminum assembly structures using welding sequence optimization. A numerical optimization framework based on genetic algorithms and Finite Element Analysis (FEA) is developed and implemented. The shrinkage method calibrated using transient approach, is used for the weld sequence optimization to reduce the computation time. The optimization results show that the proposed calibration approach can contribute substantially to reduce distortion by optimizing weld sequences. It enhances final aluminum assembly quality while facilitating and accelerating design and development.

Two alternative finite element formulations are described which consider the influence of normal stress components on sheet deformations in Quick Plastic Forming [1]. The new formulations, single field bricks and multi-field shells, were implemented in the forming simulation program PAM-STAMP [2] using a non-linear viscoelastic constitutive relation [3,4]. Simulations of two industrial components indicate that both new elements simulate local necking more accurately than the standard shells which ignore normal stresses. The multi-field shells require slightly more calculation time than the standard shells and significantly less than equivalent brick models.

The Finite Element Method (FEM) and the Statistical Energy Analysis (SEA) are standard methods in the automotive industry for the prediction of vibrational and acoustical response of vehicles. However, both methods are not capable of handling the so called “mid frequency problem”, where both short and long wavelength components are present in the same system. A Hybrid method has been recently proposed that rigorously couples SEA and FEM. In this work, the Hybrid FE-SEA method is used to predict interior noise levels in a trimmed full vehicle due to broadband structure-borne excitation from 200Hz to 1000Hz. The process includes the partitioning of the full vehicle into stiff components described with FE and modally dense components described with SEA. It is also demonstrated how detailed local FE models can be used to improve SEA descriptions of car panels and couplings.

This paper discusses the development of a computationally efficient numerical method for predicting the acoustics of rattle events upfront in the design cycle. The method combines Finite Elements, Boundary Elements and SEA and enables the loudness of a large number of rattle events to be efficiently predicted across a broad frequency range. A low frequency random vibro-acoustic model is used in conjunction with various closed form analytical expressions in order to quickly predict impact probabilities and locations. An existing method has been extended to estimate the statistics of the contact forces across a broad frequency range. Finally, broadband acoustic radiation is predicted using standard low, mid and high frequency vibro-acoustic methods and used to estimate impact loudness. The approach is discussed and a number of validation examples are presented.

Today, LRI is a proven manufacturing technology for both small and large scale structures (e.g. sailboats) where, in most cases, experience and limited prototype experimentation is sufficient to get a satisfactory design. However, large scale aerospace (and other) structures require reproducible, high quality, defect free parts, with excellent mechanical performance. This requires precise control and knowledge of the preforming (draping and manufacture of the composite fabric preforms), their assembly and the resin infusion. The INFUCOMP project is a multi-disciplinary research project to develop necessary Computer Aided Engineering (CAE) tools for all stages of the LRI manufacturing process. An ambitious set of developments have been undertaken that build on existing capabilities of leading drape and infusion simulation codes available today. Currently the codes are only accurate for simple drape problems and infusion analysis of RTM parts using matched metal molds.

Industrial requirements imply optimizing the development cycle, reducing manufacturing costs and reaching marketable product maturity as fast as possible. The design stage often involves multiple sites and various partners. In this context, the use of computer simulation becomes absolutely necessary to meet industrial needs. Nevertheless, this activity can be effective only if it is integrated correctly in the industrial organization. In the aeronautical and space systems industry, mechanical specifications often require the use of composites reinforced by continuous carbon fibers. The goal of this article is to describe how, on a time frame of nearly twenty years, a series of scientific and technical tasks were carried out in partnership in order to develop, validate and implement Resin Transfer Molding (RTM) flow simulation and cure analysis for high performance composites. The research stage started at the university in 1991.

The Hybrid FE-SEA method has been used to create a fast/efficient model to predict structure-borne noise propagation in a fully trimmed vehicle over the frequency range from 200 to 1000 Hz. The method was highlighted along with the modeling process and extensive validation results in previously published papers [1-3]. The use of the model to analyze structure-borne noise in the full vehicle, and to design and evaluate the impact of counter measures was described. In this study, the Hybrid FE-SEA method is used identify potential design changes to improve the acoustic performance. First, results from a noise path analysis are used to identify key contributors to interior noise. Next, potential design strategies for reducing the interior noise are introduced along with implications on the model. Finally, sample prediction results illustrating the impact of design changes on interior noise levels are shown along with experimental validation results.

Traditional automotive seat development has relied on a series of physical prototypes that are evaluated and refined in an iterative fashion. Costs are managed by sharing prototypes across multiple attributes. To further manage costs, many OEMs and Tier 1s have, over the past decade, started to investigate various levels of virtual prototyping. The change, which represents a dramatic paradigm shift, has been slow to materialize since virtual prototyping has not significantly reduced the required number of physical prototypes. This is related to the fact virtual seat prototyping efforts have been focused on only selected seat attributes - safety / occupant positioning and mechanical comfort are two examples. This requires that physical prototypes still be built for seat attributes like craftsmanship, durability, and thermal comfort.

The comfort assessment of seats in the automotive industry has historically been accomplished by subjective ratings. This approach is expensive and time consuming since it involves multiple prototype seats and numerous people in supporting processes. In order to create a more efficient and robust method, objective metrics must be developed and utilized to establish measurable boundaries for seat performance. Objective measurements already widely accepted, such as IFD (Indentation Force Deflection) or CFD (Compression Force Deflection) [1], have significant shortcomings in defining seat comfort. The most obvious deficiency of these component level tests is that they only deal with a seats' foam rather than the system response. Consequently, these tests fail to take into account significant factors that affect seat comfort such as trim, suspension, attachments and other components.