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Technical Paper

Predicting the Acoustics of Squeak and Rattle

2011-05-17
2011-01-1585
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.
Journal Article

An Advanced and Comprehensive CAE Approach of Piston Dynamics Studies for Piston Optimal and Robust Design

2011-04-12
2011-01-1404
A successful piston design requires eliminate the following failure modes: structure failure, skirt scuffing and piston unusual noise. It also needs to deliver least friction to improve engine fuel economy and performance. Traditional approach of using hardware tests to validate piston design is technically difficult, costly and time consuming. This paper presents an up-front CAE tool and an analytical process that can systematically address these issues in a timely and cost-effectively way. This paper first describes this newly developed CAE process, the 3D virtual modeling and simulation tools used in Ford Motor Company, as well as the piston design factors and boundary conditions. Furthermore, following the definition of the piston design assessment criteria, several piston design studies and applications are discussed, which were used to eliminate skirt scuffing, reduce piston structure dynamic stresses, minimize skirt friction and piston slapping noise.
Technical Paper

CAE Methodology for Optimizing NVH, Functional Reliability, and Mass Reduction at Engine Concept Design Phase

2011-05-17
2011-01-1511
Due to the global economic downturn and higher environmental awareness, the social demands for low cost and fuel efficient vehicles are increasing. At the same time the engine power is increasing and customer expectations of reliability and NVH levels are increasing. To meet all the requirements, engineers are challenged to design light weight parts with higher performance. However, unconsidered mass reduction carries a risk of compromised NVH, Functional Reliability, and other functional demands. In order to resolve this contradiction, it is important to establish a basic structure with minimum necessary mass at the concept design phase, when there are still many degrees of freedom in the design space. Hence, a multi-objective optimization CAE methodology applicable for designing the basic structure of the Engine system was developed and is detailed below.
Journal Article

NVH Challenges for Low Cost and Light Weight Small Cars

2011-05-17
2011-01-1687
In worldwide automotive markets, the migration of customers towards smaller cars having compact, fuel-efficient design is well established and accepted as an engineering challenge by global automotive OEMs. Tata Motors of India has established a precedent by developing an ultra low cost and light weight car (the Nano), and has thereby created a new market segment for such cars that are more affordable to most of the population. This is now becoming established as a brand of low cost, safe transport in both rural and urban market segments. Despite the market moving towards such compact, fuel-efficient designs, customers are unwilling to lose many of the vehicle attributes to which they have been accustomed in previous types of entry-level cars. Addressing this marketing requirement places some significant challenges before the designers of this type of car.
Technical Paper

New TOYOTA 4.8L V10 Petrol High Performance Engine for Lexus LFA

2011-08-30
2011-01-2024
Achieving the speed and performance of a true supercar was merely the starting point of this development. In addition, the development also focused on achieving emotive performance attributes to enhance driver appeal. For this the engine was developed to assist a vehicle handling provides unsurpassed response, the creating a feeling of infinite acceleration potential, response is instantaneous and based on close understanding of driver's reactions and Awe inspiring sound is providing. It meets the latest emission standard Euro V and achieves good fuel consumption with a wide range stoechiometric air fuel ratio, till speeds up to 240km/h.
Technical Paper

Predicting Shell Vibration and Implosion Issues in Automotive Muffler Design

2009-05-19
2009-01-2038
The muffler shell of an automotive exhaust system can cause significant NVH (noise/vibration/harshness) issues like shell vibration and radiated noise, buzzing, rattling, and implosion problems. Due to the complex relationship between the dynamic behavior of the muffler shell and many parameters like engine operating temperature, curvature of the shell, material density, shell thickness and baffle spacing, the NVH engineers have experienced difficulties identifying the root cause of problems and solutions to them. By considering all design parameters, a theoretical study on shell vibration has been conducted to investigate applicability of an analytical technique to predict and solve the NVH issues of an automotive muffler. We have identified the most promising shell vibration theories by comparing the solutions with the results from modal test and finite element analysis.
Technical Paper

Complex Mode Analysis on Disc Brake Squeal and Design Improvement

2009-05-19
2009-01-2101
Squeal noise in vehicle disc brakes is perceived by comsumers as both annoying and warranty cost. The mechanism is considered a mode coupling phenomenon also referred to as coalescence. In this paper, the system eigenvalues have been computed using a technique based on the • nite element method in order to obtain the dynamical properties of the disc brake assembly. The simulated squeal results were compared with the brake noise test that was in accordance with SAE J2521 standard and showed good correlation for some squeal frequencies which indicated that the research on disc brake squeal using complex mode could predict squeal propensity of the disc brake. Among the methods that have been used to control squeal noise, increasing the system damping has been shown to be very effective. The most commonly used method to increase system damping consists of attaching multi-layer laminates on the back of the brake pads.
Journal Article

Design and Analysis of a Gear Rattle Test Rig

2009-05-19
2009-01-2113
Gear rattle in manual transmission systems is a complex phenomenon and problematic to transmission and vehicle manufacturers. In the last three decades some inroads have been made in applying analytical and numerical analysis to understand rattle, however solutions and design methodologies for low rattle or no rattle are elusive. Problems with rattling transmissions continue to plague the industry. Controlled experiments for transmission rattle are required for research, to aid in the development of design tools and for validation of these tools. This paper presents a test rig which utilises a Hooke's joint to induce the torsional oscillations that lead to rattle. The design process relies on torsional lumped mass modeling and linear and transient nonlinear analyses and this paper details how the correct specification of the required driving motor isolation system is achieved.
Technical Paper

Analytical and Experimental Approach to Acoustic Package Design

2009-05-19
2009-01-2119
The interior noise signature of passenger vehicles is a significant contributor to a customer's perception of quality. The vehicle acoustic package can be an important piece to the acoustic signature, and can be utilized not just to reduce the sound levels inside the vehicle but also to shape the sound such that it meets the expectations of the customer. For this reason the definition, design, and development of an acoustic package can be vital to meeting vehicle-level acoustic targets. In many situations this development is conducted experimentally, requiring the availability of prototype vehicles and acoustic package components. Of more value is the ability to develop components early in the design phase, leveraging analytical tools to define component-level requirements and targets to meet the vehicle-level targets, and ultimately meet the final customer expectations.
Technical Paper

Process for the Selection of Low Cost and Weight Electrical Architectures

2011-04-12
2011-01-1436
Modern vehicle electrical architectures are extremely complex and based on large number of Electronic Control Units (ECUs) integrated with hardwiring or a network technology such as Controller Area Network (CAN), Local Interconnect Network (LIN) or FlexRay. Even a simple system such as a driver's door can contain a large number of control functions such as electric windows, electric mirrors, seat control switches and therefore a lot of internal wiring is required within the door system. To reduce cost, weight and complexity of the wiring harness, it is usual for some combination of CAN, LIN and hardwired connections to be used for electronics integration. The key problem with this is how to assess the potential for cost and weight saving of candidate architectures at the very early stage of the design process and therefore how to choose a particular electrical architecture.
Technical Paper

Systematic Multi-Disciplinary Optimization of Engine Mounts

2011-05-17
2011-01-1674
In modern vehicles, each system must meet tough demands to fulfill the many different attribute requirements, design constraints and manufacturing limitations. It becomes difficult and time-consuming to find an optimal and robust design using a traditional engineering process. Volvo Cars has for several years been using Multi-Disciplinary Optimization, MDO, that basically shows the customer attributes levels, such as NVH, ride comfort, and driveability as a function of different parameter configurations. This greatly facilitates project team understanding of the limitations and possibilities of the different systems, and has become a key enabler to achieving a good balance between different attributes. Traditionally, this type of comprehensive Design of Experiments (DOE) optimization demands huge time and computer resources. Frequently, experimental designs will not fulfill manufacturing limitations or attribute targets, making this decision process slow, tedious, and fruitless.
Technical Paper

Study of Minimum Door Closing Speed Analysis Method

2011-04-12
2011-01-0782
The minimum door closing speed is an important target in vehicle door design. Engineers need a proper method to evaluate the door closing speed during the design phase. Analytical approaches are presented to solve the difficult issues in analyzing the minimum door closing speed. First, the weather strip is simplified into a discrete model with several spring elements. This method does not need to use 3-D contact analysis for the weather strip and can save computing time with acceptable accuracy. Second, the minimum closing speed is solved by using the energy equation which needs one iteration only. The method has high efficiency and can be used to evaluate the door closing speed effectively during the design phase.
Technical Paper

Dual Rate Jounce Bumper Design

2011-04-12
2011-01-0791
Jounce bumpers are the primary component by which vertical wheel travel is limited in our suspensions. Typically, the jounce bumper is composed of closed or open cell urethane material, which has relatively low stiffness at initial compression with highly progressive stiffness at full compression. Due to this highly progressive stiffness at high load, peak loads are extremely sensitive to changes in input energy (affected by road surface, tire size, tire pressure, etc.) A “Dual Rate Jounce Bumper” concept is described that reduces this sensitivity. Additionally, various mechanizations of the concept are described as well as the specific program benefits, where applicable.
Technical Paper

A Methodology for Evaluating Body Architecture Concepts Using Technical Cost Modeling

2011-04-12
2011-01-0767
The ability to make accurate decisions concerning early body-in-white architectures is critical to an automaker since these decisions often have long term cost and weight impacts. We address this need with a methodology which can be used to assist in body architecture decisions using process-based technical cost modeling (TCM) as a filter to evaluate alternate designs. Despite the data limitations of early design concepts, TCM can be used to identify key trends for cost-effectiveness between design variants. A compact body-in-white architecture will be used as a case study to illustrate this technique. The baseline steel structure will be compared to several alternate aluminum intensive structures in the context of production volume.
Technical Paper

Mass Efficient Front Crush Can Design

2011-04-12
2011-01-0769
Crush cans are used as replaceable energy absorbing devices that minimize the damage to the front motor compartment main structural rails during a low speed crash event. This is done in an effort to reduce insurance repair costs, which is especially important in Europe where DANNER/TIC insurance ratings drive consumer cost of ownership and may influence the purchase selection. There are multiple approaches to crush can designs and methods of attachment to the motor compartment rails. One such approach is to utilize a “stick-in” design where the crush can is inserted into the rail section then bolted from the sides. Such designs typically require extra back-up brackets inside the main rails to help provide an adequate reaction structure that allows the desired crush initiation to occur within the can and prevent premature yielding in the main rails during a low speed crash incident. These added brackets, however, translate into additional mass and cost to the vehicle.
Technical Paper

Applying Design Verification Tools in Automotive Software V&V

2011-04-12
2011-01-0745
Design verification technology promises comprehensive analysis of design models against the specified properties, thereby overcoming the limitations of traditional simulation-based and testing-based approaches. It helps in detecting design bugs early, thereby reducing the software development cycle time and cost. In this paper, we present our experiences with three state-of-the-art design verification tools - Reactis Validator, Simulink Design Verifier and Embedded Validator - for Simulink/Stateflow models. We also identify some challenges in employing them in an industrial production environment. We also suggest some automation steps to ease the design verification effort.
Technical Paper

Polymer Gear Development to Improve Efficiency and NVH Performance of an Engine Mass Balance System

2011-04-12
2011-01-0405
A joint development program between Metaldyne and Victrex Polymer Solutions was established with the goal of developing a cost effective net shape injection molded gear that provides improvements in NVH (Noise Vibration and Harshness) and operating efficiency over conventional high quality iron gears. A detailed DOE (Design of Experiments) evaluating NVH performance of machined gears was performed in a calibrated NVH test cell. Variables in the DOE included material, gear geometry and backlash variation. The DOE showed the PEEK material gears had different geometric sensitivities, such as helix angle effects, on NVH performance. The results of the DOE were then used to develop an optimal injection molded PEEK polymer gear design. A production quality injection molding gear tool was constructed. Net shape production quality PEEK polymer gears were injection molded and the gears were evaluated in a current production mass balance unit for NVH, mechanical efficiency and durability.
Journal Article

Scuderi Split Cycle Fast Acting Valvetrain: Architecture and Development

2011-04-12
2011-01-0404
The Scuderi internal combustion engine is characterized by a split cycle that divides the four strokes of a conventional combustion cycle over two paired cylinders, one intake/compression cylinder and one power/exhaust cylinder, connected by a crossover port. This split cycle also has an additional high pressure “crossover” gas transfer phase versus the conventional 4-stroke cycle, during which the charge air is moved from the first to the second cylinder. The intake/compression, power/exhaust and crossover events are repeated every revolution, i.e. over two cycles, with a small phase angle between the two cylinders. The separate cylinders enable opportunities for improved combustion and the possibility for pneumatic hybridization of the engine. This paper describes the technical challenges posed by the actuation of the crossover valves in the Scuderi Split Cycle research engine.
Technical Paper

Parabolic Leaf Spring Optimization and Fatigue Strength Evaluation on the Base of Road Load Data, Endurance Rig Tests and Non Linear Finite Element Analysis

2011-04-12
2011-01-0438
The parabolic leaf spring plays a vital role in suspension systems, since it has an effect on ride comfort and vehicle dynamics. Primarily, leaf spring endurance must be ensured. Presently, there are two approaches to designing a leaf spring. In the traditional method, fatigue tests should be repeated for each case, considering different material, geometry and suspension hard points. However, it takes a long time and requires a heavy budget to get the optimized solution. In the contemporary method, a numerical approach is used to obtain the fatigue life and the leaf geometry against the environmental condition on the basis of material properties. This paper presents a more precise method based on non-linear finite element solutions by evaluating the effects of the production parameters, the geometrical tolerances and the variations in the characteristics of the material.
Journal Article

Development of Analytical Model for Design of Gerotor Oil Pump and Experimental Validation

2011-04-12
2011-01-0402
Increasing the efficiency of the Engine parts and reduction in development time with good accuracy are the challenges in the Automotive Industry. Lubricating oil pump has been selected for this study. Existing literatures explain the methodology to generate the rotor profile from the given geometrical parameters of the rotor like eccentricity, tooth radius etc. Invariably the specifications to design the pump are provided in terms of pump performance at various operating conditions. The analytical model developed in this study uses the performance and boundary specifications to generate the rotor profile and to estimate the flow rate at various operating conditions of the pump. This methodology includes the generation of trochoidal profile for inner rotor and modified conjugate profile for the outer rotor and the volume calculation of number of chambers (N) which are created between the rotors during meshing.
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