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Technical Paper

Testing Elastomers - Can Correlation Be Achieved Between Machines, Load Cells, Fixtures and Operators?

2001-04-30
2001-01-1443
At present, testing elastomeric parts is performed at a level dictated by the users of the testing equipment. No society or testing group has defined a formal standard of testing or a way to calibrate a testing machine. This is in part due to the difficulty involved with testing a material whose properties are in a constant state of flux. To further complicate this issue, testing equipment, testing procedures, fixtures, and a host of other variables including the operators themselves, all can have an impact on the characterization of elastomers. The work presented in this paper looks at identifying some of the variables of testing between machines, load cells, fixtures and operators. It also shows that correlation can be achieved and should be performed between companies to ensure data integrity.
Technical Paper

The Effects of Different Input Excitation on the Dynamic Characterization of an Automotive Shock Absorber

2001-04-30
2001-01-1442
This paper deals with the dynamic characterization of an automotive shock absorber, a continuation of an earlier work [1]. The objective of this on-going research is to develop a testing and analysis methodology for obtaining dynamic properties of automotive shock absorbers for use in CAE-NVH low-to-mid frequency chassis models. First, the effects of temperature and nominal length on the stiffness and damping of the shock absorber are studied and their importance in the development of a standard test method discussed. The effects of different types of input excitation on the dynamic properties of the shock absorber are then examined. Stepped sine sweep excitation is currently used in industry to obtain shock absorber parameters along with their frequency and amplitude dependence. Sine-on-sine testing, which involves excitation using two different sine waves has been done in this study to understand the effects of the presence of multiple sine waves on the estimated dynamic properties.
Technical Paper

Flow-Acoustic Coupling in Quarter-Wave Resonators Using Computational Fluid Dynamics

2001-04-30
2001-01-1430
Quarter-wave resonators are commonly used as acoustic silencers in automotive air induction systems. Similar closed side branches can also be formed in the idle air bypass, exhaust gas recirculation, and positive crankcase ventilation systems of engines. The presence of a mean flow across these side branches can lead to an interaction between the mean flow and the acoustic resonances of the side branch. At discrete flow conditions, this coupling between the flow and acoustic fields may produce high amplitude acoustic pressure pulsations. For the quarter-wave resonator, this interaction can turn the silencer into a noise generator, while for systems where a valve is located at the closed end of the side branch the large pressure pulsations can cause the valve to fail. This phenomenon is not limited to automotive applications, and also occurs in natural gas pipelines, aircraft, and numerous other internal and external flows.
Technical Paper

Serpentine Accessory Belt Drive Tool: Virtual Prototyping for V-Ribbed Belt Drives

2001-04-30
2001-01-1424
Serpentine accessory belts are commonly used in industries such as automotive and general machinery. The purpose of this analytical tool is to provide design engineers the capability to model belt drive systems using ADAMS (Automated Dynamic Analysis of Mechanical Systems). The generated ADAMS models can be used to analyze several different characteristics concerning V-Ribbed belt drive systems. The general solution of the governing nonlinear equations provides the coupled longitudinal and transverse response of the translating belt drive system. Typical simulation outputs include pulley hubloads, belt impact dynamic forces, and belt slip rates at the pulleys.
Technical Paper

Thermal Management for the HEV Liquid-Cooled Electric Machine

2001-05-14
2001-01-1713
The future of the Hybrid Electric Vehicle (HEV) is very promising for the automotive industry. In order to take a full advantage of this concept, a better thermal performance of the electric motor is required. In this study, Computational Fluid Dynamics (CFD) model was first verified through several prototypes testing and then is going to be used to execute a series of design of experiment via simulation. Based on the thermal studies in this paper, the integrated coolant jacket design has a better performance than that of separated one. The thermal performance of the stator with the 3M coating is better than the one with paper liner. In addition, using 3M coating reduces the packaging size of the stator.
Technical Paper

Numerical Modeling of Engine Noise Radiation through the use of Acoustic Transfer Vectors - A Case Study

2001-04-30
2001-01-1514
This paper presents the numerical modeling of noise radiated by an engine, using the so-called Acoustic Transfer Vectors and Modal Acoustic Transfer Vectors concept. Acoustic Transfer Vectors are input-output relations between the normal structural velocity of the radiating surface and the sound pressure level at a specific field point and can thus be interpreted as an ensemble of Acoustic Transfer Functions from the surface nodes to a single field point or microphone position. The modal counter part establishes the same acoustic transfer expressed in modal coordinates of the radiating structure. The method is used to evaluate the noise radiated during an engine run-up in the frequency domain. The dynamics of the engine is described using a finite element model loaded with a rpm-dependent excitation. The effectiveness of the method in terms of calculation speed, compared with classical boundary element methods, is illustrated.
Technical Paper

Experimental Determination of Automotive System Response Characteristics

2001-04-30
2001-01-1477
Vehicle NVH performance is significantly affected by the dynamics of various primary systems. In the automotive industry, different design activities or vendors are responsible for designing various different systems simultaneously. Therefore, it is highly desirable to gain a better understanding of the individual system characteristics and the interaction between the primary systems to achieve a desirable overall NVH performance. Unfortunately, it is usually quite difficult to construct a proper fixture to accurately measure and quantify the actual uncoupled system characteristics. This paper examines an alternate approach of applying the FRF-based substructuring method to back-calculate the system response characteristics from the full vehicle system measurements. The results are then used to forward-compute the dynamic response of the vehicle, which are also validated by comparison to the direct response function measurements.
Technical Paper

Experimental Study of Automotive Heat Shield Geometry with Natural Convection and Radiation Boundary Conditions

2001-05-14
2001-01-1746
Shielding a vehicle underbody is becoming a daunting task with increased exhaust temperatures due to emissions regulations and ever-increasing packaging constraints, which place components ever closer to exhaust systems. This experimental study was initiated to evaluate the two dimensional thermal effects of heat shield flange height and shield width in vehicle underbody idle conditions. The ultimate goal of this study is to develop a function to optimize the shape of heat shielding to achieve a specified floorpan temperature during vehicle idle conditions.
Technical Paper

Air Charge Estimation in Camless Engines

2001-03-05
2001-01-0581
An electromechanically driven valve train offers unprecedented flexibility to optimize engine operation for each speed load point individually. One of the main benefits is the increased fuel economy resulting from unthrottled operation. The absence of a restriction at the entrance of the intake manifold leads to wave propagation in the intake system and makes a direct measurement of air flow with a hot wire air meter unreliable. To deliver the right amount of fuel for a desired air-fuel ratio, we therefore need an open loop estimate of the air flow based on measureable or commanded signals or quantities. This paper investigates various expressions for air charge in camless engines based on quasi-static assumptions for heat transfer and pressure.
Technical Paper

Effect of Epoxy-Based Structural Foam on Energy Management: An Experimental & Analytical Investigation

2001-03-05
2001-01-0473
The effect of epoxy-based structural foam on strength, stiffness, and energy absorption of foam filled structural components is investigated and implemented to formulate design guide-lines that can be used in enhancing weight reduction and engineering functions of systems. An experimental approach is first utilized to identify design variables such as foam density, gage, and foam layer thickness, that are needed to enhance the weight/ performance ratio of structural hat-section components. A CAE approach using non-linear, large deformation finite element analysis is used to model the hat-section components. An acceptance level of confidence in the CAE analytical tools is then established based on comparisons of results between the two approaches. Upon that, the CAE analytical tools are deployed in a sensitivity study to quantify the crush/crash characteristics of foam-filled hat-section components with respect to the changes in the afore mentioned design variables.
Technical Paper

Methodology On The Testing Of The Automobile Mount Dynamic Response

2001-03-05
2001-01-0474
This paper reports the latest development of methodologies for testing and CAE modeling of the automobile mounts. The objective of this study is to provide dynamic mount properties for product evaluation and CAE modeling guideline for crashworthiness simulations. The methodology is divided into component, subsystem and full system levels. The study at the component level is to extract the dynamic parameters of mounts, such as stiffness and damping coefficient, based on the component tests. Furthermore, such parameters are employed to investigate the interaction between mount and connecting structures at the subsystem level. A robust connection mechanism from mount to surrounding structures is also developed during this process. Finally, the results from full vehicle system tests are compared with the CAE simulations to verify the methodology at the component and subsystem levels. A robust component test methodology is the first key element of this study.
Technical Paper

Spot Weld Failure Loads under Combined Mode Loading Conditions

2001-03-05
2001-01-0428
Failure loads of spot welds are investigated under static and impact loading conditions. A test fixture was designed and used to obtain maximum loads of spot welds under a range of combined opening and shear loads with different loading rates. Optical micrographs of the cross sections of spot welds before and after failure were obtained to understand the failure processes under various loading rates and different combinations of loads. The experimental results indicate that under nearly pure opening loads, the failure occurs along the nugget circumferential boundary. Under combined opening and shear loading conditions, the failure starts from the tensile side of the base metal near the nugget in a necking/shear failure mode. The effects of sheet thickness and combined load on the load carrying behavior of spot welds are investigated under static and impact loading conditions based on the experimental results.
Technical Paper

The Effect of High Mileage Spot Weld Degradation on Vehicle Body Joint Stiffness

2001-03-05
2001-01-0426
Joint stiffness is a major contributor to the vehicle body overall bending and torsional stiffness which in turn affects the vehicle NVH performance. Each joint consists of spot welds which function as load paths between adjacent sheet metal. Spot welds tend to lose structural integrity as a result of fatigue, loosening, aging, wear and corrosion of parts as a vehicle accumulates mileage. Experimental methods are used to identify potential degradation mechanisms associated with a spot weld. A CAE model which simulates a vehicle body joint generically is used to determine the effects of each individual degradation mode of a spot weld on joint stiffness. A real life B-pillar to roof joint CAE model of a production vehicle is then employed to examine the significance of weld distribution on joint stiffness degradation. The knowledge derived from this study can be used as a guidance in designing vehicle body structures with respect to spot weld distribution.
Technical Paper

An Assessment of a FEA NVH CAE Body Model for Design Capability

2001-04-30
2001-01-1401
Finite Element Analysis (FEA) models are routinely being adopted as a means of up-front design for automotive body structure design. FEA models play two important functions: first as a means of assessing design versus an absolute target; secondly they are used to assess the performance of design alternatives required to meet targets. Means of assessing model capability versus task is required to feed appropriate information into the design process. Being able to document model capability improves the credibility of the FEA model information. A prior paper addressed assessing the absolute performance of model technology using a metric based on a statistical hypotheses test that determines membership in a reference set. This paper extends the use of quality technology to determining the capability of the FEA model to span the design space using Designed Experiments.
Technical Paper

Event-Based Mean-Value Modeling of DI Diesel Engines for Controller Design

2001-03-05
2001-01-1242
Models often use time rather than strokes (crank-angle) as the independent variable to describe engine dynamics despite the fact that the dynamics of an internal combustion engine are intrinsically linked to the combustion events. In this paper, two models are developed in parallel in which not only the independent variable is changed but the notion of mass flows as well: flows are in [g/s] for the time-based model and in [g/st] for the event-based model. Both models are of the same computational complexity and show the same accuracy in validation. The investigation of the model properties shows that variations in the flow-related parameters are reduced by a factor of two to five for the event-based model. However, those of the crankshaft dynamics are increased. It is concluded that the model should be chosen in context of the control system to be designed.
Technical Paper

Overall Results: Phase I Ad Hoc Diesel Fuel Test Program

2001-03-05
2001-01-0151
The future of diesel-engine-powered passenger cars and light-duty vehicles in the United States depends on their ability to meet Federal Tier 2 and California LEV2 tailpipe emission standards. The experimental purpose of this work was to examine the potential role of fuels; specifically, to determine the sensitivity of engine-out NOx and particulate matter (PM) to gross changes in fuel formulation. The fuels studied were a market-average California baseline fuel and three advanced low sulfur fuels (<2 ppm). The advanced fuels were a low-sulfur-highly-hydrocracked diesel (LSHC), a neat (100%) Fischer-Tropsch (FT100) and 15% DMM (dimethoxy methane) blended into LSHC (DMM15). The fuels were tested on modern, turbocharged, common-rail, direct-injection diesel engines at DaimlerChrysler, Ford and General Motors. The engines were tested at five speed/load conditions with injection timing set to minimize fuel consumption.
Technical Paper

Modeling of HCCI Combustion and Emissions Using Detailed Chemistry

2001-03-05
2001-01-1029
To help guide the design of homogeneous charge compression ignition (HCCI) engines, single and multi-zone models of the concept are developed by coupling the first law of thermodynamics with detailed chemistry of hydrocarbon fuel oxidation and NOx formation. These models are used in parametric studies to determine the effect of heat loss, crevice volume, temperature stratification, fuel-air equivalence ratio, engine speed, and boosting on HCCI engine operation. In the single-zone model, the cylinder is assumed to be adiabatic and its contents homogeneous. Start of combustion and bottom dead center temperatures required for ignition to occur at top dead center are reported for methane, n-heptane, isooctane, and a mixture of 87% isooctane and 13% n-heptane by volume (simulated gasoline) for a variety of operating conditions.
Technical Paper

Frequency Response Assurance Criterion and Applications to Model Correlation of Body Structures

2003-05-05
2003-01-1737
Frequency response functions are frequently used production development to identify correlation levels between designs or between analytical simulation and tests. Frequency Response Assurance Criterion is one effective method to quantify such correlations. However, practical issues such as a large number of FRFs exist and complicated modal characteristics often prevent us using the traditional FRAC analysis. A Group FRAC method was developed and is introduced in this article to resolve these application difficulties. This Group FRAC method enables automatic and efficient processing of large number of FRFs in additional to other improvements. The benefit of using the Group FRAC is evidenced through practical applications.
Technical Paper

Local-Global Finite-Element Analysis for Cam Cover Noise Reduction

2003-05-05
2003-01-1725
Valve covers are a primary source of radiated engine noise. In this paper, we discuss an analytical approach that captures the complicated nonlinear response of the cam cover gaskets and grommets without the need for a prohibitively large finite-element model of the cam cover system. We utilize a detailed local analysis of the gasket and grommet components and abstract their isolation characteristics for later use in a global NVH (Noise-Vibration-Harshness) system analysis.
Technical Paper

Influence of Mount Stiffness on Body/Subframe Acoustic Sensitivities

2003-05-05
2003-01-1714
A comparison of acoustic sensitivities of the 2000 Ford Taurus and 1999 Toyota Camry identifies an interesting paradox: the Taurus has a competitive advantage over the Camry when comparing body-only transfer functions, but a handicap to the Camry when the subframe is included in the measurements. Further, the Taurus subframe/mount subsystem actually behaves as an amplifier rather than an isolator over most of the powertrain excited frequency range. This report attempts to explain the cause of these behaviors through a hybrid CAE/test method and recommends a design strategy to lower the Subframe to Driver's Right Ear sensitivities of the Taurus.
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