Search Results

The paper addresses compressor body temperature (crankcase) importance to the vehicle AC system long-term durability. Majority of OEM vehicle test evaluation is to see if AC system can pass compressor discharge temperature and discharge pressure targets. Most OEMs adopt 130°C max compressor discharge temperature and 2350 kpag head pressure as the target. From the field, although some of the compressor failure results from a high compression ratio, and compressor discharge temperature that are caused by the poor front end airflow, etc., high percentage compressor failed systems exhibit not too high compression ratio and compressor discharge temperature, but having the trace of high temperature in the shaft area, gasket area, etc. With introducing more and more variable swash plate compressor applications, OEMs start to see more and more compressor failures that are not related to a high compressor discharge temperature but the trace of high compressor body temperature.

Estimation and prediction of residual life and reliability are serious concerns in life cycle management for aging structures. Laboratory testing replicating fatigue loading for a typical military aircraft wing skin was undertaken. Specimens were tested until their fatigue life expended reached 100% of the component fatigue life. Then, scanning electron microscopy was used to quantify the size and location of fatigue cracks within the high stress regions of simulated fastener holes. Distributions for crack size, nearest neighbor distances, and spatial location were characterized statistically in order to estimate residual life and to provide input for life cycle management. Insights into crack initiation and growth are also provided.

As global automobile manufacturers prepare for the phase-out of R134a in Europe, they must address the issue of using the new refrigerant for European sales only or launching the product worldwide. Several factors play into this decision, including cost, service, risk, customer satisfaction, capacity, efficiency, etc. This research effort addresses the minimal vehicle-level hardware differences necessary to provide a European solution of R1234yf while continuing to install R134a into vehicles for the rest of the world. It is anticipated that the same compressor, lubricant and condenser; most fluid transport lines; and in most cases the evaporator can be common between the two systems.

With increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the automotive gasoline fuel spray has become essential. The acquisition of accurate and repeatable spray data is even more critical when a combustion strategy such as gasoline direct injection is to be utilized. Without industry-wide standardization of testing procedures, large variablilities have been experienced in attempts to verify the claimed spray performance values for the Sauter mean diameter, Dv90, tip penetration and cone angle of many types of fuel sprays. A new SAE Recommended Practice document, J2715, has been developed by the SAE Gasoline Fuel Injection Standards Committee (GFISC) and is now available for the measurement and characterization of the fuel sprays from both gasoline direct injection and port fuel injection injectors.

In this paper, an analytical procedure for prediction of shell radiated noise of air induction systems (AIS) due to engine acoustic excitation, without a prototype and physical measurement, is presented. A set of modeling and simulation techniques are introduced to address the challenges to the analytical radiated noise prediction of AIS products. A filter seal model is developed to simulate the unique nonlinear stiffness and damping properties of air cleaner boxes. A finite element model (FEM) of the AIS assembly is established by incorporating the AIS structure, the proposed filter seal model and its acoustic cavity model. The coupled acoustic-structural FEM of the AIS assembly is then employed to compute the velocity frequency response of the AIS structure with respect to the air-borne acoustic excitations.

The traditional method of engine knock detection is to compare the knock intensity with a predetermined threshold. The calibration of this threshold is complex and difficult. A statistical knock detection method is proposed in this paper to reduce the effort of calibration. This method dynamically calculates the knock threshold to determine the knock event. Theoretically, this method will not only adapt to different fuels but also cope with engine aging and engine-to-engine variation without re-calibration. This method is demonstrated by modeling and evaluation using real-time engine dynamometer test data.

Virtual design validation of an air induction system (AIS) requires a proper finite element (FE) assembly model for various simulation based design tasks. The effect of the urethane air filter seal within an AIS assembly, however, still poses a technical challenge to the modeling of structural dynamic behaviors of the AIS product. In this paper, a filter seal model and its modeling approach for AIS assemblies are introduced, by utilizing the feature finite elements and empiric test data. A bushing element is used to model the unique nonlinear stiffness and damping properties of the urethane seal, as a function of seal orientation, preloading, temperature and excitation frequency, which are quantified based on the test data and empiric formula. Point mobility is used to character dynamic behaviors of an AIS structure under given loadings, as a transfer function in frequency domain.

A test load specification is required to validate an automotive product to meet the durability and design life requirements. Traditionally in the automotive industry, load specifications for design validation tests are directly given by OEMs, which are generally developed from an envelop of generic customer usage profiles and are, in most cases, over-specified. In recent years, however, there are many occasions that a proposed load specification for a particular product is requested. The particular test load specification for a particular product is generated based on the measured load data at its mounting location on the given type of vehicles, which contains more realistic time domain load levels and associated frequency contents. The measured time domain load is then processed to frequency domain test load data by using the fast Fourier transform and damage equivalent techniques.

In an effort to understand steering systems performance and properties at the microscopic level, we developed Multibody simulations that include multiple three-dimensional gear surfaces that are in a dynamic state of contact and separation. These validated simulations capture the dynamics of high-speed impact of gears traveling small distances of 50 microns in less than 10 milliseconds. We exploited newly developed analytic, numeric, and computer tools to gain insight into steering gear forces, specifically, the mechanism behind the inception of mechanical knock in steering gear. The results provided a three dimensional geometric view of the sequence of events, in terms of gear surfaces in motion, their sudden contact, and subsequent force generation that lead to steering gear mechanical knock. First we briefly present results that show the sequence of events that lead to knock.

The present work discusses the application of multivariate statistical methods for the analysis of NVH data. Unlike conventional statistical methods which generally consider single-value, or univariate data, multivariate methods enable the user to examine multiple response variables and their interactions simultaneously. This characteristic is particularly useful in the examination of NVH data, where multiple measurements are typically used to assess NVH performance. In this work, Principal Components Analysis (PCA) was used to examine the NVH data from a benchmarking study of hydraulic steering pumps. A total of twelve NVH measurements for each of 99 pump samples were taken. These measurements included steering pump orders and overall levels for vibration and sound pressure level at two microphone locations. Application of the PCA method made it possible to examine the entire set of data at once.

The present work demonstrates the application of Design of Experiments (DOE) statistical methods to the design and the improvement of a hydraulic steering pump noise, vibration, and harshness (NVH) performance in relief. DOE methods were applied to subjective ratings to examine the effect of several different factors, as well as the interactions between these factors on pump relief NVH. Specifically, the DOE was applied to the geometry of the cross ports on a hydraulic relief valve to improve “whistle” noise in the pump. Statistical methods were applied to determine which factors and interactions had a significant effect on pump whistle. These factors were used to produce a more robust cross port configuration reducing whistle noise. Lastly, the final configuration was experimentally verified on the test apparatus and subjectively confirmed in vehicle-level testing.

Axle whine is an important driveline NVH issue that originates in the hypoid gear sets due to transmitted error excitations. Improving gear quality to reduce the transmitted error has a cost penalty, as well as practical manufacturing limitations. On the other hand, axle system dynamics play a significant role in the system response to gear excitations and in transmissibility from gears to the structure. Analytical tools can be used to tune axle system dynamics in order to alleviate noise and vibration issues. Analytical results can be utilized to evaluate design alternatives, reduce the number of prototypes, thus to reduce product development time. However, analytical results need to be verified and correlated with test results. In this paper, dynamic behavior of a driveline system is investigated. The finite element model is validated at both component and system levels using frequency response functions and mode shapes.

Determination of the critical speed of a driveshaft is critical for development and validation of its design for use in a vehicle because of its destructive effects. Typical calculations to determine critical speed are either over simplistic and not very accurate or very complicated requiring CAE software and capabilities. An analytical five-section non-prismatic beam model was developed to fill in this gap. The model was developed to compute the critical speed in a worksheet and proven to be as or more accurate as utilizing FEA methods. The model worksheet calculates the critical speed for one-piece conventional driveshafts and adapted for Visteon's Slip-In-Tube (SIT) driveshafts.

A hydraulic steering pump system will be considered in this report. The objective is to improve the design of a specific power steering pump using computational fluid dynamics (CFD) tools. The first part of this report deals with a pump oil seal leak. The thermal and fluid environments have been simulated. A variable fluid viscosity is used, showing a 15-20% increase in peak temperature. Potential improvements in product design have been suggested. The second part deals with using computer tools to reduce redundant testing. This includes use of parametric approach towards optimization. A rotating grid approach (basic moving mesh technique) is used.

A dynamic computer model of automotive air conditioning systems was developed. The model uses simulation software for the coding of 1-D heat transfer, thermodynamics, fluid flow, and control valves. The same software is used to model 3-D solid dynamics associated with mechanical mechanisms of the compressor. The dynamics of the entire AC system is thus simulated within the same software environment. The results will show the models potential applications in component and system design, calibration and control.

Data design is a very critical step in the model-based software development process. This paper discusses the importance of a data dictionary in modeling, automatic code generation and in creating model dependency graphs.

The era of the vehicle as a standalone non-connected entity is rapidly drawing to a close. The “Box” on four wheels is being opened to multiple communication channels based on consumer demand and expectations of the latest features, functions and content. Concurrently, automotive planners, marketers, engineers, and system architects are subject to increased complexity as a result of the rapidly evolving consumer electronics industry. This paper will discuss many of the limitations of existing automotive business models in attempting to successfully implement and meet consumer expectations. It will also propose a structural framework for automotive planners, marketers, engineers, and system architects to be able to better understand and predict consumer acceptance of electronics, multimedia features, and in-vehicle content access.

Manual ‘porting” of source code is often required in order to “reuse” control software in different applications with different target hardware. This process is not cost effective. Maintaining multiple “versions” of the same software also causes problems. This paper describes a way in which multiple target source code can be generated from a single model. A custom data class is developed so that it can be used to define both signal and parameter data types necessary for data dictionary-driven models. This capability allows a single model to be used to generate code for multiple target hardware architectures. A software development process using a generic model to support multiple hardware targets is compared with the hand porting process (e.g. floating-point to/from fixed-point). Auto code generation from a sample multi-target feature model will be presented. The efficiency of the auto code will also be discussed.

In the absence of prototypes, analytical methods such as finite element analysis are very useful in resolving noise and vibration problems, by predicting dynamic behavior of the automotive components and systems. Finite Element Analysis (FEA) is a simulation technique and involves making assumptions that affect analytical results. Acceptance and use of these results is greatly enhanced through test validation. In this paper, dynamic behavior of the automotive propshaft equipped with cardboard liner and torsional damper is investigated. The finite element model is validated at both component and subsystem levels using frequency response functions. Effects of the cardboard liner and torsional damper on the propshaft bending, torsional and breathing frequencies are studied under free-free boundary conditions. Effects of the U-Joint stiffness along with other design variables on the driveshaft dynamic behavior are also studied.

The fundamentals of multi-leaf spring design as determined through beam theory offers a general perspective on how finite element analysis works. Additionally, the fundamentals of combining dissimilar materials require a basic knowledge of how the combined equivalent modulus affects the overall stiffness characteristics of multi-leaf design. By capturing these basic fundamentals into finite element modeling, an analysis of a steel-composite multi-leaf contact model relative to an idealized steel-composite multi-leaf model shows the importance of contact modeling. The results demonstrate the important differences between an idealized non-contact model relative to a complete contact model.