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Finite element modeling has been used extensively nowadays for predicting the noise and vibration performance of whole engines or subsystems. However, the elastomeric components on the engines or subsystems are often omitted in the FE models due to some known difficulties. One of these is the lack of the material properties at higher frequencies. The elastomer is known to have frequency-dependent viscoelasticity, i.e., the dynamic modulus increases monotonically with frequency and the damping exhibits a peak. These properties can be easily measured using conventional dynamic mechanical experiments but only in the lower range of frequencies. The present paper describes a method for characterizing the viscoelastic properties at higher frequencies using fractional calculus. The viscoelastic constitutive equations based on fractional derivatives are discussed. The method is then used to predict the high frequency properties of an elastomer.

Gear tooth friction directly influences power losses and temperature rise as well as system dynamic behavior. Recently it attracted many attentions as friction is considered one of the main sources of power losses in geared systems, such as in automotive transmissions. Coefficient of friction has been found not a constant but varies with different contact conditions, which partly makes the measurement of friction a difficult and expensive process. Therefore an analytical model that is capable of predicting it accurately becomes very much demanded. A few empirical formulae based on experimental data and analytical models based on lubrication theory are found in the literature. However, they are either not suitable for a general gear contact or too complex to adapt in gearing. In this paper, a new coefficient of sliding friction based on a thermal Elastohydrodynamic Lubrication (EHL) model is developed by a multiple linear regression analysis.

Limited-slip differentials improve traction and handling when compared to open differentials, but offer no active modulation and can compromise typical driving. A number of passive control systems exist that attempt to reduce this compromise. Electronically controlled limited-slip differentials (eLSD) are being introduced that allow active control of the differential in all driving situations and can be operated as an open differential, a fully locked differential, or at any point between these extremes. Such an eLSD system was implemented in two General Motors front wheel drive cars-one on an automatic transmission and applied by the transmission pump, the other on a manual transmission and applied by an external pump. This eLSD system contains a multi-plate wet clutch connected to the differential carrier and right side half-shaft of an all wheel drive capable transmission.

A series of bending fatigue tests were conducted and S-N data were obtained for two groups of 4320 steel samples: (1) carburized, quenched and tempered, (2) carburized, quenched, tempered and shot peened. Shot peening improved the fatigue life and endurance limit. The S-N data exhibited large scatter, especially for carburized samples and at the high cycle life regime. Sample characterization work was performed and scatter bands were established for residual stress distributions, in addition to fracture and fatigue properties for 4320 steel. Moreover, a fatigue life analysis was performed using fracture mechanics and strain life fatigue theories. Scatter in S-N curves was established computationally by using the lower bound and upper bound in materials properties, residual stress and IGO depth in the input data. The results for fatigue life analysis, using either computational fracture mechanics or strain life theory, agreed reasonably well with the test data.

A new wheel end concept was designed and developed to allow sport utility vehicles (SUV) and light trucks the possibility of achieving a negative scrub radius. This paper will compare a production vehicle with a scrub radius of 54.8 mm with the same vehicle modified with several alternate scrub radii. The vehicle changes are completed in a way that still packages the brake components and meets the component durability needs of a light truck wheel end load cycle. Quantitative vehicle computer analysis and actual instrumented vehicle performance data will be compared and correlated to analyze the effects of scrub radius.

Fatigue testing of components is used to validate new product designs as well as changes made to existing designs. On new designs it is common to initially test parts at the design stage (design verification or DV) and then again at the production stage (production verification or PV) to make sure the performance has not changed. On changes to existing designs typically the life of the new part (B) is compared to that of the old part (A). When comparing the fatigue life Weibull analysis is normally used to evaluate the data. The expectation is that the B10 or B50 life of the new part or PV parts should be equal to or better than that of the old parts or the DV parts. However, fatigue testing has a great deal of inherent variability in the resulting life. In this paper the variability of numerous carburized and induction hardened components is examined.

The effect of multiple braze furnace exposures has been questioned by many because the rework of brazed parts is a common practice in manufacturing. However, there are process controls that limit the number of exposures for an assembly due to known issues with multiple exposures. A common concern deals with the effect of multiple braze furnace exposures on the structural integrity of the base material of the components. Another concern regards the effect of multiple exposures on the structural integrity of the braze joint itself. This paper details experimental results of a physical study to investigate these questions. The material forms used are seam-welded tube and a thin-wall stamped component, both made from 304L stainless steel. The copper paste used in the study has an industry designation of ANSI/AWS A5.8 - BCu-1a.

This paper presents a novel torque-vectoring (biasing) differential system Dynamic Trak™ that can be applied to both the inter-axle and the inter-wheel differential systems. The Dynamic Trak™ has three multi-plate clutches. The center clutch located inside the differential case provides a limited-slip or complete lock-up capability. The two outboard clutches positioned at either sides of the differential case selectively adjust the torque flow to the left or right shafts/wheels. An electronic control unit and a hydraulic circuit unit control the three clutches, realizing the active management of the torque to the two output shafts/wheels. The Dynamic Trak™ can provide maximum of 100% torque add or subtraction to the wheels, while maintaining the open differential feature. A virtual model representing a passenger car equipped with the Dynamic Trak™ has been developed. The simulation results show the handling and stability enhancements by the Dynamic Trak™.

Shaft surface texture plays a very important role in rotary oil seal system performance. Functionally, the shaft surface has to prevent oil leakage via pumping between the shaft and seal. The shaft surface texture must also provide adequate contact with the seal lip, while maintaining a lubricant film. Furthermore, the initial surface texture of the shaft plays a vital role in the process of oil seal lip break-in. The shaft surface finish specification is typically Ra, 10 to 20 μ″ with a 0° ± 0.05°lead angle. The paper will describe a new surface measurement method based on interference microscopy, which generates a visual representation of a significant portion of the shaft surface texture to allow direct lead angle detection. Using this new technique, this paper will demonstrate the heredity of lead generation. The shaft 3D surface texture measurement also provides a measure of the surface volume available for lubricant retention.

The scope of this paper is to determine the affects that non-petroleum based fuels such as: rapeseed methyl ester (RME) and soy methyl ester (SME) have on thermoset elastomers. The thermoset elastomers that have been evaluated are NBR (Nitrile Butadiene Rubber), NBR/PVC (Nitrile Butadiene Rubber & Polyvinyl Chloride), Epichlorohydrin homo- (Homopolymer of Epichlorohydrin), co- (Copolymer of Epichlorohydrin), ter- (Terpolymer of Ecpichlorohydrin), and Di-, and ter FKM (Fluorinated Rubber). The different elastomers have been subjected to aging in neat fatty acid methyl esters, RME and SME, at a variety of durations and temperatures. The effects of this exposure on the properties of thermoset elastomers are described in this paper.

The objective of this work is to test and develop monotonic tensile properties and strain controlled fatigue properties of a cast ductile iron. The test data and the related material constants will be used in conjunction with vehicle loading data to perform finite element stress-strain analysis and fatigue life prediction analysis to aid in the design of automotive components made from ductile iron. Currently, such material property data does not exist in the literature for this particular grade of ductile iron. Monotonic tension and fully reversed strain controlled fatigue tests were conducted by following ASTM E-8, ASTM E-606, and SAE J-1099 on samples machined from the cast ductile iron. Monotonic tensile properties were obtained, including Young's modulus, yield strength, ultimate tensile strength, elongation, reduction in area, strength coefficient K, and strain hardening exponent n.

Locati method is suitable in preliminary fatigue tests and production quality control. It is efficient since it uses just one test sample. The method requires that the slope of the S-N curve be known a priori, however. In this paper, a modified Locati method is presented that virtually eliminated this requirement. The method produces a point on the S-N plane that is independent of the slope of the S-N curve. The test design strategy to control the fatigue life of such a point is provided. The presented method has been successfully applied to preliminary fatigue tests of several welded components of ground vehicles.

Axle primary gearing is normally carburized for high and balanced resistance to contact fatigue, wear, bending fatigue, and impact loading. The focus of this work is on bending fatigue which is a key design consideration of automotive and commercial vehicle axle gearing. Since a carburized component is basically a composite material with steep gradients in carbon content, hardness, tensile strength and microstructure from surface to the middle of the cross section combined with non-linear residual stress, its bending fatigue life prediction is a complex and challenging task. Many factors affect the bending fatigue performance of axle gearing, such as gear design, gear manufacturing, loading history during service, residual stress distribution, steel grade, and heat treatment. In this paper, the general methodology for bending fatigue life prediction of a carburized component is investigated. Carburized steel composites are treated as two homogeneous materials: case and core.

To improve fuel economy and possibly reduce product cost, light weight and high power density has been a development goal for commercial vehicle axle components. Light weight materials, such as aluminum alloys and polymer materials, as well as polymer matrix composite materials have been applied in various automotive components. However it is still a huge challenge to apply light weight materials in components which are subject to heavy load and thus have high stresses, such as gears for commercial vehicle axles or transmissions. To understand and illustrate this challenge, in this paper we will report and review the current state of art of carburized gear steels properties and performance.

A new proprietary Atmospheric Pressure Microwave Plasma Technology, developed for various materials processing applications, has been applied to P/M sintering of cam lobes. The aims were a) to compare the new processing route with conventional process for the same alloy composition and b) to check the possibility of successful sintering at higher temperatures so that different higher temperature P/M alloys may be used. P/M green cam lobes were used, and sintering runs were carried out initially at temperatures comparable to that currently used in the conventional processes; this was followed by runs at higher temperatures that are not very practical in the conventional processing route due to equipment component constraints. Properties such as density and hardness were measured for the sintered samples, together with corresponding microstructural analysis.

This paper discusses the virtual development process used to support design of a high-tonnage hydroform press. It also discusses the optimized design for structural integrity while achieving low target cost. Other considerations included optimization of setup issues such as press fabrication and assembly. Due to tightly constrained development time, a diverse range of CAE methodologies were used to refine and validate the design. Detailed linear and nonlinear finite element models were developed to provide the required accuracy in the critical regions of the press structure. From these detailed models simplified analytical tools were developed to calculate the key press parameters such as alternating stress and predicted fatigue life. Finite element models were validated with physical strain gage measurements from an array of strain gages installed on the production presses.

Current trends in vehicle development, including both automotive and commercial vehicles, are characterized by short model life cycles, reduced development time, concurrent design and manufacturing development, reduced design changes, and reduced total cost. All of these are driven by customer demand of higher load capacity, reduced weight, extended durability and warranty requirement, better NVH performance and reduced cost. These trends have resulted in increased usage of computational simulation tools in design, manufacturing, and testing, i.e. virtual testing or virtual prototyping. This paper summarizes our work in virtual testing, i.e. fatigue life simulations using computational fracture mechanics for commercial vehicle axle gearing development. First, fatigue life simulation results by using computational fracture mechanics CRACKS software were verified by comparing with gear teeth bending fatigue test data and three point bending fatigue test data.

Traditional methods often lead to truck component designs that are overly conservative. The ever-increasing need to reduce operational costs demands innovative means for producing parts that are light, durable and capable of carrying more loads. This paper discusses the far-reaching advantages of shape-optimization, beyond the fundamental stipulation of weight reduction. A suspension link is considered to demonstrate the benefits of an optimally shaped component.

Prediction of fatigue performance of large structures and components is generally done through the use of a fatigue analysis software, FEA stress/strain analysis, load spectra, and materials properties generated from laboratory tests with small specimens. Prior experience and test data has shown that a specimen size effect exists, i.e. the fatigue strength or endurance limit of large members is lower than that of small specimens made of same material. Obviously, the size effect is an important issue in fatigue design of large components. However a precise experimental study of the size effect is very difficult for several reasons. It is difficult to prepare geometrically similar specimens with increased volume which have the same microstructures and residual stress distributions throughout the entire material volume to be tested. Fatigue testing of large samples can also be a problem due to the limitation of load capacity of the test systems available.

The Plastic Valve Cover System (PVCS) should provides a leak proof seal to the cylinder head under engine temperature, isolate the vibrations transmitted from the engine through the cover to the environment, control the crankcase pressure and house the device to separate oil from the blow-by gas. In order to increase the stiffness of PVCS, short glass fibers and minerals are added during the injection molding of the plastic valve cover. The presence of the fibers results in a component with highly anisotropic thermo-mechanical properties that was not accounted in the previously approach [1]. This paper describes the updated CAE approach with the incorporation of the short fiber anisotropy into the design of cylinder head valve covers.