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Technical Paper

Virtual Testing: Fatigue Life (S-N Curves) Simulations for Commercial Vehicle Axle Components

2004-10-26
2004-01-2700
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.
Technical Paper

Virtual Development of High-Tonnage Hydroform Press

2006-04-03
2006-01-1656
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.
Technical Paper

The Limitations of Fatigue Testing

2010-10-05
2010-01-1908
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.
Technical Paper

The Effects of Non-Petroleum Based Fuels on Thermoset Elastomers

2002-03-04
2002-01-0634
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.
Technical Paper

Testing and Finite Element Modeling of Hydroform Frames in Crash Applications

2007-04-16
2007-01-0981
Hydroformed components are replacing stamped parts in automotive frames and front end and roof structures to improve the crash performance of vehicles. Due to the increasing application of hydroformed components, a better understanding of the crash behavior of these parts is necessary to improve the correlation between full-vehicle crash tests and FEM analysis. Accurately predicting the performance of hydroformed components will reduce the amount of physical crash testing necessary to develop the new components and new vehicles as well as reduce cycle time. Virgin material properties are commonly used in FEM analysis of hydroformed components, which leads to erroneous prediction of the full-vehicle crash response. Changes in gauge and material properties during the hydroforming process are intuitive and can be reasonably predicted by using forming simulations. The effects of the forming process have been investigated in the FEA models that are created for crash analyses.
Technical Paper

Monotonic Tension, Strain Controlled Fatigue and Fracture Toughness Properties of a Ductile Iron

2003-03-03
2003-01-0832
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.
Technical Paper

Modified Locati Method in Fatigue Testing

2003-03-03
2003-01-0919
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.
Technical Paper

Microwave Plasma Carburization of Steel Alloys at Atmospheric Pressure

2005-04-11
2005-01-0989
Microwave plasmas at atmospheric pressures can be utilized for carburization of steel alloys. Due to their high frequencies, microwaves ionize and dissociate molecules with great efficiency and provide carbon for carburization by dissociating hydrocarbons that are introduced in the plasma. Also, conventional carburization techniques are not very energy efficient, as much of the heat generated is not utilized for the heating of the parts. Microwave plasmas are highly energy efficient due to very high coupling of microwaves to the plasma and then transferring of heat to the parts. Since plasma surrounds the part uniformly, heating rates over the part surface are also uniform. Preliminary results are presented for carburization of steel alloy 8620H by atmospheric microwave plasma process using acetylene as the source gas. Possible effects of application of pulsed DC bias to the parts are also discussed.
Technical Paper

Mechanical Properties of Gear Steels and Other Perspective Light Weight Materials for Gear Applications

2006-10-31
2006-01-3578
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.
Technical Paper

Investigation of the Effect of Sample Size on Fatigue Endurance Limit of a Carburized Steel

2006-04-03
2006-01-0539
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.
Technical Paper

Investigation of S-N Test Data Scatter of Carburized 4320 Steel

2007-04-16
2007-01-1006
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.
Technical Paper

Investigation and Application of Contact Methodologies in Finite Element Analyses of Hydroform Tooling Systems

2006-04-03
2006-01-0788
In this study, the finite element analysis of hydroform tooling system using three different surface-to-surface contact methodologies is evaluated, such as the traditional non-linear gap element methodology, the newer linear gap technology and the 3D non-linear surface contact algorithm. These methods are investigated with the help of case studies, from exercise model level to more complicated models of real parts. Key parameters like analysis results, computational time and ease of use for each method are discussed. Directions regarding adaptivity to local user’s software resources and implementation strategies are provided. The linear gap method is observed to be more effective as pre-processing and computing time with same accuracy results as the non-linear static method in the design stage of hydroform tools analysis with pure sliding.
Technical Paper

Development of the Methodology for 3-D Characterization of Oil Seal Shaft Surfaces

2002-03-04
2002-01-0661
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.
Technical Paper

Development of an Accelerated Testing Methodology of Rotary Oil Seals for Off-Highway Vehicles

2002-03-04
2002-01-1172
This paper will describe the development of an accelerated testing methodology for an off-highway vehicle rotary oil seal system. There are two typical field failure mechanisms associated with off-highway input pinion shaft oil seals: 1) excessive abrasive wear of soft seal lip and hard shaft surface due to abrasive environment; 2) excessive heat and degradation of the seal lip due to lack of lubricity and wear of the shaft surface run against this seal. The accelerated testing of the rotary oil seal consisted of a combination of the following factors; shaft run-out, eccentricity, testing temperature, rotation and reciprocal motion of the seal lip relative to the shaft surface. The combination of these factors especially reciprocal motion reproduces the same failure mechanism, i.e. shaft wear grooves and oil seal lip wear observed on the field usage samples with 6,300 hours service in only 350 hours of accelerated testing.
Technical Paper

Development of a Maintenance Free Self-Lubricating Ball Joint

1999-03-01
1999-01-0036
Vehicular suspension ball joints can be categorized in the family of tribological systems which can reduce useful service or working capacity through malfunction or breakdown. Detailed metallurgical analysis of the friction and wear mechanisms on typical ball joint bearing surfaces point to a Teflon-based woven fabric, self-lubricating liner as the best bearing material for the joint. Laboratory functional testing was conducted on modern, 4-axis test equipment simulating the applicable loading and motion conditions typically encountered in use. The self-lubricated bearing liner woven with Teflon thread demonstrated higher sustained load capacity, less rotating friction, excellent torque retention qualities and extended life in comparison to existing components utilizing greased metal-on-metal and/or “plastic” bearing materials.
Technical Paper

Cyclic Deformation, Fatigue and Fracture Toughness of a Nano-Composite High Strength Steel

2005-11-01
2005-01-3629
A nano-composite high strength (NCHS) steel was tested and evaluated in this work. Monotonic tension, strain controlled fatigue and fracture toughness tests were conducted at ambient temperature. Chemical composition, microstructure and fractography analysis were also performed. The NCHS steel showed excellent combination of high strength, high ductility and high fracture toughness with relatively low alloy content, compared with a S7 tool steel. Fatigue performance of the NCHS steel was also better than that of S7 tool steel. With the exceptional combination of high strength and high fracture toughness, the nano-composite high strength steel may have potential applications in gears, shafts, tools and dies where high fatigue performance, shock load resistance, wear and corrosion resistance is required.
Technical Paper

Correlation of Hydraulic Circuit Dynamic Simulation and Vehicle

2000-03-06
2000-01-0811
Higher demands from automotive customers for quieter vehicles and the reduction of noise and vibration levels from major sources like the engine necessitate better performance of other sources of noise and vibrations in a vehicle. One of these sources that Original Equipment Manufacturers (OEM) demand making quieter is the power steering system. The pressure ripple generated by the power steering pump transfers to the fluid lines where it can generate objectionable noise and vibrations. This can become an excitation force to the structure of a vehicle or the steering gear and can become a source of discomfort to the vehicle occupants. Attenuation of the pressure ripple within the hose assembly can result in significant reduction in noise inside the vehicle. The NVH research team at the Fluid System Products of Dana Corporation has developed “Dana's Virtual Test Rig (DVTR™),” - a hydraulic system simulation software.
Technical Paper

Contact Fatigue Tests and Life Simulations Using Computational Fracture Mechanics

2005-10-24
2005-01-3806
Computational fracture mechanics based FATIG3D program was used to simulate contact fatigue life of rough surface contacts in boundary to mixed lubrication regimes. Two-rollers contact fatigue tests were conducted and test results were compared with calculated contact fatigue lives. Calculated contact fatigue life agreed with test results well with the selected set of input data. The effect of several important parameters in the input data on contact fatigue life was evaluated computationally using FATIG3D. These parameters include: oil pressure distribution, crack face friction, direction of friction, friction coefficient, initial crack length, Hertzian stress, and residual stress distributions. The results obtained in this work improved basic understanding and the application of FATIG3D in simulating contact fatigue behavior.
Technical Paper

Contact Fatigue Tests and Contact Fatigue Life Analysis

2005-04-11
2005-01-0795
The main objective of this paper is to investigate contact fatigue life models and to evaluate the effect of surface finish on contact fatigue life. The effect of surface finish on contact fatigue life was investigated experimentally using two roller contact fatigue tests. The test samples, i.e. rollers, were carburized, quenched and then tempered. Two different roller surface finishes were evaluated: machined and as heat-treated surface (baseline rough surface) vs. super finished surface (smooth). Because many factors are involved in sliding/rolling contact fatigue, contact fatigue modeling is still in the early development stage. In this work, we will analyze our contact fatigue test results and correlate contact fatigue life with several empirical contact fatigue models, such as the lambda ratio, a new surface texture parameter, and a normalized pitting model which includes Hertzian Stress, sliding, surface roughness and oil film thickness.
Technical Paper

Characterize the High-Frequency Dynamic Properties of Elastomers Using Fractional Calculus for FEM

2007-05-15
2007-01-2417
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.
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