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During metal forming processes such as rolling and forging, deformable manganese sulfide (MnS) inclusions become elongated. Such elongated MnS inclusions can have considerable adverse effects on mechanical properties, if the inclusions are not aligned with the loading direction. The objectives of this study were to evaluate and compare fatigue, monotonic tensile and CVN impact behavior of SAE 4140 steel with high (0.077% S), low (0.012% S) and ultra low (0.004% S) sulfur contents at two hardness levels (40 HRC and 50 HRC). The longitudinally oriented samples at 40 HRC, where MnS inclusions were oriented along the loading direction, did not exhibit any significant sensitivity of tensile or fatigue properties to the sulfur content. For the transversely oriented MnS inclusions, however, the monotonic tensile test results indicate very low ductility of the high sulfur material at both hardness levels, where specimens failed shortly after yielding.

This paper discusses the effects of changes in specimen geometry, stress gradient, and residual stresses on fully-reversed constant amplitude uniaxial fatigue behavior of a medium carbon steel. Axial fatigue tests were performed on both flat and round specimens, while four-point rotating bending tests were performed only on round specimens. All the tests were performed using shot peened and unpeened flat and round samples, to investigate the effects of compressive residual stresses on fatigue behavior. The specimens in the rotating bending tests experienced longer life for a given stress amplitude than in the axial test. Shot-peening was found to be beneficial in the long life region, while in short life tests the shot-peened samples experienced a shorter life than the unpeened samples under both axial and bending test conditions.

A procedure for fatigue life estimation of components and structures under variable amplitude multiaxial loadings based on simple and commonly available material properties is presented. Different aspects of the analysis consisting of load cycle counting method, plasticity model, fatigue damage parameter, and cumulative damage rule are presented. The only needed material properties for the proposed procedure are hardness and monotonic and axial cyclic deformation properties (HB, K, n, K′ and n′). Rainflow cycle counting method is used for identifying number of cycles. Non-proportional cyclic hardening is estimated from monotonic and axial cyclic deformation behaviors. A critical plane approach is used to quantify fatigue damage under variable amplitude multiaxial loading, where only material hardness is used to estimate the fatigue curve, and where the needed deformation response is estimated based on Tanaka's non-proportionality parameter.

This study investigates and compares fatigue behavior of forged steel and powder metal connecting rods. The experiments included strain-controlled specimen testing, with specimens obtained from the connecting rods, as well as load-controlled connecting rod bench testing. Monotonic and cyclic deformation behaviors, as well as strain-controlled fatigue properties of the two materials are evaluated and compared. Experimental S-N curves of the two connecting rods from the bench tests obtained under R = -1.25 constant amplitude loading conditions are also evaluated and compared. Fatigue properties obtained from specimen testing are then used in life predictions of the connecting rods, using the S-N approach. The predicted lives are compared with bench test results and include the effects of stress concentration, surface finish, and mean stress. The stress concentration factors were obtained from FEA, and the modified Goodman equation was used to account for the mean stress effect.

Damping measurements on vehicle subsystems are rarely straightforward due to the complexity of the dynamic interaction of system joints, trim, and geometry. Various experimental techniques can be used for damping estimation, such as frequency domain modal analysis curve-fitting methods, time domain decay-rate methods, and other methods based on energy and wave propagation. Each method has its own set of advantages and drawbacks. This paper describes an analytical and an experimental comparison between two, widely used loss factor estimation techniques frequently used in Statistical Energy Analysis (SEA). The single subsystem Power Injection Method (PIM) and the Impulse Response Decay Method (IRDM) were compared using analytical models of a variety of simulated simple spring-mass-damper systems. Frequency averaged loss factor values were estimated from both methods for comparison.

A 2-D computational model was developed to describe the flow and filtration processes, in a honeycomb structured ceramic diesel particulate trap. This model describes the steady state trap loading, as well as the transient behavior of the flow and filtration processes. The theoretical model includes the effect of a copper fuel additive on trap loading and transient operation. The convective terms were based on a 2-D analytical flow field solution derived from the conservation of mass and momentum equations. The filtration theory incorporated in the time dependent numerical code included the diffusion, inertia, and direct interception mechanisms. Based on a measured upstream particle size distribution, using the filtration theory, the downstream particle size distribution was calculated. The theoretical filtration efficiency, based on particle size distribution, agreed very well (within 1%) with experimental data for a number of different cases.

A vehicle steering knuckle undergoes time-varying loadings during its service life. Fatigue behavior is, therefore, a key consideration in its design and performance evaluation. This research program aimed to assess fatigue life and compare fatigue performance of steering knuckles made from three materials of different manufacturing processes. These include forged steel, cast aluminum, and cast iron knuckles. In light of the high volume of forged steel vehicle components, the forging process was considered as base for investigation. Monotonic and strain-controlled fatigue tests of specimens machined from the three knuckles were conducted. Static as well as baseline cyclic deformation and fatigue properties were obtained and compared. In addition, a number of load-controlled fatigue component tests were conducted for the forged steel and cast aluminum knuckles. Finite element models of the steering knuckles were also analyzed to obtain stress distributions in each component.

The paper reviews the role of drawbeads in sheet metal stamping. The design of drawbeads is discussed in depth, with treatment of different bead cross sections, bead end shapes, and bead materials. International standards and practices are included. This is followed by the historical development of the modeling of the drawbead restraining force, starting with basic equilibrium approaches, and leading to the use of the finite element method which permits the study of drawbead effects on sheet metal flow in three dimensions. Finally, the potential of active drawbeads is described based upon ongoing research which is directed toward closed-loop computer control of the stamping process through adjustment of the drawbead penetration.

This paper describes the heat transfer model of a composite aluminum brake rotor and compares the predicted temperatures to dynamometer measurements taken during a 15 fade stop trial. The model is based on meshed surface geometry which is simulated using RadTherm software. Methods for realistically modeling heat load distribution, surface rotation, convection cooling and radiation losses are also discussed. A comparison of the simulation results to the dynamometer data shows very close agreement throughout the fade stop trial. As such, the model is considered valid and will be used for further Steel Clad Aluminum (SCA) rotor development.

The introduction of a thin fluid layer between two layers of sheet metal offers a highly effective and economical alternative to the use of constrained viscoelastic damping layers in sheet metal structures. A diesel engine gear cover, which is constructed of two sheet metal sections spot welded together, takes advantage of fluid layer damping to produce superior vibration and sound radiation performance. In this paper, the bending of a double layered plate coupled through a thin fluid layer is modeled using a traveling wave approach which results in a impedance function that can be used to assess the vibration and sound radiation performance of practical double layered plate structures. Guided by this model, the influence of fluid layer thickness and inside-to-outside sheet thickness is studied.

Fatigue behavior of two types of automotive steel, quenched and tempered SUJ2 and carburized SCM820PRH, which are applied as powertrain parts are studied. These two types of steel are different in their hardness distribution from surface to core. The hardness of quenched and tempered SUJ2 is homogenous, in contrast to that of carburized SCM820PRH (SCM) which decreases from surface to core. These steels are investigated in terms of their monotonic tensile properties and fatigue behavior. A number of predictive methods were used to describe the fatigue behavior of these steels. A simple predictive method is based on approximation of S-N curve from ultimate tensile strength. The well-known Murakami’s defect area method was also applied for the prediction of the high cycle fatigue strength.

Fatigue is the primary cause of failure of crankshafts in internal combustion engines. The cyclic loading conditions and the stress concentrations in the crank pin fillets are unavoidable, and can result in fatigue failure. The objectives of this study were to compare the fatigue behavior of forged steel and ductile iron crankshafts from a one-cylinder engine as well as to determine if the fatigue life of a crankshaft can be accurately estimated using fatigue life predictions. Monotonic tensile tests as well as strain-controlled fatigue tests were conducted using specimens machined from the crankshafts to obtain the monotonic and cyclic deformation behavior and fatigue properties of the two materials. The forged steel had higher tensile strength and better fatigue performance than the ductile cast iron. Charpy v-notch impact tests were also conducted using specimens machined from the crankshafts to obtain and compare the impact toughness of the materials.