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One of the issues in stamping of advanced high strength steels (AHSS) is the stretch bending fracture on a sharp radius (commonly referred to as shear fracture). Shear fracture typically occurs at a strain level below the conventional forming limit curve (FLC). Therefore it is difficult to predict in computer simulations using the FLC as the failure criterion. A modified Mohr-Coulomb (M-C) fracture criterion has been developed to predict shear fracture. The model parameters for several AHSS have been calibrated using various tests including the butter-fly shaped shear test. In this paper, validation simulations are conducted using the modified (M-C) fracture criterion for a dual phase (DP) 780 steel to predict fracture in the stretch forming simulator (SFS) test and the bending under tension (BUT) test. Various deformation fracture modes are analyzed, and the range of usability of the criterion is identified.

In order to understand better the operation of spark-ignition engines during the warm-up period, a computer model had been developed which simulates the thermal processes of the engine. This model is based on lumped thermal capacitance methods for the major engine components, as well as the exhaust system. Coolant and oil flows, and their respective heat transfer rates are modeled, as well as friction heat generation relations. Piston-liner heat transfer is calculated based on a thermal resistance method, which includes the effects of piston and ring material and design, oil film thickness, and piston-liner crevice. Piston/liner crevice changes are calculated based on thermal expansion rates and are used in conjunction with a crevice-region unburned hydrocarbon model to predict the contribution to emissions from this source.

In gasoline engines, a scraper ring with a step on the bottom outer edge is widely used as a second ring. However, there lacks a fundamental understanding on the effects of this feature and its dimensions on oil transport. Inspired by observations from visualization experiments, this work combining computational fluid dynamics (CFD) and theoretical analysis shows that oil can be trapped in the space bordered by a second ring step and the chamfer of a piston third land. The trapped oil can be released to a liner when the piston is approaching the top dead center (TDC). This additional oil on the liner becomes a potential source of oil consumption. Such oil transport has been observed at typically less than 1500rpm. Since road vehicles often operate in this speed range, the newly-observed oil trapping and release can be closely associated with oil consumption in gasoline engines. In this work, a comprehensive study on oil trapping and release will be demonstrated.

Battery packs for Hybrids, Plug-in Hybrids, and Electric Vehicles are assembled from a system of modules (sheets) with a tight sheet metal casing around them. Each module consists of an array of individual cells which vary in the composition of electrodes and separator from one manufacturer to another. In this paper a general procedure is outlined on the development of a constitutive and computational model of a cylindrical cell. Particular emphasis is placed on correct prediction of initiation and propagation of a tearing fracture of the steel can. The computational model correctly predicts rupture of the steel can which could release aggressive chemicals, fumes, or spread the ignited fire to the neighboring cells. The initiation site of skin fracture depends on many factors such as the ductility of the casing material, constitutive behavior of the system of electrodes, and type of loading.

The existing vehicle designs exhibit a high level of coupling. For instance the coupling in the suspension and steering systems manifests itself through the change in wheel alignment parameters (WAP) due to suspension travel. This change in the WAP causes directional instability and tire-wear. The approach of the industry to solve this problem has been twofold. The first approach has been optimization of suspension link lengths to reduce the change in WAP to zero. Since this is not possible with the existing architecture, the solution used is the optimization of the spring stiffness K to get a compromise solution for comfort (which requires significant suspension travel and hence a soft spring) and directional stability (which demands least possible change in wheel alignment parameters and hence a stiff spring).

Computer simulation of extravehicular activity (EVA) is increasingly being used in planning and training for EVA. A space suit model is an important, but often overlooked, component of an EVA simulation. Because of the inherent difficulties in collecting angle and torque data for space suit joints in realistic conditions, little data exists on the torques that a space suit’s wearer must provide in order to move in the space suit. A joint angle and torque database was compiled on the Extravehicular Maneuvering Unit (EMU), with a novel measurement technique that used both human test subjects and an instrumented robot. Using data collected in the experiment, a hysteresis modeling technique was used to predict EMU joint torques from joint angular positions. The hysteresis model was then applied to EVA operations by mapping out the reach and work envelopes for the EMU.

The present research constitutes an engineering approach to the performance level prediction of starting a vehicle without use of a throttle. The study is based on a dynamic clutch engagement model. A computer simulation of engagement dynamics is used in order to study the lock-up mechanism and to develop proper prediction procedures. In addition, the engagement model is used to develop guidelines and recommendations in order to optimize the engagement system including clutch components, clutch controls, and engine controls. The mathematical model presented in this paper incorporates important, new features in comparison to similar models from previous publications. Consisting of two inertias, it includes not only elastic properties of the clutch damper but also varying engine torque and clamping (pressure) force. Functions of engine torque and plate load simulate the actual control process, including human factors.

Ash inside a honeycomb-configured diesel particulate filter (DPF) inlet channel accumulates both as a cake layer along the channel walls and as a “plug” towards the back of the channel. Experimental studies of DPF ash distribution have shown both an axial variation of deposits along channels and accumulation towards the end plugs. This study evaluates the sensitivity of DPF pressure drop on ash axial distribution and the potential to reduce flow restrictions by controlling and optimizing the spatial distribution of ash inside DPF channels. A computational model has been used in conjunction with experimental data to illustrate the sensitivity of ash spatial distribution on DPF performance. The classical constant-thickness DPF one-dimensional models have substantially been updated to include layer thickness axial variations. Material properties, such as ash characteristics, are provided by recent experiments at the authors' laboratory.

To manage the function of a vehicle's engine, transmission, and related subsystems, almost all modern vehicles make use of one or more electronic controllers running embedded software, henceforth referred to as a Powertrain Controller System or PCS. Fully validating this PCS is a necessary step of vehicle development, and the validation process requires extensive amounts of testing. Within the automotive industry, more and more of this validation testing is being performed using Hardware-in-the-Loop (HIL) simulators to automate the extensive test sequences. A HIL simulation typically mates the physical PCS to a closed-loop real time computer simulation of a powertrain. Interfacing the physical PCS hardware to a powertrain simulation requires the HIL simulator to have extensive signal input/output (I/O) electronics and simulated actuator electrical loading.

The present paper is a continuation of engineering efforts devoted mathematical modeling and computer simulation presented in [1]. The modeling and study is extended on starting a vehicle with use of a throttle. The basic mathematical model utilized in [1] has had to be modified because clutch engagement with throttle make investigators consider new human factors contributing strongly to starting conditions. In particular, not only the clutch release but also the accelerator pedal are controlled by a vehicle operator. This has made the authors modify the definition of an ideal engagement and incorporate both the throttle level and the throttle lead time to the mathematical model. Moreover, the model has been adjusted to consolidate dissimilar low range characteristics for diesel and gas engines.

It is common for difficult shifting to occur in synchronized transmissions. High shift effort is recognized as a basic performance malfunction that takes place during synchronization. This paper examines shift quality in vehicles with synchronized transmissions. The present study is working on three categories: a mathematical model and computer simulation of transmission shifts, an experimental verification of the model and program, and an engineering method for rating shift quality. The mathematical model in this study is a refinement of a model from an earlier paper [1]. With experience, this model has seen revisions that allow the results to be more accurate than the previous ones. The model takes into considerations many elements that affect the synchronizing process such as: synchronizing torque, inertia of both clutch disc(s) and transmission components, clutch drag, viscous drag in the transmission, shifting RPM's, etc.

A detailed methodology is presented in this paper for a complete assessment of various forces, torques, and kinematic effects due to universal joint angularities and shaft yoke phasing. A modular approach has been adopted wherein constitutive equations represent each of the key elements of a driveline namely the driveshaft, coupling shaft, universal joint, and the transmission/axle shafts. Concentrated loads are used wherever loads are being transferred between the elements of a driveline. Local matrices are developed for the equilibrium of the respective driveline members. The local matrices are then assembled into a global matrix and solved for the kinematic state of the complete driveline. A 6x15 matrix has been developed to represent a general shaft in the system and a 6x10 matrix has been developed for a universal joint cross. This gives us a complete picture of all the loads on all driveline members.

A major challenge in predicting driveline torsionals is the modeling of major energy dissipation mechanisms in the driveline. Primary candidates for such mechanisms are viscous dampers and dry friction (hysteresis) dampers which are specifically included by the designers to disperse the energy of torsional vibrations. The inherent structural and other internal damping in the components of the driveline is small as compared to those of viscous and dry friction dampers. Past attempts to model clutch hysteresis have repeatedly resorted to the classical approach of modeling that has been reported many years ago. However, such an approach is oversimplified and assumes, for instance, that the hysteretic effects are independent of the frequency. In addition, the motion of the damper is assumed to be purely harmonic. Also, such studies rely solely upon the static hysteresis characterization of the elements, particularly within the clutch.

THE INCREASED use of midship-mounted transmissions in large equipment has emphasized the need for a torsionally resilient connection from the engine to reduce vibration transfer. To increase the torsional flexibility needed in these systems, the spring rate of the system must be reduced by such constructions as a flexible coupling, a spring-loaded damper, or a rubber torsional spring. This paper discusses these systems, emphasizing rubber springs. Some advantages of such a drive are: it provides an amplitude limitation with impact loads and a cushion to reduce noise and prevent clattering and contacts noises on parts with backlash, it smooths out transition periods to reduce loads on bearings and gears, its clamping characteristics can be adjusted by various rubbers, and its rubber cushion provides a degree axial flexibility.*

Extravehicular activity (EVA) is investigated through experiments testing an actual extravehicular mobility unit (EMU) performing several EVA tasks in the laboratory, and a dynamic model of the EMU space suit is developed. Building directly on earlier work in EVA simulation, the space suit model was created from mass, inertia, and performance data to augment the unsuited 12-segment human model used in previous studies. A modified Preisach model was used to mathematically describe the hysteretic torque characteristics of joints in a pressurized space suit, and implemented numerically based on observed suit parameters. Computational simulations, based loosely on a 1995 EVA involving manipulation of the Spartan astrophysics payload, were performed to observe the effect of suit constraints on simulated astronaut performance.

A model has been developed for estimating the oil vaporization rate from the cylinder liner of a reciprocating engine. The model uses input from an external cycle simulator and an external liner oil film thickness model. It allows for the change in oil composition and the change in oil film thickness due to vaporization. It also estimates how the passage of the compression and scraper rings combine with the vaporization to influence the steady-state composition of the oil layer in the upper ring pack. Computer model results are presented for a compression-ignition engine using a range of liner temperatures, several engine speeds, and two different oils. Vaporization is found to be highly dependent on liner temperature and steady-state oil composition. The steady-state oil composition near the top of the cylinder is found to be significantly different than the composition of the oil near the bottom of the cylinder.

The conventional concept of soot and ash wall deposits (i.e. cake-layers) gradually building up along the channels of a ceramic honeycomb and then periodically or continuously being swept downstream toward the end-plugs of the channels may not always occur in practice. When deposits irregularly form on or detach from the walls, causing premature clogging usually around the mid-sections of the channels (also known as Mid-Channel Collapse), and the particulate filter is prone to experiencing significantly elevated back pressure, resulting in the need for earlier repair or replacement than desired. Here we describe related experiments that were performed, accompanied by analysis and simulation, in order to investigate the factors that contribute to the patterns of wall deposits that form-particularly of ash-and the effects of these irregular patterns.