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Technical Paper

A Fatigue Crack Growth Model for Spot Welds in Square-Cup and Lap-Shear Specimens under Cyclic Loading Conditions

A fatigue crack growth model is adopted in this paper to investigate the fatigue lives of resistance spot welds in square-cup and lap-shear specimens of dual phase, low carbon and high strength steels under cyclic loading conditions. The fatigue crack growth model is based on the global stress intensity factor solutions for main cracks, the local stress intensity factor solutions for kinked cracks as functions of the kink length, the experimentally determined kink angles, and the Paris law for kinked crack propagation. The predicted fatigue lives based on the fatigue crack growth model are then compared with the experimental data. The results indicate that the fatigue life predictions based on the fatigue crack growth model are in agreement with or lower than the experimental results.
Technical Paper

A Survey of Alcohol as a Motor Fuel

Alcohol has been promoted and used as a motor fuel for more than 50 years. However, United States ethyl alcohol production is small compared with gasoline production. High latent heat of vaporization of alcohol makes possible some increase of power over gasoline. The heating value of alcohol is low and energy content of alcohol blends is less than that of gasoline; fuel consumption of blends is therefore increased. The ability of ethanol to improve the octane number of gasoline has diminished as the octane number of gasoline has improved. There is no published evidence that alcohols can appreciably reduce air pollution problems.
Technical Paper

A Survey of Automotive Occupant Restraint Systems: Where We’ve Been, Where We Are and Our Current Problems

In recent years, automotive occupant restraint system development has gained impetus, stimulated, in part, by new federal standards. But in the resolution of the basic question of whether automobiles should be equipped with restraints, many new problems have arisen, including, ironically, some brought on by regulation. While there is little doubt that restraint systems can provide the single most important contribution to occupant protection, such restraint systems remain useless unless adequately installed and properly worn. Current problems involve not only what concepts provide most promise for future restraint systems, but diverse and often conflicting industry and governmental opinion about what are the best interests of the motoring public. Restraints are still not provided in buses, trucks, and utility vehicles. In addition, the problems of child and infant restraints and restraints for retrofit in older vehicles remain unresolved.
Technical Paper

Strength and Balance Guided Posture Selection during a Battery Maintenance Task

Posture selection during standing exertions is a complex process involving tradeoffs between muscle strength and balance. Bodyweight utilization reduces the amount of upper-body strength required to perform a high force push/pull exertion but shifts the center-of-gravity towards the limits of the functional stability region. Thus balance constraints limit the extent to which bodyweight can be used to generate push/pull forces. This paper examines a two-handed sagittal plane pulling exertion performed during a battery maintenance task on a member of the family of medium-sized tactical vehicles (FMTV). Percent capable strength predictions and functional balance capabilities were determined for various two-handed pulling postures using the University of Michigan's 3D Static Strength Prediction Program (3DSSPP). Through this simulation study, preferred postures that minimize joint torques while maintaining balance were identified.
Technical Paper

Fatigue Failures of Spot Friction Welds in Aluminum 6111-T4 Sheets Under Cyclic Loading Conditions

Fatigue failures of spot friction welds in lap-shear specimens of aluminum 6111-T4 sheets under cyclic loading conditions are investigated in this paper. The paths of fatigue cracks near the spot friction welds are first discussed. A fatigue crack growth model based on the Paris law for crack propagation and the global and local stress intensity factors for kinked cracks is then adopted to predict the fatigue lives of these spot friction welds. The global stress intensity factors and the local stress intensity factors based on the recent published works for resistance spot welds in lap-shear specimens are used to estimate the local stress intensity factors for kinked cracks with experimentally determined kink angles. The results indicate that the fatigue life predictions based on the Paris law and the local stress intensity factors as functions of the kink length agree well with the experimental results.
Technical Paper

Design and Development of a Turbocharged E85 Engine for Formula SAE Racing

A summary of the design and development process for a Formula SAE engine is described. The focus is on three fundamental elements on which the entire engine package is based. The first is engine layout and displacement, second is the fuel type, and third is the air induction method. These decisions lead to a design around a 4-cylinder 600cc motorcycle engine, utilizing a turbocharger and ethanol E-85 fuel. Concerns and constraints involved with vehicle integration are also highlighted. The final design was then tested on an engine dynamometer, and finally in the 2007 M-Racing FSAE racecar.
Technical Paper

The Influence of Inlet Air Conditions on Carburetor Metering

This paper provides data concerning the enrichment of automotive carburetors with variation of inlet air pressure and temperature. These changes occur with weather and the seasons, with altitude, and because of underhood heating. The early opening of the conventional carburetor enrichment value at altitude can add greatly to the “ normal” carburetor enrichment. Means for compensating the mixture ratio for these changes in inlet air conditions are known, but will almost certainly add to the complexity and cost of the engine induction system. The cost of improved devices must be compromised with the possible reduction in exhaust emissions and improvement in fuel economy.
Technical Paper

Slip Resistance Predictions for Various Metal Step Materials, Shoe Soles and Contaminant Conditions

The relationship of slip resistance (or coefficient of friction) to safe climbing system maneuvers on high profile vehicles has become an issue because of its possible connection to falls of drivers. To partially address this issue, coefficients of friction were measured for seven of the more popular fabricated metal step materials. Evaluated on these steps were four types of shoe materials (crepe, leather, ribbed-rubber, and oil-resistant-rubber) and three types of contaminant conditions (dry, wet-water, and diesel fuel). The final factor evaluated was the direction of sole force application. Results showed that COF varied primarily as a function of sole material and the presence of contaminants. Unexpectedly, few effects were attributible to the metal step materials. Numerous statistical interactions suggested that adequate levels of COF are more likely to be attained by targeting control on shoe soles and contaminants rather than the choice of a particular step material.
Technical Paper

Integrated, Feed-Forward Hybrid Electric Vehicle Simulation in SIMULINK and its Use for Power Management Studies

A hybrid electric vehicle simulation tool (HE-VESIM) has been developed at the Automotive Research Center of the University of Michigan to study the fuel economy potential of hybrid military/civilian trucks. In this paper, the fundamental architecture of the feed-forward parallel hybrid-electric vehicle system is described, together with dynamic equations and basic features of sub-system modules. Two vehicle-level power management control algorithms are assessed, a rule-based algorithm, which mainly explores engine efficiency in an intuitive manner, and a dynamic-programming optimization algorithm. Simulation results over the urban driving cycle demonstrate the potential of the selected hybrid system to significantly improve vehicle fuel economy, the improvement being greater when the dynamic-programming power management algorithm is applied.
Technical Paper

Assessing the Fuel Economy Potential of Light-Duty Vehicles

This paper assesses the potential for car and light truck fuel economy improvements by 2010-15. We examine a range of refinements to body systems and powertrain, reflecting current best practice as well as emerging technologies such as advanced engine and transmission, lightweight materials, integrated starter-generators, and hybrid drive. Engine options are restricted to those already known to meet upcoming California emissions standards. Our approach is to apply a state-of-art vehicle system simulation model to assess vehicle fuel economy gains and performance levels. We select a set of baseline vehicles representing five major classes - Small and Standard Cars, Pickup Trucks, SUVs and Minivans - and analyze design changes likely to be commercially viable within the coming decade. Results vary by vehicle type.
Technical Paper

Transient Spray Cone Angles in Pressure-Swirl Injector Sprays

The transient cone angle of pressure swirl sprays from injectors intended for use in gasoline direct injection engines was measured from 2D Mie scattering images. A variety of injectors with varying nominal cone angle and flow rate were investigated. The general cone angle behavior was found to correlate well qualitatively with the measured fuel line pressure and was affected by the different injector specifications. Experimentally measured modulations in cone angle and injection pressure were forced on a comprehensive spray simulation to understand the sensitivity of pulsating injector boundary conditions on general spray structure. Ignoring the nozzle fluctuations led to a computed spray shape that inadequately replicated the experimental images; hence, demonstrating the importance of quantifying the injector boundary conditions when characterizing a spray using high-fidelity simulation tools.
Technical Paper

The Prospects of Using Alcohol-Based Fuels in Stratified-Charge Spark-Ignition Engines

Near-term energy policy for ground transportation is likely to have a strong focus on both gains in efficiency as well as the use of alternate fuels; as both can reduce crude oil dependence and carbon loading on the environment. Stratified-charge spark-ignition direct-injection (SIDI) engines are capable of achieving significant gains in efficiency. In addition, these engines are likely to be run on alternative fuels. Specifically, lower alcohols such as ethanol and iso-butanol, which can be produced from renewable sources. SIDI engines, particularly the spray-guided variant, tend to be very sensitive to mixture preparation since fuel injection and ignition occur within a short time of each other. This close spacing is necessary to form a flammable mixture near the spark plug while maintaining an overall lean state in the combustion chamber. As a result, the physical properties of the fuel have a large effect on this process.
Technical Paper

Development of Active Human Response Model to Ride Motion

Vehicle ride motion produces a dynamic response of the seated operator, which disturbs the intended fingertip trajectory during reach activities. This perturbation induces deviations that must be corrected to successfully complete the reach. Visual and/or proprioceptive information are necessary to detect these deviations and provide feedback to the controller of the neuromuscular system. In an attempt to predict movement alterations and adjustments under whole body vibration exposure, a trajectory planning and feedback controller was developed using split sample data from a series of reaching experiments on a six degree of freedom motion platform.
Technical Paper

Bioengineering of Impact Survival in Business Aircraft

Aircraft used for business (executive corporate transportation or personal business) and utility purposes now represent about one-third of the total United States aircraft inventory. Data from accident investigation of business aircraft involved in survivable accidents indicate serious injuries and fatality to the occupants occur most frequently as a result of the unprotected head and neck or chest flailing in contact with aircraft controls, instrument panel, or structure. Improvement of current aircraft to provide increased occupant safety and survival during crash impacts is both necessary and feasible. Design considerations include folding seat back locks to prevent collapse, increased seat tie-down to structure, instrument panels and glare shields designed to absorb energy through structural design and padding, stronger seat structure, lateral protection, design and packaging of knobs and projections to minimize injury in contact, and installation of upper torso restraint.
Technical Paper

Computerized Speed Control of Electric Vehicles

This paper presents a general control module to control the speed of an electric vehicle (EV). This module consists of a microprocessor and several C-programmable micro-controllers. It uses an identification algorithm to estimate the system parameters on-line. With the estimated parameters, control gains are calculated via pole-placement. In order to compensate for the internal errors, a cross-coupling control algorithm is included. To estimate the true velocity and acceleration from measurements, a discrete-time Kalman filter was utilized. The experimental results validate the general control module for EVs.
Technical Paper

Influence of Fuel Properties on Metering in Carburetors

This paper considers the influence of the properties of gasolines and testing fluids on metering by carburetors. Since the fuel metering is controlled by orifices, the effects of fuel properties on orifice flow are analyzed. The results of an orifice testing program are presented, using the Reynolds number as the primary correlation parameter. The influences of fuel type, fuel temperature, and orifice geometry on the discharge coefficient are discussed, and the effect of a given fuel property change is shown. Experimental values for the variations in fluid properties with fuel type and temperature are presented for commercial gasolines, carburetor testing fluids, and pure hydrocarbons. The variation of carbon-to-hydrogen ratio among gasolines is shown to cause a change in stoichiometry, which is the equivalent of an error in metering.
Technical Paper

An Analog Computer Method for Determining “g” Loads and Resulting Motions in Automobile and Truck Wheel-Frame Systems

A general analog computer procedure is presented for the dynamic analysis of a selected realistic model of an automobile or truck vehicle wheel-frame system. The elements of the model are assigned a set of values based on a preselected vehicle, and the model is then subjected to a number of inputs which correspond to test track road disturbances at various speeds. This procedure is successively applied to a number of typical vehicles. Time-varying values of wheel spindle and frame reaction “g” loads, acclerations, and displacements are recorded, and illustrative waveshapes are depicted. Tables indicating extreme values of these quantities are also included.
Technical Paper

Assessment of Alternative Strategies for Reducing Hydrocarbon and Carbon Monoxide Emissions from Small Two-Stroke Engines

Five small two-stroke engine designs were tested at different air/fuel ratios, under steady state and transient cycles. The effects of combustion chamber design, carburetor design, lean burning, and fuel composition on performance, hydrocarbon and carbon monoxide emissions were studied. All tested engines had been designed to run richer than stoichiometric in order to obtain satisfactory cooling and higher power. While hydrocarbon and carbon monoxide emissions could be greatly reduced with lean burning, engine durability would be worsened. However, it was shown that the use of a catalytic converter with acceptably lean combustion was an effective method of reducing emissions. Replacing carburetion with in-cylinder fuel injection in one of the engines resulted in a significant reduction of hydrocarbon and carbon monoxide emissions.
Technical Paper

Correlation of Spray Cone Angle and Fuel Line Pressure in a Pressure-Swirl Injector Spray

The transient cone angle of a pressure swirl spray from an injector for gasoline direct injection engines was measured from 2D Mie scattering images. Iso-octane was used as the fluid that was delivered at room temperature for two different static pressures, 5MPa and 8.5MPa. The iso-octane was injected into a chamber at room temperature and ambient pressure. After a rapid initial increase, the cone angle oscillates before stabilizing to a steady-state value very close to the nominal cone angle. The period of the oscillation was found to correlate well with oscillations measured in the fuel line pressure.
Technical Paper

Analysis and Redesign of Battery Handling using Jack™ and HUMOSIM Motions

The evaluation of maintenance tasks is increasingly important in the design and redesign of many industrial operations including vehicles. The weight of subsystems can be extreme and often tools are developed to abate the ergonomic risks commonly associated with such tasks, while others are unfortunately overlooked. We evaluated a member of the family of medium-sized tactical vehicles (FMTV) and chose the battery handling from a list of previously addressed concerns regarding the vehicle. Particularly in larger vehicles, similar to those analyzed in this paper, batteries may exceed 35 kg (77 lbs). The motions required to remove these batteries were simulated using motion prediction modules from the Human Motion Simulation (HUMOSIM) laboratory at the University of Michigan. These motions were visualized in UGS PLM Solutions' Jack™ and analyzed with the embedded 3-D Static Strength Prediction program.