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An empirical Three Stage Initiation-Propagation (TSIP) model has been developed which predicts the fatigue resistance of tensile-shear spot welds under constant amplitude loading. The improvements of tensile-shear spot weld fatigue resistance caused by changes in weld geometry, residual stresses and material properties variables are discussed with the aid of the model. The TSIP model suggests that, in addition to the influence of geometry, residual stresses at the site of crack initiation greatly influence the fatigue resistance of tensile-shear spot welds. The TSIP model predicts that material properties play a subtle role in determining the fatigue resistance of tensile-shear spot welds.

Site-Specific Crop Management (SSCM) involves use of automated seeders and chemical applicators to make spatially-variable applications to agricultural fields. Soil productivity is spatially variable and thus, SSCM provides an opportunity to reduce total applications of seed and fertilizer without reducing crop yields. Also, more complete crop use of fertilizers with SSCM could reduce the potential for environmental contamination. A key element in SSCM is a Field Information System (FIS) for preparing application maps to control application rates.

This paper describes a practical and efficient approach for determining complete transient, as well as steady state response of tractor-trailer air brake systems by recording pushrod displacement and air brake service line pressure as a function to time. The test hardware utilizes easy to fabricate “clip on” transducers to measure pushrod stroke length. Data acquisition is via LABVIEW‚. All transducers are easy to temporarily affix to any tractor- trailer and require no alteration to the vehicle. A complete system check takes less time than manually measuring pushrod stroke as required under FMCSA. This system with one treadle application and release gives digital timing and displacement history of all brakes. Useful information includes: application and release profiles (pushrod velocity), shoe compliance upon seating and crack pressure release points for both tractor and trailer relay valves.

A traditional method of controlling evaporator superheat in a vapor compression air conditioning system is the thermostatic expansion valve (TXV). Such systems are often used in automotive applications. The TXV depends on superheat to adjust the valve opening. Unfortunately, any amount of superheat causes that evaporator to operate at reduced capacity due to dramatically lower heat transfer coefficients in the superheated region. In addition, oil circulation back to the compressor is impeded. The cold lubricant almost devoid of dissolved refrigerant is quite viscous and clings to the evaporator walls. A system that could control an air conditioner to operate with no superheat would either decrease the size of its existing evaporator while maintaining the same capacity, or potentially increase its capacity with its original evaporator. Also, oil circulation back to the compressor would be improved.

Camless actuation offers programmable flexibility in controlling engine valve events. However, a full range of engine benefits will only be available, if the actuation system can control lift profile characteristics within a particular lift event. Control of the peak value of valve lift is a first step in controlling the profile. The paper presents an adaptive feedback control of valve lift for a springless electrohydraulic valvetrain. The adaptive control maintains peak value of lift in presence of variations in engine speed, hydraulic fluid temperature and manufacturing variability of valve assemblies. The control design includes a reduced-order model of the system dynamics. Experimental results show dynamic behavior under various operating and environmental conditions and demonstrate advantages of adaptive control over the non-adaptive type.

An empirical method which is based principally on estimates of the fatigue crack initiation life (NI) has been developed which predicts the fatigue resistance of tensile-shear spot welds in the long life regime. The method uses Basquin’s law and Peterson’s equation to estimate NI and thus is founded on the fatigue behavior of smooth specimens and modelling of the fatigue notch size effect. The fatigue notch factor (Kf) required in this analysis was obtained from Pook’s relationships for the stress intensity factors of tensile-shear spot welds. Estimates of NI are added to estimates of the fatigue crack propagation life NP to obtain the total fatigue life (NT) but in the long life regime NP can usually be neglected. The improvement of tensile-shear spot weld fatigue resistance through manipulation of geometry and material property variables are discussed with the aid of the model.

Fuel-injection schedules that use two injection events per cycle (“dual-injection” approaches) have the potential to simultaneously attenuate engine-out soot and NOx emissions. The extent to which these benefits are due to enhanced mixing, low-temperature combustion modes, altered combustion phasing, or other factors is not fully understood. A traditional single-injection, an early-injection-only, and two dual-injection cases are studied using a suite of imaging diagnostics including spray visualization, natural luminosity imaging, and planar laser-induced fluorescence (PLIF) imaging of nitric oxide (NO). These data, coupled with heat-release and efficiency analyses, are used to enhance understanding of the in-cylinder processes that lead to the observed emissions reductions.

Both the experimental results and the analytical predictions of this study confirm that the poor fatigue performance of weldments with longitudinal attachments is due to poor weld quality which in turn leads to either a cold-lap or a very small weld toe radius. as well as to the combination of a very high 3-D stress concentration, and very high tensile residual stresses. Consequently, a specially designed stress-concentration-reducing part termed “stress diffuser” incorporated in the wrap-around welds at the ends of the longitudinal attachments increased the fatigue strength of longitudinal attachments to equal that of transverse attachments but only when cold-laps were eliminated. The fatigue life predictions made using the a two-stage Initiation-Propagation (IP) Model were in good agreement with the experimental results. Procedures for correcting for the curved shape of the crack path are investigated.

The feasibility of automatically detecting refrigerant charge loss in mobile air conditioning (MAC) systems by analyzing inexpensive dynamic measurements was studied. An indicator of the refrigerant inventory of the evaporator was developed. This measure, termed Time to Temperature Turning (TTT), is based on dynamic measurement of the evaporator outlet refrigerant temperature, and correlates strongly with charge level. TTT correlated well with clutch cycling behavior, a metric which is employed in current shop diagnostic practice to indicate refrigerant charge loss. Laboratory data were generated from a factorial experiment design on the following factors: condenser air inlet temperature, condenser air flow rate, evaporator air inlet temperature, compressor speed, and refrigerant charge. Experiments to date were conducted with a dry evaporator.

Induction hardening of mild steel components often results in significant improvements in the static and cyclic load capability, with comparatively small increases in cost. Members subjected primarily to torsional loading are a relevant subset of the broad range of induction hardened components. Due to the variation of material properties and residual stresses, failures are “initiated” at the traditional geometric locations predicted for homogeneous materials and also at subsurface sites. The introduction of shear based fatigue parameters has necessitated the consideration of the residual stress as a three dimensional quantity, especially when analyzing subsurface failures. Not considering the tensoral nature of the residual stress can lead to serious errors when estimating fatigue life, and for larger magnitude loadings, the residual stress field may relax.

Service loading histories have the same general character for an individual route and the magnitudes vary from driver to driver. Both the magnitude and character of the loading history change from route to route and a linear scaling of one loading history does not characterize the variability of usage over a wide range of operating conditions. In this paper a technique for measuring and extrapolating cumulative exceedance diagrams to quantify the distribution of service loading in a vehicle is described. Monte Carlo simulations are coupled with the local stress strain approach for fatigue to obtain distributions of service loading. Fatigue life estimates based on the original loading histories are compared to those obtained from statistical descriptions of exceedance diagrams.

The development of automated guidance for agricultural tractors has addressed several basic and applied issues of agricultural equipment automation. Basic analyses have included the dynamics of steering systems and posture sensors for guidance. Applied issues have evaluated the potential of several commercial sensing systems and a commercial mechanical guidance system. A research platform has been developed based on a Case 7220 Magnum1 2-wheel drive agricultural tractor. An electrohydraulic steering system was used and characterized in support of automated guidance control. Posture sensing methods were developed using GPS, geomagnetic direction sensors (GDS), inertial, and machine vision sensing systems. Sensor fusion of GPS-inertial-machine vision and GPS-GDS-machine vision provided the most flexible and accurate guidance and capable for operation under dynamically changing field conditions.

The purpose this paper is to delineate why there exists a trade-off between biomechanical realism and algorithmic efficiency for human motion simulation models, and to illustrate how empirical human movement data and findings can be integrated with novel modeling techniques to overcome such a realism-efficiency tradeoff. We first review three major classes of biomechanical models for human motion simulation. The review of these models is woven together by a common fundamental problem of redundancy—kinematic and/or muscle redundancy. We describe how this problem is resolved in each class of models, and unveil how the trade-off arises, that is, how the computational demand associated with solving the problem is amplified as a model evolves from small scale to large scale, or from less realism to more realism.

Biodiesel fuel can be produced from a wide range of source materials that affect the properties of the fuel. The diesel engine has become a highly tuned power source that is sensitive to these properties. The objectives of this research were to measure and predict the key properties of biodiesel produced from a broad range of source materials to be used as inputs for combustion modeling; and second to compare the results of the model with and without the biodiesel fuel definition. Substantial differences in viscosity, surface tension, density and thermal conductivity were obtained relative to reference diesel fuels and among the different source materials. The combustion model revealed differences in the temperature and emissions of biodiesel when compared to reference diesel fuel.

A multicomponent fuel film vaporization model using continuous thermodynamics is developed for multidimensional spray and wall film modeling. The vaporization rate is evaluated using the turbulent boundary-layer assumption and a quasi-steady approximation. Third-order polynomials are used to model the fuel composition profiles and the temperature within the liquid phase in order to predict accurate surface properties that are important for evaluating the mass and moment vaporization rates and heat flux. By this approach, the governing equations for the film are reduced to a set of ordinary differential equations and thus offer a significant reduction in computational cost while maintaining adequate accuracy compared to solving the governing equations for the film directly.

The availability and low price of personal computers with suitable interface equipment has made it practical to use such a system for cylinder pressure data acquisition. With this objective, procedures have been developed to measure and record cylinder pressure on an individual crank angle basis and obtain an average cylinder pressure trace using an Apple II Plus personal computer. These procedures as well as methods for checking the quality of cylinder pressure data are described. A simplified heat release analysis technique for an approximate first look at the data quality is presented. Comparisons are made between the result of this analysis, the Krieger-Borman heat release analysis which uses complete chemical equilibrium. The comparison is made to show the suitability of the simplified analysis in judging the quality of the pressure data.

This paper presents a mapping of developing adiabatic two-phase R134a flow directly after the expansion valve until the flow is “fully developed” in a 15.3mm inner diameter pipe. Flow characteristics of separation distance, flow type in the homogenous region, void fraction as a function of tube length, and fully developed flow region void fraction and regime were quantified and described.

The transporting of live cattle involves the use of Class 8 tractors and livestock semi-trailers for transportation from farms and feedlots to processing plants. This travel may include unimproved roads, local streets, two lane highways, as well as interstate highways. Typically, cattle are compartmentalized in a “double deck” fashion as it provides utility and comports with size and weight limits for commercial Class 8 vehicles. Concern has been expressed for the effect of cattle movement upon the dynamic performance of the loaded Class 8 tractor-livestock trailer assembly. Loading guidelines exist for cattle that attempt to prevent injury or debilitation during transit, and literature exists on the orientation and some kinematics of loaded cattle. Considerable literature exists on the effect of liquid slosh in tankers and swinging beef carcasses suspended from hooks in refrigerated van trailers on the dynamic response and roll stability of those vehicles.

The detailed mechanisms by which oxygenated diesel fuels reduce engine-out soot emissions are not well understood. The literature contains conflicting results as to whether a fuel's overall oxygen content is the only important parameter in determining its soot-reduction potential, or if oxygenate molecular structure or other variables also play significant roles. To begin to resolve this controversy, experiments were conducted at a 1200-rpm, moderate-load operating condition using a modern-technology, 4-stroke, heavy-duty DI diesel engine with optical access. Images of broadband natural luminosity (i.e., light emission without spectral filtering) from the combustion chamber, coupled with heat-release and efficiency analyses, are presented for three test-fuels. One test-fuel (denoted GE80) was oxygenated with tri-propylene glycol methyl ether; the second (denoted BM88) was oxygenated with di-butyl maleate. The overall oxygen contents of these two fuels were matched at 26% by weight.

This paper introduces the concept of separation of two-phase flow in condenser as a way to improve condenser efficiency. The benefits of vapor-liquid refrigerant separation and the reason why it will improve the condenser performance are explained. Numerical studies are presented on the effects of separation on performance of an R134a microchannel condenser, with the comparison to experiment data. Model predicts that at the same mass flow rate, the exit temperature is lower by 2.2 K in the separation condenser compared with that in the baseline. Up to 9% more flow rate of condensate is also predicted by the model in the separation condenser. Experiment results confirm the same trend. In addition, the reason why a certain circuiting of passes with pre-assumed separation results in the header improves the condenser is investigated by the model and results are presented.