Search Results

This study evaluated the effect of the sharpness of the cutoff (the transition between the lighter and darker portions of the beam) of low-beam headlamps on visual vertical aiming. Out of ten lamps tested, seven had a U.S.-type beam pattern and three had a European-type beam pattern. Twenty younger and middle-aged subjects of both sexes, along with an experienced lamp aimer, were asked to adjust the vertical aim of the lamps in such a way that the cutoff of the beam was coincident with a horizontal line on a vertical surface. The subjects were instructed to make the alignment using the illumination gradient to the right of vertical for the U.S.-type lamps and to the left of vertical for the European-type lamps. Each person aimed each lamp ten times. There are two main results. First, the location of the perceived cutoff was generally near the location of the maximum contrast between adjacent vertical parts of the beam pattern.

Adhesive joining is a common autobody subassembly technique especially for outer panels, where visible spot welding is objectionable. To accommodate mass production with the use of certain adhesives very high thermal gradient usually exists, which may result in panel dimensional distortion and variation. The temperature distribution over location and over time are monitored, and its impact to panel dimension is investigated. Experimental results on the effect of the distance between panel and induction coil on the panel temperature is obtained. The thermal induced shape distortion is simulated with a simplified FEA model. The approach to improvement of the induction curing process is discussed.

Advances in electronic countermeasures for lane-change crashes, including both camera-based rear vision systems and object-detection systems, have provided more options for meeting driver needs than were previously available with rearview mirrors. To some extent, human factors principles can be used to determine what countermeasures would best meet driver needs. However, it is also important to examine sets of crash data as closely as possible for the information they may provide. We review previous analyses of crash data and attempt to reconcile the implications of these analyses with each other as well as with general human factors principles. We argue that the data seem to indicate that the contribution of blind zones to lane-change crashes is substantial.

New developments in the use of two-dimensional displays to supplement driver vision have made it more important to understand the roles that various distance cues play in driver perception of distance in more conventional ways of viewing the road, including direct vision and viewing through rearview mirrors. The current study was designed to investigate the role of binocular distance cues for perception of distance in rearview mirrors. In a field experiment, we obtained data to estimate the importance of binocular cues for distance judgments under conditions representative of real-world traffic. The results indicate that, although binocular cues are potentially available to drivers, these cues probably play little or no role in distance judgments in rearview mirrors in normal driving situations.

Sound attenuation and flow loss reduction are often two competing demands in vehicle breathing systems. The present study considers a full vehicle exhaust system and investigates both the sound attenuation and the flow performance of production configurations including the catalyst, the resonator, and the muffler. Dynamometer experiments have been conducted with a firing Ford 3.0L, V-6 engine at wide-open throttle with speeds ranging from 1000 to 5000 rpm. Measurements including the flow rates, the temperatures and the absolute dynamic pressures of the hot exhaust gases at key locations (upstream and downstream of every component) with fast-response, water-cooled piezo-resistive pressure transducers facilitate the calculation of acoustic performance of each component, as well as the determination of flow losses caused by these elements and their influence on the engine performance.

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.

This paper discusses the general principles governing the action of free spinning, self-locking bolts. The concept presented is that the bolt, and the parts it holds, acts as a spring, and it is shown that this leads logically to measuring the work done to remove a self-locking bolt as well as measuring its breakaway torque. Equipment for such tests is illustrated and typical test results are given. Finally, some remarks are made concerning the basic mechanisms by which vibratory motion loosens bolts.

Failure loads of spot welds are investigated under static and impact loading conditions. A test fixture was designed and used to obtain maximum loads of spot welds under a range of combined opening and shear loads with different loading rates. Optical micrographs of the cross sections of spot welds before and after failure were obtained to understand the failure processes under various loading rates and different combinations of loads. The experimental results indicate that under nearly pure opening loads, the failure occurs along the nugget circumferential boundary. Under combined opening and shear loading conditions, the failure starts from the tensile side of the base metal near the nugget in a necking/shear failure mode. The effects of sheet thickness and combined load on the load carrying behavior of spot welds are investigated under static and impact loading conditions based on the experimental results.

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.

In a laboratory study and in a mathematical modeling effort, we evaluated the effects of rearview mirror reflectivity on older and younger subjects' seeing ability under conditions designed to simulate night driving with headlamp glare present in the mirror. Rearview mirror reflectivity was varied while observers were required to detect both rearward stimuli seen through the mirror and forward stimuli seen directly. Lower reflectivity resulted in improved ability to see forward and reduced ability to see to the rear. The reduction in ability to see to the rear was much larger than the improvement in forward seeing. The results of the modeling and the laboratory study were in broad agreement, although there were some significant discrepancies. Although the present results cannot be used to make specific recommendations for rearview mirror reflectivity, they suggest that the reduction in rearward vision as reflectivity is lowered should be considered carefully.

This paper presents the real time implementation of detection filters for the diagnosis of incipient failures in electronically controlled internal combustion (IC) engines. The detection filters are implemented in a production vehicle. Recent results [1] have demonstrated the feasibility of a model-based failure detection and isolation (FDI) methodology for detecting partially failed components in electronically controlled vehicle subsystems. The present paper describes the real time application of the FDI concept to the detection of faults in sensors associated with the engine/controller In a detection filter, the performance of the engine/controller system is continuously compared to a prediction based on sensor measurements and an analytical model (typically a control model) of the system. Any discrepancy between actual and predicted performance is analyzed to identify the unique failure signatures related to specific system components.

In a static field study we tested drivers’ abilities to detect vehicles in the periphery of their direct fields of view while they gazed toward the driver-side exterior rearview mirror of a passenger car. The results indicate that both younger and older drivers can detect vehicles with reasonable efficiency even in far peripheral vision. However, the results also indicate that using peripheral vision entails a cost in terms of lengthened reaction time. Although that cost seems modest in comparison with the normal durations of glances to rearview mirrors and of direct looks to the rear, it is not clear from this study alone how the reaction time cost might influence the scanning strategies that drivers actually use in driving. The present study was oriented more to testing drivers’ basic visual capabilities than to outlining their overall strategies.

Rectangular aluminum sheets were stretched under in-plane plane-strain tension using a simple experimental setup. The samples can be stretched under these conditions until localized necking occurs at the centerline. The strain distributions and the loads were recorded at different strain levels. Good agreement was found between actual loads and those calculated from strain measurements assuming isotropic hardening with a high exponent yield criterion.

A semi-empirical engine piston/ring assembly friction model based on the concept of the Stribeck diagram and similarity analysis is described. The model was constructed by forming non-dimensional parameters based on design and operating conditions. Friction data collected by the Fixed-Sleeve method described in [1]* at one condition, were used to correlate the coefficient of friction of the assembly and the other non-dimensional parameters. Then, using the instantaneous cylinder pressure as input together with measured and calculated design and operating parameters, reasonable assembly friction and fmep predictions were obtained for a variety of additional conditions, some of which could be compared with experimental values. Model inputs are component dimensions, ring tensions, piston skirt spring constant, piston skirt thermal expansion, engine temperatures, speed, load and oil viscosity.

Failure behavior of spot welds is investigated under impact loading conditions. Three different impact speeds were selected to test both HSLA steel and mild steel specimens under combined opening and shear loading conditions. A test fixture was designed and used to obtain the failure loads of spot weld specimens of different thicknesses under a range of combined opening and shear loads with different impact speeds. Accelerometers were installed on the fixtures and the specimens for investigation of the inertia effects. Optical micrographs of the cross sections of failed spot welds were obtained to understand the failure processes in both HSLA steel and mild steel specimens under different combined impact loads. The experimental results indicate that the failure mechanisms of spot welds are very similar for both HSLA steel and mild steel specimens with the same sheet thickness. These micrographs show that the sheet thickness can affect the failure mechanisms.

The link between manufacturing process and product performance is studied in order to construct analytical, quantifiable criteria for the introduction of new engine technologies and processes. Cost associated with a new process must be balanced against increases in engine performance and thus demand for the particular vehicle. In this work, the effect of the Abrasive Flow Machining (AFM) technique on surface roughness is characterized through measurements of specimens, and a predictive engine simulation is used to quantify performance gains due to the new surface finish. Subsequently, economic cost-benefit analysis is used to evaluate manufacturing decisions based on their impact on firm's profitability. A demonstration study examines the use of AFM for finishing the inner surfaces of intake manifolds for two engines, one installed in a compact car and the other in an SUV.

Night vision enhancement systems (NVES), which use infrared (IR) cameras, are designed to supplement the visibility provided by standard headlamps. There are two main NVES systems: active, near infrared (NIR) systems, which require an IR source but give a complete picture of the scene in front of the driver, and passive, far infrared (FIR) systems, which do not need an IR source but only enhance relatively warm objects (such as people and animals). There are three main display alternatives: a head-up display (HUD) superimposed on the direct view of the road, a HUD just above the dashboard but separated from the direct view, and a conventional display somewhere in the dashboard. This paper analyzes what a NVES should do to improve night visibility based on night crash statistics, driver vision and visibility conditions in night driving, driver tasks and behavior, and the options offered by various technological approaches. Potential problems with using NVES are also discussed.

We conduct static experiments to investigate the influence of shear stress on the crush behavior of honeycomb materials. The aluminum honeycomb materials selected in this investigation are orthotropic due to their manufacturing processes. A test fixture and honeycomb specimens are designed such that combined compressive and shear loads along the strongest material symmetry axis can be controlled and applied accurately. The experimental results indicate that both the peak and crush strengths under combined compressive and shear loads are lower than those under pure compressive loads. A yield function is suggested for honeycomb materials under the combined loads based on a phenomenological plasticity theory. The microscopic crush mechanism under the combined loads is also investigated. A microscopic crush model based on the experimental observations is developed. The crush model includes the rupture of aluminum cell walls so that the kinematic requirement can be satisfied.

The LDH (Limiting Dome Height Test) is widely used at Ford Motor Co. stamping plants laboratories to monitor the formability of incoming sheet materials. Although the LDH test is very easy to implement and interpret, variability of the results and poor reproducibility between laboratories limit its acceptance. In this investigation, some of the causes of variability and differences between plant laboratories are discussed. Much of the experimental work was done at plant laboratories and the results are directly applicable to quality control (QC) machines. It was found that the binder force and the binder shape have a big influence on the results, and they should be carefully controlled. The binder cleaning procedure is also relevant to the test variability. Punch temperature has a much greater influence on QC machines than on research machines and a method for controlling the punch temperature in QC machines is presented.

Coordinate measurement gages dominate in the area of dimensional control and variation reduction of automotive body assembly processes. However, coordinate measurement gages do not have the capability to track certain measured features. This incapability introduces inherent measurement error created by part (feature) mislocation in constrained non-measured directions. This inherent measurement error weakens the methods used for process control and variation reduction. In this paper, a principle of measurement uncertainty is developed in order to estimate the measurement error caused by this deficiency. The developed principle describes measurement error, which is independent of any other error related to the mechanical or optical coordinate measurement machines (CMMs, OCMMs). Additionally, an error map determined by the measurement uncertainty principle is created for error compensation.