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The use of a predictive fatigue crack growth model to monitor progressive deterioration of initially small rib-tip flaws in automotive serpentine belts is presented in this paper. Model is based on computational fracture mechanics and fatigue coupon test data. A global-local finite element analysis procedure is used to compute the J-integral for a through-the-thickness crack in the rib tip. The three-dimensional global model is created with relatively coarse mesh using first order continuum elements in ABAQUS. The local model rib crack is constructed with significantly finer mesh utilizing second order continuum elements. Boundary conditions for the local model are driven by global displacements. Maximum and minimum J-integrals are calculated at two extreme configurations for a single belt running cycle. The range of the J-integral is input into the curve fitted power law to derive the fatigue crack growth rate and hence the fatigue life for the belt.

Two soot-containing turbulent non-premixed flames burning gaseous acetylene in atmospheric-pressure air were investigated by conducting non-intrusive optical experiments at various flame locations. The differences in burner exit Reynolds numbers of these flames were large enough to examine the influence of flow dynamics on soot formation and evolution processes in heavily-sooting flames. By accounting for the fractal nature of aggregated primary particles (spherules), the proper interpretation of the laser scattering and extinction measurements yielded all the soot parameters of principal interest. With the separation of spherule and aggregate sizes, the axial zones of the prevailing turbulent soot mechanisms were accurately identified. With the high propensity of acetylene fuel to soot, relatively fast particle nucleation process led to high concentrations immediately above the burner exit.

This paper investigates the effect of ambient temperature on the performance characteristics of an automotive poly-rib belt operating in an under-the-hood temperature environment. A three-dimensional dynamic finite element model consisting of a driver pulley, a driven pulley, and a complete V-ribbed belt was constructed. Belt tension and rotational speed were controlled by means of loading and boundary inputs. Belt construction accounts for three different elastomeric compounds and a single layer of helical wound reinforcing cord. Rubber was considered as hyperelastic material. Cord is linear elastic. The material model was implemented in ABAQUS/Explicit for the simulation. Analysis was focused on rib flank and tip since stress concentrations in these regions are known to contribute to crack initiation and fatigue failure.

Laminated glass consisting of two soda lime glass plies adhered by a polyvinyl butyral interlayer (PVB) is used for automotive glazing. This paper describes the application of a dynamic, nonlinear finite element method to investigate the failure modes of a laminated glass subjected to low-velocity impact with a spherical headform. Crack type, crack location and crack initiation time are evaluated using the maximum principal stress and J-integral criterion. Failure occurred due to flexural stresses and not bearing stresses. The first crack always initiated at the center of the outer impacted ply and PVB interface, and later on the exterior surface of the inner ply. The PVB thickness and velocity of impact had little or no effect on the first crack initiation.

An integrated optimization system has been developed to combine optimization algorithms with Finite Element Analysis for airbag design. A number of industry standard software packages are employed to work in coherence to complete the optimization procedure automatically with minimal user intervention. The system can be easily tailored to fit multiple performance requirements and various design constraints for different airbag systems. Compared with the commonly used Design of Experiment (DOE) method, time and computer resources requirements are greatly curtailed. The integrated optimization system was successfully used in single-chamber and dual-chamber airbag optimizations. The results proved the effectiveness of the system and demonstrated its capability in product design.

Two instrumented pulleys were developed to empirically measure the dynamic lateral forces of V-Ribbed belts used in automotive accessory drives. The first test pulley utilizes two cantilever beams cut into the pulley with strain gauges attached to measure the lateral dynamic forces in each individual belt rib caused by misalignment. A test stand which simulates multiple accessory drive configurations at low-end drive speeds typical in automotive engines was implemented to create the dynamic response necessary. This test stand allows variations in lateral offset, toe, camber, tension, and span length, as well as in the speed of the system through a variable speed AC motor. The second test pulley utilizes a unidirectional load cell oriented to measure the total lateral force on the test pulley. After conducting static calibration tests of the two experimental systems, dynamic results were obtained using real time data acquisition.

A computational study of flow developments over airfoils with backward-facing steps is conducted to explore the possibility of enhancing aerodynamic performance of the airfoils by vortex generation. The study focuses on the effects of the separated flow and subsequent vortex formation generated by the step on pressure distributions around two airfoil profiles. Step location and size are varied to determine their effect on lift, drag, and L/D ratio. A discussion of the effects and trends of the various step configurations on airfoil performance is presented along with the results that may serve as a reference for employing a control criteria to optimize airfoil geometries during flight.

Wing tip sails were investigated to determine potential aerodynamic improvements for a wing having an aspect ratio of 10 and a taper ratio of 0.43. The airfoil section used for the wing was an NLF- 0215 and the wing tip was rounded. Three tip sails were utilized for all investigations with each tip sail having a root chord that was 20 percent tip chord of the wing. The wing sails were mounted at the tip of the wing along the chord line. Looking along the span towards the wing root the orientation of each sail tip was the same as the wing tip. Initial studies used sails constructed from two Wortman airfoils. A generic cambered tip-sail was also investigated. Individual sail angle of attack as well as sail dihedral and anhedral were investigated. PMARC, an aerodynamic paneling code was used to predict lift, induced drag, and viscous drag with the use of a momentum integral analysis. All viscous predictions were calculated for a Re/foot = 2.19 × 106.

The flow over a NACA 0015 airfoil with a trailing edge jet (jet flap) is investigated using computational and experimental capabilities to determine the influence of the jet on vortex developments over the airfoil. The computational modeling of steady flow at a Reynolds number of 43,000 at fifteen and twenty degrees indicates that as the jet mass flow rate is increased, the trailing edge jet suppresses vortex development, and in some cases, reattaches the flow. Experimental visualization shows the suppression of vortex structures in both steady and accelerating flow. The trailing edge jet may thus be a possibility for vortex control.

Wings constructed using the Wortmann FX 63-137 low speed airfoil, which operates in a Reynold's number range from 0.28 * 106 to 0.7 * 106, with the addition of winglets are studied to determine the winglet geometry that produces the best increase in wing efficiency. The analysis was done using VSAERO, an inviscid panel code program. All configurations are compared to a wing without winglets to determine the percent increase in efficiency. It is demonstrated that with proper selection of winglet taper ratio, tip setback, height, cant angle, geometric twist angle, and airfoil section induced drag can be significantly reduced. Wings with winglets are shown to be more efficient than wings without winglets for all cases.

A computational method was developed for investigating boundary layer control. Solutions of the Reynolds-averaged Navier-Stokes equations were obtained using the two-equation k-∈ turbulence model which includes the low-Reynolds-number effect in the near-wall region. Stream function and vorticity together with the turbulent kinetic energy and its dissipation rate were calculated for the flowfield in a body-fitted coordinate system. By increasing the amount of suction on the upper surface, flow separation could be totally eliminated. Transition from laminar to turbulent flow was delayed. Aerodynamic performance was substantially improved.

The findings of various investigators during the past decade have greatly enhanced the ability to accurately analyze, model, design, and optimize finned tube heat exchangers, including those for automotive air conditioning condensers and evaporators. One parameter quite often neglected is the thermal contact resistance which exists for interference-fitted fin-tube geometries. This paper presents the results of including thermal contact resistance as a parameter in estimating the performance of finned tube heat exchangers.

The scissor wing configuration is analyzed for unequal forward/rearward wing area ratios and for different wing sweep schedules of the forward and rearward wings. Clα, CMα, static margin, and sweep schedule results are presented as a function of flight Mach number for various sweep schedules and two wing area ratios. Complete aircraft, lift to drag ratio, and power required results are presented for the configuration that was able to maintain static margin over the largest range of Mach numbers. The potential benefits of the scissor wing configuration are presented and discussed in terms of potential increased performance potential or smaller engine.

An experimental study is conducted to investigate the vortex developments over high angles of attack flat plate airfoils in an accelerated-decelerated flow. To preform the required experiments, a new experimental system was developed and incorporated into an open return subsonic wind tunnel. The system was employed to visualize the details of vortex structures and processes over and downstream of the airfoils for an angle of attack range between 30° and 90°. While flow acceleration encouraged flow separation and vortex convection, flow deceleration delayed the convection of the primary vortex structures as well as the reverse flow reattachment and shredding. The details provided in the article may help in developing control possibilities of vortical flow over vehicles or structures subjected to accelerating-decelerating motions. Further, the study presents guidelines to develop unsteady flow experimental arrangements suitable for incorporation into steady flow subsonic wind tunnels.

Two dimensional fourth order boundary layer calculations were made for flows over a flat plate with and without flush mounted surface heating. Constant wall temperature, increasing wall temperature and decreasing wall temperature heating cases were studied for different surface heating lengths. The boundary layer properties; temperature, tangential velocity, normal velocity, vorticity and transition location were studied for these temperature distributions. The boundary layer results indicate that with the proper selection of surface temperature variation and length the transition location can be either increased or decreased. Modified boundary layer properties, due to heating are shown to persist well after heating is stopped, even when the flow is turbulent. The results indicate that this technique may be useful in modifying transition and separation locations over airfoils.

Numerical solutions of the Reynolds-averaged Navier-Stokes equations were obtained with the two-equation K-ϵ turbulence model. Considering the low-Reynolds-number effect in the closed vicinity of a solid boundary, a stream function and vorticity method was developed to consider both the laminar and turbulent stresses throughout the two-dimensional, incompressible flowfield of any arbitrary geometry. At a low Reynolds number (Re = 30), the initially imposed disturbances around an airfoil are damped out; the flow is laminar. At a moderately high Reynolds number (Re = 1000), instability of laminar flow is obtained by exhibiting cyclic patterns in the stream function and vorticity distributions. Nevertheless, only laminar stress occurs in the entire flowfield. At a higher Reynolds number (Re = 106), turbulent stress, which is about three orders of magnitude larger than the laminar stress, occurs at a certain distance downstream of the leading edge and in the wake region.