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Notched spoilers may be used to suppress flow-induced cavity resonance in vehicles with open sunroofs or side windows. The notches are believed to generate streamwise vortices that break down the structure of the leading edge cross-stream vortices predominantly responsible for the cavity excitation. The objectives of the present study were to gain a better understanding of the buffeting suppression mechanisms associated with notched spoilers, and to gather data for computational model verification. To this end, experiments were performed to characterize the surface pressure field downstream of straight and notched spoilers mounted on a rigid wall to observe the effects of the notches on the static and dynamic wall pressure. Detailed flow velocity measurements were made using hot-wire anemometry. The results indicated that the presence of notches on the spoiler reduces drag, and thus tends to move the flow reattachment location closer to the spoiler.

In this study, friction-induced vibrations of the window sealing system of a vehicle were investigated using a detailed numerical model. A lumped element, single-degree-of-freedom model was first developed for verification of the numerical procedures. An approximate expression for the frequency of the stick-slip oscillations was obtained. The model indicated that the frequency decreased as the normal force and the difference between the static and kinetic friction coefficients were increased. Stick-slip oscillations were then simulated using a finite element model of a glass run seal using an explicit time marching method. The motion of the seal during the slipping phase was in the direction of the friction force. The peak frequency was found to vary according to the glass position on the seal surface. The results indicated that both the periods of the stick and slip phases of the seal motion affect the frequency of the stick-slip oscillations.

As the world grapples to combat the spread of COVID-19, our city streets have nearly emptied. Unprecedented community mitigation interventions have been applied in efforts to “flatten the curve” and slow the transmission of the virus. Social distancing measures have dramatically altered our daily behavior; notably, in the ways we do or do not move. This report seeks to identify emerging trends in urban mobility and road safety in respect to COVID-19. This is followed by a discussion of how we could shape our mobility future as communities begin to reopen.

Dual phase steels are being extensively considered as a structural material for automobiles because of the favourable combination of strength and formability. Crashworthiness of these new steels is an area of great importance. High strain rate testing is one approach to measure the ability of materials to absorb energy in a crash situation. The objective of this paper is to examine the effect of the deformation rate on the mechanical properties of dual-phase and multi-phase steels. Shear-punch experiments are conducted both at quasi-static and dynamic rates for this purpose. The ease of preparation of shear punch specimens compared to the tension specimen makes this approach attractive in evaluating key mechanical properties, such as ultimate tensile strength (UTS) and ductility limits, of automotive materials mostly in sheet forms.

The evolution of microstructure in a Mg 3.4%AI-0.16%Zn-0.33%Mn alloy tube was studied during deformation by ring hoop tension testing (RHTT). When the tests were carried out at moderate temperatures and relatively high strain rates, the accompanying c-axis strains were mainly accommodated by twin formation. At temperatures above 200°C and the lowest strain rate (0.001s-1), the formation of voids in the partially dynamically recrystallized regions caused premature fracture. The microstructural development in hot gasformed samples was similar to that observed during RHTT testing. These results indicate that RHTT testing is an effective way of studying the deformation behavior of Mg alloys during tube gas forming.

Aircraft development projects at Bombardier Aerospace involve a large number of tasks executed by a network of professionals from various disciplines. As the complexity of products and the development process increases, it becomes more difficult to manage the interactions among tasks and people. In fact, it may be impossible to even predict the impact of a single design decision across the development process. At Bombardier, investigation has shown that there was a lack of communication between design processes when dealing with aeroelasticity information. This resulted in duplicated design effort, reduced quality, and increased time to complete tasks when small design changes from one task induced delays in other tasks. Processes that deal with aeroelasticity work integrate system inertial, aerodynamics and structural information to make aircraft models and perform analyses. These processes have been creating similar models to perform aeroelasticity analyses.

The high computational cost of 3-D viscous turbulent aero-icing simulations is one of the main limitations to address in order to more extensively use computational fluid dynamics to explore the wide variety of icing conditions to be tested before achieving aircraft airworthiness. In an attempt to overcome the computational burden of these simulations, a Reduced Order Modeling (ROM) approach, based on Proper Orthogonal Decomposition (POD) and Kriging interpolation techniques, is applied to the computation of the impingement pattern of supercooled large droplets (SLD) on aircraft. Relying on a suitable database of high fidelity full-order simulations, the ROM approach provides a lower-order approximation of the system in terms of a linear combination of appropriate functions. The accuracy of the resulting surrogate solution is successfully compared to experimental and CFD results for sample 2-D problems and then extended to a typical 3-D case.

The high strain rate deformation behavior of commercially available dual phase steel was studied by means of split Hopkinson bar apparatus in shear punch mode with an emphasis on the influence of microstructure. The cold rolled sheet material was subjected to a variety of heat treatment conditions to produce several different microstructures. Dual phase microstructures with different fractions of martensite were obtained by changing intercritical annealing temperature and time. Various microstructures of ferrite plus pearlite, or acicular ferrite/bainite, or bainite and martensite/carbide were obtained by changing the cooling rate after annealing. The effects of low temperature tempering and bake hardening treatment were also investigated for some selected specimens.

Piezoelectrically driven Synthetic Jet Actuators (SJAs) are a class of pulsatile flow generation devices that promises to improve upon steady forced cooling methods in air flow generation, surface cleaning and heat transfer applications. Their acoustic emissions and vibrations, an intrinsic by-product of their operation, needs to be mitigated for applications in noise-sensitive contexts. Already used for aerodynamic control [1, 2], thrust vectoring [3], spray control [4], and heat transfer [5, 6], they are increasingly being considered for sensor lens cleaning in automobiles. In this study, the sound generation mechanisms of SJAs are discussed and an active noise reduction method is proposed and evaluated. Driven with a single frequency sinusoidal input, SJAs produce acoustic emissions at harmonic frequencies within the frequency range of speech communication.

Tempered martensite assisted steels are of recent research interest for good strength and ductility combination. This paper discusses the effect of tempered martensite volume fraction on the final properties of cold rolled and subcritically annealed Al containing TRIP steel. The samples were TRIP annealed and the retained austenite volume fraction was measured using X-ray diffraction technique. The steel samples were subsequently cold rolled to obtain strain induced martensite, deformed ferrite and bainite in the microstructure. The final tempered martensite volume fraction corresponds to the initial retained austenite volume fraction of the steel. The cold rolled TRIP steel samples were subsequently subcritically annealed at 500°C for 1 hour to obtain tempered martensite, fine ferrite and bainite. Shear Punch testing was used to evaluate the mechanical properties. The properties are analyzed and the results are discussed.

The deformation characteristics of a commercial AZ31 magnesium sheet alloy were investigated at elevated temperatures. Tensile experiments were conducted at temperatures 300°C, 400°C and 450°C and at strain rates, 0.001s-1, 0.01s-1 and 0.1s-1. Depending on the test temperature, fracture analysis of failed specimens revealed three different types of failure: (1) by moderate necking, (2) by interlinkage cavity, (3) by strong necking. Plastic strain ratios, r-values were derived from the strain ratios of width and thickness of the fractured tensile specimens. The r-value increased with increasing temperature and strain rate.

The development, analysis, and comparison of battery electric class-4 medium-duty trucks equipped with three possible powertrain layouts, namely, direct drive, single-speed gearbox, and two-speed transmission options, are discussed in this paper. The problem definition is included and the performance evaluation criteria for the proposed truck architectures are defined, namely, acceleration time, top speed, and efficiency. Designs of four new traction motors are proposed and their benefits compared for use in medium-duty electric trucks (e-trucks). The procedure for gear-ratio range selection is outlined, the ranges of gear ratios for the single-speed gearbox and two-speed transmission powertrains being calculated for each of the proposed electric traction motors. The simulation and gear-ratio optimization tasks for the e-trucks are formulated. The energy consumption of the e-truck with the three possible powertrain combinations is minimized over the six driving cycles.

Understanding the role of the slip systems and their evolution with temperature is critical to the correct simulation of the mechanical behavior of magnesium alloys. In this paper, relations are proposed for evolution of the CRSS values of different slip systems and strain-rate sensitivity factor, stating them as functions of temperature and strain-rate. These relations are used in conjunction with the Crystal Plasticity Finite Element (CPFE) model for prediction of stress-strain curves and r-values at elevated temperatures (75°C to 250°C). The new relations can predict the decrease in stress level, the anisotropy of the material, and the decrease in the difference between the r-values in the RD and the TD with the increase in temperature. The results confirm the trends predicted with Taylor-type and VPSC models. In particular, they confirm the high activity of the slip systems at higher temperatures.