Search Results

Nowadays, moving toward more lightweight designs is the key goal of all major automotive industries, and they are always looking for more mass saving replacements. In this study, a new methodology for the design and optimization of cross-car beam (CCB) assemblies is proposed to obtain a more lightweight aluminum design as a substitution for the steel counterpart considering targeted performances. For this purpose, first, topology optimization on a solid aluminum geometry encompassing the entire design space should be carried out to obtain the element density distribution within the model. Reinforcing locations with high element density and eliminating those with density lower than the threshold value result in the conceptual design of the CCB. To attain the final conceptual design, the process of topology optimization and removal of unnecessary elements should be addressed in several steps.

Quasicrystalline (QC) coatings were evaluated as leading-edge protection materials for rotor craft blades. The QC coatings were deposited using high velocity oxy-fuel thermal spray and predominantly Al-based compositions. Ice adhesion, interfacial toughness with ice, wettability, topography, and durability were assessed. QC-coated sand-blasted carbon steel exhibited better performance in terms of low surface roughness (Sa ~ 0.2 μm), liquid repellency (water contact angles: θadv ~85°, θrec ~23°), and better substrate adhesion compared to stainless steel substrates. To enhance coating performance, QC-coated sand-blasted carbon steel was further exposed to grinding and polishing, followed by measuring surface roughness, wettability, and ice adhesion strength. This reduced the surface roughness of the QC coating by 75%, resulting in lower ice adhesion strengths similar to previously reported values (~400 kPa).

Friction stir spot welding of Mg-alloy AZ91 is investigated. The temperature cycles within the stir zone and in the TMAZ region are examined using thermocouples, which are located within the tool itself and also by locating thermocouples in drilled holes at specific locations relative to the bottom of the tool shoulder and the periphery of the rotating pin. The measured temperatures in the stir zone range from 437°C to 460°C (0.98Ts, where Ts is the solidus temperature in degrees Kelvin) in AZ91 spot welds produced using plunge rates from 2.5 and 25 mm/s. The thermal cycle within the stir zone formed during AZ91 spot welding could not be measured by locating thermocouples within the workpiece in drilled holes adjacent to the periphery of the rotating pin.

The use of natural fibers for polymer composite materials has increased tremendously in the last few years. This type of reinforcements offers many advantages such as low density, low cost, high specific strength and low environmental impacts. The performance of the natural fiber composites are affected by the fiber loading, the individual mechanical properties of each component (fiber and matrix), and the fiber and matrix adhesion. Concerning the interfacial interaction, natural fibers present a major drawback because of poor compatibility of fibers with most hydrophobic thermoplastic and thermoset matrix. Hemp fiber/acrylic composites were manufactured with sheet molding technique recently. Although mechanical tests give promising results, they exhibit low tensile strength resulting from a poor fiber/matrix adhesion. The moisture resistance property of the sheet molded composites also needs further improvement.

A counter–flow propane/air diffusion flame (ϕ= 1.79) is used for a fundamental analysis of the effects of oxygenated additives on soot precursor formation. Experiments are conducted at atmospheric pressure using Gas Chromatography for gas sample analysis. The oxygenated additives dimethyl carbonate (DMC) and ethanol are added to the fuel keeping the total volumetric fuel flow rate constant. Results show 10 vol% DMC significantly reduces acetylene, benzene, and other flame pyrolysis products. Ethanol (10 vol%) shows, instead, more modest reductions. Peak acetylene and benzene levels decrease as the additive dosage increases for both DMC and ethanol. The additive's effect on the adiabatic flame temperature and the fuel stream carbon content does not correlate significantly with acetylene levels. However, there does appear to be a linear relationship between acetylene concentrations and both the additive's oxygen and C–C bond content.

In this work hemp fibers were chemically treated in order to improve the fiber/matrix interaction in hemp fiber/unsaturated polyester composites prepared by a Resin Transfer Molding (RTM) process. Chemicals used for paper sizing (AKD, ASA, Rosin Acid and SMA) as well as a silane compound and sodium hydroxide were used to modify the fibers' surface. The tensile, flexural and impact properties of the resulting materials were measured. A slight improvement in mechanical properties was observed for the SMA, silane and alkali treated specimens. However close analysis of these tests and of the fracture surface of the samples showed that there was no amelioration of the fiber/matrix adhesion. It was found that predicted tensile strengths using the rule of mixture were very close to the experimental values obtained in this work. Finally the properties of an hybrid glass fiber/hemp fiber composite were found to be very promising

Springback is one of the main concerns in sheet metal forming with the increased use of advanced high strength steels, among which dual phase steels are gaining popularity. Although finite element analysis (FEA) has been successfully used in simulating complicated forming processes, it is difficult to accurately predict springback due to certain complex material behaviors such as the non-linear recovery behavior. In this study, the tension-unloading-reloading (TUR) test and XRD analysis have been employed to investigate non-linear recovery through Bauschinger Effect (BE) measurement at different pre-strain levels. The results demonstrated that dual phase steels exhibited the strong BE. The FEA simulation of springback prediction in the deep-draw bending test showed that the simulation accuracy was significantly improved by incorporating the Bauschinger effect.