Energy absorption capability of thin-walled aluminium tubes under crash loading

This paper investigates the interaction of design factors such as tube thickness, tube length, and tube cross-sectional aspect ratio, along with friction and impacting mass on crashworthiness parameters such as specific energy absorption contact time, peak force and crush distance. The impact velocity is assumed to be constant at 15 m/s. The focus is on rectangular aluminium tubes and the analysis was carried out by using a validated finite element model. The analysis shows that the factors are not independent of each other and there is some degree of interaction between them. It was found that the trigger mechanism is a very important design factor to be included in the design of thin-walled tubes for energy absorption applications. The effect of the friction coefficient was found to be insignificant and finally, based on the interactions, it can be concluded that the most effective design would be a larger tube with small wall thickness, and a larger aspect ratio to avoid buckling.Universiti Tenaga Nasional, Malaysi

A learning factory: Enhancing societal needs awareness and innovation through manufacturing class

The manufacturing course is a common course in most Mechanical and Industrial Engineering programs around the world. In this course, various aspects of product design and manufacturing process selection are discussed. Students are occasionally given the opportunity to utilize and fabricate some parts by using the discussed manufacturing technologies. To bring further appreciation to the course, the Manufacturing Course in Qatar University has added innovation and entrepreneurship with active learning. Instead of teaching the course material in one daunting block, the faculty (mentor) used a "Just in Time Teaching" strategy by integrating engineering theory and product design within a business plan. The students were divided into groups, and each group had to address a societal need within Qatar. The students were given sessions about idea generation tools and creativity techniques. Once the problem had been identified and formulated, these groups were advised and coached to prepare a comprehensive business plan that included selection of materials, manufacturing processes, organizational structure, marketing of the product, market segmentation and penetration, break-even analysis and economic analysis, as well as environmental issues. From the course assessment and student course outcomes surveys, it was found that the interest and learning curve for students increased drastically for this manufacturing course compared to previous approaches. Besides improving the interest and learning curve, the approach had indirectly exposed the student to project management skills, economic analysis, lifelong learning, communication and teamwork. On the whole, the approach was an interesting and led to further enhancing the student's learning process by using different learning styles through varied and innovative teaching techniques.qscienc

Vibratory Loads Data from a Wind-Tunnel Test of Structurally Tailored Model Helicopter Rotors

An experimental study was conducted in the Langley Transonic Dynamics Tunnel to investigate the use of a Bell Helicopter Textron (BHT) rotor structural tailoring concept, known as rotor nodalization, in conjunction with advanced blade aerodynamics as well as to evaluate rotor blade aerodynamic design methodologies. A 1/5-size, four-bladed bearingless hub, three sets of Mach-scaled model rotor blades were tested in forward flight from transition up to an advance ratio of 0.35. The data presented pertain only to the evaluation of the structural tailoring concept and consist of fixed-system and rotating system vibratory loads. These data will be useful for evaluating the effects of tailoring blade structural properties on fixed-system vibratory loads, as well as validating analyses used in the design of advanced rotor systems

Investigation of the temperature-relatedwear performance of hard nanostructured coatings deposited on a s600 high speed steel

Thin hard coatings are widely known as key elements in many industrial fields, from equipment for metal machining to dental implants and orthopedic prosthesis. When it comes to machining and cutting tools, thin hard coatings are crucial for decreasing the coefficient of friction (COF) and for protecting tools against oxidation. The aim of this work was to evaluate the tribological performance of two commercially available thin hard coatings deposited by physical vapor deposition (PVD) on a high speed tool steel (S600) under extreme working conditions. For this purpose, pin-on-disc wear tests were carried out either at room temperature (293 K) or at high temperature (873 K) against alumina (Al2O3) balls. Two thin hard nitrogen-rich coatings were considered: a multilayer AlTiCrN and a superlattice (nanolayered) CrN/NbN. The surface and microstructure characterization were performed by optical profilometry, field-emission gun scanning electron microscopy (FEGSEM), and energy dispersive spectroscopy (EDS).Funding: This research was made possible by an NPRP award NPRP 5-423-2-167 from the Qatar National Research Fund (a member of The Qatar Foundation)

Osteolytic clear cell meningioma of the petrous bone occurring 36 years after posterior cranial fossa irradiation: Case report

Objective and importance While bone invasion and hyperostosis are frequent phenomena in meningiomas, primary intraosseous meningiomas are rare and their occurrence in the skull base is an extraordinary exception. Moreover, radiation-induced meningiomas represent a unique clinical dilemma given the fact that patients with these tumors had often received a prior full course of radiotherapy. Clinical presentation A 42-year-old man presented with a 3-month history of progressively worsening facial asymmetry. His medical history was consistent for a posterior cranial fossa irradiation at the age of 6 years for a non-confirmed brain stem tumor. On admission his Karnofsky performance status was graded as 50% and his neurological examination showed a complete right facial nerve paralysis and hearing impairment. Computed tomography and magnetic resonance imaging demonstrated an osteolytic tumor invading the whole right petrous bone without intracranial involvement. Intervention As the tumor reached the external auditory canal, a tissue sample was obtained locally. Pathological examination of the lesion identified a grade II clear cell meningioma and the patient was consequently addressed for an intensity modulated radiation therapy. His condition remained unchanged till the most recent follow-up examination, 8 months later. Conclusions To the best of our knowledge, a radiation induced osteolytic clear cell meningioma of the petrous bone has not been previously reported. As little literature exists regarding the use of adjuvant therapies for these tumors, intensity modulated radiation therapy remains an attractive treatment option in case of pervious irradiation and general status alteration

Mechanical and microstructure characterization of hard nanostructured N-bearing thin coating

Tools for machining are made of hard steels and cemented carbide (WC-Co). For specialized applications, such as aluminium machining, diamond or polycrystalline cubic boron nitride are also used. The main problem with steel, is that it exhibits a relatively low hardness (below 10GPa) which strongly decreases upon annealing above about 600K. Thus, the majority of modern tools are nowadays coated with hard coatings that increase the hardness, decrease the coefficient of friction and protect the tools against oxidation. A similar approach has been recently used to obtain a longer duration of the dies for aluminium die-casting. Multi-component and nanostructured materials represent a promising class of protective hard coatings due to their enhanced mechanical and thermal oxidation properties. Surface properties modification is an effective way to improve the performances of materials subjected to thermo-mechanical stress. Three different thin hard nitrogen-rich coatings were mechanically, microstructurally, and thermally characterized: a 2.5 micron-thick CrN-NbN, a 11.7 micron-thick TiAlN, and a 2.92 micron-thick AlTiCrxNy. The CrN-NbN coating main feature is the fabrication by the alternate deposition of 4nm thick-nanolayer of NewChrome (new type of CrN, with strong adhesion and low coating temperature). All the three coatings can reach hardness and elastic modulus in excess of 20, and 250 GPa, respectively. Their main applications include stainless steel drawing, plastic materials forming and extrusion and aluminum alloys die-casting. The here studied TiAlN (SBN, super booster nitride) is one of the latest evolution of TiAlN coatings for cutting applications, where maximum resistance to wear and oxidation are required. The AlTiCrxNy combines the very high wear resistance characteristic of the Cr-coatings and the high thermal stability and high-temperature hardness typical of Al-containing coatings. All the coatings were deposited on a S600 tool steels. The coatings were subjected to two different thermal cycling tests: one for 100 thermal cycles consisting of 60 s dwelling time, respectively at the high- (573 to 1173 K) and at the room-temperature, a second for 100 thermal cycles consisting of 115s dwelling time, at same temperatures of the first test, followed by 5s dwelling at room-temperature. The investigated coatings showed a sufficient-to-optimal thermal response in terms of stability of hardness, elastic modulus, and oxidation behavior. The temperature induced hardness and elastic modulus coating variations were measured by nanoindentation.NPRP grant # NPRP5–423–2–167, from the Qatar National Research Fund (a member of Qatar Foundation