Solubility of Nitrogen in Superaustenitic Stainless Steels During Air Induction Melting

The amount of nitrogen contained in super austenitic stainless steels (SASS) influences their properties significantly. The effect of maximum amount of nitrogen in the highly alloyed Cr and Ni SASS containing further additions of Mo and Mn is studied. The calculated nitrogen contents of the experimental alloys are compared with the actual nitrogen contents obtained in the alloys produced using induction melting furnace. The actual nitrogen content of the alloys is always lower than the calculated value, and this discrepancy is due to the presence of positive interaction parameters of Ni, Cu, and Si in the alloy. However, the yield of nitrogen in the liquid SASS is improved significantly with additions of Mn and Mo contents. The construction of multicomponent phase diagrams for SASS is demonstrated using Thermo-Calc software. SASS containing more nitrogen exhibited a very high strength without loss of toughness.     

Self-reported motorcycle riding behaviour among school children in India

Studies on traffic accidents among underage users of motorcycles are seldom seen in literature. This study was done in Yamunanagar, India where boys as young as 8 years ride motorcycles. It attempts to find out the behavioural and non-behavioural factors leading to motorcycle use and the predisposition to accidents among male school children aged between 10 and 16 years. A questionnaire was used to evaluate those factors among 1760 subjects in 38 schools. Fifteen percent of subjects had had an accident while riding motorcycle. Most of the behavioural and all the non-behavioural factors have a statistically significant influence on accident proneness. Aggressive behaviour and previous encounter with the police are the two strong predictors of accidents (p<0.001). Children as riders are exposed to higher risks of accident and longer life with disability. It also explains how these children behaviourally take up adult roles and seek adult risk taking attitudes. The implications of child motorcycle riders upon children themselves and on the society are discussed for a greater discourse on road safety motorcycle riding policy and to highlight the behavioural and non-behavioural factors that are associated with traffic accidents.     

Preparation and characterization of electrospun SiO2 nanofibers

The objective of this study was to prepare and characterize electrospun SiO2 nanofibers for composite (particularly dental composite) applications. We investigated (1) tetraethyl orthosilicate (TEOS) as the alkoxide precursor, (2) polyethylene oxide (PEO) and polyvinyl pyrrolidone (PVP) as the carrying polymers, (3) several solvents for making the spin dopes, and (4) the morphological and structural properties of the electrospun SiO2 nanofibers and their relationship with the pyrolysis temperatures. We also investigated the morphology durability of the prepared SiO2 nanofibers by subjecting them to vigorous ultrasonic vibrations. The results indicated that the uniform (beads-free) amorphous SiO2 nanofibers with an average diameter of approximately 500 nm were successfully prepared. These SiO2 nanofibers also retained their overall fiber morphology when subjected to vigorous ultrasonic vibrations. The electrospun SiO2 nanofibers were, therefore, nano-scaled glass (amorphous SiO2) fibers, and could be used for reinforcement of dental composites.     

A Study of the Influence of Superimposed Low-Frequency Modulation on the Drilling Process

A preliminary investigation of the effects of low-frequency modulation of the force in drilling has been completed. Important changes occur in the drilling of aluminum with the imposition of modulation at frequencies below 200 Hz. The effects depend on the amplitude of the modulation and the relationship of the frequency of modulation f_p to the frequency of rotation of the drill f_d. When f_p/f_d is an even integer, the modulation introduces no significant effects in the force, torque, or chip morphology. When f_p/f_d is an odd integer, the average drilling force decreases, and a large dynamic component of force and torque is seen with a frequency dependence f_p. For peak-to-peak amplitudes of vibration that are greater than one-half of the drill feed/rev, the chips are broken. A simple explanation of these effects is provided.