Effect of strain rate on quasistatic tensile flow behaviour of solution annealed 304 austenitic stainless steel at room temperature

Room temperature tensile test results of solution annealed 304 stainless steel at strain rates ranging between 5 × 10⁻⁴ and 1 × 10⁻¹ s⁻¹ reveal that with increase in strain rate yield strength increases and tensile strength decreases, both maintaining power–law relationships with strain rate. The decrease in tensile strength with increasing strain rate is attributed to the lesser amount of deformation-induced martensite formation and greater role of thermal softening over work hardening at higher strain rates. Tensile deformation of the steel is found to occur in three stages. The deformation transition strains are found to depend on strain rate in such a manner that Stage-I deformation (planar slip) is favoured at lower strain rate. A continuously decreasing linear function of strain rate sensitivity with true strain has been observed. Reasonably good estimation for the stress exponent relating dislocation velocity and stress has been made. The linear plot of reciprocal of strain rate sensitivity with true strain suggests that after some critical amount of deformation the increased dislocation density in austenite due to the formation of some critical amount of deformation-induced martensite plays important role in carrying out the imposed strain rate.     

Household energy consumption pattern and socio-cultural dimensions associated with it: A case study of rural Haryana, India

A survey of household energy consumption pattern was carried out in a village of Jhajjhar district of Haryana, India in the year 2007. The households surveyed covered heterogeneous population belonging to different income, educational and social groups. There was more availability and utilization of solid biomass fuels as energy resources in domestic sector as compared to the commercial fuels. Dung cakes, crop residues and firewood were found to be the three main fuels used for cooking, though LPG was also used along with biomass fuels. But complete conversion to cleaner fuels has not taken place yet even in households that has been using LPG for many years. Income was an important factor determining the choice of fuel for cooking, but there were some socio-cultural factors which were equally important in making fuel preferences at household level.     

Novel Cu/Cr/Ge/Pd Ohmic Contacts on Highly Doped n-GaAs

The thermal stability of the Cu/Cr/Ge/Pd/n⁺-GaAs contact structure was evaluated. In this structure, a thin 40 nm layer of chromium was deposited as a diffusion barrier to block copper diffusion into GaAs. After thermal annealing at 350°C, the specific contact resistance of the copper-based ohmic contact Cu/Cr/Ge/Pd was measured to be (5.1 ± 0.6) × 10⁻⁷ Ω cm². Diffusion behaviors of these films at different annealing temperatures were characterized by metal sheet resistance, X-ray diffraction data, Auger electron spectroscopy, and transmission electron microscopy. The Cu/Cr/Ge/Pd contact structure was very stable after 350°C annealing. However, after 400°C annealing, the reaction of copper with the underlying layers started to occur and formed Cu₃Ga, Cu₃As, Cu₉Ga₄, and Ge₃Cu phases due to interfacial instability and copper diffusion.     

Weldability Evaluation and Microstructure Analysis of Resistance‐Spot‐Welded High‐Mn Steel in Automotive Application

In this paper, resistance spot weldability of high‐Mn steels were investigated in order to get high reliability in welded joints of automotive components. Microstructural characterizations, cross‐tensile test (CTT), microhardness tests of spot welded parts were conducted. The effects of weld current on the microstructural characteristics, mechanical properties, and fracture modes were investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The hardness in the weld nugget was observed to be lower than that in the base metal (BM). In CTT, the failure initiation was observed to occur at the boundary of the weld nugget. Also welding imperfections of welded parts were investigated. Liquation cracking in heat affected zone (HAZ), porosity, and shrinkage cavity were found most common welding defects in welded parts. Furthermore, the effects of welding imperfections on weld quality and failure criteria were identified and discussed.     

Correlating mechanical properties of sinter phases with their chemistry and its effect on sinter quality

In this study, pot sinter tests were carried out to study the sintering properties of iron ores of different alumina (2–4–6%) level. It was observed that the 6% alumina level ores have a higher RDI values and decreased tumbler index (TI) compared to its other two counterparts. It was observed that an increase in composite fracture toughness (CFT) of sinter improves the Tumbler as well as RDI of the sinter. Beyond 4 CFT there is remarkable improvement in TI, RDI and RI values. The mechanical strength parameters of sinter phases were further correlated and analysed with respect to the chemistry of sinter and mineralogy of sinter phases. There is strong evidence which suggests that the Al₂O₃ deteriorates the strength of the phases by making them hard and thus generating cracks in them. Unlike alumina, CaO and SiO₂ tend to stabilise and improve the strength of the phase.     

Evaluating mangroves of Krishna Wildlife Sanctuary in relation to the general status of mangroves in Andhra Pradesh,India

The present study was carried out to check whether there is a decline in mangrove cover of Andhra Pradesh state, India, as cited by a few studies. The research analysed mangrove dynamics of Krishna Wildlife Sanctuary of Andhra Pradesh state, using temporal satellite data of six periods. Analysis of these data showed major changes in the mangrove areas of the sanctuary. In 1972, the mangrove cover was 82.76 km², which then decreased to 80.47 km² in 1981, and then further dropped to 69.52 km² in 1990. Comparatively an area of 13.22 km² was lost from 1972 to 1990. The area recorded in 2000 was 101.98 km² and the positive trend of increase in mangrove areas was observed in both 2009 (138.36 km²) and in 2014 (158.16 km²). Overall, an increase of 88.64 km² mangrove area was observed from 1990 to 2014. The study confirms the increase in mangrove cover in the state, disagreeing with the observations of decrease in mangrove cover made by other studies previously.