Estimation of Uncertainty in Mechanical Testing

In this paper, the concepts associated with the procedure for estimation of uncertainty is discussed, and the application of these for the determination of uncertainty in tensile testing is illustrated

Analysis of damage in high strength steels

In continuum damage mechanics (CDM) approach, damage accumulation takes place through void initiation, growth and coalescence. In this study, a Bayesian Neural Network based model has been developed to calculate the complex relationship between the extent of damage accumulation and its influencing parameters for a variety of high strength low alloy steels. The model has been applied to confirm that the predictions are reasonable

Modelling of Crack-tip Blunting using Finite Element Method (FEM) (GAP-0088)

For determination of fracture toughness in engineering structural materials, the standard procedure specifies the generation of a crack growth resistance curve (R curve) experimentally and identification of the critical toughness parameter by the intersection of an offset to a blunting line on the R curve. The use of a theoretical blunting line, as proposed in the standards, often gives conservative fracture toughness values particularly in high toughness materials. In this project, through finite element simulation of standard fracture mechanics test specimen, the crack blunting process in ductile materials is proposed to be investigated. From the load-displacement data generated by FEM, the crack tip opening displacement (CTOD) as well as J, an energy parameter of elastic plastic fracture mechanics, and Δa, the crack extension, accompanying the blunting process have been calculated. The effect of variation of material properties like Young’s modulus, E, yield stress, σy and strain hardening parameter, n, on the shape and slope of the blunting line has been established. The numerically obtained blunting line has been validated using experimental results. Important conclusions drawn from this investigation are the following ♦ the blunting line is mildly sensitive to the level of flow stress, with the inflection occurring at a lower flow stress and with reduced sharpness as the flow stress is increased. The blunting line slope is higher in low strength materials. ♦ the nature of the blunting line is greatly dependent with the work hardening capacity of the material, with the overall slope of the blunting line increases with increased hardening behaviour. ♦ the crack tip profile is elliptical not semicircular. For the low strain hardening materials the major axis is more than the minor axis i.e. CTOD2*da

Benzyl 3-[(E,E)-3-phenyl­prop-2-enyl­idene]dithio­carbazate

The title compound, C17H16N2S2, a dithio­carbazate derivative, adopts an EE configuration with respect to the C=C and C=N double bonds of the propenyl­idine group. The 3-phenyl­prop-2-enyl­idene and dithio­carbazate fragments lie essentially in the same plane, with a maximum deviation from that plane of 0.074 (2) Å, while the dihedral angle between the 3-phenyl­prop-2-enyl­idene and the benzyl group is 77.78 (7)°. In the crystal structure, mol­ecules are linked by an N—H⋯S hydrogen bond and a weak C—H⋯S inter­action involving the terminal thione S atom, forming dimers that are arranged into sheets parallel to the bc plane. The crystal structure is also stabilized by C—H⋯π inter­actions

Predatory behaviour of a perch, Nandus nandus (Ham.)

Predatory behaviour of Nandus nandus was studied by offering Cyprinus carpio as prey. The study was conducted with six N. namdus (8.2 ±0.2 cm and 7.60 ±0.3g) represented as P 1, P 2, P 3, P 4, P 5 and P 6. Three size categories of prey (C. carpio) such as small (2.0 ±0.1 cm and 0.23 ±0.01g), large (3.6 ±0.1 cm and 0.57 ±O.O.lg) and mixed group consisting of both small and large prey were used for 14 days of trial. Predatory behavior was classified as targeting, driving, catching, handling, resting and next attempt of catching prey. After introduction of prey into the aquarium predators followed the movement of preys by eye movements and tried to target smaller one first. The predator grasped the head of the prey by its jaws by a drive and engulfed it wholly into the mouth. The average handling time (time taken to manipulate and swallow prey from capture to ceasation of pharyngeal movement) was 42±2 sec and 47±2 sec for small and large prey respectively. N. nandus were ingested more small prey than large prey though the size classes were equally available in case of mixed prey used. Although the prey consumption was higher in number when small prey were ingested but in weight the consumption was higher when ingested large size of prey. The study indicated that N. nandus, ingested more small prey and grasped the headfirst

Preparation and Properties of BaBiBO4-SiO2 Glasses

Glasses in the new system (100-x) BaBiBO4–xSiO2 where x = 10–50 (mol%) were prepared by the melt-quench technique. The density of the glasses increases with an increase in BaBiBO4 content because of its higher molecular mass. Tg, Td,and Ts decrease while coefficient of thermal expansion increases with the increase in BaBiBO4 content. Vis-NIR spectra reveal that with increasing melting temperature transmission of the glasses decreases due to auto thermal reduction of Bi31 to Bi0 as confirmed by transmission electron microscopy and selected area electron diffraction analyses. Fourier transform infrared reflection spectroscopic spectra of the glasses indicate the formation of BiO6, BO3, and BO4 structural units. Ferroelectric BaBiBO4 crystalline phase is obtained from these glasses by controlled heat treatment at 5801C. X-ray diffraction analysis reveals its 45–66nm crystallite size range. Whereas, the field-emission scanning electron microscopy images show the formation of polycrystalline spherical grains of 89–194nm along with single-crystalline microrods of average diameter of 0.5–1.5 mm. Dielectric constant of the glasses increases with increase in BaBiBO4 content, which is attributed to the combined effects of high polarization and ionic refraction of both Bi31 and Ba21 ions. It is shown here that BaBiBO4–SiO2 is a promising glass system for the synthesis of glass–ceramics of novel BaBiBO4 nonlinear optical crystal

Cyclic plastic deformation behaviour of PHT piping materials - an experimental investigation

The work presents the cyclic plastic deformation behaviour of two varieties of primary heat transport piping materials to understand the hardening/softening behaviour, load history memory, strain range effect, mean stress effect and ratcheting behaviour. Microstructural changes during cyclic deformation manifest in cyclic expansion of yield that could be used to explain the hardening/softening behaviour. Both the materials memories the prior history, however, the effect disappears after some time. Both the steels exhibit non-Masing behaviour due to inhomogeneous substructural changes. Non-Masing behaviour could be explained through cyclic expansion of yield. Engineering stress controlled ratcheting experiments were noted to be inadequate and under predict the ratcheting fatigue life. Importance of true stress controlled ratcheting experiments were discussed

Low cycle fatigue and cyclic plasticity bahaviour of Indian PHWR / AHWR primary piping materials

The integrity assessment of the primary piping components needs to be demonstrated under normal operation cyclic loadings as well as under complex cycling loadings of extreme magnitude as may come during a severe earthquake event. In order to understand material's cyclic plasticity and fatigue ratcheting behaviour, systematic experimental and analytical investigations have been carried out on specimens of SA333Gr.6 carbon steel and SS304LN stainless steel. The materials specification of SA333Gr.6 is same as used in Primary Heat transport (PHT) piping of Pressurized Heavy Water Reactors (PHWRs) and materials specification of SS304LN steel is same as proposed for Indian Advanced Heavy Water Recactor (AHWRs) Main Heat Transport (MHT) piping. The test program included the properties and cyclic plasticity behaviour. The results of these tests have been investigated in detals using few popular finite element cyclic plasticity models to understand and quantify the materials' cyclic plasticity behaviour. The studies revealed the need to modify the Chaboche model to simulate the LCF/cyclic plasticity and ratcheting under different stress/strain amplitude loading conditions. On accounting for modification, the Chaboche model nicely predicted the LCF and ratcheting response for all the tests. The tests, finite element analyses results and their interpretations have been presented in this paper

Fatigue crack growth retardation in an HSLA steel in benign environments

The crack growth and closure were examined for fatigue loading of an HSLA steel in non-corroding media. R and ΔK dependent significant crack growth retardation was observed in NaOH. Presence of a passive film at high R and self repair of the film and formation of an additional oxide layer at low R could explain the retardation

Effects of SiO(2) and TiO(2) fillers on thermal and dielectric properties of eco-friendly bismuth glass microcomposites of plasma display panels

The effects of SiO(2) (amorphous) and TiO(2) (crystalline, rutile) fillers on softening point (T (s)), glass transition temperature (T (g)), coefficient of thermal expansion (CTE), and dielectric constant (E >) of zinc bismuth borate, ZnO-Bi(2)O(3)-B(2)O(3) (ZBIB) glass microcomposites have been investigated with a view to its use as the white back (rear glass dielectric layer) of plasma display panels (PDPs). The experimentally measured properties have also been compared with those of theoretically predicted values. Both the experimental and theoretical trends of these properties with added filler contents correlate very well. The interaction of fillers with glass which occurred during sintering at 560A degrees C has also been monitored by XRD and FTIR spectroscopic analyses. The microstructures and distribution of fillers in the glass matrix have been analyzed by SEM images. It is observed that the fillers have partially dissolved in the glass at the firing temperature leaving some unreacted filler as residue which results in ceramic-glass microcomposites. In consideration of the desired properties of white back of PDPs, the addition of TiO(2) filler to ZBIB glass is found to be more preferable than SiO(2) filler. The addition of 10 wt% TiO(2) filler yielded T (s), T (g), CTE and E > values of 560A degrees C, 480A degrees C, 82 x 10(-7)/K and 14 center dot 6 which are found to meet the desired values of < 580A degrees C, < 500A degrees C, < 83 x 10(-7)/K and < 15, respectively with respect to use of PD200 glass as substrate in PDP technology