Coupled phenomenological and fracture mechanics approach to assess the fracture behaviour of TWC piping component

The present study demonstrates the numerical prediction of experimental specimen J-R curve using Gurson-Tvergaard-Needleman phenomenologically based material model. The predicted specimen J-R curve is used to determine the geometric independent initiation fracture toughness (J_SZWc) value that compares well with experimental result. Using the experimentally determined and numerically predicted J_SZWc values and specimen J-R curves, the accuracy of predicting the fracture behaviour of the cracked component is judged. Thus the present study proposed a coupled phenomenological and fracture mechanics approach to predict the crack initiation and instability stages in cracked piping components using numerically predicted specimen J-R curve obtained from tensile specimens testing data.     

High Oxygen Nanocomposite Barrier Films Based on Xylan and Nanocrystalline Cellulose

Nano-Micro Letters - The goal of this work is to produce nanocomposite film with low oxygen permeability by casting an aqueous solution containing xylan, sorbitol and nanocrystalline cellulose. The...     

A Numerical Approach to Investigate the Effect of Temperature on Constraint Factor of Ti Alloy Under Static Indentation Conditions

Temperature dependence of constraint factor i.e. the ratio of static indentation hardness to uniaxial flow stress was studied for Ti–6Al–4V from RT to 673 K using FEA. Surface-to-surface contact with finite sliding, which was used to model the interaction between spherical indenter/test specimen and the constitutive equations were then applied in axi-symmetric FE model. The results obtained from numerical analysis were in good agreement with the modified Expanding Cavity Model. Meyer’s hardness increased with average strain and strain hardening index increased from 0.19 to 0.21 with rise in temperature.     

三轴感应电阻率测井新技术

一种新型感应电阻率测井仪器能够提供远离井筒地层的三维信息,提高斜井和倾斜地层的电阻率测量精度,而且不需要接触井壁就能够直接测量地层倾角大小和方位。采用这种高精度三轴电阻率测井仪器可以减少漏掉油气层的机会,加强对储层的认识。     

Determination and Validation of Average Value of National Standard of DC Voltage Using Different Methods at CSIR-NPLI

The aim of this paper is to evaluate and validate the average value of national or secondary standard of DC voltage, using four different methods; comparison, substitution, difference and ratio method. In the paper the custom made automation program developed to control the whole measurement process is discussed as well. The automation system has been developed in the view of achieving maximal quality of metrological performance i.e. minimum measurement uncertainty and maximum reliability. It is found that measurement automation provides reliable and efficient way for the calibration of Zener based standard of DC voltage.     

Modeling of fracture and crack growth in welds operating at elevated temperatures

This paper critically examines the fundamental limitations of the available nonlinear fracture mechanics based models and procedures for predicting fracture and crack growth behavior in structural welds. It is shown that the weld fracture and crack growth data show significantly more scatter than the same data in homogeneous materials. The data scatter is linked to heterogeneity in the microstructure of the weld and the resulting differences in the deformation properties of the weld region causing cracks to meander from their expected path. Some preliminary ideas for dealing with this scatter are proposed and recommendations for future work in this area are also made.     

HALF-SPACE PROBLEM IN ONE-DIMENSIONAL GENERALIZED MAGNETOTHERMOELASTICITY

The theory of generalized thermoelasticity is used to solve the problem related to magnetothermoelastic waves produced by thermal shock in a half-space possessing finite electric conductivity. Eigenvalue approach is applied to obtain solution of the basic equations. Approximate small time solution is obtained by using Laplace transform method.     

Fundamental phenomena affecting low temperature combustion and HCCI engines,high load limits and strategies for extending these limits

Low temperature combustion (LTC) engines are an emerging engine technology that offers an alternative to spark-ignited and diesel engines. One type of LTC engine, the homogeneous charge compression ignition (HCCI) engine, uses a well-mixed fuel–air charge like spark-ignited engines and relies on compression ignition like diesel engines. Similar to diesel engines, the use of high compression ratios and removal of the throttling valve in HCCI allow for high efficiency operation, thereby allowing lower CO₂ emissions per unit of work delivered by the engine. The use of a highly diluted well-mixed fuel–air charge allows for low emissions of nitrogen oxides, soot and particulate matters, and the use of oxidation catalysts can allow low emissions of unburned hydrocarbons and carbon monoxide. As a result, HCCI offers the ability to achieve high efficiencies comparable with diesel while also allowing clean emissions while using relatively inexpensive aftertreatment technologies.