Computer modelling and simulation in materials science

The paper presents a brief overview of different types of modelling and simulation along with the distinguishing features between the two. Spatial as well as temporal size scales with a special reference to multiscale modelling are explained with illustrations. The paper includes a discussion on numerical experiments and their validation based on the authors’ work on FEM simulation of crack-tip blunting during ductile fracture. Attention is drawn to the use of a 3P technique involving integrated simulation of deformation (property) at microstructural level, the process at macroscopic level and the performance at the product level.     

A web-based virtual laboratory on a frequency modulation experiment

With the rapid proliferation of Internet technologies, accessing and operating engineering instruments remotely anytime anywhere is fast becoming a reality. This paper presents a new Web-based virtual laboratory on a frequency modulation experiment for the teaching of an undergraduate course on communication principles in the National University of Singapore (NUS). The laboratory requires only a common Web browser to access and incorporate schemes for reducing data traffic and authenticating users. It enables students to have a natural hands-on experience of using an expensive spectrum analyzer on a one-to-one basis and provides a solution for distant engineering education. The system uses a double client-server structure where access to the experiment is via two rounds of client-server processing. The virtual laboratory can be accessed at the Web site http://vlab.ee.nus.edu.sg/vlab/freqmod/index.html     

The role of signaling in quality of service enabled networks

In this article we identify the common building blocks that enable some networks to provide better than best-effort transfer guarantees to the traffic they carry. We consider the role signaling plays in such a network and argue in favor of pinned routes, with a highly efficient pinning process, to improve network stability and to ease the task of maintaining QoS guarantees in the face of changing network characteristics, including failures; the use of broad QoS classes to determine the path that a particular flow should follow through the network; and providing the flexibility of specifying the detailed QoS for the flow, if needed, at any arbitrary time during the life of the flow. We conclude that a flexible signaling architecture is an essential enabling component of any QoS-aware network. We present an overview of the design and implementation of UNITE, as an example of a signaling architecture that embodies these attributes. More generally, we consider the relationship between QoS-related signaling and other protocols and mechanisms that may form part of an overall QoS-enabled network and service infrastructure     

Process capability indices and product reliability

This paper discusses process capability indices—C_p and C_pk, their underlying assumptions, and the relationships between process capability indices and product reliability. An actual case is presented to demonstrate this relationship.     

Sources of time‐varying contact stress and misalignments in wind turbine planetary sets

Recent data shows that 90% of large wind turbines include a gearbox, and industry forecasts expect this figure to remain relatively stable. With global annual volumes (2009) of around 18,600 units, the quality, cost and performance of gearboxes is of paramount importance to the wind sector. The industry has been focusing some attention on gearbox reliability, as demonstrated by a growth in the number of specific seminars and collaborative programs on this topic. One aspect that needs to be brought to an industry‐wide forum is the understanding of the complexity of bearing design in the gearbox and the careful attention that needs to be paid to ensure a reliable gearbox design. This paper seeks to address this issue by clear demonstration of design issues using a model of the gearbox from the National Renewable Energy Lab's Gearbox Reliability Collaborative. Detailed models are presented with focus on determining the quality of the function of the planetary gear stages. Key design drivers are discussed such as the quality of alignment at the gears and bearings and the loads and stresses seen on these components. Under a design load case with a significant rotor off‐axis moment the stresses in the planet gears and bearings are investigated. It is shown how the misalignment of the planet pins varies with the rotation of the planetary set and how subsequently time‐varying contact stresses and load distributions occur in the planet gears and bearings. These factors strongly influence the fatigue life of the gearbox components as well as the level of vibration. Design tools are then used to demonstrate how small variations in the clearances of the planet carrier bearings can have a big effect on the quality of the design. Numerical studies show where optimal clearance settings lie and how the misalignment of the planetary set can be improved. Furthermore, a demonstration is made of how redesign of the bearing arrangement and subsequent optimization of the planet tooth geometry further improves the misalignment and results in significantly reduced time‐varying contact stresses, better load distribution and reduced vibration. It is illustrated that small clearances, such as in the carrier bearings, can have a large effect on the performance of the design and a study shows how to identify and reduce time‐varying misalignment and contact stresses resulting in lower vibration, lower fatigue and a more reliable product. Copyright © 2011 John Wiley & Sons, Ltd.     

Plasma Arc Welding of High Strength 0.3 % C–CrMoV (ESR) Steel

0.3 % C–CrMoV (ESR) steel has been proposed as an alternate cost effective material for fabrication of solid boosters for satellite launch vehicles. PAW studies on 7.8 mm thick 0.3 % C–CrMoV (ESR) steel have been conducted with filler wires of two different compositions. Welding parameters have been established for the steel. Welding has been carried out with stainless steel and copper back-up bars and effect of the same has been evaluated. Weldment has been characterized through optical microscopy, microhardness and mechanical properties evaluation. It is found that filler wire chemistry (low carbon content) does not significantly affect the properties of weldments subjected to post weld hardening and tempering treatment. It is attributed to low dilution in thicker plate welding and diffusion of carbon from base metal side during hardening treatment of the weldment. Use of different back- up bars also show similar results, except for process difficulties noted while using stainless steel. Weld efficiency >85 % has been observed with weldments having microhardness in the range of 480–520 VHN.     

Chemical,antioxidant, functional and thermal properties of rice bran proteins after yeast and natural fermentations

The paper focuses on the chemical, antioxidant, functional and thermal properties of rice bran proteins after yeast, natural fermentations and unfermented rice bran. Protein content of yeast‐fermented rice bran protein concentrate (YFRBPC), naturally fermented rice bran protein concentrate (NFRBPC) and unfermented rice protein concentrate (UFRBPC) were 72.50%, 68.92% and 65.73%, respectively, while ash content were 4.72%, 4.61% and 3.04%, respectively. The total amino acids of YFRBPC, NFRBPC and UFRBPC were 123.16, 118.45 and 99.39, respectively. DPPH radical inhibition of YFRBPC, NFRBPC and UFRBPC were 58.62%, 55.29% and 47.14%, respectively, while ferric reducing ability power were 0.73, 0.58 and 0.41 mmol TE per gram, respectively. The highest foam capacity of UFRBPC (57.56%), NFRBPC (64.15%) and YFRBPC (76.00%) was observed at pH 9.0. YFRBPC and NFRBPC were lighter in colour than UFRBPC. YFRBPC had higher denaturation temperature and enthalpy value than NFRBPC and UFRBPC. The β‐sheets structures were more in YFRBPC and NFRBPC than UNFBPC.     

Emission and performance analysis of a diesel engine burning cashew nut shell oil bio diesel mixed with hexanol

In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel. Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10% (by volume) of hexanol and 90% (by volume) neat cashew nut shell biodiesel was referred to as CNSBD900H100 and fuel comprising 20% (by volume) of hexanol and 80% (by volume) of neat cashew nut shell biodiesel was referred to as CNSBD800H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at 10% and 20% (by volume) to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine.