Anupam Agrawal

Nanoindentation of polysilicon and single crystal silicon: Molecular dynamics simulation and experimental validation

This paper presents novel advances in the deformation behaviour of polycrystalline and single crystal silicon using molecular dynamics (MD) simulation and validation of the same via nanoindentation experiments. In order to unravel the mechanism of deformation, four simulations were performed: indentation of a polycrystalline silicon substrate with a (i) Berkovich pyramidal and a (ii) spherical (arc) indenter, and (iii and iv) indentation of a single crystal silicon substrate with these two indenters. The simulation results reveal that high pressure phase transformation (HPPT) in silicon (Si-I to Si-II phase transformation) occurred in all cases; however, its extent and the manner in which it occurred differed significantly between polycrystalline silicon and single crystal silicon, and was the main driver of differences in the nanoindentation deformation behaviour between these two types of silicon. Interestingly, in polycrystalline silicon, the HPPT was observed to occur more preferentially along the grain boundaries than across the grain boundaries. An automated dislocation extraction algorithm (DXA) revealed no dislocations in the deformation zone, suggesting that HPPT is the primary mechanism in inducing plasticity in silicon.

Anisotropy of single crystal 3C-SiC during nanometric cutting

3C-SiC (the only polytype of SiC that resides in a diamond cubic lattice structure) is a relatively new material that exhibits most of the desirable engineering properties required for advanced electronic applications. The anisotropy exhibited by 3C-SiC during its nanometric cutting is significant, and the potential for its exploitation has yet to be fully investigated. This paper aims to understand the influence of crystal anisotropy of 3C-SiC on its cutting behaviour. A molecular dynamics simulation model was developed to simulate the nanometric cutting of single-crystal 3C-SiC in nine (9) distinct combinations of crystal orientations and cutting directions, i.e. (1 1 1) ⟨-1 1 0⟩, (1 1 1) ⟨-2 1 1⟩, (1 1 0) ⟨-1 1 0⟩, (1 1 0) ⟨0 0 1⟩, (1 1 0) ⟨1 1 -2⟩, (0 0 1) ⟨-1 1 0⟩, (0 0 1) ⟨1 0 0⟩, (1 1 -2) ⟨1 -1 0⟩ and (1 -2 0) ⟨2 1 0⟩. In order to ensure the reliability of the simulation results, two separate simulation trials were carried out with different machining parameters. In the first trial, a cutting tool rake angle of -25°, d/r (uncut chip thickness/cutting edge radius) ratio of 0.57 and cutting velocity of 10 m s-1 were used whereas a second trial was done using a cutting tool rake angle of -30°, d/r ratio of 1 and cutting velocity of 4 m s-1. Both the trials showed similar anisotropic variation. The simulated orthogonal components of thrust force in 3C-SiC showed a variation of up to 45%, while the resultant cutting forces showed a variation of 37%. This suggests that 3C-SiC is highly anisotropic in its ease of deformation. These results corroborate with the experimentally observed anisotropic variation of 43.6% in Youngs modulus of 3C-SiC. The recently developed dislocation extraction algorithm (DXA) [1, 2] was employed to detect the nucleation of dislocations in the MD simulations of varying cutting orientations and cutting directions. Based on the overall analysis, it was found that 3C-SiC offers ease of deformation on either (1 1 1) ⟨-1 1 0⟩, (1 1 0) ⟨0 0 1⟩, or (1 0 0) ⟨1 0 0⟩ setups.

Development and Application of the Leadership Archetype Questionnaire

The Leadership Assessment Questionnaire (LAQ) is a 360-degree survey instrument designed to help organizational leaders identify their own style of leadership and formulate appropriate development objectives. It is designed to provide a means for developing an executive team in which multiple leadership archetypes are represented. The LAQ is based on eight leadership archetypes-Strategist, Change-catalyst, Transactor, Builder, Innovator, Processor, Coach, and Communicator. These archetypes are representations of ways of leading in a complex organizational environment. In this article we discuss the development, design, and psychometric analysis of the LAQ. We detail the conceptual foundations of the questionnaire and the psychometric methods used to confirm the validity and reliability of the instrument. We conclude with avenues for future research.

Incipient plasticity in 4H-SiC during quasistatic nanoindentation

Silicon carbide (SiC) is an important orthopedic material due to its inert nature and superior mechanical and tribological properties. Some of the potential applications of silicon carbide include coating for stents to enhance hemocompatibility, coating for prosthetic-bearing surfaces and uncemented joint prosthetics. This study is the first to explore nanomechanical response of single crystal 4H-SiC through quasistatic nanoindentation. Displacement controlled quasistatic nanoindentation experiments were performed on a single crystal 4H-SiC specimen using a blunt Berkovich indenter (300nm tip radius) at extremely fine indentation depths of 5nm, 10nm, 12nm, 25nm, 30nm and 50nm. Load-displacement curve obtained from the indentation experiments showed yielding or incipient plasticity in 4H-SiC typically at a shear stress of about 21GPa (~an indentation depth of 33.8nm) through a pop-in event. An interesting observation was that the residual depth of indent showed three distinct patterns: (i) positive depth hysteresis above 33nm, (ii) no depth hysteresis at 12nm, and (iii) negative depth hysteresis below 12nm. This contrasting depth hysteresis phenomenon is hypothesized to originate due to the existence of compressive residual stresses (upto 143MPa) induced in the specimen by the polishing process prior to the nanoindentation.

Does Organizational Forgetting Affect Vendor Quality Performance? An Empirical Investigation

The development of organizational knowledge and the depreciation of knowledge within organizations are processes that invariably occur concurrently. In the quality domain, many researchers have examined how the development of organizational knowledge organizational learning enhances quality performance. We build on this literature and investigate how the depreciation of organizational knowledge organizational forgetting affects quality performance. We analyze information on 2,732 quality improvement initiatives implemented by 295 vendors of a car manufacturer and find that organizational forgetting affects quality gains obtained from both learning-by-doing autonomous learning and quality improvement initiatives induced learning; more than 16% of quality gains from autonomous learning and 13% of quality gains from induced learning depreciate every year. Furthermore, the impact of organizational forgetting i differs across the types of quality improvement efforts quality gains from process improvement initiatives depreciate, whereas those from quality assurance initiatives do not, and ii depends on where quality knowledge was embedded depreciation is lower for knowledge embedded in technology than for knowledge embedded in organizational routines or organizational members. Our results highlight the ubiquity of organizational forgetting and suggest the need for continued attention to sustain and enhance quality performance in supply chains.

Product Networks, Component Modularity and Sourcing

This paper develops product representations as component networks that evolve from sharing of interfaces with other components in a product and links them to the external world of sourcing. The paper formally defines and develops two measures of component modularity by linking Graph Theory and Product Architecture principles. The first measure, degree modularity, is related to the strength of design dependencies with adjacent components. The second measure, bridge modularity, is related to the criticality of components. These two component modularity measures are calculated and interpreted by studying the actual product architecture of two products - a small machinery product and an automobile subsystem. A sourcing framework is suggested, treating product obsolescence as a moderating variable in the effect of modularity on sourcing. The paper concludes with a discussion of how component modularity measures can help managers to take better decisions in the arena of sourcing – both at an operational level and at the strategic level. Directions for future work are discussed.

Managing Value in Supply Chains: Case Studies on the Sourcing Hub Concept

A firms raw material sourcing knowledge can be a strategic resource. This article explores how firms can capture and use this knowledge. It examines the sourcing experiences of four firms in four different countries in the automotive industry and identifies the raw material sourcing knowledge-related parameters. Synthesizing the findings from these case studies, it proposes the concept of the sourcing hub—a collaborative center involving the firm, its suppliers, and raw material suppliers—which can effectively capture and deploy the raw material sourcing knowledge for managing value in upstream sourcing.

A Mathematical Model for Determination of Limiting Blank Holding Force and Cavity Pressure in Hydromechanical Deep Drawing

Abstract A mathematical model for the prediction of a safe zone for die cavity pressure and blank holding force/pressure, to avoid tensile and compressive instabilities in hydromechanical deep drawing is presented in this paper. Tensile instability is predicted using the load maximization principle whereas a solution for the stability equations provided the critical condition for compressive instability. Predictions of the present work are compared with results available in the literature and are in good agreement. A comprehensive parametric study is carried out to study the effect of process variables on the safe zone.

Managing raw material in supply chains

In this paper, we explore how firms can manage their raw material sourcing better by developing appropriate sourcing relationships with their raw material suppliers. We detail three empirical case studies of firms explaining their different raw material sourcing strategies: (a) firms can adopt a hands-off approach to raw material management, (b) firms can supply raw material directly to their suppliers, and this may be beneficial for some agents in the supply chain, and (c) firms can bring their component suppliers together, and the resulting cooperation between suppliers can be beneficial for supply chain. We then analytically model the three raw material scenarios encountered in our empirical work, examine the resulting profits along the supply chain, and extend the results to a competitive buyer scenario. Overall, our results show that active management of raw material sourcing can add value to supply chains.

Does Quality Knowledge Spillover at Shared Suppliers? An Empirical Investigation

We use a unique empirical setting to investigate the spillover of quality knowledge across supply chains and to the examine contingencies that affect such spillover. We analyze the quality performance of 191 suppliers, who utilize the same facilities to manufacture similar products for two distinct businesses: one that makes cars and the other that makes commercial vehicles. From 2006 to 2009, the car business undertook 2,121 quality improvement initiatives at these suppliers, while the commercial vehicles business did not undertake any such initiatives. We find that the quality knowledge developed through the quality improvement initiatives undertaken by the car business does not easily spill over to benefit the commercial vehicles business. Quality knowledge spills over under three conditions: (1) when quality improvement efforts are focused on organizational members, as opposed to when they focus on routines or technology; (2) when quality improvement efforts focus on the output activities of suppliers...