Mica Grujicic, Jennifer Snipes and S. Ramaswami
The purpose of this paper is to introduce and analyze a new blast-wave impact-mitigation concept using advanced computational methods and tools. The concept involves the use of a…
Abstract
Purpose
The purpose of this paper is to introduce and analyze a new blast-wave impact-mitigation concept using advanced computational methods and tools. The concept involves the use of a protective structure consisting of bimolecular reactants displaying a number of critical characteristics, including: a high level of thermodynamic stability under ambient conditions (to ensure a long shelf-life of the protective structure); the capability to undergo fast/large-yield chemical reactions under blast-impact induced shock-loading conditions; large negative activation and reaction volumes to provide effective attenuation of the pressure-dominated shockwave stress field through the volumetric-energy storing effects; and a large activation energy for efficient energy dissipation. The case of a particular bimolecular chemical reaction involving polyvinyl pyridine and cyclohexyl chloride as reactants and polyvinyl pyridinium ionic salt as the reaction product is analyzed.
Design/methodology/approach
Direct simulations of single planar shockwave propagations through the reactive mixture are carried out, and the structure of the shock front examined, as a function of the occurrence of the chemical reaction. To properly capture the shockwave-induced initiation of the chemical reactions during an impact event, all the calculations carried out in the present work involved the use of all-atom molecular-level equilibrium and non-equilibrium reactive molecular-dynamics simulations. In other words, atomic bonding is not pre-assigned, but is rather determined dynamically and adaptively using the concepts of the bond order and atomic valence.
Findings
The results obtained clearly reveal that when the chemical reactions are allowed to take place at the shock front and in the shockwave, the resulting shock front undergoes a considerable level of dispersion. Consequently, the (conserved) linear momentum is transferred (during the interaction of the protective-structure borne shockwaves with the protected structure) to the protected structure over a longer time period, while the peak loading experienced by the protected structure is substantially reduced.
Originality/value
To the authors’ knowledge, the present work is the first attempt to simulate shock-induced chemical reactions at the molecular level, for purposes of blast-mitigation.
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Mica Grujicic, Jennifer Snipes and S. Ramaswami
The purpose of this paper is to model a nacre-like composite material, consisting of tablets and polyurea tablet/tablet interfaces, B4C. This composite material is being…
Abstract
Purpose
The purpose of this paper is to model a nacre-like composite material, consisting of tablets and polyurea tablet/tablet interfaces, B4C. This composite material is being considered in the construction of the so-called backing-plate, a layer within a multi-functional/multi-layer armor system.
Design/methodology/approach
Considering the basic functions of the backing-plate (i.e. to provide structural support for the ceramic-strike-face and to stop a high-velocity projectile and the accompanying fragments) in such an armor system, the composite-material architecture is optimized with respect to simultaneously achieving high flexural stiffness and high ballistic-penetration resistance. Flexural stiffness and penetration resistance, for a given architecture of the nacre-like composite material, are assessed using a series of transient non-linear dynamics finite-element analyses. The suitability of the optimized composite material for use in backing-plate applications is then evaluated by comparing its performance against that of the rolled homogeneous armor (RHA), a common choice for the backing-plate material.
Findings
The results obtained established: a trade-off between the requirements for a high flexural stiffness and a high ballistic-penetration resistance in the nacre-like composite material; and overall superiority of the subject composite material over the RHA when used in the construction of the backing-plate within multi-functional/multi-layer armor systems.
Originality/value
This study extends the authors previous research on nacre-mimetic armor to optimize the architecture of the armor with respect to its flexural stiffness and ballistic-penetration resistance, so that these properties could be increased over the levels attained in the current choice (RHA) for the backing layer of multi-functional/multi-layer armor.
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Mohd Azri Pawan Teh, Nazrina Aziz and Zakiyah Zain
This paper introduces group chain acceptance sampling plans (GChSP) for a truncated life test at preassumed time by using the minimum angle method. The proposed method is an…
Abstract
Purpose
This paper introduces group chain acceptance sampling plans (GChSP) for a truncated life test at preassumed time by using the minimum angle method. The proposed method is an approach, where both risks associated with acceptance sampling, namely consumers’ and producer’s risks, are considered. Currently, the GChSP only considers the consumer's risk (CR), which means the current plan only protects the consumer not the producer since it does not take into account the producer's risk (PR) at all.
Design/methodology/approach
There are six phases involved when designing the GChSP, which are (1) identifying the design parameters, (2) implementing the operating procedures, (3) deriving the probability of lot acceptance, (4) deriving the probability of zero or one defective, (5) deriving the proportion defective and (6) measuring the performance.
Findings
The findings show that the optimal number of groups obtained satisfies both parties, i.e. consumer and producer, compared to the established GChSP, where the number of group calculated only satisfies the consumer not the producer.
Research limitations/implications
There are three limitations identified for this paper. The first limitation is the distribution, in which this paper only proposes the GChSP for generalized exponential distribution. It can be extended to different distribution available in the literature. The second limitation is that the paper uses binomial distribution when deriving the probability of lot acceptance. Also, it can be derived by using different distributions such as weighted binomial distribution, Poisson distribution and weighted Poisson distribution. The final limitation is that the paper adopts the mean as a quality parameter. For the quality parameter, researchers have other options such as the median and the percentile.
Practical implications
The proposed GChSP should provide an alternative for the industrial practitioners and for the inspection activity, as they have more options of the sampling plans before they finally decide to select one.
Originality/value
This is the first paper to propose the minimum angle method for the GChSP, where both risks, CR and PR, are considered. The GChSP has been developed since 2015, but all the researchers only considered the CR in their papers.
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Introduction: Healthcare facilities have witnessed deterioration, limited employee engagement, and communication gaps due to a lack of wireless technology. The Internet makes work…
Abstract
Introduction: Healthcare facilities have witnessed deterioration, limited employee engagement, and communication gaps due to a lack of wireless technology. The Internet makes work and life quicker and more intelligent. The Internet of Things (IoT) is a scheme of interconnection equipped with unique identifiers in recent years. Artificial intelligence (AI) and IoT advancement allow employees to develop competent and predictive services and solutions in human resource (HR) practices. This chapter has been formulated to summarise and classify the existing research and better understand the past, present, and future of employee engagement by improving IoT interrelated devices in the healthcare industry.
Purpose: This study aims to categorise and overcome the challenges involved in HR practices. Effectively embracing IoT application-connected devices in the healthcare industry can enhance human resources management’s (HRM) role and measure performance assessment to improve employee engagement and productivity.
Methodology: In this study, the authors develop propositions dependent on a theory-based review. A systematic analysis was applied to minimise the challenges of HRM. The subject-related articles from different journal sources, like Scopus, Emerald, Web of Science, Springer, etc., were analysed based on engagement criteria. It was graphically recorded in a collective and informative way to emphasise the review outcomes. The study has presented the positive impacts of AI and IoT on engagement in health care.
Summary: This chapter accumulated theory-based knowledge about healthcare employee engagement and how IoT-based technology like AI can optimise employees’ engagement effectively. Further, it draws comparative benefits for a workforce to execute performance advancements and create future progressive aspects for healthcare employees.
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Bambang Susantono, Mohammed Ali Berawi and Mustika Sari
Nusantara, Indonesia’s currently developed new capital city, aims to lead the nation toward a more efficient and sustainable future by fostering an inclusive, sustainable, and…
Abstract
Nusantara, Indonesia’s currently developed new capital city, aims to lead the nation toward a more efficient and sustainable future by fostering an inclusive, sustainable, and prosperous development for all. Envisioned to be built as a smart city, Nusantara leverages the latest technological advancements across various domains as the basis for this cutting-edge urban development. This chapter discusses the advanced technologies implemented to realize the smart city concept in the development of Nusantara. The Nusantara smart city framework encompasses six domains: smart governance, transportation and mobility, smart living, natural resources and energy, smart industry, and human resources, along with the smart built environment and infrastructure, aiming to transform Nusantara into a smart city that epitomizes efficiency, sustainability, and inclusivity. This framework outlines integrating advanced technologies to foster a resilient economy, a sustainable environment, and an enhanced quality of life for its citizens through improved administrative procedures, transportation systems, public safety, healthcare access, resource management, and infrastructure development. Implementing this framework can provide insight into the future development of smart cities in the Gulf Region, poised to significantly impact societal well-being and economic resilience significantly, demonstrating a model for future urban development that harmonizes community engagement, technological innovation, and environmental preservation.
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K. BALACHANDRAN and R.S. RAMASWAMY
In this paper, it is established that the error and error derivative can be reduced to zero simultaneously and in the shortest possible time with at most one switching reversal of…
Abstract
In this paper, it is established that the error and error derivative can be reduced to zero simultaneously and in the shortest possible time with at most one switching reversal of the relay, provided the initial values of error and error derivative fall in a controllable region.
Mica Grujicic, S. Ramaswami and Jennifer Snipes
Nacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form…
Abstract
Purpose
Nacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form individual layers and having the adjacent layers as well as the tablets within a layer bonded by a biopolymer. Due to its highly complex hierarchical microstructure, nacre possesses an outstanding combination of mechanical properties, the properties which are far superior to the ones that are predicted using techniques such as the rule of mixtures. Given these properties, a composite armor the structure of which mimics that of nacre may have improved performance over a monolithic armor having a similar composition and an identical areal density. The paper aims to discuss these issues.
Design/methodology/approach
In the present work, an attempt is made to model a nacre-like composite armor consisting of B4C tablets and polyurea tablet/tablet interfaces. The armor is next tested with respect to impact by a solid right circular cylindrical (SRCC) rigid projectile, using a transient non-linear dynamics finite-element analysis. The ballistic-impact response and the penetration resistance of the armor are then compared with that of the B4C monolithic armor having an identical areal density. Furthermore, the effect of various nacre microstructural features (e.g. surface profiling, micron-scale asperities, mineral bridges between the overlapping tablets lying in adjacent layers, and B4C nano-crystallinity) on the ballistic-penetration resistance of the composite armor is investigated in order to identify an optimal nacre-like composite armor architecture having the largest penetration resistance.
Findings
The results obtained clearly show that a nacre-like armor possesses a superior penetration resistance relative to its monolithic counterpart, and that the nacre microstructural features considered play a critical role in the armor-penetration resistance.
Originality/value
The present work indicates that for a given choice of armor material, penetration resistance may be improved by choosing a structure resembling that of nacre.
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Mica Grujicic, S Ramaswami, Jennifer Snipes, Vasudeva Avuthu, Chian-Fong Yen and Bryan Cheeseman
Fiber-reinforced armor-grade polymer-matrix composite materials with a superior penetration resistance are traditionally developed using legacy knowledge and trial-and-error…
Abstract
Purpose
Fiber-reinforced armor-grade polymer-matrix composite materials with a superior penetration resistance are traditionally developed using legacy knowledge and trial-and-error empiricism. This approach is generally quite costly and time-consuming and, hence, new (faster and more economical) approaches are needed for the development of high-performance armor-grade composite materials. One of these new approaches is the so-called materials-by-design approach. Within this approach, extensive use is made of the computer-aided engineering (CAE) analyses and of the empirically/theoretically established functional relationships between an armor-grade composite-protected structure, the properties of the composite materials, material microstructure (as characterized at different length-scales) and the material/structure synthesis and fabrication processes. The paper aims to discuss these issues.
Design/methodology/approach
In the present work, a first step is made toward applying the materials-by-design approach to the development of the armor-grade composite materials and protective structures with superior ballistic-penetration resistance. Specifically, CAE analyses are utilized to establish functional relationships between the attributes/properties of the composite material and the penetration resistance of the associated protective structure, and to identify the combination of these properties which maximize the penetration resistance. In a follow-up paper, the materials-by-design approach will be extended to answer the questions such as what microstructural features the material must possess in order for the penetration resistance to be maximized and how such materials should be synthesized/processed.
Findings
The results obtained show that proper adjustment of the material properties results in significant improvements in the protective structure penetration resistance.
Originality/value
To the authors’ knowledge, the present work is the first reported attempt to apply the materials-by-design approach to armor-grade composite materials in order to help improve their ballistic-penetration resistance.
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M. Grujicic, J.S. Snipes, R. Galgalikar, S. Ramaswami, R. Yavari, C.-F. Yen, B.A. Cheeseman and J.S. Montgomery
The purpose of this paper is to develop multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process has been improved with respect to its…
Abstract
Purpose
The purpose of this paper is to develop multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process has been improved with respect to its predictive capabilities regarding the spatial distribution of the mechanical properties (strength, in particular) within the weld.
Design/methodology/approach
The improved GMAW process model is next applied to the case of butt-welding of MIL A46100 (a prototypical high-hardness armor-grade martensitic steel) workpieces using filler-metal electrodes made of the same material. A critical assessment is conducted of the basic foundation of the model, including its five modules, each dedicated to handling a specific aspect of the GMAW process, i.e.: first, electro-dynamics of the welding-gun; second, radiation/convection controlled heat transfer from the electric arc to the workpiece and mass transfer from the filler-metal consumable electrode to the weld; third, prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; fourth, the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; and fifth, spatial distribution of the as-welded material mechanical properties.
Findings
The predictions of the improved GMAW process model pertaining to the spatial distribution of the material microstructure and properties within the MIL A46100 butt-weld are found to be consistent with general expectations and prior observations.
Originality/value
To explain microstructure/property relationships within different portions of the weld, advanced physical-metallurgy concepts and principles are identified, and their governing equations parameterized and applied within a post-processing data-reduction procedure.
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M. Grujicic, R. Yavari, J.S. Snipes, S. Ramaswami and R.S. Barsoum
The purpose of this paper is to address the problems of interaction of tensile stress-waves with polyurea/fused-silica and fused-silica/polyurea interfaces, and the potential for…
Abstract
Purpose
The purpose of this paper is to address the problems of interaction of tensile stress-waves with polyurea/fused-silica and fused-silica/polyurea interfaces, and the potential for the accompanying interfacial decohesion.
Design/methodology/approach
The problems are investigated using all-atom non-equilibrium molecular-dynamics methods and tools. Before these methods/tools are employed, previously determined material constitutive relations for polyurea and fused-silica are used, within an acoustic-impedance-matching procedure, to predict the outcome of the interactions of stress-waves with the material-interfaces in question. These predictions pertain solely to the stress-wave/interface interaction aspects resulting in the formation of transmitted and reflected stress- or release-waves, but do not contain any information regarding potential interfacial decohesion. Direct molecular-level simulations confirmed some of these predictions, but also provided direct evidence of the nature and the extent of interfacial decohesion. To properly model the initial state of interfacial cohesion and its degradation during stress-wave-loading, reactive forcefield potentials are utilized.
Findings
Direct molecular-level simulations of the polyurea/fused-silica interfacial regions prior to loading revealed local changes in the bonding structure, suggesting the formation of an interphase. This interphase was subsequently found to greatly affect the polyurea/fused-silica decohesion strength.
Originality/value
To the authors’ knowledge, the present work is the first public-domain report of the use of the non-equilibrium molecular dynamics and reactive force-field potentials to study the problem of interfacial decohesion caused by the interaction of tensile waves with material interfaces.