Internal ballistics of polygonal and grooved barrels: A comparative study

As a parameter important ballistic, the research about polygonal and grooved barrels’ behavior has not been widely carried out. The pressures, velocities, stresses, deformations, and strains generated by the firing of 9 mm × 19 mm ammunition in weapons with polygonal barrels are analyzed numerically and experimentally, compared with those generated in pistols with grooved barrels. The Finite Element Method with equal boundary and loading conditions was used in both types of guns, specifying the actual materials of the projectile and the barrels. Subsequently, experimental tests were carried out on various weapons with 9 mm ammunitions of 115, 122, and 124 gr. The results show that the 9 mm bullet fired in a polygonal barrel undergoes a maximum deformation towards its exterior of 0.178 mm and interior of 0.158 mm, with stress up to 295.85 MPa. Compared with 0.025 mm maximum external deformation and 0.112 mm internal deformation of 9 mm projectiles fired in a grooved barrel, with stress up to 269.79 MPa. The deformation in the polygonal barrel is in a greater area, but the rifling impression left is less deep, making its identification more difficult. Although there are differences in the stresses and strains obtained, similar velocity and pressure parameters are achieved in the two types of barrels. This has application in the development and standardization of new kinds of barrels and weapons.As a parameter important ballistic, the research about polygonal and grooved barrels’ behavior has not been widely carried out. The pressures, velocities, stresses, deformations, and strains generated by the firing of 9 mm × 19 mm ammunition in weapons with polygonal barrels are analyzed numerically and experimentally, compared with those generated in pistols with grooved barrels. The Finite Element Method with equal boundary and loading conditions was used in both types of guns, specifying the actual materials of the projectile and the barrels. Subsequently, experimental tests were carried out on various weapons with 9 mm ammunitions of 115, 122, and 124 gr. The results show that the 9 mm bullet fired in a polygonal barrel undergoes a maximum deformation towards its exterior of 0.178 mm and interior of 0.158 mm, with stress up to 295.85 MPa. Compared with 0.025 mm maximum external deformation and 0.112 mm internal deformation of 9 mm projectiles fired in a grooved barrel, with stress up to 269.79 MPa. The deformation in the polygonal barrel is in a greater area, but the rifling impression left is less deep, making its identification more difficult. Although there are differences in the stresses and strains obtained, similar velocity and pressure parameters are achieved in the two types of barrels. This has application in the development and standardization of new kinds of barrels and weapons

PCB Quality Metrics that Drive Reliability (PD 18)

Risk based technology infusion is a deliberate and systematic process which defines the analysis and communication methodology by which new technology is applied and integrated into existing and new designs, identifies technology development needs based on trends analysis and facilitates the identification of shortfalls against performance objectives. This presentation at IPC Works Asia Aerospace 2019 Events provides the audience a snapshot of quality variations in printed wiring board quality, as assessed, using experiences in processing and risk analysis of PWB structural integrity coupons. The presentation will focus on printed wiring board quality metrics used, the relative type and number of non-conformances observed and trend analysis using statistical methods. Trend analysis shows the top five non-conformances observed across PWB suppliers, the root cause(s) behind these non-conformance and suggestions of mitigation plans. The trends will then be matched with the current state of the PWB supplier base and its challenges and opportunities. The presentation further discusses the risk based SMA approaches and methods being applied at GSFC for evaluating candidate printed wiring board technologies which promote the adoption of higher throughput and faster processing technology for GSFC missions

Surface Properties of Advanced Materials and Their Applications in Ballistics

This thesis research investigates the surface properties and performances of gold nanoparticles, microarc oxidation coating, and epitaxial nano-twinned copper film. The research aims to understand the critical behavior of material surfaces in order to facilitate design and development of new materials for tribological applications. The research will focus on improving of the gun barrel performances. Experimental approaches will be used for combining analysis with basic thermal energy transfer principles. Results obtained here will be used for developing new materials to be used in facilitating gun barrels. Experimental approach includes scanning calorimetry-thremogravimetric analysis, tribological testing, and potentiodynamic polarization. The fundamental understanding obtained here will be beneficial for the gun barrel design, manufacturing, and military technologies followed by the results of experiments with different three types of materials. The results of this research showed that the coatings with microarc oxidation and nano-twinned structure improved wear resistance from the tribological examinations and size of AuNPs affected their thermal behaviors measured by differential scanning calorimetry and thermogravimetric analysis method

Nanostructured Multilayer Ceramic Coatings for Wood-Cutting Tools

Lo sviluppo di questo dottorato di ricerca è stato supportato e finanziato dal progetto europeo Interreg ITA-SLO NANOREGION. La missione del progetto NANOREGION consiste nel costituire un consorzio tra università ed enti di ricerca locali atti a fornire una piattaforma scientifica di supporto alle imprese del territorio comprensivo delle regioni dell'Italia nord-orientale e la Slovenia. In tali regioni, l'impatto economico-sociale dell'industria del legno è rilevante. È noto che nella manifattura di materiali legnosi la necessità di una frequente sostituzione degli utensili da lavorazione, necessaria a garantire gli standard di qualità del prodotto finito, ha un forte impatto sull'economia del processo di lavorazione. Gli utensili da taglio sono generalmente protetti con rivestimenti a film sottile costituiti da materiali duri e refrattari per aumentarne la durabilità, riducendo la frequenza di sostituzione e quindi aumentando la produttività delle aziende. Tuttavia, a causa della natura del legno come materiale da lavorazione e dei rigorosi requisiti tecnici specifici della lavorazione del legno, il rapporto costi/benefici del processo di rivestimento degli utensili si è finora dimostrato non sufficiente a giustificare i costi addizionali legati al processo di rivestimento. Questo risulta in una minore penetrazione nel mercato degli utensili rivestiti rispetto a quanto accade invece nell'industria metalmeccanica. Un'eccezione, seppure in misura limitata, è rappresentata dai rivestimenti a base di cromo, come il nitruro di cromo (CrN), che forniscono la massima protezione contro l'usura dovuta a processi di corrosione. Questi, infatti, sono riconosciuti come una delle principali cause di usura nella lavorazione del legno, favorendo la successiva usura abrasiva dei fragili prodotti d’ossidazione operata da inclusioni di minerali duri presenti all'interno di materiali a base legnosa, soprattutto prodotti secondari già sottoposti a lavorazioni precedenti. Tuttavia, a causa della relativamente bassa durezza, il CrN fornisce di per sé una scarsa resistenza all'usura abrasiva. Una possibile soluzione consiste nel sostituire rivestimenti monostrato di CrN con rivestimenti multistrato. Ricerche e applicazioni pratiche approfondite hanno dimostrato che la progettazione di rivestimenti multistrato offre numerosi vantaggi rispetto ai rivestimenti a strato singolo, soprattutto se lo spessore degli strati costitutivi è ridotto al regime nanometrico. Tuttavia, la ricerca per lo sviluppo di rivestimenti multistrato mirati a rispondere ai severi requisiti dell'industria del legno è molto limitata. Pertanto, lo scopo di questo progetto di ricerca era di effettuare preliminari studi sulle proprietà protettive dei sistemi di rivestimento PVD multistrato a base di CrN accoppiato con nitruri di indurimento. L’abbinamento di proprietà anticorrosive e migliori caratteristiche meccaniche potrebbero rendere tali sistemi di rivestimento dei potenziali candidati per il rivestimento di utensili da taglio del legno. I nitruri di tungsteno e molibdeno (WN e MoN, rispettivamente) sono stati scelti in quanto già applicati per la realizzazione di sistemi multistrato con altri nitruri, e anche per fornire uno studio comparato su due sistemi che raramente vengono studiati in parallelo nelle stesse condizioni sperimentali. L'obiettivo fondamentale dell'aggiunta di questi materiali aggiuntivi è fornire al CrN una migliore durezza meccanica mantenendo o migliorando l'elevata resistenza alla corrosione, e la letteratura pregressa suggerisce ottime potenzialità di questi materiali come nitruri indurenti.The research activity of this Ph.D. thesis is grounded is founded by the European Interreg ITA-SLO NANOREGION project. The mission of NANOREGION was to provide a scientific support to local enterprises in the region comprehending North-eastern Italy and Slovenia. In such regions the impact of the wood-industry on local economics is relevant. It is well known that the impact of tools replacement has a strong impact on the economics of the wood-working process to maintain the manufacturing standards required to obtain high quality products. Cutting tools are usually coated with hard, refractory thin film coatings to increase their service life and hence increase the manufacture productivity. Nonetheless, owing to the nature of the wood as a workpiece and to the strict technical required specific of wood-machining, the cost-to-benefits ratio of tools coating has so far proved not enough to allow the same market penetration of coated tools that is instead recorded in the metal-working industry. An exception to some extent is represented by Chromium-based coatings such as CrN, which provide the highest protection against corrosive wear, which in turn is recognized as of the main causes of wear in wood-machining, as it favors the subsequent abrasive wear of the brittle oxidation products mediated by hard mineral inclusions within the wood-based materials. Nonetheless, CrN alone is known to provide poor resistance to abrasive wear, due to its relatively low hardness. A large amount of research has demonstrated that the design of multilayer coatings offers several advantages over single-layer coatings, especially if the thickness of the constituent layers is reduced to the nanometric regime. Nonetheless, the research investigating the development of multilayer coatings specifically targeting the strict requirements of the wood industry is very limited. Hence, the purpose of this research process was to investigate preliminary protective properties of multilayer PVD coating systems based on oxidation-protective CrN coupled with hardening nitrides as potential candidate coatings for wood-cutting tools. WN and MoN were chosen due to reported literature on successful coupling of such coatings with other nitrides such as TiN or ZrN and CrN, and because of the limited number of scientific and systematic comparative investigations on these systems. The fundamental aim of the addition of these additional materials is providing CrN with improved mechanical hardness while retaining or improving high corrosion resistance

Tribological Behavior of Functional Surface: Models and Methods

Material loss due to wear and corrosion and high resistance to motion generate high costs. Therefore, minimizing friction and wear is a problem of great importance. This book is focused on the tribological behavior of functional surfaces. It contains information regarding the improvement of tribological properties of sliding elements via changes in surface topography. Tribological impacts of surface texturing depending on the creation of dimples on co-acting surfaces are also discussed. The effects of various coatings on the minimization of friction and wear and corrosion resistance are also studied. Friction can be also reduced by introducing a new oil

The Threat of Plant Toxins and Bioterrorism: A Review

The intentional use of highly pathogenic microorganisms, such as bacteria, viruses or their toxins, to spread mass-scale diseases that destabilize populations (with motivations of religious or ideological belief, monetary implications, or political decisions) is defined as bioterrorism. Although the success of a bioterrorism attack is not very realistic due to technical constraints, it is not unlikely and the threat of such an attack is higher than ever before. It is now a fact that the capability to create panic has allured terrorists for the use of biological agents (BAs) to cause terror attacks. In the era of biotechnology and nanotechnology, accessibility in terms of price and availability has spread fast, with new sophisticated BAs often being produced and used. Moreover, there are some BAs that are becoming increasingly important, such as toxins produced by bacteria (e.g., Botulinum toxin, BTX), or Enterotoxyn type B, also known as Staphylococcal Enterotoxin B (SEB)) and extractions from plants. The most increasing records are with regards to the extraction / production of ricin, abrin, modeccin, viscumin and volkensin, which are the most lethal plant toxins known to humans, even in low amounts. Moreover, ricin was also developed as an aerosol biological warfare agent (BWA) by the US and its allies during World War II, but was never used. Nowadays, there are increasing records that show how easy it can be to extract plant toxins and transform them into biological weapon agents (BWAs), regardless of the scale of the group of individuals

Barrel vibrations in small arms using combined experimental/computational methods.

Small arms are used on a global scale by militaries, hunters, competitive shooters, recreational shooters, and others. Despite this widespread use, the design and development of these tools depends heavily on prototyping and iterative testing. Additionally, the open literature concerning small arms is limited, especially in regard to those types of firearms in common use by civilians. The goal of this research was to develop a high-fidelity finite element model that would enable a detailed look into the factors governing the vibration of rifle barrels. Such a model can serve as a valuable research and development tool, reducing the high cost of prototyping. This thesis first addresses the degree of detail required in such a model to adequately capture the behavior of a sporting firearm. Experimental testing was performed in order to validate the model and lend additional insight into the factors at play. The validated model is then used to examine the influenced of curved barrel centerlines on projectile trajectories. Finally, the validity of a method of predicting shot dispersion from a single simulation is investigated

Silicon photovoltaics: experimental testing and modelling of fracture across scales

The study of the properties of materials can be addressed through a multi-scale approach, in order to have the possibility to grasp at each of the levels of analysis the peculiar aspects. Tracing a path inside the state-of-the-art in the available bibliography, historically in the field of mechanics s are found in which the material is studied through nonlocal theories based on continuous or discrete local approaches. More recently, with the advent of great computatio- nal power computers, analytical methodologies based on theories also very complex deriving from the field of chemistry and physics have been developed, capable to discretize at the ato- mic scale the material and study its behavior by applying energy approaches. Starting from the analysis of some of these theories at the nano- and micro-scales, it is possible to investi- gate the separation mechanisms at the molecular level, which may be considered as cracking processes within the material according to the adopted scale of analysis. The application of theories of this kind to large portions of material, in which there are up to some millions of particles involved is reasonably not an applicable solution, since it would require a huge effort in terms of computation time. To work around this problem and find a method suitable for the study of cracking mechanisms, a mixed method (MDFEM) was byconjugating pure molecu- lar dynamics (MD) and the finite element method (FEM), in which the material is discretized by means of one-dimensional elements whose mechanical characteristics are derived from MD. This approach is based on the application of a nonlocal theory in which the contribution of a portion of material placed within a certain distance from the point of fracture is taken into account by means of a parameter of non-locality. Moreover, the study of the evolution of cracking is addressed at the meso-scale by the application of a cohesive non-linear model. Towards the analysis of the macroscale, the theories put forward so far have been ap- plied to the study of phenomena of breakage inside Silicon cells embedded into rigid or semi-flexible photovoltaic modules. By performing various laboratory tests, useful for the characterization of the material and for understating the evolution of cracking process due to multiple causes, a study on the main issues that may compromise the durability and mainte- nance of the expected service levels of photovoltaic panels has been conducted. Experimen- tally results have been interpreted by using appropriate macro-scopic continuum models. The research carried out had the purpose to provide an introduction to a correct design of these systems of energy production in order to increase their durability and resistance to cracking

Characterisation and modelling of Ni based superalloy materials with multi-layered MCrAlY coating systems

The research and development of more efficient gas turbines has been one of the central focuses in materials design and characterisation for the past 20 years. High-temperature materials capable of maintaining their properties at elevated temperatures and under load are required for a wide range of components such as aircraft gas turbine engines, steam turbines, and industrial gas turbines. The operating temperature for gas turbine blades used for aerospace, marine and power plant applications, has been continuously increased in order to improve fuel efficiency. Nickel-based superalloys with various types of high temperature coatings have been widely and successfully used for such applications. [Continues.

Achieving Improved Reliability with Failure Analysis

Reliability is the ability of a product to properly function, within specified performance limits, for a specified period of time, under the life cycle application conditions. Failure analysis is a vital tool in the effort to ensure reliability of electronic products and systems throughout their product lifecycle. Today, organizations involved in activities within the electronics supply chain are facing new challenges, not just from complex assembly styles, harsher lifecycle environments, and sophisticated supply chains, but also from customers who are demanding a quicker turn-around. Unfortunately, root cause failure analysis is often performed incompletely, leading to a poor understanding of failure mechanisms and causes and, customer dissatisfaction due to recurring failures. The PDC (Professional Development Course) starts with an introduction to reliability concepts, physics of failure and an overview of failure mechanisms that affect PCBs (Printed Circuit Boards), PCBAs (Printed Circuit Board Assembly) and components. The PDC then dives into root cause hypothesizing techniques (Pareto, FMEA (Failure Modes and Effects Analysis), fishbone (Cause-And-Effect Diagram), FTA (Fault Tree Analysis)), non-destructive and destructive analysis and, materials characterization will be discussed. Numerous failure analysis case studies will be used to illustrate the techniques and analysis principles to arrive at the root cause(s) of field failures on printed circuit boards, active components, and assemblies. What Attendees will Learn: Topics include: Overview of Reliability Concepts Failure mechanisms of electronic products Root cause analysis Failure analysis techniques -Non-destructive techniques (optical, CSAM (Confocal Scanning Electron Microscopy) etc.) -Destructive analysis (DPA (Destructive Physical Analysis), Decap (Decapsulation), FIB (Focused Ion Beam) etc.) -Materials characterization (XRF (X-Ray Fluorescence) , EDS (Error Detection Sequential), TMA/DSC (Thermal Mechanical Analysis/Differential Scanning Calorimetry) etc.