Corrosion Behaviour of Cupronickel 90/10 Alloys in Arabian Sea Conditions and its Effect on Maintenance of Marine Structures

The composition of seawater plays a very significant role in determining the severity of corrosion process in marine assets. The influential contributors to the general and pitting corrosions in marine structures include temperature, dissolved oxygen (DO), salinity, PH, chlorides, pollutants, nutrients, and microbiological activities in seawater. The Cu-Ni (90/10) alloy is increasingly used in marine applications such as heat exchangers and marine pipelines because of its excellent corrosion resistant properties. Despite the significant advancements in corrosion shielding procedures, complete stoppage of corrosion induced metal loss, especially under rugged marine environments, is practically impossible. The selection of appropriate metal thickness is merely a multifaceted decision because of the high variability in operating conditions and associated corrosion rate in various seawater bodies across the globe. The present research study aims to analyze the early phase of corrosion behavior of Cu-Ni (90/10) alloy in open-sea conditions as well as in pollutant-rich coastal waters of the Arabian Sea. Test samples were placed under natural climatic conditions of selected sites, followed by the mass loss and corrosion rate evaluation. The corrosion rate in the pollutant-rich coastal waters was around five times higher than in the natural seawater. A case study on marine condenser (fitted with of Cu-Ni 90/10 alloy tubes) is presented, and a risk-based inspection (RBI) plan is developed to facilitate equipment designers, operators, and maintainers to consider the implications of warm and polluted seawater on equipment reliability, service life, and subsequent health inspection/ maintenance

A brief review of fatigue design criteria on offshore wind turbine support structures

In this paper, a brief review of the main fatigue design criteria and some advanced fatigue approaches applied to offshore structures (e.g. offshore wind turbines) are presented. It is extremely important to understand the fatigue phenomenon and how it affects structures since offshore structures are constantly submitted to cyclic loading and corrosive attacks that aggravate the problem. All the influencing factors and approaches used during the design phase are also discussed

Effects of fiber/matrix interactions on the properties of graphite/epoxy composites

A state-of-the-art literature review of the interactions between fibers and resin within graphite epoxy composite materials was performed. Emphasis centered on: adhesion theory; wetting characteristics of carbon fiber; load transfer mechanisms; methods to evaluate and measure interfacial bond strengths; environmental influence at the interface; and the effect of the interface/interphase on composite performance, with particular attention to impact toughness. In conjunction with the literature review, efforts were made to design experiments to study the wetting behavior of carbon fibers with various finish variants and their effect on adhesion joint strength. The properties of composites with various fiber finishes were measured and compared to the base-line properties of a control. It was shown that by tailoring the interphase properties, a 30% increase in impact toughness was achieved without loss of mechanical properties at both room and elevated temperatures

Safety Factors – IEC 61400-1 ed. 4:background document

The aim of this document is to describe the basis for the partial safety factors recommended in IEC61400-1 ed. 4.The scope is to• give the basis for selecting materials partial safety factors in ‘recognized design codes’ –taking into account inspections (e.g. in relation to fatigue)• give the basis for design assisted by testing – determination of characteristic values for material parameters and load bearing capacities on the basis of test results• give the basis for modifying load partial safety factors if compared to the ‘normal’ situation better / additional information (less uncertainty) is available for estimating loads; e.g. modification of safety factors depending on specific site conditions.Section 2 briefly describes the theoretical basis for calibration of partial safety factors using reliability based methods. The required reliability level is discussed in section 3. In section 4 three basic models for calculating the design value of the load bearing capacity is presented. Next, reliability-based calibration of material partial safety factors is described in the following cases: DLC 1.1 and 6.1 with extreme load; fatigue of welded steel details; DLC 2.1 and 2.2 with extreme load and faults; component / consequence class partial safety factor ϒc . Finally, also the load partial safety factor in typhoon conditions is considered. Section 5 how the uncertainty level influences the partial safety factors.Finally annexes are presented on Reliability and partial safety factors for tower buckling; Reliability of concrete structures for wind turbines; Safety factors for fatigue of welded details in steel structures for wind turbines; and an overview of the main changes in material partial factors in the CD IEC 61400-1: 2014 ed. 4 compared to IEC 61400-1: 2005 ed. 3

Optimization of processing parameters for As2Se3 glass for low loss, high strength fibers

Chalcogenide glasses have been widely studied due to their extraordinary transparency in the infrared (IR) region from 0.5 to 20 μm. This transparency combined with excellent thermo-mechanical properties, makes them ideal candidate for infrared optics including IR fiber optic applications. However, such non-oxide glasses generally exhibit low mechanical strength, as compared to their oxide counterpart, which are based on covalently bonded metal-oxygen species. In addition to mechanical robustness, low optical loss (hence low impurity content) is required for most IR optical materials, including the one in this study, amorphous arsenic tri-selenide, As2Se3. In this effort, As2Se3 glass was investigated and the impact of the glass purity on material physical properties quantified. Properties evaluated includes chemical composition, structure, thermal, optical and mechanical properties. There are many sources of optical loss in chalcogenide glasses, physical defects, heterogeneous phase(s), and oxide, hydroxide or hydride-containing species. These extrinsic impurities generally come from poor melting profiles, sample preparation or quality/purity of the raw materials. Reduction of intrinsic losses due of the material has also been explored. It was found that an impurity content of 0.1 ppb has to be reached to yield a total reduction of the band at 4.57 μm. Various methods, such as thermal treatment of the raw material or the addition of impurity-getters in the melt followed by distillation were performed in our lab, to achieve different level of purity in the glass specimens. The role of glass purity on these attributes was compared. The relationship between impurity concentration and mechanical properties of arsenic selenide glass, both in bulk and fiber forms has been investigated. The concentration of oxide-containing impurities embedded in the glassy matrix appeared to have a strong impact on the microhardness of the resulting material. A reduction of ~60% of the water, oxides and hydroxides content resulted in an increase of 200 MPa of the hardness of the glass system. Moreover, it has been demonstrated that the increase of the hydride (Se-H) content in the material would yield a lower microhardness of the glass. These observations have been correlated with the impact of the impurity concentration on the glass network connectivity. A material with weaker glass connectivity would exhibit smaller resistance to crack initiation. The evolution of the properties and homogeneity of the glass from small batch to preform and the effect of the drawing process have been studied. The results of the processing-related variables on final glass quality will be discussed

COMPARISON OF INTERCONNECT FAILURES OF ELECTRONIC COMPONENTS MOUNTED ON FR-4 BOARDS WITH SN37PB AND SN3.0AG0.5CU SOLDERS UNDER RAPID LOADING CONDITIONS.

Electronic circuit boards can experience rapid loading through shock or vibration events during their lives; these events can happen in transportation, manufacture, or in field conditions. Due to the lead-free migration, it is necessary to evaluate how this rapid loading affects the durability of a leading lead free solder alternative (Sn3.0Ag0.5Cu) assemblies as compared with traditional eutectic lead based solder Sn37Pb assemblies. A literature review showed that there is little agreement on the fatigue behavior of Sn37Pb solder assemblies and Sn3.0Ag0.5Cu solder assemblies subjected to rapid loading. To evaluate the failure behavior of Sn37Pb and Sn3.0Ag0.5Cu solder assemblies under rapid loading conditions, leadless chip resistors (LCR), ball grid arrays (BGA), small outline integrated circuits (SOIC), and small outline transistors (SOT) were subjected to four point bend tests via a servo-hydraulic testing machine at printed wiring board (PWB) strain rates greater than 0.1/s. The PWB strain was the metric used to evaluate the failures. The PBGAs and LCRs were examined with both Sn37Pb and Sn3.0Ag0.5Cu solders. There was no significant difference found in the resulting test data for the behavior of the two solder assembly types in the high cycle fatigue regime. PBGA assemblies with both solders were also evaluated at a higher strain rate, approximately 1/s, using drop testing. There was no discernable difference found between the assemblies as well as no difference in the failure rate of the PBGAs at this higher strain rate. The PWB strain was converted to an equivalent solder stress index using finite element analysis. This equivalent stress index value was used to compare the results from the LCR and BGA testing for Sn37Pb and Sn3.0Ag0.5Cu. Independently generated BGA data that differed with respect to many testing variables was adjusted and incorporated to this comparison. The resulting plot did not show any significant differences between the behaviors of the two solder assemblies under rapid loading outside of the ultra low cycle fatigue regime, where the assemblies with Sn37Pb solder outperformed the assemblies with SnAgCu solder

Ceramic automotive Stirling engine program

The Ceramic Automotive Stirling Engine Program evaluated the application of advanced ceramic materials to an automotive Stirling engine. The objective of the program was to evaluate the technical feasibility of utilizing advanced ceramics to increase peak engine operating temperature, and to evaluate the performance benefits of such an increase. Manufacturing cost estimates were also developed for various ceramic engine components and compared with conventional metallic engine component costs

On the Strength of the Carbon Nanotube-Based Space Elevator Cable: From Nano- to Mega-Mechanics

In this paper different deterministic and statistical models, based on new quantized theories proposed by the author, are presented to estimate the strength of a real, thus defective, space elevator cable. The cable, of ~100 megameters in length, is composed by carbon nanotubes, ~100 nanometers long: thus, its design involves from the nano- to the mega-mechanics. The predicted strengths are extensively compared with the experiments and the atomistic simulations on carbon nanotubes available in the literature. All these approaches unequivocally suggest that the megacable strength will be reduced by a factor at least of ~70% with respect to the theoretical nanotube strength, today (erroneously) assumed in the cable design. The reason is the unavoidable presence of defects in a so huge cable. Preliminary in silicon tensile experiments confirm the same finding. The deduced strength reduction is sufficient to pose in doubt the effective realization of the space elevator, that if built as today designed will surely break (according to the s opinion). The mechanics of the cable is also revised and possibly damage sources discussed