United States Coast Guard Academy

Abstract Misalignments in welded joints are increasingly prevalent in modern shipbuilding due to industry’s shift towards lighter, thinner plates. Greater susceptibility to weld-induced distortions and the need for thickness transitions introduce secondary bending stresses that adversely affect fatigue life. Despite advancements in structural analysis, current industry fatigue design guidelines for treating misaligned joints largely rely on empirical formulations from the 1970s and 1980s. An improved methodology for determining stress concentration factors (SCF) is introduced, with new solutions for pure axial misalignments and misalignments due to transitions in thickness. Analytical solutions are developed using both direct and energy method approaches for a wide range of boundary conditions and geometries. Results are independently validated using the “ASME Boiler and Pressure Vessel Code” mesh-insensitive structural stress method and master SN curve, highlighting substantial shortcomings in widely adopted industry standards. IIW’s SCF formulations contain empirical adjustment terms that lack theoretical justification and general applicability to diverse loading and boundary conditions. This is shown to often result in unconservative stress predictions and an overestimation of fatigue life by as much as seven times for simple geometries consistent with recent Coast Guard builds, compared with analytical solutions and the master SN curve. Additionally, an explicit analysis of tapered transitions in thickness yields a closed-form solution – validated against published data – that shows IIW recommendations overestimate the benefit of tapering by assigning an overly generous fatigue category.

This paper describes a teaching methodology where in order to bring a sense of importance to the potentially "dry topic" of tolerances, classroom theory is linked immediately to practical machining and assembly exercises.An introductory sophomore design course at the U.S Coast Guard Academy involves a substantial laboratory element embracing basic drafting and more advanced 3D CAD instruction followed by several weeks of machine shop/laboratory immersion and hands on technical instruction.In previous years basic tolerance theory has been taught in the CAD part of the class and a small percentage of this theory was then realized in machining exercises later in the course.The result has been somewhat "hit and miss" in the educational goal of passing on an appreciation of tolerances let alone an enthusiasm for including them in subsequent work.The new methodology described in this paper links tolerances with some very specific machining exercises that were then undertaken within the same academic week.The functionality of parts produced was directly related to successful adherence to drawing tolerances much more clearly than any class paper exercise.The end result was a dramatic improvement in both machining work and the appreciation of the importance of engineer specified tolerances for both performance and manufacturing cost implications.The use of tolerances was also seen more frequently in subsequent course design exercises.

In recent years, there has been much discussion about declining interest in engineering programs throughout U.S. colleges and universities.Several possible causes for the decline have been identified and are fodder for debate: (1) PK-12 educational systems are not adequately preparing students to comprehend the connections among science, technology, engineering, and mathematics (STEM) and future career opportunities and (2) College engineering curricula need to be more aligned with the real world needs of business and industry.Several programs such as STEM summer programs and internships have been developed to address these issues, but to a large extent, such programs are short-term based.Additionally, they mostly target high school students; are only applicable in one grade level; or are one time project-based events.What would be the impact of systematically exposing PK through high school students to engineering concepts, applications, and career opportunities on a long-term, continuous basis at each grade level?If students are constantly reminded that engineering is part of their daily lives, this could generate a lifetime interest in the engineering profession and engage them in benefiting humanity.The authors are proposing "career imprinting," similar to that espoused by Harvard Professor Monica C. Higgins in the field of business, as a possible strategy to increasing students' awareness of and appreciation for careers in engineering.The objective would be to not only assist students in cultivating and acquiring grade level appropriate, as well as discipline-specific basic skills needed by engineers, but also to help them develop the personal characteristics that are essential to be successful in the engineering profession.By connecting "engineering as a profession" to the development of these skills and characteristics, students may be sparked to have an interest in engineering and can become "imprinted" to consider careers in the field.

Marine structures and ships fight a constant battle against corrosion. Sacrificial anodes and impressed-current cathodic protection (ICCP) are two common protection techniques. Many structures employ a hybrid configuration of both, in the hope that the combination provides more protection than either does individually. Doing so, however, can create situations in which these techniques interfere with each other. It is essential to verify that protection extends adequately to all areas of the structure. This article describes instrumentation and measurement strategies to determine the corrosion potential and extent of ICCP protection in difficult-to-reach areas on ships. A case study is presented for these methods on a vessel that experienced severe galvanic corrosion damage in its stern tube. Operators of mission-critical marine structures can use these insights to tune and improve corrosion protection schemes before damage manifests.

Recent studies have documented poleward shifts in heavily targeted fish stocks on the Bering Sea Shelf. This study investigated whether commercial fishing vessels in the region have also shifted their distribution poleward in recent years. We used Vessel Management System data generated between January 1, 2013, and December 31, 2022, to identify regions over the shelf where vessel activity increased (emerging hot spots) and where it decreased (emerging cold spots) during this time period. We hypothesized that emerging hot spots would occur at the northern edge of the vessel operating range, while emerging cold spots would occur at the southern edge. Overall, northward shifts in vessel distribution were most evident during October–February and July–August, when the range of emerging hots spots was centered 204–515 km to the N, NE, or NW of the center of the range of emerging cold spots. The trend was strongest in August, when emerging hot spots were widespread in the Northern Bering Sea. We did not attempt to identify factors driving these distributional shifts, but the timing of shifts did coincide with the busiest fishing seasons over the Bering Sea Shelf and, in part, the open seasons for walleye pollock (Gadus chalcogrammus). If groundfish populations continue to move poleward with climate change, this study may serve as a window into the early stages of a long-term redistribution of commercial fishing effort in the Bering Sea, a region supporting one of the largest fishing industries in the world.

Sabbatical leave is a benefit that is commonly associated with higher education but is rarely found in the private sector. The benefits that a sabbatical provides a professor, the opportunity to “recharge and refresh” and return to their responsibilities reinvigorated, would also apply to businesses offering this benefit. In light of the recent COVID disruption, employee claims of “burn-out” and the subsequent resignations of many workers, employee retention is a serious issue for many firms. Search and hiring costs are significant. This study examines the benefits to the firm of offering sabbaticals to their employees. It also provides a framework for businesses to compare search and hiring costs with the costs of a sabbatical program. The numerical example provided demonstrates that avoiding the costs associated with a search could fund an 8-week sabbatical for an employee.