Using data obtained for a recent production 48-inch diameter X80 PSL2 pipe, the transition in fracture behavior between fully brittle and fully ductile modes was examined to assess any effects of transverse splits or delaminations. The additional surface area formed at the splits can increase and decrease the Charpy energy by expending energy to form more fracture surface and reduce constraint on the propagating crack as it extends through the unnotched Charpy ligament. Fitting of full Charpy energy transition curves for the tested material with standard hyperbolic tangent functions does not represent the behavior well. An important transition is noted in the behavior between splitting that initiates at the initial notch tip and splitting that occurs further down in the ligament. Spitting across the notch tip increases Charpy energy by releasing constraint on crack initiation behavior at the machined notch and occurs at temperatures just above the lower shelf temperature where brittle fracture dominates. The splitting behavior can also be correlated to effects on fracture toughness in the same orientation for CTOD specimens in the base material and for correlated effects on CTOD behavior in the weld heat affected zone when the crack advance is in the through thickness direction.

Correlations between Charpy energy transition temperatures and other fracture mechanics parameters have been widely used for many years in steel failure analysis and design. The primary value transferred often has been a transition temperature, such as the 27 J transition temperature. This approach does not consider the scatter in the transition temperature or in the overall Charpy data. This work uses a scatter assessment tool developed by Orynyak et al. and applies it to a wider variety of steels and weldments to see whether it can provide a second parameter to be transferred to fracture assessment. Examples include pipeline steel and structural steel, as well as weldments in both the weld metal and heat-affected zone. While Charpy transition scatter is expected to be high in heat-affected zones, examples can be found in base metals with similarly high scatter.

In the field of rotordynamics, the critical speeds of a rotating system have a wide range of implications throughout industry as the operating speeds for current machine design are pushed to the limit. Moreover, interaction or coupling of a rotordynamic system with the base and/or auxiliary structures influences the dynamic behavior as well as the critical speeds for the coupled system. In order to ensure that the critical speeds of the coupled system is not excited, structural modification of primary structures (e.g. rotordynamic, foundation, auxiliary units etc.) and/or of the coupling parameters may be necessary by passive or active means. The modeling of these coupled systems, as well as the coupling mechanism, may lead to approximation errors. These errors may deteriorate the desired dynamic response of the coupled system. In order to avoid such modeling errors, this paper investigates structural modification and control strategies that are purely based on the transfer functions of the individual subsystems of the overall coupled system. The proposed concept is demonstrated by numerical examples, in which the receptance transfer functions are used to guide structural modifications; for example, to change the critical speed of a coupled rotordynamic system to a desired value. Coupling of turbine-generator assembly and rotordynamic system with flexible base is considered here.

Engineering curricula, regardless of the specific discipline, need to evolve. Realizing also that the pedagogical value of any educational artifact is closely linked to the methods of instruction used to interact with students, it is imperative that the development of new learning materials be accompanied by the implementation of innovative techniques with demonstrated success in knowledge transfer. This paper presents details of the development of studio styled modules associated with groups of courses within the mechanical and manufacturing engineering curriculum. Within each studio, newly developed activities engage students through experiential learning techniques. These activities, or learning exercises, represent a fusion of hands-on experimentation and computational simulation/analysis in key areas of engineering, such as dynamical systems, thermal sciences and materials. This endeavor is also intended to promote STEM education through enhancements in the quality of technical content, methods of instruction, training of student as effective educators, and the establishment of outreach activities expected to have an enduring effect on the preparation and recruitment of young talent into the sciences.