Identification of residual stress directionality using anisotropic indenter in instrumented indentation testing

Instrumented indentation testing can be used to quantitatively evaluate the local residual stress on the surface. Many studies have confirmed that indentation load-displacement curves obtained from Vickers indentation and Berkovich indentation are shifted depending on the residual stress state. Based on this, many researchers have proposed models for evaluating the residual stress by comparing indentation curves obtained from stressed and stress-free specimens of the same composition and microstructure. Though Vickers and Berkovich indenters can quantitatively evaluate the residual stresses, it is difficult to evaluate their directionality such as principal direction and principal stresses because the indenters are axisymmetric. In order to overcome these limitations, we have evaluated the residual stress directionality by using less axisymmetric indenters, such as the Knoop indenter and a modified Berkovich indenter (a conventional Berkovich indenter extended along one axis). [1] With these two sorts of indenters, the degree of shifting of the indentation curve depends on the direction of the long axis of the indenter in the non-equibiaxial stress state. We introduced a conversion factor, a proportional constant between indentation load difference and stress, and proposed a method for quantitatively evaluating the directionality of surface residual stress using this conversion factor. We applied a non-equibiaxial stress state to cruciform specimens and verified the accuracy of the proposed model using the conversion factor in Knoop and modified Berkovich indentation testing. Also, the experiments and finite-element analysis of Knoop and modified Berkovich indentations showed that the ratio of the length of the major axis and minor axis of the indenter is correlated to the conversion factor ratio; a generalized formula is proposed. REFERENCES [1] Jong-hyoungKim and Huiwen Xu, “Determination of directionality of non-equibiaxial residual stress by nanoindentation testing using a modified Berkovich indenter”, JMR 33. 3849-3856, 2018

A Patterned Single Layer Graphene Resistance Temperature Sensor

Micro-fabricated single-layer graphenes (SLGs) on a silicon dioxide (SiO2)/Si substrate, a silicon nitride (SiN) membrane, and a suspended architecture are presented for their use as temperature sensors. These graphene temperature sensors act as resistance temperature detectors, showing a quadratic dependence of resistance on the temperature in a range between 283 K and 303 K. The observed resistance change of the graphene temperature sensors are explained by the temperature dependent electron mobility relationship (~T−4) and electron-phonon scattering. By analyzing the transient response of the SLG temperature sensors on different substrates, it is found that the graphene sensor on the SiN membrane shows the highest sensitivity due to low thermal mass, while the sensor on SiO2/Si reveals the lowest one. Also, the graphene on the SiN membrane reveals not only the fastest response, but also better mechanical stability compared to the suspended graphene sensor. Therefore, the presented results show that the temperature sensors based on SLG with an extremely low thermal mass can be used in various applications requiring high sensitivity and fast operation

Behavior of Connections Between SHS Columns & W-section Beams

Connections between SHS (Square Hollow Section) columns and W-section beams are generally fabricated by welding with or without endplates in the factory. These welded connections possess some finite degree of rotational stiffness which falls between fully rigid and ideally pinned joints. The influence of partially restrained connections on structural response not only changes the moment distribution but also increases frame drift. In this paper, a series of connection tests joining SHS column and W-section beam were executed and the test results compared with theoretical values. A method to utilize nonlinear moment-rotation relations of beam-to-column connections in steel framed structures is proposed. For the problem of contact in endplate-type connections, a simple and efficient method is also introduced

Unified Hierarchical Relationship Between Thermodynamic Tradeoff Relations

Recent years have witnessed a surge of discoveries in the studies of thermodynamic inequalities: the thermodynamic uncertainty relation (TUR) and the entropic bound (EB) provide a lower bound on the entropy production (EP) in terms of nonequilibrium currents; the classical speed limit (CSL) expresses the lower bound on the EP using the geometry of probability distributions; the power-efficiency (PE) tradeoff dictates the maximum power achievable for a heat engine given the level of its thermal efficiency. In this study, we show that there exists a unified hierarchical structure encompassing all of these bounds, with the fundamental inequality given by a novel extension of the TUR (XTUR) that incorporates the most general range of current-like and state-dependent observables. By selecting more specific observables, the TUR and the EB follow from the XTUR, and the CSL and the PE tradeoff follow from the EB. Our derivations cover both Langevin and Markov jump systems, with the first proof of the EB for the Markov jump systems and a more generalized form of the CSL. We also present concrete examples of the EB for the Markov jump systems and the generalized CSL.Comment: 19 pages, 4 figure

anti-9,10-Di(1-naphth­yl)anthracene pyridine disolvate

In the title compound, C34H22·2C5H5N, there is a crystallographic inversion center in the middle of the anthracene ring system. The dihedral angle between the mean planes of the anthracene and naphthalene ring systems is 83.96 (4)°. The crystal structure is stabilized by weak inter­molecular C—H⋯N and C—H⋯π inter­actions

Description of the Diadegma fenestrale (Hymenoptera: Ichneumonidae: Campopleginae) Attacking the Potato Tuber Moth, Phthorimaea operculella (Lep.: Gelechiidae) New to Korea

Diadegma fenestrale is known as a parasitoid of the potato tuber moth, Phthorimaea operculella. The potato tuber moth, Phthorimaea operculella (Zeller) is one of the most destructive pest of potatoes. Also, we found this species attacking the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae). Ratio of parasitism is 20-30% and cocoon of lepidopteran was parasitic ichneumonid species after 3 days. This species and the genus Diadegma are recorded for the first time from Korea. In this paper, description of the parasitoid and photographs of the diagnostic characteristics are provided