Fatigue,Magnetic and Mechanical Hysteresis

Abstract: The objective of this research is to explore correlations between piezomagnetic signals of initially unmagnetised ferromagnetic steel samples of AISI 1018 steel with progressive changes that take place during the fatigue process. A series of strain‐controlled fatigue tests were carried out to quantitatively study the piezomagnetic fields surrounding steel specimens by measuring magnetic field variations in the milligauss range resulting from the cyclic application of stress. It was observed that the piezomagnetic hysteresis traces change systematically with the progression of fatigue. The piezomagnetic hysteresis loop areas, when plotted as a function of the number of loading cycles, demonstrate the three principal stages of fatigue: initial accommodation, accretion of damage and terminal failure. The results derived from the piezomagnetic hysteresis traces are consistent with those obtained from mechanical hysteresis studies. However, when approaching failure, the piezomagnetic traces show more conspicuous changes than the corresponding mechanical stress–strain curves. It was also observed that the piezomagnetic field surrounding a specimen subjected to cyclic loading behaves approximately like that of a bar magnet. This study has demonstrated that the piezomagnetic effects can be exploited to evaluate the progress of fatigue in ferromagnetic steels.     

Quo Vadis?

Penetrating cut wounds of the chest and abdomen involving the perirenal fat can be complicated by chronic inflammations of the kidney. Latent progress of the pathological process in the kidney and perirenal fat caused paranephritis which was diagnosed only 51 days after the injury and removal of the kidney. This case once again confirms that pathologically changed organs (kidneys) are liable to be injured even during a slight indirect traumatic exposure, for example, just falling on the plane surface.     

A computational strategy to determine the incremental collapse envelope for framed structures

The incremental collapse behavior of elastic-perfectly plastic rigid frame structures subjected to cyclically varying loads can be analyzed by means of energy methods. This approach is based on the assumption that if the total hysteresis energy absorbed by a structure during an indefinitely prolonged repetitive loading program is unbounded, then the structure must ultimately fail. Analyses of a wide variety of multistory, multibay frames—currently extending up to 60 stories and 20 bays—have confirmed that the boundary between safe and unsafe load ranges coincides exactly with the transition from finite to unbounded hysteresis energy dissipation. The results for the larger structures have been obtained with a linear energy extrapolation method. This is a numerical technique that makes it feasible to determine the incremental collapse behavior of a 60-story, 20-bay frame on a time scale of a few hours with a “mini-supercomputer” such as a Prime 9755.     

What should be the focus of emotion regulation in children? A nonlinear dynamic mathematical model of children's peer interaction in groups

This paper questions the assumption that children's social and emotional competence be placed within the developing child, rather than in the interaction of the child with the range of peer social ecologies in which the children might function. This paper presents a new nonstatistical mathematical approach to modeling children's peer social interaction in small groups using nonlinear difference equations in which both an uninfluenced and an influenced regulatory set point of positive minus negative interaction can be separately estimated. Using this model and the estimation procedure, it is possible to estimate what a focal child and the group initially brings to the group interaction and also how these regulatory set points are influenced by the interaction to determine two influenced regulatory set points. Six-person mainstreamed and specialized groups were established involving three types of unacquainted preschool boys: children with and without developmental delays and a language disordered but intellectually normally functioning group, using a methodology that ensured appropriate matching of child and family characteristics. For each 2-week play group, the social interactions of each child were observed during a designated free play period. Handicapped children were observed in either a specialized or mainstreamed setting. The application made of this modeling process in this paper is generating theory to attempt to understand influence processes. Parameters are introduced that reflect uninfluenced target child and group set points, emotional inertia, and influence functions.     

Friendships of preschool children in mainstreamed playgroups.

The friendship patterns of 4-year-old mildly developmentally delayed and 3- and 4-year old nonhandicapped children participating in a series of mainstreamed playgroups were investigated. Results indicated that the majority of children in each of the three groups established a preference for a specific peer on the basis of a unilateral criterion, but only a small proportion of mildly delayed and 3-year-old nonhandicapped children were able to establish reciprocal friendships. The delayed group preferred nonhandicapped older children but were least preferred as friends overall by playgroup participants. For those nonhandicapped children meeting the friendship criteria, interactions with friends produced more advanced and positive social play in comparison with interactions with nonfriends. However, these differences did not occur for the mildly delayed group, suggesting that delayed children may not take advantage of the potential benefits associated with friendships. Possible reasons for these problems and the need to identify relevant social processes in friendship formation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peer-related social interactions of developmentally delayed young children: Development and characteristics.

Conducted a short-term longitudinal study of the peer-related social interactions of 111 developmentally delayed toddler and preschool age children. Initial analyses centered on 2 groups: one composed of younger and more severely delayed children (aged 1.8–6.6 yrs) and the other consisting of older and more mildly delayed children (aged 2.4–6.8 yrs). Observers coded a wide range of social and play behaviors during free-play interactions in individual classrooms, including ratings of social participation, constructiveness of play, and teacher behavior, as well as a series of sequential interactive measures. Similarities to normally developing children in the organization and developmental progression of peer interactions across the short term were noted for each of the groups. However, comparisons to normative expectations for preschool age children in relation to Ss' cognitive levels and cross-sectional analyses across CA suggested the existence of unusually marked deficits in peer interactions. These deficits may simply be a manifestation of a more basic and generalized social interaction deficit, or they may be related to the cognitive level-expressive language discrepancy characteristic of such children, or they may be due to the fact that such children are usually surrounded by other children with substantial deficits. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)