Endochronic theory, non-linear kinematic hardening rule and generalized plasticity: a new interpretation based on generalized normality assumption

A simple way to define the flow rules of plasticity models is the assumption of generalized normality associated with a suitable pseudo-potential function. This approach, however, is not usually employed to formulate endochronic theory and non-linear kinematic (NLK) hardening rules as well as generalized plasticity models. In this paper, generalized normality is used to give a new formulation of these classes of models. As a result, a suited pseudo-potential is introduced for endochronic models and a non-standard description of NLK hardening and generalized plasticity models is also provided. This new formulation allows for an effective investigation of the relationships between these three classes of plasticity models

On the quasi-yield surface concept in plasticity theory

In this paper we provide deeper insights into the concept of the quasi-yield surface in plasticity theory. More specifically, in this work, unlike the traditional treatments of plasticity where special emphasis is placed on an unambiguous definition of a yield criterion and the corresponding loading-unloading conditions, we place emphasis on the study of a general rate equation which is able to enforce elastic-plastic behavior. By means of this equation we discuss the fundamental concepts of the elastic range and the elastic domain. The particular case in which the elastic domain degenerates into its boundary leads to the quasi-yield surface concept. We exploit this concept further by discussing several theoretical issues related to it and by introducing a simple material model. The ability of the model in predicting several patterns of the real behavior of metals is assessed by representative numerical examples

Evaluation of the Highway Safety Manual Crash Prediction Model for Rural Two-Lane Highway Segments in Kansas

While there have been numerous previous studies performed to develop the rural two-lane segment crash prediction models as part of the Highway Safety Manual (HSM), no previous study has been developed to validate the accuracy of the current model for states other than those the model was developed for. To address this gap the Kansas Department of Transportation (KDOT) commissioned this study to analyze both the accuracy and the practicality of using these crash prediction models on Kansas highways before deciding whether or not to implement the models as part of their normal project development process. To accomplish these goals this dissertation first determined gaps in KDOT data versus data requirements of the HSM. This effort identified an important inconsistency between the Kansas highway system and how the HSM recommends application of the model. Next, the model was calibrated using both the HSM procedure and new procedures that address specific qualities of the Kansas highway system. The calibration procedure derived through this dissertation outperformed the HSM procedure and shows promise as a model for calibration in other jurisdictions. Finally, the accuracy of the crash prediction models for Kansas highways was determined and a calibration procedure was recommended for implementation

The Effects of Cognitive Strategy Instruction on Students\u27 Reading Comprehension

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Deformation and Failure of Amorphous Solidlike Materials

Since the 1970's, theories of deformation and failure of amorphous, solidlike materials have started with models in which stress-driven, molecular rearrangements occur at localized flow defects via "shear transformations". This picture is the basis for the modern theory of "shear transformation zones" (STZ's), which is the focus of this review. We begin by describing the structure of the theory in general terms and by showing several applications, specifically: interpretation of stress-strain measurements for a bulk metallic glass, analysis of numerical simulations of shear banding, and the use of the STZ equations of motion in free-boundary calculations. In the second half of this article, we focus for simplicity on what we call an "athermal" model of amorphous plasticity, and use that model to illustrate how the STZ theory emerges within a systematic formulation of nonequilibrium thermodynamics.Comment: 28 pages, 4 figures, submitted to Annual Reviews of Condensed Matter Physic

Characterising gross plastic deformation in design by analysis

An investigation of three simple structures is conducted to identify and characterise the condition of gross plastic deformation in pressure vessel design by analysis. Limit analysis and bilinear hardening plastic analysis is performed for three simple example problems. It is found that previously proposed plastic criteria do not fully represent the effect of the hardening material model on the development of the plastic failure mechanism. A new criterion of plastic collapse based on the curvature of the load–plastic work history is therefore proposed. This is referred to as the Plastic Work Curvature or PWC criterion. It is shown that salient points of curvature correspond to critical stages in the physical evolution of the gross plastic deformation mechanism. The PWC criterion accounts for the effect of the bilinear hardening model on the development of the plastic mechanism and gives an enhanced plastic load when compared to the limit load