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This paper presents the cyclic plasticity and low cycle fatigue (LCF) damage characterisation of thermally simulated heat affected zone (HAZ) for API 5L X100Q weldments. Microstructures representative of the HAZ for two cooling rates are generated using a Gleeble thermomechanical simulator for manufacture of strain-controlled cyclic plasticity test specimens. The simulated HAZ specimens are subjected to a strain controlled test programme which examines the cyclic effects of strain-range and the tensile response at room temperature. A modified version of the Chaboche rate independent plasticity model, which accounts for early stage damage is implemented to characterise the cyclic plasticity response, including isotropic and kinematic hardening effects. The constitutive parameters are fitted to experimental data using an optimisation procedure developed within a MATLAB code. The measured response of the simulated HAZ specimens is compared to that of the X100Q parent material (PM), and the simulated HAZ is shown to share the early stage fatigue damage behaviour of the PM, but exhibits significantly a higher yield and cyclic strength.

Abstract Background Osteosarcoma (OSA) spontaneously arises in the appendicular skeleton of large breed dogs and shares many physiological and molecular biological characteristics with human OSA. The standard treatment for OSA in both species is amputation or limb-sparing surgery, followed by chemotherapy. Unfortunately, OSA is an aggressive cancer with a high metastatic rate. Characterization of OSA with regard to its metastatic potential and chemotherapeutic resistance will improve both prognostic capabilities and treatment modalities. Methods We analyzed archived primary OSA tissue from dogs treated with limb amputation followed by doxorubicin or platinum-based drug chemotherapy. Samples were selected from two groups: dogs with disease free intervals (DFI) of less than 100 days (n = 8) and greater than 300 days (n = 7). Gene expression was assessed with Affymetrix Canine 2.0 microarrays and analyzed with a two-tailed t-test. A subset of genes was confirmed using qRT-PCR and used in classification analysis to predict prognosis. Systems-based gene ontology analysis was conducted on genes selected using a standard J5 metric. The genes identified using this approach were converted to their human homologues and assigned to functional pathways using the GeneGo MetaCore platform. Results Potential biomarkers were identified using gene expression microarray analysis and 11 differentially expressed (p < 0.05) genes were validated with qRT-PCR (n = 10/group). Statistical classification models using the qRT-PCR profiles predicted patient outcomes with 100% accuracy in the training set and up to 90% accuracy upon stratified cross validation. Pathway analysis revealed alterations in pathways associated with oxidative phosphorylation, hedgehog and parathyroid hormone signaling, cAMP/Protein Kinase A (PKA) signaling, immune responses, cytoskeletal remodeling and focal adhesion. Conclusions This profiling study has identified potential new biomarkers to predict patient outcome in OSA and new pathways that may be targeted for therapeutic intervention.

A multiaxial, physically based, continuum damage mechanics methodology for creep of welded 9Cr steels is presented, incorporating a multiple precipitate-type state variable, which simulates the effects of strain- and temperature-induced coarsening kinematics. Precipitate volume fraction and initial diameter for carbide and carbo-nitride precipitate types are key microstructural variables controlling time to failure in the model. The heat-affected zone material is simulated explicitly utilising measured microstructural data, allowing detailed investigation of failure mechanisms. Failure is shown to be controlled by a combination of microstructural degradation and Kachanov-type damage for the formation and growth of creep cavities. Comparisons with experimental data demonstrate the accuracy of this model for P91 material. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a crystal plasticity model to predict the tensile response and crack initiation in a mixed ferrite‐martensite material with a low volume fraction of pro‐eutectoid ferrite, representative of a welding‐induced intercritical heat‐affected zone. It is shown that small volume fractions of ferrite can have a significant effect on material strength and ductility depending on the ferrite grain orientation. For relatively “soft” ferrite grains, microcracks can grow across interferrite ligaments with damage accumulating in the ferrite, leading to a reduction in strength and strain hardening, but with little influence on ductility; in contrast, relatively “hard” ferrite grains act to accelerate microcrack initiation, leading to reduced ductility, with negligible influence on strain hardening up to the maximum load. [ABSTRACT FROM AUTHOR]

Failure in steel weldments operating at high temperatures often occurs in the heat-affected zone adjacent to the weld. Such failures can be a result of material inhomogeneity within the heat-affected zone and in the case of tempered martensite steels have been linked with regions of untransformed α (ferrite) phase or over-tempered martensite within the intercritical region of the heat-affected zone. In this work, two-dimensional Voronoi tessellation is used to construct polygonal Voronoi cells to represent the microstructure of the heat-affected zone of a weld in a tempered martensite steel. The Voronoi construction is treated as a representative volume element of the material and is discretised by 8-node linear brick elements, with periodic boundary conditions. The lattice orientation at each material point is specified by three Euler angles, which are assumed to be randomly distributed, to represent the initial lack of texture in the intercritical region of the heat-affected zone. The constitutive response is represented by a nonlinear, rate-dependent, finite-strain crystal plasticity model. The results indicate that small amounts of ferrite can induce significant enhancements in stress and inelastic deformation at the interface of the ferrite and martensite grains. This localisation of stress and strain may be critical for microcrack and/or void formation and may be a contributory factor to Type IV cracking. [ABSTRACT FROM AUTHOR]

A dislocation-based model for high temperature cyclic viscoplasticity in 9-12Cr steels is presented. This model incorporates (i) cyclic softening via decrease in overall dislocation density, loss of low angle boundary dislocations and coarsening of the microstructure and (ii) kinematic hardening via precipitate strengthening and dislocation substructure hardening. The effects of the primary micro-structural variables, viz. precipitate radii, dislocation density and martensitic lath width on cyclic viscoplasticity, reveal a size effect of initial precipitate radii and volume fraction, with smaller radii and a higher density of precipitate producing a stronger material. A similar effect is also predicted for initial martensitic lath width at temperatures below 500 °C. The model is intended for microstructure sensitive design of high temperature materials and components for next generation power plant technology. [ABSTRACT FROM AUTHOR]

The article examines the prevalence of inter- and intraspecies cell line contamination in a veterinary research setting. The results showed that 3 canine cell lines were misindentified or cross-contaminated by other canine cell lines. It emphasizes the importance of cell line validation as a component of good cell culture practice.

ABSTRACT--An integrated computational/experimental procedure to assess rapid axial crack propagation in a polyethylene gas pipe is described here. This is based on a first-principles fracture mechanics approach in which the fracture toughness for the pipe material and the driving force for the flawed pipe are calculated separately. The toughness is determined from an instrumented small-scale steady-state test on a short section of pipe. The driving force is calculated by using an analysis package for fluid/structure interaction in a cracked pipeline. A methodology to preclude the possibility of a long-running crack in a pipeline is presented. By way of validation, a number of comparisons are made with experimentally determined critical pressures for propagation. [ABSTRACT FROM AUTHOR]

ABSTRACT--The authors propose a simulation method for analyzing the distributions of blood flow velocity and shear stress in a cross-sectional plane of the intramyocardial coronary vessel. They compute a fully developed viscous fluid flow in a helical coiled pipe conformed in a cubic space for simulating the blood flow in an intramyocardial coronary vessel. The fluid and continuity equations are solved by the series expansion method under the small Dean number. The authors compute the axial, radial, and vertical blood flow velocities and their rates of spatial changes along the circumferential direction that are parallel to the shear stresses acting on the helical tube wall under the variable geometric changes in the helical coiling tube. The velocities and their rates of spatial changes accelerate as the number of helical coiling increases. The authors discuss the rational conformation of the helically coiled intramyocardial coronary vessel system and its relation to the effective blood perfusion. An extended version of the present method will be available for evaluating the intramyocardial coronary perfusion in relation to the coronary arterial sclerosis and surgical operation. [ABSTRACT FROM AUTHOR]

Describes the development of AGILE, a damage analysis system using a hierarchical analysis strategy based on feature-based modeling techniques and finite element alternating method. Key tasks that the system automates; Applications; Complexities in hierarchical analysis.