A parametric study of residual stresses in multi-pass butt-welded stainless steel pipes

Multipass butt welding of a very thick steel plate has been performed. Transient temperatures and residual stresses have been measured. The agreement between calculations and experiments is good. T ...

Simulation of multipass welding of a thick plate

The assessment of residual stresses in welded high strength steel box sections

Validated residual stress profiles for fracture assessments of stainless steel pipe girth welds

The integral method is a suitable calculation procedure for the determination of nonuniform residual stresses by semidestructive mechanical methods such as the hole-drilling method and the ring-core method. However, the high sensitivity to strain measurement errors due to the ill conditioning of the equations has hindered its practical use. the analysis of the influence of the strain measurment error on the computed stresses carried out in the present work has showed that, given both maximum hole depth and number of total steps, the error sensitivity depends on the particular depth increment distribution used. By means of the matrix formulation, the depth increment distribution that optimizes the numerical conditioning is investigated. Numerical simulations and an experimental test have corroborated the best performance of the proposed step distribution with respect to the constant or increasing distributions commonly used.

Optimal calculation steps for the evaluation of residual stress by the incremental hole-drilling method

Significant errors in interpreting the results of the centre-hole technique may arise where test conditions deviate from a uniform uniaxial low-level stress field. This paper demonstrates that where the stress field varies linearly with depth, the as-measured stress represents the stress at one-quarter hole depth. In cases where surface preparation for strain gauging has induced residual stress or where stress levels are sufficiently high to induce plasticity during hole forming, simple formulae are proposed to correct for these effects.

On the correction of residual stress measurements obtained using the centre-hole method

Residual Stresses in Cylinder Girth Butt Welds

Aposematism is the signalling of a defence for the deterrence of predators. We presently focus on aposematic organisms that exhibit chemical defences, which are usually signalled by some type of brightly coloured skin pigmentation (as is the case with poison frog species of the Dendrobatidae family), although our treatment is likely transferable to other forms of secondary defence. This setup is not only a natural one to consider but also opens up the possibility for rich mathematical modelling: the strength of aposematic traits (signalling and defence) can be unambiguously realised using variables that are continuously quantifiable, independent from one another and which together define a two-dimensional strategy space wherein the aposematic behaviour of any one organism can be represented by a single point. We presently develop an extensive mathematical model in which we explore the joint co-evolution of aposematic traits within the context of evolutionary stability. Even though empirical and model-based studies are conflicting regarding how aposematic traits are related to one another in nature, the majority of works allude to a positive correlation. We presently suggest that both positively and negatively correlated combinations of traits can achieve evolutionarily stable outcomes and further, that for a given level of signal strength there can be more than one optimal level of defence. Our findings are novel and pertinent to a sizeable body of physical evidence, which we discuss. 

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A. A. Scaramangas

Papers

On the correction of residual stress measurements obtained using the centre-hole method

Residual Stresses in Cylinder Girth Butt Welds

Aposematic signalling in prey-predator systems: determining evolutionary stability when prey populations consist of a single species

Evolutionarily stable levels of aposematic defence in prey populations.