Numerical modeling of the thermal contact in metal forming processes

Heat flow across the interface of solid bodies in contact is an important aspect in several engineering applications. This work presents a finite element model for the analysis of thermal contact, which takes into account the effect of contact pressure and gap dimension in the heat flow across the interface between two bodies. Additionally, the frictional heat generation is also addressed, which is dictated by the contact forces predicted by the mechanical problem. The frictional contact problem and thermal problem are formulated in the frame of the finite element method. A new law is proposed to define the interfacial heat transfer coefficient (IHTC) as a function of the contact pressure and gap distance, enabling a smooth transition between two contact status (gap and contact). The staggered scheme used as coupling strategy to solve the thermomechanical problem is briefly presented. Four numerical examples are presented to validate the finite element model and highlight the importance of the proposed law on the predicted temperature.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) under the project PTDC/EMS-TEC/1805/2012 and by FEDER funds through the program COMPETE Programa Operacional Factores de Competitividade, under the project CENTRO-07-0224- FEDER-002001 (MT4MOBI). The second author is also grateful to the FCT for the postdoctoral grant SFRH/BPD/101334/2014. The authors would like to thank Prof. A. Andrade-Campos for helpful contributions on the development of the finite element code presented in this work.info:eu-repo/semantics/publishedVersio

Good parenting may not increase reproductive success under environmental extremes

For species exhibiting parental care, the way in which parents adjust care behaviour to compensate for environmental change potentially influences offspring survival and, ultimately, population viability. Using the three‐spined stickleback (Gasterosteus aculeatus) – a species in which males provide parental care by building and tending a nest and fanning the eggs – we examined how low dissolved oxygen (DO) levels affect paternal care, embryo development and survival. While levels of nest tending were unaffected by DO level, we found that larger males fanned their embryos more under low oxygen conditions. This resulted in faster rates of embryo development within the clutches of these larger males, but reduced embryo survival at 7d post‐fertilisation compared to clutches of smaller males. Our results suggest that although parents may attempt to compensate for environmental change via alterations to care behaviour, their ability to do so can be dependent on parental phenotype. This sets up the potential for oxygen levels to act on the strength and direction of selection within populations. We discuss possible explanations for the surprising result that supposedly adaptive changes in care behaviour by large males (i.e. increased fanning) led to reduced embryo survival at 7d post‐fertilisation, and whether, as a consequence, acute environmental conditions may have the potential to overwhelm selection on sexual traits