A New Method of Creep Ruptures Data Extrapolation Based on the Work
For structural and machine components in service at high temperature and pressure, such as those used in power generating and petrochemical plants, as well as aero-engines and metallurgical machineries, creep life assessment is a major concern because of safety and economic reasons. In this paper, a new model for creep life prediction is proposed based on energy processes. The work of making the material failure of applied loads is used to describe the creep processes respectively. By mathematical technique, the expression of the model is, where is Larson-Miller constant, and is also material constant at certain condition. This function Moreover, owing to its simple expression, it is very easy to use this model to predict the creep life. To check the validity of the new model proposed in this paper, the 250000h creep rupture strength estimates for 2.25Cr1.0Mo steel under stress control at 743~793K have been performed. The results are in a good agreement with the experimental data.
Life management of refinery furnace tubing
Abstract The 2PTR and 3PTR furnaces at the MOBIL (Altona) Refinery have tubing that have been in operation for over 20 years. API RP 530 creep rupture life calculations showed that the tubes have limited remaining life. Therefore accelerated creep rupture testing was undertaken of a material from the likely worst case tube sample. However, going from creep rupture test results to assess the remaining life of furnace tubing is complicated by the fact that• the tested tubes may not have been exposed to the maximum temperature for the life of the furnace;• the test stress is different from the service stress because various pressure and wall thickness combinations exist. To overcome such issues detailed heat transfer calculations were carried out to understand tube temperatures based on thermography data and assessment of consumed life fraction was undertaken. Deterministic modelling of total life based on wall thickness data and operating pressure was carried out using most appropriate creep rupture database. It was found that there was sufficient remaining life for tubes in 2PTR furnace such that replacements were not required prior to the next normal outage. However, it is found that if high temperatures are experienced in 3PTR furnace a failure could occur in the near future. The information from the life assessment study was integrated into a risk based inspection program and set temperature limits to allow planned replacement of the tubing.
In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs
Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.