Papers by Keyword: Healing

Abstract: Extending the range of finished product sizes from a given ingot or concast bloom or billet section is often limited by the minimum area reduction required to ensure effective central consolidation and final mechanical properties. Predicting effective consolidation or level of remnant porosity for a range of steel grade, billet size, pass schedule/roll design and thermo-mechanical conditions has always been an important issue on plant, much more lately in view of recent trends for larger ingots and development of combined forging/rolling strategies. This paper will focus primarily on a fast analytical technique based on roll gap shape and consolidation factors obtained from Finite Element (FEM) Models. New developments based on FEM submodelling are presented briefly. Healing capabilities based on diffusion bonding can be obtained from [1-3].

Abstract: Hot tearing is the one of the biggest problems when casting aluminium alloys. Although there has been much research work in this field, it is still not clear what causes hot tearing and how it propagates. Furthermore, the effect of solidified structure on the hot tearing has not been clear. Therefore, this study has been carried out to correlate the solidified structure and hot tearing. Al-2.0 wt% Cu alloy was used for test alloy. To change the solidified structure, some amount of refiner was added to the molten alloy. A permanent mould, which has been developed by us, can form hot tearing intentionally in the center region of a solidified shell. The cross section of a solidified shell was metallographically investigated and solidified structure and hot tearing were characterized. The length of hot tear decreased with increasing the amount of refiner. This may indicate that it is difficult for hot tear with fine equiaxed grains to propagate. In addition to this, the residual liquid around the hot tear was moved to the cracking due to negative pressure and hot tearing was partially healed.

Abstract: A cohesive zone damage-healing model (CZDHM) derived based on the laws of thermodynamics for self-healing materials is presented. The well-known nominal, healing, and effective configurations of classical continuum damage mechanics are extended to self-healing materials. A new physically-based internal crack healing state variable is proposed for describing the healing evolution within the crack cohesive zone. The effects of temperature, crack-closure, and resting time on the healing behavior are discussed. Numerical examples are conducted to show the various novel features of the formulated CZDHM.

Abstract: Technique of including an amorphous thermoplastic film as the outermost layer of thermoset composites have been developed to join the thermoset composites using fusion bonding methods. Based on a WLF temperature dependence and a time dependence of t^1/4, isothermal and non-isothermal models were developed to relate the recovery of bonding strength to welding temperature and time. The isothermal model failed to take into account the time taken for the bonding interface to reach the glass transition temperature and final desired bonding temperature and lacked predictive power for experiments with short bonding times and low shear strength recovery. The non-isothermal model provided an excellent fit to the experimental date, showing a significant improvement over the isothermal model.

Abstract: A remediation technique of cracked concrete by bacterial mediated carbronate deposition i.e. bio-deposition is discussed. Bio-deposition is a technique that comes from a broader category of biomineralization. The aim of this study was to investigate the plugging of artificially cracked concrete using bacteria Sporosarcina pasteurii and combined with sand as a filling material in artificially made cuts in concrete specimens which was cured in urea and Ca2+ medium and to research the effects on the compressive strength and flexural load of healing of concrete specimens by bio-deposition. The remediation efficacy of cracks in concrete was studied through compressive strength test and flexural failure test. Experimental results show that bio-deposition is able to make the improvement in concrete compressive strength and flexural load. The technique can be used to improve the compressive strength and flexural load of cracked concrete specimens and the remediation of cracks.

Abstract: An effective wound dressing is not only able to protect the wound area from its surroundings to avoid infection and dehydration, but also to speed up the healing process by providing an optimum microenvironment for healing, removing any excess wound exudates, and allowing continuous tissue reconstruction. In this study, two biodegradable polymers, polycaprolactone (PCL) and polyvinyl alcohol (PVA), were used to electrospin nanofibre membranes. The wound dressing performances of these two membranes were compared with the wound dressing performances of protein coated membranes and conventional non-woven cotton wound dressings. In addition, fibre morphology, porous structural property, mechanical properties of the nanofibre membranes, and their drainage capacity and wound skin histology were examined.

Abstract: The low thermal expansion (α25-1100oC = 0.05 ~ 1.6 × 10–6/K) of Al2TiO5 ceramics are apparently due to a combination of grain boundary micro cracking caused by the large thermal expansion anisotropy of the crystal axes of the Al2TiO5 phase. During the reheating run, the individual crystallites expanded at low temperature; thus, the solid volume of the specimen expanded into the micro cracks, where as the macroscopic dimensions remained almost unchanged. As a result, the material expanded very little. The micro cracks closed at higher temperatures. This result is closely related to relatively steeper thermal expansion curves.