Fracture Toughness Determination for Aluminium Alloy 2011-T6 using Tensile Notched Round Bar (NRB) Test Pieces

While the use of notched round bar (NRB) test pieces to determine planestrain fracture toughness K _Ic is not novel, relatively few authors have so far attempted this. This letter serves to report a series of such tests conducted on Al 2011-T6, a high mechanical strength, free-machining aluminium alloy. A total of 9 specimens was used, comprising 3 specimens each of 3 different notch root radii, ρ. No fatigue precracking was carried out. A graph of apparent fracture toughness K _ρ versus ρ / D was extrapolated to zero, corresponding to a fatigue pre-cracked configuration. The resulting K _Ic for this alloy tested using the NRB specimens was thus found to be 27.9 MPa√m. This is a valid K _Ic value, as there is only a 6.8% difference between it and the median value (26.0 MPa√m) determined previously from 67 tests using the existing ASTM E399 standard. A new geometric correlation based on ρ, D and d is proposed to linearly extrapolate K _ρ values, measured on NRB specimens with arbitrary geometries (but assuming plane-strain conditions hold), back to a single value of K _Ic.     

A comprehensive approach in green space site planning: an application of a three-stage multi-criteria decision support system

ABSTRACT

To green space site planning, this paper deals with ‘Regional Park site planning’, and presents a concept of ‘criteria screening and selection’. Through a three-stage decision support system, this paper, firstly, identifies general criteria for green space site planning and then comes up with specific criteria for Regional Park site planning within Shiraz metropolitan area. The paper contributes to the literature by improving the existing approaches of criteria selection, and points out that the list of selection criteria aggregated from literature should be adapted to case specific characteristics before being used to select a new location for public green spaces.     

Recapitulating Antioxidant and Antibacterial Compounds into a Package for Tissue Regeneration: Dual Function Materials with Synergistic Effect

Oxidative damage and infection can prevent or delay tissue repair. Moreover, infection reinforces reactive oxygen species (ROS) formation, which makes the wound's condition even worse. Therefore, the need for antioxidant and antibacterial agents is felt for tissue regeneration. There are emerging up-and-coming biomaterials that recapitulate both properties into a package, offering an effective solution to turn the wound back into a healing state. In this article, the principles of antioxidant and antibacterial activity are summarized. The review starts with biological aspects, getting the readers to familiarize themselves with tissue barriers against infection. This is followed by the chemistry and mechanism of action of antioxidant and antibacterial materials (dual function). Eventually, the outlook and challenges are underlined to provide where the dual-function biomaterials are and where they are going in the future. It is expected that the present article inspires the designing of dual-function biomaterials to more advanced levels by providing the fundamentals and comparative points of view and paving the clinical way for these materials.