The fretting fatigue analysis between strands of ACSR
In this paper, self-made fretting fatigue wear test bed was used to investigate fretting fatigue and wear properties of overhead transmission line between the strands, and then the fretting fatigue fracture life and the fracture surface microscopic morphology of ACSR in different testing conditions was analysed. The results show that under larger included angle, larger ACSR tensile force and larger fretting amplitude, the fretting fatigue life of the wire was reduced. The crack initiation and propagation occurs in the contact edge, and the angle is 45° between fracture surface and the wire axis. Fretting fatigue fracture can be divided into three areas: micro-crack nucleation area, fatigue crack propagation area, crack area, and the three regions have different fatigue properties.
Single wire fretting fatigue tests for electrical conductor bending fatigue evaluation
Abstract Overhead electrical conductors are often subjected to aeolian vibrations which may induce fretting fatigue damage of individual aluminium wires in suspension clamp regions. Many bending fatigue tests have been performed on electrical conductors. Depending on the test conditions, wire fracture may be found to occur in the external as well as internal layers. Individual wire fretting fatigue is very difficult to predict due to a conductor complex structure and dynamic mechanical behaviour. The main objective of this work is to present experimental results obtained from tests on single wires under conditions simulating a typical conductor-clamp contact. A fretting fatigue test bench specifically designed for such simulation has been used on single H19 aluminium wires. They have been subjected to an initial minimal axial stress of 59 MPa. At the fretting point, a transverse compressive load of 130 N to 4000 N has been imposed, as well as an alternating displacement of 100 to 900 μm displacement amplitude. Cycling frequency has been kept at 10 Hz and test duration went up to 1.6 × 10 7 cycles. All tests were performed in the stick-slip regime occurring in the plastically deformed contact zone. No global slip was allowed. Subsequent examination of the fretting scars at the contact surface and through the cross-section have been carried out by optical microscopy and scanning electron microscopy. The mechanical parameters influence is studied and comparison with results from complete conductor fatigue tests is discussed.
Rational Design, Synthesis and Evaluation of γ-CD-Containing Cross-Linked Polyvinyl Alcohol Hydrogel as a Prednisone Delivery Platform
This study describes the in-silico rational design, synthesis and evaluation of cross-linked polyvinyl alcohol hydrogels containing γ-cyclodextrin (γ-CDHSAs) as platforms for the sustained release of prednisone (PDN). Through in-silico studies using semi-empirical quantum mechanical calculations, the effectiveness of 20 dicarboxylic acids to generate a specific cross-linked hydrogel capable of supporting different amounts of γ-cyclodextrin (γ-CD) was evaluated. According to the interaction energies calculated with the in-silico studies, the hydrogel made from PVA cross-linked with succinic acids (SA) was shown to be the best candidate for containing γ-CD. Later, molecular dynamics simulation studies were performed in order to evaluate the intermolecular interactions between PDN and three cross-linked hydrogel formulations with different proportions of γ-CD (2.44%, 4.76% and 9.1%). These three cross-linked hydrogels were synthesized and characterized. The loading and the subsequent release of PDN from the hydrogels were investigated. The in-silico and experimental results showed that the interaction between PDN and γ-CDHSA was mainly produced with the γ-CDs linked to the hydrogels. Thus, the unique structures and properties of γ-CDHSA demonstrated an interesting multiphasic profile that could be utilized as a promising drug carrier for controlled, sustained and localized release of PDN.