Effect of heat treatment on deformation and corrosion behavior of Type 422 stainless steel

High temperature tensile properties of quenched and tempered martensitic Type 422 stainless steel, a target structural material, have been evaluated in this study at temperatures ranging from ambient to 600°C as a function of three different tempering times. Results of tensile testing indicate that the ultimate tensile strength, yield strength and failure strength were gradually reduced with increasing temperature. However, as expected, the ductility parameters were enhanced due to increased plastic flow at elevated temperatures. The results of stress corrosion cracking tests performed by slow strain rate technique in the 90°C acidic solution revealed higher failure stress and reduced ductility to some extent for specimens tempered for longer time. The results of localized corrosion studies conducted by cyclic potentiodynamic polarization technique indicate that the critical corrosion potential became more active (negative) at higher testing temperature in specimens exposed to both neutral and acidic environments. Evaluation of the primary fracture face by scanning electron microscopy revealed more cracks at ambient temperature with smaller plastic zone size. Increased ductility was observed at elevated temperatures showing larger dimpled areas

The development of artificial muscles using textile structures

The aim of this project was to investigate the use of textile structures as muscles to assist people with muscular deficiency or paralysis. Due to the average life expectancy continuing to increase, support for those needing assistance to move unaided is also increasing. The purpose of this project was to try to help a patient who would normally need assistance, to move their arm unaided. It could also help with rehabilitation of muscular injuries and increasing strength and reducing muscular fatigue of manual workers. The approach considered was to develop an extra corporal device for the upper limbs, providing the main required motions. Most devices currently available use motors and gearboxes to assist in limb movement. This study investigated a way of mimicking the contraction of biological skeletal muscles to create a motion that is as human as possible with a soft, flexible and lightweight construction. Electroactive polymers (EAPs) and pneumatic artificial muscles (PAMs) were investigated. It became clear that at present, the EAPs were unable to create the forces and speed of contraction required for this application. The use of pneumatics to create artificial muscles was developed upon. PAMs, like the McKibben muscle and the pleated pneumatic muscle mimic the natural contraction of skeletal muscle. These current PAMs were used as a basis to develop a new type of pneumatic artificial muscle in this project. A 90 mm ball-like structure was developed, produced from an air impermeable rubber coated cotton fabric. Joining three oval panels together created a 3-D spherical shape. Three of these structures were linked together, and when inflated, created an acceptable level of contraction and force. This method of producing artificial muscles created a soft, lightweight and flexible actuator with scope for different arrangements, sizes and positions of the muscle structure. The contraction process was mathematically modelled. This calculated the predicted rate and level of contraction of a 2-D muscle structure. These mathematical findings were able to be compared to the practical results, and produced similar contraction characteristics. The muscle structures were incorporated into a garment to form a type of muscle suit which could be worn to assist movement. This garment has an aluminium frame to protect the wearer's bones from stresses from the contracting muscles. This study has shown that the muscle suit developed can create movement for wearers that would normally need assistance, and also reduce muscle fatigue, which would be useful for manual workers. This is incorporated into a functional and wearable garment, which is easy to dress and more lightweight and aesthetically pleasing than current muscle suits.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Chemical examination of the Echinoderms of Indian Ocean: The triterpene glycos ides of the sea cucumbers: <i>Holothuria nobilis, Bohadschia aff. tenuissima </i>and <i>Actinopyga mauritana </i>from Lakshadweep, Andaman and Nicobar Islands

1276-1282The ethanol extracts of the sea cucumbers Holothuria nobilis, Bohadschia aff. tenuissima and Actinopyga mauritana furnishes three distinct fractions; a mixture of sterol glycosides, a mixture of cerebrosides and a mixture of triterpenoid glycosides identified as holothurin B, bivittosides C and D and echinoside B, respectively, from a comparison of the 1H NMR and 13C NMR spectral data reported earlier. Hydrolysis of triterpenoid glycosides yield three new artificial genins (1,1a and 2) along with seven known genins (3-9). The structures of these new genins have been determined by their physical and spectral data (UV, [α]D, 1H NMR and mass)