The effect of corrosion thinning on the collapse pressure of a submarine pressure hull
| dc.contributor.advisor | Mahomed, N. | en_ZA |
| dc.contributor.author | Viljoen, Hermanus Carl | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. | en_ZA |
| dc.date.accessioned | 2021-03-05T14:35:29Z | |
| dc.date.accessioned | 2021-04-21T14:41:58Z | |
| dc.date.available | 2021-03-05T14:35:29Z | |
| dc.date.available | 2021-04-21T14:41:58Z | |
| dc.date.issued | 2021-03 | |
| dc.description | Thesis (MEng)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The effect of corrosion thinning on a submarine pressure hull is investigated using electrochemical and immersion corrosion testing, material characterisation techniques and nonlinear finite element analysis. HY-80 steel in as-received condition as well as heat treated for 90min at 590°C was investigated. It was found that the mechanical and microstructural properties of the two conditions were almost identical. The linear-and potentiodynamic polarization techniques were used to estimate corrosion rates of 0.17mm/year and 0.18mm/year for as received and heat treated HY-80 in seawater. These rates were verified by immersion testing which estimated a rate of 0.19mm/year. Measurement of actual remaining wall thickness on a submarine with a service life of 10 years was achieved using an ultrasonic through thickness gauge. The actual loss of material was found to be a maximum of 0.201mm/year. A finite element analysis of a 15.05m long Type 209/1400 submarine section consisting of pressure hull plating and stiffeners was conducted. Material non-linearity was incorporated by using a true stress-strain curve for HY-80 steel. Initial overall and interframe out of circularity imperfections were introduced into the model using a Matlabscript that displaced the model mesh radially. It was estimated that the submarine under investigation would collapse at a depth of roughly 560m which relates to a safety factor of 2.25 against collapse at a normal operating depth of 250m. It was found that collapse was preceded by yielding of stiffeners where the maximum out of circularity imperfection was introduced. Collapse pressures were found to reduce mostly linearly with wall thickness at a rate of approximately 27kPa per year. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die effek van korrosie verdunning op die ineenstortings druk van ’n duikboot romp is ondersoek deur elektrochemiese en onderdompelings korrosie toetse, materiaal karaktariseerings tegnieke en nie-lineêre eindige-elementontleding. HY-80 staal was ondersoek in twee materiaal toestande; soos ontvangstoestand en hitte behandeldteen 590°C vir 90 minute. Dit was bepaal dat die meganiese en mikrostrukturele eienskappe van die staal toestande amper identies is. Lineêre-en potensiodinamiese polarisasie tegnieke was gebruik om ’n korrososiesnelheid van 0.17mm/jaar en 0.18mm/jaar in natuurlike seewater vir soos ontvangde en hitte behandelde staal te bepaal. Hierdie snelhede was bevestig met onderdompelingstoetse wat’n korrosiesnelheid van 0.19mm/jaar vir beide toestande voorspel het. ’n Ultrasoniese deurdiktemeter was gebruik om die oorblywende wanddikte van ‘n duikboot te meet wat vir tien jaar in gebruik was. Dit is bevind dat die maksimum korrosiekoers tot 0.201mm/jaar was. ’n Eindige-element analise van ’n 15.05m lange Tipe 209/14000 duikboot seksie is uitgevoer. Die seksie bestaan uit ‘n romp en interne versterkers. Materiaal nie-lineariniteit was in ag geneem deur die ware plastiesegedrag van HY-80 te inkorporeer. Aanvanklike algehele en tussenraam buite sirkelvormige onvolmaakthede is in die model geïnkorporeer met behulp van ’n Matlab program wat die eindige-element-netwerk knooppunte radiaal verplaas het. Dit is beraam dat die duikboot wat ondersoek is, teen ‘n diepte van ongeveer 562m sal ineenstort wat beteken dat die veiligheidsvaktor teen ineenstorting 2.25 in plek is indien die standaard duikdiepte 250m is. Daar is bevind dat die versterkers, in die area waar die maksimum onvolmaakdhede ingevoeg is, swig voordat die romp ineenstort. Dit is voorspel dat die maksimum duik druk ongeveer lineêr teen 27kPa per jaar afneem. | af_ZA |
| dc.description.version | ns202105 | |
| dc.format.extent | 110 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110132 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | HY-80 steel | en_ZA |
| dc.subject | Corrosion thinning | en_ZA |
| dc.subject | Collapse of structures | en_ZA |
| dc.subject | Corrosive sublimate | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.subject | Corrosion fatigue of metals | en_ZA |
| dc.subject | Submarine engineering | en_ZA |
| dc.title | The effect of corrosion thinning on the collapse pressure of a submarine pressure hull | en_ZA |
| dc.type | Thesis | en_ZA |