Experimental Methods MEC3045F Non-destructive evaluation.

Experimental MethodsExperimental Methods

MEC3045FMEC3045F

Non-destructive evaluationNon-destructive evaluation

The rise of NDEThe rise of NDE

In the early 1970’s the discipline of fracture mechanics In the early 1970’s the discipline of fracture mechanics emergedemerged

This enabled one to predict whether aThis enabled one to predict whether acrack of a certain size would fail undercrack of a certain size would fail undera specific load if certain properties a specific load if certain properties were knownwere known

Laws were developed to predict theLaws were developed to predict therate of growth of cracks (fatigue) underrate of growth of cracks (fatigue) undercyclic loadingcyclic loading

Components with KNOWN defectsComponents with KNOWN defectscould still be used if it could becould still be used if it could beestablished that they were not of a critical, failure established that they were not of a critical, failure producing sizeproducing size

Ultrasonic testingUltrasonic testing

Ultrasonic testing uses high-frequency sound waves that Ultrasonic testing uses high-frequency sound waves that are directed into a material to locate changes in material are directed into a material to locate changes in material propertiesproperties

The most common approach is “pulse-echo” where sound The most common approach is “pulse-echo” where sound is introduced to the object and reflections (echoes) are is introduced to the object and reflections (echoes) are returned to a receiver from internal imperfectionsreturned to a receiver from internal imperfections

The reflected wave signalThe reflected wave signalis transformed into anis transformed into anelectrical signal by aelectrical signal by atransducertransducer

Enabling a learning environmentEnabling a learning environment

Complex theory can be engaged with Complex theory can be engaged with through practical application of ideas - labsthrough practical application of ideas - labs

Cost of a ‘traditional’ lab prohibitiveCost of a ‘traditional’ lab prohibitive– Ultrasonic probesUltrasonic probes– Unique flaw arrangementsUnique flaw arrangements

A ‘virtual environment’ can be created A ‘virtual environment’ can be created through the simulation of a processthrough the simulation of a process

Ultrasonic testing in practiceUltrasonic testing in practice

Creating the virtual environment Creating the virtual environment

33 crew rescued off Eastern Cape coast33 crew rescued off Eastern Cape coast

More than 30 crew members were forced to abandon the 299-metre More than 30 crew members were forced to abandon the 299-metre bulk carrier Alexandros T in life-rafts when it started sinking some 300 bulk carrier Alexandros T in life-rafts when it started sinking some 300 nautical miles off Port Alfred on the Eastern Cape Coast. Salvage nautical miles off Port Alfred on the Eastern Cape Coast. Salvage vessel Smit Amandla, passing ships and the National Sea Rescue vessel Smit Amandla, passing ships and the National Sea Rescue Institute (NSRI) plucked the 33 sailors to safety late last night in five-Institute (NSRI) plucked the 33 sailors to safety late last night in five-metre swells and 45 knot winds.metre swells and 45 knot winds.

The Alexandros T was sailing from Brazil to China, when it broke up, The Alexandros T was sailing from Brazil to China, when it broke up, took on water and sank. Hellenberg said the reason for the vessel took on water and sank. Hellenberg said the reason for the vessel sinking had not yet been established.sinking had not yet been established.

Sinking of Alexandros T shows a design rethink is necessary Sinking of Alexandros T shows a design rethink is necessary

These Capesize vessels - three rugby fields in length - are very These Capesize vessels - three rugby fields in length - are very susceptible to the power of the sea. With a heavy swell on the quarter, susceptible to the power of the sea. With a heavy swell on the quarter, they flex significantly, a phenomenon factored in by their designers. they flex significantly, a phenomenon factored in by their designers. Nevertheless, while the wing tanks and the ore cargo impart some Nevertheless, while the wing tanks and the ore cargo impart some rigidity to the lower part of the hull, stresses on the rest of the ribs and rigidity to the lower part of the hull, stresses on the rest of the ribs and side plating can be severe.side plating can be severe.

Corrosion around the wing tanks can be difficult to detect and treat, and Corrosion around the wing tanks can be difficult to detect and treat, and subsequent weaknesses in the plating will inevitably cause cracks that subsequent weaknesses in the plating will inevitably cause cracks that are exploited by heavy seas or by the iron ore slurry created in a are exploited by heavy seas or by the iron ore slurry created in a flooded hold.flooded hold.

Developing a three-part virtual Developing a three-part virtual laboratorylaboratory

Use an ultrasonic probe to locate the flawsUse an ultrasonic probe to locate the flaws

Process the data ‘collected’ with an Process the data ‘collected’ with an oscilloscopeoscilloscope

Write a assessment of the flaws as the ‘ship Write a assessment of the flaws as the ‘ship engineer’engineer’

Flaw locationFlaw location

Moving an ultrasonic probe across the hull Moving an ultrasonic probe across the hull of a shipof a ship

An accurate representation of what the An accurate representation of what the output on a real oscilloscope would have output on a real oscilloscope would have beenbeen

Students have their own randomly Students have their own randomly generated flaws (within set parameters) to generated flaws (within set parameters) to detectdetect

Finding the flawsFinding the flaws

Analysing the dataAnalysing the data

Each spreadsheet is personalisedEach spreadsheet is personalised

Depth and orientation of the flaws are Depth and orientation of the flaws are determineddetermined

Calculations Calculations straightforwardstraightforward

Interpretation of Interpretation of the results is not the results is not obviousobvious

Interpreting the resultsInterpreting the results

Students take the role of the ship’s Students take the role of the ship’s engineerengineer

JustifyJustify their assessment as to whether the their assessment as to whether the ship can continue in serviceship can continue in service

Alexandros T used frame the activityAlexandros T used frame the activity

Need to draw on their tacit knowledge of Need to draw on their tacit knowledge of engineering draw from other coursesengineering draw from other courses

The value of ET to meThe value of ET to me

Using technology in this way allowed me Using technology in this way allowed me to create a learning environment that is to create a learning environment that is difficult to achieve in a traditional difficult to achieve in a traditional laboratory settinglaboratory setting

It is possible to introduce complex It is possible to introduce complex practical aspects into a course that can practical aspects into a course that can help build on the theoretical content help build on the theoretical content students have traditionally received students have traditionally received