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Existing literature that reports current data on fracture toughness and fatigue crack growth tests conducted on AM parts is summarised and analysed , highlighting different steel grades and applications , with the view to illustrating the requirements for the new optimised functionally graded structures in offshore wind structures by means of AM technique .
 concept or principle: data; concept or principle: fracture; concept or principle: fatigue crack growth; machine or equipment: AM parts; material: steel; engineering feature: functionally graded structures; manufacturing process: AM technique
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 concept or principle: data; concept or principle: fracture; concept or principle: fatigue crack growth; machine or equipment: AM parts; material: steel; engineering feature: functionally graded structures; manufacturing process: AM technique