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From results of indentation , tensile and shear tests on the gradient material samples , it showed that mechanical properties of the FGM gradually changed from ductility ( metal side ) to brittle ( glass side ) .
 indentation, tensile, shear tests, material, mechanical properties, FGM, ductility, metal, brittle, glass
Please list all entity words in the text that fit the category. Output format is "word1, 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:
 indentation, tensile, shear tests, material, mechanical properties, FGM, ductility, metal, brittle, glass