M Javanmard - Master student, Department of Mechanical Engineering, Shahid Beheshti University, Tehran, Iran
S.H Dibajian - Assistant Professor, Department of Mechanical Engineering, Shahid Beheshti University, Tehran, Iran
S.M Yadavar Nikravesh - Associate Professor, Department of Mechanical Engineering, Shahid Beheshti University, Tehran, Iran

The diaphragm of sonic soot blower is commonly made of Ti-6Al-4V. It is significantly stronger thancommercially pure titanium while having the same stiffness and thermal properties. This grade is an excellentcombination of strength, corrosion resistance, weld and fabricability. Generally, Ti-6Al-4V is used in applications upto 400 degrees Celsius which is very good selection for used in boiler and catalyst for cleaning. Earlier in a research bythe NRI, the diaphragms used to begin to crash quickly. Therefore in this current research, scanning electronmicroscope (SEM) has been utilized to discover the reason of failure of diaphragms that are used by the NRI.According to the SEM image of fracture surface of diaphragms, the crack generally divides into terrace-like steps whencrossing a grain boundary is completely obvious. Moreover, the newly created different crack planes join togetherduring further crack propagation producing a characteristic river-like pattern which clarifies mentioned brittlefracture. This can be guessed from the appearance review of the fracture surface since, in fracture surfaces there seemno symptoms of thinning and plastic deformation.

Acoustic Cleaning, Diaphragm, Brittle Fracture, SEM