Papers by Author: Mohammad Jaffar Hadianfard

Abstract: This paper focuses on the optimization of ball milling as a dry mixing method and comparison with the wet method for manufacturing phenolic/multi-wall carbon nanotube (MWCNT) composites. In the ball milling, the effect of milling-time on the properties of composites containing functionalized and pristine MWCNT in two MWCNT concentrations has been investigated. At first in the wet method, polymer was dissolved in acetone and then mixed with MWCNT by sonication method. Also, the effect of functionalization by use of acid nitric refluxing was considered. The material properties were characterized by the DSC, FTIR, Raman, electrical conductivity, SEM, TEM and bending strength analyses. The results of electrical conductivity and bending tests showed that the best time for ball milling is about 2 hrs. In addition, functionalization had a positive effect on bending strength and a negative effect on electrical conductivity. The results of DSC indicated that the composite manufactured by ball milling method resulted in more thermal stability than that manufactured by the wet method. It was also shown that the functionalization increases the thermal stability; however, the increasing MWCNT concentration leads to agglomeration, thereby decreasing the thermal stability.

Abstract: Structural failure of a high pressure orifice flange of an oil refinery is studied by using visual inspection, optical and electron microscopy, tensile tests, fractography and stress calculation. This flange was located at a high pressure (2700 KPa), elevated temperature (370 C°) feeding pipe line. Failure observed during a startup at the time of increasing pressure and temperature. The results of the analysis show that brittle fracture has acted as a main factor for failure of the structure and stress concentration together with corrosion have provided minor sources for the failure. These results indicate that brittle behavior of this flange can attribute to hydrogen embrittlement of the steel material.

Abstract: The effect of strain rate in the range of 10-4 to 10-1 s-1 on localization of deformation and fracture behavior of 5754 and 5182 aluminum alloys is investigated. For this study, tensile tests, interrupted tensile tests, shear band decoration, fractography and image analysis has been used. This investigation is based on experimental work and observation of the material behavior. Results show that strain rate has some effect on the mechanical properties and deformation stability of the alloys. The area of localized plastic deformation and thickness of the shear bands were found to be sensitive to the strain rate. It was also observed that localization of plastic deformation and shear band formation is an important step in the damage propagation and final fracture of the alloys. Detail of damage development, based upon micrographs of samples interrupted at different stages of straining is presented