Ahmad Ivan Karayan

The Role of EXCO, Modified EXCO, and MASTMAASIS Environmental Exposures on Predicting Exfoliation Corrosion of the 2060-T8E30 Alloy

In this study, corrosion response of the 2060-T8E30 alloy was analyzed in the following environments: EXCO (an immersion test in accordance with ASTM G34), modified EXCO, and modified ASTM acetic a...

Transpassive Behavior of UNS N08367 Super Austenitic Stainless Steel in LiBr Solution

This study focuses on the transpassivity of super austenitic stainless steel (UNS N08367) in a LiBr solution using electrochemical techniques, i.e., cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy tests combined with the surface analysis technique, i.e., x-ray photoelectron spectroscopy (XPS). The transpassivity of UNS N08367 in 2.5 M LiBr solution corresponds to the dissolution of Cr, Mo, and Ni at high potentials. This study illustrates how the adsorption of intermediate Mo species is responsible for the appearance of an inductive loop in the Nyquist plot at low frequencies. The addition of alloying elements such as Cr and Mo successfully prevents localized corrosion; however, these alloying elements increase the susceptibility of this material to general corrosion by the formation of an anodic film. Nickel does not directly contribute to the formation of passive film in this alloy, as illustrated by the absence of passivation in the CPP curve and by the weak XPS sig...

Influence of Intermetallic Inclusion to Brittle Fracture of Electric Motor Shaft AISI 1045 under Torsion Loading

A shaft of electric motor fin-fan cooler failed after two years operation. The inspection revealed that the v-belt attached on the electric motor loosed before the failure occurred. Visual investigation results showed the brittle fracture with less plastic deformation. Multiple crack origins observed on the edge of the shaft indicates that the more than one stress concentration generated within the shaft. Microstructure observation revealed fine grain on the edge and become coarse into the center of the shaft. The hardness test results were in good agreement to the microstructure observation where the edge are is harder than the center. Fractography using SEM revealed inclusions located within the shaft and some inclusions are clustered on the area where the cracks initiate to propagate. The presence of intermetallic inclusions was identified by microanalysis using EDS. Inclusions that are brittle in nature become stress concentrations for the operating load since its properties is close to ceramic. The presence of fine grain and inclusions on the edge of the shaft become detrimental to the shaft properties and the presence of fine grain aggravate the failure for its effect according to Hall-Petch theory.

Finite Element Analysis Applications in Failure Analysis: Case Studies

The use of the finite element in engineering applications has grown rapidly in recent years. Finite element analysis (FEA) is based on numerical computation that calculates all parameters and boundaries given. Supported with powerful computer processors and continuous software development, the finite element method is rapidly advancing. The use of finite element analysis is not limited to the engineering field, as there are also medical and geospatial applications. The early development of the finite element can be traced back to the work of Courant [1], followed by the work of Martin [2], which applied the solutions for structural analyses at Boeing Company in the 1950s. Further work by Argyris, Clough, Turner, and Zienkiewicz developed the governing mathematical equation for the finite element method [3].