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M. A. Mohtadi-Bonab,M. Eskandari,R. Karimdadashi,J. A. Szpunar 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.4
In this study, the surface and cross section of an as-received API X70 pipeline steel was studied by SEM and EDStechniques in order to categorize the shape and morphology of inclusions. Then, an electrochemical hydrogencharging using a mixed solution of 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate has been utilized to createhydrogen cracks in X70 steel. After hydrogen charging experiments, the cross section of this steel has been accuratelychecked by SEM in order to find out hydrogen cracks. The region of hydrogen cracks was investigated bySEM and EBSD techniques to predict the role of different microstructural parameters involving hydrogen inducedcracking (HIC) phenomenon. The results showed that inclusions were randomly distributed in the cross section oftested specimens. Moreover, different types of inclusions in as-received X70 steel were found. However, onlyinclusions which were hard, brittle and incoherent with the metal matrix, such as manganese sulfide and carbonitrideprecipitates, were recognized to be harmful to HIC phenomenon. Moreover, HIC cracks propagate dominantlyin transgraular manner through differently oriented grains with no clear preferential trend. Moreover, adifferent type of HIC crack with about 15-20 degrees of deviation from the rolling direction was found and studiedby EBSD technique and role of micro-texture parameters on HIC was discussed.
N. Amirjani,M. Ketabchi,M. Eskandari,M. Hizombor 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11
Four Nb–V–Ti steel plates of API 5LX70 linepipe were produced with changing accelerated cooling rate and finish rollingtemperature using thermomechanical controlled process. The changes in ductile fracture surface, brittle fracture surfaces,including initial cleavage fracture and inverse fracture, arrowhead marking surfaces, and delamination were investigatedusing drop-weight tear test at temperatures of 0 °C and − 10 °C. Based on the drop-weight tear test results, an increase in theaccelerated cooling rate, resulting in an increase in the volume fraction of quasi polygonal ferrite, fine polygonal ferrite, andgranular ferrite microstructures, increased the percentage of ductile fracture surface and decreased the percentage of brittlefracture surfaces. Moreover, a reduction in the finish rolling temperature led to similar changes in the ductile fracture surfaceand brittle fracture surfaces due to an increase in the volume fraction of aciculae ferrite. Arrowhead markings surfaces,caused by the presence of banded structures, their percentage was reduced by increasing the accelerated cooling rate anddecreasing the finish rolling temperature at the temperature of 0 °C. Furthermore, as the accelerated cooling rate increased,the number, length, thickness, and depth of delaminations were reduced at temperatures of 0 °C and − 10 °C.
ANALYSIS AND OPTIMIZATION OF AIR SUSPENSION SYSTEM WITH INDEPENDENT HEIGHT AND STIFFNESS TUNING
P. KARIMI ESKANDARY,A. KHAJEPOUR,A. WONG,M. ANSARI 한국자동차공학회 2016 International journal of automotive technology Vol.17 No.5
Suspensions play a crucial role in vehicle comfort and handling. Different types of suspensions have been proposed to address essential comfort and handling requirements of vehicles. The conventional air suspension systems use a single flexible rubber airbag to transfer the chassis load to the wheels. In this type of air suspensions, the chassis height can be controlled by further inflating the airbag; however, the suspension stiffness is not controllable, and it depends on the airbag volume and chassis load. A recent development in a new air suspension includes two air chambers (rubber airbags), allowing independent ride height and stiffness tuning. In this air suspension system, stiffness and ride height of the vehicle can be simultaneously altered for different driving conditions by controlling the air pressure in the two air chambers. This allows the vehicle’s natural frequency and height to be adjusted according to the load and road conditions. This article discusses optimization of an air suspension design with ride height and stiffness tuning. An analytical formulation is developed to yield the optimum design of the new air suspension system. Experimental results verify the mathematical modeling and show the advantages of the new air suspension system.
Forghani, F.,Langaee, T.,Eskandari, M.,Seo, K.H.,Chung, M.J.,Oh, D.H. Butterworths ; Taylor Francis ; Elsevier Science 2015 FOOD CONTROL Vol.55 No.-
Bacillus cereus can cause emetic and diarrheal food poisoning. It is widespread in nature and therefore, considered a major foodborne pathogen. To develop a sensitive and reliable assay for detecting enterotoxin genes (nheA, entFM, hblD, cytK) and emetic toxin (ces), specific primers each targeting one individual gene were designed. Propidium monoazide (PMA) was coupled with the developed multiplex PCR (mPCR) for the detection of viable B. cereus. The inclusivity and exclusivity of the PMA-mPCR was confirmed using a panel of 44 strains including 17 emetic and 9 enterotoxic B. cereus reference strains and 18 non-target strains. The limit of detection (LOD) without PMA treatment in pure DNA was 2 pg/reaction tube. The LOD of mPCR assay in pure heat-killed dead bacteria was 4.0 x 10<SUP>2</SUP> CFU/mL. Also, the LOD on the viable bacteria with or without PMA treatment was similar (3.8 x 10<SUP>2</SUP> CFU/mL) showing that the PMA treatment did not significantly decrease sensitivity. Finally, the newly developed PMA-mPCR successfully detected 4.8 x 10<SUP>3</SUP> and 3.6 x 10<SUP>3</SUP> CFU/g of viable B. cereus F4810/72 (emetic) and B. cereus ATCC 12480 (enterotoxic) reference strains, respectively, in food samples. Hence, this study combines PMA and mPCR to detect viable B. cereus with a wide range of toxin detection (5 toxins). Thus, the novel PMA-mPCR assay developed in this study is a rapid and efficient diagnostic tool for the monitoring of viable B. cereus in food samples and potentially other samples via appropriate DNA extraction.