Analyzing the Influence of Welding Process Selection on Residual Stresses in Tube-to-Tubesheet Welded Joints

Manoj Kumar Jangid,Vikram Roy,M. T. Kamble,P. K. Singh 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.5

Tube-to-tubesheet joints are used in the fabrication of shell and tube type heat exchangers, steam generators, boilers, condensers, and end shields of pressure tube type nuclear reactors like CANDU (Canada Deuterium Uranium) and PHWR (Pressurized Heavy Water Reactor). The weld joints connecting the tubes to the tubesheets are of prime importance as they have a direct impact on equipment safety. In the fabrication of these critical class-1 nuclear components, full penetration weld joints are used. Typically, these full penetration weld joints are created through multi-pass Tungsten Inert Gas (TIG) welding. However, more recent techniques, such as single-pass Electron Beam Welding (EBW) and Laser Beam Welding (LBW), have also been employed for this purpose. The fabrication time of these pieces of equipment containing full penetration weld joints can be drastically reduced if single-pass welding techniques are used compared to multi-pass welding techniques. However, the residual stresses developed in these joints due to the localized heat input and the substantial constraints of the tubesheet are unknown. Different welding processes, such as TIG welding, EBW, or LBW, can lead to varying levels of residual stresses in these joints, subsequently impacting their longevity. Weld residual stress plays a significant role in the initiation of failure modes of these tube-to-tubesheet welded joints, such as stress corrosion cracking, fatigue, and corrosion fatigue. This paper analyzes the residual stresses developed at the tube-to-tubesheet interface resulting from different welding techniques, such as multi-pass TIG welding and single-pass EBW/LBW. A comprehensive three-dimensional coupled thermo-mechanical finite element analysis is employed for this purpose. The findings reveal a significant difference, with single-pass EBW exhibiting up to 32% lower residual stresses compared to multi-pass TIG welding. Additionally, the Heat Affected Zone (HAZ) in EBW is approximately 50% smaller than in TIG welding, and the equivalent distortion in EBW is reduced by 90% compared to multi-pass TIG welding. In summary, this investigation concludes that single-pass EBW offers distinct advantages for tube-to-tubesheet weld joints, including reduced residual stresses, a smaller HAZ, and lower distortions.

Fabrication of Copper Nanoparticles Incorporated P3HT: PCBM Solar Cell with solution processes

Manoj Ovhal,Sooman Lim(임수만),Jaewook Kang(강재욱) 융복합지식학회 2019 융복합지식학회논문지 Vol.7 No.1

본 연구는 용액공정 즉, 스핀 코팅, 바 코팅 및 스크린 프린팅 공정을 이용하여 구리나노입자 첨가형 P3HT : PCBM 태양 전지를 제조하였고 생산 된 효율을 비교 하였다. 여기서,은 (Ag) 상부 전극은 금속 증착에 의해 증착되고 미리 증착 된 폴리머 박막 상에 스크린 인쇄로 인쇄하여 비교실험하였다. 시트 저항 (Rsh)은 각각 0.7 Ω □<SUP>-1</SUP> 및 2 Ω □<SUP>-1</SUP> 이었고, 두께는 100 nm 및 80 nm이었다. 그 결과, OPV에서 스핀 코팅 및 바 코팅을 하고 금속 증착 된 효율은 각각 4.39 및 0.63 %의 효율을 나타냈지만 스크린 인쇄 된 Ag 전극 OPV는 단락문제를 야기시켰다. 이것은 스크린 인쇄기 압착기가 OPV에 가한 인장력으로 인해 활성층 구조가 데미지를 입었기 때문으로 사료된다. 한편, 스핀 코팅 공정은 주변 조건에서 수행 된 바 코팅 공정에 비해 신뢰성이 높았으나, 바 코팅으로 처리된 활성층은 OPV 구조에서 대면적 제조용으로 사용될 가능성을 볼 수 있었다. 그러나 스크린 프린팅의 경우, OPV 제조 공정에서 스크린 프린팅 공정을 채택하기 위해서는 스퀴즈로 인한 상층 손상을 제거하기위한 더 많은 연구가 필요하다. The present work is mainly focused on fabrication of copper nanoparticles incorporated P3HT: PCBM solar cell top electrode with spin coating, bar coating and screen-printing process and the efficiency produced by each method was compared. Herein, Silver (Ag) top electrode deposited by metal evaporation and screen printing on pre-deposited polymeric thin film. The sheet resistance (Rsh) of Ag electrodes were 0.7 Ω □<SUP>-1</SUP> and 2 Ω □<SUP>-1</SUP> with the thickness of 100 nm and 80 nm respectively. As a result, the metal evaporated Ag electrode based OPV coated by spin coating and bar coating in active layer shows 4.39 and 0.63 % efficiency, respectively. Whereas, the screen-printed Ag electrode OPVs were shorts. This short problem was raised due to the impression force applied by screen printer squeezer on the OPVs. Although spin coating process was more reliable compared with bar coating process performed in ambient condition, bar coated active layer has shown possibility to be used in OPV structure. For screen printing, however, more research to remove upper layer damage caused by squeezing was required to adapt screen-printing process in the OPV fabrication process.

Surface modified graphene oxide as a performance enhancer of anion exchange membrane for fuel cell

Manoj Karakoti,Sang Yong Nam 한국막학회 2022 한국막학회 총회 및 학술발표회 Vol.2022 No.11

Characterization of Ti–Al Intermetallic Synthesized by Mechanical Alloying Process

Manoj Kumar Yadav,Arshad Noor Siddiquee,Zahid A. Khan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

Mechanical alloying (MA) of Al60Ti40 (wt%) has been successfully done by using a planetary ball mill having mixed ballsof 5 mm and 15 mm diameter to refne the crystallite size of the elemental powder and to get the new MAed phase of AlTi. The microstructural and morphological analysis of elemental as well as the processed powder was done with help of ScanningElectron Microscope and X-Ray difraction technique. Mechanical alloying of elemental Al and Ti resulted in the formationof AlTi phases with the refection of α-Ti3Al and TiAl3. The average particle size was reduced around 7 times after 60 h ofmilling. The mean crystallite size of MAed powder was also reduced up to 85 nm after 60 h of mechanical alloying undercontrolled conditions.

Dehydrodivanillin: Multi-dimensional NMR Spectral Studies, Surface Morphology and Electrical Characteristics of Thin Films

Manoj Gaur,Jaya Lohani,V. R. Balakrishnan,P. Raghunathan,S. V. Eswaran 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

The complete structural characterization of dehydrodivanillin, an important natural product of interest to the food, cosmetics and aroma industries, has been carried out using multi-dimensional NMR spectroscopic techniques, and its previously reported 13C-NMR values have been reassigned. Dense and granular thin films of dehydrodivanillin have been grown by sublimation under high vacuum and studied using Scanning Electron Microscopy (SEM), electrical and optical techniques. The transmittance spectra of the films indicate a wide optical band gap of more than 3 eV. Typical J-V characteristics of Glass/ITO/dehydrodivanillin/Al structure exhibited moderate current densities ~10-4 A/cm2 at voltages > 25 V with an appreciable SCLC mobility of the order of 10-6 cm2/V-s.

Low-temperature formation of source–drain contacts in self-aligned amorphous oxide thin-film transistors

Manoj Nag,Robert Muller,Soeren Steudel,Steve Smout,Ajay Bhoolokam,Kris Myny,Sarah Schols,Jan Genoe,Brian Cobb,Abhishek Kumar,Gerwin Gelinck,Yusuke Fukui,Guido Groeseneken,Paul Heremans 한국정보디스플레이학회 2015 Journal of information display Vol.16 No.2

We demonstrated self-aligned amorphous-Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistors (TFTs) where the source–drain (S/D) regions were made conductive via chemical reduction of the a-IGZO via metallic calcium (Ca). Due to the higher chemical reactivity of Ca, the process can be operated at lower temperatures. The Ca process has the additional benefit of the reaction byproduct calcium oxide being removable through a water rinse step, thus simplifying the device integration. The Ca-reduced a-IGZO showed a sheet resistance (RSHEET) value of 0.7 k/sq., with molybdenum as the S/D metal. The corresponding a-IGZO TFTs exhibited good electrical properties, such as a field-effect mobility (μFE) of 12.0 cm2/(V s), a subthreshold slope (SS−1) of 0.4 V/decade, and an on/off current ratio (ION/OFF) above 108.

Accurate Computation of Interlaminar Stresses in Composite Blades Using Multifield Variational Formulation

Manoj Kumar Dhadwal,Sung Nam Jung(정성남) 한국항공우주학회 2018 한국항공우주학회 학술발표회 논문집 Vol.2018 No.11

Safety Profile and Therapeutic Efficacy of One Cycle of Lu177-PSMA in End-Stage Metastatic Castration-Resistant Prostate Cancer Patients with Low Performance Status

Manoj Gupta,Partha Sarathi Choudhury,Sudhir Rawal,G. Karthikeyan,Vineet Talwar,Kumar Deep Dutta,Amitabh Singh 대한핵의학회 2019 핵의학 분자영상 Vol.53 No.6

Purpose The aimof this study was to evaluate safety and therapeutic efficacy of lutetium 177 prostate-specific membrane antigen (Lu-177-PSMA) in metastatic castration-resistant prostate cancer (mCRPC) patients with low performance status. Methods Twenty-two patients already treated with anti-androgens and docetaxel were enrolled for one cycle of Lu-177-PSMA therapy. Haemoglobin, total leukocyte counts, platelets and serum creatinine for toxicity profile while prostate specific antigen (PSA), Eastern Cooperative Oncology Group (ECOG) performance status, visual analogue scale (VAS) and analgesic quantification scale (AQS) for therapeutic efficacy were recorded pre and 8 weeks post therapy.Wilcoxon signed-rank and ANOVA tests were used for statistical analysis. Results Partial response (PR), stable disease (SD) and progressive disease (PD) for PSAwere seen in 5 (22.7%), 13 (59.1%) and 4 (18.2%) patients respectively treated with mean 6.88 GBq dose of Lu-177-PSMA. 8/22 (36.4%) patients showed ≥ 30% drop in PSA. Grade 3 haemoglobin toxicity was seen in 5/22 (22.7%) patients. No patient developed grade 4 haemoglobin toxicity. No patients had grade 3 or 4 leukocytopenia or thrombocytopenia. Wilcoxon signed-rank test showed statistical significant (P < 0.05) difference in pre and post treatment ECOG, VAS, and AQS scores. The ANOVA test showed statistically significant difference in mean doses of Lu-177-PSMA used in three PSA response groups while difference was non-significant for other variables. Conclusion We concluded that Lu-177-PSMA therapy has adequate pain palliation in end-stage mCRPC patients with low performance status and it has a potential to become effective therapeutic option in properly selected patients.

Dietary Changes Leading to Euglycemic Diabetic Ketoacidosis in Sodium-Glucose Cotransporter-2 Inhibitor Users: A Challenge for Primary Care Physicians?

Manoj Kumar Reddy Somagutta,Utkarsha Uday,Nishat Shama,Narayana Reddy Bathula,Siva Pendyala,Ashwini Mahadevaiah,Greta Mahmutaj,Ngaba Negumadji Ngardig 대한가정의학회 2022 Korean Journal of Family Medicine Vol.43 No.6

Background: The use of euglycemic diabetic ketoacidosis (EDKA) related to sodium-glucose cotransporter 2 in-hibitors (SGLT2i) use in people with diabetes has been increasingly reported. The causes are multifactorial, and di-etary changes in SGLT2i users were observed to trigger EDKA. A ketogenic diet or very low-carbohydrate diet (VLCD) enhances body ketosis by breaking down fats into energy sources, causing EDKA. This study aimed to un-derstand the patient specific risk factors and clinical characteristics of this cohort. Methods: Several databases were carefully analyzed to understand the patients’ symptoms, clinical profile, labora-tory results, and safety of dietary changes in SGLT2i’s. Thirteen case reports identifying 14 patients on a ketogenic diet and SGLT2i’s diagnosed with EDKA were reviewed. Results: Of the 14 patients, 12 (85%) presented with type-2 diabetes mellitus (DM) and 2 (15%) presented with type-1 DM. The duration of treatment with SGLT2i before the onset of EDKA varies from 1 to 365 days. The duration of consuming a ketogenic diet or VLCD before EDKA onset varies from 1 to 90 days, with over 90% of patients hospi-talized <4 weeks after starting the diet. At presentation, average blood glucose was 167.50±41.80 mg/dL, pH 7.10±0.10, HCO3 8.1±3.0 mmol/L, potassium 4.2±1.1 mEq/L, anion-gap 23.6±3.5 mmol/L, and the average hemo-globin A1c was 10%±2.4%. The length of hospital stay ranged from 1 to 15 days. None of the patients were reinitiated on SGLT2i’s, and 50% (2/4) of the patients reported were on the ketogenic diet or VLCD upon patient questioning.Conclusion: Despite the popularity of the ketogenic diet and VLCD for weight loss, their use in diabetics taking SGLT2i’s is associated with EDKA. Physicians should educate patients with diabetes taking SGLT2i’s about the risk of EDKA. In addition, patients should be encouraged to include their physicians in any decision related to signifi-cant changes in diet or exercise routines. Further research is needed to address if SGLT2i’s should be permanently discontinued in patients with diabetes on SGLT2i and whether the ketogenic diet developed EDKA.

Flexible and Transparent Hybrid Electrode Based Supercapacitor for Wearable Energy Storage

Manoj Ovhal,긴팅 리스키 티티안,강재욱 한국고분자학회 2018 한국고분자학회 학술대회 연구논문 초록집 Vol.43 No.1