N. Jayakumar ¹, S. Mohanamurugan ², R. Rajavel ², J. Ashok Kumar ²

Affiliations
1 Department of Mechanical Engineering, AMET University, Chennai - 603112, Tamil Nadu, IN
2 Department of Automobile Engineering, Saveetha University, Chennai - 600072, Tamil Nadu, IN

Abstract

Residual stress in weldments is one of the major concerns in manufacturing industries especially in welding. They occur, sometimes during the initial processing of metals and sometimes during rolling, forging, casting etc. In welding these stresses develop due to non uniform cooling of the welded zone. Tensile stresses are primarily responsible for crack initiation and product failure. Residual stress may also lead to premature failure of the welded joints when subjected to hazardous conditions. There are various physical methods of detection of residual stress in weldments such as x-ray diffraction and deep hole drilling. Nevertheless, numerical method is also one of the most popular methods among researchers to solve various complex engineering problems. In this work, numerical simulation is carried out by creating a 2-D model of the Austenitic stainless steel weldment with various boundary conditions using ANSYS 15.0 software and the results are studied. The details of residual stress are explained with relevance to failure occurrence.

Keywords

Finite Element Method, Residual Stress, Stainless Steel, Weldment

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N. Jayakumar ¹, T. Francis ¹, P. Jawahar ¹, C. B. T. Rajagopalsamy ², R. Santhakumar ³, A. Subburaj ¹

Affiliations
1 Department of Fisheries Biology and Resource Management, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi – 628008, Tamil Nadu, IN
2 Department of Inland Aquaculture, IN
3 Department of Fisheries Extension, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi – 628008, Tamil Nadu,, IN

Abstract

Background / objective: The heavy metal, Cadmium enters aquatic environment through natural / anthropogenic sources and exerts deleterious effects in fish. Hence, the present study is aimed at investigating the acute Cd toxicity induced histological alterations in the liver and kidney of catfish, Heteropneustes fossilis. Methods: The bioassay was performed in a static renewal regime with H. fossilis exposing to varying acute toxicity concentrations viz., 18.45, 36.9, 73.7, 147.4 and 294.8 mg/l for 96 h. The LC50 was determined to be 44.13 mg/l. Since 100 % mortality occurred in the highest concentrations after 96 h, liver and kidney tissues were collected from fish exposed to the first three lower concentrations. Standard histology protocol was followed to study the histological alterations. Findings: The histological alterations like increased kupffer cell and pycnotic nucleus, ruptured hepatic tissue and nucleus, cellular necrosis and focal necrosis were observed in the liver of fish exposed to Cd. Similarly, vacuolation, increased periglomerular and peritubular space, shrunken glomerulus, melanomacrophages and loss of cytoplasm were observed in the kidney of fish treated with Cd. The intensity of the histological alterations in both liver and kidney was found to be concentration and duration dependent. Hepatic tissues were found to be ruptured in the liver of fish exposed to all the three concentrations viz., 18.45, 36.9 and 73.7 mg Cd/l. The appearance of melanomacrophage aggregates is a generalized non-specific marker, indicating environmental stress. In the present study, melanomacrophages were observed in kidney of fish exposed to 36.9 and 73.7 mg Cd/l. Our present observations on histological alterations in the liver and kidney of H. fossilis were in conformity to the histological observations made in the liver and kidney of various fish species exposed to different toxicants. Applications: The histological alterations in liver and kidney H. fossilis induced by Cd suggest that Cd can be a potential toxicant and hence these alterations can be used as biomarkers to monitor aquatic pollution.

Keywords

Acute Toxicity, Cadmium, Histology, Heteropneustes fossilis, Kidney, Liver

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