Faculty Publications
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Item Stress Analysis of a Member of Jacket Structure with Different Types of Stiffeners(Springer, 2024) Sreejith, T.S.; Kaliveeran, V.Jacket structures are subjected to very challenging environmental conditions and thus require certain reinforcements to ensure the resistance against the challenging conditions. The present study deals with the stress analysis of a member of a jacket structure with triangular type stiffener and another with second order curved stiffener. The specimen considered is of steel with dimensions 800 mm × 100 mm × 10 mm. The member is considered as a fixed bar subjected to a concentrated load of 500 N at the mid-span. The idea is to reinforce the member to strengthen up which in turn increases the life of the structure. The configuration of the stiffeners is such that the stress concentration is avoided. The triangular stiffener has a length of 200 mm and height of 20 mm and thickness of 10 mm. The second order curved stiffener has the same length, height and thickness and follows the variation y=20-x5+x22000. Four stiffeners are provided, one at the top and one at the bottom of each end. The structure is simulated and analyzed in a Finite Element Modelling (FEM) software and the necessary results are obtained. The results from this analysis are validated using the experimental results. © 2024, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Stress Analysis of Thin Rectangular Sections Subjected to Twisting Moment(Springer, 2024) Joshi, S.V.; Kaliveeran, V.The major issue in the stress analysis of thin sections is the stress concentration on the edges, especially the sharp edges. Whilst analysing thin sections for any analysis, be it flexural, torsional, axial etc., the phenomenon of sharp edge stress concentration reduces the quality of results of the analysis. Thus, it becomes necessary to determine the particular loading orientations in order to study the analysis in its purest form without the interventions of other unnecessary behaviours. The present study is about the stress analysis of thin rectangular section, when it is subjected to a twisting moment. A thin rectangular member of dimensions, length = 100 mm, depth = 40 mm, and width = 1 mm is considered with one end of the length as fixed and the other end as free. A torque of magnitude 0.1 Nmm is applied at the free end. Initially, a theoretical analysis is done and the point of maximum shear stress is determined. Then numerical analysis of the same is done on an FEM modelling software with different combinations of loadings in the form of a twisting moment. The determination of the exact load orientation which simulates the pure torsional moment behaviour for a thin rectangular section is the main objective of this study. The results obtained by FEM modelling on the software are validated theoretically and experimentally. © 2024, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Finite Element Modelling and Experimental Validation of Strain Gauge Pasted Over the Surface of a Substrate Subjected to a Transverse Load(Springer, 2024) Raveesh, R.M.; Kaliveeran, V.; Kundapura, S.The strain measurement is important as it directly involves with the deformation of a structure in the field of engineering. Strain is a measure of change in shape that occurs when an external load is applied to an engineering assembly. The evaluation of the strain is used to determine the amount of extension or deformation a structure experiences under different loading conditions. Strain gauges are electrical resistance sensors bonded at critical locations on the surface of structural components to detect surface deformation. Strain gauges are frequently used to continuously check for deformations to avoid accidents that can occur in nuclear power plants, aerospace vehicles, mechanical components, and structures. Strain gauges applied directly to the specimen are partially affected by the bonding material and thickness when tested. Present work intends to study the effect of adhesive thickness on strain values. Adhesives are used to paste strain gauges over the surface of the specimen. Three-Dimensional analysis of the strain gauge model has been carried out with the aid of the Finite element software. Experiments were conducted to study the effect of adhesive thickness by varying the thickness of the adhesive from 0.1 to 1 mm by pasting strain gauge over the surface of the Aluminium specimen of length 230 mm, width of 30 mm, and thickness of 6 mm. The strain values obtained from the finite element analysis were compared with the strain values obtained from the experiments. Finite element analysis results were found to be in good correlation with the experimental results. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Finite element analysis of rig used for fretting experiments(Elsevier Ltd, 2019) Raja Pandi, R.; Kaliveeran, V.Fretting is a damage mechanism which occurs between two tightly clamped components when these two components are subjected to very small amplitude of relative motion. Design and fabrication of fretting rig is essential to conduct fretting tests. The fretting rig has been used to clamp the pads onto the specimen. While conducting the fretting experiments, the normal load was applied through the pads and frictional force was generated at the contact interface between the pad and the specimen. Fretting experiments were conducted with a cyclic load which involves a stress ratio ('R' ratio). To decide 'R' ratio, we need to understand the load transfer ratio (LTR). LTR is the ratio between the load transferred to the top of the specimen and the load applied to the bottom of the specimen. LTR value should be optimum to conduct fretting experiments. So, the fretting rig which produces least LTR value (close to 50%) can be used as rig in fretting experiments. To ensure this condition, initially eleven cases of simple one-dimensional (1-D) fretting rig models have been designed and Finite Element (FE) analysis of these models was carried out. Afterwards four more different fretting rig models have been designed and analyzed with the inclusion of machine constraints and its results are also presented here. Among these models, the finite element model with optimum LTR was selected to conduct fretting experiments and the detailed three-dimensional (3-D) finite element study of the selected model has been performed and its results were validated with one-dimensional finite element analysis results. © 2019 Elsevier Ltd. All rights reserved.Item Finite element modeling and experimental validation of rectangular pin buckle arrestors for offshore pipelines(Elsevier Ltd, 2019) Ramachandra Rao, N.; Kaliveeran, V.Offshore pipelines used for transportation of hydrocarbons in the oil industry are subjected to external pressure, internal pressure to ensure flow, temperature and axial compression which causes buckling. Finite element modeling was performed, and experiments were conducted on pipeline models made of stainless steel of grade SS304. Present research work focuses on the improvement in buckling strength of offshore pipelines stiffened with rectangular pin buckle arrestor along the length of a pipeline using finite element analysis and their experimental validation. The results of finite element analysis showed that an offshore pipeline model without buckle arrestors has a buckling load of 4.69 kN whereas offshore pipeline stiffened with buckle arrestors of length 1000 mm along the length of a pipeline resulted in maximum buckling load of 14.075 kN. Accordingly, pipeline models were fabricated for conducting experiments. Comparison of finite element analysis results and experimental outcomes showed that the efficiency of buckle arrestor increased significantly by incorporating buckle arrestor along the length of a pipeline. © 2019 Elsevier Ltd. All rights reserved.Item Effective buckle arrestors for offshore pipelines(Elsevier Ltd, 2019) Ramachandra Rao, N.; Kaliveeran, V.Offshore pipelines are subjected to various forces, depending on the subsea conditions such as temperature, axial forces, pressure (internal and external), bending, and earthquake forces. The response of offshore pipelines in with-standing these forces involves elastic response as well as inelastic response. Buckle arrestors are installed at regular intervals along the length of the pipeline to prevent buckling occurring due to a combination of forces. Present research work focuses on the improvement in buckling strength of offshore pipelines which are stiffened with 3 different types of buckle arrestors. Buckling experiments were conducted on pipeline models fabricated from seamless stainless steel pipes of grade SS304. The pipeline models stiffened with three different buckle arrestors configurations; longitudinal continuous stiffener, sinusoidal stiffener, and angular stiffener. The purpose of our research is to study the effectiveness of buckle arrestor configuration in improving resistance to buckling and to identify optimum buckle arrestor configurations and their applicability to offshore pipelines. The study was conducted by finite element simulation of buckle arrestors using ANSYS. The stainless steel pipe models of 1 m length, 16 mm outer diameter, 11.8 mm inner diameter, 2.1 mm thickness are considered for finite element analysis and for conducting experiments. The results obtained from finite element analysis and experiment results show that the efficiency of buckle arrestor found to be more in case of pipeline stiffened with longitudinal continuous buckle arrestors. © 2019 Elsevier Ltd. All rights reserved.Item Analysis and design of inclined buckle arrestors for offshore pipeline(Elsevier Ltd, 2019) Ramachandra Rao, N.; Kaliveeran, V.Present research work focuses on improving buckling strength of offshore pipelines by strengthening them with inclined stiffeners and inclined stiffeners with connecting rods. Eigenvalue buckling analysis was carried out using Finite Element Methods to find the buckling strength of the considered pipeline models. Seamless stainless steel pipe models of SS304 grade were considered for finite element analysis. The pipeline models were provided with inclined stiffeners whose angle of inclination varies from 100° to 176°. Connecting rods of different lengths is used to improve capacity of inclined stiffeners. In this paper, the effect of inclined stiffener configurations in improving the strength of offshore pipelines against buckling is presented. The finite element analysis results show that a pipeline strengthened with inclined stiffeners and inclined stiffeners with connecting rod showed improved buckling load carrying capacity. © 2019 Elsevier Ltd. All rights reserved.Item DESIGN OF THIN CURVED SENSOR TO MEASURE CONTACT SLIP IN FRETTING EXPERIMENTS(Department of Naval Architecture and Marine Engineering, 2022) Pandi, R.R.; Kaliveeran, V.This paper proposes a new thin curved sensor/strip to measure the relative slip between pad and specimen under fretting conditions. Since the relative contact displacement is a vital parameter to categorize the fretting process, the measurement of contact displacement between pad and specimen is necessary. The spring steel has chosen to fabricate the thin curved strip because of its high yield strength and the ability to return to its initial position even with notable deflection. Before the fabrication, Finite Element Analysis (FEA) was performed on the thin curved sensor. The strip consists of different shapes (rectangular, circular, and elliptical) of slots, and the number of slots in each strip is varied from 2 to 6. The Strain Energy Approach (SEA) has been used to calculate the displacement for the curved strip, and it was compared, verified, and validated with its FEA and Experimental results. Four configurations were chosen from FEA study of thin curved strips with slots to measure micro-level displacement between pad and specimen under fretting experiments. The present study reveals that the increasing number and size of holes in the curved strip increases displacement and von-Mises stress values, which ensure higher flexibility to the strip. The reduction in the area and minimum thickness of the curved strip could be the reason for the decrease in the stiffness of the curved strip. This study explores using a new novel and straightforward instrument/sensor to capture the micro-level relative displacement between the pad and specimen under fretting conditions. © 2022 ANAME Publication. All rights reserved.Item Experimental and Numerical Studies on the Stiffening of Tubular T-joint of Offshore Jacket Structures(Springer Science and Business Media Deutschland GmbH, 2024) Murugan, N.; Kaliveeran, V.; Raveesh, R.M.; Kundapura, S.Present study investigates the stiffening effect on the behavior of tubular T-joints in offshore platform jacket structures subjected to axial compression. Stiffening is crucial to enhance the structures' strength and lifetime. Tubular cross section structures are preferred due to their mechanical properties and cost-efficiency. The study introduces an innovative technique by adding stiffeners at the interface between braces and chords to effectively distribute loads from multiple directions. The T-joint specimen used has specific dimensions: Chord length 400 mm, brace length 200 mm, chord diameter 100 mm, brace diameter 50 mm, chord thickness 4 mm, and brace thickness 3 mm. Experimental tests and Numerical simulations were conducted to measure failure loads for both stiffened and unstiffened T-joints. Stiffened configurations (4, 6, and 8 strips) has a notable impact on the ultimate capacity of the T-joint, showcasing an increase in strength compared to the unstiffened joint. Stiffened joints showed a significant increase in ultimate strength compared to unstiffened joints, with improvements ranging from 67.18 to 73.33% for different stiffener configurations. Joint local stiffness also improved substantially, with percentage increases ranging from 67.03 to 140.80% for various stiffener configurations. Present research work demonstrates the positive impact of stiffeners on tubular T-joints, improving their strength and stiffness while showing strong agreement between numerical simulations and experimental results and the study also concludes that the addition of stiffeners effectively enhances the ultimate capacity and local stiffness of tubular T-joints. These findings emphasize the effectiveness of the proposed reinforcement strategies for optimizing tubular T-joints in offshore structures. © The Author(s), under exclusive licence to Shiraz University 2023.