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Evolution and Characterization of Zirconium 702 alloy at various temperatures

Lade Jayahari, Dharavath Baloji, Badrish Anand, Kosaraju Satyanarayana, Singh Swadesh Kumar, Saxena Kuldeep Kumar

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

807--812

EN

The Zirconium 702 alloy effectively used in nuclear industry at various critical conditions like high temperature and high pressure. This survey is an assessment of insights into the mechanical properties of the metal when exposed to different temperatures along the rolling direction.The main objective of this work is to characterize the tensile properties, and fracture study of broken tensile test samples at various temperatures.The tensile samples tested in our current work are 100°C, 150°C, and 200°C temperatures in different directions (0°, 45°, 90°) along with the rolling direction of the sheet. It is evident from the experimental results that temperatures significantly affect material properties. Temperature increases cause % elongation to increase, and strength decreases. ANOVA analysis revealed that temperature significantly influenced ultimate tensile strength (UTS), and yield strength (YS), as well as % elongation.The temperature contribution for UTS, YS, and % elongation is 41.90%, 31.60%, and 77.80% respectively. SEM fractured images showing the ductile type of behavior for all the temperatures.

2

Prediction of forming limits and microstructural evolution during warm stretch forming of DP590 steel

Pandre Sandeep, Morchhale Ayush, Kotkunde Nitin, Singh Swadesh Kumar, Ravindran Sujith

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

397--419

EN

Dual-phase (DP) steel has an excellent blend of various mechanical properties; hence it is used immensely in the automotive industries. It is challenging to form high strength DP steel into desirable complex shapes because of their limited formability at room temperature conditions. One of the proven alternatives is warm/hot forming. In-detail investigation of forming limits over DP590 steel has been carried out in present work. Firstly, various constitutive models and yield criteria have been formulated for DP steel at different temperatures and strain rates. The modified Arrhenius (m-A) constitutive model and Barlat 1989 yielding function displayed the best prediction of flow stress and anisotropic yielding behavior, respectively. The experimental forming limits (FLD) were evaluated at 300, 473 and 673 K temperatures using Nakazima tests. The forming limits of the material are improved by approximately 24% on increasing the temperature from 300 to 673 K. The textural analysis of the deformed surface has been done using electron back scattered diffraction (EBSD) studies, and γ fibers are found to be responsible for improvement in the formability of the material. Additionally, Marciniak and Kuczynski (MK) model was used to predict the theoretical FLD using all the possible combinations of constitutive models and yield criteria. Finally, the m-A constitutive model, along with Barlat 1989 yielding function has shown the best prediction for forming limits at all the temperatures. The finite element study has also been performed using mentioned material models for accurate prediction of dome height, surface strain and thickness distribution across the specimens.

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Fracture limit analysis of DP590 steel using single point incremental forming: experimental approach, theoretical modeling and microstructural evolution

Pandre Sandeep, Morchhale Ayush, Mahalle Gauri, Kotkunde Nitin, Suresh Kurra, Singh Swadesh Kumar

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

138--157

EN

The single point incremental forming (SPIF) process is gaining special attention in the aerospace, biomedical and manufacturing industries for making intricate asymmetric components. In the present study, SPIF process has been performed for forming varied wall angle conical and pyramidal frustums using DP590 steel. Initially, the conventional stretch forming process has been performed for finding the fracture forming limit diagram (FFLD). Further, it has been validated with the limiting strains found using SPIF process. The conical and pyramidal frustums deformed near to the plane strain and biaxial region, respectively. The theoretical FFLD has been predicted using seven different ductile damage models. The effect of sheet anisotropy while predicting the fracture strains has been included using Hill 1948 and Barlat 1989 yielding functions. Among the used damage models, the Bao-Wierzbicki (BW) model along with Barlat 1989 yield criterion displayed the least error of 2.92% while predicting the fracture locus. The stress triaxiality in the different forming region has been thoroughly investigated and it has been found that the higher triaxiality value reveals high rate of accumulated damage which lead to early failure of the material in the respective region. The stress triaxiality and effective fracture strains have also been found to be significantly affected by the anisotropy. The micro-textural studies have also been performed and it has been found that the increase in local misorientations and shift in the textural components from γ-fiber to ε-fiber in the corner region of the frustums worked towards limiting the formability of material and ultimately leading towards the fracture of frustums.

4

Effect of pre-cut hole diameter on deformation mechanics in multi-stage incremental hole flanging of deep drawing quality steel

Gandla Praveen Kumar, Kurra Suresh, Prasad K. Sajun, Panda Sushanta Kumar, Singh Swadesh Kumar

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

260--282

EN

Incremental hole flanging (IHF) is a relatively new sheet metal forming process to produce intricate shapes without using dedicated punches and dies. The present work focuses on understanding the mechanics of the multi-stage IHF process through experimental studies and the finite element approach. The IHF experiments were performed on deep drawing quality steel sheets with a pre-cut hole diameter of 45 mm, 50 mm, 60 mm, and 70 mm. The cylindrical flanges were formed in four stages with an initial wall angle of 60° to a final angle 90° with an angle increment of 10° in each stage. The maximum and minimum hole expansion ratio was found to be 2.06 and 1.17 respectively. The fracture was observed in a blank of 45 mm pre-cut hole diameter in the third stage at 40 mm depth. The fracture forming limit diagram (FFLD) was determined from incrementally formed varying wall angle conical and pyramidal frustums. Consequently, six different ductile damage models incorporating Hill48 anisotropy plastic theory were successfully calibrated. The Ayyada model showed good agreement with experimental FFLD as compared to all other models. The fracture limit determined experimentally and using the Ayyada model was implemented in the finite element simulation of the IHF process to predict the formability in terms of in-plane strain distribution, forming forces, and thickness distribution. The predicted results matched accurately with the experimental data within a 6% error for all investigated conditions. Noticeably, the strain path in IHF had three deformation modes viz. plane strain, bi-axial stretching, and uni-axial tension, which was comprehended using texture analyses. Finally, irrespective of the initial pre-cut hole diameter, the surface roughness was found to decrease with the number of stages of the IHF process.