Stretch-flangeability of sheet metal is normally represented by hole expansion ratio. Hole expansion ratio cannot be determined from uniaxial tensile test though uniaxial tensile deformation occurs...

Fundamental aspect of stretch-flangeability of sheet metals:

Forming Limit Diagram Generation from In-Plane Uniaxial and Notch Tensile Test with Local Strain Measurement through Digital Image Correlation

This work presents a new understanding on the deformation mechanics involved in the Nakajima test, which is commonly used to determine the forming limit curve of sheet metals, and is focused on the...

Influence of the contact with friction on the deformation behavior of advanced high strength steels in the Nakajima test

Continuous annealing simulation experiment of a large sample (220 mm length and 110 mm width) is carried out for a better understanding of the role of annealing parameters on microstructure and mechanical properties so as to develop dual-phase steel with consistent quality. A typical complete annealing cycle used in industry for producing dual-phase structure was divided into several thermal stages to investigate various mechanisms at different thermal stages. A correlation among microstructure, process parameters and mechanical property is established by varying the important annealing process parameters. Based on the systematic study at each thermal stage, the annealing parameters that have greater influence on mechanical properties were identified. A modified complete thermal cycle, after control of these key parameters, produced a better distribution of fine martensite along the ferrite grain boundaries and thus enhanced mechanical properties. The study showed that higher amount and uniform distribution of fine martensite with granular morphology along the ferrite grain boundaries for a fixed composition of steel is essential for improved mechanical properties. The uniform distribution of fine martensite with required amount within the ferrite matrix not only enhanced strength–ductility balance but also improved stretch-flangeability.

Processing-Microstructure-Property Correlation for Producing Stretch-Flangeable Grade Dual-Phase Steel

Sintered NdFeB permanent magnets and steel were soldered successfully using Zn-Sn alloy. The effects of Sn content on the microstructure and mechanical properties of soldered joints were investigated. The results showed that the typical interfacial microstructure represented NdFeB/NdFe5.5Zn(B) + ξ-FeZn13/Zn + β-Sn/ξ-FeZn13 + δ-FeZn10 + Γ-Fe3Zn10/steel. With the addition of Sn, the thickness of the NdFe5.5Zn(B) phase increased, while more β-Sn was observed in the soldering seam. The maximum shear strength reached 45.3 MPa with a Sn proportion of 6 wt.%, and excessive growth of the NdFe5.5Zn(B) phase in the joints deteriorated the mechanical properties. The fracture morphology exhibited a ductile-to-brittle transition with the occurrence of interfacial fractures due to thick intermetallic compounds.

Microstructure and Interfacial Evolution of Sintered NdFeB Permanent Magnet/Steel Joint Soldered with Zn-Sn Alloy

Forming limit diagram is one of the most commonly used failure criteria for sheet metal forming analysis. Forming limit diagram generation is time-consuming, and therefore, any reduction in the tes...

Forming limit diagram generation with reduced experiments and modelling for different grades of automotive sheet steel using CrachLab

The objective of the present work is to carry out analytical and finite element analysis for commonly used coating materials for micro-milling applications on high-speed steel substrate and evaluate the effects of different parameters. Four different coating materials were selected for micro-milling applications: titanium nitride (TiN), diamond-like carbon (DLC), aluminium titanium nitride (AlTiN) and titanium silicon nitride (TiSiN). A 3D finite element model of coating and substrate assembly was developed in Abaqus to find the Hertzian normal stress when subjected to normal load of 4 N, applied with the help of a rigid ball. The radius of the rigid ball was 200 µm. For all the coating materials, the length was 3 mm, the width was 1 mm, and the thickness was 3 µm. For the high-speed steel substrate, the length was 3 mm, the width was 1 mm, and the thickness was 50 µm. Along the length and width, coating and substrate both were divided into 26 equal parts. The deformation behaviour of all the coating materials was considered as linear–elastic and that of the substrate was characterized as elastic–plastic. The maximum normal stress developed in the FEA model was 12,109 MPa. The variation of the FEA result from the analytical result (i.e., 12,435.97 MPa is 2.63%) which is acceptable. This confirms that the FEA model of coating–substrate assembly is acceptable. The results shows that the TiSiN coating shows least plastic equivalent strain in the substrate, which serves the purpose of protecting the substrate from plastic deformation and the TiSiN of 3 micron thickness is the most optimum coating thickness for micro-milling applications.

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Performance Evaluation of Different Coating Materials in Delamination for Micro-Milling Applications on High-Speed Steel Substrate

It was attempted to produce galvannealed dual-phase (DP) steel through a commercial continuous galvanizing line (CGL). The main challenge was to form the DP microstructure even with the slow cooling rate after annealing in the CGL. A two-pronged approach was adopted for this, viz. design of the steel chemistry with calculations and optimization of the CGL parameters with simulation using Gleeble-3800 thermomechanical simulator. The steel thus produced in CGL revealed ferrite and 18 ± 2% martensite microstructure, with tensile strength exceeding 600 MPa and 24% total elongation along with good formability. Weldability study using resistance spot welding indicated the possibility of achieving sound joint with a 4-kA width in weld time–current lobe despite the high carbon equivalence.

Design and Development of Galvannealed Dual-Phase Steel: Microstructure, Mechanical Properties and Weldability

The main objective of this study is to perform an abrasive wear resistance study of UMHWPE and XLPE by using different grades of abrasive paper (grade 100 (190 µm), grade 220 (50 µm), and grade 400 (40 µm)) with minor (10 N) and major (15 N) loading conditions. In this article, wear performance of the UMHWPE and XLPE materials compared to the bio-tribological data as reported earlier in the clinical studies has been investigated. The experimental result shows that the loss of materials for the XLPE was much higher than the UHMWPE under similar loading conditions. UHMWPE shows a 34% reduction in wear at minor loading conditions and a 53% reduction in wear at major loading conditions. From experimental results it was concluded that Cross-link PE has better wear resistance than UHMWPE in minor wear conditions, whereas UHMWPE shows better wear resistance under major loading conditions. Based upon these results, UHMWPE and XLPE have been recommended for use as bearing materials in orthopedics. The experimental results of this study were validated using results from the available literature.

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Experimental Study to Evaluate the Wear Performance of UHMWPE and XLPE Material for Orthopedics Application

Sandwich steel doors are used for domestic and commercial purposes. The structure of this door consists of steel sheet and paper honeycomb sandwiched and bonded to steel sheets for light weighting. These doors experience dent frequently during their regular usage. However, for such products currently there are no available standards for dent characterization. In the present work, a novel experimental method has been proposed to characterize the dent and evaluate its performance. Based on experimental results, low-cost design modification is also proposed to enhance the dent performance of the door. A method is established to use the coupon samples to evaluate the door dent performance instead of full-scale experimentation.

Rudra Bubai Sarkar

Papers

Forming limit diagram generation with reduced experiments and modelling for different grades of automotive sheet steel using CrachLab

Performance Evaluation of Different Coating Materials in Delamination for Micro-Milling Applications on High-Speed Steel Substrate

Design and Development of Galvannealed Dual-Phase Steel: Microstructure, Mechanical Properties and Weldability

Experimental Study to Evaluate the Wear Performance of UHMWPE and XLPE Material for Orthopedics Application

Experimental Evaluation of Dent Performance of Low-Cost Sandwich Doors