The work involves finite element analysis (FEA) and experimental investigation of formability and geometrical accuracy prevailing in single point incremental forming (SPIF) process. Preheating at different temperatures was performed in order to reform microstructures (grain size) and texture (spatial grain orientation distribution) of AA1050 sheet. Preheating led to removal and rearrangements of defects in the crystal structure in comparison with the distorted structures present in coldworked commercial aluminum sheets. Preheating at higher temperatures resulted in coarser grains with preferential texture and increased area fraction of homogenously oriented grains. Numerical simulation of SPIF process has been done to predict the effect of preheating on von Mises stresses, forming load, wall thickness distribution and geometrical accuracy of formed parts. For the purpose, Johnson-Cook models' parameters were evaluated by mechanical characterization of the samples with varying microstructural and texture arrangements resulted due to variations in preheating temperatures. FEA of the process revealed that preheating of the sheets resulted in reduced forming load, uniform wall thickness distribution and improved geometrical accuracy. The results were further validated by experiments and compared to the original samples with fine and randomly orientated grains.

Commercially pure titanium (CP-Ti) Grade-2 has many applications due to its good weldability, strength, ductility, formability, and superior corrosion resistance. Although, CP-Ti Grade-2 can be formed at room temperature, however, it has lower ductility at room temperature. Therefore, heat treatment or thermal activation is required to increase its ductility and formability. In this paper, the process capabilities of CP-Ti Grade-2 to form the components through warm incremental sheet forming (ISF) has been investigated. To identify the optimal temperature at which CP-Ti Grade-2 sheets can be incrementally formed, straight groove tests were performed experimentally at various temperatures. Two geometries, namely, varying wall angle truncated cone, and constant wall angle truncated cone were used as test cases to evaluate the formability of CP-Ti Grade-2, in terms of limiting wall angle. The formability was also assessed through forming limit diagram obtained by Finite Element (FE) simulation. With forming limit damage criterion, fracture in the formed component was predicted with FE simulation using Abaqus Explicit software. To assess the process capabilities of CP-Ti Grade-2 sheet formed through warm ISF, thickness distribution, forming forces, geometrical accuracy, and surface roughness were analyzed through both FE simulation and experimental work.

This work explores the effect of tool geometry on surface finish in incremental sheet forming (ISF) process. In the present work, two different tool geometries i.e. hemispherical shaped tool and ellipsoidal shaped tool are considered. Area at tool-sheet contact and scallop height were calculated for both the tool geometries. To assess the effect of tool geometry on the surface finish of the formed components, both analytical and experimental approaches have been used. A test geometry having the shape of frustum of pyramid was considered for the proposed investigation and four surface roughness parameters i.e. arithmetic mean surface roughness (Ra), root mean square surface roughness (Rq), maximum peak-to-valley height (Rt) and average peak-to-valley height (Rz) have been selected as response parameters. Based on the analytical model and experimental investigations, both qualitative and quantitative comparisons had been made among the effects of hemispherical and ellipsoidal tool geometries on surface finish. The investigation deduces that better surface finish of the formed component can be achieved by using ellipsoidal shaped tool rather than the hemispherical shaped tool.

Incremental Sheet Forming (ISF) is a sheet metal forming process, which relies on minimum part-specific tooling. Extra Deep Drawn (EDD) steel has been used for making door inners, dash panels, bodyside inners, etc. due to its good weldability and relatively low yield strength. However, to date very limited work is reported on ISF of EDD steel. Besides, no work, which exhaustively discusses the practicability of EDD steel for effectual incremental forming of components, is found to be reported. The present work discusses the ISF of EDD steel sheets and examines the limitations of ISF in forming the parts out of 1.0 mm thick EDD steel sheets. Two geometries, i.e., ellipsoidal cone (with varying wall angle) and truncated cone (with constant wall angle) were used as test cases to evaluate the formability of EDD steel sheets, in terms of Critical Wall Angle (CWA). Further, the formability of EDD steel with ISF is evaluated using both strain-based and stress-based forming limit curves. The thickness distribution, geometrical accuracy, forming forces, and surface roughness and hardness are evaluated in the formed components. The work, through numerical simulations and experimental analyses, investigates the process capabilities of ISF to form the EDD steel sheets in terms of formability, thickness distribution, geometrical accuracy, forming forces, and surface roughness and hardness to ascertain the scope of the proposed process.

No abstract