A. Sampani

Bio: A. Sampani is an academic researcher. The author has contributed to research in topics: Welding & Tensile testing. The author has an hindex of 3, co-authored 4 publications receiving 38 citations.

Failure analysis of fractured deep-drawn 1050 aluminum circles

Abstract: A failure analysis of fractured deep-drawn 1050 aluminum (Al) circles revealed that the tensile strength and especially the tensile elongation of the stock material were out of specifications, leading to fracture during the drawing process. The cracks appeared on the walls of the drawn components, which are produced from 0.40 mm thick 1050 Al circles. The circle stock originated from an unknown supplier. The microstructural characterization of the circle stock indicated a coarse grain structure (180 to 220 µm), and observations of the failure areas revealed the presence of pronounced “orange peel.” Comparison was made with a raw material that originated from a registered and certified supplier in order to demonstrate the differences between the raw materials of the defective and sound products.

Microstructure and Failure of a Welded ZnTiCu Tube

Abstract: A failure analysis of a cracked ZnTiCu welded tube was conducted primarily by using microstructural observations of the weld joint and mechanical testing of related material. The presence of pre-existing welding defects was a major contributor to the failure.

Multi-scale investigation of highly anisotropic zinc alloys using crystal plasticity and inverse analysis

Abstract: Zinc and its alloys are important industrial materials due to their high corrosion resistance, low cost and good ductility. However, the characterization of these materials remains a difficult task due to their highly anisotropic behavior, the latter being due to the influence of microstructural effects, i.e. loading orientation-dependent activation of different families of slip systems and subsequent texture evolution, rendering the development of a reliable material model considerably difficult. A micro-mechanical approach based on polycrystal plasticity would better describe the physical mechanisms underlying the macroscopic behavior. This improved model should ostensibly improve the comprehension of the mechanical behavior, compared to the macroscopic approach using solely phenomenological anisotropy models along with a prohibitively large number of experiments required to identify the material parameters. In this paper, a multi-scale Visco-Plastic Self-Consistent (VPSC) approach is used. It is based on a micro-scale model calibrated by microstructural and deformation mechanism information based on Electron Back-Scattered Diffraction (EBSD) to describe the macroscopic anisotropic mechanical response during sheet metal deformation. The critical resolved shear stress (CRSS) as well as the micro-scale crystal parameters are obtained by an inverse analysis comparing the simulated and experimental results in terms of obtained tensile curves along three different directions. In order to obtain a global solution for the identification, we then use the Covariance Matrix Adaptation-Evolution Strategy (CMA-ES) genetic algorithm to the inverse problem. We validate our approach by comparing the simulated and experimental textures and activated slip systems. Finally, the identified mechanical parameters are used to investigate the anisotropy of the alloy and predict its formability by determining the corresponding R-values and Hill yield coefficients.

Experimental and numerical study on microstructure and mechanical properties for laser welding-brazing of TC4 Titanium alloy and 304 stainless steel with Cu-base filler metal

Abstract: Laser welding-brazing of TC4 Titanium (Ti) alloy to 304 stainless steel (SS) has been applied using 38Zn-61Cu alloy as filler metal. Microstructures of the joints were studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Mechanical properties of the joints were evaluated by performing tensile tests. The temperature field and stress field distributed in laser welding based on SS-Ti alloy joint were dynamically simulated using the ANSYS in this study. A new welding process for SS-Ti alloy joint was introduced on the basis of the controlling the formation of Ti-Fe intermetallics in the joint. One process was one pass welding involving creation of a joint with one fusion weld and one brazed weld separated by remaining unmelted SS. When laser beam on the SS side was 1.5 mm, SS would not be completely melted in joint. Through heat conduction, the filler metal melted occurred at the SS-Ti alloy interface. A brazed weld was formed at the SS-Ti alloy interface with the main microstructure of (Fe, Zn)+Fe3Zn7, β-CuZn and β-CuZn + Ti2Zn3. The joint fractured at the brazed weld with the maximum tensile strength of 210 MPa. By comparing the simulation results with the corresponding experimental findings, the validity of the numerical model is confirmed.