Vernon Fernandez

Real time monitoring and quality control of resistance spot welds using voltage, current, and force data

The real time monitoring and control of resistance spot welds is a problem of critical importance in automotive and many other manufacturing industries. However, till this date, there are no reliable, low-cost, non-destructive techniques for predicting the size and strength of the weld nuggets in real time. This paper investigates the usage of voltage, current, and force data for the above tasks. A promising technique for estimation of nugget size and strength is described and some experimental results are presented.

Comparison of Inlet Curved Disk Arrangements for Suppression of Recirculation in Centrifugal Pump Impellers

The present work aims to numerically study the inlet flow recirculation and modified impeller interaction in a centrifugal pump. An optimization of modified shrouded impeller with curved disk arrangement to suppress the unsteady flow recirculation is pursued. This modification will enhance the impeller characteristics with a wider operation range at both low and high flow rates in a high speed centrifugal pump type. The unstable flow in the centrifugal pumps is a common problem that leads to damage in the pump’s internal parts, consequently increases the operating cost. At certain flow rates, generally below the Best Efficiency Point (BEP), all centrifugal pumps are subject to internal recirculation occurs at the suction and discharge areas of the impeller.For decades, experimental work has been done to investigate the complex three-dimensional flow within centrifugal pumps impellers, before computational work gains momentum due to advancement of computing power and improved numerical codes. In this study the impeller with a curved disk arrangement has been investigated by using a three-dimensional Navier-Stokes code with a standard k-e turbulence model. The purpose is to evaluate and select the optimum impeller modification that would increase the pump suction flow rate range. Three-dimensional numerical Computational Fluid Dynamics (CFD) tools are used to simulate flow field characteristics inside the centrifugal pump and provide critical hydraulic design information. In the present work, ANSYS v.16.1 Fluent solver is used to analyze the pressure and velocity distributions inside impeller suction and discharge passages.The ultimate goal of this study is to manufacture and validate the most optimized and efficient centrifugal pump impeller with a curved disk. The best case curve identifies the highest increase of total pressure difference by 22.1%, and highest efficiency by 92.3% at low flowrates.Copyright

Study and implementation of a force stepper and a part fit-up solver algorithm for a servo controlled MFDC spot welder

The goal of this research is to study the effect of a timevarying electrode force on the weld nugget size for mid frequency direct current (MFDC) resistance spot welding (RSW) systems. Using SORPASTM, a software for simulation and optimization of resistance welding process, simulations were performed for MFDC RSW with changing force profiles and weld times. Additionally, an algorithm was developed to automatically detect a bad stack fit-up and correct it by applying an additional compensating force. This was implemented on a resistance spot welding gun fitted with a 4.5 KW servo motor along with a built-in resolver, a UnidriveTM motor controller and a real time embedded program. The simulation and experimental results are presented and compared with results obtained using a constant current (CC) welding process with constant force profile.

Experimental Analysis of Thermal Energy Deburring Process by Design of Experiment

The present work aims to conduct an experimental study through Design of Experiment (DOE) to develop a better understanding of the important variables and their impact during the Thermal Energy Method deburring process. The designed experiment was based on an L9 orthogonal array using Taguchi method and tests were conducted with an S-250 Kennametal-Extrude Hone machine. The variables tested were the chamber pressure, fuel to oxygen ratio, burr thickness and material type of the specimen. Based on variance analysis, the chamber pressure was found to have the largest variance value and was therefore concluded to have the largest impact on the deburring process. A linear regression model was developed from the experiment which can help predict the deburring outcome based on various input parameters.Copyright