A method and apparatus for determination of the ultrasonic-assisted forming limit diagram

Abstract

It was recently demonstrated that ultrasonic vibrations could result in lower forming forces and a better surface finish in a wide range of metal forming processes. The Nakazima stretch-forming test is a long-established experimental procedure for the formability evaluation of sheet metals. Today, the development of a standard test is critical for assessing sheet metals’ formability enhancement due to ultrasonic vibrations, which can potentially unlock the material selection limit in various manufacturing applications. This study aims to present a method and apparatus for effectuating the forming limit diagram (FLD). At the same time, high-frequency ultrasonic vibrations are combined with the movement of the forming tool. Taking St14 steel as an example, the mechanical and microstructural properties such as formability, Micro-Vickers hardness, and grain sizes were systematically investigated. Furthermore, the conventional FLD, as well as the novel “Ultrasonic-Assisted Forming Limit Diagram” (UA-FLD), were attained and compared with a nonlinear regression-based approach. The results have indicated that superimposing ultrasonic vibrations with the amplitude of 15µm at the frequency of 20 kHz to the tool would cause a notable enhancement in forming limit diagram, a maximum of 28% increase in hardness, and a 23% reduction in average grain size of the specimens.

Investigation of Mechanical Properties of Parts Fabricated with Gas- and Water-Atomized 304L Stainless Steel Powder in the Laser Powder Bed Fusion Process

“…The Revolution Powder Analyzer (RPA) is such an instrument. It is composed of a rotating drum with maximum volume capacity of 500 cm 3 , and its measurement is done by a digital camera on the front side while the drum is illuminated from the back. 25 RPA software quantifies powder behavior from images taken by the digital camera.…”

“…2 Although new techniques have been innovated to resolve such challenges, the appearance of defects in fabricated parts is still inevitable. 3,4 The development of additive manufacturing (AM) in the past decade has eliminated several of these challenges through part fabrication in a layer-by-layer manner. In nearly all AM processes, the characteristics of the feedstock material play a significant role in final part properties.…”

A new method to exploit ultrasonic vibrations in deep drawing process

“…Sheykholeslami et al 18 investigated the effect of ultrasonic vibrations on the deep drawing process with the rubber die of circular cross sections with FEM simulation. Najafizadeh et al 19 showed that by applying ultrasonic vibrations on the forming tool, the Forming Limit Diagram (FLD) is significantly improved. Also, the application of vibrations causes an increase in hardness and a decrease in the average grain size of the formed piece.…”

A Numerical and Experimental Study into Thermal Behavior of Micro Friction Stir Welded Joints of Al 1050 and Copper Sheets

“…In this research, due to the large deformations created around the tool pin, the ALE method has been used to prevent large deformations of the elements around the tool pin. Najafizadeh et al [14,15] investigated the Conductive and radiant heat transfer models at the boundaries and measured temperature changes at different welding stages.. Assidi et al [16] measured the forces and temperature during the friction welding process of 6061 aluminum sheets and then performed a numerical simulation of the process based on the Coupled Eulerian-Lagrangian method. They aimed to obtain an accurate analysis of the contact and friction conditions between the tool and the sheet surface.…”