FEM-Simulation of the electrode temperature distribution and crater formation. Part I: Breakdown of an electrical discharge

2004 ◽  
Vol 120 ◽  
pp. 429-437
Author(s):  
F. Soldera ◽  
A. Lasagni ◽  
F. Mücklich
Keyword(s):  
Metal Forming ◽  
Electrical Discharge ◽  
Cathode Surface ◽  
Fem Simulation ◽  
Crater Formation ◽  
Impact Zone ◽  
Electrode Temperature ◽  
Material Loss ◽  
Cylindrical Samples ◽  
Good Agreement

An electrical discharge causes an energy input into the electrode, which melts and evaporates the metal forming a crater on the cathode surface. The larger part of material loss is produced by the ejection of molten particles from the molten pool. From calorimetric results, the amount of energy delivered to the cathode was estimated. Based on FEM, a model was developed to simulate the local temperature increase in the vicinity of the plasma impact zone. Considering phase transitions, it was possible to define a molten and an evaporated region, whose dimensions were compared with the dimensions of experimental craters. Single sparks were produced on cylindrical samples (Pt, Ir, Ru, Al, Au, Ag, Cu, W, Ni, Sn and Pb) in air and nitrogen with pressures ranging from 1 to 9 bar and electrode gaps of 1 and 2 mm. The volumes of experimental craters lay between the volumes of the simulated regions for 5 and 7 bar. For 1 and 3 bar, the volumes of the evaporated regions were overestimated. The shape of the simulated regions showed a very good agreement with the real craters. The relative volumes of the molten regions showed a very good agreement with the relative volumes of eroded material in the different metals.

Design of Deformable Tools for Sheet Metal Forming

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Lorenzo Iorio ◽  
Luca Pagani ◽  
Matteo Strano ◽  
Michele Monno
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Fem Simulation ◽  
Design Procedure ◽  
Industrial Process ◽  
Test Case ◽  
Compensation Algorithm ◽  
Tool Compensation ◽  
Aluminum Part

Traditionally, industrial sheet metal forming technologies use rigid metallic tools to plastically deform the blanks. In order to reduce the tooling costs, rubber or flexible tools can be used together with one rigid (metallic) die or punch, in order to enforce a predictable and repeatable geometry of the stamped parts. If the complete tooling setup is built with deformable tools, the final part quality and geometry are hardly predictable and only a prototypal production is generally possible. The aim of this paper is to present the development of an automatic tool design procedure, based on the explicit FEM simulation of a stamping process, coupled to a geometrical tool compensation algorithm. The FEM simulation model has been first validated by comparing the experiments done at different levels of the process parameters. After the experimental validation of the FEM model, a compensation algorithm has been implemented for reducing the error between the simulated component and the designed one. The tooling setup is made of machined thermoset polyurethane (PUR) punch, die, and blank holder, for the deep drawing of an aluminum part. With respect to conventional steel dies, the plastic tools used in the test case are significantly more economic. The proposed procedure is iterative. It allows, already after the first iteration, to reduce the geometrical deviation between the actual stamped part and the designed geometry. This methodology represents one step toward the transformation of the investigated process from a prototyping technique into an industrial process for small and medium batch sizes.

Microstructural Characterization of Thermal Damage on Silicon Wafers Sliced Using Wire-Electrical Discharge Machining

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Kamlesh Joshi ◽  
Upendra Bhandarkar ◽  
Indradev Samajdar ◽  
Suhas S. Joshi
Keyword(s):  
Raman Spectroscopy ◽  
Electrical Discharge ◽  
Thermal Damage ◽  
Electrical Discharge Machining ◽  
Wafer Surface ◽  
Wire Electrical Discharge Machining ◽  
Wire Edm ◽  
Material Loss ◽  
Pulse On Time

Slicing of Si wafers through abrasive processes generates various surface defects on wafers such as cracks and surface contaminations. Also, the processes cause a significant material loss during slicing and subsequent polishing. Recently, efforts are being made to slice very thin wafers, and at the same time understand the thermal and microstructural damage caused due to sparking during wire-electrical discharge machining (wire-EDM). Wire-EDM has shown potential for slicing ultra-thin Si wafers of thickness < 200 μm. This work, therefore, presents an extensive experimental work on characterization of the thermal damage due to sparking during wire-EDM on ultra-thin wafers. The experiments were performed using Response surface methodology (RSM)-based central composite design (CCD). The damage was mainly characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The average thickness of thermal damage on the wafers was observed to be ∼16 μm. The damage was highly influenced by exposure time of wafer surface with EDM plasma spark. Also, with an increase in diameter of plasma spark, the surface roughness was found to increase. TEM micrographs have confirmed the formation of amorphous Si along with a region of fine grained Si entrapped inside the amorphous matrix. However, there were no signs of other defects like microcracks, twin boundaries, or fracture on the surfaces. Micro-Raman spectroscopy revealed that in order to slice a wafer with minimum residual stresses and very low presence of amorphous phases, it should be sliced at the lowest value of pulse on-time and at the highest value of open voltage (OV).

Forming Limit Extension of High-Strength Steels in Bending Processes

2014 ◽  
Vol 611-612 ◽  
pp. 1110-1115 ◽  
Author(s):  
Mohamed El Budamusi ◽  
Andres Weinrich ◽  
Chrstioph Becker ◽  
Sami Chatti ◽  
A. Erman Tekkaya
Keyword(s):  
Hydrostatic Pressure ◽  
Metal Forming ◽  
Fem Simulation ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Limit ◽  
Forming Limits ◽  
Air Bending ◽  
Forming Technology ◽  
Bending Process

Bending is a commonly used forming technology in metal forming. The occurring springback and low forming limits of high-strength steels especially during air bending are the main disadvantages. In this paper, the conventional air bending process is applied with a hydrostatic pressure in the bending zone. This was done using an elastomer tool. The advantage of this method is that the flexibility of air bending is maintained by reducing the springback while the forming limits are extended. Furthermore, different geometries for the elastomer tool were investigated by means of a FEM simulation. The investigation leads to a reduction of the process forces by minimizing the springback and to an extension of the forming limits.

A Theoretical Analysis of the Bending into Cylindrical Dies of Metal Strips

1984 ◽  
Vol 198 (2) ◽  
pp. 99-108 ◽  
Author(s):  
T X Yu ◽  
W Johnson
Keyword(s):  
Theoretical Analysis ◽  
Metal Forming ◽  
Plastic Material ◽  
Forming Process ◽  
Rigid Plastic ◽  
Rigid Plastic Material ◽  
Punch Load ◽  
Theoretical Predictions ◽  
Metal Forming Process ◽  
Good Agreement

Based on experiments on the bending of metal strips into cylindrical dies using a semi-circular ended punch (1) a theoretical analysis of this metal forming process is presented to predict the punch load—punch travel characteristic and the clearance between the punch pole and the mid-point of the strip. Elastic/plastic and rigid/plastic material idealizations are employed, and the effect of friction between the strip and the die is also considered. The theoretical predictions show good agreement with the experimental results and are useful for designers.

Comparison of Offset and Wiping Z-Die Designs for Precision Z-Bent Part Fabrication

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Sutasn Thipprakmas ◽  
Pakkawat Komolruji ◽  
Wiriyakorn Phanitwong
Keyword(s):  
Fem Simulation ◽  
The Finite Element Method ◽  
Spring Back ◽  
Bend Radius ◽  
Dimensional Precision ◽  
Bending Process ◽  
Simulation Results ◽  
Bend Angles ◽  
Selection Of ◽  
Good Agreement

In recent years, the requirements for high dimensional precision on Z-bent shaped parts have become increasingly stringent. To attain these requirements, the suitable selection of the Z-die bending type has to be considered much more strictly. In this research, two types of Z-bending processes, offset Z-die bending and wiping Z-die bending, were investigated using the finite element method (FEM) to identify the spring-back characteristics and dimensions of Z-bent shaped parts. In the case of offset Z-die bending, the spring-back characteristics on both bend angles were similar. In contrast, in the case of wiping Z-bending, the spring-back characteristics on both bend angles were different. In addition, the dimensions of the Z-bent shaped parts were investigated. It was found, in the case of wiping Z-bending, that web thinning was generated and the outer bend radius was out of tolerance. To validate the FEM simulation results, experiments were carried out. The FEM simulation results showed good agreement with the experimental results in terms of the bend angles and the overall geometry of the Z-bent shaped parts. To achieve precise Z-bent shaped parts, the suitable selection of Z-die bending type in the Z-die bending process is very important.

Six-Dimensional Compliance Analysis and Validation of Orthoplanar Springs

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Chen Qiu ◽  
Peng Qi ◽  
Hongbin Liu ◽  
Kaspar Althoefer ◽  
Jian S. Dai
Keyword(s):  
Finite Element ◽  
Parallel Mechanism ◽  
Fem Simulation ◽  
Analytical Models ◽  
Compliance Matrix ◽  
Out Of Plane ◽  
Continuum Manipulator ◽  
First Time ◽  
Good Agreement

This paper for the first time investigates the six-dimensional compliance characteristics of orthoplanar springs using a compliance-matrix based approach, and validates them with both finite element (FEM) simulation and experiments. The compliance matrix is developed by treating an orthoplanar spring as a parallel mechanism and is revealed to be diagonal. As a consequence, corresponding diagonal compliance elements are evaluated and analyzed in forms of their ratios, revealing that an orthoplanar spring not only has a large linear out-of-plane compliance but also has a large rotational bending compliance. Both FEM simulation and experiments were then conducted to validate the developed compliance matrix. In the FEM simulation, a total number of 30 types of planar-spring models were examined, followed by experiments that examined the typical side-type and radial-type planar springs, presenting a good agreement between the experiment results and analytical models. Further a planar-spring based continuum manipulator was developed to demonstrate the large-bending capability of its planar-spring modules.

Springback Prediction Compensation and Optimization for Front Side Member in Sheet Metal Forming Using FEM Simulation

2013 ◽  
Vol 789 ◽  
pp. 436-442
Author(s):  
Agus Dwi Anggono ◽  
Waluyo Adi Siswanto ◽  
Omar Badrul
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Fem Simulation ◽  
Element Size ◽  
Springback Prediction ◽  
Element Method

Numerical simulation by finite element method has become a powerful tool in predicting and preventing the unwanted effects of sheet metals technological processing. One of the most important problems in sheet metal forming is the compensation of springback. To improve the accuracy of the formed parts, the die surfaces are required to be optimized so that after springback the geometry falls at the expected shape. This paper presents and discusses numerical simulation procedure of die compensation by using the methods of Simplified Displacement Adjustment (SDA). This analysis use Benchmark 3 models of Numisheet 2011. Sensitively analysis was done by using finite element method (FEM) show that the springback values are influenced by element size, integration points and material properties.

Sign in / Sign up

Export Citation Format

Share Document