scholarly journals Reduction of Die Wear and Structural Defects of Railway Screw Spike Heads Estimated by FEM

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1834
Author(s):  
Jackeline Alcázar ◽  
Germán Abate ◽  
Nazareno Antunez ◽  
Alejandro Simoncelli ◽  
Antonio J. Sánchez Egea ◽  
...  
Keyword(s):  
Computational Simulation ◽  
Hot Forging ◽  
Railway Track ◽  
Structural Defects ◽  
Critical Parameters ◽  
Process Conditions ◽  
Wall Angle ◽  
Die Filling ◽  
Massive Scale ◽  
Forging Load

Railway spike screws are manufactured by hot forging on a massive scale, due to each kilometer of railway track needing 8600 spike screws. These components have a low market value, so the head must be formed in a single die stroke. The service life of the dies is directly related to the amount of energy required to form a single screw. The existing standard for spike screws specifies only the required tolerances for the head dimensions, particularly the angle of the hub faces and the radius of agreement of the hub with the cap. Both geometrical variables of the head and process conditions (as-received material diameter and flash thickness) are critical parameters in spike production. This work focuses on minimizing the energy required for forming the head of a railway spike screw by computational simulation. The variables with the highest degree of incidence on the energy, forging load, and filling of the die are ordered statistically. The results show that flash thickness is the variable with the most significant influence on forming energy and forming load, as well as on die filling. Specifically, the minimum forming energy was obtained for combining of a hub wall angle of 1.3° an as-received material diameter of 23.54 mm and a flash thickness of 2.25 mm. Flash thickness generates a lack of filling at the top vertices of the hub, although this defect does not affect the functionality of the part or its serviceability. Finally, the wear is mainly concentrated on the die splice radii, where the highest contact pressure is concentrated according to the computational simulation results.

Structuring of Silicon Wafer Surfaces on the Sub-100 nm Scale by Hydrogen Plasma Treatments

2003 ◽  
Vol 788 ◽  
Author(s):  
R. Job ◽  
Y. Ma ◽  
A. G. Ulyashin
Keyword(s):  
Hydrogen Plasma ◽  
Structural Defects ◽  
Process Conditions ◽  
Force Microscopy ◽  
Czochralski Silicon ◽  
Atomic Force ◽  
Nano Structures ◽  
Plasma Treatments ◽  
The Impact ◽  
Wafer Surfaces

ABSTRACTHydrogen plasma treatments applied on standard Czochralski silicon (Cz Si) wafers cause a structuring of the surface regions on the sub-100 nm scale, i.e. a thin ‘nano-structured’ Si layer is created up to a depth of ∼ 150 nm. The formation of the ‘nano-structures’ and their evolution in dependence on the process conditions was studied. The impact of post-hydrogenation annealing on the morphology of the structural defects was studied up to 1200 °C. The H-plasma treated and annealed samples were analyzed at surface and sub-surface regions by scanning electron microscopy (SEM), atomic force microscopy (AFM), and μ-Raman spectroscopy.

Correction: Computational Simulation of Axis Symmetric Aft Wall Angle Cavity in Supersonic Flow Field

2020 ◽  
Author(s):  
Naresh Relangi ◽  
Divyasri Garimella ◽  
K Jayaraman ◽  
Jayakumar Venkatesan ◽  
S Jeyakumar ◽  
...  
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Computational Simulation ◽  
Wall Angle

Lubrication in Hot Forging with Pulsed Ram Motion

2018 ◽  
Vol 767 ◽  
pp. 149-156
Author(s):  
Ryo Matsumoto ◽  
Hiroshi Utsunomiya ◽  
Shinya Ishigai
Keyword(s):  
Stainless Steel ◽  
Motion Control ◽  
Hot Forging ◽  
Oxide Glass ◽  
Test Results ◽  
Servo Press ◽  
Lubrication Performance ◽  
Glass Lubricant ◽  
Hollow Part ◽  
Forging Load

The effect of pulsed (oscillating) ram motion control on lubrication was investigated in hot forging of stainless steel workpiece with oxide glass lubricant. During the retreat in the pulsed ram motion, the workpiece was re-lubricated by flow of lubricant through the gap between the workpiece and the die. A hot spike-type forging test on a servo press with pulsed ram motions was carried out to investigate the lubrication performance of the oxide glass. In the test, the workpiece with a temperature of 1223 K was extruded into the hollow part of the upper die together with oxide glass in a manner that combined pulsed and stepwise ram operations. The re-lubrication of the workpiece with oxide glass was confirmed by the test results showing 5–10% reduction in the forging load and 5% longer length of the backward extruded part of the workpiece under an appropriate pulsed ram motion.

Performance Uncertainty Quantification for Centrifugal Compressors: Part 2—Flange to Flange Variability

2012 ◽  
Author(s):  
Sivasubramaniyan Sankaran ◽  
Giuseppe Sassanelli ◽  
Giuseppe Iurisci ◽  
Andrea Panizza
Keyword(s):  
Probabilistic Approach ◽  
Sensitivity Study ◽  
Critical Parameters ◽  
Process Conditions ◽  
Centrifugal Compressors ◽  
Large Sets ◽  
Probabilistic Technique ◽  
Performance Variation ◽  
Compressor Performance ◽  
Performance Uncertainty

This paper presents a methodology to control flange to flange performance prediction of centrifugal compressors using a probabilistic approach. In order to have reliable prediction for the performance of centrifugal compressors, a thorough knowledge of critical parameters contributing to the deviation and an efficient way to control the variation of these parameters becomes necessary. This paper discusses about a robust methodology for identifying and controlling the variation of these parameters and hence the predicted performance. This probabilistic technique involves a Design of Experiments (DoE) study to handle large number of input parameters, sensitivity study to identify critical ones and a Monte-Carlo based approach to identify the uncertainty in flange to flange performance. This approach takes into consideration the compressor stage performance variability driven by impeller manufacturing tolerances, statoric component losses variability and leakages variability in order to compute overall performance variation in a compressor. An in-house developed probabilistic optimization code (PEZ) is interfaced with a well-validated & calibrated thermodynamic tool to analyse large sets of possible combinations and to provide best possible solution for a given design space. This concept is successfully applied for different compressor configurations by varying the stage numbers and process conditions. The results give an insight on the main sources and magnitude of variations on compressor performance, thus enabling to control the predictions in an efficient way. This methodology will provide a novel and an efficient way to generate robust compressor performance, where it will be possible to take into account design and manufacturing uncertainty. The use of this methodology can thus drastically improve the performance predictability and risk associated with each compressor selection.

Rotating Electromagnetic System for Railway Track Crack Detection

2014 ◽  
Vol 875-877 ◽  
pp. 401-405
Author(s):  
Michele Buonsanti ◽  
Giovanni Leonardi ◽  
Giuseppe Megali ◽  
Francesco Scoppelliti
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Crack Detection ◽  
High Reliability ◽  
Rotating Magnetic Field ◽  
Railway Track ◽  
Structural Defects ◽  
Electromagnetic System ◽  
Innovative System ◽  
Invasive Techniques

The aim of this paper is to provide an alternative methodology, high reliability, in order to monitor, exploiting non-invasive techniques, railway track. In this particular case study, the presence of structural defects is assessed through an innovative system. The proposed approach provides the use of rotating magnetic field. Within this framework, the Eddy Current Techniques (ECTs) have greatly increased their importance for their capacity to detect the magnetic field variations caused by the presence of material alterations. Whilst the researches in this field propose various solutions to the detection of flaws (in surface and subsurface), a still open problem concerns the difficult detection of defects due to the geometrical complexity of the structure and the particular orientations of the crack. Particularly, this contribution proposes an approach based on Finite Element (Finite Element Method, FEM) for the modeling of railway tracks, in order to obtain a rapid and precise assessment about their integrity.

Preform and Die Designs for Hot Forging Process of Linear Slide Block

2013 ◽  
Vol 419 ◽  
pp. 395-400 ◽  
Author(s):  
Cheng Hsien Yu ◽  
Jinn Jong Sheu
Keyword(s):  
Heat Treatment ◽  
Hot Forging ◽  
Laser Heat Treatment ◽  
Forging Process ◽  
Die Filling ◽  
Slide Block ◽  
Laser Heat ◽  
Wear And Corrosion ◽  
Linear Slide ◽  
Hot Forging Process

In this study, the preform and die designs of hot forging process were proposed for a long-flat slide block. This block is assembled to the linear slide for carrying the moving table. Three different billet geometry designs were proposed to obtain good die filling. The volume of the flash is limited to 30% with a flash thickness design in 3 mm. The forging die was designed with four ejectors to push up the forged part smoothly. The proposed billet geometries and die design were evaluated using CAE simulation. The simulation results indicated that the suitable perform design is able to achieve better material flow. The flash flow control is able to reduce the forming load and improve the die filling. The forging experiments were carried out to verify the proposed method, the experiment results showed good agreement with the CAE simulations. For the Improvement of wear and corrosion resistances of Inconel718 (In718) surface, high velocity oxygen fuel (HVOF) thermal spray coating of micron-sized WC-Cr-C-Ni powder was coated onto Inconel718 surface and laser heat-treatment of the coating was carried out. Porous coating of porosity 2.2±0.4% was prepared by HVOF coating, and it was improved by laser heat-treatment, reducing the porosity to 0.35±0.08%. Micro-hardness of laser heat-treated coating increased more than four times compared to the surface of In718. Friction coefficient decreased by HVOF coating and laser heat-treatment. Wear resistance improved, decreasing the wear depth by the coating and laser heating. The interface between coating and In718 was compacted, and elements diffused from both coating and inconel718 substrate to interface, forming metal rich buffer zone (interface) and enhancing the adhesion of coating. Corrosion resistance improved by coating in sea water 3.5% NaCl solution and in 1M HCl acid, but it worsened in 1M NaOH base. For the improvement of wear and corrosion resistances of Inconel718, HVOF WC-metal power coating and laser heat-treatment are recommended.

scholarly journals Finite Element Analysis of Springback of High-Strength Metal SCGA1180DUB While U-Channeling, According to Wall Angle and Die Radius

2021 ◽  
Author(s):  
Samet Karabulut ◽  
İsmail Esen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Sheet Thickness ◽  
High Strength ◽  
Sheet Forming ◽  
High Yield ◽  
Process Conditions ◽  
Wall Angle ◽  
Element Analysis ◽  
Multi Phase

Abstract Springback is a problem as important as tearing or thinning, while forming high-strength sheets. Springback is an undesirable situation and it is the form difference between the desired form of a part in theory and the form obtained due to mechanical characteristics and process inputs of the material after die forming. It affects operations in shearing, punching or bending dies in subsequent operations in forming die sets. If the part is not within the desired tolerance range, it creates problems during assembly. In order for cost effective production plans for automotive parts to be made, suitable sheet forming simulations are needed. Waste of time and failures during die construction are minimized by defining accurate parameters by finite element analyses and minimizing periods of trial-and-error. In this study, the material SCGA1180DUB in sheet thickness of 0.8 mm from multi-phase steel sheet group was U-channeled, using Autoform sheet forming analysis program, according to appropriate process conditions having wall angles of 7°,10°,12° and die radius values of R3, R5, R8 and the springback values were estimated. The results obtained were compared through the finite element program and suitable wall angle and die radius values for the material SCGA1180DUB for forming advanced high-strength sheets were determined. As the die radii increased at the same wall angles, the amount of spring back increased significantly. In particular, due to high yield and tensile strength of multi-phase high strength sheet, springback values were observed to be high. Negative springbacks were observed in the roof of the part. In the same die radii, under the same process conditions, as wall angles increase, springback values decreased. In the literature, it is interesting that there are few studies regarding forming, springback of high-strength sheets SCGA1180DUB. This study will contribute to the literature. Autoform program was used for Finite Element Analysis.

Flash Design for Automatic Transfer System of Bearing Hub in Hot Forging Process

2006 ◽  
Vol 116-117 ◽  
pp. 120-123
Author(s):  
Sang Kon Lee ◽  
Hyun Sang Byun ◽  
Byung Min Kim ◽  
Dae Cheol Ko ◽  
C.G. Kang
Keyword(s):  
Numerical Analysis ◽  
Metal Flow ◽  
Hot Forging ◽  
Experimental Results ◽  
Transfer System ◽  
Forging Process ◽  
Hot Forging Die ◽  
Forging Die ◽  
Hot Forging Process ◽  
Forging Load

The aim of this study is to design flash geometry of bearing hub to apply the automatic transfer system in hot forging process. The flash geometry is very important in hot forging process because the flash geometry effects on the metal flow, material losses, forging load, die pressure and so on. In this study, the problem of designing the flash geometry is studied with flash thickness and width considering the maximum die pressure to apply an automatic transfer system in hot forging process for bearing hub. The numerical analysis was conducted by means of the commercial S/W DEFORM. On the basis of numerical analysis the flash geometry of hot forging die was redesigned, and experiment was conducted. From the experimental results, it was possible to produce bearing hub with an automatic transfer system without any deterioration of die lifetime.

scholarly journals Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

2017 ◽  
Vol 114 (11) ◽  
pp. 2836-2841 ◽  
Author(s):  
X. Wendy Gu ◽  
Xingchen Ye ◽  
David M. Koshy ◽  
Shraddha Vachhani ◽  
Peter Hosemann ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Mechanical Behavior ◽  
Self Assembly ◽  
Structural Disorder ◽  
Structural Features ◽  
Structural Defects ◽  
Critical Parameters ◽  
Recent Developments ◽  
Self Assembled ◽  
Elastic And Plastic Deformation

Large, freestanding membranes with remarkably high elastic modulus (>10 GPa) have been fabricated through the self-assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures, which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. Thin-film buckling and nanoindentation are used to evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3–20 vol % Au are found to have an elastic modulus of ∼6–19 GPa, and hardness of ∼120–170 MPa. We find that rapidly self-assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.

Wear Prediction for Hot Forging Dies under Consideration of Structure Modification in the Surface Layer

2014 ◽  
Vol 1018 ◽  
pp. 341-348 ◽  
Author(s):  
Andreas Klassen ◽  
Anas Bouguecha ◽  
Bernd Arno Behrens
Keyword(s):  
Surface Layer ◽  
Thermal Load ◽  
Hot Forging ◽  
Great Influence ◽  
Tool Material ◽  
High Hardness ◽  
Experimental Investigations ◽  
Wear Prediction ◽  
High Cooling Rates ◽  
Forging Load

Hot forging dies are exposed to a combination of high mechanical and thermal load in each forging cycle leading to abrasive wear that is one of the most frequent causes of die failure. Due to the high difference in temperature between the dies and the workpiece the surface layer material of forging dies undergoes very high thermal shock loads. High temperatures, which occur in each cycle lead to material annealing and to a softening of the material in the surface layer. However, there are die regions, like convex radiuses, where the surface temperatures exceed the austenitizing temperature. In combination with high cooling rates martensitic structures with a high hardness are generated in these regions. Both, softening as well as hardening of the tool material have a great influence on the wear resistance of dies. Nowadays a prediction of the wear amount is possible by using Finite Element Method (FEM) in combination with wear models. The approach for hot forging processes provides an input of die hardness curves under cyclic thermal load. Only by calculating die wear using this hardness curve a good accuracy of the FE result with experimental investigations is possible. Therefore relevant tests of hot forging material under typical forging load should be designed, conducted and afterwards used in the FE based wear prediction for hot forging dies.

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