Study of Sheared Edge Formability of Ultra-High Strength DP980 Sheet Metal Blanks

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Saeid Nasheralahkami ◽  
Weitian Zhou ◽  
Sergey Golovashchenko
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Strength Steels ◽  
High Strength ◽  
Material Behavior ◽  
Element Analysis ◽  
Advanced High Strength Steels ◽  
Sheared Edge ◽  
Ultra High Strength Steels ◽  
Lower Tool

Advanced high strength steels (AHSS) and ultra-high strength steels (UHSS) have been increasingly implemented by the automotive industry for better crashworthiness and fuel economy. However, these steels are often sensitive to the trimmed edge cracking. The objective of the present paper is to study the sheared edge of ultra-high strength dual-phase steel, DP980, in mechanical trimming and hole punching by sheared edge quality assessment, stretchability, and hole expansion tests as well as finite element analysis. Furthermore, the mechanism of fracture propagation in trimming and hole punching processes of DP980 was discussed. Rather a unique fracture mechanism was observed for trimming of DP980 steel leading to the burr removal at the final stage of the trimming process. Finite element analysis revealed that, under very large clearances, a secondary crack initiates from the edge of the lower tool, and the primary propagated crack turns toward it simultaneously. Intersecting of these two cracks leads to the total separation and leaves the edge of the trimmed part with a broken burr. Fracture observation of trimmed specimens revealed that crack initiation sites under tension moved from the middle of the trimmed surface toward the burr tip with increasing the clearance. This study demonstrates the importance of stretchability tests for designing the stamping dies as well as a reliable finite element simulation for characterizing the material behavior during the shearing process.

An Investigation of Springback in U-Channel Sheet Metal by Finite Element Analysis

2012 ◽  
Vol 548 ◽  
pp. 456-460 ◽  
Author(s):  
Gopi Alagappan ◽  
Syed H. Masood ◽  
Xuan Zhi Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
High Strength Steels ◽  
High Strength ◽  
Element Analysis ◽  
Advanced High Strength Steels ◽  
Forming Tools

In sheet metal forming, springback is defined as an elastic material recovery after unloading of the forming tools. Springback causes variations and inconsistencies of final part dimensions. Therefore prediction of springback is very important for production of precise products used in automobile and aerospace industries. There are various parameters involved in the process of sheet metal forming, including Young’s modulus, coefficient of friction, Poisson’s ratio, blank thickness, blank length, die radius, punch radius and blank holder force. The aim of this paper is to investigate the springback of a U-channel part by finite element analysis (FEA) and to identify the influences of important parameters on the springback of advanced high strength steels (AHSS) using numerical simulation.

Testing and Modeling of Roll Levelling Process

2014 ◽  
Vol 611-612 ◽  
pp. 1753-1762 ◽  
Author(s):  
Elena Silvestre ◽  
Eneko Sáenz de Argandoña ◽  
Lander Galdos ◽  
Joseba Mendiguren
Keyword(s):  
Finite Element ◽  
High Strength Steels ◽  
Beam Theory ◽  
High Strength ◽  
Theoretical Models ◽  
Element Model ◽  
Forming Process ◽  
Element Analysis ◽  
Design Engineers ◽  
Ultra High Strength Steels

Roll levelling is a forming process used to remove the residual stresses and imperfections of metal strips by means of plastic deformations. During the process the metal fibres are subjected to cyclic tension-compression deformations leading to achieve flat product. The process is especially important to avoid final geometrical errors when coils are cold formed or when thick plates are cut by laser. In the last years, and due to the appearance of high strength materials such as Ultra High Strength Steels, machine design engineers are demanding a reliable tool for the dimensioning of the levelling facilities. In response to this demand, Finite Element Analysis and Analytical methods are becoming an important technique able to lead engineers towards facilities optimization through a deeper understanding of the process. Aiming to this study two different models have been developed to analyze the roll levelling operations: an analytical model and a finite element model. The FE-analysis was done using 2D-modelling assuming plane strain conditions. Differing settings, leveller configuration and materials were investigated. The one-dimensional analytical levelling model is based on classical beam theory to calculate the induced strain distribution through the strip, and hence the evolving elastic/plastic stress distribution. Both models provide a useful guide to process-sensitivities and are able to identify causes of poor leveller performance. The theoretical models have been verified by a levelling experimental prototype with 13 rolls at laboratory.

Experimental Measurement and Finite Element Analysis of Screw Spike Fatigue Loads

2007 ◽  
Author(s):  
Matthew G. Dick ◽  
David S. McConnell ◽  
Hans C. Iwand
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Failure ◽  
High Strength Steels ◽  
High Strength ◽  
Element Model ◽  
Element Analysis ◽  
Bending Fatigue ◽  
Fea Model ◽  
Bending Loads

Screw spikes, also known as coach screws, are an advanced alternative to common cut spikes for track fastening. Despite their ability to secure tie plates with a clamp load and utilization of high strength steels, they are still susceptible to bending fatigue failure from lateral wheel loads. A novel method of measuring these bending loads on screw spikes was developed and implemented to characterize the load environment of the screw spikes. Results indicated that measured peak bending loads under lateral wheel loads reached as high as 10,000 lbs for individual spikes, while others carried no load whatsoever. A finite element model was developed to determine the tensile stress fields created by the measured bending loads. A good correlation was found between the FEA model predicted point of highest stress and the location of fracture. Through the testing and analysis it was determined that lateral wheel loads are not distributed evenly among the four screw spikes of a single tie plate. Instead, it was found that one spike carried nearly no load while the spike opposite of it carried more load. Using the finite element analysis it was determined that the spike exposed to the higher loading was subjected to tensile stresses above its endurance limit, which would eventually lead to a bending fatigue failure.

Investigation on the Numerical Simulation of Hot Stamping of Advanced High Strength Steels

2011 ◽  
Vol 189-193 ◽  
pp. 2144-2147 ◽  
Author(s):  
Li Min Wang ◽  
Tian Rui Zhou ◽  
Li Juan Wang ◽  
Xiao Ling Yang
Keyword(s):  
Finite Element ◽  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Material Model ◽  
Element Analysis ◽  
Advanced High Strength Steels ◽  
Element Simulation ◽  
The Finite Element Analysis ◽  
Set Up

Hot stamping represents an innovative manufacturing process for forming of advanced high strength steels, implying a sheet at austenite temperature being rapidly cooled down and formed into a die at the same time (quenching). This affords the opportunity to manufacture components with complex geometric shapes, high strength and a minimum of springback which currently find applications as crash relevant components in the automotive industry. With regard to the numerical modeling of the process, the knowledge of thermal and thermo-mechanical properties of the material is required. The material model under hot stamping condition of advanced high strength steel should be set up. The Finite Element Analysis is an essential precondition for a good process design including all process parameters. This paper presents the finite element simulation of a hot stamping process and describes a number of procedures for the simulation of hot stamping. In addition, the development direction is pointed out at the end of this paper.

Influence of the contact with friction on the deformation behavior of advanced high strength steels in the Nakajima test

2021 ◽  
pp. 030932472110212
Author(s):  
Mohammad Mehdi Kasaei ◽  
Marta C Oliveira
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Strain Rate ◽  
Contact Pressure ◽  
Deformation Behaviour ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced High Strength Steels ◽  
Deformation Mechanics ◽  
Nakajima Test

This work presents a new understanding on the deformation mechanics involved in the Nakajima test, which is commonly used to determine the forming limit curve of sheet metals, and is focused on the interaction between the friction conditions and the deformation behaviour of a dual phase steel. The methodology is based on the finite element analysis of the Nakajima test, considering different values of the classic Coulomb friction coefficient, including a pressure-dependent model. The validity of the finite element model is examined through a comparison with experimental data. The results show that friction affects the location and strain path of the necking point by changing the strain rate distribution in the specimen. The strain localization alters the contact status from slip to stick at a portion of the contact area from the pole to the necking zone. This leads to the sharp increase of the strain rate at the necking point, as the punch rises further. The influence of the pressure-dependent friction coefficient on the deformation behaviour is very small, due to the uniform distribution of the contact pressure in the Nakajima test. Moreover, the low contact pressure range attained cannot properly replicate real contact condition in sheet metal forming processes of advanced high strength steels.

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