bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel uncoupled ductile fracture criterion for prediction of failure in sheet metal forming
Authors: Quach H , Kim J J , Sung J H , Kim Y S 
Published: November 2020

Abstract
The ductile fracture behavior of anisotropic materials was modeled by the uncoupled ductile fracture criterion. The ductile fracture model was concerned with the micro mechanisms of void nucleation, void growth, and evolution of void coalescence. The advance plastic model of Hill’48 non-associated flow rule is considered in proposed ductile fracture criterion. A series of basic fracture testing covering a wide range of stress state for aluminum alloy 6016-AC200 are carried out. Strain field on the surface of specimens is captured by the non-contact measurement DIC system. The fracture locus constructed using the proposed criterion is close to the experimental data points over a wide stress triaxiality range from negative to intermediate and high stress triaxiality. Then, a square cup drawing test is conducted in order to verify efficiency of the proposed fracture criterion in predicting fracture behavior of metal sheet. The results indicate that the proposed ductile fracture criterion can be utilized for predicting initial fracture in sheet metal forming.
An Infrared local heat-treatment method to improve local formability of forming and trimming processes
Authors: Kim Ki-Young , Park Soohyun , Lee Eun-Ho , Kang Youn Hee 
Published: November 2020

Abstract
This paper presents a local heat-treatment method to improve the local formability for stamping and trimming processes by using focused infrared (IR) rays. Although the demand of ultra-high strength steel (UHSS) has been increasing in order to reduce car weights, the low formability of the UHSS has been a limitation. In order to resolve the formability problem, heat treatment methods have been often studied, and the authors also have developed a local heat treatment method by using focused infrared (IR) rays for a decade. The difference of this method from the author’s previous works is that the new heat treatment is completed by the supplier. The supplier of the materials completes the local heat treatment on target areas of blanks where to improve the local formability, then stamping companies can conduct cold forming and trimming. The target material of this paper is a 1.5GPa steel, CR 1480M steel supplied by POSCO. This paper discusses the local formability change caused by the presented IR heat treatment.
The formability and application of hot-rolled dual-phase steel under nonlinear strain paths
Authors: Chen W J , Song H W , Pei X H , Zhang S H 
Published: November 2020

Abstract
The hot-rolled dual-phase steel 700DP was developed to reduce weight and improve safety in automobile industry. However, strain path changes inevitably occur for most of components during sheet forming process. Therefore, it’s valuable to predict the cracking accurately under nonlinear strain paths for the application of 700DP steel with finite element method (FEM). In this paper, the mechanical properties of hot-rolled dual-phase steel 580DP and 700DP were studied with tensile test. Nakazima test and two-step nonlinear loading test were used to establish the modelling with the method of equivalent plastic strain-based FLC (ep-FLC). Furthermore, the ep-FLC was applied to predict the disc forming result of three-stage process, which agreed well with the experimental results for both 580DP and 700DP compared with conventional FLC.
Enhancement of Edge Crack Predictability for Automotive High-Strength Thick Steel Sheets Considering the Pressure Effect
Authors: Bae Gihyun , Park Namsu , Song Junghan , Lee Jongsup , Jang Inje , Park Keunyoung 
Published: November 2020

Abstract
This paper deals with the prediction accuracy of edge crack of automotive high-strength thick steel sheets according to the numerical simulation method. The mechanical tests under tension, tension/compression and loading-unloading conditions were performed to evaluate anisotropy, hardening behaviour and elastic modulus change, respectively. Edge stretchability was evaluated by the HER(hole expansion ratio) test according to the hole processing method. Based on the measured data, three simulation methods were constructed with respect to the material model and the element type. The half dome test was selected for verifying edge crack predictability according to the simulation method. The simulation results show that the pressure effect along the thickness direction has significant effect on prediction accuracy of edge crack for high-strength thick steel sheets used for automotive chassis parts.
Inelastic strain recovery of magnesium alloys and a new elastic modulus model
Authors: Yan YU Hai , Hangyu WU , Lin Wang 
Published: November 2020

Abstract
Cyclic loading-unloading uniaxial tension experiments were performed for AZ31B magnesium sheets. The inelastic strain recovery behavior of the AZ31B sheets unloaded under different plastic strain was investigated. An interesting phenomenon on the elastic modulus change was presented. A new elastic modulus model was presented to characterize the inelastic strain recovery of the AZ31B sheets. Unlike the available models, this elastic modulus model takes both the instant stress and the plastic strain as the variables. The new elastic modulus model was incorporated into the ABAQUS software using the user subroutines. Validation of the subroutines and springback simulations were conducted with the presented elastic modulus models. The results showed that the inelastic strain recovery of the AZ31B sheets can reach 24% of the total strain recovery. The instant elastic modulus model can predict a perfect unloading path. The new elastic modulus model works better than the constant elastic modulus.
A Study on Effects of the Press Speed on Sheared Edge Formability
Authors: Gu J , Alamos F , Schoch D , Bornhorst J , Kim H 
Published: November 2020

Abstract
In this study, the effect of shearing speed on edge formability was investigated with two different grades of advanced high strength steel (AHSS), DP780 and GEN3-980. A straight blanking tool with adjustable shear clearance was used to shear the selected materials in two different type presses, a high-speed pneumatic press, and a mechanical servo-press. The four different shearing speeds from 0.01 meter per second up to 1.5 meters per second were realized and measured. The different shearing speed conditions result in different edge quality and work hardening levels. The half specimen dome test and micro-hardness analysis were conducted to evaluate the edge formability. The samples sheared with a pneumatic press at a higher speed showed significantly better edge quality, less hardness increase, and smoother sheared edge than the samples sheared with the servo press. The developed high-speed shearing condition has a very good potential to shear AHSS without creating significant damage and work hardening on the sheared edge, providing further advantages for the post stamping operations.
Development of springback tester and the effect of forming speed on the springback of four sheet metal bending processes
Authors: Luyi Dou , Xiaoqiang Li , Hongrui Dong , Dongsheng LI , Xingyi Peng 
Published: November 2020

Abstract
With the current increasing emphasis on issues of energy saving, emission reduction, driver and passenger safety in automotive industry, lightweight bodywork is an effective measure to reduce vehicle energy consumption. And also, high-strength bodywork structure can improve automobile safety performance because of its high impact absorption energy, and high fatigue resistance. In sheet metal forming, springback is a main defect with using high strength steel. Aiming to investigate sheet metal springback phenomenon for high-strength steel, a multi-funtional springback test machine is built. The testing machine can perform four types of springback tests: V-bend, U-bend, stretchbend and drawbend, and all these tests have been carried out to investgate the effect of springback factor in sheet metal forming processes for example forming speed. The research found that the springback angle of U-bend and drawbend increase with enlarging speed, however, V-bend and stretchbend show the opposite trend.
A new workflow for the effective distinction between necking induced spilts and direct fracture phenomena
Authors: Manopulo N , Carleer B 
Published: November 2020

Abstract
The predominant mode of failure in stamping applications is still splitting due to localized necking. This kind of failure is very effectively captured by the forming limit curve, especially if nonlinear deformation effects are modelled. With the sharp increase in low-ductility (weight efficient) materials, direct fracture phenomena (surface cracks, edge cracks, shear cracks, etc.) increasingly enter the daily industrial stamping practice, especially in follow operations. Contrary to the classical FLC analysis, there exists nowadays no industry-wide standardization for characterizing these phenomena. This drives up modelling costs and reduces the expected improvement in the overall modelling uncertainty. It therefore becomes crucial to understand and detect the circumstances in which an advanced fracture characterization is necessary, such that limited resources can be effectively allocated. The present contribution aims to propose such a workflow. Firstly a reasonable lower bound for the fracture limits is estimated based on theoretical considerations and evidence from scientific literature. This estimation is used to conduct a first analysis step which is used to categorize the process based on whether a standard modelling approach is sufficient to deliver the required accuracy. A second step of accurate fracture identification is therefore only recommended for the subset of geometries with particularly high risk. The approach is tested on data for AA6016 and DP980 from literature and validated based on published experimental results.
Potentials of an adaptive blank positioning to control material and process fluctuations in deep drawing
Authors: Briesenick David , Liewald Mathias , Cyron Patrick 
Published: November 2020

AbstractSeries production of sheet metal components in press shops is permanently subjected to an increasing pressure in time, cost and quality. Varying sheet metal properties due to batch fluctuations and changing process conditions lead to an increase of try out time phase and scrap rate, resulting in a demand for adaptive control strategies for deep drawing. Today, these chal-lenges are met by integrating sensors and actuators into tool structure which measure and control part quality, mainly through blank draw-in. However, such tool-based control systems require a complex and cost-intensive modification of the existing die or press technology. Against this background, the active adjustment of blank position prior the deep drawing process realized with an intelligent transfer and positioning system as a promising approach towards economic and technical aspects. This paper deals with blank positioning and its sensitivity to quality-related failures of deep drawn sheet metal components like splits and wrinkles. Therefore, a numerical study was conducted on a deep drawing process of an exemplary structural part geometry, wherein a typical fluctuation of material parameters and variation of local friction conditions was simulated. Subsequently, correlations between process disturbance and blank draw-in were elaborated, thus using local draw-in values as controlled variables for a closed loop system. Sim-ulation results showed that the manipulating parameter, i.e. the blank position prior deep draw-ing, reveals a significant influence on the draw-in and therefore on the component s quality. An essential finding of this study is the numerical proof of concept for this new deep drawing control strategy, demonstrated for different process conditions. Finally, disturbances in the deep drawing process considered could be successfully controlled by adapting the blank position.
Lubricant Selection and Post Forming Material Characterization in Incremental Sheet Forming
Authors: Mulay Amrut , Ben Satish , Ismail Syed 
Published: November 2020

Abstract
Single Point Incremental Forming (SPIF) is a flexible, novel and rapid sheet forming process to deform extra thin to the thick sheet with the help of computer numerical control unit, hemispherical tool and fixture. A tool follows a series of small incremental steps which deforms the sheet into the desired shape. Despite of recent development occurred in past, the little literature was reported which investigate the effect of various types of lubricants in SPIF process. This study aims to address the distinct type of lubricant to accomplish better surface roughness and formability of final parts while incremental forming of aluminium 5052 H32 sheets. After the forming process, the fractographies of the specimen were studied at optimal condition. The study is also extended to determine residual stresses generated due to incremental deformation and its effect on corrosion phenomenon with the environment. It has been found that the fracture zone material is likely to corrode more rapidly due to increased plastic deformation than the material at initial and middle forming zones.
Evaluation of 22MnB5 Steel Austenitization Sub-Models for Simulating the Heating Phase of Hot Stamping
Authors: Zhao B , Chiriac C , Daun K J 
Published: November 2020

Abstract
The heating phase of hot stamping is the most time-and energy-intensive part of the process, and therefore offers significant potential to improve process efficiency. This requires a robust thermometallurgical model that predicts the blank heating profile and the austenitization progress inside a roller hearth furnace. In this paper, an IM austenitization model for 22MnB5 steel is derived using dilatometry data and evaluated against a JMAK type model using temperature profiles of coupons heated within a laboratory-scale muffle furnace and blanks heated within a roller hearth furnace. The austenitization rates predicted by the two models are then compared to the inferred austenitization processes from those temperature profiles. The result shows that the IM model has potential to capture the trend of austenitization process, especially the rapid pearlite dissolution at the beginning of the transformation, whereas the JMAK type model is too restrictive and fails in this regard.
A simplified method for the evaluation of the layer compression test using one 3D digital image correlation system and considering the material anisotropy by the equibiaxial Lankford parameter
Authors: Camberg A A , Tröster T 
Published: November 2020

Abstract
The layer compression test is an established method for the characterization of sheet metal behavior under equibiaxial tension. Due to its ability to achieve high strains without necking and the simple experimental setup, the test is a welcome alternative to the more complex Bulge test for flow curve determination. In addition, the layer compression test provides further data for the calibration of yield loci models. However, the evaluation of the test is not trivial, since a tactile extensometer measurement incorporates the error of closing gaps between single sheet layers. Moreover, the sheet metal anisotropy is neglected. To overcome the above-mentioned drawbacks, a measurement and evaluation methodology based on the optical strain measurement of two orthogonally positioned 3D digital image correlation (DIC) systems was introduced recently. The method delivers reliable results but increases the complexity and costs of the test. Here, a simplification to this method is proposed. By the usage of only one 3D DIC system, the major in-plane strain is acquired from an online measurement. The minor in-plane strain is calculated posteriori by the consideration of the biaxial Lankford parameter. In this way, the anisotropy and thus the correct flow behavior can be studied by only one 3D DIC system. The proposed method is evaluated and discussed.
Interaction between forming and joint quality of the friction-assisted clinching
Authors: Li Zhiyong , Wang Zhiyong , Li Yong , Han Shanling 
Published: November 2020

Abstract
In order to achieve the effective joining of aluminum and magnesium alloy sheets, a friction-assisted clinching is innovatively proposed to reduce material damage during the process and improve the joint quality. 2 mm thick Al5052 aluminum sheet and 2 mm thick AZ31 magnesium alloy sheet were selected as the research objects, the interaction between different forming parameters, i.e., die depth, rotational speed and rotation time, and the joint quality, i.e., the damage, neck and interlock were explored by DEFORM-3D. The influence of sheet temperature on damage and punch load is analysed, the rotational speed and rotation time have great influence on the forming joint, the die depth mainly affects the neck and interlock. Comparing the joint qualities under different forming parameter combinations, it is found that the joint quality is the best when the bottom die depth is 2.2 mm and the bottom punch is applied at 1000 rpm for 0.5 s. The research will provide a valuable reference for the realization of joining the aluminum and magnesium sheets.
Heat generation when forming AHSS: experimental and numerical analysis of tensile and draw-bead tests
Authors: Neto D M , Barros J R , Oliveira M C , Antunes P V , Ramalho A , Amaral R L , Santos A D , Alves J L , Menezes L F 
Published: November 2020

Abstract
The increasing use of advanced high-strength steels in sheet metal forming processes requires improved knowledge concerning the thermal and contact conditions. This study presents the experimental and numerical analysis of tensile and draw-bead tests, considering a dual phase steel DP780. The temperature evolution was measured in both tests using an infrared thermal camera. The presented finite element model considers both the heat generated by plastic deformation and friction, as well as the heat loss to the environment by free convention and the contact conductance. The temperature rise in the uniaxial tensile test is accurately predicted by the numerical model. Regarding the draw-bead test, the pulling force is accurately predicted but the temperature variation is overestimated, requiring further investigation.
New tool to evaluate the fracture resistance of thin high strength metal sheets
Authors: Frómeta D , Lara A , Parareda S , Grifé L. , Casellas D 
Published: November 2020

Abstract
Fracture toughness has become a key property to predict the fracture performance of high strength metal sheets (edge cracking resistance, crash failure behaviour, local formability, etc.). However, the measurement of the fracture toughness of thin sheets still being challenging, mainly because of complex, expensive and time-consuming specimen preparation. In this work, an innovative tool to readily assess the fracture resistance of thin advanced high strength metal sheets is presented. The device consists of a special cutting tool (punch and die) designed to introduce sharp notches in sheet specimens through a simple shearing process. This new method avoids the need for fatigue pre-cracking procedures and allows measuring the fracture toughness of thin metal sheets with easy and cheap specimen preparation. It has been used in this work to evaluate the crack propagation resistance of four different advanced high strength steel sheets. The obtained toughness values are in good agreement with those measured with fatigue pre-cracked specimens and they show to be suitable to predict edge formability of AHSS sheets.
The impact of the first overseas empire on the modern French colonial service at war: the cases of Hubert Deschamps and Robert Garry
Authors: Jennings Eric T 
Published: November 2020

Abstract
How did French colonial officials, leagues removed from the metropole, decide whether to remain loyal to Vichy or to join de Gaulle in 1940? This article suggests that in addition to legalism, colonial administrators opted for Vichy in part because of a long-term anti-British imperial ethos. Cultivated in colonial circles, this ethos dwelled on humiliation by perfidious Albion in Québec, Mauritius, Madagascar and at Fashoda, rather than on points of imperial cooperation that might have been stressed, including Franco-British joint rule over the New Hebrides. In this sense, the first French overseas empire weighed mightily on mid-twentieth century colonial minds. The article focuses on two emblematic high ranking officials, Hubert Deschamps and Robert Garry. Of radically different political backgrounds, the pair served as key operatives for Vichy overseas. In so doing, they mobilized the memory of a Franco-British rivalry they saw extending from Agincourt to Mers-el-Kébir. Their colonial training coloured more than their 1940 decisions: it also conditioned the remarkable and parallel ways in which they recovered from the purges of 1944-1945.
Evolution of pulmonary valve reconstruction with focused review of expanded polytetrafluoroethylene handmade valves
Authors: Chang Te-I , Hsu Kang-Hong , Li Shao-Jung , Chuang Min-Kai , Luo Chi-Wen , Chen Yi-Jen , Chang Chung-I 
Published: November 2020

Abstract

OBJECTIVES
Many surgeons develop unique techniques for unmet needs for right ventricular outflow reconstruction to resolve pulmonary regurgitation after corrective surgery for congenital heart diseases. Expanded polytetrafluoroethylene (ePTFE) stands out as a reliable synthetic material, and clinical results with handmade ePTFE valves have been promising. This review focuses on the historical evolution of the use of ePTFE in pulmonary valve replacement and in the techniques for pioneering the translation of the handmade ePTFE trileaflet design for the transcatheter approach.

METHODS
We searched for and reviewed publications from 1990 to 2020 in the Pubmed database. Nineteen clinical studies from 2005 to 2019 that focused on ePTFE-based valves were summarized. The evolution of the ePTFE-based valve over 3 decades and recent relevant in vitro studies were investigated.

RESULTS
The average freedom from reintervention or surgery in the recorded ePTFE-based valve population was 90.2% at 5 years, and the survival rate was 96.7% at 3 years.

CONCLUSIONS
Non-inferior clinical results of this ePTFE handmade valve were revealed compared to allograft or xenograft options for pulmonary valve replacement. Future investigations on transferring ePTFE trileaflet design to transcatheter devices should be considered.