The Study of Identification Method for the Welding Defect Source of Low-Alloy High-Strength Steel Based on AE Technology

2011 ◽  
Vol 467-469 ◽  
pp. 1580-1585 ◽  
Author(s):  
Yan Tao Dou ◽  
Xiao Li Xu ◽  
Wei Wang ◽  
Si Qin Pang
Keyword(s):  
Acoustic Emission ◽  
High Strength Steel ◽  
Failure Process ◽  
Strain Curve ◽  
High Strength ◽  
Peak Frequency ◽  
Average Frequency ◽  
Bending Test ◽  
Characteristic Parameters ◽  
Deformation Stages

Three-bending test has been performed on the standard specimen and welding specimen with defect of low-alloy and high-strength steel in order to simulate the failure process of structural parts under loading, and the AE activities (number of hits) and stress-strain curve were measured during the whole loading process. The law of acoustic emission signals at different deformation stages has been investigated and the relation between AE characteristic parameters and the different deformation stages has been established. The typical AE waveforms such as friction noise, plastic deformation, welding microcrack initiation and propagation are obtained, which are analyzed by using spectrum characteristics analytical method. The spectrum characteristic parameters such as average frequency, peak frequency and frequency centroid, energy percentage of frequency spectrum part I and III of the typical AE defect signals are extracted, the distributing range of which are initially set. Study shows these five parameters have a closely relation with the nature of the AE signals, and based on these characteristics parameters different AE sources can be preliminary identified correctly. The study can provide some guidance to the practical application of AE acoustic emission technology in the industrial field.

Elasto-Plastic Property of High Strength Steel at Warm Temperature and its Springback

2013 ◽  
Vol 535-536 ◽  
pp. 385-388
Author(s):  
Naoko Saito ◽  
Mitsugi Fukahori ◽  
Daisuke Hisano ◽  
Yuya Ichikawa ◽  
Hiroshi Hamasaki ◽  
...  
Keyword(s):  
High Strength Steel ◽  
Steel Sheet ◽  
Elevated Temperatures ◽  
High Strength ◽  
Plastic Property ◽  
Bending Test ◽  
Warm Temperature ◽  
Temperature Dependent ◽  
Strain Responses ◽  
Springback Behavior

Stress-strain responses of a high strength steel sheet of 980MPa grade under uniaxial tension and its springback in V- and U-bending were investigated at elevated temperatures ranging from 573-973K. The flow stress decreased drastically with the increase of temperature, from which it was expected that springback is reduced by warm forming. In V-bending test, however, the temperature effect on springback was not so clear, while in U-bending springback decreased with temperature rise. It was found that such difference in temperature dependent springback behavior between V- and U-bending was caused by stress relaxation which took place during unloading process.

Effect of Variable Geometry on Springback of High Strength Steel Materials

2015 ◽  
Vol 1134 ◽  
pp. 154-159
Author(s):  
Muhamad Sani Buang ◽  
Shahrul Azam Abdullah ◽  
Juri Saedon ◽  
Yupiter H.P. Manurung ◽  
Mohd Shahir Mohd Hairuni ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
High Strength Steel ◽  
High Strength ◽  
Bending Test ◽  
Geometrical Parameters ◽  
Forming Process ◽  
Element Simulation ◽  
Punch Radius ◽  
Prevention Method

Springback is the phenomenon in which the material strip unbends itself after forming process. It is caused by the geometrical, mechanical properties or other process parameters. This paper focused on finite element simulation investigation on effects of geometrical parameters on the springback amount of the High Strength Steel (HSS). Two geometrical parameters, punch radius (Rp) and die opening (Wo) were selected and their effect on springback studied. Finite element simulation of U-bending test was performed using Simufact.formingTM with material database (MatILDa) and the level of the springback was measured. The result of the simulation shows that different values of punch radius (Rp) and die opening (Wo) are significant to the springback effect. 3 variable values of (Rp) and (Wo) selected in this studied are (2mm, 4mm, 6mm) and (30mm, 36mm, 48mm) respectively. The findings of the simulation could be used to accurately and reliably predict springback behavior of the tested material. The value of the springback increases, as the value of the die opening (Wo) increases. Meanwhile, the increasing value of the punch radius (Rp) will lead to decreasing springback value. From this finding, a proper prevention method can be taken to eliminate springback, achieve improvement in the forming process as well as reduce processing time and cost.

Inferences of Baking Time on Hydrogen Embrittlement for High Strength Steel Treated with Various Zinc Based Electroplating

2021 ◽  
Vol 1016 ◽  
pp. 156-161
Author(s):  
Makoto Hino ◽  
Shunsuke Mukai ◽  
Takehiro Shimada ◽  
Koki Okada ◽  
Keitaro Horikawa
Keyword(s):  
Hydrogen Embrittlement ◽  
High Strength Steel ◽  
High Strength ◽  
Film Structure ◽  
Bending Test ◽  
Hydrogen Incorporation ◽  
Three Point Bending ◽  
Vacancy Clusters ◽  
Hydrogen Vacancy ◽  
Zinc Nickel

The hydrogen embrittlement of SK85 high-strength steel sheets was evaluated using a three-point bending test. The effect of electroplating the metal with zinc-based coatings on hydrogen embrittlement was examined by baking treatment of differently electroplated steel specimens. After electroplating, all the specimens underwent hydrogen embrittlement, promoted by hydrogen incorporation into the metal frame, owing to the reduction of hydrogen ions during electroplating. The hydrogen embrittlement of both zinc-and zinc-SiO2-electroplated SK85 steel continued after baking for 24 hours at 473 K, but that of zinc-nickel-and zinc-nickel-SiO2-electroplated SK85 steel ceased. Furthermore, TDA revealed that the trapped hydrogen could be released from steel at approximately 473 K. However, after baking, hydrogen embrittlement did not completely disappear, and we suggest that the formation of hydrogen vacancy clusters also accounts for this fracture phenomenon. The hydrogen incorporated into steel during electroplating led to the formation of hydrogen vacancy clusters, which allowed the formation of embrittlement. However, zinc and zinc-SiO2 films were not permeable enough to release these voids; while the peculiar zinc–nickel and zinc-nickel-SiO2 film structure enabled the hydrogen vacancy clusters to diffuse from the substrate.

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