Design of a Continuous-Bending-Under-Tension Machine and Initial Experiments on Al-6022-T4

2015 ◽  
Author(s):  
Timothy J. Roemer ◽  
Brad L. Kinsey ◽  
Yannis P. Korkolis
Keyword(s):  
Plastic Deformation ◽  
Tensile Test ◽  
Experimental Technique ◽  
Tension Test ◽  
Gage Length ◽  
Friction Test ◽  
Plastic Bending ◽  
Three Point Bending ◽  
Continuous Bending ◽  
Bending Under Tension

An experimental technique called Continuous-Bending-Under-Tension (CBT) can produce elongations over two times that of a standard tensile test by preventing the necking instability from occurring. This is achieved by superposing plastic bending on tension along the gage length of the material using three rollers. The specimen is kept under tension as the rollers apply the three point bending and cyclically transverse along the gage length. This localizes the plastic deformation by subjecting the specimen to bending-under-tension. Details on the design of the unique CBT machine and some preliminary results for the CBT research being conducted are presented here. These results include CBT tests where the roller depth was varied to demonstrate the increased elongation compared to the traditional tension test, CBT repeatability, and a modified friction test using the CBT machine.

Numerical Investigation of Residual Formability and Deformation Localization During Continuous-Bending-Under-Tension

2012 ◽  
Author(s):  
Chetan Nikhare ◽  
Brad L. Kinsey ◽  
Yannis Korkolis
Keyword(s):  
Numerical Simulations ◽  
Numerical Investigation ◽  
Sheet Metal ◽  
Past Research ◽  
Gauge Length ◽  
Tension Test ◽  
Deformation Localization ◽  
Percent Elongation ◽  
Continuous Bending ◽  
Bending Under Tension

A ubiquitous experiment to characterize the formability of sheet metal is the standard uniaxial tension test. Past research [1–3] has shown that if the material is repeatedly bent and unbent during this test (termed Continuous-Bending-under-Tension, or CBT), the percent elongation at failure increases significantly (e.g., from 22% to 290% for an AISI 1006 steel [1]). However, past experiments have been conducted with a fixed stroke of the CBT device, which limits the formability improvements. This phenomenon has also been empirically observed in industry; the failure strains of a sheet which is passed through a drawbead (i.e., that has been bent and unbent three times before entering the die) are higher than those of the original sheet. Thus, the residual formability of the material after a specified number of CBT passes is of interest, to determine if multiple drawbeads would be beneficial in the process. Also of interest is the localization of the deformation during the process as this will provide a better physical understanding of the improved formability observed. In this paper, numerical simulations are presented to assess these effects. Results show that the formability during CBT is dictated by the uniaxial response of the material until the standard elongation at failure is exceeded. This limit can be exceeded by the CBT process. However, failure then occurs as soon as the CBT process is terminated. Also, the deformation is more uniformly distributed over the entire gauge length during the CBT process which leads to the increased elongations observed.

Experimental Investigation of Key Process Parameters During Continuous-Bending-Under-Tension of AA6022-T4

2017 ◽  
Author(s):  
Edward M. Momanyi ◽  
Timothy J. Roemer ◽  
Brad L. Kinsey ◽  
Yannis P. Korkolis
Keyword(s):  
Experimental Investigation ◽  
Aluminum Alloys ◽  
Process Parameters ◽  
Tensile Tests ◽  
Load Cycle ◽  
Gauge Length ◽  
Uniaxial Tensile ◽  
Plastic Bending ◽  
Continuous Bending ◽  
Bending Under Tension

Continuous-Bending-Under-Tension (CBT) is an experimental technique that has been shown to increase elongation-to-fracture by over 100% in aluminum alloys and over 300% in steel as compared to uniaxial tensile tests [1]. This procedure is a modified form of a tensile test in which a specimen experiences 3 point plastic bending, induced by traversing 3 rollers back and forth over the gauge length, while simultaneously being pulled in tension. This process is able to delay the occurrence of necking in pure tension by suppressing the instability. Thus, significantly more elongation is achieved in the specimen prior to fracture. In this paper, an experimental investigation of key process parameters, i.e., bending depth and pulling speed, during CBT testing of AA6022-T4 is presented. The load cycle during a CBT test will also be discussed along with the strain induced throughout the gauge length.

Magnetostrictive Self-Diagnosing Smart Bolts

2014 ◽  
Author(s):  
Vladislav Sevostianov
Keyword(s):  
Magnetic Field ◽  
Plastic Deformation ◽  
Magnetic Fields ◽  
Hall Effect ◽  
Stress Level ◽  
Experimental Validation ◽  
Rock Bolts ◽  
Three Point Bending ◽  
Bending Loading ◽  
The Magnetic Field

The paper presents the concept of self-diagnosing smart bolts and its experimental validation. In the present research such bolts are designed, built, and experimentally tested. As a key element of the design, wires of Galfenol (alloy of iron and gallium) are used. This material shows magnetostrictive properties, and, at the same time, is sufficiently ductile to follow typical deformation of rock bolts, and is economically affordable. Two types of Galfenol were used: Ga10Fe90 and Ga17Fe83. The wires have been installed in bolts using two designs — in a drilled central hole or in a cut along the side — and the bolts were tested for generation of the magnetic field under three-point bending loading. To measure the magnetic field in the process of deformation, a magnetometer that utilizes the GMR effect was designed, built, and compared with one utilizing the Hall effect. It is shown that (1) magnetic field generated by deformation of the smart bolts at the stress level of plastic deformation is sufficient to be noticed by the proposed magnetometer; however, the magnetometer using Hall effect is insufficient; (2) Ga10Fe90 produces higher magnetic fields than Ga17Fe83; (3) the magnetic field in plastically bended bolts is relatively stable with time.

scholarly journals The Plastic Deformation of RFSSW Joints During Tensile Tests / Deformacja Plastyczna Wybranych Połączeń RFSSW Podczas Rozciągania

2015 ◽  
Vol 60 (4) ◽  
pp. 2585-2592 ◽  
Author(s):  
P. Lacki ◽  
A. Derlatka
Keyword(s):  
Plastic Deformation ◽  
Tensile Test ◽  
Numerical Models ◽  
Lap Joints ◽  
Aviation Industry ◽  
Characteristic Line ◽  
Spot Welds ◽  
Tensile Direction ◽  
Maximum Deformation ◽  
Friction Stir

The dynamic development of the friction stir welding (FSW) technology is the basis for the design of durabe joints inter alia in the aviation industry. This technology has a prospective application, especially for the aluminum alloys. It is suitable for a broad spectrum of permanent joints. The joints obtained by FSW technology are characterized by good mechanical properties. In this paper, the friction stir spot welding joints were analysed. The example of a structure made using this technology were presented. The lap joints made of 2mm Al 6061-T6 sheets were the investigation subject. The different spot welds arrangements were analysed. The tensile test were performed with optical deformation measurement system, which allow to obtain the plastic deformation field on the sample surface. The plastic strain graphs for the characteristic line passing through the maximum deformation were registered and presented. The experimental results were compared to the FEM numerical analysis. The numerical models were built with 3D-solid elements. The boundary conditions, material properties and geometry of the joints were identical as during experimental investigation. The mechanism of deformation of welded joints during tensile test was described and explained. It has been found that the arrangement of the spot welds with respect to the tensile direction has an important influence on the behaviour and deformation of lap joint.

scholarly journals Strengthening of alloy AA6022-T4 by continuous bending under tension

2019 ◽  
Vol 758 ◽  
pp. 47-55 ◽  
Author(s):  
Marko Knezevic ◽  
Camille M. Poulin ◽  
Xiaodong Zheng ◽  
Shijian Zheng ◽  
Irene J. Beyerlein
Keyword(s):  
Continuous Bending ◽  
Bending Under Tension

Forming Limits of a Sheet Metal After Continuous-Bending-Under-Tension Loading

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Ji He ◽  
Z. Cedric Xia ◽  
Danielle Zeng ◽  
Shuhui Li
Keyword(s):  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Loading Condition ◽  
Hybrid Approach ◽  
Forming Limit ◽  
Forming Limits ◽  
Continuous Bending ◽  
Bending Under Tension

Forming limit diagrams (FLD) have been widely used as a powerful tool for predicting sheet metal forming failure in the industry. The common assumption for forming limits is that the deformation is limited to in-plane loading and through-thickness bending effects are negligible. In practical sheet metal applications, however, a sheet metal blank normally undergoes a combination of stretching, bending, and unbending, so the deformation is invariably three-dimensional. To understand the localized necking phenomenon under this condition, a new extended Marciniak–Kuczynski (M–K) model is proposed in this paper, which combines the FLD theoretical model with finite element analysis to predict the forming limits after a sheet metal undergoes under continuous-bending-under-tension (CBT) loading. In this hybrid approach, a finite element model is constructed to simulate the CBT process. The deformation variables after the sheet metal reaches steady state are then extracted from the simulation. They are carried over as the initial condition of the extended M–K analysis for forming limit predictions. The obtained results from proposed model are compared with experimental data from Yoshida et al. (2005, “Fracture Limits of Sheet Metals Under Stretch Bending,” Int. J. Mech. Sci., 47(12), pp. 1885–1986) under plane strain deformation mode and the Hutchinson and Neale's (1978(a), “Sheet Necking—II: Time-Independent Behavior,” Mech. Sheet Metal Forming, pp. 127–150) M–K model under in-plane deformation assumption. Several cases are studied, and the results under the CBT loading condition show that the forming limits of post-die-entry material largely depends on the strain, stress, and hardening distributions through the thickness direction. Reduced forming limits are observed for small die radius case. Furthermore, the proposed M–K analysis provides a new understanding of the FLD after this complex bending-unbending-stretching loading condition, which also can be used to evaluate the real process design of sheet metal stamping, especially when the ratio of die entry radii to the metal thickness becomes small.

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