Full Field Measurements of the Dynamic Response of AA6061-T6 Aluminum Alloy Under High Strain Rate Compression and Torsion Loads

2012 ◽  
Author(s):  
Gbadebo Owolabi ◽  
Daniel Odoh ◽  
Akindele Odeshi ◽  
Horace Whitworth
Keyword(s):  
Aluminum Alloy ◽  
High Speed ◽  
High Strain ◽  
Shear Bands ◽  
Field Measurements ◽  
Image Correlation ◽  
Deformation Analysis ◽  
Deformation And Failure ◽  
Full Field ◽  
Structural Applications

Aluminum alloys exhibit an attractive combination of mechanical and physical properties such as high stiffness and low density, which favors their utilization in many structural applications. Thus, increasing the structural applications of aluminum alloy is the driving force for the need to adequately understand its deformation and failure mechanisms under various types of dynamic loading conditions. In this study, full field plastic deformation of AA6061-T6 aluminum alloy at high strain-rates under compressive and torsion loads are measured using split Hopkinson compression and torsion bars and a high speed digital image correlation system. The stress-strain curves obtained using the high speed digital cameras are compared with results obtained from the elastic waves in the compression and torsion bars. A post deformation analysis of the specimen also shows strain localization along narrow adiabatic shear bands in the AA6061-T6 alloy.

Deformation and Failure of Pre-Notched Thin Metal Plates Subjected to Confined Blast Loading

2015 ◽  
Vol 782 ◽  
pp. 49-58
Author(s):  
Han Liu ◽  
Peng Wan Chen ◽  
Bao Qiao Guo ◽  
Shao Long Zhang ◽  
Hai Bo Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Deformation ◽  
Blast Loading ◽  
Thin Metal ◽  
Image Correlation ◽  
Deformation And Failure ◽  
Full Field ◽  
3D Digital Image Correlation ◽  
Metal Plates ◽  
Dic Technique

In this paper, the dynamic deformation and rupture of pre-notched thin metal plates subjected to confined blast loading were investigated. The thin copper plates with cross-shape pre-notch were clamped on the end of a confined cylinder vessel by a cover flange. An explosive charge with a mass of 4g was detonated in the vessel center to generate blast load acting on the metal plates. The images of metal plates were recorded by two high-speed cameras. The displacement and strain fields during the deformation and rupture process were measured by using 3D digital image correlation (3D DIC). The effects of pre-notches on the dynamic deformation and rupture of thin metal plates were analyzed. The microstructure of fracture surface was examined The 3D DIC technique is proven to be an effective method to conduct dynamic full-field deformation measurement.

scholarly journals Validation of a multi-scale Ti-6Al-4V drilling model by means of thermomechanical field measurements

2021 ◽  
Author(s):  
Camille Bonnet ◽  
Thomas Pottier ◽  
Yann Landon ◽  
Abdallah Bouzid
Keyword(s):  
High Speed ◽  
Infrared Camera ◽  
Field Measurements ◽  
Image Correlation ◽  
3D Fem ◽  
Full Field ◽  
Multi Scale ◽  
Thermal Fields ◽  
Significant Magnitude ◽  
Drilling Operations

Drilling operations lead to temperatures and forces that may locally reach significant magnitude and thus impair the surface and material integrity. Optimizing the cutting conditions could limit these degradations, which are more significant in the case of low thermal conductivity materials such as titanium alloys. Robust numerical modelling is a relevant alternative to such issues but must rely on strong in-process experimental measurements. Unfortunately, the confined nature of the cutting area during drilling prevent from any straight forward field-measurement. The proposed multi-scale strategy consists in validating the developed 3D FEM models both at micrometric and millimetric scales, using coupled full-field measurements. The limited access to the cutting area is overcome by means i) of oblique cutting tests at microscale and ii) tube drilling tests. Thermal fields are evaluated using an infrared camera while kinematic fields are determined by image correlation (DIC) using a high-speed camera. The experimental and numerical fields are then compared, and numerical results are extended over several revolutions by means of purely thermal 2D analytical model.

Dynamic Failure of Aluminum Alloy 2219-T8 Under High Strain Rate

2015 ◽  
Author(s):  
Denzell Bolling ◽  
Adewale Olasumboye ◽  
Gbadebo Owolabi
Keyword(s):  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Microstructural Analysis ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Image Correlation ◽  
Adiabatic Shear Bands

The suitability of aluminum alloys in a vast majority of engineering applications forms the basis for the need to understand the mechanisms responsible for their deformation and failure under various loading conditions. The material investigated in this study is AA 2219-T8 aluminum alloy. Supplied by the NASA Research Center, with high strength to weight ratio and corrosive resistance. Containing a unique mixture of aluminum, copper, and other trace elements, this alloy has potential applications in multiple fields including aerospace, defense, and commercial industries. In this paper, the dynamic high strain rate impact deformation of the AA2219-T8 aluminum alloy was performed using the split Hopkinson pressure bars. The evolution of localized strain in the aluminum samples during the deformation process obtained using high speed digital cameras is reported. Microstructural analysis of deformed aluminum samples was also performed using optical microscopes in order to determine the influence of impact strain rate on localized strain along narrow adiabatic shear bands in the AA2219-T8 aluminum alloys. Results obtained indicate that peak flow stress in the deformed aluminum sample depends on the strain rate at which the deformation test was performed. The non-uniformity of the strain obtained using the digital image correlation as deformation time progresses shows two distinct areas of non-uniform strains that may be indicating potential sites for the formation of adiabatic shear bands in the tested samples.

scholarly journals The Use of 2D and 3D High-Speed Digital Image Correlation in Full Field Strain Measurements of Composite Materials Subjected to High Strain Rates

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 538 ◽  
Author(s):  
Ahmed Elmahdy ◽  
Patricia Verleysen
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
High Strain ◽  
Image Correlation ◽  
Full Field ◽  
3D Digital Image Correlation ◽  
Gauge Section ◽  
2D And 3D ◽  
Dic Technique

The aim of this paper is to assess and compare the performance of both high speed 2D and 3D digital image correlation (DIC) configurations in the characterization of unidirectional carbon fiber reinforced epoxy composites in high strain rate tension in the transverse direction. The criteria for assessment were in terms of strain resolution and measuring the strain localization within the gauge section. Results showed the high-speed 3D DIC technique has lower strain resolution compared to the high-speed 2D DIC technique. In addition, the analysis of the full strain fields indicated that the 3D DIC technique could accurately locate and measure the concentrations of strains within the gauge section of the tested samples.

scholarly journals Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1602
Author(s):  
Ángel Molina-Viedma ◽  
Elías López-Alba ◽  
Luis Felipe-Sesé ◽  
Francisco Díaz
Keyword(s):  
Modal Analysis ◽  
Energy Absorption ◽  
High Speed ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Image Correlation ◽  
Composite Panel ◽  
Impact Excitation ◽  
Full Field ◽  
The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

scholarly journals Compression, Tension and Shear Testing of Fibrous Composite with the Split Hopkinson Bar Technique

2018 ◽  
Vol 183 ◽  
pp. 02006 ◽  
Author(s):  
Amos Gilat ◽  
Jeremy D. Seidt
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Fibrous Composite ◽  
Hopkinson Bar ◽  
Image Correlation ◽  
Compression Tests ◽  
Strain Rate Effects ◽  
Full Field ◽  
Split Hopkinson Bar ◽  
Split Hopkinson

The Split Hopkinson Bar (SHB) technique is used for high strain rate testing of T800/F3900 composite in compression, tension and shear. Digital Image Correlation (DIC) is used for measuring the full-field deformation on the surface of the specimen by using Shimadzu HPV-X2 high-speed video camera. Compression tests have been done on specimens machined from a unidirectional laminate in the 0°and 90° directions. Tensile tests were done in the 90° direction. Shear tests were done by using a notched specimen in a compression SHB apparatus. To study the effect of strain rate, quasi-static testing was also done using DIC and specimens with the same geometry as in the SHB tests. The results show that the DIC technique provides accurate strain measurements even at strains that are smaller than 1%. No strain rate effect is observed in compression in the 0° direction and significant strain rate effects are observed in compression and tension in the 90° direction, and in shear.

scholarly journals Deformation Behavior of a Shape Memory Alloy: Nitinol

2008 ◽  
Author(s):  
Samantha Daly ◽  
Kaushik Bhattacharya ◽  
Guruswami Ravichandran
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Rolling Texture ◽  
Image Correlation ◽  
Space Applications ◽  
Deformation And Failure ◽  
Full Field ◽  
New Information ◽  
Macro Scale ◽  
First Time

Nickel-Titanium, commonly referred to as Nitinol, is a shape-memory alloy with numerous applications due to its superelastic nature and its ability to revert to a previously defined shape when deformed and then heated past a set transformation temperature. While the crystallography and the overall phenomenology are reasonably well understood, much remains unknown about the deformation and failure mechanisms of these materials. These latter issues are becoming critically important as Nitinol is being increasingly used in medical devices and space applications. The talk will describe the investigation of the deformation and failure of Nitinol using an in-situ optical technique called Digital Image Correlation (DIC). With this technique, full-field quantitative maps of strain localization are obtained for the first time in thin sheets of Nitinol under tension. These experiments provide new information connecting previous observations on the micro- and macro-scale. They show that martensitic transformation initiates before the formation of localized bands, and that the strain inside the bands does not saturate when the bands nucleate. The effect of rolling texture, the validity of the widely used resolved stress transformation criterion, and the role of geometric defects are examined.

Finite Element Prediction of Temperature Variation of Material and Dies in Aluminum Forging

2020 ◽  
Vol 830 ◽  
pp. 93-100
Author(s):  
Jae Dong Yoo ◽  
Tae Min Hwang ◽  
Man Soo Joun
Keyword(s):  
Aluminum Alloy ◽  
Temperature Rise ◽  
High Speed ◽  
Room Temperature ◽  
High Strain ◽  
Cold Forging ◽  
Multi Stage ◽  
Aluminum Forging ◽  
The Right ◽  
Finite Element Prediction

Investigation into behaviors of aluminum alloy to be metal formed at the room temperature is conducted in this study. An index is used to evaluate the sensitivity of temperature, that is, index of relative normalized temperature rise to steel called normalized temperature rise index per steel which helps researchers to obtain some insight on new materials based on experiences of steel forging. An investigation to an aluminum alloy shows that the index is quite high, implying that temperature effect as well as rate-dependence effect on the forming processes of aluminum alloy at the room temperature cannot be neglected. Some details of thermomechanical predictions of a relatively high-speed automatic multi-stage forging process of a yoke with highly deformed region are given to reveal the importance of temperature and/or strain rate even in cold forging of aluminum alloy parts with high speed and high strain. All manuscripts must be in English, also the table and figure texts, otherwise we cannot publish your paper. Please keep a second copy of your manuscript in your office. When receiving the paper, we assume that the corresponding authors grant us the copyright to use the paper for the book or journal in question. Should authors use tables or figures from other Publications, they must ask the corresponding publishers to grant them the right to publish this material in their paper. Use italic for emphasizing a word or phrase. Do not use boldface typing or capital letters except for section headings (cf. remarks on section headings, below).

Local Elasto-Plastic Identification of the Behaviour of Friction Stir Welds with the Virtual Fields Method

2011 ◽  
Vol 70 ◽  
pp. 135-140 ◽  
Author(s):  
G. Le Louëdec ◽  
M.A. Sutton ◽  
Fabrice Pierron
Keyword(s):  
Mechanical Properties ◽  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Weld Zone ◽  
Spatial Variations ◽  
Image Correlation ◽  
Virtual Fields Method ◽  
Full Field ◽  
Friction Stir

Welding is one of the most popular joining technologies in industry. Depending on the materials to be joined, the geometry of the parts and the number of parts to be joined, there is a wide variety of methods that can be used. These joining techniques share a common feature: the material in the weld zone experiences different thermo-mechanical history, resulting in significant variations in material microstructure and spatial heterogeneity in mechanical properties. To optimize the joining process, or to refine the design of welded structures, it is necessary to identify the local mechanical properties within the different regions of the weld. The development of full-field kinematic measurements (digital image correlation, speckle interferometry, etc.) helps to shed a new light on this problem. The large amount of experimental information attained with these methods makes it possible to visualize the spatial distribution of strain on the specimen surface. Full-field kinematic measurements provide more information regarding the spatial variations in material behaviour. As a consequence, it is now possible to quantify the spatial variations in mechanical properties within the weld region through a properly constructed inverse analysis procedure. High speed tensile tests have been performed on FSW aluminium welds. The test was performed on an MTS machine at a cross-head speed of up to 76 mm/s. Displacement fields were measured across the specimen by coupling digital image correlation with a high-speed camera (Phantom V7.1) taking 1000 frames per second. Then, through the use of the virtual fields method it is possible to retrieve the mechanical parameters of the different areas of the weld from the strain field and the loading. The elastic parameters (Young’s modulus and Poisson’s ratio) are supposed to be constant through the weld. Their identification was carried out using the virtual fields method in elasticity using the data of the early stage of the experiment. Assuming that the mechanical properties (elastic and plastic) of the weld are constant through the thickness, the plastic parameters were identified on small sections through the specimen, using a simple linear hardening model. This method leads to a discrete identification of the evolution of the mechanical properties through the weld. It allows the understanding of the slight variations of yield stress and hardening due to the complexity of the welding process.

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