scholarly journals Full-Field Strain Measurement and Identification of Composites Moduli at High Strain Rate with the Virtual Fields Method

2010 ◽  
Vol 51 (4) ◽  
pp. 509-536 ◽  
Author(s):  
R. Moulart ◽  
F. Pierron ◽  
S. R. Hallett ◽  
M. R. Wisnom
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Strain Measurement ◽  
High Strain ◽  
Field Strain ◽  
Virtual Fields Method ◽  
Full Field

Feasibility of Structural Health Monitoring of High Strain Rate Events Using Fiber Bragg Grating Sensors

2012 ◽  
Author(s):  
James Ayers ◽  
Tusit Weerasooriya ◽  
Anindya Ghoshal ◽  
Collin Pecora ◽  
Allan Gunnarsson ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Fiber Bragg Grating ◽  
High Strain ◽  
Surface Strain ◽  
Back Surface ◽  
Bragg Grating ◽  
Full Field ◽  
Fbg Sensors ◽  
Strain Rate Loading

Strategically located Fiber Bragg Grating (FBG) Sensors have been proposed as an in situ method to increase the signal to noise ratio (SNR) for metallic and composite components. This paper presents a systematic study that investigates the viability of FBG Sensors under high strain rate loading by initially measuring 1D-strains in a compression Hopkinson bar experiment, followed by 2D full-field strain-tensor in impact and blast experiments on plates. Specifically, high strain rates from commercialized FBG Sensors are compared to traditional resistive and semi-conductor based strain gages under various levels of 1D high strain rate loading. In the projectile-plate impact experiments, full-field back-surface strain measured using FBG Sensor arrays are compared with that measured from 3D surface Digital Image Correlation (3D-sDIC) strain measuring technique. Finally, strains in welded steel plates subjected to high explosive discharge are monitored with mounted FBG Sensors on the back surface. From this study, potential improvements in the SNR of FBG Sensors are recommended, and the survivability of these sensors under more complex, dynamic loading is evaluated.

Effect of Isothermal Aging and High Strain Rate on Material Properties of Innolot

2013 ◽  
Author(s):  
Pradeep Lall ◽  
Geeta Limaye ◽  
Sandeep Shantaram ◽  
Jeff Suhling
Keyword(s):  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
Material Properties ◽  
Isothermal Aging ◽  
High Strain ◽  
Image Correlation ◽  
Lead Free ◽  
Strain Rates ◽  
Full Field

Industry migration to lead-free solders has resulted in a proliferation of a wide variety of solder alloy compositions. The most popular amongst these are the Tin-Silver-Copper (Sn-Ag-Cu or SAC) family of alloys like SAC105, SAC305 etc. Recent studies have highlighted the detrimental effects of isothermal aging on the material properties of these alloys. SAC alloys have shown up to 50% reduction in their initial elastic modulus and ultimate tensile strength within a few months of elevated temperature aging. This phenomenon has posed a severe design challenge across the industry and remains a road-block in the migration to Pb-free. Multiple compositions with additives to SAC have been proposed to minimize the effect of aging and creep while maintaining the melting temperatures, strength and cost at par with SAC. Innolot is a newly developed high-temperature, high-performance lead-free substitute by InnoRel™ targeting the automotive electronics segment. Innolot contains Nickel (Ni), Antimony (Sb) and Bismuth (Bi) in small proportions in addition to Sn, Ag and Cu. The alloy has demonstrated enhanced reliability under thermal cycling as compared to SAC alloys. In this paper, the high strain rate material properties of Innolot have been evaluated as the alloy ages at an elevated temperature of 50°C. The strain rates chosen are in the range of 1–100 per-second which are typical at second level interconnects subjected to drop-shock environments. The strain rates and elevated aging temperature have been chosen also to correspond to prior tests conducted on SAC105 and SAC305 alloys at this research center. This paper presents a comparison of material properties and their degradation in the three alloys — SAC105, SAC305 and Innolot. Full field strain measurements have been accomplished with the use of high speed imaging in conjunction with Digital Image Correlation (DIC). Ramberg-Osgood non-linear model parameters have been determined to curve-fit through the experimental data. The parameters have been implemented in Abaqus FE model to obtain full-field stresses which correlates with contours obtained experimentally by DIC.

scholarly journals Beyond Hopkinson's bar

2014 ◽  
Vol 372 (2023) ◽  
pp. 20130195 ◽  
Author(s):  
F. Pierron ◽  
H. Zhu ◽  
C. Siviour
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Imaging Techniques ◽  
Hopkinson Pressure Bar ◽  
Test Procedures ◽  
Full Field ◽  
Testing Procedures ◽  
Isotropic Composite

In order to perform experimental identification of high strain rate material models, engineers have only a very limited toolbox based on test procedures developed decades ago. The best example is the so-called split Hopkinson pressure bar based on the bar concept introduced 100 years ago by Bertram Hopkinson to measure blast pulses. The recent advent of full-field deformation measurements using imaging techniques has allowed novel approaches to be developed and exciting new testing procedures to be imagined for the first time. One can use this full-field information in conjunction with efficient numerical inverse identification tools such as the virtual fields method (VFM) to identify material parameters at high rates. The underpinning novelty is to exploit the inertial effects developed in high strain rate loading. This paper presents results from a new inertial impact test to obtain stress–strain curves at high strain rates (here, up to 3000 s −1 ). A quasi-isotropic composite specimen is equipped with a grid and images are recorded with the new HPV-X camera from Shimadzu at 5 Mfps and the SIMX16 camera from Specialised Imaging at 1 Mfps. Deformation, strain and acceleration fields are then input into the VFM to identify the stiffness parameters with unprecedented quality.

Full-Field Strain Measurement On Titanium Welds And Local Elasto-Plastic Identification With The Virtual Fields Method

2011 ◽  
Author(s):  
F. Tattoli ◽  
F. Pierron ◽  
R. Rotinat ◽  
C. Casavola ◽  
C. Pappalettere ◽  
...  
Keyword(s):  
Strain Measurement ◽  
Field Strain ◽  
Virtual Fields Method ◽  
Full Field
Sign in / Sign up

Export Citation Format

Share Document