The Influence of Steel Fibers on the Dynamic Response of Self-Compacting Concrete

2016 ◽  
Vol 711 ◽  
pp. 179-186 ◽  
Author(s):  
Małgorzata Pająk ◽  
Tino Kühn
Keyword(s):  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Steel Fibers ◽  
Failure Pattern ◽  
Dynamic Strain ◽  
Strain Diagram ◽  
Strain Rates ◽  
Self Compacting Concrete ◽  
High Strain Rates ◽  
Static Conditions

Concrete subjected to high strain rates behaves notably differently in comparison to quasi-static conditions, which can be affected by the addition of steel fibers. The influence of steel fibers on the dynamic compressive behavior of self-compacting concrete (SCC) was studied experimentally using Split Hopkinson Pressure Bar (SHPB) tests. The investigations were performed in a range of quasi-static rates up to dynamic strain rates of 462 1/s. The effect of steel fibers on the stress-strain diagram, dynamic increase factor (DIF) and failure pattern of SCC conducted under high strain rates was analyzed. The experimental results presented in this paper and the ones from recent works of other authors indicate that application of steel fibers reduces the strain-rate sensitivity of different concretes and has a beneficial effect on the specimen failure pattern. Moreover, the conducted SHPB tests show an important role of fibers in reduction of the strain rates reached in the specimen under the same pressure level in comparison to plain concrete specimens.

A Dynamic Mechanical Analysis of T2 Copper at High Strain Rates

2019 ◽  
Vol 812 ◽  
pp. 38-44
Author(s):  
Shuai Chen ◽  
Wen Bin Li ◽  
Xiao Ming Wang ◽  
Wen Jin Yao
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Pure Copper ◽  
Dislocation Slip ◽  
Strain Rates ◽  
High Strain Rates ◽  
Stress Strain ◽  
Shpb Test

This work compares the pure copper (T2 copper)’s stress-strain relationship at different strain rates in the uni-axial tension test and Split Hopkinson Pressure Bar (SHPB) test. Small samples were utilized in the high strain rate SHPB test in which the accuracy was modified by numerical simulation. The experimental results showed that the T2 copper’s yield strength at high strain rates largely outweighed the quasi static yield strength. The flow stress in the stress-strain curves at different strain rates appeared to be divergent and increased with the increase in strain rates, showing great strain strengthening and strain rate hardening effects. Metallographic observation showed that the microstructure of T2 copper changed from equiaxed grains to twins and the interaction between the dislocation slip zone grain boundary and twins promoted the super plasticity distortion in T2 copper.

Microstructural and Dynamic Mechanical Characterization of Biodegradable Magnesium-Calcium Alloy for Orthopedic Implants

2014 ◽  
Author(s):  
V. S. Brooks ◽  
Y. B. Guo
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Orthopedic Implants ◽  
Strain Rates ◽  
High Strain Rates ◽  
Static Compression ◽  
Metallic Biomaterial

Magnesium-Calcium (Mg-Ca) alloy is an emerging metallic biomaterial for manufacturing biodegradable orthopedic implants. However, very few studies have been conducted on mechanical properties of the bi-phase Mg-Ca alloy, especially at the high strain rates often encountered in manufacturing processes. The mechanical properties are critical to design and manufacturing of Mg-Ca implants. The objective of this study is to study the microstructural and mechanical properties of Mg-Ca0.8 (wt %) alloy. Both elastic and plastic behaviors of the Mg-Ca0.8 alloy were characterized at different strains and strain rates in quasi-static tension and compression testing as well as dynamic split-Hopkinson pressure bar (SHPB) testing. It has been shown that Young’s modulus of Mg-Ca0.8 alloy in quasi-static compression is much higher than those at high strain rates. Yield strength and ultimate strength of the material are very sensitive to strain rates and increase with strain rate in compression. Strain softening also occurs at large strains in dynamic compression. Furthermore, quasi-static mechanical behavior of the material in tension is very different from that in compression. The stress-strain data was repeatable with reasonable accuracy in both deformation modes. In addition, a set of material constants for the internal state variable plasticity model has been obtained to model the dynamical mechanical behavior of the novel metallic biomaterial.

scholarly journals Longitudinal Compressive Property of Three-Dimensional Four-Step Braided Composites after Cyclic Hygrothermal Aging under High Strain Rates

2020 ◽  
Vol 10 (6) ◽  
pp. 2061 ◽  
Author(s):  
Kailong Xu ◽  
Wei Chen ◽  
Lulu Liu ◽  
Gang Luo ◽  
Zhenhua Zhao
Keyword(s):  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Stiffness ◽  
Three Dimensional ◽  
Peak Stress ◽  
Strain Rates ◽  
Braided Composites ◽  
High Strain Rates ◽  
Stiffness Modulus ◽  
Hygrothermal Aging

The longitudinal compressive behavior of the three-dimensional four-step braided composites after cyclic hygrothermal aging was investigated using a split Hopkinson pressure bar (SHPB) apparatus under high strain rates (1100~1250 s−1, 1400~1600 s−1, 1700~1850 s−1, respectively). The SEM micrographs were examined to the damage evolution of the composites after cyclic hygrothermal aging. A high-speed camera was employed to capture the progressive damage process for the composites. The results indicate that the saturated moisture absorption of the composites was not reached during the whole 210 cyclic hygrothermal aging days. The composites mainly underwent epoxy hydrolysis and interfaces debonding during continuous cyclic hygrothermal aging time. The peak stress of the composites still behaved as a strain rate effect after different cyclic hygrothermal aging days, but the dynamic stiffness modulus clearly had no specific regularity. In addition, the peak stress and the dynamic stiffness modulus of the composites after 210 cyclic hygrothermal aging days almost decreased by half when subjected to longitudinal compression.

Compressive Behavior of Plain and Fiber-Reinforced High-Strength Concrete Subjected to High Strain Rate Loading

2011 ◽  
Vol 82 ◽  
pp. 57-62 ◽  
Author(s):  
Sha Sha Wang ◽  
Min Hong Zhang ◽  
Ser Tong Quek
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strength Concrete ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
High Strength ◽  
Strain Rates ◽  
Compressive Behavior ◽  
High Strain Rates ◽  
Strength Concrete

This paper presents a laboratory experimental study on the effect of high strain rate on compressive behavior of plain and fiber-reinforce high-strength concrete (FRHSC) with similar strength of 80-90 MPa. Steel fibers, polyethylene fibers, and a combination of these were used in the FRHSC. A split Hopkinson pressure bar equipment was used to determine the concrete behavior at strain rates from about 30 to 300 s-1. The ratio of the strength at high strain rates to that at static loading condition, namely dynamic increase factor (DIF), of the concretes was determined and compared with that recommended by CEB-FIP code. Fracture patterns of the specimens at high strain rates are described and discussed as well. Results indicate that the CEB-FIP equation is applicable to the plain high strength concrete, but overestimates the DIF of the FRHSC at strain rates beyond a transition strain rate of 30 s-1. Based on the experimental results, a modified equation on DIF is proposed for the FRHSC.

Using Split Hopkinson Pressure Bars to Perform Large Strain Compression Tests on Neoprene at Intermediate and High Strain Rates

2013 ◽  
Vol 631-632 ◽  
pp. 458-462 ◽  
Author(s):  
Peng Duo Zhao ◽  
Yu Wang ◽  
Jian Ye Du ◽  
Lei Zhang ◽  
Zhi Peng Du ◽  
...  
Keyword(s):  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Large Strain ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
High Strain Rates ◽  
Split Hopkinson ◽  
Pressure Bar

The strain rate sensitivity of neoprene is characterized using a modified split Hopkinson pressure bar (SHPB) system at intermediate (50 s-1, 100 s-1) and high (500 s-1, 1000 s-1) strain rates. We used two quartz piezoelectric force transducers that were sandwiched between the specimen and experimental bars respectively to directly measure the weak wave signals. A laser gap gage was employed to monitor the deformation of the sample directly. Three kinds of neoprene rubbers (Shore hardness: SHA60, SHA65, and SHA70) were tested using the modified split Hopkinson pressure bar. Experimental results show that the modified apparatus is effective and reliable for determining the compressive stress-strain responses of neoprene at intermediate and high strain rates.

Mechanical Behavior of Sn1Ag0.5Cu and Sn3Ag0.5Cu Alloys at High Strain Rates

2012 ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Prolonged Exposure ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Image Correlation ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
High Strain Rates ◽  
Test Technique

Electronics may experience high strain rates when subjected to high g-loads of shock and vibration. Material and damage behavior of electronic materials at high strain rates typical of shock and vibration is scarce. Previously studies have shown that second-level interconnects have a high propensity for failure under shock and vibration loads in fine pitch electronics. Exposure to shock and vibration is common in a variety of consumer environments such as automotive and portable electronics. The low strain-rate properties of commonly used SnAgCu solders, including Sn1Ag0.5Cu and Sn3Ag0.5Cu, have been found to evolve with time after prolonged exposure to high temperatures. High strain rate properties of leadfree solder alloys in the strain-rate range of 1–100 sec−1 are scarce. Previous attempts at characterizing the high strain rates properties have focused on the use of the Split Hopkinson Pressure Bar (SHPB), which enables measurements of strain rates in the neighborhood of 1000 per sec. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. Tests are conducted at strain rates 10, 35 and 50 per sec. High speed cameras operating at 75,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, SAC305 solders. Non-linear Ramberg-Osgood model has been used to fit the material data. The Ramberg-Osgood model available in Abaqus has been used for tensile test simulation and to correlate with DIC based experimental strain data.

Dynamic Testing at High Strain Rates of AZ31 Magnesium Alloys on SHPB Equipment

2013 ◽  
Vol 303-306 ◽  
pp. 2648-2651
Author(s):  
Xu Qing Chang ◽  
Tie Hua Ma
Keyword(s):  
Strain Rate ◽  
Optical Microscopy ◽  
Strain Hardening ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Mg Alloy ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
High Strain Rates ◽  
Az31 Mg Alloy

The mechanical behaviour of as-cast AZ31 Mg alloy has been investigated at strain rates up to 2.0×103s-1. Dynamic tests were carried out at room temperature using a Split Hopkinson Pressure Bar (SHPB) apparatus. Microstructural characteristic were analysed by Image MAT A1 optical microscopy. The results demonstrated that AZ31 Mg alloy exhibited obvious yield phenomena and strain hardening behaviour at high strain rates. The basically same curvature of stress-strain curves exhibited an similar strain hardening rate. The dynamic yield strength changes little and the peak stress increases with the strain rates. An examination by optical microscopy after high strain rate deformation reveals the occurrence of twinning and twin area percentage increases with the strain rate increasing.

Deformation Behavior of Ti-6Al-4V-0.1B Alloy Loaded under High Strain Rates

2016 ◽  
Vol 849 ◽  
pp. 266-270 ◽  
Author(s):  
Yang Yu ◽  
Qi Gao ◽  
Xun Jun Mi ◽  
Song Xiao Hui ◽  
Wen Jun Ye
Keyword(s):  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
High Strain Rates ◽  
The Matrix ◽  
Split Hopkinson ◽  
Pressure Bar

Deformation and fracture behaviors of Ti-6Al-4V-0.1B alloy with Widmanstätten, equiaxed and bimodal microstructures were investigated by Split Hopkinson Pressure Bar (SHPB) under high strain rates of 2100-3200 s-1. The results showed that the equiaxed and bimodal structures had a higher bearing capacity at high strain rates than that of the Widmanstätten structure. With the same microstructure, the increase of strain rate gave rise to an improved uniform plastic deformation. According to an observation on the deformed microstructure, it was found that adiabatic shear behavior was the main reason for failure and fracture of the alloy. The formation and propagation of adiabatic shear bands (ASBs) was the precursor for the failure and fracture of the material. Cavities at the interface between TiB phase and the matrix readily formed due to the uncoordinated deformation, which are not the dominate reason for the failure and fracture.

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