Strain-Rate Sensitivity of Concrete: Influence of Temperature

2011 ◽  
Vol 243-249 ◽  
pp. 453-456
Author(s):  
Dong Ming Yan ◽  
Wei Xu
Keyword(s):  
Low Temperature ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Dynamic Properties ◽  
Testing Machine ◽  
Concrete Structures ◽  
Free Water ◽  
Rate Sensitivity ◽  
Influence Of Temperature ◽  
Wide Range

Knowledge about the dynamic properties of concrete is vital to the design and safety evaluation of large-scale concrete structures subjected to seismic excitation. There are many factors affecting the dynamic properties of concrete such as moisture content and temperature. Though a lot of concrete structures have been designed to withstand low temperature, research on the strain-rate sensitivity of concrete under low temperature condition is still very limited so far. In this study, both tensile and compressive experiments were carried out to investigate the influence of temperature on the rate-dependent characteristics of concrete. Tensile experiments of dumbbell-shaped specimens were carried out on a MTS810 testing machine and compressive tests on cubic specimens were performed using a servo-hydraulic testing machine. Specimens at two types of temperature, room temperature 20oC and low temperature -30oC, were characterized. The strain rate varied over a wide range. It was concluded from the test data that the strengths of specimens at both types of temperature tended to increase as strain rate increased. Temperature had slight influence on the rate-sensitive behavior of concrete when concrete specimens were dry; however, test on saturated specimens indicated that the role of temperature on the mechanical behavior of concrete subject to dynamic loading was very significant. This phenomenon may be attributed to the state of free water in concrete.

Measurement on Strain Rate Sensitivity and Dynamic Mechanical Properties of Various Polymeric Materials

2011 ◽  
Vol 471-472 ◽  
pp. 385-390 ◽  
Author(s):  
Mohd Firdaus Omar ◽  
Md Akil Hazizan ◽  
Zainal Arifin Ahmad
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Polymeric Materials ◽  
Dynamic Mechanical Properties ◽  
Dynamic Mechanical ◽  
Wide Range

Strain rate sensitivity and dynamic mechanical properties of polymeric materials are affected to a certain extent especially by the rate of loading. However, there is limited number of works reported on that particular issue. Therefore, the paper presents on static and dynamic mechanical properties of various polymeric materials across strain rate from 10-2 to 10-3 s-1. The specimen were tested using universal testing machine (UTM) for static loading and a conventional split Hopkinson pressure bar (SHPB) apparatus for dynamic loading. From the results, the compression modulus and compressive strength of all tested specimen increased significantly with increasing strain rates. In addition, positive increment in terms of strain rate sensitivity was recorded for all tested polymers over a wide range of strain rate investigated. Meanwhile, the thermal activation volume has decreased as increasing strain rate. Of the three polymers, polypropylene shows the highest strain rate sensitivity at static region. On the other hand, at dynamic region, polycarbonate shows the highest strain rate sensitivity than that of polypropylene and polyethylene.

Effect of Consolidation and Sintering Parameters on the Mechanical Responses of Nanocrystalline Al-Fe Alloy Processed by Mechanical Alloying

2015 ◽  
Vol 719-720 ◽  
pp. 87-90
Author(s):  
Muneer Baig ◽  
Hany Rizk Ammar ◽  
Asiful Hossain Seikh ◽  
Mohammad Asif Alam ◽  
Jabair Ali Mohammed
Keyword(s):  
Mechanical Alloying ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Compressive Loading ◽  
Rate Sensitivity ◽  
Testing Temperature ◽  
Fine Grained ◽  
Mechanical Responses ◽  
Wide Range ◽  
High Frequency Induction

In this investigation, bulk ultra-fine grained and nanocrystalline Al-2 wt.% Fe alloy was produced by mechanical alloying (MA). The powder was mechanically milled in an attritor for 3 hours and yielded an average crystal size of ~63 nm. The consolidation and sintering was performed using a high frequency induction sintering (HFIS) machine at a constant pressure of 50 MPa. The prepared bulk samples were subjected to uniaxial compressive loading over wide range of strain rates for large deformation. To evaluate the effect of sintering conditions and testing temperature on the strain rate sensitivity, strain rate jump experiments were performed at high temperature. The strain rate sensitivity of the processed alloy increased with an increase in temperature. The density of the bulk samples were found to be between 95 to 97%. The average Vickers micro hardness was found to be 132 Hv0.1.

scholarly journals The Evaluation of the Fracture Surface in the AW-6060 T6 Aluminium Alloy under a Wide Range of Loads

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 324 ◽  
Author(s):  
Marcin Chybiński ◽  
Łukasz Polus ◽  
Maria Ratajczak ◽  
Piotr Sielicki
Keyword(s):  
Fracture Surface ◽  
Strain Rate ◽  
Aluminium Alloy ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Tensile Loading ◽  
Engineering Structures ◽  
Fracture Surfaces ◽  
Wide Range ◽  
Scanning Electron

The present study focused on the behaviour of the AW-6060 aluminium alloy in peak temper condition T6 under a wide range of loads: tensile loading, projectile and explosion. The alloy is used as a structural component of civil engineering structures exposed to static or dynamic loads. Therefore, it was crucial to determine the material’s behaviour at low and intermediate rates of deformation. Despite the fact that the evaluation of the strain rate sensitivity of the AW-6060 aluminium alloy has already been discussed in literature, the authors of this paper wished to further investigate this topic. They conducted tensile tests and confirmed the thesis that the AW-6060 T6 aluminium alloy has low strain rate sensitivity at room temperature. In addition, the fracture surfaces subjected to different loading (tensile loading, projectile and explosion) were investigated and compared using a scanning electron microscope, because the authors of this paper were trying to develop a new methodology for predicting how samples had been loaded before failure occurred based on scanning electron microscopy (SEM) micrographs. Projectile and explosion tests were performed mainly for the SEM observation of the fracture surfaces. These tests were unconventional and they represent the originality of this research. It was found that the type of loading had an impact on the fracture surface.

The Effect of Controlled Melt-Solidification on the Strain Rate Sensitivity of a Squeeze-Cast Hybrid-Reinforced Aluminum AA 6061 Matrix Composite

2015 ◽  
Vol 16 ◽  
pp. 1-16
Author(s):  
B.O. Malomo ◽  
O.O. Fadodun ◽  
K.M. Oluwasegun ◽  
A.T. Ogunbodede ◽  
S.A. Ibitoye ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Matrix Composite ◽  
Deformation Behavior ◽  
Squeeze Casting ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Cooling Rates

A framework based on the relationship between variations in cooling rates and volume fraction of reinforcements during solidification processing to enhance the deformation behavior of aluminum alloy AA6061 matrix composite produced with a hybrid system of reinforcements is investigated in this study. The aluminum matrix composite with 5 %, 10 % and 20 % volume fraction of reinforcements (Al2O3-SiC) was synthesized by infiltrating molten aluminum AA 6061 at a pouring temperature of 740 °C into prefabricated preforms of reinforcements at a pressure of 80 MPa, die preheat temperature of 300 °C and pressure holding time of 15 s using the squeeze casting method. By employing water jet spraying at the rate of 0.1, 0.2 and 0.3 kg/s and taking measurements using a K-type thermocouple, cooling rates were obtained in correspondence with varying volume fractions of reinforcements. The developed composites were sectioned and microstructural features were examined by optical microscopy. Tensile testing was conducted according to ASTM B557 standard using an MTS testing machine. It was observed that cooling rates decreased as the volume fraction of reinforcements was increased and the cooling time also increased accordingly during this process. With respect to deformation behavior, higher cooling rates are associated with an improvement in mechanical properties at 5 % and 10 % additions of hybrid reinforcement particles but this effect diminishes as the volume fraction of reinforcements was increased to 20 %. Also, the strain rate sensitivity (SRS) exponent increased considerably with strain rates and volume fraction of reinforcements, but the tensile elongation values decreased with increasing volume fraction of reinforcements; and the variations in these properties were most significant for samples containing 20% volume fraction of hybrid reinforcements.From the foregoing, it follows that an experimentally-determined optimal solidification range is critical to the enhancement of deformation parameters as the volume fraction of reinforcements is varied in a squeeze casting process.

scholarly journals A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10−5to 5 × 104 s−1

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Ramzi Othman
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Large Strain ◽  
Rate Sensitivity ◽  
Industrial Applications ◽  
Strain Rate Range ◽  
Strain Rates ◽  
Wide Range ◽  
Large Strain Rate

In several industrial applications, metallic structures are facing impact loads. Therefore, there is an important need for developing constitutive equations which take into account the strain rate sensitivity of their mechanical properties. The Johnson-Cook equation was widely used to model the strain rate sensitivity of metals. However, it implies that the yield and flow stresses are linearly increasing in terms of the logarithm of strain rate. This is only true up to a threshold strain rate. In this work, a three-constant constitutive equation, assuming an apparent activation volume which decreases as the strain rate increases, is applied here for some metals. It is shown that this equation fits well the experimental yield and flow stresses for a very wide range of strain rates, including quasi-static, high, and very high strain rates (from 10−5to 5 × 104 s−1). This is the first time that a constitutive equation is showed to be able to fit the yield stress over a so large strain rate range while using only three material constants.

Strain-Rate Sensitivity of Concrete: Influence of Moisture Content

2006 ◽  
Vol 326-328 ◽  
pp. 1661-1664
Author(s):  
Gao Lin ◽  
Dong Ming Yan
Keyword(s):  
Moisture Content ◽  
Strain Rate ◽  
Earthquake Engineering ◽  
Testing Machine ◽  
Dynamic Strength ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Hydraulic Testing ◽  
Wide Range ◽  
Compressive Tests

Understanding the behavior of concrete under dynamic loading conditions is an issue of great significance in earthquake engineering. Moisture content has an important influence on the strain-rate effect of concrete. In this study, both tensile and compressive experiments were carried out to investigate the rate-dependent behavior of concrete. Tensile experiments of dumbbell-shaped specimens were conducted on a MTS810 testing machine and compressive tests of cubic specimens were performed on a servo-hydraulic testing machine designed and manufactured at Dalian University of Technology, China. The strain rate varied in a wide range. The analytical formulations between the dynamic strength and strain rate were proposed for both compressive tests and tensile tests. It was concluded from the results that with the increasing strain rate, strengths of specimens with both moisture contents tended to increase and the increase seemed to be more remarkable for the saturated specimens; based on the experimental observation, a better explanation for the dynamic behavior is presented.

A Study on Rate Sensitivity of Impedance in TRIP Steel during Deformation at Various Strain Rate under Two Kinds of Deformation Mode

2014 ◽  
Vol 566 ◽  
pp. 140-145
Author(s):  
Daiki Inoshita ◽  
Takeshi Iwamoto
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Trip Steel ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Deformation Mode ◽  
Tensile Tests ◽  
Material Testing ◽  
Trip Steels ◽  
Material Testing Machine

TRIP steel possesses excellent mechanical properties dominated by strain-induced martensitic transformation (SIMT). For automotive industries, if TRIP steel can be applied to shock absorption members, it can be considered that the weight of automobile can be reduced. However, the strain rate sensitivity of TRIP steels has not been fully understood because the strain rate sensitivity and the deformation mode dependency of SIMT are still unclear. Therefore, it is important to reveal these sensitivity and dependency for confirming a reliability of TRIP steel. Therefore, in this study, it is attempted to estimate the amount of produced martensite in TRIP steel by measuring the inductance of TRIP steel. The specimen made of TRIP steel is used as a core of a prototype coil manufactured in this study. Then, the compressive and tensile tests are conducted by using a material testing machine and a drop weight testing machine using the specimen inside the coil. The inductance of the coil with the deformed specimen are measured continuously during the tests.

Dynamic Response of Magnesium Alloy AZ31B under High Strain Rate Compressive Loading

2011 ◽  
Vol 83 ◽  
pp. 60-65 ◽  
Author(s):  
Iram Raza Ahmad ◽  
Dong Wei Shu
Keyword(s):  
Magnesium Alloy ◽  
Strain Rate ◽  
High Speed ◽  
Dynamic Properties ◽  
Weight Ratio ◽  
Rate Sensitivity ◽  
Consumer Electronics ◽  
Magnesium Alloy Az31b ◽  
Wide Range ◽  
Structural Applications

Magnesium alloys have been increasingly used in automobile, aerospace, consumer electronics and communication industries due to their low density, high strength to weight ratio, good impact resistance and castability. Impact situations in vehicles and airplanes and high speed metal working are characterized with the high rates of loading. The dynamic properties of materials are critical to evaluate the materials’ response in impact situations. They are also useful to design various automotive and aerospace components that are subjected to high rates of loadings. In current study, the compressive behaviour of magnesium alloy AZ31B has been examined over a wide range of strain rate between 103 and 3x103 s-1 in order to evaluate its potential in structural applications. Higher stresses are observed at higher strain rates. The peak stress increases about 10% for an increase in the strain rate from 980 s-1 to 2450 s-1. The hardening exponent n increases from 0.65 to 0.72 with increasing strain rate from 980 s-1 to 2450 s-1 indicating that the alloy is rate sensitive. However, the rate sensitivity of the alloy is negligible at lower strains and is significantly higher at higher strains. Energy absorption during deformation in general is increased with the strain rate.

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