scholarly journals Coupled Static-Dynamic Tensile Mechanical Properties and Energy Dissipation Characteristic of Limestone Specimen in SHPB Tests

2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Qi Ping ◽  
Zhaohui Fang ◽  
Dongdong Ma ◽  
Hao Zhang
Keyword(s):  
Mechanical Property ◽  
Tensile Strength ◽  
Strain Rate ◽  
Dynamic State ◽  
Average Strain ◽  
Absorbed Energy ◽  
Dynamic Tensile Strength ◽  
One Dimensional ◽  
Average Strain Rate ◽  
Dissipation Characteristic

To investigate the dynamic splitting tensile mechanical property of limestone under coupled static and dynamic state, the dynamic split tensile tests of limestone under one-dimensional coupled static and dynamic load with different strain rates were performed with the help of modified split Hopkinson pressure bar (SHPB) equipment. The dynamic splitting tensile mechanical property and energy dissipation characteristic under two stress states were also compared in this research. Test results indicated that the dynamic tensile strength of the limestone specimen increased with the increase of average strain rate, exhibiting an obvious strain rate effect. In addition, dynamic tensile strength under uniaxial state was higher than that under one-dimensional coupled static and dynamic load state under the same test condition. Moreover, the deformation modulus increased with increasing average strain rate under uniaxial state, while it decreased with increasing average strain rate under coupled static and dynamic state. Both the reflected energy and absorbed energy linearly increased with increasing incident energy. The preload in the radial direction could increase the reflected energy and decrease the absorbed energy. Moreover, the transmitted energy with preload state was slightly lower than that under uniaxial state. Finally, the dynamic tensile strength of limestone specimen increased as a power function with increasing absorbed energy.

scholarly journals Dynamic Splitting Experimental Study on Sandstone at Actual High Temperatures under Different Loading Rates

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Qi Ping ◽  
Mingjing Wu ◽  
Pu Yuan ◽  
Haipeng Su ◽  
Huan Zhang
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Strain Rate ◽  
Failure Mode ◽  
High Temperatures ◽  
Radial Strain ◽  
Tensile Tests ◽  
Average Strain ◽  
Striker Velocity ◽  
Average Strain Rate

The tensile failure of rocks is a common failure mode in rock engineering. Many studies have been conducted on the tensile strength and failure mode of rocks after high-temperature treatment under dynamic loading. However, research on the effects of high temperature on the dynamic splitting tensile characteristics of sandstone at actual high temperatures is lacking. To investigate the dynamic tensile characteristics of rocks at actual high temperatures, split Hopkinson pressure bar (SHPB) test apparatus and high-temperature environment box were used to perform dynamic splitting tensile tests under six striker velocities for sandstone specimens at 25°C–800°C. The dynamic splitting tensile strength, radial strain, average strain rate, and failure mode of sandstone under different test conditions were investigated. Test results revealed that the brittleness of sandstone specimens is enhanced at 200°C and 400°C, but slight ductility is observed at 600°C and 800°C. The strain rate effect of dynamic tensile strength is closely related to temperature. When the striker velocity exceeds 2.3 m/s, the dynamic radial strain first decreases and then increases with rising temperature. A quadratic polynomial relationship between the dynamic radial strain and temperature was observed. The temperature effect on the average strain rate is strong at low striker velocity and weak at high striker velocity. In the dynamic splitting tensile tests, high-temperature sandstone specimens are split into two semicylinders along the radial loading direction.

Comparative study of tensile tests based on Hopkinson bar for recycled aggregate concrete

2018 ◽  
Vol 10 (1) ◽  
pp. 26-53
Author(s):  
Junzhou Duan ◽  
Yubin Lu ◽  
Shu Zhang ◽  
Xiquan Jiang
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Coarse Aggregate ◽  
Tensile Tests ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Dynamic Tensile Strength ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate ◽  
Direct Tensile

To comparatively study the tensile properties and fracture patterns of recycled aggregate concrete with various replacement percentages (i.e. 0%, 25%, 50%, 75%, and 100%) of recycled coarse aggregate, the dynamic direct tensile tests, splitting tests, and spalling tests of recycled aggregate concrete in the strain-rate range of 100–102 s−1 were carried out using large diameter (75 mm) split Hopkinson tensile bar and pressure bar. Test results show that for recycled aggregate concrete, the quasi-static direct tensile strength is more marvelous than its quasi-static splitting strength. When recycled coarse aggregate replacement percentage is 0%–75%, the replacement percentage impact minimally on the quasi-static tensile strength of recycled aggregate concrete. In dynamic tensile tests, there exists apparent difference between the dynamic direct tensile strength and dynamic splitting. The dynamic tensile strength of recycled aggregate concrete increases with the increase of average strain-rate in all three kinds of tests. The average strain-rate affects the damage form of recycled aggregate concrete, which indicates that the recycled aggregate concrete has obvious rate sensitivity. There shows no obvious regularity between the dynamic tensile strength and the recycled coarse aggregate replacement percentage. And the indirect tensile strength calculation method used in this article offers the theoretical basis for the engineering application of recycled aggregate concrete.

Effect of the Strain Rate and Water Saturation for the Dynamic Tensile Strength of Rocks

2004 ◽  
Vol 465-466 ◽  
pp. 361-366 ◽  
Author(s):  
Yuji Ogata ◽  
Woo-jin Jung ◽  
Shiro Kubota ◽  
Yuji Wada
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Water Saturation ◽  
Dynamic Tensile Strength

scholarly journals Experimental and Numerical Study on Tensile Strength of Concrete under Different Strain Rates

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Fanlu Min ◽  
Zhanhu Yao ◽  
Teng Jiang
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Numerical Study ◽  
Material Behavior ◽  
Constitutive Law ◽  
Test Machine ◽  
Strain Rates ◽  
Dynamic Tensile Strength ◽  
Dynamic Increase Factor ◽  
Versus Strain

The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10−7 s−1to 10−4 s−1in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates.

Evaluation of Fatigue Damage on Operating Plant Components in LWR Water

2004 ◽  
Author(s):  
Makoto Higuchi ◽  
Takashi Hirano ◽  
Katsumi Sakaguchi
Keyword(s):  
Strain Rate ◽  
Fatigue Damage ◽  
Austenitic Stainless Steels ◽  
Strain Range ◽  
Average Strain ◽  
Simple Method ◽  
Detailed Method ◽  
Class 1 ◽  
Average Strain Rate ◽  
Fatigue Life Reduction

The effects of LWR water environments on fatigue life reduction of LWR component materials have been evaluated quantitatively. The environmental correction factor Fen, which is determined by strain rate, temperature and dissolved oxygen content has been proposed for assessing this reduction in the case of carbon, low alloy and austenitic stainless steels. Equations to calculate Fen have been established based on fatigue data derived under constant test conditions but strain rate and temperature in actual transients are usually not constant. A method for calculating Fen under conditions of continuously changing strain rate and temperature was established in this study for use in assessing fatigue damage on actual transients, with due consideration to the effects of LWR water environments. The method should be found applicable to Class 1 vessels. It should be possible to determine the stress cycle and fatigue usage factor in air in accordance with the ASME B&PV Code Section III NB-3200. Fatigue damage in LWR water may be found by linear summation of the products of Fen and partial fatigue usage factor in stress cycles. The method is consisted of simple and detailed methods. The evaluation of Fen must be applied for the strain range in which the strain increases continuously. In the simple method, the entire range of stain increasing is used as one segment and the average strain rate and the highest temperature in it are used for computing Fen. In the detailed method, the strain increasing range should be divided into small segments and average strain rate and highest temperature in it are used for finding Fen and Fens in all segments are subsequently averaged by weighting with strain increment in it. The Fen by this latter procedure was found much less than with the former under a condition of considerable temperature change.

The Behavior of Carbon Black-Filled Natural Rubber under High Strain Rates3

2006 ◽  
Vol 34 (2) ◽  
pp. 119-134 ◽  
Author(s):  
Syeda A. Hussain ◽  
Michelle S. Hoo Fatt
Keyword(s):  
Tensile Strength ◽  
Carbon Black ◽  
Natural Rubber ◽  
Strain Rate ◽  
Characteristic Relaxation Time ◽  
Dynamic Tensile Strength ◽  
Extension Ratio ◽  
Strain Induced Crystallization ◽  
Quasistatic Loading ◽  
Induced Crystallization

Abstract Tensile tests were conducted to obtain the deformation and failure characteristics of unfilled natural rubber (NR) and natural rubber with 25, 50, and 75 phr of N550 carbon black filler under quasistatic and dynamic loading conditions. The quasistatic tests were performed on an electromechanical INSTRON machine, while the dynamic test data were obtained from tensile impact experiments using a Charpy impact apparatus. In general, the modulus of the stress-extension ratio curves increases with increasing strain rate up to about 407, 367, 346, and 360 s−1 for unfilled, and 25, 50, and 75 phr for filled NR, respectively. Above these strain rates, the unfilled and filled natural rubber stress-extension ratio curves remained unchanged. The modulus increased with increasing strain rate because there was little time for stress relaxation. Above a critical strain rate, no change in modulus was observed because the time of the experiment was short compared to the lowest characteristic relaxation time of the material. Dynamic stress-extension ratio curves did not have the very sharp upturn at break, which is observed from strain-induced crystallization in natural rubber under quasistatic loading. Strain-induced crystallization appeared to be suppressed at high rates of loading. In fact, the highest dynamic tensile strength for the 25- and 50-phr carbon black-filled natural rubbers was smaller than those under quasistatic loading, while the highest dynamic tensile strength of the 75-phr carbon black-filled NR was greater than that in the static test. This indicated that high amounts of carbon black fillers will impede strain-induced crystallization in natural rubber.

Surface strain accumulation and the seismic moment tensor

1997 ◽  
Vol 87 (5) ◽  
pp. 1345-1353
Author(s):  
J. C. Savage ◽  
R. W. Simpson
Keyword(s):  
Strain Rate ◽  
Accumulation Rate ◽  
Moment Tensor ◽  
Surface Strain ◽  
Seismogenic Zone ◽  
Strain Accumulation ◽  
Average Strain ◽  
Average Strain Rate ◽  
Double Couple ◽  
Scalar Moment

Abstract Although the scalar moment accumulation rate within the seismogenic zone beneath a given area is sometimes deduced from the observed average surface strain accumulation rate over that same area (e.g., Working Group on California Earthquake Probabilities, 1995), the correspondence between the two is very uncertain. The equivalence between surface strain accumulation and scalar moment accumulation is based on Kostrov's (1974) relation between the average strain rate over a volume and the moment-rate tensor for that volume. The average strain rate over the volume is replaced by the average strain rate measured at the free surface to deduce an approximate moment-rate tensor. Only in exceptional circumstances will that moment-rate tensor correspond to a double-couple mechanism, a mechanism that can be represented by a scalar moment accumulation rate. More generally, the moment tensor must be resolved into the superposition of two or more double-couple mechanisms, and that resolution can be done in many ways, each with its own scalar moment rate. Thus the resolution is not unique. This is demonstrated by deducing scalar moment accumulation rates for a GPS network that covers most of California south of San Francisco. It is shown that resolutions into different double-couple mechanisms lead to scalar moment accumulation rates differing by factors of ∼2. We suggest that the minimum scalar moment rate equivalent to principal surface strain rates ɛ1 and ɛ2 acting over the area A is M0(min) = 2μHA Max (¦ɛ1¦, ¦ɛ2¦, ¦ɛ1 + ɛ2¦), where μ is the rigidity and H the depth of seismogenic zone, and the function Max is equal to the largest of its arguments. Within the uncertainites of measurement, the scalar moment accumulation rate in southern California based on that approximation is in balance with the average historic seismic moment release rate so that no current earthquake deficit need be accumulating.

The Influence of Strain Rate on the Passive and Stimulated Engineering Stress–Large Strain Behavior of the Rabbit Tibialis Anterior Muscle

1998 ◽  
Vol 120 (1) ◽  
pp. 126-132 ◽  
Author(s):  
B. S. Myers ◽  
C. T. Woolley ◽  
T. L. Slotter ◽  
W. E. Garrett ◽  
T. M. Best
Keyword(s):  
Strain Rate ◽  
Tibialis Anterior ◽  
High Speed ◽  
Large Strain ◽  
Strain Rates ◽  
Average Strain ◽  
Stress Strain ◽  
Engineering Stress ◽  
Average Strain Rate ◽  
Strain Responses

The passive and stimulated engineering stress–large strain mechanical properties of skeletal muscle were measured at the midbelly of the rabbit tibialis anterior. The purpose of these experiments was to provide previously unavailable constitutive information based on the true geometry of the muscle and to determine the effect of strain rate on these responses. An apparatus including an ultrasound imager, high-speed digital imager, and a servohydraulic linear actuator was used to apply constant velocity deformations to the tibialis anterior of an anesthetized neurovascularly intact rabbit. The average isometric tetanic stress prior to elongation was 0.44 ± 0.15 MPa. During elongation the average stimulated modulus was 0.97 ± 0.34 MPa and was insensitive to rate of loading. The passive stress–strain responses showed a nonlinear stiffening response typical of biologic soft tissue. Both the passive and stimulated stress–strain responses were sensitive to strain rate over the range of strain rates (1 to 25 s−1). Smaller changes in average strain rate (1 to 10, and 10 to 25 s−1) did not produce statistically significant changes in these responses, particularly in the stimulated responses, which were less sensitive to average strain rate than the passive responses. This relative insensitivity to strain rate suggests that pseudoelastic functions generated from an appropriate strain rate test may be suitable for the characterization of the responses of muscle over a narrow range of strain rates, particularly in stimulated muscle.

Sign in / Sign up

Export Citation Format

Share Document