scholarly journals Strain Rate Effect on Mechanical Properties of Cemented Backfill under Dynamic and Static Combined Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xianglong Li ◽  
Zihao Tao ◽  
Jianguo Wang ◽  
Ting Zuo ◽  
Jun Ma ◽  
...  
Keyword(s):  
Intensity Factor ◽  
Strain Rate ◽  
Failure Mode ◽  
Three Dimensional ◽  
Extreme Value ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strain Rates ◽  
Fracture Surfaces ◽  
Cemented Backfill

In order to study the influence of pillar stopping blasting on the stability of cemented backfill, the dynamic impact test under low strain rate (61.1∼86.8 s−1) was conducted on cemented backfill with two kinds of strength using three-dimensional coupled static-dynamic SHPB equipment. At the same time, the strain rate effect of failure mode, dynamic strength factor, and energy transfer of backfill were analyzed. The results show that when the cemented backfill was loaded under different strain rates in the initial three-dimensional static pressure environment, the pore compaction process was no longer obvious but directly entered the elastic deformation stage. Within the range of strain rates, the extreme value of dynamic intensity factor (DIF) of CTB230 was 6.8, while the extreme value of dynamic intensity factor of CTB310 specimen did not appear within the range of strain rates due to the improvement of the internal cementation force between particles. The fracture surfaces of specimens were perpendicular to the direction of load, and the failure mode was mainly the axial tensile failure, and the fracture surfaces were mostly close to the loading end. According to energy calculation, reflected energy accounts for 80.4%∼86.6% of incident energy; dissipated energy, 5.5%∼14.3%; transmitted energy, 5.3%∼7.9%.

Strain Rate Effect on Shear Behavior of Open-Graded Aggregates

2017 ◽  
Vol 2655 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Thomas Gebrenegus ◽  
Jennifer E. Nicks ◽  
Michael T. Adams
Keyword(s):  
Strain Rate ◽  
Axial Strain ◽  
Shear Behavior ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strength Parameter ◽  
Strain Rates ◽  
Rate Dependency ◽  
Confining Stress ◽  
Dilation Angle

Despite their wide application as construction materials in various earthworks built by state and local transportation agencies, the role of physical and mechanical factors in the strength and deformation behavior of crushed, manufactured open-graded aggregates (OGAs) is not well studied. In this investigation, the strain rate dependency of strength–deformation behaviors of two commonly employed crushed aggregates with small (12.7 mm) and large (38.1 mm) sizes is investigated. A 150-mm diameter triaxial testing device was used to conduct a drained compression test at five strain rates, ranging from 0.000083%/s to 0.0083%/s. To evaluate the significance of confining stress and density on the effect of strain rates, the shear tests were conducted at 34 kPa and 207 kPa effective confining stress levels, with the samples compacted at loose (30%) and dense (95%) relative densities. The peak friction angle, maximum dilation angle, secant modulus, and axial strain at which the aggregates started to dilate were determined to evaluate the strain rate effect on the shear behavior of OGAs. The results demonstrate that within the imposed quasistatic strain rate ranges, only the dilation angle showed an increasing trend with the increase in strain rate, whereas other extracted strength parameters were less sensitive to strain rate for both OGAs tested. Hence, the selection of strain rates according to ASTM specifications is appropriate for conducting strength parameter tests, used by practitioners for the design of geotechnical structures, on OGAs under quasistatic conditions.

scholarly journals Fracture Initiation in Notched Specimens Subjected to Compression: Strain Rate Effect

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2613
Author(s):  
Elżbieta Bura ◽  
Andrzej Seweryn
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Fracture Process ◽  
Fracture Initiation ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Specimen Thickness ◽  
Strain Rates ◽  
Notched Specimens ◽  
Compression Strain

This paper shows the results of an experimental investigation on fracture in polymethyl methacrylate (PMMA) notched specimens subjected to compression (with unloading) including different strain rates. Three types of notches were used. Flat specimens were weakened by two types of V-notches and U-notches. Additionally, two specimen thicknesses were used (9.7 and 14.5 mm). The load was carried out at the strain rate of 8 × 10−4, 4 × 10−3, and 2 × 10−2 s−1 and the unloading stage was conducted ten times faster, i.e., 8 × 10−3, 4 × 10−2, and 2 × 10−1 s−1, respectively. By using a PHANTOM high-speed camera, fracture initiation moments and locations were indicated. Two types of crack were observed and distinguished as A-type and B-type. The first was formed by the contact stress of the closing notch surfaces, while the latter was formed by the residual stresses during the unloading stage. The type of notch, specimen thickness, and the strain rate have a significant influence on the fracture process. The strain rate has a large impact on the critical load value, which determines the fracture initiation, but does not affect the location and shape of the crack. The strain rate effect usually disappears with increasing specimen thickness.

Dynamic Mechanical Response of Renal Cortex Under Compression: Strain-Rate Effect

2009 ◽  
Author(s):  
Farhana Pervin ◽  
Weinong W. Chen ◽  
Tusit Weerasooriya
Keyword(s):  
Strain Rate ◽  
Input Data ◽  
Kidney Tissue ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
The Body ◽  
Blunt Injury ◽  
Strain Rates ◽  
Dynamic Mechanical ◽  
The Impact

The body armor can protect the soldiers from penetrating and blunt injury during the war, but its prevention standard lacks the biomedical validity. To improve the protection gear and prevention strategies, we need valid input data in mathematical modeling at different impact loading conditions. Our aim is to provide the valid data for the computer modeling and simulation based on the injury levels. Dynamic mechanical behaviors of kidney tissues are needed as input data for the impact modeling of penetrating injury. Moreover, the knowledge of mechanical responses of kidney tissues is important for diagnosis, surgical simulation and training purposes. This work investigates the impact of strain rate effect of kidney tissue under compression. The dynamic response of kidney tissues is studied using Split Hopkinson pressure bar (SHPB) technique. We have modified the classical SHPB technique to characterize the mechanical behavior of kidney tissues at high strain-rate ranging from 1000 s−1 to 3000 s−1 by incorporating quratz-crystal technique and hollow transmission bar. We have also studied the quasi-static response of kidney tissues at three different strain-rates of 0.01 s−1, 0.1 s−1 and 1 s−1 as well as the intermediate strain rate at two different strain rates of 10 s−1 and 100s−1. The experiment results indicate the non-linear stress-strain response of materials. The kidney tissue stiffens evidently with increasing strain-rate.

Impact Compressive Failure of a Unidirectional Carbon/Epoxy Laminated Composite in Three Principal Material Directions

2012 ◽  
Vol 706-709 ◽  
pp. 799-804 ◽  
Author(s):  
Takashi Yokoyama
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Laminated Composite ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Failure Behavior ◽  
Strain Rates ◽  
Compressive Failure ◽  
The Impact

The impact compressive failure behavior of a unidirectional T700/2521 carbon/epoxy laminated composite in three principal material directions or fiber (1-), in-plane transverse (2-) and through-thickness (3-) directions is investigated on the conventional split Hopkinson pressure bar (SHPB). Cubic and rectangular block specimens with identical square cross section are machined from an about 10 mm thick composite laminate. The uniaxial compressive stress-strain curves up to failure at quasi-static and intermediate strain rates are measured on an Instron testing machine. It is shown that the ultimate compressive strength and strain exhibit no strain-rate effect in the 1-direction, but a slight strain-rate effect in the 2-and 3-direction over a range of strain rates from10-3to 103/s.

Curvature Ductility of Concrete Element under High Strain-Rates

2012 ◽  
Vol 166-169 ◽  
pp. 2910-2917 ◽  
Author(s):  
Zubair Syed ◽  
Priyan Mendis ◽  
Nelson Lam ◽  
Tuan D. Ngo
Keyword(s):  
Strain Rate ◽  
Material Properties ◽  
Static Load ◽  
High Strain ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strain Rates ◽  
Material Models ◽  
Curvature Ductility ◽  
Concrete Elements

Considerable amount of studies on the ductility and flexural behaviour of normal and high strength concrete elements under static load can be found in literature. However, most of the previous theoretical investigations on moment-curvature (M-φ) relationship of concrete elements to calculate curvature ductility and flexural capacity did not take account of the strain-rate effect on the material models. M-φ analysis of concrete elements under dynamic loading are often conducted with material models developed for quasi-static load by applying Dynamic Increase Factors (DIF) to the material properties to reflect the strain-rate effect. Depending on magnitude and duration of applied dynamic load, element stiffness and boundary condition strain-rate varies over the cross section. Thus, the application of DIF to modify peak material properties often fails to reflect the strain-rate effect reliably. The improvement of using material model which incorporated strain-rate in its constitutive equations has been explored in this study. The effects of reinforcement amount, grade and concrete strength on curvature ductility for different strain rates have been studied using material models which have strain-rate effects included in theirs formulation. Based on the parametric study, a simple formula to estimate curvature ductility for concrete elements under explosive loads (high strain-rates) has been proposed.

Strain Rate Effect on Transmission Tower-Line System under Earthquake

2011 ◽  
Vol 243-249 ◽  
pp. 5845-5848
Author(s):  
Wen Ming Wang ◽  
Hong Nan Li ◽  
Guo Huan Liu ◽  
Li Tian
Keyword(s):  
Strain Rate ◽  
Seismic Analysis ◽  
Three Dimensional ◽  
Element Model ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Transmission Tower ◽  
Base Shear ◽  
Line System ◽  
Seismic Records

Using ABAQUS software, three dimensional finite element model of a transmission tower-line system is created. Nonlinear seismic responses under three seismic records with and without strain rate effect are studied. The results show that the strain rate effect on the transmission tower-line system is more obvious with an increase in intensity of the earthquake. The influence of strain rate on the top displacement and base shear of tower under certain seismic records is unneglectable. Also, it is shown that the strain rate effect on the deformation of wire is prominent. The strain rate effect on the axial force of wire is neglectable. This simple study reveals the importance of considering strain rate effect in seismic analysis for transmission tower-line system.

Sign in / Sign up

Export Citation Format

Share Document