scholarly journals Rock Dynamic Fracture Characteristics Based on NSCB Impact Method

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Yanbing Wang
Keyword(s):  
Fracture Toughness ◽  
Dynamic Fracture ◽  
High Speed ◽  
Loading Rate ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Fracture Toughness ◽  
High Speed Photography ◽  
Rate Dependency ◽  
Hopkinson Pressure Bar ◽  
Rock Materials

In 2012, the International Society for Rock Mechanics (ISRM) recommended a new Notched Semicircular Bend (NSCB) method for the determination of dynamic fracture toughness of rock materials, but it did not consider the effect of some uncontrollable factors in the course of the experiment on the test result. This thesis firstly carried out dynamic fracture toughness experiments on several typical rock materials such as sandstone using the modified Split-Hopkinson Pressure Bar (SHPB) experimental system with high-speed photography, directly compared the dynamic fracture failure characteristics of several rock materials, and examined the loading rate dependency of the dynamic fracture toughness of rock materials. Based on the numerical analysis method of Discrete Lattice Spring Model (DLSM), it focused on the effect of bullet impact loading rate, loading area of incident bar, support restraints of clamping specimen, and other uncontrollable factors in the course of SHPB experiment on test results. The findings can be referenced for the improvement of NSCB method.

scholarly journals The dynamic asymmetric fracture test and determination of the dynamic fracture toughness of large-diameter cracked rock specimens

2019 ◽  
Vol 23 (Suppl. 3) ◽  
pp. 897-905
Author(s):  
Yiqiang Lu ◽  
Mingzhong Gao ◽  
Bin Yu ◽  
Cong Li
Keyword(s):  
Fracture Toughness ◽  
Dynamic Fracture ◽  
Split Hopkinson Pressure Bar ◽  
Impact Load ◽  
Failure Process ◽  
Large Diameter ◽  
Dynamic Stress Intensity Factor ◽  
Dynamic Fracture Toughness ◽  
Hopkinson Pressure Bar ◽  
Rock Specimens

We propose large-diameter (160 mm) pre-cracked chevron notched Brazilian disc (P-CCNBD) specimens were used to study the asymmetric fracture law and determine the dynamic fracture toughness of rock. Specimens were diametrically impacted by a split Hopkinson pressure bar. The dynamic fracture failure process of each specimen was monitored by crack propagation gauges and strain gauges. Each of the large-diameter P-CCNBD specimens was found to exhibit prominent asymmetric fracture under impact load. The stress equilibrium condition cannot be satisfied. The dynamic fracture toughness values of the rocks were measured using the experimental-numerical method rather than the quasi-static method. The calculation results showed that the dynamic fracture toughness of rocks increases with the dynamic loading rate. In addition, at the 3-D crack front, the dynamic stress intensity factor was found be substantially different at each point. These data suggest that the dynamic fracture toughness of P-CCNBD specimens should be calculated by removing the value affected by an edge arc crack and taking the average value of the remaining points.

Investigation of loading rate and plate thickness effects in dynamic fracture toughness of PMMA

1997 ◽  
Vol 57 (4) ◽  
pp. 459-460
Author(s):  
H. Wada ◽  
M. Seika ◽  
T.C. Kennedy ◽  
C.A. Calder ◽  
K. Murase
Keyword(s):  
Fracture Toughness ◽  
Dynamic Fracture ◽  
Loading Rate ◽  
Plate Thickness ◽  
Dynamic Fracture Toughness

scholarly journals Dynamic Fracture Toughness of TaC/CNTs/SiC CMCs Prepared by Spark Plasma Sintering

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Qiaoyun Xie ◽  
Sylvanus N. Wosu
Keyword(s):  
Fracture Toughness ◽  
Spark Plasma Sintering ◽  
Dynamic Fracture ◽  
Split Hopkinson Pressure Bar ◽  
Ceramic Matrix Composites ◽  
Dynamic Fracture Toughness ◽  
Polished Surface ◽  
Ceramic Samples ◽  
Plasma Sintering ◽  
Spark Plasma

This study focuses on the fracture toughness of TaC and carbon nanotubes (CNTs) reinforced SiC ceramic matrix composites (CMCs), prepared by spark plasma sintering (SPS) technique. A high densification of 98.4% was achieved under the sintering parameter of 133°C/min, 1800°C, and 90 MPa pressure. Vickers indentation was employed to measure the indentation toughness on the polished surface of ceramic samples, SEM was applied to directly observe the crack propagation after indentation, and split Hopkinson pressure bar (SHPB) was developed to determine the dynamic fracture toughness within the ceramic samples subjected to an impact in a three-point bending configuration.

An improved method for compressive stress-strain measurements at very high strain rates

1992 ◽  
Vol 438 (1902) ◽  
pp. 153-170 ◽  
Keyword(s):  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Pure Copper ◽  
High Strength ◽  
Tungsten Alloy ◽  
High Speed Photography ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Split Hopkinson ◽  
Pressure Bar

This paper describes a modification of the split Hopkinson pressure bar, to allow compression testing of high strength metals at a strain rate of up to about 10 5 s –1 . All dimensions are minimized to reduce effects of dispersion and inertia, with specimens of the order of 1 mm diameter. Strain is calculated from the stress record and calibrated with high-speed photography. Particular attention has been paid to the accuracy of the technique, and errors arising from nonlinearity in the instrumentation, dispersion, frictional restraint and inertia have all been quantitatively assessed. Stress–strain results are presented of Ti 6A14V alloy, a high strength tungsten alloy, and pure copper.

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