scholarly journals Simulation and Experimental Study on the Discontinuous Dynamic Impact on Unidirectional Confined Coal-Rock Damage

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Tao Wang ◽  
Hongbao Zhao ◽  
Yang Li ◽  
Huan Zhang ◽  
Nansong Ju
Keyword(s):  
Impact Velocity ◽  
Static Load ◽  
Impact Load ◽  
Cumulative Effect ◽  
Dynamic Impact ◽  
Loading Test ◽  
Microcrack Propagation ◽  
Impact Impulse ◽  
Coal Rock ◽  
Pendulum Impact

The deformation and the damage characteristics of coal and rock under different restraint static load and different impact velocity were studied with the FEM software LS-DYNA. Based on this, the influence of impact load on the damage of coal rock under one-dimensional constraint condition was studied by using the self-developed constrained pendulum impact dynamic loading test device and ultrasonic testing device. The results show that the deformation of coal and rock increases with the increase of impact velocity and decreases firstly and then remains constant with the increase of constraint static load; when the constraint static load exceeds the compression strength, the displacement increases rapidly and the coal collapses at a strike; the damage quantity of coal and rock has a cumulative effect, and the damage quantity increases with the increase of impact number; when the constraint static load is identical, the increase of impulse contributes to microcrack propagation, and the damage quantity of coal and rock accelerates with the increase of single impact impulse; when the impulse is identical, the constraint static load restrains the microcrack propagation, and the damage quantity of coal and rock decelerates with the increase of constraint static load; the complete damage quantity range of coal and rock is 0.65∼0.75. In order to fully destroy the coal and rock, if the single horizontal impulse is greater, the number of shocks needed is less; if the constrained static load is greater, the more impact times are needed.

scholarly journals Influence of Incremental Impact on the Damage of Coal-Rock under Unidirectional Constraint

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Hongbao Zhao ◽  
Huan Zhang ◽  
Jinyu Li ◽  
Nansong Ju ◽  
Zhijie Wen
Keyword(s):  
Impact Load ◽  
Damage Model ◽  
Impact Resistance ◽  
Cumulative Damage ◽  
Axial Pressure ◽  
Loading Test ◽  
Damage Degree ◽  
Coal Rock ◽  
The Impact ◽  
Pendulum Impact

Taking the briquette sample as research object, the influence of the incremental impulse (momentum) on the damage of coal-rock under different uniaxial axial pressure was studied by using the self-developed pendulum impact dynamic loading test device, cooperating with the ultrasonic detection device. Meanwhile, the influence of constant impulse on the damage degree of coal-rock was compared. The results show that the damage degree of coal-rock increases with the increase of the impulse, and the damage fitting curve is upward concave, indicating that the coal sample tends to accelerating failure. Moreover, with the increase of axial pressure, the variation gradient of the damage degree of coal-rock tends to moderate and the cumulative damage degree decreases under the same impulse, and the impact resistance of coal-rock increases. When the impulse is constant, the damage degree of coal-rock increases with the number of impact, and the damage curve is upward convex, indicating that coal-rock has a tendency to slow down the damage. The cumulative damage degree of coal-rock decreases with the increase of axial pressure, and the number of impact needed to destroy coal-rock is increased. In addition, the damage model of coal-rock was proposed, and the criterion of coal-rock damage was obtained, which shows that the damage degree of coal-rock increases with the increase of impact load and decreases with the increase of static axial load.

scholarly journals Load Characteristics in Taylor Impact Test on Projectiles with Various Nose Shapes

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 713
Author(s):  
Jun-Cheng Li ◽  
Gang Chen ◽  
Feng-Lei Huang ◽  
Yong-Gang Lu
Keyword(s):  
Impact Velocity ◽  
Impact Analysis ◽  
Impact Test ◽  
Impact Load ◽  
Loading Test ◽  
Impact Theory ◽  
Nose Shape ◽  
Taylor Impact ◽  
Taylor Impact Test ◽  
The Impact

This study focused on the impact load produced by a projectile and its potential application in the Taylor impact test. Taylor impact tests were designed and carried out for projectiles with four types of nose shapes, and the impact deformation characteristics and variation of the impact load as a function of the nose shape and impact velocity were studied. The overall high g loading experienced by the projectile body during the impact was discussed, and based on classical Taylor impact theory, impact analysis models for the various nose-shape projectiles were established and the causes of the different impact load pulse shapes were analyzed. This study reveals that the nose shape has a significant effect on the impact load waveform and pulse duration characteristics, while the impact velocity primarily affects the peak value of the impact load. Thus, the loading of specific impact environments could be regulated by the projectile nose shape design and impact velocity control, and the impact load could be simulated. Research results support the assumption that the Taylor impact test can be applied to high g loading test.

scholarly journals Cutting Mechanical Study of Pick Cutting Coal Seams with Coal and Rock Interface

2021 ◽  
Author(s):  
Chenxu Luo ◽  
Junbei Qaio
Keyword(s):  
Compressive Strength ◽  
Coal Seam ◽  
Mechanical Model ◽  
Impact Load ◽  
Strength Analysis ◽  
Strength Condition ◽  
Rock Interface ◽  
Coal Rock ◽  
Rotary Cutting ◽  
Mining Coal

Abstract Shearer provide an effect solution for mining coal, and the cutting performance of pick largely accouts for the ability of a shearer and mining performance. We conducted pick cutting coal experiments in different seam forms on the coal and rock cutting teasted. According to the rotary cutting mechanical model of single pick cutting coal seam, combined with the strength condition of coal seam and coal-rock interface, the rotary cutting mechanical model of pick cutting coal seam with coal-rock interface is established. The stress strain and strength condition of the area in and around the interface are analyzed based on the coal-rock interface crushing theory, which provides basis for further research on the cutting mechanical model of single pick crossing the coal-rock interface. According to the analysis on the ampulitude domain, the phenomenon that force increment between the pick cutting rock and uniform coal seam linearly increases with the increase of compressive strength difference between coal seam and coal-rock interface, and the load fluctuation keep a positive correlation with the compressive strength. Analysis on the signals of the pick cutting coal seam with coal and rock interface at different conditions shows that some basic properties of the cutting load changes over times. In addition, the coal seam with coal-rock interface appears larger impact load and other time-domain characteristics.

scholarly journals Numerical Simulation of Dynamic Response and Evaluation of Flexural Damage of RC Columns under Horizontal Impact Load

2021 ◽  
Vol 11 (23) ◽  
pp. 11223
Author(s):  
Bin Hu ◽  
Jian Cai ◽  
Jiabin Ye
Keyword(s):  
Static Load ◽  
Impact Load ◽  
Bending Moment ◽  
Internal Force ◽  
Displacement Curve ◽  
Fe Model ◽  
Damage State ◽  
Rc Columns ◽  
Equivalent Static Load ◽  
The Impact

By using the ABAQUS finite element (FE) model, which has been verified by experiments, the deformation and internal force changes of RC columns during the impact process are investigated, and a parametric analysis is conducted under different impact kinetic energies Ek. According to the development path of the bottom bending moment-column top displacement curve under impact, the member is in a slight damage state when the curve rebounds before reaching the peak and in a moderate or severe damage state when the curve exceeds the peak, in which case the specific damage state of the member needs to be determined by examining whether there is a secondary descending stage in the curve. Accordingly, a qualitative method for evaluating the bending failure of RC column members under impact is obtained. In addition, the damage state of RC columns under impact can also be quantitatively evaluated by the ratio of the equivalent static load Feq and the ultimate static load-bearing capacity Fsu.

Microstructure and Impact Load Performance of Friction Stir Welded Joint of AZ31B Magnesium Alloy

2020 ◽  
Vol 866 ◽  
pp. 54-62
Author(s):  
Hong Feng Wang ◽  
Sheng Rong Liu ◽  
Xiao Le Ge ◽  
Jia Fei Pu ◽  
Lei Bao ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Magnesium Alloy ◽  
Impact Load ◽  
Base Material ◽  
Welding Parameters ◽  
Loading Test ◽  
Az31b Magnesium Alloy ◽  
Friction Stir ◽  
Joint Area ◽  
The Impact

10mm thickness AZ31B magnesium alloy was used as the friction stir welding object in this study. Different welding joints were obtained by setting different friction stir welding parameters. Metallographic analysis and impact loading test were carried out on the joint area. The experiment results show that (i) when the rotational speed of the stirring head is 600rpm and the welding speed is 120mm/min, the microstructure of the joint has the characteristics of compactness, thinning, and large-area twinning, which is beneficial to improve the plasticity of the joint area; (ii) the impact load of the joint is the highest, but lower than that of the base material, which is 95.5% of the base material; (iii) the fracture of impact specimen presents ductile fracture.

Quasi-Static Lap Shear and Dynamic Impact of High Performance VHB™ Acrylic Foam and Adhesive Transfer Tape Bonded Aluminum Joints Subjected to Environmental Degradation

2005 ◽  
Author(s):  
Manoj Anakapalli ◽  
P. Raju Mantena ◽  
Ahmed Al-Ostaz ◽  
S. Jimmy Hwang
Keyword(s):  
High Performance ◽  
Shear Failure ◽  
Electrochemical Impedance ◽  
Impact Load ◽  
Bond Quality ◽  
Dynamic Impact ◽  
Impulse Frequency ◽  
Lap Shear ◽  
Failure Loads ◽  
The Impact

A range of 3M™ VHB™ acrylic foam tapes and high performance adhesive transfer tapes were used to bond 1” × 1/8″ (25.4 mm × 3.175 mm) aluminum 2024 T-4 adherends in single-lap joint (SLJ) and three-point end-notched flexure (ENF) configurations. Three types of 0.045” thick double-coated acrylic foam tapes: Foam 41, 50 and 52 (firm, soft and softer), and three types of adhesive transfer tapes: Adhesives 69, 73 and 85 (0.005”, 0.01” and 0.005” thick, respectively) were used for this study. The samples were subjected to two types of aggressive environments simulating extreme service conditions: freeze-thaw cycling from 10°F to 50°F at 6 cycles per day (ASTM C666 Procedure A) for 21 days with samples immersed in water; heat-cool cycling (with 90% of maximum recommended temperature by the manufacturer of both acrylic foam and adhesive transfer tapes attained at 70% relative humidity) and 3 cycles per day for 21 days. Initially the impulse-frequency response vibration and electrochemical impedance spectroscopy (EIS) techniques were used for monitoring bond quality nondestructively and selecting the best out of 250 fabricated samples. After obtaining baseline data, the specimens were subjected to quasi-static lap-shear and dynamic impact loading to compare their lap-shear failure loads and shear energy along with the impact load and energy absorbed.

scholarly journals Comparison of Lifetime of the PVD Coatings in Laboratory Dynamic Impact Test and Industrial Fine Blanking Process

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2154
Author(s):  
Josef Daniel ◽  
Radek Žemlička ◽  
Jan Grossman ◽  
Andreas Lümkemann ◽  
Peter Tapp ◽  
...  
Keyword(s):  
Impact Test ◽  
Impact Load ◽  
Protective Coatings ◽  
Impact Testing ◽  
Pvd Coatings ◽  
Dynamic Impact ◽  
Repeated Impact ◽  
Suitable Alternative ◽  
Fine Blanking ◽  
Blanking Process

Protective hard PVD coatings are used to improve the endurance of the tools exposed to repeated impact load, e.g., fine blanking punches. During the fine blanking process, a coated punch repeatedly impacts sheet metal. Thus, the coating which protects the punch surface is exposed to the dynamic impact load. On the other hand, the laboratory method of dynamic impact testing is well known and used for the development and optimization of protective coatings. This paper is focused on the comparison of tool life and lifetime of the industrial prepared PVD coatings exposed to repeated dynamic impact load in the industrial fine blanking process and the laboratory dynamic impact testing. Three different types of protective coatings were tested and the results were discussed. It was shown that the lifetime of coated specimens in both the fine blanking and the dynamic impact processes was influenced by similar mechanical properties of the protective coatings. The qualitative comparison shows that the lifetime obtained by the dynamic impact test was the same as the lifetime obtained by the industrial fine blanking process. The laboratory impact test appears to be a suitable alternative for the optimisation and development of protective PVD coatings for punches used in the industrial fine blanking process.

scholarly journals Analysis of load of a powered roof support’s hydraulic leg

2018 ◽  
Vol 71 ◽  
pp. 00002 ◽  
Author(s):  
Dawid Szurgacz ◽  
Jarosław Brodny
Keyword(s):  
Rock Mass ◽  
Hydraulic System ◽  
Impact Load ◽  
Load Condition ◽  
Dynamic Impact ◽  
Registration System ◽  
Free Falling ◽  
The Impact ◽  
Impact Mass ◽  
Roof Support

The main purpose of the powered roof support is to protect headings from the impact of the rock mass. The result of such impact is static and dynamic load impacting the support section, which is carried by its construction. The basic elements of the construction of the support are hydraulic legs, whose task is to ensure adequate strength of its setting. Particularly in the case of dynamic impact of the rock mass, these legs are exposed to a very unfavourable load condition. Therefore, it is necessary to conduct tests to determine the parameters of operation for this type of loads. The paper presents the results of tests on the hydraulic leg subjected to impact load with free falling impact mass. The purpose of the research was to determine the parameters of the leg's operation, i.e. the time periods of pressure in the space under the piston and other elements of the hydraulic system. The tests were conducted in compliance with designed methodology and included innovative registration system. The obtained results clearly indicate the correctness of the adopted assumptions. According to the authors, the results should be applied during selection and operation of a powered roof support.

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