scholarly journals 3D Physical Modelling Study of Shield-Strata Interaction under Roof Dynamic Loading Condition

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Shengli Yang ◽  
Hao Yue ◽  
Gaofeng Song ◽  
Junjie Wang ◽  
Yanyao Ma ◽  
...  
Keyword(s):  
Impact Loading ◽  
Loading Condition ◽  
Impact Load ◽  
Physical Modelling ◽  
Coal Face ◽  
Dynamic Impact ◽  
Immediate Roof ◽  
Cutting Height ◽  
The Impact ◽  
Dynamic Impact Loading

The dynamic hazards in the open face area caused by the impact load of the massive strong roof become increasingly severe with the increase in the cutting height of the longwall face and its depth of cover. Understanding the strata-shield interaction under the dynamic impact loading condition may relieve the dynamic hazards. In this paper, a 3D physical modelling platform is developed to study the interaction between the roof strata and the longwall shield under the dynamic impact load conditions. A steel plate is dropped to the coal face wall at a certain height above the immediate roof to simulate the free fall of the main roof and the dynamic impact loading environment. The occurrence of major roof falls is modelled at different height above the model and at different positions relative to the longwall faceline. The large-cutting-height and top-coal-caving mining methods are modelled in the study to include the nature of the immediate roof. The results show that the level of face and roof failures depends on the magnitude of the dynamic impact load. The position and height of the roof fall have an important influence to the stability of the roof and face. The pressures on the shield and the solid coal face are relieved for the top-coal-caving face as compared to the large-cutting-height face.

scholarly journals Comparative Shear Tests of Bolt Rods Under Static and Dynamic Loading

2020 ◽  
Vol 42 (2) ◽  
pp. 151-167
Author(s):  
Andrzej Pytlik
Keyword(s):  
Impact Loading ◽  
Load Capacity ◽  
Assessment Process ◽  
Shear Tests ◽  
Dynamic Impact ◽  
Similar Work ◽  
Mathematical Relationships ◽  
The Impact ◽  
Dynamic Impact Loading ◽  
Single Shear

AbstractThis article presents the methodology and results of single shear tests of bolt rods under dynamic impact loading generated by means of a drop hammer. Comparative analysis was also performed for bolt rod load capacity, stress and shear work under static and dynamic (impact) loading. The developed method of single shear testing of bolt rods under impact loading makes it possible to obtain repeatable test results concerning maximum bolt rod shearing force, shear stress and shear work values.Comparative shear tests of four types of bolt rods under static and impact loading showed that the APB-type bolt rods made of AP770 steel, which was characterised by having the highest strength, exhibited the greatest shear work. AM22-type bolt rods exhibited a very similar work value. Though the AM22-type bolt rods made of A500sh steel demonstrated lower strength than the APB-type bolts, as well as a smaller diameter and cross section, they dissipated the impact energy better thanks to their higher plasticity. This could indicate the direction of optimisation for bolt rods in order to increase their impact strength.Mathematical relationships were also formulated for selected tests, describing the real single shear courses F d =f(t) of bolts under impact loading. The obtained relationships could be applied in the load assessment process of bolt rods intended for use under roof caving, tremor and rock burst conditions.

scholarly journals Energy Absorbing Properties Analysis of Layers Structure of Titanium Alloy Ti6Al4V during Dynamic Impact Loading Tests

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7209
Author(s):  
Dominik Głowacki ◽  
Wojciech Moćko ◽  
Michał Marczak ◽  
Anna Głowacka ◽  
Cezary Kraśkiewicz
Keyword(s):  
Plastic Deformation ◽  
Titanium Alloy ◽  
Impact Loading ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Absorbed Energy ◽  
Dynamic Impact ◽  
Titanium Alloy Ti6al4v ◽  
The Impact ◽  
Dynamic Impact Loading

This paper presents the testing methodology of specimens made of layers of titanium alloy Ti6Al4V in dynamic impact loading conditions. Tests were carried out using a drop-weight impact tower. The test methodology allowed us to record parameters as displacement or force. Based on recorded data, force and absorbed energy curves during plastic deformation and sheet perforation were created. The characteristics of the fractures were also analyzed. The impact test simulation was carried out in the ABAQUS/Explicit environment. Results for one, two, and three layers of titanium alloy were compared. The increase in force required to initialize the damage and the absorbed energy during plastic deformation can be observed with an increase in the number of layers. The increase in absorbed energy is close to linear. In the simulation process, parameters such as Huber–Mises–Hencky stress value, equivalent plastic strain, temperature increase, and stress triaxiality were analyzed.

Testing Study on Damage Fracture Responses of Rock under Dynamic Impact Loading

2011 ◽  
Vol 255-260 ◽  
pp. 1815-1819 ◽  
Author(s):  
Ping Cao ◽  
Yi Xian Wang ◽  
Kai Wen Xia
Keyword(s):  
Crack Length ◽  
Impact Velocity ◽  
Impact Loading ◽  
Test Results ◽  
Dynamic Impact ◽  
Destructive Effect ◽  
Propagation Length ◽  
Break Area ◽  
The Impact ◽  
Dynamic Impact Loading

The dynamic impact loading has the destructive effect to the surrounding rock mass. Rock specimen such as rock plate was found to become invalid under dynamic impact loading. This paper presents brittle damage evolution law for dynamic impact damage of brittle rock based on low velocity (10m/s~40m/s) impact test, when a source of impact loading is applied to a rock plate specimen, damage cracks are developed from the source to the boundaries. This paper is concerned with the description and explanation of this phenomenon. The test results show that the cracks propagation length and break area are not arbitrary, but are influenced by the angle of dynamic impact loading. According to the test results, the study found that the scope of impact resistance optimization angle is about 30°~45°, and the cuspidal point of impact velocity is about 30m/s~35m/s; The crack length and the break area increase with the increase of the impact loading; When the break area decreases abruptly, the crack length increases suddenly, which shows that there was an obvious incubation period of crack forming, at first some pits appearing on the verge of the rock plate and the propagation rate of crack length and break area decreasing with the impact velocity increasing.

scholarly journals Failure characteristics of the isolated distal radius in response to dynamic impact loading

2011 ◽  
Vol 30 (6) ◽  
pp. 885-892 ◽  
Author(s):  
Timothy A. Burkhart ◽  
David M. Andrews ◽  
Cynthia E. Dunning
Keyword(s):  
Distal Radius ◽  
Impact Loading ◽  
Dynamic Impact ◽  
Failure Characteristics ◽  
Dynamic Impact Loading

FE investigation of a spirally slotted tube under axially compressive static and dynamic impact loading

2003 ◽  
Vol 8 (5) ◽  
pp. 421-432 ◽  
Author(s):  
K Kormi ◽  
V N Wijayathunga ◽  
D C Webb ◽  
S T S Al-Hassani
Keyword(s):  
Impact Loading ◽  
Dynamic Impact ◽  
Dynamic Impact Loading

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 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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