Peak Value Of Stress Research Articles

Research on the Control of Mining Instability and Disaster in Crisscross Roadways

In order to solve the disaster caused by the instability of spatial crisscross roadways under the action of leading abutment pressure in the coal mine face, combined with a specific engineering example, the methods of theoretical analysis, numerical simulation and field measurement are adopted to simulate and analyze the stress mutual disturbance intensity and influence range of spatial crisscross roadways. The evolution law of the plastic zone in spatial crisscross roadways under the influence of mining is explored, and the key to mining instability control is made clear. The roof of the return air roadway, the shoulder angle of the two sides and the coal wall are the key parts of surrounding rock stability control. On this basis, the cooperative control scheme of changing the roadway section shape (straight wall semicircular arch), supporting (anchor cable and “U” section steel) and modifying (grouting) is put forward. Through the field measurement, within the influence range of the return air roadway, the displacement deformation of the top and bottom is less than 200 mm, which achieves the goal of roadway safety and stability. Furthermore, based on the theory of “butterfly plastic zone”, the mechanical mechanism of the overall instability of the spatial crisscross roadway is revealed; that is, during the advance of the working face, the advance mining stress is superimposed with the surrounding rock stress of the crisscross roadway, and the peak value of the partial stress of the surrounding rock mass of the crisscross roadway is increased. The expansion of the plastic zone is intensified, and beyond 7 m from the crisscross position, the shoulder angle of the two sides and the leading plastic zone of the coal wall of the working face are connected with each other, which leads to the overall failure and instability of the surrounding rock between the roadways at the intersection.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ БИОМЕХАНИЧЕСКИХ ОСОБЕННОСТЕЙ ИМПЛАНТАТОВ, РАСПОЛОЖЕННЫХ ПОД НАКЛОНОМ, С РАЗЛИЧНЫМИ КОНФИГУРАЦИЯМИ ИМПЛАНТАТ – АБАТМЕНТ – ФИКСИРУЮЩИЙ ВИНТ

Subject. Various options for internal connections of implants, abutments and screws have biomechanical features that affect the success of implant treatment.
 All structures of the implant system, including the internal connection, are subjected to masticatory stress. The most favorable location of the implant is the position coaxial to the occlusal load. However, in many clinical cases, due to anatomical limitations and the presence of contraindications for osteoplastic surgery, it becomes necessary to install implants at an angle.
 At present, angular dental implants are being successfully introduced in dental practice - implants with an orthopedic platform located at an angle to the axis of the implant and a fixing screw shaft.
 A clear understanding of the features of stress distribution within various types of implant connections allows you to optimize planning and treatment, thereby reducing the risk of complications.
 Purpose. To study the features of stress distribution in implant systems with different designs of connections between an implant located at an angle, a screw and a suprastructure.
 Methods. A study of the stress-strain state of implant systems was carried out using the finite element analysis method when using straight and angled implants for dental orthopedic treatment using non-removable structures.
 Results. Peak stress values for models with a direct implant with different options for the direction of the occlusal load varied from 43 to 45 MPa. For the model with the use of an angled implant, the maximum stresses reached 70 MPa under a coaxial load, and 265 MPa under an angled load.
 Conclusions. It is shown that the different structure of the inner connection largely affects both the localization and the absolute value of the maximum stresses. In the case of a model with a straight implant, the maximum stress values are significantly lower than the fatigue failure limits; when considering a model with an angled implant, the maximum stress values and their localization are comparable to the fatigue strength value under certain load directions, which can potentially lead to damage in the internal connection of the implant.

Effect of Butt Gap on Stress Distribution and Carrying Capacity of X80 Pipeline Girth Weld.

An unstable assembly gap is detrimental to the formation and performance of the pipeline butt girth weld joint. Therefore, a numerical model of an 18.4 mm-thick X80 pipeline girth weld by a homogeneous body heat source was established to investigate the effect of the butt gap on the joint temperature and stress field, and carrying capacity. The accuracy of the simulation results was verified by measuring the welding thermal cycle with a thermocouple. The investigation results showed that the weld pool, heat-affected zone (HAZ) width, and maximum circumferential stress of the joint rose with the increase in the butt gap. The tensile stress unfavorable to the joint quality was mainly distributed in the weld metal and partial HAZ, and the distribution areas gradually expanded as the gap increased. The Von Mises stress peak value of the joint appeared in the order of 3 mm > 2 mm > 1 mm > 0 mm gap, reaching the maximum of 467.3 MPa (3 mm gap). This variation trend is directly related to the improvement in welding heat input with increasing butt gaps. The maximum Von Mises stress of the joint was positively correlated with the carrying capacity of the pipeline, which diminished as the butt gap enlarged. The pipeline carrying capacity reached 17.8 MPa for the joint with no butt gap, and dropped to 13.1 MPa for the joint with a 3 mm gap. The relationship between the carrying capacity (P) and butt gap (C) was described by P = −0.125C2 − 1.135C + 17.715, through which the pipeline carrying capacity with other butt gaps can be predicted.

Humeri under external load: Mechanical implications of differing bone curvature in American otter and honey badger

The mechanical properties of limb long bones are impacted by bone shape and especially curvature, which is therefore likely to be of adaptive value. We use finite element analysis to compare the mechanical properties of humeri of the closely related American otter and honey badger under external loads, and to analyze the significance of bone curvature. We simulate the effects generated by loads applied in directions that differ relative to the humeral longitudinal axes, and then compare the stress characteristics with a series of humerus-inspired abstracted curved structures with increasing ratio (C/R) of eccentricity C to radius of cross section R. The humeri of the two species differ in bone curvature, with C/R of 0.6201 and 0.8752, respectively. Our analysis shows that the peak and mean stress values found within the sampling line of bone models reach a minimum when the directions of loads are 105 ± 5°, and the humerus of the American otter always experienced lower stress values than those of the honey badger in the sampling line. An analysis of stress distribution in abstract curved structures showed the greatest reduction in stress when the direction of external load was equal or greater than 95°. This suggests that the variability of the direction of external loads is an important determinant of bone curvature, and should be accounted for when assessing load carrying capacity. This study provides a basis for biomechanics research and yields insight into the form-function relationship of nature’s structural elements within limbs. It potentially contributes to the design of biomimetic robots while also highlighting the functional significance of humeral bone curvature in mammals.

Residual Stress Properties of the Welded Thick Underwater Spherical Pressure Hull Based on Finite Element Analysis

Residual stress inevitably occurs at the weld in the process of manufacturing thick pressure hulls for manned submersibles, which affects the bearing capacity of the hull. In this study, an electron-beam-welded 32 mm-thick Ti-6Al-4V plate specimen is first tested, then the measured data of residual stress distribution is applied to validate the accuracy of the simulation method. Accordingly, three-dimensional numerical analysis on the equator welding by electron beam method of a 32 mm-thick Ti-6Al-4V spherical pressure hull is conducted to obtain the variation tendency of residual stress during the welding process. The results indicate that both compressive and tensile stresses exist along the weld path on the outer surface of the hull comparing to total tensile stresses on the inner surface. The maximum tensile stress that occurs on the inner surface approximates to 850 MPa, which is almost equivalent to the yield stress of the material. Based on the acceptance criterion that the peak value of residual stress due to weld technique is restricted to be less than 40% of the material yield strength in room temperature, post-weld heat treatment must be performed. Simulation on post-weld heat treatment for optimizing process parameters can be done by taking the results of welding simulation in the present study as input.

Strain-path-dependent stress–strain model for ultrahigh-performance concrete columns constrained by stirrups

The incorporation of steel fibers improves the microscopic ductility of ultrahigh-performance concrete (UHPC) materials, and their macroscopic ductility can also be improved by the restraining effect of composite stirrups. Two defects can be found in the stress–strain model of UHPC restrained by stirrups based on the design-oriented method: the restraint coefficient of the stirrup is the effective restraint coefficient at the peak state of the specimen, while the variation in the restraint stress of the stirrup with the axial–hoop strain relationship (strain path) is ignored. In this study, a strain-path-dependent stress–strain model for UHPC constrained by stirrups and fibers is proposed through a database with 10 sets of test results on UHPC columns, which alleviates the shortcomings of the design-oriented model. (1) On the basis of the axial–hoop strain relationship curve in the test results, an axial–hoop strain model of UHPC restrained by stirrups is established. (2) The variation in the restraint stress of the stirrup with strain path is considered. (3) On the basis of the stress–strain model of actively constrained concrete, an iterative method of subsections is adopted, and a UHPC stress–strain model restrained by stirrup based on strain path is established. Results show that the established axial–hoop strain equation can better predict the hoop strain of UHPC restrained by stirrups and steel fibers, the calculated value of peak stress of UHPC constrained by stirrups based on strain path is in good agreement with the test results, and the outcomes of the path-dependent stress–strain model are in better agreement with the experimental results than those of the design-oriented stress–strain model.

Experimental cyclic behaviour and constitutive modelling of hot-rolled titanium-clad bimetallic steel

Titanium-clad (TC) bimetallic steel exhibits distinct application potential in coastal building and ocean civil and infrastructure engineering due to its promising corrosion resistance and load-bearing capacity. However, understanding on seismic performance and relevant design methodology of TC bimetallic steel structure is still limited and insufficient to support further engineering application in seismic zones. This paper is intended to clarify the experimental cyclic behaviour and suitable constitutive models of hot-rolled TC bimetallic steel. To this end, a total of 19 cyclic coupon tests are conducted on TC bimetallic steel coupons with the raw surface and polished surface. The important mechanical properties, including the hysteretic stress–strain relationship, cyclic backbones, evolutionary law with regard to the cumulative plastic strain, are thoroughly recorded and compared. The cyclic backbones are fitted through the Ramberg-Osgood model. The influences of cyclic loading protocol type on cyclic behaviour are discussed. Based upon the experimental results, material-dependent parameters of Chaboche isotropic/kinematic hardening model and Giuffre-Menegotto-Pinto constitutive model are calibrated. The fitting performances of such two constitutive models are validated through comparison between experimental results and simulation results. All simulation stress–strain relations show a favourable agreement with the experimental counterparts. The relative errors between most simulation peak stress values and experimental peak stress values are lower than 5.0%. Moreover, the cyclic behaviour of TC bimetallic steel is compared with that of mild structural steels and stainless-clad (SC) bimetallic steel. The experimental results revealed herein and constitutive models calibrated in this paper can lay a solid foundation on subsequent numerical simulation.

Study on the Influence and Control of Stress Direction Deflection and Partial-Stress Boosting of Main Roadways Surrounding Rock and under the Influence of Multi-Seam Mining

A large coal pillar (usually more than 90 m) is generally left in place to ensure the stability of main roadway groups, due to its long service lifespan, which commonly also causes a significant loss of coal resources. The design of the width of the protective coal pillar and the control system of the surrounding rock are directly determined by the characteristics of the stress field and the damage mechanism under the influence of the mining activities. However, there are few studies on the effects of the partial-stress boosting and the direction deflection of the stress field on the failure evolution of the surrounding rock (especially in multi-seam mining). In this paper, theoretical analysis and numerical simulation are used to investigate the direction evolution of the maximum principal stress in front of the working face with malposition distances between the upper and lower working faces during the influence of double coal seams mining. Furthermore, a large-scale numerical model is used to study the deviatoric stress evolution of the surrounding rock and the propagation process of the plastic zone in the main roadway group with different widths of protective coal pillars. Then, an asymmetric cooperative anchoring classification method is proposed to strengthen the roadway support, depending on the critical area of the deviatoric stress in the roadway surrounding rock. The peak zone deflection of the deviatoric stress determines the evolution direction of the plastic area, and the peak value of the deviatoric stress presents a typical asymmetric stress boosting on both sides of the roadway. These findings are validated by the on-site ground pressure monitoring results and the practical failure modes of the surrounding rock.

Investigation of the effect of fly ash content on the bonding performance of CFRP-concrete interface in sulfate environment

The present study focuses on the investigation of the interfacial bond behavior of carbon fiber-reinforced polymer (CFRP)-concrete under dry–wet sulfate cycles by double-sided shear testing. Besides, the effects of fly ash content on the interfacial failure characteristics, interfacial debonding bearing capacity, CFRP strain distribution, and interfacial shear stress peak were analyzed. The interfacial debonding capacity, maximum CFRP strain, and peak value of interfacial shear stress of the CFRP-concrete interface decreased with increasing erosion time under the sulfate dry–wet cycle's action, according to the sulfate dry–wet cycle test results. The sulfate resistance of the CFRP-concrete interface increased after the addition of fly ash. However, the final decrease amplitude of interfacial debonding capacity, CFRP maximum strain, and maximum interfacial shear stress all reduced as the fly ash content increased. The effective bond length of the interface gradually increased with increasing erosion time; however, the change in fly ash content had little effect on the effective bond length, and the final effective bond length of the samples with different fly ash content was the same. Moreover, the CFRP-concrete interfacial bearing capacity model under the sulfate dry–wet cycle was established by introducing sulfate's comprehensive influence coefficient and considering fly ash content's influence. In conclusion, the comparative analysis of the prediction model and test results revealed that the prediction model could well reflect the degradation law of interfacial debonding bearing capacity with sulfate attack time.

Dynamic pressure analysis of novel interpositional knee spacer implants in 3D-printed human knee models

Alternative treatment methods for knee osteoarthritis (OA) are in demand, to delay the young (< 50 Years) patient’s need for osteotomy or knee replacement. Novel interpositional knee spacers shape based on statistical shape model (SSM) approach and made of polyurethane (PU) were developed to present a minimally invasive method to treat medial OA in the knee. The implant should be supposed to reduce peak strains and pain, restore the stability of the knee, correct the malalignment of a varus knee and improve joint function and gait. Firstly, the spacers were tested in artificial knee models. It is assumed that by application of a spacer, a significant reduction in stress values and a significant increase in the contact area in the medial compartment of the knee will be registered. Biomechanical analysis of the effect of novel interpositional knee spacer implants on pressure distribution in 3D-printed knee model replicas: the primary purpose was the medial joint contact stress-related biomechanics. A secondary purpose was a better understanding of medial/lateral redistribution of joint loading. Six 3D printed knee models were reproduced from cadaveric leg computed tomography. Each of four spacer implants was tested in each knee geometry under realistic arthrokinematic dynamic loading conditions, to examine the pressure distribution in the knee joint. All spacers showed reduced mean stress values by 84–88% and peak stress values by 524–704% in the medial knee joint compartment compared to the non-spacer test condition. The contact area was enlarged by 462–627% as a result of the inserted spacers. Concerning the appreciable contact stress reduction and enlargement of the contact area in the medial knee joint compartment, the premises are in place for testing the implants directly on human knee cadavers to gain further insights into a possible tool for treating medial knee osteoarthritis.

Comparison of the debonding force of metal, glass and polyethylene Fiber reinforced composite retainers: Mechanical and finite element analyses

The studies evaluating the efficiency of fiber reinforce composite (FRC) retainers are few and contradictory. This study aimed to compare the debonding force of metal, glass FRC (GFRC) and polyethylene FRC (PFRC) retainers, assess the interactions between the materials and forces, and pattern of load distribution by finite element analysis (FEA). Forty-eight sound lower incisors were collected and randomly assigned to 3 groups (n=8; each sample included 2 teeth). Next, 15mm of the three retainers (multi-stranded metal wire, GFRC, and PFRC) were bonded to the lingual surface of the teeth and debonding force was measured by a universal testing machine. For FEA, 3D models were designed. The data related to geometrical models and material properties were transferred to ANSYS software. A 187-Newton load was applied to the incisal edge of the two centrals. Then different parameters were assessed. The three groups were compared by one-way Anova and Tukey's test. Type one error was considered to be 0.05. The debonding force decreased in the order: Metal (143.71N)≥GFRC (108.29N)>PFRC (45.08N). The difference between metal retainer and GFRC was not significant. In contrast, PFRC group showed significantly lower debonding force compared to other groups (P<0.05). FEA showed stress peak value in metal-composite interface. Maximum total deformation was noted in central, followed by lateral and canine. Glass-FRC can serve as an alternative to metal retainers as the difference in debonding force is not significant. However, the difficulty of repairing or replacing the Glass-FRC should be taken into account given the large number of failure in the interproximal dental area.

Solid phase transformation effects on stress and strain in the thick plate EH40 welded butt joint

To accurately predict welding-induced residual stress and strain of high strength steel thick plate EH40 butt joint in single-pass full penetration laser welding, a complete solid phase transformation model according to the actual weld microstructure was proposed through material constitutive development. At the same time, the Case 1 considering the traditional thermo-elastoplastic were used as comparative study. The simulation calculation results and experimental results of each phase content were compared and verified. The stress and strain distribution of welded joints and the evolution mechanism of nodes in three zone including fusion zone, heat-affected zone and base metal were deeply studied and compared. The results indicated that the solid phase transformation had an obvious effect on the peak and distribution of longitudinal, transverse, normal and equivalent residual stress, as well as the stress gradient at the junction of heat-affected zone and BM. It increased the peak value of longitudinal residual compressive stress from –103 MPa to –768 MPa, with an increase of 645.6%. The stress gradient at the junction of heat-affected zone and base metal was up to 1299 MPa. The state distribution of longitudinal and transverse stress in the weld and its vicinity were completely opposite to the Case 1. The peak value of transverse plastic compressive strain increased from –0.059 to –0.111, with an increase of 88.1%. The fusion zone and heat-affected zone of the plastic strain in welded joints were more easily observed. It was found that martensitic transformation was the main reason for the obvious difference of stress and strain distribution and the evolution mechanism of stress and strain in the later stage of cooling stage.

Biomechanics optimisation of the laminoplasty groove size and position: A numerical study

BackgroundThis study is focused on the opening technique of the cervical vertebrae during laminoplasty which serves to substantially reduce the most severe adverse effects of the simple resection of posterior vertebral elements. This computational study aims to clarify by an optimisation approach what shape and position upon the lamina the groove should have. MethodsThe computational model was developed in the computational software COMSOL Multiphysics 5.6a based on a computer tomography data obtained from the C4 vertebra. For finding the optimal minimum or maximum of a function (surface), optimisation algorithms are developed following the Nelder-Mead algorithm. ResultsThe reaction-opening force increases with a decreasing groove radius and an increasing position from the vertebra body. The created area increases with a decreasing groove radius and a decreasing position. As the opening happens mostly only above the groove, the opening area increases only in this location. Moreover, the von Mises stress peak value is almost twice as large as in the case of maximization of the opening area, which might result in breaking of the lamina as the thickness of the lamina would be reduced to its minimum. ConclusionThe groove radius and position can affect the opening force and the opening area in case of double door laminoplasty. The opening force is highly influenced by the groove position and radius. The best position for placing the groove is in the middle of the lamina and the radius of the groove should be as large as possible.

The effect of oscillating capping TIG welding on residual stresses of 2219-T8 butt joint

Oscillating capping TIG welding (OCW) was proved valid to increase joint properties of the 2219-T8 aluminium alloy. Its effects on the welding residual stresses (WRS) should also be clarified. In this study, the residual stresses of the 2219-T8 plate butt welding of capping welding (CW) + OCW and CW technologies were investigated by simulation and experiment. The results showed that OCW reduced the peak value of the tensile longitudinal residual stress (LRS) in the joints. And its mechanism was discussed. Differences in bead geometry, heat input and number of welding passes of OCW affected LRS. Among them, wide bead geometry resulted in lower residual plastic strain, thus decreasing LRS peak value in a great manner.

Study on stress evolution law and control technology of roadway formed by roof cutting during crossing overlying remained coal pillar

The application of roadway formed automatically by roof cutting (RFARC) technology in the working face under the goaf of close distance coal seam greatly improves the mining rate of resources. However, the existence of overlying remained coal pillar (ORCP) makes the stress environment more complex and greatly increases the difficulty of stability control of RFARC. Hence, the 9101 Working face of Xiashanmao Coal Mine was taking as engineering background. In accordance with the principle of RFARC, the process of crossing the ORCP is introduced, and the calculation formula of the bending deformation of roof is proposed. Through numerical analysis and field test, the stress evolution law of stope and RFARC in the process of crossing ORCP is analyzed. The results show that in the process of crossing the ORCP, the peak stress value of the solid coal side of the RFARC increases continuously, whereas, the stress values of the roof and floor and the gob-side are small. The stress value and caving step distance of roof cutting side of working face are less than those without roof cutting. The stress of stope and RFARC tends to be stable when the working face is lagged 80 m. The combined supporting measures composed of constant resistance and large deformation (CRLD) anchor cable, hydraulic prop and unit support can effectively control the deformation of RFARC. This work provides an effective and economical method to non-pillar mining affected by ORCP in close distance coal seam.

Mesoscale Finite Element Modeling of Mortar under Sulfate Attack.

In this paper, a 2D mesoscale finite element (FE) numerical model of mortar, considering the influence of the ITZ, was proposed to evaluate the corrosion of mortar in sodium sulfate. On the mesoscale, the corroded mortar was regarded as a three-phase composite material composed of sand, cement paste, and an interface transition zone (ITZ). Firstly, the volume fractions and mechanical parameters (elastic modulus, Poisson’s ratio, and strength) of the mesoscale phases were obtained. Then, the cement paste and the ITZ were combined to form an equivalent matrix by homogenization methods, and the calibrated constitutive relations of the equivalent matrix were established. Subsequently, a two-dimensional (2D) random circular aggregate (RCA) model and a 2D random polygonal aggregate (RPA) model of corroded mortar were established using the random aggregate model. The failure process of corroded mortar specimens under uniaxial compression was simulated by the mesoscale FE numerical model. Comparing the simulation results with the measured stress–strain curves of the uniaxial compression test, it was found that the simulation results of the 2D RP model were closer to the experimental results than those of the 2D RC model. Meanwhile, the numerical simulation results were in good agreement with the experimental results, and the error values of peak stress between the simulation results and the measured results were within 7%, which showed that the 2D mesoscale FE model could accurately predict the results of a uniaxial compression test of a mortar specimen under sulfate attack.

Prediction of Residual Stress Distribution in NM450TP Wear-Resistant Steel Welded Joints

This study developed a thermo-metallurgical-mechanical simulation method to calculate the temperature field and residual stress distribution in the NM450TP wear-resistant steel welded joints. During the simulation, the solid-state phase transformation and softening effect of NM450TP wear-resistant steel was considered. The simulation results were compared with the experimental results, which verified the feasibility of this method. The influences of solid-state phase transformation and softening effect on the welding residual stress distribution were discussed. The numerical simulation results showed that the solid-state phase transformation had a more significant effect on the magnitude and distribution of the longitudinal residual stress than that of the transverse residual stress. The softening effect had a significant influence on the peak value of the longitudinal residual stress and had little influence on the transverse residual stress. Comparing the numerical simulation results with the experimental results, it could be seen that the calculation results of the welding residual stress were in the best agreement with the experimental measurement results when the solid-state transformation and softening effects were considered at the same time.

Study on Roof Presplitting Mechanism and Deformation Control of Reused Roadway in Compound Soft Rock by Roof Presplitting Approach

Based on the compound soft rock movement law, the rock formation structural features for a mining roadway were examined. Furthermore, the presplitting, extension, and coalescence mechanism of rock formation and the engineering needs for reusing an abandoned underground roadway were studied. According to engineering and geological conditions, an analytic expression of the inertial force, the moment of inertia, and the vertical stress acting on the breakage are obtained by constructing a structural mechanical model of the overlying strata. The transfixion law, the tensile shear failure characteristics, the release rate in the fracture expansion process of presplitting fissures, and the evolution law of the plastic zone in reused roadway surrounding rock on conditions of 0 m, 0.5 m, 1 m, 1.5 m, and 2 m fissure intervals are analyzed by creating a three-dimensional numerical model. The stress distribution and deformation laws of the roadway under mining disturbance are obtained. The results show that when the fissure interval is 1 m, the peak value of the horizontal stress reaches 10~12 MPa, and the stress concentration factor is 1.8~2.2, which promotes fracture expansion and transfixion and controls plastic damage development on both sides of a fracture. The elastic strain energy of the reused roadway is reduced to 32.7% of the peak value. The deformation of the roof is coordinated and deformed. It is helpful for the compound soft rock strata to fall and plug the area, forming a stable composite reused roadway surrounding the rock structure. A 1 m presplitting fissure interval is adopted for field testing, and the monitoring results show that 0~3.0 m behind the mining face, presplitting fissures will be connected and begin to fall. Moreover, 3.0~6.0 m behind the mining face, compound soft rock strata will fall and plug the area fully, forming a reused roadway structure. Severe deformation of reused roadway was reduced, and the stability of surrounding rock was improved by implementing the roof presplitting approach.

Dynamic Response of the Steel Plate Under the Impact of High-Speed Coal Projectile

The coal-rock projectiles induced by gas explosions in coal mines have a strong destructive effect on mine facilities and equipment, which are mostly made of steel. The LS-DYNA is used to simulate the process of coal projectile striking the steel plate. The results show that during the failure process, the morphological change of the projectile consists of three stages including plastic deformation, partial crushing, and complete crushing, and the steel plate pits at the impact point. The duration of the stress peak value of the steel plate increases as the impact velocity increases. The farther away from the center point, the smaller the stress peak value is, and the shorter the duration is. When the impact velocity is 100 m/s and 300 m/s, the axial velocity curve at the impact point of the projectile is pulsating. When the impact velocity reaches 500 m/s, the axial velocity of the projectile rapidly increases and then tends to be stable. As the impact velocity increases, the energy absorbed by the steel plate increases, and the rate of increase also increases. However, the proportion between the absorbed energy of the steel plate and the initial kinetic energy of the projectile decreases. The projectile conversion energy of the 1 mm steel plate is slightly larger than that of 1.5 mm and 2 mm steel plates, and the energy absorbed by the steel plate decreases with the increase in thickness of the steel plate. When the thickness of the steel plate is more than 2 mm, the thickness of the steel plate has little effect. The results of the study have a direct sense for the antiknock design of coal mine facilities and equipment.

Study on Multisize Effect of Mining Influence of Advance Speed in Steeply Inclined Extrathick Coal Seam

Abstract Aiming at the multisize effect of mining in steeply inclined extrathick coal seam, taking the fully mechanized top-coal caving mining in B3+6 coal seam +425 level in the south of Wudong coal mine as the background, this paper studies the mining stress evolution law under the influence of advancing speed, analyzes the mechanical characteristics of coal samples under the mining action of steeply inclined extrathick coal seam, and completes the multisize effect study of mining in steeply inclined extrathick coal seam. The results show that the stress change theory of fully mechanized top-coal caving mining in steeply inclined seam is deduced, and the loading and unloading stress of fully mechanized top-coal caving mining is positively correlated with the advancing speed of the working face. The numerical simulation experiment shows that the ideal advancing condition increases with the advancing speed of the working face, and the cyclic loading and unloading amplitude under the mining stress path increases, the cyclic times decrease, the main influence area increases, and the acting time decreases. The peak value of mining stress, the width of the plastic zone, and its elastic energy under high-speed propulsion are obviously larger. A method of mechanical behavior analysis of coal samples is proposed, which takes the mining stress path of the numerical simulation experiment as the indoor scale loading and unloading stress path of coal samples. The average compressive strength of coal samples under the mining stress path increases with the advancing speed of the working face, and the damage degree of coal samples increases with the advancing speed of different stress paths. The input strain energy of coal cyclic loading and unloading increases with the increase in the advancing speed of the stress path. The input strain energy of the coal sample has obvious linear relationship with the advancing speed of different paths. The research results can be used for reference in the study of multisize effect of mining impact of advancing speed.