133 results about "Tension stress" patented technology

The invention relates to the technical field of pumped storage power station water diversion systems, and discloses a method and device for determining a pressure pipeline reinforcement ultra-high performance concrete lining structure. The method comprises the steps that internal pressure information, radius information and lining thickness information of a target water channel, the design tensile strength of a tensile steel bar, the tensile stress borne by ultra-high performance concrete and the lining section area per unit length are obtained; calculating circumferential stress information of the target water channel based on the internal pressure information and the radius information; based on the circumferential stress information and the lining thickness information, the tensile force resultant force of the lining section in unit length is determined; determining the total sectional area of the tensile steel bars based on the tensile resultant force of the section of the lining in unit length, the designed tensile strength of the tensile steel bars, the tensile stress of the ultra-high performance concrete and the section area of the lining in unit length; determining the number of to-be-assembled reinforcements based on the total sectional area of the tensile reinforcements; and the pressure pipeline reinforcement ultra-high performance concrete lining structure is determined based on the number of the to-be-assembled steel bars and a preset steel bar arrangement rule.

This invention relates to a double-sided welding process for U-rib plates used in the construction of orthogonal steel structure bridges or the reinforcement of dangerous bridges. The process includes: welding the inner weld of the U-rib plate in the patch section using a small, dedicated U-rib welding robot via gas metal arc welding (GMAW); removing the welding wire feeder and the GMAW robot from the opening of the next adjacent patch section; cleaning the root of the outer weld of the patch section; welding the outer joint of the U-rib plate using GMAW; and using ultrasonic impact to impact the outer weld of the patch section to reduce welding tensile stress. This invention addresses the problem of double-sided welding of the inner and outer joints of the U-rib patch section in orthogonal steel structure bridges, offering both economic and social benefits.

The utility model relates to the technical field of geotechnical engineering and railway construction, and particularly discloses a vibration reduction and deformation resistance steel sheet pile for deep foundation pit engineering close to an existing railway line, which comprises a steel sheet pile, a vertical load-bearing steel bar, a connecting component, a vibration isolation and reduction interlayer and a protective steel plate. By adopting a composite structure form of steel sheet piles, vibration isolation and reduction interlayers and vertical load-bearing steel bars, the structure reinforcing function and the vibration isolation function are organically combined, and a brand-new supporting structure system is formed; the vertical stressed steel bars are matched with the vibration isolation and reduction interlayer and the damping spring shock absorbers, the vertical stressed steel bars mainly share tensile stress to improve the stress state, the vibration isolation and reduction interlayer mainly absorbs vibration energy to weaken vibration transmission, and the comprehensive performance of the steel sheet pile is remarkably improved through the combined action of the vibration isolation and reduction interlayer and the damping spring shock absorbers; meanwhile, according to the scheme, by optimizing arrangement of the vertical load-bearing steel bars, selection of vibration isolation and reduction materials and arrangement of connecting components, the whole structure has the good reinforcing effect and vibration reduction performance, and construction convenience and economical efficiency are taken into consideration.

The utility model discloses an anti-fracture lifting table transmission shaft, which relates to the technical field of lifting tables, and comprises a movable component and a fixed component, the bottom end of the movable component and the top end of the fixed component are installed in a sliding manner, and the fixed component comprises a fixed shaft. Meanwhile, a plurality of reinforcing ribs are evenly distributed on the inner wall of the movable shaft in the axial direction, the bending resistance and torsional rigidity of the movable shaft are enhanced, when the transmission shaft is vibrated or impacted, the high-damping filler can absorb energy, reduce the vibration amplitude and improve the stability of the transmission shaft, the movable shaft meets the overall strength requirement, meanwhile, the weight of the shaft is reduced, and the rotational inertia is reduced; and meanwhile, the nitriding layer is additionally arranged on the outer wall of the movable shaft, so that the hardness and the wear resistance of the shaft surface can be improved, residual compressive stress can be generated on the surface, part of tensile stress generated during working is counteracted, the fatigue life of the transmission shaft is further prolonged, and the fracture resistance of the transmission shaft is further improved.

This invention discloses a ribbed prestressed concrete composite floor slab and its design method, relating to the field of prefabricated building structure design technology. The method includes calculating the total bearing capacity of prestressed steel bars required in the primary load-bearing direction and the total bearing capacity of ordinary steel bars required in the secondary load-bearing direction, based on the span and load parameters of the target floor slab. The reserved extension lengths of the two types of steel bars are determined according to the precast portion and the total thickness of the composite. The types, spacing, tensile stresses, and precise curve trajectory coordinates of the prestressed steel bars within the precast concrete are designed in detail, and the types, spacing, and arrangement coordinates of the ordinary steel bars are also designed. An internal reinforcement space model of the precast portion is generated based on the coordinate parameters of all steel bars, and a three-dimensional structural model of the ribbed precast template is generated by combining the geometric boundaries. This method achieves refined reinforcement design and digital expression of manufacturing information.

This invention belongs to the field of bridge construction, specifically a method for ensuring bridge bearings meet the requirements of tension displacement and seismic consolidation. The method involves filling the relative sliding areas inside the bridge bearing with a medium, which is a soft, elastic material. Before filling, the medium is encapsulated in a medium membrane. During bridge tensioning, if the tensioning speed is less than the design value, the medium deforms, releasing the tension stress at the relative sliding areas inside the bridge bearing. During an earthquake, if the displacement speed exceeds the design value, the medium remains unchanged, thus consolidating the bridge bearing with the bridge deck and piers as a unified whole to jointly withstand seismic forces. This invention, by filling the bridge bearing with a medium, enables the bridge bearing to function normally during bridge erection and under special conditions such as earthquakes, thus improving the functionality of bridge bearings.

The application relates to a kind of high strain rate under fiber concrete material dynamic axial tensile performance test method, comprising: setting Hopkinson tensile rod device, using the verified Hopkinson tensile rod device to pulse wave is applied to test piece, and the deformation of resistance strain gauge is collected;The deformation is converted into voltage signal, for calculating the strain of resistance strain gauge and the average compressive stress of test piece;Based on strain and average compressive stress, determine the dynamic tensile stress-strain relationship of test piece, according to the dynamic tensile stress-strain relationship of test piece, the dynamic tensile stress time history and dynamic axial strain time history are point by point corresponding pairing on time axis, and the dynamic tensile stress-strain curve of test piece under high strain rate is obtained.The application can make the performance test of fiber concrete and other materials under high strain rate more easily realized, provide the basis for the dynamic performance characterization of material, help the application and popularization of high-performance materials under extreme working conditions such as explosion impact.

This invention discloses a method for strength calculation of a detachable support device. The method includes: obtaining the supporting force and radial force per unit length of the detachable support device; calculating the bending moment and horizontal tensile force at the connecting section based on the supporting force and the radial force per unit length; establishing the static moment equilibrium equation of the connecting section and determining the neutral axis position of the connecting section through iterative calculation; calculating the moment of inertia of the connecting section based on the neutral axis position; and calculating the maximum tensile stress borne by the fastener based on the moment of inertia, the bending moment, and the horizontal tensile force, so as to perform strength verification of the connecting section. This invention derives the strength verification formula and judgment criteria for key stress sections in detachable support structures, which is convenient for engineering technicians and ensures operational safety.

A method for optimizing forming and performance of a friction stir welding head through pre-welding rolling belongs to the technical field of metal material welding processing, and comprises the following steps: before friction stir welding, a friction stir rolling welding tool is used for carrying out rolling treatment along a to-be-welded welding line path, so that a to-be-welded position is subjected to plastic deformation in advance; residual compressive stress and high-density lattice defects are introduced into the welded joint, so that residual tensile stress generated in formal welding can be effectively counteracted, residual deformation of the welded joint and the structure is reduced, and the mechanical property of the joint can be improved by promoting grain refinement of the weld joint and re-precipitation of a strengthening phase; therefore, synchronous optimization of forming and performance of the friction stir welding joint is realized. Compared with an existing welding method, the method is simple in process, high in repeatability, capable of achieving shape property common control of the large thin-wall welding structure and suitable for high-quality welding manufacturing in the fields of aerospace, rail transit, automobiles, ships and the like.

The present invention relates to safe strengthened glass with a low-variation-amplitude tensile stress region, a preparation method and an application. The change curve of the compressive stress and tensile stress of the strengthened glass meets a specific function relationship; within the range of 0.45-0.85 mm, the stress distribution meets the following condition: the stress curve is within the following Log-PI function range, the upper limit Fmax of the compressive stress meets the formula (1): Fmax=b+(2*a / PI)*(w / (4*(x−c){circumflex over ( )}2+w{circumflex over ( )}2)), and the lower limit Fmin of the compressive stress meets the formula (2): Fmin=b+(2*a / PI)*(w / (4*(x−c){circumflex over ( )}2+w{circumflex over ( )}2)); or the chemically strengthened glass comprises a first stress region and a second stress region, wherein the stress range of a first subregion in the first stress region includes that the minimum value of the stress difference value of the glass thickness t in the region of 0-10 micrometers is greater than 1 Mpa; and the pressure difference value of the second stress region is smaller than that of the first stress region. The deep compressive stress region of the strengthened glass has relatively high stress, and the tensile stress region has very-low-degree variation amplitude, so that the glass has excellent mechanical strength, very high stability and very high safety.

The invention discloses a supporting method and structure for constructing an arched anchoring ring based on a rectangular section roadway, and belongs to the technical field of roadway surrounding rock supporting. 2, differential design of anchor rods: according to the stress characteristics of different parts of the roadway, anchor rods with different lengths are designed; thirdly, the arched anchoring rings are arranged; fourthly, anchor rods are installed, and prestress is applied; and 5, monitoring and adjusting: mounting a surrounding rock deformation and stress monitoring instrument on the surface of the roadway. The method has the beneficial effects that an arched self-bearing structure can be formed, the stress state of the rectangular roadway is improved, continuous and coordinated arched anchoring rings are constructed in roadway surrounding rocks through different-length anchor rod combinations, the load of a top plate is effectively transmitted to stable rock stratums on the two sides and the deep part, the overall stability of the surrounding rocks is improved, and the service life of the surrounding rocks is prolonged. The arched anchoring ring can optimize roadway section stress distribution, reduce tension stress concentration in the middle of the top plate and reduce the risk of shear failure of two sides.

The invention discloses a transformer box edge machining method and machining equipment, a whole steel plate is adopted for welding, the size of the whole steel plate in the width direction is large, the rigidity of the whole steel plate and box edge square steel have asymmetry, the box edge square steel is a narrow strip, and the bending resistance and torsional rigidity of the box edge square steel are relatively low. And the rigidity of the whole steel plate in the plane is great. When a welding seam is cooled and contracted, huge contractility tries to pull the steel plate to deform, but the rigidity of the steel plate is enough to resist the local contractility, so that the steel plate cannot pull the whole steel plate. In addition, deformation is suppressed, which does not mean that the contractile force disappears. The force can be stored in the welding part in the form of residual stress. In other words, the materials in the welding seam area bear huge tensile stress, the surrounding steel plates bear pressure stress, a balance state is achieved on the whole, and therefore visible bending or torsional deformation is avoided macroscopically, and the leveling difficulty can be lowered.

The present application relates to a kind of spot I type nugget fracture failure constitutive model construction method, belong to the fracture mechanics and numerical simulation method technical field of spot welding joint.The technical scheme of the present application is: the parameter construction of constitutive model is carried out, parameter is directly used for spot welding joint related finite element simulation;Spot welding joint is bonded with uniaxial tensile fixture, and the tensile experiment of nugget fracture form is completed under tensile testing machine and the load-displacement curve and maximum load are recorded;Finite element model is constructed and tensile displacement is calculated;Convert and correct stress-displacement curve in combination with measured nugget area, solve maximum tensile stress and fracture energy, parameter is substituted into model and the precision of replacement connection mode is verified.The beneficial effects of the present application are: the accurate construction of spot I type nugget fracture failure constitutive model is realized, which provides standardized mechanical parameter support for spot welding joint structure reliability design and welding process optimization, and significantly improves the accuracy and engineering application value of finite element simulation.

The utility model discloses a corrosion-resistant concrete pole with high crack resistance, which is formed by pouring corrosion-resistant concrete on a framework, a plurality of GFRP (glass fiber reinforced plastic) rib rings are arranged on the framework, a plurality of GFRP ribs are distributed at intervals along the length direction of the framework, and each GFRP rib ring is respectively bound on the framework through stirrups. The GFRP rib ring forms active constraint on concrete in the framework, and when the electric pole is subjected to external force, the GFRP rib ring bears circumferential tensile stress through a shear stress transfer mechanism, so that the compressive strength and the crack resistance of the electric pole are remarkably improved; and the GFRP bars have high elasticity modulus, crack width development of the concrete pole can be displayed in a limited mode, corrosion can be reduced, and the service life can be prolonged.

The present application belongs to the technical field of corrosion simulation of coating, and discloses a method for simulating corrosion test of plated steel in extremely cold atmospheric environment, comprising the following steps: (a) pretreatment of the sample to be tested: acetone degreasing, alcohol cleaning, and pasting adhesive tape on both ends and one side of the sample; (b) stress loading on the sample to be tested by using a three-point bending device; (c) simulation of corrosion test: depositing corrosion medium NaHSO3 solution on the surface of the sample, and then placing the stress loading device and the sample in a high-low temperature alternating damp-heat test chamber, and performing the test according to "room temperature-constant low temperature-room temperature wetting-room temperature drying", each cycle being 12-24 h, and the total test time being 84 h-840 h. The present application can realize mechanical and chemical effects under stress and multi-environment factor coupling during the process of tensile stress under different loads, and conforms to the corrosion failure characteristics of structural parts in actual service.

The utility model relates to the technical field of foundation pit supporting, and discloses an adjustable foundation pit anchor cable supporting rib structure suitable for a narrow space, which comprises a supporting rib main body used for supporting the side wall of a foundation pit; the anchor cable is connected to the supporting rib main body and extends to an anchoring point on the side wall of the foundation pit; the adjustable connecting assembly is arranged between the supporting rib body and the anchor cable and used for adjusting the relative position and tension between the supporting rib body and the anchor cable, the vertical position of an adjusting nut can be adjusted through cooperation of a connecting plate and a toothed plate, and the connecting plate is hinged to a ball of the adjusting nut. And the adjusting nut can automatically rotate to a proper position according to the traction stress, so that the traction angle of the anchor cable can be adjusted, the tension stress and the tension angle of the anchor cable can be easily and conveniently adjusted, and the adjustment is simple and convenient.

The present application relates to the technical field of steel rolling, and discloses a cold-rolled strip tension setting value acquisition method, device and equipment. The method comprises the following steps: obtaining rolling process parameters; setting an entry tension stress condition, an exit tension stress condition and a roll gap front slip zone proportion critical value based on the rolling process parameters; calculating the roll gap front slip zone proportion under the entry tension stress condition and the exit tension stress condition; judging whether the roll gap front slip zone proportion reaches a preset roll gap front slip zone proportion critical value; and when the preset roll gap front slip zone proportion critical value is reached, calculating the entry tension and the exit tension according to the entry tension stress and the exit tension stress output by iteration update, respectively. The present application is based on the quantitative relationship between the cold-rolled strip rolling entry, exit tension stress and roll gap front slip zone proportion, and the entry and exit tension stresses are continuously iteratively optimized to adjust the roll gap front slip zone proportion to the critical value. The iterative calculation is stable and fast, and is used for entry and exit tension presetting calculation, so that the roll gap does not slip during the rolling process, and the production stability is improved.

Main claim: Figures 1-2-3 show a binding device for tying reinforcing steel. The invention relates to a wire binding device with a motor drive. The binding wire is guided in the sheathing tube (1b) to the binding jaws (1c) and inserted into the eyelet (1c). The binding jaws are rotatably mounted (Fig. 1, 7) and are held under tension by a return spring (8). The pair of wheels (16) feeds the binding wire to the tying arm. Due to the rotatable mounting of the tying arm, it is deflected by approximately 20 degrees from the central axis, thereby plastically deforming the binding wire. A wire loop is formed. This loop can be enlarged by further wire feed to adapt to the requirements. This ensures a secure tying of the concrete bars. Simultaneously, a parallel wire guide is created. It is therefore possible to twist the reinforcing steel.I am not aware of any binding device that can form a wire loop of the required dimensions through normal handling. The invention is based on the objective of creating a binding device that can deform the binding wire into a wire loop without a complex mechanical device. The device is characterized by the fact that the binding wire It can be processed according to DIN 1045 regulations. Reinforced concrete is a composite material with the following division of labor: Compressive stresses are absorbed by the concrete, while tensile stresses are absorbed by the steel. Accordingly, steel reinforcement must be present wherever tensile stresses occur within the structure. This reinforcement must be carefully installed. It consists, for example, of straight bars and bent sections that must be securely connected to prevent displacement, ensuring that the structural calculations remain valid and that the concrete remains stable during the pouring process.

The application discloses a spherical hinge support node for a wood structure column foot and belongs to the technical field of wood structure buildings. The structure comprises a foundation stone, a vibration isolation sleeve A, a rigid column hub and a vibration isolation sleeve B, the foundation stone is provided with a blind hole A, the vibration isolation sleeve A and the rigid column hub are arranged in the blind hole A, and the rigid column hub is located on the inner side of the vibration isolation sleeve A, the rigid column hub is provided with a component mounting hole, and the vibration isolation sleeve B is arranged in the component mounting hole. The column foot of the wood structure is kept under full-section compression in the whole service life of the structure, the material performance is fully utilized, the stress concentration of the column foot caused by local compression and the tensile stress of the surrounding area are fundamentally eliminated, the local compression damage of the lower end of the column foot is prevented, and the safety and durability of the wood structure column foot are improved. In the radial direction of the column foot, the column foot is limited through the rigid column hub, the vibration isolation sleeve A and the blind hole A on the foundation stone, and the risk that the column foot slides out of the foundation stone is eliminated. The application has the advantages of simple assembly, time saving, high efficiency and the like.

The invention discloses a finite element analysis method for reducing concrete tensile stress through a transverse joint grouting measure. Comprising the following steps that a concrete gravity dam discharge dam section and foundation model is established, finite element software is imported, and numerical simulation parameters are set; grid division is carried out on the model, and grids in the runner are encrypted; constraint and load are applied, elastic support is applied to the side surface of the dam section, and transverse joint grouting measures are simulated; and solving the model by using finite element software, and evaluating stress results of an inlet section, a gate slot section and a breast wall section of the discharge dam section. The device has the advantages that elastic support is applied to the side surface of the dam section, and the effect of transverse joint grouting measures on the dam section is simulated. Quantitative calculation results show that transverse joint grouting measures can increase the lateral rigidity of the dam section, improve the stress state of concrete and reduce the tensile stress of the concrete in the flow channel, so that the use amount of steel bars in the flow channel is reduced, and the method is safe, economical and convenient to construct.

This invention provides a method for improving joint cracking in inner liner layers, comprising: measuring at least one shrinkage rate value during the production process of the inner liner layer; and adjusting the conveying control parameters of the inner liner layer production line based on the measured shrinkage rate value. In this embodiment, the method for improving joint cracking in inner liner layers quantifies the shrinkage state during the production process of the inner liner layer and adjusts conveying control parameters such as the tension of the floating roller and the speed of the cooling roller based on the shrinkage rate measurement results. This ensures that the inner liner layer completes sufficient stress release and achieves stable conveying on the production line, fundamentally eliminating the cause of joint cracking due to continued shrinkage of the inner liner layer material. By controlling the tension and speed parameters of the conveying process, it ensures that the inner liner layer reaches a dimensionally stable state before entering the molding process, thereby avoiding tensile stress at the joint caused by subsequent material shrinkage. This solves the technical problem of frequent joint cracking of the inner liner layer during the molding of the tire blank in related technologies.

The invention discloses an adjustable wall-connecting scaffold and a using method. The adjustable wall-connecting scaffold comprises a scaffold body and a plurality of wall-connecting devices distributed on the scaffold body. The wall connecting device comprises a scaffold connecting unit and a wall connecting unit. The scaffold connecting unit is connected between an outer vertical rod and an inner vertical rod of a scaffold and applies pre-tightening force. The wall connecting unit is connected with the scaffold connecting unit and the building body, and the length of the wall connecting unit can be adjusted so that the distance between the scaffold and the building body can be adjusted. By arranging the adjusting mechanism, bidirectional adjustment of the distance between the inner vertical rod and the outer vertical rod of the scaffold and the distance between the scaffold and a building body is achieved, the problem that connection is difficult due to construction errors is effectively solved, meanwhile, inward tensile stress can be actively applied to the outer vertical rod and the inner vertical rod, and the overall rigidity of the scaffold is enhanced; and when the scaffold body horizontally deforms, the scaffold body is pulled back and corrected through the adjusting mechanism and is matched with a reasonable mounting position in the middle of a scaffold node, so that the superiority of the stress performance is ensured.

This invention discloses a stability analysis method for the bearing arch of a large-span tunnel based on compressive and tensile safety factors, belonging to the field of tunnel and underground engineering construction data analysis technology. The method includes the following steps: obtaining the tunnel geometry, surrounding rock mechanical strength, ground stress, and support parameters; simplifying the bearing arch formed by anchor spraying reinforcement into an arched beam elastically fixed to the sidewalls at both ends; determining the plastic loosening zone of the roof slab through numerical simulation, and using its self-weight as the main vertical load; calculating the internal forces and edge normal stresses of key sections of the bearing arch using structural mechanics, and classifying them into compressive and tensile stresses accordingly; calculating the compressive and tensile safety factors of each section based on the natural strength parameters of the surrounding rock, and using the minimum value as a quantitative index for evaluating the overall stability of the bearing arch. This invention establishes a quantitative mechanical model of the bearing arch, realizing accurate and convenient assessment of the safety of the anchor spraying support structure of the roof slab of ultra-large span tunnels.

The invention discloses a large-span tunnel bearing arch stability analysis method based on compressive and tensile safety coefficients, and relates to the technical field of tunnel and underground engineering construction data analysis, and the method comprises the following steps: obtaining cavern geometry, surrounding rock mechanical strength, ground stress and support parameters; a bearing arch formed by anchoring and shotcreting reinforcement is simplified into an arched beam with the two ends elastically and fixedly connected to the side walls; determining a plastic loosening area of the top plate through numerical simulation, and taking the self weight as a main vertical load; calculating key section internal force and edge normal stress of the bearing arch by using structural mechanics, and dividing the internal force and the edge normal stress into pressure stress and tensile stress; based on the natural strength parameters of the surrounding rock, the compression-resistant and tensile safety coefficients of all the sections are calculated, and the minimum value is used as a quantitative index for evaluating the overall stability of the bearing arch. According to the method, the quantitative mechanical model of the bearing arch is established, and the safety of the ultra-large-span tunnel roof anchor-shotcrete supporting structure is accurately and conveniently evaluated.

The invention discloses a lining construction monitoring method for an extra-large-section underground excavation station meeting TBM station crossing, and belongs to the technical field of TBM construction safety monitoring. The method comprises the steps that when a lining section is constructed, a strain sensor is pre-buried, and data are collected to obtain a time-strain curve of concrete; establishing a time-varying mechanical property prediction model based on the data of the constructed lining section; a TBM system planned station crossing moment and a corresponding new form removal lining section are obtained, and a finite element model is established to simulate TBM load movement to obtain a main tensile stress extreme value; calculating a stress compensation value of the new form stripping lining section based on the time-strain curve, and superposing the stress compensation value and the main tensile stress extreme value to obtain a predicted total stress; the TBM passage plan is decided by comparing the predicted total stress and the predicted tensile strength, real-time monitoring of the stress state of the early-age lining section, time-varying performance prediction and load coupling analysis are achieved, and the technical blank of quantitative safety evaluation of the concrete structure in TBM dynamic station crossing is filled.

A glass-ceramic article having one or more crystalline phases; a residual glass phase; a compressive stress layer extending from a first surface to a depth of compression (DOC); a maximum central tension greater than 70 MPa; a stored tensile energy greater than 22 J / m2; a fracture toughness greater than 1.0 MPa√m; and a haze less than 0.2.

The invention discloses a rolling auxiliary method for reducing residual stress of an electric arc additive manufacturing aluminum alloy component, and belongs to the technical field of metal additive manufacturing. The method is carried out on line in the arc layer-by-layer deposition process, and comprises the following steps: monitoring the temperature of a just deposited aluminum alloy cladding layer in real time; when the temperature of the cladding layer is reduced to a preset rolling temperature window of 50-250 DEG C, a rolling device is immediately used for applying mechanical pressure to the top surface of the cladding layer for rolling; next layer continues to be deposited, and recrystallization of the rolling area of the previous layer is induced through follow-up thermal circulation; and the process is repeated until the component is finished. According to the method, a specific warm window is selected for rolling, the problems of high-temperature roller sticking and low-temperature cracking are avoided, the thermally induced tensile stress is directly counteracted by utilizing mechanical pressure, and grains are refined in combination with subsequent thermal circulation, so that effective control over residual stress and deformation, equiaxed transformation of a thick columnar crystal structure and improvement of internal density are synchronously achieved.

The invention provides a method for determining the detonation speed of an explosive used for tunnel caving blasting by considering the influence of ground stress, and belongs to the technical field of blasting engineering and rock mass mechanics. Comprising the steps of obtaining rock mass mechanical parameters, blasting parameters and crustal stress data; establishing a stress analysis model based on ground stress and a blasting design drawing; establishing a crustal stress redistribution model caused by a cut cavity in the model, calculating radial pressure stress generated by crustal stress redistribution among the caving holes, and drawing a polar coordinate graph; establishing a collapse inter-hole explosion stress superposition model, and calculating circumferential tensile stress generated by explosion at the central points of the two holes; and based on the dynamic tensile strength and stress state of the rock, establishing a strength criterion for forming the inter-hole through crack, and deducing and solving the minimum explosive detonation speed required by the criterion. The blasting joint forming quality is effectively improved, back break is controlled, surrounding rock damage is reduced, and the safety, economical efficiency and reliability of blasting engineering are improved.

The application discloses a physical simulation device of superposition of extrusion and tensile stress field, comprising a power device, a sand box bin and an automatic sand distribution device, wherein the automatic sand distribution device is located above the sand box bin, and the power device is arranged at the bottom side of the sand box bin, and further discloses an experimental method of the physical simulation device of superposition of extrusion and tensile stress field. The application is suitable for the technical field of structural geology and can simulate the structural development of strata under the background of extrusion or tensile stress by adopting the power device to control the sand box to perform extrusion and tensile movement. The problem of frictional resistance of sand layer is solved by using the synchronously active side plate of the sand box. Through forward modeling and reproduction, the data collection of the development process of deep structure and the influence on shallow structure under the action of multi-period extrusion and tensile stress field is realized, and the application has universal applicability and operability.