Rod Body Research Articles

Field pullout test and anchorage length calculation for external anchorage of GFRP anti-floating anchors

Field pullout destructive tests of GFRP anti-floating anchors with different anchorage lengths and different anchorage forms are carried out on inverted foundation slabs. Explore the damage patterns and anchorage mechanisms of bent anchors, straight anchors and GFRP anchors with different bending configurations in relation to the concrete foundation slab. Calculate the reasonable anchorage length of anti-floating anchors. The test results show that the straight line anchor rod and bent anchor rod are mainly damaged by sliding. The displacement of anchor rod body decreases with the increase of anchorage length, bending radius and bending length. The bending treatment of anchor rods reduces the pullout bearing capacity of GFRP anti-floating anchors, but it can significantly reduce the rod displacement. The longer the length of the bent section of the anchor rod body and the larger the bending radius, the lower the strength utilization of the anchor rod body. Through the calculation of the test results of different anchorage length anti-floating anchor rods, it is found that the current calculation method for the basic anchorage length of anchor rods is too conservative. For the actual anti-floating project, a more reasonable anchorage length calculation method is proposed, and the reasonable anchorage length of anchor rods for this test condition is 370–530 mm.

Research and simulation analysis of crack failure mechanism of conductor spacer bar in ±800 kV converter station

The cracking of the conductor spacer bar in a ±800 kV converter station was detected and simulated to study the cause of failure. By means of penetration detection, fracture macroscopic inspection and metallographic inspection, it can be found that there are some casting defects such as segregation, pinhole and intergranular micro-crack in the chuck microstructure of the spacer bar, and the fatigue fracture occurs under the action of alternating stress. Through the structural simulation analysis, it can be concluded that the spacer rod body and the joint of the chuck have a structural mutation, which causes stress concentration and leads to the fracture of the spacer rod. Finally, suggestions are put forward to improve the design, manufacture and installation process of spacer rods to prevent similar failures from happening again and ensure the safe operation of the power grid.

Design of Pressure Energy-Absorbing FRP Anchors and Numerical Analysis of Mechanical Properties

Conventional FRP anchor rods have low elongation and poor impact resistance, both of which do not meet the support requirements of rock burst roadways. Therefore, a pressure energy-absorbing FRP anchor rod composed of an FRP rod body, tray, energy-absorbing sleeve and round table nut was designed. Numerical simulations were carried out to study the mechanical properties of the FRP anchor rod in static tension and impact tension, and to compare its mechanical properties with those of conventional FRP anchor rods. The results show that the pressure energy-absorbing FRP anchor rod is stretched in four stages: the front-elastic stage, constant resistance to compression, the back-elastic stage and damage, with an additional constant resistance to compression stage compared with conventional FRP anchors. The elongation, energy absorption and impact resistance time of the pressure energy-absorbing FRP anchor rods are greater than those of conventional FRP anchor rods, and the mechanical properties of the pressure energy-absorbing FRP anchor rods are better than those of conventional FRP anchor rods. As the impact velocity increases, the energy absorption rate of the pressure energy-absorbing FRP anchor increases non-linearly. The impact energy and impact velocity have less influence on the breaking load, elongation and energy absorption of pressure energy-absorbing FRP anchor rods. The research results can provide a theoretical basis for the application and parameter design of the pressure energy-absorbing FRP anchor rod, and provide support for the safe and efficient mining of the mine.

Experimental Study on Mechanical Properties of Automatic Anchoring Preloaded Energy Absorbing Anchor Rods

In order to enhance the anti-impact mechanical properties of the roadway support system, an automatic anchoring pre-tightening energy absorbing anchor composed of rod body, tray, constant resistance energy absorber, energy-absorbing casing bulging block, pre-tightening force warning washer, and nut and anchorage force warning stopper was designed and developed for the special requirements of rock burst roadway support. The anchor can automatically judge the anchoring force and pre-tightening force of the anchor, and also has the functions of energy absorption and early warning. The static load tensile test and impact test are used to study the mechanical properties of the energy absorbing anchor, such as the displacement distance, energy absorption, and impact time, and they are then compared with the mechanical properties of the conventional anchor. It is concluded that under static load, the yielding distance of the energy absorbing anchor is 1.67 times that of conventional anchor. The absorbed energy is 1.61 times that of the conventional anchor. Under the impact load, the displacement distance of the energy absorbing anchor is 2.02 times that of the conventional anchor. The absorbed energy is 1.85 times that of the conventional anchor, and the anti-impact time is 1.47 times that of the conventional anchor. The energy absorbing anchor increases the constant resistance deformation stage of the energy absorber during the deformation process, so that the anchor has better deformation ability, energy absorption, and anti-impact ability than the conventional anchor, and it can thus effectively guide and control the release and transformation of surrounding rock deformation energy.

Numerical Simulation of Anchorage Performance of GFRP Bolt and Concrete

We conducted anchoring performance, stress distribution, and full-scale indoor pulling tests on glass-fiber-reinforced polymer (GFRP) bolts. The tests were conducted using finite element software while considering the multi-interface contact and BK criterion by using the cohesive element to simulate the contact relations between the anchor rod body and concrete and building an axial symmetry calculation model of the GRFP bolt and concrete. The results indicated that the finite element model based on cohesive element accurately represents the load–displacement relationship of the GFRP bolt and the distribution law of axial stress along the anchoring length. In addition, the simulation outcomes of the load–displacement relationship were in good agreement with the measured test values. Under the same load, the axial-force-transferred depth of the bolt body was identical regardless of the anchorage length. As anchoring length increases, the pull load on the bolt and the decay rate of axial stress along the anchoring length rises gradually. There is a critical value for the anchorage length of the bolt.

Numerical simulation research on bolt supports’ mechanical properties deformation in high-stress roadway

With the rapid development of domestic mining industry, it is necessary to consider the safety of the mine when mining. In order to improve the high stress environment and the frequent failure of bolts caused by the increase of excavation depth, in this experiment, FLAC3D is creatively proposed to establish the calculation model of bolt support roadway, analyze the basic geological environment and surrounding rock structure of the research area, and conduct the numerical simulation of the mechanical characteristics of bolt support deformation (BSD) in the high stress roadway (HSR). The basic geological environment and surrounding rock structure of the study area are analyzed, and FLAC3D is adopted for establishing a calculation model of the bolt-supported roadway, which can be used to simulate the axial and lateral forces of the bolt, and then determine the boundary conditions. It is found that the supporting bolt in the roadway needs to bear not only axial tension, but also transverse shear and bending. Based on the Winkler foundation beam principle, a calculation model of the bolt’s lateral bending force in the soft rock roadway is established, the lateral force characteristics of the bolt support are analyzed, the concept of “anchoring composite bearing body” is proposed, and the force characteristics of the bearing body are calculated. The research results show that in the HSR, the bolt mainly bears the combined forces of tensile and lateral bending; among them, the bolt’s axial force remains basically unchanged at the tail part near the pallet, and the bolt’s axial force at the end part deep into the rock mass decreases rapidly. The bending moment of the bolt is “wave-shaped” distributed along the length of the rod body in the positive direction and negative direction of the axis, and the comprehensive action of the axial tension and transverse bending of the bolt increases when the stress concentration increases. A smaller roadway radius will lead to longer bolts, denser arrangement and higher support strength.

Study of fatigue damage of pumping rods based on finite element simulation

This study performed in-depth analysis of onsite fatigue damage and stress distribution in pumping rods. Two aspects of fatigue damage were analyzed: macroscopic morphology and chemical properties. In terms of chemical properties, the crystalline phase composition and hardness of the product at fatigue damage were analyzed; the stress distribution was analyzed in term so of the rod-body stress and the connection-section stress. The cross-sectional characteristics of the fatigue crack expansion were summarized, and the types of fatigue fracture and the influencing factors of the pumping rod were obtained from these cross-sectional characteristics. Finally, modeling and stress analysis of the pumping rod were performed using SolidWorks and ABAQUS software. By comparing the stress cloud diagrams of different thread root shapes, the factors that cause fracture in the pumping rod and the locations of stress concentrations and dangerous cross-sections of the rod were determined. The highest principal stresses were obtained at the rod body near the upsetting flange of the pumping rod, and fatigue damage was the most likely to occur at this location. The shoulder of the unloading groove and the upsetting flange area were relatively safe because of their large cross-sectional area and less likelihood to produce stress concentrations. The results of this study can provide scientific guidance and reference for the development of pumping rods for efficient oil production and the improvement of oil and gas production efficiency.

Field test and numerical simulation of initial support effect of negative Poisson's ratio anchor cable under strong impact and vibration

Bolt/cable support technology is widely used in the rock engineering protection field to limit large deformations of surrounding rocks, improve the anti-explosion and anti-impact mechanical properties of engineering rock mass, and increase stability and safety. The underground protective cavern suffers significant damage due to the powerful impact produced by the explosion. This paper studies the macro static and dynamic mechanical properties of the negative Poisson's ratio (NPR) constant resistance and large deformation anchor cable. In addition, an in-situ blasting test scheme is proposed to simulate the approximate plane wave generated by a nuclear explosion in the field. Hence, the anti-explosion and anti-impact properties of the NPR anchor cable support system and failure mode of ternary structure (rod body, anchor body, and rock mass) under explosion influence can be obtained. Finally, numerical modeling is utilized to validate the NPR anchor cable support and PR anchor bolt support under the high vibration condition with the same blasting equivalent. The findings showed that the cavern supported by the NPR anchor cable revealed better overall stability under strong impact and vibration than the PR anchor bolt.

Stress Loss Analysis of a Geotechnical Prestressed Anchor under a Corrosive Environment in a Coastal Area

The corrosion of geotechnical prestressed anchor rods directly affects the safety of anchor structure engineering. To this end, an experimental device for measuring the stress loss of an anchor structure was developed, which was used to study the stress loss of a prestressed anchor structure under a corrosive environment, obtain the stress change curve of the anchor structure, and analyze the influence of a corrosive environment on the stress loss of a prestressed anchor structure in coastal areas. The final experimental results show that the degree of stress damage to bolts was determined by the cross effect of the environment and stress, and most of the stress damage occurred in the early stage after loading. The stress loss of the anchor structure resulted mainly from the bond degradation of the anchor section, and partly from the degradation of the elastic modulus of the rod body. Corrosion reduced the bonding force and bolt strength of the bolt–grouting body, and the influence of corrosion on the degradation of bonding strength of the bolt–grouting body was greater than that on the degradation of bolt strength. The maximum degree of axial stress corrosion influence on the rock–soil anchor was 11.6%. When the oxygen concentration was higher, the corrosion rate was greater. Therefore, accelerated corrosion indirectly increases the stress loss of anchor bolts.

Structural Optimization Design and Strength Test Research of Connecting Rod Assembly of High-Power Low-Speed Diesel Engine

The connecting rod assembly of a high-power low-speed diesel engine has high quality and high cost. If the connecting rod component is damaged, the whole machine may be paralyzed, resulting in serious economic losses and safety problems, so it is necessary to carry out strength analysis and structure optimization, reduce the failure rate, and increase its life. This paper takes the connecting rod of a low-speed diesel engine as the research object, builds the crank connecting rod mechanism model, and carries on the strength simulation analysis through professional simulation software. During this period, the accurate S-N curve of connecting rod material is obtained through a fatigue test, and the static strength test of the connecting rod assembly is carried out by an electro-hydraulic servo universal testing machine. The numerical modeling is validated based on the test results. Therefore, the influence of the structural parameters of the cross-section and the large end transition fillet on the stress of the connecting rod is analyzed. The results show that optimizing matching between the large end fillet of the connecting rod and the long diameter of the rod section not only reduces the mass but also improves the safety factor. After optimizing the structure of the connecting rod, the mass of the connecting rod is reduced by 5.85%, the maximum stress is reduced by 13.7%, and the safety factor is increased by 16.0%. In addition, due to the low-speed diesel engine connecting rod assembly weight is big, and the simulation computation efficiency is low, this paper by studying the influence of the cross-section parameters of the rod body and the large end transition fillet on the stress of the connecting rod, fitted the empirical formula calculating the maximum stress of connecting rod, for this model and similar type in the conceptual design, technology design provides a new analysis method, improved the efficiency of structural optimization and strength analysis of connecting rod assembly, filled the research gap of strength analysis and structural optimization of low-speed diesel engine connecting rod.

Anchoring eccentricity features and rectifying devices for resin grouted bolt/cable bolt

The anchoring eccentricity of the bolt and cable bolt is a common problem in geotechnical support engineering and affects the ability of the bolt and cable bolt to control the rock mass to a certain extent. This paper reports on numerical simulation and laboratory experiments conducted to clarify the effect of eccentricity on the anchoring quality of the bolt and cable bolt, and to establish an effective solution strategy. The results reveal that the anchoring eccentricity causes unbalanced stress distribution and the uncoordinated deformation of the resin layer, which results in higher stress and greater deformation of the resin layer at the near side of the rod body. Additionally, as the degree of anchoring eccentricity increases, the effect becomes more significant, and the resin layer of the anchoring system becomes more likely to undergo preferential failure locally, which weakens the load-bearing performance of the anchoring system. This paper develops an innovative bolt anchoring rectifying device (B-ARD) and cable bolt anchoring rectifying device (C-ARD) on the basis of the structural characteristics of the bolt and cable bolt to better ensure the anchoring effect of them. The working effects of these two devices were verified in detailed experiments and analysis. The experimental results show that the anchoring rectifying devices (ARD) improve and ensure the anchoring concentricity of the bolt and cable bolt, which will help improve the supporting performance of them. The paper provides a convenient and effective method for improving the anchoring concentricity of the bolt and cable bolt, and provides a concept and reference for technical research on improving the effect of roof bolting.

Experimental and Field Investigations on the Impact-Resistance Mechanical Properties of Negative Poisson’s Ratio Bolt/Cable

Abstract Dynamic impact tests of negative Poisson’s ratio (NPR) and rebar bolts under different impact wavelengths were carried out using a self-developed NPR bolt tensile impact test system. Additionally, a field anti-impact test using blasting was performed to simulate rockburst, and the field anti-impact characteristics of the NPR and conventional cable were compared and analysed. The experimental test results revealed that the peak impact force of the NPR and rebar bolts was inversely proportional to the wavelength. The NPR bolt underwent only constant resistance structural deformation, and the rod body did not break. The rebar bolt body fractured and necked. Under the same impact wavelength, the impact force and elongation of the two bolt types were proportional to the impact velocity. Compared with the greater peak impact force of the rebar bolt, the NPR bolt output structure deformation reduced the peak impact force. At the same impact velocity, as the wavelength increased, the impact force of the NPR bolt decreased rapidly, and the number of peaks also decreased. The impact force peak value of the rebar bolt was high, the impact force-time curve had multipeak characteristics, and no apparent rapid attenuation occurred. The field test results indicated that the NPR cable could produce slip deformation under the action of an explosion impact force to absorb the impact energy and that it had special mechanical properties to maintain a constant resistance. Under the same equivalent blasting impact energy, the conventional cable test section collapsed completely. The NPR cable test section was stable overall, verifying that the NPR cable had better impact-resistance mechanical properties than conventional cable. The research results provide a reliable basis for the effectiveness of NPR bolts/cables in preventing rockbursts.

Simulation test study on fatigue characteristics of circuit breaker insulation pull rod

The insulation pull rod is the main transmission mechanism of the circuit breaker. In addition to strong electrical performance, it should also have strong mechanical properties. Studying the dynamic characteristics and response insulation pull rods during opening and closing operation and exploring the changes in mechanical characteristics of insulation pull rods during multiple openings and closings are of great significance. In this paper, a 252kV GIS circuit breaker simulator is used to carry out an opening and closing impact fatigue test on an insulation pull rod. The strain signals of the insulation pull rod during the opening and closing stages are obtained. The strain distribution of insulation pulls rod and the influence of operation times on strain are analyzed. The results show that the force on the pull rod is uneven during operation. The force on the mechanism side and contact side is small, and the force on the rod body is large. Also, the pull rod is unstable and bent under pressure force. The impact response frequency is mainly distributed between 0∼1500Hz. With the increase in operation times, the low-frequency component of frequency response basically remains unchanged, while the high-frequency component decreases. After 10000 times opening and closing operations, there was no obvious mechanical loss on the pull rod, but the mechanical properties decreased. The research results can provide reference and basis for the formulation of the performance test method, and specifications of insulating rod materials.

Numerical analysis of the use of different lattice designs and materials for reciprocating engine connecting rods

Nowadays, the use of lattice structure designs in metallic parts to produce lightweight systems has gained importance owing to advances in additive manufacturing technology. On the other hand, vehicle manufacturers are constantly looking for new ways to reduce weight due to the depletion of fossil fuels, the demand for vehicles having higher performance, global warming and increasingly stringent emission standards. In this study, in order to reduce the weight of the internal combustion engine, different lattice designs were made in the connecting rods. Four different 2.5D lattice designs, hexagonal, octagonal, square and triangular, were created in reference connecting rod body. The dimension of the lattice designs was 10x10x12 mm with the wall thickness of 1.5 mm. The fatigue behaviors of the connecting rods as well as mechanical properties under static conditions were analyzed using finite element approach. Three different materials were used in the analyzes: AISI 4140, Inconel 718 and Ti6Al4V. As a result, it was seen that weight reduction of up to 15.75% was possible in the connecting rod thanks to the lattice designs and the maximum stresses were below the yield stresses of the materials. Moreover, connecting rods with lattice design had satisfactory safety factor values.

Experimental study on grouting mortar GFRP anchor rod pulling test

Owing to that the anchor rod is easy to be cut through and maintains good mechanical properties, it is widely used in reinforcement engineering. In this paper, the performance of grouted mortar GFRP anchor rod was studied through laboratory experiments in terms of the ultimate pull-out resistance, stress change, bolt deformation, and surrounding soil deformation. The results showed that the pull-out force suddenly decreased when it reached the ultimate pull-out load, the displacement of the anchor head increased sharply, and the axial force on the anchor rod body decreased exponentially with the distance from the pulling point. Through these regulars, it can provide a theoretical basis for the application of anchor rods in the actual foundation pit engineering.

METHOD FOR PUMPING ROD CONNECTION BY FRICTION WELDING

The current stage of development of the Russian oil industry is characterized by the transition of fields to a late stage of development, a decrease in the rate of oil production and an increase in the proportion of marginal wells, the main method of operation of which is traditionally the installation of a ucker rod pump (ISRP). One of the elements of the ISRP, leading to frequent failures, are the sucker rods. The most widespread are forged rods, in which the head is formed by high-temperature upsetting. The disadvantage of this method is the frequent misalignment in the process of planting the head on the rod body, which, when the rod string is operating, causes additional vibrations, leading to high bending cyclic loads in the fillet part and, as a consequence, failure and breakage of the rods. In addition, in the process of head upsetting, accompanied by high-temperature impacts, the microstructure of the metal changes, and the interface between the structures, as a rule, a fillet, is often a break point due to the emerging stress concentrator. The objective considered in the article is to improve the technology for manufacturing rods by eliminating misalignment of elements connected by friction welding and increasing the reliability of the welded joint by increasing the area of the surfaces to be welded. The objective posed is proposed to be solved by the fact that the method of manufacturing sucker rods, including rolling a bar, its machining, processing on a straightening-polishing machine, manufacturing a separate threaded head with a rolled thread on it and connecting it to the rod body by friction welding, implies that the threaded the head and end of the rod body are tapered; the protruding truncated conical end of the rod body is inserted into the tapered recess of the threaded head, while the length of the truncated conical end of the rod body should be less than the length of the tapered recess of the threaded head. This article discusses a method of connecting the rod body and the rod head by friction welding, which avoids the head upsetting process. This ensures the alignment of the sucker rod, which could not be achieved by head upsetting, which minimizes vibrations in the string and increases the overhaul period of the pumping equipment. In addition, the process of their manufacture is simplified, which leads to a decrease in the prime cost of the rods.

Study on Mechanical Characteristics of Energy-Absorbing and Anti-Scour Bolts

In order to improve the impact resistance and mechanical performance of anchor rods and satisfy the requirements for supporting rockburst roadways, the energy balance equation of the energy-absorbing support and roadway surrounding rock system is established. Moreover, to effectively prevent rockburst disasters, the energy criterion for roadway instability is derived. From the perspective of an energy-absorbing support, a yield-absorbing anti-shock anchor composed of a rod body, tray, constant resistance energy-absorbing device, and special-shaped nut is designed and developed; compared with ordinary anchor rods, this rod has stronger mechanical properties for resisting impact. Theoretical and numerical simulation studies show that the energy-absorbing device has a repeatable deformation failure mode and a constant yield force. The paper also presents the principle involved in the design of anti-shock bolt supports. The energy-absorbing support not only effectively guides and controls the release and conversion of impact energy but also consumes the impact energy in the buffering process of the anchor to ensure the stability of surrounding rock and support protection system. This study aims to provide reference for roadway support design and to improve rock bolts used in rockburst roadways.

Experimental Study of the Failure Mechanism of the Anchorage Interface under Different Surrounding Rock Strengths and Ambient Temperatures

In order to study the anchoring instability mechanism of surrounding rock in deep roadway, the failure mechanism of the bolt‐anchoring agent interface was studied by simulating different strength rock mass and ground temperature environment, using C20, C40, and C60 strength concrete and steel pipe to simulate different surrounding rock strength environments. Indoor pull‐out tests were carried out to study the pull‐out load displacement relationship, ultimate pull‐out force, residual anchoring force, the distribution law of axial stress and tangential stress along the bar, and the energy consumption value of drawing failure at 20, 50, and 70°C. The test results show that, with the decrease of surrounding rock strength or the increase of ambient temperature, the pull‐out force, residual anchoring force, and energy consumption value of anchorage interface gradually decrease; under different axial forces, the axial force distribution of the rod body decreases exponentially from the anchoring end to the opposite end; and the shear stress transfers to the deep part of the anchor body with the increase of the load. According to the failure phenomenon of the specimen, the failure modes of the bolt bolt‐anchorage agent interface can be divided into shear slip mode and shear expansion slip mode. The shear expansion slip formula of anchorage interface is derived. Using high‐strength and temperature‐resistant resin anchoring agent for comparative test, the rationality of the mechanism analysis is proved, which provides more clear guidance for the construction of anchor support.

Theory and full-scale simulation testing of the mechanical properties of anchors under a variable lateral pressure coefficient

The mechanical behavior of the lateral pressure coefficient (LPC) of the axial stress of the anchor rod is an important factor in roadway bolt support, especially in deep mining, where the variation of the LPC is larger. In this paper, an innovative mechanical model of bolt pulling is proposed in which the influence of the LPC is considered. When the LPC is changed, the variation of the axial force along the anchor rod body is expressed by the interface normal stress of the anchoring system. In addition, a full-scale test model with a 1:1 similarity ratio was developed in the laboratory and the influence of the LPC on the deformation and stress of the anchor rod under vertical and horizontal pressure was studied by using a 2.5-m fiber Bragg grating (FBG) force-measuring anchor rod. The results demonstrate that the axial force of the bolt shows the same increasing trend under various LPC values. The theoretical solution of the bolt axial force variation value accords with the experimental data. The theoretical calculation method can effectively predict the variation distribution of the bolt axial force under various LPC changes. Increasing the LPC of the surrounding rock can effectively reduce the axial force and the deformation of the bolt under the same pulling force. The support effect of the bolt can be improved by increasing the pressure of the anchor hole and increasing the interface friction coefficient between the anchoring agent and the surrounding rock during the construction of the bolt support.

A Study on the Fatigue Strength of a Low-Speed Diesel Engine Connecting Rod Made of 42CrMoA

In recent years, diesel engine is developing rapidly in the direction of high power and super long stroke, which requires higher strength of its key moving parts. Connecting rod is one of the key moving parts of diesel engine which is subjected to complex alternating load during the working process. This loading condition has a great influence on its structural strength and reliability. In the proposed study, the strength and fatigue of a low-speed diesel engine con-rod made of 42CrMoA are analyzed. The 3-D model of the con-rod assembly built in the proposed study. The stress distribution and deformation of the con-rod assembly under the maximum explosive pressure are presented and studied. In the present paper, fatigue safety factor of all parts of con-rod assembly under the maximum explosive pressure condition is checked. According to the results carried out from the proposed work, the corresponding alternating stress is 340MPa, while the fatigue limit of 42CrMo material is above 430-540MPa, which means that the con-rod parts work under the alternating stress far below the fatigue limit. The kirasushvili method is adopted in the present paper as the standard of safety factor evaluation of con-rod. According to the allowable safety factor table of kirasushvili method, the minimum safety factor of the big and small ends of the con-rod and rod body can meet the requirements without fatigue damage.