Bolt Stress Research Articles

Analysis of Additional Load and Fatigue Life of Preloaded Bolts in a Flange Joint Considering a Bolt Bending Load

The influence of the working load on the dynamic loading of the bolt was investigated in our study for two cases of flange joints. The analytical calculation according to the Verein Deutscher Ingenieure (VDI) 2230 recommendation and the numerical analysis using the finite element method (FEM) were performed for a model of a four-bolt joint. To verify the FEM analysis, the forces in the bolts were measured during preloading and during the application of the working load on the test rig. Based on the analytical and numerical results, the influence of the working load application point on the bolt load and its fatigue life was analysed for different cases. Comparison of the results shows that the analytical method overestimates the additional bolt stresses at low working load, mainly due to the extremely large fraction of bending stress. As the working load increases, the differences between the two methods decrease, but only for the reason that the analytical method can only linearly scale the overestimated results at lower working load, and FEM analysis, on the other hand, shows a progressive increase of the additional stress in the bolt at higher working loads due to the spreading of the flange. It is also shown that a high washer significantly increases the fatigue life of the bolt for two reasons: (i) a high washer reduces the additional stress in the bolt, and (ii) the high washer shifts the critical fatigue point from the thread area to the transition of the bolt shank to the head.

Research of the Surrounding Rock Deformation Control Technology in Roadway under Multiple Excavations and Mining

To effectively control the large surrounding rock deformation of the mining roadway under multiple excavations and mining in Wangcun coal mine, the field investigation, numerical simulation, field test, and monitoring were conducted, and the characteristics of stress and deformation evolution of the surrounding rock under the influence of multiple excavations and mining were analyzed; then the collaborative supporting technology of high prestressed bolt and short anchor cables was proposed in this study. The results show the following: (1) under the influence of multiple excavations and mining, the peak vertical stress of the typical air-return roadway reaches 23 MPa, and the deformation increases by about 2.8 times after the mining of adjacent panel. (2) The principle of the roadway support under the influence of multiple excavations and mining in Wangcun coal mine is determined; from the perspective of prestress, we can conclude that the active support of short anchor cables is better than that of long anchor cables. (3) Based on the results of the field monitoring, the bolt stress can be divided into four stages: the loss stage of prestress, the sudden-decrease stage of the roof periodic weighting, the decrease stage of advanced support, and the rapid-increase stage of strong disturbance. Due to the large anchorage range of anchor cables, there is no decrease stage of advanced support. After the application of prestress, the bolt stress of side bolts and top bolts decreases, and the reduction amplitude is up to 30 kN. (4) As the panel advances, the deformation of the surrounding roadway increases, and the growth rate is also increasing gradually. However, the final displacement of the roof, floor, and two sides is within 18 mm. The bolt and anchor cables are not broken, and the control effect is good. The research results have a certain reference value for similar roadway control.

Non-linear FEA of mechanical properties of modular prefabricated steel-concrete composite joints

This paper study the seismic performance of modular prefabricated SRC column to steel beam composite joint (MPCJ) under static loading. Numerical modeling of MPCJs with three different beam-end connections was carried out in ABAQUS. Results of the numerical calculation were compared with existing quasi-static test results to verify the feasibility of the numerical model. The model was then used to analyze changes in the moment-rotation relation, failure mode, ductility, stiffness, and bolt stress in the joint between the column and joint module. Besides, stress distributions in the joints were analyzed along different stress paths. Under monotonic loading, the mechanical performance of the MPCJ is significantly affected by the beam end connection mode. Failure of the MPCJ mainly occurs at the beam end connection, thus, the aim of keeping the plastic hinge away from the joint core and preventing shear failure is achieved. Furthermore, the maximum story drift ratio is 3.9–5 times greater than the recommended limit, which indicates good ductility and deformation performance. The MPCJ of the three-beam end connection methods is all semi-rigid connections. The beam end structure will have a large influence on the bolt tension and stress distribution. According to the test research results, a nonlinear model with three parameters including joint cover plate cantilever section length, flange connecting plate thickness and flange connecting plate weld length was established. The theoretical calculation results was consistent with the results of the numerical simulation. MPCJs can be designed based on the proposed theoretical calculation formula.

Ultrasonic Measurement Method of Bolt Axial Stress Based on Time Difference Compensation of Coupling Layer Thickness Change

The accurate measurement of the axial stress of the core engine rotor bolts is of great significance for improving the assembly quality and safety of aeroengines. To solve the problem that the thickness change of the coupling layer affects the measurement accuracy in ultrasonic measurement of axial stress, a measurement method based on time difference compensation of the thickness change of the coupling layer is proposed in this article. Based on the principle that different loads applied to the ultrasonic transducer will cause the thickness of the coupling layer to change, which leads to changes in the amplitude and propagation time of the ultrasonic echo signal, the principle of time difference compensation for changes in the thickness of the coupling layer is proposed. Based on this principle, the propagation time difference caused by the thickness change of the coupling layer is compensated, thereby improving the measurement accuracy of the propagation time difference caused by the stress and reducing the measurement error of the axial stress. The experimental results show that the average errors of the axial stress measurement model based on the time difference compensation of the thickness change of the coupling layer and the conventional axial stress measurement model are 1.048 and 1.723 MPa, respectively. Therefore, the time difference compensation for the thickness change of the coupling layer can effectively reduce the measurement error of the axial stress. This study provides a promising method for the accurate measurement of the axial stress of aeroengine bolts.

Study on Mechanical Characteristics of Support Structure in Tunnel Entance Section under Mechanized Construction

In view of the mechanical characteristics of the support structure under the mechanized construction conditions of the shallow buried section of the tunnel entrance, numerical simulation methods are used to compare and analyze the different cycle footage and the different tunnel face depth before and after the tunnel face reinforcement been carried out when the shallow buried section of the tunnel entrance is constructed by the micro-step method. The results of the study show that the primary support and pipe shed force increases with the increase in the depth of the tunnel face (buried depth), and decreases with the increase of the cyclic footage; When the fiberglass bolt is used to reinforce the face, the axial tensile stress of the fiberglass bolt can reach 18kN; Without reinforcement of the tunnel face, the primary support of the arch at the entrance of the tunnel is vulnerable to cause tensile damage; After the tunnel face is reinforced, the tensile stress of the primary support is significantly reduced.

Finite Element Analysis of a Fishplate Rail Joint in Extreme Environment Condition

Railways are very efficient mode of transportation. Speed limits of the railways and loads they carry are increasing rapidly. Due to some advantages, the insulated rail joints are still the part of a rail-track system. However, a high rate of failure of joints puts the railway track at risk. Therefore, a detailed study of these joints is required. In this paper, a three-dimensional finite element model of rail-fishplate joint is created using Abaqus - a finite element method-based software. Stresses in fishplate and bolts due to wheel impact are analysed by coupling implicit and explicit methods. It is found that bolts are a critical part of a joint due to stresses and vibrations to which they are subjected. The large number of stresses and vibration can result into loosening of bolts.

Research on Roadway Supporting Effect of Different Bolt Parameters under Blasting Dynamic Load

According to the roadway characteristics and physical properties of rock, calculation model of FLAC2D established, analyzes strain and stress distribution of roadway surrounding rock under static condition and dynamic load of blasting. The results show that, by blasting dynamic loads, stress of surrounding rock will be redistribute, cause displacement increased, and vertical displacement larger than lateral displacement; with the decrease of rock bolt spacing, stress and displacement of surrounding rock under blasting dynamic load decreases, and when the distance is less than a certain value, the influence of blasting dynamic load is smaller. Combined with the results of numerical analysis, gained reasonable supporting parameters, and applied to the engineering practice, has obtained good supporting effect.

Prefabricated Urban Underground Utility Tunnels: A Case Study on Mechanical Behaviour with Strain Monitoring and Numerical Simulation

The prefabricated urban utility tunnels (UUTs) have many advantages such as short construction period, low cost, high quality, and small land occupation. However, there is still a lack of in‐depth analysis of the mechanical performance of the prefabricated urban utility tunnel (UUT) structure with bolted connections under different working conditions. In this paper, the force performance of a prefabricated UUT in Tongzhou District, Beijing, was studied under different working conditions using two methods: field monitoring and numerical simulation. The multichannel strain monitor was used for monitoring, and the internal wall concrete and bolt strain change data under the two conditions of installation and backfill were obtained. Combined with the construction process of the UUTs, a three‐dimensional numerical model was established by COMSOL, where the build‐in bolt assembly was used to simulate the longitudinal connection of the tunnel. The simulation results were compared with the measured data to verify the rationality of the computational model. The simulation results showed that the concrete and bolts on the inner wall of the tunnel work well under the two conditions of installation and backfilling; The deformation of the top plate of the prefabricated tunnel was approximately parabolic, with the largest vertical displacement (0.37 mm) in the middle and the most sensitive to the vertical load in the central part of the roof. The central portion of the side wall had the largest displacement (0.17 mm) in the inner concave. The tensile stress of bolt 3 increased the most (30.75 MPa) but was still much smaller than the yield strength of the bolt. The concrete and bolts of the UUT were found to work well through force analysis under operating conditions. In conclusion, analysis of structural forces and deformation failure modes will help design engineers understand the basic mechanisms and select the appropriate UUT structure.

Uniaxial stress in-situ measurement using EMAT shear and longitudinal waves: Transducer design and experiments

As a typical stressed state, uniaxial stress widely exists in the components, such as bolt stress, which requires to be tested in-situ regularly. In this article, the uniaxial stress in-situ measurement using the electromagnetic acoustic transducer (EMAT) shear and longitudinal waves is proposed. To improve the EMATs efficiency and meet the measurement resolution constraints based on Lorentz mechanism, the EMAT parameters are optimized through numerical analysis, including the coil size, the permanent magnet size and the distance between magnet and coil. The relationship between the propagation velocity and the stress is analyzed, and a joint model of shear and longitudinal waves for measuring the uniaxial stress is established. Finally, the pre-tightened 7075 aluminum alloy bolt is employed to verify the validity of the designed shear wave EMAT and longitudinal wave EMAT.

Ultrasonic testing of axial stress of high strength bolts for bridges

The axial stress of high strength bolts for bridges affects the service life directly, it is necessary to measure it regularly. Based on the theory of acoustic elasticity and combination of longitudinal and shear waves, a new theoretical analysis method is proposed. The stressed and non-stressed areas of bolt are separated, and the derived formula only use the flight time and difference of acoustoelastic coefficients to get axial stress. Further, the preload experiments with high strength bolts of grade 8.8S and 10.9S is designed, the experimental results show that the proposed method is applicable to the axial stress of the bridge bolts with any specifications, material and different screwing depth used in this paper, the effect of elastic deformation on the flight time is eliminated, and the measuring error is within 5%.

Durability Tests of Gaskets in Biofuels Environment

<div class="section abstract"><div class="htmlview paragraph">The production of biofuels to means of transport allows the additional development and the full maintenance of the agricultural sector. The biofuel of II generation may be produced with usage of waste fats and oils. That biofuel is total renewable source of energy. The properties of tested new biofuels were described. Their influence on pipes and especially gaskets and gasket materials during durability tests was determined.</div><div class="htmlview paragraph">Gasket materials were tested in accordance with DIN 28090-3: 2014-11 and DIN28091-2. During 1000 hours of tests at 353 K, the weight loss of the biofuel and the change in elongation (tensile stress) of the flange bolts were measured. Fuel leakage rate was calculated.</div><div class="htmlview paragraph">The gaskets were checked and no delamination was observed.</div><div class="htmlview paragraph">The value of volatile biofuels emission after 1000 hours of testing was less than allowed in DIN Standard. Fuel leakage rate was also lower too. The main conclusion of this research was the suggestion that the gasket materials used may be allowed for contact with diesel with ethyl esters and diesel with methyl esters and ethanol named BIOXDIESEL.</div></div>

Parameter Recognition of Mode-Converted Wave in Single-Source Ultrasound Using Gabor Transform for Bolt Axial Stress Evaluation

In this paper, a novel parameter recognition method of mode-converted wave in single-source ultrasound is put forward and applied to the estimation of axial stresses in bolts. To overcome the distortion and aliasing of the mode-converted wave in single-source ultrasonic signal, a time-frequency parameter recognition method based on the Gabor transform is introduced to recognize the accurate time of flight (TOF) of the mode-converted wave. Based on the mode conversion of the single-source longitudinal ultrasound, a new nonlinear evaluation model based on acoustoelastic equation is derived to determine the axial stress of bolt. The performance of the proposed method is evaluated by comparing it with the commonly used TOF ratio method of longitudinal wave and shear wave (L-S). The experiment result shows that the proposed method is more effective in detecting the connection status of bolted joints than the traditional L-S method.

Frequency spectrum and fatigue analysis of T-bolt fracture in DT III fastener based on Refined Model.

It is observed that T-bolt fracture of DT III fastener affects the safety of railway operations. The present study is aimed at finding solution to this critical issue of DT III T-bolt fracture. The paper is based on outcomes of field studies and analysis of relationship between bolt installation torque and stress. A refined DT III fastener model is established based on test data and nonlinear contact theory as per the actual size of each component. It is being observed that head-shank joint is a critical area during service. With respect to fatigue and stress, when the installation torque is less than 300 KN-mm, the bolt is prevented from yielding during installation. To a certain extent it also improves the fatigue life of bolt. From the frequency spectrum point of view, the vibration sensitive frequency band (1050-1100 Hz, 1230-1270 Hz) of bolt in service is very close to the main frequency of bolt vibration (1200 Hz). It may cause bolt fracture. In order to avoid resonance, the train operational speed should be strictly controlled between 115 km/h and 120 km/h.

Comparative Shear Tests of Bolt Rods Under Static and Dynamic Loading

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

Fatigue analysis of welds and bolts in end plate connections of I-girders

End plate connections with prestressed bolts represent economical joints in steel construction. However, the fatigue resistance of these connections is currently insufficiently covered in Eurocode 3-1-9 [1]. The weld and bolt stresses during fatigue loading of end plate connections have been examined in detail. To this end, fatigue tests have been carried out on component and small-scale specimens. In a subsequent numerical investigation, FE-models have been validated by the experimental results. Second, geometric influences were investigated. The fatigue strength of the welds has been assessed by the effective notch stress concept. Finally, a detail category recommendation is given.

Analysis of anchor bolt stress characteristics in arch ring support of super-large underground powerhouse

Taking the surrounding rock deformation and bolt stress response characteristics during arch excavation of the left bank underground powerhouse of baihetan hydropower station as the research object, On the basis of the monitoring data of anchor stress, anchor rod stress response characteristics summarized as three types including “stepped”, “one pull one press” and “load drop”, and preliminary discussed the mechanism of bolt stress. The research results can provide important technical support for the reinforcement design of cavern in the following similar projects and have guiding significance for engineering practice.

The study of the stress-strain state of the elements of the flange connection under the influence of internal pressure

One of the main requirements that is presented to flange connections (FC) is to ensure uniform tightening torque of fasteners. Violation of this condition may lead to a decrease in FC reliability and an emergency. Regulatory calculations of FC for strength and tightness are carried out under the assumption of creating and maintaining during operation a uniform tightening force of fasteners. There is no information in the literature about whether and how the uneven tightening force affects the stress-strain state of a flange joint. In this paper, we propose such a study based on the method of modeling the stress-strain state of a flange connection. At the first stage, to select the initial data and develop the model, calculations were performed on the strength and tightness of the flat weld flange based on the PASSAT software package. Based on the analysis of changes in bolt loads and stresses, the FC parameters and loading conditions were determined, which are implemented during the development of the FC model and are described in our second article.

Refined three‐dimensional numerical model for segmental joint and its application

AbstractPrevious research of segmental joints are mainly based on experimental and theoretical methods; few studies have focused on refined numerical model. Therefore, a refined numerical model is established in which eight‐node solid element and three‐dimensional beam element are adopted to simulate joint structures and reinforcement, respectively, and bolt preload is considered. Then, the numerical model is verified with full‐scale tests and applied to analyze the influence of joint deformation and bolt preload. It is confirmed that (a) the numerical model can reproduce joint deformation process with good accuracy; (b) bolt stress are controlled by tensile action caused by joint opening and bending action caused by joint vertical displacement; (c) the changes of joint deformation with bending moment can be divided into three stages; bolt preload has no effect on the change of joint deformation with bending moment but has significant impact on the value of joint deformation in each stage.

Moment-rotation-temperature model of semi-rigid cruciform flush endplate connection in fire

This paper aims to develop a model for predicting the moment-rotation-temperature (M-R-T) relationship of semi-rigid cruciform flush endplate (CFEP) connections in fire. For this purpose, a nonlinear finite element (FE) analysis was conducted to simulate the CFEP connections in the fire using ABAQUS. The FE model was verified with the experimental results conducted by others. Based on the validated FE model, a parametric study was carried out by considering effect of several parameters, such as the number of bolt rows, column section, beam section, distance of bolt rows, gauge distance, endplate thickness, bolt diameter, yield and ultimate stress of column, yield and ultimate stress of beam, yield and ultimate stress of endplate, yield and ultimate stress of bolt, and moment ratio. Accordingly, the results of the parametric study were used to establish the M-R-T model of CFEP connections at both ambient and elevated temperature. The performance of the M-R-T model was compared with the test results in the literature. The comparative study showed that the proposed model can accurately capture the M-R-T relationship of CFEP connections in fire.

Preloaded Bolted Joint Made with a Single Row of Fasteners

Abstract The purpose of this technical note is to present a method of analysis of a joint made using a single row of bolts, typical of a bolts around the edge of a closure plat or a simple bracket. Classical analysis methods are applied to the joint subjected to combinations of both in-plane and out-of-plane loads and moments. An analysis of loads and stresses in a single bolt is developed. The note brings together a number of concepts and links them into a practical design analysis process that is applicable for many cases of joints made with a single bolt or a single line of bolts and are adequate to demonstrate the structural integrity of the joint. In some cases finite element methods may be more appropriate, and the methods discussed can be used in the validation process.