Types Of Bolted Joints Research Articles

ANALYSIS OF REINFORCED BOLTED JOINTS IN HIGH-CAPACITY SILOS

ABSTRACT: This paper presents an analysis of the mechanical performance of bolted joints used in silos for storing bulk materials. In particular, we investigated the effectiveness of three types of bolted joints: one without reinforcement, one with angular reinforcement, and one with squared reinforcement. Our analysis involved the use of the finite element analysis sub-modeling technique, which allowed us to construct a large finite element model with shell elements and a sub-model with solid elements. By analyzing the stress state of each joint, we were able to determine the contact state and contact pressure of the bolted joint. Our findings showed that bolted joints reinforced with triangular and square plates were effective in maintaining contact pressure, even under high-pressure conditions. This study provides valuable insights into the design of bolted joints used in silos, which can help ensure their reliable and safe operation. Keywords: bolted joints, high-capacity silo, FEA sub-modeling.

Loosening mechanism of threaded fastener for complex structures

Threaded fasteners are widely used in mechanical structures primarily owing to their easy disassembly for maintenance and low cost. However, the loosening mechanism of threaded fasteners due to dynamic loading has remained unclear for the past six decades. Current researches on complex structures comprising three or more components are insufficient. The two most common failure modes of threaded fasteners subjected to dynamic loading are fatigue and vibration-induced loosening. This study focuses on the failure of threaded fasteners by vibration-induced loosening due to dynamic shear loads. This study comprises experimental analysis and numerical analysis. The loosening mechanism of threaded fasteners for complex structures is analytically and experimentally identified. This work provides the equations and assessment method for the loosening, and the criteria of primary and secondary loosening are established. To verify the proposed loosening mechanism, tightening and loosening experiments are conducted for three types of bolted joints. The primary and secondary loosening forces of each bolt are thus obtained, and the proposed loosening mechanism can be verified for complex structures. In numerical analysis, a three-dimensional finite element (FE) model for tightening and loosening analysis is proposed. A FE model is used to study the loosening process which is characterized by a decline of the preload and moving distance for predicting loosening states. The model seems to be well agreement in comparison with theoretical and experimental results. As a result, the assessment method shows good performance in predicting loosening state. It is expected to verify the safety of bolted structures at the design stage. The FE model is expected to be used for the effective and safe design for joint components in various industrial fields such as wheel assemblies and other mechanical components under dynamic vibration.

Full strength extended stiffened end-plate joints: AISC vs recent European design criteria

Extended stiffened end-plate bolted joints are widely used in seismic resistant steel frames. In the United States of America (USA) this type of joint is seismically pre-qualified according to AISC 358-16. At the present time, prequalification criteria for different types of bolted joints are also under development in Europe within the framework of the EQUALJOINTS (i.e. European pre-QUALified steel JOINTS) research project. The design criteria and detailing rules proposed by this European project for extended stiffened end-plate joints differ from AISC criteria in some respects. Therefore, the aim of this work is to verify and to compare the effectiveness of both design procedures through the results of a comprehensive parametric study based on finite element (FE) simulations. The FE results show that both AISC and European design procedures can guarantee the formation of a plastic hinge in the beam under cyclic loading. However, under column loss scenarios the European connections are more ductile than those designed according to both AISC 358-16 and AISC 341-16. In addition, it is investigated the possibility to use heavy columns satisfying the resistance requirements without stiffeners (i.e. continuity plates and supplementary web plates). The comparison between the response of the joints with and without stiffened columns shows that heavy unstiffened columns can be adopted without appreciably modifying the joint response.

Longevity enhancement of bolted joints for aircrafts

New designs of bolted joints with bolt countersunk heads having high longevity in comparison with the used ones were proposed. One type of joint has the bolt heads with the reduced surface taper of the bolt head and in a joined part. Two other types have a spherical head surface, which is in contact with a tapered countersink surface. The rise in the fatigue life is achieved owing to the balance of the radial tension along the contact surfaces of the head and the countersink. Designs of a washer from the direction of a nut are proposed. These washers have ring bulges of wedge-shaped cross section that form areas of plastic deformations around a bolt body during the bolt tightening and reduce the concentration of contact stresses close to an edge of the contact surfaces of the bolt and joined parts. Procedures of fatigue tests were developed. Results of tests of the proposed bolted joints supporting their high longevity are presented. Findings of experimental investigations verify the efficiency of the application of proposed types of bolted joints in the designs of aircrafts.

Fast computation of preloaded bolted circular joint aiming at fatigue bolt sizing

PurposeThis paper seeks to deal with a new modelization method which aims at fatigue sizing of preloaded bolted joints. Industrial design offices indeed need new models which, on the one hand, take bending of the bolts and geometrical non‐linearity into account and, on the other hand, run fast enough to be used for preliminary design stages. Usual sizing procedures derive from VDI recommendations, which makes them inaccurate. On the contrary, classical finite element methods are revealed to be very costly.Design/methodology/approachThe first task lies in reducing the physical problem down and model the structure using axisymmetrical elements. Then, the core of the method lies in modifying the stiffness matrix of a tube element, in order to modify the axial compression stiffness to the one used by preloaded assembly classical computations. Eventually, a 2D finite element model is programmed which takes advantage of the modified element. A mounting was built to reproduce the typical loading of a slewing bearing. Experimental tests were carried out in order to help analyse the problem and to check finite element simulation results.FindingsSample experimental results are presented which confirm the need for new models and validate the 2D model that was developed.Research limitations/implicationsThe new finite element, as well as the set of hypotheses that are used, appear to be usable for other bolted joints.Practical implicationsA software was produced for the industrial partners, which is usable by non FE‐specialists.Originality/valueThis work may serve as a basis for building fast and accurate finite element models of other types of bolted joints.

Effect of Clamping Force on the Strength of Bolted Joints in Pultruded GFRP Laminates

FRP might be widely applied to infrastructures in coast areas, because it is a corrosion-resisting material. Joints such as adhesive joints and bolted joints are required in application of FRP to infrastructures. Pultruded FRP is desirably applied to infrastructures because its mass production could bring about lower cost. The purpose of this paper is to obtain the effect of clamping force on the strength of bolted joints in pultruded GFRP laminates through the experiment. The two types of bolted joints are focused, friction-type bolted joints and bonded-bolted joints. The strength of friction-type bolted joints increases with the clamping force. The failure mode is bearing failure for joints without clamping force and shear-out failure for joints with clamping force. The strength increase with clamping force is brought about by the increase of bearing strength and the friction between the specimen and the attached plate. The strength of bonded-bolted joints also increases with the clamping force. The failure mode is adhesive failure for adhesive used joints and bearing or shear-out failure for adhesive tape used joints, because adhesive tapes have lower strength than adhesives. The strength increase of adhesive used joints with clamping force is brought about by the increase of failure stress at the end of adhesives. On the other hand, the strength increase of adhesive tape used joints with clamping force is brought about by the increase of bearing strength.

Failure Modes and Load Transfer in Sandwich T-Joints

Various T-joints of composite sandwich panels were investigated. The corresponding modes of failure at the joint were identified. The key modes of failure include debonding between the two sandwich components to be joined, debonding between the attachment and the sandwich panel, and cracking in the core of the sandwich. A new type of T-joint incorporating an aluminum U-channel in the web sandwich was found to provide much improvement over the conventional circular fillet T-joint. Two types of bolted joints were also studied to investigate the effectiveness of using bolts for suppressing debonding at the joint. It was shown that using bolts in a circular fillet joint could cause early failure in the core and would not help much to increase the ultimate joint strength. The experimental failure modes of the tested joints were explained with the help of FE analysis.

Fatigue design of bolted joints taking into account reliability concepts

A method is presented for fatigue design by comparing the load on the bolt in joints with the fatigue strength of the bolt-nut joints. Two types of bolted joints, cylindrical and T-flange joints, are treated as examples. Reliability concepts are introduced to the design. Fatigue tests of the above-mentioned bolted joints were also carried out to verify the applicability of the method. As a result, it appears that the fatigue behavior of threaded fasteners can be estimated to some extent by comparing the load on the bolt with the fatigue strength.