Fit Joint Research Articles

Effect of electromagnetic force installation method on critically reinforced interference sizes and fatigue behavior of CFRP bolted joints

AbstractThe electromagnetic force dynamic installation (DI) method of interference fit fasteners has significant advantages in improving the quality of the assembly interface of composite structure. This study aims to investigate how improving assembly interface quality may help in achieving high‐precision interference‐fit joints in composites. Single‐lap joint specimens were prepared using electromagnetic installation technique, the fatigue life and failure behaviors of the joints under different bolt‐hole clearances were measured and analyzed experimentally. In addition, a three‐dimensional finite element model was developed to predict the radial pre‐compression stresses around the hole and the progressive failure behavior of various typical damage modes in carbon fiber‐reinforced polymer induced by the interference. The results show that the critical interference range for the DI‐composite bolted structure is 1.0%–1.2%. The fatigue life of the best interference (1.0%) and the worst interference (0%, neat fit) have a difference of 36 times in amplitude. The residual stress with uniform distribution and high amplitude reduces the stress concentration of the hole wall and improves the failure evolution of the loaded hole. The contribution of this study provides vital guidance for improving the fatigue performance of CFRP bolted structures using a novel DI method.Highlights I = 1.0% is the critical damage‐enhancing interference size for dynamically installation interference fit bolts with electromagnetic forces. The residual stress amplitude introduced by the interference does not increase uniformly as the interference size increases. Excessive interference significantly reduces the uniformity and magnitude of residual stresses. Under subsequent cyclic loading, the fifth layer near the inlet and outlet of the extruded lower laminate appears to be the critical ply of extrusion deformation, and severe damage is concentrated in the critical ply of deformation. The decrease of stress amplitude and the variation of mean stress are the mechanisms of fatigue life enhancement in interference fit joints under external cyclic loading.

Simulation Analysis of the Structure of an Integrated Modular House by Flat Pack Based on the Elastic–Plastic Contact Theory and Experimental Study of Its Corner Fitting Joint

Based on the elastic–plastic contact theory, elastic–plastic contact finite element models for the integrated modular house by flat pack are established. The structural stress and displacement distributions are obtained. An experimental test is conducted to study the performance of the corner fitting joint of the house. The finite element analysis and experimental test comprehensively demonstrated the safety and reliability of the house structure. The results show that the most unfavorable stress point of the house is located at the corner fitting joint. When the end plate connection holes of the corner column seal are designed with through holes and internal screw holes, respectively, the fastening effect of bolting between the corner fitting and corner column using the internal screw hole is better. The reliability of the repeated disassembly and assembly of the house is verified via multiple loading–unloading simulation cycle experiments of the corner fitting joint. The results of the study provide technical support and a reference basis for the optimal design and ensuring the service performance of the integrated modular house by flat pack.

A tutorial on fitting joint models of M/EEG and behavior to understand cognition

We present motivation and practical steps necessary to find parameter estimates of joint models of behavior and neural electrophysiological data. This tutorial is written for researchers wishing to build joint models of human behavior and scalp and intracranial electroencephalographic (EEG) or magnetoencephalographic (MEG) data, and more specifically those researchers who seek to understand human cognition. Although these techniques could easily be applied to animal models, the focus of this tutorial is on human participants. Joint modeling of M/EEG and behavior requires some knowledge of existing computational and cognitive theories, M/EEG artifact correction, M/EEG analysis techniques, cognitive modeling, and programming for statistical modeling implementation. This paper seeks to give an introduction to these techniques as they apply to estimating parameters from neurocognitive models of M/EEG and human behavior, and to evaluate model results and compare models. Due to our research and knowledge on the subject matter, our examples in this paper will focus on testing specific hypotheses in human decision-making theory. However, most of the motivation and discussion of this paper applies across many modeling procedures and applications. We provide Python (and linked R) code examples in the tutorial and appendix. Readers are encouraged to try the exercises at the end of the document.

Možnosti využitia technológie termálneho vŕtania na účely spájania tenkostenných nerovnakých materiálov v automobilovom priemysle

The article deals with the study of the applicability of flowdrill technology for the formation of joints between thin metallic materials based on iron and aluminium alloy. This technology is primarily used to create holes in profiles with a local increase in material thickness to accommodate a greater number of threads. If used to drill two interleaved thin-walled materials, a joint is formed as a secondary effect. The quality of the resulting bushings forming the interference fit joint was investigated. The joints were formed using a combination of uncoated deep drawn steel, galvanized HSLA steel and aluminum alloy, in different positions in the joint. Subsequently, tensile shear testing of single joints was performed. The load carrying capacity of the joints was also tested in combination with adhesive bonding. The load capacity of the joints combined with bonding was significantly higher compared to flowdrill joints. The combination of both technologies yields an increase in the absorbed energy of the joint at failure.

Sulfide Stress Cracking of column overhead pipe to flange fitting joints in a petroleum industry

The light hydrocarbon containment leakage in a petroleum industry overhead piping have caused severe fire explosion. This paper reports Sulfide Stress Cracking (SSC) in an overhead piping of splitter unit which separates out lighter components from heavier hydrocarbon. The failed overhead piping has been analyzed to determine the root cause of fire incident. The piping metallurgy was SS316L and chemistry of failed fitting components & its weld have been complied with NACE specification. Initially fittings were evaluated for intergranular corrosion to determine as-received material condition and confirmed defect free material. However, metallographic evaluation clearly evidenced transgranular brittle mode of cracking while hardness was higher than NACE specification (22HRC). Furthermore, virgin pipe joint was compared with damaged pipe joint for microstructural assessment. Moreover, actual service conditions were evaluated to obtain pH and H2S concentration in overhead condensed boot water. Microstructural factors have been discussed in detail as well. The results revealed that cold deformed austenitic structure attributed to SSC and undesired manufacturing steps were employed. Further, the root cause of an accident investigation also revealed failed components were not according to NACE specified metallurgy for sour service conditions.

In-Situ Computed Tomography — Analysis of a Single-Lap Shear Test with Composite-Metal Pin Joints

Lightweight design in the form of intelligent multi-material structures that combine the advantages of high strength steel and continuous fibre reinforced thermoplastics (CFRTs) gain increasing relevance. In this context, the joining operation is a major challenge as it has to be time and cost efficient and the resulting joint has to exhibit a high mechanical durability. One possible approach is the use of cold formed pin structures, which can be inserted into the CFRT to create a form fitting joint under avoidance of fibre damage as it is commonly the case for bolted or riveted joints. The deformation phenomena of pin joints are usually investigated by macrosectioning or (ex-situ) computed tomography. However, due to resetting elastic deformations and cracks that close after unloading an inaccurate state of the inner joint structure is measured. Furthermore, an investigation of different stages with increasing load and progressing failure is very time consuming, because multiple samples have to be tested and investigated. Alternatively, in-situ computed tomography (in-situ CT) can be used to investigate the testing of pin joints. In this paper, a method for in-situ CT analysis of a single-lap shear test with composite-metal pin joints is presented. The pins are plastically extruded to a height of approx. 1.8 mm from the metal sheet (1.5 mm thick) and are pressed into a locally heated glass fibre reinforced thermoplastic (FRT) sheet (approx. 2 mm thick) creating a form fit. Specimens with quasi-unidirectional fibre reinforcement in 0° and 90° direction are tested. With this procedure, the three-dimensional deformation of the joint can be observed and failure phenomena can be identified for each reinforcement direction respectively. Thus, this method can also be used for validating numerical simulations.

Effect of diamond like carbon coatings on reducing sliding fit joint interfacial wear damage on Al5083 alloy

Wear is an important concept and is being given importance in different manufacturing industries. In every mobile joint, studies in interaction between sliding surfaces are very important. This is due to the wear that occurs in between the sliding surfaces. A lot of sliding fit joints are fabricated and used in production companies and transportation industries. In this manuscript, an attempt has been made to reduce sliding wear of Al 5083 alloy materials by coating it with diamond like carbon material. Using high velocity oxy fuel thermal spray coating, diamond like carbon materials were coated over Al 5083. Then it was subjected to wear testing by using pin on disc wear testing equipment. Wear tests were conducted by using petroleum lubricant and also in dry conditions. A considerable improvement in wear resistance was observed on using diamond like carbon coatings. Using scanning electron microscopy, the alloy Al 5083 material was evaluated for microstructural variations on conducting wear studies, before and after coating it with diamond like carbon material, with and without lubrication. The variations in coefficient of friction, specific wear rate and wear mass loss were studied under lubrication and without lubrication, with and without diamond like carbon coating. Microstructural evaluation of wear tested surfaces exhibited micro wear, micro voids, coating pull outs, abrasive wear and micro cracks.

R-package LNIRT for joint modeling of response accuracy and times.

In computer-based testing it has become standard to collect response accuracy (RA) and response times (RTs) for each test item. IRT models are used to measure a latent variable (e.g., ability, intelligence) using the RA observations. The information in the RTs can help to improve routine operations in (educational) testing, and provide information about speed of working. In modern applications, the joint models are needed to integrate RT information in a test analysis. The R-package LNIRT supports fitting joint models through a user-friendly setup which only requires specifying RA, RT data, and the total number of Gibbs sampling iterations. More detailed specifications of the analysis are optional. The main results can be reported through the summary functions, but output can also be analysed with Markov chain Monte Carlo (MCMC) output tools (i.e., coda, mcmcse). The main functionality of the LNIRT package is illustrated with two real data applications.

Structural and technological support of tightness of interference fits

The conditions for contact interaction of mating parts in interference fit joints are considered. It is shown that the main factor determining the strength and tightness of joints is the state of the surface layer. Ways are established to control the performance of joints with an interference fit by using surfactants, both in the technological preparation of parts before assembly, and in the assembly of joints. Keywords: contact interaction of surfaces, real contact area, joint tightness, influence of surfactants. kurnosov-ne@mail.ru

Automatic identification and location method for shaft-hole interference fit crack based on deep learning

Cracking on the shaft of the interference fit joint surface is a common failure form for the shaft-hole interference fit. Because the crack is small and is located at the shaft edge, the crack signal is affected by echo and reflection signals and noise when traditional ultrasonic guided wave methods are used to detect the crack. When the crack is small-sized, the crack signal may even be submerged completely in the echo and reflection signals. Therefore, the traditional detection method is unable to obtain accurate information about the crack locations easily and thus cannot evaluate the overall safety performance of the interference fit accurately. To solve these problems, this paper presents an on-axis crack monitoring system for interference fit joints using laser ultrasound and an improved YOLOv5 network that integrates early warning, detection, positioning, and analysis functions. The system detects axial cracks at the shaft-hole interface via laser ultrasonic guided waves on the workpiece, and captures the crack information by deep learning; then, the captured crack information is analyzed to extract the essential crack location information. Finally, the method is verified experimentally. The experimental results show that this method can not only identify axial cracks at the shaft-hole interference fit surface automatically, but also can locate these cracks accurately and obtain both the number of cracks and the distance between pixels.

Application of memory alloy materials in power system

The shape memory alloy (SMA) is a new kind of metal intelligent material, which has the characteristics of shape memory effect (SME), pseudo-elasticity (PE) and high damping (HD). Therefore, it is widely used in many industries, such as construction engineering, mechanical engineering, space shuttle, energy engineering, medical engineering and so on. In order to solve the heating defects of fittings, the typical six split fittings joints in the main flow circuit of converter station was selected in this paper. And the memory alloy intelligent gaskets and ordinary steel spring gaskets on both sides of the fitting joints were installed. The experimental research on the influence of current on the temperature rise of fittings with different types of gaskets were carried out. The test results showed that the shape memory alloy gasket could automatically generate the deformation force which increased with the increase of temperature, so as to reduce the contact resistance of the joint and the temperature of the contact during operation.

Effects of layup parameters and interference value on the performance of CFRP–metal interference fit joints

Abstract Based on the thick-wall cylinder theory and composite material mechanics, the stress distribution model of the CFRP shaft tube and metal shaft head has been established, and the relationship between the layup parameters and the value of interference on the maximum assembly force and failure torque in the interference fit joints of the CFRP shaft tube and the metal shaft head is deduced. Combining the three-dimensional finite element analysis model with experimental data, the result shows that the layup angles of the CFRP shaft tube have a greater influence on the joint connection performance than the layup sequence, and the larger the layup angle, the better the joint assembly performance while keeping the value of interference constant. The maximum assembly force and failure torque of the interference fit joints increase linearly while the value of the interference amount increases when the layup parameters are constant.

Experimental determination of pressure in the joint of cylindrical parts assembled with an interference fit

A device is proposed for determining the pressure in a joint with an interference fit, the sensitive element of which are balls located between the mating surfaces. Two types of contact interaction of balls and mating parts are considered: elastoplastic deformation of balls and elastoplastic deformation of parts. The pressure in the shaft-bushing interface is determined by the magnitude of the deformation. Keywords: interference fit joint, pressure, shaft, bushing, ball, elastoplastic contact, penetration, flattening. matlin@vstu.ru

Investigation of Applicability Flowdrill Technology for Joining Thin-Walled Metal Sheets

The applicability of flowdrill technology to join steel and aluminum alloys is studied. When used to flowdrill two overlapped thin-walled materials, a joint is formed as a secondary effect. The quality of the resulting bushings forming the interference fit joint was investigated by metallography. The joints were formed using a combination of uncoated deep drawn steel, galvanized high-strength low alloy steel and aluminum alloy, in different positions in the joint. Subsequently, tensile shear testing of single joints was performed. The load-carrying capacity of the joints was also tested in combination with adhesive bonding. The combination of both technologies yields an increase in the dissipated energy of the joint at failure. The bonded connection provides a high maximum force at failure, the mechanical connection through bushings leads to an increase in the displacement value at failure, thereby increasing the area under the loading curve. The DC-Al joint showed the highest load-carrying capacity, up to 9 kN, as well as dissipative energy, up to 10.3 J. The joints were fractured by shearing of the inner bushing under tensile stress. The failure surfaces exhibited a typical ductile character with dimpled morphology. It was found that from the point of view of the load-carrying capacity of the joint, it is advisable to place a material with a higher melting temperature in the upper position in the joint. The combination of flowdrill technology with adhesive bonding results in a sealed joint with high load-bearing capacity, reduction in the risk of crevice and galvanic corrosion.

Analysis of Interference-Fit Joints

Interference fit joints have been widely used in many engineering constructions, in particular in electric motors. It is of particular importance to calculate the load capacity of press-fit joints, especially in the overload ranges of construction to estimate the safety factor. The article presents a FEM numerical simulation of pressing the shaft into the hub, taking into account various types of fits. The results of numerical simulations presented in the article were positively verified with the MTS measuring device, which confirmed the correctness of the numerical model. So far, the load-bearing capacity of press-fit joints has been calculated from Lame’s formulas. The results of the load capacity of the joints obtained by the FEM simulation were compared with the results obtained from Lame’s formula. The comparison shows that when designing interference fit joints, attention should be paid to the fact that the press-in process, depending on the type of fit, may be elastic-plastic. Plastic deformations in the contact zone of the joint affect its load-bearing capacity. Therefore, the design of press-fit joints should not be based on Lame’s formulas, which do not take into account the range of plastic work of the material.

Analysis of Force Distribution of Four Rows of Bolts in Aircraft Fitting Joint

With the help of 3D modeling software and finite element analysis software, the force distribution of four rows of bolts in the aircraft fitting joint is obtained in this paper. In 3D modeling software, the solid model is segmented according to the area and height of the center of gravity of the cross-section. In finite element analysis software, the beam elements are used to replace the segmented model to obtain the internal force applied at the end of the segmented model and the stress-strain state of each segment is calculated according to the internal force applied at the end of each segment. Finally, the force distribution of the four rows of bolts is obtained according to the average force difference on the center section between the bolt rows. In order to ensure the validity of this step-by-step calculation result, it was compared with the entire calculation result. It can be concluded that the force distribution of the two calculations is consistent. Under the working conditions of the fitting joint (130 MPa), the force distribution coefficients of the four rows of bolts are 0.182, 0.215, 0.197, and 0.12. Therefore, it is feasible to use the step-by-step method to calculate the force distribution of the four rows of bolts in the fitting joint. Compared with the entire calculation, the step-by-step calculation has the advantages of less calculation amount and faster calculation speed.

АНАЛІЗ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ ФІТИНГОВОГО СТИКУ ПАНЕЛЕЙ ВІД'ЄМНОЇ ЧАСТИНИ КРИЛА ТА ЦЕНТРОПЛАНА ТРАНСПОРТНОГО ЛІТАКА

Fitting joints are widely used in aircraft structures, and they are responsible for the interconnection of important components. The stress-strain state analysis of the fitting joint must be carried out before the performance analysis of the fitting joint. With the help of 3D modeling software (CATIA) and finite element analysis software (ANSYS), the stress-strain state of each component in the fitting joint of outer wing section was calculated in this paper. In the CATIA, the solid model is simplified and segmented according to the size of the cross section and the height of the center of gravity of the model. In the ANSYS, the beam elements are used to replace the simplified segmented model to obtain the internal force distribution of the solid model and to determine the magnitude and change law of the stress applied to the end of the solid model. When calculating the force transmitted by the fastener, the pre-tightening force of the bolt and the interaction between the surfaces of the component are taken into account, so as to simulate the real force situation well. Therefore, it is a very feasible method to use the CATIA and ANSYS to obtain the stress-strain state of components in the fitting joint of center wing section and outer wing section.The results show that under the working conditions of the fitting joint (130Mpa), the fitting of outer wing section with center section has a maximum stress of 245.79Mpa and a maximum strain of 0.0035, the stringer of outer wing section has a maximum stress of 293.17Mpa and a maximum strain of 0.0047, the lower panel of outer wing section has a maximum stress of 289.53Mpa and a maximum strain of 0.0042. The connecting bolts (M8 and M6) have a maximum stress of 686.81Mpa and a maximum strain of 0.0063, which meets the design requirements. In addition, according to the analysis results of the stress-strain state of the fitting joint of outer wing section, the force distribution of the bolts in the fitting joint of outer wing section with center section was obtained in this paper. It has been confirmed that due to the different positions and force areas of the bolts, the force distribution between rows of bolts is uneven, and the first row of bolts has a more force.

A new model for stress analysis in pin–Plate interference fit joints under tension loading

The decrease of stress amplitude is generally believed as the mechanism of fatigue life enhancement in interference fit joints under cyclic loading for each load cycle. In order to exactly estimate it, a new analytical model was presented. In this model, influences of mass, geometry, and plastic deformation are considered to modify and improve the spring model, and, moreover, the stress amplitude at the smallest crossing section is investigated. Taking these factors into account, stress amplitude decrease of various interference values can be calculated more accurately; therefore, the analytical solutions have good agreement with the finite element numerical and experimental results under different interference values and load levels. The analytical model indicates that the decrease ratio of stress amplitude is of a certain value for a specific interference value with the external load under the critical value. Furthermore, the decrease ratio of stress amplitude mainly depends on the stiffness of the pin and plate, which is mostly affected by the geometric shapes and plastic deformation ranges of the pin and plate. In addition, raising the interference value leads to larger stress amplitude reduction since the plastic deformation areas expand with the increment of interference values.

Model‐based ordination for species with unequal niche widths

Abstract It is common practice for ecologists to examine species niches in the study of community composition. The response curve of a species in the fundamental niche is usually assumed to be quadratic. The centre of a quadratic curve represents a species' optimal environmental conditions, and the width its ability to tolerate deviations from the optimum. Most multivariate methods assume species respond linearly to niche axes, or with a quadratic curve that is of equal width for all species. However, it is widely understood that some species have the ability to better tolerate deviations from their optimal environment (generalists) compared to other (specialist) species. Rare species often tolerate a smaller range of environments than more common species, corresponding to a narrow niche. We propose a new method, for ordination and fitting Joint Species Distribution Models, based on Generalized Linear Mixed‐effects Models, which relaxes the assumptions of equal tolerances. By explicitly estimating species maxima, and species optima and tolerances per ecological gradient, we can better explore how species relate to each other.

Компьютерное моделирование прессового соединения

The design of modern technology is associated with increased requirements for strength and manufacturability. Press fit connections of small size parts can withstand significant workloads, so they are widely used in mechanisms and machines. Traditionally, the calculation of press fit connections is performed according to classical formulas using a large amount of reference data. The calculations use standard recommendations that make it easier to obtain solutions with a minimum investment of time. However, the time saving limits the search to a few joints, which are not always the best in some indicators. Modeling press fit joints with different combinations of parameters leads to the formation of hundreds of potential joints. To check their performance, it is necessary to use modern computing facilities. The computer has almost unlimited possibilities for computing speed and storing arrays of information. Simulation of press fit connections on a computer allows obtaining regression metamodels, accessing the statistical significance of parameters, and determining the area of workable connections. It becomes possible to optimize the design of the joint in terms of strength, weight and assembly technology. The system for calculating and statistical analysis of press fit connections has been developed on the basis of existing standards. A program has been developed providing the joints formation and verification with an assessment of their suitability for the specified requirements.