Joint Cross-section Research Articles

Experimental study of the influence of the cross section of the lonnago joint on the size of the pelvis

Practice outpaced theory on the issue of symphysiotomy. Until now, this operation has not been scientifically sufficiently substantiated due to the fragmentary, incomplete and inaccurate anatomical studies. There is still a lack of accurate pelvic measurements. Fully aware of the need and importance of filling this gap, I willingly took on the proposal and under the guidance of prof. D.O. Ott for real research.

Hitsiliitoksen geometrian vaikutus väsymismitoituksessa

Tässä tutkimuksessa tarkasteltiin kahdella eri lämmöntuonnilla MAG-hitsattujen päittäisliitosten poikkileikkausten geometriaa sekä hitsiliitoksen geometrian vaikutusta väsymiskestävyyteen lovenvaikutuslukujen avulla S700-lujuusluokan rakenneteräksellä. Hitsiliitosten poikkileikkausten geometriat tuotiin elementtimenetelmäohjelmistoon, jossa määritettiin malli lovenvaikutuslukujen laskemiseksi. Laskettuja lovenvaikutuslukuja verrattiin kirjallisuuteen, sekä lovenvaikutuslukujen avulla määritettiin S‑N ‑käyrät, joita verrattiin mitoitusohjeiden S-N -käyriin. Lisäksi tarkasteltiin elementtikoon vaikutusta lovenvaikutuslukuun sekä alkusärön koon vaikutusta kestoikään murtumismekaniikan avulla. Tutkimuksessa havaittiin, että geometria ei yksin selitä hitsiliitoksen huonompaa väsymiskestävyyttä ehjään perusaineeseen verrattuna, vaan lähes puolet erosta johtuu muusta kuin geometriasta, esimerkiksi hitsauksen aiheuttamista mikrorakenteen muutoksista tai jäännösjännityksistä. Ainoastaan lovenvaikutusluku huomioiden saadaan hitsiliitoksille ylioptimistisia väsymiskestävyyden suuruuksia sekä kirjallisuuteen että mitoitusohjeisiin verrattuna. Elementtimenetelmää mitoituksessa hyödynnettäessä on käytettävä riittävän tiheää elementtiverkkoa, jotta rakenteen ja hitsiliitoksen geometria kuvataan oikein ja laskentajännitykset ovat todellisuutta vastaavia.

The impact of oxygen content on the reliability of Au-20Sn solder hermetic package

Hermetic sealing devices are produced with Au-20Sn solder at different oxygen content levels to study the reliability of the seal joints. Cross section of Au-20Sn solder joints processed with different oxygen content were examined by SEM, which shows that the microstructure displayed an obvious deterioration with the increase of oxygen content. It was found that bonding at 16 ppm oxygen content level, an uniform bonding interface with void-free was obtained with good hermeticity. However, when the oxygen content reached 55 ppm, voids and cracks were generated along the seal joint and the helium leak rate was higher than 5 × 10−8 atm cm3/s, which is the rejected limit value of MIL-STD-883 K. According to the reliability test results, we believe that the hermeticity deterioration is attributed to voids and cracks with the extension of aging time. In addition, samples with poor hermeticity were analyzed to know the failure mechanism of the seal joints and the feasible methods were proposed for improving hermeticity.

Ultrasonic Vibration-Strengthened Adhesive Bonding of CFRP/Aluminum Alloy Joints with Anodizing Pretreatment

Ultrasonic vibration has been applied to improve the penetration of adhesive into the anodized layer, thereby enhancing the strength of carbon fiber-reinforced plastic/aluminum alloy bonding joints with anodizing pretreatment. The ultrasonic vibration-assisted adhesive bonding process was designed by orthogonal experiments, then verified experimentally. The strengthening mechanism was studied by analyzing the morphology and elemental distribution of the cross-section of the joint. The results show that the ultrasonic vibration-assisted adhesive bonding process can further strengthen the interfacial bonding. For the studied joints, the strength can reach 18.66 MPa, being 55% higher than without ultrasonic strengthening. The ultrasonic vibration creates shock waves in the adhesive layer, causing a high-speed adhesive jet toward the adherend surface, which makes the interfacial bonding tight and promotes penetration of the adhesive into the anodized layer. The bonding strength is thereby remarkably improved by forming a larger interfacial contact area and more mechanically interlocked structures.

Development of an end-to-end simulation process chain for prediction of self-piercing riveting joint geometry and strength

Abstract Self-piercing riveting (SPR) is one of the advanced mechanical joining techniques used intensively in modern automobiles. SPR is a cold forming process involving a semi-tubular rivet as fastener to join two or three similar or dissimilar materials. The present study deals with the development of a five-step simulation process chain capable of numerically predicting the SPR joint geometry and the joint strength under different loading conditions such as Shear, Cross-tension and Peel loading. The complete process chain considers a 2D axisymmetric model for the process simulation and a 3D simulation model with solid-shell interaction for the joint failure simulation. The calibration of damage models and their application in the joint strength analysis are integral parts of the present study. The comparison of joint strength analysis results with experiments under the criteria: mode of joint failure, maximum force (indicating joint failure) and displacement at maximum force provides basis for validation of the simulation process chain. Additionally, a comparison of joint geometry with joint cross-section images and force-displacement curves from experiments provides an opportunity for an intermediate verification of the numerical process flow. The study also presents an accuracy comparison of different damage models and the impact of rivet setting depth on the joint strength and mode of joint failure.

Joining of thermoset carbon fiber reinforced polymer and AZ31 magnesium alloy sheet via friction stir interlocking

Friction stir interlocking (FSI), a new derivative friction stir welding, was used to lap join AZ31 magnesium sheet and thermoset carbon fiber reinforced polymer (TS-CFRP) sheet. Instead of directly joining AZ31 and TS-CFRP, a series of magnesium interlocks were used to friction stir weld with AZ31 sheet to enable joining with TS-CFRP. Microstructural characterization of joint cross sections showed that a tool rotation rate of 800 rpm produced incomplete mixing of magnesium interlocks and the top AZ31 sheet, while 1200 rpm achieved sufficient material mixing to avoid unwelded regions. Mechanical property characterization showed that AZ31/TS-CFRP dissimilar joints failed through the magnesium interlock shanks during lap shear tensile testing, with a maximum normalized joint strength reaching ~ 100 MPa. Finite element analysis of the joints helped elucidate the presence of high stress region around the narrow band of the interlock shank providing pathway of fracture.

Comparison of properties of Al-Cu soldered and resistance welded joints

The paper presents the results of qualitative tests of Cu-Al joints made by soldering, brazing and resistance welding. Aluminum and copper tubes with a diameter of 6.9 mm, used, among others in refrigeration systems, were soldered with ZnAl2 and AlSi12 filler metal. In addition, similar connections were made by resistance welding. Macroscopic tests of soldered and welded joints were carried out and the hardness distribution on the cross-section of joints was determined. The analysis of research results allowed to state that resistance welding of Cu-Al joints can be a good alternative to the soldering process, especially in series production, due to the possibility of easy application of process mechanization.

Friction-Stir Welding of a Wrought Al-Si-Mg Alloy in As-Fabricated and Heat-Treatment States.

A wrought Al-11.3Si-0.6Mg alloy under hot extrusion (T1), solution treatment (T4), and solution treatment + artificial aging (T6) states were friction stir welded at welding speed of 100 mm/min and rotation rate of 800 rpm. The effect of prior heat-treatment on the microstructure and mechanical properties of the welds were investigated. The results show that the microstructures of the nugget zones have little dependence on the initial states of the base material. In the nugget zones, complete recrystallized structures with equaxied grains in the Al matrix were formed under all conditions. The Si particles in the nugget zones are almost unchanged compared with those of their base materials (BMs) in the three states. In contrast, the joint efficiency of the obtained welds was very sensitive to the initial material condition. The joint efficiency under the T1 state is more than 90% due to the fact that the microstructure is almost unchanged, except for the slight coarsening of the Al matrix grains and some of the Mg2Si phases during the friction stir welding process. However, the joint efficiency in the T4 and T6 conditions is only 77.22% and 62.03%, respectively. The relatively low weld strength in the T4 and T6 conditions is due to the elimination of the solid solution strengthening and age hardening effects during friction stir welding. The hardness distributions along the cross section of joints are all W-shaped under T1, T4, and T6 conditions.

Microstructures and mechanical properties of stainless steel clad plate joint with diverse filler metals

Thick stainless steel clad plate is used widely in the petroleum and petrochemical industries because of its low cost and good corrosion resistance. It is generally welded by the multilayer and multipass welding process with stainless steel filler metal matched with the clad layer. In this research, the base metal of stainless steel clad plates was filled with carbon steel filler metal, and the microstructures and mechanical properties of joints with diverse filler metals were analysed and compared. The results indicate that a local hardening zone (LHZ) forms in the weld filled with the filler metals of stainless steel and carbon steel because of the formation of martensite phase in the first layer of weld with filler metal of carbon steel. The microhardness value in LHZ reaches up to 425 HV1, which is significantly higher than that of the base metal. However, the tensile strength value of joints filled with carbon steel filler metal is equivalent to that of the joints with stainless steel filler metal. The results of the side bending test indicate that the LHZ protrudes from the weld, and the crack occurs near the LHZ if the area of the LHZ on the cross section of joint is larger than 17 % of that of the whole cross section of the joint. The studied results show that it is feasible to use carbon steel filler metal to fill the base metal of carbon steel in welding of stainless steel clad plate.

Characteristics of High-Strength Sheet Steel after Subsequent Heating

The influence of controlled rolling and the parameters of subsequent technological heating on the processes of structure formation in high-strength sheet steels EH36 and X70 is investigated. It has been established that when redistributing a thick sheet into products, it is necessary to minimize the temperature-time parameters to prevent softening processes. Welding, as one of the sources of technological heating, leads to a change in the structure in the zone of thermal influence and uneven distribution of hardness over the cross section of welded joints, which reduces the uniform strength of the structure as a whole. Short-term heating (about 15 minutes) even to temperatures above Ac1 (760 ° C) and cooling in air in the weld zone do not lead to significant changes in structure and hardness, but the degree of uniformity of the welded sheets increases.

Numerical simulation of hybrid joining processes: self-piercing riveting combined with adhesive bonding

Reliable simulation of hybrid joining processes using conventional finite element (FE) tools is challenging, because the liquid adhesive must be somehow included in the model. Thus, in this work the viscoelastic properties of the adhesive are substituted with “equivalent” mechanical properties. The complex viscosity of an epoxy-based single-component adhesive was determined at five temperatures between 20‒55 °C and at seven shear rates between 1‒150 s-1 using a rheometer. Flow stresses and strain rates were calculated from the complex viscosities and from the shear rates. For each temperature investigated the relationship between flow stress and strain rate was fitted with a power-law, which enables modeling the actually liquid adhesive as solid with strain rate-dependent flow stress. In order to validate the material model, a defined volume of adhesive was uniaxially compressed. This testing setup was also modelled using the FE software Simufact Forming 15. In the model the Young’s modulus of the adhesive was iteratively adapted until good agreement between the numerical and the experimental force-displacement curves was achieved. The obtained mechanical properties were finally used for modeling the adhesive layer between two 2.0 mm-thick 6xxx aluminum alloy blanks in the hybrid riveting-bonding process. An axisymmetric model including deformable (rivet, upper blank, lower blank, adhesive layer) and rigid (punch, die, blankholder) components was built in Simufact Forming. The cross-section of the hybrid joint obtained from simulation showed very good geometrical agreement with cross-sections obtained from the joining experiments, and just small differences between the calculated and the measured force-displacement curves was observed.

Uticaj brzine zavarivanja trenjem sa mešanjem na mehaničke karakteristike zavarenog spoja AA2024 T351 aluminijumske legure

The aim of this study is to analyze how the process parameters affect the mechanical properties of butt joints obtained by friction stir welding (FSW). The experimental study was performed by the FSW of sheets having a thickness equal to 6 mm and made of aluminum alloys AA2024 T351, varying the process parameters, namely rotational speed and welding speed. The following welding parameters were used: the rotation speed of the tool did not change and amounted to 750 rpm, and the welding speed was 73, 116,150 mm / min. The welds were obtained without the presence of errors and with an acceptable flat surface of the compound. Tensile tests were performed orthogonally to the welding direction on specimens having the welding nugget placed in the middle of gage length. Vickers hardness measurement was conducted perpendicular to the welding direction, a cross-section of the weld joint. The hardness profiles were obtained along 3 horizontal and 63 vertical directions. Bend testing was carried out according to EN 910 The bending specimens were tested using face and root side of the joint in tension.

The Joint Cross Section of Option and Stock Returns Predictability with Big Data and Machine Learning

Which market has leading informational advantage: stocks or options? Using large set of stock and option characteristics, and machine learning, we provide a comprehensive analysis of which characteristics are the first order importance predictors of options and stock returns. First, we find that options, rather than stock, characteristics are dominant predictors of options returns. Second, options, rather than stock, characteristics are also dominant predictors of stock returns. Consistent with the argument that an increase in trading activity in derivatives decreases information asymmetry about the underlying, options illiquidity is identified as the most important predictor of both stock and options returns.

Research of the influence of electron beam welding of titanium alloys on hydrogen distribution in the weld

The paper presents the results of analyzing distribution of hydrogen in welded joints obtained by electron beam welding of titanium alloys VT20 and VT23. The distribution of hydrogen in the cross section of welded joints was measured in the area of the weld, in the heat-affected zone and in the base metal by means of spectral analysis using low-voltage pulse discharge on the spectrograph ISP-51. It was established that hydrogen peaks in fixed joints obtained by electron beam welding, unlike argon arc welding, are located not only in the heat-affected area, but also in the сentral part of the welded joint. Chemical analysis of fractures of fixed joints investigated with the aid of a scanning electron microscope Hitachi S-3400N showed that the pores in the welded joints made by electron beam welding occur due to the desorption of capillary-condensed contaminants located in the defects of the edge surface into the melt and due to selective grain boundary fusion because of insufficient temperature conditions of whole grain melting. It was found that emerging variations in hydrogen content, with formation of defects, are influenced by the temperature conditions of heating of the welded edges, the welding rate and the thickness of welded blanks.

Semi-dwarf 1 (sd1) gene enhances light penetration into the canopy through regulating leaf inclination angle in rice

Manipulating leaf inclination angle is a feasible approach to improve canopy photosynthesis and dry matter production in rice (Oryza sativa) via enhancing light penetration into the canopy. The importance of the semi-dwarf 1 (sd1) gene, a loss-of-function allele of SD1 encoding GA-20 oxidase-2 in gibberellin (GA) biosynthesis, in rice yield through improving lodging resistance is well known. However, little is known about the effects of sd1 as well as GA on leaf inclination angle. A near-isogenic line carrying the ‘Takanari’ sd1 allele in the ‘Koshihikari’ genetic background (NIL-sd1) had leaves with larger (more erect) leaf inclination angle and showed a smaller canopy extinction coefficient at the ripening stage than did ‘Koshihikari’. Furthermore, the leaf inclination angle of ‘Reimei’, an sd1 mutant in the ‘Fujiminori’ background, and of several other sd1 mutants in ‘Koshihikari’ background, was larger at the ripening stage than in parental lines, ‘Fujiminori’ and ‘Koshihikari’, respectively. The flag leaves of ‘Koshihikari’ plants treated with a GA biosynthesis inhibitor, paclobutrazol (PBZ), displayed a larger leaf inclination angle than did those of mock-treated plants during ripening. Treatment at the lamina joint of a flag leaf with exogenous GA3 or brassinolide (BL) significantly decreased leaf inclination angle. BL treatment increased the thickness of lamina joint tissue and the longitudinal cell length on the adaxial side of the marginal region of lamina joint, whereas GA3 treatment only increased the longitudinal cell length. NIL-sd1 had a lamina joint with decreased longitudinal adaxial cell length, but no difference in abaxial cell length nor tissue thickness in lamina joint cross section compared with that of ‘Koshihikari’. Thus, sd1 regulates the leaf inclination angle via a GA-based mechanism but not via BL involved in the crosstalk with GA.

Microwave-assisted alumina-zirconia brazed joint for microwave tubes

Alumina-zirconia joint was fabricated by microwave-assisted brazing technique at 980 °C for 15 min using TICUSIL (68.8Ag26.7Cu4.5Ti in wt%) as the brazing alloy. The brazed joints were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, Vickers microhardness evaluation, brazing strength measurement, and helium leak test. X-ray diffraction analysis confirmed the formation of Ti-based compounds at the substrate-filler alloy interfaces of the brazed joints. SEM images showed the substrate-filler alloy interfaces of the brazed joints. The EDX analysis determined the elemental compositions along the joint cross-section. Vickers microhardness measurement indicated reliable joint performance for the microwave-assisted brazed joints during actual application. Brazing strength measurement and helium leak test proved the formation of sound alumina-zirconia brazed joint by both microwave and conventional heating techniques. Scratch tests were performed on the cross-sectional surfaces of the alumina-zirconia joints. Scratch test results established the strong interfacial strength of the microwave brazed joints.

Joining of AA6061 to polyvinyl chloride via hot extrusion

Purpose The purpose of this paper is to join aluminium alloy AA6061 with polyvinyl chloride (PVC) sheets using the friction spot technique. Design/methodology/approach The AA6061 specimen was drilled with a semi-conical hole and put over the PVC specimen with a lap configuration. A friction spot technique was used to generate the required heat to melt and extrude the PVC through the aluminium hole. In this study, three process parameters were used: time, plunging depth and rotating speed of the tool. Thermal finite element model was built to analyse the process temperature. Effect of the process parameters on the joint shear strength and temperature was analysed using the design of experiments method. The microstructure investigation of the joint cross section was examined. Findings The input heat melted and extruded the polymer into the aluminium hole with the aid of tool pressure. A mechanical interlock was observed at the interface line between the polymer and aluminium. The scattered aluminium fragments into the molten polymer increased the shear strength of the joint. The hole diameter exhibited the highest effect on the joint strength compared with the other parameters. Specimen of minimum hole diameter recorded the maximum shear strength of 224 MPa. The proposed model gave a good agreement with the experimental data. Originality/value For the first time, the PVC was joined with AA6061 by the hot extrusion using the friction spot technique. The shear strength of joint reached 7.5 times of the base material (PVC).

Modeling of 3D temperature field in butt welded joint of 6060 alloy sheets using the ANSYS program

In work, the modeling of a three-dimensional temperature field in a butt weld connection of two 6060 aluminum alloy sheets using Finite Element Method is presented. The calculations were performed for two welding methods: TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas). The Goldak's double ellipsoidal heat source model has been used in modeling. The thermal-mechanical properties of the material were assumed to depend on the temperature. The Workbench, DesignModeler, Mechanical, Fluent and CFD-Post modules of the ANSYS program were used for numerical simulations. In the description of the geometry of joints, cube type elements were used, with density of grid in the heat affected zone. The parabolic shapes of face and root were assumed based on the literature and results of the experiment. The temperature distributions in cross-sections of welded joints as well as welding thermal cycles at selected points were analyzed. The results of numerical simulations were verified experimentally. Comparison of calculated and obtained in the experiment the characteristic limits of heat affected zones showed satisfactory compatibility. The directions of heat propagation determined by vectors of cooling rates coincide with the longitudinal axis of dendritic grains determined on the basis of metallographic tests.

Consumable friction plug welding of TC4 plate: parameters, microstructures, and mechanical properties

In this paper, a technique of consumable friction plug welding (CFPW) was introduced in the welding of TC4 plate for repairing the keyhole and defects. A semi-consumable friction head composed of a nickel base super-alloy clamping shoulder and a titanium alloy plug was designed. Several defect-free welded samples have been obtained and the process window of CFPW for TC4 plate has been explored. The process window of CFPW for TC4 alloy was very narrow. The cross sections of CFPW joint were divided into five zones with different microstructure. The final microstructure in the thermal deformation (TD) zone was refined. The ultimate tensile strength and elongation of the CFPW samples were both up to 85% of the base metal, and the base heat affected (BHA) zone was a weak region in the joint. The hardness fluctuation of joint cross section was closely related to the change of microstructure in different welding zones

Optimization of Welding Process Parameters in Novel Friction Stir Welding of Polyamide 66 Joints

The friction stir welding of polyamide 66 with a specially modified tool is studied. A variation of the conventional friction stir welding is investigated by incorporating a friction plate for the purpose of heating the polymer in the course of welding process through the tool shoulder. This in turn, improves the efficiency of the weld. The association of the welding process parameters and the weld performance has been investigated by the grey relational analysis with multi response characteristics like weld tensile strength, percent elongation and hardness. Macrostructure of the weld joint cross section has been explored by Stereo microscope. The maximum weld tensile strength of 63 MPa and a Shore hardness of 60 D at the weld nugget are obtained. The hardness profiles of the welded samples have been analyzed in this investigation.