Joining Parts Research Articles

EFFECTS OF WELDING CURRENT AND SPEED ON RESIDUAL STRESS AND DISTORTION OF JOINING ST52 ROLLED PLATE IN DIFFERENT WELDING SEQUENCES

Welding is a process of permanent joining parts by different welding methods. Residual stress and distortion are the most common phenomena of this process. Reduction of the residual stresses, distortion and improving the quality of welding are the important subjects of this field. Determining and analyzing the residual stresses and distortion is the main step for these purposes. Welding sequences, speed and current are the most effective parameters of this process. In this study, effects of welding parameters such as welding speed and current, in order to reduce residual stress and distortion of welding ST52 rolled plate in different welding sequences have been studied with three-dimensional thermo-mechanical finite element model by means of ANSYS APDL. By comparing different considered situations, the most efficient welding methods with the least residual stress and distortion by considering different welding sequences have been suggested. It obtains that welding the ST52 rolled plate from edge to edge with higher current and lower speed is the best option in fatigue and load-bearing situations, and welding from the center to both sides simultaneously with lower current and higher speed is the best option for assembly problems.

A Security Refreshing Algorithm of Dynamic Node based on Fast Group-Blind Signature

In the contemporary society, electronic payment becomes a part of people’s life. It can make people’s life more convenient and faster. At the same time, security’s problem and efficiency’s problem in the electronic payment arouse the attention of many researchers. In this paper, we study group-blind signature algorithms in digital signature technology. We take LR98 group-blind signature algorithm as the research object and analyze its problems. The algorithm put the fixed value l as security parameter, which results in the low efficiency of algorithm. In this paper, new security parameters are adopted, and take blind signature method of Boldyreva into consideration, a new group-blind method is proposed, CL-LR98. New method is applied to wireless communication network (WSN). A number of communication nodes (AP) and user terminal (UE) are built, which is used as the experimental environment. New group-blind signature method is applied to dynamic refreshing of WSN nodes, which includes anonymous communication, data transmission. In the process of experiments, new group-blind method has excellent characteristics, it has short signature character length, it can be simply realized and it has better encryption performance. In the node joining part and revocation part of communication process, these excellent characteristics make computation small, make node refresh efficiency high, and it will not cause frequent movement of other communication nodes.

RESIDUAL STRESSES IN A THERMOELASTIC CYLINDER RESULTING FROM LAYER-BY-LAYER SURFACING

The article investigates the residual stresses arising in a thermoelastic cylinder as a result of layer-by-layer deposition of material on its lateral surface. Residual stresses are defined as the limiting values of internal stresses developing during the technological process. Internal stresses are caused by incompatible deformations that accumulate in the body as a result of joining parts with different temperatures. For the analysis of internal stresses, an analytical solution of the axisymmetric quasi-static problem of thermoelasticity for a layer-by-layer growing cylinder is constructed. It is shown that the distribution of residual stresses dependson the scenario of the surfacing process. In this case, the supply of additional heat to the growing body can significantly reduce the unevenness of the temperature fields and reduce the intensity of residual stresses. The most effective is uneven heating, which can be realized, for example, by the action of an alternating current with a tunable excitation frequency. This is illustrated by the calculations performed using the constructedanalytical solution.

Durability of Metal-Composite Friction Spot Joints under Environmental Conditions.

The current paper investigates the durability of the single-lap shear aluminum-composite friction spot joints and their behavior under harsh accelerated aging as well as natural weathering conditions. Four aluminum surface pre-treatments were selected to be performed on the joints based on previous investigations; these were sandblasting (SB), conversion coating (CC), phosphoric acid anodizing (PAA), and PAA with a subsequent application of primer (PAA-P). Most of the pre-treated specimens retained approximately 90% of their initial as-joined strength after accelerated aging experiments. In the case of the PAA pre-treatment, the joint showed a lower retained strength of about 60%. This was explained based on the penetration of humidity into the fine pores of the PAA pre-treated aluminum, reducing the adhesion between the aluminum and composite. Moreover, friction spot joints produced with three selected surface pre-treatments were held under outside natural weathering conditions for one year. PAA-P surface pre-treated specimens demonstrated the best performance with a retained strength of more than 80% after one year. It is believed that tight adhesion and chemical bonding reduced the penetration of humidity at the interface between the joining parts.

Development of a special specimen geometry for the experimental determination of fracture mechanical parameters of clinchable metal sheets

In order to reduce the energy demand and harmful emissions of moving masses, lightweight construction is becoming increasingly important. In many areas of product manufacturing the constructions consist of individual components and sheets that are joined together to form complex structures. Due to the simplicity of the process, clinching without auxiliary joining parts or pre-holes is often used. The utilized sheets are usually less than 2 mm thick and possibly characterized by anisotropy in the mechanical material properties because of different rolling directions. The sheets are arranged in an overlapping and partially interspersed way, so that impact extrusion results in an inseparable connection between the components made of the same or even different materials. During the joining process and due to the service load, cracks can occur in the area of the joint, propagate due to cyclic loading and consequently lead to structural failure. Within the scope of this paper experimental and numerical preliminary tests for the fracture mechanical characterization of the metal sheets used in the clinching process as well as first crack growth rate curves are presented. In order to determine the fracture mechanical parameters of the base material, the development of a new specimen geometry is necessary due to the low sheet thickness. The numerical calculation of the geometry factor function as well as the calibration function of this special specimen geometry enables the determination of the crack growth rate curves. Following the experimental validation of the numerically determined calibration function, crack growth rate curves are determined for the stress ratio R = 0.1. Furthermore, different rolling directions and further R-ratios are considered in the experimental investigations to examine the influence of the anisotropy arising during rolling and the mean stress sensitivity.

The Effect of CO2 Laser‐Induced Microhole Formations on Adhesive Bonding Strength of CFRP/CFRP Joints

There are many different techniques to improve the adhesion between carbon fiber‐reinforced plastics (CFRP) which are used in aircraft primary structures. One of the most common techniques is the specific surface structuring of the joining parts in order to obtain mechanical interlocking. In this study, laser‐induced surface structuring effect on adhesion strength of CFRP/CFRP joints was investigated by single lap shear tests. Microholes were created by CO2 laser with different configurations in x and y axis for the best mechanical interlocking effect on adhesive bonding. The effects of microhole numbers (309, 625, and 914) and microhole formations (triangle, inverted triangle, frame, and box) on the adhesive bonding strength of the CFRP/CFRP joints were determined by using single lap shear tests according to ASTM D5868‐01 standard with 60 kN DARTEC universal test machine. Single lap shear tests showed that microhole structuring has a significant effect on mechanical interlocking for adhesive bonding of CFRP/CFRP joints. Results showed that the shear strength of CFRP/CFRP joints improved at 309 microholes and frame type microhole formations. After mechanical tests, damage mechanisms were observed by using the optical microscope. POLYM. COMPOS., 40:2891–2900, 2019. © 2018 Society of Plastics Engineers

Innovative joining technology for multi-material applications with high manganese steels in lightweight car body structures

Due to restrictions imposed by legal requirements, automotive manufacturers are forced to reduce the pollutants emission of new models. A promising approach is the reduction of the vehicle weight, whereby the body in white offers great potential. This weight reduction is realized by new car body constructions, which contain the increasing usage of different materials. Furthermore, new lightweight materials like TWIP steels become more important. The successful and economic implementation of multi-material design with TWIP steels requires the availability of suitable joining technologies. Conventional thermal joining technologies can be used in consideration of specific characteristics related to welding austenitic steels. Within the project, challenging material combinations related to dissimilar materials are investigated. In this paper, high-speed joining is investigated as an innovative and promising joining technology for multi-material applications. This mechanical joining technology contains an auxiliary joining part, called tack, which is driven with high speed into the joining partners. The challenges as well as the optimization of the auxiliary joining part is shown. The investigations are attended by metallographic analysis, whereby mechanical properties are determined through destructive tests. The characteristics are compared to the results of current used standard tacks.

Numerical Simulation of Brazing Aluminium Alloys with Al–Si Alloys

Joining parts using low-melting temperature alloys has long been used for manufacturing complex components such as heat exchangers made of aluminium alloys. Investigations of the process have shown that core/ clad interaction during heating and brazing can lead to a significant decrease in the amount of liquid available for joint formation. This study presents a transient one-dimensional model for the process that takes into account the diffusion of silicon and the movement of the core/clad interface, with the model equations being implemented in the finite element software COMSOL Multiphysics; the results are compared to literature experimental data. Silicon profiles in the core are well described, while there appears a significant difference between predicted and experimental values of remaining clads which suggest a strong effect of silicon diffusion and liquid penetration at core grain boundaries.

Influence of fiber orientation and weld position in welding injection-molded fiber-reinforced thermoplastics

Several publications deal with the influence of the initial fiber orientation in joining parts on the weld strength of fiber-reinforced thermoplastics. The welding partners have been sawn before welding. Preparing the joining parts after injection molding is not suitable since it is an additional manufacturing step. Since injection molding results in a non-uniform fiber orientation, there is a possibility that the position of the weld influences weld characteristics. The influence of the initial fiber orientation was investigated by preparing parts with longitudinal or transverse initial fiber orientation. Short and long glass fiber-reinforced thermoplastics with a glass fiber content of 30% have been welded by hot-plate and vibration welding. The initial fiber orientation in non-welded parts influences the weld strength: longitudinal fibers are more advantageous for the weld strength than transverse fibers. The influence of the position of the weld in injection-molded parts was investigated by welding the plates at the end of the flow path, at the sawn gate, and at the lateral side. The weld strength is similar at the gate or at the end of the flow path. For PA-GF30, the weld strength at the gate is even higher. Positioning the weld at the lateral side in injection-molded parts results in significantly lower weld strengths for short and long glass fiber-reinforced thermoplastics in hot-plate and vibration welding.

Direct joining of 3D-printed thermoplastic parts to SLM-fabricated metal cellular structures by ultrasonic welding

The joining capability of metal cellular structures fabricated using the additive manufacturing (selective laser melting (SLM)) method is investigated herein. The metal cellular structures are composed of sub-millimeter holes and internal pores. The direct joining of 3D-printed ABS-M30i thermoplastic parts to metal cellular structures by ultrasonic welding is demonstrated. The SLM-fabricated structures comprised of partially melted powders provide micro-scale roughness, which enhances the micro-mechanical interlocking between joining parts. A shear strength 17.7 MPa and normal tensile strength of 15.2 MPa were obtained, up to 55 and 48% of ABS-M30i ultimate tensile strength, respectively. Moreover, normal tensile plastic strength up to 86% of the shear strength was obtained.

Application of and Changes in Construction Principles and Joint Methods in the Wooden Architecture of the Joseon Era: A Case Study on the Sungnyemun Gate in Seoul

Various efforts are needed to understand the construction principle of wooden architecture in the pre-modern era, as theoretical literature on this topic is lacking. This study shows that wooden construction methods are divided into two categories consisting of piled-up and integrated structures. The primary difference between the two categories is that the former is supported by a structural system weighted by a load from above, whereas the latter involves strengthening of the combination itself. In Korea, the framed system seen in a partially integrated structure is confirmed based on the structure of a piled-up framework. The Sungnyemun Gate is a representative example, and exemplifies piled-up techniques with a structural stability that is grounded by the load. However, the building′s interior is characterized by the active adoption of pass-through columns employed in the integrated structure. Such structural compromise results in great changes. When the authors examine the joining parts of major timber-framed structures like the Sungnyemun Gate, at its completion, it had weak joining connections in the piled-up structure; however, after several repairs, it was strengthened with an integrated structure. This thesis examines a regional peculiarity of the wooden architecture that adopted eclectic styles based on the piled-up structure.

Dual‐curing thermosetting monomer containing both propargyl ether and phthalonitrile groups

ABSTRACTNovel self‐curing monomer containing two thermosetting groups, namely propargyl ether and phthalonitrile (PN) in a molecular structure, is synthesized and investigated. The study of catalyzed and uncatalyzed curing is performed and high heat release during curing is observed. This disadvantage can be adjusted by catalysis of propargyl ether polymerization with Ni (II), Co (II), and Cu (II) salts. The cured monomer possesses high thermal properties featured to phthalonitrile matrices (Heat deflection temperature, HDT = 428 °C, T5% = 499 °C) and moderate mechanical properties (E = 4.9 ± 0.65 GPa, GIC = 106 ± 26 J/m2), it can be applied as a high temperature matrix for carbon fiber reinforced plastics (CFRP). Low melt viscosity (223 mPa s at 120 °C) of the monomer provides a possibility to consider its application for composite material formation by vacuum infusion or resin transfer molding (RTM) techniques, which are exceptionally rarely applied for matrices with HDT > 300 °C but allow to obtain composites of complex shape with minimal joining parts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44786.

Influence of surface treatment and purification methods of CO-115M glass-ceramics on optical contact strength

Subject of Research.We present findings of the optical contact for details made of СО-115Мglass-ceramics brand mark. The optical contact is the main method of joining parts made of CO-115M glass-ceramics brand mark in commercially available laser gyros. The existing technology has a number of unresolved issues related to the durability of the optical contact, that determine the tightness of the laser sensor internal volume. Method. Mechanical strength control of the optical contact consisted in the measurement of specific tear force of the connection. Mechanical strength tests of the optical contact were carried out with the use of RMI-250 tensile testing machine. The evenly increasing load of 50 N/s was applied to the samples in mechanical tests. The value with the occurence of the optical contact destruction was registered. Main Results. We have shown that one of the main factors determining the mechanical strength of the joint is cleanliness of the surfaces being connected. Comparison of the influence of different surface cleaning methods for optical elements on the optical contact durability has been given. The negative impact of even short-term storage of optical parts after washing on the assembly strength has been shown. The additional operation of mechanical polishing of surfaces of stored optical parts before connection enabled significantly reducing the scatter of the optical contact mechanical strength. We have also established experimentally that the heating of assembly of optical elements under vacuum at a temperature of 300°C leads to the twofold increase in the optical contact strength, while the optical contact remains separable. Practical Relevance. The carried out studies make it possible to improve the technical and operational characteristics of the laser gyroes. The use of additional mechanical cleaning of surfaces of optical parts and vacuum heating of the assembly in the process of laser sensor production may significantly improve the reliability, integrity, period of storage and operation.

СОВЕРШЕНСТВОВАНИЕ ТЕХНОЛОГИИ СБОРКИ СОЕДИНЕНИЯ ДЕТАЛЕЙ С НАТЯГОМ

The purpose of the study is to increase the strength of the collected compounds and to expand the technological accuracy of the method of Assembly with an interference fit. Fixed press-fit connection with interference are widely used in machine building, when the transfer of substantial axial forces are required, torques or combined loads from their joint action. Resistance to mutual misalignment of the parts in these compounds is created and supported by the forces of elastic deformation on the mating surface of the covered part (shaft) and stretching on the mating surfaces of the covering parts (holes) is proportional to the magnitude of the preload in the connection. In such compounds, the diameter of the shaft before Assembly is always larger than the diameter of the hole. In the article the analysis of the known different ways of joining parts with interference fit, including hydraulic presses. The second problem is solved due to the fact that the connection details with tightness is carried out by pressing the press stroke from one detail to another, and the breakdown of the compounds obtained by the relative longitudinal movement of parts, in which the breakdown is carried out periodically in the process of pushing through the transfer of force from the press stroke to pressed items to the elastic connection. The force on the press stroke is created by a hydraulic cylinder with large displacement, a resilient connection between the slider and pressed item performs in the cylinder, the fluid pressure and volume which can be adjusted by changing the stiffness and capacity of the drive RAM, as well as the magnitude of its longitudinal movement during the disruption. The scheme of Assembly of the connection de-hoist with tension. Original technical solution for press fit connection parts extends the technological possibilities of the equipment, increases the strength of the collected compounds and can be used in machine building, particularly in mechanical Assembly processes and, in particular, in the repair and production of agricultural machinery.

Design of Modifications for Constructional Elements of Manipulator Arm Aimed at Measuring of Operational Torque

There are often designed such constructional elements in the engineering practice that are specified for sensing of operational loading and for a precise setting of the individual components in the given technical device, for example components of a robot arm. Positioning of the robot arms is regulated by means of power output setting (or torque setting) of the driving parts (motors) predominately. Driving effect is transferred between the individual components by means of the connecting parts designed for transfer of force flow. There is described in this paper such design of modification for constructional element of the robot arm, which enables to perform measuring of torque in the joining parts of the robot arm during a current operation.

A New Substance to Substance Joining Technology for Glasses

Currently substance-to-substance joining procedures (bonding, soldering, welding) create an adhesive bond with filler materials. For glasses these procedures are only applicable with restrictions. Therefore the aim was the development of a new force-time-controlled substance-to-substance joining procedure without filler material. During a thermal treatment a dynamic force affects the parts to be joined. This force is transmitted to the joining parts through their rotation energy homogeneously and enables a joining of large surfaces without undesired pressure peaks. The monolithic joined body gets unstressed in a subsequent cooling regime. Significant advantages of this technology are the low-stress joining of glasses without filler materials and a combinability of different glasses.

Research on Quality and Reliability of Cold-Pressing Joining Between Aluminum and Stainless Sheets

Lightweight forming was one of the main ways to achieve energy conservation and emission reduction in advanced manufacturing. However, the cold-pressing process was easier to realize dissimilar sheets joining and could reduce the weight of both the material and the structure; therefore, this process was widely used. Taking aluminum and stainless sheets joining as an example, this study designed three kinds of joining schemes based on the theory of materials mechanics. It was concluded that the increase of the load pressure made the joining parts of the two sheets fitted quickly, but it decreased the joining thickness through the research of different joining project results. In the joining process, defects such as overlap, warping, protrusions, pitting, and partial cracking led to decreasing surface quality and reliability of the joining part. It was demonstrated by the sheet specimen unidirectional tensile test that the “embedding” and the “interlocking” were the main mechanisms of cold-pressing joining.

塑性流動結合の結合強度に及ぼす硬質穴部品内径の段差量とクリアランスの影響

In a previous study, a new metal flow joining method that enables a shaft and ring to be combined without the need for any specialized punch was examined. In this method, the shaft was loosely fitted on the ring, which has a step, and then pressed. Metal flow caused the shaft to be joined to the ring upon pressing. As a result, the maximum joining efficiency (i.e., the shaft return-proof load / joining load) of the new method was more than 25%. In this study, the method was examined in detail in the experiment using a JIS S45C shaft (soft shaft) and JIS SKD11 ring (hard ring). Specifically, the initial dimensions of the joining hole of the ring were evaluated. First, the effect of the step width at the hole on the shaft-return-proof load was investigated. For different step widths, an 18- or 19-mm-diameter hole was combined with a concentric 20-mm-diameter hole. Second, the effect of the radial clearance between the hole and shaft on the proof load was investigated. The size of the 20-mm-diameter hole was varied to create three clearances ranging from 0.015 mm to 0.055 mm. As a result of this study, the proof load and the joining efficiency were found to be increased by using a ring with a narrower step width. The proof load reached 1.3 times greater than that in the previous study. On the other hand, the proof load and the joining efficiency were not affected by the clearance, the tightness of which would be related to the cost and productivity of joining parts with holes.

Research on the influence rules of hole type on the quality of sheet embedded cold-pressing joining

The method of embedded cold-pressing joining could achieve the joining of sheets with different thickness and the joining of dissimilar sheets. Besides, it could meet the lightweight request easily. This article expounded the joining mechanism of this method deeply. To expound the joining mechanism of this method, this article has taken aluminum and stainless steel as examples. In addition, numerical stimulation studies of different hole types’ connecting processes had shown that it was easier to reach plastic yield conditions for aluminum and deform it under the same load conditions. The deformation achieved was significantly greater than that for stainless steel. The width increment of the joining parts increased with the increase of the load pressures; however, the thickness changes of the joining parts behaved in an opposite manner. When the pressing volume of the punch reached 2.4 mm, with the width increment of aluminum sheets of the square hole reaching 2.78 mm, which was the maximum width increment, followed by the hexagonal hole, and the round hole being a minimum. Hole type had a small influence on the width of stainless steel sheets. The experimental results of different hole type joining process indicated that compared with round hole and hexagonal hole, the filling of the square hole was relatively difficult. In case of unreasonable process schemes, defects such as “fake joining,” “offset loading” and “hole deformation” would occur. Thus, this article provided a theoretical basis for the scheme establishment and quality control of the embedded cold-pressing joining process.

Novel Type of Aluminum-Alloy Jacketed ${\rm Nb}_{3}{\rm Sn}$ Superconductors Manufactured by Friction Stir Welding Technique

New process to compose a reacted Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting cable with aluminum-alloys has been developed by using friction stir welding (FSW) technique. The FSW joining process, which takes place in the solid phase below the melting point of the materials, has considerable advantages such as a high strength of welding zone and much lower distortion due to both small heat affects and reliable control of joining depth as compared with conventional welding method. In order to realize practical aluminum-alloy jacketed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconductors, we have carried out elemental researches by using FSW technique. For a fabrication of aluminum-alloy jacketed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconductor of a dimension 17 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</sup> × 4.9 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sup> a Rutherford type superconducting cable having 18 reacted Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands of diameter 1.0 mm was assembled into a set of channel and fitting-cover made of aluminum-alloy A6061-T6 with filling material indium. Then, their joining parts were connected by using the FSW technique. The measurement on critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of the fabricated Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconductor achieved over 9.5 kA at 8 T, 4.26 K even after bending with a radius of 150 mm in a flatwise direction, which showed no degradation in comparison with I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> values multiplied by number of strands in the cable. As the results, we succeeded in developing novel type of aluminum-alloy jacketed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconductors manufactured by FSW technique, which have large current capacity, sufficient allowable bending strains for a coil winding and improved contact between a cable and an aluminum-alloy jacket. The developed superconductors will be applicable to react-and-wind superconducting magnets having very large current at high magnetic field such as nuclear fusion reactors and detectors for high energy physics of the next generation.