Improvement Of Joint Strength Research Articles

被着体簡易加工による接着継手強度向上の検討

被着体簡易加工による接着継手強度向上の検討

Interfacial evolution behavior of AgSbTe2.01/nanosilver/Cu thermoelectric joints

For high conversion efficiency thermoelectric generators, the preparation of fine and stable junctions between thermoelectric (TE) materials and electrodes is one of the core issues. In this paper, TE material AgSbTe2.01 applied in medium temperature (200–400°C) was successfully connected to copper electrode by low-temperature joining technique with nanosilver paste. 316 stainless steel was sputtered on the surface of TE material as the diffusion barrier layer. To investigate the interfacial evolution behavior, joints suffered from a bulk of harsh aging treatments under 200°C to 400°C in air environment. The results proved that 316 stainless steel could effectively block the diffusion between thermoelectric elements and element Ag in the solder at 200°C to 400°C. The formation of FeTe2 at AgSbTe2.01/316 stainless steel interface realized a fine metallurgical interconnection which was benefit for the improvement of joint strength. However, the mismatch of crystal structure between FeTe2 and AgSbTe2.01 might lead to defects under harsh environment. It was also concluded that the failure at Ag/Cu interface caused by the formation of CuO would be the main reason for the failure of the whole junction.

Interface evolution analysis of graded thermoelectric materials joined by low temperature sintering of nano-silver paste

Lead free solder Sn96.5Ag3.0Cu0.5 (SAC305) and nano-silver paste were used to connect graded thermoelectric (TE) arms, respectively. A series of harsh aging tests were carried out on joints of both p-type and n-type graded TE arms. The results showed that nano-silver paste printed by low-temperature joining technique was much more suitable for the stable connection of TE materials working in medium temperature range. 316 stainless steel and nickel were proved effectively as diffusion barrier layers in p-type junctions. While for n-type TE junctions, when aging at 300 °C, (Fe, Cr, Te) ternary alloy could be detected at Bi2Te2.7Se0.3/316 stainless steel interface. The formation of ternary compound realized fine metallurgical interconnection which was benefit for the improvement of joint strength. The average joint strength for p-type and n-type junctions in graded TE arms were above 20 MPa and 30 MPa, respectively.

Microstructures and mechanical properties of metal inert-gas arc welded Mg–steel dissimilar joints

The joining of Mg alloy to steel was realized by metal inert-gas arc welding, and the weld thermal cycle characteristics and Mg–steel joints were investigated. The results show that the temperature distribution in the joints is uneven. Mg alloy welds present a fine equiaxed grain structure. There exists a transition layer consisting mainly of AlFe, AlFe3 and Mg(Fe, Al)2O4 phases at Mg/steel interface, and it is the weakest link in Mg–steel joints. The welding heat input and weld Al content have the significant effect on the joint strength. The joint strength increases with increasing the heat input from 1680 J/cm to 2093 J/cm, due to promoting Mg/steel interface reaction. When weld Al content is increased to 6.20%, the joint strength reaches 192 MPa, 80% of Mg alloy base metal strength. It is favorable to select the suitable welding heat input and weld Al content for improving joint strength.

Increasing the Structural Integrity of Hybrid Plastics-Metal Parts by an Innovative Mechanical Interlocking Effect

In order to exploit full potential of hybrid materials, it is necessary to develop optimized load-dependent component designs, new manufacturing processes and joining technologies. Structural integrity concerning the interfaces between the single materials of the hybrid component poses a key factor to success. In this case, adhesion often constitutes the limiting factor for the maximum transferable load. In this investigation, a load-oriented innovative concept to increase the structural integrity of hybrid plastic-metal parts was developed. Local mechanical undercuts on the metal surface were created to generate an additional mechanical interlocking effect between the join partners. The aim is to find the best surface structure geometry to enhance mechanical bonding. Therefore, metal samples were structured by a new process and transferred to hybrid specimens by injection molding. For comparison, specimens with adhesive bonding (epoxy resin) of metal and plastic were prepared. The join partners aluminum AlCuMg1-2017 and PA6 as well as PA6GF30 were investigated. The evaluation of an increase in the structural integrity was determined using tensile tests. A significant improvement in joint strength compared with direct joining using adhesive bonding was achieved.

Application of the Taguchi method for the optimization of the strength of polyamide 6 composite hot plate welds

Abstract The purpose of this study is to investigate the influence of the welding parameters in the hot plate welding process of polymer composites, polyamide 6 glass fiber reinforcement 15 wt.-%, by using the Taguchi method. Four welding parameters, namely the plate temperature, heating time, welding displacement and welding time, were optimized under the consideration of the joint strength. The Taguchi approach of the parameter design was used as a statistical procedure to set the optimal welding parameters. For hot plate welding of the specimens, the combination of process parameters based on three levels of the L9 orthogonal array was utilized. The signal to noise and the analysis of variance were employed to find the optimum levels and to indicate the impact of the welding parameters on joint strength by tensile tests of welded joints. It was shown that choosing 270 °C as plate temperature, 1.0 mm of weld displacement and 25 s of heating time, reveals an improved joint strength. For the optimized parameters it was verified that the welding time does not have a significant influence and the most effective factor on joint strength is the plate temperature. The weld displacement and heating time only slightly influenced the joint strength. A confirmation run was also performed to prove the effectiveness of the Taguchi method after determination of the optimum levels of the process parameters. The results showed that the joint strength was improved by about 27 % as compared to the initial welding parameters and the joint efficiency increased from 56 % to 71 %.

153 被着体簡易加工による接着継手強度向上の検討

153 被着体簡易加工による接着継手強度向上の検討

Shear strength of Cu-to-Cu joints using mixed Ag particle paste

The high-temperature joining process is a key technology for electronic components and assemblies of automotive and other high-temperature applications. Recently, focusing on a sintering behavior of metal particles, the joining process using metal particles has been proposed as a solder alternative to establish a new joining technology for high-temperature applications. In this study, mixed Ag particle pastes were experimentally applied and the effect of the addition of Ag nanoparticles into micro-sized Ag particles on the joint strength has been studied to improve joint strength using Ag particle paste. Then, the effect of joining atmosphere on the joint strength of Cu-to-Cu joint using mixed Ag particle paste has been investigated.

Investigation of Hot-Staking Process Parameters and Evolution of Improvement in Joint Strength

The capability of hot-staking in providing mechanical as well as electrical joints along with its versatility and cost effectiveness makes it a process of preference in electrical and electronics appliances. However, the effectiveness of the process depends only on the mechanical contact and there is no welding or fusion between the joining surfaces. This necessitates proper selection and control of process parameters. This study investigates using Taguchi experiments the importance of process parameters for hot-staked joints in armatures of DC motors. Results show that the electrode material, geometry, and its position are significantly important. Based on the findings, a hypothesis is reasoned about process-product relationship to enable evolving in joint strength.

Effects of electric field on interfacial microstructure and shear strength of diffusion bonded α-Al2O3/Ti joints

There have been reports about electric-field-assisted diffusion bonding of electrolyte materials, but how dielectric materials behave in such process hasn’t been seen in literature. In this work, a dielectric ceramic of α-Al2O3 was successfully diffusion bonded to pure Ti under electric field with improved diffusion of elements and mechanical properties of the joints. Mechanism of the promoting effects of electric field was revealed. By turning-direction polarization of α-Al2O3 molecules and electrostatic attraction force between Ti4+ ions and electronegative O atoms, the diffusion of elements at the interface is promoted, thus resulting in thicker reaction layers and higher shear strengths, which reach the maximum of 110.1 MPa under 1100 V voltage, 50.2% higher than that without electric field treatment. Electric-field-assisted diffusion bonding may be a promising method to improve joint strength and lower undesirable bonding parameters.

Fatigue characteristics of jagged pin-reinforced composite single-lap joints in hygrothermal environments

This study aims to identify the reinforcing effects of jagged z-pins on the static and fatigue strengths of composite single-lap joints. We conducted tests on composite joints reinforced with jagged stainless-steel pins under the three environmental test conditions: room temperature and dry (RTD), elevated temperature and dry (ETD), and elevated temperature and wet (ETW). Test results showed that reinforcement with z-pins improved joint strength under all test conditions. In particular, when jagged z-pins were used under the ETW condition, static and fatigue strengths at a million cycles increased by 32.2% and 65.8%, respectively, compared with the corresponding values for an unpinned joint. When standard z-pins—without the jagged pattern—were used, the static and fatigue strengths increased by 13.4% and 11.8%, respectively. In the future, if the jagged shape and pin density are optimized, we expect that the effect of z-pinning can be further improved.

Characterization of the Si3N4/Si3N4 joints fabricated using particles modified braze

Abstract The Si 3 N 4 ceramics were brazed to themselves by using particles modified braze to control mismatch of thermal expansion and improve joint strength. The brazed joints were examined by using scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM), atomic force microscope (AFM) and nanoindentation tester. The results show that a duplex reaction layer which is composed of TiN and Ti 5 Si 3 was formed at the Si 3 N 4 ceramic/braze interface. Two kinds of particles were incorporated in the Ag–Cu–Ti braze. One is SiCp (p=particle), which would react with Ag–Cu–Ti braze and produce Ti 3 SiC 2 , TiC and Ti 5 Si 3 reaction phases. The other is Mo particles, which would not interact with Ag–Cu–Ti during brazing, but many kinds of Cu–Ti intermetallics would occur in the brazing layer after brazing. The strength tests demonstrate that the hard metal particles should be preferentially selected as the incorporation when a low Ti content (≤4 wt%) is supplied in the joint. When the Ti content (>4 wt%) was offered sufficiently, the ceramic particles exhibited an excellent ability to improve the joint strength since an optimum structure in relieving residual stresses was achieved by expediently adjusting the particles and Ti content in the joint. Compared with large sized SiCp or Mo particles, the incorporation with small size produced a relatively low joint strength since Ag–Cu matrix was segmented by an abundance of small sized particles in the brazing layer. At last, in situ AFM analysis shows that deviation of crack path occurred during bending when SiCp or Mo particles were used, retarding the joint fracture and improving the joint strength. The results obtained can provide valuable guidelines for designing a composite braze for a ceramic joint.

Interfacial Microstructural Characterization of Ti/Al Joints by Gas Tungsten Arc Welding

Ti/Al dissimilar materials were welded by gas tungsten arc welding with filler wires. Microstructure in the Ti/Al joint was studied with optical microscope, scanning electron microscope, energy-dispersive spectrometer, etc. Results show that various Ti–Al intermetallic compounds are formed along the interface. According to the degree of Ti alloy melted, interface is divided into different reaction layers. Under the effect of martensite transformation, microhardness in heat-affected zone is higher than it in titanium base metal. Element silicon enriched in the interface. The dispersive distribution of precipitated phase improved joint strength.

Contribution for the Simulation of Tube-Bulk Forming by Lateral Extrusion of Flanges and Collars in Light Weight Components

Joining using forming processes in the field of bulk metal forming is currently experiencing a renaissance both within research projects in academia and industrial manufacturing processes. One main challenge of such research activities is any improvement of joint strength. In contrast to conventionally joined interference fits, such components can be manufactured without heating or thermal loads. Within framework of the priority program SPP 1640 of the German Research Foundation, a common lateral extrusion process for a solid internal part and an external tube actually is being developed at the Institute for Metal Forming Technology, Stuttgart. Aim of this project is to manufacture a form-closed as well as force-closed joint composed by a high strength external material and a light weight internal material for light-weight components. The present work describes numerical investigations of this process and shows aspects of process development. This includes, among other things, development of a new tool concept, which provides divided punches to determine the influence of different punch motion on the forming and joining process. Spring back behavior, induced residual stress distribution and occurring contact area depending on different material combinations are also investigated. Moreover, the process limits regarding component geometry and force requirement are shown.

Self-piercing riveting of aluminum alloy and thermoplastic composites

In the present study, the feasibility of joining PA6-matrix thermoplastic composite panel and aluminum alloy is considered. Self-piercing riveting processes of PA6 panels, PA6 composite panels with reinforcing fibers (glass fiber and carbon fiber), and 5754 aluminum alloy sheets are systematically investigated. Macro characterizations of the appearance and transverse sections of the self-piercing riveting joints were conducted to provide more comprehensive understanding of the composite deformation during riveting process. In particular, the effect of reinforcing fibers on the composite deformation behaviors was characterized. Lap-shear testing of the self-piercing riveting joints was performed to evaluate joint strength, and characterization of the fractured joints as well as failure mechanics analysis was conducted to investigate the underlying failure mechanisms of the self-piercing riveting joints. The effects of reinforced fibers on the failure mechanisms and mechanical performance were also discussed. The results showed that self-piercing riveting is an effective technique for joining fiber reinforced thermoplastic composite panels and aluminum alloy sheets. In addition, self-piercing riveting joints with glass fiber reinforced composite failed in a bearing mode and exhibited improved joint strength compared with the PA6 matrix; while self-piercing riveting joints with carbon fiber reinforced composite exhibited slightly decreased joint strength but significantly reduced ductility, owing to the brittleness of the carbon fiber reinforced composite.

20403 被着体円孔の接着剤充填による投錨効果を利用した継手強度向上の試み

20403 被着体円孔の接着剤充填による投錨効果を利用した継手強度向上の試み

高張力薄鋼板の溶接継手強度を向上させるパルススポット<sup>®</sup>溶接技術の開発

高張力薄鋼板の溶接継手強度を向上させるパルススポット<sup>®</sup>溶接技術の開発

DISSIMILAR METALS CONNECTION THROUGH FRICTION STIR WELDING (CU-AL)

The aim of the paper is to analyze the existing techniques of producing copper and aluminum compounds. The subject matter was to study the possibility of using FSW for producing copper and aluminum compounds. The process of producing the copper and aluminum lap joints is described, welding conditions are discussed. The copper and aluminum overlap joints microstructure is investigated. The factors affecting the strength of copper and aluminum lap joints implemented through FSW are analyzed. The corrugation effect is investigated, and the remaining hole is studied to the strength of the welded joint. Stress distribution diagrams in the copper and aluminum lap joints are shown. The tests to the strength of various lap joints are resulted, the weld cut structure is analyzed, its processibility is estimated, and the joint strength improvement method is presented.

요철 형상의 스테인레스강 Z-핀으로 보강된 복합재 접합 구조물의 피로강도

Recently the authors had proposed the z-pinning patch concept to simply manufacture z-pinned composite structures at industrial production site and manufactured composite single-lap shear joint specimens using the concept. Through static tensile test on the specimens they had obtained 54~68% improvement of the joint strength. As a sequential study of it, in this study, fatigue test has performed to measure an improvement of joint strength under cyclic loading. The z-pin`s material is stainless steel and its surface was specially machined into zagged shapes and chemically corroded to increase the connection force with composite materials. Approximately 98~125% improvement of the joint strength under cyclic loading was obtained.

Improvement of SiC–Si/MAS Interface in the Joints via In Situ Synthesizing SiC Nanowires

Improving the SiC–Si/MAS interface is essential for enhancing the SiC–Si/MAS joint strength. In this work, well‐dispersed SiC nanowires (NWs) were in situ synthesized at the SiC–Si/MAS interface in the joints as the anchors, which made the fracture feature of the joints change from SiC–Si/MAS interface fracture to MAS fracture, resulting in an obvious improvement of the shear strength. The results showed that the average shear strength of the joints was increased by 49% by in situ synthesizing SiC NWs, which was primarily attributed to the excellent interface anchoring effects of SiC NWs involving the interfacial bonding anchoring between SiC NWs and SiC–Si layer and the mechanical interlocking anchoring between SiC NWs with the junctions and the surrounding grains. This study may provide new insight into the anchoring mechanisms and suggest a new design methodology for nanowire joints, leading to improved joint strength.