Multi-layer Joint Research Articles

Simulation of sports movement training based on machine learning and brain-computer interface

Injuries and hidden dangers in training have a greater impact on athletes ’careers. In particular, the brain function that controls the motor function area has a greater impact on the athlete ’s competitive ability. Based on this, it is necessary to adopt scientific methods to recognize brain functions. In this paper, we study the structure of motor brain-computer and improve it based on traditional methods. Moreover, supported by machine learning and SVM technology, this study uses a DSP filter to convert the preprocessed EEG signal X into a time series, and adjusts the distance between the time series to classify the data. In order to solve the inconsistency of DSP algorithms, a multi-layer joint learning framework based on logistic regression model is proposed, and a brain-machine interface system of sports based on machine learning and SVM is constructed. In addition, this study designed a control experiment to improve the performance of the method proposed by this study. The research results show that the method in this paper has a certain practical effect and can be applied to sports.

Simplified stress analysis of multilayered adhesively bonded structures

Bolting technologies have been commonly used to assemble structural members in order to carry loads. However, the main drawback of these joints is the local reduction of the strength-to-stress ratio. Compared to the bolted joints, adhesive bonding technology allows for the increase of static and fatigue strength while reducing the weight. The Finite Element (FE) method is able to address the stress analysis of bonded joints. Nevertheless, analyses based on FE models are computationally expensive. Therefore, it is profitable to develop new simplified approaches enabling extensive parametric studies. A semi-analytical technique was developed to model the joints based on the formulation of 4-node special elements, termed macro-elements, which is able to simulate an entire bonded overlap at low computational costs. In this paper, a multilayered bonded-bars and a multilayered bonded-beams macro-elements are derived from bonded-bar and bonded-beam macro-elements. 1D-bar and 1D-beam simplified stress analyses of such multilayered joints are presented in order to predict the adhesive stress distributions along the overlap. For validation purpose, the results obtained by the simplified 1D-bar and 1D-beam model are compared with the results predicted by 1D-FE models. Good agreements are shown. Finally, the parametric studies are performed in order to understand the mechanical behavior of multilayered adhesively bonded structures. This presented simplified stress analysis can be used to deduce the sizing guidelines as a consequence of these parametric studies.

Evolution of the stress field near the Arava basin located along the Dead Sea Fault system as revealed by joint sets

To reveal the development of the stress field near the Arava basin located along the Dead Sea Fault system, we characterized joint sets that were exposed mainly in the Santonian and Eocene chalk rock outcropping in the study area.In total, ~2600 strike orientations of single-layer joints (SLJ) and multilayer joints (MLJ) mirrored four main stress fields: 1) σHNW(J1-326°), 2) σHNNW(J2-343°), 3) σHNNE(J3-033°), and 4) σHN (J4-360°).The results showed that the relatively lower values of the fracture spacing ratio (FSR) and their standard deviations in J1 implied that J1 was formed during the burial stage of the Eocene chalk formations. The inconsistency between the statistical parameters of the log-normal distributions of joint spacing and FSR raised doubt about the applicability of the “saturation joint density model” in our studied area.The joint sets characteristics suggest that the regional σHNW operated during the Eocene. During the Miocene, the regional stress field changed clockwise to σHNNW, probably in association with the early stage of transform motion along the Dead Sea Fault. In the Pliocene-Pleistocene, the σHNNE and σHN local stress fields both operated and were accompanied by a tensional stress field that can be identified in the intensive normal faulting evolved along the western Arava basin margins.

Development of tungsten armored high heat flux plasma facing components for ITER like divertor application

The dome and reflector plate are the parts of divertor plasma facing components (PFCs) of ITER tokamak which are mainly aimed for the removal of heat load of maximum 5 MW/m2 in steady state condition. The dome is a curved tungsten armoured component and the reflector plate is a straight component. These components have multi-layered joints made of various materials such as tungsten (W), OFHC copper (Cu), copper alloy (CuCrZr) and stainless steel (SS316LN). Joining of such multi-layered joints is known to be problematic due to joining of several dissimilar materials. In this paper, we report the indigenous development of medium size dome and reflector plate via vacuum brazing route for ITER like tokamak application. In order to evaluate the performance of the dome against ITER-like scenarios (maximum heat flux removal of 5MW/m2), the dome has been successfully tested for 1000 number of steady-state thermal cycles at incident heat fluxes of 3.87 MW/m2 in the High Heat Flux Test Facility (HHFTF) at IPR. Subsequent testing of additional 200 thermal cycles was also done at incident heat flux of 6 MW/m2. During the High heat flux (HHF) tests, surface temperature of W tiles reached 640oC and the beam power was restricted at 6MW/m2 to limit the temperature below 450oC at the CuCrZr heat sink. Total 1200 steady-state thermal cycles have been completed. At 6 MW/m2, the absorbed heat flux was 4 MW/m2. Engineering analysis on the HHFT of the dome has been performed using Finite element method (FEM) and Computational Fluid Dynamics (CFD) to simulate and to correlate with the experimental data. Ultrasonic immersion technique – Non destructive testing (NDT) was used to inspect the brazed joint quality of the dome before and after the HHFT. The results of the experimental details, engineering analysis and methodology adopted to fabricate the medium size dome and reflector plate are presented here.

Process robustness and strength analysis of multi-layered dissimilar joints using ultrasonic metal welding

This paper investigates the effects of process parameters on the joint strength and process robustness when multi-layered joints of dissimilar metals are produced by ultrasonic metal welding (UMW). Three layers of 0.3-mm aluminium sheet are welded with a single 1.0-mm copper sheet which is representative of electric vehicle battery interconnects. A process robustness study in which welding pressure, amplitude of vibration and welding time are varied to produce satisfactory welds is reported. The weld quality is evaluated by performing lap shear and T-peel tests where maximum loads are considered as the quality indicator. Response surfaces are developed to identify the relationship and sensitivity between the input process parameters and output quality indicators. A feasible weldability zone is defined for the first time by identifying the under-weld, good-weld and over-weld conditions based on load-displacement curves and corresponding failure modes. Relying on the weldability zone and response surfaces, multi-objective optimisation is performed to obtain maximum lap shear and T-peel strength which resulted in Pareto frontier or trade-off curve between both objectives. An optimal joint is selected from the Pareto front which is verified and validated by performing confirmation experiments, and further, used for T-peel strength analysis of different interfaces of the multi-layered joint. To conclude, this paper determines both the optimal weld parameters and the robust operating range.

Uticaj temperature ivice žljeba i unete toplote na strukturu i tvrdoću zone uticaja toplote zavarenog spoja čelika P 460 NL1

The starting structures and cooling times in the temperature range 800 - 500°C (t8/5) have a decisive influence on the structures and properties of the heat affected zone of steel welded joints. At the cooling time t8/5, inter alia, the groove edge temperature has an effect. Due to heating by the electrical arc, the groove edge temperature along the joint, increases, resulting in extending of the cooling time of the heat affected zone. Therefore, the cooling time t 8/5 is extended along the joint. The paper presents the measurement results of the groove edges temperature during the welding of the multilayer joint of the microalloyed steel P 460 NL1. The influence of these temperatures on the cooling time t8/5 and on the macro and microstructure and hardness in the heat affected zone of this welded joint was determined.

<i>In Situ</i> EDXRD Study of MAG-Welding Using LTT Weld Filler Materials under Structural Restraint

Welding using low transformation temperature (LTT) filler materials is an innovative approach to mitigate detrimental welding residual stresses without cost-intensive post weld-treatments [1, 2]. Due to the local generation of compressive residual stresses in the weld line by means of a delayed martensite transformation a significant enhancement of the cold cracking resistance of highly stressed welded components can be expected. For the effective usage of these materials a deeper understanding of the microstructural evolution inside the weld material is necessary to determine the complex processes that cause the residual stress formation during welding. Solid-state phase transformation kinetics and the evolution of strain in LTT weld filler materials are monitored in-situ at the instrument ID15A@ESRF in Grenoble. The transferability to real components is implemented by using a realistic MAG welding process under consideration of structural restraint. During welding of multilayer joints, the phase transformation and phase specific strain evolution of each individual layer is investigated in transmission geometry by means of energy-dispersive X-ray diffraction EDXRD using high energy synchrotron radiation with a counting rate of 2.5 Hz. The measurement results of a 10% Cr / 10% Ni LTT weld filler are compared to data monitored for the conventional weld filler material G89. The in-situ data clearly indicate a strong effect on the local strain evolution and the formation of compressive strain. This results from the restraint volume expansion during the postponed austenite to martensite transformation of the LTT weld filler, which counteracts the thermal shrinkage. In contrast, for the conventional weld filler material the thermal contraction strains lead to tensile residual strain during welding. Furthermore, the results of in-situ observation during welding show that the transformation kinetic is dependent on the welding sequence.

Mechanical performance and electrical resistance of ultrasonic welded multiple Cu-Al layers

The mechanical performance and electrical resistance of dissimilar and multi-layered Cu-Al sheets, which represent the battery electrodes and tabs, were evaluated by ultrasonic welding (UW). Different possibilities of lap-joining configurations using sheets of Cu and Al were considered. The weld strength at each weld interface of the multi-layered joint was evaluated by 90° peel test and by heat input measured by an infrared imager (IR). The strength of each weld interface of UW joined multiple Cu-Al layers were found to be strong enough to produce a through-thickness tearing. A typical weld criterion for producing a developed nugget was achieved. Weld quality at interfaces was assessed by cross-sectioning the UW joint parts. Depending on the lap-joint configuration, weld interfaces were characterized by bonded and unbonded interfaces. Measuring the electrical resistance passing through the joints demonstrated that the unbonded weld interface produced an increase in the joint electrical resistance. The joint electrical resistance measurement is shown to be used as a criterion to validate the quality of Cu-Al battery cell joints.

Optimization of the diffusion bonding parameters for SS316L/CuCrZr with and without Nickel interlayer

Divertor & Firstwall module of ITER like tokamak has several joints of dissimilar materials such as Tungsten (W) to Copper (Cu), Cu to CuCrZr (heat sink material) and CuCrZr to Stainless Steel (SS) materials. These Plasma Facing Components (PFC) are made of multi-layered joints, which are to be exposed to the harsh environment of Plasma with the expected heat flux of 5–10MW/m2.The joining of SS316L material to CuCrZr material is proposed in this paper. As SS316L/CuCrZr being dissimilar materials, direct joining of these materials is a problem, which needs a suitable fabrication process. The joining of SS316L with heat sink material (CuCrZr) requires the good thermal transfer and sound in structural joint. Diffusion bonding technique has been adopted as a process for joining of these two dissimilar materials. The primary objective of the joining study is to obtain the best diffusion bonding parameters for ITER like tokamak application. Thermo-mechanical simulator machine (Gleeble 3800) is used to perform diffusion bonding experiments at different temperatures 650°C, 850°C, 900°C, 950°C & 1000°C, different uniaxial pressure varying from 5MPa to 15MPa and with the holding time of 15min & 30min, using pure nickel interlayer.The diffusion bonded samples have undergone Non-destructive testing (NDT) particularly the ultrasonic examination using immersion probe technique, microstructural examination by the High Resolution (HR) electron microscopy (SEM), Energy Dispersive X-ray (EDAX) analysis, micro hardness measurement and shear measurements by custom made fixture. The diffusion bonding parameter of SS316L/CuCrZr is optimized based on study with Nickel (Ni) interlayer and without interlayer. The details of fabrication procedure and the results of the characterization are discussed and presented in this paper.

Erratum [Space charge and electric field in thermally aged multilayer joints model

This paper is concerned with space charge accumulation and electric field distribution at XLPE/EPDM interfaces after thermal aging. XLPE, EPDM and multilayer XLPE/EPDM/XLPE flat samples have been manufactured and aged thermally during 240 and 480 h at 105 °C. Material degradation by oxidation during aging has been assessed by FTIR spectroscopy. The conductivities and permittivities of the samples have been measured before and during ageing. Using the values of conductivity and permittivity values obtained experimentally, the charge density values at the XLPE/EPDM interfaces and the electric field distribution across a multilayer XLPE/EPDM HVDC cable joint model has been calculated for different thermal aging times. The results show that the surface charge density values vary with the ageing time (decrease at aging beginning and then increase) and determine important enhancements of the electric field, in the vicinity of the inner but also of the outer semiconductor. The simultaneous presence of the volume and interfacial charges determines a less increase of the electric field for homocharges and more important for heterocharges, both for unaged and aged samples.

Space charge and electric field in thermally aged multilayer joints model

This paper is concerned with space charge accumulation and electric field distribution at XLPE/EPDM interfaces after thermal aging. XLPE, EPDM and multilayer XLPE/EPDM/XLPE flat samples have been manufactured and aged thermally during 240 and 480 h at 105 °C. Material degradation by oxidation during aging has been assessed by FTIR spectroscopy. The conductivities and permittivities of the samples have been measured before and during ageing. Using the values of conductivity and permittivity values obtained experimentally, the charge density values at the XLPE/EPDM interfaces and the electric field distribution across a multilayer XLPE/EPDM HVDC cable joint model has been calculated for different thermal aging times. The results show that the surface charge density values vary with the ageing time (decrease at aging beginning and then increase) and determine important enhancements of the electric field, in the vicinity of the inner but also of the outer semiconductor. The simultaneous presence of the volume and interfacial charges determines a less increase of the electric field for homocharges and more important for heterocharges, both for unaged and aged samples.

Diffusion bonding of Zr55Cu30Ni5Al10 bulk metallic glass to Cu with Al as transition layer

Abstract In this work we demonstrate the diffusion bonding of Zr 55 Cu 30 Ni 5 Al 10 bulk metallic glass (BMG) to aluminum and copper alloy. The process parameters including temperature, pressure and time are investigated experimentally, and we obtain appropriate ones for accomplishing diffusion bonding of the BMG to aluminum alloy successfully. Then we present a two-step diffusion bonding process to bond the BMG to copper alloy by using aluminum alloy as transition layers, and achieve a five-layer bonded joint of BMG/Al/Cu/Al/BMG. The mechanical properties of the multilayer joint are examined. The hardness of the BMG in the joint is enhanced while the bending strength decreases significantly compared with the as-received BMG. Besides, the crystalline metals alleviate and block the extension of cracks in the BMG, which results in the joint fracturing in an explosion-proof glass manner, dissimilar to rupturing in a catastrophic manner that is always happened in the BMGs. Therefore, diffusion bonding of BMG to crystalline metals is a promising way to extend its application.

Analysis of Weld Formation in Multilayer Ultrasonic Metal Welding Using High-Speed Images

One of the major challenges in manufacturing automotive lithium-ion batteries and battery packs is to achieve consistent weld quality in joining multiple layers of dissimilar materials. While most fusion welding processes face difficulties in such joining, ultrasonic welding stands out as the ideal method. However, inconsistency of weld quality still exists because of limited knowledge on the weld formation through the multiple interfaces. This study aims to establish real-time phenomenological observation on the multilayer ultrasonic welding process by analyzing the vibration behavior of metal layers. Such behavior is characterized by a direct measurement of the lateral displacement of each metal layer using high-speed images. Two different weld tools are used in order to investigate the effect of tool geometry on the weld formation mechanism and the overall joint quality. A series of microscopies and bond density measurements is carried out to validate the observations and hypotheses of those phenomena in multilayer ultrasonic welding. The results of this study enhance the understanding of the ultrasonic welding process of multiple metal sheets and provide insights for optimum tool design to improve the quality of multilayer joints.

Multilayer Joint Gait-Pose Manifolds for Human Gait Motion Modeling.

We present new multilayer joint gait-pose manifolds (multilayer JGPMs) for complex human gait motion modeling, where three latent variables are defined jointly in a low-dimensional manifold to represent a variety of body configurations. Specifically, the pose variable (along the pose manifold) denotes a specific stage in a walking cycle; the gait variable (along the gait manifold) represents different walking styles; and the linear scale variable characterizes the maximum stride in a walking cycle. We discuss two kinds of topological priors for coupling the pose and gait manifolds, i.e., cylindrical and toroidal, to examine their effectiveness and suitability for motion modeling. We resort to a topologically-constrained Gaussian process (GP) latent variable model to learn the multilayer JGPMs where two new techniques are introduced to facilitate model learning under limited training data. First is training data diversification that creates a set of simulated motion data with different strides. Second is the topology-aware local learning to speed up model learning by taking advantage of the local topological structure. The experimental results on the Carnegie Mellon University motion capture data demonstrate the advantages of our proposed multilayer models over several existing GP-based motion models in terms of the overall performance of human gait motion modeling.

Metallic layered composite materials produced by explosion welding: Structure, properties, and structure of the transition zone

The structure, morphology, and microhardness of the transition zone in multilayer metallic composite joints are studied, and the cohesion strength of the plates to be joined, the mechanical properties of the formed composite materials, and fracture surfaces are analyzed. The materials to be joined are plates (0.1–1 mm thick) made of D16 aluminum alloy, high-strength maraging ZI90-VI (03Kh12N9K4M2YuT) steel, BrB2 beryllium bronze, and OT4-1 titanium alloy. Composite materials made of different materials are shown to be produced by explosion welding. The dependence of the interface shape (smooth or wavelike) on the physicomechanical properties of the materials to be joined is found. The formation of a wavelike interface is shown to result in the formation of intense-mixing regions in transition zones. Possible mechanisms of layer adhesion are discussed.

Diagnostics of the Stress-Strain State of Multilayer Annular Welded Joints of Pipelines

Within the framework of the shell theory, we develop a mathematical model that describes the axisymmetric stress-strain states of multilayer annular welded joints of the pipes under the action of residual incompatible strains localized near the weld. The residual stresses are evaluated on the basis of the solutions of inverse problems of the shell theory with intrinsic stresses by using the experimental data obtained by the method of speckle interferometry. We created an experimental installation and special software that enable one to evaluate and reproduce residual stresses in the zone of multilayer welded joint. The plots of circumferential residual stresses as functions of the distance from the axis of the weld are presented.

DIFFUSIBLE HYDROGEN CONTENT IN DEPOSITED METAL OF MULTILAYER WELDED JOINTS

The article describes manufacturing technology of multilayer joints in terms of control the diffusible hydrogen content. Diffusible hydrogen content in deposited metal for multilayer welded joints made of covered rutile electrodes or covered cellulosic and basic electrodes was determined. It was found that after four beads, the diffusible hydrogen content decreases in the case of the first technology from 36 ml/100 g to 18 ml/100 g while in the second of about 40 ml/100 g to a level of 12 ml/100 g. The explanation of the mechanisms responsible for this phenomenon and directions for further study were proposed.

Thermal shock resistance of SiC/MAS–LAS multilayer joint of carbon/carbon composites to LAS glass-ceramic

Carbon/carbon (C/C) composites were joined to lithium aluminum silicate (LAS) glass-ceramic using a joining layer consisting of a SiC transition layer and a multilayer of magnesium aluminum silicate (MAS) and LAS glass-ceramic by a two-step technique of pack cementation and hot-pressing sintering. The microstructures of the as-prepared joint were characterized by scanning electron microscopy and energy dispersive spectrometry. The design of the multilayer structure could provide more possibilities for crack propagation to release the stress in the joint. Results of the thermal shock test showed that the average shear strength of the joined samples increased from 17.9MPa to 32.6MPa after 50 thermal cycles between 800°C and room temperature, which was primarily attributed to the toughening effects of microcracks. However, after 30 thermal cycles between 1000°C and room temperature, the average shear strength of the joined samples dropped to 14.2MPa since the crack size was beyond the tolerance of the joint.

Evaluation of Fracture Toughness Test Data for Multilayer Dissimilar Joint Welds Using a Weibull Stress Model

Abstract Fracture behaviour of welded joints with dissimilar weld metals (WMs) has been investigated in this paper. A low-toughness WM and a high-strength WM with a moderate toughness were layered alternately in the thickness direction. Fracture tests were conducted with 3-point bend (3PB) specimen and tension plate with a through-thickness crack. The 3PB specimen showed a multistage fracture. The first fracture was originated from the low-toughness WM. On the other hand, no multistage fracture occurred in the tension plate, although the low-toughness WM was responsible for brittle fracture initiation in the same manner as in the 3PB specimen. The fracture toughness of the multilayer dissimilar joint was apparently larger than the welded joint made with the low toughness WM only. The weakest-link model has been applied for analyzing those toughness properties of the multilayer dissimilar joint. The estimated fracture toughness by the weakest-link model was not necessarily consistent with the toughness data, which was because of the local stress elevation in the low-toughness WM area close to the high-strength WM. Because of this, a modified Weibull stress model was used to estimate fracture toughness values for the multilayer dissimilar joint WM and to account for an active fracture zone length scale in the multilayer weld joint materials.

Present of Three-layered hydro-forming analysis of a new hybrid sandwich tubes using finite element method

Multi-layered tube hydro-forming is suitable to produce multi-layered joints to be used in special application in many industries. With using a middle layer of foam and making sandwich structures, tube bending strength increases when external loads are applied. Also because of the foam is high energy absorption, in the pipelines of major industries such as the nuclear, strength increases when natural disasters, especially earthquakes happen. In this paper for the first time, three-layered new sandwich tube (inner layer of copper, middle layer of aluminum foam and outer layer of annealed brass) hydroforming processes were numerically simulated using finite element method by ABAQUS/Explicit 6.10. As the result of three-layered sandwich tube hydro-forming not reported in the literature, the results of this paper are compared with the latest experimental result of bi-layered tube hydro-forming find in literature by approaching the thickness of middle layer to zero. Finite element analysis shows that numerical and experimental results have a good agreement