Mechanical Connection Research Articles

Enabling focused ion beam sample preparation for application in reverse tip sample scanning probe microscopy

Focused ion beam (FIB) has become a powerful tool for transmission electron microscopy sample preparation in the nanoelectronics industry and has in recent years also shown its benefits for specific preparation steps in electrical scanning probe microscopy (SPM). Most recently, a novel SPM approach – so-called reverse tip sample (RTS) SPM – has been proposed in which the position of sample and tip are switched compared to standard SPM; in RTS SPM the sample is attached to the end of a cantilever beam. To achieve this configuration, the region of interest must first be extracted from a substrate and then needs to be reliably fixed to the cantilever by FIB. Therefore, we have explored and developed dedicated FIB preparation methods for RTS SPM in this work. Our established procedures ensure a strong mechanical and good electrical connection of the sample to the cantilever for both cross-section and top view sample preparation. Furthermore, we introduce an approach for mounting samples from a full wafer size workflow. This paper presents the developed FIB procedures and discusses the quality and stability of all mounted samples and their electrical evaluation in RTS SPM.

Seismic behavior test and plastic hinge theory for HRB500 prefabricated steel reinforcement cage-cast-in-situ concrete columns

An innovative method for constructing concrete columns has been proposed, namely utilizing the hot-forged double-lock mother combined mechanical sleeve connection for the HRB500 prefabricated steel reinforcement cage－cast-in-situ concrete (PRC-CISC) columns. The purpose of this method is to promote the industrialization of steel reinforcement projects and enhance the quality of structural construction. Two traditional reinforced concrete (RC) columns and four PRC-CISC columns were designed for quasi-static tests with design axial compression ratio (ACR) and reinforcement connection methods as parameters. Firstly, the results of the study showed that all specimens exhibited typical flexural failures, with well-rounded hysteresis curves, gradual stiffness degradation in the later stages, good ductility, and energy dissipation. Mechanical sleeve connections had a minor impact on the failure mode of PRC-CISC columns. Increasing the ACR improved the carrying capacity but reduced ductility, narrowed the hinge zone, and increased longitudinal bar stress. The effect of sleeve connection on energy dissipation, stiffness, ductility, and carrying capacity of the specimens was limited, and the overall behavior was stable and controllable. Furthermore, the carrying capacity and stress distribution of core area steel bars in traditional RC columns and PRC-CISC columns were further calculated to assess the differences. Finally, a two-stage plastic hinge calculation theory was formulated, which takes into account the influence of axial pressure, and construction recommendations for two types of PRC-CISC columns were provided.

Effect of hole deformation on bolt load transfer in hybrid-bonded/bolted joints

As a new type of connection methodology, hybrid-bonded/bolted (HBB) connections exhibit potential advantages over mechanical or pure adhesive connections in construction, aerospace, shipbuilding, machinery, and other fields. The key to designing HBB joints is reasonable load sharing between bolts and adhesive layers. An accurate analytical model could effectively and quickly help engineers perform design iterations and arrive at reasonable load-sharing predictions. The existing models usually consider HBB joints as a simple superposition of adhesive and bolted joints. This paper found through experiments that when the HBB joint is subjected to tension, the bolt hole undergoes a certain deformation, resulting in a different bolt-hole contact state than pure bolt joints. Therefore, in the HBB joint, the load transferred by the bolt calculated using the existing model is usually higher than the actual situation. In response to this situation, this paper proposes a new calculation approach for bolt shear stiffness for this particular deformation and develops an analytical model for HBB joints. By comparing with the finite element method (FEM) results, it has been proven that this model can accurately calculate the load-displacement curves of HBB joints of different materials and sizes, as well as the load distribution between bolts and adhesive layers. This provides favorable references for the design of HBB joints.

Applicability study of mechanical multi-pipe connections for DEMO breeding blanket maintenance concept

Maintenance of DEMO breeding blanket includes the removal and replacement of plasma facing components, for example the breeding blankets (BB). For access, multiple coolant pipes need to be removed. As an option to reduce downtime and increase maintenance speed, a so-called mechanical multi-pipe connection (MPC) concept is developed to allow removal of multiple pipes at the same time using remotely operated mechanical connections. MPC is one promising candidate to allow fast remotely controlled opening and closing of multiple pipe connections by using flanges and bolts.Some major challenges for the application of MPC are highly constrained space on top of the BBs, accessibility for appropriate tools and homogenous distribution of sealing forces on the gaskets. Numerous studies on arrangement and force application methods were performed to identify suitable concepts – of which a compact flange design using direct bolted connection is favourable. Finite Element Analyses on the shape and geometry optimization of the MPC led to analytically verified solutions. Furthermore, material selection and behaviour under radiation, vacuum, and thermal cycling at high temperature conditions requires advancement of available material treatment solutions in terms of things such as coated surfaces of threads and contact areas on flanges to avoid diffusion bonding.

Design of the Steering Feedback Controller of a Steer-by-Wire System Using Admittance Model

The steer-by-wire (SbW) system is a promising system in the realm of automotive engineering. It substitutes the mechanical connection between the steering wheel and the front road wheels with an electronic signal-based functional connection. The SbW system offers several advantages over conventional steering systems, including weight reduction, reduced vibration, and enhanced steering functionality configuration. However, the absence of a mechanical linkage in the SbW system gives rise to certain challenges. The SbW system requires endowing adequate steering feel such as damping and reaction force using feedback motor, and the road wheel needs robust control of pinion motor for normal load variation by passengers and self-aligning torque as external disturbance. The SbW system is composed of the steering feedback module (SFM) and the road wheel module (RWM). This paper proposes a control approach to generate steering feel for SFM, in which steering feel is generated using an admittance model based on velocity control. A disturbance observer is applied to ensure robustness of velocity control. The steering wheel torque versus steering wheel angle (T–A) curve is used to analyze steering feel characteristic and evaluate steering feel. The proposed steering system is validated through experiments that confirm its ability to provide satisfactory steering feel for vehicles. This work may offer a novel solution for the design of advanced steering systems in the field for the future mobility such as an autonomous driving.

Process optimization and performance verification of CFRP laser surface modification

AbstractAdhesive bonding has gradually replaced mechanical connections as the primary method for composite material bonding, with surface quality being the key factor determining the effectiveness of composite material adhesion. Laser surface treatment, known for its green and precise characteristics, has garnered widespread attention from both academia and industry. However, the process parameters of laser surface treatment are complex, efficiency is low, and the mechanism remains unclear. This paper, based on the response surface methodology (RSM), investigates the influence of laser secondary parameters on the resin removal rate of carbon fiber reinforced polymer/plastic (CFRP) surfaces and the impact of defocusing on surface treatment efficiency. The results indicate that when the total laser energy density (Et) is 69 J/cm2, the overlap ratio in the warp direction (OLs) is 76%, and the overlap ratio in the weft direction (OLh) is 85%, the surface tensile shear strength increases by 90.59% and 27.77% compared to the original surface and polished surface, respectively. When the defocus distance is +8 mm, the efficiency of laser surface treatment is 2.25 times that of non‐defocus, with minimal impact on mechanical performance. The surface treatment mechanism, with changes in Et, primarily involves the pure thermal decomposition of the resin matrix in an oxygen‐free environment, oxidative decomposition, and the synergistic action of the decomposition products' oxidation. Through the coupled optimization of laser process parameters, this work enhances the efficiency and effectiveness of composite material adhesive surface treatment, promoting the engineering application of laser technology.Highlights By establishing a response surface model, the study elucidated the impact patterns of laser secondary parameters (overlap rates in the warp and weft directions, total energy density) on the resin removal rate of CFRP surfaces. Based on the laser surface treatment phenomena at different total energy densities, the study analyzed and revealed the mechanism of near‐infrared (1064 nm) laser resin removal from CFRP surfaces. By increasing the spot size through defocusing, the efficiency of laser surface treatment was enhanced, and the impact on the interfacial properties of CFRP after defocused treatment was validated.

Critical loss of primary implant stability in osteosynthesis locking screws under cyclic overloading

Primary implant stability, which refers to the stability of the implant during the initial healing period is a crucial factor in determining the long-term success of the implant and lays the foundation for secondary implant stability achieved through osseointegration. Factors affecting primary stability include implant design, surgical technique, and patient-specific factors like bone quality and morphology. In vivo, the cyclic nature of anatomical loading puts osteosynthesis locking screws under dynamic loads, which can lead to the formation of micro cracks and defects that slowly degrade the mechanical connection between the bone and screw, thus compromising the initial stability and secondary stability of the implant. Monotonic quasi-static loading used for testing the holding capacity of implanted screws is not well suited to capture this behavior since it cannot capture the progressive deterioration of peri‑implant bone at small displacements. In order to address this issue, this study aims to determine a critical point of loss of primary implant stability in osteosynthesis locking screws under cyclic overloading by investigating the evolution of damage, dissipated energy, and permanent deformation. A custom-made test setup was used to test implanted 2.5 mm locking screws under cyclic overloading test. For each loading cycle, maximum forces and displacement were recorded as well as initial and final cycle displacements and used to calculate damage and energy dissipation evolution. The results of this study demonstrate that for axial, shear, and mixed loading significant damage and energy dissipation can be observed at approximately 20 % of the failure force. Additionally, at this load level, permanent deformations on the screw-bone interface were found to be in the range of 50 to 150 mm which promotes osseointegration and secondary implant stability. This research can assist surgeons in making informed preoperative decisions by providing a better understanding of the critical point of loss of primary implant stability, thus improving the long-term success of the implant and overall patient satisfaction.

Development and Performance Evaluation of a Mechanical Connection for Steel and Shape Memory Alloy Bars

Shape memory alloys (SMAs) demonstrate a shape memory effect and superelasticity that can provide recovery performance to structural members. In this study, a round SMA bar was designed to replace the conventional deformed steel bar, particularly within the plastic hinge section of structural members. To integrate the SMA bar and the existing steel bar, a mechanical coupler was proposed by utilizing the advantages of both one-touch and threaded couplers. Uniaxial tensile tests were conducted to analyze the performance of the proposed coupler and the mechanical properties of the SMA–steel connected bar. Stress and strain relationships were examined for steel bars mechanically connected with the SMA bar and for SMA bars before and after exhibiting the shape memory effect. To induce the shape memory effect, SMA should be heated above the finished austenite temperature. Due to the difficulty of accurately measuring strain on the heated bar using traditional contact methods, we employed digital image correlation technology for precise strain measurement of the heated SMA bar. The experimental results indicate the effective application of SMA bars within the plastic hinge region of structural members using the proposed mechanical coupler.

To Charge In-Flight or Not: A Comparison of Two Parallel Hybrid Electric Aircraft Configurations via Optimal Control

This study examines two configurations for parallel hybrid electric aircraft, one with a mechanical connection between the engines and the electric motors and the other without. A previously proposed power allocation algorithm in the context of aircraft energy management is applied to these two configurations for a 19-seat conceptual hybrid electric aircraft. The original optimal control problem is then transformed into a finite-dimensional optimization, and the second-order sufficient conditions for the global optimality of the obtained solution are validated. This is followed by a sensitivity analysis of the fuel consumption to the initial aircraft weight and flight duration. Simulation and theoretical results clarify the limited benefits of charging the battery in-flight for this class of hybrid electric aircraft for the purpose of reducing fuel consumption and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emissions.

Studs' impact on sound transmission in double-leaf partitions

Double-leaf partitions constructed by two parallel plasterboard panels installed on steel studs are widely used in building constructions. Although it is known that the studs significantly influence vibroacoustic behavior of the plates, there has not been extensive research on this topic. This study focuses on the impact of steel studs on the sound transmission in double-leaf constructions. In order to fully analyze the impact of the steel stud element, a comparison between experimental data from a double leaf partition with a mechanical connection using steel studs and a theoretical model that disregards any mechanical connection between the parallel plasterboard panels was conducted. Results presenting radiation efficiency, transmission loss, and velocity level differences in a grid of points equally distributed on the radiating side of a structure highlight the influence of steel studs in double-leaf constructions indicating frequency ranges, where the studs’ impact is mostly significant.

Motion characteristics of a modularized floating solar farm in waves

Modularized floating solar farms exhibit the potential to replace conventional steel-frame ones, effectively remedying hydroelastic issues of a very large floating structure through discrete modules with mechanical connections. However, the response of the discrete modules under cyclic wave loading has not been fully understood. This paper assesses the motion characteristics and expansibility of modularized floaters in waves, based on computational results from fluid–structural interaction simulations. A crucial factor, denoted as the ratio of frame length to wavelength R=Ls/λ, is determined to predict the motions of a large floating solar system in head waves. Results indicate that the motion characteristics is predictable based on the R value. The empirical relationship between the R value and the motion of every unit in an array is analyzed. In particular, the results calculated from using the multiple-rigid-bodies method are also compared with those from using the single-large-hydroelastic-body method, and it was found that these two results are similar when R &amp;gt; 1. This similarity allows for predicting the multi-hinged bodies' behavior in waves through a simplified hydroelastic approach. Overall, this study reports insights that are useful for the design and optimization of modularized solar farms and can help address cyclic loading and motion concerns for long-term durability.

Flexible Polyurethane Adhesives: Predictive Numerical Model Calibration through Experimental Testing at Elevated Temperature

The thermo-mechanical behavior of polyurethane adhesive joints in wood structures is a crucial aspect that needs to be understood to ensure the durability and safety of timber structures, especially in seismic regions. As mass timber, particularly cross-laminated timber, continues to gain popularity as a building material, it is important to pay special attention to the behavior of connections between the timber elements. The use of flexible polyurethane adhesives presents a promising alternative to conventional mechanical connections in seismic-resistant timber structures. This research highlights the potential of polyurethane-based joints at elevated service temperature, offers a promising alternative to traditional wood joints, and suggests viability for post-fire restoration of wood structures. The response at the interface between wood and polyurethane under flexural stresses is also evaluated, underscoring the broader application possibilities of flexible adhesives in wood construction for mechanical and physical improvements.

FEATURES OF THE DEVELOPMENT OF MATHEMATICAL IDEAS OLDER PRESCHOOL CHILDREN WITH INTELLECTUAL DISABILITIES

This article is devoted to the theoretical analysis of the problem of the development of mathematical concepts of older preschoolers with intellectual disabilities. The peculiarities of thinking as a cognitive process of the individual are analyzed. The basis of the thinking process is always analysis and synthesis. Analysis is a necessary condition for the scientific interpretation of facts. It requires completeness, depth and accuracy. This is the first stage of studying any phenomenon. Synthesis, as a thinking process, can occur at different levels in human activity, starting from a simple mechanical connection of parts of a whole to the creation of a scientific theory based on the generalization of individual facts and research materials. It can be carried out both on the basis of perception and on the basis of memories and ideas. Although opposite in nature, the operations of analysis and synthesis are actually closely related.&#x0D; The psychological features of older preschool children are analyzed. During this period of development, the child’s cognitive sphere is significantly enriched and developed; perception becomes more conscious and purposeful; voluntary and involuntary attention, the ability to analyze and the ability to reproduce what was previously learned develop; there is a transition from visual-active to visual-figurative thinking; verbal and logical thinking begins to develop; generalized ways of thinking are formed: comparison, search for similarities, differences, classification, analysis, combination; the grammatical structure of the native language is mastered.&#x0D; The psychological characteristics of mathematical representations of children with intellectual disabilities are provided. Such children in older preschool age have no desire to engage in intellectual games, there is an increased interest in mobile, non-targeted games. The pace of perception is slowed down, the volume is narrow. They can hardly distinguish the main or general thing in the picture, in the text, grasping only individual parts and not understanding the internal connection between the parts, they often confuse graphically similar letters, numbers, objects. All mental operations (analysis, synthesis, comparison, generalization, abstraction) are not sufficiently formed. A distinctive feature of thinking is uncriticalness, the inability to independently evaluate one’s work.&#x0D; The methodological foundations of the empirical study of the development of mathematical concepts of older preschoolers with intellectual disabilities are substantiated. The obtained indicators of the formation of mathematical representations of older preschoolers with intellectual disabilities are experimentally analyzed; specifics of combinatorial and conceptual thinking of children with intellectual disabilities; indicators of the development of thinking operations of children of older preschool age.

An experimental analysis of full scale light-frame timber modules

Prefabricated timber modules are being increasingly used in the load-bearing structure of entire residential buildings reaching heights up to six stories. The development is driven by the demand of high-quality housing that remains affordable while fulfilling tough environmental requirements imposed on modern construction. To enable further development of this type of buildings additional research is needed despite the considerable number of studies previously performed. This study provides an extensive experimental investigation by subjecting three modules to three different load cases. In each load case, the modules were initially loaded with dead-load placed atop of the module. Thereafter the modules were laterally loaded at the top using a servo hydraulic piston in displacement control. The main aim of the study was to assess the structural behavior of these modules under combined lateral and vertical loading, and also to generate experimental data suitable for verification of finite element models. Results from the test series reveal significant variation in racking stiffness and racking strength depending on the module’s design. Furthermore, in some cases more stiff and stronger mechanical inter-module connections are needed to enhance their global structural performance. Finally, the experimental results reveal that the modules are relatively ductile in their shear response when subjected to horizontal load.

Application of 3D Digital Image Correlation Technique to Measurement of Wind Blade Properties from Coupon Test and Small-Sized-Blade Frequency Test

As a wind blade is getting larger, its structural behavior becomes more complex and thus the risk of blade structural failure becomes higher. Generally, structural integrity is proved through blade testing with contact measurement devices such as strain gauges. However, contact measurement can only measure the physical quantities from installation points and requires lengthy cables to transmit the electrical signals to a data acquisition system, which can cause signal noise and add unnecessary weight. Recently, noncontact measurement techniques such as digital image correlation (DIC) have been widely used in various industries to process images captured from cameras and generate full-field strains and displacements without any mechanical connections such as cables. In this study, the application of three-dimensional DIC to wind blades was investigated; in addition, the material properties of glass-fiber-reinforced plastics used in blades for the measurement of the first frequency were also studied. Tensile testing was performed using coupons equipped with strain gauges and speckle patterns. In addition, a small blade from a 10 kW wind turbine was utilized to measure the first flapwise frequency using DIC and modal tests; the results showed a 2.1% difference between the two different measurements. This research showed that the DIC technique could be an alternative replacement for the traditional measurement technique upon further validation tests.

Fabrication of high aspect ratio, non-line-of-sight vias in silicon carbide by a two-photon absorption method

The future of Moore’s Law for high-performance integrated circuits (ICs) is going to be driven more by advanced packaging and three-dimensional (3D) integration than by simply decreasing transistor size. 3D ICs offer low-power consumption, high-performance and a smaller footprint compared to conventional 2D ICs. The key enabling technology to 3D integration is the interposer that provides interconnects to route signals between the chiplets that comprise the IC. However, the fabrication of high-aspect ratio through wafer vias (TWVs), that provide electrical and mechanical connection between chiplets on the top and bottom of the interposer, is one of the important challenges that limit interposer performance. Current fabrication technologies are limited by tapering effects and the need for direct line of sight to the fabrication surface. These limit the possible aspect ratios of vias and require large, complicated surface traces to connect the vias to the chiplets. Here, we demonstrate the fabrication of high-aspect ratio, non-line-of-sight TWVs in silicon carbide (SiC). SiC provides better mechanical, chemical, and thermal performance than silicon (Si). The technique uses an electro-chemical etch process that utilizes two-photon absorption to create any arbitrary 3D structure in SiC allowing for direct, subsurface routing between chiplets.

Enhancing Electrical and Physical Contacts of Copper‐Electroplated Silicon Heterojunction Solar Cells through Chemical Pretreated Seed Layers

Copper electroplating offering the potential to replace low‐temperature sintered silver pastes holds significant promise as a metallization process for silicon heterojunction (SHJ) solar cells (SCs). To unlock the full potential of copper electroplating, it is crucial to enhance the contact properties between the electroplated grids and the indium tin oxide (ITO) films, addressing both contact resistivity and physical adhesion. Herein, a zinc‐assisted Fe2+ system to modify the ITO film is used, leading to the formation of an In/Sn/SnO mixed‐metal transition layer. This transition layer serves as a seed layer for metal electroplating, reducing contact resistivity and enhancing the mechanical connection between the electroplated metals and the ITO films. Following the ITO pretreatment process, the contact resistivity is significantly reduced from 1.4 to 0.2 mΩ cm2, and the peel force value of the pretreated sample reaches 14.2 N mm−1, which is 75.3% higher than that of the untreated sample. The proof‐of‐concept SHJ SC with copper electroplating after ITO pretreatment achieves a remarkable power conversion efficiency of 22.6%. These results clearly demonstrate that ITO pretreatment using the zinc‐assisted Fe2+ system is an effective approach for enhancing contact properties and improving the performance of copper‐electroplated SHJ SCs, showcasing significant potential for industry applications.

Networking Strategies of Triboelectric Nanogenerators for Harvesting Ocean Blue Energy

The utilization of abundant blue energy in the ocean could greatly contribute to achieving carbon neutrality. However, the unsolved economic and technical challenges of traditional technologies for harvesting blue energy have resulted in slow progress. Triboelectric nanogenerators (TENGs), as a new approach for converting mechanical energy into electricity, have great potential for blue energy harvesting, which can be connected as networks with different numbers of units for varying scales of energy harvesting. Here, recent advances of networking strategies of TENGs for harvesting blue energy are reviewed, mainly concerning mechanical and electrical connection designs. Anchoring strategies of devices and networks are also discussed. The development of TENG networks could provide an effective solution for large-scale ocean blue energy harvesting, which can also serve as an in-situ energy station or power source for self-powered systems, supporting various marine equipment and activities.

Review of Carbon Nanotube Wire-to-Metal Connection Methods: Techniques, Challenges, and Prospects

This paper reviews the connection technologies between carbon nanotube (CNT) wires and metal materials, analyzes the technical principles, advantages, limitations and application prospects of different connection methods. It mainly focuses on the electrical contact issues of CNT wires in the field of microelectronics, and how to achieve a high-performance, reliable combination of metal and CNT wires through emerging material processing and connection technologies. The article also discusses the challenges these technologies face in overcoming interface resistance, improving mechanical connection performance, and maintaining the characteristics of CNT wires.

Interlayer Engineering and Prelithiation: Empowering Si Anodes for Low-Pressure-Operating All-Solid-State Batteries.

Silicon (Si) anodes, free from the dendritic growth concerns found in lithium (Li) metal anodes, offer a promising alternative for high-energy all-solid-state batteries (ASSBs). However, most advancements in Si anodes have been achieved under impractical high operating pressures, which can mask detrimental electrochemo-mechanical issues. Herein, we effectively address the challenges related to the low-pressure operation of Si anodes in ASSBs by introducing an silver (Ag) interlayer between the solid electrolyte layer (Li6PS5Cl) and anode and prelithiating the anodes. The Si composite electrodes, consisting of Si/polyvinylidene fluoride/carbon nanotubes, are optimized for suitable mechanical properties and electrical connectivity. Although the impact of the Ag interlayer is insignificant at an exceedingly high operating pressure of 70MPa, it substantially enhances the interfacial contacts under a practical low operating pressure of 15MPa. Thus, Ag-coated Si anodes outperform bare Si anodes (discharge capacity: 2430vs 1560mAhg-1). The robust interfacial contact is attributed to the deformable, adhesive properties and protective role of the in situ lithiated Ag interlayer, as evidenced by comprehensive ex situ analyses. Operando electrochemical pressiometry is used effectively to probe the strong interface for Ag-coated Si anodes. Furthermore, prelithiation through the thermal evaporation deposition of Li metal significantly improves the cycling performance.