Joint Assembly Research Articles

Loosening Phenomenon on Thin Plates Bolted Joint due to Offset Load

In this study, the new loosening behavior was discovered and investigated when offset loads were repeatedly applied to both ends of a bolted joint initially tightened to a thin plate made of high-tensile steel. In the experiments, the impact of offset distance on reduction of clamp force was investigated through multiple applications of symmetric offset axial load to the bolted joint assembly. The experimental results showed that even a slight offset load reduced the clamp force, and the larger the offset distance, the greater the reduction of the clamp force. It was also found that the decrease in clamp force depends not on the number of times the offset load is applied but on the magnitude of the offset load. Until now even if the thin plate bolted joint was subjected to an offset load, as long the plates do not deform significantly due to plastic deformation, it has been generally recognized that the clamp force is not reduced. This loosening phenomenon is new and its mechanism has not been elucidated yet. In order to clarify the mechanism that may lower the clamp force, this study conducted FE analysis using a simplified model of a bolted joint. In the FE model, the bolt and nut are considered as a single unit and the effect of slippage between the thread surfaces and the effect of plastic deformation is ignored by using elastic analysis. The results of the FE analysis showed that the main factor causing the reduction in clamp force was slippage between the thin plates to be joined, which was caused by offset load, and that the slippage didn't return to the original position resulting in the reduction in clamp force.

Seismic performance of mortise-tenon joint in prefabricated platform canopy

To optimize the prefabricated canopy joints, improve the construction efficiency, and enhance the seismic performance of assembly joints, a novel mortise-tenon joint (MTJ) was proposed. To evaluate the seismic performance along the vertical and track directions, two 1:1.5 scaled specimens were tested under low-cycle reciprocated loading. The test results find the hysteretic curves in both directions exhibit the “pinch” effect especially in the vertical direction, indicating the feature of shear slippage. The displacement ductility coefficients were all above 5.0, and the ultimate drift ratios were 4.54% and 5.88% respectively, showing excellent deformation ability and ductility. The parameters, such as the sectional strength ratio, the stirrup ratio of the prefabricated beam, the reinforcement ratio and the cross-sectional area of the enlarged section, were analyzed by the validated finite element (FE) models. The analysis shows as the section strength ratio decreases and the stirrup ratio increased, the seismic bearing capacity improved, while the plastic hinge located on the prefabricated column varied to the prefabricated beam ends. Based on the results, it is recommended the number of longitudinal rebars through the prefabricated beam is 4, the stirrup diameter in the prefabricated beam is 10mm and the the column cap is no less than 400mm. Finally, based on the truss-diagonal strut model, a method for calculating the shear strength capacity of the novel joint was proposed. Compared with the test and FE results, the theoretical equations exhibit good computational accuracy.

Collaborative timber joint assembly: Augmented reality for multi-level human-robot interaction

This research introduces an innovative Augmented Reality (AR) workflow for Human-Robot Interaction (HRI) in timber construction. The approach leverages human dexterity and adaptability alongside the strength and precision of robotic arms to assemble timber structures connected by wood-wood connections. While research in the field of automated construction generally focuses on singular interactions, such as robot agents carrying components and human agents attaching them, this paper explores multiple degrees of interaction involving cooperation or collaboration between agents. A new algorithmic framework is developed to automate the generation of holographic instructions and allocate assembly tasks to human and robot agents according to their abilities. The application to a full-scale demonstrator reveals that certain elements necessitate collaboration for assembly, while others can exclusively be assembled manually or robotically. Ultimately, the research also highlights the benefits of AR in assisting manual assembly, simulating robot trajectories, and increasing safety during collaborative tasks.

Two distinct Dehalobacter metagenome-assembled genomes from anaerobic chloroform and dichloromethane degrading consortia.

Here we present two metagenomes and two Dehalobacter metagenome-assembled genomes from subcultures of an anaerobic chloroform and dichloromethane degrading microbial community used for bioremediation. Our objective was to assemble and curate the genome(s) of Dehalobacter, key biodegraders in the culture, through repeated sequencing and joint assembly with previous datasets.

Progressive bearing failure analysis and strength prediction method for the initial assembly and tensile process of composite bolted joints

Composite bolted joints have extensive application in aerospace and marine equipment. Failure analysis and strength prediction are crucial steps in the design of composite bolted joints. This study proposes a method that can accurately analyze the progressive bearing failure and static strength of composite bolted joints under different initial assembly parameters. This method first obtains an accurate initial assembly state based on the high-fidelity finite element model with detailed thread structure. Then it uses this as an input to analyze the progressive bearing failure process and the bearing strength value. Using the above method, the formation and evolution mechanism of the tightening yielding phenomenon during the assembly process are analyzed. And the influence of the two key assembly parameters, washer type and initial bolt tension, on the bearing strength of composite bolted joints is analyzed. The experimental results verify the effectiveness and accuracy of the simulation methods and results.

Seismic performance of the ST-RC columns to RC beams exterior joint with assembled connection details

An innovative composite column type, the steel tube-reinforced concrete column (ST-RC), consists of a core of concrete-filled steel tube (CFST) and reinforced concrete (RC) encasement. This study aims to validate the reliability of two convenient and rapid assembly methods between RC beams and ST-RC columns. Four full-scale beam-column joint specimens were tested, comprising two prefabricated assembly joints of ST-RC column-RC beam frames, one integrally cast joint of ST-RC column-RC beam frames, and one traditional integrally cast joint of RC column-RC beam frames for comparison. The experiments were conducted based on the principles of a self-balanced system, and quasi-static tests under constant axial compression on the ST-RC columns were performed. Hysteresis curves, skeleton curves, failure modes, strength degradation, energy dissipation capacity, stiffness degradation, deformation capacity and the influence of connection method and joint form on mechanical performance were analyzed and obtained based on the test results. The results indicate that, compared to integral casting, the assembly surrounding method with steel sleeves reduces specimen energy dissipation by 19.8 % and damping ratio by 21 % at 4 % drift, with minimal impact on other mechanical properties. In contrast, reinforcement surrounded and connected by steel plates reduces initial stiffness and peak load-carrying capacity by 1.0 %, along with decreasing negative ductility. It also lowers total energy dissipation by 37.4 % and damping ratio by 45.4 % due to compressive effects from bottom steel plate connections. Despite these effects, its impact on negative ductility and load-carrying capacity remains minimal. Additionally, experimental observations and rebar strain data indicate higher stress on rebars at the base of steel plate connection beams, suggesting a need to strengthen transverse rebars at the beam’s base. The study confirms the feasibility of two convenient and rapid assembly methods for the joints of ST-RC column. Both methods meet current Chinese standards for MCE, with failure modes characterized by “strong columns and weak beams” in both cases.

Data-driven study on shear bearing capacity of segmental concrete joints

Segmental assembly joints with excellent shear bearing capacity are the key to ensure the integrity of precast concrete girder bridges, which directly affects the force transmission state of the girders. However, with the existence of unfavorable factors such as the multi-key shear capacity reduction effect, the traditional prediction model for calculating the concrete joints shear capacity has poor prediction accuracy and large dispersion. To overcome the shortcomings of the existing prediction model, this study established a database consisting of 311 sets of test data and 110 sets of numerical results based on existing research. A total of seven data-driven models for predicting shear capacity of concrete joints were trained and generated based on the database, namely, two linear models (Linear Regression Support Vector Machine Algorithm, Least Squares Linear Regression) and five nonlinear models (Neural Network Bayesian Regularization; Neural Network Quantized Conjugate Gradient Model, Neural Network Levenberg-Marquardt (LM), Decision Tree, and Gaussian regression). The coefficient of determination (R2), root mean square error (RMSE)，mean absolute error (MAE), error range (A20-index), and error analysis were adopted to evaluate those model's performance. The evaluation results show that the LM model has excellent prediction accuracy, stability, robustness, and can guide the engineering design. Finally, the established database (421 data sets) and trained LM algorithm model were open sourse in this study to promot the investigate of precast concrete structures.

Detection of Piston Ring Deficiency in The Assembly of Automotive Ball Joint and Tie Rod End Parts

In today's intensely competitive environment, businesses strive to optimize production efficiency to reduce costs, increase profitability, and ensure customer satisfaction. This focus on efficiency and quality enables businesses to operate more effectively, gain a competitive advantage in the market, and move towards sustainable growth. This study uses image processing techniques to detect missing segments in the assembly of ball joints automatically. In the automotive industry, performing quality control of critical components before assembly and detecting and classifying the defective ones is essential. Many quality control methods can be applied with existing technologies. This paper proposes an automatic real-time control based on image processing techniques to detect ball joint missing segments, a common defect in the automotive industry. In the company, operators perform defect detection by visual inspection. In this system, production continues in cases where the operator cannot detect the defect. This system aims to detect the errors made by the operator during the assembly operations and provide instant feedback. The developed system uses OpenCV library algorithms that are highly accurate in detecting defects in manual assembly processes so that missing components are removed from the production chain, and production quality is significantly improved. Accuracy is over 94% when identifying missing segments, about 30% better than traditional methods. In tests, 1200 ball joints were run through the system, resulting in 1150 defects being correctly identified and removed from the production line. Accuracy is high thanks to the application of various image processing techniques such as grayscale conversion, edge detection, and shape recognition. This also provides real-time feedback to the operator so the system can reduce detection and response time from 15 seconds to 5 seconds. This increases production speed and reduces the error rate in manual assembly processes by 20%. This paper also highlights the potential of image processing technology in manufacturing. It will contribute to improved quality control mechanisms to increase the reliability and efficiency of production lines in the automotive industry.

Progress on First-of-a-Kind Feeder Superconducting Machine Joints and Surrounding Structure Assembly in ITER Magnet System

Progress on First-of-a-Kind Feeder Superconducting Machine Joints and Surrounding Structure Assembly in ITER Magnet System

Developing guidelines for ethical response to infectious disease outbreaks in Islamic Republic of Iran

Background: Ethical considerations are important in pandemic preparedness and response, however, there is a noticeable scarcity of ethical codes that are tailored to disease outbreaks and health emergencies. Aim: To document the development of guidelines for ethical management of infectious disease outbreaks in Islamic Republic of Iran, as a model for low- and middle-income countries. Methods: We conducted a non-systematic scoping review on PubMed and Google Scholar for drafting the guidelines for ethical management of infectious disease outbreaks in Islamic Republic of Iran. The draft was discussed and revised following consultations with different groups of experts and the Medical Ethics Council of the Iranian Academy of Medical Sciences. Results: The joint assembly of the National Clinical Ethics Committee and the Supreme Council of Medical Ethics endorsed and introduced the revised document as official guidelines for ethical response to infectious disease outbreaks in Islamic Republic of Iran. The guidelines were based on a set of core values and principles: human dignity, liberty, maximizing benefits and minimizing risks, and justice and transparency. In 3 distinct sections, the document provides ethical guidance for healthcare system management and leadership; provision of health services; and for education, research and use of technology during health emergencies. Conclusion: The guidelines have been very useful in responding ethically to the COVID-19 pandemic, there may be a need to adapt some of the recommendations for optimum benefits in specific contexts. It is necessary to create awareness of the existence of the document and educate healthcare professionals about its importance so they can apply the recommendations in their practice.

A Novel Flexible Joint for Bamboo Structures

Joints are one of the main problems concerning the design of bamboo structures. This paper proposes a classification of the main joints applied in full-culm bamboo structures according to their constructive behavior, subdivided into semi-rigid and flexible joints. A novel flexible joint called the Hinged Flexible Connection (HFC) for lightweight bamboo structures is developed and analytically described, allowing for a deployable motion in the center of the joint and mobile assembly procedures. The joining system utilizes lashed polyester ropes and bio-composite rings coupled in the bamboo culms working as geometric and mechanical constraints. The HFC has the potential to substitute bolted joints for the engineering design of bamboo structures.

Exploring Nonlinear Behavior of Gasket Joints in DEF Dosing Units through Finite Element Analysis

Gaskets serve the crucial function of maintaining a durable seal within 2fixed components within a mechanical structure, even when subjected to varying pressures and temperatures during operation. Gasket joint is necessary in many mechanical systems to form a leak free joint. DEF dosing system is one of the examples where gasket joints are used to prevent exhaust gases leaking before going through SCR. Gasket joint requires certain minimum pressure to make leak free joints. If the gasket pressure goes below the pressure of the internal fluid in the assembly, then there are chances of leaking the fluid out. If the gasket pressure is increased by applying high bolt preload, then there may be chances of yielding of the flanges or this may cause damage to bolt/nut threads. So, there must be optimum gasket pressure in the assembly. The gasket pressure gets affected by many parameters. The present paper aims to avoid leak in case of gasket joints. There are number of parameters which affects the performance of the gaskets e.g. bolt preload, bolt tightening sequence, internal pressure, temperature of internal fluid, creep of gasket etc. Different analysis has been carried out to check effect of allthese parameter on the contact pressure at the gaskets joint. Initial gasket pressure was mainly controlled by bolt preload/torque. The effect of bolt torque on the performance of the gasket joint assembly was studied. A dimensional nonlinear finite element analysis was carried out on the gasket joint and sealing performance was correlated with experimental study. Different geometric configurations are studied at different bolt pre-load levels. Effect of bolt torque on gasket pressure as well as other components of the assembly was studied. The best configuration which gives gasket pressure above minimum required to maintain leak proof joint and with no yielding in the assembly has been recommended.

Critical load determination for preventing rotational loosening in bolted joints under dynamic transverse loads

To ensure the reliability of bolted joints, it is essential to accurately determine the critical load that prevents rotational loosening of the nuts. In this paper, the mechanical behavior of bolted joints during tightening, after tightening, and under transverse loading was analyzed. The contact status of two mating surfaces, including the thread and nut bearing surfaces, and their ability to withstand transverse loads were calculated. Based on the conditions leading to rotational loosening, defined by the occurrence of sliding across both sets of contact surfaces, the critical condition for transverse force that precipitates rotational loosening in bolted joints has been established. Furthermore, a systematic procedure for determining this critical state of rotational loosening in bolted joint assemblies has been developed. Finite element simulations on bolted joints subjected to dynamic transverse loads, using various combinations of friction coefficients, showed results in good agreement with theoretical predictions. Finally, experimental measurements of the critical rotational loosening loads were conducted. The experimental results highlight that the decrease in clamping force due to non-rotational factors has a significant impact on the critical loads. Considering this influence and adjusting the preload accordingly, the calculated results for the critical loads are in good agreement with the experimental data.

An Experimental Investigation of a Flexible Sintered Silver Joint for Micro-Joining Based on a Design of Experiments

The increasing electrification of vehicles requires the use of ever higher voltages and electrical power. The thermal stresses to which the assembly joints of electronic chips are subjected are becoming increasingly severe. As a result, thermal stresses acting on the electronic assembly, and particularly on the electrical interconnections, are becoming increasingly severe. The objective of this study is to create, characterize and optimize the structure and properties of a porous silver sintered joint using the design of experiments (DoE) method. Joints consisting of a porous network of silver particles are obtained, showing remarkable flexibility allowing for thermal stresses accommodation and having sufficient tensile strength to ensure a correct bonding of the components. Depending on the selected levels for the sintering process parameters, the microscopy analysis shows a transition of the mode of rupture from the silver layer to the intermetallic compounds forming at the interface with the substrate.

Large rectangular cross-section tunnel undercrossing urban road by micro pipe jacking and joint assembly structure (MPJ & JAS) method in soft soils

With the continuous construction of urban traffic roads, more and more new roads are cut off by existing roads to form “dead end roads”. There is an urgent need for a trenchless method suitable for urban ultra-shallow overburden to build the undercrossing tunnel. To solve this problem, this paper proposed the micro pipe jacking and joint assembly structure (MPJ & JAS) method, which has the characteristics of shallow burial depth, low cost, short construction time, flexible cross-section setting and high space utilization. The MPJ & JAS method construct a large cross-section tunnel through assembling small cross-section elements, quite different from traditional methods. Therefore, this paper designed a CT-shaped integrated joint, the mechanical performance of which was verified and clarified by tensile test. The bending test and finite element (FE) analysis proved the reliability of MPJ & JAS tunnel structure, and confirmed the structure performances such as the failure models, crack behaviors, load–deflection response and stress–strain distribution. Moreover, the influences of the steel plate thickness, concrete strength and shear connector spacing were determined by the FE analysis. On the basis of test results and reasonable assumptions, a theoretical design method considering the influence of the CT-shaped integrated joint was proposed, which can effectively predict the bending strength of the MPJ & JAS tunnel structure with an error of less than 10%. Finally, in view of the characteristics of the MPJ & JAS method, the suitable micro pipe jacking machine, soil reinforcement measure, hydraulic traction construction technology, high-precision guidance system and concrete construction quality detection method based on the phased array ultrasonic imaging technology were developed, supporting the accurate and efficient construction of the MPJ & JAS tunnel.

Measurement and assembly methods for bolted flange joints using three-dimensional digital image correlation

Bolted flange joints are extensively used in pressure vessels and piping equipment. The assembly coaxiality accuracy and bolt pre-tightening force are particularly important in causing the risk of seal and leakage failure. This paper proposed a novel non-contact measurement and assembly adjustment method to reduce the coaxiality angle deviation efficiently. The flange joint is first bolted according to standard flange joint assembly guidelines and then adjusted using the proposed method. In the proposed method, the surface deformation and the coaxiality of the flange are evaluated using a 3D-DIC (three-dimensional digital image correlation) technique; RMS (root mean square) of the surface deformation is used to drive the correction of the bolts to further reduce the coaxiality angle deviation. Compared with existing bolting patterns, the established measurement and assembly adjustment method, which combines 3D-DIC measurement and adjustment based on RMS, can effectively reduce the coaxiality angle deviation. The experiments using a correction strategy demonstrated that the coaxiality angle deviation is reduced by 48.9 % and 60.1 % on average compared with the well-known star bolting pattern and modified star bolting pattern provided by ASME PCC-1, respectively, and even by 30.6 % and 51.9 % compared with their rotational pass patterns. Further experiments with an iterative strategy showed that the coaxiality angle deviation could be reduced by around 70 % and 75 %, tending to be stable around 0.01°–0.035°, after only 5 iterative adjustments.

Human Rights Debates in the Lomé Convention: The Adoption of the Pons Grau Report at the ACP-EEC Joint Assembly (1992-1993)

The Lomé Convention was a development cooperation agreement signed in 1975 between the European Community and the ACP group (Africa, Caribbean, and the Pacific). Lomé built a unique institutional framework for debates over development and created common political institutions such as the ACP-EEC Joint Assembly, a multi-continental assembly involving European parliamentarians and ACP representatives. After the inclusion of human rights in Lomé in 1984, the Joint Assembly became the central stage for a heated debate over the universality of human rights and their relationship with development and democracy. The crucial point of this debate was the 1992-1993 Joint Assembly discussion regarding the report on human rights, democracy, and development drafted by Josep E. Pons Grau. The study analyses the difficult adoption of this report by the Assembly, which signalled a new approach to the issue of democracy and development and implied the demise of the political neutrality of Lomé.

Advanced workstations and collaborative robots: exploiting eye-tracking and cardiac activity indices to unveil senior workers' mental workload in assembly tasks.

Introduction: As a result of Industry 5.0's technological advancements, collaborative robots (cobots) have emerged as pivotal enablers for refining manufacturing processes while re-focusing on humans. However, the successful integration of these cutting-edge tools hinges on a better understanding of human factors when interacting with such new technologies, eventually fostering workers' trust and acceptance and promoting low-fatigue work. This study thus delves into the intricate dynamics of human-cobot interactions by adopting a human-centric view. Methods: With this intent, we targeted senior workers, who often contend with diminishing work capabilities, and we explored the nexus between various human factors and task outcomes during a joint assembly operation with a cobot on an ergonomic workstation. Exploiting a dual-task manipulation to increase the task demand, we measured performance, subjective perceptions, eye-tracking indices and cardiac activity during the task. Firstly, we provided an overview of the senior workers' perceptions regarding their shared work with the cobot, by measuring technology acceptance, perceived wellbeing, work experience, and the estimated social impact of this technology in the industrial sector. Secondly, we asked whether the considered human factors varied significantly under dual-tasking, thus responding to a higher mental load while working alongside the cobot. Finally, we explored the predictive power of the collected measurements over the number of errors committed at the work task and the participants' perceived workload. Results: The present findings demonstrated how senior workers exhibited strong acceptance and positive experiences with our advanced workstation and the cobot, even under higher mental strain. Besides, their task performance suffered increased errors and duration during dual-tasking, while the eye behavior partially reflected the increased mental demand. Some interesting outcomes were also gained about the predictive power of some of the collected indices over the number of errors committed at the assembly task, even though the same did not apply to predicting perceived workload levels. Discussion: Overall, the paper discusses possible applications of these results in the 5.0 manufacturing sector, emphasizing the importance of adopting a holistic human-centered approach to understand the human-cobot complex better.

Enhanced mechanical interlocking of adhesive-bonded joints via tailored serrated patterns manufactured with laser ablation

ABSTRACT Laser ablation is currently used as an effective alternative to mechanical or chemical surface pre-treatments for adhesive-bonded joints due to benefits in terms of adherend surface morphology and surface free energy. Several works have seen production of micro-scale textures on both metallic and polymeric substrates via 3D printing, while others have sought to modify the macroscopic topography by generating serrated profiles on adherends prior to joint assembly. In this work, laser ablation has been used to create micro-scale tooth-like interlocking features forming structured patterns with complementary profiles on aluminium adherends of single lap joints. In a first set of experiments, laser processing parameters were varied while an optical profiler was used to quantify the geometry of induced ablation craters and lines while assessing the distribution of re-melt in and around the exposed region. Subsequently, an ablation strategy was developed to achieve specific interlocking features. Finally, different symmetrical and asymmetrical patterns were generated for each pair of coupled adherends while differentiating the orientation of features with respect to the load direction. The results confirm the critical role that laser ablation plays in strengthening adhesive bonded-joints, with interlocking features providing additional benefits depending on the structure type and load direction.

A multi-agent resource bidding algorithm for order acceptance and assembly job shop scheduling

This study uses an agent-based approach with a combinatorial auction mechanism to solve the joint order acceptance and assembly job shop scheduling problem. A set of jobs is offered. Each job has a revenue, ready time, due date, deadline, and consists of a set of operations with precedence relationships. Jobs that deviate from their due dates incur earliness/tardiness penalties. An operation may require several units of capacity per time unit and a resource could have multiple units of capacity. The manufacturer can reject any job to satisfy the capacity constraints and maximise the overall profit. We develop a mathematical model for the problem, then use an agent-based approach to solve it. First, the relaxed problem is decomposed into a set of job-level subproblems. Each job is optimised individually without considering the capacity constraints. Profitable jobs at the individual level submit their optimal schedules as combinatorial bids to an auctioneer to acquire combinations of resource capacity-time units. Then, the auctioneer records the profit upper bound, resolves capacity conflicts to reach a feasible solution, records the profit lower bound, and updates the dual variables. Experimental results show that the proposed methodology can solve large-sized problems in reasonable CPU times.