Mechanism Of Loosening Research Articles

The loosening mechanism of tin-bronze bushing assembled by interference at connecting rod small end of heavy-duty diesel engines

The loosening mechanism of tin-bronze bushing assembled by interference at connecting rod small end of heavy-duty diesel engines

Analysis of Bolt Loosening due to Transvers Vibration

Bolt loosening is a critical issue in engineering applications where vibration-induced failures pose significant risks to the structural integrity and functionality of mechanical systems. This project aims to investigate the phenomenon of bolt loosening resulting from the transfer of vibrations and develop effective strategies to mitigate this problem. The study employs a comprehensive approach, combining experimental analysis, numerical simulations, and theoretical modeling to gain insights into the underlying mechanisms of bolt loosening. Furthermore, a theoretical model is developed to predict the susceptibility of different bolted joints to loosening based on factors such as material properties, bolt size, and tightening torque. The model is validated using experimental data, ensuring its accuracy and reliability in practical applications.

Enzymatic loosening mechanism of endosperm weakening plays a key role in promoting carrot (Daucus carota L.) seed germination by hydro-electro hybrid priming

As an innovative physical priming technique, hydro-electro hybrid priming (HEHP) tends to significantly promote the seed germination of carrot. Endosperm weakening at micropylar endosperm is a critical regulatory mechanism for seed germination, but it is unclear whether it plays a role in promoting seed germination through HEHP treatment. In the present work, we conducted association analysis between transcriptome and proteome data of the previous studies and found that HEHP promoted the mannose metabolism in carrot seeds, with key enzymes involved in mannan degradation called β-mannanase (MAN) and the coding genes were both significantly upregulated in HEHP treatment. Based on this, the subcellular structure of micropylar endosperm, the activity of key enzymes in mannan degradation and the expression pattern of MAN coding genes during the germination process were further studied. The results showed that carrot seeds subjected to the priming treatments exhibited more significant endosperm weakening during germination, with significant degradation of the cell wall of micropylar endosperm, and among the three key enzymes involved in mannan degradation, only MAN activity showed significant differences at micropylar endosperm and non-micropylar endosperm. In addition, the priming treatments, especially the HEHP treatment, significantly upregulated the expression of MANs before sowing, and the expression levels of MANs at micropylar endosperm were significantly higher than those at non-micropylar endosperm. Ultimately, it is confirmed that the rapid germination of carrot seeds is closely related to the enzymatic loosening mechanism of endosperm weakening, and that MAN plays a key role in this process. The results ulteriorly deepen the understanding of the rapid germination mechanism of carrot seeds treated with HEHP.

Leakage mechanism model of proton exchange membrane fuel cell sealing structures under vibration conditions

ABSTRACT To resolve the issue of predicting the leak rate in proton exchange membrane fuel cells (PEMFCs) under long-term random vibration conditions. Considering the mechanism of bolt vibration loosening and rubber vibration relaxation, a leakage mechanism model of the PEMFC sealing structure under vibration conditions is proposed, and the validity of the model is verified by experimental comparison. The model clearly reveals the quantitative effects of structural parameters and material parameters on the leakage rate of PEMFC under vibration conditions. The research results show that under long-term random vibration conditions, the change of PEMFC leakage rate with time is mainly divided into three stages: response stage, stable stage, and leakage stage. Compared to bolt vibration loosening, the rubber vibration relaxation has a more significant impact on PEMFC leakage, the leakage rate of the fuel cell stack is 433ppm after 10,000 hrs of vibration. In addition, increasing the bolt preload, changing the bolt distribution, reducing surface roughness, and reducing gasket thickness can effectively suppress PEMFC leakage under random vibration conditions, the minimum leakage rate of the fuel cell stack can be reduced to around 170ppm per 10,000 hours. The proposed mechanism model provides an effective method for predicting the leakage rate of PEMFC sealing structures.

Development of a leveling and loosening mechanism for fine sediments on a test track for planetary robots

Planetary robots must be extensively tested before they can be sent on a mission. Especially on loose soil, there is a need for tests with repeatable surface and soil properties to simulate the planetary use and to obtain reliable results for each test run. To achieve this, a leveling and loosening mechanism for a robotic test track is presented. By leveling and loosening in one motion, it enables easy and fast test preparation. Bio-inspired bear claws were designed and tested as loosening tools, which allow loosening with minimal resistance and a loosening effect of about 45%. The modular design allows the attachments to be easily interchanged to adapt the mechanism to different requirements or add additional functions like measurements of the soil properties. The paper provides details on the design and evaluation of the leveling and loosening mechanism.

Validated, high-resolution, non-linear, explicit finite element models for simulating screw - bone interaction

Background and ObjectivePrimary stability evaluation of screw implants through pull-out or push-in experiments is commonly used to investigate the mechanism of screw loosening. Numerical models simulating these testing methods could provide an enhanced understanding of the underlying attachment mechanisms as well as save time and cost in the development of new screws. However, previous numerical models have been limited by compromises between modelling the trabecular structure at high resolution versus incorporating sophisticated mechanical properties and boundary conditions, leading to overestimated mechanical performance. The aim of this study was to overcome these limitations. MethodsWe developed explicit models incorporating the microstructure of trabecular bone, with frictional contact, and a non-linear material model incorporating damage. One model digitally inserted the screw into the trabecular bone structure using Boolean operations, while another model simulated the screw's rotational insertion. ResultsThe results showed a strong correlation between numerical and experimental results (R2: 0.54–0.93) for force-displacement response in terms of stiffness and strength. We found that the damage induced by the screw insertion process is an important factor to be considered, as the absence of modelling it led to an overestimated stiffness in previous studies. ConclusionsThe study highlights the importance of including frictional contact and also identified screw insertion damage as an important part of the simulating screw-bone interaction. Our findings demonstrate the potential of explicit finite element models for accurately replicating experimental push-in results and optimizing orthopaedic screws. The code is available at https://github.com/zhou436/Bone-Screw-Constructs-eFEM.

Mechanisms of Loosening and Secondary Locking of Jack Bolt Nuts

Mechanisms of Loosening and Secondary Locking of Jack Bolt Nuts

Research Progress on Influencing Factors of Bolted Joint Structure Loosening

Loosening of bolted joint structure is a critical failure mode mainly caused by the slippage and friction behaviours on the thread and bearing surfaces. Domestic and foreign scholars have conducted a series of studies on the loosening mechanism and anti-loosening methods of bolted joint structures; however, there are fewer summaries on the influencing factors of loosening of bolted joint structures. This paper takes the phenomenon of loosening of bolted joint structure as the research object, summarizes the research method of loosening of bolt joint structure and the influencing factors, and summarizes the influencing law of loosening of bolted joint structure in four aspects, namely, preload force, external load factors, structural factors, and operating temperature, to provide references for the design of anti-loosening of bolted joint structure.

Method for Evaluating Bolt Competitive Failure Life Under Composite Excitation

In this study, the competitive failure mechanism of bolt loosening and fatigue is elucidated via competitive failure tests on bolts under composite excitation. Based on the competitive failure mechanism, the mode prediction model and “load ratio—life prediction curve” (ξ–N curve) of the bolt competitive failure are established. Given the poor correlation of the ξ–N curve, an evaluation model of the bolt competitive failure life is proposed based on Miner’s linear damage accumulation theory. Based on the force analysis of the thread surface and simulation of the bolt connection under composite excitation, a theoretical equation of the bolt competitive failure life is established to validate the model for evaluating the bolt competitive failure life. The results reveal that the proposed model can accurately predict the competitive failure life of bolts under composite excitation, and thereby, it can provide guidance to engineering applications.

A bionic profiling-energy storage device based on MBD-DEM coupled simulation optimization reducing the energy consumption of deep loosening

A novel bionic profiling energy storage device was designed in this research to reduce the energy consumption of deep loosening operations. As the core technology of conservation tillage, deep loosening has always been difficult to promote on a large scale in the Phaeozem region of Northeast China due to its high energy consumption. The deep loosening mechanism is mainly composed of deep loosening shovel and energy-storage profiling device. At present, optimizing the structure of deep loosening shovel to reduce consumption was the main research method in this field, but it is still difficult to meet the production demand. At the same time, energy storage-profiling device has been neglected by researchers for a long time because of the lack of suitable mechanism innovation ideas and efficient experiment optimization methods. Based on the excellent soil excavation capability of the hare, the bionic energy storage-profiling device (BSPD) was innovatively designed by drawing the unique mechanism of its fore-upper limb, and the MBD-DEM coupled simulation technology was proposed as the experimental optimization method. It was found that BSPD has significant advantages in flexible profiling, tillage depth control, elastic energy storage and deep loosening resistance reduction capabilities compared with traditional self-excited energy storage-profiling devices (SSPD) by the analysis methods of least significant difference (LSD), Regression Analysis and Redundancy analysis (RDA), based on the results of MBD-DEM coupled simulation experiments. In addition, it was found that the torsional elastic coefficient, as the core design parameter of BSPD, also had a significant impact on the above four capabilities, and its optimal value was obtained by the established torsional elastic coefficient-deep loosening energy consumption regression model. The field experiment results showed that the deep loosening energy consumption of BSPD was 16.2% lower than that of SSPD and filed experiment results also verified the accuracy of MBD-DEM coupled simulation results. In summary, this study found a more effective new research path in addition to the traditional deep loosening consumption reduction research methods, and provided mechanism innovation design ideas and experimental optimization methods for the research and development of agricultural soil-engaging components.

Experimental study on anti-loosening technology of transmission line bolts

Bolts are widely used in transmission lines and are key connecting parts of transmission lines. Transmission lines have been affected by the natural environment for a long time, and bolts are prone to frequent vibration leading to loosening or falling off. Bolt loosening endangers the safe and stable operation of transmission lines. This paper analyses the loosening mechanism of the transmission line screw connection, carries out the transverse vibration contrast test of the common bolt anti-loosening measures, and develops the integrated self-locking double nut for the hidden danger of the transmission line bolt loosening, which has good anti-loosening performance, convenient installation, and the conditions for engineering popularization and application.

Effect of deceleration intervals on the mechanism of explosive loosening of rocks

Effect of deceleration intervals on the mechanism of explosive loosening of rocks

A New Test Method for In Vitro Evaluation of Pedicle Screw Loosening Potential

Abstract This paper proposes a new test method based on the toggle effect under transverse loads (cranial–caudal) to investigate the loosening potential of pedicle screw designs. A three-step in vitro testing procedure was developed to mimic the loosening mechanism of pedicle screws. First, the pedicle screw of a certain design is inserted into a bone substitute model specifically designed for the test. Second, a controlled cyclic cranial–caudal loading is applied transversally to the longitudinal axis of the screw for three ascendent load levels (staircase) by a predetermined number of load cycles. Lastly, each pedicle screw is adjusted and subjected to axial pull-out quasi-static testing. The results are used to calculate a loosening index that, together with statistical analysis, indicates the potential for loosening of the specific design evaluated. The proposed testing method effectively provides a simulated environment to evaluate the loosening potential of pedicle screw designs. The proposed loosening index calculation may be used to compare different pedicle screw designs. The proposed methodology was verified as a valuable tool to investigate the influence of the cranial–caudal loads on pedicle screw behavior. It offers a new alternative for use in preclinical studies on the loosening potential of pedicle screw designs.

Study on self-loosening mechanism of bolted joint under rotational vibration

The self-loosening failure of bolt connection will bring a series of problems. Sakai first proposed the self-loosening theory of fixed nut and free bolt head under rotational vibration. Based on this theory, this paper proposed a more extensive self-loosening theoretical criterion under the boundary condition of free nut and free bolt head under rotational vibration. The theoretical analysis shows that there are two forms of self-loosening failure under the new boundary conditions, which are the bolt head self-loosening failure and the nut self-loosening failure. Combining with the finite element analysis, it is shown that the proposed self-loosening theory is in good agreement with the simulation results. It is concluded that the self-loosening mechanism of the first case is caused by the complete slipping of the bolt head bearing surface and the thread surface. In the second case, the self-loosening is caused by the complete slipping of the thread surface and nut bearing surface. Local slipping does not cause loosening failure, which is different from the loosening mechanism under transverse vibration. Finally, the influence of several factors on bolt loosening is studied. The results show that the vibration amplitude and initial preload have great influence on bolt loosening, while the vibration frequency has little effect on bolt loosening.

Decreased complications but a distinctive fixation loosening mechanism of fully threaded headless cannulated screw fixation for femoral neck fractures in young adults

BackgroundDespite being a commonly encountered injury in orthopedic practice, controversy surrounds the methods of optimal internal fixation for femoral neck fractures (FNF) in young patients. The objective of the present study is to compare complication rates and failure mechanisms for surgical fixation of FNF using fully threaded headless cannulated screws (FTHCS) versus partial threaded cannulated screws (PTS) in young adults.MethodsA total of 75 patients (18–65 years old) with FNF were prospectively treated with close reduction and internal fixation using three parallel FTHCS and compared to a historical control case-matched group (75 patients) with FNF treated by PTS fixation. After 2 years follow-up, rates of fixation failure (including varus collapse, fracture displacement, and femoral neck shortening), nonunion, and avascular necrosis of the femoral head (ANFH) were compared between the two cohorts. The demographic, follow-up information, and radiological images were assessed by independent blinded investigators.ResultsPatient demographics and fracture patterns were similar in the two patient groups. The overall fixation failure rates were 8% (6/75) in the FTHCS cohort, which was significantly lower than the 25.3% (19/75) seen in the PTS group. Rates of nonunion and ANFH were significantly lower in the FTHCS group when compared to the PTS control group. When stratified by injury severity (high-energy vs. low-energy fractures), the rate of fixation failure was significant lower with the use of FTHCS when compared with PTS for high-energy fractures while there was no difference in the rates of nonunion or ANFH for high or low-energy fracture patterns. Unique to the FTHCS cohort was an atypical screw migration pattern with varus collapse (6/75, 8%).ConclusionsThe results show that FTHCS fixation could significantly reduce the complication rate of young patients with FNF, especially in high-energy fracture patterns (Garden III–IV, Pauwels III, or vertical of the neck axis (VN) angle ≥ 15°). There was also confirmation that the modes of fixation loosening in the FTCHS group, including screw “medial migration” and superior cutout, were different from the screw withdrawal pattern seen in the PTS cohort.Trial registrationThe study was retrospectively registered at www.Chictr.org.cn (ChiCTR-IPR-1900025851) on September 11, 2019.

Glenoid Component Loosening in Anatomic Total Shoulder Arthroplasty: Association between Radiological Predictors and Clinical Parameters—An Observational Study

The mechanisms of glenoid component loosening in anatomic total shoulder arthroplasty (aTSA) are still unclear, and it remains undetermined which specific radiographic features are associated with clinical outcomes. Patients with primary osteoarthritis who underwent aTSA with a stemless implant and a pegged glenoid between January 2011 and December 2016 were extracted from a local registry. Anteroposterior radiographs were evaluated at six, 12, 24 months, and five years post-TSA for lateral humeral offset (LHO), joint gap (JG), acromiohumeral distance (AHD), and radiolucency (modified Franklin score); 147 patients were included. Mixed-model linear regression was used. Both constant score (CS) and subjective shoulder value (SSV) markedly decreased at five years follow-up compared to one year (p < 0.001 for both). AHD, LHO, and JG all showed a consistent and statistically significant decline over time, with the joint gap decreasing by half. Consistently, smaller JG and AHD were correlated with lower SSV (p = 0.03 and p = 0.07, respectively). Massive loosening was associated with a 14.5 points lower SSV (p < 0.01). Finally, narrowing of the JG was significantly correlated with increased radiolucency (p < 0.001) and tended toward worse SSV (p = 0.06). In summary, radiographic parameters displaying medialization and cranialization after aTSA with a cemented pegged glenoid are useful predictors of impaired shoulder function.

Integrative analyses reveal RNA regulatory network in Ti particles induced inflammation

Introduction Wear particles induced inflammatory osteolysis is the most important initiating factors in the mechanism of aseptic loosening. However, the molecular network changes in this process remain largely elusive. Methods Here, we performed whole transcriptome analysis using Ti particles induced RAW264.7 cell model to identify specific genes and pathways. Results Sequencing results totally identified 159 mRNAs, 96 lncRNAs, 31 circRNAs, and 12 miRNAs were significantly differently expressed. Of these, we selected two of each RNA for qRT-PCR validation and the results were highly consistent with the RNA-seq data. GSEA analysis shows that upregulated gene sets were related to the three classical inflammation pathway, cytokine–cytokine receptor interaction, TNF, and NF-kappa B signaling pathway. The enriched genes included not only IL-1β and TNF- α, which were independently verified before sequencing, but also other inflammatory osteolysis-related genes such as Mmp9, Fas, and Ccl2. Co-differentially expressed RNAs were employed to construct the ceRNA co-regulatory network. Conclusion: The results revealed that 4 lncRNAs and 2 circRNAs formed a regulatory network to simultaneously regulate miR-3065-3p targeting Myo18a. The present study helps to comprehensively understand the molecular mechanisms and regulatory interaction networks during early inflammatory response.

Toggling effect on pullout performance of pedicle screws: Review

Screw loosening in spine surgery is a clinical complication in patients with poor bone quality. Pedicle screws are subjected to bending moments and axial loads that may cause toggling during daily movements of spine. The purpose of this study was to assess the previous studies related to toggling effect on pullout performance of pedicle screws by surveying the whole literature and to provide some discussion for new studies about pullout performance of pedicle screws after toggling. The search was performed by combining terms of pedicle screw, toggling, screw loosening, fatigue, cyclic loading, and pullout. The retrieved articles dealing with determined terms and also their references were reviewed. Some of these articles were eliminated after review process. Toggling was determined to be crucial for the stabilization performance of pedicle screw because the loosening mechanism of screws was affected directly by cyclic loading. The toggling or cyclic loading affected the holding capacity of pedicle screws negatively, and the possibility of loosening or failure problem for pedicle screws increased with cyclic loading magnitude. Loading conditions, screw properties, test medium, level of spinal region, and cement usage were determined by many researchers as the most important parameters affecting the toggling performance as well as the pullout strength of pedicle screws. The pullout strength of pedicle screws generally decreased with cyclic loading. The parameters of cyclic loading were fairly important for pullout performance of pedicle screws. Screw properties and cement augmentation had critical effects on the stability of screws under cyclic loading, as well.

Loosening of steel threaded connection subjected to axial compressive impact loading

Loosening of threaded connection under impact loading is important in engineering structures such as the fuze on a projectile. It is difficult to predict the loosening behavior of threaded connection under impact loading due to their high nonlinearities introduced by friction and discontinuity. This paper investigated the loosening response of a threaded connection under a series of impact loadings using Hopkinson bar experiments. The loosening phase diagram was constructed by measuring the preload variation. The correlation between the preload variation and the loosening rotation angle was established by using high speed camera and digital image correlation technique. A 3D finite element model was developed to analyze the loosening mechanism of threaded connection. The transient behavior of threaded connection shows a tightening-loosening alternation process. This study provides an understanding of the loosening process of threaded connection under impact loading and is helpful for optimizing structural design under extreme conditions.

Mechanism and quantitative evaluation model of slip-induced loosening for bolted joints

PurposeBolted joints are the most common type of mechanical connections, and improving the anti-loosening performance of bolts for the reliable performance of mechanical and building structures is highly significant.Design/methodology/approachBecause of the lack of sufficient theoretical basis for the evaluation and design of anti-loosening bolts, a quantitative evaluation model exhibiting the following two evaluation criteria for anti-loosening bolts is introduced: bolt rotation angular acceleration criterion and critical transverse load criterion. Based on the relationship among bolt tension, transverse load and bolt rotation angular acceleration, a critical transverse load calculation model is put forward, and the mechanism by which the critical transverse load increases with the increase of bolt tension is revealed.FindingsBased on the above model, a new type of anti-loosening bolt is designed, which generates additional bolt tension when the transverse load increases, and then improves the critical transverse load of the bolt. The effectiveness of the new type of anti-loosening bolt is verified by theoretical calculations and experiments.Originality/valueThe proposed model and method set a preliminary theoretical foundation for the evaluation of bolt anti-loosening performance and the design of a new anti-loosening bolt.