An Experimental Study of Self-Loosening of Bolted Joints

2004 ◽  
Vol 126 (5) ◽  
pp. 925-931 ◽  
Author(s):  
Yanyao Jiang ◽  
Ming Zhang ◽  
Tae-Won Park ◽  
Chu-Hwa Lee
Keyword(s):  
Endurance Limit ◽  
Early Stage ◽  
Fatigue Curve ◽  
Relative Displacement ◽  
Shear Loading ◽  
Bolted Joints ◽  
Second Stage ◽  
Controlling Parameter ◽  
Cyclic Plastic Deformation ◽  
The Relationship

The self-loosening process of a bolted joint consists of two distinct stages. The early stage of self-loosening is due to the cyclic plastic deformation of the materials. The second stage of self-loosening is characterized by the backing off of the nut. The current work is concentrated on an experimental investigation of the second stage self-loosening. Over one hundred bolted joints with M12×1.75 bolts and nuts were experimentally tested using a specially designed testing apparatus. The experiments mimicked two plates jointed by a bolt and a nut and were subjected to cyclic transverse shear loading. During an experiment, the relative displacement between the two clamped plates, denoted by δ, was a controlling parameter. For a given preload, the relationship between, Δδ/2, the amplitude of the relative displacement between the two clamped plates, and, NL, the number of loading cycles to loosening followed a pattern similar to a fatigue curve. There existed an endurance limit below which self-loosening would not persist. A larger preload resulted in a larger endurance limit. However, a large preload increased the possibility for the bolt to fail in fatigue. The results suggest that the use of a regular nut is superior to the use of a flange nut in terms of self-loosening resistance.

An Experimental Investigation on Self-Loosening of Bolted Joints

2003 ◽  
Author(s):  
Yanyao Jiang ◽  
Ming Zhang ◽  
Tae-Won Park ◽  
Chu-Hwa Lee
Keyword(s):  
Experimental Investigation ◽  
Endurance Limit ◽  
Early Stage ◽  
Surface Condition ◽  
Fatigue Curve ◽  
Relative Displacement ◽  
Shear Loading ◽  
Bolted Joints ◽  
Transverse Load ◽  
Second Stage

The self-loosening process of a bolted joint consists of two distinct stages. The early stage of self-loosening is due to the cyclic plastic deformation of the materials. The second stage of self-loosening is characterized by the backing off of the nut. The current study is concentrated on the experimental investigation of the second stage of self-loosening with the aim to explore the mechanisms responsible for the phenomenon. Over a hundred bolted joints were experimentally tested using a specially designed testing apparatus. M12×1.75 bolts and nuts were used. The experiments mimicked two plates jointed by a bolt and a nut and were subjected to cyclic transverse shear loading. During an experiment, the relative displacement between the two clamped plates, denoted by δ, was a control parameter. The clamping force, the relative rotation between the nut and the bolt, and the applied transverse load were monitored and recorded for each loading cycle. For a given preload, the relationship between, Δδ/2, the amplitude of the relative displacement between the two clamped plates, and, NL, the number of loading cycles to loosening followed a pattern similar to a fatigue curve. There existed an endurance limit below which self-loosening would not persist. A larger preload resulted in a larger endurance limit. However, a large preload increased the possibility for the bolt to fail in fatigue. It was found that the surface condition, which influenced the friction coefficient, had a significant influence on self-loosening resistance. The results also reveal that the use of a regular nut is superior to the use of a flange nut in terms of self-loosening resistance. An “endurance diagram” concept was developed that can be used directly for the design and evaluation of the bolted joints.

An Experimental Investigation of the Effects of Clamped Length and Loading Direction on Self-Loosening of Bolted Joints

2004 ◽  
Author(s):  
Ming Zhang ◽  
Yanyao Jiang ◽  
Chu-Hwa Lee
Keyword(s):  
Experimental Investigation ◽  
Fatigue Curve ◽  
Relative Displacement ◽  
The Self ◽  
Bolted Joints ◽  
Transverse Load ◽  
External Loading ◽  
Loading Direction ◽  
Controlling Parameter ◽  
Load Carrying

An experimental investigation was conducted to study the effects of clamped length and loading direction on the self-loosening behavior of bolted joints. Specially designed fixtures were used for the study. The experiments mimicked two plates jointed by an M12×1.75 Class 10.9 bolt and a nut. The joints were subjected to cyclic external loading. A constant preload of 25 kN was used for all the experiments conducted. During an experiment, the relative displacement between the two clamped plates, δ, was a controlling parameter. The reduction in clamping force, the applied transverse load, and the nut rotation were measured cycle by cycle. The relationship between, Δδ/2, the amplitude of the relative displacement between the two clamped plates, and, NL, the number of loading cycles to loosening is referred to as self-loosening curve and was obtained for different clamped lengths and applied load directions. Similar to a fatigue curve, an endurance limit can be identified from the self-loosening curve. It was found that increasing the clamped length can enhance the self-loosening endurance limits in terms of the controlled relative displacement of the two clamped plates. However, the load carrying capability was not influenced significantly due to the thickness of the clamped plates. For a given bolted jointed structure, an angle of the external load from the pure shearing direction resulted in an increase in self-loosening resistance.

An Experimental Investigation of the Effects of Clamped Length and Loading Direction on Self-Loosening of Bolted Joints

2005 ◽  
Vol 128 (3) ◽  
pp. 388-393 ◽  
Author(s):  
Ming Zhang ◽  
Yanyao Jiang ◽  
Chu-Hwa Lee
Keyword(s):  
Experimental Investigation ◽  
Fatigue Curve ◽  
Relative Displacement ◽  
The Self ◽  
Bolted Joints ◽  
Transverse Load ◽  
External Loading ◽  
Loading Direction ◽  
Controlling Parameter ◽  
Load Carrying

An experimental investigation was conducted to study the effects of clamped length and loading direction on the self-loosening behavior of bolted joints by using specially designed fixtures. The experiments mimicked two plates jointed by an M12×1.75 class 10.9 bolt and a nut. The joints were subjected to cyclic external loading. A constant preload of 25kN was used for all the experiments conducted. During an experiment, the relative displacement between the two clamped plates, δ, was a controlling parameter. The reduction in clamping force, the applied transverse load, and the nut rotation were measured cycle by cycle. The relationship between, Δδ∕2, the amplitude of the relative displacement between the two clamped plates, and, NL, the number of loading cycles to loosening is referred to as self-loosening curve and was obtained for different clamped lengths and applied load directions. Similar to a fatigue curve, an endurance limit can be identified from the self-loosening curve. It was found that increasing the clamped length can enhance the self-loosening endurance limits in terms of the controlled relative displacement of the two clamped plates. However, the load carrying capability was not influenced significantly due to the thickness of the clamped plates. For a given bolted jointed structure, an angle of the external load from the pure shearing direction resulted in an increase in self-loosening resistance.

scholarly journals Relaxation of contact pressure and self-loosening in dynamic bolted joints

2016 ◽  
Vol 231 (18) ◽  
pp. 3462-3475 ◽  
Author(s):  
JT Stephen ◽  
MB Marshall ◽  
R Lewis
Keyword(s):  
Contact Pressure ◽  
Early Stage ◽  
Shear Loading ◽  
Bolted Joints ◽  
Joint Interface ◽  
Shear Load ◽  
Bolted Joint ◽  
Cyclic Shear ◽  
Constant Shear ◽  
Additional Constant

Bolted joints are widely used in a variety of engineering applications where they are dynamically loaded with frequencies of vibration spread over a wide spectrum with the same general effects. When under dynamic loading, bolted joints can become loose due to a loss in clamping pressure in the joints. This vibrational loosening sometimes can cause serious problems, and in some cases can lead to fatal consequences if it remains undetected. Non-intrusive ultrasonic and image processing techniques were simultaneously used to investigate the relaxation of contact pressure and loosening of bolted joints subjected to cyclic shear loading. Three critical areas, the contact interface of the bolted component, the bolt length and the rotation of the bolt head, were monitored during loosening of the joints. The results show that loosening of bolted joints can be grouped into three stages: very rapid, rapid, and gradual loosening. The earliest stage of the loosening of bolted joints is characterised by cyclic strain ratcheting–loosening of the bolted joint during vibration without rotation of the bolt head. The higher the rate of relaxation at this early stage, the lower is the resistance of the bolted joint to vibration-induced loosening. Both the dynamic shear load and an additional constant shear load in another direction were observed to affect the rate of loosening, and at this early stage, a rise in the magnitude of the additional constant shear load increases the rate of loosening. Furthermore, the contact pressure distribution affects the rate of loosening at the bolted joint interface, as loosening increases away from area of high contact pressure.

The Subject Matter of Intellectual Property

2017 ◽  
Author(s):  
Justine Pila
Keyword(s):  
Intellectual Property ◽  
Subject Matter ◽  
Final Stage ◽  
Theoretical Framework ◽  
Trade Mark ◽  
Second Stage ◽  
Essential Properties ◽  
The Subject ◽  
Three Stages ◽  
The Relationship

This book offers a study of the subject matter protected by each of the main intellectual property (IP) regimes. With a focus on European and UK law particularly, it considers the meaning of the terms used to denote the objects to which IP rights attach, such as ‘invention’, ‘authorial work’, ‘trade mark’, and ‘design’, with reference to the practice of legal officials and the nature of those objects specifically. To that end it proceeds in three stages. At the first stage, in Chapter 2, the nature, aims, and values of IP rights and systems are considered. As historically and currently conceived, IP rights are limited (and generally transferable) exclusionary rights that attach to certain intellectual creations, broadly conceived, and that serve a range of instrumentalist and deontological ends. At the second stage, in Chapter 3, a theoretical framework for thinking about IP subject matter is proposed with the assistance of certain devices from philosophy. That framework supports a paradigmatic conception of the objects protected by IP rights as artifact types distinguished by their properties and categorized accordingly. From this framework, four questions are derived concerning: the nature of the (categories of) subject matter denoted by the terms ‘invention’, ‘authorial work’, ‘trade mark’, ‘design’ etc, including their essential properties; the means by which each subject matter is individuated within the relevant IP regime; the relationship between each subject matter and its concrete instances; and the manner in which the existence of a subject matter and its concrete instances is known. That leaves the book’s final stage, in Chapters 3 to 7. Here legal officials’ use of the terms above, and understanding of the objects that they denote, are studied, and the results presented as answers to the four questions identified previously.

scholarly journals COVID-19 uncertainty and sleep: the roles of perceived stress and intolerance of uncertainty during the early stage of the COVID-19 outbreak

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Dan Wu ◽  
Tingzhong Yang ◽  
Daniel L. Hall ◽  
Guihua Jiao ◽  
Lixin Huang ◽  
...  
Keyword(s):  
Path Analysis ◽  
Perceived Stress ◽  
Mediation Analysis ◽  
Early Stage ◽  
Intolerance Of Uncertainty ◽  
Policy Implications ◽  
Self Report ◽  
Poor Sleep ◽  
The Relationship

Abstract Background The COVID-19 pandemic brings unprecedented uncertainty and stress. This study aimed to characterize general sleep status among Chinese residents during the early stage of the outbreak and to explore the network relationship among COVID-19 uncertainty, intolerance of uncertainty, perceived stress, and sleep status. Methods A cross-sectional correlational survey was conducted online. A total of 2534 Chinese residents were surveyed from 30 provinces, municipalities, autonomous regions of China and regions abroad during the period from February 7 to 14, 2020, the third week of lockdown. Final valid data from 2215 participants were analyzed. Self-report measures assessed uncertainty about COVID-19, intolerance of uncertainty, perceived stress, and general sleep status. Serial mediation analysis using the bootstrapping method and path analysis were applied to test the mediation role of intolerance of uncertainty and perceived stress in the relationship between uncertainty about COVID-19 and sleep status. Results The total score of sleep status was 4.82 (SD = 2.72). Age, place of residence, ethnicity, marital status, infection, and quarantine status were all significantly associated with general sleep status. Approximately half of participants (47.1%) reported going to bed after 12:00 am, 23.0% took 30 min or longer to fall asleep, and 30.3% slept a total of 7 h or less. Higher uncertainty about COVID-19 was significantly positively correlated with higher intolerance of uncertainty (r = 0.506, p < 0.001). The mediation analysis found a mediating role of perceived stress in the relationship between COVID-19 uncertainty and general sleep status (β = 0.015, 95%C.I. = 0.009–0.021). However, IU was not a significant mediator of the relationship between COVID-19 uncertainty and sleep (β = 0.009, 95%C.I. = − 0.002–0.020). Moreover, results from the path analysis further showed uncertainty about COVID-19 had a weak direct effect on poor sleep (β = 0.043, p < 0.05); however, there was a robust indirect effect on poor sleep through intolerance of uncertainty and perceived stress. Conclusions These findings suggest that intolerance of uncertainty and perceived stress are critical factors in the relationship between COVID-19 uncertainty and sleep outcomes. Results are discussed in the context of the COVID-19 pandemic, and practical policy implications are also provided.

scholarly journals Effect of number of medications and use of potentially inappropriate medications on frailty among early-stage older outpatients

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yuya Uragami ◽  
Kazuhiro Takikawa ◽  
Hajime Kareki ◽  
Koji Kimura ◽  
Kazuyuki Yamamoto ◽  
...  
Keyword(s):  
Early Stage ◽  
Linear Trend ◽  
Cross Sectional Study ◽  
Potentially Inappropriate Medications ◽  
Sectional Study ◽  
Antithrombotic Drugs ◽  
Cross Sectional ◽  
The Relationship ◽  
Inappropriate Medications ◽  
Frailty Score

Abstract Background Frailty is an urgent concern among an aging population worldwide. However, the relationship between frailty and number and types of medications has not been studied in detail among early-stage older patients, and it is unclear what prescriptions may have a role in preventing frailty. This study aimed to clarify the effects of number of medications and use of potentially inappropriate medications (PIMs) on frailty among early-stage older outpatients in Japan. Methods A cross-sectional study was undertaken. Frailty scores and medications of outpatients aged 65–74 years who regularly visited community pharmacies were investigated. Frailty scores were classified as 0 (non-frailty), 1–2 (pre-frailty), and ≥ 3 (frailty). The association between frailty and number of medications was analyzed by age and compared between PIM use and non-use groups. The proportion of patients who used PIMs was also analyzed by frailty score. Results Of 923 older outpatients, 49 (5.3%) and 318 (34.5%) patients had frailty and pre-frailty scores, respectively. The numbers of medications among patients with pre-frailty and frailty were significantly higher than among those with non-frailty (p <  0.001 for both). A similar increase was shown for PIM use groups aged 69–71 and 72–74 years, but not for the PIM use group aged 65–68 years and all groups without PIM use. An increasing linear trend was observed for the relationship between the proportion of patients who used any PIM, as well as some subcategories of PIMs (such as NSAIDs, benzodiazepines, loop diuretics and antithrombotic drugs) and frailty score. Conclusions Unnecessary medication use among early-stage older outpatients, especially patients aged ≥69 years who use PIMs and many medications, seems to be associated with frailty, but further research is needed to confirm these findings.

Roller–rail parameters on the transverse vibration characteristics of super-high-speed elevators

2019 ◽  
Vol 43 (4) ◽  
pp. 535-543 ◽  
Author(s):  
Shunxin Cao ◽  
Ruijun Zhang ◽  
Shuohua Zhang ◽  
Shuai Qiao ◽  
Dongsheng Cong ◽  
...  
Keyword(s):  
High Speed ◽  
Relative Displacement ◽  
Guide Rail ◽  
Coupled Vibration ◽  
Vibration Acceleration ◽  
Vibration Model ◽  
Vibration Problems ◽  
Equivalent Method ◽  
Relationship Of ◽  
The Relationship

Interaction and wear between wheel and rail become increasingly serious with the increase in elevator speed and load. Uneven roller surface, eccentricity of rollers, and the looseness of rail brackets result in serious vibration problems of high-speed and super-high-speed elevators. Therefore, the forced vibration differential equation representing elevator guide rails is established based on Bernoulli–Euler theory, and the vibration equation of the elevator guide shoes and the car is constructed using the Darren Bell principle. Then, the coupled vibration model of guide rail, guide shoes, and car can be obtained using the relationship of force and relative displacement among these components. The roller–rail parameters are introduced into the established coupled vibration model using the model equivalent method. Then, the influence of roller–rail parameters on the horizontal vibration of super-high-speed elevator cars is investigated. Roller eccentricity and the vibration acceleration of the car present a linear correlation, with the amplitude of the car vibration acceleration increasing with the eccentricity of the roller. A nonlinear relationship exists between the surface roughness of the roller and the vibration acceleration of the car. Increased continuous loosening of the guide rail results in severe vibration of the car at the loose position of the support.

scholarly journals Anosognosia in People with Cognitive Impairment: Association with Cognitive Deficits and Behavioral Disturbances

2015 ◽  
Vol 5 (1) ◽  
pp. 42-50 ◽  
Author(s):  
Antonella De Carolis ◽  
Virginia Cipollini ◽  
Valentina Corigliano ◽  
Anna Comparelli ◽  
Micaela Sepe-Monti ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Cognitive Deficits ◽  
Rating Scale ◽  
Motor Behavior ◽  
Psychiatric Symptoms ◽  
Early Stage ◽  
Functional Anatomy ◽  
Night Time ◽  
Behavioral Disturbances ◽  
The Relationship

Aims: To investigate, in a group of subjects at an early stage of cognitive impairment, the relationship between anosognosia and both cognitive and behavioral symptoms by exploring the various domains of insight. Methods: One hundred and eight subjects affected by cognitive impairment were consecutively enrolled. The level of awareness was evaluated by means of the Clinical Insight Rating Scale (CIRS). Psychiatric symptoms were evaluated using the Italian version of the Neuropsychiatric Inventory (NPI), whereas memory (memory index, MI) and executive (executive index, EI) functions were explored using a battery of neuropsychological tests and qualified by means of a single composite cognitive index score for each function. Results: A significant positive correlation between the total NPI score and global anosognosia score was found. Furthermore, both the MI and EI scores were lower in subjects with anosognosia than in those without anosognosia (p < 0.001 and p < 0.007, respectively). When the single domains of the CIRS were considered, anosognosia of reason of visit correlated with the EI score (r = -0.327, p = 0.01) and night-time behavioral disturbances (r = 0.225; p = 0.021); anosognosia of cognitive deficit correlated with depression (r = -0.193; p = 0.049) and the MI score (r = -0.201; p = 0.040); anosognosia of functional deficit correlated with the MI score (r = -0.257; p = 0.008), delusions (r = 0.232; p = 0.015) and aberrant motor behavior (r = 0.289; p = 0.003); anosognosia of disease progression correlated with the MI score (r = -0.236; p = 0.015), agitation (r = 0.247; p = 0.011), aberrant motor behavior (r = 0.351; p = 0.001) and night-time behavioral disturbances (r = 0.216; p = 0.027). Conclusions: Our study suggests that, in the early stage of cognitive impairment, anosognosia is associated with both cognitive deficits and behavioral disorders according to the specific functional anatomy of the symptoms.

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