Vibro-Impact Dynamics of a Periodically Forced Beam

2000 ◽  
Vol 122 (2) ◽  
pp. 210-221 ◽  
Author(s):  
Jakob Knudsen ◽  
Ali R. Massih
Keyword(s):  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Unilateral Contact ◽  
Contact Forces ◽  
The Other ◽  
Impact Dynamics ◽  
Harmonic Loading ◽  
Model Calculations ◽  
Contact Sites ◽  
The Impact

The vibration and impact dynamics of a periodically forced loosely supported beam are analyzed. The wear work rates at impact points are evaluated. The considered beam is clamped at one end, and constrained against unilateral contact at contact sites, with or without friction, near the other end. In this work, the structure is modeled by a Bernoulli-type beam supported by springs using finite element method. Our model calculations are compared with measurements of contact forces and displacements made on a loosely supported rod that was subjected to harmonic loading. Furthermore, the dynamics of vibro-impacts are characterized by evaluating the impact velocity as a function of harmonic excitation frequency for two idealizations of the aforementioned structure. [S0094-9930(00)01002-7]

scholarly journals A new impact dynamics model of a clearance joint considering the adhesive effects in space environment

2020 ◽  
Vol 306 ◽  
pp. 01005
Author(s):  
Ruiting Tong ◽  
Zefen Quan ◽  
Qi Wan ◽  
Xiaojun Fu ◽  
Geng Liu
Keyword(s):  
Hybrid Model ◽  
Contact Process ◽  
Contact Forces ◽  
Space Environment ◽  
Impact Dynamics ◽  
Force Model ◽  
Dynamics Model ◽  
Clearance Joint ◽  
The Impact ◽  
Adhesive Forces

In space environment, there is severe adhesive effect, and the impact contact process shows different phenomenon due to the adhesive forces. In this paper, a new impact dynamics model of a clearance joint is developed considering the adhesive effects. The Hertz contact model, L-J potential and Dugdale model are combined, and an adhesive force term is included in the original hybrid contact force model. Taking a clearance joint as an example, the theory of adhesive forces during the impact contact process is given, and the influence of the adhesive forces is investigated. Negative forces are discovered at the beginning of the contact, and the contact forces of the modified model are higher than the hybrid model. Besides, the indentation depth is also higher than the hybrid model. The energy conservation principle is employed to explain the phenomena, and the contact forces will be underestimated if the adhesive effects are ignored. This work could be contributed to estimating the contact forces and friction forces more reasonablely in the space environment.

The Comparison of Two Processing Methods of Sliding Bearing in Impact Dynamics Analysis of Finite Element Software

2012 ◽  
Vol 226-228 ◽  
pp. 798-801
Author(s):  
Xiao Han Gao ◽  
Yu Wang ◽  
Jian Ye Du ◽  
Xiao Peng Gao
Keyword(s):  
Finite Element ◽  
Single Point ◽  
The Other ◽  
Impact Response ◽  
Contact Model ◽  
Impact Dynamics ◽  
Dynamics Analysis ◽  
Spring Model ◽  
Finite Element Software ◽  
The Impact

In this article, author studied the application of two models of "single point damping-spring" model and "contact" model in the process of impact dynamic analysis. Research shows that the load and force could be transmitted smoothly in all these methods. But there still have limitations in two methods, we could not study the impact response of bearing itself and the shaft neck contacted with bearing in the "single point damping-spring" model, on the other hand, the penetration of contact parts could not be avoided completely in the "contact" model, sometimes, the numerical calculation even could not be converged if the parameters were not be set properly in this method. Of course, this two methods also have their own advantages, we could select different model according to different circumstances.

Contact time of impacting droplets on a superhydrophobic surface with tunable curvature and groove orientation

2021 ◽  
Author(s):  
Chunfang Guo ◽  
Lei Liu ◽  
Changwan Liu
Keyword(s):  
Weber Number ◽  
Contact Time ◽  
Superhydrophobic Surface ◽  
The Other ◽  
Impact Dynamics ◽  
Azimuthal Direction ◽  
Droplet Spreading ◽  
Droplet Impingement ◽  
Practical Applications ◽  
The Impact

Abstract Regulating the impact dynamics of water droplets on a solid surface is of great significance for some practical applications. In this study, the droplet impingement on a flexible superhydrophobic surface arrayed with micro-scale grooves is investigated experimentally. The surface was curved into cylindrical shapes with certain curvatures from two orthogonal directions, where axial and circumferential grooves were formed, respectively. The effects of curvature diameter and Weber number, as well as the orientation of grooves on droplet spreading and retracting dynamics were discussed and explained. Results show that the circumferential grooves promote the spreading of droplet in the azimuthal direction, where the droplet rebounds from the surface with a stretched shape. This mechanism further reduces the contact time of impacting droplets on the superhydrophobic surface compared to the other curving mode.

scholarly journals Snapping of a Shallow Arch With Harmonic Excitation at One End

2007 ◽  
Vol 129 (4) ◽  
pp. 514-519 ◽  
Author(s):  
Jen-San Chen ◽  
Der-Wei Chang
Keyword(s):  
Natural Frequencies ◽  
Stable Equilibrium ◽  
Excitation Frequency ◽  
Longitudinal Direction ◽  
Harmonic Excitation ◽  
Small Distance ◽  
The Other ◽  
Base Line ◽  
Shallow Arch ◽  
Mechanical Shaker

In this paper we demonstrate both numerically and experimentally that it is possible to make a pinned-pinned shallow arch snap to and remain vibrating on the other side by harmonic excitation in the longitudinal direction at the end. One end of the arch is fixed in space, while the other end is attached to a mechanical shaker via a spring. The shaker-mount is first moved a small distance toward the arch to ensure that the arch assembly possesses two stable equilibrium positions, one on each side of the base line. The spring connecting the arch end and the mechanical shaker is carefully chosen such that a small shaker stroke can induce a large vibration amplitude in the arch. The natural frequencies of the two (initial and snapped, respectively) positions are measured first. By adjusting the excitation frequency of the mechanical shaker to the first natural frequency of either position of the arch, we demonstrate that the arch can be snapped to and remain vibrating on the other side when the magnitude of the electric current flowing through the shaker is properly chosen. The vibrant snapping action of the arch recorded in the experiment is confirmed by numerical simulation.

scholarly journals Dynamic Analysis of Percussion Drilling System under Harmonic Impact

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yijin Zeng ◽  
Shidong Ding ◽  
Jinchao Xu ◽  
Qunai Hu ◽  
Xiaojie Cui
Keyword(s):  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Rock Breaking ◽  
Simplified Model ◽  
Vibration Displacement ◽  
Impact System ◽  
Drilling Technology ◽  
Vibration Impact ◽  
Breaking Mechanism ◽  
The Impact

As a new efficient rock-breaking technology, harmonic impact drilling technology has received great attention, but the research on its rock-breaking mechanism is insufficient, which limits its development. Based on the theory of vibration, a simplified model of high-frequency harmonic vibration impact system is established in this paper. The numerical model was solved by Matlab and the motion equations of drill bit and rock at different stages of motion are obtained, respectively. Based on the factor analysis of the mathematical model, the dynamic characteristics of the impact system under harmonic excitation are studied. Finally, numerical simulations are carried out to further analyze the drilling effect of harmonic impact drilling and verify the correctness of the simplified model. The results show that when the excitation frequency equals the resonance frequency of rock, the vibration displacement of rock reaches the peak value. The drilling speed is greatly increased by harmonic impact drilling compared with conventional drilling.

Modernism, Empiricism, and Rationalism

2016 ◽  
Vol 46 (1) ◽  
pp. 38-47
Author(s):  
Geoffrey Squires
Keyword(s):  
Twentieth Century ◽  
The Other ◽  
Modern Poetry ◽  
Philosophical Perspective ◽  
Irish Poetry ◽  
Dimensional Spectrum ◽  
Culture History ◽  
The World ◽  
The Impact ◽  
Rule Out

Modernism is usually defined historically as the composite movement at the beginning of the twentieth century which led to a radical break with what had gone before in literature and the other arts. Given the problems of the continuing use of the concept to cover subsequent writing, this essay proposes an alternative, philosophical perspective which explores the impact of rationalism (what we bring to the world) on the prevailing empiricism (what we take from the world) of modern poetry, which leads to a concern with consciousness rather than experience. This in turn involves a re-conceptualisation of the lyric or narrative I, of language itself as a phenomenon, and of other poetic themes such as nature, culture, history, and art. Against the background of the dominant empiricism of modern Irish poetry as presented in Crotty's anthology, the essay explores these ideas in terms of a small number of poets who may be considered modernist in various ways. This does not rule out modernist elements in some other poets and the initial distinction between a poetics of experience and one of consciousness is better seen as a multi-dimensional spectrum that requires further, more detailed analysis than is possible here.

HOME VISITS DURING THE FIRST MONTH OF DELIVERY FOR RECENTLY DELIVERED WOMEN IN UTTAR PRADESH, INDIA

2020 ◽  
Vol 6 (5) ◽  
pp. 1183-1189
Author(s):  
Dr. Tridibesh Tripathy ◽  
Dr. Umakant Prusty ◽  
Dr. Chintamani Nayak ◽  
Dr. Rakesh Dwivedi ◽  
Dr. Mohini Gautam
Keyword(s):  
Large Scale ◽  
National Level ◽  
Uttar Pradesh ◽  
Life Time ◽  
Structured Interview ◽  
The Other ◽  
Registration System ◽  
Action Group ◽  
Current Article ◽  
The Impact

The current article of Uttar Pradesh (UP) is about the ASHAs who are the daughters-in-law of a family that resides in the same community that they serve as the grassroots health worker since 2005 when the NRHM was introduced in the Empowered Action Group (EAG) states. UP is one such Empowered Action Group (EAG) state. The current study explores the actual responses of Recently Delivered Women (RDW) on their visits during the first month of their recent delivery. From the catchment area of each of the 250 ASHAs, two RDWs were selected who had a child in the age group of 3 to 6 months during the survey. The response profiles of the RDWs on the post- delivery first month visits are dwelled upon to evolve a picture representing the entire state of UP. The relevance of the study assumes significance as detailed data on the modalities of postnatal visits are available but not exclusively for the first month period of their recent delivery. The details of the post-delivery first month period related visits are not available even in large scale surveys like National Family Health Survey 4 done in 2015-16. The current study gives an insight in to these visits with a five-point approach i.e. type of personnel doing the visit, frequency of the visits, visits done in a particular week from among those four weeks separately for the three visits separately. The current study is basically regarding the summary of this Penta approach for the post- delivery one-month period.     The first month period after each delivery deals with 70% of the time of the postnatal period & the entire neonatal period. Therefore, it does impact the Maternal Mortality Rate & Ratio (MMR) & the Neonatal Mortality Rates (NMR) in India and especially in UP through the unsafe Maternal & Neonatal practices in the first month period after delivery. The current MM Rate of UP is 20.1 & MM Ratio is 216 whereas the MM ratio is 122 in India (SRS, 2019). The Sample Registration System (SRS) report also mentions that the Life Time Risk (LTR) of a woman in pregnancy is 0.7% which is the highest in the nation (SRS, 2019). This means it is very risky to give birth in UP in comparison to other regions in the country (SRS, 2019). This risk is at the peak in the first month period after each delivery. Similarly, the current NMR in India is 23 per 1000 livebirths (UNIGME,2018). As NMR data is not available separately for states, the national level data also hold good for the states and that’s how for the state of UP as well. These mortalities are the impact indicators and such indicators can be reduced through long drawn processes that includes effective and timely visits to RDWs especially in the first month period after delivery. This would help in making their post-natal & neonatal stage safe. This is the area of post-delivery first month visit profile detailing that the current article helps in popping out in relation to the recent delivery of the respondents.   A total of four districts of Uttar Pradesh were selected purposively for the study and the data collection was conducted in the villages of the respective districts with the help of a pre-tested structured interview schedule with both close-ended and open-ended questions.  The current article deals with five close ended questions with options, two for the type of personnel & frequency while the other three are for each of the three visits in the first month after the recent delivery of respondents. In addition, in-depth interviews were also conducted amongst the RDWs and a total 500 respondents had participated in the study.   Among the districts related to this article, the results showed that ASHA was the type of personnel who did the majority of visits in all the four districts. On the other hand, 25-40% of RDWs in all the 4 districts replied that they did not receive any visit within the first month of their recent delivery. Regarding frequency, most of the RDWs in all the 4 districts received 1-2 times visits by ASHAs.   Regarding the first visit, it was found that the ASHAs of Barabanki and Gonda visited less percentage of RDWs in the first week after delivery. Similarly, the second visit revealed that about 1.2% RDWs in Banda district could not recall about the visit. Further on the second visit, the RDWs responded that most of them in 3 districts except Gonda district did receive the second postnatal visit in 7-15 days after their recent delivery. Less than half of RDWs in Barabanki district & just more than half of RDWs in Gonda district received the third visit in 15-21 days period after delivery. For the same period, the majority of RDWs in the rest two districts responded that they had been entertained through a home visit.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Wacana Kolonial dalam Novel Max Havelaar: Sebuah Kajian Poskolonial

Metahumaniora ◽  
2017 ◽  
Vol 7 (3) ◽  
pp. 411
Author(s):  
Abu Bakar Ramadhan Muhamad
Keyword(s):  
Point Of View ◽  
The Other ◽  
The Novel ◽  
Colonial Discourse ◽  
The Impact ◽  
The Voice

AbstrakHegemoni kolonialisme dalam budaya poskolonial merupakan alasan penelitian inikemudian mengkaji wacana kolonial dalam novel Max Havellar (MH) khususnya dampakditimbulkannya. Dampak dimaksud adalah posisi keberpihakan pemikiran tersirat darikarya tersebut. Hasil pembahasan menunjukkan, secara temporal maupun permanen MHmenyuarakan ketidakadilan dalam kondisi-kondisi kolonial menyangkut penindasan sangpenjajah terhadap terjajah. Hanya saja, upaya mengatasnamakan atau mewakili suarakaum terjajah terbukti mengimplikasikan ciri ideologis statis kerangka kolonialisme(orientalisme); yakni cara pandang Eropasentris, di mana “Barat” sebagai self adalah superior,dan “Timur” sebagai other adalah inferior. Dalam konteks poskolonialisme, MH dengan sifatkritisnya yang berupaya “menyuarakan” nasib pribumi terjajah, justru menampilkan stigmapenguatan kolonialitas itu sendiri secara hegemonik. Artinya, “menyuarakan” nasib pribumidimaknai sebagai keberpihankan kolonial yang kontradiktif, di mana stigma penguatankolonialitas justru lebih terasa, ujung-ujungnya melanggengkan hegemoni kolonial. Tidakmembela yang terjajah, tetapi memperhalus cara kerja mesin kolonial.AbstractThe hegemony of colonialism in the culture of postcolonial society is the reason this studythen examines the colonial discourse in the novel Max Havellar (MH) in particular the impactit brings. The impact in question is the implied position of thought in the work. The resultsof the discussion show that, temporarily or permanently, MH voiced injustice in the colonialconditions regarding the oppression of the colonist against the colonized. However, the effort toname or represent the voice of the colonized has proven to imply a static ideological characterin the framework of colonialism (orientalism); ie Eropacentric point of view, in which “West” asself is superior, and “East” as the other is the inferior. In the context of postcolonialism, MH withits critical nature that seeks to “voice” the fate of the colonized natives, actually presents thestigma of strengthening coloniality itself hegemonicly. That is, “voicing” the fate of the pribumiis interpreted as a contradictory colonial flare, where the stigma of strengthening colonialityis more pronounced, which ultimately perpetuates the hegemony of colonialism. No longerdefending the colonized, but refining the workings of the colonial machinery.

Gifted Students' Motivation and its Impact on the Development of their Giftedness

2018 ◽  
Vol 3 (1) ◽  
Author(s):  
Hussein SALEM MUBARAK BARABWD ◽  
Mohammad YUSOFF BIN MOHD NOR ◽  
Noriah Mohd Ishak
Keyword(s):  
Extrinsic Motivation ◽  
Gifted Students ◽  
Qualitative Approach ◽  
The Other ◽  
Phenomenological Method ◽  
Self Confidence ◽  
Verbal Praise ◽  
Intrinsic Motivations ◽  
The Impact ◽  
Intrinsic And Extrinsic Motivations

The aim of the current study is to examine the intrinsic and extrinsic motivations of the gifted students from Hadhramout Gifted Center HGC in Yemen, and to investigate the impact of these intrinsic and extrinsic motivations on their giftedness development. A qualitative approach was adopted; data has been collected through an open- ended questionnaire that was prepared by the researcher and distributed among a sample of gifted students who were chosen purposively from HGC. The interpretative phenomenological method has been used to analyze the data using, Atlas ti. The results indicate that the majority of the participants consider it interesting to explore new things, and experience curiosity and desire to achieve their goals as their intrinsic motivations. Whereas, the minority consider preference to serve the community, competition preference and self-confidence as their intrinsic motivations. On the other hand, half of the participants consider rewards as their extrinsic motivation, whereas 40 % of them consider exams scores, verbal praise, parents and environment as their extrinsic motivations. Regarding the impact of intrinsic and extrinsic motivations on the development of giftedness, the majority of the participants believe that intrinsic and extrinsic motivations affect positively the development of their giftedness development. Finally, based on the findings, some recommendations were provided. 

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