scholarly journals Effect of Pressure Distribution on the Energy Dissipation of Lap Joints under Equal Pre-tension Force

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 320-328
Author(s):  
Delin Sun ◽  
Minggao Zhu
Keyword(s):  
Energy Dissipation ◽  
Pressure Distribution ◽  
Theoretical Basis ◽  
Lap Joints ◽  
Power Exponent ◽  
Lap Joint ◽  
Stick Slip ◽  
Pressure Distributions ◽  
Hysteretic Characteristics ◽  
Effective Use

Abstract In this paper, the energy dissipation in a bolted lap joint is studied using a continuum microslip model. Five contact pressure distributions compliant with the power law are considered, and all of them have equal pretension forces. The effects of different pressure distributions on the interface stick-slip transitions and hysteretic characteristics are presented. The calculation formulation of the energy dissipation is introduced. The energy dissipation results are plotted on linear and log-log coordinates to investigate the effect of the pressure distribution on the energy distribution. It is shown that the energy dissipations of the lap joints are related to the minimum pressure in the overlapped area, the size of the contact area and the value of the power exponent. The work provides a theoretical basis for further effective use of the joint energy dissipation.

Theoretical Estimation of the Frictional Energy Dissipation in a Simple Lap Joint

1966 ◽  
Vol 8 (2) ◽  
pp. 207-214 ◽  
Author(s):  
S. W. E. Earles
Keyword(s):  
Energy Dissipation ◽  
Frictional Resistance ◽  
Lap Joints ◽  
Damping Capacity ◽  
Lap Joint ◽  
Frictional Energy ◽  
Maximum Benefit ◽  
Joint Contact ◽  
Contact Surfaces ◽  
Frictional Energy Dissipation

Some recent work on fretting fatigue in lap joints has shown that certain treatments of the joint contact surfaces greatly improve the fatigue life of the joint, and suggests that maximum benefit may be obtained by arranging for force transference within the joint to take place only by frictional resistance. A simple theoretical analysis of a simple lap joint is here presented which estimates the frictional energy dissipation, and concludes that, for any pressure distribution imposed along the joint faces by the rivet clamping force, the damping capacity of the joint is a maximum when force transference is only by friction throughout the joint.

Effect of Pressure Distribution on Energy Dissipation in a Mechanical Lap Joint

AIAA Journal ◽  
2005 ◽  
Vol 43 (2) ◽  
pp. 420-425 ◽  
Author(s):  
Yaxin Song ◽  
D. Michael McFarland ◽  
Lawrence A. Bergman ◽  
Alexander F. Vakakis
Keyword(s):  
Energy Dissipation ◽  
Pressure Distribution ◽  
Lap Joint ◽  
Effect Of Pressure

scholarly journals Dynamic flight load measurements with MEMS pressure sensors

2021 ◽  
Author(s):  
Christian Raab ◽  
Kai Rohde-Brandenburger
Keyword(s):  
Pressure Distribution ◽  
Pressure Sensors ◽  
Flow Characteristics ◽  
Flight Test ◽  
Measurement Technology ◽  
Test Program ◽  
Aerodynamic Pressure ◽  
Pressure Distributions ◽  
Time Histories ◽  
Mems Pressure Sensors

AbstractThe determination of structural loads plays an important role in the certification process of new aircraft. Strain gauges are usually used to measure and monitor the structural loads encountered during the flight test program. However, a time-consuming wiring and calibration process is required to determine the forces and moments from the measured strains. Sensors based on MEMS provide an alternative way to determine loads from the measured aerodynamic pressure distribution around the structural component. Flight tests were performed with a research glider aircraft to investigate the flight loads determined with the strain based and the pressure based measurement technology. A wing glove equipped with 64 MEMS pressure sensors was developed for measuring the pressure distribution around a selected wing section. The wing shear force determined with both load determination methods were compared to each other. Several flight maneuvers with varying loads were performed during the flight test program. This paper concentrates on the evaluation of dynamic flight maneuvers including Stalls and Pull-Up Push-Over maneuvers. The effects of changes in the aerodynamic flow characteristics during the maneuver could be detected directly with the pressure sensors based on MEMS. Time histories of the measured pressure distributions and the wing shear forces are presented and discussed.

scholarly journals Influence of the Spatial Pressure Distribution of Breaking Wave Loading on the Dynamic Response of Wolf Rock Lighthouse

2021 ◽  
Vol 9 (1) ◽  
pp. 55
Author(s):  
Darshana T. Dassanayake ◽  
Alessandro Antonini ◽  
Athanasios Pappas ◽  
Alison Raby ◽  
James Mark William Brownjohn ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Pressure Distribution ◽  
Distinct Element ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Wave Loading ◽  
Wave Impact ◽  
Pressure Distributions ◽  
Impact Area ◽  
The Impact

The survivability analysis of offshore rock lighthouses requires several assumptions of the pressure distribution due to the breaking wave loading (Raby et al. (2019), Antonini et al. (2019). Due to the peculiar bathymetries and topographies of rock pinnacles, there is no dedicated formula to properly quantify the loads induced by the breaking waves on offshore rock lighthouses. Wienke’s formula (Wienke and Oumeraci (2005) was used in this study to estimate the loads, even though it was not derived for breaking waves on offshore rock lighthouses, but rather for the breaking wave loading on offshore monopiles. However, a thorough sensitivity analysis of the effects of the assumed pressure distribution has never been performed. In this paper, by means of the Wolf Rock lighthouse distinct element model, we quantified the influence of the pressure distributions on the dynamic response of the lighthouse structure. Different pressure distributions were tested, while keeping the initial wave impact area and pressure integrated force unchanged, in order to quantify the effect of different pressure distribution patterns. The pressure distributions considered in this paper showed subtle differences in the overall dynamic structure responses; however, pressure distribution #3, based on published experimental data such as Tanimoto et al. (1986) and Zhou et al. (1991) gave the largest displacements. This scenario has a triangular pressure distribution with a peak at the centroid of the impact area, which then linearly decreases to zero at the top and bottom boundaries of the impact area. The azimuthal horizontal distribution was adopted from Wienke and Oumeraci’s work (2005). The main findings of this study will be of interest not only for the assessment of rock lighthouses but also for all the cylindrical structures built on rock pinnacles or rocky coastlines (with steep foreshore slopes) and exposed to harsh breaking wave loading.

Effects of different wind directions on ventilation of surrounding areas of two generic building configurations in Hong Kong

2021 ◽  
pp. 1420326X2110160
Author(s):  
Kai Yip Lee ◽  
Cheuk Ming Mak
Keyword(s):  
Wind Velocity ◽  
Natural Ventilation ◽  
Urban Environments ◽  
Air Pressure ◽  
Pressure Distributions ◽  
Air Intake ◽  
Dynamics Simulations ◽  
Surrounding Areas ◽  
Effective Use ◽  
Velocity Zone

This study investigated effects of incident wind angles on wind velocity distributions in wakes of two generic building configurations, namely, ‘T’- and ‘+’-shaped, and the air pressure distributions along their leeward walls by using computational fluid dynamics simulations. Results show that when the wind approaches laterally (90°) (vs. when the wind is direct (0°)), the downwind length and maximum bilateral width of the low-wind velocity zone in the wake of ‘T’-shaped building decrease by 11.5% and 37.9%, respectively. When the incident wind is oblique (45°) (vs. when it is direct), the length and width of this low-wind velocity zone in the wake of ‘+’-shaped building decrease by 15.0% and 30.9%, respectively. Furthermore, results show that the air pressure on the leeward walls of the ‘T’- and ‘+’-shaped buildings gradually decreases along with the building height. The resulting low-wind conditions on upper floors of buildings reduce the fresh air intake of their leeward units utilizing natural ventilation. It is particularly apparent in the case of direct approaching wind. Thus, the appropriate selection of building configurations and their orientations allows for the most effective use of wind to enhance ventilation in indoor and urban environments.

Active Control Comparison of Vibration in Flexible Spacecraft Using Different Active Friction Joints

2013 ◽  
Vol 446-447 ◽  
pp. 1160-1164
Author(s):  
Sahar Bakhtiari Mojaz ◽  
Hamed Kashani
Keyword(s):  
Energy Dissipation ◽  
Attitude Control ◽  
Vibration Suppression ◽  
Excitation Amplitude ◽  
Step Function ◽  
Flexible Spacecraft ◽  
Control Effort ◽  
Stick Slip ◽  
Control Comparison ◽  
Frictional Joints

Vibration properties of most assembled mechanical systems depend on frictional damping in joints. The nonlinear transfer behavior of the frictional interfaces often provides the dominant damping mechanism in structure and plays an important role in the vibratory response of it. For improving the performance of systems, many studies have been carried out to predict measure and enhance the energy dissipation of friction. This paper presents a new approach to vibration reduction of flexible spacecraft with enhancing the energy dissipation of frictional dampers. Spacecraft is modeled as a 3 degree of freedom mass-spring system which is controlled by a lead compensator and System responses to step function evaluated. Coulomb and Jenkins element has been used as vibration suppression mechanisms in joints and sensitivity of their performance to variations of spacecraft excitation amplitude and damper properties is analyzed. The relation between frictional force and displacement derived and used in optimization of control performance. Responses of system and control effort needed for the vibration control are compared for these two frictional joints. It is shown that attitude control effort reduces, significantly with coulomb dampers and response of system improves. On the other hand, due to stick-slip phenomena in Jenkins element, we couldn’t expect the same performance from Jenkins damper.

Determination of Three-Dimensional Body Forms from Given Pressure Distribution Over Their Surfaces

1996 ◽  
Vol 40 (01) ◽  
pp. 22-27
Author(s):  
V. M. Pashin ◽  
V. A. Bushkovsky ◽  
E. L. Amromin
Keyword(s):  
Pressure Distribution ◽  
Three Dimensional ◽  
Bodies Of Revolution ◽  
Design Constraints ◽  
Pressure Distributions ◽  
Axisymmetric Bodies

A method for solving inverse three-dimensional problems in hydromechanics is proposed which makes it possible to fit desired pressure distributions within design constraints immediately in the course of calculations. Examples of the method of application are given for bodies of revolution in flows at nonzero drift angles. These flows are not axisymmetric. Bodies of revolution in them are very handy examples of demonstrations of the method, and these examples have many technical applications.

Measurement of Seat Pressure Distributions

1987 ◽  
Vol 29 (5) ◽  
pp. 563-575 ◽  
Author(s):  
Delia Treaster ◽  
W. S. Marras
Keyword(s):  
Pressure Distribution ◽  
Video Signals ◽  
Optical Reflection ◽  
Pressure Distributions ◽  
Experimental Apparatus ◽  
Image Digitization ◽  
Novel Method ◽  
Measurement And Evaluation ◽  
Peak Pressures ◽  
Chair Design

Knowledge of seating pressures is important for proper chair design. This study demonstrates the usefulness of a new methodology for measuring pressure distributions. It refines and advances an optical-reflection technique introduced several years ago. In this way precise quantitative measures of the pressure distribution can be obtained. Video image digitization, which converts analog video signals to digital ones, provided data in a form that could be easily submitted for computer analysis. Additionally, a novel method of analysis is presented that allows for the measurement and evaluation of the distribution of seated pressures, rather than peak pressures alone. A preliminary experiment with eight subjects was conducted to demonstrate the validity of the experimental apparatus and the data treatment.

Determination of Stresses in Cemented Lap Joints

1953 ◽  
Vol 20 (3) ◽  
pp. 355-364
Author(s):  
R. W. Cornell
Keyword(s):  
Differential Equations ◽  
Infinite Number ◽  
Lap Joints ◽  
The Other ◽  
Complete Analysis ◽  
Stress Distributions ◽  
Lap Joint ◽  
Analogy Method ◽  
Set Up

Abstract A variation and extension of Goland and Reissner’s (1) method of approach is presented for determining the stresses in cemented lap joints by assuming that the two lap-joint plates act like simple beams and the more elastic cement layer is an infinite number of shear and tension springs. Differential equations are set up which describe the transfer of the load in one beam through the springs to the other beam. From the solution of these differential equations a fairly complete analysis of the stresses in the lap joint is obtained. The spring-beam analogy method is applied to a particular type of lap joint, and an analysis of the stresses at the discontinuity, stress distributions, and the effects of variables on these stresses are presented. In order to check the analytical results, they are compared to photoelastic and brittle lacquer experimental results. The spring-beam analogy solution was found to give a fairly accurate presentation of the stresses in the lap joint investigated and should be useful in analyzing other cemented lap-joint structures.

scholarly journals Plantar pressure distribution evaluation in children with down syndrome from 2 to 5 years old

2019 ◽  
Vol 32 ◽  
Author(s):  
Paula Silva de Carvalho Chagas ◽  
Riuraly Caroline Barreiros Fortunato Rangel ◽  
Sulamita Saile de Jesus Oliveira Dornelas ◽  
Anderson Daibert Amaral ◽  
Flávio Augusto Teixeira Ronzani ◽  
...  
Keyword(s):  
Down Syndrome ◽  
Pressure Distribution ◽  
Plantar Pressure ◽  
Cross Sectional Study ◽  
Measurement Instruments ◽  
Standing Posture ◽  
Cross Sectional ◽  
Plantar Pressures ◽  
Pressure Distributions ◽  
Plantar Pressure Distribution

Abstract Introduction: Some peculiar features of Down Syndrome (DS), such as ligament laxity, hypotonia, delay in gait acquisition, among others, may generate alterations in the distribution of plantar pressures, modifying the plantar support. Objective: To verify whether there are differences in the evaluation of plantar pressure distributions in standing posture between the measurement instruments (Baropodometer, SAPO, and Radiography). Method: This was a cross-sectional study, evaluating ten children with SD and ten children with normal development (ND), aged from two to five years old. Bio-photogrammetry, baropodometry, and foot radiography were used to assess the plantar pressure distribution. Kappa analysis was used to evaluate the agreement index between the different instruments. Results: Children with DS and ND had a higher prevalence of pronated feet in all three instruments, with poor to substantial agreement among the instruments. Conclusion: According to this study instruments, there was a greater prevalence of pronated feet in the two groups . Differences in the evaluation of the distribution of plantar pressures in the standing posture between the Baropodometer, SAPO, and radiography were observed. These instruments should be used in a complementary manner, as they propose to evaluate different aspects of the feet alignment.

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