Impact Load Measurements in an Erosive Cavitating Flow

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Jean-Pierre Franc ◽  
Michel Riondet ◽  
Ayat Karimi ◽  
Georges L. Chahine
Keyword(s):  
Scaling Laws ◽  
Pressure Pulse ◽  
Impact Load ◽  
Pulse Height ◽  
Impact Loads ◽  
Similar Data ◽  
Two Dimensional ◽  
Test Results ◽  
Test Technique ◽  
The Impact

Impact load measurements were carried out in a high-speed cavitation loop by means of a conventional pressure sensor flush-mounted in the region of closure of the cavity where maximum damage was observed. The sensor was dynamically calibrated by the ball drop test technique. Pressure pulse amplitudes were measured at different velocities and constant cavitation number and cavity length. It was found that pressure pulse height spectra follow a simple exponential law, which depends upon two parameters interpreted as a reference peak rate and a reference load. By exploring the dependence of both parameters on flow velocity, it was possible to show that the various histograms measured at different velocities can be reduced to a unique non-dimensional one and derive scaling laws, which enable to transpose results from one velocity to another. The measured values of impact loads are compared to similar data in the literature, and the impact load spectra are discussed with respect to pitting test results available from a previous investigation. It is concluded that an uncertainty remains on the measured values of impact loads and that a special effort should be made to compare quantitatively pitting test results and impact load measurements. To evaluate the coherence of both sets of data with each other, it is suggested to introduce two-dimensional histograms of impact loads by considering the size of the impacted area in addition to the measured impact load amplitude. It is conjectured that the combination of impact load measurements and pitting test measurements should allow the determination of such two-dimensional histograms, which are an essential input for analyzing the material response and computing the progression of erosion with exposure time.

On the Distribution of Wave Impact Loads on Offshore Structures

2017 ◽  
Author(s):  
Thomas B. Johannessen ◽  
Øystein Lande ◽  
Øistein Hagen
Keyword(s):  
Model Test ◽  
Load Distribution ◽  
Impact Load ◽  
Peak Load ◽  
Offshore Structures ◽  
Impact Loads ◽  
Test Results ◽  
Wave Impact ◽  
The Impact ◽  
Crest Height

For offshore structures in harsh environments, horizontal wave impact loads should be taken into account in design. Shafts on GBS structures, and columns on semisubmersibles and TLPs are exposed to impact loads. Furthermore, if the crest height exceeds the available freeboard, the deck may also be exposed to wave impact loads. Horizontal loads due to waves impacting on the structure are difficult to quantify. The loads are highly intermittent, difficult to reproduce in model tests, have a very short duration and can be very large. It is difficult to calculate these loads accurately and the statistical challenges associated with estimating a value with a prescribed annual probability of occurrence are formidable. Although the accurate calculation of crest elevation in front of the structure is a significant challenge, industry has considerable experience in handling this problem and the analysis results are usually in good agreement with model test results. The present paper presents a statistical model for the distribution of horizontal slamming pressures conditional on the incident crest height upwave of the structure. The impact load distribution is found empirically from a large database of model test results where the wave impact load was measured simultaneously at a large number of panels together with the incident crest elevation. The model test was carried out on a circular surface piercing column using long simulations of longcrested, irregular waves with a variety of seastate parameters. By analyzing the physics of the process and using the measured crest elevation and the seastate parameters, the impact load distribution model is made seastate independent. The impact model separates the wave impact problem in three parts: – Given an incident crest in a specified seastate, calculate the probability of the crest giving a wave impact load above a threshold. – Given a wave impact event above a threshold, calculate the distribution of the resulting peak load. – Given a peak load, calculate the distribution of slamming pressures at one spatial location. The development of the statistical model is described and it is shown that the model is appropriate for fixed and floating structures and for wave impact with both columns and the deck box.

Load Pulse Determination in Gas Gun Impact Tests

2007 ◽  
Vol 7-8 ◽  
pp. 259-264 ◽  
Author(s):  
Stefan Andreas Ritt ◽  
Alastair F. Johnson
Keyword(s):  
Impact Load ◽  
Axial Strain ◽  
Impact Loads ◽  
Test Results ◽  
Measuring Device ◽  
Gas Gun ◽  
Load Pulse ◽  
Longitudinal Wave Propagation ◽  
Force Time ◽  
The Impact

This paper is concerned with methods to determine the resultant impact load pulse on test structures during gas gun tests. The muzzle of a gas gun carries an instrumented target support designed to measure force-time-pulses of the impact event on structures mounted on the device. The target during impact is supported on two long slender metallic bars with axial strain gauges. By measuring the impact strain pulses in the support bars and assuming longitudinal wave propagation, it is possible to determine the impact load pulse on the target. The paper describes the strain measuring device and methods for determining the impact loads during impact. Gas gun test results with different projectiles are presented and the load pulses compared with a direct load measurement from a target load cell. The paper discusses possibilities and limitations of the device for quantitative force pulse measurements.

Experimental and Numerical Investigation on the Load Carrying Behavior of Large Ship Windows

2014 ◽  
Author(s):  
Wolfgang Fricke ◽  
Bjarne Gerlach ◽  
Matthias Guiard
Keyword(s):  
Ultimate Load ◽  
Impact Loads ◽  
Test Results ◽  
Lateral Loads ◽  
Load Range ◽  
Filled Rubber ◽  
Load Carrying ◽  
Drop Tests ◽  
Load Tests ◽  
The Impact

Aboard ships windows are exposed to static as well as dynamic loads, e.g. impact loads. Failure can lead to serious consequences. Therefore two research projects were initiated in order to analyze the load carrying behavior of windows. In addition to quasi-static ultimate load tests and drop tests with water filled rubber bags special attention is paid to the Finite Element (FE) modeling. In particular the response — stresses and deformations — to quasi-static lateral loads can be calculated with good agreement to test results. Hence FE calculations can be useful to determine and compare failure mechanisms of different window designs. An ultimate load range can be estimated by taking into account the breaking strength range of glass. A comparison between FE calculations and results of the impact tests showed that these are sensitive to conditions which could hardly be measured during the test, e.g. the shape of the approaching water-filled rubber bag. Varying of parameters eventually yielded that window response to impact loads can also be calculated sufficiently, at least, to evaluate different window designs. Further investigations on this topic are in progress.

A Case for Avoiding Hydraulic Shock Suppressors (Snubbers) in the Vibratory Environments

2018 ◽  
Author(s):  
Kshitij P. Gawande ◽  
Phillip Wiseman ◽  
Alex Mayes
Keyword(s):  
Dynamic Load ◽  
Impact Load ◽  
Pressure Vessels ◽  
Mechanical Equipment ◽  
Internal Dynamic ◽  
Impact Loads ◽  
Hydraulic Shock ◽  
Dynamic Events ◽  
Piping Systems ◽  
The Impact

Whenever undesirable dynamic events occur within power plant, refinery, or process piping systems, specialty supports and restraints have the task of protecting the mechanical equipment and connecting piping from damaging loads and displacements. The array of components that may be affected include, but are not limited to, piping systems, pumps, valve assemblies, pressure vessels, steam generators, boilers, and heat exchangers. In particular, the dynamic events can be classified into two distinct types that originate from either internal events or external events. The internal dynamic load generating events include plant system start-up and shut-down, pressure surges or impacts from rapid valve closures such as steam and water hammer, boiler detonations, pipe rupture, and operating vibratory displacements that may be either low frequency or high frequency vibrations. The external dynamic load generating events include wind loads, earthquake, airplane impact to supporting structures and buildings, and explosions. Most of the aforementioned dynamic load generating events can be defined quite simply as impact loads, i.e., forces and moments that are applied over very short periods of time, for example, less than one second. While earthquake loads may be applied over a total time period of an hour or so, the peak loads and resulting displacements occur on a more sinusoidal basis of peak-to-peak amplitudes. One of the most common specialty restraint components utilized in the piping industry to absorb and transfer the dynamic load resulting from impact events is the hydraulic shock suppressor, otherwise known as the snubber. The snubber is a formidable solution to protecting plant piping systems and equipment from impact loading while not restricting the thermal displacements during routine operations. In the dynamic events that may be characterized by an impact type loading, snubbers provide an instantaneous, practically rigid, axial connection between the piping or other component to be secured and the surrounding structure whether it be concrete or steel (for example). In this way, the kinetic energy can be transmitted and harmlessly dissipated. In the vibratory environment, however, neither the impact load scenario nor the rapid translations are imposed upon snubbers, thereby presenting the competing intended application of the snubber to protect against impact loads versus, in many cases, the improper selection of the snubber to dampen vibratory (other than seismic) loads. The details of the hydraulic shock suppressor design are reviewed and discussed to exemplify why a case can and should be made against the use of snubbers in piping systems within an operating vibratory environment.

scholarly journals Failure Characteristics of Joint Bolts in Shield Tunnels Subjected to Impact Loads from a Derailed Train

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Qixiang Yan ◽  
Zhixin Deng ◽  
Yanyang Zhang ◽  
Wenbo Yang
Keyword(s):  
Impact Load ◽  
Numerical Study ◽  
Design Method ◽  
Shield Tunnel ◽  
Failure Behavior ◽  
Impact Loads ◽  
Fe Model ◽  
Fe Modelling ◽  
Bolt Failure ◽  
The Impact

Impact loads generated by derailed trains can be extremely high, especially in the case of heavy trains running at high speeds, which usually cause significant safety issues to the rail infrastructures. In shield tunnels, such impact loads may not only cause the damage and deformation of concrete segments, but also lead to the failure of segmental joint bolts. This paper presents a numerical study on the failure behavior of segmental joint bolts in the shield tunnel under impact loading resulting from train derailments. A three-dimensional (3D) numerical model of a shield tunnel based on the finite element (FE) modelling strategy was established, in which the structural behavior of the segmental joint surfaces and the mechanical behavior of the segmental joint bolts were determined. The numerical results show that the occurrence of bolt failure starts at the joints near the impacted segment and develops along the travel direction of train. An extensive parametric study was subsequently performed and the influences of the bolt failure on the dynamic response of the segment were investigated. In particular, the proposed FE model and the analytical results will be used for optimizing the design method of the shield tunnel in preventing the failure of the joint bolts due to the impact load from a derailed HST.

Rigid-plastic analysis of floating ice sheets under impact loads

1981 ◽  
Vol 8 (4) ◽  
pp. 409-415
Author(s):  
John B. Kennedy ◽  
K. J. Iyengar
Keyword(s):  
Impact Load ◽  
Design Method ◽  
Yield Criterion ◽  
Ice Sheets ◽  
Contact Radius ◽  
Impact Loads ◽  
Rigid Plastic ◽  
Deformation Response ◽  
Safe Thickness ◽  
The Impact

The deformation response of floating ice sheets under high intensity, short duration loads is examined. Using a rigid-plastic theory, together with a Tresca yield criterion, expressions are derived for the total time of response and the final deformed configuration of floating ice sheets. The influence of the magnitude of the impact load and the load-contact radius on the various design quantities such as deflection profile and stress distribution is discussed. Based on the results derived, a design method is presented to find the safe thickness of a floating ice sheet to sustain a given impact load. The method is illustrated with a numerical example.

scholarly journals Resistance to the piercing of composite materials

2018 ◽  
Vol 19 (6) ◽  
pp. 540-543
Author(s):  
Lesław Kyzioł
Keyword(s):  
Composite Materials ◽  
High Strain ◽  
Physical Nonlinearity ◽  
Impact Loads ◽  
Strain Rates ◽  
Test Results ◽  
The Impact ◽  
The Mathematical Model ◽  
Different Thickness ◽  
Optimal Calculation

For structures that carry dynamic loads, the requirements are imposed for safety reasons. The requirements apply to both materials and construction. This requires searching for optimal calculation methods, including geometric and physical nonlinearity, which are results from the construction of the structure. An example is various ballistic structures (ballistic shields), which are hit by bullets in which huge energy is accumulated. In this case, the hitting in the shield with a bullet can be considered as a load due to mass impact. Loads at high strain rates are described by various mathematical models. The mathematical model is complex because a large number of "coefficients" is required, moreover, the obtained test results are not always repeatable. The paper presents the results of shooting multilayer plates with composite materials with 7.62 mm caliber bullets. The shield consisted of three layers, the outer layers were steel or aluminum, the inner layer was natural or modified wood. The samples had the shape of a shield and were 50 mm in diameter and of different thickness. The results of the research allowed to assess the impact of wood modification on its puncture resistance.

scholarly journals Influence of Voids Ratio on Impact Behavior of Circular Ferrocement Slabs

2019 ◽  
Vol 5 (1) ◽  
pp. 117
Author(s):  
Muyasser M. Jomaah ◽  
Muna Zead Baraa
Keyword(s):  
Impact Energy ◽  
Structural Strength ◽  
Impact Load ◽  
Low Cost ◽  
Load Test ◽  
Wire Mesh ◽  
Impact Behavior ◽  
Experimental Program ◽  
Test Results ◽  
The Impact

The objective of using materials is to fully utilize the properties of these materials in order to obtain the best performance of the structure. The merits of material are based on many factors like, workability, structural strength, durability and low cost. Ferrocement is an excellent construction system. This paper studies the behavior of ferrocement circular slabs under impact load. The experimental program include testing four sime fixed supported ferrocement circular slabs of 800mm diameter and 50mm thickness. The Influence of the use of styropor voids was investigated in different ratios (24% and 48%) and a number of wire mesh layers four and six layers. Impact load test results revealed that increasing number of wire mesh from 4 to 6 led to an increase in the impact energy for first crack by (41.991% ,37.62%) respectively when using voids ratio by (24% and 48%) respectively and impact energy for full perforation by (21.7% and 9.94%) respectively when using voids ratio by (24% and 48%) respectively. Ferrocement circular slabs are used in construction fields such as roofs, tanks, manholes, etc.

scholarly journals Numerical Simulation of Modified Rubberized Concrete Block Under Impact Loads

2021 ◽  
Vol 1200 (1) ◽  
pp. 012022
Author(s):  
T Y Pei ◽  
S N Mokhatar ◽  
N A N A Mutalib ◽  
S J S Hakim
Keyword(s):  
Energy Absorption ◽  
Impact Load ◽  
Concrete Strength ◽  
Constitutive Models ◽  
Numerical Procedure ◽  
Concrete Block ◽  
Crumb Rubber ◽  
Impact Loads ◽  
Rubberized Concrete ◽  
The Impact

Abstract Rubberized concrete was innovated by many researchers to enhance energy absorption under impact load and by reusing scrap tires. Thus, this research was aims to develop the numerical procedure using the Finite Element Method (FEM) to simulate modified rubberized concrete under impact loads and predict its energy absorption under different impact loads. Three existing constitutive models: Concrete Damage Plasticity (CDP), Drucker-Prager (DP), and Modified Drucker-Prager Cap (MDPC) available in ABAQUS software were used to replicate the rubberized concrete with 10% of Rice Hush Ash (RHA) as cement substitution and different percentages (0%, 5%, 10%, 15%, and 20%) of crumb rubber as sand replacement. All three models produced successful FEM results with reasonable modelling assumption, and the CDP model was more effective in simulating rubberized concrete under impact to predict energy absorption than DP and MDPC models. Further, it was concluded that crumb rubber could enhance the energy absorption of concrete. Generally, the energy absorption of the concrete increased as the crumb rubber increase. However, the strength decreased as the crumb rubber increased, but 10% of RHA in concrete mix can maintain the concrete strength. Overall, this study reveals that FEM incorporated with the CDP model is able to predict the impact response of modified crumb rubber as an application of concrete road barrier.

scholarly journals DYNAMIC IMPACT WEAR AND IMPACT RESISTANCE OF W-B-C COATINGS

2020 ◽  
Vol 27 ◽  
pp. 37-41
Author(s):  
Josef Daniel ◽  
Jan Grossman ◽  
Vilma Buršíková ◽  
Lukáš Zábranský ◽  
Pavel Souček ◽  
...  
Keyword(s):  
Impact Test ◽  
Impact Load ◽  
Protective Coatings ◽  
Impact Resistance ◽  
Impact Testing ◽  
The Novel ◽  
Test Results ◽  
Dynamic Impact ◽  
Impact Deformation ◽  
The Impact

Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. Aim of this paper is to describe the method of dynamic impact testing and the novel concepts of evaluation of the impact test results, such as the impact resistance and the impact deformation rate. All of the presented results were obtained by testing two W-B-C coatings with different C/W ratio. Different impact test results are discussed with respect to the coatings microstructure, the chemical and phase composition, and the mechanical properties. It is shown that coating adhesion to the HSS substrate played a crucial role in the coatings’ impact lifetime.

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