An Arrow-Shaped Honeycomb Pedestal With Negative Poisson Ratio and its Impact Resistance

2019 ◽  
Author(s):  
Haoran Wu ◽  
Xiaobin Lin ◽  
Jie Zhang
Keyword(s):  
Fracture Toughness ◽  
Shear Modulus ◽  
Dynamic Load ◽  
Static Load ◽  
Poisson Ratio ◽  
Impact Resistance ◽  
Honeycomb Structure ◽  
Vibration Damping ◽  
Damping Effect ◽  
The Impact

Abstract The ship’s pedestal is the connection structure between the ship’s equipment and the hull, and is also the basis for the installation of the equipment. The pedestal bears both the static load generated by the weight of the equipment and the dynamic load generated during the operation of the equipment, and at the same time transmits the external load received by the hull to the equipment, and the load it bears is very complicated. If there is a problem with the pedestal in an impact environment, the accuracy of the system equipment will be affected, the system equipment will not work properly. Negative Poisson’s ration structures have a unique set of properties because of their tensile expansion, such as increased shear modulus, enhanced fracture toughness, better energy absorption and co-curvature. In recent years, the negative Poisson’s ration honeycomb structure has been applied to the pedestal of marine equipment, which demonstrates good vibration damping effect. However, the pedestal has two functions: vibration damping and impact resistance, there is not much research on the impact resistance of the pedestal. In this paper, an “arrow-shaped” honeycomb pedestal is taken as the research object. Firstly, the analytical expression of the Poisson’s ration of the honeycomb pedestal is derived theoretically and the influence of each parameter on the Poisson’s ration is analyzed. Secondly, the effect of Poisson’s ration on the impact resistance of the pedestal was analyzed by ensuring that the pedestal height was constant. It was found that with the reduction of Poisson’s ration, the impact resistance of the pedestal and the output impact environment of the pedestal panel were effectively optimized. Finally, by ensuring that the height of the pedestal is constant and the Poisson’s ration is the same, the influence of the number of honeycomb layers on the impact resistance of the pedestal is analyzed.

Concrete and Fiber Reinforced Concrete Subjected to Impact Loading

1985 ◽  
Vol 64 ◽  
Author(s):  
Surendra P. Shah
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Reinforced Concrete ◽  
Impact Resistance ◽  
Fiber Reinforced Concrete ◽  
Basic Material ◽  
Strain History ◽  
Moderate Increase ◽  
Fiber Reinforced ◽  
The Impact

ABSTRACTDespite its extensive use, low tensile strength has been recognized as one of the major drawbacks of concrete. Although one has learned to avoid exposing concrete structures to adverse static tensile load, these cannot be shielded from short duration dynamic tensile stresses. Such loads originate from sources such as impact from missiles and projectiles, wind gusts, earthquakes and machine vibrations. The need to accurately predict the structural response and reserve capacity under such loading has led to an interest in the mechanical properties of the component materials at high rates of straining.One method to improve the resistance of concrete when subjected to impact and/or impulsive loading is by the incorporation of randomly distributed short fibers. Concrete (or Mortar) so reinforced is termed fiber reinforced concrete (FRC). Moderate increase in tensile strength and significant increases in energy absorption (toughness or impact-resistance) have been reported by several investigators in static tests on concrete reinforced with randomly distributed short steel fibers. A theoretical model to predict fracture toughness of FRC is proposed. This model is based on the concept of nonlinear elastic fracture mechanics.As yet no standard test methods are available to quantify the impact resistance of such composites, although several investigators have employed a variety of tests including drop weight, swinging pendulums and the detonation of explosives. These tests though useful in ascertaining the relative merits of different composites do not yield basic material characteristics which can be used for design.The author has recently developed an instrumented Charpy type of impact test to obtain basic information such as load-deflection relationship, fracture toughness, crack velocity and load-strain history during an impact event. From this information, a damage based constitutive model was proposed. Relative improvements in performance due to the addition of fibers as observed in the instrumented tests are also compared with other conventional methods.

The Specific Characteristics of Shock and Blast Impacts on Construction Sites

2021 ◽  
pp. 81-88
Author(s):  
A.A. Komarov ◽  
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Dynamic Loads ◽  
Potential Hazard ◽  
Construction Sites ◽  
Static Loads ◽  
Equivalent Static Loads ◽  
Plane Crash ◽  
Nuclear Plants ◽  
The Impact

The practices of hazardous and unique facilities’ construction imply that specific attention is paid to the issues of safety. Threats associated with crash impacts caused by moving cars or planes are considered. To ensure safety of these construction sites it is required to know the potential dynamic loads and their destructive capacity. This article considers the methodology of reducing dynamic loads associated with impacts caused by moving collapsing solids and blast loads to equivalent static loads. It is demonstrated that practically used methods of reduction of dynamic loads to static loads are based in schematization only of the positive phase of a dynamic load in a triangle forms are not always correct and true. The historical roots of this approach which is not correct nowadays are shown; such approach considered a detonation explosion as a source of dynamic load, including TNT and even a nuclear weapon. Application of the existing practices of reduction of dynamic load to static load for accidental explosions in the atmosphere that occur in deflagration mode with a significant vacuumization phase may cause crucial distortion of predicted loads for the construction sites. This circumstance may become a matter of specific importance at calculations of potential hazard of impacts and explosions in unique units — for instance, in the nuclear plants. The article considers a situation with a plane crash, the building structure load parameters generated at the impact caused by a plane impact and the following deflagration explosion of fuel vapors are determined.

scholarly journals Research on Fault Activation Law in Deep Mining Face and Mechanism of Rockburst Induced by Fault Activation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lyu Pengfei ◽  
Bao Xinyang ◽  
Lyu Gang ◽  
Chen Xuehua
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Coal Pillar ◽  
Fault Structure ◽  
Fault Activation ◽  
Fault Type ◽  
Stress Behavior ◽  
Mining Face ◽  
And Control ◽  
The Impact

To effectively monitor and control the severe mining-induced rockburst in deep fault area, the fault activation law and the mechanical essence of rockburst induced by crossing fault mining were studied through theoretical analysis, microseismic monitoring, field investigation, and other methods; numerical simulation was employed to verify the obtained fault activation law and the mechanical nature. First, the distribution of microseismic sources at different mining locations and the fault activation degree were analyzed. According to the microseismic frequency and the characteristics of the energy stage, the fault activation degree was divided into three stages: fault stress transfer, fault pillar stress behavior, and fault structure activation. It was determined that the impact disaster risk was the strongest in the stage of the fault pillar stress behavior. Based on the periodic appearance law of microseisms in fault area, three types of conceptual models of fault-type rockburst were proposed, and the rockburst carrier system model of “roof-coal seam-floor” in the fault area was established. The mechanical essence of fault-type rockburst was obtained as follows: under the action of fault structure, the static load of the fault coal pillar was increased and superimposed with the active dynamic load of the fault, leading to high-strength impact disaster. Finally, the prevention and treatment concepts of fault-type rockburst were proposed. The monitoring and prevention measures of fault-type rockburst were taken from two aspects: the monitoring and characterization of fault rockburst and weakening control of the high static load of the fault coal pillar and dynamic load of fault activation. The proposed concepts and technical measures have been verified in the working face 14310 of Dongtan Coal Mine with sound results. The research results have a guiding significance for the prevention and control of rockburst in a similar mining face under crossing fault mining.

scholarly journals Impact Improvement of Tape Carbon Fiber Composite Modified by Submicron Glass Fiber

2019 ◽  
Vol 8 (4) ◽  
pp. 21
Author(s):  
Nhan T.T. Nguyen ◽  
Naoto Miyakita ◽  
Obunai Kiyotaka ◽  
Okubo Kazuya
Keyword(s):  
Fracture Toughness ◽  
Carbon Fiber ◽  
Glass Fiber ◽  
Fiber Composite ◽  
Impact Resistance ◽  
Mode Ii ◽  
Brittle Matrix ◽  
Mode Ii Fracture Toughness ◽  
The Impact ◽  
Delamination Area

It is well known that thermoplastic composite is vulnerable to impact fracture. Submicron glass fiber (sGF) was used to modify the matrix of chopped tape carbon fiber reinforced polypropylene composite. The impact resistance improved 20% and 7.4% coressponding to the dimeter sGF of 0.28 and 0.69 µm used in modified-composite. To shed light upon the mechanism of this improvement, the internal damage statement of post-impact specimens was observed by the CT scanner. The results pointed out that the increase of the impact resistance was due to the enlargement of delamination area under impact load. The micro droplet test and end notch flexure test suggest that the decrease of Mode II fracture toughness in modified-composite comes from narrowing the difference between the interfacial shear strength (IFSS) and the bending strength of matrix thanks to significant improving of IFSS with the addition of sGF while the flexural strength remains the unchanged. Consequently, the failure mode changed from debonding fiber/matrix in unmodified composite into brittle matrix failure in modified composite, resulting in the decrease of the Mode II interlaminar fracture toughness and the enlargement of delamination area. The stress transfer test also indicates that the modified composites is prone to the brittle matrix failure.

scholarly journals Dynamic behavior of coal under true triaxial prestressed by using a Hopkinson bar

2021 ◽  
Vol 14 (20) ◽  
Author(s):  
Shiwei Zhang ◽  
Wen Wang ◽  
Kai Liu ◽  
Shuang Gong ◽  
Donngyin Li ◽  
...  
Keyword(s):  
Principal Stress ◽  
Stress Wave ◽  
Dynamic Load ◽  
Static Load ◽  
Intermediate Principal Stress ◽  
Coal Specimen ◽  
Hopkinson Pressure Bar ◽  
Internal Damage ◽  
True Triaxial ◽  
The Impact

AbstractDeep mining is faced with severe rock dynamic problems. Coal bears high-strength static load in the deep and is prone to impact under the influence of dynamic load disturbance such as roof breaking. The true triaxial Hopkinson pressure bar system is used to conduct dynamic load impact tests on coal specimens under different triaxial prestressing forces to simulate the bearing characteristics of coal under different engineering conditions. The results show that the dynamic mechanical characteristics of coal are confinement-dependent under the same dynamic load, and the energy transmission of each component are significantly different, which is obviously different from that under static load; Furthermore, the influence range of intermediate principal stress on dynamic characteristics of coal specimen is 6~8 MPa. Based on the failure characteristics, the enhancement of the intermediate principal stress will increase the integrity and the internal damage of a coal specimen after failure; It should be noted that the strain signals obtained in the Y/Z axis direction are mainly the response to the triaxial prestress, and the stress wave of coal specimen is mainly influenced in the impact direction. In underground coal mining, by changing the triaxial prestressed state of coal, the buffering effect of stress wave is improved, and the damage of coal caused by the impact is reduced.

Effects of Truck Impacts on Bridge Piers

2013 ◽  
Vol 639-640 ◽  
pp. 13-25 ◽  
Author(s):  
Anil K. Agrawal ◽  
Guang Yong Liu ◽  
Sreenivas Alampalli
Keyword(s):  
Static Load ◽  
Impact Resistance ◽  
Bridge Piers ◽  
Steel Girder ◽  
Federal Highway ◽  
Steel Girder Bridge ◽  
Girder Bridge ◽  
Bridge Failure ◽  
Aashto Lrfd ◽  
The Impact

According to Federal Highway Administration, impact by moving trucks is the 3rd leading cause of bridge failure or collapse in the country. Although current AASHTO LRFD Guide Specifications prescribe designing bridge piers by applying a 400 kips static load at a height of 4ft to improve their impact resistance, recent studies have shown that the dynamic forces because of truck impacts may be significantly higher than that recommended by the AASHTO Guide Specifications. In this paper, we present an extensive investigation on the impact of a three-span steel girder bridge with reinforced concrete piers by trucks running at different speeds through models of bridge and the truck in LS-DYNA, including a correlation between seismic and impact resistance of bridge piers. Results also present a comparison between static load prescribed by AASHTO Guide Specifications and dynamic impacts loads observed during numerical simulations. A performance based approach is proposed to design bridge piers against truck impacts.

scholarly journals Response analysis of tunnel lining structure under impact and fire loading

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401983447
Author(s):  
Qian Zhang ◽  
Wen-yu Wang ◽  
Song-song Bai ◽  
Ying-hua Tan
Keyword(s):  
Fire Resistance ◽  
Static Load ◽  
Impact Load ◽  
Impact Resistance ◽  
Load Ratio ◽  
Tunnel Lining ◽  
Response Analysis ◽  
Fire Load ◽  
Tunnel Support ◽  
The Impact

Accidents and fires in tunnels hinder traffic and threaten the safety of personal and material resources, moreover, impact and temperature effects often cause damage to structures, affect structural performance, and shorten the service life of structures. In this article, the response behavior of the tunnel lining under the action of vehicle impact and fire load is simulated and analyzed. As the failure criterion of the lining dome settlement and the sidewall convergence displacement, the system compares the two interaction effect of the load, namely, the influence of the fire load on the impact resistance of the lining and the influence of the impact load on its fire resistance. The results show that the fire load reduces the impact resistance of the lining. Compared with the initial static load, the impact of temperature on the impact resistance is more significant; the impact load has an adverse effect on the fire resistance of the lining, when the tunnel lining is subject to explosion first. After the impact load working on the fire, the fire resistance of the lining will be significantly reduced with the increase of the static load ratio and the dynamic load ratio. The research can provide the reference for the design of fire protection and explosion protection parameters of tunnel support structures.

The Study on Impact Resistance of Metal Rubber for a Product

2019 ◽  
Vol 821 ◽  
pp. 125-130 ◽  
Author(s):  
Fu Wei Duan ◽  
Yuan Tao ◽  
Cheng Bin Ding
Keyword(s):  
Impact Resistance ◽  
Great Influence ◽  
Impact Response ◽  
Test Results ◽  
Damping Effect ◽  
Cylindrical Metal ◽  
Metal Rubber ◽  
The Impact ◽  
Rubber Damper ◽  
Better Than

A metal rubber damper was designed for the too large impact response of a product. The impact response of products which bears big shocks with and without metal rubber damper were studied and compared. The damping performance of the metal rubber damper with different pre-compression was tested and studied. The test results show that the metal rubber damper can effectively reduce the impact response of the product in three directions; The damping effect of cylindrical metal rubber damper in the direction of cylinder axis is better than that in the other two axial directions; different pre-compression amounts have great influence on the impact response, so the optimum damping effect is obtained by adjusting the pre-compression amount of the metal rubber damper.

scholarly journals IMPACT OF INTERLAMINAR ELLIPTICAL DEFECTS UPON BEHAVIOR OF RECTANGULAR CARBON PLASTIC PLATE AT STATIC AND DYNAMIC LOADS

2020 ◽  
Vol 2020 (12) ◽  
pp. 19-30
Author(s):  
Aleksandr Medvedskiy ◽  
Mihail Martirosov ◽  
Anton Homchenko ◽  
Darina Dedova
Keyword(s):  
Rectangular Plate ◽  
Dynamic Load ◽  
Static Load ◽  
Dynamic Loads ◽  
Carbon Plastic ◽  
Plastic Plate ◽  
Investigation Methods ◽  
Static And Dynamic Loads ◽  
The Impact ◽  
Distribution Of Stresses

The purpose of this work is to investigate the impact of the inner defects of elliptical stratification type upon behavior of the rectangular carbon plastic plate at the impact of static and dynamic loads. The investigation methods: the problem is solved in a numerical way with the aid of a finite ele-ment method (FEM) in the LS-DYNA software com-plex (Livermore Software Technology Corp.). The investigation results: the distribution of stresses in plate layers under the impact of static and dynamic loads is obtained. The distribution of destruc-tion indices with the use of different destruction criteria for unidirectional composites (on the basis of carbon band) is defined. Conclusions: the impact of defects of the type of specified shape stratification, dimensions, amount and places of location with regard to the plate under consideration under the action of compressive static load does not practically tell. Under the action of the compressive dynamic load there is observed a noticeable impact of inner defects upon rectangular plate behavior.

AMPCO 18.22 and 18.136

Alloy Digest ◽  
2011 ◽  
Vol 60 (1) ◽  
Keyword(s):  
Fracture Toughness ◽  
Shear Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Ultimate Strength ◽  
Impact Resistance ◽  
The Impact

Abstract AMPCO 18.22 and 18.136 are variations of AMPCO 18 to produce a higher ultimate strength and to improve the impact resistance, respectively. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and compressive and shear strength as well as fracture toughness and fatigue. It also includes information on casting. Filing Code: Cu-795. Producer or source: AMPCO Engineered Alloys.

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