scholarly journals Research of ANSYS Autodyn capabilities in evaluating the landmine blast resistance of specialized armored vehicles

2021 ◽  
Vol 3 (1(59)) ◽  
pp. 6-15
Author(s):  
Sergii Shlyk
Keyword(s):  
Blast Resistance ◽  
Detonation Front ◽  
Experimental Studies ◽  
State Equation ◽  
Explosive Loading ◽  
Velocity Variation ◽  
Mathematical Apparatus ◽  
Principal Stresses ◽  
Loaded Surface ◽  
Armored Vehicles

The object of research is the processes of pulse explosive loading in an explicit formulation for simulation of complex nonlinear dynamics of solids, gases, and their interactions. One of the most problematic areas of modern studies of nonlinear dynamic loads of materials using a numerical analysis is that such studies usually do not take into account the characteristic transition of the stationary deformation zone of the loaded material to the unsteady one and the front pressure and shockwave velocity variation by time. The work is aimed at developing a mathematical model of a pulsed load of materials by a shockwave, developing a mathematical apparatus for calculating the parameters of a shockwave, creating analytical dependences of the interaction of a shockwave with a loaded surface. A study of dynamic explosive loading using software based on an explicit method for solving the equations of continuum mechanics is proposed. In this work, the stress-state equation at a point of the material under pulsed load conditions was further developed, methods for determining the principal stresses and the invariant of the stress tensor, taking into account the pulsed nature of the load, were established. The character of the behavior of the shockwave formed as a result of the detonation of the explosive has been established. Analytical dependences of the interaction of a shockwave with a loaded surface are compiled. A mathematical apparatus has been developed for calculating such parameters of the shockwave as the detonation front pressure and its change in time and the velocity of the shockwave at the moment when it reaches the surface. Mathematical dependences have been developed and proposed, which, in contrast to the existing ones, make it possible to determine the current values of stresses and strains passing through the points of the actual stress curve, as well as the intensity of stresses and strains under pulse loading of metals. On the basis of theoretical and experimental studies of the parameters of body material deformation under the action of explosive loading, the mechanisms of destruction of the KrAZ «Shrek» and KrAZ «Fiona» (Ukraine) specialized armored vehicles body were clarified to establish the compliance of the declared landmine resistance of vehicles with the STANAG 4569 standardization agreement.

Experimental study of H∞ control for a flexible plate

2011 ◽  
Vol 18 (11) ◽  
pp. 1631-1649 ◽  
Author(s):  
Zhao Tong ◽  
Chen Long-Xiang ◽  
Cai Guo-Ping
Keyword(s):  
Time Delay ◽  
Integral Transformation ◽  
External Disturbance ◽  
Experimental Studies ◽  
State Equation ◽  
Small Time ◽  
Linear Matrix ◽  
Structural Parameter ◽  
Flexible Plate ◽  
Standard State

This paper presents theoretical and experimental studies of H∞ control for a flexible plate. Firstly, the dynamic equation of the plate with time delay is established with consideration of external disturbance. Then the standard state equation without explicit time delay is deduced by using a particular integral transformation to the time-delay equation. Finally, a H∞ time-delay controller is designed based on the standard state equation using the method of linear matrix inequality. In the controller designed, it contains not only the current step of state feedback but also the linear combination of some former steps of control. In the experiment, piezoelectric patches are used as actuators and sensors. The experiment system is structured based on the DSP TMS320F2812. Single time delay and double time delay are both considered in the experiment. The robustness of H∞ controller against the structural parameter of the plate and time delay is experimentally investigated. Simulation and experimental results indicate that the control system may suffer from instability if time delay is not treated in control design. The time-delay controller presented in this paper can effectively deal with time delay in the system, and is available for small-time delay and large-time delay as well. Furthermore, this delay controller is robust to the variance of structural parameter of the plate and time delay.

scholarly journals Melting Point of Carbon Particles behind the Gas Detonation Front

2022 ◽  
Vol 16 (2) ◽  
pp. 59-70
Author(s):  
E. S. Prokhorov
Keyword(s):  
Melting Point ◽  
Detonation Front ◽  
Molar Fraction ◽  
Experimental Studies ◽  
Oxygen Mixture ◽  
Detonation Products ◽  
Gas Detonation ◽  
Nanoscale Particles ◽  
Carbon Particles ◽  
Carbon Condensate

A mathematical model of gas detonation of fuel-enriched mixtures of hydrocarbons with oxygen has been formulated, which makes it possible to numerically study the equilibrium flows of detonation products in the presence of free carbon condensation. Reference data for graphite were used to describe the thermodynamic properties of carbon condensate. The calculations are compared with the known results of experimental studies in which, when detonating an acetylene-oxygen mixture in a pipe closed at one end, it is possible to obtain nanoscale particles from a carbon material with special properties. It is assumed that the melting point of such a material is lower than that of graphite and is about 3100 K. Only with such an adjustment of the melting temperature, the best agreement (with an accuracy of about 3 %) was obtained between the calculated and experimental dependence of the detonation front velocity on the molar fraction of acetylene in the mixture.

Characterization of Limit State for Seismic Fragility Assessment of T-Joints in Piping System

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Ankit R. Dubey ◽  
Abhinav Gupta ◽  
Sung Gook Cho
Keyword(s):  
Limit State ◽  
Experimental Studies ◽  
State Equation ◽  
Cyclic Behavior ◽  
Piping System ◽  
Damage State ◽  
T Joints ◽  
Performance Function ◽  
A Performance

Abstract Fragility assessment requires characterization of a component or system's performance through a performance function/limit-state equation. The exceedance of limit-state is representative of failure or damage state. For the purposes of evaluating piping fragility, characterizing the behavior of T-joints through an appropriate performance function is critical, as failures in piping are generally localized at the location of T-joints, elbows, and nozzles. Past studies have utilized a monotonic rotation-based performance function. However, the existing criteria does not account for the effect of cyclic behavior. As observed during prior experimental studies, the T-joint behavior under cyclic loading is different from that under monotonic loading, and therefore, it is important to include the effects of cyclic behavior while characterizing a performance function. Moreover, the monotonic rotation-based performance function could not replicate all the leakage locations observed during experimental studies on a full-scale two-story piping system. Therefore, it is important to develop a new limit-state for accurate piping fragility assessment. This paper presents the development of a new limit state which considers the cyclic behavior of a T-joint and quantifies the number of cycles to failure.

A discussion on detonation

1950 ◽  
Vol 204 (1076) ◽  
pp. 1-33 ◽  
Keyword(s):  
Reaction Zone ◽  
Chemical Reactions ◽  
Detonation Front ◽  
Experimental Studies ◽  
The United States ◽  
Finite Width ◽  
Von Neumann ◽  
War Effort ◽  
Plane Detonation ◽  
Steady Plane

The fundamental physical, chemical and mechanical processes which occur when a detonation wave passes through an explosive were imperfectly understood at the beginning of the recent war. As part of the scientific war effort in the British Common-wealth and in the United States of America, many theoretical and experimental studies were made of detonation processes. Much of the work has recently been declassified and some has been published. Several centres of research in this country and elsewhere are vigorously continuing with these studies. As later papers will show, the quality and general scientific interest of much of this work was considered sufficient to form the basis of a Discussion of the Royal Society. If one neglects the finite width of the zone in the detonation front where chemical reactions occur, a freely running steady plane detonation front can only advance through an explosive with the Chapman-Jouguet velocity defined by D = u + c . Once the explosive products are formed, their subsequent chemical reactions and motion in the detonation front may be considered as adiabatic. Although Chapman (1899) and Jouguet (1901) correctly stated their equation, neither attempted to discuss the reaction zone itself. It was therefore thought necessary that the recent views on the reaction zone should be described in a manner which throws new light on the Chapman-Jouguet equation. Professor J. von Neumann, Dr⋅ S. F. Boys and Dr A. F. Devonshire were the principal contributors on the theoretical side and von Neumann’s theory (1942) will be outlined later.

scholarly journals Spatial thin-walled reinforced concrete structures taking into account physical nonlinearity in SCAD software. Rod finite element

2019 ◽  
Author(s):  
Sergiy Fialko ◽  
Viktor Karpilowskyi
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Plastic Flow ◽  
Deformation Theory ◽  
Numerical Solutions ◽  
Experimental Studies ◽  
Particle Method ◽  
Reinforced Concrete Beams ◽  
Principal Stresses ◽  
Theory Of Plasticity

This paper considers a spatial frame bar finite element for modeling reinforced concrete beams and columns. Both concrete and reinforcement are described by the equations of the deformation theory of plasticity and the theory of plastic flow. Degradation of concrete during cracking is modeled by the descending branch of the σ – ε diagram (the deformation theory of plasticity), as well as the compression of the yield surface and its displacement in the space of principal stresses (the plastic flow theory). The longitudinal reinforcement is considered discretely. It is assumed that there is no reinforcement slipping in concrete. The paper provides the results of the studies that reveal the causes of computational instability related to the presence of a descending branch of the σ – ε diagram for concrete, and proposes ways to overcome it. The reliability of the obtained results is confirmed by comparing them with the results of experimental studies performed by other researchers, as well as with the results of numerical solutions obtained by the particle method. This paper also provides an example of the nonlinear analysis of the fragment of a multi-storey building from the SCAD Soft collection of problems (www.scadsoft.com).

scholarly journals A Novel Defect Estimation Approach in Wind Turbine Blades Based on Phase Velocity Variation of Ultrasonic Guided Waves

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4879
Author(s):  
Renaldas Raišutis ◽  
Kumar Anubhav Tiwari ◽  
Egidijus Žukauskas ◽  
Olgirdas Tumšys ◽  
Lina Draudvilienė
Keyword(s):  
Phase Velocity ◽  
Wind Turbine ◽  
Relative Error ◽  
Defect Detection ◽  
Guided Waves ◽  
Experimental Studies ◽  
Ultrasonic Guided Waves ◽  
Velocity Variation ◽  
Relative Errors ◽  
New Criterion

The reliability of the wind turbine blade (WTB) evaluation using a new criterion is presented in the work. Variation of the ultrasonic guided waves (UGW) phase velocity is proposed to be used as a new criterion for defect detection. Based on an intermediate value between the maximum and minimum values, the calculation of the phase velocity threshold is used for defect detection, location and sizing. The operation of the proposed technique is verified using simulation and experimental studies. The artificially milled defect having a diameter of 81 mm on the segment of WTB is used for verification of the proposed technique. After the application of the proposed evaluation technique for analysis of the simulated B-scan image, the coordinates of defect edges have been estimated with relative errors of 3.7% and 3%, respectively. The size of the defect was estimated with a relative error of 2.7%. In the case of an experimentally measured B-scan image, the coordinates of defect edges have been estimated with relative errors of 12.5% and 3.9%, respectively. The size of the defect was estimated with a relative error of 10%. The comparative results obtained by modelling and experiment show the suitability of the proposed new criterion to be used for the defect detection tasks solving.

scholarly journals The precision calculating method of robots moving by the plane trajectories

2019 ◽  
Vol 16 (6) ◽  
pp. 172988141988955
Author(s):  
Pavol Božek ◽  
Alexander Lozhkin
Keyword(s):  
Characteristic Equation ◽  
Linear Transformation ◽  
Geometric Modeling ◽  
Experimental Studies ◽  
New Method ◽  
Mathematical Apparatus ◽  
Complex Motion ◽  
Main Obstacle ◽  
Calculating Method ◽  
Motion Paths

Robots with complex motion paths are very rarely designed. The main obstacle is the lack of the necessary mathematical apparatus, despite the fact that the theory was proposed by Newton. We managed to formulate a new method for obtaining linear transformation parameters. It can be used for ellipse, hyperbola, as well as for other complex flat differentiable curves. A theorem for receiving the values of a transformed curve is formulated in the general case. The theoretical algorithm and the results of experimental studies using the geometric modeling method are presented. The proposed method works for all test curves, but this does not mean that it can always be used. Separation of the characteristic equation imposes additional complexity. Additional research is necessary, but it can be applied to many mechatronic frameworks now.

scholarly journals DEFINITION DURABILITY OF REINFORCED CONCRETE MATRICES FOR EXPLOSIVE STAMPING BY TENSOMETRIC METHODS

2018 ◽  
Vol 8 (4) ◽  
pp. 4-9
Author(s):  
Gennady V. MURASHKIN ◽  
Antonina I. SNEGIREVA ◽  
Dmitry A. KRETOV ◽  
Yury V. ZHILTSOV
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Strain Gauge ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Explosive Loading ◽  
Serial Testing ◽  
The Matrix

In this paper experimental studies of ring-shaped reinforced concrete matrices for explosive stamping on deformation indexes under the eff ect of impulse loads are viewed. The study was carried out on sample, which was subjected to explosive loading. The results of calibration tests using the “Dynamics- 1” strain gauge complex are presented. The dependence of the tension in the matrix on the reaction of the strain gauge system is obtained. The obtained experimental data are compared with theoretical calculations. The general results of the studies obtained are given taking into account their further use for serial testing of matrices in order to determine their durability.

Petrofabrics: A critical review

1970 ◽  
Vol 7 (2) ◽  
pp. 477-497 ◽  
Author(s):  
M. Friedman ◽  
G. M. Sowers
Keyword(s):  
Experimental Studies ◽  
The Body ◽  
Displacement Fields ◽  
Principal Stresses ◽  
Anisotropic Models ◽  
Principal Axes ◽  
Deformation Features ◽  
Alternative Hypotheses ◽  
Kinematic Analyses ◽  
Stress And Deformation

Petrofabric contributions are here classified into seven categories, namely: (1) descriptive techniques; (2) kinematic analyses; (3) geometric analyses of folds; (4) absolute strain analyses; (5) studies of experimentally deformed single crystals and rocks; (6) dynamic analyses of deformation features in naturally deformed rocks; and (7) studies for engineering rock mechanics. The nature of each subfield is given, and items (2) and (6) are discussed in detail.The principles of kinematic analysis through symmetry are reviewed with the aid of simple models of brittle and ductile deformations in which componental displacements are specified and the symmetry of the initial and final fabric is known. The models illustrate the degree of similarity among the symmetries of the fabric, componental displacements, deformation (strain and rigid-body rotation), and states of stress that exist in rocks at the time a fabric element forms. Both isotropic and anisotropic models are considered. In the more realistic cases the symmetry of the pattern of componental displacements is identical to the symmetry of the resulting fabric. If the body behaves isotropically during the deformation, symmetry elements in the final fabric will be common to corresponding elements in the symmetries of the states of stress and deformation. If, however, the body behaves anisotropically one cannot relate symmetry elements in the final fabric to the symmetry of the states of stress and deformation without making assumptions about the symmetry of the anisotropy. The study of fabric symmetry may contribute some detail to the geometric pattern of the strain or displacement fields, but is otherwise of little use in furthering understanding of the mechanics of geologic deformation.Results of dynamic analysis, which involve determination of the orientations and relative magnitudes of principal stresses in naturally deformed rocks, are critically reviewed. The principal axes inferred from fractures, twin lamellae, deformation lamellae, etc., are those within the material at the instant the fabric element forms. As such they correspond to the incremental stresses which are coincident with the incremental strains in linear materials. Certain generalizations are drawn from previous work on slightly and moderately deformed rocks in which the orientation of the incremental stresses and strains are probably coincident with the total stresses and strains. The critique leads to a working philosophy to guide future studies, namely: dynamic petrofabric analyses provide the means for testing hypotheses generated through theoretical and experimental studies of rock deformation. A study should be designed to test specific hypotheses. Samples should be collected from critical domains where the results may provide a basis of choice between alternative hypotheses. The techniques need to be refined to distinguish small differences in the orientations of principal stress axes deduced from fabric data. The chronological sequence in the development of the fabric elements requires attention. Several suggestions along these lines are offered.

Experimental Studies on Blast-Resistance of HFR-LWC Beams Enhanced with Membrane Action

2020 ◽  
Vol 20 (12) ◽  
pp. 2050142
Author(s):  
Wanxiang Chen ◽  
Lisheng Luo ◽  
Fanjun Meng ◽  
Hang Sun
Keyword(s):  
Failure Modes ◽  
Blast Resistance ◽  
Experimental Studies ◽  
Field Tests ◽  
Lightweight Aggregate ◽  
Failure Pattern ◽  
Lightweight Aggregate Concrete ◽  
Hybrid Fibers ◽  
Membrane Action ◽  
Close Range

Support-induced membrane action can enhance the resistance, while altering the failure pattern, of reinforced concrete (RC) members under static/dynamic loadings. Nevertheless, the membrane effect on the load-response is regarded as a safety factor in current design guides, hence, a thorough understanding of the resistance capability of RC members in the presence of membrane actions is considered essential. To quantitatively depict the membrane behavior and its influence on the blast-resistance and failure pattern of Hybrid Fiber Reinforced-Lightweight Aggregate Concrete (HFR-LWC) beams, a specially built end-constraint clamp is developed to provide membrane actions on the structural component subjected to the blast load simultaneously. A series of field tests are conducted to investigate the dynamic behaviors of the HFR-LWC beams under close-range detonations. Overpressure-time histories of shock waves induced by the close-range explosive charge are captured. Then the deflection-responses and failure modes of the HFR-LWC beams are further investigated. The responses of the clamped HFR-LWC beam under blast loadings can be well simulated, and the blast-resistances of the beam-type members with membrane action are evaluated reasonably. The results show that membrane action is beneficial for the bridging effects of hybrid fibers and the interlocking effects of coarse aggregate, thereby giving rise to the ductile failures of HFR-LWC beam. The maximum deflections of the clamped HFR-LWC beam decrease by about 60% compared with simply-supported HFR-LWC beam in this paper, illustrating that the blast-resistance may be seriously underestimated if the membrane effects are ignored in structural design.

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