Estimation of Ballistic Limit Velocities for Woven Composite Beams

2009 ◽  
Author(s):  
E. Sevkat ◽  
B. M. Liaw ◽  
F. Delale ◽  
B. B. Raju
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Damage Model ◽  
Experimental Tests ◽  
Composite Beams ◽  
Ballistic Limit ◽  
Gas Gun ◽  
Graphite Fibers ◽  
Ballistic Limit Velocity ◽  
Good Agreement

This paper presents an experimental and numerical study to estimate ballistic limit velocity, V50, of plain-weave hybrid S2 glass-IM7 graphite fibers/toughened SC-79 resin (cured at 177°C) composite beams. The tests were conducted on hybrid S2 glass-IM7 graphite fibers/toughened SC-79 resin and nonhybrid S2 glass-fiber/toughened SC-79 resin composites beams using high-speed gas-gun. The ballistic impact tests were then modeled using 3-D dynamic nonlinear finite element (FE) code, LS-DYNA, modified with a proposed user-defined nonlinear-orthotropic damage model. The ballistic limit velocities, V50, for both composite beams were then estimated using (a) only experimental tests, (b) combined experimental and numerical tests, (c) FE calculated residual velocities, and (d) FE calculated residual and transferred energies. For each type of composite beams, the parameters for the well-known Lambert-Jones equation were also computed. Good agreement between experimental and numerical results was observed.

Numerical Investigation of Ductile Fracture in Pipelines Under Complex Loading Using a Phenomenological Damage Model

2021 ◽  
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa
Keyword(s):  
Ductile Fracture ◽  
Mechanical Response ◽  
Numerical Study ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Numerical Procedure ◽  
Complex Loading ◽  
Experimental Tests ◽  
Compact Tension ◽  
Axial Tensile

Abstract This paper presents a numerical study on pipes ductile fracture mechanical response using a phenomenological computational damage model. The damage is controlled by an initiation criterion dependent on the stress triaxiality and the Lode angle parameter, and a post-initiation damage law to eliminate each finite element from the mesh. Experimental tests were carried out to calibrate the elastoplastic response, damage parameters and validate the FEM models. The tested geometries were round bars having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture toughness tests in deeply cracked bending specimens SE(B) and compact tension samples C(T). The calibrated numerical procedure was applied to execute a parametric study in pipes with circumferential surface cracks subjected to tensile and internal pressure loads simultaneously. The effects of the variation of geometric parameters and the load applications on the pipes strain capacity were investigated. The influence of longitudinal misalignment between adjacent pipes was also investigated.

The Numerical Method as Applied to Impact Resistance Analysis of Ogival Nose Projectiles on 6061-T651 Aluminum Plates

2012 ◽  
Vol 28 (4) ◽  
pp. 715-726 ◽  
Author(s):  
Y.-L. Chen ◽  
H.-C. Chen
Keyword(s):  
Numerical Method ◽  
Predictive Model ◽  
Penetration Depth ◽  
High Speed ◽  
Ballistic Limit ◽  
Residual Velocity ◽  
Finite Element Software ◽  
Limit Velocity ◽  
Aluminum Plates ◽  
Ballistic Limit Velocity

ABSTRACTThis research takes the resistance formula of spherical cavity expansion theory as its foundation. It establishes a predictive model of the residual velocity, ballistic limit velocity, and penetration depth of ogival nose projectiles striking metal target plates at high speed. They are aimed at 6061-T651 aluminum plates of different thicknesses using the iterative algorithm of the numerical method, thereby investigating the theoretical calculation of the residual velocity, penetration depth, ballistic limit velocity, and changes in resistance of ogival nose projectiles when making a normal impact target. In addition to analyzing the resistance undergone by the projectile nose section, this predictive model also considers the effects of friction resistance of the projectile shank section. In this research, we also used the finite element software LS-DYNA to perform a simulated analysis on the penetration depth of the aluminum plate after normal perforation by ogival nose projectiles. Ballistic test experiments were then performed using 0.30” AP (armor piercing) bullets. Finally, a comparative analysis was performed based on the theoretical model, experiments, and numerical simulation results.

scholarly journals Experimental and numerical study of the interaction between dynamically loaded cracks and pre-existing flaws in edge loaded PMMA specimens

2020 ◽  
Author(s):  
Chuzhali Nilath Irfan Habeeb ◽  
shmuel osovski
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Numerical Study ◽  
Damage Model ◽  
Image Correlation ◽  
High Speed Photography ◽  
Dynamic Fracture Tests ◽  
Micromechanical Damage ◽  
Fracture Tests ◽  
Micromechanical Damage Model

Dynamic fracture tests are carried out for four groups of hole-containing edge loaded specimens. The crack growth velocity, crack path, and dynamic toughness are extracted from the experiments using high-speed photography and digital image correlation. The importance of the interaction between the in-coming stress wave and the pre-existing hole is revealed and analyzed. A micromechanical damage model is calibrated to the experimental data from two of the specimens' designs and evaluated for its predictive capabilities using the other experimental configurations. The studied model is shown to be in reasonable agreement with the experimental data, and its limits are discussed

Experimental Tests on Composite Beam with Various Slab Systems

2012 ◽  
Vol 166-169 ◽  
pp. 33-36
Author(s):  
Anis Saggaff ◽  
M.Md. Tahir ◽  
Norwati Jamaluddin ◽  
Poi Ngian Shek ◽  
Cher Siang Tan
Keyword(s):  
Composite Beam ◽  
Experimental Tests ◽  
Composite Beams ◽  
Full Scale ◽  
Structural Behaviour ◽  
Theoretical Predictions ◽  
Floor Systems ◽  
Staggered Arrangement ◽  
The Moment ◽  
Good Agreement

This paper presents the structural behaviour of composite beams with various floor systems tested in full-scale arrangement. Six full-scale specimens with staggered and non-staggered arrangement of studs on the composite beams were tested until failure. The moment capacities obtained from the experiment are compared with the theoretical values established from BS 5950 and Eurocode 4. The experimental results showed good agreement with theoretical predictions while no significant influences were found between staggered and non-staggered arrangement of studs.

Advanced Experimental and Numerical Analysis of the Pressurized Air Wave Bearings

2007 ◽  
Author(s):  
Adrian Sescu ◽  
Florin Dimofte ◽  
Carmen Sescu ◽  
Abdollah A. Afjeh ◽  
Robert Handschuh
Keyword(s):  
Finite Difference ◽  
Reynolds Equation ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Two Dimensional ◽  
Commercial Code ◽  
Type Boundary ◽  
Experimental Rig ◽  
Good Agreement

Experimental, analytical, and numerical investigations have been done in the field of gas lubrication, but few people focused on details of fluid flow between the sliding surfaces. In this work the entire pressurized wave bearing is analyzed in detail. The numerical study using a three-dimensional commercial code and a two-dimensional finite difference code gives information about the flow at many levels. The numerically computed flow rates using the commercial code are compared with experimental results determined at NASA Glenn Research Center on an experimental rig. The calculated discharge coefficient is used in the finite difference code which solves the Reynolds equation. The holes effect is considered as a source term, instead of applying hybrid type boundary conditions on the holes contours. Data from experimental tests, commercial three-dimensional code, and two-dimensional code are reported and compared to each other. Good agreement was found between numerical study and experiment.

scholarly journals Experimental And Numerical Study Of Single And Multiple Imapcts Of Angular particles On Ductile Metals

2021 ◽  
Author(s):  
Mahdi Takaffoli
Keyword(s):  
Solid Particle ◽  
High Speed ◽  
Numerical Study ◽  
Solid Particle Erosion ◽  
Fe Model ◽  
Particle Erosion ◽  
Erosion Mechanisms ◽  
The Impact ◽  
Good Agreement ◽  
Angular Particles

Solid particle erosion occurs when small high speed particles impact surfaces. It can be either destructive such as in the erosion of oil pipelines by corrosion byproducts, or constructive such as in abrasive jet machining processes. Two dimensional finite element (FE) models of single rhomboid particles impact on a copper target were developed using two different techniques to deal with the problem of element distortion: (i) element deletion, and (ii) remeshing. It was found that the chip formation and the material pile-up, two phenomena that cannot be simulated using a previously developed rigid-plastic model, could be simulated using the FE models, resulting in a good agreement with experiments performed using a gas gun. However, remeshing in conjunction with a failure model caused numerical instabilities. The element deletion approach also induced errors in mass loss due to the removal of distorted elements. To address the limitations of the FE approach, smoothed particle hydrodynamics (SPH) which can better accommodate large deformations, was used in the simulation of the impact of single rhomboid particles on an aluminum alloy target. With appropriate constitutive and failure parameters, SPH was demonstrated to be suitable for simulating all of the relevant damage phenomena observed during impact experiments. A new methodology was developed for generating realistic three dimensional particle geometries based on measurements of the size and shape parameter distributions for a sample of 150 µm nominal diameter angular aluminum oxide powder. The FE models of these generated particles were implemented in a SPH/FE model to simulate non-overlapping particle impacts. It was shown that the simulated particles produced distributions of crater and crater lip dimensions that agreed well with those measured from particle blasting experiments. Finally, a numerical model for simulating overlapping impacts of angular particles was developed and compared to experimental multi-particle erosion tests, with good agreement. An investigation of the simulated trajectory of the impacting particles revealed various erosion mechanisms such as the micromachining of chips, the ploughing of craters, and the formation, forging and knocking off crater lips which were consistent with previously noted ductile solid particle erosion mechanisms in the literature.

Impact damage assessment of carbon fiber reinforced composite with different stacking sequence

2019 ◽  
Vol 54 (2) ◽  
pp. 193-203
Author(s):  
Rahul S Sikarwar ◽  
R Velmurugan
Keyword(s):  
High Speed ◽  
Stacking Sequence ◽  
High Speed Camera ◽  
Ballistic Limit ◽  
Limit Velocity ◽  
Post Impact ◽  
Damage Extent ◽  
Ballistic Limit Velocity ◽  
Energy Absorbing ◽  
The Impact

This work examines the experimental and analytical investigation of impact on the carbon/epoxy laminates of various stacking sequence. The impact tests were carried out by using gas gun equipped with high-speed camera. Projectile velocities selected were 80 m/s and 30 m/s where 80 m/s was above ballistic limit velocity and 30 m/s was below ballistic limit velocity. The impact process was recorded with high-speed camera which facilitated to identify different energy absorbing mechanisms. High-speed images were also used to measure pre-impact and post-impact velocities of the projectile accompanied by photo diode and aluminum foil method. Total energy absorbed by the laminates, which is the difference between pre-impact and post-impact kinetic energy of the projectile, was calculated for the laminates with different stacking sequences. Damage extent in the laminates of different stacking sequences were also assessed by C-Scan of the laminates. Then effect of stacking sequences on damage extent and energy absorbing capacity was established. An analytical model was proposed to predict the residual velocity of the projectile at above ballistic limit velocity, which was based on the total energy absorbed by different energy absorption mechanisms. The analytical model was validated with experimental results for different stacking sequences. Additionally, effect of fiber orientation on damage shape at below ballistic limit velocity was also studied.

A Numerical Study of Squeeze Film Dampers

2013 ◽  
Author(s):  
Praneetha Boppa ◽  
Gerald L. Morrison ◽  
Aarthi Sekaran
Keyword(s):  
Steady State ◽  
High Speed ◽  
Numerical Study ◽  
Squeeze Film ◽  
Numerical Studies ◽  
Whirling Motion ◽  
Squeeze Film Dampers ◽  
Absolute Frame ◽  
Bearing System ◽  
Good Agreement

Squeeze film dampers (SFDs) are used in the high speed turbomachinery industry as a means to reduce vibration amplitude, provide damping, and improve dynamic stability of the rotor bearing system. Past numerical studies analyzing SFDs, have been computationally expensive and time consuming. The present study investigates the feasibility of applying a steady state solver to obtain computational efficiency while ensuring that the parameters of interest are captured. This is done via the application of the Moving Reference Frame (MRF) solver in ANSYS® Fluent. A steady state solver in an absolute frame of reference was used to produce whirling motion of the rotor. The results are validated by comparison to the experimental data of Delgado [1]. The numerical model shows good agreement with these results.

Evaluation of hetro-stacked target plate response toward different nose shaped projectile impact

2021 ◽  
pp. 030932472110471
Author(s):  
Danish Iqbal ◽  
Vikrant Tiwari
Keyword(s):  
High Speed ◽  
Impact Behavior ◽  
Target Plate ◽  
Full Field ◽  
Projectile Impact ◽  
Perforation Hole ◽  
Numerical Investigations ◽  
Gas Gun ◽  
Post Impact ◽  
Good Agreement

Detailed experimental and numerical investigations were carried out for evaluating the dynamic response of the stacked target plates toward moderate (100–250 m/s) velocity projectile impact. A single stage gas gun was utilized to launch the hemispherical and the blunt projectile toward two different hetro-stacked configurations (Al-St and St-Al). A comprehensive experimental (high speed 3D-DIC) and numerical (FE) evaluation was conducted to obtain the transient and post-impact behavior of the target plates. Influence of different projectile shapes on the full-field transient deformation profiles of different stacking configurations was studied in detail. Also, typical perforation parameters like plug size, shape, and perforation hole diameters were carefully measured and analyzed. A comprehensive error measure was utilized to quantify the similarity between the experimental and simulation results, a very good agreement was observed.

Mono-Disperse Spray Generation by a Flow Focusing Atomizer: A Numerical Study

2012 ◽  
Author(s):  
Babak Samareh ◽  
Arash Kashani ◽  
Javad Mostaghimi
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Numerical Study ◽  
Theoretical Models ◽  
Flow Focusing ◽  
Flow Solver ◽  
Jet Breakup ◽  
Compressible Turbulent Flow ◽  
Controlled Flow ◽  
Good Agreement

Pneumatic flow focusing technology is a relatively new atomizing process first introduced in 1998. A liquid microjet is formed by a high speed co-flowing gas stream when a pressure drop is applied across an orifice. The microjet eventually disintegrates into fine droplets by the perturbing gas downstream of the atomizer exit. Under certain controlled flow regimes the resulting spray demonstrates strong monodispersity. In the present study, the gas flow is numerically modeled by a compressible turbulent flow solver and the liquid jet evolution is captured using Volume of Fluid (VOF) interface tracking method. Jet breakup parameters and drop size distribution are studied for different liquids and flow rates. Results are in good agreement with experiments and theoretical models.

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