Quantification of impact of a cricket ball

The cricket is one of most popular games in the Asian subcontinent and its popularity is increasing every day. The issue of replacement of the cricket ball amidst the matches is always an uncomfortable situation for teams, umpires and even supporters. At present the basis of the replacement is solely on the judgement, experience and expertise of the umpires, which is subjective, controversial and debatable. In this paper, we have attempted a new approach to quantify the number of impacts or impact factor of a 4-piece leather ball used in the Intemational one-day and test cricket matches. This gives a more objective and scientific basis/ criteria for the replacement of the ball. Here, we have used a well known and widely used Thermal Infra-Red (TIR) imaging to capture the dynamics of the thermal profice of the cricket ball, which has been heated for about 15 seconds. The idea behind this approach is the simple observation that an old ball (ball with a few impacts) has different thermal signature/profice compared to the that of a new ball. This could be due to the change in the surface profice and internal structure, minor de-shaping, opening of seam etc. The TIR video and its frames, which is inherently noisy, are restored using Hebbian learning based FIR (sic), which performs optimal smoothing in relatively less number of iteration. We have focussed on the hottest region of the ball i.e., the inner core and tracked its thermal profice dynamics. Finally we have used multi layer perceptron model (MLP) to quantify the impact factor with fairly good accuracy.

Micro and macroscopic features of impact failed defect induced carbon-epoxy composites

Laminated composite structures are susceptible to damage under impacts with attendant properly degradation. While studies on damage tolerance behaviour are emphasised and the findings reported, the citations correlating impacts with the fracture features are limited. In the present study, therefore, attempts have been made to depict how the transition of the fracture features take place depending on the type and extent of defect introduced onto the carbon-epoxy system. The test specimens were subjected to differing levels of low energy pendulum impacts with a view to have specimens with varying levels of intial impacts history. Into such specimens, additional defect in the form of slits of varying depths were introduced by a mechanical process. The test coupons were then allowed to fail by impact. The fracture surface was studied under scanning electron microscope. The fractographic features that appear, based on the induced/inserted defects, are presented in this paper. It was noticed that the energy absorbed for final fracture could be associated with the defect introduced into the system. It was also observed that the size of the mechanically inserted defect had a significant influence on the features of the fracture surface.

Detection and Evaluation of Impact damage in CFRP Laminates Using Ultrasound C-Scan and IR Thermography

Advanced composite structural components made up of Carbon Fibre Reinforced Polymers (CFRP) used in aerospace structures such as in Fuselage, Leading & Trailing edges of wing and tail, Flaps, Elevator, Rudder and entire wing structures encounter most critical type of damage induced by low velocity impact (<10 m/s) loads. Tool dropped during maintenance & service,and hailstone impacts on runways are common and unavoidable low-velocity impacts. These lowvelocity impacts induce defects such as delaminations, matrix cracking and debonding in the layered material, which are sub-surface in nature and are barely visible on the surface known as Barely Visible Impact Damage (BVID). These damages may grow under service load, leading to catastrophic failure of the structure. Hence detection, evaluation and characterization of these types of damage is of major concern in aerospace industries as the life of the component depends on the size and shape of the damage.In this paper, details of experimental investigations carried out and results obtained from a low-velocity impact of 30 Joules corresponding to the hailstone impact on the wing surface,simulated on the 6 mm CFRP laminates using instrumented drop-weight impact testing machine are presented. The Ultrasound C-scan and Infrared thermography imaging techniques were utilized extensively to detect, evaluate and characterize impact damage across the thickness of the laminates.

Optimised form of acceleration correction algorithm within SPH-based simulations of impact mechanics

In the context of SPH-based simulations of impact dynamics, an optimised and automated form of the acceleration correction algorithm (Shaw and Reid, 2009a) is developed so as to remove spurious high frequency oscillations in computed responses whilst retaining the stabilizing characteristics of the artificial viscosity in the presence of shocks and layers with sharp gradients. A rational framework for an insightful characterisation of the erstwhile acceleration correction method is first set up. This is followed by the proposal of an optimised version of the method, wherein the strength of the correction term in the momentum balance and energy equations is optimised. For the first time, this leads to an automated procedure to arrive at the artificial viscosity term. In particular, this is achieved by taking a spatially varying response-dependent support size for the kernel function through which the correction term is computed. The optimum value of the support size is deduced by minimising the (spatially localised) total variation of the high oscillation in the acceleration term with respect to its (local) mean. The derivation of the method, its advantages over the heuristic method and issues related to its numerical implementation are discussed in detail. (C) 2011 Elsevier Ltd. All rights reserved.

Stabilized SPH-based simulations of impact dynamics using acceleration-corrected artificial viscosity

Artificial viscosity in SPH-based computations of impact dynamics is a numerical artifice that helps stabilize spurious oscillations near the shock fronts and requires certain user-defined parameters. Improper choice of these parameters may lead to spurious entropy generation within the discretized system and make it over-dissipative. This is of particular concern in impact mechanics problems wherein the transient structural response may depend sensitively on the transfer of momentum and kinetic energy due to impact. In order to address this difficulty, an acceleration correction algorithm was proposed in Shaw and Reid (''Heuristic acceleration correction algorithm for use in SPH computations in impact mechanics'', Comput. Methods Appl. Mech. Engrg., 198, 3962-3974) and further rationalized in Shaw et al. (An Optimally Corrected Form of Acceleration Correction Algorithm within SPH-based Simulations of Solid Mechanics, submitted to Comput. Methods Appl. Mech. Engrg). It was shown that the acceleration correction algorithm removes spurious high frequency oscillations in the computed response whilst retaining the stabilizing characteristics of the artificial viscosity in the presence of shocks and layers with sharp gradients. In this paper, we aim at gathering further insights into the acceleration correction algorithm by further exploring its application to problems related to impact dynamics. The numerical evidence in this work thus establishes that, together with the acceleration correction algorithm, SPH can be used as an accurate and efficient tool in dynamic, inelastic structural mechanics. (C) 2011 Elsevier Ltd. All rights reserved.

CAE-based prediction of projectile residual velocity for impact on single and multi-layered metallic armour plates

The present, paper deals with the CAE-based study Of impact of jacketed projectiles on single- and multi-layered metal armour plates using LS-DYNA. The validation of finite element modelling procedure is mainly based on the mesh convergence study using both shell and solid elements for representing single-layered mild steel target plates. It, is shown that the proper choice of mesh density and the strain rate-dependent material properties are essential for all accurate prediction of projectile residual velocity. The modelling requirements are initially arrived at by correlating against test residual velocities for single-layered mild steel plates of different depths at impact velocities in the ran.-c of approximately 800-870 m/s. The efficacy of correlation is adjudged, in terms of a 'correlation index', defined in the paper: for which values close to unity are desirable. The experience gained for single-layered plates is next; used in simulating projectile impacts on multi-layered mild steel target plates and once again a high degree of correlation with experimental residual velocities is observed. The study is repeated for single- and multi-layered aluminium target plates with a similar level of success in test residual velocity prediction. TO the authors' best knowledge, the present comprehensive study shows in particular for the first time that, with a. proper modelling approach, LS-DYNA can be used with a great degree of confidence in designing perforation-resistant single and multi-layered metallic armour plates.

The role of the interface in foam-bearing glass-epoxy composites subjected to impact loading

foam, either stacked together as three layers (MC) or inserted at three different positions (3L) while arranging the stacking sequence during the fabrication of glass fiber-epoxy composites, form the subject of investigation. This stacking variation resulted in a different interfacial area between these foam materials and the glass-epoxy regions in the laminates. This area in designed to be maximum for the 3L variety. The energy of impact being high enough to cause development of the crack in the samples, how the change in interfacial area affects the traverse of the crack front and the failure feature of the laminated composite are reported in the form of photomacrographs in this work. The results point to significant changes for the impact data, like for instance the peak load attained by the different samples, through thickness crack propagation and tensile fracture features on the non-impacted end for the plain variety, separation about the mid-zone for the MC laminates and two or more layer separations for the 3L variety. The separation for the foam-bearing systems occur invariably at the interface and here again one of the (two identical) interfaces only is chosen for the separation.

Simulation-driven design of helmets for head impact protection using an injury-based criterion

The current paper suggests a new procedure for designing helmets for head impact protection for users such as motorcycle riders. According to the approach followed here, a helmet is mounted on a featureless Hybrid 3 headform that is used in assessing vehicles for compliance to the FMVSS 201 regulation in the USA for upper interior head impact safety. The requirement adopted in the latter standard, i.e. not exceeding a threshold HIC(d) limit of 1000, is applied in the present study as a likely criterion for adjudging the efficacy of helmets. An impact velocity of 6 m/s (13.5 mph) for the helmet-headform system striking a rigid target can probably be acceptable for ascertaining a helmet's effectiveness as a countermeasure for minimizing the risk of severe head injury. The proposed procedure is demonstrated with the help of a validated LS-DYNA model of a featureless Hybrid 3 headform in conjunction with a helmet model comprising an outer polypropylene shell to the inner surface of which is bonded a protective polyurethane foam padding of a given thickness. Based on simulation results of impact on a rigid surface, it appears that a minimum foam padding thickness of 40 mm is necessary for obtaining an acceptable value of HIC(d).

On the impact of a concave nosed axisymmetric body on a free surface

We report on an experimental study of the vertical impact of a concave nosed axisymmetric body on a free surface. Previous studies have shown that bodies with a convex nose, like a sphere, produce a well defined splash with a relatively large cavity behind the model. In contrast, we find that with a concave nose, there is hardly a splash and the cavity extent is greatly reduced. This may be explained by the fact that in the concave nosed case, the initial impact is between a confined air pocket and the free surface unlike in the convex nosed case. From measurements of the unsteady pressure in the concave nose portion, we show that in this case, the maximum pressures are significantly lower than the classically expected ``water hammer'' pressures and also lower than those generally measured on other geometries. Thus, the presence of an air pocket in the case of a concave nosed body adds an interesting dimension to the classical problem of impact of solid bodies on to a free surface. (C) 2015 AIP Publishing LLC.

In quest of a reliable and efficient computational test for detection of isomorphism in kinematic chains

The test based on comparison of the characteristic coefficients of the adjancency matrices of the corresponding graphs for detection of isomorphism in kinematic chains has been shown to fail in the case of two pairs of ten-link, simple-jointed chains, one pair corresponding to single-freedom chains and the other pair corresponding to three-freedom chains. An assessment of the merits and demerits of available methods for detection of isomorphism in graphs and kinematic chains is presented, keeping in view the suitability of the methods for use in computerized structural synthesis of kinematic chains. A new test based on the characteristic coefficients of the “degree” matrix of the corresponding graph is proposed for detection of isomorphism in kinematic chains. The new test is found to be successful in the case of a number of examples of graphs where the test based on characteristic coefficients of adjancency matrix fails. It has also been found to be successful in distinguishing the structures of all known simple-jointed kinematic chains in the categories of (a) single-freedom chains with up to 10 links, (b) two-freedom chains with up to 9 links and (c) three-freedom chains with up to 10 links.

Transcriptional Silencing of a tRNA1Gly Copy from within a Multigene Family Is Modulated by Distal cis Elements

Individual copies of tRNA1Gly from within the multigene family in Bombyx mori could be classified based on in vitro transcription in homologous nuclear extracts into three categories of highly, moderately, or weakly transcribed genes. Segregation of the poorly transcribed gene copies 6 and 7, which are clustered in tandem within 425 base pairs, resulted in enhancement of their individual transcription levels, but the linkage itself had little influence on the transcriptional status. For these gene copies, when fused together generating a single coding region, transcription was barely detectable, which suggested the presence of negatively regulating elements located in the far flanking sequences. They exerted the silencing effect on transcription overriding the activity of positive regulatory elements. Systematic analysis of deletion, chimeric, and mutant constructs revealed the presence of a sequence element TATATAA located beyond 800 nucleotides upstream to the coding region acting as negative modulator, which when mutated resulted in high level transcription. Conversely, a TATATAA motif reintroduced at either far upstream or far downstream flanking regions exerted a negative effect on transcription. The location of cis-regulatory sequences at such farther distances from the coding region and the behavior of TATATAA element as negative regulator reported here are novel. These element(s) could play significant roles in activation or silencing of genes from within a multigene family, by recruitment or sequestration of transcription factors.

DockYard-a repository to assist modeling of protein-protein docking

In the absence of interlogs, building docking models is a time intensive task, involving generation of a large pool of docking decoys followed by refinement and screening to identify near native docking solutions. This limits the researcher interested in building docking methods with the choice of benchmarking only a limited number of protein complexes. We have created a repository called dockYard (http://pallab.serc.iisc.ernet.in/dockYard), that allows modelers interested in protein-protein interaction to access large volume of information on protein dimers and their interlogs, and also download decoys for their work if they are interested in building modeling methods. dockYard currently offers four categories of docking decoys derived from: Bound (native dimer co-crystallized), Unbound (individual subunits are crystallized, as well as the target dimer), Variants (match the previous two categories in at least one subunit with 100% sequence identity), and Interlogs (match the previous categories in at least one subunit with >= 90% or >= 50% sequence identity). The web service offers options for full or selective download based on search parameters. Our portal also serves as a repository to modelers who may want to share their decoy sets with the community.

Repeated drop weight impacts and post-impact ILSS tests on glass-epoxy composite

E glass epoxy laminates of thicknesses in the range 2-5 mm were subjected to repeated impacts. For each thickness the number of hits to cause tup penetration was determined and the value of this number was higher the larger the thickness of the laminate tested. The C-scan, before and after impact, was done to obtain information regarding flaw distribution. Short beam shear test samples were made from locations at fixed distances from impact point and tested. The samples closer to the zone of impact showed lower strength values. Scanning fractography revealed shear deformation features for these samples and brittle fracture features for the region near the zone of impact.

RS and GIS in mapping of geomorphic records and understanding the local controls of glacial retreat from the Baspa Valley, Himachal Pradesh, India

We report here the role of remote sensing (RS) and geographical information system (GIS) in the identification of geomorphic records and understanding of the local controls on the retreat of glaciers of the Baspa Valley, Himachal Pradesh, India. The geomorphic records mapped are accumulation zone, exposed ablation zone, moraine-covered ablation zone, snout, deglaciated valley, lateral moraine, medial moraine, terminal moraine and hanging glacier. Details of these features and stages of deglaciation have been extracted from RS data and mapped in a GIS environment. Glacial geomorphic data have been generated for 22 glaciers of the Baspa Valley. The retreat of glaciers has been estimated using the glacial maxima observed on satellite images. On the basis of percentage of retreat and the critical analysis of glacial geomorphic data for 22 glaciers of the Baspa Valley, they are classified into seven categories of very low to very very high retreat. From the analysis of the above 22 glaciers, it has been found that other than global warming, the retreat of glaciers of the Baspa Valley is inversely proportional to the size of the accumulation zone and the ratio of the moraine covered ablation/exposed ablation zone.

Use of maleic anhydride-grafted polyethylene as compatibilizer for HDPE-tapioca starch blends: Effects on mechanical properties

Tapioca starch in both glycerol-plasticized and in unplasticized states was blended with high-density polyethylene (HDPE) using HDPE-g-maleic anhydride as the compatibilizer. The impact and tensile properties of the blends were measured according to ASTM methods. The results reveal that blends containing plasticized starch have better mechanical properties than those containing unplasticized starch. High values of elongation at break at par with those of virgin HDPE could be obtained for blends, even with high loading of plasticized starch. Morphological studies by SEM microscopy of impact-fractured specimens of such blends revealed a ductile fracture, unlike blends with unplasticized starch at such high loadings, which showed brittle fracture, even with the addition of compatibilizer. In general, blends of HDPE and plasticized starch with added compatibilizer show better mechanical properties than similar blends containing unplasticized starch. (C) 2001 John Wiley & Sons, Inc.