Duane S Cronin

University of Waterloo, Ватерлоо, Ontario, Canada

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Publications (71)56.5 Total impact

  • Luis F. Trimiño · Duane S. Cronin
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    ABSTRACT: Improved energy efficiency in transportation systems can be achieved with multi-material lightweight structures; however, joining often requires the use of adhesive bonding and design efforts are challenged by the paucity of data required to represent adhesives in numerical models. The data for three epoxy structural adhesives tested in tension and shear over a range of strain rates (0.001–1000 s−1) is reported. The range of experimentation addresses regular operation and extreme conditions (crash scenarios) for vehicles. The data was implemented with cohesive and solid elements; and the models were assessed on their ability to reproduce adhesive material response. Good agreement was achieved using both approaches. In average the coefficients of determination (r2) between measured experimental response and simulations were 0.81 for tension and 0.59 for shear, with 2 % difference in the prediction of stress at failure. The cohesive formulation was computationally efficient and reproduced rate effects, but was limited in representing the response of the non-toughened epoxy. The solid element formulation required longer simulation times, but yielded similar accuracy for tension (2 % difference in stress to failure and r2 values of 0.98, on average). However, the shear response accuracy (r2 = 0.53) was reduced by coupling between shear and tension strain rate effects. Numerical simulation of structural adhesives requires constitutive models capable of incorporating uncoupled deformation rate effects on strength. The results of this study indicate that a cohesive model can provide adequate representation of an adhesive joint for tensile and shear loading across a range of deformation rates.
    No preview · Article · Feb 2016
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    ABSTRACT: Foam materials are widely used for energy absorbing applications, and are often addressed in a modeling environment at a macroscopic or continuum level by measuring the mechanical properties, which may be size dependent, and implementing the properties in a continuum-level constitutive model. However, foams are known to exhibit a characteristically low wave speed and an understanding of the deformation mechanics of foams at the micro-scale and dependence on morphology are essential to understand the performance of foam material in impact scenarios. In this study, experimental testing and finite element modeling were used to investigate a viscoelastic polychloroprene closed-cell foam at the cell level, subject to large deformation and high deformation rates. A numerical model was created with solid hexahedral elements and a repeated tetrakaidecahedron cell structure using measured foam cell size and wall thickness, and mechanical properties measured from non-porous polychloroprene. The finite element model predictions were evaluated using experimental compression tests on the foam material at high deformation rates. The enclosed nitrogen in the closed cell foam was modeled using an Arbitrary Lagrange–Eulerian method so that this contribution could be included or removed, and demonstrated the significant effect of the enclosed gas on the mechanical response of the foam. The foam cell dimensions were varied to investigate morphological factors including cell size, cell aspect ratio and cell wall thickness. Increasing wall thickness, decreasing cell size and decreasing the cell aspect ratio resulted in increased material stiffness, with wall thickness having the most significant effect. Investigation of the wave transmission speed demonstrated a low value compared to the constituent materials, which was explained by the path of the stress wave through the foam structure and wave reflections within the cells, attenuating the stress wave. The consequence of this low wave speed was non-uniform deformation of the foam sample demonstrating that the measured mechanical properties of porous foams depend on the sample thickness, an important consideration for foam material testing and characterization.
    Preview · Article · Jul 2015
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    ABSTRACT: Solid and foamed polymeric materials demonstrate a significant increase in stiffness with increasing deformation rate, and existing hyper-viscoelastic constitutive formulations are often limited in applicability across large ranges of deformation rate and finite deformations. The development of micro-level pore-based foam models requires the mechanical properties of the constituent non-porous material coupled with efficient and representative constitutive models. In this study, the mechanical properties of non-porous polychloroprene were measured at low deformation rates using a conventional hydraulic test apparatus and at high deformation rates using a polymeric split Hopkinson pressure bar apparatus. A constitutive model was developed using an additive formulation to describe the hyper-viscoelastic material response for large deformations and a range of deformation rates from quasi-static (0.001 s−1) up to 2700 s−1. The material coefficients were determined using a constrained optimization technique that simultaneously fit all of the data, and iterated to determine the required number of material constants. The constitutive model was implemented into an explicit finite element code and accurately predicted the response of non-porous polychloroprene rubber (R2 = 0.996) over the range of tested strain rates. Importantly, the finite element implementation minimized the required computational storage, addressing limitations in existing constitutive models, and was computationally efficient, which was necessary for the large finite element micro-scale simulations of foamed polychloroprene undertaken in a follow-on study.
    Preview · Article · Jul 2015
  • Hamed Shateri · Duane S Cronin
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    ABSTRACT: Objective: Whiplash injuries can occur in automotive crashes and may cause long-term health issues such as neck pain, headache, and visual and auditory disturbance. Evidence suggests that nonneutral head posture can significantly increase the potential for injury in a given impact scenario, but epidemiological and experimental data are limited and do not provide a quantitative assessment of the increased potential for injury. Although there have been some attempts to evaluate this important issue using finite element models, none to date have successfully addressed this complex problem. Methods: An existing detailed finite element neck model was evaluated in nonneutral positions and limitations were identified, including musculature implementation and attachment, upper cervical spine kinematics in axial rotation, prediction of ligament failure, and the need for repositioning the model while incorporating initial tissue strains. The model was enhanced to address these issues and an iterative procedure was used to determine the upper cervical spine ligament laxities. The neck model was revalidated using neutral position impacts and compared to an out-of-position cadaver experiment in the literature. The effects of nonneutral position (axial head rotation) coupled with muscle activation were studied at varying impact levels. Results: The laxities for the ligaments of the upper cervical spine were determined using 4 load cases and resulted in improved response and predicted failure loads relative to experimental data. The predicted head response from the model was similar to an experimental head-turned bench-top rear impact experiment. The parametric study identified specific ligaments with increased distractions due to an initial head-turned posture and the effect of active musculature leading to reduced ligament distractions. Conclusions: The incorporation of ligament laxity in the upper cervical spine was essential to predict range of motion and traumatic response, particularly for repositioning of the neck model prior to impact. The results of this study identify a higher potential for injury in out-of-position rear collisions and identified at-risk locations based on ligament distractions. The model predicted higher potential for injury by as much as 50% based on ligament distraction for the out-of-position posture and reduced potential for injury with muscle activation. Importantly, this study demonstrated that the location of injury or pain depends on the initial occupant posture, so that both the location of injury and kinematic threshold may vary when considering common head positions while driving.
    No preview · Article · Feb 2015 · Traffic Injury Prevention
  • Stephen F E Mattucci · Duane S Cronin
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    ABSTRACT: Experimental testing on cervical spine ligaments provides important data for advanced numerical modeling and injury prediction; however, accurate characterization of individual ligament response and determination of average mechanical properties for specific ligaments has not been adequately addressed in the literature. Existing methods are limited by a number of arbitrary choices made during the curve fits that often misrepresent the characteristic shape response of the ligaments, which is important for incorporation into numerical models to produce a biofidelic response. A method was developed to represent the mechanical properties of individual ligaments using a piece-wise curve fit with first derivative continuity between adjacent regions. The method was applied to published data for cervical spine ligaments and preserved the shape response (toe, linear, and traumatic regions) up to failure, for strain rates of 0.5s(-1), 20s(-1), and 150-250s(-1), to determine the average force-displacement curves. Individual ligament coefficients of determination were 0.989 to 1.000 demonstrating excellent fit. This study produced a novel method in which a set of experimental ligament material property data exhibiting scatter was fit using a characteristic curve approach with a toe, linear, and traumatic region, as often observed in ligaments and tendons, and could be applied to other biological material data with a similar characteristic shape. The resultant average cervical spine ligament curves provide an accurate representation of the raw test data and the expected material property effects corresponding to varying deformation rates. Copyright © 2014 Elsevier Ltd. All rights reserved.
    No preview · Article · Jan 2015 · Journal of the Mechanical Behavior of Biomedical Materials
  • Donata Gierczycka · Brock Watson · Duane Cronin
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    ABSTRACT: Side impact continues to be a significant source of vehicle occupant injuries and fatalities requiring an improved understanding of response sensitivity to occupant position and the potential for injury. The primary interaction between the occupant and vehicle in near-side impact is the intruding door and vehicle structure where contact with the intruding structures is observed to be the most frequent cause of injuries. Restraints and protective systems are tested for a specific driving position with a prescribed set of anthropometric test devices; however, studies have shown that the initial position and posture of the occupant within the vehicle may have an influence on occupant response. In this study, a finite-element human body model with a detailed representation of the thorax and an ES-2re anthropomorphic test device (ATD) model were integrated with a mid-sized sedan vehicle model to investigate occupant response from a moving deformable barrier side impact. All models were verified using established tests (pendulum, side sled) and physical test data available in the literature. A parametric study was undertaken to evaluate the effect of arm position and car door material properties on thoracic response, assessed using thoracic deflection and the viscous criterion. In the standard driving position, the human and ATD model responses were similar. The human body model demonstrated significant sensitivity, relative to the ATD, to different arm positions with a lesser sensitivity to the door interior properties. It was found that in side impact which has the characteristics of high energy and limited displacement, the arm aligned with the body can act as a significant source of load transmission to the thorax, increasing the potential for injury. This study demonstrates that the choice of occupant model, injury metric and occupant arm position plays an important role in evaluating side impact safety.
    No preview · Article · Jan 2015 · International Journal of Crashworthiness
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    Brett Campbell · Duane Cronin
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    ABSTRACT: The goal of this study was to evaluate side impact crash conditions using a detailed human body model and side impact crash model to provide an improved understanding of side impact injury and the primary contributing factors. This study builds on an advanced numerical human body model, including a detailed thorax, which has been validated using available PMHS test data for pendulum and side sled impact tests. Crash conditions were investigated through use of a coupled side impact model, used to reproduce full scale crash tests. The model accounts for several important factors that contribute to occupant response as noted in the literature: the relative velocities between the seat and door, the occupant to door distance, the door shape and compliance. The coupled side impact model was validated using FMVSS 214 and IIHS side impact test data, comparing the thoracic response predicted by the model to that of the ES-2 dummy used in the crash tests. Importantly, the door and seat models were developed based on experimental data in the literature. The side impact model was used to investigate the effects of door to occupant spacing, door velocity profile, restraint system, and seat foam properties. The current study was limited to the use of velocity profiles in the direction of impact and did not consider rotational effects or motion perpendicular to the impact direction. It was found that injury as predicted using the detailed human body model and the Viscous Criterion (VC) was controlled by the second velocity peak typically found in door velocity profiles.
    Preview · Article · Dec 2014 · International Journal of Crashworthiness
  • Jeffrey B Barker · Duane S. Cronin · Naveen Chandrashekar
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    ABSTRACT: Numerical finite element models of the neck have been developed to simulate occupant response and predict injury during motor vehicle collisions. However, there is a paucity of data on the response of young cervical spine segments under dynamic loading in flexion and extension, which is essential for the development or validation of Detailed Finite Element (DFE) models. This limitation was identified during the development and validation of the DFE model used in this study. The purpose of this study was to measure the high rotation rate loading response of human cervical spine segments in flexion and extension, and to investigate a new DFE model of the cervical spine with the experimental data to address a limitation in available data. Four test samples at each segment level from C2-C3 through C7-T1 were dissected from eight donors and were tested to 10 degrees of rotation at 1 and 500 degrees per second in flexion and extension using a custom built test apparatus. There was strong evidence (p < 0.05) of increased stiffness at the higher rotation rate above six degrees of rotation for four segment level tests in extension, and one segment level in flexion. Below six degrees of rotation, there was no evidence of increased stiffness between the two rotation rates at any segment level. Cross-correlation software, CORA, was used to evaluate the fit between the experimental data and model predictions. CORA calculated an average score 0f 0.771, demonstrating good fit to the data.
    No preview · Article · Jul 2014 · Journal of Biomechanical Engineering
  • Dilaver Singh · Duane S Cronin · Tyler N Haladuick
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    ABSTRACT: Mild traumatic brain injury caused by blast exposure from Improvised Explosive Devices has become increasingly prevalent in modern conflicts. To investigate head kinematics and brain tissue response in blast scenarios, two solid hexahedral blast-head models were developed in the sagittal and transverse planes. The models were coupled to an Arbitrary Lagrangian-Eulerian model of the surrounding air to model blast-head interaction, for three blast load cases (5 kg C4 at 3, 3.5 and 4 m). The models were validated using experimental kinematic data, where predicted accelerations were in good agreement with experimental tests, and intracranial pressure traces at four locations in the brain, where the models provided good predictions for frontal, temporal and parietal, but underpredicted pressures at the occipital location. Brain tissue response was investigated for the wide range of constitutive properties available. The models predicted relatively low peak principal brain tissue strains from 0.035 to 0.087; however, strain rates ranged from 225 to 571 s-1. Importantly, these models have allowed us to quantify expected strains and strain rates experienced in brain tissue, which can be used to guide future material characterization. These computationally efficient and predictive models can be used to evaluate protection and mitigation strategies in future analysis. Copyright © 2013 John Wiley & Sons, Ltd.
    No preview · Article · Apr 2014
  • Nasim Paryab · Duane S Cronin · Pearl Lee-Sullivan
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    ABSTRACT: Helical polymeric stents have been proposed as a suitable geometry for biodegradable drug-eluting polymer-based stents. However, helical stents often experience nonuniform local expansion (dog boning), which can prohibit full stent expansion using conventional methods. The development of stents and deployment methods is challenging and can be supported by numerical analysis; however, this complex problem is often approached with simplified boundary conditions that may not be appropriate for helical stents. The finite element method (explicit and implicit) was used to investigate three common stent expansion approaches with a focus on helical stent geometry, which differs from traditional wire mesh stent expansion. Although each of the three methods considered provided some insight into the expansion characteristics, common displacement controlled, and uniform expansion methods were not able to demonstrate the characteristic local deformations observed in expansion. A coupled stent-balloon model, although computationally expensive, was able to demonstrate the expected nonuniform deformation. To address nonuniform expansion, a progressive expansion approach has been investigated and verified numerically. This method may also provide a suitable solution for nonuniform expansion in other stent designs by minimizing loading and potential damage to the artery that can occur during stent deployment. Copyright © 2013 John Wiley & Sons, Ltd.
    No preview · Article · Mar 2014
  • Philip A Lockhart · Duane S Cronin
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    ABSTRACT: Head injury resulting from blast loading, including mild traumatic brain injury, has been identified as an important blast-related injury in modern conflict zones. A study was undertaken to investigate potential protective ballistic helmet liner materials to mitigate primary blast injury using a detailed sagittal plane head finite element model, developed and validated against previous studies of head kinematics resulting from blast exposure. Five measures reflecting the potential for brain injury that were investigated included intracranial pressure, brain tissue strain, head acceleration (linear and rotational) and the head injury criterion. In simulations, these measures provided consistent predictions for typical blast loading scenarios. Considering mitigation, various characteristics of foam material response were investigated and a factor analysis was performed which showed that the four most significant were the interaction effects between modulus and hysteretic response, stress-strain response, damping factor and density. Candidate materials were then identified using the predicted optimal material values. Polymeric foam was found to meet the density and modulus requirements; however, for all significant parameters, higher strength foams, such as aluminum foam, were found to provide the highest reduction in the potential for injury when compared against the unprotected head.
    No preview · Article · Feb 2014 · Computer Methods in Biomechanics and Biomedical Engineering
  • Luis F. Trimiño · Duane S. Cronin
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    ABSTRACT: The use of lightweight materials in vehicle structures requires appropriate joining techniques, among them adhesive bonding. Testing full-scale structures such as vehicle crush tubes can be prohibitive in terms of cost and appropriate facilities may not be available, so it is often desirable to test sub-size structures. To address this need, the suitability of scaling to accurately describe the behavior of bonded crush tube structures during axial impact scenarios was investigated. A numerical simulation was validated using literature sources and experimental testing, and then used to investigate scaling. The predictions for structures constructed out of a single material, in terms of stress distributions and deformations were in good agreement between the numerical simulations of the model (experiment modified in size by a scale factor) and the prototype tubes (actual size experiment). When considering bonded structures with the possibility for joint separation, the Non-Direct Similitude technique was applied to scale the structure and the results showed a small departure between the predictions of the model and the prototype. For bonded crush tubes, where the presence of a second material in the form of an adhesive layer was small, the scaling method provides acceptable results. The limitations of the scaling technique were discussed.
    No preview · Article · Feb 2014 · International Journal of Impact Engineering
  • Philip A Lockhart · Duane S Cronin · Brock Watson
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    ABSTRACT: Objective: Vehicle impacts with fixed roadside structures, such as poles, constitute a significant portion of road fatalities in North America. The purpose of this study was to evaluate occupant response in pole crash scenarios and compare the current vehicle kinematic-based injury metrics to occupant-based metrics to determine whether the vehicle metrics are representative of the injury levels sustained by an occupant. Methods: To better understand vehicle and occupant response during impact with a pole, frontal crash scenarios with 3 common pole types (a rigid pole, a rigid pole with a frangible base, and a deforming or energy-absorbing pole) were investigated at various impact velocities. A numerical model of a Hybrid III human surrogate was integrated with a numerical model of a mid-size sedan, including improvements to the vehicle and seat models, and implementation of an air bag and restraint system. The vehicle model was validated using the National Highway Traffic Safety Administration's (NHTSA) frontal crash data for varying impact velocities into a rigid wall. A numerical model of a high-energy-absorbing pole was developed and validated, along with a rigid pole and a previously developed breakaway pole, to examine the effects of pole compliance on the vehicle and occupant response. Occupant response was investigated at varying impact velocities with the poles aligned with the vehicle centerline. Offset impacts were then investigated with the energy-absorbing pole aligned with the driver-side crush structure. Results: The vehicle kinematic response metrics currently used to evaluate poles were compared to the currently accepted occupant injury response metrics and it was found, in general, that the occupant-based injury criteria predicted lesser injury than the vehicle kinematic response metrics for the same impact scenario. Specifically, the occupant impact velocity provided trends that differed from all other metrics. This can be attributed in part to the improvement in vehicle safety systems not accounted for by the vehicle-based metrics. Conclusions: For the same impact scenario, the breakaway pole resulted in the lowest predicted injury metrics for the vehicle occupant but was noted to be a potential threat to pedestrians and other nearby road users. The rigid pole resulted in the highest occupant injury predictions, whereas the energy-absorbing steel pole resulted in injury metrics below the threshold values, controlled the vehicle deceleration, and detached from the base only at higher velocity impacts. Appropriate evaluation of energy-absorbing poles requires consideration of the occupant response in addition to the current kinematic criteria.
    No preview · Article · Jul 2013 · Traffic Injury Prevention
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    ABSTRACT: Craniovertebral ligaments were tested to failure under tensile loading. Ligaments tested included: transverse ligament, anterior atlanto occipital membrane, posterior atlanto occipital membrane, capsular ligaments between Skull-C1 and C1-C2, anterior atlantoaxial membrane, posterior atlantoaxial membrane and the tectorial membrane/vertical cruciate/apical/alar ligament complex. The objective of this study was to obtain mechanical properties of craniovertebral ligaments of a younger population, at varying strain rates representative of automotive crash scenarios, and investigate rate and gender effects for use in numerical models of the cervical spine. There have been few studies conducted on the mechanical properties of human craniovertebral ligaments. Only one study has tested all of the ligaments, and previous studies use older age specimens (mean age 67, from most complete study). Further, tests were often not performed at elongation rates representative of car crash scenarios. Previous studies did not perform tests in an environment resembling in vivo conditions, which has been shown to have a significant effect on ligament tensile behaviour. Fifty-four craniovertebral ligaments were isolated from twenty-one spines, and tested to failure in tension under simulated in vivo temperature and hydration levels, at quasi-static (0.5s(-1)) and high strain rates (150s(-1)). Values for failure force, failure elongation, stiffness, and toe region elongation were obtained from force-displacement curves. Values were analyzed for strain rate and gender effects. Increased strain rate produced several significant effects including: higher failure forces for the transverse ligament and capsular ligament (Skull-C1), lower failure elongation for the tectorial membrane complex, higher stiffness for the tectorial membrane complex and capsular ligament (Skull-C1), and lower toe region elongation for capsular ligament (Skull-C1). Gender effects were limited. Ligament tests demonstrated expected rate effects. Younger specimens had a higher failure force and stiffness and failed at lower elongations than older specimens from previous studies. Gender effects suggest there may be a difference between male and female properties, but require further testing to establish greater significance.
    No preview · Article · Apr 2013
  • A. Hosseini · D. Cronin · A. Plumtree
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    ABSTRACT: Cracks may occur coincident with corrosion representing a new hybrid defect in gas and oil pipelines known as crack in corrosion (CIC) that is not directly addressed in the current codes or assessment methods. Hence, there is a need to provide an assessment of CIC and evaluate the line integrity, as well as identify the requirements for defect repair or line hydrotest. An experimental investigation was undertaken to evaluate the collapse pressures of lines containing corrosion, cracks, or (CIC) defects in a typical line pipe (API 5L Grade X52, 508 mm diameter, 5.7 mm wall thickness). The mechanical properties of the pipe were measured using tensile, Charpy, and J-testing for use in applying evaluation criteria. Rupture tests were undertaken on end-capped sections containing uniform depth, finite length corrosion, cracks, or CIC defects. Failure occurred by plastic collapse and ductile tearing for the corrosion defects, cracks, and CIC geometries tested. For the corrosion defects, the corroded pipe strength (CPS) method provided the most accurate results (13% conservative on average). The API 579 (level 3 failure assessment diagram (FAD), method D) provided the least conservative collapse pressure predictions for the cracks with an average error of 20%. The CIC collapse pressures were bounded by those of a long corrosion groove (upper bound) and a long crack (lower bound), with collapse dominated by the crack when the crack depth was significant. Application of API 579 to the CIC provided collapse pressure predictions that were 18% conservative. Sixteen rupture tests were successfully completed investigating the failure behavior of longitudinally oriented corrosion, crack, and CIC. The pipe material was characterized and these properties were used to predict the collapse pressure of the defects using current methods. Existing methods for corrosion (CPS) and cracks (API 579, level 3, method D) gave conservative collapse pressure predictions. The collapse pressures for the CIC were bounded by those of a long corrosion groove and a long crack, with collapse dominated by the crack when the crack depth was significant. CIC failure behavior was determined by the crack to corrosion depth ratio, total defect depth and its profile. The results showed that the failure pressures for CIC were reduced when their equivalent depths were similar to those of corrosion and using crack evaluation techniques provided an approximate collapse pressure.
    No preview · Article · Apr 2013 · Journal of Pressure Vessel Technology
  • Duane S Cronin
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    ABSTRACT: The rate of soft tissue sprain/strain injuries to the cervical spine and associated cost continue to be significant; however, the physiological nature of this injury makes experimental tests challenging while aspects such as occupant position and musculature may contribute to significant variability in the current epidemiological data. Several theories have been proposed to identify the source of pain associated with whiplash. The goal of this study was to investigate three proposed sources of pain generation using a detailed numerical model in rear impact scenarios: distraction of the capsular ligaments; transverse nerve root compression through decrease of the intervertebral foramen space; and potential for damage to the disc based on the extent of rotation and annulus fibre strain. There was significant variability associated with experimental measures, where the range of motion data overlapped ultimate failure data. Average data values were used to evaluate the model, which was justified by the use of average mechanical properties within the model and previous studies demonstrating predicted response and failure of the tissues was comparable to average response values. The model predicted changes in dimension of the intervertebral foramen were independent of loading conditions, and were within measured physiological ranges for the impact severities considered. Disc response, measured using relative rotation between intervertebral bodies, was below values associated with catastrophic failure or avulsion but exceeded the average range of motion values. Annulus fibre strains exceeded a proposed threshold value at three levels for 10g impacts. Capsular ligament strain increased with increasing impact severity and the model predicted the potential for injury at impact severities from 4g to 15.4g, when the range of proposed distraction corresponding to sub-catastrophic failure was exceeded, in agreement with the typically reported values of 9-15g. This study used an enhanced neck finite element model with active musculature to investigate three potential sources of neck pain resulting from rear impact scenarios and identified capsular ligament strain and deformation of the disc as potential sources of neck pain in rear impact scenarios.
    No preview · Article · Feb 2013
  • S. Quellet · D.S. Cronin · J. Moulton · O.E. Petel
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    ABSTRACT: Polymeric foams including expanded polystyrene and low-density polyethylene have been used extensively in the design of military protective systems to help mitigate threats that can range from low velocity impacts to explosive events. Polymeric foams are significantly rate dependent and have very low wave speeds, which can complicate their response in specific conditions. In the present study, two polymeric foams were characterized in compression at quasi-static and high strain rates. Rates from 1 s-1 were obtained with a standard hydraulic test machine. Acrylic Hopkinson bars were used to generate compression rates on the order of 103 s-1. The two closed-cell polymeric foams investigated in this study were of similar density but with a significantly different macro-structure. Low and high strain rate testing on a relatively consistent cell-size material (low density polyethylene) demonstrated expected trends and results, while the effect of strain rate was masked for a material with high structural variability (expanded polystyrene).
    No preview · Article · Jan 2013
  • B. Bedairi · D. Cronin · A. Hosseini · A. Plumtree
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    ABSTRACT: Cracks occurring coincidentally with corrosion (Crack-in-Corrosion or CIC), represent a new hybrid defect in pipelines that are not directly addressed in the current codes or assessment methods. To understand the failure response of these defects, the finite element method using an elastic–plastic fracture mechanics approach was applied to predict the failure pressures of comparable crack, corrosion and CIC defects in 508 mm diameter pipe with 5.7 mm wall thickness. Failure pressure predictions were made based on measured tensile, Charpy impact and J testing data, and validated using experimental rupture tests. Plastic collapse was predicted for corrosion and crack defects using the critical strength based on the material tensile strength, whereas fracture was predicted using the measured J0.2 value. The model predictions were found to be conservative for the CIC defects (17.4% on average), 12.4% conservative for crack-only defects, and 3.2% conservative for corrosion defects compared to the experimental tests, demonstrating the applicability of the material-based failure criteria. For the defects considered in this study, all were predicted to fail by plastic collapse. The finite element method provided less conservative predictions than existing corrosion or crack-based analytical methods.
    No preview · Article · Aug 2012 · International Journal of Pressure Vessels and Piping
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    ABSTRACT: The cervical spine ligaments play an essential role in limiting the physiological ranges of motion in the neck; however, traumatic loading such as that experienced in automotive crash scenarios can lead to ligament damage and result in neck injury. The development of detailed neck models to evaluate the response and the potential for injury requires accurate ligament mechanical properties at relevant loading rates. The objective of this study was to measure the mechanical properties of the cervical spine ligaments, by performing tensile tests at elongation rates relevant to car crash scenarios, using younger specimens (≤50 years), in simulated in vivo conditions, and to provide a comprehensive investigation of gender and spinal level effects. The five ligaments investigated were the anterior longitudinal ligament, posterior longitudinal ligament, capsular ligament, ligamentum flavum, and interspinous ligament. Ligaments were tested in tension at quasi-static (0.5 s(-1)), medium (20 s(-1)) and high (150-250 s(-1)) strain rates. The high strain rates represented typical car crash scenarios as determined using an existing cervical spine finite element model. In total, 261 ligament tests were performed, with approximately even distribution within elongation rate, spinal level, and gender. The measured force-displacement data followed expected trends compared to previous studies. The younger ligaments investigated in this study demonstrated less scatter, and were both stiffer and stronger than comparable data from older specimens reported in previous studies. Strain rate effects were most significant, while spinal level effects were limited. Gender effects were not significant, but consistent trends were identified, with male ligaments having a higher stiffness and failure force than female ligaments.
    No preview · Article · Jun 2012
  • Jennifer A DeWit · Duane S Cronin
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    ABSTRACT: Many detailed cervical spine models have been developed and primarily used to investigate kinematic response of the neck in impact scenarios. However, the goal of detailed models is to predict both kinematic response and provide insights into injury mechanisms and thresholds through tissue-level response. The objective of this study was to verify and validate an enhanced cervical spine segment finite element model to predict tissue-level failure under four load conditions: tension, flexion, and extension using a C4-C5 segment, and compression using a C5-C6-C7 segment. Mechanical tissue test data in relevant modes of loading was used in the model, and this data was also used to model ultimate tissue failure. The predicted failure locations were representative of reported cervical spine injuries for the different modes of loading, and the predicted peak failure forces were within the reported experimental corridors. The displacement to failure of the tension simulation was lower than expected in some cases, attributed to limitations in the constitutive model. This study provided a validated approach to predict tissue-level failure for cervical spine segments, predicting the location and sequence of tissue failure, and can be applied to future full cervical spine models for the prediction of injurious loading in automotive crash scenarios.
    No preview · Article · Jun 2012