The interaction between fluids and solids is becoming increasingly important in the design and analysis of machines, buildings and systems. Due to the fluid-mechanical phenomenon of turbulence and the associated flow and vortex shedding, the fluid structure interaction must be considered, for example, in aircraft wings, civil engineering (e. g. television towers or bridges), the rotor blades of wind turbines or in the field of sensor technology. Due to the increasing computing power, increasingly complex tasks can be calculated with the help of numerical simulations. In this paper, an elastic beam has been defined as test case and has been analyzed in different ways with the methods of the fluid structure interaction (FSI), i.e. with analytical and numerical approaches. For this purpose, the plastic beam has been fixed on one side in a water channel and the flow around it and the beam deflection have been measured. The deformation of the beam due to the flow load around it has been analyzed for varied flow velocities. First, the beam deformation has been estimated based on the analytical equations from structural mechanics and an assumed stagnation pressure on the beam surface. Additionally, the drag coefficient from experimental data of the literature was used to estimate the force on and the bending of the beam. Then two numerical simulations with different FSI coupling methods have been performed with Ansys Workbench 2020 R1. On the one hand, a one-way coupling analysis has been performed in which the pressure field was calculated from the CFD simulation and then transferred to the mechanical analysis. On the other hand, a two-way coupling computation has been performed, which also takes transient effects into account. For this purpose, the flow field and the pressure field have been exchanged iteratively between the fluid and the mechanical solver. This coupling approach is general and corresponds to reality since large deformations and non-linearities are considered. However, this approach always requires a very computation intensive, non-stationary calculation. The results obtained from these parameter studies have then been evaluated and compared in order to determine the accuracy of each analysis methodology. The elaborated results have been discussed and analyzed in detail.

Unreinforced 12 in. × 23 in. (305 mm × 584 mm) galvanized steel flat oval ducts were tested to measure deformations when internal static gauge pressures were applied. The experiments were performed on spiral seam non-corrugated duct. Finite element models with discrete ring seams and an average wall thickness approach were utilized to represent the continuous spiral seam, and therein predict duct deflections at prescribed locations along the duct wall. Predicted deflections from the finite element models were tabulated and compared to experimental data. Satisfactory agreement between model predictions and test data were obtained from a non-linear finite element analysis that employed a simplified average wall thickness to characterize the spiral seam and duct wall. It is straightforward to implement the average wall thickness methodology in finite element modeling of duct deformation.

The authors investigate the effect of carbon nanotubes (CNT) on the microstructure, nanomechanical properties, and fracture performance of three-phase polymer matrix composites (PMC). Two types of carbon fiber (CF)-Epoxy-CNT composites with different nanofiller distribution were studied at the nanoscale with PeakForce Quantitative Nanomechanical mapping technique (PFQNM) and macroscale with mode I fracture testing to clarify the relationship between nanofiller interphase properties and mode I fracture performance. CNT agglomerates were identified on the polished sample surface in well-dispersed and agglomerated form. AFM data showed the inhomogeneity of nanoscale local mechanical properties in CNT-rich zones. Variation in material properties is attributed to voids, CNT alignment, and changes in density of the matrix and CNT nanoparticles. A higher resolution AFM scanner and Field Emission Scanning Electron Microscopy are necessary to observe nano-scale interphase mechanical properties and CNT orientation, respectively. Mode I interlaminar fracture testing demonstrated the effectiveness of CNT nanoparticles in preventing crack-jump and fiber-bridging effects. G IC for FCNT is 0.345±0.06 N-mm/mm 2 at crack initiation, compared to 0.28±0.03 N-mm/mm 2 for the plain epoxy reference sample. CNT nanoparticles increase the energy required for interlaminar fracture by promoting crack deflection and strengthening the interphase between CF and epoxy matrix through increased interfacial surface area.

A configuration of a plain (sliding) bearing system is the use of a reinforced fabric comprising a woven structure of polytetrafluoroethylene (PTFE) and other fibers integrated with a phenolic resin system used to both encapsulate the fibrous materials and provide adhesion to metallic and other substrates. This construction promotes dimensional stability and improves thermal conductivity. These PTFE linings offer exceptionally low coefficient friction. The bushing is recommended for high loads when combined with low surface speeds. These fully self-lubricating bushings offer good contamination resistance, no stick-slip and excellent cold flow resistance. This technique has shown longer life of 7 to 10 times that of standard steel-backed, bronze-sintered and PTFE overlay. Proprietary self-lubricating PTFE fibers are applied directly to the steel. This polytetrafluoroethylene is woven onsite and applied directly to the steel. The woven liner is compressible and able to absorb distortions in mating surfaces. PTFE fabrics processed with phenolic resins can entrap air within the cured fabric liner. The entrapped air has the potential to affect bearing performance by reduction of bonding area and reduction in load carrying capabilities. Air release agents can be used to limit the amount of air entrapment within the liner system. The intent of this research is to determine what, if any, affect the addition of commercially available air release agents would have on PTFE bearing performance. Experimental wear testing at various static and dynamic bearing conditions with and without contamination (de-ice fluid), including at high temperature (325°F) were conducted on eighteen specimens. Peel strength test were also conducted. All these tests were conducted based on prevalent industry standards. Parameters of static load resistance (deflection and permanent set) and loaded torque were found to be unaffected by the use of an air release agent when compared to baseline articles manufactured without such air releasing agents. Results showed that by integration of a commercially available air release agent into the processing of a PTFE based, phenolic resin bearing liner system, one can reduce variability and help stabilize wear performance. Specimens prepared with air release agent showed improved oscillation (fatigue) test results. Further, air release agent also resulted in a 35% increase in peel strength performance when tested per industry standard methods. Contamination with de-ice fluid showed no negative performance results. While the investigations here used only one ratio of additive among all tested bearings, but other concentrations are possible. Authors would like to pursue additional studies in future to determine the amount of air release agent that can reliably be added to remove the maximum air release without affecting the overall bearing performance. By finding this, a threshold of additive can also be determined.

The deflection of a matrix crack near 0°/90° interface in a cross-ply laminate was studied numerically. In the finite element (FE) model, an initial matrix crack was introduced in the 90° layers away from the 0°/90° interface. The initial matrix crack could be initiated either at the middle of 90° layer or at one side of 0°/90° interface. The 0° layers and a part of the initial matrix crack were modeled using homogenized layer properties to simplify the model. The nonuniformly distributed fibers were modeled explicitly close to the 0°/90° interface in order to study the influence of this nonuniformity on the crack deflection process. The Energy Release Rate (ERR) of debond crack tip was calculated using Virtual Crack Closure Technique (VCCT) to study the debond growth. Maximum principal stress was then adopted to access the debond crack kinking qualitatively. It’s found that when a macro-size matrix crack forms and propagate towards ply interface, the subsequent debonding and debond cracking process in nearby intact fiber shows some distinct differences compared to the same processes at single isolated fiber without considering the interaction with nearby debonded fiber and existing matrix crack. Meanwhile, present analysis shows clear influence of microstructures on the crack deflection process by affecting the fiber/matrix debonding and debond kinking processes.

Insects steer their stingers effortlessly to a specific target and release their venom in a certain path through the skin with minimal pain. These unique traits inspire the idea to develop bioinspired needles to reduce the insertion forces and to decrease the needle path deviation (deflection) for improved targeting accuracy. Our approach in this work focus on the design of mosquito-inspired needle and evaluation of the needle performance using vibration during tissue insertion. The mosquito-inspired needle design specifically consists of maxilla-shaped and labrum-tip design. The insertion force was measured using a force sensor, which was fixed at the needle end to measure the uniaxial force of needles. The applied vibration on the needle was measured along linear axis using piezoelectric actuator with a frequency of 150 Hz and an amplitude of 5μm. The needle was inserted at a constant speed by attaching the needle to a motorized linear stage. It was observed that the insertion forces of the proposed needle design with vibration showed a reduction by 27% compared to that of a conventional needle. This reduction in insertion force means that there is decrease in tissue gel phantom damage and it was also observed that needle bending has reduced due to reduction in bending stiffness of the tissue phantom. Furthermore, the needle insertion tests in real tissues (bovine kidney) considering the proposed needle geometry and vibration will be studied in future work to understand the bioinspired needle-tissue interactions.

To probe the complexity of biological systems, large numbers of independent experiments are needed to gather statistically reliable information. A platform that performs these experiments at high-throughput demands precise control over the formation and delivery of microcapsules. Microfluidics enables passive and active modes of droplet formation, manipulation, and mixing. Aqueous- and organic-based emulsions serve as well-defined compartments that encapsulate target materials (e.g., cells, reagents, nucleic acid, and nanoparticles) in femto- to picoliter volumes surrounded by an immiscible fluid. In this work, we demonstrate a high-throughput PDMS-based microfluidic device for fabrication and control of uniform micron-size water-in-oil and oil-in-water emulsions. Passive and active modes of droplet generation (i.e., hydrodynamic flow focusing and electrospray, respectively) are utilized to form droplets in the size range of 1 to 100 μm. We also leverage dielectrophoretic forces to steer the microemulsions across flows of organic or inorganic phases. The dielectrophoretic force provides high-speed separation with no moving elements and does not require droplet charging. Two electrode designs of AC- and DC-based circuits incorporated into the PDMS block are proposed. We investigate the effect of frequency and voltage on the degree of deflection and separation efficiency of the emulsions. We show that the fabricated microcapsules can be used as templates to build synthetic lipid bilayer model membranes that more accurately mimic physiological conditions. In addition, our microfluidic-based device integrated with on-board electronics can be used as an essential component in high-speed screening bioassays.

Metal additive manufacturing has transformed the product design process by enabling the fabrication of components with complex geometries that cannot be manufactured using conventional methods. Initial designs can be further enhanced by employing topology optimization software and Design for Metal Additive Manufacturing (DFMAM) guidelines. In this study, a commercially available bicycle spider-crank was optimized for three-dimensional (3D) metal manufacturing. The 3D surface geometry of the original spider-crank was acquired using a white light scanner and used to generate a 3D solid model of the part. Boundary conditions were obtained from cycling loads found in published literature and applied to an ANSYS Finite Element Analysis (FEA) model. The FEA model was analyzed to determine the von Mises stress throughout the part. ANSYS Topology Optimization software was applied to the model. The software uses an iterative process to remove low stress material and recalculate stress within the part until no more material can be removed without exceeding a target maximum stress value. Following topology optimization, DFMAM principles were applied to enable the part to be 3D printed. Results from the FEA showed the DFMAM optimized design to be 41.5% lighter than the original design. The maximum stress increased from 41.2% of the material yield strength to 61.5% in the DFMAM optimized design, which exceeded the target optimization value of 50% yield strength. Analysis results were verified experimentally. The original design and DFMAM optimized design were printed using an EOS M 290 metal additive manufacturing machine. Parts were separated from the support structure and tested on a universal testing machine. A custom testing apparatus was designed and built to conduct the testing. Testing was performed at 15 degrees intervals throughout the range of motion. Strain gages attached to the arm of the crank were used to obtain stress values at specific locations and dial indicators were used to measure the deflection of the crank arm under load. Experimental results closely matched results obtained from the FEA, validating the model. With the model validated at specific locations, it was assumed that the stress calculated by the FEA at the critical points were also accurate. The results showed the topology optimization software to be an effective and useful tool for optimizing the design of 3D metal printed parts. However, topology optimization alone was not enough to finalize a design prior to printing. The application of DFMAM principles were needed to ensure that the overhanging structures would not collapse during printing. Because the determination of what constitutes an overhang is determined by the part orientation when printed, some modification will generally be required prior to printing. In conclusion, using a bicycle spider-crank as an example, this research has shown that the use of topology optimization software and Design for Metal Additive Manufacturing principles is able to reduce the weight of a 3D metal printed part while simultaneously achieving a maximum stress near a target value.

Drill string vibrations have resulted in an increase in non-productive time, drilling cost, and a need for drill string system optimization in the oil and gas industry. Higher vibrations can lead to washout, blow-out phenomena, and a rapid wear and tear of drill string components. An in-depth understanding of the root causes of the drill string vibrations is of utmost importance. The effects of mass imbalance, bottom hole assembly (BHA) design, weight on bit, hole angle, hole size, RPM, drilling fluid viscosity, bit and formation type on drill string vibrations have been studied in the past. The main objective of this paper is to propose a novel drill string vibration model taking into consideration the effects of axial compression load, borehole clearance, and contact force in conjunction with Euler-Bernoulli, Rayleigh, and Shear beam theories. The proposed model studies the effects of axial compression load, borehole clearance, and stiffness on the natural frequency and frequency response of drill string. The drill string is considered as a cantilever beam with a circular cross-sectional area in a horizontal drilling condition, while the fluid (water) around it is considered as a spring and dashpot model. Drill string vibrations are modeled based on a distributed system approach. The forces acting on the cantilever beam element are axial compression load, shear forces, bending moment, fluid stiffness and damping forces. A fourth order partial differential equation is derived and the solution is obtained based on the assumed modes approach to obtain the characteristic equation and mode shapes. Natural frequency is determined using the eigen values obtained from the characteristic equation. The orthogonality conditions are further derived to decouple the derived equation. The drill string is initially assumed unbounded, hence the amount of contact force required to restrict the drill string within the borehole is determined. An iterative process is employed to restrict the drill string deflection within the borehole with a corresponding increase in the stiffness of the drill string system. This will help in determining the experienced down hole contact forces and the stiffness requirements of the bottom hole assembly. Dominant frequencies are identified, compared with field results, further guiding the operator to avoid rotating the drill string at particular frequencies. A detailed study of the effects of contact forces, borehole clearances, and axial compression load will provide comprehensive guidelines in BHA design of drill string assembly. To conclude, this paper proposed an accurate model to identify dominant frequencies and provides a thorough BHA design guidelines for the drill string design manufacturers and field operators leading to a reduction in drilling cost and unproductive time, and environmentally friendly drilling operations.

Piezoelectric fans have attracted attentions in the past decades because of their low energy consumption, low noise level, light weight and reliability. A novel form of piezoelectric flapping fan is characterized experimentally and numerically. An experimental setup was built to measure the pressure and flow rate of piezoelectric fans with low static pressure at various frequencies. The fan performance curve was established. A high speed camera system was used to analyze the oscillation motion of the fan wings. The displacement of the leading edge and trailing edge of the piezoelectric fan wings are used as inputs to describe the deflection of the fan in the numerical model. The flow field obtained from the model is analyzed. The vortex shedding is observed and discussed. The pressure and flow rate obtained from the 2D numerical model are compared with the experimental results. The results provide a fundamental understanding of a piezoelectric fan with opposing oscillating wings.

This study presents the testing and numerical modeling results of composite sandwich beams. The sandwich beams are constructed from balsa wood in the core and high strength steel wire and E-glass fiber reinforced polymer composite in the facings. The testing of these beams is performed using a monotonic static four-point loading to failure in accordance with ASTM C393-00. Local strain distribution in the mid-span of the beams is obtained using strain gauges. Mid-span deflections of the beams are real-time measured using linear variable displacement transducer (LVDT). From the experimental results, flexural properties of the beams are calculated, including bending stiffness, bending strength, core shear strength, and facing modulus, core modulus, etc. The experimental results have shown that the beams have all failed in the compression zone by local buckling of the top face and shear of the core. The bottom skin does not exhibit any type of premature failure or distress. No bond failure of the composite in the tension zone is observed in any of the tested beams. Finite element modeling of the beam has been conducted using ANSYS. The mechanical properties of the skin and core material used in finite element modeling have been determined by testing of coupons. The predicted results are compared to experimental results, with a reasonable agreement.

The helicopter is an essential means of transport for numerous tasks including carrying passengers and equipment, providing air medical services, firefighting, and other military and civil tasks. While in operation, the nature of the unsteady aerodynamic environment surrounding the rotor blades gives rise to a significant amount of vibration to the helicopter. In this study, the unsteady forced response of the Bo 105 hingeless helicopter rotor blade is investigated at the forward flight in terms of the coupled flapping, lead-lag, and torsional deformations. The mathematical model for the steady-state response of the rotor blade is modified to include the unsteady airfoil behavior by using the Theodorsen’s lift deficiency function for three degrees of freedom of motion. The nonlinear mathematical model is solved by the generalized method of lines in terms of the time-varying deflections of the rotor blade. The unsteady airloads are found to create larger deformations compared to that of the steady-state condition for a given advance ratio. The azimuth locations of the peak loadings also vary with different degrees of freedom. The first three natural frequencies and mode shapes of the rotor blade are presented. The model for the forced response analysis is validated by finite element results.

Directional permeability membranes were designed, fabricated, and tested with the potential application of facilitating drug delivery. Membranes were constructed from two porous polyimide sheets with offset pores and bonded with double sided tape with thickness values of 20 or 70 μm at the perimeter. The pores ranged in diameter from 0.25 to 1.0 mm and were cut using a laser micromachining apparatus. The pores were arranged in a square array with distance of 2 mm from center to center. The membranes were tested under pressure-driven water flow in the range of 0.01–0.10 m of H 2 O and flow rates were measured for two configurations: one with the thicker sheet upstream (forward direction) and one with the thinner sheet upstream (reverse direction) and the ratio of forward/reverse flow was calculated. In order to better understand membrane behavior, the maximum deflection of the thinner sheet was measured using an imaging system composed of a lens with small depth of field, digital camera, motorized linear translation stage, and a motion controller. Results show that in forward flow, by increasing hydrostatic pressure from 0.01 to 0.10 m H 2 O the mass flow rate increased by 40–55%. Conversely, increasing the hydrostatic pressure in the reverse direction from 0.01 to 0.10 m H 2 O considerably reduces the flow rate. The ratio of forward to reverse flow rate of the membrane varied in the range of 1.5 to 9529, depending on the pressure head.

This paper investigates the construction, instrumentation, and dynamical modeling of a coupled three degrees of freedom compliant parallel arm mechanism. The compliant parallel arm, whose complete construction is carried out using 3D printing of polylactide (PLA) filaments, is a folded beam type mechanism, which is comprised of one primary and two secondary masses connected to two large deflecting beams. Dynamical model of the complete mechanism is obtained using Elastica Theory, where the large deflecting beams are considered as fixed-free cantilever beams subjected to a vertical tip load. Nonlinear load deflection curve, which is derived from the solutions of elliptical integrals, is approximated by a high-order polynomial function. Finally, the dynamics of the complete mechanism is derived using a classical lumped mass-spring-damper second order system. A linear actuator, PCB triaxial accelerometers, two laser displacement sensors and Arduino are utilized to gather acceleration and position information of each mass to identify the parameters of the lumped second order model using the offline Elastica Theory-based approach and polynomial fitting method. Numerical and experimental results verify the effectiveness of the proposed parameter identification schemes. Since system is nonlinear, state feedback linearization approach is adapted to linearize system equations at all operating points to control the trajectory of primary mass using a PID controller.

This study presents the design and development of a novel, low-cost load-deflection test setup providing the testing of flexible links and compliant mechanisms. Test bench consists of two stepper motors, lead screw, rail system, two carts, two clamps, bearings and a force sensor. Clamps are designed in a way to attach various types of compliant members such as pinned-pinned buckling beam, fixed-fixed beam and 3D printed links. Mechanism enables to calculate the stiffness of compliant and 3D printed flexible systems. Sliders are displaced quasi-statically to slowly stretch or compress the flexible members attached in between two clamps. Displacement of the carts and deflection of the midpoint of the buckling beams are captured using machine vision measurement. Force applied from one of the carts to the end of the attached link is recorded using the force sensor. Stiffness of 3D printed flexible translational vibratory mechanisms is obtained using the displacement of the carts and load deflection curve of buckling beams are obtained using deflection curve and load data. Experimental results are compared with the same simulations performed by FEA analysis.

This paper presents a numerical study of the influence of different factors on tumor detection via a 2D tactile sensor. The 2D tactile sensor entails a polydimethylsiloxane (PDMS) microstructure embedded with a 3 × 3 sensing-plate/transducer array. By pressing the sensor against a tissue region with a predefined indentation depth pattern, the tissue stiffness distribution is extracted from the measured slopes of the deflections of the sensing-plate array versus the indentation depth. In this work, we numerically investigate the influence of curved tissue surface, curved substrate and tissue viscoelasticity on the measured sensor deflection distribution, which is representative of the tissue stiffness distribution. A set of numerical models are created in COMSOL Multiphysics to investigate the influence of the above-mentioned factors separately. A purely elastic numerical model with a flat substrate and a flat tissue surface is created as the reference model. Two other numerical models are created with one having a curved surface and the other having a curved substrate. The same tumor is embedded in these three models. Given the same 2D sensor, how the measured sensor deflection distribution is affected by different curved surfaces and curved substrates is compared with the results from the reference model. The three tumor parameters (elasticity, size and depth) are also varied for their influence on the measured results. A separate viscoelastic numerical model is created to study how the time-dependent behavior of a tumor varies with its viscoelasticity. This model provides the guidance on tailoring the testing parameters in a pre-defined indentation protocol for quantitatively maximizing the difference in viscoelasticity among different tumors.

The current trend in the wind power market is to develop large diameter rotors in order to maximize the power extraction from the wind. Those rotors exhibit issues related to blade deflection and structural integrity that can be mitigated implementing design variations that were present on the early wind turbine designs, such as rotors with less than three blades located behind the tower in downwind configuration. This work assesses the aerodynamic performance of a downwind two-bladed wind turbine based on CFD simulations coupled with the Actuator Line Model (ALM). This design is compared with the MEXICO project upwind three-bladed wind turbine, for which experimental data is available. The simulations showed good agreement with measurements especially upstream the rotor and for higher inlet velocities. Furthermore, the downwind configuration was successfully modeled using ALM and the performance prediction of the turbines was physically accurate since realistic variations were obtained between the evaluated wind turbines and none of their performance coefficients exceeded Betz theoretical limit.

In our group, we are developing flexure hinge based manipulators made of nitinol for minimally invasive surgery. On the one hand, sufficient flexibility is required from flexure hinges to be able to cover the surgical workspace. On the other hand, the bending amount of the flexure hinges has to be limited below the yielding point to ensure a safe operation. As a result of these considerations, it has to be questioned how much bending angle a nitinol flexure hinge with given geometric dimensions can provide without being subject to plastic deformation. Due to the nonlinearities resulting from large deflections and the material itself, the applicability of the suggested approaches in the literature regarding compliance modeling of flexure hinges is doubtful. Therefore, a series of experiments was conducted in order to characterize the rectangular cross section nitinol flexure hinges regarding the flexibility-strength trade-off. The nitinol flexure hinge samples were fabricated by wire electrical discharge machining in varying thicknesses while keeping the length constant and in varying lengths while keeping the thickness constant. The samples were loaded and unloaded incrementally until deflections beyond visible plastic deformation occured. Each pose in loaded and unloaded states was recorded by means of a digital microscope. The deflection angles yielding to permanent set values corresponding to 0.1% strain were measured and considered as elastic limit. A quasilinear correlation between maximum elastic deflection angle and length-to-thickness ratio was identified. Based on this correlation, a minimal model was determined to be a limit for a secure design. The proposed guideline was verified by additional measurements with additional samples of random dimensions and finite element analysis.

The Hybrid-III Rail Safety (H3-RS) anthropomorphic test device (ATD), also known as a crash test dummy, was developed by the Rail Safety and Standards Board (RSSB), DeltaRail (now Resonate Group Ltd.), and the Transport Research Laboratory (TRL) in the United Kingdom between 2002 and 2005 for passenger rail safety applications [1]. The H3-RS is a modification of the standard Hybrid-III 50th percentile male (H3-50M) ATD with additional features in the chest and abdomen to increase its biofidelity and eight sensors to measure deflection. The H3-RS features bilateral (left and right) deflection sensors in the upper and lower chest and in the upper and lower abdomen; whereas, the standard H3-50M only features a single unilateral (center) deflection sensor in the chest with no deflection sensors located in the abdomen. Additional H3-RS research was performed by the Volpe National Transportation Systems Center (Volpe Center) under the direction of the U.S. Department of Transportation, Federal Railroad Administration (FRA) Office of Research, Development, and Technology. The Volpe Center contracted with TRL to conduct a series of dynamic pendulum impact tests [2]. The goal of testing the abdomen response of the H3-RS ATD was to develop data to refine an abdomen design that produces biofidelic and repeatable results under various impact conditions with respect to impactor geometry, vertical impact height, and velocity. In this study, the abdominal response of the H3-RS finite element (FE) model that TRL developed is validated using the results from pendulum impact tests [2]. Results from the pendulum impact tests and corresponding H3-RS FE simulations are compared using the longitudinal relative deflection measurements from the internal sensors in the chest and abdomen as well as the longitudinal accelerometer readings from the impactor. The abdominal response of the H3-RS FE model correlated well with the physical ATD as the impactor geometry, vertical impact height, and velocity were changed. There were limitations with lumbar positioning of the H3-RS FE model as well as the material definition for the relaxation rate of the foam in the abdomen that can be improved in future work. The main goal of validating the abdominal response of the dummy model is to enable its use in assessing injury potential in dynamic sled testing of crashworthy workstation tables, the results of which are presented in a companion paper [3]. The authors used the model of the H3-RS ATD to study the 8G sled test specified in the American Public Transportation Association (APTA) workstation table safety standard [4]. The 8G sled test is intended to simulate the longitudinal crash accleration in a severe train-to-train collision involving U.S. passenger equipment. Analyses of the dynamic sled test are useful for studying the sensitivity of the sled test to factors such as table height, table force-crush behavior, seat pitch, etc., which help to inform discussions on revisions to the test requirements eventually leading to safer seating environments for passengers.

Fixed workstation tables in passenger rail coaches can pose a potential injury hazard for passengers seated at them during an accident. Tables designed to absorb impact energy while minimizing contact forces can reduce the risk of serious injury, while helping to compartmentalize occupants during a train collision. The Rail Safety and Standards Board (RSSB) in the U.K. issued safety requirement GM/RT2100, Issue 5 [1] and the American Public Transportation Association (APTA) in the U.S. issued safety standard APTA PR-CS-S-018-13, Rev. 1 [2] with the goals of setting design and performance requirements for energy-absorbing workstation tables. The U.S. Department of Transportation, Federal Railroad Administration (FRA) Office of Research, Development and Technology directed the Volpe National Transportation Systems Center (Volpe Center) to evaluate the performance of the Hybrid-III Rail Safety (H3-RS) anthropomorphic test device (ATD), also known as a test dummy, in the APTA sled test in order to incorporate a reference to the H3-RS in the safety standard. The Volpe Center contracted with the manufacturer of the H3-RS, Transport Research Laboratory (TRL), in the U.K. to conduct a series of sled tests [3] with energy-absorbing tables, donated by various table manufacturers. The tables were either already compliant with the RSSB table standard or were being developed to comply with the APTA table standard. The sled test specified in Option A of the APTA table standard involves the use of two different 50th percentile male frontal impact ATDs. The H3-RS and the standard Hybrid-III (H3-50M) ATDs performed as expected. The H3-RS, which features bilateral deflection sensors in the chest and abdomen, was able to measure abdomen deflections while the H3-50M, which features a single sensor measuring chest compression, was not equipped to measure abdomen deflection. This study attempts to validate a finite element (FE) model of the APTA 8G sled test with respect to the thorax response of the H3-RS and H3-50M. The model uses a simplified rigid body-spring representation of one of the energy absorbing tables tested by TRL. The FE models of the H3-RS ATD and the H3-50M ATD were provided by TRL and LSTC, respectively. Results from the sled tests and FE simulations are compared using data obtained from the chest accelerometer, the chest and abdomen deflection sensors, and the femur load cells. Using video analysis, the gross motion of the dummies and table are also compared. Technical challenges related to model validation of the 8G sled test are also discussed. This study builds on previous analyses conducted to validate the abdomen response of the H3-RS FE model, which are presented in a companion paper [4].