Component Level Testing Research Articles

Full-Scale Gear Tooth Bending Fatigue Tests Obtained Early in the Development of a Rotorcraft Transmission

A new gear testing method is introduced to reduce development cost and time. It allows component-level testing of individual gear meshes and new gear designs. Instrumented gear sets are tested at full load while the rest of gearbox components are still being built. Since the fatigue strength of the gears is determined earlier in the development cycle, design deficiencies are identified and understood earlier. In this new method, an individual gear mesh installed in a stiff facility housing is used to mimic the contact pattern and bending stress demonstrated by the same mesh in an actual aircraft housing. Analytical gear models are used to identify the displacement difference between the stiff test facility and the aircraft housing. The test stand is designed so it can be adjusted accurately to provide gear and pinion positions that are representative of the deflected positions under load in the aircraft housing. A spiral bevel mesh and a split torque double helical reduction stage with multiple meshes are evaluated using the developed method. The contact pattern and strain survey results of the gear meshes are correlated with predicted results.

Experimental investigation on retrofitting effects of circular steel rod damper systems on non-seismic detailed reinforced concrete frames

Existing non-seismically detailed low-rise reinforced concrete (RC) buildings are vulnerable to seismic attacks due to their insufficient seismic details including the spacing of transverse reinforcements and splice length at column critical regions. In order to mitigate those deficiencies, various retrofit strategies using externally-bonded reinforcing materials and adding external braced frames have been suggested, and adopted on the construction fields. Although various retrofit methods have been verified their retrofitting effects, there have been architectural concerns and difficulties in providing appropriate connections between supplemental structural systems and existing RC frames. One of the methods applying supplemental energy dissipating devices, this study introduces an externally retrofit method using circular steel rod dampers (CSRDs) which are installed between the existing RC frame and the external sub-frame. The existing RC frame have relatively long natural period and large displacement demand while the external sub-frame has short natural period and small displacement demand. Such relative displacement between two frames is a main mechanism acting the CSRDs. When the interaction of two frames occurs in the CSRD due to the seismic load, the load-transfer mechanism ensures stable hysteretic behaviors of the CSRD even during extreme earthquakes. To verify retrofitting effects of CSRD systems on non-seismically detailed RC frames, this study carried out component-level tests of CSRD systems and their hysteretic characteristics are investigated, especially in terms of their fatigue resistance. Then, full-scale cyclic tests are carried out with non-seismic detailed RC frames with and without CSRD systems in order to confirm the effectiveness of the introduced external retrofit method.

Radiation tests of a CubeSat OBC

Nano-satellites, which are following the CubeSat standard have established for demanding industrial and scientific applications with critical requirements on reliability and radiation tolerance. The employment of commercial off-the-shelf components enables a state-of-the-art performance but requires extensive testing to avoid and mitigate malefunctions due to the space environment. The CubeSat mission CLIMB is representative for future missions with a complex payload, a high power budget and a harsh radiation exposure. For this reason, a comprehensive irradiation study of its on-board-computer was done. The total ionizing dose damage of 50krad was evaluated at a 60Co source. As a consequence of this test, specific components were exchanged before performing single event effect studies at the synchrotron accelerator MedAustron. A board-level test revealed that the majority of effects concern the central micro controller wherefore was followed by a component-level test. Those irradiation tests make use of a pencil beam to map the device under test, which provides additional information to localize effects - by the timestamp - at the expense of an increased irradiation time compared to a homogeneous exposure. In this paper, we summarize the major findings of the test campaign and mitigation means and present a procedure for single event effect studies at medical accelerators.

Prediction of full-scale crashworthiness performance based on component-level testing: application to bus structures

The growing interest in vehicle crashworthiness necessitates efficient methods to predict full-scale crash performance from component-level testing. This study introduces a framework for predicting vehicle crashworthiness using component-level tests. The framework employs a scaling procedure incorporating factors like total energy, deformation mode, and vehicle dimensions. The feasibility of this method was validated both experimentally and numerically in a study on the rollover performance of paratransit buses, utilizing two decades of data from full-scale and component testing of six buses. Wall-to-floor connections, prone to plastic deformation during rollovers, were tested for component bending. A rollover performance index was developed as a scaling procedure, establishing a clear correlation between full-scale and component tests. Additionally, extensive finite element simulations confirmed the framework applicability to numerical simulations, demonstrating its practical use in vehicle crashworthiness evaluations to foster resource-efficient design and reduce dependence on full-scale tests.

Characterization of fracture behavior under impact-like loading conditions of elastomeric grades for high-pressure gas applications

Rapid gas decompression (RGD) is a major concern for elastomeric sealing components in cyclic gas exposure conditions as it generates cracks and can even cause total mechanical damage threatening the sealing integrity. Therefore, to analyze the fracture behavior of elastomeric grades under impact-like loading conditions, a test methodology was developed using a single edge notch in tension (SENT) specimen. To gain more insights into the behavior of differently formulated four nitrile butadiene rubber (NBR) grades (carbon black (CB) or Silica-filled, with different curing characteristics), tests were conducted at a wide range of temperatures, −20, 23, and 80 °C and under a wide range of loading rates (0.2–5 m/s). The single fracture parameters, strain energy release rate (G) at stable crack initiation and G at maximum load, as well as multiple fracture parameters from crack resistance curves (R-curves), G–Δa and crack growth rate vs crack extension curves, da/dt–Δa, were derived. All the grades showed distinct temperature and loading rate sensitivity on fracture behavior, however, the effect was more pronounced in sulfur-cured grades. Higher cross-link density, delivered a lower resistance to fracture and a uniform higher crack growth rate, conversely higher filler loading improved the fracture resistance. Within the tested conditions, the component-level instrumented tests on RGD failure revealed a similar ranking to the tested grades and it emphasizes the importance and relevance of intrinsic fracture properties. The generated information on single fracture parameters and crack growth kinetics is vital in phenomenological modeling attempts of the actual failure of components as well.

Analysis of full-scale wind and pressure measurements on a low-rise frame-supported fabric expedient aircraft hangar

The use of lightweight fabric structures as a substitute for traditional building materials, such as wood, concrete, masonry, and steel has become more commonplace. Attractive selection criteria include speed of construction as well as being an economically affordable alternative for many owners. However, lightweight fabric structures come with unique engineering considerations such as the increased vulnerability to environmental loading from wind and snow when compared to more traditional and massive (i.e., heavier) building systems. This paper examines the wind-induced response of an in-service 818 SM (8,800 sf) frame-supported fabric Large-Area Maintenance Structure monitored using a suite of structural and environmental instrumentation. Analysis of such structures is missing in the published literature. The study evaluates structural performance relative to the structural design parameters and assumptions using a combination of an in-situ monitoring study, numerical modeling, and targeted material and component-level testing that characterized accurate fundamental material properties and the behavior of key connections. The study finds a high degree of uncertainty in the longitudinal load path for the Main Wind Force Resisting System (MWFRS) due to the flexibility of the structure. Additionally, irregularly shaped structures that deviate significantly from rectangular, gable-roofed structures, wind tunnel testing or other means should be used to demonstrate that the maximum wind effects are adequately enveloped. This study also demonstrates a framework for fully remote structural monitoring systems that can provide near-continuous monitoring of the structural response of in-service structures.

Incorporating Component-Level Testing Into Bayesian Degradation Distributions to Estimate a Voltage Regulator’s Radiation Failure Probabilities

Device-level failure probabilities derived from historical, similar radiation datasets can be inputted into a system-level radiation reliability model to provide insight into that system’s failure probability. A linear voltage regulator reliability model that utilizes historical TID (<100 krad(SiO2) and DDD measurements (<9×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> equivalent 1 MeV neutrons/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) is used as a demonstration system. This methodology aims to reduce engineering uncertainty at early design stages before radiation test data is available, or on quick turn-around projects without radiation test budgets.

Transition from earth mining toward urban mining: up-cycling post-consumer scraps to produce automotive grade aluminum extrusions

Aluminum extrusions encompass a range of structural components for managing crash energy. Currently automotive grade aluminum extrusions are made from primary aluminum of high carbon footprint. This study proposes a pathway to significantly reduce carbon footprint of automotive grade aluminum extrusions via using post-consumer scrap. Guided by thermodynamics-based simulations, 0.25 wt% was set as the iron tolerance limit for aluminum AA6082 alloy extrusion. This enables a scrap utilization ratio exceeding 70% in casting, which has been demonstrated in a production trial. Extrusions made from the low-carbon AA6082 alloy has a yield strength of 316.3 ± 3.5 MPa, an ultimate tensile strength of 343.9 ± 1.9 MPa, and a tensile elongation of 13.4 ± 1.2%, all of which are comparable to those of the commercial AA6082 extrusion made from 100% primary aluminum. Component-level 3-point bending test shows that front bumper beams made from low-carbon and commercial AA6082 alloys have the same performance. These results indicate that up-cycling post-consumer aluminum scrap to produce automotive grade extrusions is a promising route to help decarbonize vehicle manufacturing process.

A material characterisation framework for assessing brickwork masonry arch bridges: From material level to component level testing

This paper aims to present a systematic framework for material characterisation to assess brickwork masonry arch bridges. An extensive laboratory campaign was carried out to characterise brickwork and backfill material in masonry arch bridges. Initially, the strength and Young’s modulus of bricks and mortar, as well as the internal friction angle and cohesion of the backfill materials (e.g., crushed limestone and puddling clay), were characterised by undertaking small-scale material level tests. Then, the compressive strength and Young’s modulus of masonry prisms, as well as unit-to-mortar bond properties (e.g., tensile strength, angle of friction and cohesion) were assessed at the component level. Further, large-scale shear box tests were carried out to identify the frictional properties, including the interface friction angle and cohesion, between the brickwork and backfill material. Moreover, both static and high-cycle fatigue three-point bending tests were performed on masonry flat arches to obtain fatigue crack growth and stiffness degradation parameters. Outputs from this experimental campaign can be used for parameter identification and model calibration of complex/high-fidelity numerical models developed to assess masonry arch bridges.

Temperature Dependence in Responses of Lithium-Ion Pouch Cells Under Mechanical Abuse

Unveiling the role of environmental temperature in the overall response of lithium-ion batteries under mechanical abuse and the underlying mechanism is necessary for comprehensively assessing crash safety of electric cars. In this study, both fresh samples and aged samples of a pouch-type battery cell are subjected to hemispherical indentation test at five different temperatures. Mechanical-electrical-thermal responses of all the cases are analyzed and compared. The mechanical response data indicate that higher temperature tends to lower the stiffness and the peak force of the cell under indentation. Component level tests focusing on tensile and compression behavior of electrodes are carried out to help understanding the dominant mechanism. Regarding electrochemical activity of electrodes, an argon-protected testing method is developed to keep the electrode samples from air exposure so as to inspect the mechanical properties as close to the in situ state as possible. Analysis on the uniform compression and hemispherical indentation of the stacked anode samples reasonably addresses the temperature dependence of the cell level mechanical response. Besides, it can be concluded that coupling effect in the mechanical behavior is almost negligible for the two factors, i.e., the environmental temperature and the aging degree, no matter at cell level or component level.

Experimental and Numerical Investigation of Prefabricated Concrete Barrier Systems Using Ultra-High-Performance Concrete

The functionality and crashworthiness of concrete barriers in bridge systems can be affected by the deterioration of the connection between bridge decks and concrete barriers. A set of details for barrier-to-deck connections for accelerated bridge construction (ABC) applications are proposed. Component-level testing was carried out on a conventional cast-in-place (CIP) detail and two versions of connections using ultra-high-performance concrete (UHPC). The use of UHPC allows for shorter development length and lap splice length for dowel bars and the material characteristics provide strength and durability to the connection. Two connection details were proposed: (1) UHPC connection within the barrier segment (U-shape connection) and (2) UHPC connection in a recess inside the bridge deck (recessed connection). Besides simplified details, the construction sequence of the proposed recessed connection is suitable for ABC applications. It is observed that the proposed U-shape connection detail is emulative of the equivalent CIP concrete barrier system. However, the recessed connection system can undergo significantly larger deflections at ultimate load compared with the CIP barrier system and exhibits a preferred mode of failure while the deck does not undergo significant damage. The results of the component testing were used to calibrate non-linear finite element models. Using validated models, numerical analyses were performed to investigate the structural performance of conventional 15 ft long barrier modules connected to the deck overhang using the recessed connection. The model was subjected to the end-loading configuration and it was found that the proposed barrier system meets the strength requirement for the corresponding test level.

Performance of coupled CLT shear walls with internal perforated steel plates as vertical joints and hold-downs

Cross-laminated timber (CLT) constitutes a promising solution for numerous structural applications, including as shear walls in lateral load resisting systems. The research presented herein investigated the viability of internal-perforated-steel-plates with self-drilling dowels as high-performance connections for CLT shear walls. To achieve this objective, quasi-static monotonic and reversed cyclic tests at the material level (dowels and steel plates), the component level (shear connections and hold-downs), and the system level (full-scale shear walls) were conducted. The component level tests demonstrated that it is possible to control the strength, stiffness, and ductility only through the yielding of the internal-perforated-steel-plates and avoid bending of the self-drilling dowels or crushing of the CLT. The full-scale shear walls achieved coupled-wall kinematic behaviour at yield and ultimate loads, enhancing the energy dissipation. The strength of the coupled wall system was governed by the capacity of the vertical joints.

Wind tunnel test of gust load alleviation for a large-scale full aircraft model

Wind tunnel test is an important way to test the performance of Gust Load Alleviation (GLA). At present, some component-level wind tunnel tests have been carried out in big aviation countries, but there is a lack of full aircraft model GLA tests. In this study, a set of large-scale GLA test system in low-speed wind tunnel is developed, which includes a gust generator, a five-degree-of-freedom suspension system, a full elastic aircraft model with control system, and gust load measuring devices. Two control schemes based on closed-loop feedback control and open-loop feed forward control are respectively designed and verified by the full-model GLA tests in the wind tunnel. The experimental results show that the designed gust generator can generate a stable wideband, wide-area gust wind field; the suspension support system can sustain static and dynamic stability during wind tunnel test, and enables the model moving in the horizontal, vertical, pitching, rolling and yawing directions. The results show that the closed-loop feedback control can obtain good control performance of reducing the peak values of elastic vibration response induced by gust excitation, but has little effect on suppressing the rigid body motion excited by low-frequency gust, while the open-loop feed forward control presents superior performance in alleviating the high-frequency elastic vibration as well as the low-frequency rigid body motion with more than 40% overall reduction rate.

Experimental and analytical study on performance of seismic sway braces for suspended piping systems

The severe damages to nonstructural components (NSCs) are frequently reported following earthquakes. Suspended piping systems are among the most common NSCs, since they are widely installed in modern buildings. As demonstrated by the failures reported after earthquakes, piping systems are often subjected to piping connection damage, or damage resulted from inadequate braces. Therefore, there is an increasing need to understand the seismic performance of widely used seismic sway braces for suspended piping systems. In the current study, a series of component-level tests were conducted to estimate the performance of seismic sway braces. The tested specimens were constructed from C-shaped square steel channel struts, vertical threaded rod, screw fastener, top connection, bottom connection, and pre-tightening bolt. The variables considered in these tests including installation distance from the floor slab to the bottom connection, the diagonal channel inclined angle, and the number of diagonal channels. The tested specimens were subjected to cyclic loading based on loading protocol suggested by FM1950. The experimental data were then utilized to develop fragility curves for seismic sway braces. In addition to the experimental tests, analytical models for seismic sway braces were developed and calibrated using the experimental data.

Accurate Modeling of Material Nonlinearities in a Wind Turbine Spar Cap

This study presents component-level testing of carbon fiber sandwich beams and the effect of carbon fiber material nonlinearity in its strain response in bending. A simple material model is presented and validated that accurately captures the carbon fiber longitudinal nonlinearity in both the tensile and compressive response. This material model is implemented in a finite element model of the BAR-DRC reference wind blade, a downwind 100-meter rotor blade, and the effects of the nonlinearity on ultimate limit states of the blade are analyzed. The material nonlinearity has negligible effect on the deflection, and material failure predictions. The buckling analysis revealed significant reductions in buckling load factor in the controlling flap direction caused by the material nonlinearity, revealing the importance of including this material model for buckling analyses of wind blade with carbon fiber reinforced spar caps.

Validation of Seismic Performance of Stainless Press-to-Connect Piping System under Cyclic Loadings

Earthquakes with magnitudes over 5.0 occurred near Gyeongju and Pohang in southern Korea in 2016 and 2017, respectively. These earthquakes had both low- and high-frequency components. Due to earthquakes with high-frequency motions, damage to nonstructural systems has been observed to be relatively more than that in structural systems. Consequently, the seismic design or performance evaluation of nonstructural components in critical facilities has emerged as a key research area in Korea. This study presents the results of experimental and numerical analyses using a high-fidelity finite element (FE) simulation in the ABAQUS platform for a press-to-connect piping system as a nonstructural component. Press-to-connect piping systems based on NFPA-13 with two elbows, a flexible coupling, and a T-joint were used. In addition, a cyclic loading protocol was applied using the KBC 2016 and IBC 2015. Based on the component-level experimental test, an FE model of the press-to-connect elbow was developed, and the high-fidelity large-scale piping system with an elbow was validated in this study. In both the experimental and analytical results, no leakage or plastic deformation of the piping system was observed under cyclic loading conditions. The results of the high-fidelity simulation model of the large-scale piping system were identical to those of the experimental test. More specifically, the error of the von-Mises stress at the upper and lower elbows was less than 9%, and the angle between the elbows was less than 2%, corresponding to the limit state of the drift ratio of the building system. Therefore, the high-fidelity simulation model of a large-scale piping system can have high application value. In addition, the design requirements and engineering demands of the piping system, such as the condition of ASME B and PV section III for service level D, were satisfied.

Residual seismic capacity of beam-column components with corroded reinforcement

Several concrete structures in tectonically active regions of the world are exposed to chloride ingress from seawater, saltwater, and other sources, making them vulnerable to corrosion-induced deterioration. Although it is well-known that corrosion-induced deterioration influences the force-displacement behaviour of corroded concrete components under cyclic loading, no adequate provisions have been incorporated into state-of-practice seismic assessment procedures to account for the influence of corrosion on the modeling parameters and acceptance criteria for concrete components. Using an extensive database of 418 material-level and 271 component-level test specimens with deformed bars, this paper presents simple formulations for evaluating the residual yield strength, ultimate strength, ultimate strain capacity, and bond strength of corroded deformed bars. Conclusions from the material-level study are then used in proposing approaches for predicting the flexural strength, shear strength and failure mode of beam-column components with corroded deformed bars. Subsequently, a simple reduction factor formulation is proposed for predicting corrosion-induced deformation capacity deterioration in corroded concrete components. The proposed reduction factor is demonstrated to be applicable to current deformation capacity formulations in ASCE/SEI 41–17 and Eurocode 8.

Experimental and numerical study of bending-induced buckling of stiffened composite plate assemblies

Despite their importance in benchmarking numerical simulations, buckling tests still feature compromises between component-level and high-fidelity large-scale tests. For example, compression-induced buckling tests cannot capture the through-thickness or span-wise stress gradients in wing skins. Consequently, the results obtained often require careful interpretation and conservative considerations before applying to a structure. Alternatively, a system-level large-scale test can be used, yet at considerably increased time and expense. There has been little progression towards capturing system-level behaviour in a simplified test. Herein, for buckling behaviour assessment, a three-point bending test is used, which is quick, simple to implement, and cost-effective compared to existing conventional methods. The proposed method relies on subjecting a panel with auxiliary stiffeners to bending to introduce compression-induced buckling in the skin. The three-point bend test is used, because it provides readily controllable loading and boundary conditions. The location of the neutral plane can be tailored via design of the stiffeners, thus allowing for control of the through-thickness stress gradient induced in the skin. This method is applicable to buckling of stiffened structures subject to bending (e.g., aircraft wingboxes). Numerical models are used to explore the limits of the proposed method and comparing it against traditional coupon and full-scale structural level tests. The test method is experimentally demonstrated for capturing the buckling behaviour of a thermoplastic composite panel made via automated fibre placement. The proposed approach is shown to reliably capture the buckling behaviour of a large-scale test using a simpler and more time and cost-efficient setup than conventional methods.

Research on Electromagnetic Susceptibility of Electronic Modules in Component-Level HEMP PCI Test

The study of electromagnetic sensitivity of electronic modules is crucial for the selection of a component-level pulse current injection (PCI) waveform, which will determine whether a component-level PCI test is equivalent to a system-level pulse illumination test of the system to which the electronic module belongs. For electromagnetic sensitivity analysis, the equivalence between the injection waveform and a typical high-altitude electromagnetic pulse (HEMP) conducted disturbance waveform in a component-level PCI test is studied. Based on an RF low noise amplifier (LNA) test board, component-level PCI tests were performed using 20 ns/500 ns double exponential wave and square-wave pulse with multiple pulse-widths. The damage threshold was analyzed and determined by using vector norm and its internal damage was observed and validated by optical microscopic analysis. The conclusions are demonstrated as follows: first, during square-wave PCI tests of RF LNA, the electromagnetic sensitive parameter action is divided into three regions by pulse-width range, called ∞-norm, 2-norm and competitive failure-dominating regions; second, the electromagnetic damage effect of the RF LNA is mainly caused by the burning of its two cascaded transistors, forming a pulse energy transmission channel with short-circuit impedance from the input port to the ground; third, the 100 ns-width square waveform can be determined as the equivalent injection waveform of a HEMP conducted waveform, and the pulse peak value of injected current is determined as the electromagnetic sensitive parameter for square-wave PCI tests of the RF LNA. The conclusions verified the feasibility of establishing the equivalence between different pulse waveforms according to the electromagnetic sensitivity analysis based on the vector norm theory and effect mechanism analysis.

Microwave absorption analysis of graphene-based hybrid nanocomposites: experimental, numerical and component level testing studies

ABSTRACT An effective nanocomposite-based microwave absorber made of polyurethane /graphene/glass/epoxy with different weight percentages of graphene (0 to 2.5 wt%) is proposed. Microstructural characterization of samples is done with the help of XRD, FESEM and TEM. Graphene crystalline structure maximum diffraction peak is observed at 26o associated interlayer d-spacing is 0.341 nm (plane 002), the same affirmed with TEM analysis. Graphene flake structure is identified from FESEM results. Firstly, experimental investigation is done using wave guide setup, later numerical model is developed using RF module in COMSOL. The experimental results reveal more than 90% absorption capability in broad bandwidth i.e., 3 GHz and maximum Reflection loss -35.9 dB is attained at 12.1 GHz. Also, maximum shielding effectiveness is -47 dB for 2.5 wt% PU/graphene composite due to its semi conduction. Further, a composite concrete block using 2.5 wt% PU/graphene is analysed using numerical model for the application of anechoic.