Journal articles: 'Load spectra'

1

Hu, Sheng, Fujie Zhou, and Tom Scullion. "Load Spectra–Incorporated Fatigue Cracking Model Implementation and Case Study." Transportation Research Record: Journal of the Transportation Research Board 2640, no. 1 (January 2017): 1–10. http://dx.doi.org/10.3141/2640-01.

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Traffic loading is one of the key factors that may cause asphalt concrete pavement fatigue cracking. Axle load spectra input provides an opportunity for evaluating the pavement response under real traffic loads throughout the pavement design life. This paper describes the methodology of incorporating axle load spectra into the mechanistic–empirical fatigue cracking model that uses a fracture mechanics method to determine crack propagation. The paper also presents the incorporation of the method into the Texas mechanistic–empirical flexible pavement design system. Several load spectra cases were studied, and the percentages of the corresponding fatigue cracking areas were predicted and compared. The comparison results confirmed the necessity of load spectra analysis. Overall, the implemented load spectra–incorporated asphalt concrete fatigue cracking model generated rational results. Further research is continuing on field validation and calibration.

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Mirosław, Rodzewicz, Głowacki Dominik, and Hajduk Jaroslaw. "Comparative Analysis of the Load Spectra Recorded During Photogrammetric Missions of Lightweight Uavs in Tailless and Conventional Configurations." Fatigue of Aircraft Structures 2022, no. 14 (December 1, 2022): 114–34. http://dx.doi.org/10.2478/fas-2022-0009.

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Abstract The purpose of this article is to present the results of the investigation regarding the differences of the load spectra of two unmanned fixed-wing aircraft performing photogrammetry missions: X-8 (flying wing) and PW-ZOOM (conventional configuration). The focus was on the analysis of a number of load cycles for various load increments within the range of the operational loads. The load spectra were determined using the acceleration signal recorded in the autopilot logs as an input. This signal was transferred to the chain of local extreme values scaled in the form of discrete load levels, and then the transfer arrays were derived with use of the rainflow counting algorithm. On this basis, the incremental load spectra were determined for each flight. These load spectra were subjected to statistical analyses to determine the load spectra representative of the flight sessions in a few ways between non-conservative (i.e., focused on average load histories) and conservative (i.e., focused on the worst load histories observed during the flight session). Finally, the fatigue life was calculated by having the structural element of the assumed fatigue properties subjected to the load spectra of both airplanes. A large (exceeding one order of magnitude) difference in the number of load cycles for larger load increments in the analyzed load spectra was shown. This difference is related to the different dynamic characteristics of the two aircraft, in particular the gust response. As a result, there is a several-fold difference in fatigue life.

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Zhao, Jingnan, Hao Wang, Pan Lu, and Jiaqi Chen. "Mechanistic–Empirical Analysis of Pavement Performance Considering Dynamic Axle Load Spectra Due to Longitudinal Unevenness." Applied Sciences 12, no. 5 (March 2, 2022): 2600. http://dx.doi.org/10.3390/app12052600.

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Pavement distresses are induced by mechanistic responses in pavement structure subjected to dynamic loads of moving vehicles. Pavement surface evenness deteriorates as pavement distresses propagate, which results in dynamic axle loads and faster pavement deterioration. It is vital to consider the dynamic axle load spectra to predict pavement deterioration using traffic-monitoring data. This study aimed to evaluate the effect of dynamic loads and overweight traffic on asphalt pavement overlay performance using mechanistic–empirical (M–E) pavement analysis. The relationship between dynamic load coefficients (DLCs), axle loads, and international roughness index (IRI) was obtained for accurate quantification of dynamic axle loads. Then the dynamic axle load spectra were derived by shifting the static axle load spectra in weigh-in-motion (WIM) data, given the DLC value. AASHTOWare Pavement ME software was used to analyze pavement performance with static and dynamic axle load spectra, and the impact of overweight traffic on asphalt pavement overlay performance. The impact of dynamic loads on reflective fatigue cracking was distinguished at an early stage of the service period and eliminated after the 10-year analysis period, when the propagation of reflective cracking reached a specific level. On the other hand, the consideration of dynamic axle loads increased the impact of overweight truck traffic on pavement distresses, and pavement structures of major highways tend to be more sensitive to overweight traffic because of greater DLC excitement at higher operational speeds.

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JOHANNESSON, P. "Extrapolation of load histories and spectra." Fatigue Fracture of Engineering Materials and Structures 29, no. 3 (March 2006): 209–17. http://dx.doi.org/10.1111/j.1460-2695.2006.00982.x.

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Wang, Yiqiang, Yazhou Jia, Jian Qiu, and Guixiang Shen. "Load spectra of CNC machine tools." Quality and Reliability Engineering International 16, no. 3 (2000): 229–34. http://dx.doi.org/10.1002/1099-1638(200005/06)16:3<229::aid-qre314>3.0.co;2-u.

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6

Kliment, Linda K., and Kamran Rokhsaz. "Comparison of the Flight Loads Spectra of Two Business Jets." Fatigue of Aircraft Structures 2014, no. 6 (June 1, 2014): 5–20. http://dx.doi.org/10.1515/fas-2014-0001.

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Abstract Operational flight loads have been analyzed from two business jets, a Global 5000 and a Global Express XRS. It is shown that both airframes were subjected to nearly the same number of ground-air-ground cycles, even though the flight times were much different. Flights have been divided into various phases, and loads and turbulence data have been categorized by altitude bands within each phase. Cumulative occurrences of incremental vertical gust load factors have been compared and shown to be comparable for the two airframes. Maneuver load factors have been shown to spread over a wider range of values for the 5000 in every phase. This has been confirmed through comparison of combined loads with those from a CRJ100 and an ERJ-145XR. Derived gust velocities, obtained from the load factors are presented in the form of exceedance spectra. These results from both aircraft are shown to agree well

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Govardhan, T., Achintya Choudhury, and Deepak Paliwal. "Load Distribution in a Rolling Element Bearing under Dynamic Radial Load." Applied Mechanics and Materials 592-594 (July 2014): 1099–103. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.1099.

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External load in a bearing is transferred from one race to another race through the rolling elements. In the present work, an investigation has been made to estimate the load on a rolling element in a bearing subjected to dynamic loading. The dynamic loading, in the present study, included harmonic and periodic loadings which are deterministic functions of time. The roller load is also investigated under random loading with known statistical values of mean and variance. Numerical values have been obtained for NJ204 bearing with known radial clearance. These results show the variation in the spectra obtained for different nature of external loadings. These results can be expected to satisfy the difference in theoretical and experimental spectra obtained by earlier researchers.

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HEULER, P., and H. KLATSCHKE. "Generation and use of standardised load spectra and load–time histories." International Journal of Fatigue 27, no. 8 (August 2005): 974–90. http://dx.doi.org/10.1016/j.ijfatigue.2004.09.012.

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9

Nagode, Marko, and Jernej Klemenc. "Modelling of load spectra containing clusters of less probable load cycles." International Journal of Fatigue 143 (February 2021): 106006. http://dx.doi.org/10.1016/j.ijfatigue.2020.106006.

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Rodzewicz, Miroslaw, and Dominik Glowacki. "Investigations into Load Spectra of UAVS Aircraft." Fatigue of Aircraft Structures 2013, no. 5 (August 21, 2014): 40–52. http://dx.doi.org/10.2478/fas-2013-0004.

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Abstract The paper contains a description of a novel approach to the load spectra estimation applied to UAVs. The authors have developed a number of tools in the LabVIEW environment enabling an in-depth analysis of flight-log data. One major achievement was the separation of the load spectra induced by steering and the load spectra induced by turbulence. The authors have shown a significant influence of both of the main load sources on the fatigue life of the UAV airframe, calculated based on the P-M hypothesis. This approach to fatigue testing of composite UAV airframes needs to take into account the rate of load variations as these may affect the fatigue life of tested structures. The paper presents several schemes of calculation algorithms and a number of well-illustrated examples of the tests and investigations results.

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Lucan, Kevin, and Bernd Bertsche. "Standard Load Spectra for Commercial Vehicle Brakes." ATZ worldwide 121, no. 5 (April 26, 2019): 72–77. http://dx.doi.org/10.1007/s38311-019-0043-1.

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12

Cerrini, Angela, P. Johannesson, and Stefano Beretta. "Superposition of Manoeuvres and Load Spectra Extrapolation." Applied Mechanics and Materials 5-6 (October 2006): 255–62. http://dx.doi.org/10.4028/www.scientific.net/amm.5-6.255.

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To face the increasing demand for long lasting, versatile and performing machines, a detailed analysis of the load conditions is required especially when structural integrity assessment has to be achieved. Usually acquisitions of load histories are shorter than the machine working life and an extrapolation of the signal for the total service life is needed. Traditional methods for load spectra extrapolation are based on conservative choices in terms of worst case scenario. Methods based on extreme value statistics have been developed. The problem addressed in this paper concerns the extrapolation of load histories on a welded boom in which different manoeuvres are superimposed. Different ways of extrapolating the load measurement have been derived, both in time domain and in Markov domain, in order to account for the superposition of bigger and more damaging cycles and smaller cycles caused by two different service operations.

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Ballo, Federico, Francesco Comolli, Massimiliano Gobbi, and Giampiero Mastinu. "Motorcycle Structural Fatigue Monitoring Using Smart Wheels." Vehicles 2, no. 4 (December 17, 2020): 648–74. http://dx.doi.org/10.3390/vehicles2040037.

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The paper is devoted to the measurement and to the processing of load spectra of forces and moments acting at the wheel hub of a motorcycle. Smart wheels (SWs) have been specifically developed for the scope. Throughout the paper, the extreme case of a race motorcycle is considered. Accurate load spectra were measured in two race circuits. Standardized load spectra are derived by processing measured data. A way to easily generalize the measured load spectra is proposed for the first time for motorcycles. Several loading conditions, related to the motorcycle straight line motion, cornering, curb hit and gear shift, are identified and extracted from the experimental measures. For each loading condition, by means of simple semi-analytical models (SAMs), a relationship is found between the vertical force on the wheel, the tilt angle of the motorcycle and the remaining forces and moments acting at the wheel hub. Such relationships are nothing else than the standardized load spectra. Additionally, a simple and efficient method based on smart wheels for real-time structural monitoring is proposed. Standardized load spectra prove to provide consistent results even when compared to real-time structural monitoring data. By means of the presented smart wheels, advanced lightweight motorcycle construction is enabled by derivation of standardized load spectra or real time estimation of the damage of structural components.

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14

Li, Jie, Chongyang Han, Weibin Wu, Ting Tang, Xiao Ran, Zefeng Zheng, and Shunli Sun. "Load Spectrum Compilation Method of Hybrid Electric Vehicle Reducers Based on Multi-Criteria Decision Making." Energies 15, no. 9 (April 30, 2022): 3293. http://dx.doi.org/10.3390/en15093293.

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This article proposes a method for compiling the load spectra of reducers for hybrid electric vehicles. Selecting typical working conditions for real vehicle data collection, the load data under each typical working condition were divided into five categories according to the state of the power source and the data were preprocessed. The optimal sample loads for compiling load spectra were obtained based on a multi-criteria decision-making method, rainflow counting for optimal sample loads was performed according to different power source output patterns, non-parametric extrapolation was performed to obtain the full-life two-dimensional load spectrum after dimensionality reduction, and a full-life eight-level programmed load spectrum that could be used for bench tests was obtained. Using the programmed load spectrum and the extracted sample load as the load input, a fatigue life prediction simulation of the reducer gear of a hybrid electric vehicle was carried out. The reducer gear fatigue life from the programmed load spectrum was compared to the gear fatigue life under actual load. The fatigue life of the reducer gear when the programmed load spectrum was used as the input was 1.412 × 103. When the actual load was used as the input load, the fatigue life of the reducer gear was 1.933 × 103. The relative error between the two is only 26%, which is in the normal range. The results show that the programmed load spectrum is effective and reliable and that the load spectrum compilation method provides a basis for accurately evaluating the reliability of the hybrid electric vehicle reducer.

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15

Zhao, Fang Wei, Ji Long Xie, and Tie Han Yi Xiao. "Damage Analysis of High-Speed Axle Press-Fit Part." Applied Mechanics and Materials 148-149 (December 2011): 437–41. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.437.

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The relation between the load and the damage on the axle press-fit part is analyzed according to the load on the axle. Abaqus is used to calculate the load-strain transfer coefficient of measured points on the axle press-fit part. The stress spectra are got by load identification. Using GoodMan equation, the equivalent stress spectra on the press-fit part are obtained. According to the equivalent stress spectra, the damage on the axle press-fit part is analyzed.

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Demjan, Ivo, and Michal Tomko. "Frequency of the Analysis Response of Reinforced Concrete Structure Subjected to Road and Rail Transport Effects." Advanced Materials Research 969 (June 2014): 182–87. http://dx.doi.org/10.4028/www.scientific.net/amr.969.182.

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A 3D model of a reinforced concrete building was created using a dynamic analysis which focused on the spectral response of the object represented by a random excitation experiment found in records in the form of load spectra.

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17

Facchinetti, Matteo Luca. "Load spectra and fatigue damage: applications to the automotive industry." MATEC Web of Conferences 165 (2018): 17008. http://dx.doi.org/10.1051/matecconf/201816517008.

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High cycle fatigue behaviour of materials is historically assessed with constant amplitude and variable amplitude loads, respectively. Thus, a long-lasting debate is extremely active in the academic community, trying to link experimental results coming from these different approaches. Overcoming all this, since the 1970s several industrial fields have been choosing to consider representative customer load spectra (in terms of amplitude, not frequency) as the best way to test both materials and structures. In particular, the automotive industry makes use of specific car loading spectra, regularly fed by the customer knowledge and practised on proving grounds. This paper presents a highlight on such spectra, neglecting any sequence effect of the load time history, thus accepting the Palmgren-Miner’s rule as an assumption. Whereas a recent communication on this very topic focused on the basic occurrence spectra, which is absolutely independent from the material properties of the car parts, here we deal with the final damage assessment. Obviously, it is worth knowing which part of the spectrum is mainly responsible for the most relevant fatigue damage.

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Lu, Naiwei, Jing Liu, Honghao Wang, Heping Yuan, and Yuan Luo. "Stochastic Propagation of Fatigue Cracks in Welded Joints of Steel Bridge Decks under Simulated Traffic Loading." Sensors 23, no. 11 (May 25, 2023): 5067. http://dx.doi.org/10.3390/s23115067.

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The fatigue cracking of orthotropic steel bridge decks (OSDs) is a difficult problem that hinders the development of steel structures. The most important reasons for the occurrence of fatigue cracking are steadily growing traffic loads and unavoidable truck overloading. Stochastic traffic loading leads to the random propagation behavior of fatigue cracks, which increases the difficulty of the fatigue life evaluations of OSDs. This study developed a computational framework for the fatigue crack propagation of OSDs under stochastic traffic loads based on traffic data and finite element methods. Stochastic traffic load models were established based on site-specific, weigh-in-motion measurements to simulate fatigue stress spectra of welded joints. The influence of the transverse loading positions of the wheel tracks on the stress intensity factor of the crack tip was investigated. The random propagation paths of the crack under stochastic traffic loads were evaluated. Both ascending and descending load spectra were considered in the traffic loading pattern. The numerical results indicated that the maximum value of KI was 568.18 (MPa·mm1/2) under the most critical transversal condition of the wheel load. However, the maximum value decreased by 66.4% under the condition of transversal moving by 450 mm. In addition, the propagation angle of the crack tip increased from 0.24° to 0.34°—an increase ratio of 42%. Under the three stochastic load spectra and the simulated wheel loading distributions, the crack propagation range was almost limited to within 10 mm. The migration effect was the most obvious under the descending load spectrum. The research results of this study can provide theoretical and technical support for the fatigue and fatigue reliability evaluation of existing steel bridge decks.

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Demjan, Ivo, and Michal Tomko. "Dynamic response of reinforced concrete building from the effects of rail transport." Selected Scientific Papers - Journal of Civil Engineering 9, no. 1 (June 1, 2014): 69–78. http://dx.doi.org/10.2478/sspjce-2014-0008.

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Abstract A 3D model of a reinforced concrete building and was created in software ANSYS. The dynamic analysis was focused on the spectral response of the object represented by a random excitation experiment found in records in the form of load spectra

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Mariscotti, Andrea. "Non-Intrusive Load Monitoring Applied to AC Railways." Energies 15, no. 11 (June 4, 2022): 4141. http://dx.doi.org/10.3390/en15114141.

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Non-intrusive load monitoring takes place in residential and industrial contexts to disaggregate and identify loads connected to a distribution grid. This work studies the applicability and effectiveness for AC railways, considering the highly dynamic behavior of rolling stock as an electric load, immersed in varying contexts of moving loads. Both voltage–current diagrams and harmonic spectra were considered for identification and extraction of features relevant to classification and clustering. Principal components were extracted, approaching the problem using principal component analysis (PCA) and partial least square regression (PLSR). Clustering methods were then discussed, verifying separability performance and applicability to the railway context, checking the performance by means of the balanced accuracy index. Based on more than one hundred measured spectra, PLSR has been confirmed with superior performance and lower complexity. Independent verification based on dispersion and correlation were used to spot relevant spectrum components to use as clustering features and confirm the PLSR outcome.

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Wei, Jin Cheng, Cheng Yu, and Shi Jie Ma. "Load Spectra Development for a Heavy Traffic Expressway." Advanced Materials Research 243-249 (May 2011): 4235–39. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4235.

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To study the traffic characteristic and axles load spectra of a heavy load expressway, WIM data was collected, axle configuration and vehicles classification was determined. The characteristic of truck traffic monthly distribution and the truck hourly distribution was studied and axle load spectra for major tuck types were developed. The results show that there were more than 30 truck types running on the expressway, the peaks of truck traffic monthly distribution was in April, September and December and the rush hour of the hourly distribution was at midnight. All major axles had a bimodal pattern of load spectra. The second peak of single axle was about 12 to 13 ton, tandem axle 14 to 22 ton and the tridem axle 28 to 32 ton. More than 50% of axles were overloading.

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Zhao, Fang Wei, Ji Long Xie, Yu Qing Yuan, and Xiao Ling Shi. "Damage Calculation and Fatigue Life Prediction for Freight Car Body." Advanced Materials Research 652-654 (January 2013): 1357–61. http://dx.doi.org/10.4028/www.scientific.net/amr.652-654.1357.

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The load of C80B gondola freight car body is analyzed in railway. Measured load spectra of fatigue key parts of the freight car body are got. According to the measured load spectra, combined with the load-strain transfer coefficient, the fatigue damage of freight car body is calculated. Then fatigue life of C80B freight car body is predicted by using fatigue cumulative damage theory.

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NOROUZI, MAHDI, and EFSTRATIOS NIKOLAIDIS. "EFFICIENT METHOD FOR RELIABILITY ASSESSMENT UNDER HIGH-CYCLE FATIGUE." International Journal of Reliability, Quality and Safety Engineering 19, no. 05 (October 2012): 1250022. http://dx.doi.org/10.1142/s0218539312500222.

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Fatigue causes about 90% of service failures in machines. Fatigue analysis involves significant randomness in the loads, material properties and geometry. Designers often use Monte Carlo simulation to estimate fatigue reliability under dynamic, random loads such as those due to ocean waves. Monte Carlo simulation is computationally expensive because it requires calculation of the stresses for thousands of simulated time histories of the loads. This paper presents and demonstrates a method to estimate efficiently the fatigue life of a structure subjected to a dynamic load, which is represented by a stationary, Gaussian random process, for many different spectra of the excitation. The method requires only one Monte Carlo simulation for one power spectral density function of the excitation.

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Timm, David H., S. Michelle Tisdale, and Rod E. Turochy. "Axle Load Spectra Characterization by Mixed Distribution Modeling." Journal of Transportation Engineering 131, no. 2 (February 2005): 83–88. http://dx.doi.org/10.1061/(asce)0733-947x(2005)131:2(83).

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Volk, Matej, Matija Fajdiga, and Marko Nagode. "Load spectra growth modelling and extrapolation with REBMIX." Structural Engineering and Mechanics 33, no. 5 (November 30, 2009): 589–604. http://dx.doi.org/10.12989/sem.2009.33.5.589.

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Rodzewicz, Mirosław. "Determination and extrapolation of the glider load spectra." Aircraft Engineering and Aerospace Technology 80, no. 5 (September 5, 2008): 487–96. http://dx.doi.org/10.1108/00022660810899856.

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Vine, John, Luther Krake, and Beau Krieg. "Helicopter Airframe Fatigue Spectra Truncation and Verification." Advanced Materials Research 891-892 (March 2014): 714–19. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.714.

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Helicopter airframe fatigue cracking is a cause of significant and growing cost of ownership and operational readiness concerns for the operators of (primarily) metallic airframe helicopters. Airframe fatigue has often had relatively low priority for helicopters, with research and design concentrated on the fatigue of flight critical rotating structural components such as rotor blades and pitch links. The Australian Defence Science and Technology Organisation (DSTO) and Naval Air Systems Command (NAVAIR) of the US Navy are collaborating to develop improved methods and technologies that can be used to assess the fatigue damage accrued by ageing helicopter airframes. The flight load sequences, or fatigue spectra, experienced by a helicopter airframe in its lifetime contain many billions of load cycles due to rotor revolutions. The application of spectra containing such vast numbers of load cycles is often impractical for reasons of test duration and cost, therefore spectra simplification techniques must be employed. To this end, truncation is a technique that is used to eliminate non-or lesser-damaging load cycles, producing spectra equivalent in terms of theoretical fatigue damage but with substantially fewer load cycles. This paper describes several truncation techniques that have recently been developed at DSTO specifically to deal with the very large numbers of load cycles that are characteristic of helicopter airframe fatigue spectra. These techniques, which include both sequence and frequency based approaches, feature tunable levels of truncation and allow for large reductions in numbers of turning points while maintaining high-fidelity and realistic fatigue spectra. Also detailed are preliminary results from a comprehensive coupon test program, which DSTO is using to experimentally verify that truncated and un-truncated spectra are approximately equivalent in terms of the fatigue damage that they produce.

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Prozzi, Jorge A., and Feng Hong. "Optimum statistical characterization of axle load spectra based on load-associated pavement damage." International Journal of Pavement Engineering 8, no. 4 (December 2007): 323–30. http://dx.doi.org/10.1080/10298430600949902.

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Kouta, R., and D. Play. "Correlation Procedures for Fatigue Life Determination." Journal of Mechanical Design 121, no. 2 (June 1, 1999): 289–96. http://dx.doi.org/10.1115/1.2829456.

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Fatigue life determination of vehicle parts requires fine definition of load spectra applied. Significant load spectra must be defined from experimental data. Then, using Gram-Charlier-Edgeworth mathematical developments, global shapes of loading distribution curves are obtained. In addition to considering the physical aspect of material fatigue behaviour, a local definition of extreme loading is introduced. Frequency analyses are linked to the distribution of amplitudes. 200 practical recordings are analysed. Equivalent load spectra are compared to S-N curves and correlations between real loading of vehicle parts in service and laboratory test loading are obtained.

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Guo, Lan Ying, Jin Cheng Wei, and Shi Ping Cui. "Study of Load Spectra of the Jaozhou Bay Expressway Based on MEPDG." Applied Mechanics and Materials 97-98 (September 2011): 402–7. http://dx.doi.org/10.4028/www.scientific.net/amm.97-98.402.

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To study the traffic characteristic and axles load spectra of Jaozhou bay expressway, WIM data was collected, axle configuration and vehicles classification was determined. The characteristic of truck traffic monthly distribution and the truck hourly distribution was studied and axle load spectra for major tuck class groups were developed. The results show that there were more than 22 truck types running on the expressway, the peaks of truck traffic monthly distribution was in December and the rush hour of the hourly distribution was at noon. All major axles had a bimodal pattern of load spectra.

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Krake, Luther. "Helicopter Airframe Fatigue Spectra Generation." Advanced Materials Research 891-892 (March 2014): 720–25. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.720.

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Helicopter airframe fatigue cracking is a cause of significant and growing cost of ownership and operational readiness concerns for the operators of (primarily) metallic airframe helicopters. Airframe fatigue has often had relatively low priority for helicopters, with research and design concentrated on the fatigue of flight critical rotating structural components such as rotor blades and pitch links. The Australian Defence Science and Technology Organisation (DSTO) and the US Naval Air Systems Command are collaborating to develop improved methods and technologies that can be used to assess the fatigue damage endured by ageing helicopter airframes. The flight load sequencesor fatigue spectraexperienced by a helicopter airframe in its lifetime contain many billions of load cycles due to rotor revolutions. Fatigue spectra developed for helicopter airframe certification tests are heavily simplified for reasons such as computational efficiency, test practicality and cost. Real airframe fatigue spectra are likely to be influenced by the modes of vibration that might be present on the airframe, the attenuation of the vibratory loading that is introduced at the main and tail rotors and the relative magnitudes and influences of both quasi-static (manoeuvre induced) and vibratory loading. To better capture such complexity, more realistic, higher fidelity fatigue spectra are required. Fatigue spectra generation involves creating realistic flight-by-flight sequences of flight conditions and assigning high-fidelity flight loads data to those sequences. This paper details DSTOs development of a novel computer-automated process which pseudo-randomly generates realistic sequences of flight conditions to match a known or assumed usage spectrum.

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Govardhan, T., and Achintya Choudhury. "Numerical Simulation and Vibration Analysis of Dynamically Loaded Bearing with Defect on Rolling Element." International Journal of Acoustics and Vibration 23, No 3, September 2018 (September 2018): 332–42. http://dx.doi.org/10.20855//ijav.2018.23.31179.

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The external loading on a rolling element bearing is often not of pure static nature but has a dynamic component associated with it. In the present study, the analysis of vibration response of rolling element bearing with localized defect on its rolling element subjected to external dynamic loading has been carried out. The dynamic component of external loading considered is either harmonic or random in nature. The defect-induced vibration signals have been processed with the FFT of their enveloped signal obtained from the Hilbert transform of band-passed signal around the resonant frequency band. Numerical results have been obtained for the NJ 204 bearing for different amplitude contributions of dynamic components of external load. For harmonic loading, the vibration spectra show additional spectral components through loading frequency as sidebands about each significant spectral components result due to static load. The experimental investigation confirms the presence of these additional components in the spectra. In the case of random loading, the noise level tends to rise with an increase in the value of standard deviation. The rise in noise level becomes so significant that some spectral components are masked by the noise for higher values of standard deviation.

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Cunagin, Wiley, Richard L. Reel, Mohammad S. Ghanim, Drew Roark, and Michael Leggett. "Generating Site-Specific Axle Load Factors for the Mechanistic–Empirical Pavement Design Guide." Transportation Research Record: Journal of the Transportation Research Board 2339, no. 1 (January 2013): 98–103. http://dx.doi.org/10.3141/2339-11.

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Use of the AASHTO DARWin-ME mechanistic–empirical pavement design software requires that truck loading data be provided in the form of normalized axle load frequency distributions (spectra). Default axle load frequency spectra are provided in the software. However, these default distributions were derived from national data and may not suit the needs of individual states. This study analyzed the Florida Department of Transportation's substantial database of truck weight data taken from its network of high-quality weigh-in-motion stations to determine whether site- or state-specific axle load spectra could be generated and how they should be applied. Several analytical procedures were developed and applied to the data, including analysis of variance and cluster analysis. The results of this work were used to develop Level 2 axle load spectra that could be applied to design sections. This paper presents detailed information about the traffic data requirements of the new guide, the process followed for deriving Florida's input values, and the resulting recommended values.

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Liu, Wen Feng, Xing Pan Fu, and Jie Ying Sui. "Probability Analyses of Response Spectra on Soft Soil Site." Advanced Materials Research 261-263 (May 2011): 1058–63. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1058.

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The analyses on the statistical probability of the response spectra have an important role in determining the earthquake demand. Elastic and inelastic spectra on acceleration of the 369 records with a long characteristic period for SDOF systems were presented in statistical analyses. The empirical probability distributions of the spectral values were derived according to the Kolmogorov-Smirnov (KS) goodness-of-fit test. And the spectra considering the probability guaranty were developed to investigate the characteristic of the response spectra. The formula for statistical average spectra of the ground motion ensemble were recommended, which were valuable for current research and code revisal. The results show:(1)the inelastic responses decrease with the increase of ductility demand μ when μ<4, and they decrease unclearly when μ≥4;(2) the inelastic spectra has a large value of Cov (coefficient of variance),the Cov range from 0.2 to 0.3 when T<1s,and it increases linearly when T≥1s;(3)the probabilistic distribution of the spectra value on acceleration is validated as the lognormal or the Gumbel type I distributions;(4) the probabilistic spectra may be a feasible way to determine earthquake load in the future.

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Mizuno, Y., and T. Mizuno. "Photon emission accompanying deformation and fracture of ice." Canadian Journal of Physics 81, no. 1-2 (January 1, 2003): 71–80. http://dx.doi.org/10.1139/p03-012.

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We observed photon emission during deformation and fracture of axially loaded polycrystalline ice. Emission of visible photons (300650 nm) was correlated with crack generation and fracture, based on time-resolved photon emission signals taken during load changes. Emission intensity, including the entire spectra ranging from 300 to 650 nm, was roughly correlated with increasing strain energy released by fracturing, while considerable scattering of the intensity data implied that emission intensity also depended on the characteristics of each individual crack. Correlation was taken between simultaneous emissions detected with two photomultiplier tubes with different ranges of spectral sensitivity. Brief, intense emissions were clearly associated with load drops, and these probably included wavelengths shorter than 320 nm, indicating that near ultraviolet light is also emitted. On the other hand, weak but continuous signals with wavelengths longer than 650 nm were emitted the entire time the ice was subjected to a load. Emission intensity and spectra may be attributed to microprocesses during fracturing. Experimental evidence for emission of visible photons indicates that the generated electric charges on crack surfaces and at crack tips have energy ranging from 2 to 6 eV. PACS No.: 46.50

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Yoon, Sae Moon, Nam Joon Cho, and Kay Kanazawa. "Analyzing Spur-Distorted Impedance Spectra for the QCM." Journal of Sensors 2009 (2009): 1–8. http://dx.doi.org/10.1155/2009/259746.

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The quartz crystal microbalance (QCM) is a sensitive device for determining the properties of materials loading it. One of the fundamental means of making these measurements is the so-called impedance (or admittance) spectra method. The resonant properties of the piezoelectric QCM sensor are measured over a spectral range in the neighborhood of a resonance, both with load and without load. The changes in the spectrum upon loading can be compared to models that describe the changes based on the mass density, the shear modulus, and the viscosity of the load. This comparison can be made with confidence so long as the spectrum corresponds to the model assumption of a single main resonance. Often, there exists a spurious resonance lying above the main resonance which is not included in the models. This can change the shape of the spectrum in ways not included in the model analysis. We describe a method we have used that separates the spur resonance from the main resonance, permitting the parameters of the main resonance to be isolated from that of the spur. These corrected parameters of the main resonance can then be used with confidence in model analyses.

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Rennert, Roland. "Measured load spectra of rail vehicle car-bodies and their application as design loads." International Journal of Fatigue 144 (March 2021): 106030. http://dx.doi.org/10.1016/j.ijfatigue.2020.106030.

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Zhang, Qing, Jian Jie Zhang, Ji He, Yong Feng Li, and Xian Rong Qin. "A Method of Dynamic Modeling of a Large Floating Crane and its External Excitations." Advanced Materials Research 139-141 (October 2010): 2440–45. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.2440.

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According to the characteristics of floating cranes, an affordable numerical method to model the floating cranes and the external excitations such as wind, wave and shimmy loads was proposed. Local coordinates modifying wind, wave and shimmy loads which are determined separately were combined in the global coordinate system according to the geometric positions. The spectra of wind loads and wave loads were converted into time domain separately according to the linear method, while a shimmy load is determined according to the Lagrange’s Equation. As an example, the external excitation caused by random wind, wave and shimmy loads on a 7500-ton giant floating crane were simulated, and the transient dynamic response was predicted and discussed. Focusing on the characteristics of structure of floating cranes, the research indicates that the dominant frequency of the wave load is low, as compared to wind and shimmy loads, and that the shimmy load is closely related to the environmental excitations such as wind and wave loads. The results also suggest that the transient response of the crane is mainly related to the shimmy load.

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CARBONI, M., A. CERRINI, P. JOHANNESSON, M. GUIDETTI, and S. BERETTA. "Load spectra analysis and reconstruction for hydraulic pump components." Fatigue & Fracture of Engineering Materials and Structures 31, no. 3-4 (March 2008): 251–61. http://dx.doi.org/10.1111/j.1460-2695.2008.01221.x.

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He, D. T., J. F. Williams, R. Ibrahim, D. Rees, and R. Jones. "Response of AL 7050—T7451 to complex load spectra." Journal of Strain Analysis for Engineering Design 29, no. 2 (April 1, 1994): 101–4. http://dx.doi.org/10.1243/03093247v292101.

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The Ramaswamy-Stouffer—Laflen constitutive model (1) has recently been extended (2) to account for the inelastic response of 7050—T7451 aluminium alloy. This paper presents the results of a combined analytical and experimental investigation into the ability of this model to predict the inelastic response to complex load spectra.

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Wilson, J. F., and J. C. Tinsley. "Vortex Load Reduction: Experiments in Optimal Helical Strake Geometry for Rigid Cylinders." Journal of Energy Resources Technology 111, no. 2 (June 1, 1989): 72–76. http://dx.doi.org/10.1115/1.3231408.

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Vortex-induced lift loads and their energy spectra were measured on laboratory-scale models of isolated, rigid, right circular cylinders subjected to steady, transverse currents. The control cylinder was smooth and the others were fitted with right-handed or left-handed, constant angle helical strakes that protruded one-tenth the cylinder diameter. For Reynolds numbers of the order of 104, the results clearly show that, compared with the smooth cylinder counterpart, the geometry that most effectively reduces both the lift coefficient and also the peaks of the lift load energy spectra in the low frequency band is three evenly spaced strakes at a 60-deg angle with the cylinder’s transverse axis.

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Rys, Dawid. "Investigation of Weigh-in-Motion Measurement Accuracy on the Basis of Steering Axle Load Spectra." Sensors 19, no. 15 (July 25, 2019): 3272. http://dx.doi.org/10.3390/s19153272.

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Weigh-in-motion systems are installed in pavements or on bridges to identify and reduce the number of overloaded vehicles and minimise their adverse effect on road infrastructure. Moreover, the collected traffic data are used to obtain axle load characteristics, which are very useful in road infrastructure design. Practical application of data from weigh-in-motion has become more common recently, which calls for adequate attention to data quality. This issue is addressed in the presented paper. The aim of the article is to investigate the accuracy of 77 operative weigh-in-motion stations by analysing steering axle load spectra. The proposed methodology and analysis enabled the identification of scale and source of errors that occur in measurements delivered from weigh-in-motion systems. For this purpose, selected factors were investigated, including the type of axle load sensor, air temperature and vehicle speed. The results of the analysis indicated the obvious effect of the axle load sensor type on the measurement results. It was noted that systematic error increases during winter, causing underestimation of axle loads by 5% to 10% for quartz piezoelectric and bending beam load sensors, respectively. A deterioration of system accuracy is also visible when vehicle speed decreases to 30 km/h. For 25% to 35% of cases, depending on the type of sensor, random error increases for lower speeds, while it remains at a constant level at higher speeds. The analysis also delivered a standard steering axle load distribution, which can have practical meaning in the improvement of weigh-in-motion accuracy and traffic data quality.

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Muhammad, Zandy O., and Paul Reynolds. "Probabilistic Multiple Pedestrian Walking Force Model including Pedestrian Inter- and Intrasubject Variabilities." Advances in Civil Engineering 2020 (January 10, 2020): 1–14. http://dx.doi.org/10.1155/2020/9093037.

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A probabilistic walking load model that accounts for inter- and intrasubject variabilities has been developed to generate synthetic vertical load waveforms induced by pedestrians. The mathematical model is based on a comprehensive database of continuously recorded pedestrian walking forces on an instrumented treadmill, having a wide range of walking frequencies. The proposed model is able to replicate temporal and spectral features of real walking forces, which is a significant advantage over conventional Fourier series models. The load model results in more realistic force time histories than previous models, since it incorporates significant components of the spectra that are omitted in Fourier series approaches. The proposed mathematical model can be implemented in vibration serviceability assessment of civil engineering structures, such as building floors and footbridges, to estimate more realistically dynamic structural responses due to people walking.

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HO, Y. B., and J. S. KUANG. "DAMAGE EVOLUTION SPECTRA FOR SEISMIC ANALYSIS OF HIGH-RISE BUILDINGS." Journal of Earthquake and Tsunami 06, no. 03 (September 2012): 1250021. http://dx.doi.org/10.1142/s1793431112500212.

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Seismic response spectra are amongst one of the most important tools for characterizing earthquake ground motions. In design practice, the response spectra are presented without including any load history, hence the nonlinear analysis of structures based solely on conventional earthquake response spectra is theoretically unsound, particularly for long-period or vertically irregular high-rise buildings. In this paper, a concept of seismic damage evolution is introduced and the method of analysis for characterizing the process of seismic damage to structures under earthquakes is presented. Seismic damage evolution spectra for analysis and design of high-rise buildings are then developed as an effective means of describing and simplifying earthquake ground motions. These spectra are shown to be very useful in selecting the ground motion-time history and, particularly, validating the equivalent static-load analysis and design of high-rise buildings under near-fault pulse-like ground motions. Case studies of the seismic inelastic performance of two vertically irregular, tall buildings are presented considering the seismic damage evolution spectra.

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Sriramula, Srinivas, Devdas Menon, and Anumolu Meher Prasad. "AXLE LOAD VARIATIONS AND VEHICLE GROWTH PROJECTION MODELS FOR SAFETY ASSESSMENT OF TRANSPORTATION STRUCTURES." TRANSPORT 22, no. 1 (March 31, 2007): 31–37. http://dx.doi.org/10.3846/16484142.2007.9638093.

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The design formulations of pavements and bridges are significantly influenced by the uncertainties associated with the prevailing vehicle weight characteristics. Accurate modelling of load spectra and the estimation of possible vehicle growth and composition are the main components in the safety assessment of transportation structures. The vehicle weights from the existing traffic form the basis for load spectra development, and the vehicle projections are subjective to the socio‐economic conditions. In this paper, the methodologies of appropriate data consideration for such representation are discussed and demonstrated based on the data from India. The load spectra are also developed for vehicular data from Interstate 95 (I‐95) in New York State. In lieu of the current status of the design codes for pavements and bridges worldwide, most of the developing countries are in need of analogous models for the calibration of the design basis.

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Rashid, Fayaz. "Analysis and Determination of Axle Load Spectra and Traffic Input for Pavement Design." International Journal for Research in Applied Science and Engineering Technology 9, no. 8 (August 31, 2021): 2536–42. http://dx.doi.org/10.22214/ijraset.2021.3761.

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Abstract: This study examines the vehicle class distribution, hourly distribution factors, weekly distribution factors, monthly distribution factors, axle load spectra for each vehicle class, and each axle of each vehicle class for the WIM station installed on the N-55 highway to aid analysis and design of new Mechanistic-Empirical Pavement Design Guide. The maximum, minimum and permissible load limit for the different vehicle class, average gross vehicle weight (GWV) and permissible load limits also being incorporated. The directional distribution for north bound and south bound traffic were observed to be almost 50% for both directions, except for 5 axle trucks which was 74% for north bound and 26% for south bound. The truck class most prevalent on the highway were identified to be 3-axle tandem truck (47.50%) and also it was observed that 94.1% of this vehicle class carried load above permissible limits. Keywords: Traffic characteristics, Load distribution factor, Axle Load Spectra.

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Ligaj, Bogdan, and Robert Sołtysiak. "Problems of Equivalent Load Amplitude in Fatigue Life Calculations." Polish Maritime Research 23, no. 1 (January 1, 2016): 85–92. http://dx.doi.org/10.1515/pomr-2016-0012.

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Abstract This paper presents issues of fatigue life calculations in operational load conditions. The assumed runs were so processed as to get a set of sinusoidal cycles by using the following methods: full cycles counting method and rainflow counting method. On the basis of such sets of cycles of the varying parameters Sm i and Sa i were prepared block load spectra of equivalent amplitudes Saz , obtained with the use of an original method of these authors, in which two-parameter fatigue characteristics were applied. The work resulted in comparison of fatigue life results for load spectra determined by using the assumed cycles counting methods and the assumed two-parameter fatigue characteristics: the model IM, model II, model III and model IV, respectively.

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MacKay, Rebecca Noel, and Paul A. Moore. "Parasites differentially impact crayfish personality in different contexts." Behaviour 158, no. 10 (June 9, 2021): 921–43. http://dx.doi.org/10.1163/1568539x-bja10101.

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Abstract The expression of an individual animal’s behaviour can be placed along many different personality spectra. Parasite load can alter animal behaviour and, thus, fitness. The personality traits of rusty crayfish, Faxonius rusticus, were analysed in three different behavioural contexts: foraging, exploration, and threatened. Each crayfish was tested in each context 3 times, giving a total of 9 assays per crayfish. After assays were completed, crayfish were dissected, and the hepatopancreas of each crayfish was photo analysed to determine the parasite load of the trematode, Microphallus spp. A composite personality score for each assay and parasite load was loaded into a PCA. The PCA model showed that as parasite load increased, crayfish became bolder in threatening contexts and less exploratory in novel environments, whether or not a food stimulus was present. Thus, parasite load alters the placement of crayfish on different personality spectra, but this change is context specific.

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Myl’nikov, V. V., D. I. Shetulov, O. B. Kondrashkin, E. A. Chernyshov, and A. I. Pronin. "Fatigue Resistance Changes of Structural Steels at Different Load Spectra." Steel in Translation 49, no. 10 (October 2019): 678–82. http://dx.doi.org/10.3103/s0967091219100097.

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Timm, David H., Julia M. Bower, and Rod E. Turochy. "Effect of Load Spectra on Mechanistic–Empirical Flexible Pavement Design." Transportation Research Record: Journal of the Transportation Research Board 1947, no. 1 (January 2006): 146–54. http://dx.doi.org/10.1177/0361198106194700114.

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Journal articles on the topic 'Load spectra'

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