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1
Rehacek, Stanislav, Petr Hunka, David Citek, Jiri Kolisko i Ivo Simunek. "Impact Testing of Concrete Using a Drop-Weight Impact Machine". Advanced Materials Research 1106 (czerwiec 2015): 225–28. http://dx.doi.org/10.4028/www.scientific.net/amr.1106.225.
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Fibre-reinforced composite materials are becoming important in many areas of technological application. In addition to the static load, such structures may be stressed with short-term dynamic loads or even dynamic impact loads during their lifespan. Impact loading of structural components produces a complex process, where both the characteristics of the design itself and the material parameters influence the resultant behavior. It is clear that fibre reinforced concrete has a positive impact on increasing of the resistance to impact loads. Results of two different impact load tests carried out on drop-weight test machine are presented in this report.
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Komarov, A. A. "The Specific Characteristics of Shock and Blast Impacts on Construction Sites". Occupational Safety in Industry, nr 9 (wrzesień 2021): 81–88. http://dx.doi.org/10.24000/0409-2961-2021-9-81-88.
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The practices of hazardous and unique facilities’ construction imply that specific attention is paid to the issues of safety. Threats associated with crash impacts caused by moving cars or planes are considered. To ensure safety of these construction sites it is required to know the potential dynamic loads and their destructive capacity. This article considers the methodology of reducing dynamic loads associated with impacts caused by moving collapsing solids and blast loads to equivalent static loads. It is demonstrated that practically used methods of reduction of dynamic loads to static loads are based in schematization only of the positive phase of a dynamic load in a triangle forms are not always correct and true. The historical roots of this approach which is not correct nowadays are shown; such approach considered a detonation explosion as a source of dynamic load, including TNT and even a nuclear weapon. Application of the existing practices of reduction of dynamic load to static load for accidental explosions in the atmosphere that occur in deflagration mode with a significant vacuumization phase may cause crucial distortion of predicted loads for the construction sites. This circumstance may become a matter of specific importance at calculations of potential hazard of impacts and explosions in unique units — for instance, in the nuclear plants. The article considers a situation with a plane crash, the building structure load parameters generated at the impact caused by a plane impact and the following deflagration explosion of fuel vapors are determined.
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Řeháček, Stanislav, Petr Huňka, David Čítek, Jiří Kolísko i Ivo Simunek. "Impact Resistance of Fibre-Reinforced Concrete". Advanced Materials Research 1054 (październik 2014): 48–53. http://dx.doi.org/10.4028/www.scientific.net/amr.1054.48.
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Fibre-reinforced composite materials are becoming important in many areas of technological application. In addition to the static load, such structures may be stressed with short-term dynamic loads or even dynamic impact loads during their lifespan. Impact loading of construction components produces a complex process, where both the characteristics of the design itself and the material parameters influence the resultant behavior. It is clear that reinforced concrete with fibers has a positive impact on increasing of the resistance to impact loads. Results of two different impact load tests carried out on drop-weight test machine are presented in this report.
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Řeháček, Stanislav, Petr Huňka, David Čítek, Jiří Kolísko i Ivo Šimúnek. "Impact Resistance of Thin-Walled Shell Structures". Applied Mechanics and Materials 617 (sierpień 2014): 96–99. http://dx.doi.org/10.4028/www.scientific.net/amm.617.96.
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Fibre-reinforced composite materials are becoming important in many areas of technological application. In addition to the static load, such structures may be stressed with short-term dynamic loads or even dynamic impact loads during their lifespan. Dynamic effects can be significant especially for thin-walled shell structures and barrier constructions. Impact loading of construction components produces a complex process, where both the characteristics of the design itself and the material parameters influence the resultant behavior. It is clear that reinforced concrete with fibers has a positive impact on increasing the resistance to impact loads. Results of impact load tests carried out on drop-weight test machine are presented in this paper. The results are supplemented by compression strength test.
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Zhao, Jingnan, Hao Wang, Pan Lu i Jiaqi Chen. "Mechanistic–Empirical Analysis of Pavement Performance Considering Dynamic Axle Load Spectra Due to Longitudinal Unevenness". Applied Sciences 12, nr 5 (2.03.2022): 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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Fan, Wenbing, Junwen Zhang, Yang Yang, Yang Zhang, Xukai Dong i Yulong Xing. "Study on the Mechanical Behavior and Constitutive Model of Layered Sandstone under Triaxial Dynamic Loading". Mathematics 11, nr 8 (21.04.2023): 1959. http://dx.doi.org/10.3390/math11081959.
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In construction engineering, rock is an important building material. During the construction process, layered rock masses are typically subjected to varying dynamic load disturbances under triaxial loads. It is thus essential to investigate the mechanical response of layered rocks under various disturbances of the triaxial loads. By using a three-dimensional SHPB, triaxial dynamic compression tests with various impact dynamic load disturbances and identical triaxial static loads were carried out on sandstones with differing bedding angles. The impact pressures were 0.8, 1.2, and 1.6 MPa, and the bedding angles were 0°, 30°, 45°, 60°, and 90°. The results showed that the ductility of the sandstone considerably increased under triaxial static loading. With the increasing bedding angle, the sandstone’s dynamic strength and coupling strength first declined and subsequently rose. As the impact pressure increased, the reflective energy ratio, peak strain, and dynamic growth factor of the sandstone essentially rose progressively. The bedding angles and dynamic loads had a major impact on the damage pattern of the layered sandstones. Additionally, a constitutive model considering bedding angle, dynamic load, and static load was established and verified. The constitutive model was able to accurately characterize the dynamic behavior of the rock under load disturbances.
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Sterndorff, M. J., J. Waegter i C. Eilersen. "Design of Fixed Offshore Platforms to Dynamic Ship Impact Loads". Journal of Offshore Mechanics and Arctic Engineering 114, nr 3 (1.08.1992): 146–53. http://dx.doi.org/10.1115/1.2919966.
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A ship impact is a dynamic phenomenon and the dynamic global load effects can be significant, especially for small platforms where dynamic loads from the ship impact can be larger than the extreme environmental loads and the ship impact can govern the design of the platform. This paper describes a detailed procedure for dynamic analysis of fixed offshore platforms exposed to ship impacts. The procedure includes: • a consistent description of the motion of the vessel and dynamic interaction with the platform during the impact; • a realistic description of the global dynamic behavior of the platform during the impact; • detailed calculation of the transient hydrodynamic pressure forces acting on the vessel during the impact; and • a realistic description of the local deformation zone at the point of impact. The equations of motion for the vessel and the platform are solved simultaneously in the time domain, and the overall dynamic loads acting on the platform during the impact are determined by means of the modal superposition principle. The procedure has been applied for the design and subsequent risk analysis of three small tripod tower-type platforms to impacts from drifting supply vessels. The effect of the number of mode shapes used for representation of the dynamic behavior of the platforms, and the influence of the transient hydrodynamic pressure forces have been investigated. Critical velocity tables for different impact situations have been developed. For nearly all the situations investigated, the critical collapse criterion was overturning of the platform due to pull-out of piles in tension.
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Řeháček, Stanislav, Petr Huňka, David Čítek i Ivo Šimúnek. "Impact Resistance of Steel Fibre Reinforced Thin-Walled Shell Structures". Advanced Materials Research 1000 (sierpień 2014): 203–6. http://dx.doi.org/10.4028/www.scientific.net/amr.1000.203.
Pełny tekst źródłaStreszczenie:
Fibre-reinforced composite materials are becoming important in many areas of technological application. In addition to the static load, such structures may be stressed with short-term dynamic loads or even dynamic impact loads during their lifespan. Dynamic effects can be significant especially for thin-walled shell structures and barrier constructions. Impact loading of construction components produces a complex process, where both the characteristics of the design itself and the material parameters influence the resultant behavior. It is clear that reinforced concrete with fibers has a positive impact on increasing the resistance to impact loads. Results of impact load tests carried out on drop-weight test machine are presented in this paper. The results are supplemented by static modulus of elasticity.
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Lysmer, J., P. Arnold, M. Jakub i N. J. Krutzik. "Dynamic behaviour of tunnels under impact loads". Nuclear Engineering and Design 85, nr 1 (luty 1985): 65–69. http://dx.doi.org/10.1016/0029-5493(85)90272-9.
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Zhou, Ruihe, Hua Cheng, Haibing Cai, Xiaojian Wang, Longhui Guo i Xianwen Huang. "Dynamic Characteristics and Damage Constitutive Model of Mudstone under Impact Loading". Materials 15, nr 3 (31.01.2022): 1128. http://dx.doi.org/10.3390/ma15031128.
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The mechanical response characteristics of mudstone from the ingate roadway of the west ventilation shaft in Yuandian No. 2 coal mine, Huaibei City, Anhui Province, China to dynamic loads were quantified in single- and cyclic-impact compression tests, using the split-Hopkinson pressure bar test device. The dynamic stress–strain relationships and the failure characteristics of mudstone samples under different impact loads were analyzed systematically. Considering the “rate effect” of the mudstone dynamic strength, the dynamic strength criterion of mudstone was proposed, and the dynamic damage constitutive model of mudstone was established, based on the statistical damage theory. In response to single-impact loads, with increasing impact pressure, the mudstone peak stress and strain gradually increased, and the peak stress and average strain rate increased nonlinearly. In response to cyclic-impact loads, with an increasing number of impacts, the mudstone peak stress first increased and then decreased, and the peak strain increased gradually. With increasing impact pressure, the number of impacts to the samples’ failure decreased gradually. By parameter identification and comparative analysis of the test results, the proposed dynamic damage constitutive model of mudstone was validated. The model can be used for stability analysis of roadway-surrounding rock under dynamic loads.
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Dapeng, Zhu, Qin Liangkai i Lin Yundian. "Analytical Study on Dynamic Response of Deep Foundation Pit Support Structure under the Action of Subway Train Vibration Load: A Case Study of Deep Foundation Pit of the New Museum Near Metro Line 2 in Chengdu, China". Shock and Vibration 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/535196.
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Presently, foundation pit support structures are generally regarded as the temporary structures and the impact of vibration loads is often overlooked. As opposed to static and seismic loads, the vibration loads of subway trains are a type of cyclic load with a relatively long duration of action and a definite cycle; it is of great importance for the design of foundation pit support structures to correctly evaluate the impact of subway train vibrations on deep foundation pit and support works. In this paper, a dynamic three-dimensional numerical model is built that considers the vibration load of subway trains on the basis of the static numerical model for deep foundation pit support structures and simplified train loads to study the impact of train vibrations on deep foundation pit and permanent support structures. Studies have shown that the dynamic response of surface displacement mainly occurs in the early period of dynamic load, the vibration load of subway trains has little impact on ground subsidence, the support pile structure is in an elastic state during dynamic response under the action of subway train vibrations, and the action of train vibration loads is inimical to the safety of foundation pit support structures and should be closely studied.
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Nguyen, Xuan Toan, Cong Thuat Dang, Thi Kim Loan Nguyen, Duy Thao Nguyen i Van Duc Tran. "Analysis of dynamic response of three-span bridge using vehicle load data from Road Administration Department IV in Vietnam". IOP Conference Series: Materials Science and Engineering 1289, nr 1 (1.08.2023): 012001. http://dx.doi.org/10.1088/1757-899x/1289/1/012001.
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Abstract In many studies, the dynamic response of bridges is influenced by various factors. Multiple factors, such as vehicle loads, road roughness, vehicle-bridge interactions, and travel speed, impact the dynamics of a three-span bridge on highways. Because the mass of the vehicle, including the cargo, fluctuates randomly, a probabilistic methodology based on the Monte Carlo method is utilized to produce random anomalies for dynamic analysis. To examine the Song Gieng bridge, data from the Road Administration Department IV on heavy vehicle loads and overloaded vehicles are utilized to produce random vehicle loads. The analytical results indicate that there is a discrepancy in the probability distribution rules between the vehicle load (input random variable) and the dynamic impact factor (output random variable). This implies that their mapping connection is not monotone. Compared with the threshold values specified in the bridge design standards of Vietnam and the United States, the dynamic impact factor obtained in this study is significantly different. These findings can provide additional guidance for practicing engineers.
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Kulikov, Vladimir, Olga Stafeeva i Magomed Magomedov. "MODELING OF THE INFLUENCE OF THE LOCATION OF STIFFNESS CORES ON THE DEFORMATIVE BEHAVIOR OF BUILDINGS UNDER DYNAMIC INFLUENCES". Construction and Architecture 10, nr 1 (20.03.2022): 46–50. http://dx.doi.org/10.29039/2308-0191-2021-10-1-46-50.
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It is known that buildings and structures oscillate from wind, earthquakes, and the operation of various machines and equipment. The dynamics of the behavior of a residential building is considered from the point of view of developing principles and methods for calculating structures for the impact of various dynamic loads in order to ensure their bearing capacity under the combined impact of static and dynamic loads, as well as limiting the level of vibrations to exclude the harmful effects of vibrations on people and on technological processes. The article analyzes the wind impact on a 25-storey building, considers the parameters of regional and local winds, considers the main aspects of determining wind loads on buildings and structures. The nature of the wind load is investigated, as well as methods of its calculation. the task of further development of the method of calculating wind impact using computer modeling is envisaged.
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MIMURA, K., T. UMEDA, M. YU, Y. UCHIDA i H. YAKA. "EFFECTS OF IMPACT VELOCITY AND SLENDERNESS RATIO ON DYNAMIC BUCKLING LOAD FOR LONG COLUMNS". International Journal of Modern Physics B 22, nr 31n32 (30.12.2008): 5596–602. http://dx.doi.org/10.1142/s0217979208050875.
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In this research, the buckling behavior of long columns under dynamic load was investigated both experimentally and numerically, and an effective buckling criterion for dynamic load was derived from the results in terms of the impact velocity and the slenderness ratio. In the experiments, a free fall drop-weight type impact testing machine was employed. The dynamic buckling loads were measured by the load sensing block, and the displacements were measured by a high speed magnetic-resistance device. In the numerical analyses, dynamic FEM code 'MSC-Dytran' was used to simulate the typical experimental results, and the validity and the accuracy of the simulations were checked. The dynamic buckling loads at various impact velocities were then systematically investigated. From both experimental and simulated results, it was found that the dynamic to static buckling load ratios can be successfully described as a square function of the slenderness ratio of the columns, while they can be also described by a power law of the applied impact velocity.
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Zheng, Qiangqiang, Hao Hu, Anying Yuan, Mengyao Li, Haibo Wang, Mengxiang Wang, Qi Zong i Shouyang Zhang. "Impact Dynamic Properties and Energy Evolution of Damaged Sandstone Based on Cyclic Loading Threshold". Shock and Vibration 2020 (27.11.2020): 1–12. http://dx.doi.org/10.1155/2020/6615602.
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Rocks in deep coal mines are usually in varying degrees of damage state before they are destabilized by impact loads such as rock bursts. For the problem of the mechanical properties and energy evolution of damaged rocks under impact loads, the authors use static loads with different cyclic load thresholds to act on sandstone specimens to make them in distinct degrees of damage. Then, the rock mechanics system (MTS-816) and the Split Hopkinson pressure bar (SHPB) are employed to perform uniaxial compression and impact dynamics tests on sandstones with different degrees of damage. The results show that, from the perspective of mechanical properties, the uniaxial compressive strength and dynamic compressive strength of the damaged sandstone gradually decrease with the increase of the upper limit of the cycle threshold and both obey the growth law of the quadratic function, and the dynamic strength increase factor (DIF) also decreases with the increase of the cyclic load threshold. In terms of energy, with the increment of the cyclic load threshold, the number of cracks in the damaged sandstone is large and the scale is enormous. Due to the effect of cracks, when the incident energy is a fixed value, the transmission energy decreases with the increase of the damage degree and the change law of the reflection energy is the opposite. The systematic study of the dynamic mechanical properties and energy evolution law of the damaged sandstone provides some reference for the prevention and mechanism research of rock bursts.
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Cruz, Daniel Magalhães da, Antonio Henrique Monteiro da Fonseca Thomé da Silva, Fernanda Mazuco Clain i Carlos Eduardo Marcos Guilherme. "Experimental study on the behavior of polyamide multifilament subject to impact loads under different soaking conditions". Engineering Solid Mechanics 11, nr 1 (2023): 23–34. http://dx.doi.org/10.5267/j.esm.2022.11.001.
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This article studies the mechanical characterization of impact loads on polyamide fibers. Using synthetic ropes in mooring systems, these are subject to static loads, but dynamic loads are also expected. One of the dynamic loads that can occur on cables are sudden loads, which makes the analysis of impact loads important. In this study, impact cycles were applied to polyamide multifilaments until rupture with different impact masses, and considering the conditions: dry, after 6 hours of immersion in water and after 24 hours of immersion in water. The analysis of the immersed conditions allows us to interpret the plasticizing effect that moisture exerts in polyamide, through loss stiffness in the rupture test. The results show that the increase in immersion time represents decrease in the breaking strength, and also in the resistance to impact cycles. A curve parameterization is proposed that relates the number of impact cycles and the percentage of Yarn Break Load used in the impact, getting through the coefficient of determination the best model. For force versus time graphs, obtained in each impact cycle, the energy dissipation in the multifilament can be observed in two main mechanisms: the first is the elastic deformation in form of ricochets, the second is the plastic deformation by stretching/elongation. The force-time graphs of impact cycles and the number of impact cycles to failure are measures that show performance for impact dynamic loads. Attention should be the plasticizing effect caused by water, as it reduces the static and dynamic mechanical strength of polyamide.
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MIMURA, Koji. "Instability of Structures under Dynamic and Impact Loads". Proceedings of Conference of Kansai Branch 2013.88 (2013): _3–11_—_3–14_. http://dx.doi.org/10.1299/jsmekansai.2013.88._3-11_.
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Mousseau, R., i G. Markale. "Obstacle Impact Simulation of an ATV Using an Efficient Tire Model". Tire Science and Technology 31, nr 4 (1.10.2003): 248–69. http://dx.doi.org/10.2346/1.2135271.
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Abstract When a vehicle travels over a large obstacle at a significant speed, dynamic loads are created that are severe enough to cause damage to its components. Prediction of these impact loads early in the design can greatly aid the vehicle development process. Thus, automobile manufactures have devoted considerable effort developing computer models to simulate durability events. An important part of any durability simulation is the tire model. This paper focuses on the problem of efficiently predicting dynamic loads that occur when an all terrain vehicle (ATV) impacts obstacle impact. An ATV simulation model that uses an efficient and simple tire model to represent the enveloping behavior and dynamic response was developed with the AUTOSIM multibody dynamics program. This program, using Kane's Method and symbolic algebra to automatically generate fully parametric simulations that are both efficient and easy to use, was used to model both the tire and ATV rigid body dynamics. This paper describes the combined ATV multi-body vehicle dynamics and tire simulation. To demonstrate the effectiveness of tire simulation, results from the efficient tire model isolated from the vehicle are compared to output from a nonlinear finite element model. Also, the paper compares results from the full vehicle ATV simulation and a field test.
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Si, Liang, Yijun Cao i Guixia Fan. "Breakage Characterization of Magnetite under Impact Loads and Cyclic Impact Loading". Energies 13, nr 20 (19.10.2020): 5459. http://dx.doi.org/10.3390/en13205459.
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A series of impact compression tests were conducted to study the breakage characteristics of magnetite, as well as the impact pressure on its strain rate and dynamic compressive strength. The dynamic mechanical properties and fragmentation size distribution of magnetite under diverse impact loads and cyclic impact were investigated, with fractal theory as a basis and split Hopkinson pressure bar (SHPB). Breakage methods were also employed to analyze the fracture morphology of magnetite. According to the result, the fractal dimension can reflect the distribution of fragments in various sizes. If the strain rate increases, the fractal dimension will be larger, the fragment size will be finer, and the fragmentation degree will be more influential. A micro-analysis of SEM images demonstrates that the fracture morphology is determined by mineral properties. Under low load cyclic impact, intergranular fracture is the main fractography. Besides, the intergranular fracture will be changed to a transgranular one as the impact load increases.
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Lee, Youngmyung, i Gyung-Jin Park. "Non-linear dynamic response structural optimization for frontal-impact and side-impact crash tests". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 231, nr 5 (18.07.2016): 600–614. http://dx.doi.org/10.1177/0954407016658146.
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Vehicle crash optimization is a representative non-linear dynamic response structural optimization that utilizes highly non-linear vehicle crash analysis in the time domain. In the automobile industries, crash optimization is employed to enhance the crashworthiness characteristics. The equivalent-static-loads method has been developed for such non-linear dynamic response structural optimization. The equivalent static loads are the static loads that generate the same displacement field in linear static analysis as those of non-linear dynamic analysis at a certain time step, and the equivalent static loads are imposed as external loads in linear static structural optimization. In this research, the conventional equivalent-static-loads method is expanded to the crash management system with regard to the frontal-impact test and a full-scale vehicle for a side-impact crash test. Crash analysis frequently considers unsupported systems which do not have boundary conditions and where adjacent structures do not penetrate owing to contact. Since the equivalent-static-loads method uses linear static response structural optimization, boundary conditions are required, and the impenetrability condition cannot be directly considered. To overcome the difficulties, a problem without boundary conditions is solved by using the inertia relief method. Thus, relative displacements with respect to a certain reference point are used in linear static response optimization. The impenetrability condition in non-linear analysis is transformed to the impenetrability constraints in linear static response optimization.
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Ahmed, B. A., i A. H. Rasheed. "Experimental Analysis of the Dynamic Response of Saturated Clayey Soil Under Impact Loading". Engineering, Technology & Applied Science Research 12, nr 6 (1.12.2022): 9787–94. http://dx.doi.org/10.48084/etasr.5388.
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The impact of loads on machine foundations is a typical cause of vibrations in industrial applications. Typically, these foundations will transfer vertical dynamic loads to the surface, which will result in earth vibrations that may cause structural damage to nearby structures. Dynamic impacts can vary from significant failure of sensitive sensors or systems to evident structural damage. The current work investigates the behavior of saturated clay soil under a single impulsive load. Deflectometry via falling weights was conducted to produce single pulse energy by dropping different weights from various elevations. The reactions of soils at various places were investigated (vertical displacement at topsoil surface). Such reactions consist of displacements, velocities, and accelerations caused by the impact occurring at the surface depth. The maximum displacement reaction of stiff soil was reduced by 80% in comparison with soft soil under the same impact load. The average percentage of change for stiff soil was 49% larger than for soft soil, as a result of kinetic energy caused by an increased contact surface. Maximum displacements increased with increasing operational frequency and dynamic load.
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Stojic, Dragoslav, i Stefan Conic. "Structural vehicle impact loading". Facta universitatis - series: Architecture and Civil Engineering 11, nr 3 (2013): 285–92. http://dx.doi.org/10.2298/fuace1303285s.
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In contemporary design, vehicle impact into the structures is paid great attention since they can be dominant, depending on the type of structure. The key issue in the vehicle impact analysis is the proper determination of intensity and way of action of dynamic forces on the structural element and its behavior after the imparted load. The Eurocodes, in the annexes provide recommendations for determination of force intensity depending on mass and velocity of the colliding vehicle. Equivalent static loads causing approximate effects on the structural elements are used as quite approximate and efficient methods. The paper comprises the analysis of deformation of columns having the same characteristics, exposed to impact loads via the equivalent static loads, depending on the stress state in columns, and a comparative analysis has been done.
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Akira AIKAWA. "Determination of dynamic ballast characteristics under transient impact loading". Electronic Journal of Structural Engineering 13, nr 1 (1.01.2013): 17–34. http://dx.doi.org/10.56748/ejse.131581.
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Train-related impact loads acting on a sleeper bottom were directly measured and spectral analysis was performed to determine the dynamic characteristics of ballast layer under traffic impact loads. The results indicate that broadband vibration components act on the ballast layer, which exhibits two different types of behavior depending on dynamic stiffness characteristics. For vibration components over 100 Hz, the layer has high rigidity, resists dynamic loading sufficiently and absorbs impact loading adequately. However, in the low-frequency range, it easily deforms and is hard to absorb load components. FE vibration analysis of ballast aggregate was also performed to examine related characteristics. The mechanisms by which wave propagation velocity inside a ballast layer is reduced and wave motion inside it is greatly reduced were numerically simulated using only elastic body analysis without consideration of material nonlinearity.
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Iurii, Geller, i Belkina Olga. "Studying the possibility of controlling the dynamic state of an impact ripper". Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal, nr 2 (20.04.2022): 19–26. http://dx.doi.org/10.21440/0536-1028-2022-2-19-26.
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Introduction. Vibratory and impact loads transferred to the operator workplace limit the efficiency enhancement of rock or firm ground preparatory destruction by impact ripping equipment. One way to reduce the dynamic load transfer to the base machine and the operator is to include additional links into the implement kinematic chain, which redistribute dynamic loads to the zone of rock mass destruction. Methods of research are based on an integrated and systematic approach to the object of study as a multi-mass system, the state of which depends on the physical and mechanical properties of the medium, technological and structural factors affecting the energy efficiency of the mining and earthworks process. The research focuses on analyses of the effect the additional links parameters have on dynamic loads redistribution to the zone of rock or firm ground destruction. The research focus is conditioned by the need to develop structural solutions for the work equipment that controls the dynamic state of technological systems. When the constructive modernization solutions are completely exhausted, the need to improve the existing equipment and develop the fleet for special mining and earthworks necessitate such studies. Results. Removing the impact tool beyond the limits of the attachment point on the base machine is considered as one of the possible ways to protect the base machine and the operator from vibration loads. For this reason, the work equipment design provides for a rod with a counterweight pivotally connected to a toolbar. Force balance equations, including inertia forces as well, were derived considering the dynamic load impact. A relationship has been established between the impact tool layout on the rod, the impact energy and the reactive force in the rod rotation support. Conclusions. Graphical dependencies analysis established the range of variable parameters, which ensure the energy-efficient operation of the ripping equipment with a minimum transfer of dynamic loads to the operator’s workplace.
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Capanni, Felix, Kirk Hansen, Daniel C. Fitzpatrick, Steven M. Madey i Michael Bottlang. "Elastically Suspending the Screw Holes of a Locked Osteosynthesis Plate Can Dampen Impact Loads". Journal of Applied Biomechanics 31, nr 3 (czerwiec 2015): 164–69. http://dx.doi.org/10.1123/jab.2014-0193.
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Impact damping by elastic fixation is a principal engineering strategy to increase the durability of load-bearing structures exposed to prolonged dynamic loading. This biomechanical study evaluated axial impact damping provided by a novel dynamic locking plate. In this design, locking screw holes are elastically suspended within a silicone envelope inside the locking plate. Axial impact damping was assessed for 3 distinct fixation constructs applied to bridge a 10-mm fracture gap of a femoral diaphysis surrogate: a standard locking plate, a dynamic locking plate, and an Ilizarov ring fixator. First, the 3 fixation constructs were characterized by determining their axial stiffness. Subsequently, constructs were subjected to a range of axial impact loads to quantify damping of force transmission. Compared with standard locked plating constructs, dynamic plating constructs were 58% less stiff (P < .01) and Ilizarov constructs were 88% less stiff (P < .01). Impact damping correlated inversely with construct stiffness. Compared with standard plating, dynamic plating constructs and Ilizarov constructs dampened the transmission of impact loads by up to 48% (P < .01) and 74% (P < .01), respectively. In conclusion, lower construct stiffness correlated with superior damping of axial impact loads. Dynamic locking plates provide significantly greater impact damping compared with standard locking plates.
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Liu, Jianyu, Yiping Yin, Yunlei Zhao i Yuan Li. "Dynamic Behavior Analysis of I-Shaped RC Beams under Combined Blast and Impact Loads". Applied Sciences 13, nr 3 (2.02.2023): 1943. http://dx.doi.org/10.3390/app13031943.
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The existing literature mainly focuses on the research of reinforced concrete (RC) beams under a single load such as blast or impact. In this paper, the slab–rib–slab RC beam, a new type of structure widely used in bridge structures, was taken as the research object. The explicit dynamic analysis software LS-DYNA was used to numerically analyze the dynamic response and failure behavior of I-shaped RC beams under combined blast and impact loads. For this reason, an effective numerical analysis model was obtained by carrying out experiments on I-shaped RC beams under contact explosion. The key factors affecting the dynamic response of the structure under combined loads were numerically analyzed. Numerical results showed that different load application sequences have important effects on the dynamic response of the structure. When the impact load was first applied to the structure, more severe concrete damage and deformation occured in the depth direction of the beam. However, when the blast load was first applied to the structure, the concrete at the lower flange was damaged in the span direction of the beam due to tension, and no large-scale concrete spallation occurred in the depth direction. This was mainly due to the different mechanisms of blast and impact loads. In addition, the vulnerability of the I-shaped RC beams varied with some structural parameters, including span, depth, and configuration of reinforcement. At the same time, the results showed that the structure is more sensitive to changes in structural parameters when it is first subjected to impact loads.
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Chen, Yuxiang, Mutellip Ahmat i Zhong-tang Huo. "Dynamic meshing incentive analysis for wind turbine planetary gear system". Industrial Lubrication and Tribology 69, nr 2 (13.03.2017): 306–11. http://dx.doi.org/10.1108/ilt-12-2015-0203.
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Purpose Irregular windy loads are loaded for a wind turbine. This paper aims to determine the form of gear failure and the working life of the gear system by assessing the dynamic strength of gears and dynamic stress distribution. Design/methodology/approach The helical planetary gear system of the wind turbine growth rate gearbox was investigated, and while a variety of clearance and friction gear meshing processes were considered in the planetary gear system, a finite element model was built based on the contact–impact dynamics theory, solved using the explicit algorithm. The impact stress of the sun gear of the planetary gear system was calculated under different loads. An integrated planetary gear meshing stiffness, and the error of system dynamic transmission error were investigated when the planetary gear meshes with the sun or ring gears. Findings The load has little effect on the sun gear of the impact stress which was known. The varying stiffness is different while the planetary gear meshes with the sun and ring gears. There were differences between the planetary gear system and the planetary gear, and with load, the planetary gear transmission error decreases. Originality/value This study will provide basis knowledge for the planetary gear system.
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Xiao, Hui, Guo Lai Yang i Peng Wang. "Review of Loads Transfer Laws and their Applications in Artillery". Applied Mechanics and Materials 328 (czerwiec 2013): 609–13. http://dx.doi.org/10.4028/www.scientific.net/amm.328.609.
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In terms of the requirements of lightweight design, high reliability and long life for dynamic systems, especially heavy machinery and artillery, the methods to achieve the law of loads transfer path were studied based on some history and latest related research. So far, there is no systematic ways to research that in dynamic system, especially in artillery with instantaneous and strong impact load. This paper elaborated the application prospect of loads transfer law in artillery, discussed the main possible methods in research of artillery emission loads transfer laws. Those are topology optimization based on finite element, Multi-body dynamics, and method of vibration load transfer path analysis method. Through simulation and experiments those can be verified their correctness and effectiveness. This article is to find some feasible methods to achieve optimal load-carry structure, so as to improve its tactical and technical performance, especially the mobility, firing accuracy and shooting stability, and it has certain guiding or referenced significance for future related research.
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Jukowski, Michał, Krzysztof Śledziewski i Mateusz Hypki. "Assessment of the impact of vibrations on the track surface from impact loads". MATEC Web of Conferences 252 (2019): 01007. http://dx.doi.org/10.1051/matecconf/201925201007.
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Dynamic development of the linear infrastructure in Poland directly contributed to the increase in the number of engineering sites and facilities. Due to ground conditions and values of exploitation loads, in some cases bridge supports must be placed on foundation piles, the method of execution of which may cause significant dynamic impact on the structures located in the close vicinity. The paper assesses the impact of dynamic actions resulting from impact loads during impact pile driving of FRANKA piles with the use of a guide pipe on the railway track surface, on which there is continuous railway vehicle traffic. The tests have shown that the serviceability limit condition has been met and that the construction works do not result in exceeded values of vibration acceleration.
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Abed, Farid, Akrum Abdul-Latif i Zin Mahaini. "Behavior of BFRP bars subjected to dynamic impact loads". MATEC Web of Conferences 304 (2019): 01011. http://dx.doi.org/10.1051/matecconf/201930401011.
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Fiber Reinforced Polymer (FRP) bars are deemed to be one of the best solutions to the corrosion dilemma associated with steel reinforcement. This paper presents an experimental study on the behavior of Basalt FRP bars subjected to impact loading. Dynamic tests were conducted on eighteen BFRP bars of 17 mm and 20 mm diameters (B17 and B20) using the drop hammer test procedure. Different loading rates were achieved through varying the weight of mass and height of fall. The paper evaluated the maximum stresses attained by the BFRP bars at various loading rates. As the loading rate increased, the B20 bars reported a higher strength value. However, the B17 bars showed a drop in the strength with the increase of the loading rate, which requires further investigation. The crushing was observed to be most prominent in the top part of the bars where the bars exhibited a conical shape after failure.
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Wu, Nan, Zhende Zhu, Cong Zhang i Zhihua Luo. "Dynamic Behavior of Rock Joint under Different Impact Loads". KSCE Journal of Civil Engineering 23, nr 2 (17.12.2018): 541–48. http://dx.doi.org/10.1007/s12205-018-0799-7.
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Yang, J., i J. Q. Ye. "Dynamic elastic local buckling of piles under impact loads". Structural Engineering and Mechanics 13, nr 5 (25.05.2002): 543–56. http://dx.doi.org/10.12989/sem.2002.13.5.543.
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Stolte, J., i R. C. Benson. "An Extending Dynamic Elastica: Impact With a Surface". Journal of Vibration and Acoustics 115, nr 3 (1.07.1993): 308–13. http://dx.doi.org/10.1115/1.2930350.
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The study of the dynamic transport of paper, film, and tape is of increasing importance as process speeds increase. In earlier machines, transport velocities were slow enough that inertia loads did not appreciably affect the deformation of the material. In many applications, material is pushed from a channel or clamp and can be modeled as a cantilevered beam or plate until it reaches another guide or barrier. In this paper, we are concerned with modeling the behavior of such a cantilevered sheet after it strikes a guide. The guide may be any two-dimensional curve. We are able to determine leading edge velocities and reaction forces necessary to keep the sheet from penetrating the guide. Friction is included in the model. The sheet is allowed to exit the channel at an arbitrary angle and may have a nonconstant transport velocity. Inertial loads become noticeable at speeds greater than one copy per second and are necessary for the resolution of impact loads.
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Xu, W., A. Z. Zhu i K. Gao. "Parameter Analysis on the Anti-Impact Behavior of Pcfst Columns under Lateral Impact Load". MATEC Web of Conferences 206 (2018): 01020. http://dx.doi.org/10.1051/matecconf/201820601020.
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Concrete-filled steel tubular (CFST) structures have been widel y used in civil engineering structures, due to its good behaviors under both static and dynamic loads. In this paper, numerical studies were carried out to investigate the anti-impact behavior of partially concrete-filled steel tubular (PCFST) columns under lateral impact loads. Finite element analysis (FEA) model was established using ABAQUS. To validate the FEA model, the numerical results were compared with experimental results. Moreover, parameter analysis was carried out to further study the anti-impact behaviors of the PCFST columns. The concrete filling height, the impact energy, the impact direction, and the yield strength of steel were the main parameters considered in this study. The dynamic responses under the impact load, including the impact force, the failure mode, and the displacement response, were all analyzed. The results of parameter analysis showed that the anti-impact behaviors of the PCFST columns significantly increased when the concrete filling height or the yield strength of steel increased greatly. The impact energy and direction also greatly affected the anti-impact behaviors of the PCFST columns.
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Nagaya, Kosuke. "Effects of Impact on the Behavior of a Flexible Multiple Disk Clutch and Brake". Journal of Vibration and Acoustics 109, nr 4 (1.10.1987): 416–21. http://dx.doi.org/10.1115/1.3269462.
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This paper discusses the dynamic behavior of a flexible multiple disk clutch subjected to dynamic loads. The expressions for obtaining the dynamic response and the transmission torque of the clutch have been derived from the equation of motion of a circular plate by applying the Laplace transform procedure. The results for the clutch subjected to a static load have also been obtained. The comparison between both static and dynamic results has been made to clarify the effect of the impact of the load on the behavior of the clutch.
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Kurakina, Elena, i Sergey Evtiukov. "Impact of static and dynamic loads of vehicles on pavement". E3S Web of Conferences 164 (2020): 03025. http://dx.doi.org/10.1051/e3sconf/202016403025.
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The present paper substantiates urgency of studies on early deterioration of pavement layers and on reasons entailing it. The aim was to investigate static and dynamic loads imposed on a road surface by vehicles in order to detect signs of early deterioration of pavement and understand its reasons. Certain tasks were set: to define diagnostic capacity for performing test works on road surface with the use of static and dynamic loading equipment; to carry out an elastic modulus analysis on the basis of static and dynamic loading tests performed; to assess strength properties of flexible pavement. The paper describes methods for determining strength properties of a road surface with the use of special static and dynamic loading equipment. The authors provide data on diagnostic capacity of tests of a pavement performed with the use of special testing equipment. The paper gives a list of potentials, advantages and fundamental features of the following units of equipment: apparatus for plate bearing tests, Dina-3M, UDN-NK, Dynatest apparatus. The main parameters of equipment for dynamic loading tests are provided. The results of both dynamic and static loading tests performed in Saint Petersburg and the Leningrad region are given. Deflection bowls and elastic modulus were determined. Coefficients of the dynamic elastic modulus being reduced to the static one were calculated. Strength properties of flexible pavement were assessed.
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Lian, Xiaoyong, Jun Li, Housheng Jia i Peng Ding. "The Anti-Impact Characteristics of Cables under Impact Load". Energies 16, nr 2 (5.01.2023): 633. http://dx.doi.org/10.3390/en16020633.
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The cable plays a vital role in roadway support. As the last barrier to prevent roof collapse and impact disaster accidents, it is of great significance to study stress characteristics of cables under impact dynamic load to guide the rock burst roadway support. With high-strength cables of Ф21.6 and Ф21.8 mm and low-resistance high-extension cables of Ф21.5 mm as examples, this paper studied the instantaneous mechanical state and energy dissipation characteristics of different types of cables under impact loads by using impact testing machines and high-frequency data acquisition system. The results show that the impact process can strengthen the strength of the cable. The strength and elongation of anchor cables are a pair of characteristic indexes with an inverse relationship. Simply increasing one index cannot improve the overall impact resistance of the cable. To quantitatively characterize the impact resistance and energy absorption effect of cables, the impact resistance index k was introduced. The smaller the index, the better the energy absorption effect of cables. In the process of dynamic load impact of high-strength cable, about 43.7% of the total energy is dissipated disordered in the form of mechanical energy. The dynamic load impact process of low-resistance and high-extension cables is similar to the viscoelastic impact. In the collision compaction stage, the force of the cable is basically constant. Most of the impact energy is absorbed or transformed by the cable, about 17.7% of which is mostly dissipated in the form of mechanical energy. The disordered dissipated mechanical energy is less, so the impact resistance and energy absorption effect of this cable are better. The cable plays an important role in the process of bearing the dynamic load of surrounding rock. The anti-impact performance index of cables should be considered in dynamic load impact roadway support design.
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Lin, Jie, Chao Deng i Jia Chu Xu. "Nonlinear Dynamic Buckling of FGM Shallow Conical Shells under Triangular Pulse Impact Loads". Advanced Materials Research 460 (luty 2012): 119–26. http://dx.doi.org/10.4028/www.scientific.net/amr.460.119.
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In this paper, nonlinear dynamic buckling of FGM shallow conical shells under the action of triangular pulse impact loads are investigated. The nonlinear dynamic governing equation of symmetrically FGM shallow conical shells is built. Using Galerkin method, the nonlinear dynamic governing equation is solved, and the nonlinear dynamic response equation of symmetrically FGM shallow conical shells is obtained. The Runge-Kutta method is introduced to numerically solve the nonlinear dynamic response equation and the impact response curve is achieved. Budiansky-Roth motion criterion expressed by the displacement of the peak of the shell is employed to determine the critical impact buckling load. The influences of geometric parameters and gradient constants on impact buckling are discussed as well.
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Pei, Shiling, Yongle Li, Yulong Bao, Xin Li i Shizhong Qiang. "Impact of train-induced vibration on railway cable-stayed bridges fatigue evaluation". Baltic Journal of Road and Bridge Engineering 11, nr 2 (27.06.2016): 102–10. http://dx.doi.org/10.3846/bjrbe.2016.12.
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Under repetitive heavy train traffic, railway steel truss bridges tend to have many fatigue related performance issues, especially at welded joints. Accurate estimation of the stress history at critical locations of welded joints under vehicle loading is important for joint fatigue design. Traditionally, vehicle loads were treated as moving static loads without considering their dynamic effects. In this study, a numerical procedure was introduced to incorporate the effect of dynamic response of the train–bridge coupled system on nodal fatigue damage. The proposed approach employs a twolevel modelling scheme which combines dynamic analysis for the full train-bridge system and detailed stress analysis at the joint. Miner rule was used to determine the cumulative fatigue damage at critical locations on the welded joint. A sensitivity analysis was conducted for different train loading configurations. It was determined that dynamic vibration negatively influences fatigue life. The calculated cumulative damage at investigated locations can more than the damage estimated using only static moving load method.
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Liu, Z., R. Igland i S. Bruaseth. "Local and global assessments of a subsea riser-spool connection under dropped impact loads". IOP Conference Series: Materials Science and Engineering 1201, nr 1 (1.11.2021): 012049. http://dx.doi.org/10.1088/1757-899x/1201/1/012049.
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Abstract Subsea riser tube and spool is often used together to connect the riser of jacket to flowline or pipeline. Due to its limited size (less than 200 m), the location is within the lifting zones of the platform. Consequently, the dropped object hazard has potential high risk and needs to be checked. This paper presents a numerical study on accessing the structural dynamics of a subsea riser connection under the dropped container impact loads. De-coupled local and global models were established. The impact impulse was obtained from local impact analysis by Abaqus Explicit solver, in which deformations from container and pipeline are both captured. The impact energy level is in line with the risk assessment. The global model was built by ANSYS APDL macros. A simple input file is only needed for end users. The nonlinear pipe and soil interaction are included in a simplified manner. The model comprises of static and dynamic analysis parts. The static analysis captures the in-place configuration and the functional loads. The dynamic analysis is a restart with inherited stress state from static analysis. The impact impulse was applied by point loads in a certain time range. The nonlinear soil stiffness was approached by spring elements (compression only). The dynamic analysis was done in a longer time, ensuring to capture any dynamic effects. The interface loads at the riser stick-out and riser anchor are both extracted and discussed. It is shown that present structure design can withstand the dropped loads at the input energy level.
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Jeon, Sang Youn, i Young Shin Lee. "An Estimation of the Dynamic Buckling Load for the Spacer Grid of Pressurized Water Reactor Fuel Assembly". Key Engineering Materials 326-328 (grudzień 2006): 1603–6. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1603.
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This study contains an estimation of the dynamic buckling load for the spacer grid of fuel assembly in pressurized water reactor. Three different estimation methods were proposed for the calculation of the dynamic buckling loads of spacer grid. The dynamic impact tests and analyses were performed to evaluate the impact characteristics of the spacer grids and to predict the dynamic buckling load of the full size spacer grid. The estimation results were compared with the test results for the verification of the estimation methods.
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Van Dyk, Brandon J., J. Riley Edwards, Marcus S. Dersch, Conrad J. Ruppert i Christopher PL Barkan. "Evaluation of dynamic and impact wheel load factors and their application in design processes". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 231, nr 1 (4.08.2016): 33–43. http://dx.doi.org/10.1177/0954409715619454.
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A sustained increase in heavy axle loads and cumulative freight tonnages, coupled with increased development of high-speed passenger rail, is placing an increasing demand on railway infrastructures. Some of the most-critical areas of the infrastructure in need of further research are track components used in high-speed passenger, heavy haul and shared infrastructure applications. In North America, many design guidelines for these systems use historical wheel loads and design factors that may not necessarily be representative of the loading currently experienced on rail networks. Without a clear understanding of the nature of these loads and how design processes reflect them, it is impossible to adequately evaluate the superstructure in order to make design improvements. Therefore, researchers at the University of Illinois at Urbana-Champaign are conducting research to lay the groundwork for an improved and thorough understanding of the loading environment imparted into the track structure using wheel loads captured by wheel impact load detectors. This paper identifies several design factors that have been developed internationally, and evaluates their effectiveness based on wheel loads using several existing and new evaluative metrics. New design factors are also developed to represent the wheel-loading environment in a different manner. An evaluative approach to historical and innovative design methodologies will provide improvements to designs, based on actual loading experienced on today’s rail networks.
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Medvedskiy, Aleksandr, Mihail Martirosov, Anton Homchenko i Darina Dedova. "IMPACT OF INTERLAMINAR ELLIPTICAL DEFECTS UPON BEHAVIOR OF RECTANGULAR CARBON PLASTIC PLATE AT STATIC AND DYNAMIC LOADS". Bulletin of Bryansk state technical university 2020, nr 12 (1.12.2020): 19–30. http://dx.doi.org/10.30987/1999-8775-2020-12-19-30.
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The purpose of this work is to investigate the impact of the inner defects of elliptical stratification type upon behavior of the rectangular carbon plastic plate at the impact of static and dynamic loads.
The investigation methods: the problem is solved in a numerical way with the aid of a finite ele-ment method (FEM) in the LS-DYNA software com-plex (Livermore Software Technology Corp.).
The investigation results: the distribution of stresses in plate layers under the impact of static and dynamic loads is obtained. The distribution of destruc-tion indices with the use of different destruction criteria for unidirectional composites (on the basis of carbon band) is defined.
Conclusions: the impact of defects of the type of specified shape stratification, dimensions, amount and places of location with regard to the plate under consideration under the action of compressive static load does not practically tell. Under the action of the compressive dynamic load there is observed a noticeable impact of inner defects upon rectangular plate behavior.
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BAGIŃSKI, Paweł, i Grzegorz ŻYWICA. "EXPERIMENTAL INVESTIGATION OF A FOIL BEARING STRUCTURE WITH A POLYMER COATING UNDER DYNAMIC LOADS". Tribologia 281, nr 5 (1.11.2018): 5–12. http://dx.doi.org/10.5604/01.3001.0012.7640.
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This paper presents the results of research on the structural elements of a prototypical foil bearing in terms of its dynamic loads. In the framework of dynamic tests, several dozens of measurement series were carried out on a test rig specially prepared for this purpose. Dynamic excitations were applied using an electromagnetic exciter that enables changing the amplitude and frequency of the excitation force. Owing to this, it was possible to determine characteristics of the tested system in a wide range of loads and frequencies. A value of 400 Hz was assumed as the upper limit of the excitation frequency. The test rig enabled considering the direction of dynamic loads, which, as it turned out, had a significant impact on the obtained results. The research findings show that both the amplitude and frequency of an excitation force have a major impact on the stiffness and damping of the structural part of the foil bearing. The results of dynamic load tests complement the results of static tests performed earlier.
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Jiang, Jinhui, Shuyi Luo i Zhongzai Liang. "Online identification of impact loads of multi-degree-of-freedom system based on Kalman filter". International Journal of Applied Electromagnetics and Mechanics 64, nr 1-4 (10.12.2020): 359–67. http://dx.doi.org/10.3233/jae-209341.
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Dynamic load identification is the second kind of inverse problem in structural dynamics. It is a process of reconstructing load applied to structure in case of structural dynamic model and information of structural response. Online identification is one of the frontier problems in dynamic load identification, which has high difficulty and broad application prospects. In this paper, an online identification of dynamic load of the multi-degree-of-freedom system based on Kalman filter in modal space is proposed. Since the Kalman filter has excellent real-time performance and robustness, it is possible to be used in dynamic load online identification. We start from the theoretical derivation in detail for the multi-degree-of-freedom system, then the feasibility and effectiveness of the method is verified by numerical simulation of three-degree-of-freedom system with the single impact load and continuous multiple impact load.
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Yılmaz, Tolga, i Hasan Selim Şengel. "Numerical evaluation of reinforced concrete slabs with fixed support under impact load". Challenge Journal of Structural Mechanics 8, nr 3 (29.09.2022): 122. http://dx.doi.org/10.20528/cjsmec.2022.03.005.
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Reinforced concrete (RC) structural members may be subjected to impact load besides quasi-static load or other dynamic loads like earthquake and wind loads in their service periods. Many research emphasized that although impact load acts on structural members for a short time, it caused considerable damage to these members or even collapses the whole structure. Thus, it becomes crucial to consider and accurately evaluate the impact load effect in the design process. The present study intends to introduce a finite element model (FEM) verified with the test data for the accurate evaluation of load-deflection behavior and damage patterns of the fixed supported RC slabs exposed to impact load. First, a nonlinear FEM including strain-rate effect for both concrete and steel reinforcement, and crack visualization algorithm has been established by using LS-DYNA software. Then, the dynamic responses obtained by the present FEM have been compared with the experimental data presented in a previous study existing in the literature and it is found that the present FEM yields accurate results for the RC slab subjected to impact load and it can be safely used in the design process. In the second part of the study, using the verified FEM, the effects of applied input impact energy, the application point of impact load, and hammer geometry on the dynamic responses and failure characteristics of the RC slabs exposed to the impact loading were investigated and interpreted in detail.
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Wang, Jianguo, Yang Liu i Kegang Li. "Dynamic Characteristics of Deep Dolomite Under One-Dimensional Static and Dynamic Loads". Journal of The Institution of Engineers (India): Series A 101, nr 1 (31.12.2019): 49–56. http://dx.doi.org/10.1007/s40030-019-00424-5.
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AbstractThe failure characteristics of rock subjected to impact disturbance under one-dimensional static axial compression are helpful for studying the problems of pillar instability and rock burst in deep, high geostress surrounding rock under blasting disturbances. Improved split Hopkinson pressure bar equipment was used for one-dimensional dynamic–static combined impact tests of deep-seated dolomite specimens under axial compression levels of 0, 12, 24, and 36 MPa. The experimental results demonstrate that the dolomite specimens exhibit strong brittleness. The dynamic strength always maintains a strong positive correlation with the strain rate when the axial compression is fixed; when the strain rate is close, the dynamic elasticity modulus and peak strength of the specimens first increase and then decrease with the increase in axial compression, and the peak value appears at 24 MPa. The impact resistance of specimens can be enhanced when the axial compression is 12 or 24 MPa, but when it increases to 36 MPa, the damage inside the specimen begins to cause damage to the dynamic rock strength. Prior to the rock macroscopic failure, the axial static load changes the rock structure state, and it can store strain energy or cause irreversible damage.
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Chawda, Denil, i Senthil Murugan. "Dynamic Response of a Cantilevered Beam Under Combined Moving Moment, Torque and Force". International Journal of Structural Stability and Dynamics 20, nr 05 (maj 2020): 2050065. http://dx.doi.org/10.1142/s0219455420500650.
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This paper studies the dynamic response of a cantilevered beam subjected to a moving moment and torque, and combination of them with a moving force. The moving loads are considered to traverse along the length of the beam either from fixed-to-free end or free-to-fixed end. The beam is considered to have constant material and geometric properties. The beam is modeled using the Rayleigh beam theory considering the rotary inertia effects. The Dirac-delta function used to model the moving loads in the governing partial differential equations (PDEs) has complicated the solution of the problem. The Eigenfunction expansions coupled with the Laplace transformation method is used to find the semi-analytical solution for the resulting governing PDEs. The effects of moving loads on the dynamic response are studied. The dynamic effects are quantified based on the number of oscillations per unit travel time of the moving load and the Dynamic Amplification Factor (DAF) of the beam’s tip response. Numerical results are also analyzed for the two-speed regimes, namely high-speed and low-speed regimes, defined with respect to the critical speed of the moving loads. The accuracy of the analytical solutions are verified by the finite element analysis. The numerical results show that the loads moving with low speeds have significant impact on the dynamic response compared to high speeds. Also, the moving moment has significant impact on the amplitude of dynamic response compared with the moving force case.
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Tan, Lihai, Ting Ren, Xiaohan Yang i Xueqiu He. "Numerical study on the fracture characteristics and failure mode of hard coal under coupled static and dynamic loads". E3S Web of Conferences 192 (2020): 04002. http://dx.doi.org/10.1051/e3sconf/202019204002.
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It has been well accepted by mining researchers that coal tends to undergo abrupt fracture under the coupling effect of dynamic and static loads. Hence, the study of influence of coupled static and dynamic loads on coal failure behaviour is meaningful for the understanding of coal burst. In this paper, PFC modelling of SHPB test is adopted to investigate the fracture mode and energy evolution of Australian hard coal under different combinations of pre-stress levels and impact velocities. Results have shown that high dynamic load will make the fracture mode and energy release of coal samples more violent even the static load is low. Although the strain energy increases with pre-stress level, the kinetic energy remains on a low level with the increase of pre-stress level when the impact velocity is 4 m/s.
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Tang, Liping, Wei He i Xiaohua Zhu. "The effect of high-frequency torsional impacts on the dynamic response of a drill string in a stick state". Advances in Mechanical Engineering 11, nr 3 (marzec 2019): 168781401982857. http://dx.doi.org/10.1177/1687814019828579.
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Stick–slip vibration is common in the oil well drilling process and is detrimental to down-hole equipment and drilling efficiency. In recent years, a new type of drilling technology, torsional impact drilling, has been developed to mitigate the stick–slip phenomena, particularly in the drilling of deep or abrasive formations. With this drilling technique, high-frequency torsional impacts are generated and applied to the drill bit, providing the drill bit with auxiliary energy. By mitigating or suppressing the stick–slip vibration, part of the energy wasted as a result of vibration can be regained. However, the effect of these impact loads on the dynamic response of a drill string in a stick state is unknown. In order to address this issue, a continuous system model of a drill string that includes torsional impact load was constructed. In the model, a Fourier series approach was used for the impact load, and the mechanical model was resolved with the mode superposition method. Case studies were done to understand the drill string dynamics, with and without the impact. The case study results demonstrate that high-frequency torsional impacts have little influence on the dynamic response of a drill string in a stick state.