Effect Of Impact Loading Research Articles

Fracture Mode and Thermal Damage Evolution of Sandstone Under the Coupling Effect of Thermal Treatment and Impact Load

The dynamic properties of high-temperature sandstone quickly deteriorate with different cooling methods, which leads to the instability of underground engineering rock structures. Therefore, it is of great significance to quantify the changes in the dynamic characteristics of high-temperature cooled sandstone under impact loads. Therefore, the sandstone is heated to different temperatures and cooled using three methods. A dynamic tensile test is performed using the Splitting Hopkinson Pressure Bar (SHPB) test set for high-temperature cooled sandstone. At the same time, the transient process of rock failure was examined using high-speed cameras. The influence of different temperatures and cooling methods on the thermal damage value of sandstone was analyzed, and the prediction equation was formed. The change in rock energy during rock failure under impact load was calculated.

Effect of impact loading and acidic drying-wetting cycles on fragmentation and energy dissipation characteristics of sandstone

Effect of impact loading and acidic drying-wetting cycles on fragmentation and energy dissipation characteristics of sandstone

Effect of High-Velocity Impact Loading on Concrete Slabs Reinforced by Metallic Strips from Soft Drink Cans as Fiber

Effect of High-Velocity Impact Loading on Concrete Slabs Reinforced by Metallic Strips from Soft Drink Cans as Fiber

Cold temperature effects on the impact behaviour of glued-laminated timber beams

Engineered wood products, such as glued-laminated timber (glulam), have been and are continuously being utilized in the construction of tall timber buildings and notable landmark bridges. This infrastructure, particularly the latter, may be exposed to hazardous impact loads throughout their service life. As little research has been conducted on the impact behaviour of glulam beams under cold temperature conditions, there is a need to investigate the potential effects of impact loading on glulam structural elements at cold temperatures. This paper presents an experimental investigation aimed at understanding the effects of cold temperatures on the impact behaviour of glulam timber beams. Fifteen glulam beams were tested under quasi-static and impact loading, under ambient and cold temperatures. Drop weight impact testing was performed to simulate dynamic loading conditions similar to those experienced in real-world scenarios. The results indicate that both the loading regime and cold temperatures have a significant influence on the strength and stiffness of glulam beams, whereby statistically significant increases in the moduli of rupture and elasticity were observed, however, no interaction between the two variables occurred. A single-degree-of-freedom (SDOF) model was developed and validated using the experimental test results and found to provide good accuracy.

Experimental and Numerical Investigation of Impact Behaviour of Anchored CFRP-to-Concrete Bonding Interface

In the last 20 years, Carbon Fiber Reinforced Polymers (CFRP) have become a common alternative to strengthening and retrofitting. The performance of the strengthened specimens is closely related to the bond slip between the CFRP strips and the adhesion surface. Therefore, researchers have begun to concentrate on the various anchoring methods to delay the debonding of the CFRP from the surface of strengthened specimens. When the literature review of the adhesion behavior between the anchored CFRP strips and the concrete surface is examined, it has been shown that the investigations are mostly done under the effect of static or reversible cyclic loads. In the literature review, there is not any research related to the adhesion behavior between anchored CFRP strips and the concrete surface under the effect of sudden dynamic impulsive impact loading. Therefore, the variables examined in the experimental study are the anchor type used in the CFRP strips, CFRP strip adhesion length, and the number of anchors placed on the strip. As a result of the experiments, the acceleration-time, displacement–time curves of the beams, and the strain–time curves along the CFRP strips were interpreted. In addition, simulation models of the test specimens were created with ABAQUS software, and non-linear finite element analyzes were performed. Finally, by comparing numerical results with experimental ones, the effects of variables such as bond length, applied anchor types and numbers on the impact behavior of the beam and the strain distributions along the CFRP strips were interpreted.

Destabilization of Cylindrical Shells Coupling Effect of Local Impact Load and Circumferential Pressure

Destabilization of Cylindrical Shells Coupling Effect of Local Impact Load and Circumferential Pressure

Investigation of notch position and fiber ratio on the fracture mode and energy of sfrc beam under the impact load

When the literature is examined, it is seen that a lot of study has been done on the crack propagation and fracture modes that occur under the influence of static loads in reinforced concrete (RC) structures. Studies in the literature show the effect of crack initiation, concrete compressive strength, and fiber volume fraction on the tension mode (Mode-I), shear mode (Mode-II), and mixed fracture mode that occurs in crack propagation under static load. However, the literature has not found a comprehensive study in which the fracture modes are examined under the effect of dynamic impact loading. For this reason, an experimental study has been planned in which hybrid steel fiber reinforced concrete (SFRC) notched beams with varying compressive strength will be tested under impact loading with a free-fall drop weight device designed by the authors. The experimental variables studied were determined as the change of the crack initiation point in the beams, the compressive strength of the concrete used to produce the beams, and the fiber volume fraction in the concrete mixture. The acceleration and impact load-time histories under the constant-energy-level impact loading applied to the beams were measured. Also, the crack shape, fracture mode, crack angle, and energy absorption capacities of the beams under impact load were interpreted. While the transition from Mode-I fracture form to Mode-II fracture form occurs under impact loading, the effects of concrete compressive strength and steel fiber ratio variables on energy absorption capacity, crack angle, and crack shape are studied. Increasing the distance of the notch from the beam midpoint in notched beams produced with concrete without fiber from 0 to 40, 80 and 120 mm caused the energy absorption capacity values to increase by an average of 39 %, 66 % and 86 %, respectively. Increasing the distance of the notch to the beam midpoint from 0 to 40, 80 and 120 mm in beams with 0.75 % and 1.5 % fiber ratio increased the energy absorption capacity values by an average of 40 %, 65 % and 86 %, respectively. In beams with 2.25 % fiber ratio, increasing the notch distance from 0 to 40, 80 and 120 mm increased the energy absorption capacity values by an average of 38 %, 62 % and 83 %, respectively.

Low-velocity impact behavior of two-way SFRC slabs strengthened with steel plate

Structural systems and structural elements can often suffer severe damage or even completely collapse under the effect of sudden dynamic impact loading, which is a different type of loading that is not considered during their design. Research on how structures behave under impact loading and how they can be strengthened to perform better against this type of loading has increased to avoid such undesirable severe damage. Within the scope of this study, it is aimed to improve the behavior and increase the performance of two-way steel fiber-reinforced concrete (SFRC) slabs, one of the leading structural elements that can be affected by impact loading, using steel fiber concrete (SFC) and placing steel plates on the surface of the RC slab. Within the scope of the study, the effects of placing FRC as layers in different positions within the slab and placing the steel plate on different surfaces of the slabs were examined. Impact loading was applied using a drop weight test setup designed by the authors, and the acceleration–time, displacement–time, and impact loading–time behaviors of the RC slabs were measured and interpreted. The use of fiber concrete in RC slabs and strengthened with steel plates increased the maximum acceleration values by an average of 3% and 113%, respectively. The use of fiber concrete in RC slabs reduced the maximum displacement and residual displacement values by an average of 2% and 25%, respectively. Placing steel plates on the slabs reduced the maximum displacement and residual displacement values by an average of 270% and 199%, respectively. In addition, the energy absorption capacities of RC slabs were calculated, and how they were affected by experimental variables was examined. Numerical analyses of the RC slabs tested in the study were also conducted using ABAQUS finite element software, and the results obtained were compared with the experimental ones.

Enhancing Structural Performance: Fiber Reinforcement in Sintered Flyash Lightweight Concrete for Impact Resistance and Toughness

Objectives: The goal of this project is to better understand the interaction between fibers and concrete in order to produce Light Weight Aggregate Concrete (LWAC) with improved structural performance that is made from recycled materials, such as sintered flyash aggregate, and LWAC structures that are more resistant to impact loads and other dynamic forces. Methods: The sintered flyash aggregates are added as coarse aggregate to the concrete and basalt fiber (0.25% of mix) is used as a secondary reinforcement to improve the energy absorption, impact resistance and toughness behaviour. M30 grade of concrete was arrived after laboratory trials after which the mechanical properties were evaluated. The effect of drop impact load on slabs of size 300mm x 300mm x 50mm reinforced with two layers of bundled wire mesh was studied. The flexural properties of concrete reinforced with fiber prism of size 500mm x 100mm x 100mm were evaluated. Findings: With the addition of fiber, flexural toughness index and post-cracking toughness were increased notably on the initial deflections and cracks. The conventional fiber reinforced concrete exhibited a superior peak load capacity compared to normal weight concrete, with a measured increase of 7.5%. Conversely, normal-weight concrete demonstrated a significantly higher deflection under load, exceeding that of fiber reinforced concrete by 47%. LWAC displayed a distinct increase in both peak load (18.7%) and deflection (39.13%) when compared to Normal Weight Aggregate Concrete (NWAC). The incorporation of basalt fiber enhanced the energy absorption by 150% in NWAC and 80% in LWAC. Novelty: The incorporation of fiber into lightweight concrete reduces the brittle nature of failure. The post-cracking toughness behaviour was enhanced because of the effect of crack-arresting by fibers. After the first break, it was discovered to retain residual strength, and removing the fibers from the matrix required more force. Keywords: Sintered flyash aggregate, Light weight concrete, Basalt fiber, Toughness, Impact load, Energy absorption

The features of interlayer fracture of composite materials with a variable layup angle under impact loading

Interlayer defects in structural components made of composite materials are caused by the imperfection of the manufacturing process, complex interactions of the constituents, and the effect of impact loads. The presence of these defects decreases the strength of such components and severely affects residual strength. The paper presents a numerical and experimental study of the behavior of a composite material plate with a variable layup angle under impact loading. Impactor velocities before and after multilayer plate perforation, as well as the dimensions of delamination-type defects, are determined experimentally. The Ansys LS-DYNA software in double precision mode is used to simulate the failure of composite plates under impact loading. It has been found that a significant contribution to the decrease in the impact energy is made by the delamination dimensions depending on the layup angle in the stack. The delamination area is related to the residual velocity of the impactor; namely, the larger the delamination area, the greater the decrease in the impactor velocity.

Effect of impact and flexural loading on hybrid composite made of kevlar and natural fibers

In this work, four varieties of hybrid Fiber-Reinforced Polymer (FRP) panels made of kevlar-29 and natural fibers are studied. All panels have kevlar-29 face sheets and natural fiber core, such as jute, flax, sisal, and hemp. This research focuses on the behavior of these hybrid FRP panels under flexural and impact loading so that the panels can be explored for the structural/semi-structural members of army shelters, portable helipad, and roofing panels in high-altitude areas. Natural fibers are chemically treated with NaOH to improve hydrophobicity. The panels are vacuum bagged, the fiber volume fraction is 0.39, and the thickness is close to 4 mm. Three-point flexural loading using the universal testing machine and low-velocity impact loading up to 24 J under drop weight impact test setup is carried out to characterize the panels. Damage area, delamination, permanent deformation, indentation depth, energy absorbed, flexural strength, and modulus are measured. The hybrid flax/kevlar panel and hemp/kevlar panel, each resist impact with permanent deformation less than 0.5 mm up to 24 J. Without significant face sheet or core fiber breakage, the delamination is spread over a small radial distance of 18.5 and 24.5 mm, respectively. Interface matrix breakage causes delamination. The load vs deflection curve is almost linear under flexural loading, and specimens failed under compression at 240 MPa. The numerical simulation is also done using ANSYS and LS-DYNA for detailed study.

The Effect of Impact Load on the Atomistic Scale Fracture Behavior of Nanocrystalline bcc Iron.

Nanocrystalline metals have many applications in nanodevices, especially nanoscale electronics in aerospace. Their ability to resist fracture under impact produced by environmental stress is the main concern of nanodevice design. By carrying out molecular dynamics simulations under different fast loading rates, this work examines the effect of impact load on the fracture behavior of nanocrystalline bcc iron at an atomistic scale. The results show that a crack propagates with intergranular decohesion in nanocrystalline iron. With the increase in impact load, intergranular decohesion weakens, and plastic behaviors are generated by grain boundary activities. Also, the mechanism dominating plastic deformation changes from the atomic slip at the crack tip to obvious grain boundary activities. The grain boundary activities produced by the increase in impact load lead to an increase in the threshold energy for crack cleavage and enhance nanocrystalline bcc iron resistance to fracture. Nanocrystalline bcc iron can keep a high fracture ductility under a large impact load.

Dynamic and Residual Static Behavior of Axially Loaded RC Columns Subjected to Low-Elevation Impact Loading

Columns can suffer heavy damage due to dynamic impact effects, which are ignored during their design. The impact effect could be a vehicle crash to columns of streetside buildings, parking garages or bridges. However, the effect of impact loading on the behavior of reinforced concrete columns has not been sufficiently studied. In this study, an experimental and numerical investigation is carried out on the impact behavior of axially loaded reinforced concrete columns. Dynamic experiments were carried out by dropping a mass from different heights to apply low-elevation impact on axially loaded, full-scale (30 × 30 × 320 cm) columns. After evaluating the performance of the columns under varied impact loadings, the residual load carrying capacities of the columns were also obtained by static loading. Additionally, a three-dimensional finite element model was developed and validated by using drop weight experimental results. The effect of increasing the impact energy on the behavior of RC columns was also examined numerically. As a result of the research, it has been observed that, as the applied impact energy increases, the dynamic damage/failure mode changes from flexure to shear. When a column was impacted by 75.8% of its total impact energy capacity, a decrease of 38.1% in its stiffness and a decrease of 49.7% in its load carrying capacity were determined compared to its previous unimpacted state. Additionally, the static energy dissipation capacity loss of the column was reached, up to 81.7% of its preloading state. The developed finite element model can also be utilized to determine the dynamic performance and the damage modes of columns under vehicle collision-type low-elevation impacts, which can be a guide for structural engineers in the design of such vulnerable columns and will contribute to safer structural designs.

Theoretical and experimental studies on effect of impact load on dynamic characteristics of multi-link press mechanisms with clearances

Theoretical and experimental studies on effect of impact load on dynamic characteristics of multi-link press mechanisms with clearances

Molecular dynamics simulation of the heterostructure of the CoCrFeMnNi high entropy alloy under an impact load

There have been numerous experimental studies conducted on the CoCrFeMnNi high entropy alloys (HEAs) at the macroscopic level. However, it is challenging to quantitatively analyze the shock behavior of the HEAs from a microscopic level through experiments. In this study, we construct single-crystal, twin-crystal, multilayer, hole, and two-phase structures of the CoCrFeMnNi HEAs using the molecular dynamics method. The effects of impact loading on the microscopic level are investigated for CoCrFeMnNi HEAs with different structures. By analyzing the evolution of their microstructure and the changes in physical parameters, the response laws and propagation characteristics of shock waves in various heterogeneous of CoCrFeMnNi HEAs are revealed at the atomic scale.

Smart Elastic Material with a Moving Local Stiffness Zone for Reducing the Effects of Impact Loading

The elastic material properties which change momentarily and locally under the high deformation rate due to the movement of a wavefront are presented. The work contains mathematical formulation, semianalytical results, numerical formulations, and simulation results demonstrating the effectiveness of modifying the rheological properties of the elastic material upon shock load or contact with a rigid obstacle. While the semianalytical solutions can be obtained in a narrow time interval, numerical solutions allow us to track the process of wavefront reflections from edges. The effectiveness of reducing the physical quantities significant for impact in the presented examples reaches 30–70% of forces or accelerations, depending on the adopted criteria.

Influence of cyclic dynamic disturbance on damage evolution and zoning effect of coal-rock under local static load constraint

In order to obtain the characteristics of the effects of cyclic impact loading on the damage of coal-rock in the presence of a local static load constraint, the evolution of the damage factor and the fracture rate during the process and incremental cyclic impact on raw coal and briquettes has been studied. Experimental results show that the presence of local static load restraint improves the impact resistance of the coal-rock, and the damage factor of the coal-rock shows obvious zoning characteristics. When the coal-rock is in an elastic state, the partition with a larger static load restraint area has stronger impact resistance, when the coal-rock is in a plastic state, the partition with a larger static load restraint area has a weaker impact resistance. Increasing impulsive cyclic impacts have a higher damage efficiency to coal-rock than constant impulsive cyclic impacts. The difference in rock breaking efficiency between the two cyclic impact methods is mainly reflected in the partition with the largest constrained area. The crack propagation on the coal-rock surface is more consistent with the partition characteristics of the damage factor. When the static load constrained zone is in an elastic state, the static load has an inhibitory effect on the crack growth. When the static load confinement zone is in a plastic state, the cracks mainly propagate in the static load confinement zone, and the constrained zone mainly consists of tensile cracks that grow in the vertical direction, while the cracks in the non-constrained zone mainly grow in an oblique direction. Finally, fracture mechanics was applied to analyze the failure type of the sample.

Analyzing the Response of Structural Members to Impact Loads Using Finite Element Analysis: A Review

Background: The use of Finite Element Analysis (FEA) has become widespread in simulating the response of structural members subjected to impact loads. This review paper aims to provide an overview of FEA's application for predicting the response of structural members under impact loads. Objectives: The objectives of this review are to analyze the analytical and experimental methods used for studying the dynamics of vibration and impact loads, including Finite Element Analysis, Modal Analysis, Experimental Modal Analysis, Response Spectrum Analysis, and Design of Experiments Analysis. Methods: The review paper thoroughly examines the principles of FEA, the various types of impact loads, and the different structural members involved. It analyzes the definitions, causes, effects, and analytical and experimental methods used to study vibration and impact loads. Results: The review paper highlights the significance of studying these dynamics, as failure to do so can result in catastrophic failures of structures and machines. It presents a comprehensive review of the effects of vibration and impact loads on structures and machines and the advantages and limitations of different analytical and experimental methods. Conclusion: This review provides valuable insights into the dynamics of vibration and impact loads and their potential consequences on structural integrity. The findings emphasize the importance of employing appropriate analytical and experimental methods to accurately predict and assess the response of structural members under impact loads.

Investigating the behavior of hollow steel section beam under repetitive transverse impact loading

When a load is exerted on a structural element several times, it is called repetitive loading. This type of loading causes more damage to structural elements than monotonic loading. This paper presents the effects of repetitive transverse impact loading on the weak axis of rectangular hollow steel section beam. For this purpose, three simply supported beams were tested with a constant drop weight of 75 kg and three different heights (400 mm, 800 mm and 1200 mm). Transverse impact load was exerted on each specimen 3 times repeatedly. In the numerical studies, finite element models of all specimens were developed using ABAQUS finite element analysis software. In order to obtain reliable numerical models, finite element models were verified using the experimental data. To investigate the effects of repetitive transverse impact loading on hollow section steel beam, parameters such as displacement, reaction forces, stress distributions and out of plane plastic denting were evaluated comparatively. The obtained results showed that, when the height value is increased twice as the initial height in test series RIA and RIB, the displacement value increased by 57% in the first hit, 68% in the second hit and 79 % in the third hit. Thus, it seems that the increase in the displacement value due to the increase in the damage of subsequent hits is not linear, but rather logarithmic. Finally, it was understood that with increase in the plastic deformation and displacement occurring in an element subjected to repeated impact loading, a decrement occurs in the reaction force transferred to the supports.

Flexural Behavior of Ferrocement Composite Slab

Abstract: This project presents a Flexural behaviour of composite ferrocement slabs to investigate the effect of impact and ultimate flexural load on ferrocement slabs of size 600mmx400mmx15mm (thickness) reinforced with PVC coated steel weld mesh, and compare the results with slabs made of GI-coated steel weld mesh. PVC-coated weld mesh is used as non-corrosive reinforcement in ferrocement slab. The ferrocement slab was cast using Ordinary Portland Cement, locally available river sand and portable water with cement mortar ratio of 1:3 and water cement ratio of 0.5. The aim of this study is to observe the influence of PVC coated weld mesh ferrocement slab using ferrocement in enhancement of the mechanical properties of slabs subjected to impact and flexural load. The flexural load, maximum deflection, crack- pattern and crack-width of ferrocement slabs reinforced with PVC and GI coated weld mesh were analysed. Finally, the analytical results were compared with experimental results to predict the effectiveness of ferrocement techniques in structural applications.