Dynamic Mechanical Performance Research Articles

Dynamic Mechanical Performance of Sulfate-Bearing Soils Stabilized by Magnesia-Ground Granulated Blast Furnace Slag

Sulfate soils often caused foundation settlement, uneven deformation, and ground cracking. The distribution of sulfate-bearing soil is extensive, and effective stabilization of sulfate-bearing soil could potentially exert a profound influence on environmental protection. Ground granulated blast furnace slag (GGBS)–magnesia (MgO) can be an effective solution to stabilize sulfate soils. Dynamic cyclic loading can be used to simulate moving vehicles applied on subgrade soils, but studies on the dynamic mechanical properties of sulfate-bearing soil under cyclic loading are limited. In this study, GGBS-MgO was used to treat Ca-sulfate soil and Mg-sulfate soil. The swelling of the specimens was analyzed by a three-dimensional swelling test, and the change in compressive strength of the specimens after immersion was analyzed by an unconfined test. The dynamic elastic properties and energy dissipation of GGBS-MgO-stabilized sulfate soils were evaluated using a fatigue test, and the mineralogy and microstructure of the stabilized soils were investigated by X-ray diffraction and scanning electron microscopy. The results showed that the maximum swelling percentage of stabilized Ca-sulfate soil was achieved when the GGBS:MgO ratio was 6:4, resulting in an expansion rate of 14.211%. In contrast, stabilized Mg-sulfate soil exhibited maximum swelling at GGBS:MgO = 9:1, with a swelling percentage of 5.127%. As the GGBS:MgO ratio decreased, the dynamic elastic modulus of stabilized Ca-sulfate soil diminished from 2.8 MPa to 2.69 MPa, and energy dissipation reduced from 0.02 MJ/m3 to 0.019 MJ/m3. Conversely, the dynamic elastic modulus of stabilized Mg-sulfate soil escalated from 2.16 MPa to 6.12 MPa, while energy dissipation decreased from 0.023 MJ/m3 to 0.004 MJ/m3. After soaking, the dynamic elastic modulus of Ca-sulfate soil peaked (4.01 MPa) and energy dissipation was at its lowest (0.012 MJ/m3) at GGBS:MgO = 9:1. However, stabilized Mg-sulfate soil exhibited superior performance at GGBS:MgO = 6:4, with a dynamic elastic modulus of 0.74 MPa and energy dissipation of 0.05 MJ/m3. CSH increased significantly in the Ca-sulfate soil treated with GGBS-MgO. The generation of ettringite increased with the decrease in the GGBS-MgO ratio after immersion. MSH and less CSH were formed in GGBS-MgO-stabilized Mg-sulfate soil compared to Ca-sulfate soils. In summary, the results of this study provide some references for the improvement and application of sulfate soil in the field of road subgrade.

Axial Impact Resistance of High-Strength Engineering Geopolymer Composites: Effect of Polyethylene Fiber Content and Strain Rate

High-strength engineered geopolymer composite (EGC) materials exhibit excellent mechanical properties under quasistatic loading, thus showing great potential in military and civilian facilities subjected to impact or explosive loading. However, its dynamic mechanical response under high-speed loading is not fully understood. In this study, dynamic compressive test was performed on EGC with PE fiber contents of 0%, 0.5%, 1.0%, 1.5%, and 2.0% using the Split Hopkinson Pressure Bar (SHPB) test. The results indicated that EGC reinforced with 1.5% fiber exhibited optimal static and dynamic mechanical performance. In the strain rate range of 181 s−1 to 201 s−1, when the fiber content increased from 1.0% to 1.5% and 2.0%, the dynamic compressive strength of the EGC increased by 24.3%, 28.8%, and 44.0%, respectively, compared to the matrix without fiber. Dynamic parameters of the EGC, including dynamic compressive strength, dynamic increase factor, and impact toughness, showed sensitivity to strain rates and increased with strain rate. A modified model, incorporating the fiber bridging effect, was proposed based on the CEB-FIP model, providing important guidance for practical engineering applications.

Experimental study and multi‐scale refinement model of high damping acrylic polymer matrix VEDs for civil structural seismic retrofit

AbstractThe viscoelastic dampers (VEDs), which can provide both stiffness and damping, have been recently introduced into the field of structural vibration control for seismic enhancement of civil engineering structures. In this study, a kind of high damping acrylic polymer matrix VEDs (HDPVED) is developed independently, and this innovative HDPVED can solve the significant problem of service performance under medium‐high temperature environments, as well as low‐frequency vibration control under earthquake actions for civil engineering structures. To systematically investigate the influencing rules of frequency, temperature, and displacement amplitude on the mechanical properties and damping dissipation performance of HDPVEDs, a series of dynamic mechanical performance tests of the developed HDPVEDs are carried out at different frequencies, temperatures, and displacement amplitudes. The research results show that HDPVED exhibits excellent damping dissipation capability and adaptability under medium‐high temperature environments and low‐frequency excitations. The mechanical properties and energy dissipation performance present a strong correlation with frequency, temperature and displacement amplitude, and there is an obvious coupling effect between the three influencing factors. Based on the macroscopic mechanical property research of HDPVED, the microscopic damping mechanism and microscopic mechanical properties of HDPVED are then investigated. High‐order fractional derivative fraction Voigt and Maxwell model in parallel (FVMP) models are preferred to characterize the combined hyper‐elasticity and viscoelasticity owned by networked molecular chains and free molecular chains. The breaking and reconstruction theory of microphysical bonds is used to assess the effect of packing particles, and the time‐temperature equivalence principle is introduced to assess the effect of temperature. The multi‐scale refinement model is proposed, and the validity and accuracy of this model are verified by testing data of HDPVED. The study results show that the proposed model can accurately describe the effects of frequency, temperature, displacement amplitude, and microstructure on the multi‐scale mechanical properties of HDPVED. It provides a theoretical basis for the multi‐scale design and development of high damping VEDs.

Dynamic mechanical properties and energy release characteristics of Mg-Na-Al alloy under impact load

To investigate the ignition behavior of Mg-Na-Al alloy under impact load and its mechanical properties under different strain rates, the universal testing machine and Separated Hopkinson Pressure Bar (SHPB) experimental system were used to conduct static and dynamic mechanical performance tests of Mg-Na-Al alloy, and the mechanical properties of Mg-Na-Al alloy under different strain rates were discussed. The light gas gun experimental setup was used to launch Mg-Na-Al alloy projectiles and impact rigid target plates to study the energy release behavior of Mg-Na-Al alloy under impact loads. Finally, based on the 12.7mm ballistic gun experimental platform, the penetration of 12.7mm armor-piercing projectiles equipped with Mg-Na-Al alloy wind caps into the homogeneous armor steel plates with a thickness of 15mm, and the ignition test of the oil box behind the steel plates were conducted. The results indicate that the yield strength of Mg-Na-Al alloy under static compression is 265MPa, while under high strain rates (from 2490s-1 to 5640s-1), the yield strength of Mg-Na-Al alloy is 406~423MPa, which is 53%~60% higher than that under quasi-static compression. When reaching a certain impact velocity, the Mg-Na-Al alloy projectile breaks and induces ignition behavior, releasing energy. The 12.7mm armor-piercing projectile equipped with an Mg-Na-Al alloy wind cap penetrated the homogeneous armor steel plate with a thickness of 15mm and ignited. The released energy and the kinetic energy of the fragments ignited the oil box behind the steel plate.

FCA-based efficient prediction of effective properties for 3D braided composites considering the effect of strain rate

The existing fast concurrency algorithms are difficult to predict the dynamic mechanical performance of three-dimensional (3D) braided composites from different scales. A modified Finite Element Method Cluster Analysis (FCA) method is employed to address this challenge. The modified FCA method is consisted of an offline and an online stage. In the offline stage, the high-fidelity Representative Unit Cell (RUC) is compressed to form a cluster-based RUC via the k-means method. Additionally, the cluster interaction matrix is calculated. In the online stage, the cluster interaction matrix is updated according to the strain rate levels for predicting the stress–strain curves for the RUC. Based upon the comparison with the data obtained from the Split Hopkinson Pressure Bar (SHPB) experiments, it is found that the modified FCA method can accurately predict the stress–strain curves under different strain rates for RUCs. Additionally, the modified FCA method provides a great improvement on computing efficiency when predicting the dynamic behavior of 3D braided composites.

Experimental Study on Dynamic Mechanical Performance of Post-Fire Concrete Confined by CFRP Sheets.

Impact tests on post-fire concrete confined by Carbon Fiber-Reinforced Polymer/Plastic (CFRP) sheets were carried out by using Split Hopkinson Pressure Bar (SHPB) experimental setup in this paper, with emphasis on the effect of exposed temperatures, CFRP layers and impact velocities. Firstly, according to the measured stress-strain curves, the effects of experiment parameters on concrete dynamic mechanical performance such as compressive strength, ultimate strain and energy absorption are discussed in details. Additionally, temperature caused a softening effect on the compressive strength of concrete specimens, while CFRP confinement and strain rate play a hardening effect, which can lead to the increase in dynamic compressive strength by 1.8 to 3.6 times compared to static conditions. However, their hardening mechanisms and action stages are extremely different. Finally, nine widely accepted Dynamic Increase Factor (DIF) models considering strain rate effect were summarized, and a simplified model evaluating dynamic compressive strength of post-fire concrete confined by CFRP sheets was proposed, which can provide evidence for engineering emergency repair after fire accidents.

Dynamic mechanical behavior of steel fiber reinforced-recycled aggregate concrete subjected to uniaxial loading

The objective of this study was to investigate the dynamic mechanical performance of steel fiber reinforced-recycled aggregate concrete (SFRAC) under uniaxial loading. A total of 22 groups of cylindrical samples, each measuring 100 mm × 200 mm, were subjected to uniaxial compression. The investigation placed particular emphasis on examining the influence of variables such as the strain rate, volume fraction of steel fiber (Vsf), volume fraction of polyvinyl-alcohol (PVA) fiber (Vpf) and substitution ratio of recycled coarse aggregate (SRCA) on the failure modes, stress-strain curves and deformation ability. The results revealed that the incorporation of steel fibers and PVA fibers enhanced the overall integrity of fractured samples, and induced changes in the failure modes. In particular, the maximum increase in uniaxial compressive strength attributed to strain rate, Vsf and Vpf reached up to 15.0%, 23.57% and 8.57%, respectively. Although the inclusion of recycled aggregates had no significant influence on the failure mode, it decreased the compressive strength by up to 16.34%. Finally, a dynamic stress-strain theoretical constitutive model was established in this paper. The predictions derived from this model closely aligned with the experimental stress-strain curves obtained during the conducted tests. This study provides valuable insights for applications of SFRAC in structural engineering.

Static and Modal Analysis of a Coil Needle Structure

This paper mainly conducts static and dynamic mechanical analysis of the coil needle structure in the battery cell winding machine device. As the coil needle structure directly supports the battery cell and performs the cell winding process, the rationality and stability of its design directly affect the accuracy of cell winding formation. Therefore, static and modal analysis of the coil needle mechanism is carried out to verify its static and dynamic mechanical performance under working conditions.

Mechanical Characterization and Dynamic Mechanical Analysis of Recycled Low Density Polyethylene Filled Unsaturated Polyester Composite

Unsaturated polyester resin (UPR) is widely used as matrix in composite development; however, it has poor toughness property. To solve this problem, many researchers have used different tougheners to modify the resin, but the use of recycled low-density polyethylene (RLDPE) has not been explored. This work is aimed at modifying unsaturated polyester resin (UPR) with recycled low-density polyethylene (RLDPE) as a toughener and establishing the effects on the mechanical and dynamic mechanical performance of the RLDPE-filled polyester composite. Unsaturated polyester resin was modified with 1.18 mm RLDPE at different proportions of 1-4 wt%. Casting method was used for the production and the mechanical and dynamic mechanical analyses of the produced composite materials were carried out using ASTM standards. UPR modified with 1.5 wt% RLDPE exhibited the best impact than the un-modified UPR. The control (un-modified) sample had the highest flexural and tensile strength of 18 MPa and 14.02 MPa respectively which was about 26% and 25% higher than UPR modified with 1 wt% RLDPE. The Dynamic Mechanical Analysis (DMA) result showed that the composite does not depend strongly on the modifier loading as no regular pattern was observed for storage modulus, loss modulus and damping factor respectively.

On the collapse stress of tubular enhanced anti-tetra-missing rib structure

In the contemporary landscape of engineering, escalating demands for advanced material and structural performance have brought metamaterials to the forefront. Among them, the enhanced anti-tetra-missing rib structure has gained prominence owing to its auxetic behavior under significant strain. However, the lack of research on its quasi-static and dynamic mechanical performance have hindered its practical application. To address this, we introduce the tubular enhanced anti-tetra-missing rib structure (TEATMRS) and derive its collapse stress expression under various conditions. Through extensive simulations and experiments, we explore its deformation mechanisms and assess the influence of the structural geometric parameters and impact velocity on collapse stress. The results demonstrate excellent agreement among theoretical description, numerical analysis, and experimental tests, establishing the feasibility of the proposed collapse stress expression. These findings provide a theoretical foundation and design guidance for TEATMRS in engineering applications.

Mechanical Analysis of the Quasi-Static and Dynamic Composite Action in PV Modules with Viscoelastic Encapsulant.

The mechanical analysis of photovoltaics and building integrated photovoltaics is a key step for their optimal design and certification, and requires careful consideration, alongside solar power, durability and functionality issues. The solar cells are encapsulated in thin interlayers that are usually composed of a viscoelastic Ethylene-Vinyl Acetate compound, and protected by thin glass and/or plastic layers. This paper investigates the out-of-plane bending response of a full-scale commercial PV module and focuses attention on the shear bonding efficiency of the thin encapsulant for quasi-static and dynamic mechanical considerations. The parametric analytical analysis, carried out in this study for a laminated glass plate, highlights the possible consequences of the viscoelastic shear coupling on the cross-section load-bearing demand in the covers. As a direct effect of severe operational conditions (i.e., ageing, non-uniform/cyclic thermal gradients, humidity, extreme mechanical/thermal loads, etc.) the shear rigidity and adhesion of these films can suffer from repeated/progressive modification and even degradation, and thus induce major stress and deflection effects in the out-of-plane mechanical response of the PV module components. The minimum shear bond efficiency required to prevent mechanical issues is calculated for various configurations of technical interest. Accordingly, it is shown how the quasi-static and dynamic mechanical performance of the system modifies as a function of a more rigid or weak shear coupling.

Tensile and Interfacial Mechanical Properties for Single Aramid III Fibers under Dynamic Loading.

In this study, the traditional mini split Hopkinson tension bar (SHTB) was enhanced for the dynamic mechanical performance testing of single fiber/resin interface of composites. Single Aramid III fibers were modified using a polyamine modification treatment. Quasi-static and dynamic tensile tests of modified single Aramid III fibers were conducted using an electronic tensile testing machine and mini SHTB. The test results indicated that the surface modification employing the Catechol-Tetraethylenepentamine (Cat-TEPA) approach had a negligible effect on the tensile mechanical properties of single Aramid III fibers. The microdroplet method was introduced to measure the dynamic interfacial shear strength (IFSS) of Aramid III fiber/waterborne polyurethane resin using a mini SHTB. The dynamic shear test results revealed an increase in the dynamic shear strength of the modified Aramid III fiber/resin interface from 36.16 MPa to 41.51 MPa. Furthermore, the Scanning Electron Microscope (SEM) photography of the modified single Aramid III fiber after debonding exhibited regular grid structures on the debonding area, which can prevent debonding between the single fiber and the microdroplet, thereby enhancing interfacial shear performance.

Impact performance of unconventional trigger holes

Abstract Crash boxes in vehicles are one of the passive safety measures that aim to reduce injury to passengers and damage to the vehicle during a collision. Their function is to absorb the mechanical energy resulting from a collision by deforming plastically. Considering human safety, not only the energy must be damped, but also the forces acting on the passengers must be controlled. This force control can be adjusted to some extent using trigger mechanisms. There is a wide variety of research on hole type triggers, but they concentrated on traditional shapes; unique or hybrid shapes have not been sufficiently tested. This study examined the effects of various hole profiles with equal areas on dynamic mechanical performances of Al 6063-T6 rectangular crash boxes. Four types of trigger shapes were formed: upward keyhole, downward keyhole, U-shaped, and S-shaped. The dynamic performance evaluation was carried out experimentally by testing five types of geometries, the fifth one being the geometry without any trigger. In addition, dynamic Finite element analyses were conducted and validated using the experimental data, with the aim of employing the Finite element models in future geometry improvement studies. The experimental results were interpreted with some common evaluation parameters: peak force, crash force efficiency, mean crash force, and total energy absorption. The downward keyhole profile generally gave the best results, while the lowest peak force was observed in the U-shaped profile.

Effect of microcrystalline cellulose on the mechanical properties of flax reinforced methylmethacrylate and urethane acrylate composites

Many structural applications are attracted to natural fibre-reinforced polymeric composites due to their eco-friendliness, recyclability, and cost-effectiveness. While significant progress has been made, their interface compatibility with the polymeric matrix is still challenging. Therefore, the present study proposed a method for improving the mechanical and dynamic mechanical performance of flax-reinforced novel methylmethacrylate (Elium®) and urethane acrylate (Crestapol®) composites. The technique involved the dispersion of microcrystalline cellulose (MCC) in the matrix at different weight percentages (0.5–0.75%) to improve the fibre/matrix interface. Flax/Elium® (FE) and flax/Crestapol® (FC) composites with varying weight percentages of MCC were manufactured using the vacuum infusion method. The resulting improvements in mechanical and dynamic properties were evaluated through in-plane shear (± 45° tensile), flexural, short beam shear, and dynamic mechanical analysis (DMA). The effects of MCC on these properties of flax/Elium® were compared to those of flax/Crestapol® composites. The addition of MCC improved the in-plane shear strength (FE: 13–20%, FC: 10–17%), flexural strength (FE: 6–13%, FC: 13%) and interlaminar shear strength (FE: 9–17%, FC: 10–20%). Also, FE composite showed 7–11%, 10–14% and 10–17% higher in-plane shear, flexural and interlaminar shear strengths, respectively, compared to FC composites. The DMA results confirmed the positive effect of Elium® resin and MCC on the dynamic storage and loss modulus.

Development of green engineered cementitious composites with acceptable dynamic split resistance utilising recycled polymer fibres

Using recycled tyre polymer fibres (RTPF) to replace part of polyvinyl alcohol fibres (PVAF) is a strategy to produce green and economical engineered cementitious composites (ECC). This paper systematically investigated the influence of RTPF dosage (0.25–1.0 vol%) on split tensile performance of ECC under different strain rates. Results indicated that replacing PVAF with RTPF up to 0.5 vol% could still show a pronounced strain-hardening behaviour for ECC, although accompanied by a decrease in static split tensile strength. The dynamic split tensile performance of all ECC mixes was strongly sensitive to strain rate and all hybrid fibre reinforced ECC presented a greater strain rate effect than the mono-PVAF reinforced ECC. Under dynamic split tension, the specimens with various RTPF dosages could maintain their structural integrity. This paper suggested that RTPF can be adopted to replace part of PVAF to produce a greener and more economical ECC with satisfactory static and dynamic mechanical performance but the highest substitution amount should be set to 0.5 vol%.

Experimental study and failure criterion analysis of dynamic mechanical performance of hydraulic asphalt concrete under combined compression-shear stresses

Experimental study and failure criterion analysis of dynamic mechanical performance of hydraulic asphalt concrete under combined compression-shear stresses

Consolidation of water-atomized chromium–nickel-alloyed powder metallurgy steel through novel processing routes

When processing powder metallurgy (PM) steels, the conventional press and sinter route can reach a relative density up to 95%, which is insufficient for applications when dynamic mechanical performance is critical. In this study, a novel route is demonstrated consisting of cold isostatic pressing (CIP) followed by sintering and capsule-free hot isostatic pressing (HIP), allowing to achieve full density PM steels. Water-atomized steel powder admixed with 2 wt.% Ni was subjected to CIP and followed by sintering in 90N2/10H2 atmosphere at 1120 and 1250°C, and in vacuum (10−2 mbar) at 1250 and 1350°C, respectively. At the highest explored CIP pressure of 600 MPa, the three high-temperature sintering runs at 1250°C in 90N2/10H2 atmosphere and vacuum, and 1350°C in vacuum resulted in relative density of ∼94% and closed surface pores. This condition with necessary closed porosity then allowed subsequent capsule-free HIP after sintering, resulting in full densification of the components.

Dynamic mechanical performance of geogrid–waste tyre-reinforced railway ballast under cyclic loading

The accumulation of permanent deformation under cyclic loading in the granular bed is the main source of ballast track settlement. Therefore, studying the dynamic mechanical behaviour of reinforced railway track beds under cyclic loading is crucial. To reduce the accumulated of permanent deformation of railway track bed, geogrids–waste-tyre reinforced railway track bed was used to study in order to effectively control the permanent deformation of ballasted railway track bed. The test was conducted to investigate the mechanism of permanent deformation of geogrid–waste tyre-reinforced railway track bed through the evolution of cumulative plastic strain, permanent strain rate and dynamic elastic modulus of railway track bed under different confining pressures, dynamic stress amplitude, and amount of reinforcement. Results show that geogrid and waste tyre reinforcement have significant effects on the accumulated permanent deformation of the railway ballast. Geogrid reinforcement is better than waste tyres in improving the performance of the ballast fill. Reinforcement with geogrid significantly reduces the permanent strain rate, although the impact on this rate varies depending on the position and amount of reinforcement used. Notably, reinforcing the middle three layers of the track bed sample with waste tyres substantially decreases the permanent deformation rate. In contrast, the application of reinforcement across all five layers with waste tyres increases the permanent deformation rate. The dynamic elastic modulus of the track bed sample not only increases significantly but also rises with the dynamic stress amplitude due to the reinforcement of the geogrid and the waste tyre. The dynamic elastic modulus gradually stabilises with the increase in cyclic loading, indicating a stable accumulated deformation in the railway track bed.

Static, dynamic and impact properties of a high-performance flax-fiber composite

As environmental issues become increasingly relevant nowadays, the need to develop new materials entirely or partially based on renewable resources is one fundamental step to reduce the consumption of fossil fuels and CO2 emissions. In that sense, natural fiber composites might represent an environmentally sustainable alternative to conventional solutions such as glass and carbon fiber composites, standard today for many lightweight structural applications; however, solutions are several and diverse in terms of technological process, base materials, mechanical properties, and analysis of their behaviour, necessary for safe industrial use, is still lacking for most resin-fiber combinations. Consequently, this work presents a comprehensive material characterization of a flax-fiber reinforced composite material, analyzing both the static and dynamic mechanical performances, targeting future crashworthiness applications. In particular static tensile, compressive, flexural and shear properties were investigated, while low-speed indentation, high strain-rate tensile and ballistic tests were carried out to probe the dynamic and impact features.

Dynamic mechanical performance of FeNiCoAl-based high-entropy alloy: Enhancement via microbands and martensitic transformation

The non-equiatomic FeNiCoAlTaB high-entropy alloy exhibits outstanding quasi-static mechanical properties. Here, we investigate the microstructural evolution and mechanical response of this alloy subjected to dynamic loading, which has not been done before. A novel strategy combining extensive microbanding and martensitic transformation improves the resistance to the plastic instability by deterring the formation of adiabatic shear bands, that only occur beyond a critical shear strain larger than 4. The aged alloy, with grain sizes up to 400 μm, exhibits a dynamic yield stress over 1300 MPa with good deformability in this regime. This investigation sheds light on potential strategies for the enhancement of dynamic mechanical properties of structural materials through the use of a stress-induced martensitic transformation.