Dynamic Mechanical Behavior Research Articles

Unlocking the potential of lignin: Towards a sustainable solution for tire rubber compound reinforcement

This study tackles the persistent challenge of producing highly reinforced lignin-rubber composites, emphasizing the transformation of agro-industrial residues into value-added products. To address this challenge, we introduce a novel approach termed “in-situ surface modification utilizing a thermo-chemo-mechanical approach” which incorporates the utilization of biomass-derived kraft lignin and a thermally stable organofunctional surface modifier, specifically (3-aminopropyl) triethoxysilane. The resulting material exhibits unprecedented tensile strength (∼15 MPa) along with ∼300 % elongation at break, while typical gum rubber offers 1–2 MPa tensile strength. Additionally, for the other tensile properties like 100 %, and 200 % tensile modulus, the improvement is 7-fold (∼5.6 MPa) and 10-fold (∼11.3 MPa), respectively. Furthermore, this composite presents a higher degree of reinforcement than a passenger car radial (PCR) tire model compound (tensile strength ∼14.5 MPa, 100 % tensile modulus ∼2.2 MPa, and 200 % tensile modulus ∼5.6 MPa) comprised of silica and polysulfide-based coupling agent, with exactly a similar loading of filler. The dynamic mechanical and stress relaxation behavior of the composites are critically discussed concerning the dispersion of the lignin in the sSBR/BR rubber matrix. The morphological orientation and involved chemical interaction in the presence of a surface modifier are also studied in detail. Tear fatigue analysis using pure shear specimens indicates superior fracture toughness at a lower tearing energy regime compared to silica-filled PCR tire compounds. Overall, this study showcases the potential of lignin-reinforced elastomers, offering a promising route for sustainable engineering materials and commercial viability.

Microstructural evolution and modified constitutive model of nanoscale Al2O3 dispersion-strengthened copper under high strain rate deformation

The dynamic mechanical properties and behaviors of an oxide dispersion strengthened copper alloy (ODS Cu) are investigated herein within a strain rate range of 1000–5000 s−1 using a split Hopkinson pressure bar to offer theoretical guidelines for potential applications. The mechanisms of plastic deformation and dynamic recrystallization of ODS Cu were studied by analyzing the microstructure evolution during dynamic compression. The results demonstrate that the strain rate sensitivity of ODS Cu exceeds that of pure Cu, which is beneficial for resisting dynamic high-speed impacts. The accumulation of dislocations and generation of an adiabatic temperature rise during high strain rate deformation promote the splitting of the original grains and the formation of dynamically recrystallized grains. The dominant Goss and cube textures transformed into R-cube textures with increasing strain due to the continuous rotation of subgrains and recrystallized grains. By considering the coupled effects of strain and strain rate, the Johnson-Cook model was modified according to the Voce hardening law. The modified Johnson-Cook model exhibits good agreement with the experimental data across a wide range of strain rates. This study provides insight into the dynamic mechanical behavior of ODS Cu.

Comparative Study on Mechanical Response in Rigid Pavement Structures of Static and Dynamic Finite Element Models

The safety of airport runways is important to guarantee aircraft taking-off, landing, and taxiing, and the comparison of the mechanical response of pavement structures under dynamic and static loading by LS-DYNA has rarely been studied. The purpose of this work is to separate two analysis methods to investigate the mechanical response of rigid airport pavements. Firstly, a tire–road coupling model of an airfield was established to evaluate the suitability of dynamic and static analyses. Then, the effects of landing pitch angles, sinking speeds, and tire pressures on the effective stress, effective strain, and z-displacement of the runway were investigated for both dynamic and static analysis. Finally, the significance of influence factors was analyzed by regression analysis in Statistical Product and Service Solutions (SPSS). The results indicated that the effective stress, effective strain, and z-displacement of the runway increased with a decrease in the landing pitch angle, which also increased with an increase in the sinking speed and tire pressure. It was demonstrated that the difference in pavement mechanical response between dynamic and static analyses progressively widened at high tire pressure and sinking speed. In other words, the static analysis method can be adopted to assess the dynamic mechanical behavior when the landing pitch angle is large and the tire pressure is small. Among the various factors of mechanical response, the effect of tire pressure was the most obvious, followed by sinking speed and landing pitch angle. The work proposes a new approach to understanding the mechanical behavior of runways under complicated and varied conditions, evaluates the applicability of the dynamic and static mechanical analysis methods, identifies key factors in the dynamic and static mechanical analysis of rigid runways, and provides technical support for improving and maintaining the impact resistance of pavement facilities.

Analysis of the dynamic contact behaviour of high-speed train transmission gear excited by wheel defects

Studies on wheel flatness and polygonal wear have demonstrated that wheel defects cause severe impact forces at the wheel–rail interfaces. This study investigated the dynamic contact mechanical behaviour of high–speed train transmission gears when subjected to wheel defects. First, a train-track coupling dynamics model was established, considering the localized contact characteristics of transmission gears. This model was developed using the slice method and the Hertz contact model, exploring the spatial coupling effects between the gear contact interface and the train–track interface. Subsequently, the dynamic model was employed to extract essential contact mechanical parameters of the transmission gear under the influence of wheel defects, including gear meshing load, gear contact stress, and sliding velocity. Furthermore, an analysis was conducted to uncover and elucidate the mechanism by which wheel flatness and polygonal wear impact the dynamic contact behaviour of the transmission gear. This study underscores the importance of considering wheel defects when assessing the contact fatigue and wear performance of high-speed train transmission gears.

Dynamic mechanical behaviors of foamed concrete using modified viscoelastic SHPB

This study aims to investigate the dynamic mechanical behaviors of foamed concrete (FC) utilizing a modified viscoelastic split Hopkinson Pressure Bar (VE-SHPB). The VE-SHPB proposed in this study enables impedance matching between bars and FC, enhancing measurement precision. Dynamic mechanical behaviors of FC with different densities (400, 700, 1000, 1300 kg/m3) under various incident pressure (0.2, 0.5, 0.8, 1.1 MPa) are examined using the VE-SHPB. The failure modes of FC are categorized into Spalling (Mode I), Disintegration (Mode II), and Comminution (Mode III) based on fracture states of post-impact. The mechanism of strain rate and density on failure mode, dynamic strength, dynamic increase factor (DIF), and energy consumption density are discussed. The results show that FC's dynamic mechanical properties increase with increasing strain rate, but present different strain rate sensitivities at different densities. The dynamic mechanical properties of FC are determined by both the pore structure and matrix properties. Notably, Mode II shows better ability of energy consumption, specifically FC with a density around 700 kg/m³ demonstrates higher energy absorption density.

Investigation on role of heat-treated barley husk biosilica on fatigue, creep, and dynamic mechanical behavior of cotton microfiber-vinyl ester composite

Investigation on role of heat-treated barley husk biosilica on fatigue, creep, and dynamic mechanical behavior of cotton microfiber-vinyl ester composite

Dynamic mechanical behavior of CNT-reinforced epoxy under medium-strain rate: A comparative study

Carbon nanotubes (CNTs) are generally recognized as one of the most effective fillers to improve the properties of polymeric materials. Subjected to dynamic loading, polymer-based materials often exhibit high strain rate sensitivity. This research investigates the effectiveness of CNTs fillers on the mechanical properties of an epoxy resin at low to medium strain rates through conducting a comparative experimental study. Performing tensile and shear tests, the elastic modulus and strength properties of CNT/epoxy and pure epoxy resin are measured at different strain rates. By proposing an empirical logarithmic relationship, the prediction of dynamic elastic modulus and strength properties at any desired low to medium strain rate is facilitated. For measuring the dynamic fracture toughness of CNT/epoxy and pure epoxy resin at medium strain rate, the instrumented charpy impact test based on the Dynamic Key Curves (DKC) method is used. Experimental measurements still imply on significant enhancements in axial and shear properties and also dynamic fracture toughness up to medium strain rates of 150 s−1 by adding small portion of CNTs.

Dynamic mechanical response and failure behavior of solid propellant under shock wave impact

Solid rocket motor propellants are typically subjected to shock wave loads during ignition. To analyze the dynamic mechanical response and failure behavior of hydroxyl-terminated polybutadiene (HTPB) propellant under varying shock intensities, this study innovatively employed a shock tube apparatus in conjunction with schlieren imaging and 3D-DIC techniques. Shock loading experiments were conducted on propellant samples of three different thicknesses under pressures ranging from 0.3 to 0.7 MPa, capturing the dynamic deformation processes. Results revealed that deformation initiated at the clamped region, extending towards the center and forming a parabolic shape. The maximum deformation of the samples shows an approximately linear relationship with the launch pressure and decreases with increasing sample thickness. The 5 mm sample failed under a 0.6 MPa shock pressure, with electron microscopy images identifying matrix damage, particle debonding, and particle fracture as the principal failure mechanisms. Finite element simulations based on the generalized Maxwell linear viscoelastic constitutive model were conducted, demonstrating good agreement with experimental data. The critical stress for fracture was determined to be 4.12 MPa, and the ultimate shock wave pressures for 3, 6, 9, and 12 mm thicknesses were approximately 0.3 MPa, 0.65 MPa, 1.1 MPa, and 1.4 MPa, respectively. These findings provide valuable insights for assessing the structural integrity of solid rocket motors under ignition shock conditions.

Static and dynamic mechanical behavior and constitutive parameters determination of high nitrogen austenitic stainless steel

Static and dynamic mechanical behavior and constitutive parameters determination of high nitrogen austenitic stainless steel

Effects of ZrO2 ceramics doped with varying content on the mechanical properties and energy release characteristics of W-Zr alloys

A W-Zr alloy doped with ceramic powder W54.5Zr35-xNi6.7Fe3.3Mo0.5 (ZrO2) x was prepared by powder metallurgy. The effects of the ceramic content on the dynamic and static compressive mechanical behavior and energy release properties of the alloy were studied. The results showed that the addition of ceramics enhanced the energy release characteristics of the W-Zr alloy, and made the alloy break more thoroughly and the fragment cloud distribute evenly. The reaction delay time was shorter and the energy release reaction was more complete. However, the maximum temperature of the alloy reaction decreased. In addition, the addition of ceramics improves the mechanical properties of the material, and its compressive strength is much higher than that of traditional W-Zr alloys.(ZrO2)1 exhibited good mechanical behavior and energy release characteristics. The aftereffect damage performance was further verified using a ballistic gun experiment. Ballistic gun test results showed that (ZrO2) 1 can penetrate A92124 aluminum targets with a thickness of 2 mm at a speed of 809.3 m s−1 and ignite post-target absorbent cotton, with both penetration and post-target damage capabilities.

Dynamic mechanical properties and constitutive model of oil-immersed and thermally-treated red sandstone

To thoroughly investigate the stability of reservoir rock mass in heavy oil thermal recovery projects, this study explored the dynamic mechanical properties and deformation behaviors of thermally-treated red sandstone from the oil-immersed reservoir, taking the dry and water-saturated reservoirs as the comparison. The results show that the dynamic compression strength and energy transmission rate of oil-immersed and thermally-treated red sandstone are enhanced. With the help of scanning electron microscopy (SEM) tests, we observed the grain-coating on the surface of the mineral particles of oil-immersed rock. The grain-coating enhances the rock matrix integrity and leads to the mechanical strengthening effect of oil-immersed rock. The fractal dimension of oil-immersed samples is smaller than that of dry and water-saturated samples. In addition, the theoretical values of the damage constitutive model are consistent with the experimental data, which verifies the validity of the damage model. Our new findings support that the oil weakens the deformation resistance ability of the micro-crack part but strengthens that of the rock matrix.

Dynamic mechanical behaviours of frozen rock under sub-zero temperatures and dynamic loads

Dynamic mechanical behaviours of frozen rocks are essential for dealing with the design and stability of various engineering structures in cold regions. A dynamic-cryogenic testing system integrated with high-speed Digital Image Correlation (DIC) is adopted to investigate the dynamic mechanical behaviours of rock subjected to ambient room and sub-zero temperatures, along with high-rate loading. Dynamic compression, tensile and Mode I dynamic fracture tests were performed at 20, -20, −50 and −70 °C using dry and saturated sandstone from Yulong Copper Mine at high-altitude cold region. A DIC-based approach using pixel-based virtual extensometers is proposed to accurately capture the real-time cracking speed with high precision. The proportion of ice and unfrozen water in rock pores across various temperatures is quantified using the nuclear magnetic resonance (NMR) method. The results indicate significant temperature and rate dependencies in dynamic fracture toughness, crack propagation velocity, dynamic tensile strength, dynamic compressive strength, and failure modes; These parameters exhibit an increase with decreasing ambient temperature as unfrozen water transitions into ice, demonstrating the frozen effect of ice filling pores, supporting the rock skeleton, and bonding ice-rock interfaces. With decreasing temperature, crack branching becomes more pronounced in dynamic notched semi-circular bending (NSCB) tests. Additionally, dynamically compressed frozen rocks tend to transition from pulverization (Type II) to splitting (Type I) with multiple elongations, attributed to the strengthening effect. The findings elucidate the failure mechanisms observed in a higher proportion of larger blast blocks and hold valuable implications for blasting designs and dynamic disaster prevention in cold regions.

Dynamic failure of magnesia-carbon refractories under uniaxial compressive load

The thermo-mechanical stress, which was a combination of thermal stress from rapid temperature changed and dynamic mechanical stress from scrap impact, accelerated the damage to MgO–C refractories during service. The influence of graphite content (8 wt% and 16 wt%), heat treatment temperature, and oxidation level (partially oxidized or not) on dynamic mechanical stress damage behavior was investigated using the Split-Hopkinson pressure bar test at various loading velocities. The results indicated the SHPB test could form dynamic stress, and the parameters obtained post-test could characterize the dynamic mechanical properties of MgO–C refractories. Furthermore, all of the specimens' dynamic compressive strength clearly demonstrated the strain rate hardening effect; this phenomenon was particularly evident in the low-graphite specimens. Additionally, the thermally treated specimens dissipated impact energy by destroying the whole volume, whereas the oxidized specimens suffered damage layer by layer, and the specimens’ dynamic mechanical characteristics were weakened by oxidization or heat treatment.

Mechanical behavior and fiber reinforcing mechanism of high-toughness recycled aggregate concrete under high strain-rate impact loads

Fiber-reinforced recycled aggregate concrete (FRRAC) is renowned for its excellent mechanical properties and environmental benefits, making it a popular choice in construction engineering. However, the impact damage mechanisms of FRRAC remain unclear. This study leverages advanced in-situ 4D CT technology to investigate the fiber-reinforcing mechanisms of High-Toughness Recycled Aggregate Concrete (HTRAC) using construction waste as a sustainable building material. Under high strain-rate conditions, the dynamic mechanical behaviors of both plain recycled aggregate concrete (PRAC) and HTRAC were examined using the Split Hopkinson Pressure Bar (SHPB) method. The experiments revealed significant strain rate sensitivities in both materials, with HTRAC showing superior fiber reinforcement that markedly enhances its toughness. Quantitative models for dynamic increasing factors of key mechanical parameters, including peak stress, peak strain, initial elastic modulus, ultimate strain, and toughness index, were developed. These findings offer critical design insights for using HTRAC in impact load conditions and other extreme environments, promoting its wider adoption in the construction industry.

The dynamic mechanical behavior of SAP based porous cement-based materials suitable for EMAS

Superabsorbent polymers (SAP) voids have the potential to prepare cement-based materials (CBMs) that meet the engineered materials arresting system (EMAS) requirements due to their similarity to entrained air voids. This idea was validated using a crushing test and an immersion softening test in this paper. The pore structure and micromechanical properties of CBMs incorporating SAP were analyzed using an image analysis, a boiling method, a microhardness test, and a nanoindentation test. Moreover, the influence of SAP on the quasi-static and dynamic mechanical properties of CBMs was studied using a rigid press machine and an SHPB system. The results show that the crushing and immersion softening properties of CBMs can meet the EMAS requirements when SAP dosages are 10 % and 12 %. The optimal dosage of SAP is 10 %. Under quasi-static and dynamic compression, the compressive strength and elastic modulus decrease with increasing SAP dosage, due to the growth of the total porosity of samples and the decline in the micromechanical properties of the matrix. Increasing the SAP dosage can raise the total porosity, thereby enlarging the DIF-fc value and decreasing the DIF-E value. Raising the strain rate results will enlarge the DIF-fc and DIF-E values. This is due to the growth in the damage degree of the specimen and the change in the cracking behavior under dynamic compression.

Curing behavior and thermal properties of phthalonitrile resins derived from benzyl alcohol

A series of phthalonitrile resins were synthesized through innovative reactions between compounds derived from benzyl alcohol and nitro functionalities. The synthesis commenced with the reaction of specific alcohols (4-hydroxybenzyl alcohol, vanillyl alcohol, and 1,4-benzenedimethanol) with 4-nitrophthalonitrile, resulting in the formation of three phthalonitrile monomers. These monomers were then cured using 4,4′-diaminodiphenyl ether as a curing agent, resulting in the phthalonitrile resins, namely BCDPN, XCDPN, and DBDPN. The investigation revealed that these resins possessed remarkable properties, particularly in terms of thermal stability and dynamic mechanical behavior. Notably, BCDPN exhibited superior thermal stability, achieving a Td10 % of 534 °C. XCDPN and DBDPN demonstrated outstanding dynamic mechanical properties, characterized by a storage modulus exceeding 3400 MPa. The synthesis approach, leveraging compounds derived from benzyl alcohol and nitro reactions, not only broadens the scope of raw materials but also offers novel and alternative preparation strategies for phthalonitrile resins. This study enhances the understanding of the curing behavior and thermal properties of these resins, providing valuable insights into their potential applications in high-performance polymer materials.

Influence of high-strain-rate compression and subsequent heat treatment on (TiNbZr)89(AlTa)11 refractory high-entropy alloys: Dynamic-mechanical behavior and microstructural changes

This study explored the dynamic-mechanical behavior of a novel low-density (TiNbZr)89(AlTa)11 refractory high-entropy alloy (RHEA) across strain rates ranging from 1.0 × 103 to 3.5 × 103 s−1. A significant increase in the yield and ultimate compressive strengths with rising strain rates up to 3.0 × 103 s−1 was observed and attributed to enhanced dislocation activities and stress-induced microstructural transformations. The formation of the B2 phase and Zr5Al3 precipitates was found to be crucial in bolstering the alloy strength at high strain rates. Beyond strain rates of 3.0 × 103 s−1, a decrease in strength occurred due to thermal softening and strain localization. Microstructural analyses at 3.5 × 103 s−1 revealed grain refinement, the development of micro shear bands, and dislocation tangles, which were indicative of dynamic recrystallization. Besides, the findings also revealed that the post-dynamic compression heat treatment further enhanced the hardness and microstructural stability of the alloy. These results highlight the potential of the (TiNbZr)89(AlTa)11 RHEA for applications requiring materials with high strength-to-weight ratios, particularly in dynamically loaded environments. It is expected that the results of this study will further advance our fundamental understanding of the behavior of RHEAs under extreme conditions, thereby opening new avenues for material innovation.

Experimental study and numerical simulation of the impact of under-sleeper pads on the dynamic and static mechanical behavior of heavy-haul railway ballast track

AbstractLaying the under-sleeper pad (USP) is one of the effective measures commonly used to delay ballast degradation and reduce maintenance workload. To explore the impact of application of the USP on the dynamic and static mechanical behavior of the ballast track in the heavy-haul railway system, numerical simulation models of the ballast bed with USP and without USP are presented in this paper by using the discrete element method (DEM)—multi-flexible body dynamic (MFBD) coupling analysis method. The ballast bed support stiffness test and dynamic displacement tests were carried out on the actual operation of a heavy-haul railway line to verify the validity of the models. The results show that using the USP results in a 43.01% reduction in the ballast bed support stiffness and achieves a more uniform distribution of track loads on the sleepers. It effectively reduces the load borne by the sleeper directly under the wheel load, with a 7.89% reduction in the pressure on the sleeper. Furthermore, the laying of the USP changes the lateral resistance sharing ratio of the ballast bed, significantly reducing the stress level of the ballast bed under train loads, with an average stress reduction of 42.19 kPa. It also reduces the plastic displacement of ballast particles and lowers the peak value of rotational angular velocity by about 50% to 70%, which is conducive to slowing down ballast bed settlement deformation and reducing maintenance costs. In summary, laying the USP has a potential value in enhancing the stability and extending the lifespan of the ballast bed in heavy-haul railway systems.

Dynamic mechanical response and failure characteristics of coal and rock under saltwater immersion conditions

The stability of coal and rock masses in water-rich mines is affected by both mine water erosion and dynamic disturbances. Thus, it is necessary to study the dynamic mechanical response and failure characteristics of coal and rock under the combination of saltwater and a high strain rate. To this end, a split Hopkinson pressure bar device was employed to investigate the effects of impact velocity, water content, and immersion liquid on the dynamic mechanical behaviours of coal and rock. The results revealed that the weakening effect of saltwater on the dynamic mechanical properties of coal and rock is much greater than that of distilled water. With increasing moisture content, the dynamic compressive strength of the coal specimens decreases monotonically, while that of the rock shows a trend of first increasing and then decreasing. The failure process and destruction of coal and rock are comprehensively affected by both the external impact load and the physical and mechanical properties of the material. The degree of damage of the coal and rock specimens increases with increasing impact velocity and water content. Moreover, the influence of various factors on the impact fracture mechanism of coal and rock under saltwater immersion conditions was revealed. These findings are highly important for the design and maintenance of underground coal and rock building structures.

Impact response characteristics and damage mechanism of continuous carbon-fiber-reinforced magnesium matrix composite materials

The continuous carbon-fiber-reinforced magnesium matrix composite (C_f/Mg) is a new type of composite material made of a magnesium alloy sheet and carbon-fiber-reinforced composite material with alternating layers. It has the advantages of high damage tolerance, light weight, and corrosion resistance, and has become the first choice of lightweight materials in aerospace, transportation, and other fields. Because impact-resistance serves as an important index for its structural design and performance stability, a continuous carbon-fiber-reinforced magnesium matrix composite with indirect bonding using a modified epoxy resin was designed in this study. Moreover, C_f/Mg was chosen to be the object of research through the selection of constituent materials such as magnesium alloys, carbon fibers, resins, and other properties, which matched the aim of realizing a lightweight material. With the help of hot-compression molding technology, dynamic impact mechanical behavior, and damage analysis technology, the structural design and preparation process optimization of epoxy resin carbon-fiber prepregs and magnesium alloy layer materials, as well as the dynamic impact mechanical response characteristics and damage evolution process under different impact energy conditions, were studied. Accordingly, through a combination of low-velocity impact experiments and numerical simulations, the effects of continuous multiple impacts at the same location with the same impact energy, as well as impacts with the same impact energy and different punch diameters, on the low-velocity impact damage behavior and dynamic impact response characteristics of C_f/Mg were investigated. The results of this study show that when the 5J impact is applied four times consecutively, the peak impact load gradually increases with the increasing number of impacts. Moreover, the peak impact loads of the second, third, and fourth impacts increase by 6.09%, 10.7%, and 14.5%, respectively, compared with the results of the first impact.