Dynamic Mechanical Behavior Research Articles

Experimental and Numerical Study on the Blast Resistant Performance of Geopolymer Concrete

Geopolymer, with its notable benefit of low carbon dioxide emissions, holds the potential to substantially curtail environmental pollution. According to the existing related research on geopolymer materials, it is obvious that it has great development potential in many engineering application fields, and it is a new generation of green and environmentally friendly recycled materials. Nowadays, there is a growing concern regarding explosion protection. Explosions near buildings can cause catastrophic damages on the building external and internal structure, and the most important thing is that can cause injuries and loss of life to the occupants of these buildings. This study investigates the mechanical performance of the fiber-reinforced geopolymer concrete under explosive testing. Furthermore, the finite element analysis models have been established through LS-DYNA software to simulate the explosive testing using Structure-Arbitrary Lagrangian Eulerian Method (S-ALE). The model is used to assess the dynamic mechanical behavior of geopolymer materials.

Impact response and constitutive model of basalt-polypropylene fiber-reinforced coral aggregate concrete

Basalt-polypropylene fiber-reinforced coral concrete (BPFRCAC) is a popular choice for engineering materials in the reef environment, but the dynamic behavior of BPFRCAC under extreme dynamic loads remains unclear. This study explores the impact response of BPFRCAC at strain rates ranging from 31 to 141 s−1 using split Hopkinson pressure bar (SHPB). It examines the effects of strain rate on the dynamic mechanical properties of BPFRCAC, and establishes quantitative models of the relationship between the strain rate and key mechanical parameters, including dynamic compressive strength, critical strain, dynamic elastic modulus, and toughness index. The results showed that these properties of BPFRCAC are significantly influenced by the strain rate, showing increases that correlate with the strain rate. The addition of basalt fibers (BF) and polypropylene fibers (PF) not only mitigates the failure extent of BPFRCAC but also enhances the strain rate's impact on its dynamic compressive strength and dynamic modulus of elasticity, particularly when both fibers are mixed. The failure modes of BF and PF depend on the strain rate; at lower strain rates, the probability of fiber pull-out is higher than at higher strain rates, where BF and PF are more likely to snap. A viscoelastic dynamic damage constitutive model suitable for BPFRCAC is proposed, which accurately describes the dynamic mechanical behavior of BPFRCAC. These findings provide important design insights into the use of BPFRCAC under impact conditions, and promote its wide application in reef construction projects.

Dynamic mechanical behavior of titanium matrix composites reinforced with graphene nanoplatelets

In this investigation, graphene nanoplatelets reinforced pure titanium matrix (GNPs/TA1) composites were synthesized via short-term ball milling followed by spark plasma sintering. The mechanical properties and microstructure evolution of these composites were examined under both quasi-static and dynamic compression conditions. The results indicate that as the strain rate increases from 10−3 to 3000 s−1, the yield strength rises from 436.9 MPa to 1209.6 MPa, consistent with the positive strain rate effect. The superior yield strength of GNPs/TA1 composites arises from the dynamic Hall-Petch effect, dislocation strengthening and load transfer strengthening, with the contribution from load transfer strengthening being the most significant due to the reinforcement's (TiC-GNPs-TiC) facilitation of load transfer. As the strain rate increases, interfacial debonding gradually extends along the reinforcement and grain boundaries, but no macroscopic fracture occurred in this study. At a strain rate of 3000 s−1 during compression, {112‾2}, {101‾2}, and {11 2‾ 1} twins were generated. However, at a strain rate of 10 s−1, only {112‾2} and {101‾2} twins were produced, while {11 2‾ 1} twin was inhibited. Under high strain rate loading, the plastic flow behavior of GNPs/TA1 composites was predicted using the Johnson-Cook constitutive model, modified to account for adiabatic temperature rise, and the predictions showed good agreement with experimental results.

Experimental and crystal plasticity finite element study of dynamic shear behavior of CoCrNiSi0.3 medium-entropy alloy

Single-phase CrCoNi-based medium-entropy alloys (MEAs) have garnered considerable attention as a promising class of metallic materials. However, despite this growing interest, the dynamic mechanical response of CrCoNi-based MEAs at high strain rate remains controversial. The dynamic shear mechanical behavior of CoCrNiSi0.3 was characterized through Hopkinson-bar experiment utilizing hat-shaped specimen. In this study, a damage model based on the maximum shear strain of each slip system was chosen to describe the damage initiation and evolution. Combined with this micro-scale damage and dislocation density-based crystal plasticity theory, two constitutive models were proposed to perform predictions of the dynamic shear behavior of CoCrNiSi0.3. The strain rate effect, adiabatic temperature rising, damage evolution, and twin volume fraction during dynamic shear deformation were tracked by investigating the influence of resolved shear stress, dislocation density, texture evolution, and twinning systems shear strain. The presented model effectively predicts the deformation state of specimen, the formation and evolution of Adiabatic Shear Bands (ASBs), and the variations in strain rate and temperature at different locations within the shear region. Adiabatic Shear Bands and texture evolution are caused by the local dislocation density rising and misorientation distributions.

Two-stage work-hardening of a transformable B2-enhanced metallic glass composite by molecular dynamics simulation

The crystalline-amorphous interfaces play vital roles in affecting martensitic transformation, shear band nucleation and interface stability. Though both quasi-static and dynamic mechanical behaviors of shape memory enhanced bulk metallic glass composites have been studied via experiments, the atomic-level interactions among martensitic transformation, localized shear softening and interfacial strain concentration imposed by strain rate remain elusive. We employ molecular dynamics simulations to study strain rate effect on uniaxial compression behavior of transformable B2–CuZr enhanced bulk metallic glass composite. As strain rate increases, the proportion of martensitic transformation accelerates. During the competition among martensitic transformation induced-hardening, shear induced-softening and interface debonding, a two-stage work-hardening is observed, which is in agreement with experimental findings.

Copper-MOF and tannic acid-empowered composite cryogel as a skin substitute for accelerated deep wound healing

The effective management of deep skin wounds remains a significant healthcare challenge that often deteriorates with bacterial infection, oxidative stress, tissue necrosis, and excessive production of wound exudate. Current medical approaches, including traditional wound dressing materials, cannot effectively address these issues. There is a great need to engineer advanced and multifunctional wound dressings to address this multifaceted problem effectively. Herein, a rationally designed composite cryogel composed of a Copper Metal-Organic Framework (Cu-MOF), tannic acid (TA), polyvinyl alcohol (PVA), and zein protein has been developed by freeze-thaw technique. Cryogels display a remarkable swelling capacity attributed to their interconnected microporous morphology. Moreover, dynamic mechanical behaviour with the characteristics of potent antimicrobial, antioxidant, and biodegradation makes it a desirable wound dressing material. It was further confirmed that the material is highly biocompatible and can release TA and copper ions in a controlled manner. In-vivo skin irritation in a rat model demonstrated that composite cryogel did not provoke any irritation/inflammation when applied to the skin of a healthy recipient. In a deep wound model, the composite cryogel significantly accelerates the wound healing rate. These findings highlight the multifunctional nature of composite cryogels and their promising potential for clinical applications as advanced wound dressings.

Strain rate dependence of mechanical behavior in an AlSi10Mg alloy with different states fabricated by laser powder bed fusion

The strain rate dependence of mechanical behavior in an AlSi10Mg alloy with different states fabricated by laser powder bed fusion (LPBF) was investigated systematically via thermodynamic calculations, microstructure characterization and mechanical characteristic evaluation in the present study. The results show that there is a close relationship among the material state, microstructure and dynamic mechanical behavior. Before tensile deformation, the as-built specimen possesses a fine equiaxed grain structure and a typical cellular structure surrounded by continuously distributed particles; the annealed specimen has coarser equiaxed grain structures and particles, but no cellular structure is present. Both the as-built and annealed specimens exhibit weak strain rate sensitivity, and the strain rate sensitivity parameters are 0.01 and 0.024, respectively. Under specific strain rate conditions, the as-built specimen has a higher strength and lower elongation than the annealed specimen. After tensile deformation, there is a significant increase in the dislocation density. Independent of the material state, the dislocation density increases with increasing strain rate. Compared with the as-built specimen, the annealed specimen has a stronger strain rate sensitivity because of the greater dislocation density variation.

Effect of halloysite addition on the dynamic mechanical and tribological properties of carbon and glass fiber reinforced hybrid composites

Composite materials have become prominent in the aerospace, automotive, wind energy, biomedical, and machine tool industries. This has demanded the evaluation of the dynamic mechanical and tribological behaviour of composites to understand their performance and ensure their reliability and safety in varied operating conditions. In this study, the effect of halloysite nano-clay addition on the dynamic mechanical and tribological properties of the carbon/glass hybrid composites was investigated. The composites were produced with the vacuum assisted resin infusion process. by varying the content of halloysite nano-clay (1, 3, and 5 wt%). The dynamic mechanical properties of the manufactured composites were examined at temperatures ranging from 30 °C to 180 °C. The tribological properties of the specimens were assessed by varying the applied load (10, 20, and 30 N), sliding speed (1.5, 3, and 4.5 m/s) and sliding distance (500, 1000, and 1500 m). Box-Behnken design was utilized to optimize the number of experiments. The results showed that the halloysite-added samples had better dynamic mechanical and tribological properties than the carbon/glass hybrid composites. Especially, hybrid composites containing 3 wt% halloysite outperformed the other composites investigated. A scanning electron microscope (SEM) was used to examine the worn surface and wreckage in the investigated composite specimens.

Radial Inertia Effect of Ultra-Soft Materials from Hopkinson Bar and Solution Methodologies.

The split-Hopkinson pressure bar technique is widely used to determine the dynamic mechanical behavior of materials. However, spike-like stress features appear in the initial stress behavior of ultra-soft materials tested with a split-Hopkinson bar. These features are not intrinsic characteristics of the materials. Potential causes were investigated through experiments and numerical simulations. It was found that the spike feature represents derived stress resulting from the radial inertia effect during dynamic loading. In this work, we propose and experimentally verify effective methods to reduce this effect. The influences of density, strain acceleration, ratio between inner and outer diameter, and Poisson's ratio on the radial inertia effect were investigated. The spike stress was found to change linearly with density and strain acceleration but decrease significantly when the inner/outer diameter ratio was below 0.3, after which it remained nearly constant. A parabolic stress distribution was observed along the radial direction due to the Poisson effect, especially when the ratio exceeded 0.3, leading to higher spike stress. Finally, suggestions were proposed as experimental guidance when testing ultra-soft materials.

Study on interfacial mechanical properties of bonded pipe joint under dynamic load

This study analyses the interfacial mechanical behaviour of adhesive-bonded pipe joints under dynamic loading conditions. First, a mechanical model of the bonding interface of a pipe joint was established. Next, computational formula for the interfacial slip and shear stress in the pipe joints were obtained using variable separation, eigenfunction expansion, and Laplace transform methodologies. Further, the effects of various parameters, including the loading duration, bond length, adhesive layer thickness, stress rate, adhesive shear modulus, elastic moduli of the main pipe and coupler pipe, and adhesive-layer thickness, on the mechanical response of the pipe joints were assessed. The goal is to study the impact of these parameters on the maximum shear stress, interfacial slip, and normal stress in the main and coupler pipes, their effects on the pipe joint strength can be determined, thereby providing a theoretical basis for the design of practical pipe–joint configurations. The innovation of this study is as follows: it considers high-stress-rate dynamic loads for formulating complete mathematical equations. Further, it employs theoretical methods to calculate the relative slip and shear stress in pipe joints, through which theoretical formulas for engineering applications of adhesive-bonded pipe joints were derived. Additionally, the study analyses the impact of various parameters on the dynamic mechanical behaviour of the adhesive layer at the pipe joint interface, leading to a deeper understanding of the interface mechanical behaviour characteristics and key parameters to be considered while receiving dynamic loads in pipe joints.

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.