Dynamic Mechanical Methods Research Articles

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.

Characterization of viscoelastic properties of yarn materials: Dynamic mechanical analysis in the transversal direction

Abstract Warp knitting creates very challenging dynamics due to its high production speeds. On the one hand, this makes it method of choice for many products in various fields. On the other hand, not all materials are suitable for such high productivity. With the current generation of machines being limited to only achieve their maximum speed of around 4,400 min−1 with highly elastic yarns, it is desired to gain a deeper insight into yarn behavior in such highly dynamic environments. Among other influences, resonance effects gain high significance as they may result in high loads on the used materials; therefore, yarn breakages interrupt the production and decrease the quality of the product. To extend the material choice, especially high-performance fibers, for high productivity, a deep understanding of the intrinsic properties of the yarn is required. In particular, the viscoelastic properties are of importance. This study proposes a method to determine these characteristics using the dynamic mechanical analysis method. For the purpose of finding the damping in the transversal direction to the yarn axis, the variant of free oscillation is chosen. For the trials, a high-speed camera is suspended above a testing rig. On this rig, a yarn sample is clamped and then displaced from its rest position. The resulting oscillation is recorded and later extracted from the video. From the decrement of the maxima of the amplitude and corresponding time intervals, the damping factor is determined. It decreases with higher initial deflection. Summarised the developed trial setup proved suitable for the determination of the viscoelastic properties in transversal direction.

Determination of the ignorable boundary condition and standard sample for a novel in-situ dynamic mechanical analysis method on soft matter

An in-situ Dynamic Mechanical Analysis (DMA) method for soft matter developed by our group [Wu. et.al. 2022] encounters the problem of irregular samples, which significantly vary in shape and size in practice, therefore a standard sample “large enough” to ignore the boundary and size effects is necessary to determine the baseline of test and build the correspondence between this new method to classical mechanical tests. In this work, we use finite element analysis to approach the optimal size of a brick sample where the stress on the boundaries in three spatial directions are ignorable, and certified the results by testing a series of silicone gel samples on the in-situ DMA device. The stress-strain of tensile and compression are characterized. The material properties of gel are chosen to be close to the biological soft tissue. The size of 40mm(L)×40mm(W)×20mm(H) is determined to be the optimal result.

Isothermal curing analysis and properties of ultra heat‐resistant polyimide composites by DMA method

AbstractThe isothermal curing process of T700 carbon fiber/P450 polyimide prepreg is characterized by dynamic mechanical analysis method and the gelation points are analyzed by torsional braid analysis theory. The growth mechanisms of the mechanical property at different constant temperatures are investigated by the relative mechanical growth rate of storage modulus and the curing kinetics models are established. The theories of Flory and Hsich are used to calculate the activation energy during the curing reaction of prepreg. The results indicates that the gelation times which are detected by the method of torsional braid analysis at 300, 310, 330, and 350°C were 293.7, 213.8, 104.1, and 45.4 min, respectively. The activation energies of curing reaction are calculated by Flory theory and Hsich theory, they are 112.35 and 119.96 kJ/mol, respectively. The feasibly of curing system 300°C × 4 h + 330°C × 2 h + 350°C × 2 h + 370°C × 2 h is verified by the mechanical properties and the heat resistance of polyimide composite.

Dynamic Characteristics of a Novel Right-Angle Viscoelastic Damper (RVD) Using Polyurethane Damping Materials

Excessive plastic deformation may occur at the beam-column joints under seismic action and lead to connection failure, increasing the possibility of collapse of the entire frame structure. In order to improve the seismic performance of assembled steel structure joints, a right-angle viscoelastic joint damper with polyurethane as the core energy dissipation material is proposed in this paper. First, the temperature scanning tests of polyurethane materials were carried out based on the dynamic mechanical analysis method. Second, the dynamic mechanical test and numerical simulation analysis of the designed right-angle viscoelastic damper were performed to reveal the dynamic energy dissipation characteristics of the right-angle damper. Finally, the dynamic time-history damping analysis was performed on the steel frame structure equipped with RVDs. The results show that the TA value of polyurethane material reached its peak at 2.0 Hz, which is the ideal frequency for the material’s damping ability. The right-angle damper made of polyurethane material has a softening nonlinear characteristic, and the peak value of the loss factor was obtained at 2.0 Hz, which is consistent with the results of the dynamic performance of the polyurethane material. The numerical simulation results demonstrate that stress on the steel plates and viscoelastic layers is reasonable. When the excitation level did not exceed 9 mm displacement amplitude, the energy input to the damper was dissipated by polyurethane, and the steel plates never showed plastic deformation. The time-history analysis of the steel structure shows that the dampers designed in this paper have a good control effect on the interstory displacement, acceleration, and interstory shear force of the structure. The research results lay the necessary foundation for the engineering application of polyurethane materials in the field of beam-column joints vibration damping.

Static and dynamic quantum mechanical methods for exact interpretation of Infrared Multiple Photon Dissociation Spectra: current state and development perspectives

Static and dynamic quantum mechanical methods for exact interpretation of Infrared Multiple Photon Dissociation Spectra: current state and development perspectives

A vehicle-bridge interaction vibration model considering bridge deck pavement

The bridge pavement subjected to vehicle loads is the most vulnerable component in the highway bridge and overloaded vehicles can result in serious damage to the bridge pavement more easily. Therefore, it is necessary to consider the pavement in vehicle-bridge interaction (VBI) system. However, the bridge pavement is not considered in the traditional VBI system or the viscoelasticity of bridge pavement is ignored. In this study, a new vehicle-pavement-bridge interaction (VPBI) system is established. The viscoelastic asphalt pavement is simulated with the continuously and uniformly distributed spring-damper. The equivalent stiffness coefficient and equivalent damping coefficient of the pavement are determined through dynamic mechanical analysis (DMA) test and finite element method. The equations of motion for VPBI system can be derived using Lagrange equation and the modal superposition method. Then the crucial parameters such as displacement at mid-span of bridge, acceleration of vehicle body, tire contact force, and pavement deformation are obtained. The effects of vehicle velocity, bridge span, tire contact area, pavement stiffness coefficient, and pavement damping coefficient on VPBI responses are analyzed. The results show that (1) The pavement is compressive during vehicle passing bridge and its dynamic deformation fluctuates around initially static deformation of pavement. (2) Increasing the stiffness of pavement can rapidly reduce the deformation of pavement, while the pavement damping has the opposite effect. (3) The increase of bridge span can conduct exponentially growth of dynamic responses of VPBI system. The pavement deformation will increase by 7.9% if the bridge span is lengthened by 5 m. This study provides a reliability response analysis method for VPBI system.

Long-Term Performance Evolution of RIOHTrack Pavement Surface Layer Based on DMA Method.

Asphalt mixture is a typical viscoelastic material, and its road performance will change with the action of environment and load during actual service. This study conducted experimental research on the surface course asphalt mixture of three categories and six typical structures of RIOHTrack based on the Dynamic Mechanical Analysis method. Moreover, this study explored the performance evolution law of asphalt mixture under the coupling action of load and environment in the process of loading from 0 million to 54 million standard axle times. Results demonstrated that the phase transition characteristic temperature of the surface course materials of the three types of typical structures showed a trend of first increasing and then decreasing with the accumulation of load and environmental effects, indicating the presence of two stages of the dual coupling effect of environmental aging and load rolling on the asphalt mixture during service. In addition, the results suggested that the phase transition characteristic temperature, modulus, and phase angle of the surface layer materials have obvious material differences and structure dependencies.

An experimental investigation on the thermal and mechanical characterization of boron/flax/PLA sustainable composite

The current study deals with the effect of boron compounds, zinc borate (ZB), borax: boric acid combines (BxBc), and ulexite which are used to improve fire resistance, on the thermal, microstructural, and mechanical properties of the flax/PLA biocomposites. For this purpose, the mechanical properties of the biocomposites were determined by tensile, impact, and three-point bending tests. Thermogravimetric analysis and the UL-94 burn test were conducted to determine the thermal properties of composites, such as thermal stability and flammability. Thermo-mechanical properties and viscoelastic characteristics of biocomposites were determined by the dynamic mechanical thermal analysis method. Test results showed that ulexite addition could significantly reduce the burning rate by 80%. However, although mechanical properties were adversely affected by the incorporation of boron compounds resulting in a drop of up to 20%, it is believed that boron compound-filled flax/PLA composites have mechanical and thermal properties that can be considered as an alternative material, especially for the automotive industry.

Damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders with different thicknesses and preparation directions

PurposeThis study aims to experimentally assess the effect of thickness and preparation direction on the damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders.Design/methodology/approachSn58Bi and Sn3.0Ag0.5Cu solder strips with different thicknesses were prepared from the bulk in longitudinal and horizontal directions, and the ratio of loss modulus and storage modulus of the samples was measured by the dynamic mechanical analysis method as the index of damping properties.FindingsSn58Bi and Sn3.0Ag0.5Cu solders exhibited viscoelastic relaxation, and their damping properties decreased with decreasing thickness. The damping properties of both solders had no obvious difference in longitudinal and horizontal directions. Sn58Bi has a more obvious high-temperature damping background than Sn3.0Ag0.5Cu solder. In addition, compared with Sn58Bi solder, Sn3.0Ag0.5Cu solder had an obvious internal friction peak, which moved toward high temperature with increasing frequency. The activation energies of Sn58Bi solder with a thickness of 0.5 mm at the longitudinal and horizontal directions were 0.84 and 0.67 eV, respectively, which were 0.39 and 0.53 eV, respectively, for the Sn3.0Ag0.5Cu solder.Originality/valueThe damping properties of Sn58Bi and Sn3.0Ag0.5Cu solder decreased with decreasing thickness, while their damping properties changed insignificantly when they were prepared from different directions. The internal friction peak of Sn3.0Ag0.5Cu solder moved to higher temperatures with increasing frequency.

Static and Dynamic Mechanical Characterization of Polydimethylsiloxane (PDMS) under Uniaxial Tensile Loading

The present study is based on performing mechanical characterization of polydimethylsiloxane (PDMS) under tensile loading. PDMS samples are developed by mixing prepolymer and curing agent with 10:1 ratio. Mechanical characterization of the PDMS samples is carried out using static and dynamic mechanical testing methods. In particular, the material is characterized under monotonic loading, different strain rates, and force-controlled cyclic loading. The monotonic loading tests are performed at different grip tightening levels to optimize gripping that avoids slipping and reaches failure point. The strain rate dependency and cyclic loading tests are performed to study the viscoelastic behaviour of the material. Strain rate dependency tests are carried out at the strain rates of 6.7×10-3 s-1, 3.2×10-2 s-1, and 6.2×10-2 s-1. The hysteresis tests are performed at the force rates of 0.1 – 2 N/s. The obtained results show that fixing the testing specimen made of soft hyperviscoelastic material such as PDMS is challenging and can significantly affect its stress-strain behaviour and mechanical properties. A higher strain rate increases the stiffness of the material due to the viscoelastic nature of the material. Observing the stress-strain curves, with respect to the lowest strain rate case, the curve for 6.2×10-2 s-1 strain rate diverges at 40% strain compared to 3.2×10-2 s-1 strain rate curve that diverges at 80% strain. The material shows a nonlinear hysteresis behaviour and similar energy dissipation for the considered force-controlled cyclic loading cases.

Structure and properties comparison of poly(ether-urethane)s based on nonpetrochemical and petrochemical polyols obtained by solvent free two-step method

The application of thermoplastic polyurethanes (TPU) is becoming more and more extensive, and the decreasing of used petrochemical monomers and reduction of energy for the polymerization and processing processes is getting increasingly important. In this paper, we confirmed the positive influence of high bio-based monomers contents (by replacing petrochemical polyol and glycol by bio-based counterparts) on processing and properties of obtained materials. A series of partially bio-based thermoplastic poly(ether-urethane)s (bio-based TPU) were obtained from bio- and petrochemical-based polyols, bio-based 1,4-butanediol, and 4,4′-diphenylmethane diisocyanate by the two-step method without using any solvents. Both the monomers’ origin and polyurethane prepolymer processing parameters were taken into account in characterization of the obtained materials. The TPUs' chemical structure was analyzed by FTIR spectroscopy and 1H NMR and the number average molecular weight was examined by 1H NMR and GPC. The measurements of dynamic mechanical thermal analysis, tensile test, hardness, density method, and rheological behavior provided useful information about the properties of prepolymers and TPUs. The processing properties and an activation energy of prepared materials was examined using the melt-flow index. It has been confirmed that despite the origin of polyols obtained thermoplastic poly(ether-urethanes) exhibited comparably good mechanical and thermo-mechanical properties, and an appropriate melt flow index facilitates their processing. Nevertheless, the use of high amount of bio-based monomers resulted in obtaining more eco-friendly materials.

Interlayer bonding between thermoplastic composites and metals by in‐situ polymerization technique

AbstractFiber‐metal laminates (FMLs) offer the superior characteristics of polymer composites (i.e., light weight, high strength and stiffness) with the ductility and fracture strength of metals. The bond strength between the two dissimilar materials, composite and metal, dictates the properties and performance of the FMLs. The bonding becomes more critical when the polymer matrix is thermoplastic and hydrophobic in nature. This work employed a novel bonding technique between thermoplastic composites and a metal layer using six different combinations of organic coatings. The flexural, and interlaminar shear strength of the thermoplastic fiber metal laminates (TP‐FMLs) were examined to investigate the bond strengths in the different cases along with fracture characteristics revealed from the tested samples using scanning electron microscopy. The viscoelastic performance of the fabricated TP‐FMLs were also investigated using the dynamic mechanical thermal analysis method.

Dynamic characteristics of three-layer beams with load-bearing layers made of alumino-glass plastic

Aluminum-fiber-reinforced plastics (GLARE) are promising aviation materials with increased characteristics of specific stiffness and strength, fatigue strength, impact resistance, and residual strength after impact. Nowadays, GLARE are used for making elements of the fuselage of the long-haul passenger aircraft Airbus A380, as well as some other elements of aircraft structures. The results of experimental studies of eigenfrequencies and damping coefficients of three-layer beams made with face sheets of five-layer GLARE and with a core made of polyimide foam are presented. The tests were performed using the method of free bending vibrations of cantilever samples. The dynamic parameters of the three-layer beams were calculated based on the analysis of amplitude-frequency characteristics obtained by the fast Fourier transform method. Mechanical characteristics of GLARE and filler samples are preliminary determined in static and dynamic tests. The damping factor of the core is determined by the dynamic mechanical analysis method. The core shear modulus is determined by measuring the flexural rigidity of manufactured three-layer beams in a quasi-static three-point bending test. Based on a comparison of the design data and the results of the experiments, it is shown that in dynamic tests, the flexural rigidity of three-layer specimens is reduced in comparison with the estimated values, which may be due to the peculiarities of changing the characteristics of the foam core under dynamic loading. The value of the damping factor of GLARE samples was ~0.02, the foamed core was ~0.08 and three-layer beams were ~0.067 in the range of vibration frequency up to 60 Hz.

A comparative study on the rheological, thermal, and mechanical performance of epoxy resin modified with thermoplastics

Thermoplastics and functional polymers are commonly used modifiers for epoxy (EP) resin. In this study, an EP system was fabricated and modified with methyl methacrylate block copolymer (BMG), polyphenylene oxide (PPO) and polysulfone (PSF). This was carried out to study the influence of thermoplastic polymers and functional polymers on the properties of EP resins, and the performance of the different modified EP systems was studied and compared. The curing reaction, rheological performances, heat resistance, and mechanical properties of the EP blends were investigated. Curing process of EP resin was determined as 110 °C for 1 h and 150 °C for 3 h by using non-isothermal differential scanning calorimetry (DSC) method. The rheological test revealed that the EP/BMG and EP/PPO blends exhibited low viscosity and wide processing window compared to the EP/PSF blend, thereby indicating good processing performance. The thermal stability of the modified EP blends was evaluated by using dynamic mechanical analysis methods. The results showed that the glass transition temperature (Tg ) of EP/BMG, EP/PPO and EP/PSF blends were 123 °C, 129 °C, and 131 °C, respectively. BMG showed an excellent toughening effect on EP resin compared to PPO and PSF. In addition, the flexural strength and impact strength of EP/BMG were 114 MPa and 21.2 kJ/m2, respectively. The influence of polymers on the properties of EP resin stems from their molecular structures.

A dynamic mechanical method to assess bulk viscoelastic behavior of the dentin extracellular matrix

ObjectivesTo develop a protocol for assessment of the bulk viscoelastic behavior of dentin extracellular matrix (ECM), and to assess relationships between induced collagen cross-linking and viscoelasticity of the dentin ECM. MethodsDentin ECM was treated with agents to induce exogenous collagen cross-linking: proanthocyanidins (PACs) from Vitis vinifera – VVe, PACs from Pinus massoniana - PMe, glutaraldehyde – (GA), or kept untreated (control). A dynamic mechanical strain sweep method was carried out in a 3-point bending submersion clamp at treatment; after protein destabilization with 4 M urea and after 7-day, 6-month, and 12-month incubation in simulated body fluid. Tan δ, storage (E’), loss (E”), and complex moduli (E*) were calculated and data were statistically analyzed using two-way ANOVA and post-hoc tests (α = 0.05). Chemical analysis of dentin ECM before and after protein destabilization was assessed with ATR-FTIR spectroscopy. ResultsSignificant interactions between study factors (treatment vs. time points, p < 0.001) were found for all viscoelastic parameters. Despite a significant decrease in all moduli after destabilization, PAC-treated dentin remained statistically higher than control (p < 0.001), indicating permanent mechanical enhancement after biomodification. Covalently crosslinked, GA-treated dentin was unaffected by destabilization (p = 0.873) and showed the lowest damping capacity (tan δ) at all time points (p < 0.001). After 12 months, the damping capacity of PMe and VVe groups decreased significantly. Changes in all amide IR resonances revealed a partial chemical reversal of PAC-mediated biomodification. SignificanceViscoelastic measurements and IR spectroscopy aid in elucidating the role of inter-molecular collagen cross-linking in the mechanical behavior of dentin ECM.

Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications

Abstract The development and advancement of polymeric implant materials is a frequent focus in current research. The combination of polymeric materials with diverging properties provides a wide range of new materials with innovative characteristics. One technology for combining materials is to apply a coated layer onto a base material. In this work, a hyperelastic, synthetic base material was combined with a rigid biopolymer coating layer. A multilayered material with combined characteristics of both was built. In the field of processed polymers, the analysis of coating adhesion is not feasible using established methods. Therefore, a dynamic-mechanical method was investigated, which supplements the uniaxial tensile test and provides knowledge regarding mechanical resistance of the multilayered polymer structure. Furthermore, the method gets validated by SEM-imaging and evaluation of coating composition before and after testing under dynamic conditions.

Study on Preparation Method of Terminal Blend Rubberized Asphalt Binder

Terminal Blend rubberized asphalt binder is generally prepared under high temperature conditions. Unlike asphalt plants that produce asphalt in sealed asphalt tanks, the process of laboratory interaction of asphalt and crumb rubber is mostly in contact with air, which can easily cause asphalt aging. To alleviate this phenomenon, TB-B and TB-C asphalt were prepared using crumb rubber in a nitrogen environment and soluble crumb rubber in an atmospheric environment, respectively.As a comparison group, TB-A asphalt was prepared using crumb rubber under atmospheric environment. A practical method for preparing TB asphalt was explored by changing the amount of crumb rubber and the interaction temperature. Their rheological characteristics were measured by dynamic mechanical methods using dynamic shear rheometer (DSR) and binding beam rheometer (BBR). It was found that under high interaction conditions, the crumb rubber in TB-A asphalt undergoes desulfurization and degradation reactions, which caused the hinge structure in the asphalt to be damaged and the high-temperature performance decreased. But the aliphatic compounds generated by the degradation of crumb rubber are beneficial to improve the low temperature performance of asphalt. Through polymer isolation experiments, it was found that the degradation of crumb rubber caused TB-A and TB-B asphalt to form a homogeneous system. While the soluble crumb rubber in TB-C asphalt was mainly swelling reaction, so the larger the amount of soluble crumb rubber, the more severe the segregation. Besides, the aging degree of three TB asphalts was studied by using viscosity experiments, thermal analysis and Fourier transform infrared (FT-IR) spectroscopy. The results show that compared with TB-A asphalt, the aging degree of TB-B and TB-C asphalt is greatly reduced. Therefore, both preparation methods effectively alleviate the aging phenomenon in the laboratory preparation of TB asphalt.

ВЛИЯНИЕ НЕСКОЛЬКИХ ВИДОВ СМОЛ НА ДИНАМИЧЕСКИЕ МЕХАНИЧЕСКИЕ СВОЙСТВА ПОЛИМЕРНОЙ СМЕСИ НА ОСНОВЕ БУТИЛКАУЧУКА

this work is devoted to the problem of developing vibration-damping polymer materials with high damping properties in a wide temperature range. The study of the effect of modifying additives on the strength, damping, adhesive and cohesive properties of a butyl rubber composite is the aim of this work. The task is to identify the actual temperature, frequency, dynamic and mechanical characteristics of a composite material based on butyl rubber depending on the type and concentration of resins. The key methods for studying this problem is the dynamic mechanical analysis method, aimed at obtaining information about changes in the dynamic properties of polymer materials (bond strength with metal when peeling samples of composites, determining the flow resistance of samples, determining the migration of plasticizer). Due to the established experimental dependences, it was found that the addition of resins (3% by weight) in the composition based on butyl rubber leads to an increase in the damping properties of composite materials, and an increase to (4.25% by weight) leads to their decrease. It was established that the obtained filled mixtures with a high damping peak and good adhesive and strength properties are mixtures with the addition of alkyl phenol-formaldehyde resins.

Revealing the ultra-low-temperature relaxation peak in a model metallic glass

By systematically investigating the relaxation behavior of a model metallic glass based on the extensive molecular dynamics (MD) simulations combined with the dynamic mechanical spectroscopy method, a pronounced ultra-low temperature peak on the loss modulus spectrum was discovered for the first time in MD simulations. It was found that the relaxation peak occurs at a much lower temperature than the typical temperature for the conventional β relation peak as reported in the literature. According to the atomic displacement analysis, we unravel that the reversible atomic motions, rather than the thermal vibrations or local structural rearrangements, mainly contribute to this relaxation peak. We further identify the atomic level mechanism of this fast relaxation process by characterizing the local geometrical anisotropy. Furthermore, by tracing the dynamic behaviors of these “reversible” atoms, we demonstrate the intrinsic hierarchy of the relaxation modes, which are triggered by atomic vibrations and gradually developed to include the reversible and irreversible atomic movements. Our findings provide an important piece of the puzzle about the holistic picture of the rich relaxation processes in metallic glasses.