Analysis of dynamic mechanical properties and impact response of X80 pipeline girth welds: An experimental and numerical investigation

In order to obtain the effect of porosity on the dynamic mechanical properties and impact response characteristics of high aluminum content PTFE/Al energetic materials, PTFE/Al specimens with porosities of 1.2%, 10%, 20%, and 30% were prepared by adding additives. The dynamic compression properties and impact response characteristics of high aluminum content PTFE/Al energetic materials with porosity were studied by using a split Hopkinson pressure bar (SHPB) impact loading experimental system. Based on the one-dimensional viscoplastic hole collapse model, an impact temperature rise analysis model including melting effects was used, and corresponding calculation analysis was performed. The results show that with the increase of porosity, the yield strength and compressive strength of the material will decrease. Under dynamic loading, the reaction duration of PTFE/Al energetic materials with different porosities generally shows a tendency to become shorter as the porosity increases, while the ignition delay time is basically unchanged. In this experiment, the material response has the optimal porosity with the lowest critical strain rate, the optimal porosity for PTFE/Al energetic materials with different porosity and high aluminum content (50/50 mass ratio, size of specimens Φ8 × 5 mm) is 10%. The research results can provide an important reference for the engineering application of PTFE/Al energetic materials.

The dynamic response of contact mechanics has significance important for durability and reliability design of gears. A finite element analysis model for dynamic response of contact mechanics of gear pair is established, and then the contact fatigue life of gear pair is analyzed based on the finite element model. The key parameters of contact finite element model is determined through the contact finite element analysis of thin cylinder. The precise finite element analysis model of the gear meshing is established and calculated by transient dynamics. The contact force and contact stress of different position is obtained. Through change friction coefficient of finite element model, the influence of friction coefficient for contact force and contact stress is obtained. Comparing the life of traditional risk point calculated in most of the standard and dangerous point which has the max stress through simulation. The influence of friction coefficient on contact life is determined.

Dynamic mechanical response of rock target under impact loading was analyzed by LS-DYNA finite element method.Stress-time curves in different impact velocities were obtained by sensors buried in rock target. The comparative analysis of experiment and simulation shows that the main reason of rock failure is the joint action of longitudinal compression wave and transverse sparse wave,and the conclusions can put forward reference on guiding farther dynamic mechanical experiment of rock.

Shape Memory Alloys (SMA) represent a class of advanced smart materials that have gained significant traction in the realm of composite material applications over the past few decades. This study utilizes the VARI technique to fabricate four distinct configurations of composite sandwich panels. Low-speed impact tests were conducted at an impact energy level of 25 J, allowing for a comprehensive analysis of structural damage modes and dynamic mechanical responses. The investigation elucidates the failure mechanisms and the impact of SMA on the impact resistance of the composite structures. The results demonstrate that the incorporation of a single SMA layer within the structure leads to a 23.32% increase in the maximum load-bearing capacity. Moreover, when the number of fiber layers is constant, positioning the SMA on the lower face of the sandwich structure significantly enhances impact performance compared to placement on the upper face. Additionally, an increase in the quantity of SMA layers correlates with improved low-speed impact resistance; specifically, an increase in SMA layers from one to two results in a 5.73% enhancement in the maximum load capacity of the fiber-reinforced sandwich panel.

ABSTRACTA proper understanding of the dynamic mechanical properties of polymers is essential for safety and practicality in industrial production and daily life. The conventional analysis of dynamic mechanical properties of materials at high strain rates relies on the split Hopkinson pressure bar (SHPB) under the assumption of a constant strain rate. However, in experiments, the strain rate often cannot be considered constant, leading to systematic errors. In response to this limitation, a higher‐accuracy calibration method for the entire process of dynamic mechanical properties of the materials, based on the fractional‐order Kelvin–Voigt model, has been developed. Using polyethylene as an example of a viscoelastic material, we determined the fractional order with the best accuracy, verified the rationality of the method through comparative analysis, and analyzed the principle of the method by adjusting the fractional order and fitting the results of SHPB tests conducted at different strain rates. The results indicate that, compared to the traditional method assuming a constant strain rate, the fractional‐order Kelvin model significantly improves the fitting accuracy of SHPB experimental data for the material. Fractional orders of 0.88 and 0.89 show the best accuracy, suggesting that the fractional‐order Kelvin–Voigt model with these orders can more effectively capture the dynamic mechanical properties of the material throughout the process. In addition, the proposed method is particularly useful for analyzing the dynamic mechanical properties of materials under varying strain rates. These findings can be used to investigate the dynamic mechanical response of materials in a holistic manner and provide a reference for the improvement of polymer materials for industrial applications.

The growing concerns over nuclear power plant safety in the wake of extreme impact events have highlighted the need for containment structures with superior resistance to large commercial aircraft strikes. Conventional reinforced concrete containment has shown limitations in withstanding high-mass and high-velocity impacts, posing potential risks to structural integrity and operational safety. Addressing this challenge, this study focuses on the dynamic impact resistance and vibration behavior of steel–ultra-high-performance concrete (S-UHPC) composite containment, aiming to enhance nuclear facility resilience under beyond-design-basis aircraft impact scenarios. Validated finite element models in LS-DYNA were developed to simulate impacts from four representative large commercial aircraft types, considering variations in wall and steel plate thicknesses, UHPC grades, and soil–structure interaction conditions. Unlike existing studies that often focus on isolated parameters, this work conducts a systematic parametric analysis integrating multiple aircraft types, structural configurations, and foundation conditions, providing comprehensive insights into both global deformation and high-frequency vibration behavior. Comparative analyses with conventional reinforced concrete containment were performed, and floor response spectra were evaluated to quantify high-frequency vibration characteristics under different site conditions. The results show that S-UHPC containment reduces peak displacement by up to ~24% compared to reinforced concrete of the same thickness while effectively localizing core damage without through-thickness failure. In addition, aircraft impacts predominantly excite 90–125 Hz vibrations, with soft soil conditions amplifying acceleration responses by more than four times, underscoring the necessity of site-specific dynamic analysis in nuclear containment and equipment design.

Dynamic mechanical response and damage analysis of steel fiber-reinforced recycled aggregate concrete under repeated impact loading

To obtain a large number of dynamic mechanical responses of asphalt pavement structures under falling weight dynamic (FWD) loading in order to construct a deep learning training set, a method for transforming the dynamic–static mechanical responses of pavements based on a theoretical solution of the layered elastic system was constructed. Firstly, Abaqus was used to establish a three-dimensional mechanical analysis model of an asphalt pavement considering structural damping and to calculate the dynamic mechanical response of a typical pavement structure. Then, the main factors affecting the dynamic mechanical response of pavement surfaces structures were thoroughly analysed and a multi-variate regression analysis method was used to establish a transformation model for the dynamic and static mechanical responses of a three-layer basic pavement structure system. Finally, using a structural conversion method, the conversion model was extended to a multi-layer asphalt pavement structure to complete the calculation of the dynamic mechanical response. The measured dynamic mechanical response under FWD loading was found to be very consistent with the calculation results based on the proposed method, meaning that the model is reliable and accurate.

Dynamic response and reliability analysis of non-linear stochastic structures

Stress wave propagation effect and failure characteristic of limestone were studied by one-stage lightgas gun induced-plate impact experiment technology. The experiment results indicate that dispersion effect and attenuation characteristic exist in impacting rock. The failure of rock sample has division characteristics, which are head failure zone, middle tension-compression failure zone and tail fracture failure zone. On this basis, the dynamic mechanical response of rock target under impact loading was analyzed by LS-DYNA finite element method. Stress-time curves in different impact velocities were obtained by sensors buried in rock target. The comparative analysis of experiment and simulation show that the main reason of rock failure is the joint action of longitudinal compression wave and transverse sparse wave, and the conclusions have some significance on guiding farther dynamic mechanical experiment of rock.

Effects of different mechanical deformations such as cyclic bending and compressive flexing and temperature on electrical and dynamic mechanical properties of elastomeric composites have been investigated. Conductive elastomeric composites were prepared by incorporating different carbon blacks in an insulating polychloroprene (CR) rubber matrix. The filler loading was varied between 10 and 110 phr (parts per hundred rubber) i/r/o different carbon blacks to assess the percolation threshold of different composites. Due to the spatial arrangement of conductive filler particles at certain critical concentration, some conducting networks are formed leading to abrupt increase in conductivity of polymer composites. This critical concentration is known as percolation threshold. The increase in conductivity well below and above percolation threshold is relatively less compared to that around percolation. The variation of electrical conductivity and dynamic mechanical modulus due to bending and compressive flexing are found to be similar, that is, both characteristics show a drop in magnitude with increase in number of flex cycles. The conductivity of system changes when composites are subjected to changes in temperature. This is mainly due to the destruction of existing conducting networks as well as formation of some new conducting networks. The net change depends on the degree of formation or destruction of networks. It is interesting to see that conductivity does not follow the same path during heating–cooling cycles thereby causing electrical hysteresis. POLYM. COMPOS., 39:3912–3923, 2018. © 2017 Society of Plastics Engineers

The paper examines the dynamic response of a two-bogie vehicle to the symmetrical and antisymmetrical excitations, due to bounce and pitch of the axles’ planes, derived from the track vertical irregularities. Part I introduced the theoretical model and the response functions of the vehicle, as well as the theoretical elements required for the analysis of the dynamic response of the vehicle to the track stochastic irregularities. Part II comprises the results of the numerical analysis of the vehicle dynamic response in three reference points of the carbody, based on which a series of properties of the vertical vibrations behaviour of the railway vehicle is pointed out at. The excitation modes that trigger the carbody response in its reference points are identified. Hence, the influence of the geometrical filtering effect of the excitation modes upon the ride quality and ride comfort is established.

Structural members commonly employed in marine and off-shore structures are usually fabricated from plates and shells. Collision of this class of structures is usually modeled as plate and shell structures subjected to dynamic impact loading. The understanding of the dynamic response and energy transmission of the structures subjected to low velocity impact is useful for the efficient design of this type of structures. The transmissions of transient energy flow and dynamic transient response of these structures under low velocity impact are presented in the paper. The structural intensity approach is adopted to study the elastic transient dynamic characteristics of the plate structures under low velocity impact. The nine-node degenerated shell elements are adopted to model both the target and impactor in the dynamic impact response analysis. The structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of the structures. Numerical results, including contact force and transient energy flow vectors as well as structural intensity stream lines, demonstrate the efficiency of the present approach and attenuating impact effects on this type of structures.

Honeycomb sandwich structures, composed of many regularly arranged hexagonal cores and two skins, often show excellent impact performance due to strong energy absorption ability under impact loads. This paper studies dynamic mechanical responses of aluminum honeycomb sandwich structures. Parametric geometry modeling using UG software and finite element analysis using ANSYS explicit dynamics module are performed. Finite difference algorithm based on time-stepping integration is used to get the impact displacement, and stress and strain with time. Effects of different impact velocities, core length and wall thickness on the distributions of plastic stress and strain are also explored. Results show that thinner honeycomb side length and thicker wall thickness lead to stronger impact resistance. This research provides theoretical support for promoting optimal design of lightweight structures against impact loads.

We investigate the dynamic response of industrial rubbers (styrene-butadiene random copolymers, SBR) in torsion and compare against common small amplitude oscillatory shear measurements by using a torsion rectangular fixture, a modified torsion cylindrical fixture, and a conventional parallel plate fixture, respectively, in two different rheometers (ARES 2kFRTN1 from TA Instruments, USA and MCR 702 from Anton Paar-Physica, Austria). The effects of specimen geometry (length-to-width aspect ratio) on storage modulus and level of clamping are investigated. For cylindrical specimens undergoing torsional deformation, we find that geometry and clamping barely affect the shear moduli, and the measurements essentially coincide with those using parallel plates. In contrast, a clear dependence of the storage modulus on the aspect ratio is detected for specimens having rectangular cross section. The empirical correction used routinely in this test is based on geometrical factors and can account for clamping effects, but works only for aspect ratios above a threshold value of 1.4. By employing a finite element analysis, we perform a parametric study of the effects of the aspect ratio in the cross-sectional stress distribution and the linear viscoelastic torsional response. We propose a new, improved empirical equation for obtaining accurate moduli values in torsion at different aspect ratios, whose general validity is demonstrated in both rheometers. These results should provide a guideline for measurements with different elastomers, for which comparison with dynamic oscillatory tests may not be possible due to wall slip issues.