Effects of Fatigue Characteristics on Static and Dynamic Performance of Eucommia Rubber Isolators

This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators with different formulations. For this purpose, we used five formulations of Eucommia ulmoides gum isolators and set different fatigue test methods to study the static and dynamic performance changes of Eucommia ulmoides gum isolators with different formulations by changing the amplitude. The experimental results showed that the addition of Eucommia ulmoides gum had an impact on the performance of the isolator, and the number of fatigue cycles would lead to the hardening of the Eucommia ulmoides gum isolator and changes in its static and dynamic performance. In the range of two million vibrations, the performance change of the isolator was significant in the early stage and then tended to be flat, indicating that the impact of fatigue on the performance of the isolator would not continue to persist. It is worth noting that the study found that the addition of 30% Eucommia ulmoides gum had the least impact on the performance of the isolator under fatigue. Therefore, for long-term use of Eucommia ulmoides gum isolators, attention should be paid to their fatigue characteristics to ensure their stability and reliability. Additionally, this study provides a reference for the design and application of Eucommia ulmoides gum isolators. In summary, this study provides important reference value for a deeper understanding of the fatigue characteristics of Eucommia ulmoides gum isolators and for ensuring their stable and reliable performance. .

Research on Analytical Method of Fatigue Characteristics of Soft Yoke Mooring System Based on Full-Scale Measurement

By focusing on the vulnerability of the structure of marine equipments, together with considering the randomness of meta-ocean load in statistics, a kind of analytical method of fatigue characteristics of marine structure based on full- scale and actual measurement of prototype is proposed. On the basis of short-term field measurement results of structural response, research is carried out on the fatigue analysis of hinge joints at the upper part of the Soft Yoke single point Mooring System （SYMS） by simultaneously monitoring the environmental load and considering the design criteria of offshore structure. Through analysis of finite element modeling, the time-histories of typical stress response are obtained, and then the assessment of fatigue damage at key hinge joints is conducted. The simulation results indicate that the proposed method can accurately analyze the fatigue damage of offshore engineering structure caused by the effect of wave load. The present analytical method of fatigue characteristics can be extended on other offshore engineering structures subjected to meta-ocean load.

In-Situ Test on Fatigue Characteristics of Top-Mounted Dividable Pile-Board Subgrade for High-Speed Railway

To simulate the fatigue characteristics of the pile-board structure under long-term dynamic load, using the in-situ dynamic testing system DTS-1, the forced vibration loading was repeated one million times at different cross-sections of the pile-board structure for high-speed railway. The dynamic deformation, permanent deformation and dynamic stress of main reinforcements were measured. The test results show that the dynamic responses of the pile-board structure almost did not vary with the forced vibration times under the simulated trainload. After one million times of forced vibration, the permanent deformations of the midspan section of intermediate span and midspan section of side span were 0.7 mm and 0. 6 mm, respectively, and there was no accumulative plastic deformation at the bearing section of intermediate span.

Numerical investigation on the fatigue failure characteristics of waterbearing sandstone under cyclic loading

The strength of sandstone decreases significantly with higher water content attributing to softening effects.This scenario can pose a severe threat to the stability of reservoirs of pumped storage power stations developed from abandoned mines,especially when subjected to the cyclic loading condition caused by the repeated drainage and storage of water(fatigue damage).Based on this,it is essential to focus on the fatigue failure characteristics.In this study,the mineral composition of the used sandstone of Ruineng coal mine in Shanxi Province,China,was first tested to elucidate the rock softening mechanism after absorbing water.Next,a numerical model for replicating the mechanical behavior of water-bearing sandstone was established using twodimensional particle flow code(PFC2D)with a novel contact model.Then,16 uniaxial cyclic loading simulations with distinct loading parameters related to reservoir conditions(loading frequency,amplitude level,and maximum stress level)and different water contents were conducted.The numerical results show that all these three loading parameters affect the failure characteristics of sandstone,including irreversible strain,damage evolution,strain behavior,and fatigue life.The influence degree of these three parameters on failure behavior increases in the order of maximum stress level,loading frequency,and amplitude level.However,for the samples with different water contents,their failure characteristics are similar under the same loading conditions.Furthermore,the failure mode is almost unaffected by the loading parameters,while the water content plays a significant role and causing the transformation from the tensile splitting with low water content to the shear failure with higher water content.

Mechanical behavior of entangled metallic wire materials-polyurethane interpenetrating composites

Composite materials exhibit the impressive mechanical properties of high damping and stiffness,which cannot be attained by employing conventional single materials.Along these lines,a novel material architecture is presented in this work in order to fabricate composites with enhanced mechanical characteristics.More specifically,entangled metallic wire materials were used as the active matrix,whereas polyurethane was employed as the reinforcement elements.As a result,an entangled metallic wire material-polyurethane composite with high damping and stiffness was prepared by enforcing the vacuum infiltration method.On top of that,the mechanical properties(loss factor,energy consumption,and average stiffness)of the proposed composite materials were characterized by performing dynamic tests,and its fatigue characteristics were verified by the micro-interface bonding,as well as the macro-damage factor.The impact of the density,preloading spacing,loading amplitude,and exciting frequency on the mechanical properties of the composites were also thoroughly analyzed.The extracted results indicate that the mechanical properties of the composites were significantly enhanced than those of the pure materials due to the introduction of interface friction.Moreover,the average stiffness of the composites was about 10 times the respective value of the entangled metallic wire material.Interestingly,a rise in the loading period leads to some failure between the composite interfaces,which reduces the stiffness property but enhances the damping dissipation properties.Finally,a comprehensive dynamic mechanical model of the composites was established,while it was experimentally verified.The proposed composites possess higher damping features,i.e.,stiffness characteristics,and maintain better fatigue characteristics,which can broaden the application range of the composites.In addition,we provide a theoretical and experimental framework for the research and applications in the field of metal matrix composites.

Effect of heat treatment on strain–controlled fatigue behavior of cast Mg–Nd–Zn–Zr alloy

The influence of heat treatment on the strain-controlled fatigue behavior of cast NZ30 K alloy was investigated. Compared with the as-cast and solutionized（T4） alloys, the peak-aged（T6） and over-aged（T7）counterparts have a higher cyclic stress and a lower plastic strain value due to the precipitation strengthening. The as-cast and T4-treated alloys have a higher fatigue strength/yield strength ratio than the aged alloys, which is mainly attributed to their higher cyclic hardening. Under stress-controlled loading,the aged alloys show lower hysteresis energies than the as-cast and T4-treated counterparts, leading to longer fatigue lifetimes. For the T4-treated alloy, the cyclic hardening and fatigue failure are controlled by the dislocations-slip and twinning, while for both the as-cast and T6-treated counterparts, they are controlled by the dislocation-slip. For the T7-treated alloy, cyclic deformation and failure behavior are mainly dependent on dislocations-slip and grain boundary sliding.

FATIGUE LIFE PREDICTION OF SUS 630(H900) STEEL UNDER HIGH CYCLE LOADING

The fatigue life prediction of high strength steel SUS 630 （H900） under high cycle loading is conducted with consideration of a characteristic fatigue length of material. Based on the WShler curve of smooth materials, a modified method for fatigue life prediction is approached. The characteristic fatigue length of material under cyclic loading is associated with the polycrystalline material. Rather than the stress at a point, the average stress within the characteristic fatigue length is implemented for the fatigue life prediction. The method can be applied to both the smooth and the defected material. The fatigue life prediction is also verified experimentally by specimens with various small circular holes. Through the comparison, it is found that the method can be adopted to predict the fatigue lives with different size effects.

Reliability of Au/PZT/BIT/p-Si ferroelectric diode

A ferroelectric memory diode that consisted of Au/PZT/BIT/p-Si multilayer configuration was fabricated by pulsed laser deposition (PLD) technique. The reliability issues (I–V characteristics, capacitance retention, fatigue and imprint) were investigated. The I–V curve showed the conventional Schottky diode characteristics with a small current density of ?5.3×10?10 A/cm2 at a voltage of ?4 V and 6.7×10?8 A/cm2 at a voltage of +4 V, and this characteristic can be maintained below 50°C. The capacitance variety of the ferroelectric diode was only 5% in 10 hours after withdrawing the applied bias of +5 V or ?5 V, indicating the diode had good capacitance retention. By applying 100 kHz bipolar pulses of 5 V amplitude, the decay in remanent polarization was only 10% after 109 switching cycles, and meanwhile the increase in coercive field was 12%. After being irradiated for 20 min with a 200 W ultraviolet ray lamp, the remanent polarization and coercive field had both varied, and a voltage shift was observed, but the figure of merit FOM was about 0.2 and the diode had no imprint invalidation.