Failure mechanisms of sand under asymmetrical cyclic loading conditions: experimental observation and constitutive modelling

Forces acting on the stator teeth of the 400 kVA, 4 pole synchronous generator were analyzed for asymmetric electric load conditions. Measurement of the flux density was performed with the measuring coils installed on the stator teeth and calculations were done by finite element method. Measured data was processed to determine stator teeth radial forces through Maxwell stress tensor integration algorithm. Processed data was used for detection of asymmetric load condition. Parameters of the measuring coil sensors and their adequate position can be determined with finite element calculation before performing sensor installation on the machine.

Analysis of Asymmetric Stress Ratio in Shallow Buried Tunnels

O71: Skeletal and anthropometric determinants of gait balance in asymptomatic adult subjects

Carrying asymmetric loads during stair negotiation

P36: Relation between navicular mobility and multi-segment foot kinematics during walking

In this paper, the damage mechanisms of reinforced composite panels subjected to symmetrical and asymmetrical flexural loading conditions have been investigated. The composite components are representative of a regional aircraft fuselage. Three-point bending tests numerical simulations have been used to assess the influence of the different test parameters on the damage behavior of the investigated component. Then, the most representative configuration has been selected for the experimental bending test. the outputs from the numerical simulations, in terms of stiffness and damage onset and propagation, has been employed, in combination with the experimental data, to accurately describe the damage mechanisms associated to the asymmetric application of the load.

Uniaxial ratcheting behavior of an automotive-grade dual-phase steel sheet of 1.6 mm thickness has been investigated through engineering stress-controlled asymmetric cyclic loading experiments in the elastoplastic regime at ambient temperature (~ 28°C). Experiments have been performed keeping mean stress, stress amplitude or maximum stress constant. The effect of stress combinations on ratcheting deformation has been rationalized in terms of plastic strain amplitudes, both in loading and in unloading directions. It is found that for all stress combinations the steady-state ratcheting rate follows a perfect power relationship. Scanning electron fractography reveals that failure under asymmetric cyclic loading conditions occurs in a ductile manner through the formation of voids as it happens under tensile loading.

Crack propagation kinetics under asymmetric cyclic loading for 316LN SS in high-temperature solution

Fatigue damage of a material is particularly deleterious when it occurs under asymmetric cyclic loading conditions. Ratcheting is the process of fatigue damage in which plastic strain accumulates during asymmetric cyclic loading (with non-zero mean stress) of structural parts. The aim of this investigation was to study the ratcheting behaviour and its effect on strain-controlled low cycle fatigue (LCF) behaviour of AISI 4340 steel in differently heat treated conditions. For this purpose, AISI 4340 steel was first given different heat treatments viz. annealing and normalizing and studied for basic microstructural characterizations and hardness. The heat treated steel rods were used to fabricate tensile and fatigue specimens according to ASTM standards. A series of stress controlled ratcheting tests were carried out on the heat treated specimens at room temperature with different stress ratios (R) of −0.4, −0.6 and −0.8. In order to assess imposed fatigue damage, post-ratcheting LCF studies were done on the annealed specimens. The results showed that accumulation of ratcheting strain increased with increasing stress ratios in both annealed and normalised conditions. Maximum accumulation of ratcheting strain (1.16% for annealed and 1.02% for normalised specimens) was observed at R = −0.4. The increase in strain accumulation with increasing stress ratio can be attributed to the increased dislocation generation and their multiplication, at higher levels of stress ratios. Post-ratcheting LCF studies indicated increased stress amplitudes of the ratcheted specimens as those compared to only LCF specimens; this can be attributed to the previous cyclic hardening during ratcheting tests.

During steam turbine rotor operation, the startup and showdown processes can cause asymmetric loading stress, leading to fatigue damage. To research the cyclic deformation behavior and fatigue failure mechanisms of 9% Cr‐based steel under asymmetric loading conditions, the strain ratios including −1, 0, and 0.1 are introduced into the low cyclic fatigue tests at 430°C. The results show the cyclic softening behavior is observed under three strain ratios at 430°C. As the strain ratio increases, the crack initiation sources, plastic strain, and consumed energy present an increasing trend. Comparing the microstructure morphology at different strain ratios, the coarsening lath and carbides affect fatigue crack initiation. Besides, the grain rotation and dynamic recrystallization can be observed, resulting in the cyclic softening behavior during the fatigue test. Finally, a new fatigue life prediction model is proposed at 430°C.

Influence of asymmetric cyclic loading on substructure formation and ratcheting fatigue behaviour of AISI 304LN stainless steel

The purpose of this study was to investigate the effect of different load carriage modes on coordinative patterns in the lower extremities during walking. Twenty-five university students walked on a treadmill at their preferred pace under three different load conditions: symmetric load (5% of body mass in messenger bags on each shoulder hanging vertically and against the hips), asymmetric load 1 (10% of body mass in a messenger bag on one shoulder hanging vertically against the ipsilateral hip), and asymmetric load 2 (10% of body mass in a messenger bag on one shoulder with the bag draped across the trunk to the contralateral hip). Altered thigh-shank and shank-foot couplings were found for the loaded side during the stance of gait when comparing the asymmetric 1 and 2 to the symmetric load. In addition, thigh-thigh coupling was changed during gait when comparing the asymmetric load 2 and symmetric load. However, we did not find any significant differences in intralimb and interlimb couplings between the two different asymmetric load conditions. The results suggest potential benefits when carrying symmetrical loads in order to decrease abnormal limb coordination in daily activities. Thus, it may be advisable to distribute load more symmetrically to avoid abnormal gait.

Abstract: This research describes the evolution of the spatial effects of foundation pits considering internal support and external loads. Based on the existing concept of “plane strain ratio”, the term “plane strain ratio considering maximum surface settlement” is proposed to characterize the spatial effects of an asymmetric foundation pit. A series of finite element model calculations were carried out using the Nanchang Aixi Lake foundation pit, including 1) the calculation of simulated actual conditions, 2) the calculation of simulated full symmetric load, and 3) the calculation of simulated asymmetric load. The results indicate that for the symmetric condition at 20 kPa and below, the spatial effect range increases as the load increases. For the symmetric condition above 20 kPa, the load has a negligible impact on the spatial effect range. On the side with a larger load under asymmetric loading conditions, the spatial effect of the working condition below 30 kPa is smaller than the corresponding symmetric load. On the side with a smaller load, the spatial effect of the working condition above 80 kPa increases compared with that of the corresponding symmetrical load. Given and verified are the modified fitting equations that take into account the influence range of spatial effect on both sides of the foundation pit under symmetrical and asymmetrical loads.

Since photovoltaic systems, wind energy, and other renewable energy resources are concerned as sustainable and environmental friendly for the future grid, conventional energy supply systems are facing a huge change regarding their integration. To assure and provide a flexible and a system compatible integration of those decentralized energy resources, power electronic inverters as grid interfaces between energy conversion systems (ECS) and the main grid getting more important. Hence, the inverter has to join the grid operation functions, e.g. frequency and voltage stabilization, similar to the conventional power plants. By implementation of a new control approach based on symmetrical components, the control speed at asymmetrical load and grid conditions is improved. The control approach is verified in a FPGA based smart grid inverter platform, confirming the potential at a hardware system. When using fast control functions for asymmetrical grid conditions it is possible to guarantee stability of future smart grids at rising penetration of distributed energy resources to the main grid.

Generalized simple model for predicting the modulus degradation and strain accumulation of clay subject to long-term undrained cyclic loading