Papers by Keyword: Biaxial Loading

Abstract: The effects of biaxial loading and creep mismatch on creep fracture parameter C(t) and constraint effect are investigated for the plane strain central crack plate. The studied biaxialities in this paper are limited to the range of [-1,1]. Based on the three-term asymptotic solution for creep crack tip field, the higher-order terms coefficient parameter A₂(t) is introduced to characterize the creep mismatch constraint effect. The impacts of loading level on the parameter A₂(t) for different biaxialities and creep mismatch factors are also examined in this paper. The result shows that the steady creep fracture parameter C^* decreases with the increments of mismatch factor and biaxiality B. The creep constraint parameter A₂(t) is insensitive to loading level for the creep mismatch crack plate under biaxial loading. The steady creep constraint parameter increases with the increments of biaxialities and decreases as m increases, which indicates the higher under-match plate with higher biaxiality has higher creep constraint effect.

Abstract: Fiber reinforced laminate design is a challenging problem in the field of composite laminates. It provides us a systematic way to design the laminates of desired properties while conveniently incorporating the thick-ness and mass constraints. In this paper, we pursue the multivariate graphite fiber reinforced laminate design problem using Ant Colony Optimization (ACO) algorithm. Classical lamination theory is used to determine mid-plane strains, curvatures and stresses in individual lamina under applied biaxial loading conditions. The fiber orientations, lamina thickness, number of layers and fiber volume fractions of lamina are considered as the optimization variables. Failure of the lamina is analyzed by Tsai–Wu failure criterion. Objective of the study is to maximize the load carry capacity of the composite laminate structure and minimize the areal mass density under multivariate/multiobjective optimization.

Abstract: This research discussed on the determination of the appropriate fatigue damage parameter to predict the fatigue life when material subjected to the biaxial loading condition with the consideration of the energy dissipated. Servo-hydraulic machine is used for the constant amplitude cyclic testing on smooth solid mild steel. The results showed that in the low cycle fatigue, the total strain energy density can represent the accumulative of fatigue damage and characterize on the damage parameters. The relationship has been proposed which the data satisfactorily correlated for the R² is 0.8656. In addition, the hysteresis loop represent the area under the graph was the energy stored in the material during the loading and unloading condition. Hence the circumstances showed the deformation process governing the nucleation and propagation of fatigue cracks associated with the energy dissipated.

Abstract: This article deals with multiaxial fatigue strength of notched round bars made of Cr-Al-Mo steel and tested under combined tension and torsion loading. Fatigue life is one of the important factors in design since majority of engineering components are subjected to variable loading. Most of mechanical components in engineering practice are subjected to combined loading, which can lead to sudden fatigue failure. In present work the fatigue life of specimens made of low-alloy Cr-Al-Mo high-strength steel is studied. Experiments were focused on the high-cycle fatigue region (over 100 000 cycles to final failure). The most relevant goal of this paper is to verify the efficiency of modified classical multiaxial fatigue criteria. The criterion proposed by Goncalves, Araujo and Mamiya was found to be the best in the fatigue life prediction for bending-torsion loading of notched specimens.

Abstract: The designing of composite structures for modern and precision application is complicated due to its anisotropic and inhomogeneous material behaviour. Therefore, reliable methodology for fully predicting the performance of composite structures must be developed. Hence, analytical and numerical solution will be implemented in order to perform failure analysis of composite laminates under biaxial loading. There are many approaches developed in order to study the failure behaviour of composites materials. This paper reviews and proposes a research framework that employs analytical method, numerical method using MATLAB programming and finite element method using ANSYS 14.0 to investigate the failure behaviour of composite structures. The First Ply Failure (FPF) and Last Ply Failure (LPF) analysis will be performed to determine the failure curves. Finally, the failure curves obtained from both analytical and finite element simulation will be compared with results published from previous experiments.

Abstract: This paper presents the results of an experimental investigation into the Ultimate Elastic Wall Stress (UEWS) of ±55° filament wound composite pipes. The UEWS test appears to provide an attractive alternative to the current method, and has proved to be one of the most effective in term of accuracy and speed. Moreover, it has been found to be sensitive to changes in key manufacturing and raw material parameters. The pipes were subjected to biaxial loading, which was achieved by combinations of hoop and axial stress. Loads were applied as groups of cycles which, were gradually increased until the UEWS had been determined. Various ratios of hoop to axial stress were applied to the pipes, ranging from pure axial to pure hoop loading at room temperature and at 65°C. These ratios were investigated by applying different pressures in both the main and small chambers built inside the pipe, and therefore it was unnecessary to add any external loads to the pipe wall. Tests were also conducted to observe leakage through the pipe wall. The main failure mode observed was weepage through the pipe wall, which was due to intensive matrix microcracking. The results from the UEWS tests are presented in the form of failure envelopes showing the effects of testing at an elevated temperature. Finally, degradation in the elastic properties of the pipe wall is also discussed and plotted against wall stress.

Abstract: In this paper, we have developed a seepage-damage coupling analytical procedure based on FLAC-3D, which can simulate and analyze the crack initiation, propagation and coalescence process of jointed rock under coupling effect. It simulates the failure process of inhomogeneous specimen with two existing fractures under pore water pressure and biaxial loading. Meanwhile compare the results with corresponding non-seepage working condition. By showing the dynamic damage state and analyzing the stress-strain relationship, the mass damage and progressive failure process of jointed rock under the influence of seepage were studied.

Abstract: Elastic-plastic J-integral and plastic limit load were described by finite element (FE) analysis for single hole-edge crack in plate under far field biaxial load. In this paper, the effect of biaxial load ratio (from -1 to 1) on elastic-plastic J-integral and plastic limit load was studied, the values of coefficient h1 for J-integral engineering estimation formulas were given and the effect of material hardening on plastic limit load was discussed. The result obtained from this work provides reference for fracture evaluation, so it can be used in engineering accurately and expediently.

Abstract: This paper presents the modelling of a general lifetime performance for glass fibre reinforced epoxy (GRE) composite pipes similar to the well-known Tsai-Hill interactive failure criterion. Tsai Hill criterion is based on the Von Misses distortional energy criterion which was modified to satisfy the orthotropic nature of GRE composite pipes. The effects of stress developed in each ply from ultimate elastic wall stress (UEWS) test were expressed in a single quadratic term of axial and hoop stress through laminate theory. The term then solved to produce limits with respect to axial and hoop stress, which represented in a graphical form of failure envelope. The modelled envelop shows a good agreement with experimental data from the multiaxial UEWS test of ±55° GRE composite pipes. This indicates that such model can be used to predict the long-term performance of GRE pipes under combine loadings.

Abstract: This paper presents an experimental investigation into the influence of winding angles in multiaxial ultimate elastic wall stress (UEWS) tests of glass-fibre reinforced epoxy (GRE) composite pipes. Currently, UEWS test is one of the alternative methods used to the 1000-hour test procedure detailed in ASTM D2992 for the detection of manufacturing changes and reconfirmation of the design basis of composite pipes. A stress-strain response was obtained for each winding angle and the results then compared with those computed through conventional laminate theory. Experimental data showed that the UEWS point varies for each winding angle, and the difference becomes even more pronounced, especially when the angles deviated from the ideal ±55°. It is also concluded that the UEWS stresses, which represent the onset of non-linearity were very much dependent on the transverse and shear stress responses, and these values were found to be consistent with the predicted values from the commonly used Tsai Wu failure criterion.