Papers by Keyword: Mixed Mode Loading

Abstract: This paper presents experimental and numerical results on the deformations and failureof integral composite T-joints subjected to a realistic combined tensile and bending (mixed mode)load case. For this reason, standard pull-off and mixed mode load cases are experimentally studiedby means of a novel test fixture which keeps the force angle constant to the T-joint’s base and allowsfor repositioning of the specimen in order to minimize constraining forces. Two types of specimenswith varying deltoid radius are investigated. Additionally, kinematically nonlinear numerical simulationsare performed to locate damage onset and deformations of the specimens. It is found that thesimulations are in good agreement with the experimental results.

Abstract: This paper presents the experimental investigation on adhesive joint under three loading angles using a modified Arcan jig. Fracture test was performed using the fabricated Arcan specimens and Araldite adhesive with loading angle of 0°, 90° and 45° to represent Mode I, Mode II and mixed Mode loading, respectively. Eighteen specimens were prepared with adhesive thickness of 6 mm and nine of them with interface crack length of 5 mm. The result shows the stress intensity factor, K is influenced by the loading angle and the initial crack-line directions. KI was found greater than KII .

Abstract: Determination of fatigue crack growth characteristics under shear-mode loading is a rather complicated problem. To increase an efficiency and precision of such testing, special specimens enabling simultaneous propagation of shear cracks under II, III and II+III loading modes started to be used rather recently. However, a description of crack growth rate in terms of appropriate fracture mechanics quantities demands a precise assessment of plastic zone size under various shear-mode loading levels. This contribution is focused on the numerical elasto-plastic analysis of stress-strain field at the crack tip in specimens made of a pure polycrystalline (ARMCO) iron loaded by mixed mode II+III. The dependence of plastic zone size on the J-integral value described the wide region of loading. The results reveal that formixed mode II+III the small scale yielding conditions are fulfilled in the region where plastic zone size is smaller than 1/10 of the total crack length.

Abstract: Four-point bending tests are conducted on fiber reinforced cementitious composites (FRCC) overlaid concrete beams with a “T” notch. The objective is to evaluate the fracture behavior of the interface between the FRCC and the concrete substrates. Two types of FRCC overlays are prepared including a traditional steel fiber reinforced concrete (SFRC) composite and an ultra high toughness cementitious composite (UHTCC), which has a very high tensile strain capacity. All two types of FRCC are prepared in two forms: cast on-situ and prefabricated. Test results indicate that, in comparison with others, the prefabricated UHTCC overlay system has exhibited most desirable behavior in terms of the energy absorption in the interface as well as the crack distributions in the overlay, and therefore has a great potential for use in repair of concrete structures.

Abstract: Fatigue crack growth under mixed mode loading conditions is simulated using S-version FEM. By using S-FEM technique, only local mesh should be re-meshed for new crack configuration, and it becomes easy to simulate crack growth. By combining with auto-meshing technique, local mesh easily re-meshed and curved crack path is modeled easily. Fully automatic crack growth simulation system in 3-dimensional problem is developed. Using this system, several kinds of plural surface cracks problems are simulated. It is shown that intereaction effect between two surface cracks appear in complicated manner depending on intial distances between two cracks.

Abstract: In this paper a higher order crack path simulation algorithm for multiple interacting cracks is presented using piecewise parabolic curved increments including the consideration of the plastic limit loads. For this reason, the program PCCS-2D has been extended to analyse the crack growth and the plastic limit load for each crack propagation step in a fully automatic simulation. The proposed solution algorithm provides a powerful tool for flaw assessment with the FAD proce¬dure in combination with a numerical crack path simulation. Several numerical examples are pre¬sented to show the accuracy and the efficiency of the crack path simulation including the analysis of the plastic limit loads

Abstract: This work focuses on determining the influence of mixed stress conditions on the initiation of fatigue cracks from corrosion pits in a UNS S31603 stainless steel. Fatigue limit was established as a threshold stress criteria for fatigue crack initiation from semi-elliptic surface pits. The strain energy release rate range (G) around semi-elliptic surface pits was determined as a function of the pit aspect ratio (depth/major width axes: a/c), pit contour and the orientation of the nominal stress from a linear elastic fracture mechanics approach. Results indicated that stress conditions for crack initiation in mixed mode overcome the minimum stress level or single threshold stress established from the fatigue limit concept. Under mixed mode condition a crack will grow at the surface zone (φ = 0˚) when a/c ≥ 0.60 and for orientation angles from 5˚ to 75.

Abstract: Dimple fracture under mixed mode loading condition is studied experimentally and numerically. By the mixed mode loading, it is found that fracture surface becomes much rougher than that of mode I fracture. It is also found that ductile fracture growth direction deviates from the original plane. It becomes clear that there are two factors affecting ductile fracture processes, one is mixed mode ratio and another is thickness effect. Three-dimensional finite element analyses are conducted to study effects of these factors. For the simulation of ductile fracture, Gurson’s constitutive equation is used with large deformation theory. These numerical results agree with experimental observation very well qualitatively.

Abstract: Our purpose is to propose a methodology for assessing dynamic crack propagation laws under mixed-mode loading. Dynamic brittle fracture experiments are performed on polymethylmethacrylate (PMMA) in which mode combination changes and crack arrest phases occur. Then, these experiments are numerically reproduced by using the eXtended Finite Element Method (X-FEM) in order to validate the algorithms and the criteria assumed.

Abstract: This paper summarizes recent work on a new theory of fatigue crack growth in ductile solids based on the total plastic energy dissipation per cycle ahead of the crack. The fundamental hypothesis of the theory proposes a unified criterion for crack extension under monotonic and fatigue loading, so that the fatigue crack growth rate is given explicitly in terms of the total plastic dissipation per cycle and the monotonic fracture properties of the material. The total plastic dissipation per cycle is obtained by 2-D elastic-plastic finite element analysis of a stationary crack under constant amplitude loading, for both mode I (C(T)) and general mixed-mode I/II specimen geometries. Both elastic-perfectly plastic and bi-linear kinematic hardening constitutive behaviors are considered, and numerical results for a dimensionless plastic dissipation per cycle are presented over a wide range of relevant mechanical properties and mixed-mode loading conditions. Results are further extended to include fatigue delamination of layered material systems, where either discrete mismatches or a continuous grading of mechanical properties can exist across the interface.