Short fiber reinforced metal-matrix composites (MMCs) have widely adopted as structural materials and many experimental researches have been performed to study fracture toughness of it. Fracture toughness is often referred as the plane strain(maximum constraint) fracture toughness K_Ic determined by the well-established standard test method, such as ASTM E399. But the application for dynamic fracture toughness K_Id has not been popular yet, because of reliance in capturing the crack propagating time. This paper deals with dynamic fracture toughness testing and simulation using finite element method to evaluate fracture behaviors of MMCs manufactured by squeeze casting process when material combination is varied with the type of reinforcement (appearance, size), volume fraction and combination of reinforcements, and the matrix alloy. The instrumented Charphy impact test was used for K_Id determination and continuum damage model embedded in commercial FE program is used to investigate the dynamic fracture toughness with the influence of elasto-visco-plastic constitutive relation of quasi-brittle fracture that is typical examples of ceramics and some fibre reinforced composites. With Compared results between experimental method and FE simulation, the determination process for K_Id is presented. FE simulation coupled with continuum damage model is emphasized single shot simulation can predict the dynamic fracture toughness, K_Id and real time evolution of that directly.

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In tropical countries such as Indonesia and Malaysia, the empty fruit bunches are wastes of the oil palm industry. The wastes are abundantly available and has reached a level that severely threats the environment. Therefore, it is a great need to find useful applications of those waste materials; but firstly, the mechanical properties of the EFB fiber should be quantified. In this work, a small tensile test machine is manufactured, and the tensile test is performed on the EFB fibers. The results show that the strength of the EFB fiber is strongly affected by the fiber diameter; however, the fiber strength is relatively low in comparison to other natural fibers.

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The objective of this study is to present a methodology that can properly simulate three-dimensional fatigue crack propagation with consideration of the crack closure effect. To simulate fatigue crack growth in three-dimensional elastic structures, the superposition finite element method (S-FEM) is employed. A local model is used to represent the near crack area to overcome difficulties that appear in the process of re-meshing the FE model during crack propagation; therefore, many complex crack geometries that may be generated under mixed mode conditions can be easily modeled. Considering the plasticity-induced crack closure effect, elastic-plastic analysis was first conducted to study the behavior of the crack closure effect along the crack tip. Normalized crack opening level along the direction of thickness was obtained and applied to simulations. Experiments on single edge notch specimens under Mode I, Mode I+II or Mode I+II+III loading conditions were conducted to verify the method. Experimental results related to crack growth direction, crack shape and fatigue life were compared with simulation results. Better predictions on crack path were shown. Significant improvement of crack shape evolution in the simulation model was obtained considering the crack closure effect.

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The effect of local plastic deformation on the fatigue life in a holed specimen was investigated. The local plastic deformation was applied around the hole by inserting a pin into the hole, and the pin was removed before the testing. The material used was aluminum alloy 2024-T3. After removing the pin, there was a circular hole or elliptical hole in the center of the flat section of the specimen. Due to the application of local deformation, the fatigue life of holed specimens became longer. In particular, in specimens where the hole shape was made elliptical, the fatigue life was clearly improved. Hardness distribution around the hole was measured to understand the effect of the local plastic deformation on the fatigue life expansion. Consequently, it is concluded that the local plastic hardening and compression residual stress in the vicinity of the hole are the cause of the strengthening of the holed specimen.

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The numerical evaluation of impact characteristics of a cue in billiards is performed for the case where the ball trajectory is deviated from the hitting direction and curved by hitting a ball on its upper left or right part with an inclined cue. The effective numerical method developed in the previous papers, in which a cue and a ball are assumed to be isotropically elastic and rigid, respectively, is extended for this case. The extended method is verified with an experiment using a high speed camera. The result obtained with the extended method shows that the radius of curvature of the ball trajectory is large for the impact on its almost exactly left part with a slightly inclined cue, and this result agrees with an empirical one. It is found from a numerical simulation that if the Young's modulus or mass density of a shaft of a cue is large, the ball trajectory immediately after the impact is deviated largely and then is curved with a large radius of curvature. Because the extended method can evaluate quantitatively this kind of effects of material properties, it is useful for a design of a cue.

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