Papers by Keyword: Failure Mode

Abstract: Reinforced concrete dapped end beams (RC-DEBs) in service suffer damage near the reentrant section under unknown loading conditions, reducing service life, particularly when recurrent loading is considered. In this investigation, a Finite Element Model (FEM) of a standard RC-DEB was used, together with a 3-dimensional concrete model and a fixed constitutive model. The girder reinforcement was designed in compliance with Eurocode 2 (EN-2) criteria for shear and deflection analysis. The level of deterioration under fatigue difficulties was determined by doing a fatigue analysis of moving and fixed pulsing loads at the midpoint and offset loading. A scaled-down experimental validation of the FEM for fixed pulsing loading was considered to better understand fatigue deterioration for practical applications. The major mode of damage observed is shear brittle failure at the beam's reentrant region. Although the moving load proved to be more damaging than the fixed pulsing load, loading at an offset of a/d of unity had an effect on the reentrant portion. The EN-2 code is nonconservative when it comes to describing the reinforcement at the reentrant section; for optimal performance, the hanger reinforcement must be properly anchored to the shear.

Abstract: This paper deals with failure modes of a steel-concrete-steel sandwich loaded by pure in-plane shear. Current research together with the developed models imply that increase of reinforcement ratio leads to decrease of ductility and possibly to change a failure mode from yielding of steel in tension to crushing of concrete in compression which results in brittle failure. In order to give a reader basic information about in-plane shear behavior of a steel-concrete-steel sandwich, an analytical model is introduced. Japanese experimental program that researched a behavior of SCS panels with reinforcement ratio 2.3%, 3.2% and 4.5% is also shown. In addition to the effect of changing the reinforcement ratio, the experimental program also investigated the effect of the transverse steel plate on the ductility of test panels with a degree of reinforcement of 3.2%. The next chapter describes the methodology used by the author to model the individual parts of the model, the loads, and especially the method of supporting the model. This is followed by the presentation of the results of the analysis on the calibration and extrapolation models. Finally, a discussion is conducted on the agreement of the analysis results on the calibration models with the Japanese experimental results, followed by an evaluation of the analysis results on the extrapolation models. According to the results on the extrapolation models the critical degree of reinforcement at which a change in the failure mode of the structure occurs under in-plane shear loading is around 13%.

Abstract: The objectives of this study are to analyze the pattern crack and failure mode of the GFRP concrete beam by using GFRP sheet as shear reinforcement (GFB) compared with the two types of the conventional reinforced concrete beam (CB and GB). One of the conventional reinforced concrete beams is reinforced with the steel bar (CB) and the other is the GFRP bar (GB) as longitudinal reinforcement. The nine beams were cast from one concrete batch with dimensions of 150 mm width, 250 mm depth and 3300 mm length. This study focuses on a simply-supported beam using a roller and pinned supports at the end of the beam. Control beam (CB) that using steel reinforcement shows three phases of deformation based on the deflection load curve, ie before crack, after crack, and after yield, while GB and GFB beams that use GFRP bar reinforcement only show two phases of linear deformation namely the deformation phase before cracking and after cracking. From the crack pattern, CB beams experience the flexural cracks which starting from the mid-span on the tensile side of the constant moment region and propagated to the compression region along with the increase in load. All GB beams show the crack starts from the mid-span and then propagates towards the support. Whereas GFB beam show the flexural cracks that occur in the constant moment region and in the shear span, also diagonal cracks that divide the GFRP sheet occurred. From the failure mode, CB experienced flexural failure, while GB experienced compression failure and shear failure in all GFB beams.

Abstract: Objective: To study the fracture resistance and failure modes of different type of ceramic crowns. Methods: Four groups of crown including zirconia-veneering porcelain crown (Group 1), whole zirconia crown (CAD/CAM, Group 2), cast ceramic crown (Group 3) and glass ceramic crown (CAD/CAM, chairside, Group 4) with the same thickness were manufactured, each group own 12 crowns. The fracture resistance test and failure modes analysis of the specimens were conducted, SPSS22.0 was used to analyze the difference among the groups. Results: The fracture strength of Group 2 is significantly higher than other three group (P<0.05), Statistical significance was found between group 3 and group 1, group 4. No Statistical significance was found between group 1 and group 4. The failure modes of the whole zirconia crown, the cast ceramic crown and the glass ceramic crown are complete crown fracture; 33% of the zirconia-veneering porcelain crown showed veneering layer fracture, the other 67% showed complete crown fracture. Conclusion: The fracture resistance of the whole zirconia crown are higher than the cast ceramic crown, the zirconia-veneering crown and the glass ceramic crown and the glass ceramic crown (CAD/CAM) is a very convenient prostheses. The failure modes are significantly influenced by the type of the crown.

Abstract: The experimental investigation on the compressive properties of honeycomb sandwich composite panels was carried out in this paper. The local compressive specimens and global compressive specimens were manufactured for compressive experiment. The test fixture has been designed and manufactured to examine the compressive behavior of honeycomb sandwich panel. The results indicate that there is no buckling occurred in local compressive specimen skin during the whole compressive experiment. The average failure load of local compressive specimens is 106884 N. The local buckling increases with the loading until the global compressive specimens are unstable. The fracture positions locate along the horizontal line at the middle height of global compressive specimen, which is different from local compressive specimens. The average buckling load and failure load of global compressive specimen are 31850 N and 82282 N respectively.

Abstract: This present study has been re-established to investigate failure mode and resistance characteristics of the PC/ABS blends and their ABS constituents under impact for a range of rubber contents. This present study has still been experimentally performed under an instrumented-drop weight impact test (DWIT) at a room temperature. It has been finally revealed that with a particular size of rubber particle, content of rubber significantly influenced impact failure modes and impact resistances of the PC/ABS blends and their ABS constituents as well. The test results showed that impact strength of the blends was improved about 23.22% and 155.33% due to increase in content of rubber up to 15 wt% and 20 wt%, respectively. There was also found that an increase in impact toughness of the blends for 57.48% and 239.23% was due to increase in content of rubber up to 15 wt% and 20 wt%, respectively. Whilst, impact strength of the ABS was improved about 392.98% and 190.12% due to increase in content of rubber up to 15 wt% and 20 wt%, respectively. An increase in impact toughness of the ABS for 308.20% and 172.56% was due to increase in content of rubber up to 15 wt% and 20 wt%, respectively.

Abstract: Experimental work has been performed on the behaviour of glass/epoxy, aluminum, and aluminum-glass/epoxy empty and polyurethane foam filled tubes subjected to three-point bending. Tubes were of circular and square cross section area. Hand layup method was used to fabricate the tubes. Each tube is made of six layers. Inner diameter and total length of the tubes were 50 mm and 250 mm respectively. Bending load-displacement response, crush force efficiency, and absorbed energy were drawn and discussed. Effect of foam filler, material of the tube and stacking sequence on the maximum bending load was investigated. Energy absorption was determined and discussed. failure mode was investigated. It has been found that the polyurethane foam filler increased the maximum bending load and the energy absorption of the circular and square cross section area tubes. Using hybrid aluminum-glass/ epoxy enhanced the bending load and absorbed energy of the aluminum tubes. Cracks were observed at the upper and lower surfaces at the centre of the glass/epoxy tubes. While the aluminum tubes deformed significantly with either no cracking or with one crack appeared at the centre of the top surface of the tube.

Abstract: This study presents an experimental study on failure modes and resistances of polycarbonate (PC)/Acrylonitrile Butadiene Styrene (ABS) blends and their ABS constituents under a drop weight impact test (DWIT). Failure modes and impact resistances such as impact strength and impact toughness of such blends are generally influenced by molecular weight of the PC, rubber content and size of rubber particle in ABS system. A preliminary study on ABS materials using a DWIT showed that size of rubber particle not only determined their failure modes but also influencing their resistance characteristics. However, in a previous study performed using the similar DWIT on PC/ABS blends with a 10 wt% rubber content, it was revealed that size of rubber particle did not significantly influence their resistances. Their failure modes were even macroscopically very difficult to be distinguished. This study, hence, is aimed to further explore role of the size of rubber particle on failure mode and impact resistance characteristics of the PC/ABS blends and their ABS constituents with a higher rubber content. The impact test results have revealed that with a 20 wt% rubber content, size of rubber particle only influenced the resistances of the PC/ABS blends. It did not significantly contribute to affect failure mode of the PC/ABS blends. Whilst, it significantly influenced failure modes and resistances of the ABS. The DWIT results also re-confirmed that blending a brittle ABS into PC led to produce a tougher PC/ABS blend.

Abstract: Mid-Life Refurbishment (MLR) is a process conducted in many industries to improve or extend the life span of assets such as machines, infrastructures and systems. The objective of MLR works execution is to extend the life span, sustain the train performance and achieve system reliability. Typically, the refurbishment scope consists of overhaul, upgrading and rectification works. The biggest challenge is to determine) the scope of refurbishment works and to create equilibrium between the feasibility and viability of the project. Therefore, the main objective of this paper is to discuss the current practice of performing MLR maintenance through the utilization of Failure Mode and Effect Analysis (FMEA) and to transform the existing FMEA used by the automotive industry to fulfil the needs of Rolling Stock. The use of FMEA is critical in determining) the scope of train refurbishment work. It was carried out at the initial stages of the process in order to determine Risk Priority Number (RPN) to prioritize the type of refurbishment plans and scope. The design of the FMEA Worksheets, De-sign of FMEA severity Evaluation Criteria, Design of Occurrence Evaluation Criteria and Design of FMEA Prevention/Detection Criteria were adopted and adapted from the generic format so that it is coherent with Railway Industries. The results based on the transformation framework, the plan and scope of overhaul, upgrading and rectification were defined using the FMEA. Out of the 80 elements of MLR works that were analyzed using the FMEA approach, it was found that 46 elements needed overhaul, 23 elements needed upgrading and 11 elements needed rectification works. Finally, the application of the FMEA helped determine the MLR scope of work from 13 systems. The case study was taken from the Malaysia LRT Project, and currently the fleet has been in operation for more than 20 years (operated since year 1998).

Abstract: A meso-structure model of three-dimensional spacer fabric composite (3D composite) was built by using the finite element software Workbench, and simulation analysis of in-plane compression on the 3D composite was studied according to the model. The results show that the upper and lower face-sheet is the main load-bearing section macroscopically, while the piles are the secondary load-bearing one when the 3D composite is subjected to in-plane compressive load. The fibers play a major role microscopically, while the resin plays a minor one. From part magnifying stress distribution, it can be found that the maximum stress occurs in the warp yarns, interlaced with weft yarns, when the 3D composite is subjected to in-plane compressive loads in warp direction, and fracture appearance is parallel. Meanwhile, the maximum stress occurs in the weft yarns, interlaced with binder warp yarns, when the 3D composite is subjected to in-plane compressive loads in weft direction, and fracture appearance is random. From strain distribution of each component, it can be seen that the failure mode is the interfacial de-bonding between the fibers and resin when the 3D composite is subjected to in-plane compressive loads.