Applied Mechanics and Materials Vol. 606

Abstract: In this study, the effect of bond thickness upon shear strength and fracture toughness of epoxy adhesively bonded joint with dissimilar adherents was addressed. The bond thickness, t between the adherents was controlled to be ranged between 0.1 mm and 1.2 mm. Finite element analyses were also executed by commercial ANSYS 11 code to investigate the stress distributions within the adhesive layer of adhesive joint. As a result, shear strength of adhesive joint reduces with increasing bond thickness. The strength of shear adhesive joint was also depended on elastic modulus of adherent. Moreover, the failure of dissimilar adherents bonded shear joint originated at a location with critical stress-y which was the interface corner of ALYH75/epoxy. In the case of shear adhesive joint with an interface crack, the fracture also occurred at the ALYH75/epoxy interface even in the steel-adhesive-aluminum (SEA) specimens. Fracture toughness, Jc of aluminum-adhesive-steel (AES) joints was similar to those of SES and demonstrates strong dependency upon bond thickness. Furthermore, the interface crack in SEA specimen has relatively large fracture resistance if compared to those in AES specimen. Finally, Kc fracture criterion was found to be appropriate for shear adhesive joints associated with adhesive fracture.

Abstract: Topographgy optimization is a special kind of size optimization and it has been widely used to enhance the stiffness of sheet metal formed component by adding beads to the geometry. In this paper we present a methodology on how this concept can be employed in order to reduce formed part geometry deviation due to springback. An automotive part from Numisheet benchmark 2008 was used in this study. Several bead patterns were first generated by topography optimization subject to load constraints. Then the effects of these bead patterns location and size were studied by numerical forming and springback simulation. Our results show that the bead patterns have a significant effect on the springback. Finally, a methodology has been developed so that springback-free design can be incorporated in the early stage of part design.

Abstract: Patchwork blank is usually comprised of two different thickness of HSS sheet metals spot welded on top each other. Designed to provide an increased stiffness, it is widely used in many structural formed parts. The correct number of spot-welds is important in terms of cost and safety. In this study, the effects of spot-weld locations on an automotive part called B-Pillar with patchwork blank design was investigated by numerical hot forming simulation. The spot weld was modeled as a rigid link between parent blank and additional blank. Throughout the forming simulation, maximum stress and formability of the part were monitored. The same procedure was repeated for different spot-weld number and location. An optimum number of the spot-weld was then determined by the onset of wrinkle disappearance. Performance of the optimized spot-weld part was validated by actual part.

Abstract: An experimental investigation was conducted to compare the crush characteristics and energy absorption capacity of circular and square tubes with located through-hole crush initiator. Circular through-holes were fabricated at three different configurations based on location into steel tubes which had a length of 200 mm. Furthermore, two different side configurations along the tube were considered for introducing the crush initiators. The results found that adding crush initiator onto the tubes were effectively reduced the initial peak force of a thin-walled circular and square tubes under axial quasi-static loading. The peak crush force was reduced within a range 3-10% and 5-16% for circular and square tubes respectively when compared with corresponding tubes without crush initiator. Moreover, the energy absorption capacity of the tubes was independent with the incorporation of through-hole crush initiators. However, the energy absorption of circular and square tubes were slightly decreases when compared with the tubes fabricated four sided crush initiation and tubes without crush initiator. Overall, the effect of location and number of crush initiation proved significantly influences the initial peak forces while maintain the energy absorbed.

Abstract: Magneto-rheological (MR) fluid technology has made it possible to develop reliable, revolutionary vibration control systems for a variety of commercial, medical and military applications. MR fluid shock absorber systems are enabled by remarkably versatile MR fluid technology, which allows the system to respond instantly and controllably to varying levels of vibration or shock with simple, robust designs. This paper presents a parametric study of the MR dampers for semi-active vibration control. The influence of gap size of the damper on the viscous stress of the MR fluid is examined. It is inferred from the study that the viscous stress of the MR fluid for different parameters such as gap size influences the dynamic range of MR fluid dampers.The simulated results depict a maximum viscous stress of 1765.441 N/m² for a gap size of 1.85 mm. The developed dynamic range would allow for smaller size of the device, higher dynamic yield stress and low power consumption. The simulated results using COMSOL multiphysics for the verification of the parametric strategy have been presented. Results of this study shall enhance the design of MR dampers for different control applications.

Abstract: Electro chemical machining seems to be the future of micro and nanomachining due to its advantages like high MRR, no tool wear, highly precise, reliability, better control over machining and so on. Surface roughness is an important factor in electro chemical machining. ECM can produce surface roughness of the order of 0.4μm. This paper is devoted to the study of micro ECM process to obtain a surface roughness of about 0.3μm in an alluminium alloy specimen using a copper electrode.

Abstract: Productivity plays a significant role for most companies in order to measure the efficiency. In reality there is an essential need to evaluate the different factors which increasing productivity and achieving the high level of quality, high production rate , machine utilization. On the other hand, manufacturing companies are striving to sustain their competitiveness by improving productivity and quality of manufacturing industry. So it can be acquired by finding ways to deal with various industrial problems which have affected the productivity of manufacturing systems. This paper aims at applying statistical analysis and computer simulation to recognize and to weight the significance of different factors in the production line. Based on the final result the two factors which are B (Number of labor) and C (Failure time of lifter) have the most significant effect on the manufacturing system productivity. In order to achieve the maximum productivity the factors should be placed on the levels which are: A= -1, B=1, C=1 and D=1. This means that the service rate of mixer = UNIF (20, 40), number of labor=20, failure time of lifter =60 min and number of permil=5 respectively.

Abstract: Ceramic materials have been widely utilized due to its attractive properties including high resistance to extremely harsh environments; chemical and heat, and its durability to the remarkable mechanical strength. Inorganic flat sheet films in this study were prepared by dry-wet phase inversion process followed by sintering method, which expected to produce very unique micro-structures leading to improvement in performance for various applications including catalytic reactions and filtration processes. Aluminium oxide was chosen as the main material due its known capability in filtration processes, membrane reactors and membrane catalysis applications. Polyethersulfone (PES) was used as an organic binder in the membrane dope formulation. Besides alumina and PES, the dope solution was consisted of N-methyl-2-pyrrolidone (NMP) and arlacel as solvent and additive, respectively. The main aim of this study is to investigate the effect of sintering temperature on the morphology and structure of the prepared membranes. Scanning electron microscope (SEM) was used to examine the membrane structure. Since the morphology of a membrane highly influences its mechanical properties, the membrane strength was measured using tensile test. From the SEM, preliminary cast membrane structure displayed a long finger-like near the outer and inner walls sandwiched a sponge-like structure that provided the membrane strength.

Abstract: Continuous research is conducted to improve the available coastal protection scheme, including to develop an innovative concrete armor unit with interlocking capability. Interlocking Concrete Unit-V (ICU-V) has light weight characteristic and developed specifically for mild wave condition. This paper discusses the performance of ICU-V represented by the Stability coefficient, K_D and results of the damage progression investigation under different wave conditions. These were achieved by conducting a 2-D physical model investigation by using JONSWAP random wave spectrum. The damage ratio method was used to assess the damage progression. The optimum K_D obtained was 12 with highest damage level of 0.4%, which is comparable with available armor units

Abstract: Progressive failure process of adhesive joint under cyclic loading is of particular interest in this study. Such fatigue failure is described using damage mechanics with the assumed cohesive behaviour of the adhesive joint. Available cohesive zone model for monotonic loading is re-examined for extension to capture cyclic damage process of adhesive joints. Damage evolution in the adhesive joint is expressed in terms of cyclic degradation of interface strength and stiffness. Mixed-mode fatigue fracture of the joint is formulated based on relative displacements and strain energy release rate of the interface. A power-law type variation for each of these cohesive zone model parameters with accumulated load cycles is assumed in the presence of limited experimental data on cyclic interface fracture process. The cyclic cohesive zone model (CCZM) is implemented in commercial finite element analysis code and the model is validated using adhesively bonded 2024-T3 aluminium substrates with epoxy-based adhesive film (FM73M OST). The CCZM model is then examined for cyclic damage evolution characteristics of the adhesive lap joint subjected to cyclic displacement of Δδ = 0.1 mm, R=0 so as to induce shear-dominant fatigue failure. Results show that the cyclic interface damage started to initiate and propagate symmetrically from the both overlap edges and degradation of interface strength and stiffness started to accumulate after 0.5 cycles of displacement elapsed. The predicted results are consistent with the mechanics of relatively brittle interface failure process.