Papers by Keyword: Flexure

Abstract: This paper presents a design of the 1 degree-of-freedom (DOF) compliant mechanism to support rotation, which can be used as the compliant bearing in rotary motor. With the simple idea of replacing the traditional bearings with the compliant counterparts, the compliant motor built by the developed mechanism is capable of creating frictionless and repeatable rotations for precise applications. The compliant bearing is synthesized based on a specific connection of beam-type flexures; its stiffness characteristic is analytically determined in this paper. Finite element analysis (FEA) is then used to verify the analytical results. The correctness of the bearing design is demonstrated through the small deviation between the analytical and FEA methods. With the simple structure of this compliant mechanism, a low-cost flexure-based bearing can be achieved to support rotary motions in precision devices such as actuators, sensors, positioners, etc.

Abstract: This paper presents the development of a low-cost linear motor with precise – frictionless motion. The motor is constructed by two main modules: Compliant bearing and voice coil actuator (VCA). The mechanical property of the bearing is determined by its 6×6 stiffness matrix which is formulated based on the relationships between beam-type flexure elements within a compliant mechanism. To run the motor, a VCA is specifically designed to fit the desired dimensions and able to create enough input force for compliant bearings to reach their largest elastic deformation. Subsequently, the finite-element-analysis (FEA) is conducted to evaluate the performance of the motor through the simulations of bearing deformation and electromagnetic force from the VCA. The good agreement between analytical and FEA results demonstrates the correctness of the proposed design. With the low-cost due to the simple structure and the ability to produce frictionless motion, the motor presented in this paper can be considered as a potential candidate for the development of various applications in precision engineering field.

Abstract: 3D printing has been on the rise in recent times and the civil engineering industry has adopted this technology due to its various advantages. However, printing is largely restricted to concrete members while the reinforcement is introduced manually. The current work looks at the possibility of using 3D printed thermoplastics as formwork and reinforcement for concrete beams. Three different polymeric materials, namely PETG, PLA, and TPU were utilized in this research to fabricate formwork-like reinforcement for 150×150×500 mm concrete beams. The reinforcements were 3D-printed using a fused deposition modelling (FDM) printer in the shape of a formwork to serve as moulds and external reinforcement. The reinforcing formwork geometry was designed with trapezoidal corrugations to ensure strong bonding with the concrete. The beams were tested in four-point bending configuration, and their flexural behaviour was characterized and compared with plain and steel reinforced concrete (RC) reference beams. Results indicate that all 3D printed beams reached a load capacity of around 30 kN. The post-peak behaviour of these beams was dependent on the type of polymer used. The PLA and TPU reinforced beams exhibit large post-peak deflection however their load carrying capacity was compromised, while the PETG exhibited a strain hardening behaviour but with much lower deflections. Overall, the results indicate that 3D-printed thermoplastics are a promising economical alternative to the conventional steel reinforcement.

Abstract: Alkaline activated materials and geopolymers are recently widely involved in studies concerning their potential for advanced composites with enhanced electrical properties. This paper reports self-sensing behaviour of fly ash mortar doped with carbon black or graphite conductive admixture subjected to loading in three-point flexural test. Development of self-sensing properties and deformations of all mortars was initially investigated under flexural loading cycles with constant amplitude, final stage of the experimental part consisted in loading till fracture. Both reference and modified geopolymers failed to achieve satisfactory self-sensing performance during the cyclic loading but certain differences in fractural properties were observed.

Abstract: Tensile, compressive and flexural (3-point bending) tests are performed on electromechanical universal testing machine (Zwick/Roell 250kN) to determine mechanical characteristics of an aluminium hybrid composite fabricated through stir casting process at different rates of quasi-static loadings in room temperature 25°C. Influence of heat treatment (annealing) is observed on the material properties. After annealing, the tensile, compressive and flexural strengths decrease while ductility, malleability and bending capability of the composite increase. Bending tests are conducted at different crosshead speeds (1-100mm/min) to study its effects on flexural stresses. It is found that the specimen geometry affects the stress-strain behaviour of the composite.

Abstract: Electron beam melting (EBM) technology has been popularly used to fabricate flexible devices that performance is directly determined by the elastic deformation of thin beams/flexures. This paper presents the experimental investigation on the effective thickness which determines the mechanical properties of beam-based flexures built by EBM method and Ti6Al4V material. The findings show that the effective thickness of EBM-printed beams is different from the designed value regarding to the building direction. A coefficient factor is proposed to compensate this difference. The experimental results suggest that with EBM-printed flexures having large thickness of ≥ 0.7 mm, the coefficient factors become consistent.

Abstract: Fiber reinforced polymer (FRP) is widely used in the construction industry for structural strengthening due to their outstanding mechanical properties. However, the production of synthetic fibers such as FRP is detrimental to the environment. Alternatively, natural fiber composite may be used as external strengthening material. This paper presents the potential of bamboo fiber composite plate (BFCP) to strengthen the reinforced concrete (RC) beams in flexure. The bamboo of species Dendrocalamus asper was used to produce the fiber and fiber-to-volume ratio was set at 2:5. The composite plate was fabricated by binding bamboo fibers with epoxy using a hand-lay-up method. The flexural and tensile strength of the BFCP was measured and all the beams were tested to failure under four-point bending test. It was found that BFCP exhibited a higher flexural and tensile strength compared to pure epoxy samples. Meanwhile, the RC beams strengthened using BFCP exhibited an increment of 10-12% in beam structural capacity compared to the un-strengthened beams. Bonding of BFCP in the flexure zone was able to divert the vertical cracks into diagonal at the edge of the composite plate. Findings from this work may serve as a useful guide to strengthen RC beams using a BFCP.

Abstract: Calcium sulfate dehydrate β (CaSO₄. 0,5H₂O) is a material obtained from the calcination of gypsite (CaSO₄.2H₂O). This is a low cost ceramic material very used in building industry. The improvement of their applications is of fundamental technological interest. Polymers are an interesting alternative of reinforcement. Polyvinyl acetate (PVAc) is an addition polymer obtained by the polymerization of vinyl acetate. This polymer is well known to achieve good adhesion to cellulosic surfaces. The aim of this work was to evaluate the mechanical properties of porous plaster bodies reinforced with PVAc. Mechanical behavior was characterized by compression and bending strength. Three water / gypsum ratios: 0.5 0.6 and 0.7 were used on this work. An amount of 5% and 10% PVAc promoted increase on the mechanical properties of gypsum. Higher amounts polymer promoted further decrease of the mechanical properties.

Abstract: The potential of natural resources such as pumice and sisal fiber for simple housing structural components is investigated in this research. Behavior of sisal fiber reinforcement of lightweight concrete beam under flexural loading was examined. The purpose of this study is to identify the prospect of sisal fiber as a replacement of steel bar reinforcement for structural element. The variations of reinforcement ratios were considered in order to optimize the performance of sisal fiber reinforcement. Twelve beam specimens size 100 x 150 mm with clean span of 1.5 m were examined in this investigation. Four variations of beam reinforcement were explored consist of 3 sisal fiber variation and 1 steel reinforcement as a control; where every variation was presented with three samples. Enerpac hydraulics Jack with 50 ton capacity connected to the load cell was operated as a source of loading. LVDT was fitted in the mid-span to measure vertical deflections during the loading. Test results indicated that the crack moment experiments were higher than the crack moment calculations. The valued were 1.44, 1.52, and 2.72 higher for sisal fiber reinforcement of B-LF, B-MF and B-HF, respectively. Whilst for steel reinforcement of B-LS the valued were 3.32 higher. Observation results also indicated that the moment resistant capacities of the specimens were twice higher compare to the calculated moment capacity. However, The lowest sisal reinforcement (B-LF) has only about 10% different service moment compare to the steel reinforcement (B-LS) where they both have equal ρ = 1.206 %. This indicate that the use of sisal fiber have considered as insignificant different service moment capacity to the steel reinforcement.

Abstract: Repair materials have been produced using an unsaturated polyester resin (UPR) as a matrix of a binder. Other ingredients are sand, cement and fly ash. No water is added to the mixture, so both the cement and fly ash only act as fillers. The UPR content is in the range of 50-60% by weight of total filler (cement plus fly ash). Their flexural performance has been characterized in term of the load-deflection behaviour, modulus of rupture, flexural modulus and stiffness. The results show that the flexural capacity of these materials at early age is at least 20 MPa, but they tend to have a lower elastic modulus. At early age, the higher amount of UPR content tends to gain a higher flexural characteristic. However, at later age there is a little influence of UPR content.