Applied Mechanics and Materials Vol. 493

Abstract: This paper presents a modular system for testing the performance of a poly-articulate robotic arm (snake like) with the push-pull actuation redundancy. Mechanical structure contains modules that allow testing of robots with different structures of the robotic arm (discrete hyper-redundant, continuous). Sensory system can be configured depending on the product and testing program adapting the sensors of position, velocity, time and vibrations. The monitoring system developed allows the automatic calibration of actuators and sensors, data and signal acquisition.

Abstract: In this paper, the numerical study of designing on navigation and stability control system for AUV is studied. The study started by initiating hydrostatic forces, added masses, lift force, drag forces and thrust forces. Determining the hydrodynamic force which is the basic need to know the numerical case study on designing on navigation and stability control system for AUV where Autonomous Underwater vehicles (AUV). AUV is capably underwater vehicle in moving automatically without direct control by humans according to the trajectory. The result of numerical study is properly to be the reference for the next developing for AUV.

Abstract: Salat as a daily Muslim activitiy in praying contains several movements which are not suggested by orthopaedic doctor to be conducted by patient with total hip replacement (THR). Sujud and sitting are two movements in Salat which is recommended to be done above the chair for THR patients. There are lacks of scientific discussions about the consequences of the normal salat movement for Muslim THR patients. This paper observes the effect of these movements to the artificial hip joint in THR patient body. A three-dimensional finite element simulation is used to investigate the resisting moment, the contact pressure and the von Mises stress. An artificial hip joint model proposed by previous researcher is used in the simulations. The results show that sujud induces the impingement and plastic deformation whereas sitting is relatively safe to be conducted by THR patients. Some suggestions are also discussed with respect to the design of new artificial hip joint model which allows THR patients to conduct Salat in a normal way. The reduction of inset at the liner, the new profile at circumferential edge inner liner and the increase in the femoral head diameter can be considered as a guideline for new design of the artificial hip joint for Muslim.

Abstract: Conceptual design plays an important role in design stage as an initiation to interpret an abstract idea into a design concept. However, conceptual modeling in previous engineering designs provided premature detailed modeling. Such methodologies delivered almost pure quantitative techniques to do the modeling, which have made it difficult to do agile design process for specific-purposed products. Such products require unique approach for each situation. This paper proposes physiological concept modeling to overcome such phenomenon by combining process and functional modeling with qualitative interpretation. Physiological modeling incorporates derivation to transform idea into a design concept with almost no quantitative postulates. A case study on competition-based electric car is also provided to show an overview of application. The study concludes that there are seven steps required to do physiological modeling. The derivation can also bring flexibility for dynamic or continuous system by introducing cyclical & dynamic relationship between processes, including interventions from outside observed system and function of residue to accommodate side residues. By looking at previous techniques, this study brings a new light to produce design concept which is feasible but can be visibly modeled even by novice designers.

Abstract: The main function of the vehicle suspension is to improve ride and handling performance. In vehicle active suspension, better ride comfort is usually required larger control input and larger suspension deflection. However, the actuator that deliver the control signal have a limitation which is commonly known as actuator saturation. There is also a structural constraint that limits the suspension deflection. In this study, an alternative approach to the vehicle active suspension system is proposed. In this approach, some separation in the controller such that one part is devoted to achieve nominal performance and the other part is devoted to constraint handling is performed. In addition, the actuator power consumption of the proposed control strategy is further investigated numerically. The simulation results show that the proposed control strategy can manage the trade-off between performance and the actuator power consumption.

Abstract: Blade root fatigue stress, primarily resulting from wind shear and turbulence, is a critical factor in wind turbine design. Blade mounted aerodynamic control devices have been shown to have the potential to reduce this. However, limited research exists into suitable devices, with great challenges being involved in meeting the requirements for use on large turbines. The blade designed in this work addresses this by employing a piezoceramic actuated compliant mechanism, contained within a flexible matrix composite structure. The resulting mechanism design achieves a sectional change in lift coefficient of ΔC_L +0.4 to 0.15. The performance of the blade is analysed with a quasi-steady time marching BEM model, employing optimal control. A reduction of 21.59% in the standard deviation of the flap-wise bending moment was achieved, a comparable result to previous load control investigations.

Abstract: The work in this paper presents the effect of material and blank dimension on the dimensions ofexternal rolled threads. This paper will be helpful for the auto industry, one of the largest fastenersmarkets, that typically consumes between 2800 to 3100 fasteners in the assembly of an average familyvehicle. Externally threaded fasteners comprise the bulk of fasteners used in these applications withover 90% of being produced by thread rolling. The thread rolling process is now widelyacknowledged as the fastest and most efficient method of producing accurate external threads, withsurface finish and mechanical properties. The typical production rates are around one piece persecond. In order to ensure a perfect thread rolling process, it is important for blank of work piece to beproperly pre-machined. The size of the blank is dependent on material, surface finish, type of threadsetc. This paper describes the effect of blank material and dimensions on nominal diameter of externalrolled threads. The work has been carried out at M/s Gayatri Auto Industries on Master ReciprocatingDies Thread Rolling Machine using HSS die. Mild Steel (C 15), EN-8 (C40), and EN-47 (SpringSteel) materials have been taken as blank material for the analysis to produce M8x1.25 6g threads.The result indicates that the variation on surface roughness, carbon percentage and dimension of blankaffects significantly the nominal diameter and PCD of threads. This paper is helpful for theprofessionals to determine the accurate dimension of thread rolling blank for desired threads tominimize rejections.

Abstract: The emergy values of three different scenarios for the new landfill in Yogyakarta City were calculated to evaluate the sustainability and efficiency. The assessment included the environmental parameters which are Environmental Yield Ratio (EYR), Net Emergy, Environmental Loading ratio (ELR) and Emergy Sustainability Index (ESI).The calculation of emergy indices showed that treatment in landfill requires the largest emergy input for all scenarios with the percentage between 92% and 97%. Scenario 0 contains the lowest total solar emergy implying that it requires lower emergy input compared to other scenarios. Scenario 1 needs the lowest emergy investment. Meanwhile, Scenario 2 offers the highest emergy recovery contributed mainly by the output from higher scavenging rate. Scenario 2 is the best option for the municipal waste management in Yogyakarta since it meets more criteria for sustainability and efficiency.

Abstract: The use of cutting fluid is to reduce the friction between tool and workpiece, reduce and dissipate generated heat. The application of cutting fluid is also to improve the surface quality of workpiece and increase the tool life. On the other side, cutting fluid contains chemical carcinogens that causes serious health risks for machine operators and have inherent waste disposal concern on the environment. Due to these problems, some alternative have been sought to minimize or avoid the use of cutting fluid in machining processes. Air cooling techniques were proposed as alternative cooling mediums, i.e air jet cooling (AJC) and cooled-air jet cooling (CAJC), the liquid less method. In this work, air cooling techniques were investigated to be a possible solution of machining problem for cooling medium. This studi was also motivated by economics point of view that the application of AJC and CAJC would be more efficient than liquid method. The purpose of this study is to investigate the effect of AJC and CAJC on turning process of St 60 steel because it is used widely for production of components especially in small and medium enterprises in Indonesia. The tool tip temperatures, surface roughness and tool wear were measured for a range of cutting times. For a comparison purposes, experiments were also carried out with using traditional liquid coolant and without any cooling applied to the tool tip (dry cutting method). Experiments have shown that air cooling technques (AJC, and CAJC) can be used as cooling medium in machining process. Experimental results show that machining with CAJC have shorter tool life compare to machining with AJC and dry cutting, but liquid coolant in this studi is still the best cooling medium for machining of St 60 steel..

Abstract: This paper presents simulation of drawing force and thickness deformation in deep drawing which employs semi-active blank holder force system, to solve the problem of cracking and wrinkling. The method of slab with feed back control failure criteria, was employed to make the modeling system and the semi-active blank holder to prevent wrinkling and cracking in forming low carbon steel sheet, without lubrication (μ=0.4). In this study, the mechanical properties of the material were chosen since that they equivalent to those of low carbon steel with its thickness of 0.2 mm, k = 572 N/mm², UTS = 391 N/mm², yield stress = 309 N/mm² and n = 0.2. The diameter and the depth of the cylindrical cup-shaped product were 40 mm and 10 mm, respectively. Results from simulation have shown that the semi-active blank holder system can control very responsive against changing of deformation condition. The optimum of initial blank holder force is approximately 3000 N up to 4000 N. In the early stages (initial stroke), blank holder force system could be responsive to prevent cracking, and at the end of the punch stroke, it is very effective to prevent wrinkling. Simulation of semi-active blank holder force control system is excellent in model formation to prevent cracking and wrinkling.