Purpose This study aims to present a new haptic-enabled virtual assembly system for the automatic generation and objective assessment of assembly plans. The system is intended to be used as an assembly planning tool along the product development process. Design/methodology/approach The generation of product assembly plans is based on the analysis of the assembly movements and operations performed by the user during the virtual assembly execution, and the objective assessment of product assembly is based on the definition and computation of new proposed assembly metrics. Findings To evaluate the system, a case study corresponding to the assembly of a mechanical component is presented and analyzed. The results demonstrate that the proposed system is an effective tool to plan and evaluate different product assembly strategies in a more practical and objective approach than existing assembly planning methods. Research limitations/implications Although the virtual assembly execution time is larger than the real assembly execution time, the assembly planning and evaluation results provided by the system are valid. However, the development of higher performance collision detection algorithms is needed to reduce the simulation time. Originality/value The proposed virtual assembly system is able to not only simulate and automatically generate assembly plans but also objectively assess them from the virtual assembly task execution. The introduction and use of several assembly performance metrics to objectively evaluate assembly strategies in virtual assembly also represents a novel contribution.
The use of hydroxyapatite (HA) scaffolds for bone regeneration is an alternative procedure to treat bone defects due to cancer, other diseases or traumas. Although the use of HA has been widely studied in the literature, there are still some disparities regarding its mechanical performance. This paper presents a complete analysis of the structural performance of porous HA scaffolds based on experimental tests, numerical simulations and theoretical studies. HA scaffolds with variable porosity were considered and fabricated by the water-soluble polymer method, using poly vinyl alcohol as pore former. These scaffolds were then characterised by scanning electron microscopy, stereo microscopy, X-ray diffraction, porosity analysis and mechanical tests. Different scaffold models were proposed and analysed by the finite element method to obtain numerical predictions of the mechanical properties. Also theoretical predictions based on the (Gibson LJ, Ashby MF. 1988. Cellular solids: structure and properties. Oxford: Pergamon Press) model were obtained. Finally the experimental, numerical and theoretical results were compared. From this comparison, it was observed that the proposed numerical and theoretical models can be used to predict, with adequate accuracy, the mechanical performance of HA scaffolds for different porosity values.
Traditional computer aided design (CAD) and computer aided assembly planning (CAAP) systems are still limited because they do not consider human experience and knowledge capture to support intuitively the assembly planning. Moreover, some aspects such as quality testing, shop floor layout, human ergonomics and physical constraints are not considered during the assembly evaluation. Virtual reality (VR) systems can be used to simulate, analyze and optimize manufacturing processes including assembly. The use of (VR) and haptic systems can improve the efficiency of assembly process planning, evaluation and training. This paper describes an experiment conducted to investigate the benefits of a haptic aided virtual reality system for assembly training of real assembly tasks. Three groups of individuals with different level of training were considered in the evaluation. The first group received training by the virtual reality system including haptic feedback. The second group also received the same virtual training but without haptic feedback. The third group received no training in the virtual environment. Upon completion of the training, the assembly performance of the three different groups was evaluated by the construction of a real assembly task. The results have shown a significant improvement in the assembly performance of individuals who undertook a virtual training with force feedback, compared with those who did not take training.
The development of hydroxyapatite (HA) scaffolds for tissue regeneration, particularly for bone regeneration, is an alternative to treat bone defects due to cancer, other diseases or trauma. Although the hydroxyapatite has been widely studied in the literature, there are still some disparities regarding its mechanical performance. This paper presents the analysis of the structural performance of hydroxyapatite scaffolds based on experimental tests and numerical simulations. HA scaffolds with variable porosity were fabricated by the water soluble polymer method, using the Poly Vinyl Alcohol (PVA) as pore former. These scaffolds were then characterized by scanning electronic microscopy (SEM), stereo microscope and X ray diffraction (XRD). Different porous structures models were considered and analyzed by the finite element method (FEM). Compressive tests were carried out and used to validate the proposed numerical models. Also a theoretical analysis based on the Gibson and Ashby [1] model was performed. Finally the experimental, numerical and theoretical results were compared and the results show that the proposed numerical and theoretical models can be used to predict, with adequate accuracy, the mechanical behavior of HA scaffolds for different porosity values.
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