Innovative design technology: An optimal surgical aid system for Hip Resurfacing Arthroplasty

Hip Resurfacing Arthroplasty (HRA) is a treatment option for the patients with the advanced hip disease; it is considered as the most technically difficult techniques of all procedures recommended for osteonecrosis of the hip. Technically, the currently applied HRA surgeries lead to unstable and inconsistent results. Surgeons rely a lot on the manual technique and conventional tools as well as their skills to determine the right drilling angle for locating the implant system. Although the robotic and surgical planning systems are available for HRA, the drilling line is still defined geometrically and intra-operatively, not fully considering about the biomechanics aspects of the implant and bone structure. In this paper, an optimal surgical aid system for HRA is proposed. With the integration of the state of the art biomedical modelling, pre-operative planning and personalised surgical tools, knowledge based and expert system, as well as biomechanics modelling and analysis, the precision, safety and speed of surgery are improved, the complexity of surgery is reduced, and therefore the survival rate of the implant is increased. Especially, the proposed system provides a cheap and practically feasible solution with the integration of expertise from both engineering and medicine for improving the treatment quality of the patients

Virtual testing of composites: Imposing periodic boundary conditions on general finite element meshes

Predicting the effective thermo-mechanical response of heterogeneous materials such as composites, using virtual testing techniques, requires imposing periodic boundary conditions on geometric domains. However, classic methods of imposing periodic boundary conditions require identical finite element mesh constructions on corresponding regions of geometric domains. This type of mesh construction is infeasible for heterogeneous materials with complex architecture such as textile composites where arbitrary mesh constructions are commonplace. This paper discusses interpolation technique for imposing periodic boundary conditions to arbitrary finite element mesh constructions (i.e. identical or non-identical meshes on corresponding regions of geometric domains), for predicting the effective properties of complex heterogeneous materials, using a through-thickness angle interlock textile composite as a test case. Furthermore, it espouses the implementation of the proposed periodic boundary condition enforcement technique in commercial finite element solvers. Benchmark virtual tests on identical and non-identical meshes demonstrate the high fidelity of the proposed periodic boundary condition enforcement technique, in comparison to the conventional technique of imposing periodic boundary condition and experimental data

A new constitutive model for prediction of impact rates response of polypropylene

This paper proposes a new constitutive model for predicting the impact rates response of polypropylene. Impact rates, as used here, refer to strain rates greater than 1000 1/s. The model is a physically based, three-dimensional constitutive model which incorporates the contributions of the amorphous, crystalline, pseudo-amorphous and entanglement networks to the constitutive response of polypropylene. The model mathematics is based on the well-known Glass-Rubber model originally developed for glassy polymers but the arguments have herein been extended to semi-crystalline polymers. In order to predict the impact rates behaviour of polypropylene, the model exploits the well-known framework of multiple processes yielding of polymers. This work argues that two dominant viscoelastic relaxation processes – the alpha- and beta-processes – can be associated with the yield responses of polypropylene observed at low-rate-dominant and impact-rates dominant loading regimes. Compression test data on polypropylene have been used to validate the model. The study has found that the model predicts quite well the experimentally observed nonlinear rate-dependent impact response of polypropylene

Virtual testing of advanced composites, cellular materials and biomaterials: A review

This paper documents the emergence of virtual testing frameworks for prediction of the constitutive responses of engineering materials. A detailed study is presented, of the philosophy underpinning virtual testing schemes: highlighting the structure, challenges and opportunities posed by a virtual testing strategy compared with traditional laboratory experiments. The virtual testing process has been discussed from atomistic to macrostructural length scales of analyses. Several implementations of virtual testing frameworks for diverse categories of materials are also presented, with particular emphasis on composites, cellular materials and biomaterials (collectively described as heterogeneous systems, in this context). The robustness of virtual frameworks for prediction of the constitutive behaviour of these materials is discussed. The paper also considers the current thinking on developing virtual laboratories in relation to availability of computational resources as well as the development of multi-scale material model algorithms. In conclusion, the paper highlights the challenges facing developments of future virtual testing frameworks. This review represents a comprehensive documentation of the state of knowledge on virtual testing from microscale to macroscale length scales for heterogeneous materials across constitutive responses from elastic to damage regimes

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Numerical assessment of the effect of void morphology on thermo-mechanical performance of solder thermal interface material

The presence of voids in solder thermal interface material (STIM) layers affects the reliability and mechanical performance of formed solder joint. Previous studies suggest that the level of void effect depends not only on the size of the voids but also on the distribution and location of voids. In this work, a void morphology generating algorithm was used to generate representative volume elements (RVEs) depicting the seeming randomness of voids in a given STIM layer. The generated 2D RVEs were converted to 3D RVEs within a finite element modelling (FEM) environment and subsequently incorporated into the chip and heat spreader to complete the geometric model. The maximum damage site in the Sn-3Ag-0.5Cu (SAC305) solder joint as predicted by finite element analysis (FEA) of the geometric model showed a good qualitative agreement with experimental observations elsewhere. Further numerical assessment of the thermo-mechanical performance of SAC305 alloy as STIM layer due to the different generated void morphology was carried out. Results showed that solder voids can either influence the initiation or propagation of damage in the STIM layer, depending on the configuration, size and location of voids. While the small voids around the critical region of the solder joints appeared to enhance stress and strain localisation around the maximum damage site thus facilitating damage initiation; small voids also showed potentials of arresting damage propagation. In addition, results from this study indicated that void located in the surface of the solder joint, particularly voids at the solder/silicon die interface are more detrimental compared to void embedded in the middle of the solder layer. The innovative technique employed in this study to numerically generate realistic solder void morphologies would be beneficial to the solder voids modelling research community

The effect of thermal constriction on heat management in a microelectronic application

Thermal contact constriction between a chip and a heat sink assembly of a microelectronic application is investigated in order to access the thermal performance. The finite element model (FEM) of the electronic device developed using ANSYS software was analysed while the micro-contact and micro-gap thermal resistances were numerically analysed by the use of MATLAB. In addition, the effects of four major factors (contact pressure, micro-hardness, root-mean-squared (RMS) surface roughness, and mean absolute surface slope) on thermal contact resistance were investigated. Two lead-free solders (SAC305 and SAC405) were used as thermal interface materials in this study to bridge the interface created between a chip and a heat sink. The results from this research showed that an increase in three of the factors reduces thermal contact resistance while the reverse is the case for RMS surface roughness. In addition, the use of SAC305 and SAC405 resulted in a temperature drop across the microelectronic device. These results might aid engineers to produce products with less RMS surface roughness thereby improving thermal efficiency of the microelectronic application

A virtual framework for prediction of full-field elastic response of unidirectional composites

This paper presents a virtual framework for deriving a full-field elastic response of continuous fibre unidirectional (UD) composites using a micromechanical modelling approach. This implies determining all possible elastic constants for the UD composite based solely on knowledge of the constitutive behaviour of the composite constituents. The framework is based on a microscale three-dimensional representative volume element (3DRVE) of a test composite, with random spatial arrangement of the fibre reinforcement. The 3DRVE was determined based on a Monte Carlo style geometric model generation algorithm. Periodic boundary conditions and representative loading cases were prescribed on the 3DRVE to determine the microscale response of the test composite. Appropriate lengthscale bridging algorithms, modelled after a 2D RVE direct macro–micro homogenization approach – but here extended to 3D RVEs, were used to determine macroscale properties of the test composite. The virtual framework has been validated against experimental data and the model was shown to give reliable predictions. Also, in comparison with other comparable computational, analytical and semi-analytical micromechanical models, the proposed framework was shown to give the widest holistic set of elastic properties of the test composite. This framework represents a suitable substitute for realistic experiments and therefore can be used in design of different virtual experiments. Parametric studies have also been carried out and interesting conclusions drawn on the constitutive behaviour of the test composite while also exploring the different features of the virtual framework