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1 – 10 of 36This paper is devoted to the evaluation of the T-stress for a hypocycloid hole in an infinite plate. The remote tractions are applied for the infinite plate containing the…
Abstract
Purpose
This paper is devoted to the evaluation of the T-stress for a hypocycloid hole in an infinite plate. The remote tractions are applied for the infinite plate containing the hypocycloid hole. After using the conformal mapping, an elasticity solution is obtained, and the T-stress at the cusp tip can be abstracted from this solution. The paper aims to discuss these issues.
Design/methodology/approach
Conformal mapping technique is used for solving the T-stress problem for a hypocycloid cusp hole problem.
Findings
The present study proves that the cusp configuration has a significant influence to the value of T-stress at cusp crack tip.
Originality/value
A closed form solution for the T-stress in cusp crack is first obtained in the submission.
Details
Keywords
Krzysztof Majerski, Barbara Surowska, Jarosław Bieniaś, Patryk Jakubczak and Monika Ostapiuk
The purpose of this paper is to present microstructural and fractographic analysis of damage in aluminum (2024T3)/carbon-fiber reinforced laminates (AlC) after static tensile…
Abstract
Purpose
The purpose of this paper is to present microstructural and fractographic analysis of damage in aluminum (2024T3)/carbon-fiber reinforced laminates (AlC) after static tensile test. The influence of fiber orientation on the failure was studied and discussed.
Design/methodology/approach
The subject of examination was AlC. The fiber–metal laminates (FMLs) were manufactured by stacking alternating layers of 2024-T3 aluminum alloy (0.3 mm per sheets) and carbon/epoxy composites made of unidirectional prepreg tape HexPly system (Hexcel, USA) in [0], [± 45] and [0/90]S configuration. The fractographic analysis was carried out after static tensile test on the damage area of the specimens. The mechanical tests have been performed in accordance to ASTM D3039. The microstructural and fractographic analysis of FMLs were studied using optical (Nikon SMZ1500, Japan) and scanning electron microscope (Zeiss Ultra Plus, Germany).
Findings
FMLs based on aluminum and carbon/epoxy composite are characterized by high tensile properties depending on their individual components and the orientation of the reinforcing fibers, failure of hybrid laminates indicates the complexity process of degradation of these materials. The nature of damage in FML layers is similar to that typical in polymer composites with interlaminar delaminations, transverse cracks of the composite layers, degradation of fiber/matrix interface, damage process in FMLs is also associated mainly with interface between metal and fiber reinforced composite. The mixed damage – cohesive and adhesive – was observed.
Originality/value
One of the most important aspect in the designing and manufacturing process in the service life of composite structures is damage mechanisms. The damage processes in composite materials, particularly in FMLs, are more complex in comparison to metal materials and fiber reinforced polymers.
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Keywords
Qianyong Chen, Jinghua Xu and Shuyou Zhang
Compared with cusp height and area deviation ratio, volume error (VE) caused by the layer height could represent the stair-case effect more comprehensively. The proposed relative…
Abstract
Purpose
Compared with cusp height and area deviation ratio, volume error (VE) caused by the layer height could represent the stair-case effect more comprehensively. The proposed relative volume error (RVE)-based adaptive slicing method takes VE rather than cusp height as slicing criteria, which can improve part surface quality for functionalized additive manufacturing.
Design/methodology/approach
This paper proposes a volumetric adaptive slicing method of manifold mesh for rapid prototyping based on RVE. The pre-height sequences of manifold mesh are first preset to reduce the SE by dividing the whole layer sequence into several parts. A breadth-first search-based algorithm has been developed to generate a solid voxelization to get VE. A new parameter RVE is proposed to evaluate the VE caused by the sequence of the layer positions. The RVE slicing is conducted by iteratively adjusting the layer height sequences under different constraint conditions.
Findings
Three manifold models are used to verify the proposed method. Compared with uniform slicing with 0.2 mm layer height, cusp height-based method and area deviation-based method, the standard deviations of RVE of all three models are improved under the proposed method. The surface roughness measured by the confocal laser scanning microscope proves that the proposed RVE method can greatly improve part surface quality by minimizing RVE.
Originality/value
This paper proposes an RVE-based method to balance the surface quality and print time. RVE could be calculated by voxelized parts with required accuracy at a very fast speed by parallel.
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Keywords
Vitalija Masteikaite, Virginija Saceviciene, Elmira Kopbajeva and Maira Nurjasarova
To produce a coated fabric, a base fabric may be completely or partially coated with a polymer layer, which changes the properties of the new system relative to the base fabric…
Abstract
Purpose
To produce a coated fabric, a base fabric may be completely or partially coated with a polymer layer, which changes the properties of the new system relative to the base fabric. The purpose of this paper is to analyze the influence of the thermal transfer material and its shape on the deformability of knitted fabrics during the uniaxial extension and to determine the residual deformation of the thermoplastic transfer element of coated fabrics after unloading.
Design/methodology/approach
Knitted fabrics were partially and entirely coated with heat transfer material. For partial coating, square pieces of three different transfer materials were bonded on the middle of the specimen. They were solid, perforated with either nine circular holes or six rectangular holes. A heat seal press was used to laminate knitted fabrics. The samples were subjected to uniaxial tensile testing. The characteristics such as strain at maximum force, strain at break, and strain at low stress were measured. After stretching and relaxation of the specimens, the residual deformation of the heat transfer element was also investigated.
Findings
The results indicated that coating knitted fabrics with transfer material may decrease their stretchability. The experiments show that the decrease in stretchability and in the degree of residual deformation after stretching and relaxing depend on the knitted structure, the shape of the transfer element, and the degree to which the fabric is coated.
Originality/value
This study examines the influence of heat transfer material which may be not only entirely but also partially joined with knitted fabric layer on the deformability and shape stability of this system.
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Bin Huang and Sarat B Singamneni
This paper aims to develop a new slicing method for fused deposition modelling (FDM), the curved layer adaptive slicing (CLAS), combining adaptive flat layer and curved layer…
Abstract
Purpose
This paper aims to develop a new slicing method for fused deposition modelling (FDM), the curved layer adaptive slicing (CLAS), combining adaptive flat layer and curved layer slicing together.
Design/methodology/approach
This research begins with a review of current curved layer and adaptive slicing algorithms employed in the FDM and further improvement of the same, where possible. The two approaches are then integrated to develop the adaptive curved layer slicing based on the three-plane intersection method for curved layer offsetting and consideration of facet angles together with the residual heights for adaptive slicing. A practical implementation showed that curved layer adaptive layers respond in similar lines to the flat layer counterparts in terms of the mechanical behaviour of FDM parts.
Findings
CLAS is effective in capturing sharply varying surface profiles and other finer part details, apart from imparting fibre continuity. Three-point bending tests on light curved parts made of curved layers of varying thicknesses prove thicker curved layers to result in better mechanical properties.
Research limitations/implications
The algorithms developed in this research can handle relatively simple shapes to develop adaptive curved slices, but further developments are necessary for more complex shapes. The test facilities also need further improvements, to be able to programmatically implement adaptive curved layer slicing over a wide range of thicknesses.
Practical implications
When fully developed and implemented, CLAS will allow for better FDM part construction with lesser build times.
Originality/value
This research fills a gap in terms of integrating both curved layer and adaptive slicing techniques to better slice and build a part of given geometry using FDM.
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With the growing importance of services in the overall economy, it is surprising that the notion of service firms investing in systematic and dedicated innovation activities has…
Abstract
Purpose
With the growing importance of services in the overall economy, it is surprising that the notion of service firms investing in systematic and dedicated innovation activities has taken so long to materialize. This is now set to change as service firms undertake the kind of research, design and development disciplines which for more than a century have been mainstays of modern manufacturing.
Design/methodology/approach
S&L interviews the well-known former editor of Harvard Business Review Thomas A. Stewart and his co-author, former BloombergBusinessweek.com editor Patricia O’Connell, in their latest book, Woo, Wow and Win: Service Design, Strategy and the Art of Customer Delight (Harper Business, 2016). They believe we are on the cusp of a “design revolution” in services.
Findings
The central thesis of their book is that services “should be designed with as much care as products are” and they include service “delivery” in that premise.
Practical implications
Service design principles offer powerful new ways to address the three basic strategy questions: What do we sell? To whom? And how do we win?
Originality/value
Service design helps you understand how to configure a set of activities, behaviors and touchpoints–a journey–that allows you to serve that customer well.
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Under this heading arc published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States…
Abstract
Under this heading arc published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued
Hossein Ahari, Amir Khajepour and Sanjeev Bedi
This paper proposes sheet thickness determination in manufacturing of laminated dies as an optimization problem. The aim of this optimization procedure is finding the best set of…
Abstract
Purpose
This paper proposes sheet thickness determination in manufacturing of laminated dies as an optimization problem. The aim of this optimization procedure is finding the best set of thicknesses which minimizes the volume deviation between actual computer‐aided design (CAD) model and assembled slices.
Design/methodology/approach
This works uses a modified version of genetic algorithms for the optimization purpose. Each set of thicknesses that can cover the whole CAD model surface is considered as a chromosome. Genetic operators such as crossover and mutation have to be modified to be used in this application.
Findings
A new method for finding the total volume deviation between assembled slices and the actual CAD model was developed in this research. On the other hand, the results show how the program can automate the slice plane locations search process.
Research limitations/implications
Premature convergence does not allow the algorithm to search the entire solution space before getting trapped in a local optimum. Even the mutation operator cannot postpone this untimely convergence.
Practical implications
The proposed method is a good substitute for the manual methods that are currently used in industry. These experience‐based methods are mostly based on the decision made by a well‐trained technician on picking up the thicknesses for a specific CAD model.
Originality/value
This is the first attempt at optimizing the slicing method in laminated tooling. Other methods are mostly based on rapid prototyping (RP) and they are not applicable in the laminated tooling process since, despite RP, here not all optimization outputs can be used in practical procedure.
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This bibliography is offered as a practical guide to published papers, conference proceedings papers and theses/dissertations on the finite element (FE) and boundary element (BE…
Abstract
This bibliography is offered as a practical guide to published papers, conference proceedings papers and theses/dissertations on the finite element (FE) and boundary element (BE) applications in different fields of biomechanics between 1976 and 1991. The aim of this paper is to help the users of FE and BE techniques to get better value from a large collection of papers on the subjects. Categories in biomechanics included in this survey are: orthopaedic mechanics, dental mechanics, cardiovascular mechanics, soft tissue mechanics, biological flow, impact injury, and other fields of applications. More than 900 references are listed.
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Andrea Zani, Alberto Speroni, Andrea Giovanni Mainini, Michele Zinzi, Luisa Caldas and Tiziana Poli
The paper aims to investigate the comfort-related performances of an innovative solar shading solution based on a new composite patented material that consists of a cement-based…
Abstract
Purpose
The paper aims to investigate the comfort-related performances of an innovative solar shading solution based on a new composite patented material that consists of a cement-based matrix coupled with a stretchable three-dimensional textile. The paper’s aim is, through a performance-based generative design approach, to develop a high-performance static shading system able to guarantee adequate daylit spaces, a connection with the outdoors and a glare-free environment in the view of a holistic and occupant-centric daylight assessment.
Design/methodology/approach
The paper describes the design and simulation process of a complex static shading system for digital manufacturing purposes. Initially, the optical material properties were characterized to calibrate radiance-based simulations. The developed models were then implemented in a multi-objective genetic optimization algorithm to improve the shading geometries, and their performance was assessed and compared with traditional external louvres and overhangs.
Findings
The system developed demonstrates, for a reference office space located in Milan (Italy), the potential of increasing useful daylight illuminance by 35% with a reduced glare of up to 70%–80% while providing better uniformity and connection with the outdoors as a result of a topological optimization of the shape and position of the openings.
Originality/value
The paper presents the innovative nature of a new composite material that, coupled with the proposed performance-based optimization process, enables the fabrication of optimized shading/cladding surfaces with complex geometries whose formability does not require ad hoc formworks, making the process fast and economic.
Details