1,720,978 research outputs found
Manufacturing, process simulation and mechanical tests of a thick component produced by compression-RTM process
No full textAdvanced composite materials have been attracting the interest of many automotive companies for producing light and high-performance components. Out-Of-Autoclave methods have been recognized as the most promising processes to produce CFRP components. One of the most interesting process is Compression-RTM. The aim of this research is to demonstrate the validity of the C-RTM process for producing parts with a thickness greater than 10 mm. The authors fabricated a preform made by 17 layers of PAN based carbon fibre 800 g/m2 and 600 g/m2 twill fabric and injected more than 700 g of matrix. Process simulations have been run to test different boundary conditions without producing physical prototypes. Flexural tests have been performed to compare the behavior of thick parts produced by C-RTM with the ones produced by prepreg and autoclave. The results show comparable strength values between the samples tested. DSC, void content and ultrasound measurements have been investigated to fully understand the physical properties of the finished component. Moreover, cycle times has been analysed to demonstrate the effectiveness of the method both from process and product performances points of view. Results show that thanks to the use of C-RTM the manufacturing time decreases by 68% with respect to the autoclave processes
A multi-objective and multi-level design optimization method for oil & gas ducts
No full textThe paper proposes a methodological approach to support the multi-objective (i.e. cost and structural performance) optimization of complex systems, typical of the oil & gas sector. The complexity is managed through a double-level of optimization. The first one, based on simplified product models (1-D and 0-D), considers an analytical approach for the structural behavior and a parametric one for the cost estimation. The second level considers the use of a 3-D FEM solver for structural simulations, and an analytical tool for the cost estimation. As case study, the paper proposes the design optimization of an oil & gas chimney for gas turbines. The workflow analyzed during the case study describes the use of a multi-objective and multilevel approach to optimize cost, weigh, and structural behavior of oil & gas ducts
Comparative life cycle assessment of low-pressure RTM, compression RTM and high-pressure RTM manufacturing processes to produce CFRP car hoods
No full textAdvanced composite materials, especially those based on carbon fibers, have been attracting the interest of industrial companies for producing light and high-performance components. Resin Transfer Molding (RTM) and its variants have been recognized as the most promising processes to manufacture CFRP (Carbon Fiber Reinforced Polymer) products in a cost-effective way. However, recent research studies highlighted environmental concerns regarding the use of CFRP parts due to the high environmental load related to their production. In this context, the main scope of the present paper is to investigate and compare the environmental impacts of three alternative manufacturing processes for producing CFRP car hoods: RTM, High-Pressure RTM and Compression-RTM. This analysis has been carried out through the standard Life Cycle Assessment methodology. The system boundaries include all the flows related to manufacturing of the hood and an end of life. Results calculated by using the ReCiPe mid-point/end-point method suggest that the eco-friendliest variant is the Compression-RTM
A method for the cost optimization of industrial electrical routings
No full textThe cost reduction is one of the most spread strategy adopted by companies for guaranteeing profits in a competitive market. This paper presents an approach for the cost optimization of industrial electrical routings. The proposed optimization process consists of two levels: the arrangement of the cables within the cable trays and the 3D routing of the cable trays for connecting the modules of a product. The arrangement of the power and signal cables and the selection of the cable trays are carried out considering specific configuration rules. A genetic algorithm, coupled with the Hightower's algorithm, is used to solve the routing optimization problem. The proposed cost functions consider the raw materials and manufacturing/assembly operations. The optimization process has been used for optimizing a portion of the electric cable harness of a 43 MWe power plant with a size of 44 × 20 meters, and a total of 40,60 kilometers of cables. The optimization process let to a cost saving of about 15% compared to the design carried out with the traditional approach. Abbreviations:CTs: cable trays; CUi: hourly rate for the installation phase [€/hour]; CUrmtk: hourly rate for the k-th cost center used for transforming a semi-finished component [€/hour]; Cut: hourly rate for the test phase [€/hour]; CUtray: unitary cost of a cable tray [€]; DOE: design of experiment; GA: genetic algorithm [€]; Ic: installation cost [€]; If: installation factor [-]; PAc: cost for the preliminary analysis [€]; PAcp: percentage used for calculating the cost of the preliminary analysis [%]; RMc: cost of the raw material and relative transformation operations [€]; RMcci: cost of the i-th commercial component [€]; RMoc: percentage of the overhead costs related to the management of the raw material [%]; RMsc_scrapsj: cost of the scraps for the j-th semi-finished component [€]; RMscj: cost of the j-th semi-finished component [€]; RMtc: cost for transforming semi-finished components [€]; Tcl: commercial length of a straight cable tray [meter]; Tii,j: standard installation time for the i-th or j-th component [hour]; Tl: linear distance between two points of the wiring system that need to be connected [meter]; Trmtk: time for the k-th operation for transforming a semi-finished component [hour]; Ttk: standard test time for the k-th skid of the electrical system [hour]
A multi-objective sequential method for manufacturing cost and structural optimization of modular steel towers
No full textThis paper proposes a methodological approach for the multi-objective optimization of steel towers made from prefabricated cylindrical stacks that are typically used in the oil and gas sector. The goal is to support engineers in designing economical products while meeting structural requirements. The multi-objective optimization approach involves the minimization of the weights and costs related to the manufacturing and assembly phases. The method is based on three optimization levels. The first is used in the preliminary design phase when a company receives a request for proposal. Here, minimal information on the order is available, and the time available to formulate an offer is limited. Thus, parametric cost models and simplified 1-D geometries are used in the optimization loop performed by genetic algorithms. The second phase, the embodiment design phase, starts when an offer becomes an order based on the results of the first stage. Simplified shell geometries and advanced parametric cost models are used in the optimization loop, which present a restricted problem domain. In the last phase involving detailed design, a full 3-D computer-aided design model is generated, and specific finite-element method simulations are performed. The cost estimations, given the high levels of detail considered, are analytic and are performed using dedicated software
Comparative life cycle assessment and cost analysis of autoclave and pressure bag molding for producing CFRP components
No full textDeciphering short stature in children
No full textShort stature is a common reason for referral to pediatric endocrinologists. Multiple factors, including genetic, prenatal, postnatal, and local environmental factors, can impair growth. The majority of children with short stature, which can be defined as a height less than 2 standard deviation score below the mean, are healthy. However, in some cases, they may have an underlying relevant disease; thus, the aim of clinical evaluation is to identify the subset of children with pathologic conditions, for example growth hormone deficiency or other hormonal abnormalities, Turner syndrome, inflammatory bowel disease, or celiac disease. Prompt identification and management of these children can prevent excessi ve shor t stature in adulthood. In addition, a thorough clinical assessment may allow evaluation of the severity of short stature and likely growth trajectory to identify the most effective interventions. Consequently, appropriate diagnosis of short stature should be performed as early as possible and personalized treatment should be started in a timely manner. An increase in knowledge and widespread availability of genetic and epigenetic testing in clinical practice in recent years has empowered the diagnostic process and appropriate treatment for short stature. Furthermore, novel treatment approaches that can be used both as diagnostic tools and as therapeutic agents have been developed. This article reviews the diagnostic approach to children with short stature, discusses the main causes of short stature in children, and reports current therapeutic approaches and possible future treatments
Design of an experimental approach based on the contrast-to-noise ratio measurement for X-ray computed tomography parameters optimization applied to a carbon fiber-reinforced polymer materials scan
Full text linkThis paper proposes a systematic approach for the optimization of scan parameters for industrial X-ray computed tomography (XCT), as regard its specific application as diagnostic tool on carbon fiber-reinforced polymer materials (CFRP). This procedure allows the system operator to overcome suboptimal scan results due to a subjective choice of XCT parameters. In this work, XCT scan quality has been measured in terms of contrast-to-noise ratio (CNR) metric, by calculating it on collected XCT 2D projection images. A four-factor five-level central composite design (CCD) was implemented to perform experiments, and a quadratic polynomial model was chosen to describe the effects of XCT scanning parameters combination on CNR measurement and finally to predict optimal results. Analysis of variance was carried out to evaluate the significance of the model on the response, reporting a R2 of 97.1 %, and response surface analyses were also performed for CNR optimization purposes. In order to validate the CCD results, different XCT parameters combinations, coming from the CCD analysis on projection images, were used to run different scans, and, as result, the optimal CNR predicted from the model was also reflected in an optimal CNR measured on the reconstructed XCT image
A framework to support the optimization of modularized oil&gas structures
No full textModularization is a current issue in the context of plant design. A modular system aims to reduce lead time and cost in design phases. An oil & gas plant consists of many Engineered-To-Order solutions to be submitted and approved during the negotiation phase. In this context, design tools and methods are necessary to support the design life cycle from the conceptual study to the detailed project. The paper proposes an approach to optimize the design of modularized oil & gas plants with a focus on the related steel structures. A test case shows the configuration workflow applied to a modular steel structure of about 400 tons. The modularized layout has been optimized using genetic algorithms. A Knowledge Base has been described to support the configuration phase related to the conceptual design. Design rules and metrics have been formalized from the analysis of past solutions
A design to cost method for electric cable harness
No full textThe Design to Cost method is a well-known methodology for developing cost-competitive products. In the context where the Industry 4.0 initiative is pushing the research on innovative systems for data exchange and analysis, the electric aspect of a product is becoming more and more important. The scientific and industrial literature contains several methods and tools for the cost estimation of electric cable harness, but they essentially calculate the cost by simply considering the Bill of Material and computing the cost of the raw material. The installation cost is not considered. The paper presents a Design to Cost method for electric cable harness, based on the analytic cost analysis of the raw material and routing process. The inputs of such a method are the electric Bill of Material and the 3D path of the cable harness. The cost consists of three items: purchasing, installation and cutting. The method, once implemented within a prototype software tool, has been applied for the cost optimization of the electric cable harness of an on-shore module for power generation. The average accuracy, measured comparing the results with experimental data, was 10.5%
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