6,306 research outputs found
Machine Learning-Based Analysis of a Wind Turbine Manufacturing Operation: A Case Study
This study analyzes the lead time of the bending operation in the wind turbine tower manufacturing process. Since the operation involves a significant amount of employee interaction and the parts processed are heavy and voluminous, there is considerable variability in the recorded lead times. Therefore, a machine learning regression analysis has been applied to the bending process. Two machine learning algorithms have been used: a multivariate Linear Regression and the M5P method. The goal of the analysis is to gain a better understanding of the effect of several factors (technical, organizational, and experience-related) on the bending process times, and to attempt to predict these operation times as a way to increase the planning and controlling capacity of the plant. The inclusion of the experience-related variables serves as a basis for analyzing the impact of age and experience on the time-wise efficiency of workers. The proposed approach has been applied to the case of a Spanish wind turbine tower manufacturer, using data from the operation of its plant gathered between 2018 and 2021. The results show that the trained models have a moderate predictive power. Additionally, as shown by the output of the regression analysis, there are variables that would presumably have a significant impact on lead times that have been found to be non-factors, as well as some variables that generate an unexpected degree of variability
Advanced Rotorcraft Transmission (ART) program
Work performed by the McDonnell Douglas Helicopter Company and Lucas Western, Inc. within the U.S. Army/NASA Advanced Rotorcraft Transmission (ART) Program is summarized. The design of a 5000 horsepower transmission for a next generation advanced attack helicopter is described. Government goals for the program were to define technology and detail design the ART to meet, as a minimum, a weight reduction of 25 percent, an internal noise reduction of 10 dB plus a mean-time-between-removal (MTBR) of 5000 hours compared to a state-of-the-art baseline transmission. The split-torque transmission developed using face gears achieved a 40 percent weight reduction, a 9.6 dB noise reduction and a 5270 hour MTBR in meeting or exceeding the above goals. Aircraft mission performance and cost improvements resulting from installation of the ART would include a 17 to 22 percent improvement in loss-exchange ratio during combat, a 22 percent improvement in mean-time-between-failure, a transmission acquisition cost savings of 23 percent of 24K per flight hour. Face gear tests performed successfully at NASA Lewis are summarized. Also, program results of advanced material tooth scoring tests, single tooth bending tests, Charpy impact energy tests, compact tension fracture toughness tests and tensile strength tests are summarized
Optimising non-destructive examination of newbuilding ship hull structures by developing a data-centric risk and reliability framework based on fracture mechanics
This thesis was previously held under moratorium from 18/11/19 to 18/11/21Ship structures are made of steel members that are joined with welds. Welded connections may contain various imperfections. These imperfections are inherent to this joining technology. Design rules and standards are based on the assumption that welds are made to good a workmanship level. Hence, a ship is inspected during construction to make sure it is reasonably defect-free. However, since 100% inspection coverage is not feasible, only partial inspection has been required by classification societies. Classification societies have developed rules, standards, and guidelines specifying the extent to which inspection should be performed.
In this research, a review of rules and standards from classification bodies showed some limitations in current practices. One key limitation is that the rules favour a “one-size-fits-all” approach. In addition to that, a significant discrepancy exists between rules of different classification societies.
In this thesis, an innovative framework is proposed, which combines a risk and reliability approach with a statistical sampling scheme achieving targeted and cost-effective inspections. The developed reliability model predicts the failure probability of the structure based on probabilistic fracture mechanics. Various uncertain variables influencing the predictive reliability model are identified, and their effects are considered. The data for two key variables, namely, defect statistics and material toughness are gathered and analysed using appropriate statistical analysis methods.
A reliability code is developed based Convolution Integral (CI), which estimates the predictive reliability using the analysed data. Statistical sampling principles are then used to specify the number required NDT checkpoints to achieve a certain statistical confidence about the reliability of structure and the limits set by statistical process control (SPC). The framework allows for updating the predictive reliability estimation of the structure using the inspection findings by employing a Bayesian updating method.
The applicability of the framework is clearly demonstrated in a case study structure.Ship structures are made of steel members that are joined with welds. Welded connections may contain various imperfections. These imperfections are inherent to this joining technology. Design rules and standards are based on the assumption that welds are made to good a workmanship level. Hence, a ship is inspected during construction to make sure it is reasonably defect-free. However, since 100% inspection coverage is not feasible, only partial inspection has been required by classification societies. Classification societies have developed rules, standards, and guidelines specifying the extent to which inspection should be performed.
In this research, a review of rules and standards from classification bodies showed some limitations in current practices. One key limitation is that the rules favour a “one-size-fits-all” approach. In addition to that, a significant discrepancy exists between rules of different classification societies.
In this thesis, an innovative framework is proposed, which combines a risk and reliability approach with a statistical sampling scheme achieving targeted and cost-effective inspections. The developed reliability model predicts the failure probability of the structure based on probabilistic fracture mechanics. Various uncertain variables influencing the predictive reliability model are identified, and their effects are considered. The data for two key variables, namely, defect statistics and material toughness are gathered and analysed using appropriate statistical analysis methods.
A reliability code is developed based Convolution Integral (CI), which estimates the predictive reliability using the analysed data. Statistical sampling principles are then used to specify the number required NDT checkpoints to achieve a certain statistical confidence about the reliability of structure and the limits set by statistical process control (SPC). The framework allows for updating the predictive reliability estimation of the structure using the inspection findings by employing a Bayesian updating method.
The applicability of the framework is clearly demonstrated in a case study structure
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Project MAXWELL: Towards Rapid Realization of Superior Products
We describe a new methodology for the design and manufacture of mechanical
components. The methodology is a synergism of a new, mathematically rigorous
procedure for the concurrent design of shape and material composition of components,
and a new manufacturing process called MD* for their realization. The concurrent design
strategy yields information about the global shape of the component and its material
composition. The fabrication of such designs with novel microstructural configurations
require unconventional manufacturing processes. MD* is a shape deposition process for
the free-form fabrication of parts from single or composite materials and is ideally suited
for realizing the aforementioned designs. Project MAXWELL, therefore, promotes the use
of layered manufacturing beyond prototyping tasks and offers the possibility of their
integration into the mainstream product development and fabrication process..Mechanical Engineerin
980H Port Package Rear Bumper Redesign
Completed in Shanghai, China and sponsored by Caterpillar (Suzhou) Co., Ltd., a team of mechanical engineering students from Shanghai University and Worcester Polytechnic Institute redesigned the rear bumper of a Cat® 980H medium wheel loader (980H). Communication with the project sponsor clarified the product need and provided feedback for an iterative design process incorporating dynamic and static computer simulations. Of three designs created, the team chose one with additional functionality, greater user safety, comparable durability, and significant profitability. For future designs, the team recommends material substitution, center of gravity consideration, and finite element analysis preparation
An evaluation of the structural integrity of HSLA steels exposed in simulated flue-gases under dynamic conditions for anthropogenic CO2 transport.
Carbon capture and storage (CCTS) is a transitional technology offering a nearterm
method of mitigating climate change. Pipelines are considered to be the
most suitable systems for CCTS; however, structural integrity of pipeline has to
be guaranteed in order for this technology to become a practical technical
solution.
The investigation detailed here is based on a systematic experimental approach
to investigate the structural integrity of API X100, X60 and X70 steels exposed
in simulated flue-gas under dynamic conditions. A core of the structured
experiments through some methods such as aging test, tensile properties,
fracture toughness, residual stress and engineering critical assessment was
accomplished in parent material and exposed samples on flue-gas.
The temperature range of evaluation for tensile test covers -70C to 21C while
fracture toughness was over the range -196C to 21C. Tensile properties of
virgin material show that steels meet standard specification while aging samples
do not show significant scatter compared with parent steels. Ovalisation of the
fracture surface and splitting phenomenon was observed which is related with
steel anisotropy. Fracture toughness obtained from experiment was compared
with that calculate by two existing correlations. However both correlations did
not predict the level of fracture toughness expected indicating the methods used
in this work has limited applicability under the test conditions used here.
Residual stress (RS) induced in API X100 steel by cold rolling method was
characterised using two complementary techniques known as Neutron
Diffraction (ND) and Incremental Hole Drilling (IHD). The RS distribution shows
good agreement for both techniques used but reproducibility of them depends
on their own inaccuracies. An Engineering Criticality Assessment (ECA) was
performed based in Failure Assessment Diagram (FAD) approach using all the
experimental data obtained by a leak-before-break method under three
operational pressures. The results showed the effect on the integrity of material
under the presence of a flaw length assessed.
Overall, the thesis presents a combined engineering critical assessment which
involved the examination of materials used to transport flue-gas and established
a methodology to determine fracture toughness alongside with the FAD to
assess the integrity of pipelines
Active thermography for the investigation of corrosion in steel surfaces
The present work aims at developing an experimental methodology for the analysis
of corrosion phenomena of steel surfaces by means of Active Thermography (AT), in
reflexion configuration (RC).
The peculiarity of this AT approach consists in exciting by means of a laser source the sound
surface of the specimens and acquiring the thermal signal on the same surface, instead of the
corroded one: the thermal signal is then composed by the reflection of the thermal wave
reflected by the corroded surface. This procedure aims at investigating internal corroded
surfaces like in vessels, piping, carters etc. Thermal tests were performed in Step Heating and
Lock-In conditions, by varying excitation parameters (power, time, number of pulse, ….) to
improve the experimental set up. Surface thermal profiles were acquired by an IR
thermocamera and means of salt spray testing; at set time intervals the specimens were
investigated by means of AT. Each duration corresponded to a surface damage entity and to a
variation in the thermal response. Thermal responses of corroded specimens were related to
the corresponding corrosion level, referring to a reference specimen without corrosion. The
entity of corrosion was also verified by a metallographic optical microscope to measure the
thickness variation of the specimens
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