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Hybrid manufacturing of titanium Ti-6Al-4V combining laser metal deposition and cryogenic milling
(2020)
Hybrid manufacturing, which, e.g., combines additive manufacturing with conventional machining processes, can be a way of overcoming limitations currently encountered in additive manufacturing. Cryogenic milling might be a viable option for hard-to-cut materials, as it leaves a contamination-free surface and can increase surface quality and tool life compared to conventional cooling concepts. In this study, the influence of cryogenic milling with carbon dioxide on titanium Ti-6Al-4V specimens manufactured with laser metal deposition (LMD) was investigated regarding tool wear and surface integrity in comparison to dry machining and machining with cooling lubricants. Moreover, additional layers of material were deposited on top of conventionally and cryogenically machined surfaces by means of LMD. The interface zone was then examined for defects. The milling process was closely monitored by means of thermal and high-speed imaging. Optical and tactile surface analysis provided evidence that lower roughness values and improved surface qualities could be obtained with cryogenic machining in comparison to dry machining. Moreover, significantly less tool wear was observed when a cryogenic cooling medium was applied. Although the utilization of conventional cooling lubricants resulted in satisfying surface qualities, substantial residual contamination on the milled surface was detected by means of fluorescence analysis. These contaminants are suspected to cause defects when the next layer of material is deposited. This is supported by the fact that pores were found in the weld bead applied on top of the milled specimens by means of LMD. Conversely, cryogenic machining resulted in very clean surfaces due to the residue-free evaporation of the coolant. Hence, a good metallurgical bonding between the weld bead and the milled substrate could be achieved. The results indicate the great potential of cryogenic milling in hybrid manufacturing, especially in terms of intermediate machining, as it provides residue-free surfaces for subsequent material deposition without an additional cleaning step and can significantly prolongate tool life.
Dissipation energy based parameter identification of anisotropic linear viscoelastic composites
(2020)
The current work presents a relaxation analysis based procedure to identify effective material parameters of the multiaxial generalized Maxwell model (GMM) by a numerical homogenization of the microscopic dissipation energy density for anisotropic linear viscoelastic composites. The employed GMM enables the derivation of a thermodynamically consistent constitutive law and a function of the dissipation energy density for direction‐dependent viscoelastic materials. The identity of this energy function to the microstructure's homogenized dissipation energy density is utilized for the identification of effective relaxation times. Furthermore, the identified relaxation times enable a simple determination of the remaining stiffness parameters. Finally, the presented procedure is demonstrated and evaluated for a randomly endless fibre‐reinforced plastic with a polymer matrix exhibiting a significant viscoelastic behaviour.
Hypotrochoidal profile contours have been produced in industrial applications in recent years using two-spindle processes, and they are considered effective high-quality solutions for form-fit shaft and hub connections. This study mainly concerns analytical approaches to determine the stresses and deformations in hypotrochoidal profile shafts due to pure bending loads. The formulation was developed according to bending principles using the mathematical theory of elasticity and conformal mappings. The loading was further used to investigate the rotating bending behaviour. The stress factors for the classical calculation of maximum bending stresses were also determined for all those profiles presented and compiled in the German standard DIN3689-1 for practical applications. The results were also compared with the corresponding numerical and experimental results, and very good agreement was observed. Additionally, based on previous work, the stress factor was determined for the case of torsional loading to calculate the maximum torsional stresses in the standardised profiles, and the results are listed in a table. This study contributes to the further refinement of the current DIN3689 standard.
This paper presents an analytical method for determining the bending stresses and deformations in prismatic, noncircular profile shafts with trochoidal cross sections. The so-called higher trochoids can be used as form-fit shaft-hub connections. Hybrid (mixed) higher trochoids (M-profiles) were developed for the special application as a profile contour for the form-fit shaft and hub connections in an earlier work by the author. M-profiles combine the advantages of the two standardised polygonal and spline contours, which are used as shaft-hub connections for the transmission of high torques. In this study, the geometric and mechanical properties of the higher hybrid trochoids were investigated using complex functions to simplify the calculations. The pure bending stress and shaft deflection were determined for M-profiles using bending theory based on the theory of mathematical elasticity. The loading cases consisted of static and rotating bends. Analytical, numerical, and experimental results agreed well. The calculation formulas developed in this work enable reliable and low-cost dimensioning with regard to the stresses and elastic deformations of profile shafts subjected to bending loads.
A novel approach to consider triaxial tensile stresses within the framework of a failure criterion
(2022)
For use in micromechanical simulations of continuous fiber reinforced polymers, a more general form of the paraboloid failure criterion by Stassi‐D'Alia for matrix failure was developed with explicit consideration of the hydrostatic tension strength. Regarding polymers, limits for hydrostatic tensile strength based on isotropic linear elasticity could be derived. The comparison of the newly developed extended paraboloid criterion with experimental data for yielding as well as for material separation (fracture) shows good agreement.
The atomizing gas dynamics and the applied process energy have a significant influence on the produced particles. The melting process of the two wires can be influenced by current modulation. As for arc welding processes, more and more electronic and software-controlled machines are being used for arc spraying and will have replaced conventional power sources in the future. Due to the highly dynamic, fast regulating computing technology in the latest energy source, technology arcs can be operated with different current forms and types. The modern machines allow process-stable, reproducible variation of the particles and heat input into the substrate. Constant and pulsed current can be used as current forms. Usable current types are direct current (DC) and alternating current (AC). The electrical parameters must be analyzed to evaluate the process behavior. The consumable used is a wire-shaped iron-based alloy with a diameter of 1.6 mm. Relevant process parameters such as basic current Iground, pulse current Ipulse, pulse duration tpulse, impulse frequency fpulse, and alternating current frequency, fAC, are varied and recorded using appropriate measurement technology. The aim is to change the process performance and thereby the particle formation in a broad band. High-speed images are used to observe the arc and the deposition process. In addition, particle sizes are determined.
Traffic calming is introduced to minimise the negative results of motor vehicle use, for example, low safety level or quality of life, high noise and pollution. It can be implemented through the introduction of road infrastructure reducing the velocity and the traffic volume. In this paper, we studied how traffic-calming influences the traffic assignment. For the research, a traffic-calming measure of speed cushions on the Stachiewicza street in Krakow was taken. A method of extracting trajectories from aerial footage was shown, and it was used to build a model. For a given example, through driving characteristics research and microscopic modelling, volume–delay BPR functions were estimated—for a street with and without traffic calming. Later, a toy network of two roads of the same length, connecting the same origin and destination, was simulated using an equilibrium traffic assignment method. Simulations were conducted both with the use of PTV Vissim and Visum software and through individual calculations. According to the results of this paper, there was a difference in traffic volume according to the equilibrium traffic assignment in the aforementioned toy network as a function of total network traffic volume.
Lewis–Mogridge Points: A Nonarbitrary Method to Include Induced Traffic in Cost-Benefit Analyses
(2020)
We propose a new method to estimate benefits of road network improvements, which allows to include the induced demand without arbitrary assumptions. Instead of estimating induced demand (which is nontrivial and hardly possible in practice), we search for demand induction where initial benefits are mitigated to zero. Such approach allows to formulate a dual measure of benefit, covering both the potential benefits and the likelihood of consuming them by the induced traffic. We first estimate benefits of road network improvement assuming that traffic demand is fixed. Consequently, we find demand model configurations at which the benefits of the new investment become null, i.e., all the initial benefits are consumed by the traffic demand growth. We call such states of induced demand the Lewis–Mogridge points of the analysed improvement. We select the most probable of such points and use it to calculate the proposed novel indicator μ, for which the initial benefits (obtained under a fixed-demand assumption) are multiplied with a demand increase rate needed to consume them. We believe that such measure allows to include the critical phenomena of induced traffic and, at the same time, to overcome problems associated with reliable estimation of induced demand. As we illustrate with the case of two alternative road improvement schemes in Kraków, Poland, the proposed method allows to estimate maximal threshold of induced traffic and to select scenario more resilient to induced traffic.
Effect of acoustic excitation on fiber-reinforced polypropylene and the influence on melt viscosity
(2021)
The paper describes a novel technological approach to influencing the rheological properties of thermoplastic materials exposed to acoustic energy. The flow behavior of polypropylene with different mass percentages of glass fibers is investigated in a parallel plate rheometer under high-frequency longitudinal excitation. The influence of oscillation frequency on the melt viscosity is explained by means of shear thinning criteria. The dependence of the oscillation shape using sinusoidal excitation on shear thinning as a function of different fiber reinforcement percentages is also investigated. A phenomenological view describes the mutually influencing parameters with regard to different material compositions and different excitation frequencies over the time course of the rheometric measurement. Interacting relationships are analyzed and discussed and the potential of the actuator system to influence the plastic melt is worked out. Based on this, a technological approach follows which describes the transfer of an oscillating mold surface to plastics processing methods, which, especially in the case of energy-intensive injection molding technology, leads to the expectation of possible resource efficiency in energy and material.
1 In an increasingly populated and technological world, manufacturing processes have become faster and data more voluminous. With this comes the need to store this massive production data and use real-time data monitoring tools to facilitate decision making in a plant. Concepts, derived from Pharma 4.0.
| 2 In the manufacturing environment there is, however, a big challenge in data collection and transmission, i.e. the communication between different equipments, sensors, and software. Since each manufacturer tends or has tended to use its own standards for programming and manufacturing the devices and tools.
| 3 Another major challenge is the secure transmission of data to avoid theft and cyber attacks, thus affecting the company's credibility and financial losses.
| 4 In this project the data transfer from Programmable Logic Controller (PLCs) was performed through the Matrikon Server and an interface belonging to the OPC Foundation, this technology allows the collection of data from different sources and delivers them safely to the process visualization software in a single language.
| 5 For software and hardware installation in a regulated environment, standards and validation methods need to be followed before, during and after installation of the required system.
| 6 This project aims to transfer data continuously and contemporaneously from a local source to the could environment and present the validation method used by pharmaceutical industries to validate this process in a GMP-regulated environment.
| 7 For the performance of the software installation, documents have been prepared and used to record and evidence the procedure. These documents were prepared and executed based on standards and methods relevant to the validation process.
| 8 The workers were also trained to know how to handle the data coming from production, and to be able to extract the value from it for different sectors, such as quality, raw material sector, energy sector, etc.
| 9 Finally, improvements were suggested for the documents and validation process used in this project. Since this installation will be used as a basis for future customer installations, not only for interfaces, but also for 1st and 2nd generation connectors.
BIM (Building information modeling) is becoming a reliable method for the planning, design, implementation, and maintenance stages of construction projects due to its ability to improve the quality of project stages, reduce project time, and ensure costs. From 2000 onwards, the trend of using BIM method increased in the world. And in the last decade, many developed countries have introduced BIM as a reasonable and efficient method with the aim of optimizing project stages, and many employers have paid attention to training and persuading consulting and contracting companies.
In the meantime, the BIM method is constantly being updated. Many researchers are looking to modify existing sub-methods to help the project achieve all of the great BIM goals.
Although BIM has great goals such as those mentioned, in some cases, projects are not able to achieve all of them for various reasons.
This thesis has put its hypothesis on the existence of deficiencies in the content of the EIR (Employer's Information Requirements) document and its writing methods.
This document, which is a kind of project guide in BIM format, is compiled by the client and its task is to announce the needs of the client to the members involved in the project and to clarify the different stages of the project. In many construction projects, due to the complexity of the EIR, the employer's lack of attention to some information, or the failure to include the opinions and views of the project's stakeholders in the writing of this document, the EIR cannot fulfill its key role with its maximum potential performance in the project.
This thesis is written with the aim of finding a comprehensive solution to maximize the power of the BIM method in a project through correct and complete document writing.
Also, this thesis seeks to prove its claims by focusing on the ABS 38 project as a case study. In addition, a literature review on important and key issues in the field of BIM and EIR documents has been done. After that, a scoring system (Relative rating method) was used to find the best variant and compare it to prove the proposed hypothesis.
ABSTRACT:
Multimodal transportation system which is also called as Combined transportation system. This type of transportation is seen in two methods i.e., movement of passengers from one place to another and movement of cargo using different types of transportation vehicles (Trains, trams, metro, bus, ship, truck, bicycle, airplane and air cargos). This type of system can also be derived
as single ticket (passengers) and single contract (freight) transportation. This will help in reducing the travel time, air pollution, economy, environmental changes, and unorganized journey. The main goal of the thesis is to bring ease in the multi-modal transportation system in India and to make people choose public transport over private and to provide end to end transportation facilities for people, so that people opt for public transportation as it is budget friendly as well. For instance, prevailing the single ticket (passengers) and single contract (freight) transportation system in Germany could be implemented in India. A single transport operator system is needed to meet the desired target in implementing multi-modal transportation
system feasibly. The main issue lies in the implementation of this system in Indian conditions which can be fulfilled by integration of various institutions involved in it for instance linking up the network channels of various modes of transport (end to end transportation). The rising concerns of funding by Indian government can be resolved by the implementation of this system
in the form of subsidies.
My research paper also includes the phases of MMTS, how it was earlier and how it has been in contemporary times. Major Factors like total cost, reliability, transportation capability, total time and security drive forward to developing multi-modal transportation system. This system is helpful in the growth of a nation's economy and is energy-efficient. Reliability of this system shall be based on the funding from the government because the absence of multi-modal transportation system leads to pollution, and ill health. The amount of funding plays a vital role in determining country to country (MMTS) development. Having been considering the advantages and uses of this system it is important to look into the disadvantages of the system.
For instance, How can implementing multi-modal transportation system in India be feasible?
Analysis of Traffic Management using Microscopic Simulation and Markov chain Modeling in Hyderabad
(2022)
Many developing countries around the world have been affected by globalization. India is one of the countries that has gained the most benefits. Hyderabad is the capital of the Indian state of Telangana. Because of population growth and the migration of people from rural to urban areas, traffic in Hyderabad is rapidly expanding. With commercial enterprise quarters, purchasing departmental stores, schools, and hospitals, Hyderabad has evolved into a financial hub. As a result, the number of people who own and use automobiles is increasing. Traffic congestion and regular traffic jams have become widespread in central areas, as they have traffic gridlocks on major corridors. The majority of the city’s transportation needs are currently met by bus transit (42 percent), the Multimodal Transport System (MMTS) based on the rail (1.5 percent), vehicles with three and seven seats (8 percent), and two and four-wheeled private automobiles (48.5 percent). Hyderabad is located at a crossroads of three national highways that connect it to six other states. The primary purpose of this article is to understand the city’s existing traffic challenges, find solutions that have been effectively adopted in established cities, and discuss the many projects and actions undertaken by local authorities to manage traffic congestion issues.
Traffic congestion can occur in any mode of transportation, but we focused on traffic congestion on the road network caused by vehicles. Lower velocity, lengthier travels, and car queuing for an extended period are some of the characteristics that distinguish street networks. In this paper, the causes of traffic congestion are identified, including illegal parking, traffic rules, seasonal factors, pavement failures, encroaching on footpaths, the passage of heavy goods vehicles on narrow roads, accidents, and incorrect lane management, as well as remedial measures to reduce congestion at the study location of Hyderabad.