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Friction interaction between brake materials see a rise in temperatures of over 1000 oC contributing to thermal fade of brakes and deterioration/cracking of rotors. Various microstructural features like graphite, ferrite and pearlite could influence the mechanical and thermal properties and related friction performance of the brake materials. Even more relevant impact on properties and friction performance of rotors can be expected after coatings or surface treatments. The primary purpose of this research is to identify the impact of microstructure and surface treatment on properties and friction performance of four types of pearlitic gray cast irons. The C30, C20 and FC150 rotors were surface treated by bombarding with heavy ions which diffused into cast iron and created a coating with different chemistry and properties when compared to the “non-treated” rotors. Complete chemical and material characterization of the brake rotors using optical emission spectrometer (OES), carbon-sulfur combustion analyzer, polarized light microscopy, density (analytical balance and Archimedes principle), Brinell hardness tester, laser flash apparatus, scanning electron microscopy, and energy dispersive X-ray microanalysis. The pearlitic gray cast iron rotors are typified by the presence of graphite, carbides, and inclusions in an almost fully pearlitic matrix with a minimum amount (2-4 vol.%) of “free” ferrite. Graphite can be further classified based on its morphology. The investigated cast irons contained two different graphite types: type VII-E5 for the F150 OEM rotor, and type VII-C5 characteristic for the ASTM A48 classes C30 and C20, as well as the “Japanese” JIS G5501 FC150 rotors. It was identified from the initial curve fitting models that the observed microstructural differences in individual cast iron types are responsible for the observed mechanical (density – decreases with increasing ferrite and decreasing pearlite contents; hardness – decreases with increasing ferrite contents) and thermal properties (increase with increasing ferrite and pearlite contents), and friction performance (increases with increasing ferrite and decreasing graphite contents) of the studied rotors. The applied surface treatment also contributed to the modification of the mechanical and thermal properties, as well as friction performance of the studied rotors. However, there were not enough statistically relevant models developed from the generated data, which could identify the combined influence of various microstructural features observed and applied surface treatment over the properties and friction performance of the studied rotors.

This work seeks to characterize the impact of build interruptions to additively manufactured Al-Si-10-Mg produced by the powder bed fusion (PBF) process. Additive manufacturing represents a significant investment in overhead, machine, and material making an interruption to the process a potential waste of money and time. Interruptions in the form of power outages, lack of powdered feedstock, and/or shielding gas will cause the machine to operate in an unintended manner, potentially even stopping the build process. The process of manufacturing will influence the microstructure, which determine the material’s properties and performance. An interrupted PBF process could exhibit unique microstructural features and reduced mechanical properties that distinguish the resulting material from a continuous PBF process. Experiments were performed to simulate a production interruption with varying time periods of interruption and air exposure. The zone of interruption was characterized using optical micrographs, EDS, and hardness measurements to determine any effects of the interruption.

The following report conducted by the theoretical research and experimental study in the University of Halmstad. The focus of the project is experimental investigation on weld characteristics for shield metal arc welding with SS304 & SS409. Welding is a joining process of similar metals but nowadays it is also joined dissimilar metals by the application of heat. The different types of welding process are available in industry. Welding can be done with or without the application of pressure and filler materials in shielded metal arc welding (SMAW), an arc between a covered electrode and a weld pool is used to accomplish a weld. As the welder steadily feeds the covered electrode into the weld pool, the decomposition of the covering evolves into gases that shield the pool. Austenitic stainless steel and Martensitic chrome alloys is widely used materials in the current industrial area including higher and lower temperature applications such as storage tanks, pressure cups, furnace equipment’s etc. This paper concentrated to the investigate the dissimilar material joining by using shield metal arc welding and study the welding characteristics and do the mechanical tests. The aim of this study performance of steel and maximum hardness of welded material, microstructure of steel on next phase of project. The results will be used to character of dissimilar material performance.

In cardiac biomechanics, there is an apparent knowledge gap in 3D cardiac elastin structure and its biomechanical roles. In this study, we fill this knowledge gap via novel biomedical imaging and bioengineering means. In Aim 1, we created an overall mapping of 3D microstructures of the epicardial elastin fibers on porcine left ventricles (LV) using a laser scanning confocal microscope. We demonstrated the location- and depth-dependencies of the epicardial elastin network. Histological staining was also applied to reveal the patterns of endocardial and interstitial elastin fibers, as well as elastin fibers associated with the Purkinje fibers. In Aim 2, a novel algorithm was developed to better reconstruct the elastin fiber network and extract topological fiber metrics. We created a “fiberness” mask via fiber segmentation and fiber skeletonization to obtain the one-voxel-thick centerline skeleton and remove spurious fiber branches, thus generating topological and geometrical descriptors and bringing the study of cardiac elastin to a new level. In Aim 3, we successfully developed a semi-quantitative approach to characterize the residual stress in the epicardial layer by calculating the total angular change due to curling. Our novel curling angle characterization clearly reveals the existence of residual stress as well as the direction (circumferential vs. longitudinal) and location-dependency of the residual stress. In Aim 4, for the first time we estimated the regional residual stress of the epicardial layer on the intact LV via a four-step methodology: (i) quantify regional residual strains by comparing in situ and stressree marker dimensions; (ii) obtain regional tension-stretch/stress-stretch curves along the circumferential and longitudinal directions; (iii) adjust the biaxial curves to the 0g load reference; (iv) estimate the circumferential and longitudinal residual stresses via residual strains. This method accurately estimates the residual stress in the epicardial layer in various LV anatomical locations. We found that the location-dependency of circumferential and longitudinal residual stresses correlates with the curvature of heart surfaces. Our studies show that the epicardial layer, with its rich elastin content, might function as a balloon that wraps around the heart, and the residual stress sets up a boundary condition that assists with LV contraction.

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No description available.

In metal cutting applications, development of coatings to reduce friction between tool and chip and also enhance wear resistance of the tool is an important objective. The effectiveness of such coatings is ultimately evaluated through metal cutting trials; however, bench-scale tests can play a role in predicting some aspects of a candidate coating’s performance. This dissertation further develops the concept of an on-axis rotation pin-on-disc tribometer for the evaluation of friction coefficient between tool and work material pairs under temperature and stress conditions similar to those experienced between tool and chip in metal cutting. Firstly, the characteristics of the imprint formed by the spherical-tipped pin in the disc during tribometer tests are studied. Specific focus is given to the growth of the imprint during the rotating stage of the test; the severity of pile-up of work material around the periphery of the imprint; different zones of contact at the imprint surface; and evidence of (or lack thereof) of bulk shear in the surrounding work material below the surface of the disc. The importance of estimating the actual temperature at the pin-disc interface (inaccessible for direct measurement) is also raised. Evidence is presented that suggests the pin-disc interface is higher for tests involving coatings with higher electrical resistivity, despite exhibiting similar temperatures 2 mm above the interface (accessible for direct measurement). A numerical model is developed in an effort to estimate the pin-disc interface during stationary specimen tests for specific pin and disc materials under controlled conditions. An empirical relationship is also established to express the variation of electrical resistivity with temperature for cemented tungsten carbide (6% cobalt content). Finally, coefficient of friction results for coated and uncoated cemented carbide pins in contact with AISI 1045 steel discs are related to short duration turning trials involving the same material pairs. Coatings exhibiting low friction coefficient result in appreciably lower cutting forces, reduced built-up edge intensity and more tightly curled chips. The possibility that the low thermal conductivity of such coatings could be producing similar effects by forcing more heat into the chips is also explored. / Dissertation / Doctor of Philosophy (PhD) / This dissertation further develops the concept of a pin-on-disc apparatus for evaluating the friction coefficient between materials under temperature and stress conditions similar to those experienced in metal cutting. Firstly, characteristics of the imprint formed by the pin in the disc during tests with the apparatus are studied. Specific focus is given to the growth of the imprint during the rotating stage of the test and different zones of contact at the imprint surface. Secondly, the importance of estimating the actual temperature at the pin-disc interface, inaccessible for direct measurement, is raised and a numerical model developed to aid in its estimation. Finally, coefficient of friction results generated on the apparatus are correlated to the magnitude of forces measured and other observations made during metal cutting trials involving the same material pairs.

No / Degrading infrastructure and applications of structural demolition create tremendous amounts of construction and demolition waste (CDW) all around the world. To address this issue in an effective way, recycling CDW in a most appropriate way has become a global concern in recent years. To this end, this study focused on the utilization of CDW-based materials such as hollow brick (HB), red clay brick (RCB), roof tile (RT), glass (G) and concrete (C) in the production of geopolymer mortars. These materials were first collected from an urban transformation area and then subjected to an identical two-step crushing-milling procedure to provide sufficient fineness for geopolymerization. To investigate the influence of blast furnace slag (S) addition to the CDW-based mixtures, 20% S substituted mixture designs were also made. Fine recycled concrete aggregates (FRCA) obtained from crushing and sieving of the waste concrete were used as the aggregate. A series of mixtures were designed using different proportions of three distinct alkali activators such as sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and calcium hydroxide (Ca[OH]2). To improve their applicability, the mixtures were left to cure at room temperature rather than the heat curing which is frequently applied in the literature. After 28 days of ambient curing, the 100% CDW-based geopolymer mortar activated with three different activators reached a compressive strength of 31.6 MPa, whereas the 20% S substituted geopolymer mortar achieved a compressive strength of 51.9 MPa. While the geopolymer mortars activated with only NaOH exhibited poor performance, it was found that the use of Na2SiO3 and Ca(OH)2 improved the compressive strength. Main geopolymerization products were related to NASH, CASH, and C(N)ASH gel formations. Our results demonstrated that mixed CDW-based materials can be employed in the manufacturing geopolymers, making them potential alternatives to Portland cement-based systems by being eco-friendly, energy-efficient, and comparable in compressive strength. / This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 894100.