To be able to supervise the quality of a sintering process, furnace control pieces are therefore used. The current furnace control piece is not sensitive enough small variations during insert production. The goal of the project was to find and evaluate a new suitable cemented carbide grade, which better captures temperature variations during sintering process, likewise, evaluate the alternative placing in the production furnace and methods to supervise and follow the status of the sintering process. The cemented carbide grade 592, which is a DQ-grade, captured larger temperature variations during the sintering compared to the current furnace control piece. The process charge for 592 that captured the largest variations also had the highest charge weight, which indicates that the new grade is also sensitive to the charge weight. The purpose of the project was fulfilled when a more suitable cemented carbide grade, 592, was evaluated for both sintering temperatures 1410 ℃ and 1450 ℃.

No description available.

Many studies and experiments have been conducted over the years to find solutions to the electricity problem. This issue is not just related to how fossil fuels are dispensed. Also, the environmental concerns associated with using fossil fuels have become a severe issue, which is a major cause of environmental pollution and ozone layer damage. As such, the need for energy becomes one of the essential goals. Therefore, research has begun to revolve around thermoelectrics, which is a straightforward approach for generating energy, by converting heat directly into electricity. Cobalt antimonide (CoSb3) belongs to a broad family of materials with the skutterudite structure, which have been recently identified as potential new thermoelectric materials with high performance. The CoSb3 is one of the numerous promising thermoelectric materials in the intermediate temperature range. The binary CoSb3 is a narrow bandgap semiconductor with a relatively flat band structure and excellent electrical performance. The thermoelectric performance efficiency of binary CoSb3 is measured by its figure of merit. The figure of merit is important for thermoelectric materials and is primarily governed by the Seebeck coefficient because it exhibits a square dependence. The Seebeck coefficient of the CoSb3 can be affected by many factors that can either increase or decrease it. Strain is an important aspect for the transport properties, including the Seebeck coefficient. The goal of this thesis project is to study the effect of point defects and strain on the Seebeck coefficient of skutterudite CoSb3. The binary CoSb3 skutterudite was explored through density functional theory (DFT) to calculate the ground-state properties, in particular the Seebeck coefficient. Two different CoSb3 structures were considered, an ideal one (without any defects) and the other was termed real (containing defects). In both cases, the Seebeck coefficient and its response were studied while strain was applied by changing the volume of the structure. The non-equilibrium Green's function was used within a DFT simulation to get a transmission distribution, where it was essential for calculating the Seebeck coefficient. Moreover, oxygen molecules were placed over the (001) surface of 2 × 2 × 1 CoSb3 supercell to establish if oxidation leads to point defect formation. These simulations were carried out by DFT-based molecular dynamics. It is found that the strain affects the Seebeck coefficient in the ideal structure. At compression, the absolute value of the Seebeck coefficient increases.  By contrast, the Seebeck coefficient changed its sign from negative to positive and increased to 894 μVK−1at tension, which was unexpected. The electron density distribution map was explored to explain the behavior of the Seebeck coefficient at equilibrium, compression, and tension. It can be seen that the electron distribution between Co and Sb is increased at compression, implying an increased orbital overlap (covalent interaction). By contrast, the tension reduces the electron distribution between Sb and Co. The real structure induced by oxidation exhibits Sb vacancies. The See-beck coefficient is affected differently than that of the ideal structure. At equilibrium, the Seebeck coefficient increases to 151 μVK−1. The electron density distribution between Sb and Co is enhanced in the real structure compared to the ideal one. The most drastic change is found at tension, where the Seebeck coefficient reaches−270 μVK−1. It may be speculated that this occurs due to O which increases the orbital overlap. The strategy introduced in this work, an interplay of defects and strain effects, may be beneficial for other thermoelectric materials.

This project presents an attempt to construct a setup and implement a reliable technique for measuring the magnetocaloric effect (MCE) on various materials via a direct method for the acquisition of the data. The main objective of the latter is to produce a ∆Tadiabatic vs T graph over a reasonable temperature span (-100◦C up to 220◦C) by thermal monitoring of a magnetic material exposed to an oscillating magnetic field with a maximum strength of 1.2T. The setup consists of a vacuum-insulated glass tube containing the sample placed between two electromagnets of a vibrating-sample magnetometer (VSM) and increasingly heated by a resistance wire, while the temperature is recorded directly by a thermocouple. The first experiments are performed on Gadolinium (Gd) samples as a reference material in order to verify the overall reliability of the system. The obtained results on Gadolinium show that meaningful data can be acquired with this direct method, although the initially-extracted ∆Tadiabatic near room temperature stands at the accuracy limit (25%) generally accepted with this method. Unexpected interference signals from the thermocouple are encountered for high temperatures and are shown to be due to magnetic dependence from one of its constituents. Data from high temperatures can however be reliably corrected with respect to a baseline signal from a neutral nonmagnetic material. As such magnetocaloric properties of two Manganese-rich high entropy alloys are investigated with one exhibiting at most ∆Tadiabatic = 0.2◦C at its Curie temperature TC = 60◦C. Suggestions regarding the possibility of operating the setup at sub-zero temperatures are put forward and promising results from a new spot- welded thermocouple show a significantenhancement of the initial setup accuracy. / Detta projekt presenterar ett försök att konstruera en installation och implementera en pålitlig teknik för att mäta den magnetokolorisk effekten (MCE) på olika material via en direkt metod för insamling av data. Det sistnämnda syftet är att producera en ∆Tadiabatisk vs T över ett rimligt temperaturintervall (-100◦C up to 220◦C). Detta genom en termisk övervakning av ett magnetiskt material utsatt för ett oscillerande magnetfält med en maximal magnitud på 1.2 T. Utrustningen utgörs av ett vakuumisolerade glasrör som innehåller provet, vilket är placerat mellan två elektromagneter från en vibrating-sample magnetometer (VSM) och som stegvis värms upp av en resistanstråd, medan temperaturen registreras direkt av ett termoelement. De inledande experimenten utförs på prover av Gadolinium (Gd) som referensmaterial för att verifiera systemets totala tillförlitlighet. De erhållna resultaten från Gadolinium proverna visar att meningsfulla data kan produceras med denna direkta metod. Även om de extraherade ∆Tadiabatisk vid rumstemperatur befinner sig inom precisions gränsen (25%), vilken är allmänt accepterad med avseende på den direkta metoden. Oväntade missvisande signaler från termoelementet uppträder vid höga temperaturer och visar sig bero på magnetiskt beroende från instumentet. Data från höga temperaturer kan emellertid pålitligt korrigeras med en baslinjesignal från ett neutralt icke-magnetiskt material. Därmed undersöks de magnetokoloriska egenskaper hos två Mangan-rika hög entropi legeringar, där en uppvisar som högst ∆Tadiabatisk = 0.2◦C vid dess Curie-temperatur TC = 60◦C. Förslag beträffande möjligheten att använda installationen vid temperaturer under noll läggs fram. Lovande resultat från ett nytt punktsvetsat termoelement visar en betydande förbättringav den inledande installationens noggrannhet.

This master thesis work has been carried out at the company SSAB EMEA in Oxelösund which is a global leader in quenched and tempered high-strength steel. The aim is to examine the importance of the material properties for the bendability of the specific steel grade Weldox. There are many conditions for various applications such as mobile cranes and vehicles that need to be fulfilled in order for the material to be approved, where one main prerequisite is the bendability. It is very important to be able to bend the material without the occurrence of cracks. The purpose of this work has therefore been to investigate and try to find the relationship between the material properties and the critical bending radius. Furthermore has another aim been to find the most suitable treatment process for the composition of this specific steel grade.The work was divided into two parts, where the first part was to examine two equally treated Weldox 960 plates that differed significantly in properties such as bendability and toughness. In the second part seven different plates of the steel grade Weldox 1100 have been investigated where all the plates were treated in various ways. The leveling of the plates was performed in two different ways; either according to the standard leveling or to the property affected leveling (ERIK). The experimental part includes tests such as bending, hardness, toughness, tensile and inclusions measurements.The results have shown that the most significant material properties affecting the bendability are the yield strength and the purity close to the plate surface. Leveling with ERIK as the last treatment step has shown that the toughness of the material can be increased but it does not affect the bendability for these specific steel grades. Other properties such as hardness, ultimate tensile strength and elongation have no major impact on the bendability for this specific composition. The most suitable treatment proved to be tempering at 200°C as the last step in the process chain.

Scania has experienced difficulties with large variations of the slope of the back plane after press quenching of case hardened crown wheels of especially type R780 Steg supplied from ingot cast material. This leads to that a large number of crown wheels has to be remeasured and sorted according to back slope which is time consuming for operators. Also, after sorting of the crown wheels, hard machining has to be adjusted according to the different slopes of the back plane of the crown wheels. In some cases, it also leads to scrapping of the crown wheels.This master’s thesis was divided in two parts. The aim of the first part was to confirm that the crown wheel type and casting technique that exhibits the largest variations in slope of the back plane is the R780 Steg originating from ingot cast material. The crown wheel types that were compared were the R780 Steg, R780 Slät and R885 Slät. Crown wheels manufactured from ingot cast material and from continuous cast material were compared. Hence, 6 combinations were examined. The slope of the back plane was measured with the measuring probe FARO after press quenching. The slope of the crown wheels was found to depend on both casting technique and the geometry of the crown wheel. The results confirmed that the crown wheel type and supplier combination that by far yields the largest variations in slope of the back plane is the R780 Steg supplied by Steel Plant A who uses the ingot casting technique. For this combination the variation exceeds 0,1 mm. All other combinations of crown wheels and suppliers yield acceptable variations.The second part of this master’s thesis was composed of determining if segregations in the cast ingot are the cause of the variations in slope of the back plane of the crown wheel type R780 Steg. This was done by measuring if there is a correlation between the slope of the back plane of the crown wheel after press quenching, the chemical composition and the original position of the crown wheel in the ingot. As in the first part of the study, the distortion was measured by the measuring probe FARO. The samples were sent to Degerfors Laboratorium for chemical analysis. Analyses of C, S and N were made by using combustion analyses. For As, P, B and Al optic spectrometry (spark) was used. All other elements were analysed by x-ray fluorescence. Segregations were found to be present and in combination with the geometry of R780 Steg to be the cause of the large variations in slope of the crown wheels.The results of this thesis show that, for the crown wheel type R780 Steg, Scania should not use suppliers that employ the ingot casting technique. Instead, only suppliers using the continuous casting technique should be used. However, for the other crown wheel types ingot or continuously cast material can be used.

The centrifugal casting process is a common method for manufacturing the tubes, etc. Due to its high temperature and invisible mold, it is really difficult to know the mechanism of molten steel inside the mold. It is important to know the mechanism of the molten steel inside mold, since it will help the manufacturer to know more accuracy of the flow of the molten steel so that it can work for improving the productivity and quality of the products. Casting funnel design is the designed by Åkers for their funnel which will result in different flow behavior. In thesis work, casting funnel design will be investigated so that it can make sure that the casting funnel design can affect the flow behavior of molten steel or not. Another method of changing the diameter of nozzle was also carried out and investigated with both simulation and experiment to changing flow behavior of molten steel. It will give Åkers alternative method for changing the flow behavior to liquid steel. The mechanism of solidification in centrifugal casting is also really important since it can give manufacturer the general view of solidification process. So solidification of centrifugal casting is also investigated in the thesis work.

In this work cold model experiments in combination with Comsol modeling have been carried out to investigate the possibilities of a new method for industrial inline measurements of slag viscosities. The method aims at measuring the mass of the drag force as a sphere is dragged upwards in a liquid. The sphere was connected to a balance that was elevated at constant velocity. The liquids used were silicon oils of two different viscosities; 0.1 Pa*s and 0.5 Pa*s. A computer logged the mass from which the viscosity was calculated. Comsol modeling was used to show approximately at which time the drag force is constant, and to investigate the wall effect. The importance of laminar flow is discussed. The results show that the method is more suitable for liquids of higher viscosities. The reason is that the drag force is one order of magnitude lower than the other forces in the system. Since the drag force is directly proportional to the viscosity, it becomes larger with higher viscosity. The Comsol model shows that the drag force becomes constant in a few seconds from start of the movement. Comsol gives approximately the same values for the drag force as can be calculated by hand. The viscosities calculated from the experimental data are between two and five times too large for the higher viscosity tested, and between two and ten times too large for the lower viscosity tested. There is a wall effect for the two containers used in the experiments that can be seen both experimentally and by Comsol. Further work and development of the model has to be done before this method possibly could work for industrial purposes.

The convergence of the digital and physical world encourages advances in high-speed telecommunication and fifth generation technology. Two-phase heat transfer systems are common engineering solutions. However, due to the large frequency spectra in 5G, the systematic heat generation increases requiring more efficient thermal management. The surface characteristics of solid materials in these systems is vital making micro-architectured materials a novel pathway to improve heat transfer. The coefficient of thermal expansion and thermal conductivity of the Schoen-Gyroid, a triply periodic minimal surface structure is studied along with a classical cylindrical porous structure. Graphite and graphene are considered as materials with excellent thermal and mechanical properties and are thus the base materials considered in this project. A comprehensive manufacturability study was conducted in order to gain knowledge regarding different graphite/graphene options and it was concluded that commercially available isotropic graphite was the best suited material for the purpose of this project. A decoupled thermo-mechanical analysis of the coefficient of thermal expansion and thermal conductivity of said structures as a function of volume fraction was conducted using computational homogenization with finite element analysis. A linearly elastic constitutive material model in COMSOL Multiphysics was used. As expected, the homogenized effective material is governed by linear constitutive model. Moreover, the results displayed a linear dependency on the porosity for both the CTE and thermal conductivity. The mechanical FEM model was validated using an analytical model derived by Gibson and Ashby and the thermal conductivity FEM model was validated using experimental data.

For many materials and components like in high speed trains and airplanes fatigue failures occur in the range of over 107 load cycles which is called the high cycle fatigue range. A modern version of the springs was invented which are applied in a certain application. Ultrasonic fatigue testing (20 kHz machine) was conducted for evaluating the steel of the springs. This research explores the fundamental understanding of high cycle fatigue testing of strip steel and assesses a stainless martensitic chromium steel at the high cycle fatigue range. Finite element modeling was conducted to gain knowledge about the effect of various parameters. Significant attention was devoted to the fatigue failure initiations by SEM/EDS. The work demonstrated that the method of investigation for high cycle fatigue test is reliable. Fatigue failure at this range was initiated by internal defects which all included non-metallic inclusion. A critical distance was defined Within the strip fatigue specimen where all the fatigue failure initiated. The 3D stress field in the specimen was determined by FEM modeling and the local applied stress at the whole of the flat part of specimen and critical distance was estimated. FEM was also employed to give additional information about the effect of parameters. It was established that damping had the largest influence. The local applied stress of the fatigue test was calculated by means of FEM and SEM analysis. It was used to adjust the S-N curve which resulted in 15% lower values than the nominal applied stress.