Slagsegheten hos stål är komplext beroende av ett antal olika parametrar, som i olika grad påverkar varandra. Många betydande och viktiga ledtrådar har hittats som förhoppningsvis kan ge en bredare förståelse varför slagsegheten varierar och varför den inte alltid uppnås i nuvarande process. Studien har utförts på kalldragna sömlösa rör, med stålsort EN 10305-1. Projektet innefattar ett antal olika produkt specifikationer med olika dimensioner, med lite olika kemiska sammansättning. På grund av slagseghetskraven på industriella produkter var det viktigt att utvärdera vilka parametrar som påverkar. En utvärdering gjordes dels av resultat från slagseghetsprovning efter påverkande processer, och dels från utvärdering av stålets mikrostruktur. Förutom dimension och kemisk sammansättning, varierar processlinjens faktorer. Den första processen som påverkar är kalldragningen som i denna studie har haft reduktioner mellan 15% och 31%. Avspänningsglödgningens temperatur påverkar även, där temperaturerna 525 oC, 575 oC och 600 oC är de som använts på produkterna i projektet. Vissa av projektets produkter har även normaliserats, och resultaten tyder på att detta är en mycket viktig process om man ser till slagseghet. Målsättningen var att får fram omslagskurvor vid olika tillstånd av stålet. Utifrån dessa tillsammans med utvärdering av stålets mikrostruktur och kemisk sammansättning kunde flera diskussioner föras. Den viktiga slutledningen som kunde dras var att inga faktorer är ensam avgörande för slagsegheten i den här studien. Den kemiska sammansättningen påverkar ihop med processlinjens olika faktorer. Man bör ligga på en temperatur för avspänningsglödgning över 550 oC. Projektet visar även på att större dimensioner påverkar slagsegheten negativt. Två viktiga felmarginaler kan ha påverkat resultaten i projektet, dels positionen för vart anvisningen görs på provstaven i förhållande till rören och dels användandet av en praxis som beräknar resultat från provning med reducerade provstavar. En undersökning av dessa felmarginaler gjordes, och resultaten var tydliga. En mer noggrann provuttagning bör göras, och man bör vara mer försiktig vid användandet av praxisen.

No description available.

<p>The overall objective of this work has been to develop aluminium alloys, which after hot and cold deformation are able to withstand high temperatures without recrystallising. This has been done by investigating aluminium alloys with various additions of hafnium, scandium and zirconium, with a main focus on Hf and to which extent it may partly substitute or replace Zr and/or Sc as a dispersoid forming elements in these alloys.</p><p><i>What is the effect of hafnium, alone and in combination with Zr and/or Sc and how do hafnium containing alloys perform?</i></p><p>It is shown that hafnium may alter or modify the casting structure, though, not to the better as it can form TCGs in combinations with Zr and/or Sc. This is not advantageous neither as far as it concerns grain refining nor precipitation of dispersoids.</p><p>When precipitation of binary Al-Hf is compared to Al-(Hf)-(Zr) alloys, hafnium shows even slower precipitation than in Al-(Hf)-(Zr) alloys and also much slower and with a poorer spatial distribution of dispersoids than in Al-Sc or Al-Hf-Sc alloys. As a consequence, it may be concluded that binary aluminium-hafnium alloys are of limited interest as they display a poor recrystallisation resistance when no other alloying elements are added.</p><p>However, when hafnium is added together with scandium and/or zirconium, precipitation may actually improve both in Al-Hf-Zr alloys and in scandium containing alloys like Al-Hf-Sc and Al-Hf-Sc-Zr. Hafnium can still not completely replace neither Zr nor Sc due to its poor precipitation properties. However, Al-Hf-Sc-Zr alloys show a better dispersoid distribution (number density and volume fraction) than what was observed in Al-Sc-Zr alloys after extrusion. The Al-Hf-Sc-Zr alloys also show extreme high temperature properties, by withstanding recrystallisation at high temperatures and long annealing times. After severe cold deformation, the extruded profiles of both the Al-Sc-Zr alloy and the Al-Hf-Sc-Zr alloy displayed a remarkable recrystallisation resistance.</p><p>The reason why the Al-Zr-Sc- and the Al-Hf-Zr-Sc alloys behave so well has been investigated by detailed 3D Atom Probe investigations. Due to the homogeneous precipitation of Al3Sc dispersoids and the retarding effect from Hf and/or Zr containing shells, thus limiting the coarsening of these dispersoids, these combinations have been shown successful.</p><p>As we have seen when Hf and Zr are added in combination equal or improved recrystallisation properties can be obtained. This is specially the case when both these elements are added together with scandium. Since Hf and Zr are extremely difficult (and thus costly) to separate, Al-Zr master alloys used in industry today can in the future probably contain more Hf, lowering the cost of master alloys.</p><p>The work presented in this thesis have hopefully added some new insight and a better understanding of the effects of adding various dispersoid forming elements to aluminium, alone and in various combinations, which may be useful for industry today and a basis for further alloy development.</p>

No description available.

<p>Slagsegheten hos stål är komplext beroende av ett antal olika parametrar, som i olika grad påverkar varandra.</p><p>Många betydande och viktiga ledtrådar har hittats som förhoppningsvis kan ge en bredare förståelse varför slagsegheten varierar och varför den inte alltid uppnås i nuvarande process.</p><p>Studien har utförts på kalldragna sömlösa rör, med stålsort EN 10305-1. Projektet innefattar ett antal olika produkt specifikationer med olika dimensioner, med lite olika kemiska sammansättning. På grund av slagseghetskraven på industriella produkter var det viktigt att utvärdera vilka parametrar som påverkar. En utvärdering gjordes dels av resultat från slagseghetsprovning efter påverkande processer, och dels från utvärdering av stålets mikrostruktur.</p><p>Förutom dimension och kemisk sammansättning, varierar processlinjens faktorer. Den första processen som påverkar är kalldragningen som i denna studie har haft reduktioner mellan 15% och 31%. Avspänningsglödgningens temperatur påverkar även, där temperaturerna 525 oC, 575 oC och 600 oC är de som använts på produkterna i projektet. Vissa av projektets produkter har även normaliserats, och resultaten tyder på att detta är en mycket viktig process om man ser till slagseghet.</p><p>Målsättningen var att får fram omslagskurvor vid olika tillstånd av stålet. Utifrån dessa tillsammans med utvärdering av stålets mikrostruktur och kemisk sammansättning kunde flera diskussioner föras.</p><p>Den viktiga slutledningen som kunde dras var att inga faktorer är ensam avgörande för slagsegheten i den här studien. Den kemiska sammansättningen påverkar ihop med processlinjens olika faktorer. Man bör ligga på en temperatur för avspänningsglödgning över 550 oC. Projektet visar även på att större dimensioner påverkar slagsegheten negativt.</p><p>Två viktiga felmarginaler kan ha påverkat resultaten i projektet, dels positionen för vart anvisningen görs på provstaven i förhållande till rören och dels användandet av en praxis som beräknar resultat från provning med reducerade provstavar. En undersökning av dessa felmarginaler gjordes, och resultaten var tydliga. En mer noggrann provuttagning bör göras, och man bör vara mer försiktig vid användandet av praxisen.</p>

<p>Applications relying on a high static friction include various types of fixtures, couplings, bolted joints, torsion joints, etc. The common characteristic of these applications is that they rely on the friction force to maintain the relative position of two mating surfaces. Also applications relying on high dynamic friction are common, the main example being brakes, where a low friction could be devastating.</p><p>The plateau model for the friction of brakes has been refined. By using advanced electron microscopy, it has been shown that during braking a partly amorphous friction film, comprising nanosized iron oxide agglomerates, dissipates the friction energy. The film is only about 100 nm thick. It is separated from the underlying less mobile material by a thin boundary. The actual braking power is thus localised to this very thin film, leading to remarkably high power densities. In a typical case it was estimated to 40 GW/dm3.</p><p>Squeal and vibrations are critical problems for brakes. The present work has shown that a textured disc pattern may counteract squeal efficiently. The most successful pattern has spiral shaped arms in which wear resistant ceramic particles are embedded. The different wear characteristics of treated and untreated disc surface lead to an elevation of the patterned area above the rest of the disc. In a related experiment, laser technique was used to inject the particles deeper into the disc surface, and thus prolonging the time of silence. </p><p>Textured diamond surfaces have been used to study the influence of load, repeated scratching and surface roughness on the static coefficient of friction. It was shown that these surfaces were remarkably stable at high friction levels. A maximum load limit was found above which the coefficient of friction falls. This and a number of other factors were found important for the successful design of high-friction joints.</p>

No description available.

The overall objective of this work has been to develop aluminium alloys, which after hot and cold deformation are able to withstand high temperatures without recrystallising. This has been done by investigating aluminium alloys with various additions of hafnium, scandium and zirconium, with a main focus on Hf and to which extent it may partly substitute or replace Zr and/or Sc as a dispersoid forming elements in these alloys. What is the effect of hafnium, alone and in combination with Zr and/or Sc and how do hafnium containing alloys perform? It is shown that hafnium may alter or modify the casting structure, though, not to the better as it can form TCGs in combinations with Zr and/or Sc. This is not advantageous neither as far as it concerns grain refining nor precipitation of dispersoids. When precipitation of binary Al-Hf is compared to Al-(Hf)-(Zr) alloys, hafnium shows even slower precipitation than in Al-(Hf)-(Zr) alloys and also much slower and with a poorer spatial distribution of dispersoids than in Al-Sc or Al-Hf-Sc alloys. As a consequence, it may be concluded that binary aluminium-hafnium alloys are of limited interest as they display a poor recrystallisation resistance when no other alloying elements are added. However, when hafnium is added together with scandium and/or zirconium, precipitation may actually improve both in Al-Hf-Zr alloys and in scandium containing alloys like Al-Hf-Sc and Al-Hf-Sc-Zr. Hafnium can still not completely replace neither Zr nor Sc due to its poor precipitation properties. However, Al-Hf-Sc-Zr alloys show a better dispersoid distribution (number density and volume fraction) than what was observed in Al-Sc-Zr alloys after extrusion. The Al-Hf-Sc-Zr alloys also show extreme high temperature properties, by withstanding recrystallisation at high temperatures and long annealing times. After severe cold deformation, the extruded profiles of both the Al-Sc-Zr alloy and the Al-Hf-Sc-Zr alloy displayed a remarkable recrystallisation resistance. The reason why the Al-Zr-Sc- and the Al-Hf-Zr-Sc alloys behave so well has been investigated by detailed 3D Atom Probe investigations. Due to the homogeneous precipitation of Al3Sc dispersoids and the retarding effect from Hf and/or Zr containing shells, thus limiting the coarsening of these dispersoids, these combinations have been shown successful. As we have seen when Hf and Zr are added in combination equal or improved recrystallisation properties can be obtained. This is specially the case when both these elements are added together with scandium. Since Hf and Zr are extremely difficult (and thus costly) to separate, Al-Zr master alloys used in industry today can in the future probably contain more Hf, lowering the cost of master alloys. The work presented in this thesis have hopefully added some new insight and a better understanding of the effects of adding various dispersoid forming elements to aluminium, alone and in various combinations, which may be useful for industry today and a basis for further alloy development.

Applications relying on a high static friction include various types of fixtures, couplings, bolted joints, torsion joints, etc. The common characteristic of these applications is that they rely on the friction force to maintain the relative position of two mating surfaces. Also applications relying on high dynamic friction are common, the main example being brakes, where a low friction could be devastating. The plateau model for the friction of brakes has been refined. By using advanced electron microscopy, it has been shown that during braking a partly amorphous friction film, comprising nanosized iron oxide agglomerates, dissipates the friction energy. The film is only about 100 nm thick. It is separated from the underlying less mobile material by a thin boundary. The actual braking power is thus localised to this very thin film, leading to remarkably high power densities. In a typical case it was estimated to 40 GW/dm3. Squeal and vibrations are critical problems for brakes. The present work has shown that a textured disc pattern may counteract squeal efficiently. The most successful pattern has spiral shaped arms in which wear resistant ceramic particles are embedded. The different wear characteristics of treated and untreated disc surface lead to an elevation of the patterned area above the rest of the disc. In a related experiment, laser technique was used to inject the particles deeper into the disc surface, and thus prolonging the time of silence. Textured diamond surfaces have been used to study the influence of load, repeated scratching and surface roughness on the static coefficient of friction. It was shown that these surfaces were remarkably stable at high friction levels. A maximum load limit was found above which the coefficient of friction falls. This and a number of other factors were found important for the successful design of high-friction joints.

In the turbine industry today, thermal barrier coatings are a commonly used, these are 0.1-2mm thick. So to be able to do some type of mechanical testing to receive material data so one can build an opinion regarding the health of the material. One needs a procedure that can work with small specimens and achieve clear results that can be transformed and compared with known data and known procedures. One of those methods is Small Punch Testing. This thesis describes one way to develop and test a functioning prototype of a Small Punch Testing device. The thesis includes; the reason it was developed in the beginning and how it has been developed throughout the decades, also in which areas the main research is made. It also shortly describes a working procedure in Ansys to get a Finite Element Method [FEM] model working. This method showed itself as useful, when just a small sample is at hand. The trials in this thesis also show that repetitive test can be done with good results which can be compared with real and FEM analysis data such as σ uts· / Inom turbin industrin idag så är keramiska värme barriärer vanligt förekommande dessa är normalt 0,1-2mm tjocka. För att kunna utföra mekanisk provning som grund för att bilda en åsikt om materialets kondition. Så behöver man en metod som kan åstadkomma tydliga data med små provbitar, Small Punch Testing är en av dem. Den här rapporten beskriver hur man kan gå tillväga för att få en fungerande prototyp. Den tar upp metodens ursprung och hur den har utvecklats under år tiondena, också mot vad den nuvarande forskningen riktar sig. Den beskriver även kort hur man ställer upp en finita element metod [FEM] modell i Ansys. Metoden visade sig användbar när man bara har en liten provbit att tillgå. Försöken visade att repetitiva tester kan göras med bra resultat som går att jämföra med verkliga och FEM analys data.