Release of soil phosphorus during runoff as affected by ionic strength and temperature

Selostus: Ympäristöolosuhteiden vaikutus maan fosforin liukenemiseen pintavalunnan aikana

Statistical variation of weld profiles and their expected influence on fatigue strength

The general objective of this study was to conduct astatistical analysis on the variation of the weld profiles and their influence on the fatigue strength of the joint. Weld quality with respect to its fatigue strength is of importance which is the main concept behind this thesis. The intention of this study was to establish the influence of weld geometric parameters on the weld quality and fatigue strength. The effect of local geometrical variations of non-load carrying cruciform fillet welded joint under tensile loading wasstudied in this thesis work. Linear Elastic Fracture Mechanics was used to calculate fatigue strength of the cruciform fillet welded joints in as-welded condition and under cyclic tensile loading, for a range of weld geometries. With extreme value statistical analysis and LEFM, an attempt was made to relate the variation of the cruciform weld profiles such as weld angle and weld toe radius to respective FAT classes.

The influence ofvariable amplitude loading on the fatigue strength of rhs corners

Rectangular hollow section (RHS) members are components widely used in engineering applications because of their good-looking, good properties in engineering areas and inexpensive cost comparing to members with other sections. The increasing use of RHS in load bearing structures makes it necessary to analyze the fatigue behavior of the RHS members. In this thesis, concentration will be given to the fatigue behavior of the RHS members under variable amplitude pure torsional loading. For the RHS members, failure will normally occur in the corner region if the welded regions are under full penetration. This is because of the complicated stress components' distributions at the RHScorners, where all of three fracture mechanics modes will happen. Mode I is mainly caused by the residual stresses that caused by the manufacturing process. Modes II and III are caused by the applied torsional loading. Stress based Findleymodel is also used to analyze the stress components. Constant amplitude fatigue tests have been done as well as variable amplitude fatigue tests. The specimens under variable amplitude loading gave longer fatigue lives than those under constant amplitude loading. Results from tests show an S-N curvewith slope around 5.

Constant and variable amplitude fatigue strength of high strength steel welds treated with ultrasonic impact treatment

Hitsattujen rakenteiden väsymiskestävyyttä pystytään parantamaan jälkikäsittelymenetelmillä, joistayksi, ultraäänikäsittely muokkaa hitsin geometriaa ja aiheuttaa puristusjäännösjännitystilan. Tässä tutkimuksessa verrataan kokeellisesti kuormaa kantamattoman hitsatun ja ui -käsitellyn rivan väsymislujuutta toisiinsa. Tutkimusohjelmaan kuuluu kahta teräslajia ja sekä vakio - että vaihtuva - amplitudista kuormitusta. Ultraäänikäsittelyllä saavutetaan väsymiskestoiän parantuminen vakio - ja vaihtuva - amplitudisella kuormituksella. Perusaineen lujuudella ei ole merkittää vaikutusta väsymislujuuteen kun liitos on hitsatussa tilassa. Tällöin väsymiskestävyyden määrää hitsin rajaviivan jännityskeskittymä. Ultraäänikäsitellyn hitsatunliitoksen väsymiskestävyys on suurempi korkeamman lujuuden omaavilla teräksillä. Tästä syystä korkealujuuksisten terästen käyttö ultraäänikäsiteltynä väsyttävästi kuormitetuissa kevytrakenteissa on perusteltua.

An Assessment ofFatigue Strength of Load Carrying Welded Joints with Lack of Penetration

On yleisesti tiedossa, että väsyttävän kuormituksen alaisena olevat hitsatut rakenteet rikkoutuvat juuri hitsausliitoksista. Täyden tunkeuman hitsausliitoksia sisältävien rakenteiden asiantunteva suunnittelu janykyaikaiset valmistusmenetelmät ovat lähes eliminoineet väsymisvauriot hitsatuissa rakenteissa. Väsymislujuuden parantaminen tiukalla täyden tunkeuman vaatimuksella on kuitenkin epätaloudellinen ratkaisu. Täyden tunkeuman hitsausliitoksille asetettavien laatuvaatimuksien on määriteltävä selkeät tarkastusohjeet ja hylkäämisperusteet. Tämän diplomityön tarkoituksena oli tutkia geometristen muuttujien vaikutusta kuormaa kantavien hitsausliitosten väsymislujuuteen. Huomio kiinnitettiin pääasiassa suunnittelumuuttujiin, joilla on vaikutusta väsymisvaurioiden syntymiseen hitsauksen juuren puolella. Nykyiset määräykset ja standardit, jotka perustuvat kokeellisiin tuloksiin; antavat melko yleisiä ohjeita hitsausliitosten väsymismitoituksesta. Tämän vuoksi muodostettiin kokonaan uudet parametriset yhtälöt sallitun nimellisen jännityksen kynnysarvon vaihteluvälin, ¿¿th, laskemiseksi, jotta vältettäisiin hitsausliitosten juuren puoleiset väsymisvauriot. Lisäksi, jokaiselle liitostyypille laskettiin hitsin juuren puolen väsymisluokat (FAT), joita verrattiin olemassa olevilla mitoitusohjeilla saavutettuihin tuloksiin. Täydentäviksi referensseiksi suoritettiin useita kolmiulotteisia (3D) analyysejä. Julkaistuja kokeellisiin tuloksiin perustuvia tietoja käytettiin apuna hitsausliitosten väsymiskäyttäytymisen ymmärtämiseksi ja materiaalivakioiden määrittämiseksi. Kuormaa kantavien vajaatunkeumaisten hitsausliitosten väsymislujuus määritettiin käyttämällä elementtimenetelmää. Suurimman pääjännityksen kriteeriä hyödynnettiin murtumiskäyttäytymisen ennakoimiseksi. Valitulle hitsatulle materiaalille ja koeolosuhteille murtumiskäyttäytymistä mallinnettiin särön kasvunopeudella da/dN ja jännitysintensiteettikertoimen vaihteluvälillä, 'K. Paris:n yhtälön numeerinen integrointi suoritettiin FRANC2D/L tietokoneohjelmalla. Saatujen tulosten perusteella voidaan laskea FAT tutkittavassa tapauksessa. ¿¿th laskettiin alkusärön jännitysintensiteettikertoimen vaihteluvälin ja kynnysjännitysintensiteettikertoimen, 'Kth, perusteella. ¿Kth arvoa pienemmällä vaihteluvälillä särö ei kasva. Analyyseissäoletuksena oli hitsattu jälkikäsittelemätön liitos, jossa oli valmis alkusärö hitsin juuressa. Analyysien tulokset ovat hyödyllisiä suunnittelijoille, jotka tekevät päätöksiä koskien geometrisiä parametreja, joilla on vaikutusta hitsausliitosten väsymislujuuteen.

A novel procedure for establishing clinching parameters for high strength steel sheet

The building industry has a particular interest in using clinching as a joining method for frame constructions of light-frame housing. Normally many clinch joints are required in joining of frames.In order to maximise the strength of the complete assembly, each clinch joint must be as sound as possible. Experimental testing is the main means of optimising a particular clinch joint. This includes shear strength testing and visual observation of joint cross-sections. The manufacturers of clinching equipment normally perform such experimental trials. Finite element analysis can also be used to optimise the tool geometry and the process parameter, X, which represents the thickness of the base of the joint. However, such procedures require dedicated software, a skilled operator, and test specimens in order to verify the finite element model. In addition, when using current technology several hours' computing time may be necessary. The objective of the study was to develop a simple calculation procedure for rapidly establishing an optimum value for the parameter X for a given tool combination. It should be possible to use the procedure on a daily basis, without stringent demands on the skill of the operator or the equipment. It is also desirable that the procedure would significantly decrease thenumber of shear strength tests required for verification. The experimental workinvolved tests in order to obtain an understanding of the behaviour of the sheets during clinching. The most notable observation concerned the stage of the process in which the upper sheet was initially bent, after which the deformation mechanism changed to shearing and elongation. The amount of deformation was measured relative to the original location of the upper sheet, and characterised as the C-measure. By understanding in detail the behaviour of the upper sheet, it waspossible to estimate a bending line function for the surface of the upper sheet. A procedure was developed, which makes it possible to estimate the process parameter X for each tool combination with a fixed die. The procedure is based on equating the volume of material on the punch side with the volume of the die. Detailed information concerning the behaviour of material on the punch side is required, assuming that the volume of die does not change during the process. The procedure was applied to shear strength testing of a sample material. The sample material was continuously hot-dip zinc-coated high-strength constructional steel,with a nominal thickness of 1.0 mm. The minimum Rp0.2 proof stress was 637 N/mm2. Such material has not yet been used extensively in light-frame housing, and little has been published on clinching of the material. The performance of the material is therefore of particular interest. Companies that use clinching on a daily basis stand to gain the greatest benefit from the procedure. By understanding the behaviour of sheets in different cases, it is possible to use data at an early stage for adjusting and optimising the process. In particular, the functionality of common tools can be increased since it is possible to characterise the complete range of existing tools. The study increases and broadens the amount ofbasic information concerning the clinching process. New approaches and points of view are presented and used for generating new knowledge.

A novel approachfor assessing the fatigue strength of ultrasonic impact treated welded structures.

It is commonly observed that complex fabricated structures subject tofatigue loading fail at the welded joints. Some problems can be corrected by proper detail design but fatigue performance can also be improved using post-weld improvement methods. In general, improvement methods can be divided into two main groups: weld geometry modification methods and residual stress modification methods. The former remove weld toe defects and/or reduce the stress concentrationwhile the latter introduce compressive stress fields in the area where fatigue cracks are likely to initiate. Ultrasonic impact treatment (UIT) is a novel post-weld treatment method that influences both the residual stress distribution andimproves the local geometry of the weld. The structural fatigue strength of non-load carrying attachments in the as-welded condition has been experimentally compared to the structural fatigue strength of ultrasonic impact treated welds. Longitudinal attachment specimens made of two thicknesses of steel S355 J0 have been tested for determining the efficiency of ultrasonic impacttreatment. Treated welds were found to have about 50% greater structural fatigue strength, when the slope of the S-N-curve is three. High mean stress fatigue testing based on the Ohta-method decreased the degree of weld improvement only 19%. This indicated that the method could be also applied for large fabricated structures operating under high reactive residual stresses equilibrated within the volume of the structure. The thickness of specimens has no significant effect tothe structural fatigue strength. The fatigue class difference between 5 mm and 8 mm specimen was only 8%. It was hypothesized that the UIT method added a significant crack initiation period to the total fatigue life of the welded joints. Crack initiation life was estimated by a local strain approach. Material parameters were defined using a modified Uniform Material Law developed in Germany. Finite element analysis and X-ray diffraction were used to define, respectively, the stress concentration and mean stress. The theoretical fatigue life was found to have good accuracy comparing to experimental fatigue tests.The predictive behaviour of the local strain approach combined with the uniformmaterial law was excellent for the joint types and conditions studied in this work.

Dynamics of Appropriability - Finding a Balance between Efficiency and Strength in the Appropriability Regime

Building and sustaining competitive advantage through the creation of market imperfections is challenging in a constantly changing business environment - particularly since the sources of such advantages are increasingly knowledge-based. Facilitated by improved networks and communication, knowledge spills over to competitors more easily than before,thus creating an appropriability problem: the inability of an innovating firm to utilize its innovations commercially. Consequently, as the importance of intellectual assets increases, their protection also calls for new approaches. Companies have various means of protection at their disposal, and by taking advantage of them they can make intangibles more non-transferable and prevent, or at leastdelay, imitation of their most crucial intellectual assets. However, creating barriers against imitation has another side to it, and the transfer of knowledge in situations requiring knowledge sharing may be unintentionally obstructed. Theaim of this thesis is to increase understanding of how firms can balance knowledge protection and sharing so as to benefit most from their knowledge assets. Thus, knowledge protection is approached through an examination of the appropriability regime of a firm, i.e., the combination of available and effective means ofprotecting innovations, their profitability, and the increased rents due to R&D. A further aim is to provide a broader understanding of the formation and structure of the appropriability regime. The study consists of two parts. The first part introduces the research topic and the overall results of the study, and the second part consists of six complementary research publications covering various appropriability issues. The thesis contributes to the existing literature in several ways. Although there is a wide range of prior research on appropriability issues, a lot of it is restricted either to the study of individual appropriability mechanisms, or to comparing certain features of them. These approaches are combined, and the relevant theoretical concepts are clarified and developed. In addition, the thesis provides empirical evidence of the formation of the appropriability regime, which is consequently presented as an adaptive process. Thus, a framework is provided that better corresponds to the complex reality of the current business environment.

Analytical Study on the Influence of Geometrical Parameters on the Fatigue Strength of Welds with Undercuts

The purpose of this study is to analyze the influence of geometric parameters on the fatigue strength of the welded joint. The thesis includes the analytical study pertaining to variation of undercut and the weld toe radius. The theoretical part includes the concepts of fracture mechanics, different stages of the crack propagation and finally the results. The numerical results are obtained from FRANC2D/L. The results show that the fatigue strength of the welded structure depends on the parameters of the welds such as the weld toe radius, weld angle, height of the undercut and plate thickness. The results show that the fatigue life can be improved by having the undercut as minimum as possible. However there has been significant variation on the fatigue life of the structure when the weld toe radius is increased.

Protection of the high-voltage equipment with reduced insulation strength

Power transformer is the most expensive equipment on a substation. It is always necessary to get needed benefit with the lowest expenses. Producing of power transformers with reduced insulation strength is one of the possible ways to reduce expenses. Exploitation of such transformers was begun in the end of 70-th in the last century. Protection from overvoltages was done with valve-type magnetic combined surge arresters with increased blanking voltage during switching overvoltages. Nowadays there is the necessity of replacement of those devices. That’s why modernized nonlinear surge arrester was invented. This master’s thesis is focused on the use research of that modernized device in comparison with usual nonlinear surge arresters. The goal is to show the lightning overvoltages level using different types of nonlinear surge arresters and then calculations of the lightning protection reliability.

Measurement and Improvement of Wet Paper Web Strength

Various strength properties of paper are measured to tell how well it resists breaks in a paper machine or in printing presses. The most often measured properties are dry tensile strength and dry tear strength. However, in many situations where paper breaks, it is not dry. For example, in web breaks after the wet pressing the dry matter content can be around 45%. Thus, wet-web strength is often a more critical paper property than dry strength. Both wet and dry strength properties of the samples were measured with a L&W tensile tester. Originally this device was not designed for the measurement of the wet web tensile strength, thus a new procedure to handle the wet samples was developed. The method was tested with Pine Kraft (never dried). The effect of different strength additives on the wet-web and dry paper tensile strength was studied. The polymers used in this experiment were aqueous solution of a cationic polyamidoamine-epichlorohydrin resin (PAE), cationic hydrophilised polyisocyanate and cationic polyvinylamine (PVAm). From all three used chemicals only Cationic PAE considerably increased the wet web strength. However it was noticed that at constant solids content all chemicals decreased the wet web tensile strength. So, since all chemicals enhanced solid content it can be concluded that they work as drainage aids, not as wet web strength additives. From all chemicals only PVAm increased the dry strength and two other chemicals even decreased the strength. As chemicals were used in strong diluted forms and were injected into the pulp slurry, not on the surface of the papersheets, changes in samples densities did not happen. Also it has to be noted that all these chemicals are mainly used to improve the wet strength after the drying of the web.

Natural and synthetic fibres improving tensile strength and elongation of paper products

The theory part of the Master’s thesis introduces fibres with high tensile strength and elongation used in the production of paper or board. Strong speciality papers are made of bleached softwood long fibre pulp. The aim of the thesis is to find new fibres suitable for paper making to increase either tensile strength, elongation or both properties. The study introduces how fibres bond and what kind of fibres give the strongest bonds into fibre matrix. The fibres that are used the in manufacturing of non-wovens are long and elastic. They are longer than softwood cellulose fibres. The end applications of non-wovens and speciality papers are often the same, for instance, wet napkins or filter media. The study finds out which fibres are used in non-wovens and whether the same fibres could be added to cellulose pulp as armature fibres, what it would require for these fibres to be blended in cellulose, how they would bind with cellulose and whether some binding agents or thermal bonding, such as hot calendaring would be necessary. The following fibres are presented: viscose, polyester, nylon, polyethylene, polypropylene and bicomponent fibres. In the empiric part of the study the most suitable new fibres are selected for making hand sheets in laboratory. Test fibres are blended with long fibre cellulose. The test fibres are viscose (Tencel), polypropylene and polyethylene. Based on the technical values measured in the sheets, the study proposes how to continue trials on paper machine with viscose, polyester, bicomponent and polypropylene fibres.

Effect of pulps fractionation on formation and strength properties of laboratory hand sheets

The objectives of the work were to study the effect of dewatering time varying on formation properties of papersheets, to determine the role of fines fraction in creation of paper with good formation and strength properties of papersheets, and also to study the effect of charge modification of fibers fractionations on formation properties of handsheets. The paper formation is one of the most important structural properties of paper. This property has effect on physical and optical characteristics of paper. In thi work the effect of formation on tensile strength was determined. The formation properties were analyzed by using the AMBERTEC Beta Formation Tester. The PAM addition as a f;locculant agent did some changes in the formation of paper. Paper sheets were also made from different furnishes of both birch and pine pulps. The fibers particles as a fines have great effect on drainability changes. Fines fraction played important role in papermaking. The two kinds of pulps (pine and birch pulps) were also used in this work for investigation of fines role. As it was expected the fines fraction gave positive effect on paper formation, but when fines fraction was added above initial fines content the formation of paper was deteriorated. The effect of paper formation on tensile strength was also determined. In many cases the poor formation of paper had negative effect on strength properties of paper..

Influence of Heat Treatment on Strength Properties of Finger-jointed Components

The purpose for the thesis was to study the thermo treatment of finger-jointed wood. The thesis concentrated on examining the tensile and bending strength of finger-jointed and thermo treated wood. The aim was to find out how different treatment temperature levels and adhesives influence the strength of wood that has been finger-jointed before heat treatment. Secondary objectives were to examine the influence of the treatment time at one temperature, determine differences in the strength between the joints in heartwood and sapwood, examine the visual appearance of the finger joints after the treatment and establish possibilities to reach a characteristic strength level corresponding to C14. Only minor differences in strength properties were measured between the finger-jointed wood treatments II and III. A greater difference was shown between these two treatment temperatures I, which lead to reduced strength. The average strength of joints glued with adhesive 2 was higher after treatments II and III compared to those glued with the adhesive 1. At the treatment temperature I, the adhesive 1 strength properties were at the same level compared to the adhesive 2 or better. There were not any significant differences.

Improvement of Surface Strength of Paper

Offset printing is a popular printing method that is especially suitable for large and fast print jobs. Newspapers, magazines and books are typical examples of products printed with offset method. In high volume printing production high efficiency is essential. Offset printing uses tacky inks that cause serious stress to the paper surface. Dusting and linting are terms that describe how loose and weakly bonded particles are removed from the paper surface in the printing process. The removed particles accumulate in the process causing deteriorating print quality. This forces the printing operators to stop production for washing and cleaning. Time and money are lost. Dusting and linting tendency of paper can be decreased by improving the surface strength of paper. In the present work a method to increase the surface strength of paper was studied. In the literature part offset printing method and challenges related to offset printing are presented. A review of new methods for surface sizing of paper is also presented. The experimental part presents trials where an apparatus for improving paper surface strength was tested and developed in mill scale. Laboratory work supporting the actual mill scale operations is also presented. The acquired results provide a solid base of information to make decisions on how to proceed with research in the present field of study.