Benefits of establishing legumes into permanent pastures have been well studied. Successful establishment of legumes in pastures can be challenging, however, and more information is needed about different seeding methods and variables that affect legume establishment. A pasture and a small plot experiment were conducted in Blacksburg, Va from 2009 to 2011to gain better understanding of how seeding method and management variables affected red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) establishment into permanent cool season grass pasture and sod. In the pasture experiment, seedling density was measured two months after sowing and grass, white clover, red clover, and weed biomass were periodically measured during the experiment. Broadcast seeding treatment had 93% more clover seedlings than drill treatment (P = 0.1087) two months after sowing. No difference (P > 0.10) for clover biomass was observed between sowing treatments in any year and clover establishment was considered successful (over 25% of pasture composition) in both treatments. In the drill treatment, clover seedling density was negatively affected by the residual grass biomass at sowing (P = 0.0196). In the broadcast treatment, a quadratic relationship between clover seedling density and residual grass biomass at sowing was found (P = 0.0516). Clover seedling density in April 2009 determined the amount of clover biomass in August 2009 (P = 0.0008) and the 2010 clover biomass mean (P = 0.0249). Further exploration of the influence fertilization with P and K, grass biomass at sowing, and defoliation frequency on clover establishment were studied in a split-split plot study. Fertilization with P and K was assigned to whole plots that were split in half and assigned a high or low grass biomass at sowing treatment, the subplots were split in and designated either a high or low cutting frequency. Prior to cutting, samples from each plot were sorted to grass, white clover, red clover, and weed. Plots with a low grass biomass at sowing (232 seedlings m-2) had a higher seedling density (P < 0.0001) compared with plots with a high grass biomass at sowing plots (111 seedlings m-2). Greater biomass of white and red clover depended both on having a low grass biomass at sowing and a high frequency of defoliation (P = 0.0026 and P < 0.0001, respectively). Red clover yield was also determined by interactions between fertilization and a high frequency of defoliation (P < 0.0001), as well as between fertilization and low grass biomass at sowing (P = 0.0026). Dry conditions resulted in low clover yields (6% of total herbage mass) with red clover producing four times the herbage mass of white clover. These data show that creating a favorable environment for seedlings to germinate and establish was more important than seeding method. / Master of Science

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Finita elementmetoden (FEM) utvärderas för att i framtiden kunna undvika mycket av den fysiska provning som idag används vid optimering av maskininställningar, både vid införandet av nya maskiner men även på befintliga. Fräsmaskinen som granskas grovbearbetar fyrcylindriga vevaxlar under åtta bearbetningstempon. Resonansfrekvenser skulle kunna identifieras med hjälp av en FEM-modell och sedan undvikas genom att justera skärhastigheten. Litteraturstudien innefattar skärande bearbetning, vibrationer, svängningsteori och FEM. Modeller av vevaxlar ges av arbetsgivaren och egenfrekvensanalyser utförs i programvaran Abaqus för samtliga bearbetningstempon. Egenfrekvenser jämförs med den drivande frekvensen från fräsverktyget. Fräsning i vevaxelns egenfrekvens inträffar vid ett tillfälle, bearbetningstempo två. Vibrationerna antas inte påverkas i stor utsträckning på grund av fräsverktygets differentialdelade skär som gör att fräsning i egenfrekvens endast inträffar var sjätte skär. Vibrationsdata från arbetsgivaren visar även att vibrationerna är låga för bearbetningstempot. FEM-modellerna verifieras med fysiska experiment (slagimpulsprov) på fritt upphängd vevaxel och jämförs med resultat från FEM-analys för fri axel. Skillnaden i egenfrekvens mellan experiment och FEM-simulering är maximalt 5 %, vilket bekräftar modellernas tillförlitlighet. Vidare skapas en förenklad modell av fräsverktyget som analyseras angående egenfrekvenser i Abaqus. Egenfrekvenserna visar sig vara betydligt högre än högsta skärfrekvensen, vilket verifierar att bearbetning inte sker i verktygets egenfrekvens. Finita elementmetoden är en mycket lämplig metod för att fastställa egenfrekvenser och därmed undvika bearbetningsvibrationer som uppstår p.g.a. resonans. Fräsverktygens differentialdelade skär ger dock en ständigt varierande frekvens, vilket tyder på att vibrationerna i fräsmaskinen troligtvis inte orsakas av resonansfenomenet. / The finite element method (FEM) is evaluated with the purpose of avoiding time consuming physical testing which is currently used for optimizing machine settings, both in new and existing machines. The studied milling machine machines crankshafts through eight machining steps. Resonance frequencies could be identified with a FEM-model and then be avoided by adjusting the cutting speed. The literature study includes machining through cutting, vibrations, oscillation theory and FEM. Crankshaft models are provided by the employer and eigenfrequency analyses are carried out with the software Abaqus, simulating the crankshaft mounted in the milling machine during all machining steps. The eigenfrequencies are compared to the cutting frequency from the milling tool. Milling with eigenfrequency occurs during machining step two. The influence on the vibrations is assumed to be small due to the variable teeth spacing on the tool. The machine will therefore only be machining in eigenfrequency every sixth cut. Vibration data created by the employer also indicate that vibrations are low during the machining step. Verification of the FEM-models is conducted through physical experiments with impact hammer testing. The test is carried out on a freely hinged crankshaft and compared to the FEM-results for a constraint-free crankshaft. The difference in eigenfrequency between the impact hammer test and the FEM-analysis is a maximum of 5 %, which demonstrates the reliability of the model. Furthermore a simplified model of the cutting tool is made and analyzed for eigenfrequencies in Abaqus. The eigenfrequencies are shown to be higher than the highest possible cutting frequency which confirms that the cutting tool is not machining in its own eigenfrequency. FEM is a useful method for determining eigenfrequencies and thereby avoiding machining vibrations caused by resonance. However, due to the variable teeth spacing the cutting frequency is constantly changing for the operation, which indicates that the vibrations are not caused by the resonance phenomena.

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