Thermal cutting methods, are commonly used in the manufacture of metal parts.Thermal cutting processes separate materials by using heat. The process can be donewith or without a stream of cutting oxygen. Common processes are Oxygen, plasma andlaser cutting. It depends on the application and material which cutting method is used.Numerically-controlled thermal cutting is a cost-effective way of prefabricatingcomponents. One design aim is to minimize the number of work steps in order toincrease competitiveness. This has resulted in the holes and openings in plate partsmanufactured today being made using thermal cutting methods. This is a problem fromthe fatigue life perspective because there is local detail in the as-welded state that causesa rise in stress in a local area of the plate. In a case where the static utilization of a netsection is full used, the calculated linear local stresses and stress ranges are often over 2times the material yield strength. The shakedown criteria are exceeded.Fatigue life assessment of flame-cut details is commonly based on the nominal stressmethod. For welded details, design standards and instructions provide more accurateand flexible methods, e.g. a hot-spot method, but these methods are not universallyapplied to flame cut edges.Some of the fatigue tests of flame cut edges in the laboratory indicated that fatigue lifeestimations based on the standard nominal stress method can give quite a conservativefatigue life estimate in cases where a high notch factor was present. This is anundesirable phenomenon and it limits the potential for minimizing structure size andtotal costs.A new calculation method is introduced to improve the accuracy of the theoreticalfatigue life prediction method of a flame cut edge with a high stress concentrationfactor. Simple equations were derived by using laboratory fatigue test results, which arepublished in this work. The proposed method is called the modified FAT method(FATmod). The method takes into account the residual stress state, surface quality,material strength class and true stress ratio in the critical place.
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