Symptomatic spinal epidural lipomatosis is a rare disorder characterized by overgrowth of fat in the extradural space. Most patients have an underlying endocrine disorder, such as Cushing's syndrome, or have taken exogenous steroids chronically. Although less common, obesity alone is thought to be a cause of spinal epidural lipomatosis, representing <25% of reported cases. Patients rarely become symptomatic before middle age without chronic exogenous steroid use. The usual clinical manifestations are similar to degenerative lumbar stenosis with neurogenic claudication, resulting in decreased walking and standing endurance with variable neurological deficits.This article describes 2 unique cases of spinal epidural lipomatosis, both in young patients with underlying morbid obesity who presented with acute progressive leg weakness and urinary retention. The patients had no underlying endocrinopathy, nor any history of exogenous steroid use. They underwent emergency laminectomy and removal of epidural fat, and histopathological examination confirmed the diagnosis of epidural lipomatosis. Postoperatively, the patients demonstrated significant improvement.We conducted a review of the available English literature and compared the age distribution in each group. Based on our review, our 2 patients are considerably younger than those in past reports, especially in the patient group to which the steroid was not administered. In addition, few cases exist of spinal epidural lipomatosis with acute sphincter dysfunction and paraparesis. Our cases suggest that morbid obesity can lead to juvenile spinal epidural lipomatosis with acute neurological changes.

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Temperature and thermal stress in cylindrical vessels were analysed for the thermal stratification of contained fluid. Two kinds of temperature analysis results were obtained such as the exact temperature solution of eigenfunction series and the simple approximate one by the temperature profile method. Furthermore, thermal stress shell solutions were obtained for the simple approximate temperatures. Through comparison with FEM analyses, these solutions were proved to be adequate. The simple temperature solution is described by one parameter that is the temperature decay coefficient. The thermal stress shell solutions are described by two parameters. One is the ratio between the temperature decay coefficient and the load decay coefficient. Another is the nondimensional width of stratification. These solutions are so described by few parameters that those are suitable for the simplified thermal stress evaluation charts. These charts enable quick and accurate thermal stress evaluations of cylindrical vessel of this problem compared with conventional methods.

The prevention of excessive deformation by thermal ratcheting is important in the design of high-temperature components of fast breeder reactors (FBR). In an experimental study that simulated a fast breeder reactor vessel near the coolant surface, it was reported that the long distance travel of temperature distribution causes a new type of thermal ratcheting, even in the absence of primary stress. In this paper, we propose a simple screening criterion to prevent continuous accumulation of plastic strain derived from long distance travel of temperature distribution. The major cause of this ratcheting is the lack of residual stress that brings shakedown behavior at the center of yielding area. Because residual stresses are derived from constraint by the neighboring elastic region, we focused on the distance from the center of yielding area to the elastic region. Accordingly, the proposed criterion restricts the axial length of the full-section yield area, which is the double of the above distance. We validated the proposed criterion based on finite element analyses using an elastic-perfectly plastic material. As a result of the validation analyses, we confirmed that the accumulation of plastic strain saturates before second cycles in the cases satisfying the proposed criterion, regardless of the shape of temperature distribution.

Crack initiation and propagation process of fatigue test in semicircular notched plates at elevated temperature were conducted under strain-controlled condition in order to study the crack initiation/propagation/coalescence process and load decrease in structure having stress concentration. Test specimens made of SUS304 stainless steel are tested at 550°C and the geometry of the semicircular notched plate specimens are changed by diameter size of the circular notch in both of single-notched specimens and double-notched specimens. Photographs in all cycles were recorded to investigate crack initiation/propagation/coalescence as a function of number of applied cycle. The typical crack process is predicted by using the simplified method, namely, stress redistribution locus method as well as Neuber’s formula.