The stress effects of splinting configurations used with I-bar retained bilateral distal extension RPD the abutment teeth were periodontally involved have been studied. The purpose of this study was to photoelastically assess the effect of splinting on the stress induced in supporting structures by a distal extension I-bar RPD when all residual teeth were periodontally involved.
Three composite photoelastic models were made of a mandible bilaterally edentulous distal to the first premolars. Individual simulant materials were used for tooth structure, periodontal ligament, and alveolar bone. The alveolar bone configuration represented a normal periodontal condition, as well as horizontal bone loss of 20 and 35%. I-bar partial dentures with mesial restsand distal guide planes were fabricated for the three models.
Simulated vertical and lateral occlusal loads were applied to the dentures for the condition of the premolar abutment not splinted. The abutment teeth were then sequentially fixed splinted, so that all combinations of intra-arch splinting were studied. The stress patterns developed for each condition were recorded.

View full abstract

The bodies of steam turbine casings used at power plants are divided into top and bottom, in order to facilitate maintenance such as replacements and repairs. The two parts (top and bottom) are joined together with bolts in order to maintain internal pressure. As the structure is not a single unite, it is not an ideal pressure container. Analysis of contact stress at the flange contact surface of pressure containers is, therefore, especially important in terms of both safety and efficiently. This study investigated the safety of casings using the three-dimensional photoelastic stress freezing method and the Finite Element Method. We investigated safety aspects from the viewpoint of contact stress distribution, which is affected by, the distance between bolt holes, flange outside diameter, and changes in the position of bolt holes.

View full abstract

In the field of linear elastic fracture mechanics, the stress intensity factor approach has been widely accepted as a valid means for predicting the behavior of a material in the presence of a crack or flaw. To optimize their dimension and to ensure their safety in service, a practical study of the strength under centrifugal force is important. In this paper, it is investigated that the stress intensity factors K_I and K_II on the rotating elliptic disks having outside cracks by means of combining the photoelastic freezing method and the caustics method. Stress intensity factors K_I and K_II were determined by using two experimental methods, as a function of ellipticity of the elliptic disk (R₂/R₁=0.9, 0.8, 0.7, 0.6, 0.5) and at two different velocities. The results of these experimental methods was nearly agreement, and attracted the interest.

View full abstract

The stress distribution in bolts of variously bolted joints have been determined theoretically and experimentally. Theoretical stress distributions involved the determination of shear lag analyses from ratio of tensile rigidity of bolt and nut. By means of a theory of elasticity, loosening predictions were make for four specimens. Three-dimensional photoelastic experiments were conducted on one ordinary nut and three flange-lip nuts subjected to end load without torsional moment. The agreement between the theoretical results and the experimental values was found to be excellent.

View full abstract

In an elastic body under stress, it is important to know the place where a singular point or, more particularly, an isotropic point is present and the type of such isotropic point, for design of machines and structures, from the theoretical aspect of dynamics that the isotropic point is a dynamically stable place. However, it is difficult to know where the isotropic point is present because it often appears irregularly at an unexpected place.
The author previously reported the following two points as examples of the property of the isotropic point or the study that the isotropic point in an elastic body under a stress condition presents the following properties depending on the form and the load condition of the elastic body.
The one is the movement of isotropic point. This is the property that an isotropic point present at a certain place in an elastic body under a stress condition moves along a certain locus under a certain condition. The other property is the disappearance of isotropic point. This is the property that an isotropic point present at certain place in an elastic body under a stress condition disappears under a certain condition or, conversely, an isotropic point comes to appear at a certain place where there was no isotropic point was present.
In the present report, the result of study of the former property of isotropic point is presented with respect to an isotropic point in a strip with a circular hole as an example of movement of isotropic point.

View full abstract