Determination of Stress Intensity Factor for Interface Crack under Uniform Heat Flow by Crack Tip Stress Method

This paper deals with the analysis of the thermal stress intensity factor for interfacial crack in dissimilar materials under uniform heat flow by using the finite element method. This method is based on the fact that the singular stress field near the interface crack tip is controlled by the stress values at the crack tip node calculated by FEM. The calculation shows that the present method has the sufficient accuracy in the interface crack problems under thermal stress.23rd International Congress of Theoretical and Applied Mechanics, August 19-24, 2012, Beijing, Chin

Accurate stress intensity factors for kinked interface crack in bonded dissimilar half-plane

In this study, the stress intensity factor (SIF) of an interface kinked crack is analyzed by the singular integral equation of the body force method. The problem can be expressed by distributing the body force doublets of the tension and shear types along all the boundaries of the kinked and interface crack parts. The SIFs can be obtained directly from the densities of the body force doublets at the crack tips. Although the problem has already been calculated using the crack connection model, the accuracy of the analysis has not been clarified. From the analysis results in this study, it can be seen that the SIFs calculated by the crack connection model have a nonnegligible error, and the present method gives more accurate results. The advantage of the present method is that the SIFs of the kinked and the interface crack tips can be obtained at the same time with high accuracy

Coming out prevention by stopper for the shrink fitted sandwiched shaft from the ceramic sleeve

Ceramic roller can be used in the heating furnace conveniently because of its high temperature resistance. The roller consists of sleeve and steel shaft connected only under a small shrink fitting ratio because of the brittleness. However, the coming out of the shaft may often happen from the ceramic sleeve under repeated bending load. Therefore, how to prevent the coming out failure becomes an important issue. Based on the previous study, a two-dimensional shrink fitted structure is considered by replacing the shaft with the inner plate and by replacing the sleeve with the outer plate. Then, this research focuses on preventing the inner plate coming out from the outer plate by introducing a newly designed stopper on the outer plate. The simulation results shows that the coming out phenomenon can be prevented effectively due to the contact between the inter plate and the stopper installed on the outer plate. In order to evaluate the contact force between the inner plate and the stopper, the coming out mechanism is clarified. To prevent the coming out by stopper safely, the effects of the magnitude of repeated load and the friction coefficient upon the contact compressive force are investigated under large number of loading cycles by using 2D simulation.12th International Conference on Damage Assessment of Structures, 10–12 July 2017, Kitakyushu, Japa

Macroeconomic Impact of Population Aging in Japan: A Perspective from an Overlapping Generations Model

Due to a sharp decline in the fertility rate and a rapid increase in longevity, Japan's population aging is the furthest advanced in the world. In this study we explore the macroeconomic impact of population aging using a full-fledged overlapping generations model. Our model replicates well the time paths of Japan’s macroeconomic variables from the 1980s to the 2000s and yields future paths for these variables over a long horizon. We find that Japan’s population aging as a whole adversely affects GNP growth by dampening factor inputs. It also negatively impacts on GNP per capita, especially in the future, mainly due to the decline in the fraction of the population of working-age. For these findings, fertility rate decline plays a dominant role as it reduces both labor force and saver populations. The effects of increased longevity are expansionary, but relatively minor. Our simulations predict that the adverse effects will expand during the next few decades. In addition to closed economy simulations, we examine the consequences of population aging in a small open economy setting. In this case a decline in the domestic capital return encourages investment in foreign capital, mitigating the adverse effects of population aging on GNP

Stress intensity factor solution for edge interface crack based on the crack tip stress without the crack

In this paper, a new solution is discussed for the stress intensity factor of an edge interface crack. The intensity of the singular stress field (ISSF) at the interface end before appearing the edge interface crack is distinguished from the stress intensity factor (SIF) of the interface crack itself. By considering those two distinct double singular stress fields, the ISSF and the SIF are discussed under arbitrary material combinations. By focusing on the crack tip stress without the interface crack σy(a), the SIF of the edge interface crack can be expressed conveniently. This is because the crack tip stress without the interface crack is reflecting the ISSF at the interface end. The SIFs based on the crack tip stress without the interface crack are indicated by varying the crack length and material combination. It is found that the normalized SIFs (F1,int and F2,int) based on σy(a) are independent of the geometrical condition for the wide range of the crack length

Effects of root radius and pitch difference on fatigue strength and anti-loosening performance for high strength bolt–nut connections

The fatigue strength improvement and anti-loosening performance are studied experimentally and analytically for JIS M16 bolt–nut connections. Three different root radii are considered coupled with three different pitch differences. The enlarging the bolt root radius improves the fatigue limit of the bolt by more than 30% because both stress amplitude and mean stress can be reduced. Furthermore, suitable pitch difference improves the fatigue limit by more than 25%. This is because under no pitch difference the crack initiation always occurs at No.1 or No.2 threads close to the bolt head causing the final failure; however, under a suitable pitch difference the crack initiation occurs at No.6 or No.7 threads far away from the bolt head. Good anti-loosening performance can be expected for the bolt–nut connections having enlarged root radius because the prevailing torque TP = 19 Nm and the residual prevailing torque TuP=10Nm are not smaller compared to other special bolt–nut connections

Importance of absorbable surgical sutures for the prevention of stitch abscess after surgery in patients with oral squamous cell carcinoma

To elucidate the significance of absorbable surgical sutures in the occurrence of stitch abscess after surgery in patients with oral squamous cell carcinoma (SCC). The subjects were 251 patients who underwent excision and/or reconstruction and/or neck dissection for oral SCC using absorbable surgical sutures. Detection rates and characteristics of patients with stitch abscess were retrospectively evaluated by comparing between our present and previous data. There was only one stitch abscess among the 251 patients. A significant difference in the incidence of stitch abscess was found between the present data and our previous data. Of course, no significant correlations were found between the occurrence of stitch abscess using absorbable surgical sutures and the various factors seen in our previous analysis. A complete switch of surgical sutures from silk to absorbable surgical sutures is needed for surgery in patients with oral SCC

Advanced Clinical Usefulness of Ultrasonography for Diseases in Oral and Maxillofacial Regions

Various kinds of diseases may be found in the oral and maxillofacial regions and various modalities may be applied for their diagnosis, including intra-oral radiography, panoramic radiography, ultrasonography, computed tomography, magnetic resonance imaging, and nuclear medicine methods such as positron emission tomography. Of these modalities, ultrasound imaging is easy to use for the detection of noninvasive and soft tissue-related diseases. Doppler ultrasound images taken in the B-mode can provide vascular information associated with the morphology of soft tissues. Thus, ultrasound imaging plays an important role in confirming the diagnosis of many kinds of diseases in such oral and maxillofacial regions as the tongue, lymph nodes, salivary glands, and masticatory muscles. In the present article, we introduce three new applications of ultrasonography: guided fine-needle aspiration, measurement of tongue cancer thickness, and diagnosis of metastasis to cervical lymph nodes