Contact Analysis and Simulation of Rolled Plastic Film Used for Roof Ventilation in Japanese Greenhouses

Greenhouses are capable of producing a variety of high-value crops year-round. A novel Japanese greenhouse design is gaining popularity because of its automated roll-up ventilation system that is integrated into the roof. However, due to the frequent movement of the roll-up system, the plastic film deteriorates rapidly and typically lasts for only three or four months. In order to better understand the film deterioration, we studied the mechanics involved at the point of contact between the film and the metal greenhouse frame. We found that film deformation and failure were closely related to stretching and creasing, and these processes were observed at the microscopic level. An experimental device was developed to further study the damage to greenhouse film due to the roll-up movement. We concluded that the reduction in film thickness due to static loading or rolling contact was the best predictor of future film damage

Analysis of Multiple Interfacial Cracks in Three Dimensional Bimaterials Using Hypersingular Integral-Differential Equation Method

By using the concept of finite-part integral, a set of hypersingular integro-differential equations for multiple interfacial cracks in a three-dimensional infinite bimaterial subjected to arbitrary loads is derived. In the numerical analysis, unknown displacement discontinuities are approximated with the products of the fundamental density functions and power series. The fundamental functions are chosen to express a two-dimensional interface crack rigorously. As illustrative examples, the stress intensity factors for two rectangular interface cracks are calculated for various spacing, crack shape and elastic constants. It is shown that the stress intensity factors decrease with the crack spacing

Intensity of Singular Stress Field over the Entire Bond Line Thickness Range Useful for Evaluating the Adhesive Strength for Plate and Cylinder Butt Joints

Our previous research has indicated that the bonded strength can be expressed in terms of the intensity of the singular stress field (ISSF). Since the ISSF is quite useful for evaluating the bonded strength, in this study, the variation of the ISSF is investigated over the entire bondline thickness range of plate and cylinder butt joints. Here, an effective mesh-independent technique combined with a standard FEM approach is used to obtain the ISSFs under arbitrary material combinations. A reference solution of simply bonded plate is used to eliminate FEM error since the exact ISSF is available. This paper clarifies the differences between the fracture behaviors of the bonded plate and cylindrical butt joints

Most suitable evaluation method for adhesive strength to minimize bend effect in lap joints in terms of the intensity of singular stress field

The lap joint testing is designed to investigate the adhesive strength under pure shear loading. However, actually pure shear testing is very difficult to be realized in the experiment because of the bend deformation during testing causing the peeling force appearing at the adhesive region. To reduce the bend effect, this paper focuses on the intensity of singular stress field (ISSF) at the interface end in order to minimize the ISSF for lap joints. The results show that the ISSF decreases with increasing the adherend thickness. The minimum ISSF is obtained when the adherend thickness is large enough with the small deformation angle defined at the interface end. Since the strength of double lap joint (DLJ) is sometimes about two times larger than the strength of single lap joint (SLJ), the equivalent strength condition is discussed by changing adherend thicknesses of DLJ and SLJ. It is found that the strength of SLJ with adherend thickness t1=7 mm is nearly equal to that of double lap joint with t1=1.5 mm prescribed in Japanese Industrial Standard

Recent Results from LHD Experiment with Emphasis on Relation to Theory from Experimentalist’s View

he Large Helical Device (LHD) has been extending an operational regime of net-current free plasmas towardsthe fusion relevant condition with taking advantage of a net current-free heliotron concept and employing a superconducting coil system. Heating capability has exceeded 10 MW and the central ion and electron temperatureshave reached 7 and 10 keV, respectively. The maximum value of β and pulse length have been extended to 3.2% and 150 s, respectively. Many encouraging physical findings have been obtained. Topics from recent experiments, which should be emphasized from the aspect of theoretical approaches, are reviewed. Those are (1) Prominent features in the inward shifted configuration, i.e., mitigation of an ideal interchange mode in the configuration with magnetic hill, and confinement improvement due to suppression of both anomalous and neoclassical transport, (2) Demonstration ofbifurcation of radial electric field and associated formation of an internal transport barrier, and (3) Dynamics of magnetic islands and clarification of the role of separatrix

Cardiovascular reactions for whole-body thermal therapy with a hot pack and Waon therapy

Background Waon therapy (WT) is the predominant thermal therapy for chronic heart failure in Japan, involving use of a far-infrared dry sauna. As sauna therapy requires certain equipment not readily available in hospitals, we tested the use of whole-body hot pack thermal therapy (HPTT). We compared the magnitude of skin vasodilation post-HPTT with that post-WT. Methods We recruited 19 healthy men (age [mean ± S.D.]: 26.8 ± 4.6 years) and employed a simple randomized crossover design. The HPTT required subjects to remain in a supine position on a bed for at least 10 min. Hot packs were then applied on the back, lower abdomen, and popliteal regions for 15 min (warming phase). Participants continued bed rest for 30 min (heat-retention phase) after removal of the hot pack. WT was performed as previously described. Blood pressure (BP), heart rate (HR), tympanic temperature (TT), and peak and average flow velocity of the right radial artery (PFV and AFV, respectively) and right brachial artery (BA) diameter were measured during HPTT and WT. Results HR, TT, PFV, and AFV persistently and significantly increased during warming and heat-retention phases of HPTT. In WT, HR and TT significantly increased during warming but decreased and plateaued during heat-retention. BP did not change significantly after either therapy; however, BA was dilated equally in both (HPTT: 3.70 ± 0.57 ⇒ 4.05 ± 0.59 mm, p = .001; WT: 3.63 ± 0.63 ⇒ 3.93 ± 0.61 mm, p < .001). Conclusion HPTT may be equivalent to WT with respect to vasodilation response of the skin

Residual Stress Differences between Uniform and Non-Uniform Heating Treatment of Bimetallic Roll: Effect of Creep Behavior on Residual Stress

The work roll is one of the most important tools in the steel rolling industry. Work rolls are used under extremely severe conditions such as high temperature, high loading, and an aggressive atmosphere. To meet those demands, bimetallic rolls have recently been used to replace conventional single material rolls. Usually, a compressive residual stress is introduced to prevent surface cracking. However, a tensile residual stress at the center appears to balance the compressive residual stress. This center residual stress sometimes causes roll failure. In this paper, therefore, a simulation is performed using the finite element method (FEM) for the quenching process of the bimetallic roll by considering the creep behavior. Then the effect of pre-heating conditions is discussed. The results show that the maximum stress point for the tensile stress at the roll center for non-uniform heating is 24% less than that achieved with uniform heating, although the same compressive stresses appear at the surface. Then, using different work roll diameters, the center tensile residual stress for non-uniform heating is found to be smaller than the uniform heating. Also, it is found that the area ratios of the shell-core only have a small influence on the residual stress of the bimetallic roll for both heating treatments