Thermoplastic resins, which are lighter than metals and ceramics, have many features such as excellent processability. They are used in widely various fields for daily necessities and for transportation equipment. Even for the same material, the elastic properties of the thermoplastic resin can vary depending on the molecular weight, molding temperature and conditions. Therefore, the elastic properties required for structural analysis must be evaluated each time. After this study derived a formula for yield initiation stress of injection-molded thermoplastics, the formula was applied for a method of obtaining the longitudinal elastic modulus and Poisson's ratio from results of a three-point bending test. From actual examination using polypropylene (PP) and polystyrene (PS), the calculated longitudinal elastic modulus and Poisson's ratio showed good agreement with literature values. Results clarified that these values depend on the injection molding temperature. Furthermore, the bulk modulus and shear modulus were obtained from the longitudinal modulus and Poisson's ratio. Their injection molding temperature dependences were investigated. The shear modulus showed the same tendency as that of the longitudinal elastic modulus, but results indicated the dependence of bulk modulus as small in PP: bulk modulus of PS increased with increasing injection molding temperature.
Annular Blowout Preventer (BOP) is the core device for snubbing service in gas wells. The wellhead can be sealed by operating the BOP. Rubber core of annular BOP is the main part of the sealing process, and its failure will cause blowout accidents and endanger the operators. Rubber core failure is mainly caused by the serious wear and fracturing damage, compared with oil well, during the snubbing service of the gas well, there is dry friction between rubber core and tubing, which is more prone to rubber core wear. Based on the Yeoh constitutive model, this paper fits the material parameters through the data measured by the rubber tensile experiment, and establishes the sealing performance evaluation model of the annular BOP based on the theory of rubber hyperelastic, large deformation theory and dynamic sealing theory. Meanwhile, compare it with the rubber core failure cases which used in field to verify the accuracy of the model. Based on these, this paper studies the influence of piston stroke, tubing size, friction coefficient between rubber core and tubing, rubber core attrition rate on sealing performance, and fitting the relationship between tubing size and piston stroke. The results show that: properly increasing the piston stroke by 2 to 3 mm will help to improve the sealing performance; when the tubing size is smaller, the rubber core is deformed too much while the seal process completed, which is easy to cause the rubber core to fracturing; friction coefficient between rubber core and tubing has no significant effect on static sealing performance; the friction coefficient less than 0.2 has little effect on the dynamic sealing performance; when the friction coefficient exceeds 0.4, the dynamic sealing performance is reduced significantly; when the wear of rubber core is within 10 mm, the sealing performance gradually decreases, but the sealing requirements can still be met. When it is more than 10 mm, it cannot meet the sealing requirements of 35 MPa. The research work in this paper has certain guiding significance for the design, selection and use of the rubber core of annular BOP.
The axisymmetric problem of a multi-layer composite with a penny-shaped crack, which is parallel to the interface between elastic layers, in the center plane is considered. It is assumed that each elastic layer, which has a unique elastic constant, is perfectly bonded to its adjacent elastic layers. The multi-layer composite is subjected to uniform internal pressure on the crack surface. The dual integral equations obtained for the problem are reduced to an infinite system of simultaneous equations by expressing the normal displacements on the crack surface as an appropriate series function. The boundary conditions between adjacent elastic layers can be generally formulated using the transfer matrix method. Numerical results were obtained in hard- and soft-layer composite systems, for which the elastic properties of each layer linearly increase and decrease towards the crack plane, respectively. This study shows not only the results of the mode I stress intensity factor at the crack tip, but also the distribution of normal stress and displacement at the crack plane. Furthermore, sandwich structures composed of three materials with different mechanical properties were considered. Numerical calculations show several conclusions that a stiffer layer should be placed father away from the crack surface to decease the stress intensity factor and the hardness of the middle layer contributes to the stress intensity factor for the sandwich structures.
The in-cylinder flow in diesel engines significantly affects fuel-air mixing, combustion, and emissions. The present study investigates how engine properties such as the engine speed and intake port affect the swirl flow of a single cylinder diesel engine. Using the obtained velocity data, the strength of the swirl flow was calculated and represented by swirl ratio. It is observed from experiments that, the swirl flow of a diesel engine is affected by changing the engine speed and the area of the intake port, in which the center position of the swirl flow was identified during intake and compression strokes. Besides, the in-cylinder flow is also affected by the opening area of the helical port such that when the opening increases, the center of swirl flow moves away from the center of cavity and the swirl ratio becomes smaller. Furthermore, by reducing the aperture of the helical port a more stable swirl was acquired. The obtained experimental results revealed that, the tangential port which generates a large-scale intake flow interacted with the small-scale swirl flow generated by the highly tilted helical port. Additionally, the inflow created by the helical port disturbed the swirl flow generated by the tangential port. The results also illustrated that the tangential port showed a higher amount of turbulent kinetic energy inside the piston concavity. In addition, tangential port leads the turbulent kinetic energy toward the outer periphery and helical port resulted to the inner side of piston concavity.
This paper describes a design method of a friction reducer device using a loading cam to suppress unstable vibration. Nonlinear simulation and energy analysis of numerical solutions demonstrates that destabilization is caused by the large phase difference between the slipping velocity in the translation direction and that in the rotation direction. It was found that similarly unstable vibration occurs in various structures using wedge rollers with translational and rotational motion. The analytical equation could be simplified by focusing on the motion factor that affects the slip velocity of the power transmission surface, which is the factor of vibration. Consequently, the design method for suppressing vibration could be expressed by a mathematical formula. This equation is validated by using the results of experiments conducted in the previous work of the current authors. Furthermore, from this equation, we proposed that vibration could be suppressed by the parameter balance of the power transmission device without using damping. The power transmission surface slips when a quick torque is input and damping is used. The proposed design can handle a quick torque response and reduce the weight of the reducer. Specifically, the shape of the wedge roller is made lighter, so that the moment of inertia of the roller is not lowered, or the wedge roller is set as a small roller.
This study concerned the circular path-following control of a vehicle. For a circular path, two methods can be applied to the vehicle system, namely, rotational coordinate transformation and expansionary coordinate transformation. Via numerical simulations of the application of these two methods, we discovered that the former provides undershoot in its initial response; however, this does not appear if the latter method is also applied to the former. The undershoot phenomenon is undesirable for tracking control. In order to investigate the reason for the occurrence of the undershoot phenomenon, a condition for the undershoot was derived from an analysis of the first step response in the control system model. The obtained condition depended on the relationship between the initial value and the target value of the vehicle. As a result, we found that the former method satisfied the undershoot condition. Second, we analyzed the condition for the method which included expansionary coordinate transformation, and we found that this approach includes additional feedforward control input in comparison with the former method. Subsequently, we demonstrated that the feedforward input allowed the latter system to avoid undershoot.
In recent years, with the maturing of society and advances in technology, consumers' demand for manufacturing has been increasing. Of particular note in demand is the appearance quality of the product. Under visual inspection at the time of manufacture, skilled workers have classified the causes of defects in the product's appearance according to their experience and have dealt with them quickly. Due to a serious shortage of workers and the aging of skilled workers, there are many opportunities for inexperienced workers, such as foreign technical interns, to take charge of the work at manufacturing sites. While introducing "automatic visual inspection by a camera," the authors have developed a system that can automatically classify the causes of defects. Also, when the classification work was carried out for the inexperienced workers, the application to the education was seen. The authors propose a classification method based on machine learning with skilled workers' knowledge. This paper analyzes the process of classifying production data into the causes of contaminated products (CP) by skilled workers. First, the occurrence interval of CP was divided into sparse or dense groups. Second, a decision tree learned from causes' labels with a skilled worker was developed as a group label classifier (GLC). When production data were used to validate the prediction capability, high accurate predictions were obtained. This indicates that even inexperienced workers can take measures according to the cause of product defects during production, which is useful for the education of field workers by the GLC.
In order to synthesize a human-friendly flexible machine with a simple structure, multi-directionally flexibly constrained revolute pair (MFCRP), which is a revolute pair with a flexible kinematic constraint in multiple directions, has been proposed as a novel type of a kinematic pair. However, since the relative motion between two links of the MFCRP is limited to the one pattern, the concept of MFCRP is extended as a ”flexibly constrained pair” (FCP) and its design method to achieve the specified relative motion including translational motion is proposed. Firstly, a method to specify the relative motion between the links is proposed, where DOF between the links is divided into main-DOF and sub-DOF and the main relative motion is specified. Next, a design method of the flexible constraint to achieve the specified difference in stiffness between the main-DOF and sub-DOF is proposed, here linear springs are optimally arranged to reduce stiffness in main-DOF and the specified non-linear stiffness is implemented in sub-DOF by designing the contact surfaces between the links. Some examples of the FCPs including MFCRP are designed with the proposed design method as demonstration. Then, an example is prototyped and examined by some experiments to confirm validity of the proposed design method.
The semi-dry plasma and chemical hybrid process (PCHP) has been used for the simultaneous removal of NOx and SOx emitted from a glass melting furnace. In this study, PCHP was conducted through a laboratory-scale model experiment that simulated the aftertreatment system of a full-scale semi-dry glass bottle manufacturing system. The process consisted of two methods: the plasma process in which NO is oxidized using nonthermal plasma and the chemical process in which NO2 produced from NO oxidation is removed using Na2SO3 resulting from the reaction between SO2 and NaOH. Herein, the position of ozone injection was transferred to the inside wall of the reactor to improve the efficiency of simultaneous denitrification and desulfurization through the efficient oxidation of NO. First, NO removal experiments were conducted by changing the spray position, spray liquid flow rate, and flow rate of a mixed simulated gas of NO and SO2. Therefore, over the gas flow rate range from 5 to 15 L/min, the localized cooling area where NO and O3 could be efficiently reacted at the nozzle spray position of z = 400 mm was formed. A NOx removal efficiency of 74% with a ratio of decreased NO to injected O3 (ΔNO/O3) of 88% and SO2 removal efficiency of 100% were achieved by injecting O3 from the inside wall of the reactor when the liquid-gas ratio was 1.17 L/m3.