Stress analysis of a stepped rounded D‐ring with a ratio of H1/H2 = 3.0 under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

Stresses occurring in a stepped rounded D‐ring designed to have a ratio of H₁/H₂ = 3.0 and compressed to 20% squeeze and pressurized with internal pressures of 0 MPa, 0.98 MPa, 1.96 MPa, 3.92 MPa, 4.9 MPa and 5.89 MPa are analyzed using photoelastic experimental hybrid method. It was observed that when a pressure of 0 MPa and 20% compression are applied, the photoelastic isochromatic fringes of the stepped rounded D‐ring with a ratio of H₁/H₂ = 3.0 were almost symmetrical. However, as the applied internal pressure increased, the circular portion of the D‐ring moved over the step on the front side along the points 1_r–2_r towards the restraining wall of the front side of the groove. During the motion of the circular portion, the space between the restraining wall and the step on the front side was slowly filled; but unlike the D‐ring with a ratio of H₁/H₂ = 1.0 where complete filling occurred earlier before extrusion, complete filling of this space delayed until the portion of the D‐ring near the extrusion gap extruded. It was further noted that an internal pressure of up to 5.89 MPa was required to initiate extrusion in the D‐ring with a ratio of H₁/H₂ = 3.0.     

A study on the behaviors and stresses of O-ring under uniform squeeze rates and internal pressure by transparent type photoelastic experiment

The behaviors and stresses of an O-ring under uniform squeeze rates and internal pressure change with real time. Therefore, the behaviors and stresses of O-rings under uniform squeeze rates and internal pressures should be studied with real time. To achieve this, a loading device for a transparent type photoelastic experiment, through which various internal pressures and uniform squeeze rates are applied, was developed. The validity of the loading device in analyzing the behaviors and stresses of the O-ring under uniform squeeze rates and internal pressures with real time was verified. It was observed that the filling phenomenon of the O-ring into the space between the lower and front side occurred after forcing out continued for a duration of time. The study also indicated that maximum shear stress would be more effective as a fracture parameter than the maximum normal stress fracture criterion for an O-ring made from rubber.     

A study on the analysis of O-ring under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

There are three kinds of loading conditions applied to the O-ring, The first loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the O-ring (the strain condition). The second loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the Oring and other squeeze rates are applied to the front side of the O-ring. The third loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the O-ring, other squeeze rates are applied to the front side of the O-ring, and internal pressures are applied to another front side of the O-ring(loading condition is the combination of stress condition and the strain condition). In this research, a new photoelastic experimental hybrid method under the third loading condition was developed and it was verified. The stresses of the O-ring under the third loading condition were analyzed by the new photoelastic experimental hybrid method developed in this research. The internal pressures applied to the O-ring were 0.98 MPa, 1.96 MPa, 2.94 MPa and 3.92 MPa. This paper was recommended for publication in revised form by Associate Editor Jooho Choi Jai-Sug Hawong received a B.S. degree in Mechanical Engineering from Yeungnam University in 1974. Then he received his M.S. degree and Ph.D. degree from Yeungnam University in Korea in 1976 and from Kanto Gakuin University in Japan in 1990, respectively. Prof. Hawong is currently a professor at the school of Mechanical Engineering at Yeungnam University, in Gyeongsan city, Korea. He is currently serving as an vise-president of Korea Society Mechanical Engineering. Prof. Hawong’s research interests are the areas of static and dynamic fracture mechanics, stress analysis, experimental mechanics for stress analysis and composite material etc.     

A study on the initial crack curving angle of isotropic/orthotropic bimaterial

In this paper, when the initial propagation angle of a branched crack is calculated from the maximum tangential stress criterion (MTSC) and the minimum strain energy density criterion (MSEDC), it is essential that you use stress components in which higher order terms are considered and stress components at the position in a distance 0.005 mm from the crack tip ( =γ . When an interfacial crack propagates along the interface at a constant velocity, the initial propagation angles of the branched crack are similar to the mode mixities (phase angle) and the theoretical values obtained from MTSC and MSEDC. The initial propagation angle of the branched crack depends considerably on the stress intensity factor K{IN2}.     

Contact stress of O-ring under uniform squeeze rate by photoelastic experimental hybrid method

In this paper, photoelastic experimental hybrid methods using the external traction free boundary condition and that using the relative equation of two stress functions in contact problems are developed. The validities of these two methods are confirmed through experiments and discussions. Hertz’s contact theory and the two photoelastic experimental hybrid methods explained are applied to the analysis of the contact stress of an O-ring under 10% or 20% squeeze rate. The photoelastic experimental hybrid method using the relative equation of two stress functions in contact problems was found to be more effective. When the squeeze rates of an O-ring were 10% or 20%, the maximum of absolute σ _x was greater than the maximum of absolute σ _y , but was almost equal. Maximums of absolute τ _xy were 1/8 of absolute σ _x and 1/5 of absolute σ _x when the squeeze rates of the O-ring were 10% and 20%, respectively. This paper was recommended for publication in revised form by Associate Jai-Sug Hawong received a B.S. degree in Mechanical Engineering from Yeungnam Uni-versity in 1974. Then he received his M.S. degree and Ph.D. degree from Yeungnam University in Korea in 1976 and from Kanto Gakuin University in Japan in 1990, respectively. Prof. Hawong is currently a professor at the school of Mechanical Engineering at Yeungnam University, in Gyeongsan city, Korea. He is currently serving as an vise-president of Korea Society Mechanical Engineering. Prof. Hawong’s research interests are the areas of static and dynamic fracture mechanics, stress analysis, experimental mechanics for stress analysis and composite material etc.     

Evaluation of O-ring stresses subjected to vertical and one side lateral pressure by theoretical approximation comparing with photoelastic experimental results

Contact and internal stresses of an elastomeric O-ring which is subjected to a vertical compression and lateral pressure at one side are evaluated experimentally and theoretically for a failure analysis and a life prediction. In the experiment, the O-ring specimen was made of epoxy resin. The applied fractional compression was 20% and the lateral pressure was varied as 1.96, 2.94 and 3.92 MPa. The photoelastic experimental hybrid method was used to obtain both the contact and internal stresses. To develop a theoretical approximation method for the stresses, the contact length and peak stress were evaluated by the conventional Hertz theory. It was found that the correction factors could resolve the difference between the experimental and theoretical results. In turn, the internal stress was evaluated by using the Flamant theory and a numerical approach. The pattern and values of the experimentally and theoretically obtained internal stresses also coincided well with each other.     

Internal stress analysis of a stepped rounded D-ring under a uniform squeeze rate and internal pressure using a photoelastic experimental hybrid method

Internal stresses occurring in a stepped rounded D-ring compressed to 20% squeeze and pressurized with internal pressures of 0, 0.98, 1.96, 2.94, 3.92 and 4.9 MPa are analyzed using a photoelastic experimental hybrid method. At a pressure of 0 MPa and 20% squeeze, the photoelastic isochromatic fringes of the stepped rounded D-ring were almost symmetrical. As the internal pressure increased, the isochromatics shifted and curved towards the extrusion gap. By supplying a radius of 0.33 mm at the corners of the stepped D-ring, the high stresses at the sharp corners were reduced by up to 25%. These results further indicate that extrusion of the stepped rounded D-ring occurred at an internal pressure of 4.9 MPa which was about 25% higher than the pressure at which the extrusion of the stepped unrounded D-ring occurred.     

3-Dimensional stress analysis of O-ring under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

Until now, studies have shown that stresses on the plane (y-z plane) perpendicular to the circumferential direction (x-axis) of an O-ring do exist. Stresses on the planes (x-y plane and x-z plane) parallel to the circumferential direction of the O-ring have not been reported to exist. In this study however, it is demonstrated through a 3-dimensional stress analysis that stresses on the x-y plane and x-z plane of the O-ring under uniform squeeze rate and internal pressure do exist. Therefore, to study effectively 3-dimensional stress distributions of an O-ring under these loadings, stress distributions of every plane should be analyzed. This study develops a photoelastic experimental hybrid method to analyze 3-dimensional stress distributions of an O-ring under uniform squeeze rate and internal pressure, and uses it to determine the stress distributions in every plane, including the Von Mises equivalent stresses, at any arbitrary point of the O-ring under uniform squeeze rate and internal pressure.     

Study on contact stresses of un‐stepped rounded D‐ring under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

The stresses that occur in an un‐stepped rounded D‐ring loaded with various internal pressures and compressed to a 20% squeeze rate are analyzed using photoelastic experimental hybrid method. The analysis shows that the contact stresses on both the upper and front sides of the D‐ring increase as the applied internal pressure increases with the magnitudes of σ_X and σ_Y being considerably higher than those of τ_XY. At a pressure of zero and 20% compression, the isochromatic fringe patterns of the un‐stepped D‐ring are almost symmetrical. However, as the internal pressure applied to the D‐ring increases the isochromatic fringe patterns shift and curve smoothly towards the extrusion gap making the upper and front sides to be more stressed than the lower side. At a pressure of 1.96 MPa and above, the contact stresses on the upper side were found to be almost constant along the contact length. By supplying a fillet radius of 2.1 mm at the corners of the un‐stepped D‐ring the high stresses at the corners were reduced by up to 45%. The results from the study further demonstrated that the un‐stepped rounded D‐ring with a ratio of r/d = 0.3 to be can be an alternative choice to the O‐ring for sealing applications. Interestingly, the pressures that the un‐stepped D‐ring can withstand before extrusion are higher than those of an O‐ring.     

Evaluating the stresses of a stepped unrounded D-ring under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

The stresses that develop in a stepped unrounded D-ring loaded with internal pressures at a 20% squeeze rate are analyzed using the photoelastic experimental hybrid method. The analysis demonstrated that the contact stresses on both the upper and front sides of the Dring increased as the applied internal pressure increased, with the magnitudes of ??_X/p_i and ??_Y/p_i being considerably higher than those of ??_XY/p_i. Moreover, as applied internal pressure increased, the semi-circular portion of the D-ring moved to fill the space ahead of the step before contacting the restraining wall of the front side. The order of magnitude of stresses in region 1 of the front side of the D-ring was lower than those in region 2. At an internal pressure of 3.92 MPa, the contact stresses on the upper side decreased before increasing again at points away from the region of extrusion. The study further showed that a sharp corner in the geometry of the D-ring does not contribute to the generation of detrimental stresses that may lead to failure of the D-ring before extrusion.