For the needle valve sealing cone bottom diameter of 0.3 mm, the load P₠is 228 ± 1.4 N, representing the elastic force at full lift. The internal boring machine uses oil injection and control with a pressure PZ = 12.55 (x 10^0.7) × 9.8315 ± 15.5 N. The formula for calculating the spring shear stress T is given by T = (SPIDK7rd³)/2, which results in 523.5 N/mm². The shear stress r is 23.5 N/mm². When the number of load cycles reaches N = 10, the r.Ac line represents the maximum stress line and corresponds to the torsional yield limit.
From the origin, the ray r-i is used as a reference, and point E on this line is the working stress point of the spring. The intersection of this ray with the AC line at point G defines the limit stress point under an asymmetric cycle. By analyzing the similar triangles △AGH and △CGF, the ultimate stress of the projectile can be determined. The maximum stress distribution is 13.85, with a value of 723.5 N/mm². The stress of the asymmetric spring is an asymmetric cyclic stress, and its cycle characteristic is constant at 0.7238.
The limit of the asymmetric cycle should be considered carefully. The maximum stress value of the asymmetric cycle characteristic r is used to determine the ultimate stress rlim via the Goodmann limit stress diagram. The point C, located at 1079 N/mm², represents the material's torsion strength. The OC line forms a 45-degree angle with the abscissa, acting as the minimum stress line. Since the minimum and maximum stresses are equal on this line, it is referred to as the static stress line. Point A on the vertical axis represents the material’s pulse fatigue limit, set at 506.6 N/mm². The coefficient of variation of the ultimate stress and the material strength are also taken into account.
Similarly, the standard deviation of the asymmetric cycle’s ultimate stress is calculated using the formula S = σ₀.014, resulting in Sr = 12.293. The reliability of the spring depends on the normal distribution of both material strength and working stress. In actual spring manufacturing, shot peening and strong pressure treatment are commonly used to enhance fatigue strength. The shot peening diameter typically ranges from 0.75 to 1.0 mm, often around 0.8 mm, and is usually made of steel. During the firing process, the projectile speed is between 50–84 m/s, and the fatigue strength of the spring improves after shot peening.
Strong pressure treatment of the spring can increase its strength by up to 535% under the same working conditions. Data shows that the spring treated with shot peening and strong pressure has a fatigue strengthening coefficient k = 1.3. Using a Z table, it is evident that the reliability R > 0.999999, making the failure probability F = 1 - R < 1×10â»â¶. The reliability safety factor n is 7:2, corresponding to 21.25. Based on these calculations, the design and material selection for the injector pressure regulating spring are deemed reliable.
The flow area negatively affects the dynamic sealing performance of the hydrodynamic valve. As a result, the valve's lift and sealing hydraulic power tend to cause it to close, so the taper angle must be properly matched to ensure good dynamic characteristics and response time. At the same time, rapid discharge is achieved. The size of the valve is influenced by various factors such as the valve core structure, overcurrent area, and input voltage. Increasing the input voltage appropriately and reducing the winding turns reasonably can optimize performance.
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