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Drive Pins Size Ladder

Jun 12, 2017

Drive Pins Size ladder

Reciprocating pump drive pin basic situation reciprocating pump drive pin overall structure for the slender size of the diameter ladder. Pin in the process of reciprocating motion, due to the fork pull, shear force and fork contact surface friction, will inevitably bear the pull, pressure alternating stress. The most sensitive to the effect of this alternating stress is the path and the large diameter transition, the so-called stress concentration. In fact, from the use of the pump pin failure records found in the fracture, the phenomenon all occurred in this area. Therefore, to change the structure of this part is imperative, from the increase in strength, to overcome or reduce the stress concentration to consider improvements. Transmission pin in the process of reciprocating motion, due to the fork pull, shear force and fork contact surface friction, the drive pin diameter wear serious.

Reciprocating pump transmission pin fault analysis on the reciprocating pump drive pin failure, I first thought that may be used to drive the material selection is not appropriate (material for the 45 steel). The strength does not reach the allowable stress required for work

, So the original damage to the transmission pin was analyzed, and then found that the original drive pin allowable stress: [󰀁] = 󰀁 sns = 353MPa1.8 = 196.11MPa which: 󰀁 s, 45 steel yield strength. Ns, safety The coefficient value is taken as ns = 1.8 and then the pressure of the reciprocating pump to the drive pin is analyzed. It is found that the stress on the drive pin is less than the allowable stress of the 45 steel [󰀁] 45 steel = 353MPa. This shows that the choice of transmission material is perfectly suitable. So the material of the drive pin is no problem at all. So only the structure of the transmission pin there is a problem. The structure of a reasonable drive pin design requirements: (1) can facilitate the installation; (2) the original location can not be changed; (3) long service life. Conventional use of the size of the transmission pin diameter connection for the right angle, a large number of test results and the theory shows that the cross section straight rod by axial stretching or compression, the cross-section of the stress is evenly distributed. Sometimes stress is not evenly distributed on the cross-section of a sudden change in the size of the part, and the stress will increase sharply in the vicinity of the sudden change in size. The maximum stress on the cross section of the stress concentration is 󰀁max, and the average stress on the same section is: The ratio K = 󰀁max 󰀁 is called the theoretical stress concentration factor, which reflects the degree of stress concentration, which is greater than 1 Of the coefficient: the test shows that the cross-sectional size changes the more dramatic, the more concentrated stress concentration. The stress at the drive path is:

󰀁 = NA = 834N25󰀁10 -3 = 33720Pa When the transmission pin diameter and large diameter connected to the right angle when the connection of the stress = NA = 843N A 󰀁84300pa (due to the connection between the large diameter and diameter is a straight line, so Area is the value of 0), which shows how stress is large.