SAE J1927 pdf download
SAE J1927 pdf download.Cumulative Damage Analysis for Hydraulic Hose Assemblies.
Hydraulic hose assemblies have a finite life and the exposure to surge pressures above the maximum working pressure will substantially reduce their service life. This analysis Is intended to show the loss of hose working life du. to elevated hydraulic pressures. Use of this SAE Information report Is Intended for those IndIviduals that can produce a recorded history of pressure peaks and the frequency of the peaks. Under no circumstances should cumulative damage analysis be used unless recorded pressure history can be verified before implementing the design. Without proper documentation of the system pressure history, the application of any hose assembly above the rated working pressure Is not recommended by hose manufacturers and will substantially decrease ti. working life of the hose. The userinstalling company Is accountable for the analysis and application of results.
Scope—This SAE Information Report is intended to provide the hydraulic system analyst with a procedure which will assist in the selection and use of high-pressure wire reinforced hydraulic hose asserrlies. Many construction, agricultural, industrial, or commercial equipment systems utilize hydraulic hose assemblies that are sub1octed to irregular cyclic pressure variations (cannot be approximated by a constant amplitude pressure cycle). This document relates damage done by pressure cycles with the pressure-lile performance curve for the hose assembly being evaluated, using a linear damage rule to predict fatigue life similar to that used for predicting metal fatigue liie. More detailed information on the subject may be found in SAE Paper No 880713. The accuracy of cumulative damage calculations is directly related to proper measurement ci the service pressure history and pressure-life performance for the hose assembly being evaluated. Final selection 01 a hose assembly must also consider installation and maintenance as noted In SAE J1273.
1.1 Background—In the current SAE J517 for hydraulic hose, each style and size hose is assigned a maximum operating pressure rating to assure the user reasonable service life in a wide variety of applications. (See Appendix A for further explanation of nomenclature used in this document.) This rating is based on assessment of many factors, including repeated pressure cycling under controlled laboratory conditions at a pressure equal to or greater than the assigned maximum operating pressure. This standard test procedure. as detailed in SAE .J343 minimizes variables so as to provide a baseline br performance capability SAE J51 7 takes note that actual pressure cycling in a hyckaulic system will seldom duplicate those test parameters precisely. It provides basic hose construction details; SAE J343 establishes standard test procedures—which may be utilized to develop data at pressures other than the established test value for any hose assembly. SAE J1273 provides a guide for selection, installation, and maintenance for hose and hose assemblies.
Many hydraidic systems will be subjected to variable amplitude pressure cycles, and in some of these the highest surge peaks will occur only a few times, Strict interpretation of SAE J5l 7 indicates the use of hose assemblies with a maximum operating pressure equal to or greater than the highest peak—even II that peak should occur only once In the life of the system. If this were done, the hose would have more reinforcement, larger outside diameter, less flexibility, and higher cost than might be needed- It should not be necessary to use a hose that has over a million cycle capability at a pressure which is likely to occur only a few times in the appIicabon What is needed, then, is a design venfication procedure that assures adequate fatigue lite for appbcations with variable amplitude pressure usage where the highest surge peaks are between 100 and 200% of rated pressure.
1.1.1 Cumulative damage of hydraulic hose is in many ways comparable to cumulative damage of metal components. The design verification of metal components is done in two ways depending on whether loading is of constant amplitude or variable amplitude
a- Size the part cross section so the constant amplitude (maximum) load will not produce a stress at the highest stressed area in excess of the material “endurance limit stress. This is a stress that will not cause failure in a million cycles of loading
b- Do a cumulative damage analysis on the variable amplitude load or strain history to predict fatigue life as is normally done to evaluate prototype machines In the ground vehicle Industry.
1-1.2 In a similar manner, hydraulic hose design verification should be done in two ways:
a- Select a hose assembly so the constant amplitude (maximum) pressure during service is less than the SAE J5t7 rated pressure!
b. Do a cumulative damage analysis with the variable amplitude pressure history to determine if the fatigue life will meet the design life of the product. The block diagram In Figure 1 illustrates how both the pressure history and the P-N curve information are the essential inputs for this procedure.
