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2. Materials and Methods: Vibration Testing Each of the products is subjected to a series of six vibration tests, Table 2.1. The primary evaluation is between the current ASTM D4169 Truck Level II Test and the proposed truck profiles from the ASTM D4169 Truck Profile Update Rationale. The proposed ASTM D4169 profile consists of three 60 minute cycles, Table 2.2. Each cycle consists of three levels of vibration: Low, Medium, and High. The Medium level is the same as the ISTA Steel Spring Truck profile and the Low and High levels are scaled down and up respectively. Figure 2.1 illustrates the PSD plot of all the profiles used in the study. Two modifications of the proposed ASTM D4169 vibration test are considered to evaluate the effect of combining the three test loops into one longer loop. These alternatives are explored in the interest of reducing the number of loops required in the case of Modified 1, Table 2.3, and eliminating the low level testing profile to reduce the test time in Modified 2, Table 2.4. A final evaluation is performed using the current ISTA Steel Spring profile that is the basis for the proposed ASTM D4169 method. Two separate tests are performed, one is the ISTA Steel Spring profile for 180 minutes and another for 60 minutes. 19 ista views • December 2015 • www.ista.org Table 2.1: Summary of Vibration Tests Vibration Profile Current ASTM D4169 Truck Level II Test Proposed ASTM D4169 (Run low – med – high vibration profiles) Modified 1 (Combined low – med – high vibration profiles) Modified 2 (Eliminate low vibration profile – reduce time) ISTA Steel Spring Suspension Test ISTA Steel Spring Suspension Test Test 1 2 3 4 5 6 Duration of Test Duration: 180 Minutes Three, 60 min. cycles (40 min low – 15 min med – 5 min high) Total Duration: 180 Min. One cycle (120 min low – 45 min med – 15 min high) Total Duration: 180 Minutes One cycle (45 min med – 15 min high) Total Duration: 60 Minutes Total Duration: 180 Minutes Total Duration: 60 Minutes Test Sequence A (Low) B (Medium) C (High) Loop Overall Grms 0.40 0.54 0.70 Proposed Test Time (Minutes) 40 15 5 60 180 Total Loop Time 3 Total Loops Table 2.2: Proposed ASTM D 4169 Truck Vibration Profile > MORE ON PAGE 20

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