Thermal Cycling Test for Life Assessment of Powertrain Sealing Systems
|Publication Date:||1 August 2010|
Note: Nothing in this standard supercedes applicable laws and regulations.
Note: In the event of conflict between the English and domestic language, the English language shall take precedence.
Note: The words "must", "shall" or "will" as used in this document mean a mandatory requirement.
This test is used to predict the life of powertrain sealing as it applies to the intended system design. The system includes the gasket, fasteners, structural interfaces and circulating media.
This test is used on components and assemblies (up to entire engines and transmissions) to identify and eliminate marginal seal designs and/or materials. Design has a significant influence on test results. Production released or production intent parts shall be used.
Foreword. This document describes methods for evaluating sealing systems in their intended subsystem assembly using engine oil, transmission fluid, coolant, or air as a circulating medium. Test fixtures are cycled through hot and cold temperature extremes for approximately 12 to 18 weeks continuously (24 h/day, 7 days/week). The performance measure is determined by test completion without unacceptable leakage (successful test).
Media Cycles. For each liquid testing medium, there is a thermal test cycle. Table 2 is for Engine Oil/Transmission Fluid. Table 3 is for Engine Coolant. Table 4 is for Air.
Before initially running, and at the end of the selected test procedure, the following tests are recommended:
• GMW3137 Dynamic Sealing Stress Measurement for Powertrain Sealing Systems. A method for measuring continuous stress distribution between the gasket and joint surfaces using an electronic sensor film. Films are capable to 200 °C continuous, permitting the sensor to be left in the joint during testing for select data capture at desired test intervals.
• GMW3149 Air Leak Testing for Leak Rate Determination of Powertrain Sealing Systems. This test establishes if the test fixtures and test joints have been sufficiently sealed prior to the start of test, and any leak path has been created at the end of test (EOT). The test shall be performed at 35 kPa (5 psi) air pressure holding for 2 minutes. No air pressure decay shall be observed.
• GMW3152 Static Sealing Pressure Measurement for Powertrain Sealing Systems. Commonly referred to as a Fuji Paper test, it measures the initial contact sealing pressure distribution achieved in the test joint using contact pressure sensitive color developing film. Measurement during initial assembly confirms if the seal to joint contact is continuous and sufficient to survive the test. It may also be used as a diagnostic tool for leaking parts at EOT.
This test is suited to the evaluation of all static powertrain gaskets and seals that experience thermal cycling during service. It is based on European and North American passenger vehicle and light duty truck applications. Other regional or vehicle applications, e.g., heavy duty (HD) trucks, may not experience the thermal cycle described in this document.
This test permits the optional use of mechanical devices to impart motion or load on any test fixture(s).
High temperature applications, (e.g., head, exhaust or Exhaust Gas Recirculation (EGR) gaskets) are beyond the limits of this test.
Test Oils. The test fluid circulatory system (3.2.2) of each test unit shall permit steady and progressive oxidative degradation of the test oil to EOT. Fluid degradation is measured using the appropriate fluid industry tests (184.108.40.206). With no blow-by or Positive Crankcase Ventilation (PCV) recirculation provisions, this test does not replicate oil degradation under engine operating conditions.
Fluid Leak Requirements. All tested samples for validation have one sealing performance requirement. This is defined in a restricted GMW document and supersedes all previous and existing statements. Other non-leak criteria for evaluation during or after GMW3155 must be defined and/or have measurable values. If not, they are not required for the Production Part Approval Process (PPAP).