Thermal Cycling Test for Life Assessment of Powertrain Sealing Systems
|Publication Date:||1 October 2014|
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 means 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.
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, turbo 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 End of Test (EOT). Fluid degradation is measured using the appropriate fluid industry tests (126.96.36.199). 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 defined in a restricted General Motors Worldwide (GMW) document and supercedes all previous and existing statements. Any no leak criteria for evaluation during or after GMW3155 must be defined and/or have measurable values listed on the print, advance development and validation plan and/or the Performance and Quality Management System Test Request.
High Pressure Fixture Integrity (Start and End of Test). For high pressure coolant and oil joints (no spray), at start of test apply the maximum fluid pressure as supplied by the component Design Responsible Engineer (DRE) or supplier. The default test time is 2 minutes. Repeat the high fluid pressure at EOT. No fluid leakage should occur.
Air Leak Requirements - Fluid Spray Joints Only. All tested samples for validation have media specific sealing performance requirements defined in a restricted GMW document and supercedes all previous and existing statements. Other no leak criteria for evaluation during or after GMW3155 must be defined and/or have measurable specified values listed on the print, advance development and validation plan and/or the Performance and Quality Management System Test Request.
- For oil joints operating under atmospheric conditions, unless otherwise specified the air leak default test condition is 2 minutes at 14 kPa (-0.3 kPa, +0 kPa) with no leak detected at start of test, each of the designated frequency intervals and at EOT.
Purpose of Air Leak Testing Fluid Spray Joints. Test fixture leak integrity at the specified test intervals is measured with air because fluid media spray patterns are not always 100% effective in properly distributing fluid to the evaluated joint. All evaluated fluid joints must pass air at the minimum default condition in 1.2.6 (no exceptions).
Test Fixture Limit Testing. Fixtures shall be at Least Material Condition (3.3.4) at the lowest torque unless otherwise specified. Maximum material condition testing is optional. 1.3 Remarks. 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 weeks 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 4 is for Engine Oil/Transmission Fluid. Table 5 is for Engine Coolant. Table 3 is for Air.
Before initially running, and at the end of the selected test procedure, the following tests are required:
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. This is optional if GMW3152 is used.
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 EOT.
GMW3152 Static Sealing Pressure Measurement for
Powertrain Sealing Systems. Commonly referred to as a Fuji
Fluid Exposure. Fluid exposure to evaluated joint sealing is by spray or direct fluid contact at pressure. Coolant joints are only evaluated by direct contact at pressure.