1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW16598 Windshield Glass Abrasion Stress Test Copyright 2011 General Motors Company All Rights Reserved August 2011 Originating Department: North American Engineering Standards Page 1 of 4 1 Scope Note: Nothing in this standard supercedes applicable l
2、aws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. This test will simulate scratches (damage sites/flaws) on the windshield, which will result in breakage if excessive residual stresses exist in the
3、glass sample. By simulating these scratches/defects in the glass, an evaluation of the residual manufacturing stresses (thus, susceptibility for breakage) is possible. Performing this evaluation will help ensure the final product will not exhibit these concerns. 1.2 Foreword. Due to varying residual
4、 stresses developed within the glass during the forming process, windshield breakage can result if the stresses are excessive or not counterbalanced by inherent compressive stresses. These excessive or unbalanced stresses are due to insufficient heating or cooling of localized regions within the gla
5、ss during the bending process (improper annealing). The design and geometry of bending rings or oven parameters are often the root cause for these residual stresses. Breakage can occur after delivery of the vehicle to the customer, typically when a small or minor scratch occurs, (e.g., stone chip).
6、Glass breakage results in undesirable warranty costs and customer dissatisfaction. A method has been developed that can identify susceptible parts and then help pinpoint the root cause so resolution can be sought. This methodology is described and should be followed by all GM windshield suppliers. N
7、ote that another common cause or contributor to windshield breakage is installation or applied stresses, but the affect of these stresses cannot be evaluated using this test procedure. Also note that a combination of installation and residual manufacturing stresses may lead to windshield breakage, f
8、urther confounding and obscuring the root-cause for a glass breakage concern as installed in a vehicle. 1.3 Applicability. All GM windshields worldwide. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. None 2.2 GM
9、 Standards/Specifications. None 3 Resources 3.1 Facilities. Windshield suppliers test lab/facility. 3.2 Equipment. The following equipment (or equivalent) is required: 3.2.1 Glass checking fixture or equivalent peripheral support device for the windshield tested. 3.2.2 Racks capable of holding all g
10、lass test samples in a vertical orientation. 3.2.3 Picture or sample of an abraded piece of glass (see Figure 1). Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE
11、ENGINEERING STANDARDS GMW16598 Copyright 2011 General Motors Company All Rights Reserved August 2011 Page 2 of 4 Figure 1: Image of an Abraded Piece of Glass for Reference in Creating Other Samples 3.2.4 Sandpaper Belt., Aluminum Oxide seaming belt sandpaper 100-Y grit long enough to cut into 100 mm
12、 squares. One (1) square will be needed for each windshield tested 3.2.5 Paint Pen. 3.2.6 Digital Camera. 3.3 Test Vehicle/Test Piece. Quantity of test specimens required will depend on the manufacturing processes and other design variables, but evaluating three (3) windshields per bending ring for
13、a gravity-sag process is an acceptable starting point. For parts produced on a press-bend process, a minimum of 30 windshields shall be tested. These 30 samples must be randomly selected throughout the whole glass run (at minimum, every tenth part). Test samples shall be representative of final prod
14、uction windshields. 3.4 Test Time. Calendar time: 2 days Test hours: 12 to 24 hours Coordination hours: 4 hours 3.5 Test Required Information. Not applicable. 3.6 Personnel/Skills. A lab test technician or engineer should conduct these tests. At a minimum, the Subsystem Validation Engineer (SVE) and
15、 Design Engineer (DE) shall review the results of the test by implementing the Design Review Based on Failure Modes (DRBFM) process. 4 Procedure 4.1 Preparation. 4.1.1 Each bending ring shall be labeled with its own unique identification plate or marking system. 4.1.2 Label each windshield test samp
16、le as it is manufactured and ensure the bending ring used to manufacture the part is also tracked along with this identification scheme. 4.1.3 Place the windshield to be tested on the horizontal peripheral support device so that the number 1 surface is up. 4.2 Conditions. 4.2.1 Environmental Conditi
17、ons. After abrasion, each of the test samples shall be stored at 20 C to 23 C and a minimum of 35% relative humidity. 4.2.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, r
18、eports, etc. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16598 Copyright 2011 General Motors Company All Rights Reserved August 2011
19、Page 3 of 4 4.3 Instructions. 4.3.1 Using a circular motion, abrade the number 1 surface of the windshield over a strip 10 mm from the edge of the glass to 60 mm from the edge of the glass (Figure 2). Use four (4) fingers on the sandpaper and apply sufficient (fairly strong) pressure to create a hea
20、vily frosted region. Cover the entire periphery of the windshield using approximately 20 swirls per 300 mm length. The entire area should be heavily frosted. Use a fresh portion of the sandpaper for each of the windshields. Figure 2: Region of Windshield to be Abraded 4.3.2 Compare the abraded test
21、specimen to the sample picture of abraded glass to ensure a consistent level of abraded haze. 4.3.3 Carefully place the windshield vertically in the rack. 4.3.4 Store abraded glass at the environmental conditions specified in 4.2.1 for 24 h. 4.3.5 Data Acquisition. 4.3.5.1 Check condition of the gla
22、ss samples every hour for the first 4 h and then every 4 h thereafter. 4.3.5.2 Note the size, specific crack initiation site, and time of any crack/breakage on the test report along with the windshield sample and bending ring identifications. 4.3.5.3 At the conclusion of the test, all broken windshi
23、elds will be photographed. Any cracks/breakage should be highlighted with a paint pen. 5 Data 5.1 Calculations. Not applicable. 5.2 Interpretation of Results. Breakage or propagation of cracks within 24 h of abrasion indicates a residual tensile stress in the glass. If a crack begins to propagate wi
24、thin this time frame, then further investigation of the manufacturing processes and tool designs must be conducted to eliminate this susceptibility to cracking. Generally, the higher the stress in the glass, the sooner a crack will propagate. Also note that most (not all) samples with a level of res
25、idual tensile stress that is higher than allocated in the stress budget for windshields, will crack within 1 h of abrasion. 5.3 Test Documentation. It is critical to carefully document the bending ring used and initiation site of any cracks found on a windshield when root-causing the residual stress
26、 concern with the windshields. Note these details for each cracked windshield and include this information in the final report. 6 Safety This standard may involve hazardous materials, operations, and equipment. This standard does not propose to address all the safety problems associated with its use
27、. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction
28、 or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16598 Copyright 2011 General Motors Company All Rights Reserved August 2011 Page 4 of 4 7 Notes 7.1 Glossary. Bending Ring: A tool used to form the (bent) shape of the glass as it is passed through a furnace
29、or oven. The heat of the oven allows the glass to flow and fall into the tool, which will impart the (bent or surface) shape of the final lite. The bending ring only makes contact with the surface of glass at the periphery, overlapping the edge of glass by only a few millimeters. Lite: A thin sheet
30、of glass for automotive applications is referred to as a lite of glass, in lieu of pane a more commonly used term for glass. Number 1 Surface: The outer-most (top) surface of a windshield assembly. Standard Sample: A sample of glass which is test-ready prepared as a reference for ensuring all test s
31、amples are properly treated for test purposes. It will visually exhibit all necessary conditions for a valid test, (e.g., proper amount of edge abrasion, etc.) 7.2 Acronyms, Abbreviations, and Symbols. DE Design Engineer DRBFM Design Review Based on Failure Modes SOR Statement of Requirements SQE Su
32、pplier Quality Engineer SSTS Subsystem Technical Specification VE Vehicle Engineer 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: Test to GMW16598 9 Release and Revisions This standard was originated in April 2011. It was first approved by the Fixed
33、 Glass GSSLT in August 2011. It was first published in August 2011. Issue Publication Date Description (Organization) 1 AUG 2011 Initial publication. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
