1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW16599 Windshield and Backlight Static Stress Test Strain Gage Method Copyright 2011 General Motors Company All Rights Reserved June 2011 Originating Department: North American Engineering Standards Page 1 of 9 1 Scope Note: Nothing in this standard
2、supercedes applicable laws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. The purpose of the static stress test is to determine the induced strain on the windshield or backlight due to types of adhes
3、ion materials, windshield supporting methods, installation residual stress, windshield molding installation, and/or body opening build variations. 1.2 Foreword. This procedure is used to determine/develop a windshield/backlight installation fit and installation process having minimum localized stres
4、ses. It is also used to resolve field problems of glass cracking by determining the root cause and resulting fixes. 1.3 Applicability. This procedure applies to all passenger cars and light duty trucks. While written specifically for windshields and backlights, it may also be used to evaluate variou
5、s other stationary glass installations. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. None 2.2 GM Standards/Specifications. None 2.3 Additional References. Master Process Documents (MPD) Service Manuals Subsyst
6、em Technical Specification (SSTS) Vehicle Technical Specification (VTS) 3 Resources 3.1 Facilities. GMNA Body Test Lab, or similarly equipped test facility. 3.2 Equipment. The following list(s) include fixturing and instrumentation typically used by the GMNA Body Test Lab to perform this test. Other
7、 equipment may be substituted at the discretion of the testing facility as long as it provides the same data and/or data record, with equivalent accuracy as specified herein or by the requester. 3.2.1 Fixturing. 3.2.1.1 Glass Checking Fixture. Glass checking fixture for the vehicle windshield being
8、tested (fixture is obtained from glass manufacturer). 3.2.1.2 Miscellaneous Tools. Windshield removal and installation tools, such as suction cup handlers, knives or cutters, etc. Adhesive caulking gun (manual or pneumatic). Foam padding low density 0.635 cm (0.25 in). Copyright General Motors Compa
9、ny Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16599 Copyright 2011 General Motors Company All Rights Reserved June 2011 Page 2 of 9 3.2.2 Instrumentation. 3.2.2.1 St
10、rain Gages. Enough strain gages to satisfy the layout diagram (3.5.3) for each windshield to be strain gaged (typically twelve per windshield). 3.2.2.2 Signal Amplifiers/Conditioners. An appropriate number of signal amplifiers/conditioners, equal to the number of strain gages used. 3.2.2.3 Data Reco
11、rding. Data recording and/or charting equipment such as computers, strip chart recorders, etc. Note: All instrumentation is to be calibrated as required. Record instrumentation details and date of calibration on Data Sheet 1 unless the information is otherwise preserved in the testing laboratory rec
12、ords or corporate archives. 3.3 Test Vehicle/Test Piece. 3.3.1 Test Material. 3.3.1.1 A dimensionally certified design intent test buck or a non-drivable vehicle for a Static Only Test. 3.3.1.2 Minimum of two (2) windshields (the second windshield serves as a backup to minimize delay, should the fir
13、st one break during installation). 3.3.1.3 Acoustical strips, windshield spacers, windshield moldings, cowl screens, adhesive, primer, and anything else needed to install a windshield. It is recommended that the test parts/assembly be dimensionally certified before testing is started. 3.4 Test Time.
14、 Calendar time: 3 days Test hours: 12 h Coordination hours: 36 h The following is an estimate of the amount of time (work-hours) needed to perform this procedure. Note: These time estimates are approximate averages. They may vary considerably depending on early component failures (and subsequent ava
15、ilability of replacement parts), testing to varying multiple of cycle lives, varying requirements for frequency of environmental test conditions, scheduling problems for test facilities, test equipment malfunctions, scheduling of overtime and or multiple shifts, scheduling of “witnesses” for tests,
16、actual readiness of test samples upon receipt, unique or additional requests for test details, running multiple samples (times shown are for one system), etc. These times consider preparation and other downtime, actual test, and analysis of data in capturing a total calendar time. Report writing, ap
17、proval, processing, etc., are not part of this time. Technician Resource: 24 Man Hours Engineer Resource: 12 Man Hours 3.5 Test Required Information. The following specifications or information are required to run this test: 3.5.1 Desired windshield fit, spacers, moldings, installation process, etc.
18、 3.5.2 Frequency of strain measurements during adhesive cure. 3.5.3 A diagram depicting the desired layout of the gages on the windshield. This should be provided by the requesting engineer. Typically, the gages should be placed at anticipated points of stress, such as points where the cowl screen,
19、windshield moldings, side molding, or other items are attached. 3.5.4 A diagram depicting the body position angle of the windshield. 3.5.5 Any deviations or exceptions to the contour and size limitations already marked on the checking fixture. 3.5.6 If dynamic testing is to be performed on the test
20、material. 3.6 Personnel/Skills. Prior experience in setting up and running similar tests and experience in the use of the referenced test equipment are critical to achieving the estimated times shown in 3.4. Prior experience in windshield removal and installation and strain gage installation are man
21、datory. 4 Procedure 4.1 Preparation. 4.1.1 Sample Inspection. The test and requesting engineers should inspect the test items to ensure all material listed in Section 3.3 is of correct design level and assembled properly. Thoroughly inspect the Copyright General Motors Company Provided by IHS under
22、license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16599 Copyright 2011 General Motors Company All Rights Reserved June 2011 Page 3 of 9 windshield test samples for possible flaws (chips, scratch
23、es, etc.) which might increase the likelihood of cracking. 4.1.2 Sample Preparation. This test is normally run on the test subject in an as received condition. If it is requested to be run in a specifically adjusted condition, follow the applicable procedure(s). Note: Take proper safety precautions
24、during testing because of the possibility of glass breakage (safety glasses and gloves). Do not apply any tape to the windshield (to minimize spread of broken glass fragments) as it may affect the stiffness. 4.1.2.1 Carefully remove all windshield trim and hardware. These items may be required for t
25、he installation of the test sample. 4.1.2.2 Remove the existing windshield from the test vehicle (exercise due care and wear proper hand and eye protective equipment, since the removal process often results in the breakage of the windshield). Remove all adhesive (urethane) from the windshield and th
26、e body flanges, and prepare the vehicle for manual installation of the strain gaged windshield. 4.1.2.3 Place the windshield test sample(s) on the glass checking fixture and visually verify its contour and size are within the limits (as specified on the fixture or as supplied by the requesting engin
27、eer). 4.1.2.4 Install strain gages on the test windshield according to the layout diagram (3.5.3). 4.1.2.5 Place strips of 0.635 cm (0.25 in) low density foam around the perimeter of the windshield opening area of the glass checking fixture. This will provide a soft flexible surface upon which the w
28、indshield can rest and minimize stress that might be induced by less than perfect nesting into the body opening area. 4.1.2.6 Align the glass checking fixture to match the vehicle body position windshield angle (3.5.4). 4.1.2.7 Place the strain gaged test windshield on the glass checking fixture (on
29、 top of the foam), connect the instrumentation, and zero out the strain gages. Once zeroed, and while still connected to all the instrumentation, the windshield should be removed from the checking fixture and “reinstalled” on the checking fixture a minimum of three (3) times to ensure that the zero
30、readings are stable. If stability cannot be achieved, determine the cause and resolve before continuing. Note: If no checking fixture is available, rest the windshield approximately vertical on its widest edge to obtain zero readings. 4.2 Conditions. 4.2.1 Environmental Conditions. Unless otherwise
31、specified in this documents text or by the requesting engineer, the typical environmental conditions for this test are the temperature, humidity and pressure at the major test facility (3.1). Unless otherwise noted, these conditions are typically 22 3 C (72 5 F), relative humidity of 40% + 20%, and
32、atmospheric pressure equivalent to the local barometric pressure (variable during any given day and from day-to-day). 4.2.2 Test Conditions. Deviations from the requirements of this test procedure shall have been agreed upon. Such requirements shall be specified on component drawings, test certifica
33、tes, reports, etc. 4.3 Instructions. 4.3.1 Setup Instructions. 4.3.1.1 If testing for the stress caused by spacers of various sizes, locations and durometer, body build variations, glazing materials, different durometer acoustical strips, or different cowl screen designs, develop a matrix of tests f
34、or each desired combination and dry run these tests first, without the use of an adhesive. 4.3.1.2 After completing a data sheet for each test variant, analyze and select the combination that exhibits the least stress and proceed to 4.3.2. 4.3.2 Test Operation Instructions. 4.3.2.1 For installation
35、induced stress, assemble the windshield per the MPD/Service Manual with all the appropriate hardware and place the windshield in the body opening. Perform at least three (3) dry runs of this procedure, checking that the windshield is correctly nested into the proper plane. Record the strain gage rea
36、dings during each dry run to ensure that the readings are fairly stable, with very little deviation. 4.3.2.2 If no problems are encountered, apply the primer and adhesive (and any other installation steps) and proceed with the final installation. During final installation, take strain gage readings
37、at every step (placing windshield in opening, wetting out windshield, installation of cowl screen, 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 ENGINEERI
38、NG STANDARDS GMW16599 Copyright 2011 General Motors Company All Rights Reserved June 2011 Page 4 of 9 4.3.2.3 Once the windshield is installed, the adhesive (typically a urethane) must be allowed to cure for a 24 h period. Readings should be taken every 30 minutes for the first 4 h or until the data
39、 readings stabilize. A final reading is taken at the expiration of the 24 h curing period. During this curing time, the amplifiers should not be turned off. Doing so will result in the loss of the zero mark. 4.3.2.4 Evaluate and rank each strain gage reading in accordance with the following criteria
40、. The most stress-free areas exhibit the least amount of psi (for laminate glass windshields, the psi is determined by multiplying the micro strain readings by 10.6). Glass crack in tension 6000 psi (Windshield or Backlight) TENSILE STRAIN (psi) RATING 100 to 300 Excellent 300 to 500 Good 500 to 700
41、 Poor 700+ NOT ACCEPTABLE COMPRESSION STRAIN (psi) RATING 0 to 1500 Acceptable 1500+ NOT ACCEPTABLE 4.3.3 Post-Test Instructions. 4.3.3.1 Inspect for any damage to the windshield. 4.3.3.2 The strain gages should be removed and the vehicle returned. 5 Data Unless otherwise requested in 3.5, no specif
42、ic format for data presentation is required (other than as may be required by various report records systems). Data Sheets 1 and 2 are provided for convenience only, and are not required to be used, but any alternative data sheet(s) should record equivalent data. 5.1 Calculations. Not applicable. 5.
43、2 Interpretation of Results. The requesting engineer is responsible for providing specifications appropriate to the vehicle line being tested (VTS/SSTS paragraph numbers if applicable See 2.2.3). Testing worst case scenarios may uncover some potential problems. Discuss with the requesting engineer i
44、f testing should include some worst case scenarios. Depending on which test is being performed and which level of parts or systems is being tested, consider if any of the following may apply: tolerance stack-ups, build variations, misalignment, minimum/maximum fastener torque(s), lubrication, enviro
45、nmental extremes, location of customer representative load application, symmetry (Left Hand vs. Right Hand), color, mold or die source, etc. 5.3 Test Documentation. Not applicable. 6 Safety This standard may involve hazardous materials, operations, and equipment. This standard does not propose to ad
46、dress all the safety problems associated with its use. 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. 7 Notes 7.1 Glossary. Glass Checking Fixture: A pre-formed fixture
47、, built to nominal body design dimensions, used to check the contour and overall size of a specific model windshield. Wetting: The process of applying an adhesive to the windshield. Windshield/Backlight: The term windshield will be used throughout this procedure to simplify terminology, but, unless
48、specifically noted, will always mean either the windshield or the backlight. Backlight (Backlite): The fixed, rear window of a vehicle. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from
49、 IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16599 Copyright 2011 General Motors Company All Rights Reserved June 2011 Page 5 of 9 7.2 Acronyms, Abbreviations, and Symbols. MPD Master Process Document SSTS Subsystem Technical Specification VTS Vehicle Technical Specification TWO Test Work Order 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: Test to GMW16599 9 Release and Revisions This standard w
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