1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW14136 Grain Variation of Leather Copyright 2011 General Motors Company All Rights Reserved October 2011 Originating Department: GME Specification Center Page 1 of 5 1 Scope Note: Nothing in this standard supercedes applicable laws and regulations. N
2、ote: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. This Test Procedure is used to determine the grain variation of leather, i.e., loose grain. This standard is applicable to non-laminated leather up to a thickness of 2.0
3、mm as well as laminated leather up to a thickness of 5 mm. 1.2 Foreword. Not applicable. 1.3 Applicability. Additionally, a root cause analysis procedure is described for test samples, where grain variation appears. This method contains two procedures: x Method A - for non-laminated leather x Method
4、 B - for laminated leather 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ISO 2598 2.2 GM Standards/Specifications. None 2.3 Additional References. “Leather Surface Defects and Natural Markings Manual”, availabl
5、e from GM Engineering “GM Appearance Limit Sample Catalogue”, available from GME 3 Test Equipment 3.1 Standard Metal Half Pipe. Dimensions are: length 300 mm, inner diameter 36 mm, and outer diameter 40 mm; and two fixation rolls with dimensions of length 71 mm, outer diameter 32 mm, and mass (210 5
6、) g, belonging to it. 3.2 Large Metal Half Pipe. Dimensions are: length 300 mm, inner diameter 74 mm, and outer diameter 77 mm; and two fixation rolls with dimension of length 71 mm and outer diameter 64 mm belonging to it. 3.3 Standard metal ring with an inner diameter of 36 mm and a height of 20 m
7、m. 3.4 Large metal ring with an inner diameter of 74 mm and a height of 20 mm. 3.5 Sharp scissors and razor blades. 3.6 Microscope. 3.7 Test Time. Calendar time: 1 day Test hours: 2 hours Coordination hours: 1 hour Provided by IHSNot for ResaleNo reproduction or networking permitted without license
8、from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14136 Copyright 2011 General Motors Company All Rights Reserved October 2011 Page 2 of 5 3.8 Personnel/Skills. Trained personnel. 4 Test Material Single sided adhesive tape with the following properties: x 50 mm width x carrier poly vinyl chloride (
9、PVC), transparent x total thickness, 65 m x adhesive strength to steel, (3.0 to 3.5) N/cm x tearing force, 60 N/cm x elongation at break, 60 % Example material: Tesa 4172, standard plastering tape. 5 Test Method 5.1 Summary of Test Method. The leather under test is bent concave over a defined radius
10、 using a half pipe (Halpi). The produced crinkling of the grain is compared with photos of standard leather of the grain under test. 5.2 Test Sample Preparation. 5.2.1 Method A. Two (2) test samples (one longitudinal and one transversal to the line of the back bone) with 300 mm x 55 mm size are take
11、n from the leather under test. The test samples shall be taken in the middle third between neck and tail of the leather and shall be 5 cm minimum apart from the line of the back bone. For outgoing or incoming inspection (nondestructive testing), the test may be executed on complete hides. The adhesi
12、ve tape shall be applied on the relevant spots on the flesh side of the hide. 5.2.2 Method B. Two (2) test samples with 300 mm x 100 mm size are taken from the leather under test, perpendicular to each other. If the direction of the line of the back bone is unknown, test sample preparation is orient
13、ed on the part geometry. 5.3 Test Procedure. 5.3.1 Determination of Grain Variation for Non-laminated Leather Method A. Place the test samples (see paragraph 5.2.1) with the grain side downwards on a smooth plane base. Then laminate one half of the test sample (150 mm) on the flesh side with the adh
14、esive tape (according to paragraph 4.1), starting from the middle of the test sample moving outwards. To achieve a steady down force during this lamination, one of the fixation rolls (according to paragraph 3.1) is rolled without additional pressure over the adhesive tape (according to Figure 1). No
15、 tension shall appear within the leather. Figure 1: Laminating the Leather with Adhesive Tape A Fixation roll B Adhesive Tape C Leather flesh side D Leather grain side Place the now laminated leather with the grain side upwards into the standard half pipe (see paragraph 3.1). Install the leather in
16、the intended position by placing the fixation rolls on top (flush-fitted with the ends of the half pipe). Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14136 Copyright 2011 General Motors Company All Rights Res
17、erved October 2011 Page 3 of 5 5.3.2 Determination of Grain Variation for Laminated Leather Method B. Place both test samples (see paragraph 5.2.2) into the large half pipe (see paragraph 3.2). Install the leather in the intended position by placing the fixation rolls on top (flush-fitted with the e
18、nds of the half pipe). 6 Evaluation and Rating 6.1 Definitions. 6.1.1 Loose Grain Effect. Visible crinkling of the grain side of laminated leather during a concave bend is called loose grain effect. This crinkling can be caused by the following: x The leather has a loose grain. x The leather has a l
19、oose fiber structure. This loose fiber structure is fixed by the lamination of the backside. This fixation results in vertical tension when concavely bent. The result is crinkling. x When concavely bent the laminated material is subjected to vertical tension. As a result rough crinkles are visible.
20、6.1.2 Loose Grain. A leather has loose grain, if: x The grain layer sits loose on the lower leather layers, x An insufficient joint between the grain layer and the lower leather layers exists, or x The grain layer of unlaminated leather under bending (concave to the inner side) partly or completely
21、separates from the remaining leather hide. The result is crinkling under bending. 6.2 Evaluation. Evaluate the crinkling of the leather surface in the area of the adhesive tape as well as in the non laminated area according to the Leather Surface Defects and Natural Markings Manual (see paragraph 6.
22、4). Note in addition any irregularities, which are not described in the rating of the photo standard. 6.2.1 Method A - Results. Evaluation of non-laminated leather results in four rating values: x lo longitudinal direction, without lamination x lw longitudinal direction, with lamination x to transve
23、rsal direction, without lamination x tw transversal direction, with lamination 6.2.2 Method B - Results. Evaluation of laminated leather results in two rating values: x l longitudinal direction x t transversal direction 6.3 Root Cause Analysis. If test samples have poor evaluation, the root cause sh
24、all be analyzed. The cause of failure varies considerably (see definitions in paragraph 6.1). The following procedures are used for the analysis: 6.3.1 Procedure for Non-Laminated Leather. 6.3.1.1 Select the poorer of the two test sample (longitudinal or transversal). 6.3.1.2 Cut two strips (one fro
25、m the area with adhesive tape, one from the area without adhesive tape) of 10 mm width from the selected test sample (the poorer of the two). 6.3.1.3 Determine the thickness (TL) of the leather according to ISO 2598. 6.3.1.4 Calculate the needed strip length (L) with the following equation: L = (36
26、mm 2TL) (36 mm = inner diameter of the used standard metal ring as in paragraph 3.3). 6.3.1.5 Cut the strips to the determined length. 6.3.1.6 Ensure that one of the longitudinal edges of each strip is cut smooth in normal direction. Use the razor blade to achieve such a longitudinal edge. Provided
27、by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14136 Copyright 2011 General Motors Company All Rights Reserved October 2011 Page 4 of 5 6.3.1.7 Place both strips into the standard metal ring. The grain side of the strips
28、 shall show to the center of the ring. The smooth edge of the strips shall be flush-fitted to the metal ring edge. This position ensures the same bending of the strips as the test sample during testing according to paragraph 5.3.1. 6.3.1.8 Evaluate with the microscope, on which places crinkling appe
29、ars. 6.3.1.9 If the leather without adhesive tape is separated from a lower fiber structure, then the leather has loose grain. If the fiber structure on the flesh side of the leather with adhesive tape is vertically expanded, then a loose fiber structure of the leather combined with the rear side fi
30、xation through the adhesive tape is responsible for the observed loose grain effect. 6.3.2 Procedure for Laminated Leather. For laminated leather the procedure is in general the same as in 6.3.1 with the following deviations: 6.3.2.1 The large metal ring (see paragraph 3.4) is used. The width of the
31、 test sample shall be 20 mm. The length is calculated as: L = (74 mm 2TL) (74 mm = inner diameter of the large metal ring) 6.3.2.2 If a vertical tension of the laminate is visible in addition to the tension of the leather fiber structure under the microscope, the laminate material is not well tuned
32、to the used leather. 6.4 Leather Surface Defects and Natural Markings Manual. For each leather quality, the Leather Surface Defects and Natural Markings Manual is available through GM Engineering. The Leather Surface Defects and Natural Markings Manual includes a 5-scale rating system for grain vari
33、ations. Note: Regional deviating naming exists for this manual, e.g., at GME, the name GM Appearance Limit Sample Catalogue was used. 6.5 Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, repo
34、rts, etc. 7 Report The evaluation report shall contain the following: x Reference of this standard including the used method (e.g., GMW14136-A) x Exact description of the test sample including all relevant specifications x Resulting values x All observations, not defined in the rating scale x Deviat
35、ions to this standard x If applicable, notes which resulted from root cause analysis for problematic test pieces 8 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. It is the res
36、ponsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 9 Notes 9.1 Glossary. Not applicable. 9.2 Acronyms, Abbreviations, and Symbols. Halpi Half pipe L Sample strip length PVC Poly vinyl c
37、hloride tesa 4172 Standard plastering tape TL Thickness Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14136 Copyright 2011 General Motors Company All Rights Reserved October 2011 Page 5 of 5 10 Coding System Th
38、is standard shall be referenced in other documents, drawings, etc., as follows: Test to GMW14136-A Where: GMW14136 Document identification A Test procedure according to paragraph 5.3 11 Release and Revisions This standard was originated in May 2005. It was first approved by the Global Textiles Commi
39、ttee in August 2005. It was first published in August 2005. Issue Publication Date Description (Organization) 1 AUG 2005 Initial publication (Global Textiles Committee) 2 OCT 2011 5-Year-Refresh with minor content changes, NOT TO TEMPLATE (Worldwide Fabric Specification Team) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
