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GB/T 11640-2021 English PDF

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GB/T 11640-2021: Seamless aluminium alloy gas cylinders
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GB/T 11640: Evolution and historical versions

Standard IDContents [version]USDSTEP2[PDF] delivered inStandard Title (Description)StatusPDF
GB/T 11640-2021English839 Add to Cart 7 days [Need to translate] Seamless aluminium alloy gas cylinders Valid GB/T 11640-2021
GB 11640-2011English150 Add to Cart 0--9 seconds. Auto-delivery [GB/T 11640-2011] Seamless aluminum alloy gas cylinders [Renamed to GB/T 11640-2011] Obsolete GB 11640-2011
GB/T 11640-2001English919 Add to Cart 6 days [Need to translate] Seamless aluminum alloy gas cylinders Obsolete GB/T 11640-2001
GB/T 11640-1989EnglishRFQ ASK 3 days [Need to translate] Seamless aluminium alloy gas cylinder Obsolete GB/T 11640-1989

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Basic data

Standard ID GB/T 11640-2021 (GB/T11640-2021)
Description (Translated English) Seamless aluminium alloy gas cylinders
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard J74
Word Count Estimation 45,486
Issuing agency(ies) State Administration for Market Regulation, China National Standardization Administration

GB/T 11640-2021: Seamless aluminium alloy gas cylinders

---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
(Aluminum alloy seamless gas cylinder) ICS 23.020.30 CCSJ74 National Standards of People's Republic of China Replace GB/T 11640-2011 Aluminum alloy seamless gas cylinder (ISO 7866.2012, Gascylinders-Refilableseamlessaluminiumaloy Released on 2021-04-30 2021-11-01 implementation State Administration of Market Supervision and Administration Issued by the National Standardization Management Committee

Table of contents

Foreword Ⅰ 1 Scope 1 2 Normative references 1 3 Terms and definitions, symbols 2 4 Types and parameters 3 5 Technical requirements 5 6 Test method and qualification index 9 7 Inspection rules 15 8 Marking, coating, packaging, transportation and storage 17 9 Product qualification certificate and batch inspection quality certificate 18 Appendix A (Normative) Corrosion Test 20 Appendix B (Normative) Constant load crack resistance test 27 Appendix C (Normative) Valve Torque of Aluminum Bottles 31 Appendix D (Informative) Thread Shear Stress Safety Factor Calculation Method 32 Appendix E (informative) Description and determination of aluminum bottle manufacturing defects 35 Appendix F (Normative) Flattening Test Method 40 Appendix G (Informative) Quality Certificate for Batch Inspection of Aluminum Alloy Seamless Gas Cylinders 42

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1.Structure and Drafting Rules of Standardization Documents" Drafting. This document replaces GB/T 11640-2011 "Aluminum Alloy Seamless Cylinders", and compared with GB/T 11640-2011, the main technical changes as follows. ---In the scope of applicability, the range of nominal volume is changed, and the upper limit of the volume is adjusted to 150L (see Chapter 1, Chapter 1,.2011 Edition). Chapter 1); ---Added the aluminum alloy material grades 7032, 7060 for aluminum bottles (see 5.1.1.1); --- Changed the compatibility requirements (see 5.1.1.3, 5.1.3 of the.2011 edition) ---Changed the wall thickness design calculation formula (see 5.2.2.3, 5.2.1.3 of the.2011 edition); ---Added the control requirements for heat treatment temperature and time (see 5.3.5.2); ---Added the provision that aluminum bottles of 12L and below can be exempted from the determination of the volumetric residual deformation rate (see 6.6.2); ---Added the relevant provisions for the unexploded first leak test of high-strength aluminum cylinders with a minimum yield strength greater than 380MPa (see 6.10); ---Deleted the provision that the gas should be filled in aluminum cylinders (see Appendix C of the.2011 edition). This document is prepared with reference to ISO 7866.2012 ``Design, Manufacturing and Testing of Aluminum Alloy Seamless Gas Cylinders with Refillable Gas Cylinders'', and The degree of consistency of ISO 7866.2012 is non-equivalent. Please note that some of the contents of this document may involve patents. The issuing agency of this document is not responsible for identifying patents. This document was proposed and managed by the National Gas Cylinder Standardization Technical Committee (SAC/TC31). Drafting organizations of this document. Shenyang Silinda Anke New Materials Co., Ltd., Shanghai Special Equipment Supervision and Inspection Technology Research Institute, Zhejiang Wei Energy Fire Fighting Equipment Co., Ltd., Jiangsu Jiuwei Pressure Vessel Manufacturing Co., Ltd., Shenyang Zhongfu Kejin Pressure Vessel Co., Ltd., Liaoning Mei Support Technology Co., Ltd. The main drafters of this document. Jiang Jiang, Yin Airong, Yang Shujun, Wang Xiaodong, Song Zuotao, Deng Hong, Liu Yangtao, Meng Lili, Li Yu. The previous versions of this document and the documents replaced are as follows. ---First released in 1989 as GB 11640-1989; ---GB/T 11640-2001 was revised for the first time in.2001, and revised for the second time in.2011; ---This is the third revision. Aluminum alloy seamless gas cylinder

1 Scope

This document specifies the terms and definitions, symbols, types and parameters, technical requirements, and tests of aluminum alloy seamless gas cylinders (hereinafter referred to as "aluminum cylinders") Requirements for methods and qualification indicators, inspection rules, marking, coating, packaging, transportation, storage, and product qualification certificates and batch inspection quality certificates. This document is applicable to the design and manufacture of nominal working pressure not greater than 30MPa, nominal volume not greater than 150L, and operating environment temperature -40℃~60℃, refillable aluminum bottle used to contain compressed gas or liquefied gas. This document does not apply to bottle-type pressure vessels attached to transportation tools and machinery and equipment.

2 Normative references

The contents of the following documents constitute an indispensable clause of this document through normative references in the text. Among them, dated reference documents, Only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document. file. GB/T 192 Ordinary thread basic tooth form GB/T 196 Basic size of ordinary thread GB/T 197 Common thread tolerance GB/T 228.1 Tensile Test of Metallic Materials Part 1.Room Temperature Test Method GB/T 230.1 Rockwell Hardness Test of Metallic Materials Part 1.Test Method GB/T 231.1 Brinell Hardness Test of Metallic Materials Part 1.Test Method GB/T 232 Bend test method for metallic materials GB/T 3191 Aluminum and aluminum alloy extruded bars GB/T 3246.1 Microstructure inspection method for deformed aluminum and aluminum alloy products Part 1.Microstructure inspection method GB/T 3246.2 Microstructure inspection method for deformed aluminum and aluminum alloy products Part 2.Macrostructure inspection method GB/T 3880.1 General industrial aluminum and aluminum alloy plates and strips Part 1.General requirements GB/T 3880.2 General industrial aluminum and aluminum alloy plates and strips Part 2.Mechanical properties GB/T 3880.3 General industrial aluminum and aluminum alloy plates and strips Part 3.Dimensional deviation GB/T 3934 General thread gauge technical conditions GB/T 4437.1 Aluminum and aluminum alloy hot extruded pipes Part 1.Seamless round pipes GB/T 6519 Ultrasonic inspection method for deformed aluminum and magnesium alloy products GB/T 7144 Gas cylinder color mark GB/T 7999 Aluminium and aluminum alloy photoelectric direct reading emission spectrum analysis method GB/T 8335 special thread for gas cylinders GB/T 8336 Special thread gauge for gas cylinders GB/T 9251 Gas cylinder water pressure test method GB/T 9252 Gas cylinder pressure cycle test method GB/T 12137 Test method for air tightness of gas cylinders GB/T 13005 Gas cylinder terminology GB/T 15385 Test Method for Water Pressure Blasting of Gas Cylinders GB/T 15970.6-2007 Corrosion stress corrosion test of metals and alloys Part 6.Pre-cracking under constant load or constant displacement Preparation and application of pattern samples GB/T 20975 (all parts) Chemical analysis methods for aluminum and aluminum alloys YS/T 67 deformed aluminum and aluminum alloy round ingot ISO 11114-1 Gas Cylinders, Gas Cylinders and Cylinder Valve Materials Compatibility with Gas Containing Part 1.Metallic Materials (Gascylinders- Compatibilityofcylinderandvalvematerialswithgascontents-Part 1.Metalicmaterials) 3 Terms and definitions, symbols 3.1 Terms and definitions The following terms and definitions defined in GB/T 13005 apply to this document. 3.1.1 Solution treatment Heat the aluminum bottle body to an appropriate temperature and keep it warm, so that the excess phase is fully dissolved in the solid solution, and then quickly cooled to obtain a supersaturated solid. The heat treatment process of the solution. 3.1.2 Batch According to the same design, the same retort number material, the same manufacturing process and the same heat treatment specification, the aluminum bottles that are heat-treated in the same period Limited number. Note. When the quality control conditions are the same, products heat-treated in different furnaces can form a batch. 3.1.3 Yieldstress Specifies the strength when the non-proportional elongation is 0.2%. 3.1.4 Design stress factor The ratio of the equivalent wall stress to the guaranteed value of the yield strength under the hydraulic test pressure. 3.1.5 Artificialageing After solid solution treatment, the aluminum bottle body is kept at an appropriate temperature to precipitate the strengthening phase to improve its yield strength and tensile strength. Heat treatment process. 3.2 Symbols The following symbols apply to this document. A --- Elongation after breaking, %; a --- Fatigue crack length, in millimeters (mm); a0 --- the original thickness of the tensile specimen, in millimeters (mm); b0 --- the original width of the tensile specimen, in millimeters (mm); C ---The circumferential tearing width of the blasting opening, in millimeters (mm); Df --- the diameter of the indenter of the bending test, in millimeters (mm); Di --- the nominal inner diameter of the cylinder, in millimeters (mm); Do --- the nominal outer diameter of the cylinder, in millimeters (mm); E --- modulus of elasticity, in megapascals (MPa); F --- design stress factor (see 5.2.2.3); KIAPP --- the applied elastic stress strength, in units of megapascals one-half square meter (MPa·m1/2); L0 --- artificial defect length, in millimeters (mm); l0 --- The original gauge length of the tensile specimen, in millimeters (mm); pb --- Measured burst pressure, in megapascals (MPa); ph --- hydraulic test pressure, in megapascals (MPa); pw --- Nominal working pressure, in megapascals (MPa); py ---Measured yield pressure, in megapascals (MPa); R ---The radius of the indenter edge of the flattening test, in millimeters (mm); Rc --- the cutting radius of the tool, in millimeters (mm); Re --- Guaranteed minimum yield strength of the bottle material after heat treatment, in megapascals (MPa); Rea ---Measured yield strength, in megapascals (MPa); ReSLC --- At room temperature, the average yield stress of two specimens representing the part of the SLC specimen prepared from the test aluminum bottle Value in megapascals (MPa); Rg --- the guaranteed minimum tensile strength of the bottle material after heat treatment, in megapascals (MPa); Rm ---Measured tensile strength in megapascals (MPa); r ---The corner radius inside the bottom of the bottle, in millimeters (mm); rc ---The radius of the tip angle of the tool tip, in millimeters (mm); r1 ---The inner radius of the bottom of the bottle, in millimeters (mm); S --- Design wall thickness of the cylinder, in millimeters (mm); Sa ---The measured wall thickness of the cylinder, in millimeters (mm); Sa0 --- The measured average wall thickness of the cylinder, in millimeters (mm); SLC --- Constant load crack; S0 --- the original cross-sectional area of the tensile specimen, in square millimeters (mm2); S1 ---The thickness of the center of the bottom of the bottle, in millimeters (mm); T ---The distance between the indenters of the flattening test, in millimeters (mm); V ---Nominal volume, in liters (L); V1 --- Crack opening displacement (CMOD), in millimeters (mm), refers to the mode of crack displacement caused by elasticity and plastic deformation The component of 1 (also called open mode) is measured on the crack surface where the elastic displacement per unit load is the largest.

4 Types and parameters

4.1 Type The typical structure of the aluminum bottle body should generally conform to the type shown in Figure 1. 5.2.5 Base design When the aluminum bottle is designed with a base structure, it should be ensured that the base has sufficient strength, and the base material should be compatible with the bottle body material. Base shape It should be cylindrical and can ensure the vertical stability of the aluminum bottle. The connection between the base and the bottle body should not be welded, and its structure should not cause water accumulation. 5.2.6 Collar design When the aluminum bottle is designed with a collar, it should be ensured that the collar has sufficient strength, and the material of the collar should be compatible with the material of the bottle body. Collar and bottle Welding should not be used for connection. The axial pull-off force of the collar should not be less than 10 times the weight of the empty bottle and not less than 1000N, and the anti-rotation torque should Not less than 100N·m. 5.3 Manufacturing 5.3.1 General requirements The manufacture of aluminum bottles shall meet the requirements of product design drawings and related technical documents. 5.3.2 Barrel 5.3.2.1 The bottle body is made of ingots and extruded bars as raw materials, and is made by cold extrusion or hot extrusion, or cold deep drawing after extrusion. 5.3.2.2 The bottle body is made of pipes as raw materials by spinning and other processes. 5.3.2.3 The body of the bottle is made of plate material, which is made by stamping, deep drawing, spinning and other processes. 5.3.3 End 5.3.3.1 The shoulder can be formed by molding or spinning. 5.3.3.2 The surface of the transition part between the bottle mouth and the bottle shoulder should be smooth, and there should be no sudden changes or obvious wrinkles on the surface. 5.3.3.3 The end should be heated evenly during the forming process to ensure that the material has no overburnt structure. 5.3.3.4 No welding treatment should be carried out. 5.3.4 Batch Manufacturing should be managed in batches, and the number of each batch is not more than.200 plus the number of bottles for destructive testing. 5.3.5 Heat treatment 5.3.5.1 The body of the aluminum bottle shall be heat treated as a whole, and the heat treatment shall be carried out according to the qualified solid solution and artificial aging heat treatment process. 5.3.5.2 When the aluminum bottle body undergoes solid solution and artificial aging heat treatment, the allowable deviation of temperature and time should meet the requirements of Table 3. Table 3 Allowable deviation of heat treatment temperature and time of aluminum bottle body 5.3.6 Bottle top thread The tooth type, size and tolerance of bottle thread, taper thread should comply with GB/T 8335, ordinary thread should comply with GB/T 192, GB/T 196, GB/T 197 or related standards. 5.3.7 Water pressure test The aluminum bottle body should be subjected to a hydraulic test one by one, and the inner surface should be dried after the hydraulic test, and there should be no residual water stains. 5.3.8 Accessories 5.3.8.1 Select the corresponding bottle valve according to the nature of the filling gas, and assemble the bottle valve according to the specified torque (see Appendix C). 5.3.8.2 The aluminum bottle needs to be equipped with a protective cover. When leaving the factory, the protective cover can be made of metal or resin material and can ensure sufficient strength.

6 Test method and qualification index

6.1 Wall thickness and manufacturing tolerances 6.1.1 Test method 6.1.1.1 The wall thickness of the bottle body shall be detected by an ultrasonic thickness gauge or a special measuring tool. 6.1.1.2 The manufacturing tolerances of the cylinder body shall be inspected using standard or special measuring tools and samples. The inspection items include the average outer diameter, roundness, and roundness of the cylinder body. Verticality and straightness. 6.1.2 Qualified Index 6.1.2.1 The wall thickness at any point of the bottle body shall not be less than the design wall thickness. 6.1.2.2 The roundness of the cylinder shall not exceed 2% of the average outer diameter of the section on the same section. 6.1.2.3 The straightness of the cylinder shall not exceed 0.3% of the length of the cylinder. 6.1.2.4 The average outer diameter of the cylinder shall not exceed ±1% of the nominal outer diameter. 6.1.2.5 The verticality of the bottle body should not exceed 1% of the length of the cylinder body. 6.2 Internal and external surfaces 6.2.1 Test method Visual inspection. The surface inspection should have enough light, and the inner surface can be inspected with the help of an endoscope or an appropriate tool. 6.2.2 Qualified Index 6.2.2.1 The inner and outer surfaces of the bottle should be smooth and round, and there should be no visible pits, depressions, cracks, bulges, wrinkles, interlayers, etc., which may affect the strength. Defects. Internal and external defects can be evaluated in accordance with Appendix E. 6.2.2.2 The end of the aluminum bottle and the cylinder should be smoothly transitioned, and there should be no groove marks on the shoulder. 6.3 Bottle top thread 6.3.1 Test method Visual inspection and gauge inspection. The gauge should meet the requirements of GB/T 8336, GB/T 3934 or related standards. 6.3.2 Qualified Index 6.3.2.1 The tooth type, size and tolerance of the thread should meet the requirements of GB/T 8335 or related standards. 6.3.2.2 The effective number of threads shall meet the design requirements. Pass the test. 6.10.3.2.2 If the crack propagation deviates from the radial direction during the pressure cycle test, 2 aluminum bottles can be re-tested, if any of them If one aluminum bottle fails the test, the aluminum bottle fails the test. 6.10.3.2.3 Aluminum cylinders whose diameter and pressure are not greater than those that have passed the test may not be subjected to this test. 6.10.4 Pressure leak 6.10.4.1 Test method Carry out pressurization leak test according to 6.6.1, pressurization time is not less than 1min to 2/3ph×(Sa/S), keep the pressure for 10s, and continue to increase the pressure to leakage. 6.10.4.2 Qualified Index 6.10.4.2.1 The total length of the measured leakage defect does not exceed 1.1L0, then the aluminum bottle passes the test. 6.10.4.2.2 If the aluminum bottle leaks, and the leakage pressure is less than 2/3ph×(Sa/S), then select 2 aluminum bottles to process one less than the above For defects in the depth of the test, the test is performed again, and the test results meet the requirements of 6.10.4.2.1, and the aluminum bottle passes the test. 6.10.4.2.3 If the aluminum bottle bursts, and the burst pressure is greater than 2/3ph×(Sa/S), then select 2 aluminum bottles to process one more than the above For defects in the depth of the test, the test is performed again, and the test results meet the requirements of 6.10.4.2.1, and the aluminum bottle passes the test. 6.11 Collar assembly test 6.11.1 Test method 6.11.1.1 Perform an axial pull-off test on the collar with 10 times the weight of the empty cylinder of the gas cylinder and a tensile force of not less than 1000N. 6.11.1.2 Apply a torque of 100N·m to the collar for a rotation test. 6.11.2 Qualified index The collar does not fall off during the axial pull-off test, and the collar does not loosen when the torque is applied for the rotation test.

7 Inspection rules

7.1 Factory inspection 7.1.1 Inspection one by one Aluminum bottles should be inspected one by one according to the items specified in Table 5. 7.1.2 Batch inspection 7.1.2.1 Aluminium bottles should be inspected in batches according to the items specified in Table 5. 7.1.2.2 At least one aluminum bottle shall be randomly selected from each batch of aluminum bottles for tensile test, metallographic test, bending test or flattening test. 7.1.2.3 One aluminum bottle shall be randomly selected from each batch of aluminum bottles for hydraulic blasting test. 7.1.3 Re-inspection rules If the test result is unqualified, proceed as follows. a) If the unqualified test result is caused by equipment abnormality or measurement error, re-test, if possible, the test should be performed on the same aluminum bottle. Perform a secondary sampling test. If the second test is qualified, the first test can be ignored; A.1.3 Preparation of the surface before corrosion A.1.3.1 Reagents A.1.3.1.1 Nitric acid HNO3 is analytically pure, with a concentration of 1.33g/mL. A.1.3.1.2 Hydrofluoric acid HF is analytically pure, with a concentration of 1.14g/mL. A.1.3.1.3 Deionized water or distilled water. A.1.3.2 Method Put the following solutions in a beaker and heat to 95°C. ---HNO3(A.1.3.1.1). 63mL; ---HF(A.1.3.1.2). 6mL; ---H2O (A.1.3.1.3). 931mL. Hang the sample on a wire made of aluminum or other inert materials and soak in the above solution for 1 min. Rinse with running water and use it again Rinse with ionized water or distilled water (A.1.3.1.3). Immerse the sample in the nitric acid solution for 1 min at room temperature to remove the copper deposits that may be formed, and then use deionized water or distilled water rinse. After the above preparations are completed, in order to prevent oxidation of the samples, they should be immediately immersed in the following corrosion solution. A.1.4 Test process A.1.4.1 Corrosion solution The solution consists of 57g/L sodium chloride and 3g/L hydrogen peroxide. A.1.4.2 Preparation of corrosion solution A.1.4.2.1 Reagents A.1.4.2.1.1 Sodium chloride NaCl crystals, analytically pure. A.1.4.2.1.2 Hydrogen peroxide H2O2, (100~110) volume. A.1.4.2.1.3 Potassium permanganate KMnO4, analytically pure. A.1.4.2.1.4 Sulfuric acid H2SO4, analytically pure, with a concentration of 1.83g/mL. A.1.4.2.1.5 Deionized water or distilled water. A.1.4.2.2 Calibration of hydrogen peroxide Since hydrogen peroxide is not stable, it should be calibrated for titer before use. Use a pipette to take 10mL hydrogen peroxide (A.1.4.2.1.2), Place it in a graduated ampoule, dilute it to 1000 mL with deionized water or distilled water, and the resulting hydrogen peroxide solution Liquid is called C. Use a straw to put the following solutions into the triangular cup. 10mL hydrogen peroxide solution C; about 2mL sulfuric acid (A.1.4.2.1.4) solution. Titration with a concentration of 1.859g/L potassium permanganate solution (A.1.4.2.1.3), potassium permanganate acts as an indicator. A.1.4.2.3 Titration instructions In sulfuric acid solution, the chemical reaction formula of potassium permanganate and hydrogen peroxide is. 2KMnO4 5H2O2 3H2SO4=K2SO4 2MnSO4 8H2O 5O2 According to the above reaction formula, 316gKMnO4 needs 170gH2O2 to react. Therefore, 1g of pure hydrogen peroxide interacts with 1.859g of potassium permanganate, that is, 1.859g/L potassium permanganate solution (saturated) needs equal volume 1g/L hydrogen peroxide solution for the reaction. Since the hydrogen peroxide used is diluted 100 times during the titration process, the 10mL test The agent only represents 0.1 mL of initial hydrogen peroxide. By multiplying the number of milliliters of potassium permanganate used for titration by 10, the initial hydrogen peroxide titer T (g/L) can be obtained. A.1.4.2.4 Preparation of corrosion solution Method for preparing 10L solution. Dissolve 570g of sodium chloride (A.1.4.2.1.1) in deionized water or distilled water (A.1.4.2.1.5) to obtain The total volume of the solution is about 9L, then add the required amount of hydrogen peroxide, mix and add deionized water or distilled water to 10L. Add melt The volume and dosage of hydrogen peroxide in the liquid is calculated according to formula (A.1). V=(1000×30)/T (A.1) Where. V --- The volume and dosage of hydrogen peroxide, in milliliters (mL); The amount of hydrogen peroxide in 30 - 10L corrosion solution; T ---Hydrogen peroxide titer, that is, the content of hydrogen peroxide per liter of corrosion solution. A.1.4.3 Corrosion process A.1.4.3.1 Place the corrosive solution in the crystallization tray immersed in the water tank (or in a beaker as large as possible), and the water tank is stirred with a magnetic stirrer, and Use a contact thermometer to control the temperature. The sample can be suspended in the corrosive solution with aluminum wire (or other inert materials), or the sample can be directly connected with the edge Put the container into the corrosive solution in contact, the latter method is better. The corrosion time is 6h, and the temperature is controlled at 30℃±1℃. Pay special attention It is important to ensure that there is at least 10 mL of solution per square centimeter on the surface of the sample. After corrosion, rinse the sample with water and then soak in 50% dilute nitric acid About 30s, rinse with water and dry with compressed air. A.1.4.3.2 If the samples are of the same alloy and do not touch each other, several samples can be corroded at the same time. The minimum quantity of reagents required. A.1.5 Preparation before sample inspection A.1.5.1 Device A.1.5.1.1 Mold. ---Outer diameter. 40mm; ---Height. 27mm; ---Wall thickness. 2.5mm. A.1.5.1.2 The mold material is epoxy resin plus curing agent or similar substances. A.1.5.2 Method Put each sample into the mold vertically, use the sample a1a2a3a4 surface as a support, and mix the epoxy resin and cured in a certain proportion. The agent mixture is injected around the sample. Use a lathe to go 2mm along the a1a2a3a4 surface to remove the effect of end surface corrosion. Or distance a1a2a3a4 Saw a sample with a plane of 5mm~10mm (see Figure A.2 and Figure A.3), and inlay the sample to expose a'1a'2a'3a'4 surface to facilitate mechanical polishing. The test surface should be mechanically polished with water sandpaper, diamond compound or magnesium oxide compound.

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