FORD FLTM BU 017-1-2000 NONDESTRUCTIVE INSPECTION (NDI) OF ADHESIVE BONDS.pdf

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1、 FORD LABORATORY TEST METHOD BU 017-01 Date Action Revisions 2000 11 13 Revised Editorial no technical change A. Cockman 1992 08 10 Printed copies are uncontrolled Page 1 of 8 Copyright 2000, Ford Global Technologies , Inc. NONDESTRUCTIVE INSPECTION (NDI) OF ADHESIVE BONDS Application This procedure

2、 is used to locate unbonded regions in adhesively bonded plastic assemblies including fiber - reinforced composite assemblies. Apparatus and Materials Required Bond Tester Auto mation Industries model S - 2B Sondicator or equivalent, including: . Battery charger/eliminator and/or . Rechargeable batt

3、ery, . 25 kHz two - transducer/alarm probe, . Instruction manual. Reference Specimens Three adhesively bonded lap - joints are required. They must be made of the same type of adhesive and material as the assemblies to be inspected. Each must have minimum bond dimensions of 25 x 150 mm and the panel

4、size must be larger than 150 x 150 mm. Two of these reference specimens must have bonds of known acceptable bond integrity (selected according to the procedure described in Appendix A). 1. One should be kept with the instrument for hourly use as a reference or “calibration standard“. 2. The other sh

5、ould be retained as a “primary standard“ and kept in a protected place for daily comparison to the first, in order to detect unequal bond degradation of either reference specimen. The third reference specimen must contain an unbonded area about 25 x 25 mm. Refer to Appendix A for information on th e

6、 preparation, selection and certification of adhesive bond NDI reference specimens. FORD LABORATORY TEST METHOD BU 017-01 Page 2 of 8 Copyright 2000, Ford Global Technologies, Inc. Conditioning and Test Conditions All test values indicated herein are based on material conditioned in a controlled atm

7、osphere of 23 +/ - 2 C and 50 +/ - 5 % relati ve humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. Procedure 1. Connect the 25 kHz dual transducer/alarm probe to the instrument. 2. Insert a charged battery pack or battery eliminator/c h

8、arger in the compartment located on the side of the instrument. Lock it in place. 3. Turn power on and select “PHASE + AMPTD“ as the alarm mode. Note: The BTRY indicator indicates a fully charged battery when the needle deflects fully to the right (w hite area). As the battery discharges, the needle

9、 will begin to drop, indicating that inspection time is becoming limited. To provide maximum instrument stability and battery life, the instruments power supply is programmed to automatically turn the ins trument off at a predetermined state of battery discharge. At this time, the BTRY indicator nee

10、dle drops to the center portion of the scale. The battery pack will rejuvenate itself to a degree, when line voltage is not available for recharging, if the in strument is switched off for approximately 15 or 20 minutes, possibly allowing the operator to finish a test. Battery Recharging To recharge

11、 the battery, proceed as follows: (a) Interconnect the battery eliminator/charger and the battery pack. Use the c harging cable supplied. The cable is coded for proper interconnection. (b) Connect the charger to a 115 volt AC, 60 Hz source using the power cable supplied with the instrument. (c) Mome

12、ntarily press the small red button at the rear of the charger to st art the charging cycle. When the battery has reached essentially full charge, the red light - emitting diode (LED) on the rear of the charger will light, indicating that the charging power has been reduced to trickle charge. The cha

13、rger will remain in this mode until AC power is disconnected. Approximately 10 hours are required to bring the battery to full charge. A full charge can provide up to eight hours of operation. To check for adequate battery charge, press the red button at the rear of the charge r, and then release. I

14、f the red LED does not go off when the button is released, the battery has accumulated a full charge. FORD LABORATORY TEST METHOD BU 017-01 Page 3 of 8 Copyright 2000, Ford Global Technologies, Inc. CAUTION DO NOT USE ANY OTHER MEANS OF CHARGING THE BATTERY THAN THE BATTERY ELIMINATOR/CHARGER SUPPLI

15、ED. THIS CHARGER IS DESIGNE D TO RECHARGE THE BATTERY ACCORDING TO THE BATTERY MANUFACTURERS RECOMMENDED SPECIFICATIONS. THE USE OF ANY OTHER TYPE OF CHARGER MAY DAMAGE THE BATTERY PACK. 4. Allow the instrument to equilibrate to ambient temperature which must be above 5 C. 5. All materials to be ins

16、pected or used as reference specimens must be clean and free of loose dirt, paint flakes, heavy grease or oil buildup, and other detrimental residues. 6. Adjust the warmed - up instrument according to the following operating instructions : (a) Place the probe down firmly over a known good area on th

17、e hourly reference or calibration standard. A probe hold -down force of approximately 9.8 N is recommended. The transducer contacts should be at least 6 mm in from the bond edge. Set the AMPL ITUDE potentiometer to 250 and the PHASE potentiometer to zero. Then rotate the phase potentiometer clockwis

18、e (CW) and observe as the phase meter peaks in deflection to the right and then falls back to the left. Continue rotating the PHASE potentiometer CW until it reaches the maximum stop, while counting the number, N, of full peaks observed on the phase meter. Then rotate the PHASE potentiometer counter

19、clockwise (CCW) until it again reaches its minimum stop at zero. Now, rotate the PHASE potentiometer CW again until N - 2 peaks on the phase meter have been observed and passed. Continue rotating the PHASE potentiometer CW, slowly approaching the N - 1 peak, until a phase meter reading of 0.6 is att

20、ained on the ascending side of the next - to - the - last peak. Readjust the AMPLITUDE potentiometer to obtain an amplitude meter reading of 0.7. Because these controls interact to a degree, continue readjusting them alternately until the meters read the prescribed values. Note: A fixed location on

21、the bond of both the hourly and daily reference specimens, and a fixed orientation of the transducer probe, should be identified (marked) and used for each referencing, or calibrating operation, in order to insure reproducible results. (b) The alarm level is set while the transducer probe is held do

22、wn firmly over the identified area on the hourly reference specimen. Turn the alarm switch ON. Rotate the ALARM LEVEL potentiometer clockwise until the alarm is activated. Then rotate the ALARM LEVEL knob CCW until the alarm turns off. Set the ALARM LEVEL knob two numbered scale divisions CCW from t

23、his point; i.e., if the alarm turns off when knob points to 7, setting for testing then is 5. (c) Check the alarm to ascertain that it is activated by a known unbond about 25 x 25 mm in size. FORD LABORATORY TEST METHOD BU 017-01 Page 4 of 8 Copyright 2000, Ford Global Technologies, Inc. 7. Monitor

24、the identified location on the daily reference specimen and record the amplitude and phase meter readings in a permanent log. A day - to - day comparison of these meter readings will provide monitoring of the continued acceptability of the reference specimens. 8. Inspect each bond by moving the tran

25、sducer probe along the bond joint, aligned with tips parallel to and about 13 mm from the bond edge. Press down firmly and move probe slowly - about 150 mm/s. 9. When an unbonded area is detected (alarm), move the probe laterally across the bond joint, first to one side and then to the other side of

26、 the disbond to search for nearby bonding, while maintaining the probe alignment so that the transducer contact tips are parallel to the bond l ine as shown in the figure. 10. If bonding is located (alarm stops) within the area, such that the width of the unbonded region is estimated to be no more t

27、han 2/3 the total width of the bond joint, a partial disbond is indicated. Many disbonds are of th is nature and should be identified as partial disbonds by recording the disbond length with a P suffix in a permanent data record, which can be a sketch or a table designed to permit easy identificatio

28、n of the proportion of disbonding along the bond line. 11. A complete disbond is indicated when the alarm continues over a width greater than 2/3 of the total bond joint width as the probe is moved laterally from one side of the bond joint to the other, while maintaining the probe alignment parallel

29、 to the bond joint edges. Such disbonds should be identified as complete by recording their length with a C suffix in the data record. 12. Repeat the instrument referencing procedure described in step 6 of Procedure whenever the bond tester has been (a) turned off and back on, (b) left unattended, (

30、c) upset, mechanically or thermally shocked, (d) operating for more than one hour without re - referencing. FORD LABORATORY TEST METHOD BU 017-01 Page 5 of 8 Copyright 2000, Ford Global Technologies, Inc. Data Reduction and Interpretation After an assembly or region thereof has been inspected, a bon

31、d merit fac tor (BMF) can be estimated for each specified bonded region by BMF = L - C - 0.5 x P L Where L = total length of bond - joint region inspected C = total length of all complete disbonds within the region P = total length of all partial disbonds within the region The minimum required bond

32、merit factor (BMF) for each lineal 250 mm span of bond is as specified on the engineering drawing. This value usually is in the range of 0.75 to 0.90. When necessary, different BMFs for selected bonded region s of an assembly can be specified and used as the acceptance criteria. Chemicals, materials

33、, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its fac ilities. FORD LABORATORY TEST METHOD BU 017-01 Page 6 of 8 Copyright 2000, Ford Global Technologies, Inc. NONDESTRUCTIVE INSPECTION OF AD

34、HESIVE BONDS APPENDIX A The Preparation, Selection and Certification of Adhesive Bond NDT Reference Specimens for FLTM BU 017 - 01 The proper preparation and selection of a bond reference specimen is a prerequisit e to obtaining meaningful and consistent results in the sonic NDI of bond joints. A re

35、ference specimen is required for use as a calibration standard because the Sondicator R bond tester essentially operates as a difference detecting device. It compares th e acoustic characteristics of unknown parts with those of a reference of known acceptable integrity. It is therefore essential tha

36、t the reference specimen resemble the parts to be inspected in material composition and have bond integrity equal to or only slightly better than that required in the final product. Specimen Preparation: A sample set of about 25 adhesively bonded specimens should be taken from production stock or pr

37、epared by the normal production procedure. The specimens must be prepared under adhesive bonding conditions that simulate accepted and expected production practice. Each specimen should be at least 150 x 150 mm with a 26 mm wide bonded lap joint running the length of the specimen. The specimens shou

38、ld be selected or prepared from d ifferent lots and batches, produced on different days by different shifts, in order to represent the distribution of the bond - quality population at that source. These specimens comprise a sample set from which at least two specimens will be selected. Selection: Th

39、e initial reference specimens for each new adhesive/adherend assembly are selected from the sample set by the following procedure. 1. Use one arbitrary bonded specimen as an interim reference to initially adjust the bond tester according to inst ructions in FLTM BU 017 - 01, or the instrument instru

40、ction manual. During this referencing, and all subsequent measurements in the procedure, each specimen should be supported by a material of low acoustic impedance, such as a soft plastic foam sheet about 2 cm thick, to reduce acoustic interferences from the supporting structure. 2. Monitor several b

41、ond joint locations on each of the specimens by placing the probe down firmly on a location along the bond line. A one kilogram mass is recommended for use as a probe hold - down weight, to assure the application of evenly distributed, reproducible and operator - independent firm pressure on the pro

42、be. (About four locations per specimen are suggested). Avoid locations where sharp changes in the readings are obser ved for small changes in probe position. Record phase, amplitude, and Alarm Activation Level (AAL) values for each monitored location. 3. Permanently identify (mark) each location and

43、 indicate the transducer probe orientation for future reference and dup lication. FORD LABORATORY TEST METHOD BU 017-01 Page 7 of 8 Copyright 2000, Ford Global Technologies, Inc. 4. Rank each monitored location according to its AAL value. Phase and amplitude values are recorded to verify that the ar

44、bitrary interim reference specimen was indeed bonded. AAL values are the combined results of phase and amplitude values and are used here to indicate bond integrity. 5. Select those bond locations ranking at or near the 40th percentile as reference candidates. These reference candidates should have

45、bond integrities, as indicated by their AAL values, higher than 35 % but no h igher than 45 % of the AAL values at bond locations monitored in the sample set. Each specimen containing one or more of these locations is a reference specimen candidate. 6. Reference the bond tester on the reference spec

46、imen candidate nearest the 40th percentile according to the described procedure. Then inspect each specimen ranked below the 40th percentile to find the highest ranking specimen causing bond - tester alarm activation. 7. Destructively test the highest ranked specimen causing alarm activa tion, and i

47、ts two nearest neighbors according to a prescribed tensile test or durability test procedure, to determine whether they met engineering bond specifications. 8. If the bond strength meets minimum requirements for the intended adhesive system app lication, the candidate specimens from the 40 th percen

48、tile are confirmed as valid initial reference specimens for the subject adhesive/adherend assembly application. If the bond joint does not meet minimum requirements, the engineer and the supplier shoul d be notified, a new sample set supplied and this selection procedure repeated. Subsequent referen

49、ce specimens may be selected from a new sample set of bonded specimens for the same adhesive/adherend assembly application by a somewhat more simple procedur e. 1. The initial reference specimen is used to adjust the bond tester according to the instructions in FLTM BU 17 - 1. 2. The same as step 2 above. 3. The same as step 3 above. 4. Select those bond locations having phase, amplitude, and AAL values very nearly equal to those obtained from the initial reference specimen as secondary reference specimen candidates. 5. Destructively test several bon