Opsens strain gauge installation guide

Transcription

1 Opsens strain gauge installation guide Opsens inc 2014 rue Cyrille Duquet, Suite 125 Quebec, Quebec G1N 4N6, Canada Tel. : Fax: info@opsens.com STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 1

2 WARRANTY All products manufactured by Opsens inc. are warranted to be free of defects in workmanship and materials for a period of one year from the date of shipment. No other express warranty is given, and no affirmation of Seller, by words or actions, shall constitute a warranty. SELLER DISCLAIMS ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSES WHATSOEVER. If any defect in workmanship or material should develop under conditions of normal use and service within the warranty period, repairs will be made at no charge to the original purchaser, upon delivery of the product(s) to the factory, shipping charges prepaid. If inspection by Opsens or its authorized representative reveals that the product was damaged by accident, alteration, misuse, abuse, faulty installation or other causes beyond the control of Opsens, this warranty does not apply. Service, repairs or disassembly of the product in any manner, performed without specific factory permission, voids this warranty. OPSENS MAKES NO WARRANTY OF ANY KIND WITH REGARD TO THIS MANUAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Opsens shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material. This warranty does not apply to the transducers sold for use with Opsens signal conditioners. IMPORTANT NOTICE The product specifications and other information contained in this manual are subject to change without notice. Opsens has made a concerted effort to provide complete and current information for the proper use of the equipment. If there are questions regarding this manual or the proper use of the equipment, contact Opsens inc at: TEL WEB SITE FAX info@opsens.com PACKAGING FOR SHIPMENT If the product must be shipped to a different location or returned to Opsens for any reason through a common carrier it must be properly packaged to minimize risks of damage. STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 2

3 HANDLING PRECAUTIONS Epoxy resins and hardeners may cause dermatitis or other allergic reactions, particularly with persons with sensitive skin. The user is cautioned to: (1) avoid contact with either the resin or hardener; (2) avoid prolonged or repeated breathing of the vapors; and (3) use these materials only in well-ventilated areas. If skin contact occurs, thoroughly wash the contaminated area with soap and water immediately. In case of eye contact, flush immediately and secure medical attention. Rubber gloves and aprons are recommended, and care should be taken not to contaminate working surfaces, tools, container handles, etc. Spills should be cleaned up immediately. For additional health and safety information, consult the Material Safety Data Sheet which is available upon request. INTRODUCTION The procedures for bonding fiber optic strain gauges should be similar to the procedures recommended for bonding conventional strain gauges. Epoxy and ceramics adhesives and even metal arc spraying can be used to bond fiber optic strain gauges. High residual compression strain occurs with conventional strain gauges when adhesive is heat cured at elevated temperature. When gauges adhered to the piece at elevated temperature, compressive strains are generated in the gauges as the piece cools down. Residual compression strain can be controlled by curing the adhesive while the piece is put into tension prior to cooling, or consideration may be given to this behavior while ordering the gauges. Contact Opsens for information. Opsens suggests using the following adhesives: - M-BOND AE-10/15 (provides better adhesion) or GA-2 epoxy adhesive (easy to use due to high viscosity) for low temperature applications up to 95 C. - For high temperature applications we recommend the use of the M-BOND 610 (up to 370 C short term and 260 C long term) from MEASUREMENTS GROUP (Micro-Measurements Division). Opsens provides some basics steps for bonding fiber optic strain gauges with in the following paragraphs. Please consult also the following accessories and products which will be required for strain gauge bonding procedures: CSM-1A Degreaser (from Measurements Group) or Isopropyl Alcohol; MJG-2 Mylar Tape (from Measurements Group) or "Scotch" Tape; M-Prep Conditioner A (from Measurements Group) or mild phosphoric acid compound (10 % concentration in distilled water); M-Prep Neutralizer 5A (from Measurements Group) or ammonia-based neutralizer compound made of Isopropanol (15 % conc), Ammonium Hydroxide (5 % conc), and Distilled Water (80 % conc); Five Minute type epoxy; Electrical Tape; Silicon-Carbide Abrading Paper (Grit 220 or 320 and grit 400); Low lint wipers (Kimwipes wipers); Cotton tipped applicators (Cotton Swabs). Optional STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 3

4 M-Coat Protective Coating (from Measurements Group). 1.0 SURFACE PREPARATION The surface preparation techniques are similar to basic procedures as for conventional strain gauges STEP 1.1 Clean and thoroughly degrease the surface on which the gauge will be bonded with. CSM-1A Degreaser is recommended. The substitution of Isopropyl Alcohol as a degreasing agent should be considered for materials that may be sensitive to strong solvents. Any degreasing should be done with clean solvents. STEP 1.2 Dry-abrade the gauging area with 220- or 320-grit silicon-carbide paper to remove any scale or oxides on the base material. Apply M-Prep Conditioner A (or the equivalent compound) and wet-abrade the gage area. Keep the surface wet while abrading. Remove the residue and Conditioner by slowly wiping through the gauging area with clean low lint wipers. Repeat the wet-abrade and wiping procedure with 400-grit silicon-carbide paper. Rewet the surface with Conditioner A (or the equivalent compound) and scrub with cotton tipped applicators until a clean applicator is no longer discolored by the scrubbing. Remove the residue and Conditioner by slowly wiping through the gauging area with a clean Kimwipes. STEP 1.3 Apply a liberal amount of M-Prep Neutralizer 5A (or the equivalent compound) to the gauge area. Keeping the surface wet, scrub with cotton tipped applicators. Do not allow evaporation of the cleaning material on the specimen surface since this would leave a thin, unwanted film between the adhesive and the specimen. Remove the Neutralizer by slowly wiping through the gauge area, allowing the clean Kimwipes to absorb the Neutralizer. Do not wipe back and forth over the gage area since this may allow contaminants to be redeposit on the cleaned area. STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 4

5 2.0 SENSOR ATTACHMENT TECHNIQUES STEP 2.1 The fiber optic gauge is first hold in place by applying a piece of electrical tape on the incoming optical fiber 2.5 cm away from the micro capillary to maintain proper alignment. The gauge sensitive region is collinear to the axis of the fiber. (See the schematic description printed on the lid of the strain gauge container for the location of the gauge sensitive region). If the gauge is not in good contact with the specimen, another piece of Scotch tape or Mylar adhesive tape may be applied, with caution!, at the tip of the gauge (over 1 mm only). The part of this tape that installs over the micro-capillary must be non-adhesive. Use a separate smaller piece of tape and bound their adhesive faces together so to form a non-adhesive part on the tape. NOTE: The gauge micro-capillary is made of glass and doesn't have any protective coating so it should be handled with care prior to bonding the gauge. Any scratches made to the glass micro-capillary may impair the efficiency and the lifetime of the gauge Micro-capillary Gauge sensitive region Incoming optical fiber Fiber optic cable Electrical tape STEP minute epoxy micro-capillary 3 mm The incoming optical fiber must then be secured on the specimen with a very small drop (less than 1 mm) of 5-minute epoxy about 3 mm away from the micro capillary. The purpose of this step is to maintain the gauge alignment while the adhesive will be applied and cured. CAUTION: To ensure that the 5-minute epoxy will not flow to the micro-capillary, we recommend letting the epoxy cure slightly before applying it on the fiber in order to increase viscosity. STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 5

6 Remainder: To avoid surface contamination, do not touch the micro-capillary of the fiber optic strain gauge with your hands. The gauge micro-capillary must be free of grease, dust, etc. If necessary, use a Duster can or clean dry air to blow away dust, dirt and grit on the microcapillary STEP 2.3 DO DON'T Once the 5-minute epoxy is cured, gently remove the tape at the tip of the microcapillary if you had applied one. Mix the adhesive by following the mixing instructions of the adhesive manufacturer. However we recommend mixing the resin and hardener of the epoxy adhesive slowly to prevent entraining excessive amount of air Adhesive (bubbles). Use a clean stick (or brush) and apply the adhesive slowly using a linear motion parallel to the gauge orientation. Make sure the entire gauge is covered from the tip to the 5-minute epoxy. To prevent Side view entraining air (bubbles), the adhesive must be applied in the direction collinear to the gauge. Risk of air bubbles Side view STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 6

7 Remainder: the key for successful strain gauge bounding is to have a good contact between the gauge and the specimen to measure STEP Minutes Epoxy You may also apply a protective coating like the M-Coat Protective Coating (from Measurements Group) over the adhesive for improved protection against chemical attack, moisture, etc. Protective coating Electrical tape 3.0 MATING THE GAUGES TO THE CONDITIONING INSTRUMENT For proper use of the fiber optic strain gauges, the gauge fiber optic connectors must be kept clean and free of dust at all times. Any dust may obstruct the light transmitted from one connector to the other, and reduce the signal-to-noise ratio to an unusable level. IT IS A GOOD PRACTICE TO ALWAYS CLEAN THE GAUGE CONNECTOR BEFORE MATING TO THE INSTRUMENT. Gauge connectors are cleaned by wiping the end with low lint tissue such as Kimwipes or with lens cleaning tissues. By keeping your gauge connectors clean you will also prevent the contamination of the conditioner input connectors. However, we recommend cleaning these input connectors once in a while. Consult Opsens IMP0044 How to clean the probes and conditioner connectors.doc STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 7

8 M-Bond AE-10 Adhesive (Supplier Vishay Micro-Measurements) Curing process recommended by Opsens The curing process should be C follows by 60 C and finishes with C. Description Two-component, 100% solids epoxy system for general-purpose stress analysis. Transparent, medium viscosity. A cure time as low as six hours at +75 F (+24 C) may be used. ( AE-15 is recommended for more critical applications, including transducers.) Elevated-temperature postcure is recommended for maximum stability, and/or tests above room temperature. Highly resistant to moisture and most chemicals, particularly when postcured. For maximum elongation, bonding surface must be rough. Cryogenic applications require very thin gluelines. M-Bond AE-10 Kit Cure Requirements Preferred Room-Temperature Cure : hours at +75 F (+24 C) Recommended Postcure: 2 hours at 25 F (15 C) above the maximum operating temperature. Operating Temperature Range Long Term: -320 to +200 F (-195 to +95 C) Elongation Capabilities 1% at -320 F (-195 C) 6% to 10% at +75 F (+24 C) 15% at +200 F (+95 C) Shelf Life * 12 months at +75 F (+24 C) 18 months at +20 F (-7 C) STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 8

9 Operating Temperature Range Long Term: -320 to +200 F (-195 to +95 C) Elongation Capabilities 1% at -320 F (-195 C) 6% to 10% at +75 F (+24 C) 15% at +200 F (+95 C) Shelf Life * 12 months at +75 F (+24 C) 18 months at +20 F (-7 C) If crystals form in resin bottle, heat to +120 F (+50 C) for 30 minutes. Cool before mixing. Pot Life 15 to 20 minutes at +75 F (+24 C) Can be extended by cooling jar or by spreading adhesive on clean aluminum plate. Operating Temperature Range Long Term: -320 to +200 F (-195 to +95 C) Elongation Capabilities 1% at -320 F (-195 C) 6% to 10% at +75 F (+24 C) 15% at +200 F (+95 C) Shelf Life * 12 months at +75 F (+24 C) 18 months at +20 F (-7 C) If crystals form in resin bottle, heat to +120 F (+50 C) for 30 minutes. Cool before mixing. Pot Life 15 to 20 minutes at +75 F (+24 C) Can be extended by cooling jar or by spreading adhesive on clean aluminum plate. Clamping Pressure 5 to 20 psi (35 to 140 kn/m 2 ) Instruction Manual B-137 Operating Temperature Range Long Term: -320 to +200 F (-195 to +95 C) Elongation Capabilities 1% at -320 F (-195 C) 6% to 10% at +75 F (+24 C) 15% at +200 F (+95 C) Ordering Information M-Bond AE-10 Kit (as shown above) with 6 mixing jars (10 g each) Resin, 1 bottle (15ml) Curing Agent 10, 6 calibrated pipettes, 6 stirring rods. M-Bond AE-10 Bulk includes of 200 g Resin, 40 g Curing Agent 10, 3 calibrated pipettes STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 9

10 M-Bond 610 Adhesive (Supplier Vishay Micro-Measurements) Description Two-component, solvent-thinned, epoxy-phenolic adhesive for high-performance applications, including high-precision transducers. Solids content 22%. Widest temperature range general-purpose adhesive available. Low viscosity, capable of gluelines < in (0.005 mm). Extremely thin, hard, void-free gluelines minimize creep, hysteresis, and linearity problems. Life limited by oxidation and sublimation effects at elevated temperatures. M-Bond 610 Kit Cure Requirements Elevated temperature required. Recommended Postcure : 2 hours at 50 to 70 F (30 to 40 C) above the maximum operating temperature, or cure temperature, whichever is higher. High Precision Transducer Postcure: 2 hours at +400 F to +450 F (+205 C to +230 C) after wiring. Operating Temperature Range Short Term: -452 to +700 F (-269 to +370 C) Long Term: -452 to +500 F (-269 to +260 C) Transducers: to +450 F (+230 C) Elongation Capabilities 1% at -452 F (-269 C) 3% at +75 F (+24 C) 3% at +500 F (+260 C) Shelf Life * 9 mo at +75 F (+24 C) 15 mo at +40 F (+5 C) STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 10

11 Pot Life 6 weeks at +75 F (+24 C) 12 weeks at +40 F (+5 C) Clamping Pressure 10 to 70 psi (70 to 480 kn/m 2 ) 30 to 40 psi (200 to 275 kn/m 2 ) Instruction Manual B-130 Ordering Information M-Bond 610 Kit (as shown above) with 4 bottles (14g each) Resin, 4 bottles (11g each) Curing Agent, 4 brush caps for dispensing mixed adhesive, 4 disposable mixing funnels. STRAIN GAUGE INSTALLATION2005R1 - SIMPLIFY.DOC VER1.0, REV. 08/01/07 11