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Technical Support 5 How to Get Technical Support 5 Before You Contact MTS 6 If You Contact MTS by Phone 7 Problem Submittal Form in MTS Manuals 9 Preface 11 Before You Begin 11 Documentation Conventions 12 Introduction 15 Axial Extensometer Functional Description 17 About DC Conditioning 17 About Wheatstone Bridge 18 Transducer Calibration 19 Axial Extensometer Overtravel Protection 19 Extensometer Zero Reference 20 Axial Extensometer Accessories 20 Contents 3
Configuration 23 About Quick Attachment Spring Installation 23 How to Install Anchored Springs 24 How to Install an Attachment Adapter 25 How to Install Sliding Springs 26 How to Install Extension Springs or Elastic Bands 30 How to Change Knife Edges 32 About Gage Lengths 35 How to Use Gage Length Extenders 35 How to Use Gage Length De-Extenders 37 How to Connect the Cable 38 Calibration 41 Calibration Overview 41 Certified Calibration 41 Gain 41 Delta K 42 Symmetrical versus Asymmetrical Extensometers 42
Technical Support How to Get Technical Support Start with your manuals The manuals supplied by MTS provide most of the information you need to use and maintain your equipment. If your equipment includes MTS software, look for online help and README files that contain additional product information. If you cannot find answers to your technical questions from these sources, you can use the internet, e-mail, telephone, or fax to contact MTS for assistance.
Before You Contact MTS MTS can help you more efficiently if you have the following information available when you contact us for support. Know your site number and system number The site number contains your company number and identifies your equipment type (material testing, simulation, and so forth). The number is usually written on a label on your MTS equipment before the system leaves MTS. If you do not have or do not know your MTS site number, contact your MTS sales engineer.
Know relevant computer information If you are experiencing a computer problem, have the following information available: • Manufacturer’s name and model number • Operating software type and service patch information • Amount of system memory • Amount of free space on the hard drive in which the application resides • Current status of hard-drive fragmentation • Connection status to a corporate network Know relevant software information For software application problems, have the following informa
Identify system type To assist the Call Center agent with connecting you to the most qualified technical support specialist available, identify your system as one of the following types: • Electromechanical materials test system • Hydromechanical materials test system • Vehicle test system • Vehicle component test system • Aero test system Be prepared to troubleshoot Prepare yourself for troubleshooting while on the phone: • Call from a telephone when you are close to the system so that you can t
Problem Submittal Form in MTS Manuals Use the Problem Submittal Form to communicate problems you are experiencing with your MTS software, hardware, manuals, or service which have not been resolved to your satisfaction through the technical support process. This form includes check boxes that allow you to indicate the urgency of your problem and your expectation of an acceptable response time. We guarantee a timely response—your feedback is important to us.
Technical Support
Preface Before You Begin Safety first! Before you attempt to use your MTS product or system, read and understand the Safety manual and any other safety information provided with your system. Improper installation, operation, or maintenance of MTS equipment in your test facility can result in hazardous conditions that can cause severe personal injury or death and damage to your equipment and specimen. Again, read and understand the safety information provided with your system before you continue.
Conventions Documentation Conventions The following paragraphs describe some of the conventions that are used in your MTS manuals. Hazard conventions As necessary, hazard notices may be embedded in this manual. These notices contain safety information that is specific to the task to be performed. Hazard notices immediately precede the step or procedure that may lead to an associated hazard. Read all hazard notices carefully and follow the directions that are given.
Note Resources that are put back on the hardware lists show up at the end of the list. Special terms The first occurrence of special terms is shown in italics. Illustrations Illustrations appear in this manual to clarify text. It is important for you to be aware that these illustrations are examples only and do not necessarily represent your actual system configuration, test application, or software.
Preface
Introduction This manual describes the MTS axial extensometer family. Axial extensometers measure changes along the length of a specimen. Axial extensometers are suitable for a variety of static and dynamic testing applications including tension/compression testing, low and high cycle fatigue, creep/stress relaxation testing, and strain rate testing. Several accessories are available such as gage length extenders, gage length deextenders, knife edges, and attachment methods.
What you need to know This manual assumes that you know how to use your system controller. See the appropriate manual for information about performing any controller-related step in this manual’s procedures. You are expected to know how to: • Select a control mode. • Manually adjust the actuator position. • Zero a sensor output. • Install a specimen. Related documentation This manual covers topics that are common among all axial extensometers.
Axial Extensometer Functional Description An axial extensometer is a sensor attached to a specimen that measures a dimensional change (gage length or strain) that occurs in the specimen while being tested. Extensometers use a Wheatstone bridge circuit to detect the dimensional changes. Because they are DC devices, they require a DC conditioner for signal processing. The following paragraphs describe the functions of the axial extensometers.
About Wheatstone Bridge The axial transducer uses precision, resistance-type, foil strain gages bonded to a metallic element to form a Wheatstone bridge. Two knife edges on the transducer arms contact the specimen. Elongation or compression of the specimen causes movement of the transducer arms. This movement bends the metallic element, changing the resistance of the strain gages.
Transducer Calibration The DC conditioner and the transducer signal must be calibrated. Calibration ensures that the transducer signal accurately represents the gage length measure by the transducer. Calibration involves adjusting the excitation voltage and gain of the DC conditioner to achieve the desired transducer signal. The purpose of calibration is to equate a specific transducer displacement to a specific voltage. When the transducer is calibrated, it is matched to a DC conditioner.
Extensometer Zero Reference There are three zero reference methods used by MTS’s extensometers: zero pin, zero stop, and fixture. The zero reference position is important when calibrating the extensometer output signal or when mounting an extensometer to a specimen. Zero pin Some extensometers includes a zero pin that can be inserted into a zero reference hole. This locks the extensometer arms in the zero reference position. This is useful for specimen installation.
• • Introduction A variety of knife edges allow the extensometer to be used with different specimen shapes: – Straight knife edge sets for round specimens. Kits are available for standard, heavy duty, and extended length straight knife edges. – Three-point contact knife edge sets for flat specimens. Kits are available for standard, heavy duty, and extended length three-point contact knife edges.
Introduction
Configuration This section describes how to configure an axial extensometer with quick attachment springs, elastic bands, or metal extension springs. It also describes how to change the knife edges, gage length of the extensometer, and how to connect it to a controller.
CAUTION Excessive torque on the extensometer arms can damage the extensometer. The extensometer arms can be damaged when mishandled. Do not hold the extensometer case when loosening or tightening the socket head cap screws. Use an adjustable wrench to hold the extensometer arm or attachment adapter. Loosen or tighten only those socket head cap screws on the arm being held with the wrench.
1. Check your installation drawing. If your extensometer needs an attachment adapter, perform the appropriate procedure before proceeding. 2. Separate the spring retainers from the springs by loosening (do not remove) the socket head cap screws. 3. Mount one spring in the appropriate hole in the attachment adapter as determined by the specimen dimensions (see the installation drawing). 4. Slide the spring retainer over the end of the spring and tighten the socket head cap screw.
2. Using a small adjustable wrench, grasp the sides of the upper arm. 3. Loosen the socket head cap screws with a hex wrench. 4. Repeat Step 2 and Step 3 to loosen the socket head cap screws on the lower arm. 5. With the attachment hook in place, loosely attach the quick attachment spring attachment adapter to the extensometer arm. Repeat this step for the other arm. 6. Slide the selected knife edge under the attachment adapter and between the two socket head cap screws on each extensometer arm.
Slide Spring Components 1. Zero the arms of the extensometer. Depending on the extensometer, this can be accomplished using the zero pin, stop block, or a special fixture. 2. Using a small adjustable wrench, grasp the sides of the upper arm. . Hex Wrench Adjustable Wrench 3. While securely holding the extensometer arm, loosen the socket head cap screws with a hex wrench. 4. Repeat Step 2 and Step 3 to loosen the socket head cap screws on the lower arm. 5.
10. Place one edge of a machinist’s square against the front edge of the top extensometer arm. Adjust the attachment adapter until the alignment rod contacts the perpendicular edge of the square. . Perpendicular Alignment of Rod and Square Slider Spring 90o Attachment Adapter Square 11. To align the alignment rods vertically, place the flat surface of the machinist’s square against the alignment rod in the upper attachment adapter.
. Hex Wrench Attachment Adapter Grasp the attachment adapter with a small adjustable wrench when using the hex wrench. 14. While securely holding the attachment adapter, fully tighten the socket head cap screws in that arm of the extensometer with a hex wrench. 15. Repeat Step 13 and Step 14 to tighten the other attachment adapter. 16. Remove the alignment rod from the attachment adapter.
How to Install Extension Springs or Elastic Bands Installing the extension spring or elastic band attachment system involves replacing the quick attachment spring attachment adapters on each arm of the extensometer with knife edge hold-downs and attachment hooks. Attachment Hook Extension Spring Upper Arm m MODEL xxx.xxx-xx Lower Arm Component Identification CAUTION Excessive torque on the extensometer arms can damage the extensometer. The extensometer arms can be damaged when mishandled.
To install the attachment hooks: 1. Zero the arms of the extensometer. Depending on the extensometer, this can be accomplished using the zero pin, stop block, or a special fixture. 2. Using a small adjustable wrench, grasp the sides of the upper arm. Hex Wrench Adjustable Wrench 3. While securely holding the extensometer with the wrench, loosen the socket head cap screws with a hex wrench. 4. Repeat Step 2 and Step 3 to loosen the socket head cap screws on the lower extensometer arm. 5.
8. Loosely attach the upper knife edge hold-down to the upper extensometer arm using the two socket head cap screws removed in Step 5. Ensure that the attachment hook is behind both socket head cap screws. 9. Repeat Step 7 and Step 8 for the lower arm. 10. Tighten the socket head cap screws only enough to secure the knife edges. 11.
Knife edges are available in the standard size, in a heavy duty size, and in an extended length size. The heavy duty and extended length knife edges are approximately twice as thick as the standard ones. To maintain the proper gage length, the contact edge is off center. Heavy duty and extended length knife edges also require special knife edge hold-downs or special attachment adapters for quick attachment springs.
3. While securely holding the extensometer arm or attachment adapter, loosen the socket head cap screws with a hex wrench just enough to remove the knife edges. 4. Repeat Step 2 and Step 3 to loosen the socket head cap screws in the lower arm. 5. Slide out the existing knife edge. Note When using heavy duty or extended length knife edges, the contact edges are off center to maintain the proper gage length. The orientation of the knife edges will vary depending on the extensometer model being used.
8. If necessary, use a small adjustable wrench to grasp the sides of one extensometer arm or attachment adapter (see the figure in Step 2). 9. While securely holding the extensometer arm or attachment adapter, fully tighten the socket head cap screws in that arm with a hex wrench. 10. Repeat Step 8 and Step 9 to tighten the socket head cap screws in the other extensometer arm.
The following procedure describes a typical gage length extender installation. Actual installation may vary, see the installation drawing accompanying the gage length extender for specific details. 1. Zero the arms of the extensometer. Depending on the extensometer, this can be accomplished using the zero pin, stop block, or a special fixture. 2. Remove the existing knife edge hold-down or quick attachment adapter from the upper arm of the extensometer.
How to Use Gage Length De-Extenders Gage length de-extenders let you change where the extensometer contacts the specimen. The following figure shows a typical gage length de-extender. Cap Screw Each gage length de-extender comes with a knife edge holddown, knife edge and spring attachment hook already installed. De-extender Knife Edge m Hold-down MODEL xxx.xxx-xx The following procedure describes a typical gage length de-extender installation. Actual installation may vary.
How to Connect the Cable The extensometer cable connects to the system controller via an extension cable. The extensometer has a small cable and connector built in. An extension cable is installed between the extensometer connector and the system controller. Ensure that the extensometer is connected to the appropriate controller connector. The controller connector must be associated with a DC conditioning circuit. The following figure shows the circuitry and connector pin assignments from the extensometer.
2. Connect the connector, attached to the cable extending from the extensometer, to the mating connector on the appropriate system cable. Note An adapter cable (MTS part number 039-704-601) is available which allows connection between the PT connector on the extensometer cable and an Amphenol connector on an existing system cable. 3. Mount the connector assembly in the plastic holder.
Configuration
Calibration This section describes how to calibrate an axial extensometer with a controller. Calibration ensures that the output from the extensometer accurately represents the displacement measured by the extensometer. Three adjustment methods are described. Contents How to Use a Vernier Caliper 43 How to Use a Calibration Block 46 How to Use a Calibration Stand 47 Calibration Overview The calibration process coordinates the interaction between the transducer, a DC conditioning circuit, and a cable.
the full travel range of the transducer. (Full-scale ranges of 5% may be possible, but some increase in drift and noise will result.) In most transducers, the best linearity is obtained by setting the gain between 70% and 90% of the desired travel range instead of 100%. The adjustment procedures in this manual use 80% full scale as the reference value. Delta K Delta K is a feature of DC conditioners manufactured by MTS Systems Corporation.
and calculate the new conditioner output value for the displacement. For example, suppose the calibration block is set for 7.94 mm. Then your desired output would be 7.94 V. The following table shows the proper conditioner output for each extensometer displacement of the preceding example. .
D. Prepare to use the calibration controls on your controller. E. Adjust the excitation control to set the excitation to +6 V DC or the voltage specified in the extensometer documentation. 2. Zero the conditioner output. The arms of the extensometer must be in the zero reference position. Depending on the extensometer, this can be accomplished using the zero pin, stop block, or a special fixture. Adjust the zero control to set the extensometer signal to 0.00 V DC.
C. Adjust the gain control to set the extensometer signal to -8 V DC (or 80% of your calculated output). 4. Readjust the zero and compression. Repeat Step 2 and Step 3 until the zero and gain outputs can be measured without readjustment. 5. Adjust tension. . m True Measurement Since a true measurement is from the middle of each extensometer arm knife edge, you must add the thickness of one of the knife edges. Calibration A. Measure the extensometer arms as shown.
• If the extensometer signal is below +8 V DC (or your calculated output), the ΔK adjustment cannot be made. Return the ΔK adjustment to its original setting and use the gain control to increase the voltage halfway from its present value to +8 V DC (this splits the difference between compression and tension). How to Use a Calibration Block MTS recommends using a calibration block to establish the initial gain setting of the conditioner. The calibration block is a metal block with grooves cut into it.
A. Remove the zero pin, fixture, or release the zero stop and install the extensometer on the calibration block so that the extensometer arms are in the grooves that represent about 80% compression displacement. B. Adjust the gain control to set the extensometer signal to -8 V DC (or 80% of your calculated output). 4. Readjust the zero and compression. Repeat Step 2 and Step 3 until the zero and gain outputs can be measured without readjustment. 5. Adjust tension.
. m A. Connect the extensometer to your controller. B. Monitor the excitation voltage. C. Monitor the extensometer signal. D. Mount the extensometer onto the calibrator. Install it for the zero position. Use the zero pin if it is available. This figure shows a typical installation. Each extensometer can use a variety of extensions, attachments, and other mounting accessories. E. Prepare to use the calibration controls on your controller. F.
3. Adjust compression. A. Remove the zero pin, fixture, or release the zero stop. B. Adjust the calibrator between zero and 100% compression of the extensometer's full-scale range three times. This exercises the extensometer to remove any hysteresis. C. Adjust the calibrator for the 80% compression setting (or the range being calibrated) and note the voltmeter reading. • If the meter reading is less than -8 V DC you can adjust gain.
Calibration
Installation This section describes how to mount the extensometer to a specimen and zero the extensometer output. Contents How to Mount an Extensometer About Quick Attachment Springs About Metal Extension Springs About Elastic Bands 52 53 57 60 WARNING Handling the extensometer while it is selected as the active control mode can cause the actuator to move unpredictably. Unpredictable actuator movement can cause personnel injury or damage to the test equipment.
See your controller manual for information on establishing the extensometer zero output signal. The electrical output of the extensometer is adjusted so that zero strain equals zero volts output. Depending on the extensometer, the zero reference can be accomplished using the zero pin, stop block, or a special fixture. • Some extensometers includes a zero pin that can be inserted into a zero reference hole. This locks the extensometer arms in the zero reference position.
1. Zero the arms of the extensometer. Depending on the extensometer, this can be accomplished using the zero pin, stop block, or a special fixture. 2. Hold the extensometer so that its knife edges contact the specimen. 3. Secure the upper arm around of the extensometer the specimen. • If you are using an anchored spring mount, clip the spring around the specimen. If you need to change the anchor position, see the appropriate procedure.
out of the attachment adapter or by anchoring the spring in a different hole on the attachment adapter. Note If the specimen dimension is outside the range of the quick attachment springs, other attachment methods must be used, such as metal extension springs or elastic bands (an assortment is provided with the extensometer), half disks, or wireform springs.
1. The arms of the extensometer must be in the zero reference position. Depending on the extensometer, this can be accomplished using the zero pin, stop block, or a special fixture. CAUTION The extensometer arms can be damaged when mishandled. Excessive torque on the extensometer arms can damage the extensometer. Use an adjustable wrench to hold the extensometer arm or attachment adapter. Loosen or tighten only those socket head cap screws on the arm being held with the wrench.
Specimen Dimension Wire End Length 6. Ensure that the plane of the spring end is perpendicular to the side of the extensometer. 7. While securely holding the attachment adapter with the adjustable wrench, tighten the spring locking screw on that attachment adapter. 8. Repeat Steps 1–6 for the other spring. 9. Check to ensure that both springs are parallel to each other and perpendicular to the side of the extensometer.
Spring Attachment Adapter l Spring Retainer MODEL 632.xx l MODEL 634.xx 2. Mount one spring in the appropriate hole in the attachment adapter as determined by the specimen dimensions (see the installation drawing). 3. Slide the spring retainer over the end of the spring and tighten the socket head cap screw. Orient the spring retainer in such a way that it will not interfere with movement of the extensometer arm.
One spring can be used on smaller diameter specimens. Two springs can be used for larger diameter specimens. Flat specimens An extensometer can be mounted to a flat specimen with extension springs using a disk or wireform attachment. When using a wireform attachment, it is necessary to replace the attachment adapters with knife edge hold-downs. The disk attachment is for narrow, flat specimens. The wireform attachment is for wide, flat specimens.
SPRING FREE LENGTH MM (IN) SPECIMEN DIAMETER MM (IN) Free Length Measurement for Single Spring 12.7 (0.50) 2.0 (0.08) 340 3.0 (0.12) 670 4.0 (0.16) 950 15.9 (0.62) 19.0 (0.75) Free Length Measurement for Multiple Springs 22.2 (0.87) 25.4 (1.00) 28.6 (1.12) 31.8 (1.25) 34.9 (1.37) 38.1 (1.50) 440 5.0 (0.20) 660 300 6.0 (0.24) 840 480 7.0 (0.28) 1000 640 340 8.0 (0.32) 780 495 9.0 (0.35) 925 620 360 10.0 (0.39) 1080 750 500 315 11.0 (0.43) 880 620 470 12.0 (0.
About Elastic Bands Elastic bands are commonly used for testing at near room temperature. The contact force may be varied by the cross-section size of the elastic band and its overall length. Elastic bands can be used by all axial extensometers. • Elastic bands (rubber bands) of the type provided with the extensometer are available from stationery supply stores. • Orthodontic elastic bands may also be used and are available from medical supply houses.
The disk attachment is for narrow, flat specimens. The wireform attachment is for wide, flat specimens. Contact force Determining the specimen contact force when using elastic bands is difficult. • Greater contact force will provide a more secure attachment under conditions where slippage may occur such as operating at high cyclic frequencies. The knife edges can damage the specimen at high contact forces.
Installation
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