Series 647 Hydraulic Wedge Grips Reference Manual Axial Grips Axial-Torsional Grips All-Temperature Grips 100-027-131 N be certain.
© 2013 MTS Systems Corporation. All rights reserved. Original Instructions (English): 100-027-131 N Trademark Information MTS, be certain., Bionix, ElastomerExpress, FlatTrac, FlexTest, Just In Case, LevelPlus, MTS Criterion, MTS EM Extend, MTS Insight, MTS Landmark, RPC, ServoSensor, SWIFT, Temposonics, TestWare, TestWorks are registered trademarks of MTS Systems Corporation within the United States.
Contents Technical Support 7 How to Get Technical Support.................................................................................................................7 Before You Contact MTS.........................................................................................................................7 If You Contact MTS by Phone.................................................................................................................9 Problem Submittal Form in MTS Manuals..............
Practice good housekeeping.......................................................................................................33 Do not exceed the Maximum Supply Pressure..........................................................................33 Do not disable safety devices.....................................................................................................33 Provide adequate lighting........................................................................................................
About Grip Pressure Determination...........................................................................................79 Determine Gripping Pressure - Axial for Round Specimens (and Axial/Torsional for Flat Specimens).81 Determine Gripping Pressure - Axial-Torsional for Round Specimens Only............................82 Change/Install Wedges...........................................................................................................................83 Change Model 647.02 - 647.100 Wedges.
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 software, look for online help and README files that contain additional product information. Technical support methods MTS provides a full range of support services after your system is installed. If you have any questions about a system or product, contact Technical Support in one of the following ways.
When you have more than one MTS system, the system job number identifies your system. You can find your job number in your order paperwork. Example system number: US1.
If You Contact MTS by Phone A Call Center agent registers your call before connecting you with a technical support specialist. The agent asks you for your: • Site number • Name • Company name • Company address • Phone number where you can be reached If your issue has a notification number, please provide that number. A new issue will be assigned a unique notification number.
After you call MTS logs and tracks all calls to ensure that you receive assistance for your problem or request. If you have questions about the status of your problem or have additional information to report, please contact Technical Support again and provide your original notification number.
Preface Before You Begin Safety first! Before you use your MTS product or system, read and understand the safety information provided with your system. Improper installation, operation, or maintenance can result in hazardous conditions that can cause severe personal injury or death, or damage to your equipment and specimen. Again, read and understand the safety information provided with your system before you continue. It is very important that you remain aware of hazards that apply to your system.
Caution notices indicate the presence of a hazard with a low level of risk which, if ignored, could cause moderate or minor personal injury or equipment damage, or could endanger test integrity. Other special text conventions Important: Important notices provide information about your system that is essential to its proper function. While not safety-related, if the important information is ignored, test results may not be reliable, or your system may not operate properly.
Introduction Topics: • Overview Reference..............................................................................................................................14 • Series 647 Hydraulic Wedge Grips Component Identification...............................................................16 • Series 647 Hydraulic Wedge Grips Functional Description...................................................................19 • About Gripping Specimens.........................................................
Introduction Overview Reference The MTS Series 647 Hydraulic Wedge Grips grasp and hold a specimen in place during testing, and provide a constant, hydraulically actuated gripping force regardless of the applied test loads. The grips are specifically designed for static or fatigue testing applications in MTS testing systems. A variety of wedges allow the grips to be used to test a variety of materials. Optional equipment includes a cooling/warming kit and an external hydraulic grip supply.
Introduction • Turn hydraulic pressure on and off. • Select a control mode. • Manually adjust the actuator position. • Monitor a sensor signal. Related products See the following product information manuals for information about the related products. • • The hydraulic controls for the Series 647 Hydraulic Grips can be located on the front panel of the load unit or on an external unit (controls and a hydraulic power unit for the grips).
Introduction Series 647 Hydraulic Wedge Grips Component Identification Series 647 Hydraulic Grip Components 16 Series 647 Hydraulic Wedge Grips Reference Manual
Introduction Item Description Item Description A Axial Grips B All Temperature Grips 1 Load Unit Crosshead 13 Water Cooling Lines 2 Force Transducer 14 Upper Grip Assembly 3 Shim 15 Environmental Chamber 4 Spiral Washer Set 16 Lower Grip Assy 5 Connector Stud 17 Water Cooling Lines 6 Upper Grip C Axial/Torsional Grips 7 Hydraulic Pressure and return Lines 18 Adapter Plate 8 Wedges (647.
Introduction Item Description hydraulic grip supply. Each grip has two hydraulic lines connected to it; a hydraulic pressure port and a hydraulic return port. Wedges Contacts and holds the specimen in place. A variety of wedges are available, for flat specimens, round specimens, hard specimens, and soft specimens. Wedges are available as matched sets of four. Each model has wedges that are designed for its use. The 647.
Introduction Item Description • Adapter plate Allows axial-torsional grips to be mounted to a force transducer. The adapter provides the thread needed to use the couplings. • Upper and lower couplings Clamps the grips to the to the actuator and force transducer (via an adapter). The couplings have left and right handed threads that preloads the grip connection and prevents offsets in the force train.
Introduction Item Description Item Description 3 Wedges 13 Cylinder 4 Specimen Guide (flat specimens only) 14 Grip Piston 5 Wedge Chamber 15 Preload Chamber 6 Hydraulic Release 16 End Cap 7 Hydraulic Pressure 17 Piston Extension 8 Preload Chamber 18 Hydraulic Release 9 End Cap 19 Hydraulic Pressure 10 Grip Piston About Gripping Specimens The grips provide a constant, hydraulically actuated gripping force regardless of the applied test loads.
Introduction • Smooth surfaces can grip specimens that cannot tolerate imperfections on the grip surface. This surface also has a lower force rating. Water-cooled wedges are available for applications where the specimen is heated. A water cooling kit includes the parts to connect the wedges to a water source and regulate the water flow. About Spiral Washers The optional Model 601 Spiral Washers are commonly used when installing axial grips.
Introduction About Environmental Chambers The grips can be mounted for room temperature testing or testing in an environmental chamber. The temperature range of the grips is determined by the type of seals used in the grips and the type of fluid used for the grips. There are two methods for using grips in an environmental chamber (as shown in the following figure).
Introduction Hydraulic Fluid Recommendations All frame mounted 3000 psi and 10,000 psi grip supplies use standard Mobile DTE-25 hydraulic fluid from the HPU. The grips that use this fluid are rated to 65 °C (150 °F) maximum. All other hydraulic grips that are used within a chamber are rated to maximum of 177 °C (350 °F). These grips require the use of a stand alone grip supply that uses Mobile SHS 525 hydraulic fluid. This fluid has a flash point and overall temperature rating higher than 177 °C (350 °F).
Introduction Series 647 Hydraulic Wedge Grip Force and Torque Capacities The amount of torque the grips can produce is reduced with biaxial operation. The amount of torque is affected by the amount of axial force and the diameter of the specimen. The graphs, which follow the table, illustrate the axial-torsional performance envelope of the Model 647.02B and Model 647.10 Hydraulic Wedge Grips and the Model 647.25 Axial-Torsional Wedge Grips.
Introduction Model 647.
Introduction Model 647.
Introduction Model 647.
Safety Topics: • General Safety Practices: Grips and Fixtures........................................................................................30 • General Precautions for Environmental Components...........................................................................35 • Hazard Placard Placement....................................................................................................................
Safety General Safety Practices: Grips and Fixtures Typically, grips and fixtures are part of equipment used in MTS testing systems. This section provides general information about safety issues that pertain to systems that use grips and fixtures.
Safety Because of these variables (and the possibility of others), your system can operate under unforeseen circumstances that can result in an operating environment with unknown hazards. Improper installation, operation, or maintenance of your system can result in hazardous conditions that can cause death, personal injury, or damage to the equipment or to the specimen.
Safety Know facility safe procedures Most facilities have internal procedures and rules regarding safe practices within the facility. Be aware of these safe practices and incorporate them into your daily operation of the system. Know controls Before you operate the system for the first time, make a trial run through the operating procedures with the power off. Locate all hardware and software controls and know what their functions are and what adjustments they require.
Safety Check bolt ratings and torques To ensure a reliable product, fasteners (such as bolts and tie rods) used in MTS-manufactured systems are torqued to specific requirements. If a fastener is loosened or the configuration of a component within the system is modified, refer to information in this product manual to determine the correct fastener, fastener rating, and torque.
Safety Provide means to access out-of-reach components Make sure you can access system components that might be out of reach while standing on the floor. For example, ladders or scaffolding might be required to reach load cell connectors on tall load units. Wear appropriate personal protection Wear eye protection when you work with high-pressure hydraulic fluid, breakable specimens, or when anything characteristic to the specimen could break apart.
Safety Stay alert Avoid long periods of work without adequate rest. In addition, avoid long periods of repetitious, unvarying, or monotonous work because these conditions can contribute to accidents and hazardous situations. If you are too familiar with the work environment, it is easy to overlook potential hazards that exist in that environment. Contain small leaks Do not use your fingers or hands to stop small leaks in hydraulic or pneumatic hoses.
Safety • Use protective gear (such as gloves) if it is necessary to handle hot objects. Hot objects can include specimens tested at elevated temperatures or furnace surfaces. • When using an environmental chamber or furnace, be aware of possible crush points between the grip and any attachment fixture and the chamber or furnace. Hazard Placard Placement Hazard placards contain specific safety information and are affixed directly to the system so they are plainly visible.
Installation Topics: • Series 647 Hydraulic Grip Lift Points.....................................................................................................38 • Install Axial Grips...................................................................................................................................39 • Install Axial-Torsional Grips...................................................................................................................44 • Install 647.250 Grips..............
Installation Series 647 Hydraulic Grip Lift Points 647.01 through 647.100 Item Description A Two holes 180° apart Model Thread 647.01/02 None. Lift by hand. 647.10 M10 X 1.5 5/8” DP 647.25 M10 X 1.5 5/8” DP 647.50 M10 X 1.5 5/8” DP 647.100 M10 X 1.
Installation 647.250 Item Description A Bottom View Install Axial Grips About the Installation of Axial Grips Grip installation in a load unit force train involves attaching one grip onto the end of the actuator rod and one grip to the force transducer. The grips are mounted to the load unit with conductor studs. The following figure shows the components used for most installations.
Installation Axial Grip Installation Components Item Description 1 Crosshead or Force Transducer 2 Spiral Washer Set 3 Stud 4 Shim Washer 5 Shim Washer 6 Actuator Rod 7 Load Unit Base Plate 8 Spiral Washer Set 9 Stud Required equipment The following materials and equipment are required for installation: • The appropriate attachment kit. • Two sets of spiral washers. • Two connector studs. • Shim washers. • Lubricant.
Installation • Appropriately sized double swivel eyebolts, adequately sized wood blocks and plywood sheet (or equivalent), and an appropriately sized lifting device. Shims If a specific orientation of the grips is required, shims are typically used to achieve that desired orientation. Use the following table to determine the proper shims. Shim Specifications Part Rev Thread Number Size (Kit number) Actuator Ref. (OD) travel of full th'd Approx. Approx. 1/2 turn 1/4 turn (180º) (90º) Approx.
Installation Part Rev Thread Number Size (Kit number) Actuator Ref. (OD) travel of full th'd Approx. Approx. 1/2 turn 1/4 turn (180º) (90º) Approx. 1/8 turn (45º) Approx. Approx. 1/16 turn full turn (22.5º) (360º) Shim Shim Number Number Shim Number Shim Number Shim Number Thickness Thickness Thickness Thickness Thickness Qty 521050-08 A 521050-09 A 521050-10 A M36 x 2 mm 2"-12 M52 x 2 mm 318 act (3.62) 318 act (4.62) 318 act (4.62) .079" .083" .
Installation 2. Mount the lower grip to the actuator piston rod. Thread the stud into the lower grip. The connector stud should turn freely. If any resistance is encountered, disassemble and correct the problem before proceeding. a) Add any required shims, spacer, or spiral washers to the stud. Note: The attachment kit drawing shows what components (such as shims, spiral washers, etc.) should be installed. b) Position the lower grip to align it with the connecting stud and stabilize the grip.
Installation You might need to insert the double swivel eyebolts into the threaded holes on the grip chamber. Attach a lifting device to the double swivel eyebolts and position the grip on top of the lower grip. Important: NO STANDARD EYEBOLTS should be used to lift the grip. d) With the connector stud facing up, add any required shims, spacers, or spiral washers to the stud.
Installation Axial-Torsional Grip Installation Components Item Description Item Description 1 Adapter 10 Crosshead 2 Socket Head Cap Screw 11 Force Transducer 3 Upper Coupling 12 Left Hand Thread 4 Release Pressure 13 Right Hand Thread 5 Clamp Pressure 14 Upper Grip 6 Release Pressure 15 Lower Grip 7 Clamp Pressure 16 Left Hand Thread 8 Lower Coupling 17 Right Hand Thread 9 Actuator Rod 18 Load Unit Base Plate Required equipment The following materials and equipment
Installation • Lubricant. • Appropriately sized double swivel eyebolts, adequately sized wood blocks and plywood sheet (or equivalent), and an appropriately sized lifting device. Important: NO STANDARD EYEBOLTS should be used to lift the grip. Install Axial-Torsional Grip If you are installing the grip on an axial-torsional force transducer, perform the force transducer alignment procedure before proceeding (see the appropriate load unit product manual).
Installation a) Remove the socket head cap screws from the lower coupling and place the screws and coupling halves within easy reach and oriented properly for installation on the grips. Note: The label on the coupling indentifies which component should be connected to each side of the coupling. Each end of the coupling has different threads. b) Position the lower grip to align it with the connecting stud and stabilize the grip.
Installation 3. Warning: The upper grips are very top heavy and will have a tendency to tip over when lifted by the double swivel eyebolts. Dropped grips can cause injury to personnel and damage to equipment. Never attempt to control the grip by holding onto the eyebolts. Use the connector stud to help control the grip balance. Mount the upper grip to the force transducer on the crosshead using an adapter between the force transducer and the upper grip.
Installation Item Description Item Description 1 Load Unit Crosshead 7 Wood Block 2 Force Transducer 8 Lower Grip 3 Adapter Plate 9 Lower Coupling 4 Upper Coupling 10 Actuator Piston Rod 5 Upper Grip 11 Load Unit Base Plate 6 Load Unit Columns e) Carefully position the grip on top of the wooden spacer on the lower grip. Note: You will need to construct a proper support or have someone available to help balance the upper grip on the lower grip.
Installation Item Description 1 Numbers show the rotation pattern. 2 Full (100%) torque listed here. 5. Connect the hydraulics. Using the provided hydraulic hoses, make connections between the pressure and release ports on the grip and the pressure and release ports on the load unit or the external hydraulic grip supply. See the your load unit product manual or hydraulic grip control manual for their port locations. 6. Install the wedges.
Installation • • If the environmental chamber has upper and lower U-plugs, install the grips first, then install the environmental chamber. Simply remove the U-plugs from the chamber, move the environmental chamber around the grips, and reinstall the U-plugs (see Install Environmental Chambers with U-Plugs on page 51). Item Description 1 Lower U-plug If the environmental chamber has no U-plugs, the environmental chamber must installed first.
Installation Environmental chambers that have U-plugs can be installed after the grips are installed. The following figure shows the components used for most installations.
Installation Item 9 Description Item Description Spiral Washer Set 1. Warning: Grip installation is dangerous because it occurs within the crush zone of the force train while full hydraulic pressure is applied and actuator movement is required during the installation. Unexpected actuator movement can cause personal injury and damage to the equipment. Take every precaution to avoid unexpected actuator movement while installing the grips. Set up the load unit. a) Turn on the system hydraulic pressure.
Installation f) Turn the hydraulic pressure off. Ensure that system hydraulic pressure has been reduced to zero before proceeding. To do this, turn off the hydraulic power unit and exercise the actuator until it stops moving. 3. Warning: The upper grips are very top heavy and will have a tendency to tip over when lifted by the double swivel eyebolts. Dropped grips can cause injury to personnel and damage to equipment. Never attempt to control the grip by holding onto the eyebolts.
Installation Turn the hydraulic pressure off. Ensure that system hydraulic pressure has been reduced to zero before proceeding. To do this, turn off the hydraulic power unit and exercise the actuator until it stops moving. Using the provided hydraulic hoses, make connections between the pressure and release ports on the grip and the pressure and release ports on the load unit or on the external hydraulic grip supply.
Installation All-Temperature Grip Component Assemblies Item Description Item Description 1 Hydraulic Chamber 5 Eye Bolt Holes (2) 2 Cylinder 6 Wedge Chamber 3 Piston Extension 7 Socket Head Bolt 4 Eye Bolt Holes (4) The following table lists the approximate weights for the components of the all-temperature grips. Model Location Wedge Chamber Cylinder Piston Extension Hydraulic Chamber Assembled Weight 647.02 top 6 kg (13 lb) 1.3 kg (3 lb) 3 kg (6 lb) 5.
Installation Model 647.25 Location Wedge Chamber Cylinder Piston Extension Hydraulic Chamber Assembled Weight bottom 24 kg (52 lb) 5 kg (11 lb) 12 kg (26 lb) 16 kg (34 lb) 64 kg (142 lb) top 72 kg (158 lb) 5 kg (11 lb) 17 kg (37 lb) 37 kg (82 lb) bottom 72 kg (158 lb) 7 kg (16 lb) 24 kg (53 lb) 37kg (82 lb) 131 kg (288 lb) 141 kg (310 lb) The following procedure assumes the actuator is mounted in the base of the load unit and the force transducer is mounted to the crosshead.
Installation b) If necessary, remove the wedges from each grip. Go to “Change Wedges 647.02 - 647.100” and return to this procedure when done. c) Separate the hydraulic chamber from the grip assembly. Remove the socket head bolt which secures the piston extension to the hydraulic chamber. Perform this step for both grips. d) If necessary attach a strap wrench to the cylinder and the hydraulic chamber. Unscrew the hydraulic chamber from the cylinder. Perform this step for both grips.
Installation d) Turn on hydraulic pressure and raise the actuator rod until it just makes contact with the connector stud. Reposition the grip, as necessary, to center the stud over the actuator rod. e) Slowly screw the grip into the actuator rod, raising the actuator rod as you go, until it is snug. The connector stud should turn freely. If any resistance is encountered, disassemble and correct the problem before proceeding. f) Turn the hydraulic pressure off.
Installation Item Description Item Description 1 Load Unit Crosshead 6 Spiral Washers 2 Force Transducer 7 Wood Block 3 Connector Stud 8 Load Unit Columns 4 Hydraulic Chamber 9 Actuator Rod 5 Lifting Device 10 Load Unit Base Plate Note: You will need to construct a proper support or have someone available to help balance the upper grip on the lower grip. c) Carefully position the grip on top of the wooden spacer on the lower grip.
Installation 6. Install the cylinder assemblies and piston extensions. Once the hydraulic chambers of the grips and the environmental chamber are installed, the cylinder and piston extensions can be installed. a) Lubricate the threads of the lower hydraulic chamber.
Installation Item 3 Description Item Piston Extension 6 Description Lower Hydraulic Chamber b) Lubricate the threads and the interior wall of the cylinder. c) Position the cylinder assembly of the lower grip into the environmental chamber. Move the cylinder assembly through the hole in the environmental chamber. Align it with the threads of the hydraulic chamber. d) Rotate the cylinder until you feel the thread ends engage. Hand-tighten the cylinder to the hydraulic chamber until it is snug.
Installation Item 3 Description Item Description Lower Wedge Chamber b) Attach a lifting strap to the eye bolts. Note: Ensure that you stabilize the wedge assembly while you install it. c) Position the lower wedge assembly in the environmental chamber, using a lifting device if needed. d) Lower the wedge chamber until it contacts the cylinder assembly. e) Remove the lifting strap and eye bolts. f) Rotate the wedge chamber until you feel the threads engage.
Installation Note: Ensure that you stabilize the wedge assembly while you install it. d) Position the upper wedge assembly in the environmental chamber, using a lifting device if needed. e) Place the upper wedge chamber on the wood block. f) Remove the lifting strap and eye bolts. g) Turn on hydraulic pressure. h) Adjust the actuator to raise the upper wedge chamber until it contacts the upper cylinder. i) Rotate the wedge chamber until you feel the threads engage.
Installation Note: Two water manifolds are supplied, one for each grip. Mount a water manifold on each column to keep the temperature of each column balanced. a) Mount one water valve clamp to a load unit column. Mount the other water valve clamp to the other load unit column. b) Connect water lines (supply and drain) between the water lines attached to the columns and the upper and lower grips. c) Connect the water supply (and drain) to the water valve/drain mounted to the load unit columns.
Installation Install Extension Rods About Extension Rod Installation The Series 647 Hydraulic Wedge Grips can have extension rods mounted so that the grips can be inside an environmental chamber for testing at extreme temperatures. Grip installation in a load unit with an environmental chamber involves attaching the grips to the end of the actuator rod and the force transducer or crosshead using extension rods.
Installation Item Description Item Description 2 Shim Washer 11 Upper Extension Rod 3 Spiral Washer Set 12 To Water Valve 4 Environmental Chamber Top 13 Water to Lower Extension Rod 5 Hydraulic Pressure and Return Lines 14 To Upper Extension Rod 6 Hydraulic Pressure and Return Lines 15 To Water Drain Connection 7 Environmental Chamber Bottom 16 Lower Extension Rod 8 Hydraulic Pressure and Return Lines 17 Actuator Rod 9 Load Unit Base Plate High temperature equipment Using
Installation b) Adjust the actuator and crosshead position as necessary to allow adequate room to install the environmental chamber and grips. c) Turn the hydraulic pressure off. Ensure that system hydraulic pressure has been reduced to zero before proceeding. To do this, turn off the hydraulic power unit and exercise the actuator until it stops moving. d) Lubricate all of the surfaces that will contact each other (screw threads, spacers, and so forth).
Installation a) Thread the stud into the lower extension rod. The connector stud should turn freely. If any resistance is encountered, disassemble and correct the problem before proceeding. b) Add any required shims, spacer, or spiral washers to the stud. The attachment kit drawing shows what components (such as shims, spiral washers, and so forth) should be installed. Note: Ensure that you stabilize the wedge assembly while you install it. c) Position the lower grip to align it with the connecting stud.
Installation Note: The upper grip might need help to balance it on the wooden spacer on the lower grip. d) Carefully position the grip on top of the wooden spacer on the lower grip. You might need to insert double swivel eyebolts into the threaded holes on the grip chamber. Attach a lifting device to the double swivel eyebolts and position the grip on top of the lower grip. e) With the connector stud facing up, add any required shims, spacers, or spiral washers to the stud.
Installation 7. Install the cooling water lines. a) Mount the cooling water valve clamp to a load unit column. b) Connect the cooling water lines to the extension rods as shown in the figure “Extension Rod Installation Components” and between the extension rods and the cooling water valve/drain. c) Connect a cooling water line between the upper and lower extension rods. 8. Tighten the grips. Go to “Preload the Spiral Washers” to preload all of the connector studs. Return to this procedure when done. 9.
Installation Kit Part Number Grip Rotations and Shim Part Number 1/16 Turn (22.
Installation 6. Warning: Performing the next step can apply a force greater than the force train capacity. Exceeding the tensile load capacity of any element in the force train can cause personal injury or equipment damage. It is necessary to temporarily exceed the tensile load capacity to achieve the requirements of the next step. This is accomplished by increasing the output pressure of the HPU. Apply a static tensile force 10 to 20% higher than the maximum force to be applied during testing. 7.
Installation Item Description Item Description 1 Connector Stud 4 Increase Thickness 2 Medium Thickness 5 Connector Stud 3 Decrease Thickness 6 30 deg. (Do Not Exceed) Grip Water Cooling Configurations Grip Water Cooling Assembly Configuration for Electromechanical Frames Cut hoses to required length at installation. MTS provides 48 ft (14.63 m) of hose (quantity 1) with the water cooling assembly for conection to the water service.
Installation Item Description B Detail "B" - Applies to Return 1 Hoses to water service Series 647 Hydraulic Wedge Grips Reference Manual 75
Operation Topics: • Basic Operation.....................................................................................................................................78 • About Grip Controls...............................................................................................................................78 • Determine Gripping Pressure................................................................................................................79 • Change/Install Wedges................
Operation Basic Operation Operation of the hydraulic wedge grips consists of the following: • Determine the minimum required specimen gripping pressure to accommodate a specific specimen and testing application. • Select the appropriate wedges. • Load a specimen into the grips. About Grip Controls The grip controls are located on the front panel of a load unit or on the front panel of an external hydraulic grip supply.
Operation Item Description 3 Hydraulic Grip Supply Determine Gripping Pressure About Grip Pressure Determination The output pressure of the hydraulic grip supply determines the gripping force applied to the specimen by the wedges. The optimum gripping force is great enough to securely grip the specimen, yet low enough to minimize specimen deformation or prevent specimen slippage during the test. Warning: Improper grip pressure can damage the grips.
Operation Term Definintion D Diameter of the round specimen (mm or in) (see “Specifications”) Fc Lateral clamping force of the wedge on the specimen (kN or lb) fc-w Frictional force between the grip chamber and the wedge fw-s Frictional force between the wedge and the specimen fT Frictional forces reacting the torque L Maximum axial load applied to the specimen (kN or lb) Nc-w Normal forces between the grip chamber and the wedge Nw-s Normal forces between the wedge and the specimen P Gri
Operation Gripping Principles Item Description 1 Wedges for Round Specimens 2 Wedges for Flat Specimens Determine Gripping Pressure - Axial for Round Specimens (and Axial/Torsional for Flat Specimens) The following procedure determines the minimum gripping pressure for axial testing of round specimens and axial/torsional testing for flat specimens. 1. Determine the maximum axial load to be applied to the specimen for the test. 2.
Operation For fatigue testing: For monotonic testing: 3. If desired, determine the actual clamping force (Fc) applied to the specimen by using the following formula: To derive the above equation, the static coefficient of friction (μc-w) between the grip and wedge was assumed to be 0.06 for lubricated steel on steel. If a different coefficient of friction is needed, use the following formula, substituting your own value for μ.
Operation Change/Install Wedges Change Model 647.02 - 647.100 Wedges Standard and optional wedges are available for the grips. The standard wedges include: • Narrow flat wedges for flat specimens. • Round wedges for specific diameter round specimens. • Vee-notched wedges for round specimens in general. The optional wedges include wide wedges for flat, full width specimens. See “Specifications” for a listing of all available wedges. Caution: The wedges can rust. Over time, rust can damage the wedges.
Operation 2. Using the utility packing hook, disconnect both springs from the spring posts on the corresponding wedge. It is not necessary to remove the springs from the spring anchors. 3. Inspect the springs and replace them, if necessary. 4. Remove the wedge by sliding it towards the center of the grip and then lifting it out of the grip. 5. Repeat Steps 2 and 3 for the remaining wedges. 6.
Operation 2. Remove the specimen guide from flat wedges. 3. Remove the wedge set from the grip as follows: a) Using the utility packing hook, disconnect both springs from the spring posts on the corresponding wedge. b) It is not necessary to remove the springs from the spring anchors. However, inspect the springs and replace them, if necessary. c) Remove the wedge by sliding it towards the center of the grip and then lifting it out of the grip. d) Repeat Step A through Step C for the remaining wedges. 4.
Operation Item Description 1 Rebar specimen 2 Aluminum insert 3 Wedge Install Model 647.250 Wedges and Liners Several different wedges are available for the Model 647.250 Grips. There are v-wedges for round specimens and wedges for flat specimens. Liners are available to accomodate speciments of different thicknesses or diameters. Install Model 647.250 Wedges Note: The callouts in the following figure relate to the procedure steps. 1.
Operation Caution: The wedges can rust. Over time, rust can damage the wedges. Use cloth or latex gloves when handling the wedges. Also coat the wedges with LPS (a rust preventative oil) and place them in their original packing material for storage. Attach the wedge to the wedge installation tool. Note: The grip must be in the fully open position for wedge replacement. 2. Apply a thin film of Molycote Gn Paste to the wedge contact surface on the new wedge.
Operation Install/Remove Test Specimen Install a Specimen Prerequisite steps for installation. • Before installing the specimen, install the appropriate set of wedges for the specimen to be tested. Use the installation instructions in this chapter for the type of wedge you are using. • Warning: Make sure that the specimen shank is within the required tolerance. Failure to comply with specimen tolerances can cause wedges to fail.
Operation 6. Caution: The contact area between the wedge face and specimen should be as large as possible. A small contact area between the wedge face and specimen can cause premature wear to the wedge face surface. MTS recommends that specimens should be machined to provide the largest possible surface contact area between the wedge face and the specimen. Caution: Wedges can be installed incorrectly. Improper specimen installation can damage the wedges.
Operation 7. Extend the actuator until the specimen is positioned in the upper grip allowing a space of at least 3 mm (0.12 in) but not greater than 6 mm (0.25 in) between the top of the specimen and the inner top edges of the wedges. Lock the upper grip. 8. Caution: Specimen slippage during the test can damage the grips. Specimen slippage typically occurs when: • Insufficient grip pressure is used to securely grip the specimen. • Wedges with worn (rounded or flattened) serrations are used.
Operation Warning: The environmental chamber and the grips can be subjected to extreme temperatures during the test. Opening the door after a test will vent the hot or cold air from the chamber. Touching chamber or grip parts before they have been allowed to reach a tolerable handling temperature or without adequate protective clothing or tools can result in serious freeze or burn injury. Do not stand or put unprotected hands in the path of the venting heated air while opening the door.
Maintenance Topics: • Hydraulic Hoses and Fittings.................................................................................................................94 • Wedges..................................................................................................................................................94 • Water Cooling Components...................................................................................................................94 • Daily Inspections...................
Maintenance Hydraulic Hoses and Fittings Check the hydraulic hoses and fittings monthly. Ensure that hoses are routed properly and not wearing. Also ensure fittings are not leaking. Wedges After approximately 100 lock and release cycles, remove the wedges from the hydraulic wedge grips and apply an anti-seizing compound to the edges of the wedge which contact the wedge chamber and grip piston. 1. Remove the wedges from the grip chamber. 2.
100-027-131 N
