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50KN stress rig for use on SALSA

REFERENCE GUIDE INTRODUCTION A 50KN rated INSTRON stress rig is available for use on SALSA for in-situ tension or compression testing. Additionally the testing machine may be used for fatigue cycling a sample before or during an experimental session. This guide is intended as a brief introduction to the use of the machine. A complete INSTRON manual is available for consultation. SAFETY The test machine is capable of forces up to 50KN, applied at rapid rates. It is therefore a dangerous machine and should be treated carefully and with respect. Users must only use the machine after training by the local contact. There are 2 main sources of danger: Crush risk : The standard cross-head set-up does not allow the grip faces to move fully together. However it is still necessary to take care that nobody else is likely to use the machine whilst you are changing specimens. Remember that a load equivalent to the weight about 3 average cars can be applied through the grips within a fraction of a second. This would be painful! Hydraulic risk: The test-rig is a servo-hydraulic unit and is supplied with oil by the HPU at 210 bar. There are flexible hoses between the HPU and rig actuator. Great care must be taken not to damage these hoses. Do not stand on the hoses. Do not excessively bend the hoses. Do not move the hoses under load. If you suspect a hose may be damaged, turn off the HPU and inform the local contact immediately. There are emergency STOP buttons on the rig, the HPU and the 8800 controller. Any of these will immediately turn off the HPU and release the load.

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When you expect to require modifications to the test machine (grips, orientation, hose connection) notify the local contact who will be on hand to assist if required. SYSTEM COMPONENTS The tensile testing machine has 4 principal components

o Load frame. The load frame is rated to 50KN and is based on a 2 column design. There is an actuator, load cell and fatigue grips. The load frame as a whole (with fatigue grips) weighs approximately 300 Kg. The load frame is shared between SALSA and ID15 at the ESRF. It may also be used in the FaME38 laboratory.

o Hydraulic Power Unit (HPU). The HPU is permanently installed near to SALSA. It is powered by a three-phase supply and is water cooled. The HPU runs at 210 bar.

o 8800 control tower. The INSTRON control tower links to both the HPU and the rig.

o User PC. The PC contains INSTRON software required to operate the test rig. A GPIB interface is provided between the controller and the PC.

Additional components are:

o Monitor, keyboard, mouse for PC. o Power strip

CONNECTIONS It is imperative that the correct connections are made if the machine is to operate. Some connections are made with long cables to allow feeds from the control tower into the SALSA experimental area. Figure 1 shows a diagrammatic representation of the complete set of electrical connections necessary. All connections are labelled on both the connector and cable. Note the two connections that pass in from the back of the 8800 controller, under the unit, to the front of the controller. Never disconnect any cables from on the test frame.

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8800 controller

50KN test frame

HPU

PC

Power strip

Monitor,keyboard,mouse

AC power IN (mains)

AC power IN (3 phase)

GPIB

Earth cable

Emergency STOP

Communications/Power

Emergency STOP

Communications

Figure 1 : Electrical connections for the stress rig

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The cable list is as follows:

o HPU-8800 cable #1 : Emergency STOP, length 10m o HPU-8800 cable #2 : Control, length 10m o Rig-8800 earth strap : Earth, length 20m o Rig-8800 Emergency STOP, 20m o Rig-8800 Control, 20m o 8800-PC GPIB o Power strip for 8800-PC

TRANSPORTATION For most experiments transportation and installation of the machine will have been performed by the local contact. However the procedure is detailed below. There is a HPU based at SALSA permanently. It is connected to the mains water supply and a 3-phase power supply. The two cables which connect to the 8800 should remain with the HPU. A set of three flexible hoses is also based at SALSA. The following procedure assumes that the rig is fully connected at another location, for example the FaME38 lab. 1 - Turn off the HPU by rotating the handle through 90 degrees (clockwise), the front panel display goes off. Turn off the 8800 control panel (black switch at top left of back panel). Take out the AC-in cable from the 8800 (top of back panel). Shutdown and turn off the PC. 2 - Disconnect the hydraulic hoses from the rig. The hoses are equipped with a quick release type fitting at the actuator end of the rig. Pull back the metal ring and withdraw the hose. A small amount of oil will remain in the end of the hose. It is advisable to have some cloths to absorb this excess oil. 3 - Disconnect the GPIB cable between the PC and 8800 controller. 4 - Unplug and disconnect the PC from the mains (AC-out on 8800). Disconnect the monitor and keyboard. 5 - Remove the two HPU-8800 cables from the 8800 controller. One cable is on the back panel. The second cable runs under the bottom of the controller and is connected to the front panel (use a small

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screwdriver). You may need to remove the front cover of the 8800 to access this connector. 6 – Disconnect the earth (green/yellow) wire from the back panel of the 8800 (top). 7 - Disconnect the rig-8800 control cable from the back of the 8800. This cable should be tied to the metal support with plastic cable ties. Cut these with sharp scissors or a knife taking care not to damage the cable. 8 – Disconnect the rig-8800 emergency stop cable. The cable runs under the bottom of the controller and is connected to the front panel (use a small screwdriver). The machine is now fully disconnected and can be transported. The 8800 controller is on a wheeled base. There are two lifting rings on the rig that can be used to hoist using a crane. The weight of the rig is approx 300 Kg. Note that the centre of gravity is slightly towards the actuator side of the machine and therefore be careful not to damage the actuator during initial lifting. It is very important not to remove the three cables from the stress rig. In particular the control cable is prone to damage at the rig connector that will render the machine unusable. INSTALLATION AND LOCATION Essentially the installation process is a reverse of the process described above. Figure 2 shows the typical run of cables/hoses for SALSA. The HPU is permanently positioned under the stair platform. The hydraulic hoses between HPU and rig run under the hollow flooring to the SALSA experimental area. The cables between the HPU and 8800 also use this channel. Presently the SALSA crane is unable to lift the stress rig into the experimental area. It is necessary to lift the rig onto the experimental floor using the guide hall crane (contact operator) and then to manoeuvre the rig onto the hexapod using the SALSA crane.

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HPU

HPU

water3-phase

3 hoses

2 cables

8800PCrig

3 cables

Figure 2 : SALSA layout for the stress rig

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It is advisable to mount the stress rig on the hexapod table prior to connecting the flexible hoses. A specific top plate is provided which is of a heavy duty design. Four M12 threaded holes in the plate match with a set of holes in the base of the rig. M12 bolts of 60mm length are appropriate. Use all four bolts with a washer and make sure they are tightened.

Figure 3 : Hexapod top plate for the stress rig

When the rig is firmly in place, the hoses can be pushed back onto the actuator. Pull back the metal ring on the quick release fixture to ease reconnection. Make sure that the hoses are firmly pushed into place and do not slide off. Expect some rotation of the joint. OPERATION Start-up When all of the system elements are connected you can begin the start-up procedure. It is important to follow the sequence below. 1 – Turn on water supply to HPU (flow in and flow out). 2 – Rotate handle on HPU unit 90 degrees anti-clockwise. The display will tell you checks are being performed and then the unit will be ready. 3 – Turn on and start up the PC. There is no password for the machine.

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4 – When the PC is running, double-click the Instron ‘Fast track console’ icon on the desktop. This will open the window in which you can control the actuator. 5 – Turn on the 8800 controller (black switch on back panel). The window on the PC will report that the controller is online and you will see a load appear in the monitor window. (This may take about a minute). The interface will look similar to that in figure 4.

Figure 4 : Start-up screen for ‘Fast Track’ software In the top right is a set of 5 command panels (from left : LOAD control, POSITION control, set point, specimen protect, actuator control) and a STOP panel. Below this are two displays giving the current values for the actuator position (mm) and the load cell reading (kN). A log window appears in the middle of the screen.

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You will notice that an ‘R’ appears in the LOAD panel. The load cell is waiting to be re-calibrated. Right click with the mouse on this panel and re-calibrate. The ‘R’ will disappear. The load cell needs to be balanced. Right click again on the panel and select balance. The load will now read zero. Effectively you can operate in LOAD CONTROL or POSITION CONTROL. In position control you effectively move the actuator to a given translation. In load control you tell the actuator to load to a given force. Most experiments will be in load control. The current mode is shown by green shading. In figure 4 the machine is in position control. To change mode, right click and select ‘mode change’, select ‘immediate’ and the green shading will change. Starting the HPU When all of the components are switched on as described above you can start the HPU. The HPU is started remotely using the three buttons at the top of the front panel of the 8800 controller. Initially push the ‘BAS’ (low pressure) button and keep it depressed. The HPU will begin to generate pressure but you must keep the button depressed for several seconds. When low pressure is reached, the tone of the HPU changes and low pressure is reported in both the actuator panel (top right of monitor) and in the test log. If you release the button too early then the HPU will stop. Begin the process again. When the HPU is running in low pressure, depress the ‘HAUT’ button briefly and the HPU will transfer to high pressure mode. The machine is now fully enabled and the actuator can be moved. Before using the machine it is advisable to set the limits. Limits It is good practice to set limits so that the machine will trip out if they are exceeded. This not only protects your sample but also yourself. Figure 5 shows the limits setting window. You should set limits for both load and position. To access the limits window, right click on the panel (load or position) and select ‘limits’. Set the Primary limits to the desired values and tick the enabled boxes. NOTE to set the value for the limit it is necessary to type the value and press return, if you do not press return the value change will not be accepted.

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It is good practice to set limits tight to your operating range. It is better to hit the trip than do damage to your sample or worse. For example if you plan to operate up to 10KN in tension; an appropriate setting for load limits would be -0.5KN and 12KN. Additionally you should protect your sample using position limits. For example once your sample is in the grips you may set limits at ± 3mm from the current position. If your sample begins to fail the actuator will not continue the loading. If you hit a limit, the HPU will trip and the load will go to zero. A red flashing indicator will be seen in the position or load panel. This shows whether the high or low limit has been reached. To restart the machine you should re-set your limits, taking care that they are enabled, and then restart the HPU as described earlier.

Figure 5 : Setting load limits

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Mounting your sample The existing grips are 50KN rated fatigue grips. In fact the size of them introduces some limitations and plans are underway to provide a range of grips of different designs. The grips are wedge type and can hold flat or round samples up to 16mm in thickness/diameter. The grip faces will be generally changed by the local contact in preparation for your experiment. A specific description of the procedure for changing grip faces may be found in the EXTRAS section. The grips are tightened using 4 bolts located on the front face of the grip housing. A ratchet spanner is provided with the appropriate hexagonal key. It is easiest to tighten one bolt until your sample is gripped and then tighten the others. Remember that you will need to tighten all four several times. It is possible that a certain amount of pre-loading may be applied to your sample as you tighten both grips. A feature of the test machine is ‘specimen protect’ which enables the actuator to maintain load below a given threshold. To set this, click on the specimen protect panel (top right of screen). A window will open in which you can set the threshold stress, for example 0.1KN. The shield symbol in the panel will show as active. As you tighten you sample, the actuator will respond interactively to maintain the load below this value. When your sample is fully gripped, remember to disable specimen protect, otherwise it will overrule any load commands that you input. A manual jog is provided on the machine which allows movement of the actuator using a button (fast) or roller (slow). Loading/unloading Assuming that you have, turned on all components, started fast-track console, applied pressure to the HPU, mounted your sample and set the limits, then you are ready to go! This section will only describe the simplest method of applying load. It will probably be sufficient for all on-line experiments. For off-line fatigue work then either consult the local contact or the FaME38 lab. It is possible to apply a specific load using the setpoint panel (top right of screen). You should first ensure that you are in load control mode.

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Click on the setpoint panel and a window will appear (figure 6). In the box type the load value that you require and the rate of application. Check that the mode tab reads load. Remember to type return in each box for the value to be accepted. When you are satisfied the values are correct, click start and the machine will load to the given load value at the given rate depending upon the current limits. Unload to zero in the same way.

Figure 6: Using the set point box to apply a load.

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PHOTOS

Stress rig mounted on SALSA. The grips are mounted horizontally.

Stress rig mounted on SALSA. Rig axis bisecting slits (along q).

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Slits retracted, using hexapod to rotate stress rig. Note the use of the crane as a back up device.

EXTRAS Changing grip faces Four types of grip faces are available for flat and round samples. Each type has four wedge faces (two for each grip).

- flat samples 0-6mm - flat samples 6-12mm - round samples 6-12mm - round samples 12-16mm

The procedure for changing the faces is relatively simple. Firstly turn off the pressure from the HPU so that the actuator cannot move accidentally. 1 – Open the jaw faces to the maximum extent using the four bolts. The jaw is at its maximum when the central plunger is flush with the rest of the grip. 2 – Undo the hex-headed bolt holding one of the triangular metal restrainers at the side of the grip faces. 3 – Remove the triangular flat restrainer. 4 – Carefully unclip the four springs (per grip) from the wedge faces.

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5 – Remove the faces. 6 – Apply a thin coating of grease to the outside edges of the new wedge faces (not to the inside where the sample is held). 7 – Position the faces in the same place as previously and carefully re-attach the springs. 8 – Re-attach the triangular restraining plate. Rotating the grips For almost all cases the grips will be used with the central opening horizontal. Rotating the grips is complicated and should only be attempted with the help of the local contact. For reference the basic procedure is outlined below, however it is recommended that the manual is also consulted. The grips are pre-loaded to reduce fatigue to the load chain components. In order to pre-load it is necessary to apply maximum load (50KN) therefore a sample capable of supporting this stress is required. A steel bar is provided for this purpose. 1 – Mount securely the steel bar in the grips (for round specimens). 2 – Apply a load of 47KN. It is recommended that this load is achieved gradually and that appropriate position limits are set. 3 – At 47KN it should be possible to carefully tap out the two thin metal shims between the grip and the load cell. If this is not possible take the load to 50KN, remove the shims. Reduce the load back to 47KN. Turn the metal joint so that the half-holes align in the centre (see figure 8, unloaded assembly). 4 – Reduce the load to zero. 5 – Loosen the two bolts supporting the actuator shaft (anti-rotation fixture). See figure 7. 6 – The pair of grips can now be rotated together. Use a level to make the grip faces horizontal or vertical as desired. 7 – Re-tighten the two bolts securing the actuator shaft. 8 – It is now necessary to pre-load the load chain. It is advisable to do this just below the maximum rating to aid removal of the shims in the future. For this reason, set the load back to 47KN. 9 – Put the shims back into place and then rotate the two halves of the joint to expand and tighten it. Use the two (Tommy) bars provided to turn the two halves. Do not over tighten as it will make it very difficult to remove in the future. Ensure that the gap between the holes is less than 40mm. See figure 8. 10 – Set the load back to zero. The grips should now be immovable and are now pre-loaded and ready to use.

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Figure 7 : Anti-rotation fixture and bolts.

Figure 8 : Pre-loading. Compression platens Currently two sets of simple compression platens are available. One set has a face diameter of 25mm and one a diameter of 10mm or 13mm. The platens are designed to be gripped by the fatigue grips (round specimen faces).

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Future modifications

o A range of grips are to be designed in the future. If you would like to use your own grips then see the local contact before the experiment. The fitting system for grips is an M30 thread.

o It is intended that much of the flexible hose length will be

replaced by fixed piping. KNOWN ISSUES/TIPS

o Not accepting input values. To set the value in the boxes it is necessary to type the value and press return, if you do not press return the value change will not be accepted.

o HPU tripped. Occasionally the HPU may trip. In fact this is very

unlikely to occur but was experienced during commissioning. The display on the HPU panel reads TRIPPED. Turn off the HPU at the handle. Open the case using the metal key. TAKE CARE; THE 3 PHASE SUPPLY IS STILL CONNECTED! There is a dark blue trip switch in the lower-middle area, push this switch. Close and lock the door, restart the machine.

o No load. In some cases you will enter a load and it appears to

stay close to zero. This could be that the specimen protect has been left enabled. Disable load protect.

o Load lower than desired set point. If the pressure is set to low,

the actuator will attempt to apply the load but will stall at several KN. Turn on high (haut) pressure.

FURTHER HELP If you encounter problems do not hesitate to call your local contact or any of the responsibles for SALSA. For technical issues the INSTRON support office in the UK (High Wycombe) is available during office hours. DJH Jul 05