HIGHWAY TECHNET VIRTUAL
EXPO PAVEMENTS INDEX
Direct Tension Testing System Specifications
| 1.1 | This document defines the specifications and requirements for a testing system capable of testing asphalt binder materials to characterize failure properties of these materials from -36 °C to +6 °C. The testing system shall be able to perform the test as described in AASHTO TP3 and include the following capabilities. |
| 1.2 | The test system shall be fully integrated and capable of performing to the following specifications. |
| 1.3 | The test system shall be integrated with all the necessary components to make it fully functional (liquid cooling bath, temperature control system, cooling unit, direct tension test fixture with specimen end inserts, Windows™ software, extensometer strain measurement). |
| 2.1 | All vendors shall provide a proposal which includes a line-by-line detailed response to each numbered section of this specification. |
| 2.2 | All vendors shall provide a proposal which includes descriptive literature, drawings, and schematics for the purpose of bid evaluation. |
| 2.3 | All vendors shall provide evidence of current system installations where equipment similar in nature to the equipment specified by this solicitation have been supplied and maintained. |
3.1 General
| 3.1.1 | The supplier shall supply one (1) DC servo motor loading unit which incorporates complete direct digital closed loop command and feedback motion control. The unit shall consist of a pre-loaded ball screw with a guidance column for increased lateral stiffness and linear actuator travel. The screw and guidance column shall be fully enclosed to eliminate pinch points and protect surfaces from contamination or damage. |
| 3.1.2 | The electromechanical loading unit shall be capable of tension and compression forces of at least 500N and actuator travel of 20mm (0.78in). The system stiffness shall be at least 3 MN/m including load cell. |
| 3.1.3 | The unit shall have a transducer to measure and control grip separation and provide a feedback for strain control with a displacement resolution of 1.0 µm. |
| 3.1.4 | The unit shall be freestanding for installation on a laboratory table. It shall not require structural floor modifications. |
3.2 Load Frame and Cooling Bath
| 3.2.1 | The frame shall be table mounted. The loading pins shall be completely submerged under the cooling fluid. The loading pins shall be a minimum of 1 inches (25 mm) under the cooling fluid surface. An emergency stop switch shall be mounted to the front of the load frame structure. |
| 3.2.2 | The distance between the load frame's loading points shall accommodate specimens with a gauge length of at least 27mm, figure 1. |
| 3.2.3 | The cooling bath shall have minimum dimensions of 195 mm (7.68 in) width, 240mm (9.5in) depth, and sufficient length for the specimen, end inserts, and total actuator travel. The cooling bath shall have sufficient space for storing at least eight (8) specimens and allow a liquid depth of at least 100mm (3.94 in.). |
| 3.2.4 | The system shall have the capability to be supplied to run at either 120, 220 or 240 single phase 50Hz or 60Hz. To be specified at time of order. |
| 3.2.6 | The temperature control range for the cooling bath without asphalt binder specimens, at all points within the bath, shall be from +6°C to -36°C with temperature stability as a minimum of ±0.1°C. Placing cold specimen in bath may cause the bath temperature, at all points in the bath, to fluctuate ±0.2°C from the target test temperature, consequently bath fluctuations of ±0.2°C during testing and iso-thermal conditioning of the specimen shall be allowed. Temperature gradient at any location in the bath shall not exceed ± 0.1°C. The temperature control shall be accomplished with a calibrated remote Platinum RTD located in the bath in proximity of test area (NIST Traceable, calibrated at 8 temperatures in the range +6°C to -36°C). |
3.3 Actuator Control
| 3.3.1 | The actuator shall provide a minimum speed of 0.001mm/min (0.00004in/min) to a maximum of 600mm/min (23.6in/min). The speed shall be continuously variable over this range. |
| 3.3.2 | The actuator position resolution shall be at least 0.053µm (2.1µin). |
| 3.3.3 | The actuator speed accuracy shall be at least +/- 0.1% of set speed (Zero or constant load). |
| 3.3.4 | The system shall be capable of closed loop strain rate control accurate to at least 1% of the commanded specimen elongation rate using feedback from a displacement transducer (or other Federal Highway Administration approved strain measurement device) mounted between the loading pins. The closed loop strain rate control algorithm shall also be capable of real time compliance correction. The necessary calculations for the amount of compliance to be corrected shall be decided by mutual agreement between the vendor and the Federal Highway Administration personnel. |
| 3.3.5 | The system shall be capable of automatically ramping in position control to a operator specified preload at which point the strain is automatically balanced and the test continues in strain rate control. |
3.4 Load Cell
| 3.4.1 | The load frame shall include a tension/compression load cell with a overload capacity without permanent zero shift of 150%. whichever is greater. Load cell shall employ temperature compensation from -40 to 5 °C (-40 to 40 °F). |
| 3.4.2 | The load measurement accuracy shall be +/- 0.5% or reading down to at least 2% of the load cell capacity according to ASTM E4-94 standard method. Load system resolution shall be at least 0.05% of the full range of the load cell and shall be constant over the full range of the load cell. |
| 3.4.3 | The load cell must be traceable to NIST standards and must meet or surpass the following standards: ASTM E4, BS1610 Grade 0.5, DIN 51221 Class 1, JIS (B7721, B7733), AFNOR Class 0.5, ISO 10002 Part 2 and ISO 7500/1 Class 0.5. |
4.1 General
| 4.1.1 | The System shall include a test control panel for start, stop, return, jog, fine jog, and specimen protect functions. The panel shall also include at least two programmable keys for load balance, strain balance, exclude specimen, and other functions. |
| 4.1.2 | The setup of test methods, display of test information, reporting general operation shall be through a graphical user interface based on Microsoft Windows. The software shall adhere to Windows standards. |
| 4.1.3 | The system shall provide up to four live numerical data displays with selectable engineering units. The user shall be able to change the selection of display variables during a test. Data for display shall include load, stress, strain, extension, time, and strain from extension. |
| 4.1.4 | The Testing System shall provide up to four selectable analog data displays in addition to the numerical displays. The analog displays shall be independently scaleable and shall include current value and limit values for each channel. |
| 4.1.5 | The computer interface must be compatible with a PC running Windows 98 or Windows 95. |
| 4.1.6 | The user shall be able to select SI, Metric, and US Customary units. |
4.2 Closed-loop Controller
| 4.2.1 | A digital controller shall have fully digital closed-loop control with a sampling rate at least 500 Hz. |
| 4.2.2 | The Testing Instrument shall include an active control mode to protect against excessive load being applied to the test specimen during specimen mounting into loading pins or fixtures prior to starting the test. This mode shall function at the stated load weighing system accuracy and include an automatic turn-off at the start of a test. |
| 4.2.3 | Test Control and Safety Limits shall be separate. There shall be at least three user selectable events for test control (strain, extension, load) with independent channel and actuator action selections. Electronic Limits shall be provided for each transducer channel with independent minimum and maximum settings. Limit actions shall include stop and unload. |
| 4.2.4 | The usual transducer warm-up time shall be eliminated by providing excitation to all connected transducers while the system computer is turned off. The load frame power amplifier shall be automatically disabled during this time for safety. |
| 4.2.5 | The Testing Instrument shall provide automatic recognition and automatic calibration of transducers. |
| 4.2.6 | Automatic and user selectable data acquisition modes shall be provided. Incremental data logging shall allow user specification of three independent channel/value combinations to trigger data sampling. |
| 4.2.7 | The Testing Instrument shall include an on-line Help and Documentation system incorporating context sensitivity with hypertext and hyper graphics navigation. |
4.3 Transducer Signal Conditioners
| 4.3.1 | Separate A/D signal conditioners shall be provided for each data channel. |
| 4.3.2 | The sensor conditioners, digital control and data acquisition electronics must be located outside the PC chassis to reduce exposure to electrical noise from the PC’s 120 VAC. |
| 4.3.3 | Each signal conditioner will use AC excitation to reduce noise. |
| 4.3.4 | The system shall include self-test diagnostics with an external display for hardware and communication status. |
| 4.3.5 | The system shall maintain specified load and strain accuracy’s with interchangeable transducers. |
| 4.3.6 | The signal conditioners shall allow computer control of transducer zeroing to allow balancing 50% of full scale to zero +/-0.1% of full scale for fully automated testing. |
| 4.3.8 | The system shall have automatic and manual transducer calibration. |
| 4.3.9 | The system shall have built-in transducer over range protection. |
| 4.3.10 | The system shall have auto switch to frame standby mode if PC is shut down or fails. |
| 4.3.11 | Each conditioner shall have the capability to detect cable faults and signal loss for operator and system safety. The conditioners must be capable of detecting disconnection of the transducer and must prohibit the operator from attempting to use that conditioner for control. |
| 4.3.12 | The system shall have data rate - user selected up to 500Hz simultaneous all channels. |
| 4.3.13 | The system shall be capable of storing at least 100 data points for every 1% strain measured (assuming a specimen gauge length of 26.66mm). |
4.4 Safety
| 4.4.1 | The system shall have critical functions such as overload protection, safety limit monitoring, and emergency stop, handled by a dedicated controller independent of PC. |
| 4.4.2 | The system shall comply with new EC standards for the electro-magnetic susceptibility and emissions. |
| 4.4.3 | The system shall have passed FCC class A emissions test. |
| 4.4.4 | The system shall have service diagnostic port. |
5. Fixtures for Making Asphalt Specimen
| 5.1 | Four sets of aluminum molds with 20 plastic inserts shall be provided. For details about the aluminum molds please refer to AASHTO TP3 Standard Test Method for Direct Tension of Asphalt Binders. The plastic inserts given in the above standards shall be modified as shown in the attached drawing (Figure 2). The material used to manufacture these plastic inserts, however, shall be according to AASHTO TP3. |
| 5.2 | Two sets of aluminum specimen holders shall be provided. For details refer to the attached drawing (Figure 3). |
6.1. General
| 6.1.1 | The software shall include pre-programmed ASHTO TP3 procedures and calculations (Standard Test Method for Determining the Fracture Properties of Asphalt Binder in Direct Tension(DT). |
| 6.1.2 | The software shall be allow storage of sample data in individual files for minimizing data loss in the event of file corruption. |
| 6.1.3 | The software shall be Microsoft Windows™ based with a graphical user interface adhering to Windows™ standards. |
6.2 Data File
6.2.1 Data File Specifications
Data files must collect and store the following information:
- Specimen Identification supplied at the time of testing, time and date stamp, and specimen dimensions
- Test temperature - actual and set (or entered) at test time by the operator
- At least 250 characters for pre and post test remarks for each specimen
- Specimen Elongation Rate - Actual and set rate
- Following information at Failure Load (N):
- Time to failure, seconds
- Elongation at failure load, mm
- Failure Load, N
- Failure Stress, MPa
- Failure Strain, %
- Failure Energy, MN-m/m3
- Temperature at the beginning and end of the
- Failure Type from post test remarks
NOTE: Failure energy shall be computed by numerically estimating the area under the stress-versus strain curve using the trapezoidal or Simpson’s quadrature rule. Other methods of computing the area under the stress versus strain curve are permitted if sufficient proof of its accuracy is demonstrated.
- Data files shall also store all the data points collected during the test up to and including the point of failure. If pre-deformation is used for obtaining initial rate control information, the data collected for that purpose must also be recorded separately and saved along with the calculated initial guess for rate control. Complete data set of all the acquired data points must be saved for the following measured an/or calculated variables:
- Load, N
- Specimen Elongation, mm
- Real test time, seconds
- Raw data initial strain, stress, and time used as reference point for zeroing, %, Mpa, and seconds
- A hardcopy, or printout to a file, of results shall be provided at the end of each test in the following format in SI units
- Software shall provide a choice for printing stress versus strain plots as well as specimen elongation rate plots if the operator chooses at the end of each test
- Software shall provide capability of retrieving stored test results and exporting them in their entirety to an ASCII comma delimited file for further analysis
6.3 Hard Copy Output
6.3.1 Hard Copy Output Format for Direct Tension Test Results
Specimen Identification:
File name:
Replicate No.:
Time and Date:
Operator:
Project:
Asphalt:
Specimen Dimensions:
Test Temperature:Target:
Test Start:
Test End:Actual Specimen Elongation Rate:
Results:Failure Stress (MPa):
Failure Strain (%):
Failure Energy (MN-m/m3):Remarks:
Pre Test:
Post Test:
An acceptance test shall be performed at the supplier's site prior to shipment. This acceptance test shall include a complete explanation and demonstration of all specified features in this document.
8. Installation, Training, and Documentation
8.1 Installation
The supplier shall be responsible for the complete integration of all subsystems specified herein.
8.2 Training
The supplier shall provide on-site training for one day with installation.
8.3 Documentation
Full documentation for every portion of the test system described in the sections above shall be provided by the supplier. Two sets of operating and reference manuals shall be provided as well as any pertinent assembly or installation drawings, site preparation instructions, and spare parts lists.
8.4 System Warranty and Support
| 8.4.1 | All items supplied by vendor shall carry a one-year on-site warranty against defects in material and workmanship. |
| 8.4.2 | All vendors shall provide information regarding the service staff that would be used to support the installation, maintenance, and repair of the system defined by this specification. |
HIGHWAYTECHNET VIRTUAL
EXPO PAVEMENTS INDEX
U.S.
Department of Transportation
Federal Highway Administration