| Ultrasonic Mill Roll Inspection System |
| Ultrasonic Mill Roll Inspection System |
Dynamic Systems Inc. utilizes Toro-16 DSP boards to provide multi-axis servo-control in advanced metal forming simulators Short Project Description Dynamic Systems' new HDS-V40 machine provides simulation of casting and forming of metal alloys and utilizes two Innovative Integration TORO-16 DSP board as the core of the control and data acquisition system. The system has eight closed-loop servo-controlled axes, five hydraulic and three thermal, as well as a 16-channel data acquisition. This is the most advanced equipment in the field for its high-performance control and extensive in-situ data gathering capability. It is used to develop new alloy materials and processes in labs worldwide.  Company Profile Dynamic System, Inc. (DSI) designs and manufactures equipment for the physical simulation of melting, casting and in-situ roll forming of metal alloys. These machines control the melting and quenching of a material specimen and, at a given temperature, apply a series of precisely controlled deformations with powerful hydraulic actuators while various performance parameters are measured and recorded for later analysis. Combined with a metallurgical analysis of the specimen, the equipment provides a close simulation of continuous casting and roll-forming mill production processes, with the benefit of extensive data gathering. This method results in substantial cost savings since new alloy characterization and their casting/forming process optimization can be done "off-line". DSI Products provide a cost effective way to physically simulate high temperature processes and applications at a far lower cost than full scale tests while providing excellent correlation and results which can then be applied to the actual process or application. The tools are used for process simulation (such as continuous casting, hot rolling, forging, extrusion), testing (fatigue, stress vs. strain, creep/stress rupture) and basic material studies (diffusion, stress relaxation, hardening) End-Product Overview The photo above shows the overall elevation view of the new machine. Briefly, the mechanical unit is on the right containing the electrical and hydraulic systems. The vacuum/atmospheric tank is located to the left of the mechanical unit. The control console with plasma screen readout for the machine variables is to the left with the programming and data retrieval computer pictured to the left of the control console. Mechanical Systems The mechanical configuration of the system is based on handling a large melt zone. Since the specimen has no strength while in the liquid state, a composite crucible using a ceramic fiber liner with a perforated metal shell is used to support the melt. The crucible has an open top with both sides and bottom of the specimen supported. The ceramic fiber is porous, as is the metal shell, permitting cooling medium to be sprayed completely around the specimen, top, sides and bottom. The amount of cooling by this method is adjusted to provide the cooling and shell formation desired on the cast material. The ends of the specimen are retained in water-cooled grips, which provide adequate cooling on the specimen ends to prevent melting beyond the end of the crucible. Since the crucible is mounted under the specimen, two retractable arms are provided to support the crucible against the lower side of the specimen during the casting process. The overall system has eight servo controlled axes. Five axes are servo hydraulic and three axes are thermal. The fragile liquid specimen with a thin shell requires that deformation be balanced, so the specimen does not move in the direction of deformation force while being deformed. Two vertical servo hydraulic rams are mounted with one in the top crosshead of the machine and the other in the bottom crosshead of the machine. These 40 ton capacity rams each travel toward the specimen, one from the top and the other from the bottom. The rams are synchronized to start and end deforming the specimen at the same time and velocity. Each ram has a maximum velocity of 850 mm/s. The opposing rams have a combined velocity of 1.7 m/s with a minimum pause time of 0.2 s. Each ram has an 80 ton capacity Hydrawedge to provide precise control of strain at high strain rates. Each Hydrawedge is also a servo hydraulic control axis. The two Hydrawedge axes are programmed as one, similar to the way the rams are programmed. Therefore, the operator only needs to program the amount of strain and the strain rate desired for each compression hit. The software provided with the machine calculates all the movements needed for the hydraulic rams and the Hydrawedge stops. When the specimen mid span melts, the level of liquid at the top of the specimen is depressed. The liquid level is brought back to the original height by reducing the length of the specimen. The space between the jaws is controlled by the fifth servo hydraulic system. The amount the grips are brought together to level up the liquid may be programmed either manually or done automatically as part of the computer program. This returns the specimen to its original 10 mm thickness before solidification. During solidification the specimen is further reduced in length to accommodate the shrinkage, which occurs as the specimen cools. Failure to bring the grips closer together during cooling could fracture the specimen shell before adequate strength has been recovered. The procedure is usually continued until the temperature is below the nil-ductility temperature. The grips holding the ends of the specimen are free to move up and down in parallel linear guides against a small pneumatic force, which holds them in place. This limits the force required to move the specimen vertically. There is also a small spring force on each end of the specimen and guides, which allow the specimen to expand lengthwise during deformation. Another feature of the new physical simulator is a mechanical system which permits moving the entire specimen and jaw system off center. Normally the specimen is deformed at the center of the mid span, where the liquid thickness during solidification is the same on both sides of the anvil. However as a means of more accurately simulating semi-solid rolling, the specimen can be moved to one side allowing deformation of the specimen, where the thickness of the remaining liquid is greater on one side of the anvil than on the other. Thermal Systems Heating of the specimen is by self resistance to electric current flow. The electric current is supplied by a 150 kva transformer with a low voltage, high current secondary. The thermal control circuit uses a thermocouple for temperature measurement and feedback. The output of the thermocouple is compared with the thermal program providing a difference signal. The electric heating current is continuously adjusted by the thermal servo control to minimize the difference signal and make the thermocouple value and program temperature match. The thermocouple is placed under the specimen between the specimen bottom and crucible, which keeps the thermocouple in place, while the material is liquid. The anvils are moved away from the specimen at all times except during deformation. Deforming at very high temperatures causes an undesirable loss of heat from the specimen to the anvils, when the anvils are cold. The new machine is equipped with two servo controlled thermal systems for heating the anvils to programmed temperatures. The temperature of each anvil may be adjusted or programmed independently using the computer program. The heated anvils limit thermal losses from the specimen during deformation. Measurement Systems The machine utilizes two computer systems. One computer system is used to store all of the programs and run the machine (the control computer). This computer is located inside the control console. The second computer for programming and data retrieval is located externally, usually on a computer table adjacent to the control console. The second computer is used to create test programs, down load programs to the control computer, gather all the data from the measuring systems on the machine and manipulate/print the data. The control computer is stand alone and can run the machine independently from the second computer. This permits data plotting of prior tests using the second computer while a new test is being performed using the control computer. Alternately, the machine may be run manually from the front panel controls on the control console. The data acquisition system has 16 channels, which can simultaneously gather data at speeds up to 50,000 data points per second on all channels. The physical simulation of real processes requires extensive data gathering if good analyses are to be possible. The unique data gathering system sets this simulator apart from pilot plants and other means of studying processes. A scanning laser allows the measurement of phase transformations in the material after deformation. Operation The system uses specimens that are 10 mm thick, 50 mm wide and 165 mm long. The system is designed to accommodate steel and stainless steel specimens. Other metals may be used in the system. The photo below shows a plane strain specimen mounted in the grips after completion of multiple deformations.  Specimen mounted in grip system The process of loading a specimen for melting, solidification and deformation in situ starts with welding a thermocouple to the bottom side of the specimen. The next step is placing the crucible under the specimen with the thermocouple exiting between the crucible and the specimen at the midpoint of the specimen length. Once the specimen is placed in the crucible the entire assembly is loaded into the grips as shown in Figure 6. This Figure shows the crucible (with perforated metal shell) in place and the extended support arms holding the crucible up against the specimen.  Crucible mounted with support arms in place The support arms are spring loaded to maintain adequate support for the specimen during melting and are retracted under computer control during the test. The ceramic liner of the crucible is an insulator, so the electric heating current will not flow in the extended support arms. During the cooling process deformation may be desired before the specimen is completely solid. In this case the crucible can be retracted as soon as an outer shell has formed on the molten material. Deformation when only an outer shell has been formed provides semi-solid information. By changing the cooling rate and the time at which the deformation begins the percentage of liquid in the specimen during deformation can be varied. To remove the crucible one of the support arms (in this case the left support arm) is attached to one end (the left end) of the crucible. When both support arms are retracted by an electric solenoid the crucible is removed from the specimen and retracted out of the way of the deforming anvils. Below are pictures of the specimen showing the melted region during a test and the specimen after solidification and deformation. The crucible is shown removed from the specimen and resting on the left side of the lower anvil base. Single or multiple deformations may be run in a single test. The time between deformations, strain rates, strain and temperatures are all programmed using the computer. Simulations with up to 10 deformations after melting have been run on the system.  The melted region  The specimen after deformation with crucible removed The system software supports programs to run all axes simultaneously. Once all programs have been arranged, they are synchronized to each other in time by the computer. Along with the programs, the data gathering channels are also arranged to obtain the desired information at suitable times and rates during the overall program. A windows based user interface was developed for programming the tests. This new simulator significantly reduces development time for new steels, processes and products. The simulator permits optimizing continuous casting and direct rolling in both semi solid and solid regimes to allow new developments to be made at lower costs. The technologies under study using this simulator offer potential for significant energy savings and new materials and products. Product Benefits The main reasons for choosing the TORO board for this system were: · High channel count, simultaneous and of high dynamic range · Low I/O latency for tight servo-control · Reconfigurable logic for adding quadrature decoding functions · Data streaming infra-structure for high-speed recording data · Application-oriented, open-architecture SW framework · Low Cost |
