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Test compression was developed to help address this problem. When an ATPG tool generates a test for a fault or a set of faults, only a small percentage of scan cells need to take specific values. The rest of the scan chain is do not care and are usually filled with random values. Loading and unloading these vectors is not a very efficient use of tester time. Test compression takes advantage of the small number of significant values to reduce test data and test time. The idea is to modify the design to increase the number of internal scan chains, each of shorter length. These chains are then driven by an on-chip decompressor, usually designed to allow continuous flow decompression where the internal scan chains are loaded as the data is delivered to the decompressor.One common choice is a linear finite state machine where the compressed stimuli are computed by solving linear equations corresponding to internal scan cells with specified positions in partially specified test patterns.The major difference between the two types of loading is the strain which would have opposite signs for tension (positive—it gets longer) and compression (negative—it gets shorter).When a specimen of material is loaded in such a way that it extends it is said to be in tension. On the other hand if the material compresses and shortens it is said to be in compression.Ceramics typically have a much higher compressive strength than tensile strength. Composite materials tend to have higher tensile strengths than compressive strengths. Industrial and consumer packages other than boxes can also be subjected to compression testing: drum, pail, bottle, etc. Package components are also evaluated for compression resistance. Tension testing is by far the most extensively developed and widely used test for material behavior, and it can be used to determine all aspects of the mechanical behavior of a material under tensile loads, including its elastic, yield and plastic deformation and its fracture properties.Compression tests and torsion tests are alternative approaches that overcome this limitation. Compression-test specimens are simpler in shape, do not require threads or enlarged ends for gripping and use less material than tension-test specimens. Compression tests are often useful for subscale testing and for component testing where tension-test specimens would be difficult to produce.In highly textured materials that deform by twinning, as opposed to dislocation slip, compressive and tensile deformation characteristics differ widely. The failure of unidirectionally reinforced composite materials, particularly along the direction of reinforcement, is much different in compression than in tension.The characteristics of deformation during axial compression testing are described, including the deformation modes,compressive properties and compression-test deformation mechanics.Higher compression ratios will however make gasoline engines subject to engine knocking if lower octane-rated fuel is used, also known as detonation. This can reduce efficiency or damage the engine if knock sensors are not present to retard the timing. Vikas Gupta ,for information on Total Station Compression Testing Machine,Digital Compression Testing MachineAuto Level,Garmin GPS,Flexure Testing Machine,Test Sieves,Vibrating Table and Cube Mould,Curing Tank.please visit our website www.uniquetestinginstruments.info
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