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HYSTERESIS – Load Cell Nonlinearity – Oscar Zavaleta Weighing Industry

A field of study for classical mechanics, magnetic fields and superconductivity. It can be rate dependent or independent and elastic or nonelastic. The post covers the mechanical field of study and application only.

ETYMOLOGY In 1881 Sir James Alfred Wing coined the word to define magnetic behaviour. Hysteresis comes from the ancient Greek word ὑστέρησις, meaning deficiency. The word can also mean lag behind, which is also a characteristic.

DEFINITION Load cell signal difference between load increase and its decrease. In fact, the loading curve is different from the unloading one.

PHYSICS The work required to return to its original state is less than one to deform it. Elastic hysteresis develops when stress/strain curves follow different paths. Measurement has to be fast enough to prevent creep effects.

MATH It can be measured as the difference in the area under the stress/strain curves—the difference between load cell signal readings, load increase and decrease.

CYCLE A signal is dependent on the load and its associated history. An input load response is a function of its prior output. Repeated loading diminishes its effects, but is never eliminated.

THERMODYNAMICS Upon load, the molecules undergo displacement resulting in internal friction. Some of the heat generated by friction dissipated to the surroundings. Conservation of energy can be seen on the hysteresis curve.

METALLURGY An increase in the stress maxima indicates material hardening. A decrease in the stress minima indicates material softening. Freezing and furnace heat may have an effect on hysteresis.

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