Signal processing method and material testing machine

A signal processing method, comprising:

• separating two end parts of a test piece by a pair of grippers;
• detecting physical quantity of the test piece by a physical quantity detector;
• an interval data generating process of dividing an input signal into interval data of time-domain by cutting out the input signal by a predetermined time length, wherein the input signal is a detecting result output by the physical quantity detector;
• a reference function determining process of determining a function as a reference function, wherein the function matches a gradient of a tangent with a tangent point falling on a starting point of the interval data with a gradient of an approximately straight line near a starting position of the interval data and matches a gradient of a tangent with a tangent point falling on an end point of the interval data with a gradient of an approximately straight line near an end position of the interval data;
• and
• a transform process of transforming the interval data into adjustment data adjusted using the reference function determined in the reference function determining process so that both ends of a waveform of the interval data smoothly converge to zero.