In Tofacitinib Citrate 540737-29-9 the present work a weld defect detection technique based on welding stability evaluation through the sound produced by the welding electric arc was developed.1.1. Inhibitors,Modulators,Libraries Welding Electrical Arc and Acoustical SignalsIn the present work the relationship between sound pressure, sound pressure level and spectrum frequency profile behavior with the arc voltage and welding current have been studied. The sound pressure is a longitudinal mechanical wave, produced by the difference of pressure in a medium that can be solid, liquid or gaseous; in this work the transport medium is the air. The metallic transference in the welding process produces changes in the air volume Inhibitors,Modulators,Libraries on the electric arc environment. This change produces pressure variations that are transported through air and sensed by a microphone.

The sound pressure Inhibitors,Modulators,Libraries from the electric arc is a consequence of the amplitude modulation of the Inhibitors,Modulators,Libraries arc voltage and welding current [2,3]. This relation is expressed by Equation 1.The sound pressure level��SPL��also called equivalent continuous sound pressure level, is a comparative measurement with the microphone sensitivity. It is defined as twenty times the base ten logarithm iof the ratio of a root-mean��square sound pressure during a time interval to the reference sound pressure. Equation 2 expresses the sensibility function.Sa (t)=d(k.V(t).I(t))dt(1)where, Sa (t) is the sound signal (V), V (t) the arc voltage (V), I(t) welding current (A) and K the geometric factor.SPL=20.Log[1��t ��tt+��t P2 (��)d��/po](2)The relation between the microphone pressure response and its sensibility is give by Equation 3 and therefore the SPL in function of the sound pressure is give by Equation 4.

Relating the results of Equations 1 and 4, Equation 5 expresses the SPL in function of the arc voltage and welding current:P(��)=S(��)50E?3(3)SPL=20.Log[1��t ��tt+��t (S(��)50E?3)2d��/po](4)SPL=20.Log[201��t AV-951 ��tt+��t (d(k*V (��)*I (��))d��)2d��/po](5)In which SPL is the sound pressure level, V the arc voltage, I the arc current, K the geometrical factor, Po the reference sound pressure (20 uPa), �� is a dummy variable of time integration over the mean time interval, t the start time of the measurement, ��t the averaging time interval, S the sound signal.For the spectrum frequency profile analysis the continuous Fourier transform has been used; it is a linear transformation that converts the acoustic pressure signal from the time domain to the frequency domain.

This transformation is made using the Discrete Fourier Transform – DFT and it is expressed by Equation 6.S (k)=1N ��n=0N?1 s (n)e?j2��kn/N(6)Octave frequency fractions analysis allows one to evaluate the behavior of frequency strips instead of any frequency. A frequency octave is defined as an interval among two selleck chem DZNeP frequencies where one of them is the double of the other. The octave band limits are calculated by Equations 7 to 9. After obtaining the acoustic pressure spectra S(k), the octave frequency strips G(n) is obtained from Equation 10.