6 mm Mild steel plate was purchased locally, the material was cut into four (4) pieces coupons measuring 100 × 40 × 3 mm, and welded. The process parameters in Table 1 were emplyed in the welding process, using the stick arc welding machine having a constant voltage of 62 volts and an adjustable current. The reason for varying the current was to introduce different magnitude of residual stresses to the weldment. The four (4) pieces were welded to form two specimen, A₁₁ and B₁₁ of 200 × 40 × 3 mm respectively. This specimen was measured using

the magnetic device developed locally by [14], the unit readings obtained from this measuring device are in milli-volts. During measurment, minute voltages which result from magnetic domain flip in the mild steel material, are detected by the pickup coil as the device moved over the surface of the specimen. The pulsating voltages are continously fed to the inbult amplifier in the device for magnification, presented in Figure 1 is the setup of the device for measurement. The graphical user interphase (GUI) was developed using LabVIEW as shown in Figure 2. The Residual stress measuring device was designed using arduino nano, and enhanced to 16 bits resolution using ADS1115 which was connected directly to the pickup coil in Figure 3. The welded specimens were tack welded as seen in Figure 4 before actual welding and chamfering to the dogbone shaped shown in Figure 5. The tensile testing machine used for the mechanical test is presented in Figure 6.

Specimen A₁₁ and B₁₁ were measured using the magnetic residual stress (R.S) measuring device [14]. Five repeated readings were collected and compared for consistency, with combined time series plot for A₁₁ and B₁₁ presented in Figure 7 and Figure 8. Thirty-seven signals were generated per reading from the welded metal in milliVolts. Thereafter, the two specimens were subjected to tensile test with the hope that the specimen with more residual stress would fail first under tensile loading. The weld RS was measured along the longitudinal directions of the plate as shown in Figure 9. Measurements using the magnetic device were carried out on the specimens, before the materials were subjected to mechanical test.

Table 2 shows the magnetic R.S signals generated in millivolts from the welded specimen A₁₁ and B₁₁ using the device.

The 1st, 2nd, 3rd, 4th and 5th reading presented in Figure 7 and Figure 8 for A₁₁ and B₁₁ shows a good agreement. First (1st) magnetic readings from A₁₁ and B₁₁ were selected to form Table 2. The A₁₁ and B₁₁ from Table 2, were then employed to plot the time series graph shown in Figure 10. From this graph, it was observed that Specimen A₁₁ had the highest peak signal at the weld zone with magnetic R.S signal of 20.3983 mV compared to B₁₁ with 19.358 mV. After the readings where obtained, the two specimen were subjected to tensile test. After the readings were obtained from the specimen, the two specimen were subjected to tensile test, with results presented in Table 3.

Is a great way to examine the strength of a material by pulling on it. During the pulling of the specimen by the machine, the machine scale would indicate how much force it is applying to pull the specimen apart. When tensile test is performed, it is used to measure how much stress is built-up in the material. Specimen A₁₁ and B₁₁ already have some accumulated residual stresses as result of the weld activity on the material, therefore it is expected that the material with more accumulated R.S would fail first under tensile loading. Table 3 present the results of the tensile test experiment.

From the result presented in Table 3, it was observed that it took a minimum load of 1.63 kN to cause failure to specimen A₁₁ under tensile loading while specimen B₁₁ withstood up to 8.65 kN before failure which also concur to the Magnetic device estimated readings obtained for sample A₁₁ and B₁₁.

Ferromagnetic materials can exhibit attraction when a magnet is brought close to or away from them, which creates a magnetic attractive effect on them. This magnetic effect is generated due to the magnetic domains flipping into positions inside the ferromagnetic material, creating an imbalance on the net magnetic effect inside the material, making the ferromagnetic material behave like a magnet, this imbalance usually cancels out when a lightly tap or shake is delivered to the material. The principle, discovered by bark hausen has been applied to measure residual stresses in ferromagnetic material as it is known that magnetic domain usually experience obstacles while flipping into position due to presence of impurities or inherent stresses in the material [15]. The Magnetic Barkhausen principle was applied in this work using a locally made magnetic device to estimate the magnitude of stresses present in the material. The results were then compared to the tensile test experiment performed on both specimen. It was observed from Figure 7 in the comparison of all A₁₁ results that good agreement existed between the 1st, 2nd, 3rd, 4th and 5th readings. Good agreement was also established for B₁₁ in Figure 8, the repeated experiment was applied to certify the reliability of the device in reproducing experiments of approximate results. The first responses from A₁₁ and B₁₁ presented in Table 2 were chosen after Figure 7 and Figure 8 produced a strong correlation between repeated readings respectively. The results in Table 2 were applied to create the time series plot presented in Figure 10, A₁₁ was then observed to have higher signal of 20.3983 mV, as compared to B₁₁ with 19.358 mV, and according to [16], material that has higher residual stresses tends to fail first under a given load. From the tensile test carried out on both A₁₁ and B₁₁, A₁₁ failed under a lesser load of 1.63 kN, while B₁₁ withstood a better load of up to 8.65 kN as predicted by the device.