This paper proposes a high-strain sensitivity turning dynamometer that combines several thin-film resistor grids into three Wheatstone full-bridge circuits that can measure triaxial cutting forces. This dynamometer can replace different cutter heads using flange connections. In order to improve the strain effect of the dynamometer, the strain film sensor is fixed on the regular octagonal connection plates on both ends of the elastomer by vacuum brazing, and the stepped groove structure is also designed inside the elastomer. The dynamometer model is simplified as a four-segment cantilever beam which has different sections. The measurement mechanism model of the dynamometer system is established by the transformation relationship between deflection and strain, under external force. The standard turning tool of 20 mm square is used as a reference. The influence of the structural dimensions of the dynamometer on its strain sensitivity coefficient K is studied. The applicability of the theoretical model of dynamometer strain is verified by finite element analysis. Finally, the dynamometer with the largest K value is subjected to the bending test and compared with a standard turning tool. The experimental results show that the measurement sensitivity of the dynamometer is 2.32 times greater than that of the standard turning tool. The results also show that this dynamometer can effectively avoid the influence of the pasting process on strain transmission, thus indicating its great potential for measuring cutting force in the future.

The existing detection device for unexploded ordnance (UXO) based on geomagnetic anomaly and electromagnetic induction suffers from issues such as functional separation, large size, and low efficiency due to the constraints of sensors. The centimeter-sized magnetostrictive/piezoelectric composite demonstrates static and dynamic wideband frequency response capabilities for measuring magnetic fields. Here, a novel dual-mode detection method is proposed for receiving magnetic anomalies and transient electromagnetic responses in parallel by the FeNiMoSiB/PZT-5A composite. The transient primary field generated by a transmitting coil can not only cause the target to induce a secondary field, but also drive the operation of the magnetoelectric (ME) composite. The FeNiMoSiB layer excited by a high amplitude field generates nonlinear magnetostriction. Under the magnetic-mechanical-electrical conversion, the ME composite driven by the transient primary field undergoes a step response to output oscillating voltage. Due to the nonlinear ME effect, the oscillating voltage is modulated by the magnetic anomaly, resulting in an amplitude change. The magnetic anomaly information can be obtained by demodulating the resonant voltage signal. After the voltage oscillation ends, it begins to decay. Moreover, the dominant secondary field will hinder the voltage attenuation, and its information can be obtained by analyzing the late attenuation voltage signal. In the experiment, the ferromagnetic metal targets at different depths are detected, and the maximum detection depth is about 1.2m. In field environments, the targets buried at a depth of 0.5m in the soil are successfully located along the survey line, demonstrating good positioning performance.

Under a high amplitude AC excitation field, the magnetostrictive/piezoelectric composite exhibits the nonlinear magnetoelectric (ME) effect. A weak DC/AC magnetic field can be measured by demodulating the odd harmonics generated by the composite structure due to the nonlinear ME effect. The AC excitation magnetic field created by an external signal source will introduce crosstalk noise. Here, a novel method for measuring the weak magnetic field via FeNiMoSiB/PZT-5A/FeNiMoSiB composite excited by step magnetic field is presented. The ME composite excited by the step magnetic field will vibrate at its natural frequency to significantly enhance the ME effect. In addition, the resonance frequency of the ME composite is not affected by the excitation signal, which reduces the noise introduced by the external excitation source. Due to the nonlinear ME effect, the induced ME voltage is modulated by a weak DC/AC magnetic field to be measured. The weak magnetic field signal can be recovered from the ME voltage by the lock-in demodulation method. The ME unit for sensing the magnetic field is designed based on the longitudinal free vibration model excited by a step magnetic field. In the experiment, the step magnetic fields generated by a 2 kHz bipolar square-wave signal are used to excite the ME composite. The sensitivity of 29.77 mV/Oe and linearity error of 0.22% are achieved in the DC magnetic field of -3~3 Oe. The sensitivity to 1~50kHz AC magnetic field to be measured in the flat area is about 37.5 mV/Oe.

Thin-film strain sensors are widely used because of their small volume, fast strain response and high measurement accuracy. Among them, the thin-film material and preparation process of thin-film strain sensors for force measurement are important aspects. In this paper, the preparation process parameters of the transition layer, insulating layer and Ni-Cr alloy layer in a thin-film strain sensor are analyzed and optimized, and the influence of each process parameter on the properties of the thin film are discussed. The surface microstructure of the insulating layer with Al₂O₃ or Si₃N₄ transition layers and the film without transition layer were observed by atomic force microscopy. It is analyzed that adding a transition layer between the stainless steel substrate and insulation layer can improve the adhesion and flatness of the insulation layer. The effects of process parameters on elastic modulus, nanohardness and strain sensitivity coefficient of the Ni-Cr resistance layer are discussed, and electrical parameters such as the resistance strain coefficient are analyzed and characterized. The static calibration of the thin-film strain sensor is carried out, and the relationship between the strain value and the output voltage is obtained. The results show that the thin-film strain sensor can obtain the strain generated by the cutting tool and transform it into an electrical signal with good linearity through the bridge, accurately measuring the cutting force.