Experimental Techniques最新文献

Shaft design assumes that the end supports of the shaft are simply supported that is not entirely correct. This article investigates the effects of simply supported ends and fixed-fixed supported ends on the bending moment developed in shafts. The bending moments and hence bending stress are life limiting parameters of shafts. Moreover, the effects of transverse loading inclination, loading spacing, and loading variation on the bending moment developed in shafts are studied. Analytical, numerical, and experimental approaches were adopted. Notched steel rods were used in fatigue experiments. The fatigue lives of those rods were measured and recorded. The bending moment applied to the rod specimen was calculated and compared to those obtained from the analytical and numerical approaches. The studies revealed that the simply supported end conditions will result in a shaft diameter that is 88% larger. However, the fixed-fixed end condition will result in a shaft diameter that is 67% smaller. The average bending moments of the simply supported and the fixed-fixed end conditions will result in the most accurate shaft diameter. Moreover, the maximum bending moment occurred when the load inclination angle θ = 0.0. It also increased with increasing the load ratio P₁/P₂ and the load spacing ratio l₁/L, where P₁, P₂, l₁, and L are respectively the left-hand load, the right-hand load, the position of P₁ from the left-hand support, and the total length of the shaft.

Elastic modulus is the core of mechanical spectroscopy to study the actuation-based performance, lifetime, reliability, and stability of pure metals as well as alloys. In this investigation, a prototype system has been discussed for measuring the elastic properties of pure metals such as Cu (99.99%), Al (99.99%), and Ni (99.99%) using electrostatic force. The samples were processed by cold rolling producing specimens of 10–100 microns thickness. A variable potential difference ranging from 1 to 370 V DC was supplied, thus applying a variable electrostatic force to the specimen. The whole system is concentrated on the measurement of micro- to macroscale levels, and a powerful optical microscope evaluates the deflection. The current system has been used to estimate the samples' elastic moduli and then compare it with those obtained by the well-known tensile stress–strain testing method. Finally, the experimental principle of measuring elastic modulus was developed to conduct further research on the metallic materials that are induced by external stimuli like magnetic fields, lasers, and/or heat.

This paper presents a novel control strategy to improve the performance of a low-frequency vibration calibration system. The low-frequency vibration calibration system based on a linear motor is first developed. The amplitude sensitivity and phase sensitivity are then derived. Subsequently, the composite control strategy of the iterative learning control (ILC) and Luenberger observer is established to improve the performance of the linear motor vibration generator. Finally, the frequency stability of the linear motor is measured, and a tri-axial accelerometer is calibrated. Experimental results indicate that the linear motor controlled by the proposed composite strategy can fulfill accelerometer calibration with high precision, and maintain the performance in the full frequency band.

Grinding is usually adopted as the final step in the workpiece machining to improve the surface quality. The wrapping deformation of sheet parts caused by grinding directly affects the surface accuracy and the performance of the parts. In this paper, the grinding experiments were designed and conducted under different conditions. Combined with theoretical analysis, the finite element model was established to reveal the mechanism of wrapping deformation. A new evaluation method of wrapping deformation in grinding was proposed, and the prediction model of the wrapping deformation and temperature in the grinding zone were established and verified. Finally, the grinding parameters were optimized through genetic algorithm with small error. The optimized grinding parameters were v_s = 28 m/s, a_p = 5 μm, v_w = 3 m/min. This method can provide guidance for the grinding process of sheet parts, which is beneficial for improving efficiency and precision in grinding.

Tribological performance of epoxy (EP) composites reinforced with short glass fibers (SGF), graphite, polytetrafluoroethylene (PTFE), and B₄C nanoparticles was investigated under oil lubrication. The effects of different types of SGF, graphite, PTFE, and B₄C nanoparticles on the friction and wear properties of EP were examined using a ball-on-block machine. The worn surfaces were characterized using optical microscopy, SEM-EDX, XPS, and TEM. The anti-wear mechanisms were proposed based on the experimental observations and analysis. The results demonstrate that the addition of SGF significantly reduces wear and friction in the EP matrix. In contrast, the incorporation of B₄C nanoparticles and other solid lubricants does not have a significant effect on friction and wear. The remarkable tribological properties observed in the SGF-reinforced EP composites can be attributed to the superior load-bearing capabilities and wear durability of SGF. These fibers effectively withstand the load and exhibit excellent durability during sliding, resulting in reduced wear and friction.

Cast iron is widely used as a grinding tool material in the field of ultra precision manufacturing. To explore the friction and wear properties of cast iron materials under magnetic-mechanical coupling conditions, theoretical research was conducted to reveal the wear mechanism of cast iron materials. A self-developed free abrasive line contact tribometer was used to study the evolution law of different process parameters on the friction and wear properties, surface roughness, and surface morphology of cast iron. The experimental results reveal that, under the magnetic field conditions, the mean value of friction coefficient is less than 0.218, the wear capacity of cast iron rings is less than 42 mg, and the surface roughness value Ra is less than 0.139 μm, additionally, the friction coefficient, wear capacity, and roughness values are all lower than those under no magnetic conditions. For cast iron materials, the surface roughness value Ra ranges from 0.094 to 0.253 μm after the experiment, it is negatively correlated with relative sliding ratio, load, abrasive particle size, and concentration, while is positively correlated with magnetic induction intensity; The friction coefficient is negatively correlated with relative sliding ratio and magnetic induction intensity in the range of 0.051 to 0.268, and positively correlated with abrasive particle size and concentration. With the load increasing, the friction coefficient first decreases and then increases; The wear capacity of cast iron ring is within the range of 8 to 140 mg. It is negatively correlated with magnetic induction intensity, and positively correlated with relative sliding ratio, load, abrasive particle size, and abrasive concentration. This study provides support for the theoretical research of cast iron as a grinding tool material and provides reference for the rational application of cast iron materials in the field of ultra precision manufacturing.