Applied Mechanics and Materials Vols. 117-119

Abstract: Critical strain is the basis to determine whether the dynamic recrystallization occurs during hot deformation process, it is important for designers to control hot forming process and microstructure of final product. In order to investigate the influence of deformation temperature and strain rate on critical strain of Cr4 steel, hot compression simulation experiment was conducted for Cr4 steel in the temperature range of 750～1200°C and strain rate of 0.002～5S^-1 by means of Gleeble−1500D thermo-simulation machine. The results showed that the critical strain increase with decreasing deformation temperature and increasing strain rate. Based on the experimental data and regression analysis method, the mathematical model of the critical strain of Cr4 steel is constructed. The critical strain model provides data support to predict the dynamic recrystallization during Cr4 heavy supporting roller hot forging process.

Abstract: With the balance of elastic mechanics differential equation and basic solution(Kelvin solution) As the foundation introduced the boundary element method for calculating the stress and displacement of elastomer. With a numerical example of the algorithm proved. The results show that the method can be more accurate solving 2 D elastic stress and displacement problem.

Abstract: Through using dual Fourier transform quantitative analysis and harmonic loss calculation on the output voltage of three phase voltage-Sinusoidal Pulse Width Modulation (SPWM) inverter, a valid harmonic inhibition scheme is presented. Carrier frequency is reasonably selected to eliminate low times harmonics, harmonics of carrier frequency times and triple frequency sideband. Analysis of fast Fourier transform is achieved in MATLAB. Simulation results show that harmonics are effectively inhibited, output voltage waveform is improved and voltage distortion factor is decreased from1.16% to 0.71%.

Abstract: Heat damage caused by deep mining is the inevitable trend in coal mine development. HEMS cooling system is a process system for high-temperature heat damage controlling in deep coal mine, in which cool energy in mine water extracted to reduce work face’s ambient temperature, to achieve heat damage controlling. We analyze the energy consumption of every subsystem during operation of the HEMS system, which could provide a theoretical basis and technical guidance on more efficiently running of cooling system deep in the future.

Abstract: It is necessary for cutting simulation to determine the friction model at the tool-chip interface suitable for metal cutting process. Cutting force experiments in orthogonal turning titanium alloy TI6AL4V are carried out with cement carbide tool KW10. The Coulomb frictions at the tool-chip interface are calculated based on measured cutting force, and the friction model is regressed, where cutting speed and feed rate are presented.

Abstract: Hot rolled added phosphorus high strength IF steel was used to study the effect of cold reduction ratio and annealing temperature on the microstructures and mechanical properties of experimental steel. The experimental results showed that the recrystallization has finished under 840°C to 880°C annealing temperature followed 65% to 75% cold reduction ratio. Under 600°C coiling temperature, 840°C annealing temperature and 65% to 75% cold reduction ratio, the yield strength, tensile strength ,elongation percentage, yield point elongation, the plastic strain ratio and strain hardening exponent were approximate 240MPa, 410MPa, 36.0%, 1.6%, 0.26 and 1.9. Under 650°C coiling temperature, 860°C annealing temperature and 65% to 75% cold reduction ratio, and that were approximate 240MPa, 415MPa, 35.0%, 2.0%, 0.24 and 1.9. Under 700°C coiling temperature, 880°C annealing temperature and 65% cold reduction ratio, and that were approximate 190MPa, 380MPa, 35.0%, 0.8%, 0.26 and 2.0. Therefore, the suggested the optimal coiling temperature6 is 600°C, cold reduction ratio is 65% to 75%, annealing temperature is 840 °C, and it obtains optimally match of high strength and punching property.

Abstract: A simple mathematical model that correlates the temperature and extrusion speed of a 6061 aluminum bar extruded from the die has been established based on the principle of heat transfer in this paper. The 6061 alloy bar is extruded from the die orifice and is cooled through heat exchanged between the bar and ambient. The temperature of the bar decreases as the distance increases away from the die orifice. The more rapidly the temperature drops, the slower the extrusion speed is. A flexible online quenching apparatus has been set up before the critical quenching position to guarantee good supersaturation of alloying elements. The calculations have shown that at the extrusion speeds of 10m/min, 15 m/min and 20 m/min, the critical quenching positions are 0.44m, 0.88m and 1.30m from the die orifice, respectively for the temperature of 520°C; and for the different temperatures, the critical quenching positions from the die orifice are 0.66m, 1.31m, 1.95m at 530°C and 0.88m, 1.75m, 2.6m at 540°C, respectively.

Abstract: IS0-13660 has defined line attributes in digital prints. In order to investigate the effect of these attributers on perceived text definition (PTD), the correlation model between the two was developed in this study. The test target with a multi-stroke Black Type Chinese character in two sizes of 6.5 and 10.5 points, as well as some single lines, was designed and printed, coming into being 16 test samples with different qualities. The objective line attribute measurements and subjective definition evaluations were carried out, and linear correlation model was built between the two. The experimental results indicate that the PTD could be relevant to line’s contrast, raggedness, blurriness and width, and is always positively relevant to the contrast and negatively relevant to the later three attributes.

Abstract: The ball defects generated in skew rolling process have restricted to large extent the further application of skew rolling technology in ball manufacturing industry. Research was carried out so as to find the factors and laws of influencing on skew rolling ball quality. It was found by analyzing the forces exerting on the ball that the deforming velocity of ball had the largest influence on the resistance to deformation. Simulations were done respectively under different roller obliquities, different distances between two guide plates, and different rotation speeds of rollers by means of DEFORM-3D software. Finally, the influencing factors and laws on ball quality were discovered.

Abstract: The seed adsorption disk is an important component of the seed metering device. The differences in size and shape of suction hole on the adsorption disk result in variation of the airflow field formed. A finite element analysis of airflow field for the suction holes of different size and shape was conducted in this paper. The two dimensional simulation of airflow field for different shaped suction hole under the condition of identical bore diameter and air pressure difference reveals that the average airflow velocity inside the different shape of suction holes are the highest one in cylindrical hole and the lowest in tapered hole, the airflow speed at inlet opening of three different suction hole does not vary evidently. Both the result of airflow field two dimensional finite element analysis of different bore diameter suction hole and its proof under the condition of the shape of suction holes and air pressure difference being identical reveal that with the bore diameter being enlarged, the airflow speed inside the suction hole increases in comparison of the airflow speed field for three different suction holes of different bore diameter. To enlarge the bore diameter of suction hole and expand the adsorption surface area of the seed will result in the airflow rate and airflow speed getting higher and the adsorption function on the seed growing stronger.