Key Engineering Materials Vol. 621

Abstract: This paper discusses the influence factors in the process of hot stamping of high strength steel TRB(Tailor rolled blank) by simulation,using the numerical model referred tothe typical part of vehicle B column structure and BR1500HSas the material model in Abaqus for simulation.By means of numerical simulation using theorthogonal and control variables methods,different models have been designed to research the influence of transition zone gradient (A),fillet radius of punch and die (B), clearance between punch and die (C), friction coefficient (D), thetemperature (E), taking the hoop strain and the material movement along the direction of thick change as the evaluation index.in order to draw the infect law of TRB for hot stamping to find out the best technological parameters group for stamping, which can make theoretical contribute to the TRB application. The research shows that the influencedegree order of different factorsis:D>E>C>A>Conly taking the hoop thick into consideration,then influence order is E(A)>D>B>C only taking the material movement along the direction of thick change.

Abstract: This paper researched the crack propagation and the variation of microstructure for ZTA ceramics under ultrasonic vibration grinding. To interpret the phenomenon, the nonlocal theory was introduced to establish the constitutive model under the ultrasonic vibration. Grinding experiments on surface quality of nanoZrO2 ceramic are carried out using diamond grinding in different condition, both with and without ultrasonic vibration. Experimental results show the surface quality after two-dimensional ultrasonic assisted grinding is superior to that after common grinding. Meanwhile, the effects of amplitudes and frequencies on ZrO2 ceramics crack propagation were analyzed by SEM. The results show that the crack propagation rate decrease with the amplitudes and frequencies increasing, this is because that the nonlocal attenuation ratio reduced and the nonlocal effects also the strongest. The results of experiments are in accordance with the theoretical conclusions drawn from the nonlocal theory, which verifies that the act ion of ultrasonic vibration can actually postpone the ceramic crack propagation rate.

Abstract: On the basis of the cylindrical plunge grinding and intermittent axial feed grinding experiment, the grind-hardened layer structure and its property of the loader clevis pin were studied. The result shows that there are some arc shape medium/high-temperature tempered zones and some annular unhardened zone in external circumference surface, which is result of temperature gradient, induced grinding heat when circumferential feed and axial grinding heat conduction. The microstructure of hardened zone is mixture martensite, and the microstructure of tempered zone is tempered martensite and troostite. Different structure zone has same microhardness distribution regulation, but the microhardness of hardened zone can reach 640HV0.5. The loader clevis pin processed by grind-hardening meets the property request for working.

Abstract: Ultrasonic lapping can effectively improve machining efficiency and obtain higher machining precision, which can be as the final process. This paper discusses the ultrasonic lapping mechanism through simulating the lapping tracks. Based on the contrast experiments between common and ultrasonic lapping, the influence of different lapping parameters on material removal rate and surface roughness were studied and the surface microstructure of workpiece was analyzed. The experimental results show that material removal rate of ultrasonic lapping is nearly two times that of the common lapping, especially in ultrasonic axial lapping, and the better surface quality can be obtained during ultrasonic lapping. Meanwhile, the reasons for material removal rate increasing and surface quality improving were analyzed.

Abstract: Due to intermitted cut characteristics, ultrasonic elliptical vibration cutting offers many benefits e.g. reducing tool force, improving surface finish and extending tool life. This paper presents the model-based development of an ultrasonic elliptical vibration cutting device with 1st resonant mode of longitudinal vibration and 3 rd resonant mode of bending vibration. The development of the device was assisted with the finite element program ANSYS. Based on theoretical and experimental studies, the requirements of the device are estimated. The maximum displacement amplitude of the ultrasonic elliptical vibration cutting device is 13.1μm and 8.3μm for bending vibration and longitudinal vibration respectively at an exciting voltage of 400V_p-p.

Abstract: Micro/meso forming, as an emerging manufacturing process for miniature metallic workpieces, has attracted great attention since the 1990s due to its high production efficiency, low material waste and high precision. Due to the so-called size effects in the scaling down, many traditional theories in metal forming cannot be simply applied to the micro/meso forming. In this study, the micro/meso upsetting experiments of Brass H62 were conducted at various temperatures. The stress−strain curves in the experiments were measured and compared. The effects of the temperature and the sample size on the flow stress were discussed. It is found that the flow stress of the material decreased with the decrease of the sample size at room temperature. However, the flow stress of the material may increase with the decrease of the sample size at elevated temperatures. The results indicate that the size effects in the micro/meso forming are significantly affected by the processing temperature.

Abstract: This paper introduces the defect formation and compensation method of Invar during hot stamping with multi point flexible mould. In cylindrical and spherical, for example, through Solidworks 3-d modeling, using Dynaform to do forming numerical simulation, we study multi point hot stamping defects of thick Invar, mainly including indentation and rebound. Then we get the rules of indentation and rebound with thickness and curvature, compensate these defects and control the error within the requirements.

Abstract: In the field of machinery manufacture, broken state at the time of the cutting tool in cutting metal, recognition has always been a study is of great significance. Currently, for the state of tool wear and collapse edge damage identification method already has a mature experience. However the existing condition monitoring methods are often used in accuracy and convenience has limitations, this paper USES the acoustic emission technology, as a kind of integrated online test sys tem design lay the foundation. This paper aimed at the sensor in the wireless transmission module, the performance characteristics of tool condition monitoring system of the main structure was designed, and then by acoustic emission signal from the cutting tool in cutting process as the research object, studies the cutting tool characteristics of acoustic emission signal under different damage state, for the on-line monitoring system design and calibration to provide theoretical support.

Abstract: Tacho plate is a common speed regulation mechanism in automobile, but because of its complex structure, high precision, there has been no ideal processing method. Based on the Pro.E, this paper compiles the processing technic of the Tacho plate which combining with the practical situation and comprehensive considering the precision, economy, efficiency, roughness, lifetime and other factors, and digital design a specific work fixture regarding one of the most important procedure. Eventually it achieves a very satisfactory result. First of all, understand the working condition of Tacho plate through on-the-spot investigation, reviewing the literature and some other methods, and then preliminary analyze the processing technic of Tacho plate. Secondly, constantly improve the processing technic of Tacho plate through in-depth analysis of the actual situation and comprehensive considering the machining precision, economic benefit, efficiency and some other aspects to make the best processing procedures. Furthermore, make in-depth analysis for the fixture of drilling Φ10 hole. Considering the machining accuracy, use the ganged clamping mechanism with the support plate, regulative support nail, and rhombic pin for joint locating to meet the requirements to the greatest extent. Finally, use the Pro.E software for three-dimension model and further verify the fixture plan designed before through this digital design.

Abstract: The transmission gear, bearing and hub and important component of wind field prone to fatigue failure under thermal load and alternating stress. The core component of MW class wind turbine gear box is bearing parts, according to the Betz principle bearing dynamic characteristic is analyzed including deduction and calculation of axial force and radial force, this paper simulates contact stress under the typical conditions of cylindrical roller bearing by finite element method, meanwhile analyzes the stress variation of the rolling body and a holding frame, the simulation results show that bearings bear a greater impact load in the starting process, retainer and rolling body produce large instantaneous stress value in the process, while the stress value is relatively small in the smooth operation and at braking speed, The simulation results has some practical value in engineering of optimization design.