共查询到20条相似文献,搜索用时 437 毫秒
1.
Smart portable noninvasive instrument for detection of internal air leakage of a valve using acoustic emission signals 总被引:1,自引:0,他引:1
Acoustic emission (AE) can be used to detect and determine the internal leakage rate through a valve in many applications. However, a general AE data acquisition system is expensive and bulky. This paper presents a novel low-cost instrument based on microcontroller and a novel theoretical model based on AE technique to predict the leakage rate. The system is an embedded system instead of a general PC-based data acquisition. AERMS parameter is used to infer the leakage rate, and the effects of various process variables on the model are also studied. The experimental results have shown that the instrument is capable of detecting possible valve leakage encountered in online operation. With its portability, ease of use and compactness, the proposed system provides faster and low cost valve leakage detection. 相似文献
2.
Chien-Sheng Liu Yu-An Li 《The International Journal of Advanced Manufacturing Technology》2018,99(5-8):1109-1117
In the industrial manufacturing field, machining is a major process. Machining operations involve grinding, drilling, milling, turning, pressing, molding, and so on. Among these operations, grinding is the most precise and complicated process. The surface condition of the grinding wheel plays an important role in grinding performance, and the identification of grinding wheel loading phenomena during the grinding process is critical. Accordingly, this present study describes a measurement method based on the acoustic emission (AE) technique to characterize the loading phenomena of a Si2O3 grinding wheel for the grinding mass production process. The proposed measurement method combines the process-integrated measurement of AE signals, offline digital image processing, and surface roughness measurement of the ground workpieces for the evaluation of grinding wheel loading phenomena. The experimental results show that the proposed measurement method provides a quantitative index from the AE signals to evaluate the grinding wheel loading phenomena online for the grinding mass production process, and this quantitative index is determined via some experiments in advance in the same grinding environment to help the monitoring and controlling of the grinding process. 相似文献
3.
切入磨削与纵向磨削的磨削力分析与比较 总被引:1,自引:0,他引:1
研究了同时包含切入磨削和纵向磨削的复杂外圆磨削过程。根据纵向磨削过程的特点,将砂轮等效成若干个小砂轮,在传统阶梯模型的基础上构建了砂轮磨损的抛物线模型。推导了基于两种模型的纵向磨削切向分力和切入磨削切向分力的比较公式,两切向分力的比值反映了切入磨削和纵向磨削转换时切向分力的变化情况,它主要与磨削系数、砂轮宽度和纵向进给速度有关。采用砂轮主轴功率信号分析磨削切向分力,通过实验验证了抛物线模型更符合实际情况的结论。研究结果为采用磨削力信号和功率信号研究复杂磨削过程的监控提供了参考依据。 相似文献
4.
砂轮精确修整时的声发射检测方法 总被引:2,自引:0,他引:2
砂轮修整状态严重地影响砂轮的磨削性能,这在精磨及成形磨削过程中显得尤为突出。本文提出了一种砂轮精确修整的新方法,利用声发射试验检测系统实时提取砂轮修整过程中声发射信号的特征参量,有效地实现了砂轮型面的精确修整。 相似文献
5.
6.
Investigation of the relationship between internal fluid leakage through a valve and the acoustic emission generated from the leakage 总被引:3,自引:0,他引:3
The detection of acoustic emission (AE) signals produced by liquid and gas leakage through valves can be related directly to the qualitative leakage rate. This allows for cost estimation of losses in processes for several industries. However, to find out the relationship between qualitative leakage rate and AE signal large amounts of experimental data is needed. This paper presents a theoretical investigation of the acoustic emission to detect the internal leakage rate through a valve and experimental validation. The AE signals generated by internal liquid and gas leakage through valves were characterised. The effect of the influenced factors of leakage rates, inlet pressure levels, valve sizes and valve types, on AE parameter, AERMS, were studied and explained. The results of theoretical and experimental showed that AE signal power computed from the power spectral density (PSD) correlated well with influenced factors of leakage rates. Finally, a novel and inexpensive AE instrument has been invented for predicting qualitative leakage rate using a micro processor and derived relationship. 相似文献
7.
8.
M. Prakash 《Machining Science and Technology》2013,17(2):209-227
Recently researchers and manufacturers have shown keen interest in fabricating micro-components through tool based mechanical micromachining processes namely micromilling, microdrilling, microturning, etc. In this scenario, microendmilling is used in the manufacture of micro-molds, micro-dies, micro-channel, micro-gear, etc. The major issue in microendmilling process is the unpredictable life of the micro-tool and its premature failure during operations. Therefore in this work, an attempt has been made to monitor the tool condition (in-process) using acoustic emission (AE) sensor in microendmilling of different materials such as aluminum, copper and steel alloys. From this study, it is observed that there is a strong relationship between the tool wear (flank wear) and acoustic emission (AERMS) signals, surface roughness (Ra) as well as chip morphology. In order to understand the mechanism of tool wear, SEM and EDAX analyses were carried out on the microendmill after machining. Scanning Electron Microscope (SEM) and energy dispersive X-ray spectroscopy (EDAX) analyses indicated occurrence of the tool wear mechanism such as adhesion and plastic deformation in all three materials. Coating delamination is also observed while machining steel alloy. This work provides significant and new knowledge on the usage of AE sensor in monitoring the tool condition and understanding the tool wear mechanism in microendmilling of different materials. 相似文献
9.
Zhensheng Yang Zhonghua Yu 《The International Journal of Advanced Manufacturing Technology》2013,68(9-12):2439-2449
Grinding burn is a discoloration phenomenon according to the thickness of oxide layer on the ground surface. This study tries to establish an automatic grinding burn detection system with robust burn features that are caused by burn and not by the design parameters. To address this issue, a method based on acoustic emission sensor, accelerator, electric current transducers, and voltage transducers was proposed in an attempt to extract burn signatures. A trial-and-error experimental procedure was presented to find out burn threshold. Vitrified aluminum oxide grinding wheel and AISI 1045 steel workpiece were used in the grinding test, as they were the most commonly used wheel–workpiece combinations in conventional grinding process. With the help of fast Fourier transform and discrete wavelet transform, the spectral centroid of AE signal, the maximum value of power signal, and the RMS of the AE wavelet decomposition transform from wavelet decomposition levels d1 to d5 were extracted as burn features. The spectral centroid of AE signal was believed not to be affected by grinding parameters. A classification and prediction system based on support vector machine was established in order to identify grinding burn automatically. Results indicate that the classification system performs quite well on grinding burn classification and prediction. 相似文献
10.
针对精密外圆切入磨削加工的在线监测需求,提出一种采用声发射信号实现轴类零件材料去除率在线监测的方法。根据声发射信号强度与磨削力之间的联系,建立了声发射信号均方根曲线的预测模型,利用该预测模型研究了砂轮进给阶段和驻留阶段磨削系统时间常数的理论计算方法,推导了声发射信号均方根曲线与工件材料去除率的关系;编写了在线监测软件,利用声发射传感器实现了精密外圆切入磨削的材料去除率预测。实验证明,所建立的声发射信号均方根曲线模型具有良好的预测精度,基于该模型能够实现磨削系统时间常数在线评估,并实现精密轴类零件材料去除率的实时在线监测。 相似文献
11.
12.
13.
J. M. Crichigno Filho C. R. Teixeira L. V. O. D. Valentina 《The International Journal of Advanced Manufacturing Technology》2007,33(7-8):730-737
Lapping is a precision manufacturing process. However, the material removal rate and surface roughness show significant variation
between trials for repeated experiments and, thus, the repeatability of the results depends on the machine operator’s skill.
Acoustic emission (AE) seems to be capable of monitoring the process. Therefore, an understanding of AE generation during
lapping is important to predict the performance of the grains and hence the lapping results. Based on a theoretical analysis
and experimental results collected during flat lapping, the AE signal was investigated for the situation when slurry is supplied
without replenishment. The experiments were carried out with a wireless rotating AE sensor mounted in the middle of the lapping
plate. Three parameters related to the AE curve are proposed to monitor the process. The influence of process parameters (lapping
pressure, velocity, average grain size, concentration of grains in lapping compound and the number of conditioning rings)
on the characteristics of the AE curve was investigated. 相似文献
14.
During cylindrical traverse grinding processes, two types of regenerative chatter—workpiece and grinding wheel—may degrade the accuracy of the surface finish. To maintain productivity and quality, a closed-loop vibration control system should be provided for the grinding system. An algorithm for automated classification by type is essential in developing such a system. In cylindrical traverse grinding, the chatter vibration signals display unstable dynamic characteristics, which makes the task of chatter classification especially difficult. This paper introduces an approach that combines entropy techniques with morphological preprocessing to classify traverse grinding regenerative chatter by type based on the vibration spectrum. Experimental data analysis is used to demonstrate that the proposed method can effectively distinguish workpiece regenerative chatter from wheel regenerative chatter. Because both the entropy function and morphological processing are computationally easy, this method is not only readily understood, but also conveniently adaptable to system expansion and real-time applications. 相似文献
15.
16.
针对球面、非球面及自由曲面超精密磨削加工用圆弧形金刚石砂轮难以精密修整的问题,提出基于旋转绿碳化硅(GC)磨棒的端部在位精密修整方法及修整过程的声发射在线监测技术。基于圆弧形金刚石砂轮的结构特性,制订圆弧形金刚石砂轮的在位精密修整与修整过程的声发射在线监测技术方案。依据修整与在线监测方案,对D64圆弧形金刚石砂轮进行修整实验及其声发射信号采集,修整后跳动误差小于10μm,比修整前减小30μm左右,砂轮精度显著提高。利用声发射信号均方根值获取砂轮修整结束的特征预警阈值,实现了旋转GC磨棒端部在位精密修整过程的在线监测以及修整结束时间的准确判断,可以有效提高球面非球面磨削加工过程的效率。 相似文献
17.
18.
Acoustic emission as an indicator of material-removal regime in glass micro-machining 总被引:2,自引:0,他引:2
Acoustic emission (AE) spectra were recorded during microgrinding of brittle materials. It was found that the specific AE energy (i.e., the measured AE energy divided by the material removal rate) was lower for fracture-dominated grinding than for plastic flow-dominated grinding. Two subsequent experiments were performed to measure AE energy while holding the material-removal rate constant. By controlling either the critical depth of cut (for ductile-brittle transition) of the workpiece material, or the actual depth of cut of the grinding machine, the sensitivity of AE energy to grinding regime was investigated for grinding with a constant material-removal rate. Contrary to conventional thinking about the relative contributions of plastic flow and fracture in generation of AE activity, it was found that the AE energy was larger in ductile-regime grinding than in brittle-regime grinding, for identical material removal rates. As a result of the experiments described in this paper, it can be concluded that AE energy measured during microgrinding is sensitive to changes in the mechanism of material removal. For a given volume of material removed, there is more AE energy in a plastic flow-dominated process than in a fracture-dominated process. The relationship found between AE energy and material removal regime could lead to an in-process sensing strategy for controlling grinding ductility. 相似文献
19.
Sun Ho Kim Tae Jo Ko Jung. Hwan Ahn 《The International Journal of Advanced Manufacturing Technology》2001,17(4):252-256
Air-grinding time is inevitable in the grinding process. Since the low feedrate during air grinding makes the process inefficient,
air-grinding time should be reduced. This paper presents a technology for reducing air-grinding time in cylindrical plunge
grinding operations. The main idea is to estimate a distance, NAP (nearest approaching point), between the workpiece surface
and the position of the grinding wheel. After detecting the NAP using an ultrasonic sensor, a CNC controller adjusts the feedrate
using the feedrate override function with the help of the AE signal that gives the CP (contact point) information. The experimental
results show that an ultrasonic and an AE sensor are good enough for detecting the NAP and the CP, respectively, and the system
reduces the conventional air-grinding time by two-thirds. 相似文献
20.
针对阿基米德滚刀加工渐开线圆柱齿轮,用阿基米德造型的滚刀在刃磨滚刀齿形时,为了提高齿形精度,改变加工工艺和检测工艺,使用先进的"砂轮修正器"和"齿轮测量中心",缩短了设计和加工时间,提高了齿轮滚刀齿形磨制的效率,保证了滚刀加工渐开线圆柱齿轮齿形精度,使大于4模数的阿基米德滚刀齿形(A级﹑AA级)易于保证被加工渐开线圆柱齿轮的齿形精度。 相似文献