机械专业论文中英文对照

Gearbox Noise

Correlation with Transmission Error and Influence of Bearing Preload

Doctoral Thesis in Machine Design

TRITA-MMK 2008:19

ISSN 1400-1179

ISRN/KTH/MMK/R-08/19-SE

Department of Machine Design

Royal institute of Technology

SE 100 44 Stockholm, Sweeden

? Mats ?kerblom 2008

ABSTRACT

The five appended papers all deal with gearbox noise and vibration. The first paper presents a review of previously published literature on gearbox noise and vibration.

The second paper describes a test rig that was specially designed and built for noise testing of gears. Finite element analysis was used to predict the dynamic properties of the test rig, and experimental modal analysis of the gearbox housing was used to verify the theoretical predictions of natural frequencies.In the third paper, the influence of gear finishing method and gear deviations on gearbox noise is investigated in what is primarily an experimental study. Eleven test gear pairs were manufactured using three different finishing methods. Transmission error, which is considered to be an important excitation mechanism for gear noise, was measured as well as predicted. The test rig was used to measure gearbox noise and vibration for the different test gear pairs. The measured noise and vibration levels were compared with the predicted and measured transmission error. Most of the experimental results can be interpreted in terms of measured and predicted transmission error. However, it does not seem possible to identify one single parameter,such as measured

peak-to-peak transmission error, that can be directly related to measured noise and vibration. The measurements also show that disassembly and reassembly of the gearbox with the same gear pair can change the levels of measured noise and

vibration considerably.This finding indicates that other factors besides the gears affect gear noise.In the fourth paper, the influence of bearing endplay or preload on gearbox noise and vibration is investigated. Vibration measurements were carried out at torque levels of 140 Nm and 400Nm, with 0.15 mm and 0 mm bearing endplay, and with 0.15 mm bearing preload. The results show that the bearing endplay and preload influence the gearbox vibrations. With preloaded bearings, the vibrations increase at speeds over 2000 rpm and decrease at speeds below 2000 rpm, compared with bearings with endplay. Finite element simulations show the same tendencies as the measurements.The fifth paper describes how gearbox noise is reduced by optimizing the gear geometry for decreased transmission error. Robustness with respect to gear deviations and varying torque is considered in order to find a gear geometry giving low noise in an appropriate torque range despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error, noise, and housing vibrations were measured. The correlation between dynamic transmission error, housing vibrations and noise was investigated in speed sweeps from 500 to 2500 rpm at constant torque. No correlation was found between dynamic transmission error and noise. Static loaded transmission error seems to be correlated with the ability of the gear pair to excite vibration in the gearbox dynamic system.

Keywords: gear, gearbox, noise, vibration, transmission error, bearing preload. ACKNOWLEDGEMENTS

This work was carried out at Volvo Construction Equipment in Eskilstuna and at the Department of Machine Design at the Royal Institute of Technology (KTH) in Stockholm. The work was initiated by Professor Jack Samuelsson (Volvo and KTH), Professor S?ren Andersson (KTH), and Dr. Lars Br?the (Volvo).The financial support of the Swedish Foundation for Strategic Research and the Swedish Agency for Innovation Systems – VINNOVA – is gratefully acknowledged. Volvo Construction Equipment is acknowledged for giving me the opportunity to devote time to this

work.Professor S?ren Andersson is gratefully acknowledged for excellent guidance and encouragement.I also wish to express my appreciation to my colleagues at the Department of Machine Design, and especially to Dr. Ulf Sellgren for performing simulations and contributing to the writing of Paper D, and Dr. Stefan Bj?rklund for performing surface finish measurements.The contributions to Paper C by Dr. Mikael P?rssinen are highly appreciated. All contributionsto this work by colleagues at Volvo are gratefully appreciated.

1 INTRODUCTION

1.1 Background

Noise is increasingly considered an environmental issue. This belief is reflected in demands for lower noise levels in many areas of society, including the working environment. Employees spend a lot of time in this environment and noise can lead not only to hearing impairment but also to decreased ability to concentrate, resulting in decreased productivity and an increased risk of accidents. Quality, too, has become increasingly important. The quality of a product can be defined as its ability to fulfill customers’ demands. These demands often change over time, and the best competitors in the market will set the standard.Noise concerns are also expressed in relation to construction machinery such as wheel loaders and articulated haulers. The gearbox is sometimes the dominant source of noise in these machines.Even if the gear noise is not the loudest source, its pure high frequency tone is easily distinguished from other noise sources and is often perceived as unpleasant. The noise creates an impression of poor quality. In order not to be heard, gear noise must be at least 15 dB lower than other noise sources, such as engine noise.

1.2 Gear noise

This dissertation deals with the kind of gearbox noise that is generated by gears under load.This noise is often referred to as “gear whine” and consists mainly of pure tones at high frequencies corresponding to the gear mesh frequency and multiples thereof, which are known as harmonics. A tone with the same frequency as the gear

mesh frequency is designated the gear mesh harmonic, a tone with a frequency twice the gear mesh frequency is designated the second harmonic, and so on. The term “gear mesh harmonics” re fers to all multiples of the gear mesh

frequency.Transmission error (TE) is considered an important excitation mechanism for gear whine. Welbourn [1] defines transmission error as “the difference between the actual position of the output gear and the position it would occupy if the gear drive were perfectly conjugate.” Transmission error may be expressed as angular displacement or as linear displacement at the pitch point. Transmission error is caused by deflections, geometric errors, and geometric modifications.In addition to gear whine, other possible noise-generating mechanisms in gearboxes include gear rattle from gears running against each other without load, and noise generated by bearings.In the case of automatic gearboxes, noise can also be generated by internal oil pumps and by clutches. None of these mechanisms are dealt with in this work, and from now on “gear noise” or “gearbox noise” refers to “gear whine”. MackAldener [2] describes the noise generation process from a gearbox as consisting of three parts: excitation, transmission, and radiation. The origin of the noise is the gear mesh, in which vibrations are created (excitation), mainly due to transmission error. The vibrations are transmitted via the gears, shafts, and bearings to the housing (transmission). The housing vibrates, creating pressure variations in the surrounding air that are perceived as noise (radiation).Gear noise can be affected by changing any one of these three mechanisms. This dissertation deals mainly with excitation, but transmission is also discussed in the section of the literature survey concerning dynamic models, and in the modal analysis of the test gearbox in Paper B. Transmission of vibrations is also investigated in Paper D, which deals with the influence of bearing endplay or preload on gearbox noise. Differences in bearing preload influence a bearing’s dynamic properties like stiffness and damping. These properties also affect the vibration of the gearbox housing.

1.3 Objective

The objective of this dissertation is to contribute to knowledge about gearbox

noise. The following specific areas will be the focus of this study:

1. The influence of gear finishing method and gear modifications and errors on noise and vibration from a gearbox.

2. The correlation between gear deviations, predicted transmission error, measured transmission error, and gearbox noise.

3. The influence of bearing preload on gearbox noise.

4. Optimization of gear geometry for low transmission error, taking into consideration robustness with respect to torque and manufacturing tolerances.

2 AN INDUSTRIAL APPLICATION ? TRANSMISSION NOISE REDUCTION

2.1 Introduction

This section briefly describes the activities involved in reducing gear noise from a wheel loader transmission. The aim is to show how the optimization of the gear geometry described in Paper E is used in an industrial application. The author was project manager for the “noise work team” and performed the gear optimization.

One of the requirements when developing a new automatic power transmission for a wheel loader was improving the transmission gear noise. The existing power transmission was known to be noisy. When driving at high speed in fourth gear, a high frequency gear-whine could be heard. Thus there were now demands for improved sound quality. The transmission is a typical wheel loader power transmission, consisting of a torque converter, a gearbox with four forward speeds and four reverse speeds, and a dropbox partly integrated with the gearbox.The dropbox is a chain of four gears transferring the powerto the output shaft. The gears are engaged by wet multi-disc clutches actuated by the transmission hydraulic and control system.

2.2 Gear noise target for the new transmission

Experience has shown that the high frequency gear noise should be at least 15 dB below other noise sources such as the engine in order not to be perceived as disturbing

or unpleasant.Measurements showed that if the gear noise could be decreased by 10 dB, this criterion should be satisfied with some margin. Frequency analysis of the noise measured in the driver's cab showed that the dominant noise from the transmission originated from the dropbox gears. The goal for transmission noise was thus formulated as follows: “The gear noise (sound pressure level) from the dropbox gears in the transmission should be decreased by 10 dB compared to the existing transmission in order not to be perceived as unpleasant. It was assumed that it would be necessary to make changes to both the gears and the transmission housing in order to decrease the gear noise sound pressure level by 10 dB.

2.3 Noise and vibration measurements

In order to establish a reference for the new transmission, noise and vibration were measured for the existing transmission. The transmission is driven by the same type of diesel engine used in a wheel loader. The engine and transmission are attached to the stand using the same rubber mounts that are used in a wheel loader in order to make the installation as similar as possible to the installation in a wheel loader. The output shaft is braked using an electrical brake.

2.4 Optimization of gears

Noise-optimized dropbox gears were designed by choosing macro- and microgeometries giving lower transmission error than the original (reference) gears. The gear geometry was chosen to yield a low transmission error for the relevant torque range, while also taking into consideration variations in the microgeometry due to manufacturing tolerances. The optimization of one gear pair is described in more detail in Paper E.Transmission error is considered an important excitation mechanism for gear whine. Welbourn [1] defines it as “the difference between the actual position of the output gear and the position it would occupy if the gear drive were perfectly conjugate.” In this project the aim was to reduce the maximum predicted transmission error amplitude at gear mesh frequency (first harmonic of gear mesh frequency) to less than 50% of the value for the reference gear pair. The first harmonic of

transmission error is the amplitude of the part of the total transmission error that varies with a frequency equal to the gear mesh frequency. A torque range of 100 to 500 Nm was chosen because this is the torque interval in which the gear pair generates noise in its design application. According to Welbourn [1], a 50% reduction in transmission error can be expected to reduce gearbox noise by 6 dB (sound pressure level, SPL). Transmission error was calculated using the LDP software (Load Distribution Program) developed at the Gear Laboratory at Ohio State University [3].The “optimization” was not strictly mathematical. The design was optimized by calculating the transmission error for different geometries, and then choosing a geometry that seemed to be a good compromise, considering not only the transmission error, but also factors such asstrength, losses, weight, cost, axial forces on bearings, and manufacturing.

When choosing microgeometric modifications and tolerances, it is important to take manufacturing options and cost into consideration. The goal was to use the same finishing method for the optimized gears as for the reference gears, namely grinding using a KAPP VAS 531 and CBN-coated grinding wheels.For a specific torque and gear macrogeometry, it is possible to define a gear microgeometry that minimizes transmission error. For example, at no load, if there are no pitch errors and no other geometrical deviations, the shape of the gear teeth should be true involute, without modifications like tip relief or involute crowning. For a specific torque, the geometry of the gear should be designed in such a way that it compensates for the differences in deflection related to stiffness variations in the gear mesh. However, even if it is possible to define the optimal gear microgeometry, it may not be possible to manufacture it, given the limitations of gear machining. Consideration must also be given to how to specify the gear geometry in drawings and how to measure the gear in an inspection machine. In many applications there is also a torque range over which the transmission error should be minimized. Given that manufacturing tolerances are inevitable, and that a demand for smaller tolerances leads to higher manufacturing costs, it is important that gears be robust. In other words, the important characteristics, in this case transmission error, must not vary much when the torque is varied or when

the microgeometry of the gear teeth varies due to manufacturing tolerances.LDP [3] was used to calculate the transmission error for the reference and optimized gear pair at different torque levels. The robustness function in LDP was used to analyze the sensitivity to deviations due to manufacturing tolerances. The “min, max, level” method involves assigning three levels to each parameter.

2.5 Optimization of transmission housing

Finite element analysis was used to optimize the transmission housing. The optimization was not performed in a strictly mathematical way, but was done by calculating the vibration of the housing for different geometries and then choosing a geometry that seemed to be a good compromise.Vibration was not the sole consideration, also weight, cost, available space, and casting were considered. A simplified shell element model was used for the optimization to decrease computational time. This model was checked against a more detailed solid element model of the housing to ensure that the simplification had not changed the dynamic properties too much. Experimental modal analysis was also used to find the natural frequencies of the real transmission housing and to ensure that the model did not deviate too much from the real housing.Gears shafts and bearings were modeled as point masses and beams. The model was excited at the bearing positions by applying forces in the frequency range from 1000 to 3000 Hz. The force amplitude was chosen as 10% of the static load from the gears. This choice could be justified because only relative differences are of interest, not absolute values. The finite element analysis was performed by Torbj?rn Johansen at Volvo Technology. The author’s contribution was the evaluation of the results of different housing geometries.A number of measuring points were chosen in areas with high vibration velocities. At each measuring point the vibration response due to the excitation was evaluated as a power spectral density (PSD) graph. The goal of the housing redesign was to decrease the vibrations at all measuring points in the frequency range 1000 to 3000 Hz.

2.6 Results of the noise measurements

The noise and vibration measurements described in section 2.3 were performed after optimizing the gears and transmission housing.The total sound power level decreased by 4 dB.

2.7 Discussion and conclusions

It seems to be possible to decrease the gear noise from a transmission by decreasing the static loaded transmission error and/or optimizing the housing. In the present study, it is impossible to say how much of the decrease is due to the gear optimization and how much to the housing optimization. Answering this question would have required at least one more noise measurement, but time and cost issues precluded this. It would also have been interesting to perform the noise measurements on a number of transmissions, both before and after optimizing the gears and housing, in order to determine the scatter of the noise of the transmissions. Even though the goal of decreasing the gear noise by 10 dB was not reached, the goal of reducing the gear noise in the wheel loader cab to 15 dB below the overall noise was achieved. Thus the noise optimization was successful.

3 SUMMARY OF APPENDED PAPERS

3.1 Paper A: Gear Noise and Vibration – A Literature Survey

This paper presents an overview of the literature on gear noise and vibration. It is divided into three sections dealing with transmission error, dynamic models, and noise and vibration measurement. Transmission error is an important excitation mechanism for gear noise and vibration. It is defined as “the difference between the actual position of the output gear and the position it would occupy if the gear drive were perfectly conjugate” [1]. The literature survey revealed that while most authors agree that transmission error is an important excitation mechanism for gear noise and vibration, it is not the only one. Other possible time-varying noise excitation mechanisms include friction and bending moment. Noise produced by these mechanisms may be of the same order of magnitude as that produced by transmission

error, at least in the case of gears with low transmission error [4]. The second section of the paper deals with dynamic modeling of gearboxes. Dynamic models are often used to predict gear-induced vibrations and investigate the effect of changes to the gears, shafts, bearings, and housing. The literature survey revealed that dynamic models of a system consisting of gears, shafts, bearings, and gearbox casing can be useful in understanding and predicting the dynamic behavior of a gearbox. For relatively simple gear systems, lumped parameter dynamic models with springs, masses, and viscous damping can be used. For more complex models that include such elements as the gearbox housing, finite element modeling is often used. The third section of the paper deals with noise and vibration measurement and signal analysis, which are used when experimentally investigating gear noise. The survey shows that these are useful tools in experimental investigation of gear noise because gears create noise at specific frequencies related to the number of teeth and the rotational speed of the gear.

3.2 Paper B: Gear Test Rig for Noise and Vibration Testing of Cylindrical Gears

Paper B describes a test rig for noise testing of gears. The rig is of the recirculating power type and consists of two identical gearboxes, connected to each other with two universal joint shafts. Torque is applied by tilting one of the gearboxes around one of its axles. This tilting is made possible by bearings between the gearbox and the supporting brackets. A hydraulic cylinder creates the tilting force.

Finite element analysis was used to predict the natural frequencies and mode shapes for individual components and for the complete gearbox. Experimental modal analysis was carried out on the gearbox housing, and the results showed that the FE predictions agree with the measured frequencies (error less than 10%). The FE model of the complete gearbox was also used in a harmonic response analysis. A sinusoidal force was applied in the gear mesh and the corresponding vibration amplitude at a point on the gearbox housing was predicted.

3.3 Paper C: A Study of Gear Noise and Vibration

Paper C reports on an experimental investigation of the influence of gear finishing methods and gear deviations on gearbox noise and vibration. Test gears were manufactured using three different finishing methods and with different gear tooth modifications and deviations. Table3.3.1 gives an overview of the test gear pairs. The surface finishes and geometries of the gear tooth flanks were measured. Transmission error was measured using a single flank gear tester. LDP software from Ohio State University was used for transmission error computations. The test rig described in Paper B was used to measure gearbox noise and vibration for the different test gear pairs. The measurements showed that disassembly and reassembly of the gearbox with the same gear pair might change the levels of measured noise and vibration. The rebuild variation was sometimes of the same order of magnitude as the differences between different tested gear pairs, indicating that other factors besides the gears affect gear noise. In a study of the influence of gear design on noise, Oswald et al. [5] reported rebuild variations of the same order of magnitude.

Different gear finishing methods produce different surface finishes and structures, as well as different geometries and deviations of the gear tooth flanks, all of which influence the transmission error and thus the noise level from a gearbox. Most of the experimental results can be explained in terms of measured and computed transmission error. The relationship between predicted peak-to-peak transmission error and measured noise at a torque level of 500 Nm is shown in Figure 3.3.1. There appears to be a strong correlation between computed transmission error and noise for all cases except gear pair K. However, this correlation breaks down in Figure 3.3.2, which shows the relationship between predicted peak to peak transmission error and measured noise at a torque level of 140 Nm. The final conclusion is that it may not be possible to identify a single parameter, such as peak-to-peak transmission error, that can be directly related to measured noise and vibration.

3.4 Paper D: Gearbox Noise and Vibration ?Influence of Bearing

Preload

The influence of bearing endplay or preload on gearbox noise and vibrations is investigated in Paper D. Measurements were carried out on a test gearbox consisting of a helical gear pair, shafts, tapered roller bearings, and a housing. Vibration measurements were carried out at torque levels of 140 Nm and 400 Nm with 0.15 mm and 0 mm bearing endplay and with 0.15 mm bearing preload. The results shows that the bearing endplay or preload influence gearbox vibrations. Compared with bearings with endplay, preloaded bearings show an increase in vibrations at speeds over 2000 rpm and a decrease at speeds below 2000 rpm. Figure 3.4.1 is a typical result showing the influence of bearing preload on gearbox housing vibration. After the first measurement, the gearbox was not disassembled or removed from the test rig. Only the bearing preload/endplay was changed from 0 mm endplay/preload to 0.15 mm preload. Therefore the differences between the two measurements are solely due to different bearing preload. FE simulations performed by Sellgren and ?kerblom [6] show the same trend as the measurements here. For the test gearbox, it seems that bearing preload, compared with endplay, decreased the vibrations at speeds below 2000 rpm and increased vibrations at speeds over 2000 rpm, at least at a torque level of 140 Nm.

3.5 Paper E: Gear Geometry for Reduced and Robust Transmission Error and Gearbox Noise

In Paper E, gearbox noise is reduced by optimization of gear geometry for decreased transmission error. The optimization was not performed strictly mathematically. It was done by calculating the transmission error for different geometries and then choosing a geometry that seemed to be a good compromise considering not only the transmission error, but also other important characteristics. Robustness with respect to gear deviations and varying torque was considered in order to find gear geometry with low transmission error in the appropriate torque range despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error as well as noise and housing vibrations were

measured. The correlation between dynamic transmission error, housing vibrations, and noise was investigated in a speed sweep from 500 to 2500 rpm at constant torque. No correlation was found between dynamic transmission error and noise.

4 DISCUSSION AND CONCLUSIONS

Static loaded transmission error seems to be strongly correlated to gearbox noise. Dynamic transmission error does not seem to be correlated to gearbox noise in speed sweeps in these investigations. Henriksson [7] found a correlation between dynamic transmission error and gearbox noise when testing a truck gearbox at constant speed and different torque levels. The different test conditions, speed sweep versus constant speed, and the different complexity (a simple test gearbox versus a complete truck gearbox) may explain the different results regarding correlation between dynamic transmission error and gearbox noise. Bearing preload influences gearbox noise, but it is not possible to make any general statement as to whether preload is better than endplay. The answer depends on the frequency and other components in the complex dynamic system of gears, shafts, bearings, and housing. To minimize noise, the gearbox housing should be as rigid as possible. This was proposed by Rook [8], and his views are supported by the results relating to the optimization of a transmission housing described in section 2.5. Finite element analysis is a useful tool for optimizing gearbox housings.

5 FUTURE RESEARCH

It would be interesting to investigate the correlation between dynamic transmission error and gearbox noise for a complete wheel loader transmission. One challenge would be to measure transmission error as close as possible to the gears and to avoid resonances in the connection between gear and encoder. The dropbox gears in a typical wheel loader transmission are probably the gears that are most easily accessible for measurement using optical encoders. See Figure 5.1.1 for possible encoder positions.

Modeling the transmission in more detail could be another challenge for future

work. One approach could be to use a model of gears, shafts, and bearings using the transmission error as the excitation. This could be a finite element model or a multibody system model. The output from this model would be the forces at the bearing positions. The forces could be used to excite a finite element model of the housing. The housing model could be used to predict noise radiation, and/or vibration at the attachment points for the gearbox. This approach would give absolute values, not just relative levels.

REFERENCES

[1] Welbourn D. B., “Fundamental Knowledge of Gear Noise ? A Survey”, Proc. Noise & Vib. of Eng. and Trans., I Mech E., Cranfield, UK, July 1979, pp 9–14.

[2] MackAldener M., “Tooth Interior Fatigue Fracture & Robustness of Gears”, Royal Institute of Technology, Doctoral Thesis, ISSN 1400-1179, Stockholm, 2001.

[3] Ohio State University, LDP Load Distribution Program, Version 2.2.0,

https://www.wendangku.net/doc/3e11133931.html,/ , 2007.

[4] Borner J., and Houser D. R., “Friction and Bending Moments as Gear Noise Excitations”,SAE Technical Paper 961816.

[5] Oswald F. B. et al., “Influence of Gear Design on Gearbox Radiated Noise”, Gear Technology, pp 10–15, 1998.

[6] Sellgren U., and ?kerblom M., “A Mode l-Based Design Study of Gearbox Induced Noise”, International Design Conference – Design 2004, May 18-21, Dubrovnik, 2004.

[7] Henriksso n M., “Analysis of Dynamic Tran smission Error and Noise from a Two-stage Gearbox”, Licentiate Thesis, TRITA-AVE-2005:34 / ISSN-1651-7660, Stockholm, 2005.

[8] Rook T., “Vibratory Power Flow Through Joints and Bearings with Application to Structural Element s and Gearboxes”, Doctoral Thesis, Ohio State University, 1995.

变速箱噪声

相关的传输错误和轴承预压的影响

摘要

论文描述了该试验台是专门设计和建造噪音齿轮测试。有限元分析，用于预测试验台的动态特性和实验的变速箱壳体模态分析用于验证自然试验台。这第三个文件，齿轮精加工方法和变速箱齿轮的偏差影响的理论预测噪声主要是研究在什么的实验研究。十对被测试设备制造使用三种不同的整理方法。传输错误，这被认为是一个重要的激励机制齿轮噪音，测量以及预测。该试验台是用于测量变速箱噪音及不同的测试装置对振动。测得的噪音和振动水平进行比较，预测和实测的传输错误。实验结果大多可以解释和预测传输测量误差项。但是，它似乎并不能够确定一个单一的参数，如测得的峰- 峰值传输错误，可直接与测得的噪声和振动。测量结果还显示，拆卸和使用相同的变速箱齿轮副重组可以改变测得噪声和振动.这个水平发现表明，除了其他因素的影响齿轮齿轮噪音。第四，轴承影响或变速箱噪音和振动预紧力进行了调查。振动测量均在140牛米和400nm 的扭矩水平，用0.15毫米和0毫米轴承间隙，并用0.15 mm轴承预紧力。结果表明，轴承间隙和预紧力影响变速箱的振动。预装轴承，振动增加超过2000转和2000转的速度低于下降速度，相比与轴端间隙轴承。有限元模拟表现出同样的倾向作为测量值。第五本文介绍如何通过优化变速箱噪声为减少传输错误齿轮几何减少。关于齿轮偏差和不同扭矩的鲁棒性考虑，以便找到一个齿轮几何给予尽管从名义几何由于制造公差偏差范围内以适当的扭矩，噪音低。静态和动态的传输错误，噪声，振动测量和该。之间的动态传输错误，房屋振动和噪声的相关性研究了扫描速度从500到2500在恒转矩转速。没有相关关系的动态传递误差和噪声。静态加载的传输错误似乎与齿轮副的能力，激发动力系统中的齿轮箱振动相关。

关键词：齿轮，变速箱，噪声，振动，传输错误，轴承预紧力。

1 引言

1.1背景

噪音是越来越认为是环境问题。这种信念体现在许多领域中的社会，包括工作环境，降低噪音水平的要求。在这种环境下员工花了很多时间和噪声不仅会导致听力损伤，而且要集中能力下降，生产力下降和事故造成的风险增加。质量也变得越来越重要。一个产品的质量可以被定义为有能力满足客户的需求。这些要求往往随时间而改变，而在市场上最好的竞争对手将设置标准。噪音问题也涉及到工程机械的轮式装载机和铰接式这样表示。变速箱是有时在这些机械中。甚至噪音的主要来源，如果齿轮噪音并不是最响亮的来源，它的纯高频音很容易区别于其他噪声源，通常为不愉快的感觉。噪音创建了一个质量差的印象。为了不被听到，齿轮噪声必须至少15分贝外，其他噪声源，例如发动机噪音低

1.2齿轮噪音

随着变速箱噪声是一种由下负载。这种噪音齿轮生成此论文交易是通常被称为“齿轮哀鸣”，并包括在高频率所对应的齿轮啮合频率和倍数，这是已知的纯色调为主为谐波。一个与齿轮啮合频率相同的频率音调被指定为谐波齿轮啮合，一个频率音调的两倍齿轮啮合频率被指定为二次谐波，依此类推。术语“谐波齿轮啮合”指的是齿轮啮合频率。变速箱错误（TE）的倍数被认为是重要的激励机制齿轮哀鸣。Welbourn [1]定义为“之间的输出齿轮的实际位置和地位，将占据如果齿轮传动是完美结合的差异。”传输错误传输错误可能表现为角位移或在球场上点线位移。传输错误是由变形，几何误差和几何变动。除了齿轮嗲引起的，其他可能产生噪声的机制，包括在变速箱齿轮嘎嘎从对对方的情况下运行负荷齿轮，噪音轴承的情况下产生的自动变速箱，噪音也可以由内部生成的油泵和离合器。这些机制没有得到处理，在此工作，并从“齿轮噪音”或“齿轮箱噪音”现在是指“齿轮哀鸣”。奥尔登描述了从以三部分组成的变速箱噪音的产生过程：激发，传播和辐射。噪声的来源是齿轮啮合，其中振动产生（激励），主要是由

于传输错误。的振动传输通过齿轮，轴和轴承的该（传输）。该震动，创造了周围的空气都作为噪声（辐射）感知压力的变化。齿轮噪音可以通过改变任何这三种机制之一的影响。本论文主要涉及激励，但传输也是在文献关于动态模型统计调查组讨论，并在文件中B.振动模态分析传输测试变速箱也是，这与交易调查影响轴承的轴端间隙或变速箱噪音预紧力。轴承预紧力影响的差异像轴承刚度和阻尼的动态特性。这些属性也影响了变速箱外壳的振动。

1.3目标

本论文的目的是帮助有关变速箱噪声的知识。以下具体领域将是本研究的重点：

1.齿轮的加工方法和齿轮噪音和修改，并从变速箱振动误差的影响。

2.齿轮之间的偏差的相关性，预测传输错误，传输测量误差和变速箱噪音。

3.对变速箱的噪声影响轴承预紧力。

4.齿轮低传输错误几何优化，同时考虑到稳健性方面的扭矩和制造公差。

2 工业应用 - 传输降噪

2.1简介

本节简要介绍了减少从轮式装载机传动齿轮噪音所涉及的活动。其目的是展示如何在文件中所述的齿轮结构优化在工业应用。作者是项目经理“噪音工作队”，并进行了齿轮的优化。在发展的要求为轮式装载机新的自动输电之一就是提高传动齿轮的噪音。现有的电力传输被称为是嘈杂。当在四档高速驾驶，高频齿轮嗲可闻。因此，现在有改善音质的要求。传输是一种典型的轮式装载机动力传输，扭矩转换器，带有四个前进速度和四速变速箱扭转，部分与变速箱。升降梭箱升降梭箱是一个集成了四个转移功率到输出轴齿轮链组成。所从事的齿轮由湿式多盘由液压传动和控制系统驱动离合器。此液压系统油是由内部提供的石油由输入轴驱动泵。

2.2齿轮传动噪声的新目标

经验表明，高频齿轮噪音至少应为15分贝以下，如发动机等噪声源分贝，以免被视为干扰或不愉快的。测量值表明，如果齿轮噪音可降低10分贝，这个标准应该满足于一定的余量。频率在驾驶室测量的噪声分析表明，从传输主要的

噪音从投寄箱齿轮起源。对传输噪声的目标是这样表述为如下：“齿轮噪音在传输的升降梭箱齿轮（声压级）应10分贝下降相比，以现有的传输不被视为不愉快的感觉。”位置在投寄箱齿轮。有人认为有必要使这两个齿轮和变速器壳体的变化，以减少齿轮噪音10分贝的声压水平。

2.3噪声和振动测量

为了建立一个新的传输参考，噪音和振动测量的现有传输。传输是由相同的柴油发动机在轮式装载机的类型。发动机和变速器连接到使用相同的立场是在一个橡胶轮式装载机使用，以使安装尽可能类似的安装在轮式装载机坐骑。输出轴制动采用电气制动。

2.4优化的齿轮

噪音优化的升降梭箱齿轮的设计选择宏观和微观给予低于原（参考）齿轮传动误差。齿轮的几何形状是选择产量为相关的扭矩范围低传输错误，同时也将在微观几何形态由于制造公差考虑到变化。一对齿轮的优化是描述纸张E.传输错误被认为是重要的激励机制齿轮哀鸣在更多的细节。 Welbourn [1]定义在这个项目它的目的是减少传输的最大预测在齿轮啮合误差幅度为“之间的输出齿轮的实际位置和地位，将占据如果齿轮传动是完美结合的差异。”频率（首先是齿轮啮合频率谐波）小于50的参考价值齿轮副％。对传输错误第一谐波是总传输错误的一部分，其频率等于齿轮啮合频率变化幅度。扭矩范围

100至500牛顿米的选择，因为这是扭矩区间，其中齿轮副在其设计中的应用产生的噪音。据Welbourn [1]，在传输错误减少50％，可以预计将减少6分贝（声压级，SPL）变速箱噪音。传输错误计算自民党软件（负载分配方案）在实验室开发的齿轮在俄亥俄州立大学[3]。“优化”是没有严格的数学。该设计进行了优化，通过计算不同几何形状的传输错误，然后选择一个几何这似乎是一个很好的妥协，不仅考虑传输错误等因素，还得考虑损失，重量，成本，对轴承的轴向力和制造的影响。当选择微观几何形态修改和公差，重要的是要考虑选择和制造成本。我们的目标是要利用作为参考齿轮优化的齿轮精加工方法相同，即使用一个卡普磨VAS 531和CBN涂层磨轮。输入特定的扭矩和齿轮转速，它可以定义一个齿轮微观几何形态的最大限度地减少传输错误。例如，在无负载，如果没有错误，没有其他球场几何偏差，齿的齿轮渐开线形状应是真实的，没有像尖或渐开线救

济加冕修改。对于一个特定的扭矩，在齿轮几何设计应以这样一种方式，它在挠度与在齿轮啮合刚度变化差异进行补偿。然而，即使有可能确定最佳齿轮微观几何形态，它可能无法制造它，鉴于齿轮加工的局限性。还必须考虑如何在指定的图纸和如何衡量在验机的齿轮几何。在许多应用中也有一个以上的扭矩范围传输错误应尽量减少。由于制造公差是不可避免的，而且为更小的公差要求导致制造成本较高，这是很重要的齿轮是强大的。换句话说，重要的特征，在这种情况下传输错误，必须变化不大时，扭矩是多种多样的，或当齿轮微观几何形态变化由于制造误差。LDP [3]是用来计算的传输错误参考和不同层次优化扭矩齿轮副。在自民党的鲁棒性功能是用来分析到，由于制造公差偏差的灵敏度。而“最小，最大，水平”的方法包括三个层次分配给每个参数。

2.5优化传输该

有限元分析，用于优化传输该。优化是在不进行严格的数学方法，但通过计算不同几何形状的房屋震动，然后选择一个几何形态，这似乎是一个很好的妥协。振动不是唯一要考虑的，重量，成本，可用做空间，铸造进行了审议。一个简化的壳单元模型进行优化，以减少计算时间。这种模式是核对更详细的房屋实体单元模型，以确保简化并没有改变太多的动态特性。实验模态分析也被用来寻找真正的变速器壳体的固有频率，并确保该模型并没有偏离实际外壳。齿轮分别为轴和齿轮，梁建模轴承太多。该模型是兴奋，通过在轴承位置的频率范围内的力量，从1000到3000赫兹。这支部队的幅度被选为10从齿轮静载荷％。这种选择可能是合理的，因为只有相对差异的利益，而不是绝对值。有限元分析是由罗多约翰森沃尔沃技术。作者的贡献是选择了不同的测量点。数量评价结果分别在高振动速度的地区选择。在每个测点的振动响应，由于激励被认定为功率谱密度（PSD）的图形。房屋重新设计的目标是减少在频率范围1000至3000赫兹的所有测点的振动。

2.6噪声测量的结果

噪声和振动测量在2.3节中描述了进行优化后的齿轮和变速器壳体。

2.7讨论和结论

这似乎是可以减少通过减少静态加载的传输错误和/或优化该从传动齿轮的

噪音。在本研究中，是不可能说有很大的下降是由于齿轮的优化和多少该优化。要回答这个问题将需要至少有一个更大的噪音测量，但时间和成本问题排除这一点。它也有很有趣上执行的传输次数的噪音测量，前和优化后的齿轮和该，以确定的传输噪声分散。即使在10分贝降低齿轮噪音的目的没有达到，减少在轮式装载机驾驶室齿轮噪音低于15分贝噪音的总体目标是实现。因此，噪音优化成功。

3 追加论文摘要

3.1 齿轮噪音和振动

本文介绍了对齿轮噪音和振动的文献概述。它分为三段处理传输错误，动态模型，以及噪声和振动测量。传输错误是一个齿轮噪音和振动的重要激励机制。这是定义为“之间的输出齿轮的实际地位和它的位置差异如果将占据了绝对的齿轮传动共轭“[1]。文献调查显示：虽然大多数作者同意，传输错误是一个重要的激励机制齿轮噪音和振动，它不是唯一的一个。其他可能随时间变化的噪声激励机制包括摩擦和弯矩。这些机制可能产生的噪音是同一数量级顺序产生的传输错误，至少在情况下，他与低传输错误齿轮[4]。与齿轮箱的动态建模的文件涉及第二部分。动态模型通常用来预测齿轮引起振动和调查的变动的影响齿轮，轴，轴承和该。文献调查显示，动态模型系统的齿轮，轴，轴承和齿轮箱外壳组成，可以理解有用和预测的变速箱的动态行为。对于相对简单的齿轮系统，集总参数与弹簧，贴近群众，粘性阻尼动态模型都可以使用。对于更复杂的模型，包括为变速箱壳体，有限元等元素.造型经常被使用。该文件的第三部分涉及噪音和振动测量和信号分析，这是用来实验调查时齿轮噪音。调查显示，这些都是有用的工具，齿轮噪音实验调查，因为在特定的齿轮制造噪音关系到牙齿的数量和齿轮的转速频率。

3.2齿轮噪音和振动试验台测试圆柱齿轮。

描述了噪声测试试验台的齿轮。该钻机是循环功率型和两个相同的连接有两个万向节传动轴对方变速箱，组成。扭矩是由围绕应用其倾斜轴之一的变速箱之一。这种倾斜成为可能，齿轮箱之间的支架及配套轴承。液压缸产生的倾斜力。有限元分析是用来预测自然频率和个别部件和完整的变速箱模式形状。实验模态

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木工机械专业词汇中英文对比精选版

木工机械专业词汇中英 文对比 Document serial number【KKGB-LBS98YT-BS8CB-BSUT-BST108】

一画 一字螺丝批 slot type screwdriver 一点透视 one-point perspective 二画 二合一黏合剂 epoxy resin adhesive 二合胶；混合胶 epoxy glue 二维的；平面的 two-dimensional 二进制 binary 二极管；整流子 diode 二号螺丝攻 second tap 二路开关 two-way switch 十进制的；公制的 metric 人工制品 artefact 人造板 man-made board 人体工程学 ergonomics; human engineering 人体尺寸 human dimension 人体测量学 anthropometry; anthropometrics 刀片 blade 刀身 blade 刀具 tool 刀具溜座 carriage 刀柱 tool post 刀架 tool rest 刀架底座 tool rest bracket 刀座帷；床鞍 apron 刀座鞍；溜板座 saddle 力 force 力三角形 triangle of force 力平行四边形 parallelogram of force 力多边形；多边形力学 polygon of force 力的分解 force resolution 力架；亮漆 lacquer 力矩 moment 力偶 couple 力矩定律 law of moment 力-距离图表 force-distance graph 力图 force diagram 力线 line of force 力点 effort 十字榫 cross halving joint 十字螺丝 Philip's head screw 十字螺丝批 Philip's type screwdriver 丁字尺；T 尺 tee square三画三爪夹头 three-jaw chuck 三角尺 set square 三角形结构系杆 triangulation tie 三角锉 triangular file 三维的；立体的 three-dimensional 三氯甲烷；哥罗芳 chloroform 三聚氰胺；蜜胺 melamine 三点透视 three-point perspective 上油漆 painting 上釉 enamelling 凡立水 varnish 叉形顶尖 fork centre 口罩 mask 士力；虫漆 shellac 士巴拿；扳手 spanner 大芯夹板；宽条芯夹板 blockboard; solid corestock-laminated board 大量制造 mass production 子口刨；槽口刨；边刨 rebate plane 小型平槽刨 miniature router plane 小型线料弯曲器 small wire bender 小型弯折机 mini bender 小型电路断路器；跳菲 miniature circuit breaker (MCB) 小齿轮 pinion 山樟 San Cheong 工件 workpiece 工字梁 I beam 工作面 working surface 工作图；制作图 working drawing 工作台 bench; working table 工具 tool 工具贮存室 tool storage 工具槽 well

机械专业英文翻译

启动轴starting axle 启动齿轮starting gear 启动棘轮starting ratchet wheel 复位弹簧restoring, pull back spring 弹簧座spring seating 摩擦簧friction spring 推力垫圈thrust washer 轴挡圈axle bumper ring 下料filling 切断cut 滚齿机gear-hobbing machine 剪料机material-shearing machine 车床lathe 拉床broaching machine 垂直度verticality, vertical extent 平行度 parallelism同心度 homocentricity 位置度position 拉伤pulling damage 碰伤bumping damage 缺陷deficiency 严重缺陷severe deficiency 摩擦力friction 扭距twist 滑动glide 滚动roll 打滑skid 脱不开can’t seperate 不复位can’t restore 直径diameter M值= 跨棒距test rod span 公法线common normal line 弹性elasticity 频率特性frequency characteristic 误差error 响应response 定位allocation 机床夹具jig 动力学dynamic 运动学kinematic 静力学static 分析力学analyse mechanics 拉伸pulling 压缩hitting 机床machine tool 刀具cutter 摩擦friction 联结link 传动drive/transmission 轴shaft 剪切shear 扭转twist 弯曲应力bending stress 三相交流电three-phase AC 磁路magnetic circles 变压器transformer 异步电动机asynchronous motor 几何形状geometrical 精度precision 正弦形的sinusoid 交流电路AC circuit 机械加工余量machining allowance 变形力deforming force 变形deformation 电路circuit 半导体元件semiconductor element 拉孔broaching 装配assembling 加工machining 液压hydraulic pressure 切线tangent 机电一体化mechanotronics mechanical-electrical integration 稳定性stability 介质medium 液压驱动泵fluid clutch 液压泵hydraulic pump 阀门valve 失效invalidation 强度intensity 载荷load 应力stress 安全系数safty factor 可靠性reliability 螺纹thread 螺旋helix 键spline 销pin 滚动轴承rolling bearing 滑动轴承sliding bearing 弹簧spring 制动器arrester brake 十字结联轴节crosshead 联轴器coupling 链chain 皮带strap 精加工finish machining 粗加工rough machining 变速箱体gearbox casing 腐蚀rust 氧化oxidation 磨损wear 耐用度durability 机械制图 Mechanical drawing 投影projection 视图view 剖视图profile chart 标准件standard component 零件图part drawing 装配图assembly drawing 尺寸标注size marking 技术要求 technical requirements 刚度rigidity 内力internal force 位移displacement 截面section 疲劳极限fatigue limit 断裂fracture 塑性变形plastic distortion 脆性材料brittleness material 刚度准则rigidity criterion 垫圈washer 垫片spacer 直齿圆柱齿轮 straight toothed spur gear 斜齿圆柱齿轮 helical-spur gear 直齿锥齿轮 straight bevel gear 运动简图kinematic sketch 齿轮齿条pinion and rack 蜗杆蜗轮worm and worm gear 虚约束passive constraint 曲柄crank 摇杆racker 凸轮cams 反馈feedback 发生器generator 直流电源DC electrical source 门电路gate circuit 外圆磨削external grinding 内圆磨削internal grinding 平面磨削plane grinding 变速箱gearbox 离合器clutch 绞孔fraising 绞刀reamer

Manufacturing Engineering and Technology(机械类英文文献+翻译)

Manufacturing Engineering and Technology—Machining Serope kalpakjian；Steven R.Schmid 机械工业出版社2004年3月第1版 20.9 MACHINABILITY The machinability of a material usually defined in terms of four factors: 1、Surface finish and integrity of the machined part; 2、Tool life obtained; 3、Force and power requirements; 4、Chip control. Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone. Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below. 20.9.1 Machinability Of Steels Because steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels. Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in

中英文论文对照格式

英文论文APA格式 英文论文一些格式要求与国内期刊有所不同。从学术的角度讲，它更加严谨和科学，并且方便电子系统检索和存档。 版面格式

表格 表格的题目格式与正文相同，靠左边，位于表格的上部。题目前加Table后跟数字，表示此文的第几个表格。 表格主体居中，边框粗细采用0.5磅；表格内文字采用Times New Roman，10磅。 举例： Table 1. The capitals, assets and revenue in listed banks

图表和图片 图表和图片的题目格式与正文相同，位于图表和图片的下部。题目前加Figure 后跟数字，表示此文的第几个图表。图表及题目都居中。只允许使用黑白图片和表格。 举例： Figure 1. The Trend of Economic Development 注：Figure与Table都不要缩写。 引用格式与参考文献 1. 在论文中的引用采取插入作者、年份和页数方式，如"Doe (2001, p.10) reported that …" or "This在论文中的引用采取作者和年份插入方式，如"Doe (2001, p.10) reported that …" or "This problem has been studied previously (Smith, 1958, pp.20-25)。文中插入的引用应该与文末参考文献相对应。 举例：Frankly speaking, it is just a simulating one made by the government, or a fake competition, directly speaking. (Gao, 2003, p.220). 2. 在文末参考文献中，姓前名后，姓与名之间以逗号分隔；如有两个作者，以and连接；如有三个或三个以上作者，前面的作者以逗号分隔，最后一个作者以and连接。 3. 参考文献中各项目以“点”分隔，最后以“点”结束。 4. 文末参考文献请按照以下格式：

机械类英文文献

Available online at https://www.wendangku.net/doc/3e11133931.html, Physica A334(2004)243–254 https://www.wendangku.net/doc/3e11133931.html,/locate/physa Stability and transition in multiple production lines Takashi Nagatani? Department of Mechanical Engineering,Shizuoka University,Hamamatsu432-8561,Japan Received28October2003 Abstract We present the dynamical model of the multiple production lines composed of M parallel and u series machines.We extend the single-series production line model to the multiple production lines.We study the e ect of the multiple lines on the dynamical behavior of the production process.We apply the linear stability analysis to the production process in the multiple lines. The linear stability criterion is derived for the production system with the multiple lines.It is shown that the production process in the multiple lines is more unstable than that in the single line.The phase diagram(region map)is given for the multiple production lines.The nonlinear instability and dynamical transition are investigated by using computer simulation.It is shown that the dynamical transitions occur between the stable and oscillatory productions. c 2003Elsevier B.V.All rights reserved. PACS:05.90.+m;89.90.+m;89.40.+k Keywords:Production process;Instability;Dynamical transition;Transportation;Multiple lines 1.Introduction Concepts from statistical physics and nonlinear dynamics have been very successful in discovering and explaining dynamical phenomena in transportation systems[1–5]. Many of these phenomena are based on mechanisms such as delayed adaptation to changing conditions and competition for limited resources.The delayed adaptation is relevant for production systems as well[6–10].Mathematicians,physicists,tra c sci-entists,and economists have suggested that tra c dynamics has also implications for the dynamical behavior of production process. ?Fax:+81-53-478-1048. E-mail address:tmtnaga@ipc.shizuoka.ac.jp(T.Nagatani). 0378-4371/$-see front matter c 2003Elsevier B.V.All rights reserved. doi:10.1016/j.physa.2003.11.002

印染机械中英文对照大全

一、烘燥和加湿预处理机械： 烘燥和加湿预处理机械Dry and wet pre-treatment machinery 1.1.炭化机Carbonisingmachines 1.2.烧毛机Singeringmachines 1.3.织物清洗机、打浆和除杂机Fabric cleaning machines, Beating and Dustremoval machines 1.4.煮呢机、煮布锅、沸煮设备Crabbing machines, Kiers, Boiling apparatus 1.5.退浆机Desizingmachines 1.6.分批漂白机Bleaching apparatus and machines, Batch 1.7.连续漂白机Bleaching plant, Continuous 1.8.纱线洗涤机Yarn washing machines 1.9.绳状洗涤机Rope washing machine 1.10.平幅洗涤机Open-width washing machines 1.11.溶剂洗涤机Solvent washing machines 1.1 2.缩呢机、缩绒机Milling/fulling machines 1.13.纱线丝光机Mercerizing machines for yarns 1.14.机织和针织织物丝光机Mercerizing machines for woven and knitted fabrics 二、染色机和染色设备： 染色机和染色设备Dyeing machines and apparatus 2.1.连续式丝束及毛条染色生产线Continuous dyeing lines for tows and tops 2.2.连续式纱线染色生产线Continuous dyeing lines for yarn 2.3.经纱连续染色生产线Continuous dyeing lines for warp 2.4.窄幅织物连续染色机Continuous dyeing lines for narrow fabrics 2.5.地毯织物连续染色机Continuousdyeing lines for carpets 2.6.其他织物连续染色机Continuous dyeing lines for other fabrics 2.7.地毯织物匹染机Piecedyeing machines for carpets 2.8.高温筒子纱线染色机HT dyeing apparatus for cones 2.9.高温经轴染色设备HT dyeing apparatus for beams 2.10.常压纱线染色设备Yarn dyeing apparatus, atmospheric pressure 2.11.轧染机Padding mangles 2.12.绞纱染色机Cabinet hank dyeing machines 2.1 3.常压织物染色装置Fabric dyeing apparatus, atmospheric pressure 2.14.喷射染色机Jet dyeing machines 2.15.高温溢流染色机HT overflow dyeing machines 2.16.常压溢流染色机Overflow dyeing machines, atmosphericpressure

机械工程专业英语 翻译

2、应力和应变 在任何工程结构中独立的部件或构件将承受来自于部件的使用状况或工作的外部环境的外力作用。如果组件就处于平衡状态,由此而来的各种外力将会为零,但尽管如此,它们共同作用部件的载荷易于使部件变形同时在材料里面产生相应的内力。 有很多不同负载可以应用于构件的方式。负荷根据相应时间的不同可分为: (a)静态负荷是一种在相对较短的时间内逐步达到平衡的应用载荷。 (b)持续负载是一种在很长一段时间为一个常数的载荷, 例如结构的重量。这种类型的载荷以相同的方式作为一个静态负荷; 然而,对一些材料与温度和压力的条件下,短时间的载荷和长时间的载荷抵抗失效的能力可能是不同的。 (c)冲击载荷是一种快速载荷(一种能量载荷)。振动通常导致一个冲击载荷, 一般平衡是不能建立的直到通过自然的阻尼力的作用使振动停止的时候。 (d)重复载荷是一种被应用和去除千万次的载荷。 (e)疲劳载荷或交变载荷是一种大小和设计随时间不断变化的载荷。 上面已经提到，作用于物体的外力与在材料里面产生的相应内力平衡。因此,如果一个杆受到一个均匀的拉伸和压缩，也就是说, 一个力,均匀分布于一截面,那么产生的内力也均匀分布并且可以说杆是受到一个均匀的正常应力,应力被定义为 应力==负载 P /压力 A, 因此根据载荷的性质应力是可以压缩或拉伸的,并被度量为牛顿每平方米或它的倍数。 如果一个杆受到轴向载荷，即是应力，那么杆的长度会改变。如果杆的初始长度L和改变量△L已知，产生的应力定义如下: 应力==改变长△L /初始长 L 因此应力是一个测量材料变形和无量纲的物理量 ,即它没有单位;它只是两个相同单位的物理量的比值。 一般来说,在实践中,在荷载作用下材料的延伸是非常小的, 测量的应力以*10-6的形式是方便的, 即微应变, 使用的符号也相应成为ue。 从某种意义上说，拉伸应力与应变被认为是正的。压缩应力与应变被认为是负的。因此负应力使长度减小。 当负载移除时，如果材料回复到初始的，无负载时的尺寸时，我们就说它是具有弹性的。一特定形式的适用于大范围的工程材料至少工程材料受载荷的大部分的弹性, 产生正比于负载的变形。由于载荷正比于载荷所产生的压力并且变形正比于应变, 这也说明,当材料是弹性的时候, 应力与应变成正比。因此胡克定律陈述, 应力正比于应变。 这定律服从于大部分铁合金在特定的范围内, 甚至以其合理的准确性可以假定适用于其他工程材料比如混凝土，木材，非铁合金。 当一个材料是弹性的时候，当载荷消除之后，任何负载所产生的变形可以完全恢复,没有永久的变形。

(完整word版)机械专业英语文章中英文对照

英语原文 NUMERICAL CONTROL Numerical control(N/C)is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols, The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular work part or job. When the job changes, the program of instructions is changed. The capability to change the program is what makes N/C suitable for low-and medium-volume production. It is much easier to write programs than to make major alterations of the processing equipment. There are two basic types of numerically controlled machine tools：point—to—point and continuous—path(also called contouring).Point—to—point machines use unsynchronized motors, with the result that the position of the machining head Can be assured only upon completion of a movement, or while only one motor is running. Machines of this type are principally used for straight—line cuts or for drilling or boring. The N/C system consists of the following components：data input, the tape reader with the control unit, feedback devices, and the metal—cutting machine tool or other type of N/C equipment. Data input, also called “man—to—control link”,may be provided to the machine tool manually, or entirely by automatic means. Manual methods when used as the sole source of input data are restricted to a relatively small number of inputs. Examples of manually operated devices are keyboard dials, pushbuttons, switches, or thumbwheel selectors. These are located on a console near the machine. Dials ale analog devices usually connected to a syn-chro-type resolver or potentiometer. In most cases, pushbuttons, switches, and other similar types of selectors are digital input devices. Manual input requires that the operator set the controls for each operation. It is a slow and tedious process and is seldom justified except in elementary machining applications or in special cases. In practically all cases, information is automatically supplied to the control unit and the machine tool by cards, punched tapes, or by magnetic tape. Eight—channel punched paper tape is the most commonly used form of data input for conventional N/C systems. The coded instructions on the tape consist of sections of punched holes called blocks. Each block represents a machine function, a machining operation, or a combination of the two. The entire N/C program on a tape is made up of an accumulation of these successive data blocks. Programs resulting in long tapes all wound on reels like motion-picture film. Programs on relatively short tapes may be continuously repeated by joining the two ends of the tape to form a loop. Once installed, the tape is used again and again without further handling. In this case, the operator simply loads and