机械设计外文翻译---机器和机器零件的设计

Design of machine and machine elements

Machine design

Machine design is the art of planning or devising new or improved machines to accomplish specific purposes. In general, a machine will consist of a combination of several different mechanical elements properly designed and arranged to work together, as a whole. During the initial planning of a machine, fundamental decisions must be made concerning loading, type of kinematic elements to be used, and correct utilization of the properties of engineering materials. Economic considerations are usually of prime importance when the design of new machinery is undertaken. In general, the lowest over-all costs are designed. Consideration should be given not only to the cost of design, manufacture the necessary safety features and be of pleasing external appearance. The objective is to produce a machine which is not only sufficiently rugged to function properly for a reasonable life, but is at the same time cheap enough to be economically feasible.

The engineer in charge of the design of a machine should not only have adequate technical training, but must be a man of sound judgment and wide experience, qualities which are usually acquired only after considerable time has been spent in actual professional work.

Design of machine elements

The principles of design are, of course, universal. The same theory or equations may be applied to a very small part, as in an instrument, or, to a larger but similar part used in a piece of heavy equipment. In no ease, however, should mathematical calculations be looked upon as absolute and final. They are all subject to the accuracy of the various assumptions, which must necessarily be made in engineering work. Sometimes only a portion of the total number of parts in a machine are designed on the basis of analytic calculations. The form and size of the remaining parts are designed on the basis of analytic calculations. On the other hand, if the machine is very expensive, or if weight is a factor, as in airplanes, design computations may then be made for almost all the parts.

The purpose of the design calculations is, of course, to attempt to predict the stress or deformation in the part in order that it may sagely carry the loads, which will be imposed on it, and that it may last for the expected life of the machine. All calculations are, of course, dependent on the physical properties of the construction materials as determined by laboratory tests. A rational method of design attempts to take the results of relatively simple and fundamental tests such as tension, compression, torsion, and fatigue and apply them to all the complicated and involved situations encountered in present-day machinery.

In addition, it has been amply proved that such details as surface condition, fillets, notches, manufacturing tolerances, and heat treatment have a market effect on the strength and useful life of a machine part. The design and drafting departments must specify completely all such particulars, must specify completely all such particulars, and thus exercise the necessary close control over the finished product.

As mentioned above, machine design is a vast field of engineering technology. As such, it begins with the conception of an idea and follows through the various phases of design analysis, manufacturing, marketing and consumerism. The following is a list of the major areas of consideration in the general field of machine design:

①Initial design conception;

②Strength analysis;

③Materials selection;

④Appearance;

⑤Manufacturing;

⑥Safety;

⑦Environment effects;

⑨Reliability and life;

Strength is a measure of the ability to resist, without fails, forces which cause stresses and strains. The forces may be;

①Gradually applied;

②Suddenly applied;

③Applied under impact;

④Applied with continuous direction reversals;

⑤Applied at low or elevated temperatures.

If a critical part of a machine fails, the whole machine must be shut down until a repair is made. Thus, when designing a new machine, it is extremely important that critical parts be made strong enough to prevent failure. The designer should determine as precisely as possible the nature, magnitude, direction and point of application of all forces. Machine design is mot, however, an exact science and it is, therefore, rarely possible to determine exactly all the applied forces. In addition, different samples of a specified material will exhibit somewhat different abilities to resist loads, temperatures and other environment conditions. In spite of this, design calculations based on appropriate assumptions are invaluable in the proper design of machine.

Moreover, it is absolutely essential that a design engineer knows how and why parts fail so that reliable machines which require minimum maintenance can be designed. Sometimes, a failure can be serious, such as when a tire blows out on an automobile traveling at high speeds. On the other hand, a failure may be no more than a nuisance. An example is the loosening of the radiator hose in the automobile cooling system. The consequence of this latter failure is usually the loss of some radiator coolant, a condition which is readily detected and corrected.

The type of load a part absorbs is just as significant as the magnitude. Generally speaking, dynamic loads with direction reversals cause greater difficulties than static loads and, therefore, fatigue strength must be considered. Another concern is whether the material is ductile or brittle. For example, brittle materials are considered to be unacceptable where fatigue is involved.

In general, the design engineer must consider all possible modes of failure, which include the following:

①Stress;

②Deformation;

③Wear;

④Corrosion;

⑤Vibration;

⑥Environmental damage;

⑦Loosening of fastening devices.

The part sizes and shapes selected must also take into account many dimensional factors which produce external load effects such as geometric discontinuities, residual stresses due to forming of desired contours, and the application of interference fit joint.

Selected from” design of machine elements”, 6th edition, m. f. sports, prentice-hall, inc., 1985 and “machine design”, Anthony Esposito, charles e., Merrill publishing company, 1975.

Mechanical properties of materials

The material properties can be classified into three major headings: (1) physical, (2) chemical, (3) mechanical

Physical properties

Density or specific gravity, moisture content, etc., can be classified under this category.

Chemical properties

Many chemical properties come under this category. These include acidity or alkalinity, react6ivity and corrosion. The most important of these is corrosion which can be explained in layman’s terms as the resistance of the material to decay while in continuous use in a particular atmosphere.

Mechanical properties

Mechanical properties include in the strength properties like tensile, compression, shear, torsion, impact, fatigue and creep. The tensile strength of a material is obtained by dividing the maximum load, which the specimen bears by the area of cross-section of the specimen.

This is a curve plotted between the stress along the This is a curve plotted between the stress along the Y-axis(ordinate) and the strain along the X-axis

(abscissa) in a tensile test. A material tends to change or changes its dimensions when it is loaded, depending upon the magnitude of the load. When the load is removed it can be seen that the deformation disappears. For many materials this occurs op to a certain value of the stress called the elastic limit Ap. This is depicted by the straight line relationship and a small deviation thereafter, in the stress-strain curve (fig.3.1)

. Within the elastic range, the limiting value of the stress up to which the stress and strain are proportional, is called the limit of proportionality Ap. In this region, the metal obeys hookes’s law, which states that the stress is proportional to strain in the elastic range of loading, (the material completely regains its original dimensions after the load is removed). In the actual plotting of the curve, the proportionality limit is obtained at a slightly lower value of the load than the

elastic limit. This may be attributed to the time-lagin the regaining of the original dimensions of the material. This effect is very frequently noticed in some non-ferrous metals.

Which iron and nickel exhibit clear ranges of elasticity, copper, zinc, tin, are found to be imperfectly elastic even at relatively low values low values of stresses. Actually the elastic limit is distinguishable from the proportionality limit more clearly depending upon the sensitivity of the measuring instrument.

When the load is increased beyond the elastic limit, plastic deformation starts. Simultaneously the specimen gets work-hardened. A point is reached when the deformation starts to occur more rapidly than the increasing load. This point is called they yield point Q. the metal which was resisting the load till then, starts to deform somewhat rapidly, i. e., yield. The yield stress is called yield limit Ay. The elongation of the specimen continues from Q to S and then to T. The stress-strain relation in this plastic flow period is indicated by the portion QRST of the curve. At the specimen breaks, and this load is called the breaking load. The value of the maximum load S divided by the original cross-sectional area of the specimen is referred to as the ultimate tensile strength of the metal or simply the tensile strength Au.

Logically speaking, once the elastic limit is exceeded, the metal should start to yield, and finally break, without any increase in the value of stress. But the curve records an increased stress even after the elastic limit is exceeded. Two reasons can be given for this behavior:

①The strain hardening of the material;

②The diminishing cross-sectional area of the specimen, suffered on account of the plastic deformation.

The more plastic deformation the metal undergoes, the harder it becomes, due to work-hardening. The more the metal gets elongated the more its diameter (and hence, cross-sectional area) is decreased. This continues until the point S is reached.

After S, the rate at which the reduction in area takes place, exceeds the rate at which the stress increases. Strain becomes so high that the reduction in area begins to produce a localized effect at some point. This is called necking. Reduction in cross-sectional area takes place very rapidly; so rapidly that the load value actually drops. This is indicated by ST. failure occurs at this point T. Then percentage elongation A and reduction in reduction in area W indicate the ductility or plasticity of the material:

A=(L-L0)/L0*100%

W=(A0-A)/A0*100%

Where L0 and L are the original and the final length of the specimen; A0 and A are the original and the final cross-section area.

Selected from “testing of metallic materials”

Quality assurance and control

Product quality is of paramount importance in manufacturing. If quality is allowed deteriorate, then a manufacturer will soon find sales dropping off followed by a possible business failure. Customers expect quality in the products they buy, and if a manufacturer expects to establish and maintain a name in the business, quality control and assurance functions must be established and maintained before, throughout, and after the production process. Generally speaking, quality assurance encompasses all activities aimed at maintaining quality, including quality control. Quality assurance can be divided into three major areas. These include the following:

①Source and receiving inspection before manufacturing;

②In-process quality control during manufacturing;

③Quality assurance after manufacturing.

Quality control after manufacture includes warranties and product service extended to the users of the product.

Source and receiving inspection before manufacturing

Quality assurance often begins ling before any actual manufacturing takes place. This may be done through source inspections conducted at the plants that supply materials, discrete parts, or subassemblies to manufacturer. The manufacturer’s source inspector travels to the supplier factory and inspects raw material or premanufactured parts and assemblies. Source inspections present an opportunity for the manufacturer to sort out and reject raw materials or parts before they are shipped to the manufacturer’s production facility.

The responsibility of the source inspector is to check materials and parts against design specifications and to reject the item if specifications are not met. Source inspections may include many of the same inspections that will be used

during production. Included in these are:

①Visual inspection;

②Metallurgical testing;

③Dimensional inspection;

④Destructive and nondestructive inspection;

⑤Performance inspection.

Visual inspections

Visual inspections examine a product or material for such specifications as color, texture, surface finish, or overall appearance of an assembly to determine if there are any obvious deletions of major parts or hardware.

Metallurgical testing

Metallurgical testing is often an important part of source inspection, especially

if the primary raw material for manufacturing is stock metal such as bar stock or structural materials. Metals testing can involve all the major types of inspections including visual, chemical, spectrographic, and mechanical, which include hardness, tensile, shear, compression, and spectr5ographic analysis for alloy content. Metallurgical testing can be either destructive or nondestructive. Dimensional inspection

Few areas of quality control are as important in manufactured products as dimensional requirements. Dimensions are as important in source inspection as they are in the manufacturing process. This is especially critical if the source supplies parts for an assembly. Dimensions are inspected at the source factory using standard measuring tools plus special fit, form, and function gages that may required. Meeting dimensional specifications is critical to interchangeability

of manufactured parts and to the successful assembly of many parts into complex assemblies such as autos, ships, aircraft, and other multipart products. Destructive and nondestructive inspection

In some cases it may be necessary for the source inspections to call for destructive or nondestructive tests on raw materials or p0arts and assemblies. This is particularly true when large amounts of stock raw materials are involved.

For example it may be necessary to inspect castings for flaws by radiographic, magnetic particle, or dye penetrant techniques before they are shipped to the manufacturer for final machining. Specifications calling for burn-in time for electronics or endurance run tests for mechanical components are further examples of nondestructive tests.

It is sometimes necessary to test material and parts to destruction, but because of the costs and time involved destructive testing is avoided whenever possible. Examples include pressure tests to determine if safety factors are adequate in the design. Destructive tests are probably more frequent in the testing of prototype designs than in routine inspection of raw material or parts. Once design specifications are known to be met in regard to the strength of materials, it is often not necessary to test further parts to destruction unless they are genuinely suspect.

Performance inspection

Performance inspections involve checking the function of assemblies, especially those of complex mechanical systems, prior to installation in other products. Examples include electronic equipment subcomponents, aircraft and auto engines, pumps, valves, and other mechanical systems requiring performance evaluation prior to their shipment and final installation.

Selected form “modern materials and manufacturing process”

Electro-hydraulic drum brakes

Application

The YWW series electro-hydraulic brake is a normally closed brake, suitable for horizontal mounting. It is mainly used in portal cranes, bucket stacker/reclaimers’slewing mechanism.

The YKW series electro-hydraulic brake is a normally opened brake, suitable for horizontal mounting, employing a thruster as actuator. with the foot controlling switch the operator can release or close the brake. It is mainly used for deceleration braking of portal cranes’slewing mechanism. In a non-operating state the machinery can be braked by a manual close device.

The RKW series brake is a normally opened brake, which is operated by foot driven hydraulic pump, suitable for horizontal mounting. Mainly used in the slewing mechanism of middle and small portal cranes. When needed, the brake

is activated by a manual closed device.

Main design features

Interlocking shoes balancing devices (patented technology) constantly equalizes the clearance of brake shoes on both sides and made adjustment unnecessary, thus avoiding one side of the brake lining sticking to the brake wheel. The brake is equipped with a shoed autoaligning device.

Main hinge points are equipped with self-lubricating bearing, making high efficiency of transmission, long service life. Lubricating is unnecessary during operation.

Adjustable bracket ensure the brake works well.

The brake spring is arranged inside a square tube and a surveyor’s rod is placed on one side. It is easy to read braking torque value and avoid measuring and computing.

Brake lining is of card whole-piece shaping structure, easy to replace. Brake linings of various materials such as half-metal (non-asbestos) hard and half-hard, soft (including asbestos) substance are available for customers to choose.

All adopt the company’s new types of thruster as corollary equipment which work accurately and have long life.

Hydraulic Power Transmission

The Two Types Of Power Transmission

In hydraulic power transmission the apparatus (pump) used for conversion of the mechanical (or electrical,thermal) energy to hydraulic energy is arranged on the input of the kinematic chain ,and the apparatus (motor) used for conversion of the hydraulic energy to mechanical energy is arranged on the output (fig.2-1)

The theoretical design of the energy converters depends on the component of the bernouilli equation to be used for hydraulic power transmission.

In systerms where, mainly, hydrostatic pressure is utilized, displacement

(hydrostatic) pumps and motors are used, while in those where the hydrodynamic pressure is utilized is utilized gor power transmission hydrodynamic energy converters (e.g. centrifugal pumps) are used.

The specific characteristic of the energy converters is the weight required for transmission of unit power. It can be demonstrated that the use of hydrostatic energy converters for the low and medium powers, and of hydrodynamic energy converters of high power are more favorite (fig.2-2). This is the main reason why hydrostatic energy converters are used in industrial apparatus. transformation of the energy in hydraulic transmission.

1.driving motor (electric, diesel engine);

2.mechanical energy;

3.pump;

4.hydraulic energy;

5.hydraulic motor;

6.mechanical energy;

7.load variation of the mass per unit power in hydrostatic and hydrodynamic energy

converters

1、hydrostatic; 2.hydrodynamic

Only displacement energy converters are dealt with in the following. The elements performing converters provide one or several size. Expansion of the working chambers in a pump is produced by the external energy admitted, and in the motor by the hydraulic energy. Inflow of the fluid occurs during expansion of the working chamber, while the outflow (displacement) is realized during contraction.

Such devices are usually called displacement energy converters.

The Hydrostatic Power

In order to have a fluid of volume V1 flowing in a vessel at pressure work spent on compression W1 and transfer of the process, let us imagine a piston mechanism (fig.2-3(a)) which may be connected with the aid of valves Z0 and Z1 to the external medium under pressure P0 and reservoir of pressure p1.in the upper position of the piston (x=x0) with Z0 open the cylinder chamber is filled with fluid of volume V0

and pressure P0. now shut the value Z0 and start the piston moving downwards. If Z1 is shut the fluid volume in position X=X1 of the piston decreases from V0 to V1, while the pressure rises to P1. the external work required for actuation of the piston (assuming isothermal change) is

W1=-∫0x0(P-P0)Adx=-∫v1v0(P-P0)dv

Select from Hydraulic Power Transmission

机器和机器零件的设计

机器设计

机器设计为了特定的目的而发明或改进机器的一种艺术。一般来讲，机器时有多种不同的合理设计并有序装配在一起的部件构成的，在最初的机器设计阶段，必须基本明确负载、元件的运动情况、工程材料的合理使用性能。负责新机器的设计最初的最重要的是经济性考虑。一般来说，选择总成本最低的设计方案，不仅要考虑设计、制造、销售、安装的成本。还要考虑服务的费用，机械要保证必要的安全性能和美观的外形。制造机器的目标不仅要追求保证只用功能的合理寿命，还要保证足够便宜以同时保证其经济的可行性。负责设计机器的工程师，不仅要经过专业的培训，而且必须是一个准确判断而又有丰富经验的人，具有一种有足够时间从事专门的实际工作的素质。

机器零件的设计

相同的理论或方程可应用在一个一起的非常小的零件上，也可用在一个复杂的设备的大型相似件上，既然如此，毫无疑问，数学计算是绝对的和最终的。他们都符合不同的设想，这必须由工程量决定。有时，一台机器的零件全部计算仅仅是设计的一部分。零件的结构和尺寸通常根据实际考虑。另一方面，如果机器和昂贵，或者质量很重要，例如飞机，那麽每一个零件都要设计计算。

当然，设计计算的目的是试图预测零件的应力和变形，以保证其安全的带动负载，这是必要的，并且其也许影响到机器的最终寿命。当然，所有的计算依赖于这些结构材料通过试验测定的物理性能。国际上的设计方法试图通过从一些相对简单的而基本的实验中得到一些结果，这些试验，例如结构复杂的及现代机械设计到的电压、转矩和疲劳强度。

另外，可以充分证明，一些细节，如表面粗糙度、圆角、开槽、制造公差和热处理都对机械零件的强度及使用寿命有影响。设计和构建布局要完全详细地说明每一个细节，并且对最终产品进行必要的测试。

综上所述，机械设计是一个非常宽的工程技术领域。例如，从设计理念到设计分析的每一个阶段，制造，市场，销售。以下是机械设计的一般领域应考虑的主要方面的清单：

①最初的设计理念②受力分析③材料的选择④外形

⑤制造⑥安全性⑦环境影响⑧可靠性及寿命

在没有破坏的情况下，强度是抵抗引起应力和应变的一种量度。这些力可能是：

①渐变力②瞬时力③冲击力④不断变化的力

⑤温差

如果一个机器的关键件损坏，整个机器必须关闭，直到修理好为止。设计一台新机器时，关键件具有足够的抵抗破坏的能力是非常重要的。设计者应尽可能准确地确定所有的性质、大小、方向及作用点。机器设计不是这样，但精确的科学是这样，因此很难准确地确定所有力。另外，一种特殊材料的不同样本会显现出不同的性能，像抗负载、温度和其他外部条件。尽管如此，在机械设计中给予合理综合的设计计算是非常有用的。

此外，显而易见的是一个知道零件是如何和为什麽破坏的设计师可以设计出需要很少维修的可靠机器。有时，一次失败是严重的，例如高速行驶的汽车的轮胎爆裂。另一方面，失败未必是麻烦。例如，汽车的冷却系统的散热器皮带管松开。这种破坏的后果通常是损失一些散热片，可以探测并改正过来。零件负载类型是一个重要的标志。一般而言，变化的动负载比静负载会引起更大的差异。因此，疲劳强度必须符合。另一个关心的方面是这种材料是否直或易碎。例如有疲劳破坏的地方不易使用易碎的材料。一般的，设计师要靠考虑所有破坏情况，其包括以下方面：

①应力②应变③外形④腐蚀⑤震动⑥外部环境

破坏⑦紧固件的松脱

零件的尺寸和外形的选择也有很多因素。外部负荷的影响，如几何间断，由于轮廓而产生的残余应力和组合件干涉。

选自《机械元件设计》第六版，斯鲍特、普瑞特斯等，1985年和《机械设计》埃斯普特斯、查里斯、麦瑞欧出版公司，1975年。

材料的机械性能

的机械性能可以被分成三个方面：物理性能，化学性能，机械性能。

物理性能

密度或比重、温度等可以归为这一类。

化学性能

这一种类包括很多化学性能。其中包括酸碱性、化学反应性、腐蚀性。其中最重要的是腐蚀性，在外行人看来，腐蚀性被解释为在某处的零件抵抗腐蚀的能力。

机械性能

机械性能包括拉伸性能、压缩性能、剪切性能、扭转性能、冲击性能、疲劳性能和蠕变。材料的拉伸强度可以通过试件的横截面积出试件承受的最大载荷得到，这是在拉伸试验中，应力沿Y轴，应边沿X轴变化的曲线。一种材料加载时开始发生变化的初值取决于负载的大小。当负载去掉时可以看到变形消失。对于很多材料而言，在达到弹性极限的一定应力值A之前，一直表现为这样。在应力--应变图中，这是可以用线性关系来描述的。这之后又一个小的偏移。

在弹性范围内，达到应力的极限之前，应力和应变是成比例的，这被称为比例极限Ap。在这个区域，零件符合胡克定律，即应力与应变是成比例的，在弹性范围内（材料能完全恢复到最初的尺寸，当负载去掉时）。曲线中的实际点，比例极限在弹性极限处。这可以认为是材料恢复初值时落后于前者。这种影响在不含铁的材料中经常提到。

铁和镍有明显的弹性范围，而铜、锌、锡等，即使在相对低的应力下也表现为不完全弹性。实际上，能否清楚地分辩弹性极限和比例极限取决于测量设备的灵敏度。

当负载超过弹性极限时，塑性变形开始，逐渐的试件被硬化。变形比负载增加得更快时的点被称成为屈服点Q。金属开始抵抗负载转变成快速变形，这时的屈服力成为屈服极限Ay。

试件的延伸率继续由Q到T再到，在这种塑性流动时，应力—应变关系在曲线上处于QRST区域。在点，试件破坏且这种负载称为破坏负载。最大负载S除以试件初始的截面积，被定义为这种金属的最终拉伸极限或试样的拉伸强度Au。

按逻辑说，在应力不增加的情况下，一旦超出弹性极限，金属开始屈服，并最终破坏。但是当超出弹性极限后，在纪录曲线上应增大。

这种变化主要有两个原因：

①材料的应力硬化

②由于塑性变形而引起的试件横截面积的变小

由于加工硬化，金属塑性变化越大，硬化越严重。金属拉伸越长，他的直径（横截面积）越小。直到到达点为止。点之后，减少的速率开始变化，超过了应力增加的速率，应变很大以至于在局部的某些点的面积减少，被称为颈缩。横截面积减少得非常快，以至于抗负载的能力下降，即ST阶段。破坏发生在T点。延伸率A和截面积变化率u被描述成材料的延展性和塑性：

a=(L0-L)/L0*100%

u=(A0-A)/A0*100%

在这里，L0和L分别是试件的最初和最终长度，A0和A分别是试件的最初截面积和最终截面积。

选自《金属材料的测试》

质量保证与控制

产品质量是生产中最重要的。如果放任质量恶化下去，生产者会很快发现销售量锐减，可能从而会导致产业的失败。用户期望他们买的产品质量性能好，而

且如果制造商想建立并维持其信誉，必须在产品制造前制造过程中及制造过程后进行质量控制和质量保证。一般来说，质量保证包括所有的活动，其包括质量建立和质量控制。质量保证可以被分为三个主要领域，他们如下所述：

①制造之前的原材料的检查

②在制造加工过程中的质量控制

③制造之后的质量保证

生产制造后的质量控制包括保证书和面对产品用户的服务。

生产制造之前的原材料检验

质量保证常常在实际生产制造之前就开始了。这些都是生产者在供应原材料、散件或配件的车间里进行检验。生产制造公司的原材料检验员到供应厂并且检查原材料及于制造的另配件。原材料检验为生产者提供了一次机会，那就是在原料及散件被运到生产车间之前先进行挑选淘汰。原料检察员的责任是去检查原料和零件是否达到设计规格并且淘汰那些未达到特殊指标的原料。原料检验有很多于检查产品相同的检验。其如下所述：

①目测

②冶金测试

③尺寸测试

④损伤检验

⑤性能检验

目测

目测检验一种产品或原料的某些特征，如颜色、纹理、表面光洁度或部件的总体外观，从而判断其是否具有明显的缺损。

冶金测试

冶金测试常常是原料间严厉的一个很重要的部分，尤其是像棒料、建筑材料毛坯一些原材料。金属测试包含所有主要的检验类型，其中有目测，化学检验，光谱检验和机械性能检验，其包括硬度、伸缩性能、剪切性能、压缩性能和合成成分的光谱分析。冶金测试既可用于成品件也可用于预制件。

尺寸检验

质量控制的一些领域是重要的生产件的要求尺寸。尺寸在检验过程中，像其

在生产过程中一样重要。如果这些零件是为总成供应的，那尺寸尤其严格。一些尺寸在生产车间用标准测量工具进行检验，像特种接头、造型和需求的功能标准度量。符合尺寸规格对所制造多部件的互换性和对多部件成功组装成复杂的装置，如汽车、轮船、飞机和其他多部件产品都地极其重要的。

损伤检验

在一些情况下，对原材料或零部件采取损伤测试的原始测验是很必要的。特别是涉及到大批的原材料时。例如，在被运到生产车间作最终机器之前，对铸件进行X-射线、电磁离子、染色渗透剂技术的探伤是很必要的，又对机器总成的电子或持久运作测试而确定的规格，是无损测试的又一例证。有时，对材料及零件的测试是很必要的，但由于无损测试的花费和成本及时间不是任何时候都允许的。

例如，有压力测试决定在设计中其是否安全。损伤测试经常用于设计样机的测试，而不是原材料或零件的常规检验。一旦设计达到了所希望的材料强度，通常对零件做进一步的损伤测试是不必要的，除非他们确实存在疑点。

性能测试

性能测试在零部件被其他产品被安装之前，检查部件的功能，尤其是那些机械构造复杂的部件。例如电子设备零件，飞机和汽车发动机，泵、阀及其他需要在装运和最后安装前进行性能测验的机械系统。

选自《现代材料和制造工艺》

汽车起重机的不同类型

根据汽车吊的使用情况，像：工作的范围，工作的自然情况。他们的构造装备体现着不同的理念。

1、工作范围（不同的设计）

当起重机工作在一个小范围内（仓库，码头，戏台等）告诉是没有必要的。根据这种应用，我们的装置最高速为35km/h。

驱动装置布置在后面，集成了车辆和起重机的控制，这种类型称为：单驱起重机。当起重机在大场地内工作时，有几个较远的工作点，高速轴就是必要的了。随之而来的，布置在车辆后端的单驱动是不可能的。由于这个原因，提供两个驱

动是必要的，相对的允许像传统卡车那样驱动车辆。这种类型的起重机，在构造上必须装备一个特殊的变速箱，对起重机允许像传统车辆那样的前进和后退。我们这种类型的起重机装备了一个特殊的变速箱，可以提供一个前进速度和一个后退速度，一般其最大运输速度为：55/60km/h，这种类型称为双驱起重机。

2、地面情况

当起重机操作困难时，在平整的路面上（体育场，码头，仓库等）起构造是传统概念的单驱动的运输工具。

如果起重机离开路面移动到恶劣路况下（脏且沙软的路面）不平的，其构造根据“全工况路面”的限定标准而建立，其要求实现：

双驱甚至是三驱；两种速度范围，有一个特别慢的值；不同驱动轴的转换系统；轴端的特殊轴承；特殊的制动；提供低压的大尺寸的轮胎，在软地面上运转；独立的大车轮；悬空的地面监视和清晰的构造是非常重要的；安装及驾驶服务所有的主要点是绝对必要的对于在无路的情况下的各种类型的车辆，有一个良好的运行。

当然起重机不得不在各种路况下工作，为此其装备了双驱。

（附图见英文资料）

液力传动

动力传动的两种类型

在液力传动中，用来将机械能（电能、化学能）转化成液力能的装置（泵）被布置在传动链的输入端，而用来将液力能转化成机械能的装置（马达）被布置在输出端。（图2-1）

这种能量转化的理论上的设计依据是液力传动的各部分的伯努里方程。

在系统中，流体静压力主要用来替代泵和马达，而在某些方面，流体动力是作为液力能转化后的力传动而被利用的（如离心泵）这种能量转换的特征取决于单位力的传动。他能说明这种微小力的液体静压力能转换和高压力的液体动力能转换更受人们的欢迎。（图2-2）者是液力转换被应用于工业器械的主要原因。液力传动的能量转换1、原动机（电机、内燃机）2、机械能3、泵4、液力能5、液压马达6、机械能7、负载

在流体静力能和流体动力能中单位里的质量变化

替代能量转换仅应用以下几方面，在液体静压力转换中相关的替代执行元件提供一个或数个工作室，他们恒定或尺寸可变。

泵的工作室在外部能量进入时伸长，马达是靠液力能，工作是伸长时液体流入，而收缩时实现流体流出。这些装置通常被称为能量转换装置。液体充满一个体积为V1的容器，在压力P1下所作的功W是压缩功W1和改变液体的功W2组成的。

为了分析这个过程，让我们假设一个活塞机构（图2-3（a）），它是有两个阀Z0、Z1和贮液器连接而成，表面压力为P0，贮

液器内部压力为P1，活塞处于上部的X=X0处，Z0打开，液体充满体积为V0的汽缸，压力为P0，现在关闭阀Z0，并且开始向下移动活塞，如果Z1关闭，当活塞下降到X=X1处时，液体体积由V0变为V1，此时压力升至P1，驱动活塞所作的外部功是（假设热量改变）

W1=-∫X1X0(P-P0)Adx=-∫V1V0(P-P0)dv

制动器的应用

YWW系列电力液压块式制动器是一种常闭、卧式安装的制动器，主要用于门座式起重机、斗轮堆取料机以及中大型塔式起重机回转机构的制动。

YKW系列电力液压块式制动器是一种常开、卧式安装的制动器，推动器为闭合（上闸）驱动装置，它通过脚踏开关控制，司机在司机室内可随意空。主要用于门座式起重机和塔式起重机等回转机构的减速制动。当需要在机构断电时（非工作状态）进行制动，可通过增设手动闭合（上闸）来实现。

RKW系列制动器为常开式、液压驱动、卧式安装的制动器。通过脚踏式液压泵进行控制，可实现随意制动。主要用于中小型门座式起重机和塔式起重机的回转机构。带有手动闭合（上闸）装置，在非工作状态下有需要时，可通过其进行维持制动。

主要设计特点

联锁式退距均等装置，专利技术，在使用过程中可始终保持两侧瓦块制动衬浮贴制动轮的现象；设有瓦块自动随位装置。