| 词或词组 | 中文 | 英文解释中文解释 |
|---|---|---|
| Partial annealing | 不完全退火 |
An imprecise term used to denote a treatment given cold-worked material to reduce the strength to a controlled level or to effect stress relief. To be meaningful, the type of material, the degree of cold work, and the time-temperature schedule must be stated. 一个不精确的术语，用于表示冷加工材料的处理，以将强度降低到受控水平或消除应力。为了有意义，必须说明材料类型、冷加工程度和时间-温度计划。 |
| Pascal (Pa) | 帕斯卡（Pa） |
The SI unit of pressure, 1 Pa = 1 N/m². 压力的国际单位制，1Pa=1N/m²。 |
| Pascal’s law | 帕斯卡定律 |
When there is a change in pressure at any point in a confined fluid at rest, there is an equal change at every other point in the fluid volume. 当处于静止状态的受限流体中任何一点的压力发生变化时，流体体积中的每一点的变化都相等。 |
| Peel strength (Unit N) | 剥离强度（单位：N） |
(peel test) The strength of an adhesive bond between two materials as measured by the force required in a given direction to peel apart adhered strips. This force depends on the dimensions and thickness of the adhered strips and their yield stress, together with the fracture toughness of the bond. （剥离试验）两种材料之间的粘合强度，通过给定方向上剥离粘合条所需的力来测量。该力取决于粘合条的尺寸和厚度及其屈服应力，以及粘合剂的断裂韧性。 |
| Percent error | 误差百分比 |
For testing machines, the ratio, expressed as a percentage, of the error to the correct value of the applied load. 对于试验机，以百分比表示的误差与所施加载荷的正确值之比。 |
| Permanent set | 永久变形 |
The deformation or strain remaining in a previously stressed body after release of load. 释放荷载后，先前受力物体中剩余的变形或应变。 |
| Permissible variation | 允许偏差 |
For testing machines, the maximum allowable error in the value of the quantity indicated. It is convenient to express permissible variation in terms of the percent error. 对于试验机，所示数量值的最大允许误差。用误差百分比表示允许偏差是很方便的。 |
| Physical crack size (ap) | 物理裂纹尺寸（ap） |
The distance from a reference plane to the observed crack front. This distance may represent an average of several measurements along the crack front. The reference plane depends on the specimen form, and it is normally taken to be either the boundary or a plane containing either the load line or the centerline of a specimen or plate. 从基准面到观察到的裂纹前沿的距离。该距离可以表示沿裂纹前沿的若干测量的平均值。基准面取决于试样形状，通常视为边界或包含试样或板的载重线或中心线的平面。 |
| Physical properties | 物理性质 |
Properties of a material the determination of which does not involve the deformation or destruction of the specimen—for example, density, electrical conductivity, coefficient of thermal expansion, magnetic permeability, and lattice parameter. Does not include chemical reactivity or the properties more appropriately regarded as mechanical properties. 不涉及试样变形或破坏的材料特性，例如密度、电导率、热膨胀系数、磁导率和晶格参数。不包括化学反应性或更适当地视为机械的性质。 |
| Physical testing | 物理测试 |
Methods used to determine the entire range of physical properties of a material. In addition to density and thermal, electrical, and magnetic properties, physical testing methods can be used to assess simple fundamental physical properties such as color, crystalline form, and melting point. 用于确定材料整个物理特性范围的方法。除了密度和热、电、磁特性外，物理测试方法还可用于评估简单的基本物理特性，如颜色、结晶形式和熔点。 |
| Pin expansion test | 插头膨胀试验 |
A test for determining the ability of a tube to be expanded or for revealing the presence of cracks or other longitudinal weaknesses in it, made by forcing a tapered pin into the open end of the tube, similar to flare test. 通过将锥形销压入管道开口端来确定管道膨胀能力或揭示其存在裂纹或其他纵向缺陷的试验，类似于扩口试验。 |
| Pin or mandrel | 销或心轴 |
In bend testing, the plunger or tool used in making semiguided, guided, or wrap-around tests to apply the bending force to the inside surface of the bend. In free bends or semiguided bends to an angle of180°, a shim or block of the proper thickness may be placed between the legs of the specimen as bending is completed. This shim or block is also referred to as a pin or mandrel. 在弯曲测试中，用于进行半导向、导向或环绕测试以将弯曲力施加到弯曲内表面的柱塞或工具。在180°角的自由弯曲或半导向弯曲中，弯曲完成后，可在试样支腿之间放置适当厚度的垫片或垫块。该垫片或垫块也称为销或心轴。 |
| Piston pump | 活塞泵 |
A positive-displacement pump in the basic configuration of which a piston reciprocates in a cylinder. On the suction stroke, fluid is drawn into a chamber through the inlet valve, which is then open while the outlet valve is closed. On the delivery stroke the fluid is forced out of the chamber through the outlet valve, which then opens while the inlet valve is closed. Both axial and radial configurations are common. 活塞在气缸中往复运动的一种容积泵。在吸入冲程，流体通过入口阀吸入腔室，然后在出口阀关闭时打开。在输送冲程中，流体通过出口阀被迫流出腔室，然后出口阀打开，同时入口阀关闭。轴向和径向配置都很常见。 |
| Pitch | 沥青节距 |
The nominal distance between two adjacent thread roots or crests. In screw threads, the distance from a point on one thread to a corresponding point on the next thread measured parallel to the axis. In the case of spur gears, indicates the size of the gear teeth and is correctly called diametral pitch. 两个相邻螺纹根部或顶部之间的标称距离。在螺纹中，从一根螺纹上的一点到下一根螺纹对应点的距离，平行于轴线测量。对于正齿轮，表示齿轮齿的尺寸，正确地称为径向节距。 |
| Pitch (Unit m) | 间距（单位：m） |
1. In a cascade of identical turbine or compressor blades, the distance between successive blades measured parallel to the leading edges. 2. For a screw thread, the distance between adjacent thread forms measured parallel to the thread axis. 3. For an aircraft, the vertical relationship between the nose and the horizon. The pitch axis is an axis in the plane of the wings of an aircraft, perpendicular to the centreline, about which the aircraft rotates. Pitch motion is the corresponding up or down movement of the aircraft nose. Pitch attitude is the angle between the centreline of an aircraft and the horizontal. The angle is positive when the nose is above its position when the centreline is horizontal. 1.在相同涡轮或压缩机叶片的叶栅中，平行于前缘测量的连续叶片之间的距离。2.对于螺纹，平行于螺纹轴线测量的相邻螺纹形状之间的距离。3.对于飞机，机头和水平线之间的垂直关系。俯仰轴是飞机机翼平面内垂直于中心线的轴，飞机绕中心线旋转。俯仰运动是飞机机头的相应向上或向下运动。俯仰姿态是飞机中心线与水平线之间的角度。当中心线水平时，当机头高于其位置时，角度为正。 |
| Pitch angle (Unit °) | 俯仰角（单位°） |
For a bevel gear, the angle between the axis and the pitch-cone generator. 对于锥齿轮，轴与节锥生成器之间的角度。 |
| Pitch diameter | 中径 |
For screw threads, the diameter of an imaginary cylinder, the surface of which would pass through the threads at such points that would make the width of the groove and width of the land equal to one half the pitch. 对于螺纹，指一个假想圆柱体的直径，其表面将在使凹槽宽度和焊盘宽度等于螺距一半的点穿过螺纹。 |
| Pitch-circle diameter (Unit m) | 节圆直径（单位：m） |
The diameter of the circle (the pitch circle) centred on a component’s axis, around which holes or bolts are equally spaced. 以部件轴为中心的圆（节圆）的直径，孔或螺栓围绕其等距分布。 |
| Pitting | 点蚀 |
In tribology, a type of wear characterized by the presence of small, sharp surface cavities formed by processes such as fatigue, local adhesion, wear, corrosion, or cavitation. 在摩擦学中的一种磨损，其特征是存在由疲劳、局部粘附、磨损、腐蚀或空穴等过程形成的小而尖锐的表面空穴。 |
| Planar anisotropy | 平面异向性 |
A variation in physical and/or mechanical properties with respect to direction within the plane of material in sheet form. 在片状材料平面内，物理和/或机械性能相对于方向的变化。 |
| Plane strain | 平面应变 |
The stress condition in linear-elastic fracture mechanics in which there is zero strain in a direction normal to both the axis of applied tensile stress and the direction of crack growth (i.e., parallel to the crack front); most nearly achieved in loading thick plates along a direction parallel to the plate surface. Under plane-strain conditions, the plane of fracture instability is normal to the axis of the principal tensile stress. 线弹性断裂力学中的应力条件，其中在垂直于施加拉应力轴和裂纹扩展方向（即平行于裂纹前沿）的方向上存在零应变；最接近于沿平行于板表面的方向加载厚板。在平面应变条件下，断裂失稳平面垂直于主拉应力轴。 |
| Plane stress | 平面应力 |
The stress condition in linear-elastic fracture mechanics in which the stress in the thickness direction is zero; most nearly achieved in loading very thin sheet along a direction parallel to the surface of the sheet. Under plane-stress conditions, the plane of fracture instability is inclined 45° to the axis of the principal tensile stress. 线弹性断裂力学中厚度方向上的应力为零的应力条件；在沿着平行于薄片表面的方向加载非常薄的薄片时最接近。在平面应力条件下，断裂失稳平面与主拉应力轴倾斜45°。 |
| Plane-strain fracture toughness (KIc) | 平面应变断裂韧性（KIc） |
The crack extension resistance under conditions of crack-tip plane strain. 裂纹尖端平面应变条件下的裂纹扩展阻力。 |
| Plane-stress fracture toughness (Kc) | 平面应力断裂韧性（Kc） |
In linear-elastic fracture mechanics, the value of the crack-extension resistance at the instability condition determined from the tangency between the R-curve and the critical crack-extension force curve of the specimen. 在线弹性断裂力学中，由试样的R曲线和临界裂纹扩展力曲线之间的切线确定的不稳定条件下裂纹扩展阻力的值。 |
| Plastic deformation | 塑性变形 |
The permanent (inelastic) distortion of a material under applied stress that strains the material beyond its elastic limit. 材料在施加应力下的永久（非弹性）变形，使材料应变超过其弹性极限。 |
| Plowing | 犁 |
In tribology, the formation of grooves by plastic deformation of the softer of two surfaces in relative motion. 在摩擦学中，通过相对运动的两个表面中较软的表面的塑性变形形成凹槽。 |
| Plug | 螺塞 |
1. An object, usually tapered, used to block a hole to prevent fluid from escaping or flowing. 2. The central moveable part of a valve. 3. In the flow of a yield-stress fluid through a pipe or duct, the central region is often assumed to take the form of a plug with uniform axial velocity. 4. In thermoforming, a shaping tool that forces a heated plastic sheet into a female mould. 1.一种物体，通常为锥形，用于堵塞孔以防止流体逸出或流动。2.阀门的中心可移动部分。3.在屈服应力流体通过管道或管道的流动中，中心区域通常假定为具有均匀轴向速度的塞子形式。4.在热成型技术中，一种成型工具，将加热的塑料板压入阴模中。 |
| Plug gauge | 塞规 |
A steel gauge used to determine the dimension or dimensions of a hole. It may be straight or tapered, and is typically circular, but in principle can have any cross section. 用于确定孔的尺寸的钢制量规。它可以是直的或锥形的，通常是圆形的，原则上可以有任何横截面。 |
| Pneumatic control valve | 气动控制阀 |
(pneumatic valve) A valve in which the position of the valve stem, which varies the open area, is determined by the net force generated by compressed air acting on a diaphragm operating against the force of a compression spring. Depending upon the arrangement of the spring, in the event of air-supply failure, the valve may open or close. （气动阀）一种阀门，其中阀杆的位置随开口面积的变化而变化，由压缩空气作用在隔膜上产生的净力决定，隔膜克服压缩弹簧的力进行操作。根据弹簧的布置，在供气故障的情况下，阀门可以打开或关闭。 |
| Poisson’s ratio (ν) | 泊松比（ν） |
The absolute value of the ratio of transverse (lateral) strain to the corresponding axial strain resulting from uniformly distributed axial stress below the proportional limit of the material. 横向（侧向）应变与相应轴向应变之比的绝对值，该比值由低于材料比例极限的均匀分布的轴向应力产生。 |
| Pop rivet | 拉钉 |
A hollow rivet that enables a connexion to be made from one side only of an assembly. 一种空心铆钉，使连接只能从组件的一侧进行。 |
| Population | 集合 |
The hypothetical collection of all possible test specimens that could be prepared in the specified way from the material under consideration. Also known as universe. 从所考虑的材料中以规定方式制备的所有可能试样的假设集合。也称为体系。 |
| Positive-displacement compressor | 容积式压缩机 |
Any type of compressor, including piston and rotary-screw types, that delivers a fixed volume of gas at high pressure per unit time. A positive-displacement pump delivers a fixed volume of fluid, usually a liquid, per unit time. 任何类型的压缩机，包括活塞式和旋转螺杆式，在单位时间内以高压输送固定体积的气体。容积泵每单位时间输送固定体积的流体，通常为液体。 |
| Positive-displacement flow meter | 容积式流量计 |
An instrument of high accuracy that determines volumetric flow rate by dividing the flowing fluid into successive fixed volumes, and measuring their times of passage through the meter. 一种高精度仪器，通过将流动的流体分成连续的固定体积并测量其通过流量计的时间来确定体积流量。 |
| Positive-displacement machine | 正排量机 |
A machine that incorporates pistons, valves, etc. to ensure positive admission and delivery of a working fluid and prevent undesired reversal of flow. This class of machine incorporates all reciprocating compressors and expanders and some types of rotary compressor, the Roots blower, agear pump, a lobe pump, and a vane pump. 包含活塞、阀门等的机器，以确保工作流体的正向进入和输送，并防止不期望的反向流动。这类机器包括所有往复式压缩机和膨胀机以及一些类型的旋转压缩机、罗茨鼓风机、抽水机、凸轮泵和叶片泵。 |
| Power | 力能 |
The rate of doing work or of producing or consuming energy. The unit of power is the watt, W, where 1 W = 1 N m/s. 做功或产生或消耗能量的速度。功率单位为瓦特，W，其中1W=1N m/s。 |
| Pre-stress | 预应力 |
To induce stresses into a component or structure before it is subjected to operating loads. 在部件或结构承受操作载荷之前，将应力引入部件或结构。 |
| Precipitation hardening | 沉淀硬化 |
Hardening caused by the precipitation of a constituent from a supersaturated solid solution. 因成分从过饱和固溶体沉淀而导致的硬化。 |
| Precipitation heat treatment | 沉淀热处理 |
Artificial aging in which a constituent precipitates from a supersaturated solid solution. 成分从过饱和固溶体沉淀的人工时效。 |
| Precipitation-hardenable stainless steels | 沉淀硬化不锈钢 |
Precipitation-hardenable stainless steels contain typically 11–18% chromium, 3–10% nickel, 0.05–0.2% carbon, and small additions of manganese, silicon, aluminium, molybdenum, niobium and titanium. These steels can be supplied in a solution-treated condition, which is readily fabricated or machined, and then hardened by an ageing treatment that produces a fine dispersion of second-phase precipitates. They are available in austenitic, semi-austenitic, and martensitic grades. Uses include springs, knives, and pressure vessels. 沉淀硬化不锈钢通常含有11-18%的铬、3-10%的镍、0.05-0.2%的碳以及少量添加的锰、硅、铝、钼、铌和钛。这些钢可在固溶处理条件下供应，该条件易于制造或机加工，然后通过时效处理硬化，从而产生细小的第二相沉淀。它们有奥氏体、半奥氏体和马氏体等级。用途包括弹簧、刀具和压力容器。 |
| Precision | 精确 |
The closeness of agreement between the results of individual replicated measurements or tests. The standard deviation of the error of measurement may be used as a measure of “imprecision.” 单个重复测量或测试结果之间的一致性。测量误差的标准偏差可用作“不精确性”的度量 |
| Preheating | 预热 |
Heating before some further thermal or mechanical treatment. For tool steel, heating to an intermediate temperature immediately before final austenitizing. For some nonferrous alloys, heating to a high temperature for a long time, to homogenize the structure before working. In welding and related processes, heating to an intermediate temperature for a short time immediately before welding, brazing, soldering, cutting, or thermal spraying. 在进一步热处理或机械处理之前加热。对于工具钢，在最终奥氏体化之前立即加热至中间温度。对于一些非铁合金，在工作前长时间加热到高温，以使结构均匀化。在焊接和相关工艺中，在焊接、钎焊、钎焊、切割或热喷涂之前，立即加热到中间温度。 |
| Preload | 预载 |
The tension created in a threaded fastener when the nut is first tightened. Often used interchangeably, but incorrectly, with Working load or bolt force or bolt tension 第一次拧紧螺母时螺纹紧固件中产生的张力。经常与工作载荷或螺栓力或螺栓张力互换使用但容易使用不当。 |
| Preload accuracy | 预载精度 |
A measure of the precision with which a given tool or procedure creates preload in a bolt when the bolt is tightened. A common torque wrench, for example, is said to produce preload with an accuracy of +30%. The mean preload, however, may not be that which the designer intended, or may not be what he should have intended. Accuracy as used here, in other words, is synonymous with Scatter. 当螺栓拧紧时，给定工具或程序在螺栓中产生预紧力的精度度量。例如，一个普通的扭矩扳手据说可以产生精度为+30%的预载。然而，平均预载可能不是设计者预期的。这里使用的准确度是分散度的同义词。 |
| Preload adjustments | 预载调整 |
Preloads may be applied directly by axial loading or indirectly by turning of the nut or bolt. When preload is applied by turning of nuts or bolts, a torsion load component is added to the desired axial bolt load. 预载荷可通过轴向载荷直接施加，或通过转动螺母或螺栓间接施加。当通过转动螺母或螺栓施加预载荷时，扭转载荷分量被添加到所需的轴向螺栓载荷中。 |
| Preload relaxation | 预载松弛 |
Local yielding, due to excess bearing stress under nuts and bolt heads (caused by high local spots, rough surface finish, and lack of perfect squareness of bolt and nut bearing surfaces), may result in preload relaxation after preloads are first applied to a bolt. 由于螺母和螺栓头下的轴承应力过大（由局部斑点高、表面粗糙以及螺栓和螺母轴承表面缺乏完美的方正度造成），局部屈服可能会在首次向螺栓施加预载荷后导致预载荷松弛。 |
| Press quenching | 压淬 |
A quench in which hot dies are pressed and aligned with a part before the quenching process begins. Then the part is placed in contact with a quenching medium in a controlled manner. This process avoids part distortion. 一种淬火方法，在淬火过程开始之前，热模具被压制并与零件对齐。然后将零件以受控方式放置在与淬火介质接触的位置。该过程避免了零件变形。 |
| Pressure (p) (Unit Pa) | 压力（p）（单位Pa） |
In thermodynamics and fluid mechanics, the compressive force exerted by the fluid per unit area. The pressure exerted by a fluid on a surface acts normal to the surface. 在热力学和流体力学中，每单位面积流体施加的压缩力。流体施加在表面上的压力垂直于表面。 |
| Pressure chamber | 压力室 |
A chamber in which components or devices can be subjected to high or low fluid (liquid or gas) pressure. 部件或装置可承受高或低流体（液体或气体）压力的腔室。 |
| Pressure control valve | 压力控制阀 |
A valve used to set the pressure level in a pressure vessel or piping system. 用于设置压力容器或管道系统中压力水平的阀门。 |
| Pressure difference (Unit Pa) | 压差（单位Pa） |
(pressure differential, Δp) The difference between two pressures, one of which may be a reference pressure such as barometric pressure. In many flow processes, the pressure difference is more important than the absolute pressure level. （压差，Δp）两个压力之间的差值，其中一个压力可以是参考压力，如大气压力。在许多流动过程中，压差比绝对压力水平更重要。 |
| Pressure gauge | 压力表 |
An instrument used to measure absolute or gauge pressure. The sensing element may be a tube which deflects when pressurized, as in a Bourdon gauge, a bellows as in an aneroid barometer, a piezoelectric crystal, a piezoresistive element, etc. 测量绝对压力或表压的仪器。传感元件可以是加压时会偏转的管，如波登压力表、无液气压计中的波纹管、压电晶体、压阻元件等。 |
| Pressure loss (Unit Pa) | 压力损失（单位Pa） |
The loss in stagnation pressure in internal flow due to wall friction and minor losses in fittings. 壁面摩擦引起的内部流动停滞压力损失和配件的微小损失。 |
| Pressure rating (Unit Pa or bar) | 额定压力（单位Pa或bar） |
The internal pressure at which a pressure vessel, boiler, tank, piping, etc. is designed to operate safely. 压力容器、锅炉、储罐、管道等设计用于安全运行的内部压力。 |
| Pressure ratio | 压力比 |
One pressure divided by another which may be a reference pressure. In many flow and thermodynamic processes, the pressure ratio is more important than the absolute pressure levels. For example, in compressible gas flow the Mach number is determined by the ratio of the stagnation pressure to the static pressure. 一个压力除以另一个压力，该压力可以是参考压力。在许多流动和热力学过程中，压力比比绝对压力水平更重要。例如，在可压缩气流中，马赫数由停滞压力与静压之比决定。 |
| Pressure recovery (Unit Pa) | 压力恢复（单位Pa） |
The progressive increase in static pressure for unseparated flow through a diverging nozzle or diffuser. 通过发散喷嘴或扩散器的未分离流的静压逐渐增加。 |
| Pressure regulator | 压力调节器 |
(pressure-regulating valve) A device installed in a pneumatic or gas system to maintain the downstream pressure at the required level. （压力调节阀）安装在气动或气体系统中以将下游压力保持在所需水平的装置。 |
| Pressure snubber | 压力缓冲器 |
(pressure-pulse snubber) A device used for filtering, dampening, and the protection of transducers, pressure gauges, and switches, from pressure surges, pressure spikes, and water hammer. A typical design uses a fixed mesh or porous metal disc installed in an inline body. In a piston-type pressure-gauge snubber, a piston is forced against an orifice leading to the gauge. （压力脉冲缓冲器）一种用于过滤、阻尼和保护传感器、压力表和开关免受压力浪涌、压力尖峰和水锤影响的装置。典型的设计使用安装在内联阀体中的固定网格或多孔金属盘。在活塞式压力表缓冲器中，活塞被压靠在通向压力表的孔口上。 |
| Pressure storage tank | 压力贮存器 |
(pressure vessel) A closed container for storing gases or volatile liquids, such as liquefied gases, at pressures significantly above atmospheric pressure. Such tanks are commonly cylindrical with domed ends, spherical, spheroidal, torispherical or hemispherical. （压力容器）密闭容器：在大气压以上的压力下储存气体或挥发性液体，如液化气体的密闭容器。此类贮存器通常为圆柱形，具有半球形端部、球形、球面或半球形。 |
| Pressure surface | 压力面 |
The high-pressure surface of an aerofoil, turbine, or compressor blade. In normal aircraft applications, this is the lower surface of a wing. For applications, such as to high-performance motor vehicles, where the aerofoil is inverted to generate downforce, it is the upper surface. 机翼、涡轮或压缩机叶片的高压表面。在正常的飞机应用中，这是机翼的下表面。对于高性能机动车辆等应用，机翼翻转以产生下压力，它是上表面。 |
| Pressure tap | 测压口 |
A small hole in the wall of a pipe or pressure vessel to which is attached a tube, the other end of which is connected to one side of a pressure transducer. 管子或压力容器壁上的小孔，与管子相连，管子的另一端与压力传感器的一侧相连。 |
| Pressure-relief valve | 减压阀 |
A valve that limits the maximum pressure in a pressure vessel or fluid-power system to a specified level. 将压力容器或流体动力系统中的最大压力限制在规定水平的阀门。 |
| Prevailing torque | 有效扭矩 |
Torque required to run a nut down against the joint when some obstruction, such as a plastic insert in the threads, or a noncircular thread, or other, has been introduced to help the fastener resist vibration loosening. Prevailing torque, unlike normal torque on a nut or bolt, is not proportional to the Preload in the fastener. 当引入了一些障碍物（如螺纹中的塑料插件或非圆螺纹或其他障碍物）以帮助紧固件抵抗振动松动时，将螺母向下压靠接头所需的扭矩。与螺母或螺栓上的正常扭矩不同，主要扭矩与紧固件中的预载不成比例。 |
| Principal stress (normal) | 主应力（正常） |
The maximum or minimum value of the normal stressat a point in a plane considered with respect to all possible orientations of the considered plane. On such principal planes the shear stress is zero. There are three principal stresses on three mutually perpendicular planes. The state of stress at a point may be: (1) uniaxial, a state of stress in which two of the three principal stresses are zero; (2) biaxial, a state of stress in which only one of the three principal stresses is zero; or (3) triaxial, a state of stress in which none of the principal stresses is zero. Multiaxial stress refers to either biaxial or triaxial stress. 相对于所考虑平面的所有可能方向，所考虑平面中某点处的法向应力的最大值或最小值。在这样的主平面上，剪切应力为零。在三个相互垂直的平面上有三个主应力。一点的应力状态可以是：（1）单轴，三个主应力中的两个为零的应力；（2）双轴，三个主应力中只有一个为零的应力状态；或（3）三轴，即主应力均不为零的应力状态。多轴应力是指双轴或三轴应力。 |
| Process annealing | 中间退火 |
An imprecise term denoting various treatments used to improve workability. For the term to be meaningful, the condition of the material and the time-temperature cycle used must be stated. 一个不精确的术语，表示用于改善可加工性的各种处理方法。为了使术语有意义，必须说明材料的条件和使用的时间-温度循环。 |
| Profile | 轮廓 |
The shape of a cross section of an object, such as an aerofoil or cam. 物体的横截面形状，如机翼或凸轮。 |
| Profiling machine | 仿形机 |
(profile milling machine) A milling machine in which the cutter is guided by the contour of a pattern having the required shape. （仿形铣床）铣刀由具有所需形状的图案轮廓引导的铣床。 |
| Profilometer | 轮廓仪 |
An instrument used to quantify the roughness of a surface. For a contact profilometer, a diamond stylus sweeps across the surface along a series of parallel lines. Noncontact profilometers use optical techniques to map the surface irregularities. 用于量化表面粗糙度的仪器。对于接触式轮廓仪，钻石触针沿一系列平行线扫过表面。非接触式轮廓仪使用光学技术绘制表面不规则。 |
| Progressive aging | 渐进时效 |
Aging by increasing the temperature in steps or continuously during the aging cycle. 通过在时效周期中逐步或连续升高温度进行增加时效。 |
| Proof load | 验证载荷（单位 N） |
The maximum, safe, static, tensile load which can be placed on a fastener without yielding it. Sometimes given as a force (in lb or N) sometimes as a stress (in psi or MPa). The test load in quality control to which different components made of different materials must be subjected without failing in order to perform properly. 可施加在紧固件上而不使其屈服的最大安全静态拉伸载荷。有时以力（lb或N）表示，有时以应力（psi或MPa）表示。质量控制中的测试负荷，由不同材料制成的不同部件必须经受该负荷，才能正常运行。 |
| Proof strength (Unit Pa) | 验证强度（单位Pa） |
(proof stress, Rp, Rp,) The yield strength (offset yield strength) at some fixed value of the permanent strain given by the intersection of a line offset from, but parallel to, the elastic loading line and the engineering stress-engineering strain curve. The offset is arbitrary but is usually 0.1, 0.2, or 0.5% permanent strain (the proof strain). Used for materials which do not exhibit a sharply defined yield point. The notation Rp0.2 or Rp0.2 is employed for the 0.2% proof stress. （验证应力，Rp）在永久应变的某个固定值下的屈服强度（偏移屈服强度），由偏离但平行于弹性加载线的线与工程应力-工程应变曲线的交点给出。偏移是任意的，但通常为0.1、0.2或0.5%的永久应变（验证应变）。用于没有明确定义屈服点的材料。对于0.2%的验证应力，采用符号Rp0.2。 |
| Proof stress | 弹性极限应力 |
(1) The stress that will cause a specified small permanent set in a material. (2) A specified stress to be applied to a member or structure to indicate its ability to withstand service loads. （1）在材料中引起规定的小永久变形的应力。（2）施加在构件或结构上的规定应力，以表明其承受工作荷载的能力。 |
| Proportional limit | 比例极限 |
The greatest stress a material is capable of developing without a deviation from straight-line proportionality between stress and strain. 材料能够产生的最大应力不偏离应力和应变之间的直线比例。 |
| Prying | 撬动 |
The magnification of an External load by a pseudolever action when that load is an Eccentric tensile load. 当外部荷载为偏心拉伸荷载时，通过伪杠杆作用放大外部荷载。 |
| PSI (pounds per square inch) | PSI（磅/平方英寸） |
Pressure measurement. Psia (pounds per square inch absolute) measures actual pressure with no allowance for atmospheric pressure. Psig (pounds per square inch gauge) measures pressure with the gauge set to zero (0) at atmospheric pressure (14.7 psia). In other words psig = psia – 14.7. 压力测量。Psia（绝对磅/平方英寸）测量实际压力，不考虑大气压力。Psig（磅/平方英寸表压）在大气压（14.7 psia）下，将表压设置为零（0）时测量压力。换句话说，psig=psia–14.7。 |
| Pulley | 带轮 |
A free or driven wheel on a shaft with an appropriately shaped rim to carry a flat belt, vee belt, notched belt, rope, or chain. Used to transmit power or motion. 轴上的自由轮或从动轮，具有适当形状的轮缘，以承载平皮带、V形皮带、槽口皮带、绳索或链条。用于传递动力或运动。 |
| Pulse | 脉冲 |
An increase or decrease in the magnitude of a physical quantity, such as pressure, voltage, or force, with a time scale short compared with other time scales in a process, after which there is a return to the original level. 物理量的大小的增加或减少，如压力、电压或力，与过程中的其他时间尺度相比，时间尺度较短，之后返回到原始水平。 |
| Pump | 泵 |
A machine designed to cause a liquid, gas, vapour, or slurry to flow due to the reciprocating motion of pistons, rotation of vanes, or rotation of an impeller. 通过活塞的往复运动、叶片的旋转或叶轮的旋转而使液体、气体、蒸汽或泥浆流动的机器。 |
| Punch | 冲床 |
1. A hand tool with a sharp point, used to mark the position of a hole centre in a workpiece prior to drilling. 2. A flat-ended tool with sharp edges, used to shear out a hole in a plate that is supported underneath on a die having a slightly larger same-shaped orifice. 1.一种带有尖头的手动工具，用于在钻孔前标记工件中孔中心的位置。2.一种具有锐边的平头工具，用于剪切板上的孔，该板支撑在具有稍大相同形状孔口的模具下方。 |
| Push rod | 推杆 |
A rod which opens and closes a valve via a valve rocker in an overhead-valve piston engine. The rod is actuated by a camshaft located in the crankcase. 在顶置气门活塞发动机中，通过气门摇臂打开和关闭气门的杆。连杆由曲轴箱中的凸轮轴驱动。 |