制作無(wú)損檢測(cè)參考標(biāo)準(zhǔn)和試塊時(shí)表面光潔度的重要性（中英文）
表面光潔度使用測(cè)量系統(tǒng)量化結(jié)果來(lái)描述表面的粗糙度或不規(guī)則度。該系統(tǒng)涵蓋范圍廣泛，從質(zhì)地極其粗糙的表面一直到高度拋光的鏡面表面。主要參數(shù)是粗糙度平均值，用“Ra”表示，即輪廓的算術(shù)平均偏差。數(shù)字越高，表面越粗糙。粗銑表面的粗糙度在 250 到 500 Ra μin（6.3 至 12.5 μm）范圍內(nèi)。使用帶有溢流冷卻液的表面磨床通過(guò)連續(xù)輕磨加工而成的光滑表面的光潔度在 16 至 32 Ra μin（0.4 至 0.8μm）范圍內(nèi)。16 至 500 Ra μin（0.4 至 12.5 μm）的范圍涵蓋了當(dāng)今工業(yè)中大多數(shù)的機(jī)加工工具和零件。當(dāng)然，超出該范圍的極端情況也存在，但就無(wú)損檢測(cè) (NDT) 標(biāo)準(zhǔn)而言，這些情況很少見(jiàn)。
Surface finish describes the roughness or irregularity of a surface using a measurement system to quantify the results. This system covers a wide range from extremely rough-textured surfaces all the way to those that are highly polished, mirror-like surfaces. The predominant parameter is Roughness Average, denoted by “Ra,” which is the arithmetic mean deviation of a profile. The higher the number, the rougher the finish. Roughly milled surfaces will be in the 250 to 500 Ra μin (6.3 to 12.5 μm) range. Smooth surfaces machined by successive light passes on a surface grinder with flood coolant will yield finishes in the 16 to 32 Ra μin (0.4 to 0.8μm) range. The span of 16 to 500 Ra μin (0.4 to 12.5 μm) covers the majority of machined tools and parts in industry today. There are extremes beyond that range of course, but for purposes of Non-Destructive Testing (NDT) standards, they are rare.
用于測(cè)量表面光潔度的主要儀器是輪廓儀。輪廓儀是一種接觸式表面光潔度測(cè)量方法，采用自動(dòng)驅(qū)動(dòng)的觸針劃過(guò)零件表面。觸針觀察并記錄表面的峰谷，通常與刻度垂直。刻度是指使用銑刀、砂輪、車床或其他工藝加工時(shí)形成的主導(dǎo)圖案的方向。對(duì)于無(wú)方向性的加工方法，如電火花加工 (EDM)，由于沒(méi)有明確的方向需要考慮，所以方向性不太重要。另一種常用且更簡(jiǎn)單的估計(jì)表面光潔度的方法是使用表面光潔度比較儀。這種手持式測(cè)量?jī)x包含一系列表面處理和方法的小樣本，可以通過(guò)視覺(jué)與相關(guān)表面進(jìn)行比較。雖然不如輪廓儀精確，但它是一種快速簡(jiǎn)便的方法來(lái)獲得大致結(jié)果。
The primary instrument used to measure surface finish is a profilometer. The profilometer is a contact method of finish measurement that employs a stylus that is automatically driven across the part’s surface. The stylus observes and records the peaks and valleys of the surface, typically perpendicular to the lay. Lay is described as the direction of dominant pattern from machining with a milling cutter, grinding wheel, lathe, or other process. For non-directional machining methods such as electrical discharge machining (EDM), lay is less important as there is no clear direction to consider. Another common and simpler method for estimating surface finishes is to use a Surface Finish Comparator. This handheld gauge contains small samples of a range of finishes and methods that can be visually compared to the surface in question. While not nearly as precise as a profilometer, it is a fast and easy method to get in the ballpark.
當(dāng)在獨(dú)特的無(wú)損檢測(cè)領(lǐng)域考慮表面光潔度時(shí)，需要記住一些事項(xiàng)。無(wú)損檢測(cè)標(biāo)準(zhǔn)設(shè)計(jì)和制造規(guī)范中始終包含這樣的規(guī)定：標(biāo)準(zhǔn)光潔度必須代表被測(cè)部件。對(duì)于特定應(yīng)用的參考標(biāo)準(zhǔn)（火箭發(fā)動(dòng)機(jī)部件、核反應(yīng)堆螺柱、ASME 管道校準(zhǔn)標(biāo)準(zhǔn)等），匹配的表面光潔度與被測(cè)部件具有相同的幾何形狀、合金、熱處理?xiàng)l件、超聲波速度或電磁電導(dǎo)率測(cè)量同樣重要。
When we consider surface finish in our unique world of NDT, there are a few things to keep in mind. Specifications governing the design and manufacture of NDT standards always include language stating that the finish of the standard must be representative of the part under test. For application-specific reference standards (rocket engine components, nuclear reactor studs, ASME pipe calibration standards, etc), having a matching surface finish is just as important as having the same geometry, alloy, heat-treat condition, ultrasonic velocity or electromagnetic conductivity measurement as the component under test.
對(duì)于非代表性 NDT 標(biāo)準(zhǔn)（又名標(biāo)準(zhǔn)測(cè)試塊），例如 IIW 型測(cè)試塊、DSC 測(cè)試塊和無(wú)數(shù)其他測(cè)試塊，則采用不同的方法。這些是簡(jiǎn)化設(shè)計(jì)的通用工具，用于校準(zhǔn)和標(biāo)準(zhǔn)化 NDT 儀器的響應(yīng)。標(biāo)準(zhǔn)測(cè)試塊的表面光潔度是需要考慮的重要因素，但與特定于應(yīng)用的標(biāo)準(zhǔn)的原因不同。管理標(biāo)準(zhǔn)測(cè)試塊的圖紙和規(guī)范通常要求表面光潔度均勻、光滑，以便每次都能從測(cè)試儀器獲得一致、可重復(fù)的響應(yīng)。標(biāo)準(zhǔn)測(cè)試塊的掃描表面通常具有 32 Ra 或更光滑的光潔度。為實(shí)現(xiàn)此目的，制造商必須在這些區(qū)域使用表面磨削技術(shù)。
There is a different approach for non-representative NDT standards (a.k.a. standard test blocks), such as the IIW-Type Block, DSC Block, and countless others. These are general purpose tools of a simplified design that are used to calibrate and standardize the response from an NDT instrument. Surface finish is important to consider on standard test blocks, but for a different reason than on application-specific standards. The drawings and specifications that govern standard test blocks typically call for a uniform, smooth finish that will yield a consistent, repeatable response from the testing instrument every time. The scanning surfaces of standard test blocks typically have a finish of 32 Ra or smoother. To achieve this, the manufacturer must use surface grinding techniques on those areas.
制定標(biāo)準(zhǔn)時(shí)忽略表面光潔度是確保標(biāo)準(zhǔn)不適合預(yù)期校準(zhǔn)的必然方法。如果要檢查的管道測(cè)量值為 125 Ra μin (3.2 μm)，則沒(méi)有 UT Level III 會(huì)希望使用表面拋光掃描表面測(cè)量值為 16 Ra μin (0.8 μm) 的管道標(biāo)準(zhǔn)進(jìn)行校準(zhǔn)。相反，使用過(guò)于粗糙的標(biāo)準(zhǔn)會(huì)導(dǎo)致失敗。
Ignoring finish when making standards is a sure way to ensure your standard is not fit for the intended calibration. No UT Level III would want to calibrate on a pipe standard with a polished scanning surface measuring 16 Ra μin (0.8 μm) if the pipe to inspect measured 125 Ra μin (3.2 μm). Conversely, using a standard that is too rough for the job is a recipe for failure.
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