掌知視通訊技術 發表於 2020-12-29 15:57:34
在與VOGT Ultrasonics GmbH的合作中，設計了一個用於電子束焊接WCu部件和坯料的無損測試的試驗臺，通過超聲波相控陣技術在批量生產條件下進行檢測。通過用戶的設置和軟體分析，可以清晰、容易地識別WCu觸頭的焊接區質量，提高了工藝穩定性。超聲波測試臺的一個基本特性是可以根據定義的質量標準立即在線對工件進行分類。該測試的最大挑戰是生產中高頻次地掃描粉末冶金工藝生產的WCu複合材料組件，並評估焊接區質量。WCu部分通常是焊接到銅合金或鋼材上。由於種種原因，超聲波束在任何情況下都無法穿過均勻的材料。因此對不均勻的WCu部件進行測量，我們面臨的挑戰是如何避免由於WCu複合材料的微觀結構在密度、重量和均勻性方面存在較大差異而引起的超聲反射或偏轉。
01
高壓電弧觸頭的工作原理
Figure 1 shows a sketch how an arcing contact component system, consisting of a pin and a so called tulip, works. It is shown that by means of the design of the tulip a minimum spring force has to be achieved to get an optimized and reliable contact to the pin surface. Therefore a maximum of energy transmission can be guaranteed and arcing between the two components can be avoided.
圖1是由觸指和梅花觸頭組成的弧觸頭系統的工作簡圖。事實證明，通過對梅花觸頭進行優化設計，可以實現以最小的彈力獲得與觸指表面最佳和可靠的接觸。因此，可以保證最大限度的電能傳輸，並避免兩個觸頭之間起弧。
圖1 電弧觸點系統在閉合、導電位置的功能示意圖
02
WCu材料
A cross section of a typical WCu microstructure gained by sintering and infiltrating with copper is shown in figure 2. Typical compositions are 60 to 80 wt.-% W and 20 to 40 wt.-% Cu.
圖2中顯示了通過燒結和熔滲獲得的典型WCu微觀組織，其組成成分是60～80wt.%的W和20～40wt.-%的Cu。
圖2 典型WCu (80/20)微觀結構的截面
The inhomogeneous microstructure is caused by the very low solubility of W and Cu. The combination of the excellent electrical conductivity of Cu together with the good arcing resistance and high melting temperature as well as high arcing resistance of W, see Table I, results in the usage of contact material for energy transmission up to voltages of 1200kV.
鎢和銅的溶解度極低，導致了微觀結構的不均勻性。由於Cu具有優良的導電性，加上W具有良好的耐燒蝕性和較高的熔點（見表1），鎢銅觸頭材料適用於特高壓的斷路器滅弧室中。
03
超聲相控陣原理
In general the ultrasonic device transmits electrical pulses to the probe where these pulses are converted to ultrasound waves. After transmitting the waves the probe receives the reflected echos waves as well. All received waves are converted to electrical pulses again and are evaluated by the software. Phased Array probes are composed of several piezoelectric crystals that can transmit/receive independently at different times [5]. To focus or to steer the ultrasonic beam, time delays are applied to the elements to create constructive interference of the wavefronts. Due to this the ultrasonic beam can be steered within a range of angle and/or the energy can be focused at any depth in the test specimen (see Fig. 3).
一般情況下，超聲波設備將電脈衝傳送到探頭，這些脈衝被轉換成超聲波。在發射超聲波後，探頭也會收到反射的回波。所有接收到的波再次轉換為電脈衝，並由軟體進行評估。相控陣探頭由多個壓電晶體組成，可以在不同時間獨立發射/接收[5]。為了聚焦或引導超聲波束，對元件施加時間延遲，以產生波束的建設性幹擾。因此，超聲波波束可以被控制在一定的角度範圍內，並且/或者能量可以在測試樣品的任何深度聚焦（見圖3）。
圖3 波束控制和聚焦原理
04
相控陣超聲波試驗臺
The task of the ultrasonic scanning system is to test the weld of the tulip within the production cycle with an offline system. Thereby it detects non connected areas in the weld seam, measures the sizes and classifies the tulips in 「good」 or 「bad」 according to given guidelines. The inspection is done by immersion technique.
超聲波掃描系統的任務是在檢測周期內用離線系統檢測梅花觸頭的焊縫。因此，它檢測焊縫中的非連接區域，測量尺寸，並根據給定的準則將梅花觸頭分為 "好 "或 "壞"。檢測是通過浸入式技術完成的。
Depending on the type of tulip there are two possible probe positions to insert the ultrasonic beam perpendicular to the welding. Inspecting the 45 degree weld requires a probe position along the body. The 90 degree weld needs to be inspected from above (see figure 4).
根據梅花觸頭的類型，超聲波束檢測位置有兩種：檢查45度焊縫需要沿著焊縫主體的探頭位置，90度焊縫需要從上方檢查（見圖4）。
圖4 典型梅花觸頭的剖面圖（圖中標明了超聲束方向）
05
相控陣測試示例
Figure 7 (right picture) shows the C-Scan image recorded with a Phased Array system, the result of the conventional immersion inspection is shown in figure 6 as a linear illustration and in figure 7 (left picture) as a round illustration. Comparing both C-Scan images it is to be seen clearly the same results but the way of recording is different. Using Phased Array technique the whole data acquisition and scan imaging lasts no longer than 10 seconds, while the conventional inspection method needs about 2 minutes. Due to the limited capability of the chosen probe in this case the resolution is slightly worse compared to the immersion probe, but it is no effort to get the same resolution like in figure 9 by using another probe.
圖7（右圖）為相控陣系統記錄的C-Scan圖像，圖6為線性圖，圖7（左圖）為圓形圖。比較兩個C-Scan圖像，可以看到記錄方式不同，但結果相同。使用相控陣技術，整個數據採集和掃描成像的時間不超過10秒，而傳統的檢測方式需要2分鐘左右。由於所選探頭的能力有限，在這種情況下，解析度比浸入式探頭稍差，但要想得到圖6那樣的解析度，可以使用另一個探頭。
圖7 LS系統記錄的圓形圖像（左）和相控陣手持裝置記錄的圖像（右）
原文標題：輸配電用的W-Cu觸頭的無損超聲檢測過程控制
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