Luyện nói tiếng Anh bằng Shadowing qua video: WELDING DEFECTS!! Porosity, Arc Strikes, Undercut
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Hola, buenos dias.
Xin chào, chào buổi sáng.
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Bienvenidos para weld .com.
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Oh, wait, sorry.
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Hey guys, welcome back to another episode of weld .com.
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Today we're gonna talk about discontinuities.
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So it's gonna be the first video of a series
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and we're just gonna go through and take you step by step and we're gonna address different weld discontinuities, how to avoid them, what they are,
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common mistakes involved with them.
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Note that a welding discontinuity does not automatically call for a rejection okay
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so while all defects are discontinuities not all discontinuities are well defects
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so depending on
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which code book you're working with you are a lot of a certain amount of undercut per linear inch
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you're allowed a certain amount of porosity per diameter and linear inch
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so there's just different things and it all depends on
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which code you're working with i don't want to get into the specifics of it
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because if i say one thing somebody's going to say well that's not how it is in my code
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and this is just a general weld discontinuities how to identify them
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and then how to avoid them in the future
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so we're going to go ahead
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and get right into it probably the most we're going to address the three most common today
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which is undercut porosity and arc strikes
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so we're going to start there they're pretty basic we're going to show you how to avoid them
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and what exactly what they are okay
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so the first one we're going to talk about is undercut
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so undercuts pretty common what that is it's an eroded edge along the toe of one
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if not both of the toes of the weld so essentially what
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that does is
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if i have undercut on both sides of this material this material is 3 8 thick
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and i have a 16th undercut on each side i've basically deducted a 16th from the thickness of this material
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so i have that's roughly uh 6 16ths
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now i'm down to 516 thickness the plate is no longer 3 8 of an inch thick don't know what
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that is a metric for you folks across the pond
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I do apologize camera guys got
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you covered he's gonna put some notes here maybe here somewhere
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he'll put some notes in what can cause undercut is improper travel speed
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so if I travel down this joint too fast I can get undercut
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and that's because I'm not giving that rod or that electrode time to fill in another thing is poor work angle.
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Ideally, what I want to have is half of my weld on the vertical part of this plate
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and half of it on the horizontal part of this plate.
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Now, I want to maintain an even angle between the two, so 45 is roughly where I want to be.
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If I start getting too far one way or the other, I'm bound to get undercut.
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I'm going to show you that here in a second.
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If I have a travel angle, or I'm sorry, a work angle that's too high, I'm going to get undercut along this top edge.
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So another thing that can cause undercut is if my arc length is too long.
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So ideally I want to keep my arc length no more than the diameter of this electrode.
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So if I have eighth inch electrode, I don't want to be any more than an eighth inch off the edge of that puddle.
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I like to stay close to the puddle.
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That's just me personally.
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It's just a habit I've developed, but you don't want to go any further than one eighth.
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You start getting outside of that area, you're going to start getting undercut.
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You have to think as I pull this rod further away from this plate, my voltage is going to increase.
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Okay, this is a constant current process.
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Stick welding is a constant current process.
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If I pull back far enough, the voltage becomes my variable.
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Okay, it'll increase when I pull back too far.
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It'll decrease when I get in too close.
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Because that additional voltage, it's going to start cutting away in the sides and it's not going to fill in properly.
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So we'll go ahead and we'll put all those together and we'll see if we can whip you up some undercut.
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So as you can see the work angle that I have here is improper.
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It's way too high.
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It's a lot higher than what I need.
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If you want to bring this down you can bring it down to about a 45 degree angle
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and that should be about where you want it.
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This weld we're doing everything wrong.
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Okay travel speed is too high, work angle is incorrect, amperage is set up you know a little bit above normal just
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so I can produce that undercut so I can show those that don't know exactly what it is what to look for.
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But because the angle, the speed, I ended up with that undercut on that top edge, which is where I wanted it.
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You know, if I was welding vertical, you know, you could get undercut on the left
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or the right -hand side just because you're not spending enough time on the sides.
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But here, it's going to be more prevalent on the vertical piece
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or the top leg or the top toe of that weld that you're going to put in there.
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Another thing you see in here because that excessive arc length
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when I pulled back is I had excessive spatter on the workpiece as well
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so that's just kind of like molten metal that's that's popping off
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or because the puddle's too hot you know it's kind of bouncing out there's too much energy in there
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and this stuff's going to spray all over the place.
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You want to get rid of that also you don't want to leave
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that on your plates especially if you know you're getting and weld inspections, you know, the inspectors are gonna look for that.
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Go ahead, take your time, clean up your plate.
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Next thing we're gonna talk about is arc strikes.
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So arc strikes happen for mainly one reason.
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and possibly two arc strikes are typically caused due to carelessness recklessness
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you're not paying attention accidentally touch the work piece you know with a live electrode
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and you scrape down there it's discontinuity
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you want to avoid arc strikes in your weld material
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they can cause micro cracks outside of the welding area especially
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if on a building or a structure that's cyclically loaded
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that little micro structure those little cracks in there they can start propagating through the weld metal or the base metal.
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So you don't want arc strikes on your material.
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It's going to be up to the inspector whether he's going to have you cut that piece out,
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remove it, repair it, whatever the case may be.
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So you want to avoid arc strikes.
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The biggest thing that I see that causes arc strikes, like I said, is carelessness.
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But when students are first, well, students and experienced welders, when they strike the arc and they get stuck,
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they want to fight the rod back and forth
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and just kind of pop it off
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there you know versus just disconnecting the stinger letting the electrode sit there for a second cool off
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and then snap it what happens is once this becomes stuck
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and I start moving back and forth I don't know
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when it's gonna break free this thing breaks free
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and then I get arc strike all the way across my plate way outside of my welding zone
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that's what you want to try to avoid all right next we're going to talk about piracy
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or tiny little weld bubbles that are in your weld what can cause porosity is
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if you're welding and it is too windy outside so
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if you're using a gas metal arc welding process outside
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and it's too windy
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you can get porosity using flux core outside up to a certain amount of miles per hour of the wind
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you can get porosity that way
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if you're not using the appropriate cubic feet per hour of shielding gas for gas metal arc welding process
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you can get porosity hydrocarbons such as wd -40 or paint or anything like that that is on the base material
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If you don't clean that off, that can cause porosity as well.
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So we're going to go ahead and get into it and show you exactly what porosity looks like.
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So we're welding along normal.
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Now Man Cub's going to hit the weld zone with a
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little bit of compressed air to simulate a big gust of wind coming through or welding outside.
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So as you can see, everything's pretty unruly.
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No gas coverage, getting porosity, trailing the weld.
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It's not a good condition.
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Very blustery day under here.
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All right guys, so that's pretty much porosity in a nutshell.
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You can get porosity with pretty much any welding process that you do.
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It's all about gas coverage and shielding that weld pool, keeping everything nice and clean in that area, taking off any mill scale,
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dirt, debris, hydrocarbons, oils, solvents, anything like that.
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Fluxicore arc welding is also prone to wormhole porosity,
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so that's a different type of porosity you typically don't get with shielded metal arc welding or gas metal arc welding.
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Go ahead and check out our previous video, How to Avoid Wormholes, if that's something you're experiencing.
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That pretty much concludes this episode.
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Like I said, it's the first of a series.
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So I hope you guys learned something.
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Make sure you like and subscribe to the channel.
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Follow us on Facebook and Instagram.
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Make sure you hit that little bell button down here.
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You'll get new notifications every Monday, Wednesday, and Friday at 5 .30 Eastern Standard Time when we release new videos.
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And until next time, make every weld better than your last.
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Take three. And action.
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What the .
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Did you guys see that?
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That's what I got to put up with.
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Hello again.
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Từ vựng và ghi chú luyện nói cho bài học này
Bài luyện nói này dựa trên video “WELDING DEFECTS!! Porosity, Arc Strikes, Undercut”. Những từ được nhắc lại nhiều nhất trong bài: arc, weld, undercut, welding, porosity. Video này có 139 câu và 1686 từ để luyện shadowing. Phần lời nói dài 8:29. Người nói nói nhanh, khoảng 199 từ mỗi phút, nên sẽ có nhiều chỗ nối âm và nuốt âm. Chỉ 81% số từ nằm trong 3.000 từ tiếng Anh thông dụng nhất, nên từ vựng khá khó.
Từ vựng quan trọng trong video
15 từ đáng học trong video, kèm phiên âm và nghĩa:
| Từ | Phiên âm | Nghĩa |
|---|---|---|
| angle danh từ | /ˈæŋ.ɡəl/ | gốc |
| shield danh từ | /ˈʃild/ | khiên, lá chắn |
| eighth tính từ | /eɪtθ/ | thứ tám |
| voltage danh từ | /ˈvəʊltɪd͡ʒ/ | điện áp, hiệu điện thế |
| thick tính từ | /θɪk/ | dày |
| inspector danh từ | /ɪnˈspɛk.tɚ/ | người thanh tra, người kiểm tra |
| depend động từ | /dɪˈpɛnd/ | phụ thuộc |
| diameter danh từ | /daɪˈæmɪdɚ/ | đường kính |
| microwave danh từ | /ˈmaɪkɹoʊˌweɪv/ | vi ba, vi sóng |
| thickness danh từ | /ˈθɪknəs/ | dày |
| defect danh từ | /ˈdiːfɛkt/ | tật, lỗi |
| windy tính từ | /ˈwɪn.di/ | có gió |
| repair động từ | /ˈɹiːpɛɚ/ | chửa, sửa chữa |
| mill danh từ | /mɪl/ | cối xay |
| versus | /ˈvɝsəs/ | đối, đối đầu |
Cụm động từ bạn sẽ nghe
| Từ | Nghĩa |
|---|---|
| check out động từ | tính tiền, trả phòng |
| clean up động từ | quét dọn, quét tước |
| take off động từ | bỏ |
Những câu đáng luyện lại
Các câu ngắn, trọn ý trong video mà bạn có thể dùng lại khi giao tiếp hằng ngày:
- Today we're gonna talk about discontinuities.
- It'll decrease when I get in too close.
- It's a lot higher than what I need.
- This weld we're doing everything wrong.
- Did you guys see that?
Phát âm cần chú ý
Người nói dùng 59 dạng rút gọn, ví dụ we're, you're, don't. Hãy nói theo dạng ngắn đúng như bạn nghe.
- Âm “th”: eighth /eɪtθ/, thick /θɪk/, thickness /ˈθɪknəs/
- Âm “sh” và “zh”: shield /ˈʃild/, essentially /ɪˈsɛnʃəli/, inspection /ɪnˈspɛkʃən/, notification /ˌnoʊtɪfɪˈkeɪʃn̩/, rejection /ɹɪˈd͡ʒɛkʃən/
- Từ dài — đặt trọng âm cho đúng: diameter /daɪˈæmɪdɚ/, ideally /aɪˈdi.ə.li/, essentially /ɪˈsɛnʃəli/, accidentally /ˌæk.sɪˈdɛnt(ə)li/, apologize /əˈpɑləˌd͡ʒaɪz/
Những âm người Việt thường gặp khó:
- Cụm phụ âm cuối — đọc đủ từng âm, đừng nuốt âm cuối: shield /ˈʃild/, eighth /eɪtθ/, depend /dɪˈpɛnd/, defect /ˈdiːfɛkt/, bounce /baʊns/
- Âm /tʃ/, /dʒ/ và /ʒ/ — tiếng Việt không có, đừng đọc thành “ch” hay “gi”: voltage /ˈvəʊltɪd͡ʒ/, apologize /əˈpɑləˌd͡ʒaɪz/, rejection /ɹɪˈd͡ʒɛkʃən/, amperage /ˈæm.pəɹ.əd͡ʒ/
- Âm /æ/ — mở miệng rộng hơn âm “e”: angle /ˈæŋ.ɡəl/, crack /kɹæk/, diameter /daɪˈæmɪdɚ/, habit /ˈhæb.ɪt/, accidentally /ˌæk.sɪˈdɛnt(ə)li/
Cách luyện với video này
- Nghe hết video một lần, chưa cần nói, và ghi lại những từ bạn chưa biết.
- Bắt đầu ở tốc độ 0,75×, nói đuổi từng câu, rồi quay lại tốc độ bình thường khi đã quen.
- Ghi âm giọng mình rồi so với bản gốc, chú ý các từ như angle, shield, eighth.
Phương Pháp Shadowing Là Gì?
Shadowing là kỹ thuật học ngôn ngữ có cơ sở khoa học, ban đầu được phát triển cho chương trình đào tạo phiên dịch viên chuyên nghiệp và được phổ biến rộng rãi bởi nhà đa ngôn ngữ học Dr. Alexander Arguelles. Nguyên lý cốt lõi đơn giản nhưng cực kỳ hiệu quả: bạn nghe tiếng Anh của người bản xứ và lặp lại to ngay lập tức — như một "cái bóng" (shadow) đuổi theo người nói với độ trễ chỉ 1–2 giây. Khác với luyện ngữ pháp hay học từ vựng bị động, Shadowing buộc não bộ và cơ miệng phải đồng thời xử lý và tái tạo ngôn ngữ thực tế. Các nghiên cứu khoa học xác nhận phương pháp này cải thiện đáng kể phát âm, ngữ điệu, nhịp điệu, nối âm, kỹ năng nghe và độ lưu loát khi nói — đặc biệt hiệu quả cho người luyện IELTS Speaking và muốn giao tiếp tiếng Anh tự nhiên như người bản ngữ.