쉐도잉 연습: Material Properties 101 - 영상으로 영어 말하기 배우기
레슨 만드는 중...
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This video is going to be a bit different to my usual videos, but I want to talk about material properties and the words we use to describe them.
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This is information you are going to need to fully understand future videos.
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By the end of this video, I want you to understand 6 keywords that we use to describe materials.
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These are stiff, strong, ductile, brittle, tough and hard.
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With these words, you will be able to describe pretty much any material
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and better understand why certain materials are used in different applications.
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More technical videos like this will be uploaded to my second channel from now on, which you can subscribe to by following this link.
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I'll try and back up the technical stuff with interesting real-world examples.
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First we are going to learn what a tensile test is.
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A tensile test is a fundamental test in material mechanics.
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It's performed by pulling a sample of material apart until failure, while measuring the force and displacement.
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It provides us with something called a stress strain curve, which tells us a lot about the material's reactions to forces.
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In this scenario, the stress is defined by the force applied to the test sample, divided by the cross-sectional area.
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This gives us units of newtons per meter squared, which you may recognize as the metric unit for pressure, Pascals.
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Stress goes on the y-axis.
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Strain describes how much deformation has occurred with that applied force, and it is found by dividing the change in length by the original length.
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This is placed on the x-axis.
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Let's watch this test again and see what information we can get from the stress strain graph.
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As the stress rises, the material begins to deform.
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This initial linear region is elastic deformation, That means if we remove the force, the material will regain its original shape.
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Think of how a rubber band can deform hugely and still come back to its original shape.
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The end of this linear elastic deformation is marked by the yield point.
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From here out, any additional stress will cause permanent deformation.
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This is called plastic deformation.
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The stress continues to rise until it hits the ultimate tensile strength point.
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This is the ultimate strength of the material, the most stress it can handle.
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From here, less stress is needed as the material begins to decrease in cross section, which you can see happening here.
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This is called necking.
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This continues until the material fractures.
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We can get a lot of really useful information from this graph.
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The first is Young's modulus, otherwise known as the elastic modulus.
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This describes how stiff the material is, and it is obtained by finding the slope of this linear region.
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A steeper slope means a stiffer material.
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For example, a high carbon steel may look like this, whereas a flexible material with the low Young's modulus, like rubber, would look like this.
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This graph is not to scale, but it should give you an idea of how this information is represented.
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Young's modulus is one of the most used properties in engineering, as we can use it to predict deflection in a huge range of scenarios.
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Yield strength and ultimate tensile strength are two other important properties.
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An engineer will divide the yield or ultimate strength by the safety factor to achieve the max allowable stress, which is used to influence the design of the product.
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Usually engineers will aim to keep the max possible stress well below failure, but safety factors differ between industries.
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So we've seen a stiff material and a flexible material.
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Now let's look at a material in between.
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This material can be described as tuff and ductile.
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Tuff simply means the material can absorb a lot of energy without breaking.
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The area under the graph here defines how much energy is absorbed.
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Ductile means it deforms under pressure.
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The two previous materials could also be considered ductile.
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Springsteel is a tough and ductile material with a high yield strength which is why it is used in springs.
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Springs need to absorb energy without permanently deforming.
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The opposite of ductile is brittle.
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A brittle material is a material that breaks with very little deformation.
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Glass, ceramics and cast iron all fall into this category.
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You can actually tell if a material is brittle or ductile by examining the fracture surface after they have broken.
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A ductile material will have this characteristic cup and cone fracture surface, whereas brittle fractures have granular flat looking fracture surfaces.
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Some materials can go from ductile to brittle when their temperatures are lowered.
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This was actually a massive problem during World War 2 with the Liberty ship.
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Several Several of these ships literally broke in half with no warning, including the SS John P.
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Gaines, which broke in half in the frigid waters of the Bering Sea.
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It was later discovered that the grade of steel being used became brittle at lower temperatures.
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This problem was made worse by the stress concentration at the hatches, which you learned about in my first video, Why are plane windows round?
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This embrittlement is also thought to have contributed to the fracture of the titanic's hull.
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The final material property I want to talk about is hardness.
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It is directly related to the stiffness and yield strength of the material, but it is used to describe how difficult it is to dent, scratch and abrade materials.
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One way this material property is measured is with the Rockwell hardness test.
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This test involves three steps.
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First a minor load is applied to the material by an indenter.
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This establishes a zero point.
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For the second step, a major load is then added, which indents the material.
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And for the final step, the major load is removed, while maintaining the initial load.
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The difference in depth between the first and third step is then used to calculate the hardness of the material.
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Diamond is a very hard material, which is why it is used in cutting tools.
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One of the fantastic properties of steel is its ability to be heat treated, to have its hardness tailored in different areas.
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For example, with swords you want your cutting edge to be hard but the core of the blade to be ductile.
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This means the sword can bend under pressure without breaking, while the cutting edge can resist damage.
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As always, thanks for watching.
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이 레슨의 어휘와 말하기 포인트
이 C1 수준 말하기 레슨은 영상 “Material Properties 101”을(를) 바탕으로 합니다. 가장 자주 반복되는 단어는 다음과 같습니다: material, stress, ductile, brittle, strength. 이 영상에는 섀도잉할 문장 85개와 단어 1264개가 있습니다. 말하는 구간의 길이는 6:06입니다. 화자는 분당 약 207단어로 빠르게 말하므로 연음과 약하게 발음되는 소리가 많습니다. 단어의 82%가 영어에서 가장 많이 쓰이는 3,000단어에 속합니다. 나머지는 연습 전에 미리 확인해 두세요.
이 영상의 핵심 어휘
영상에서 가장 어려운 단어 15개를 발음, 뜻과 함께 정리했습니다.
| 단어 | 발음 | 뜻 |
|---|---|---|
| fracture 명사 | /ˈfɹæk.t͡ʃʰəː/ | 골절 |
| stiff 형용사 | /stɪf/ | 딱딱한 |
| graph 명사 | /ɡɹæf/ | 그래프, 도표 |
| tuff 명사 | /tʌf/ | 응회암 |
| axis 명사 | /ˈæksɪs/ | 축 |
| keyword 명사 | /ˈkiː.wɜːd/ | 키워드, 핵심어 |
| tailor 명사 | /ˈteɪlɚ/ | 재단사 |
| ceramic 명사 | /səˈɹæmɪk/ | 세라믹스, 세라믹 |
| metre 명사 | /ˈmiːtəɹ/ | 미터, 메터 |
| mechanic 명사 | /mɪˈkænɪk/ | 정비공, 기계공 |
| hatch 동사 | /hæt͡ʃ/ | 부화(孵化)하다 |
| cone 명사 | /ˈkoʊn/ | 원뿔 |
| calculate 동사 | /ˈkælkjʊleɪt/ | 정산하다, 계산하다 |
| newton 명사 | /ˈn(j)uːtən/ | 뉴턴 |
| characteristic 명사 | /ˌkæɹ(ə)ktəˈɹɪstɪk/ | 특성, 특징 |
이 영상의 문법
화자가 가장 많이 쓰는 문형을 영상 속 실제 표현과 함께 정리했습니다.
| 문형 | 영상 속 표현 |
|---|---|
| 수동태 be + 과거분사 — 누가 하는지보다 무슨 일이 일어나는지에 초점 | will be uploaded · is defined · is found |
| 현재완료 have/has + 과거분사 — 과거의 일이 지금도 관련이 있을 때 | has occurred · we've seen · have broken |
| 관계절 who / which + 절 — 사람이나 사물에 대한 추가 정보 | stress, which is · strength which is · material, which is |
주의할 발음
화자는 I'll, we've, wouldn't 같은 축약형과 약화된 형태를 3번 사용합니다. 들리는 대로 짧게 발음하세요.
- “sh”와 “zh” 소리: deformation /ˌdɛfəˈmeɪʃən/, deflection /dəˈflɛkʃən/, sectional /ˈsɛkʃənəl/, consultation /ˌkɑnsəlˈteɪʃən/
- 긴 단어 — 강세 위치에 주의: deformation /ˌdɛfəˈmeɪʃən/, allowable /əˈlaʊ.əbəl/, personalize /ˈpɜː.sə.nə.laɪz/, characteristic /ˌkæɹ(ə)ktəˈɹɪstɪk/, consultation /ˌkɑnsəlˈteɪʃən/
한국어 화자가 어려워하는 소리:
- /f/ — ㅍ(/p/)으로 바꾸지 말고 윗니를 아랫입술에 대기: deformation /ˌdɛfəˈmeɪʃən/, fracture /ˈfɹæk.t͡ʃʰəː/, deform /dəˈfɔɹm/, stiff /stɪf/, graph /ɡɹæf/
- /r/과 /l/ 구별하기: brittle /ˈbɹɪtəl/, embrittlement /ɛmˈbɹɪtl̩mənt/, granular /ˈɡɹæn.jə.lə(ɹ)/, counselor /ˈkaʊnsələ(ɹ)/
이 영상으로 연습하는 방법
- 먼저 말하지 않고 영상을 끝까지 듣고 모르는 단어를 적어 둡니다.
- 0.75배속으로 한 문장씩 섀도잉을 시작하고, 익숙해지면 보통 속도로 돌아갑니다.
- 자신의 목소리를 녹음해 원본과 비교하고, fracture, stiff, graph 같은 단어에 특히 주의합니다.
쉐도잉이란? 영어 실력을 빠르게 키우는 과학적 방법
쉐도잉(Shadowing)은 원래 전문 통역사 훈련을 위해 개발된 언어 학습 기법으로, 다언어 학자인 Dr. Alexander Arguelles에 의해 대중화된 방법입니다. 핵심 원리는 간단하지만 매우 강력합니다: 원어민의 영어를 들으면서 1~2초의 짧은 지연으로 즉시 소리 내어 따라 말하는 것——마치 '그림자(shadow)'처럼 화자를 따라가는 것입니다. 문법 공부나 수동적인 청취와 달리, 쉐도잉은 뇌와 입 근육이 동시에 실시간으로 영어를 처리하고 재현하도록 훈련합니다. 연구에 따르면 이 방법은 발음 정확도, 억양, 리듬, 연음, 청취력, 말하기 유창성을 크게 향상시킵니다. IELTS 스피킹 준비와 자연스러운 영어 소통을 원하는 분들에게 특히 효과적입니다.