تدريب Shadowing: Material Properties 101 - تعلم التحدث بالإنجليزية عبر الفيديو
جارٍ إنشاء الدرس...
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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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المفردات وملاحظات التحدث لهذا الدرس
هذا الدرس في المحادثة بمستوى C1 مبني على الفيديو “Material Properties 101”. أكثر الكلمات تكرارًا في الفيديو: material, stress, ductile, brittle, strength. يحتوي هذا الفيديو على 85 جملة و1264 كلمة للتدرب على الترديد. مدة الكلام 6:06. يتكلم المتحدث بسرعة، نحو 207 كلمة في الدقيقة، لذا ستسمع كثيرًا من وصل الكلمات واختزال الأصوات. 82% من الكلمات ضمن أكثر 3,000 كلمة شيوعًا في الإنجليزية، ويُستحسن مراجعة الباقي قبل البدء.
أهم المفردات في هذا الفيديو
أصعب 15 كلمة في الفيديو، مع النطق والمعنى:
| الكلمة | النطق | المعنى |
|---|---|---|
| distress اسم | /dɪˈstɹɛs/ | مِحْنَة |
| fracture اسم | /ˈfɹæk.t͡ʃʰəː/ | كَسْر, اِنْكِسَار |
| graph اسم | /ɡɹæf/ | مُخَطَّط بَيَانِيّ |
| elastic صفة | /ə-/ | مَرِن |
| absorb فعل | /æbˈsɔɹb/ | اِتَّسَعَ, اِحْتَوَى |
| slope اسم | /sloʊp/ | مُنْحَدَر |
| axis اسم | /ˈæksɪs/ | مِحْوَر |
| abrade فعل | /əˈbɹeɪd/ | كَشَطَ, قَشَطَ |
| tailor اسم | /ˈteɪlɚ/ | خَيَّاط, خَيَّاطَة |
| displacement اسم | /dɪsˈpleɪsmɪnt/ | إِزَاحَة, نُزُوح |
| ceramic اسم | /səˈɹæmɪk/ | خَزَف |
| metre اسم | /ˈmiːtəɹ/ | مِتْر |
| mechanic اسم | /mɪˈkænɪk/ | مِيكَانِيكِيّ |
| hatch فعل | /hæt͡ʃ/ | حَضَنَ |
| cone اسم | /ˈkoʊn/ | مَخْرُوط |
القواعد في هذا الفيديو
أكثر التراكيب التي يستخدمها المتحدث، مع العبارات نفسها من الفيديو:
| التركيب | في الفيديو |
|---|---|
| المبني للمجهول be + اسم المفعول — التركيز على ما يحدث لا على من يفعله | will be uploaded · is defined · is found |
| المضارع التام have/has + اسم المفعول — حدث ماضٍ ما زال له أثر الآن | has occurred · we've seen · have broken |
| جمل الوصل who / which + جملة — معلومة إضافية عن شخص أو شيء | stress, which is · strength which is · material, which is |
نطق يحتاج إلى انتباه
يستخدم المتحدث 3 من الصيغ المختصرة، مثل I'll, we've, wouldn't. انطقها بصيغتها القصيرة كما تسمعها.
- أصوات “sh” و“zh”: deformation /ˌdɛfəˈmeɪʃən/, deflection /dəˈflɛkʃən/, sectional /ˈsɛkʃənəl/, consultation /ˌkɑnsəlˈteɪʃən/
- الكلمات الطويلة — انتبه لموضع النبر: deformation /ˌdɛfəˈmeɪʃən/, allowable /əˈlaʊ.əbəl/, personalize /ˈpɜː.sə.nə.laɪz/, characteristic /ˌkæɹ(ə)ktəˈɹɪstɪk/, consultation /ˌkɑnsəlˈteɪʃən/
أصوات يجدها متحدثو العربية صعبة:
- /p/ — ليس /b/: انطقه مع نفخة هواء: slope /sloʊp/, aspire /əˈspaɪɚ/, personalize /ˈpɜː.sə.nə.laɪz/, displacement /dɪsˈpleɪsmɪnt/, upload /ˈʌpˌloʊd/
- تتابع الصوامت — لا تضف حركة بينها: distress /dɪˈstɹɛs/, brittle /ˈbɹɪtəl/, fracture /ˈfɹæk.t͡ʃʰəː/, deform /dəˈfɔɹm/, hardness /ˈhɑɹdnəs/
كيف تتدرب بهذا الفيديو
- استمع إلى الفيديو كاملًا مرة واحدة دون أن تتكلم، ودوّن الكلمات التي لا تعرفها.
- ابدأ بسرعة 0.75×، وردّد جملة جملة، ثم عُد إلى السرعة العادية عندما يصبح الأمر سهلًا.
- سجّل صوتك وقارنه بالأصل، مع الانتباه إلى كلمات مثل distress, fracture, graph.
ما هي تقنية التظليل الصوتي؟
التظليل الصوتي (Shadowing) تقنية تعلم لغة مدعومة علمياً، طُورت أصلاً لتدريب المترجمين الفوريين المحترفين. الطريقة بسيطة لكنها قوية: تستمع لصوت إنجليزي أصلي وتكرره فوراً بصوت عالٍ — كظل يتبع المتحدث بتأخير 1-2 ثانية. تُظهر الأبحاث تحسناً كبيراً في دقة النطق والتنغيم والإيقاع وربط الأصوات والاستماع والطلاقة.