วีดีโอ

Rob, General belief is that the presence of chlorine will corrode metals and it is true. However, I do not have data for your type of application. It is interesting for me to know more about the additive molecule you are using. Could you share? Thank you.

@@engineeringmaterials-tribo5142 sure, can i contact you via email?

Good question. For any polymeric material, increasing temperature means reduction in tensile strength. This will happen very drastically. Even within a day or during seasonal changes from winter to summer, you can observe this change. For glass fibre reinforced composite, the same will happen but some what delayed effect. That means GFRP will be able to retain its strength at a higher temperature than the pure plastic. You will need to generate data if you want to know quantitative answer. Please do check in books or research papers.

Plastics Engineering by R J Crawford Mechanical Properties of Solid Polymers by I M Ward and J Sweeney. drive.google.com/file/d/11LTR8GDOGwYCE7fWBEV-vck6uKlRbmBd/view?usp=sharing

@@engineeringmaterials-tribo5142 Thank You 🙂

Thanks for the suggestion. This channel is for the general theory and concept understanding without too much of specialization.

If the yoghurt is easily flowable then the rheometer described in this video can be used. For yoghurt that does not flow like a fluid then perhaps you should conduct compression test, just like we do for cheese.

You are right, vacuum could be tried. Our specimen was quite large which prevented us from using vacuum. I also do not know if vacuum can help absorb more epoxy inside the bamboo fibres.

Thanks for asking. As relative speed increases, greater amount of fluid is pulled between the two surfaces because of the stick wall boundary condition between the fluid and the surfaces. More liquid coming in causes a hydrodynamic pressure at the interface and hence greater load bearing capacity is created. This causes the surfaces to move apart with thicker fluid film. Hence, the coefficient of friction decreases because there is no solid to solid contact anymore. In EHL, the above action happens but one more thing happens which is that the contacting surfaces deform elastically providing even thicker liquid film formation. For example, this is also the cause of hydroplaning when you drive at high speed through a pool of water when it is raining. The tyres deform and provide more water coming in between the tyre and the road surface. This effect is large when the tyres of the vehicle are little worn-out or smooth.

You make some equivalence between hardness (MPa) and the yield strength of the material which is the stress at which plastic deformation begins in tensile test. There is direct proportionality with the constant being somewhere between 2.8 to 3. Stiffness is the elastic modulus and hence not connected to hardness in the traditional sense.

mehanat karna hoga. practice kijiye.

Sorry, on that day I could not find a better one. Rightly pointed out.😊

@@engineeringmaterials-tribo5142 Sir, I'm in my final semester of UG Mech. Engg. Have discovered your teaching on tribology, of late; and found your lectures to be lucid and fluent which helped me to understand some of the Machine Elements lab experiments pertaining to the subject. Thanks!

Briefly storage modulus is actually the elastic modulus part and hence we can say Young's modulus. The word storage is used because it means the elastic energy is stored and can be recovered upon release of stress. The loss modulus is the part of energy that is lost due to viscous flow within the material. It is called loss modulus because that part of energy is lost in heat and other dissipative work.

kindly elaborate your question/comment. Thanks. 👍

It can also be applied to the contact between sphere and flat by just taking the radius of the flat as infinity.

Thank you for your response. But if I want to consider the JKR adhesive force between two spherical cylinders, would this formula still be applicable? Or what modifications should I make?@@engineeringmaterials-tribo5142

Friction coefficient is always calculated as the ratio of tangential force to the normal force. Please let me know if your question is different.

The final stress a specimen can withstand before fracture initiates. In a tensile stress-strain curve it should be the highest point on the stress axis.

And also what do you mean by volume percentage 70 of fiber can you explain it elaborately please

% can be calculated as weight % and also as volume %. For composites, always use volume %. This means 70% of the volume of the whole composite is the fibre.

preferably use same ASTM for continuous fibre composite. If short fibre composite then please check if ASTM has another standards for that.

time 23:55. Yes you have pointed out an important aspect of the data collection. Often the initial couple data may be totally different and need to be omitted. Also, every test must be repeated at the same set of conditions three times, at least.

you may kindly ask here in this comment section.

Energy required for fibre pull out depends upon the fibre-matrix adhesion strength. The adhesion strength is optimized so that the fibre fracture will happen after some fibre-matrix debonding. This is essential for toughness. Hence, it is a combination of the adhesion strength between the fibre and the matrix, and the fibre tensile strength which will decide the final toughness of the composite. Both are necessary.

It depends which department you are in. Rheological studies are generally carried out for polymers, lubricants etc. If you have conducted your research well then you should definitely try in similar kind of companies. You will need broad domain knowledge of the department you are in.

This has to be found in textbooks. Papers do not provide the basic understanding stuff.

You may be right. I have followed the case-studies and the news/video reports that came out after the failure. Modern nozzle design must be different than what was available at that time. Thanks for the comment.

@@engineeringmaterials-tribo5142 i worked in the anchor industry for 38 years. The only adhesive anchor that was mixed by spinning the rods into the holes was a glass capsule containing polyester resins. This project employed injected epoxy.

I keep hardcopy book. I do not have softcopy. It is worth buying if you are in this field.

@@engineeringmaterials-tribo5142 thanks a lot . Could you please tell me the full name of that book?

Time 5:45: You are correct in saying that this ratio is wrong. I rechecked and it should be 0.005. So, in subsequent calculations epsilon nought should be used as 0.005 which will give slightly changed values for all. The procedure of calculation is right. Thank you for pointing out this mistake. 👍👍

@@engineeringmaterials-tribo5142 Thanks!

I am not aware of a standard of GFRP reinforced concrete. What I can say is ASTM D7957/D7957M-17 can be used as Standard Specification For Solid Round Glass Fiber Reinforced Polymer Bars For Concrete Reinforcement. Standard D7205/D7205M − 06 also provides for the same application.

It can be used as long as it is tensile strength. The composite we used was also sandwich of woven fabric of glass fibre in epoxy.

Thanks. Both oil will turn very viscous at lower temperatures with non-Newtonian behaviour. Excel is directly obtained from the machine with columns of stress and strain rate data. So, it is easy to plot them and obtain viscosity.

The bituminous layer is highly viscous at normal temperatures but a higher temperatures it flows. This company makes instruments for bitumen at high temperature. For a very viscous liquid we can also use the capillary flow method (Saybolt) to measure kinematic viscosity.

You are right. Using the proper theory, the rheometer can be used to find out the viscosity of the liquid such as a lubricating oil that you put in your car.