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  2. CORRELATION BETWEEN HUMAN FACTORS AND ERGONOMICS.pdf
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  5. I can't comment on the content but the author is unfamiliar with formatting using MS Word.
  6. Why is there a sudden change in spacing on p. 8 and again on p. 11? This makes for a strange looking document. DrD
  7. Anyone have information how to manually calculate the strength and a life time of a modular/any spreader bar? Thank you!
  8. Wet region has dof 1 but we require 2 intensive properties (pressure and dryness fraction ) to tell the state of system so its dof should be 2 this is my doubt?
  9. In the endurance limit modifying factors, there was a Kb or size factor. In the book that I have, it is expressed in maximum diameter of 254 mm. How if I have diameter larger than 254 mm? Thank you.
  10. Hi Danyhil Its a simple moment calculation....the force of the weight of the table the moment (or hinge effect) against the fulcrum (in this case the corners). As the castors are on the corners, any load that will cause the table to topple will be overhanging the edge. 1. find CoG 2. calculate moments to edge of table. (force time distance) 3. Determine CoG of item being calculated and the distance from the fulcrum the force applies - calculate the moment. If both moments apply in the same direction, they are balanced by the legs...if they are in different directions, it is down to whatever is the highest whether it topples or not....but as the legs are on the corners, the CoG would have to overhang which would cause the item ON the table to fall off before the table toppled anyway.
  11. That's a near perfect example of fatigue stress crack propagation. Basically, the repeated impact loading from the jumping has caused a crack to propagate from the thread extend to the point that the material has suffered catastrophic failure. the "tree-ring" appearance on the RHS of the image shows this...but that said, the vertical cracking is a little "odd" and out of place...it's not a simple as it first appears. Whilst it is difficult to be sure with out a full analysis, I would suggest that this is a minor manufacturing defect that has been the propagation source, and that this is unlikely to repeat, but again... Basically, if properly preloaded, the direct load on the axle is minimal, and you should get a cup/cone fracture if any....ie a failure in tension. This is a stress propagation failure, suggesting that one of two possibilities... 1: there was a minor flaw which was the source of a fatigue stress crack and ultimately the failure. 2: the bolt was not suitably preloaded, allowing the stress to act in a non-design way. Thinking through....I think its a combination of both 1 and 2. If preloaded, the "cones" (or the bearings - subject to the design) take the loading by friction on the load-faces and the axle, only tension. The image sort of suggests (and again there is insufficient information to be 100% sure) that the loading has been a flexing one for a significant period of time. The other failure mode would be shear...which this sort of indicates...but again this would be down to a bolt not tight enough as the friction of the load-faces should take all of the loading thus eliminating the shear. I'd suggest just getting hold of a new standard axle and tighten the bolts properly...and if jumping regularly...checking it is tight regularly! All the best
  12. Image: https://postimg.cc/BX74G6BZ Hey, I need some help. I want to build an automatic pill dispenser. But I just can´t find a good (good in terms of cheap) solution. So here´s the deal: I want to make sure that only ONE pill can fall down at a time. One problem is that every drug has a different size, so therefore you need a system, that can handle every size. As you can see in the image, my idea was to use some sort of rotable roll, which has a gap. Inside that gap only one pill can fall into, since there is no more space left. Then the roll rolls over and the drug just falls down. Due to the fact that I would like to have 9 different sizes and that only 3 different sizes can fit on one roll, I would need 3 rolls. Doesn´t sound expensive? Well first of all I would need an engine, since I want to move the rolls, so different sizes can be under the output. Secondly, if you imagine having 200 boxes and under each of these boxes you want to place 3 rolls, than I would need 600 rolls and 200 small engines. That sounds like a lot of work. Maybe one of you guys has an idea. I just have to make sure that only one pill can fall down at a time. Note: Sorry for bad english Thanks!
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  14. Hi mates, I need some help in a project. In short, I have a part of a mechanical assembly, and this part broke due to material failure. I need to propose a solution only by changing the material, not the desing (at least, the main focus have to be only change the metal...). This is an axle from a BMX jump bike, it failed on me suddenly. Actually, I didn't realize at the moment that it broke into 2 pieces. A friend of mine asked for the bike and I gave it to him, he jumped in and asked what's wrong with the front hub since it was like "loose"... The nuts were in place, all seemed fine but it really had a little gap. When we were loosening the nut, we realized that we had two separate pieces of the axle, lol. Here are some amplified images of the axles and the fractures from the two perspectives. I noticed that the failure started right in the last thread of the axle, meaning that it had stress concentration caused by the thread cavity. What information can you deduce when looking at the fracture? The axle is made of Chromoly (I think it's 4130 or 4140 Cr-Mo, correct me if I'm wrong). The diameter (almost uniform along the axle) is 3/8" of an inch (around 0.95 mm). The total lenght of the axle is around 16.25 mm = a little bit more than 5/8 inch. I will attach a diagram to show up what's the situation. The words are "gancho"=dropout, where the fork of the bike sits the axle. "Apoyo rodamiento" = where the bearing seats on the axle. The distance (c to c) of the two sites is 18.5 mm = almost 3/4 inch, so I assume that there's some bending involved due to the separation, and it's not only shear stress. There's also a lot of fatigue because of the abusive nature of BMX tricks (mostly street BMX tricks, when you ussually land tricks with your bike from more than 5 ft). Looking at the image where the 2 pieces are, we can see the threaded piece and at left there's the another one, the mirror-like polished site right there is where the bearing sits (it's a sealed catridge bearing). The fracture occured closer to the bearing seat, on the first thread like I said before (stress concentration?)... Images at https://filebin.net/6j8yeglbvyylqgwg Thank you in advance for any reply! Matt.-
  15. Can an engineer, review and stamp plans prepares by someone else?
  16. Is there any Job for fresher btech mechanical 2016 passout

  17. There is a vide range of bearing blocks readily available in the market, if the required design doesn't falls in that, prepare detailed manufacturing drawings of all the parts and get it made from the supplier. After all any machine is an assembly of standard bought out parts, manufactured parts and hardware.Bill of materials to prepared first.
  18. Does anyone know what the principle of the work is a valnut cracking and shelling machine, how they work, does anyone have any drawings about it. For example, like the ones in the picture
  19. I'm facing this problem from a very long time. Let's say you founded a Patent/Design that fits perfectly for your needs. Now the problem is how can you realize that design? ( Design in Solidworks is ready but physically it's not ) How can you make from a block steel to the required machine? I know that has to happen using milling machine, lathe and other different types machines and processes but what's the exact procedure? How the marking has to be done? Any books or documentation about this? I know that this is vague but there should be something about this. Eg. Let's say a bearing block. How that has to be made ?
  20. 304 stainless steel and 316 stainless steel—What’s the difference?

    Selecting the best grade for stainless steel investment casting can mean longer lasting performance, especially in challenging corrosive environments.304 and 316 are the two of the most widely used stainless steel casting grades in the world. For 304 stainless steels and 316 stainless steels,There is no such definition of “which is good” because different stainless steel materials have different uses.The difference between 304 stainless steel and 316 stainless steel is as below.

    1-Different chemical composition:

      304 is Gai’s stainless steel . Its material composition is OCr18Ni9. 304 Stainless steel: C ≤ 0.08 Ni 8.00 to 10.00 Cr 18.00 to 20.00, Mn <= 2.0 Si <= 1.0 S <=0.030P <=0.035.

      316 is Austenitic stainless steel.The material composition is OOCr12Mo2Ti. 306 Stainless steel C≤0.08 Ni10.00~14.00 Cr16.00~18.00, Mo2.00—3.00 Mn<=2.0 Si<=1.0 S<=0.030 P<=0.035 And 306L stainless steel C≤0.03 Ni10.00~14.00 Cr16.00~18.00, Mo2.00—3.00 Mn<=2.0 Si<=1.0 S<=0.030 P<=0.035.It is a low carbon stainless steel with titanium-containing, resistant to alkali and acid (except medium containing chloride ions).

      The Big difference between 304 and 316 is that 306 stainless steel has 2-3 more nickel than 304 stainless steel.

      304-vs-316-stainless-steel

      2. Performance is different:

      304 steel can resist corrosion by sulfuric acid, phosphoric acid, formic acid and urea. Applicable to general water, control gas, wine, milk, CIP cleaning liquid and low occasions or no corrosive materials.

      The 316L steel grade adds molybdenum based on 304 Steel. It can significantly improve its resistance to intergranular corrosion and oxide stress corrosion. It also reduces the hot cracking tendency during welding. It also has good resistance to chloride corrosion.

      It is often used in applications of pure water, distilled water, medicines, sauces, vinegar, etc.With high hygienic requirements and strong media corrosion resistance.The price of 316L is almost twice than 304.

    On Mechanical properties: 304 is better than 316L. Because 304, 316 has excellent corrosion resistance and heat resistance. It is widely used as stainless steel. 304,316 has similar strength and hardness.

      The difference between them is that the corrosion resistance of 316 is much better than 304. The more important point is that molybdenum metal is added to 316. The molybdenum metal can improve its heat resistance prosperity.

      3. Different maintenance methods:

      We can use electroplating or oxidation-resistant metals to ensure the carbon steel surface, but this protection is only a film. If the protective layer is destroyed, the underlying steel begins to rust.

      The corrosion resistance of stainless steel depends on the chromium element. When the amount of chromium added reaches 10.5%, the atmospheric corrosion resistance of stainless steel will increase significantly. But if the chromium content is higher, it still can improve certain corrosion resistance. But not obvious.

      The reason is that this treatment changes the type of surface oxide to a surface oxide like that formed on pure chrome metal. But this oxide layer is very thin. Through it, you can directly see the natural luster of the steel surface. To give stainless steel a unique surface.If the surface is destroyed, the exposed steel surface will react with the atmosphere. This process is actually a self-repairing process. Re-forming this passivation film can continue to protect.

      Therefore, all stainless steels have a common characteristic. The chromium content is above 10.5% and the preferred steel grade also contains nickel. Such as 304 .If the addition of molybdenum can further improve atmospheric corrosive. Especially against chloride-containing atmospheres. That is 316.

    What is the 304 Stainless Steel Types and Applications?

    304 Stainless Steel Types Different Applications
    Stainless Steel 304 (S30400): 
     
    Low-carbon modification of type 302 for restriction of carbide precipitation during welding. Chemical and food processing equipment; brewing equipment; cryogenic vessels; gutters; downspouts; flashings.
     Stainless Steel 304L (S30403): Extra-low-carbon modification of type 304 for further restriction of carbide precipitation during welding. Coal hopper linings; tanks for liquid fertilizer and tomato paste.

    What is the 316 Stainless Steel Types and Applications?

    316 Stainless Steel Types Different Types’ Applications
      Stainless Steel 316 (S31600): Higher corrosion resistance than types 302 and 304; high creep strength. Chemical and pulp handling equipment; photographic equipment; brandy vats; fertilizer parts; ketchup cooking kettles; yeast tubs.
     Stainless Steel 316L (S31603): Extra-low-carbon modification of type 316 Welded construction where intergranular carbide precipitation must be avoided. Type 316 application requiring extensive welding.
     Stainless Steel 321 (S32100): Stabilized for weldments subject to severe corrosive conditions, and for service from 800 to 1600 F. Aircraft exhaust manifolds; boiler shells;process equipment; expansion joints; cabin heaters; fire walls; flexible couplings, pressure vessels.

      We are a professional stainles steel foundry in China with 22 years history.We can make all types of stainless steel castings, not only limited to 304 and 316, but can also make stainless steel investment castings with other grades, such as PH17-4, CG8M, 2205, ect. Any project or product about stainless steel casting, welcome contact us freely.

  21.   We are the lleading investment casting foundry for various metal components in 1997. And we have started our exporting business all over the world.Such as American, Japan, German,Australia, UK, Canada,ect.

      Currently, our investment casting company has 2 units: one is foundry,Another one is CNC Machining Factory.There are total 310 workers in our factory, with 265 workers, 7 engineers, 23 QC man, 10 sales person, and 5 management.Via many years’ hard working,we are now have become one of the largest investment casting manufacturer and supplier

  22. Dear Alban, Absolute symmetry is truly rare. Consider the case of a table on four legs of equal length. By your argument, all four legs each carry 1/4 of the total weight. Everything is perfect, the floor is level, the table is flat, the legs are all equally long. But now enter a tiny bit of reality (ever so slightly!). One of the legs is short by 0.0001 mm. To the eye, it appears that perfect symmetry still exists, but in actual fact, one of the four legs no even longer touches the floor. Do you still think that each leg in contact with the floor carries only 1/4 of the weight? What holds up the remaining quarter of the weight? DrD
  23. Hello, in some cases you may circumvent the problem of solving a statically indeterminate system, if symmetry exists. In the ideal case of a table you have quarter symmetry, what makes it easy, to determine the leg forces. However, you have to be able to identify existing symmetry. In other cases solving the problem may be simplified by the existence of some guiding equipment. Regards Alban
  24. The effect of several hot pressing parameters on the internal mat environment was investigated by using the mathematical model and the results were compared to data collected experimentally. The different pressing parameters included three initial mat moisture contents (5, 8.5, 12 %), three final panel densities (609, 641, 673 kg/m3 or 38, 40, 42 lb/ft3), two press platen temperatures (150, 200 °C), and three press closing times (40, 60, 80 s). The variation of temperature and total gas pressure during the press cycle at six points in the vertical mid-plane of a single layer, random mat structure was predicted with the heat and mass transfer model using the different pressing conditions. Twenty-four boards were manufactured according to the same specifications, and the temperature and internal gas pressure were measured with thermocouples and gas pressure probes at the same six locations. The model predicted data described the major trends during the hot-compression operation qualitatively. However, further work is needed to make quantitative predictions. A hot-compression model was developed based on fundamental engineering principles. The material physical and transport properties were the best available values from the literature or best estimates based on engineering judgment. A sensitivity study assessed the relative importance of the different transport properties during the hot-compression process. The response of selected variables of the hot-compression model for a perturbation of the parameter values was investigated. The sensitivity analysis of the model parameters revealed that the thermal conductivity and gas permeability of the mat have the greatest influence on model results. The assessment of these transport properties experimentally, as a function of mat structure, is highly desirable and can considerably improve the model predictions. EFFECT OF HOT PRESSING ON THE INTERNAL MAT ENVIRONMENT.pdf
  25. Very little investigation has been carried out to study the performance of flat heat pipes, though researchers recently turned their attention to the same. The results of the literature review on heat pipes indicate the necessity and scope for further theoretical and experimental studies on flat rectangular heat pipes. The present work is an attempt to study the steady state operation of the flat rectangular heat pipes, both theoretically and experimentally. It also aims at the study of the influence of the amount of working medium and wick porosity on the performance of heat pipes. Heat Transfer and Fluid Flow Studies on Flat Heat Pipes.pdf
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