I’m confused about the impact test, I can’t figure it out
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This post is finally written by Jushi_YYVE on 2018-12-13 19:51 The editor read several posts on the forum yesterday and today, talking about impact tests. After reading this I became even more confused. The pressure vessel design training textbook states that the transverse performance of steel plates is worse than the longitudinal performance, so GB713 stipulates that transverse samples should be taken. But after looking at the standards, I feel conflicted. This is the sampling position specified in GB/T2975. From the picture, the V-shaped groove should run through the thickness direction. I found a video online that confirmed this. https://www.bilibili.com/video/av8799439/ screenshot: From the picture above, the impact direction of the pendulum in the impact test should be perpendicular to the length direction of the specimen. If the sample is taken along the rolling direction of the steel plate, which is what we call a longitudinal sample, then during the impact test, the impact is along the transverse direction. If the sample is taken along the width direction of the steel plate, which is what we call a transverse sample, then during the impact test, the impact is along the longitudinal direction. If this is correct, the transverse performance of the steel plate is better than the longitudinal performance, which is obviously the impact energy: The longitudinal impact energy of transverse specimens is greater than the transverse impact energy of longitudinal specimens. After searching on Baidu, the answer to some exam questions is that the longitudinal impact energy of the transverse specimen is > greater than the transverse impact energy of the longitudinal specimen. See picture below: Doesn’t this contradict what the book says? I asked a colleague and she didn’t understand it either. She said she was confused when looking at the standards in the past. He also showed me the previous standards.: Let’s not discuss the subsequent revision of the GB713-2008 version. Just say the picture above. One is Q345R of GB713, and the other is Q345B of structural steel GB/T1591. The impact energy index of the former is 34J for the transverse specimen, and the latter is 34J for the longitudinal specimen. If the conclusion mentioned above is true, it is reasonable that the impact energy of Q345R should be greater than 34J. After all, it impacts along the rolling direction, and the test value should be higher.
The impact performance in this direction is not difficult to understand. You can understand it by turning the pattern in the green picture 90 degrees.
You will understand when the sample in the green picture is rotated 90 degrees.
My understanding is that the longitudinally sampled transverse impact work pattern is what we need.
It seems that this is the only way to understand it. After reading the above content, I feel that I have been deceived. It is true that I cannot understand it from the words alone and the pictures. The steel material turned over GB713-2014 is indeed a transverse specimen. It seems that transverse specimens and transverse impact are not the same thing. I can't figure it out. @wanlirn @taozb What do you think?
The so-called longitudinal and transverse directions should refer to the direction of fiber elongation during rolling. The mechanical properties such as tension, bending and punching along the rolling direction of the steel plate are definitely better than those in the transverse direction.
The inspection rules in GB713-2014 say that transverse specimens should be taken for impact. Looking at the picture above, it seems that the transverse sample is taken in the direction of the plate width, so the impact is in the rolling direction. This kind of impact is equivalent to longitudinal impact, and the mechanical properties are excellent, which seems to be contrary to the original intention of the standard.
The diagram is correct. The length direction of the pattern is perpendicular to the rolling direction of the steel plate.
“There is no doubt that the transverse performance of the steel plate is worse than the longitudinal performance. As for the sampling direction and test direction, you can understand it according to that sentence. Sampling is taken in the vertical rolling direction - transverse sampling. The normal situation is rectangular. This is to make the test plate from the raw material and then sample from the test plate - still transverse. Normally, it is a "small strip", and the cross-section is mostly rectangular. At this time, the length direction of the small strip is the rolling direction of the steel plate, but when you do experiments, such as impact and drop weight, they are all in the vertical length direction, so the test is still the lateral performance of the plate. Generally speaking, this is the idea. If you are intuitive, you can use a pen to draw a picture, which will help your understanding. Let me add that this is a general situation and special cases will be treated specially. :)
Is this picture a horizontal sample? But when doing impact, the direction is the rolling direction. The impact force produced should be great. If this is the case, longitudinal specimens and transverse impacts should be made so that weak links can be tested.
You should think about it again, or find a piece of wood to look at. :lol