student85

Hi all, Currently i'm have obtained results which shows that both longtiudinal and shear wave velocities increases after every round of fatigue test. Is there anyone can help me explain this phenomenon? is it due to the atomic structure in the material? if possible, plz give some websites or sources that can read more about them. thanks

Hi, currently i'm having question regarding the internal stress distribution for circular and rectangular shape soild. May i ask why their internal stress distribution is different? Is it because the inner sturcture or composition of the soild is different? Or is it their calculation of stress is different? Please kindly advice Thanks

Hi Enthalpy, thanks for your information. By the way, the material that i'm going to test is a strainless steel rod. So Enthalpy,do you mean that before i can do the calculation for force needed and number of cycle, i need to come out with the S-N curve? How do i come out with the curve? Either i go online to a find a similar one or i go collect information like the maximum stress of strainless steel and start doing experiment to produce a S - N curve myself? Sorry Enthalpy. just to inform you that actually i'm a electrical student. I do not have any background regarding material science.So thats why i need to ask a bit more detail. By the way, i found a website that indicates a kind of calculation for the force for the fatigue test, without using the S - N curve. http://blog.mechguru.com/machine-design/fatigue-stress-design-calculation-example/ May i ask is it accurate and am i able to use it?

Hi, I'm now facing problem on how to calculate the force, frequency and cycle needed for fatigue testing of a test sample. The force is refer to compression and tensile stress. Please kindly advice an solution regarding the above problem. thanks

By the way, i have another question. What is the different between x-ray tomography and x-ray micro-tomography? Is micro-tomography suitable to measure large material, example a metal rod ? It is because the reviews that i have read up seem like both methods can measure large material. while micro-tomography seem like can measure smaller things compare with tomography. Please kindly advice

Hi Enthalpy, thanks for your reply. Currently, i did not have the equipment in my hand, So i dont know which manufacturer should i ask. And: I want to detect micro-cracks, see its shape, exact position and measure its length.

Hi guy, currently i doing research on SAM (scanning acoustic microscope technique) techniques to measure the internal micro-crack for material. But now the problem i facing is, most of the reviews i found are using SAM technique to measure internal crack for IC chips. May i ask is SAM technique suitable for larger material, such as metal rod( length = 400 mm, diameter= 30mm)? Next , i was researching on the suitable frequencies to measure the internal crack for the metal rod. The frequencies range is 10MHz to 2000MHZ. But i also found out when the frequency increase, the penetration ability will decrease. So may i ask, what is the suitable frequencies range to measure the internal mirco- crack for a metal rod which is length = 400 mm, diameter= 30mm. Please kindly advice.

Basically, i will set a timing for the scanning. After finished scanning a small area, the stepper motor will rotate the rod for about 1 degree. After the rod rotated and in position, the scanning will start again. the process will keep looping, until the whole scanning cycle finished. the rotate speed will not be fast. it will be the normal speed to rotate a rod.

Thanks Enthalpy for your information and suggestion Please advice the minimum length that can be measured by your suggestions Besides that, i will like to check with you that is it possible to provide me websites for the above techniques that you mention. So that i can have better understanding for it. Thanks

There will be a sensor place on top of the rod. So after scanning the area, i will rotate the rod 1 degree and continue scanning on a new area. So i have to control the stepper motor to rotate the rod in either clockwise or anticlockwise direction. Therefore , i need to know the amount of torque needs

Hi actually I'm looking for a stepper motor and a driver for my Project. I have most of the specs needed but still left with an important factor which is torque. I have to use a stepper motor to turn a aluminum rod which is 320mm for Length and 28mm for diameter in one direction. I do not know the Formulae to calculate the torque with only the dimension. Please kindly advice the formulae needed for the calculation. Thanks

Basically i'm still at the research stage( might not be using x-ray methods), and i have yet to access any X- ray equipment. And i have just confirmed that i have to measure both surface and embedded micro-crack. Besides x-ray, please kindly advice do you have any better suggestion for the measurement

Sorry for not updating the post. There is changes for the project. Now, i just need to find way to measure micro- crack on the sample. studio-> the micro-crack is on a aluminum rod sample. it is about length 310 mm, diameter 25 mm louis wu-> i need to measure both surface and embedded micro-crack on the aluminum sample. Currently, i only can think of X-ray methods. But, there is only little material regarding this technical on the websites. Is there any suggestion for me or any review for me to read up? Thanks

Actually, have not been brief with the budget matter. i was just being told to look for ways to measure micro-crack length. But i think most probably, i think they will ask me to use the equipments which are available in the lab. By the way, what do u mean the access to the specimen. I will be testing the sample at 100 to 110 degree Celsius. thanks

Hi, i'm a electrical student but recently i have been task to do a assignment which is material science related. I don't have any background for that, so i have quite a number of problem for it. My assignment is to measure crack length ( micro-crack length / very small crack length) for aluminum at HIGH TEMPERATURE. I have read up some methods example like using ultrasonic, DC potential, x -ray and so on. But the problem is i do not know which method is effective and simple. Is that any suggestion or information for me to read up. thanks