I have work piece of metal to forge in hot forging process. The dimensions of work piece before and after is given. I want to calculate how much load is required in to deform the work piece to know dimension. Thanks in advance
Hi Abdul,
As per my point of you, if any unknown dimension you have for your work piece condition so
Step no. 1: volume of work piece before forging = volume of work piece after forging. With the help of this you can find unknown dimensions.
Step 2: minimum initial force required = yield stress of material × initial cross section area.
Find same considering final area of work piece.
Step3: than take avg of both forces to find avg force (F)min.
Step 4: Find actual force required (F)act = (F)min/efficiency of forging. Generally varies between 50-60%
Another method (F)act = yield stress × final area (1+(3×co efficient of friction bet die and workpiece material× final radius of component/ 4×final height of component)
Hope this will be helpful to you...
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Please Sir. If you want, follow the steps showed in the attached file.
Excuse that the text is in spanish.
For calculate the load is very important to take the maximum area (flash included), that the part presents in normal direction to the forging load.
Abdul,
Sumeet and Daniel offer some good basics and rules of thumb. You can estimate the force needed by the flow stress of the material times the finished area and add in a friction factor.
In the ideal case (perfect die lubrication, the flow stress independent of strain and strain rate, isothermal dies, etc.), the forging load is simply the area times the flow stress.
In real cases, the friction between the die and forging will markedly increase the force needed--it can stall the forging press if the lubricity is low, the area is high and the forging is thin. Sumeet provides an empirical estimate of this effect (1+3fxR/4t). Or if the coefficient is not known use a factor of 0.3-0.5.
Also in hot forging the dies are often much cooler than the material being forged. The surfaces in contact with the dies are chilled and undergo very little deformation (since the flow stress of alloys are temperature dependent). Similarly, the flow stresses of real materials are dependent on the strain rate (which varies from center to surface). This flow stress can depend on the structure/grain size--which is a function of the forging parameters.
Elastic-plastic modeling of these processes are computationally complex and the suite of material and friction properties are rarely available. I hope the case you describe and be handled as an ideal forging with a friction fudge factor.
Refer to the NPTEL website's metal forming course in mechanical engineering, presented by Dr.R.Chandramouli of SASTRA University.
You will find the detailed derivation for calculating the load during forging.
Here is the link : http://www.nptel.ac.in/courses/112106153/
How can I know the load and strain rate distribution for case of Duplex SS grade F55 for wall thickness 70 mm as valve body with size 2 inches . how it will different from 3 inches or 4 inches valve if there is any modeling of stress -strain distribution ?
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