MM Math

For the preceding problem, the labor rates for the welder and fitter are $35.00/hr and $25.00/hr, respectively, and the equipment cost rate = $10.00/hr, which includes the cost of the new two-position fixture. All three rates include applicable overheads. Power during arc-on time = 6,000 W, and cost of electricity = $0.128/kWH. Determine the cost of each weldment produced in the operation

$6.19/pc

A cylindrical billet is 200 mm long and 100 mm in diameter. It is reduced by indirect extrusion to a 30-mm diameter. Die angle = 90°. In the Johnson equation, a = 0.8 and b = 1.5. In the flow curve for the work metal, strength coefficient = 250 MPa and strain-hardening exponent = 0.15. Determine the ram force.

8,592,256 N

A 30-mm-thick plate made of low carbon steel is reduced to 25 mm in one pass in a rolling operation. As the thickness is reduced, the plate widens by 4%. Yield strength of the steel = 174 MPa, and tensile strength = 290 MPa. The entrance speed of the plate = 77 m/min. Roll radius = 300 mm, and rotational speed = 45 rev/min. Determine exit velocity of the plate.

89 m/min

After 20 minutes of cutting steel on a lathe using 0.1mm/rev feed and 2 mm cut depth, a cemented carbide bit will remove ___ mm3 of steel volume.

945741

A 4-in-thick aluminum slab is 10 in wide and 100 in long. It is reduced in one pass in a two-high rolling mill to a thickness = 3.5 in. The roll rotates at a speed = 12 rev/min and has a radius = 20 in. The aluminum has a strength coefficient = 25,000 lb/in2 and a strain hardening exponent = 0.20. Determine power required to accomplish this operation

265 hp

In Example 29.4 of Groover, the welder works alone, performing not only the welding but also loading and unloading the parts. Suppose a fitter is used in the work cycle to load the starting parts and unload the weldment, and a two-position fixture is installed so that the welder and fitter can work simultaneously. The fixture is designed to index (rotate) between the two positions at the end of each work cycle; indexing time = 0.15 min. The fitter performs the work handling elements, and the welder performs all elements related to welding and changing electrodes. The welder and fitter take 30 min of rest breaks during the 8-hr work shift. The "Arc-on-time", measured as a fraction of an 8 hour work shift, is:

29.6%

A work part with starting height h = 100 mm and diameter = 55 mm is compressed to a final height of 50 mm. During the deformation, the relative speed of compressing the part = 300 mm/s. Determine the strain rate at h = 100 mm

3

A high-speed steel tool is used to turn a steel work part with length = 350 mm and diameter = 75 mm. The parameters in the Taylor equation are n = 0.13 and C = 75 (m/min) for a feed of 0.4 mm/rev. The operator and machine tool rate = $36.00/hr, and the tooling cost per cutting edge = $4.25. It takes 3.0 min to load and unload the work part and 4.0 min to change tools. Determine the cutting speed for minimum cost.

42.8 m/min

A high-speed steel tool is used to turn a steel work part with length 350 mm and diameter 75 mm. The parameters in the Taylor equation are n = 0.13 and C = 75 (m/min) for a feed of 0.4 mm/rev. The operator and machine tool rate = $36.00/hr, and the tooling cost per cutting edge = $4.25. It takes 3.0 min to load and unload the work part and 4.0 min to change tools. Determine the cutting speed for maximum production rate. The cost, per unit, is:

48.9 m/min $5.44/pc

The following data were collected during tool life tests in turning: (1) when v = 100 m/min, T = 9 min; (2) when v = 75 m/min, T = 35 min. Tool life for a speed of 110 m/min is:

5.7 min

Austenitic stainless steel has a flow curve with strength coefficient = 1200 MPa and strain-hardening exponent = 0.40. A tensile test specimen with gage length = 100 mm is stretched to a length = 145 mm. Determine average flow stress that the metal experienced

577

Cemented carbide inserts are used to turn a part with length = 21.0 in and diameter = 4.0 in. Feed = 0.015 in/rev. The parameters in the Taylor equation are n = 0.25 and C = 800 (ft/min). The operator and machine tool rate = $45.00/hr, and the tooling cost per cutting edge = $2.00. It takes 2.5 min to load and unload the work part and 1.50 min to change inserts. Determine cycle time.

6.67 min/pc

A cylindrical part is upset-forged in an open die. The starting diameter is 50 mm and height is 40 mm. Height after forging is 30 mm. Coefficient of friction at the die-work interface is 0.20. Yield strength of low-carbon steel is 105 MPa; its strength coefficient is 500 MPa and strain-hardening exponent is 0.25. Determine the force in the operation at a height of 35 mm,

760,989 N

A 30-mm-thick plate made of low carbon steel is reduced to 25 mm in one pass in a rolling operation. As the thickness is reduced, the plate widens by 4%. Yield strength of the steel = 174 MPa, and tensile strength = 290 MPa. The entrance speed of the plate = 77 m/min. Roll radius = 300 mm, and rotational speed = 45 rev/min. Determine minimum required coefficient of friction that would make this rolling operation possible

0.129

Determine the value of the strain-hardening exponent for a metal that will cause the average flow stress to be 75% of the final flow stress after deformation

0.333

A hot working operation is carried out at various speeds. The strength constant = 30,000 lb/in2 and the strain‑rate sensitivity exponent = 0.15 in the strain rate sensitivity equation. Determine the flow stress if the strain rate is 0.01/sec

15 ksi