The Charpy testing machine shown in Figure P14-46 consists of a weight (19 lb) o

Question

The Charpy testing machine shown in Figure P14-46 consists of a weight (19 lb) on the end of an arm (12 lb).

Material to be tested is clamped at the bottom, and the weight is raised, released, and allowed to break the test material.

Determine the energy absorbed by the test material if the initial and final positions of the arm are as shown.

Please show all work for credit.

The Chary testing machine shown in Figure P14-46 consists of a weight (19 lb) on the end of an arm (12 lb). Material to be tested is clamped at the bottom, and the weight is raised, released, and allowed to break the test material. Determine the energy absorbed by the test material if the initial and final positions of the arm are as shown.

Explanation / Answer

centre of mass of (arm+bloack sys) = ((12lb*27/2inch) + (19lb*(27+3)inch ) / (12lb+19lb) =23.61 inch from pivot

initial vertical distance of Centre of mass from pivot = 23.61cos60 = 11.805 inch

final vertical distance of CoM from pivot = 23.61cos10 = 23.25 inch

change in vertical distance = 23.25 inch - 11.805 inch = 11.45inch

applying work energy theorem, we have

energy lost = mg(h_initial)-mg(h_final) = energy abserbed = m*g*1.25 = (19lb+12lb)*11.45 = 355in-lb

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