. Agricultural engineering; a text book for students of secondary schools of agriculture, colleges offering a general course in the subject and the general reader. Agricultural engineering. Tension Fig. 255. A sketch illustrat- ing a tensile stress. -ten- Equilibrium of Moments. The forces acting upon a body are in equilibrium when the algebraic sum of their moments about any one point is equal to zero. Stress. A stress is the resistance offered by a rigid body to an external force tending to change its form. A rope suspending a weight is under stress. If a section of the rope be taken at any
. Agricultural engineering; a text book for students of secondary schools of agriculture, colleges offering a general course in the subject and the general reader. Agricultural engineering. Tension Fig. 255. A sketch illustrat- ing a tensile stress. -ten- Equilibrium of Moments. The forces acting upon a body are in equilibrium when the algebraic sum of their moments about any one point is equal to zero. Stress. A stress is the resistance offered by a rigid body to an external force tending to change its form. A rope suspending a weight is under stress. If a section of the rope be taken at any point, the force exerted by the part of the rope on one side of the section on the part on the other side to prevent the rope from part- ing or breaking, is termed the stress at a section. The word strain is often used incorrectly for stress, but strain is the change of form pro- duced by a stress. Simple stresses are of three kinds, sile, compressive, and shearing. Stresses are measured in pounds or tons in countries using English units. The pound is the more often used. Tensile stresses are those tending to pull the object or material in two, or to stretch it. A rope suspending a weight is under a tensile stress. A tie rod in a truss is subjected to tensile stress. Compressive Stresses. Compressive stresses are those tending to crush the object or ma- terial, as the load that is placed on a column or on a foundation. Shearing Stresses. Shearing stresses are those tending to slide one portion c^t f i , -h—,t t^—,„ of the material over another, or _,. ,_- Fig. 257. 777777777777777 Compre as ion Fig. 256. A sketch illustrat- ing a compres- sive stress. A sketch illustrat- ing a shearing stress. when there is a tendency to cut. The stress on riveted joint is a good example. Complex Stresses. Complex stresses are those formed by a combination of simple stresses. The stresses in beams are usually Please note that these images are extracted from scanned page images t
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