. The strength of materials; a text-book for engineers and architects. 28 5-25 128 6-50 80 2-80 477 4-05 223 5-30 126 6-55 79 2-85 460 4-10 217 5-35 124 6-60 77 2-90 444 4-15 212 5-40 121 6-65 76 2-95 430 4-20 207 5-45 118 6-70 74 30 418 4-25 202 5-50 116 6-75 73 3-05 402 4-30 196 5-55 114 6-80 71-5 3-10 387 4-35 192 5-60 112 6-85 70 315 375 4-40 187 5-65 , 109 6-90 69 3-20 364 4-45 183 5-70 1 107 6-95 68 For other test loads, the hardness numbers are proportionalto those in the table. Within certain limits the Brinell Hardness Number of a 404 THE STRENGTH OF MATERIALS material gives a very fa
. The strength of materials; a text-book for engineers and architects. 28 5-25 128 6-50 80 2-80 477 4-05 223 5-30 126 6-55 79 2-85 460 4-10 217 5-35 124 6-60 77 2-90 444 4-15 212 5-40 121 6-65 76 2-95 430 4-20 207 5-45 118 6-70 74 30 418 4-25 202 5-50 116 6-75 73 3-05 402 4-30 196 5-55 114 6-80 71-5 3-10 387 4-35 192 5-60 112 6-85 70 315 375 4-40 187 5-65 , 109 6-90 69 3-20 364 4-45 183 5-70 1 107 6-95 68 For other test loads, the hardness numbers are proportionalto those in the table. Within certain limits the Brinell Hardness Number of a 404 THE STRENGTH OF MATERIALS material gives a very fair indication of its tensile for steels with a hardness number less than 175, theultimate tensile stress in tons per sq. in. is obtained approxi-mately by multiplying the hardness number by -23. TESTING CEMENT AND CONCRETE Tension Tests.—The form of briquette in accordancewith the Specification of the British Engineering StandardsCommittee is shown in Fig. 190, the cross-section being 1 sq. the weakest point. We have given on p. 78 the require-. FiG. 190.—Cement Briquette. ments as to tensile strength in accordance with this specifica-tion. As the strength obtained under test is found to dependupon the rate of loading, being higher for quick loading, theabove specification stipulates that the loading shall be at arate of 500 pounds per minute. A simple form of lever machine, made by W. H. Bailey& Co., is illustrated in Fig. 191. The specimen is gripped inthe shackles and the load is applied by allowing shot to fallinto the bucket, the leverage being such that the tensionapplied is fifty times the weight of the shot. The shot-hopperis provided with a valve, the operating arm of which passesover the lever, so that when the specimen breaks the supplyof shot is automatically cut off. The shot is then weighed, a THE TESTING OF MATERIALS 405 spring-balance being often used which gives readings equal tofifty times the weight of the shot, thus giving the breakin
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