Tham khảo tài liệu 'asm metals handbook - desk edition (asm_ 1998) episode 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | ữ ữ. selữtied on ĨMSi of ul1ijn te strength QÍ maleriiĩ fl. mm in. Wm jL ._ J r I z .n I n 0 DEn J D TdUỄítd 0. inm lữ 50 Ibl 17 mm 10 40 II .1 . 5 lu ID rnm la i 1 I MlHEad 0 1 baais dF uHimatry Mrạngtlì rji Tialorini ft. S01O 750 mmuỉiốso iri I tí M mm í I 0 0 3Smm 17 in I 3B mm 1 in. I Id 0 D. wlwtad on batis of oltimãie sưeíìglli ũl mnEerial R. 75 1q 25Õ Him 3 la 10 in. M Fig. 37 Typical fatigue life test specimens. a Torsional specimen. b Rotating cantilever beam specimen. c Rotating beam specimen. d Plate specimen for cantilever reverse bending. e Axial loading specimen. The design and type of specimen used depend on the fatigue testing machine used and the objective of the fatigue study. The test section in the specimen is reduced in cross section to prevent failure in the grip ends and should be proportioned to use the upper ranges of the load capacity of the fatigue machine . avoiding very low load amplitudes where sensitivity and response of the system are decreased . Test Methods Testing machines are defined by several classifications the controlled test parameter load deflection strain twist torque etc. the design characteristics of the machine direct stress plane bending rotating beam etc. used to conduct the specimen test or the operating characteristics of the machine electromechanical servohydraulic electromagnetic etc. . Machines range from simple devices that consist of a cam run against a plane cantilever beam specimen in constantdeflection bending to complex servohydraulic machines that conduct computer-controlled spectrum load tests. Axial and rotating-bending machines are most commonly used for fatigue tests. Surface preparation of specimens is critical in all fatigue life tests. Axial Fatigue Life Tests. ASTM E 466 specifies specimens to be used in axial fatigue tests. The specific dimensions of specimens depend on the objective of the experimental program machine to be used and available material. ASTM
