Phân tích ảnh hưởng của vận tốc cắt trên máy cắt dây CNC đến ứng suất dư bề mặt của khuôn dập nguội sử dụng nhiễu xạ tia x

NGHIEN CUTU - TRAO B0\ PHAN TICH ANH Hi/dNG COA VAN T C CAT TREN MAY CAT DAY CNC D^N UNG SUAT D U B^ MAT COA KHUON DAP NGUOI SCf DUNG NHliU XA TIA X STUDY ON THE RELATION BETWEEN CUTTING SPEED AND SURFACE LAYER RESIDUAL STRESS OF COLD-FORGING MOLD AFTER CNC WIRE CUTTING MACHINING USING X-RAY DIFFRACTION Le Chi CUdng, Dang Thiin Ngon Trudng Dai hpc SU pham Ky thuat TP Hd Chi Minh TOMTAT tyng sudt dii tdn tai trin bi mat thep SKDl ditng ldm Idiudn ddp ngudi dnh hudng ldn din tuo thg cda khudn Khi gia cdng bang mdy cdt ddy CNC, vdn tic cdt cd dnh hiidng ldn din dng sudt dU Bd bdo trinh bdy kit qud nghien cdu sU liin quan gida vdn tic cdt vd dng sudt dU sd dung nhiiu xsi X quan Kit qud cho thdy van toe ldn hdn 200 xung/ms itng sudt dU co xu hiidng Sn dinh, vd chiiu ddy ldp ddc la Id nhd nhdt TU khoa: tjng sudt dU, mdy cdt ddy CNC, thep SKDl 1, nhieu xa X-quang ABSTRACT Residual stress in the surface layer of cold forging steel SKDU has significant influence t performance and duration of mold In the case of fabrication of CNC wire cutting machine, the cut speed strongly affects to the residual stress This research studies the relation between cutting speed residual stress using X-ray diffraction This result shows thatfor the speed of higher than 200pulses/ residual stress tends to remain constant, thus give the minimum thickness of recasting layer Keywords: Residual stress, CNC wire cutting machine, steel SKDll, X-ray diffraction I.DATVXNDE Thep hpp kim SKDll dUpc sfl dpng rdng rai de ldm khudn dip ngudi dp bin, dO cdng, dp dai va kha ndng chdng mai mdn tdt sau nhi|t luyen II] Ddi vdi khudn dap loai nay, bong nflt trin cdc be mat cac loai khudn dap ngupi Id mdt dang hU hdng thUdng xudt hi|n, Iam giam tudi thp cua khudn Mpt nhflng nguyen nhan chu ylu cua hiln tUpng ndy Id flng suat dU tdn tai trin bl mat cda khudn Yeu cdu cua khudn dap ngudi la vat U|u khudn phai dUdc nhilt luyen trUdc dl dat dp cdng khoang td 58 din 60HRC Do dd, sau tdi, bl mat khudn dap thudng dUpc gia cdng tinh bang mdy cat ddy dilu khienbangCNCviphUdngphj^ndygiacdngbdngtia'^ TAP CHf CO KHl VIETNAM • Sd (Thdng ndm 2013) ^ NGHIEN CUfU - TRAO D6\ Ifla dien cho chilu day vung anh hfldng nhilt thdp va khdng phu thudc vdo dp cdng cua vdt Ueu [1] Tuy nhiln, hien nay, hau het cdc c h l dp gia cdng bang may cat day thfldng dUpc xdc dinh vdi muc dich bao ddm tudi thp cua rady, tdng nang sudt va giam chi phi day rad chUa chu trpng d i n chat lupng b l mat cua san pham gia cdng Do do, vi|c xdc dinh che dp cat bang may cat ddy, ddc bilt Id van tdc cat t^ 11 vdi sd lUpng xung phdt Hinh 2.1: Hi true tga dd trin bi mat mau mdt gidy, lam cd sd cho vi|c toi Uu hda gifla lpi n h u | n kinh te vd chdt lUpng san pham cd y nghia Trong dd: E va v la md dun dan h6i va he dac bilt quan trpng anh hUdng den flng sudt dU sd Poisson TrUdng hpp khdng cd ylu cau tinh cfla khudn dap toan chinh xdc flng sudt theo phUdng phdp tuyln Hiln nay, tren t h i gidi cd nhieu phUdng vdi be mat mau, ta coi vdt lieu d trang thai flng phdp xac dinh dng sudt dU tren b l mat chi tilt suat phang, khdng cd cac thdnh phan thfl tM nhu phUdng phdp: dpc Id, cat Idp, silu am, quang cdng thflc (2.1) trd thanh: l+ V dan hdi, nhieu xa X-quang hoac neutron, [6, 8] Trong dd, phfldng phdp nhilu xa X-quang cd nhilu Uu dilm: xac dinh chinh xac flng suat, de dang tu ddng hda, raa khdng pha hfly chi tilt radu [2,4] Bai nghien cdu ndy se khdo sdt sU thay ddi cua dng sudt dU t r i n b l mat thep ldm khudn d i p ngudi flng vdi van tdc cat khdc sd dung nhieu xa X quang, td de xuat van tdc cat tdi Uu (2.2) TK+O-J Trong a Id flng suat phdn theo phUdng vi (p, dupe cho bdi: cr^ = a^ cos^ ^ + cr^ sin Itjf + cr^ sm^ ^ N O I DUNG NGHIEN CCU (2.3) Ta cd the vilt Iai, nhU sau: 2.1 Biln dang t r i n be mat mau thuC Xet he tpa dp (x,y,z) nhU hinh 2.1, dd biln dang va flng sudt dpc theo cac true lan lupt la a^, a^ a^, E^, E^ vd e^ Td ly thuylt dan hdi, ta cd mdi quan he dng suat - biln dang [3,10]: _^t,w~^o _l +v ( a - „ c o s ' ^ (2.1) - ' ' o - ( o - , + o - , ) + d„ TU dinh luat Bragg va qua bien ddi tU bifo dang mang tmh t h i sang vi tri dinh nhieu xa, ta cd: •>a-r, 2(1+ v ) t a n g , 180 E 7t 2vtanfl, 180 (rr, + o - ) + 2ft l+V V , + - ^ ^ 3 - - ( O i l +CT- +0-33) + l + V, + - — C luyen Bdng 2.1 Thanh phan hoa hoc vd CO tinh ciia thip SKDl [7, 9] Thanh phan (%) C Si Mn 1,4-1,6