buletinul institutului politehnic din iaşi - Universitatea Tehnică ...

More documents

Recommendations

Info

198 Ovidiu Niţă et al. rejection of the piece. Therefore, it is particularly important that, in addition to plotting FLD, to establish a relationship of interdependence between maximum stamped parts deformation values and the parameters imposed by rejection criteria (Banabic et al., 2005; Altmeyer et al., 2012). In the literature are presented several experimental methods used to determine the deformation limits (Marciniak et al., 2002; Ramir et al., 2012). One of the methods that deserve a special attention is the method called after Kobayashi (Banabic et al., 1992). Together with his colleagues, Kobayashi found, after analyzing the influence of deformation of work piece on surface roughness, that, the appearance of necking coincides with a sharp increase in surface roughness. This sudden increase of surface roughness is used, by Kobayashi, as a criterion for the occurrence of localized necking. To define this moment, in the deformation processes, is necessary to measure surface roughness at different stages of deformation and develop a chart with roughness variation depen<strong>din</strong>g on major strain ε1. Based on the method developed by Kobayashi and his team, we wanted to establish, using the tensile method, a mathematical relationship between thin sheets surface roughness and the deformation of analyzed material. 2. Preparing an Conducting the Experiments For this approach we have conducted a series a tensile test which were aimed to obtain a different numbers of deformation stages for each material analysed. For the tensile experiments we took into account three of the most common used metallic sheets produced in Romania. Thus, in the experimental research we used rectangular specimens cut from thin sheets of the following materials: steel (wide strip steel B2), brass (CuZn37) and aluminium (Al 99.5%). In order to determine the number of experimental tests and, of course, to determine the number of samples necessary to meet the proposed approach, we resorted to a factorial plan. Given that the ultimate goal of the entire process is to make a chart that will reflect the changes of specimen surface roughness depen<strong>din</strong>g by deformation, the tensile force is considered the main parameter to be change during the test. Thus, we used five different levels of the force generated by the universal test machine (Table 1). Nr. Crt. 1 2 Factor Cod Table 1 Factors of influence Factor level 1 2 3 4 5 6 Lamination direction A 6 0 0 30 0 45 0 60 0 75 0 Tensile force (FkN) B 6 F1 F2 F3 F4 F5 90 0 F6
Bul. Inst. Polit. Iaşi, t. LVIII (LXII), f. 4, 2012 199 Another aspect that was taken into account for evaluating the behaviour of material is the lamination direction of blanks. Thus, six different directions to the direction of rolling were taking into account for the tests: 0 0 , 30 0 , 45 0 , 60 0 , 75 0 and 90 0 (Table 1). In conclusion, for the specific experimental tensile tests of the study two factors were considered the main influential factors of the system. Should be noted that, for conducting the experimental research we used the universal test machine WDW-50E and the strain rate was considered constant at 10mm/min. Also, the measurements of the surface roughness were undertaken using TAYLOR HOBSON-Surtronic25. Both experimental planning and data processing was made in Minitab v.15 (trail version). In Fig. 1 are captured two specimens in various stages of deformation. From the images we can, easily, see the direction of localized necking or how the rupture is propagate. a b Fig. 1 – Specimens subjected to tensile test: a – aluminium specimen; b – brass specimen. Since the first phase of the research was found that, from all of the three types of material studied, steel and brass specimens showed the most pronounced elongation compare with tensile force applied to the sample. In aluminium specimens case, necking and material failure occurred very early and elongation value stood at less than a third of the elongation recorded by brass or steel. 3. Experimental Results 3.1. Thin Sheets Deformation Capability in Relation to Lamination Direction The aspect that stood out even during the first phase of experimental tests was that the lamination direction has a significant influence on the deformation capability of specimens. For example, in Fig. 2 are illustrated the characteristic diagrams, obtained from the tensile test, for specimens orientated at 0 0 and 90 0 degrees orientation to main rolling direction. As can be seen from Fig. 2,
Page 1:
BULETINUL INSTITUTULUI POLITEHNIC D
Page 5 and 6:
Page 7:
VICTOR COTOROS şi EMIL BUDESCU, As
Page 10 and 11:
ALEXANDRU RADU, CONSTANTIN PANĂ an
Page 13 and 14:
Page 15 and 16:
Bul. Inst. Polit. Iaşi, t. LVIII (
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39:
Page 42 and 43:
30 Daniel Dragomir-Stanciu and Mari
Page 44 and 45:
32 Daniel Dragomir-Stanciu and Mari
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61:
Page 64 and 65:
52 Ionel Oprea and low viscosity ar
Page 66 and 67:
54 Ionel Oprea COP PT Puterea speci
Page 68 and 69:
56 Ionel Oprea 8. GWP - global warm
Page 70 and 71:
58 Ionel Oprea suplimentari, cum ar
Page 72 and 73:
60 Răzvan Florin Barzic et al. Cur
Page 74 and 75:
62 Răzvan Florin Barzic et al. 3-
Page 76 and 77:
64 Răzvan Florin Barzic et al. 3.
Page 78 and 79:
66 Ionel Ivancu et al. the second s
Page 80 and 81:
68 Ionel Ivancu et al. a b Fig. 4 -
Page 82 and 83:
70 Ionel Ivancu et al. Gut J.A.W.,
Page 84 and 85:
72 Ion Zabet and Graţiela-Maria Ţ
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
82 Victor Pantilie et al. many rese
Page 96 and 97:
84 Victor Pantilie et al. industria
Page 98 and 99:
86 Victor Pantilie et al. Another i
Page 100 and 101:
88 Victor Pantilie et al. At the en
Page 102 and 103:
90 Victor Pantilie et al. Tang X.,
Page 104 and 105:
92 Alexandru Radu et al. Furthermor
Page 106 and 107:
94 Alexandru Radu et al. Spark timi
Page 108 and 109:
96 Alexandru Radu et al. Fig. 3 - B
Page 110 and 111:
98 Alexandru Radu et al. 4. The bes
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127:
Page 130 and 131:
118 Eugen Rusu et al. in PM emissio
Page 132 and 133:
120 Eugen Rusu et al. also be used
Page 134 and 135:
122 Eugen Rusu et al. Fig. 3 - Maxi
Page 136 and 137:
124 Eugen Rusu et al. Fig. 6 - HC e
Page 138 and 139:
126 Eugen Rusu et al. Pe lângă ce
Page 140 and 141:
128 Adrian Sabău et al. arguments
Page 142 and 143:
130 Adrian Sabău et al. The energy
Page 144 and 145:
132 Adrian Sabău et al. during fue
Page 146 and 147:
134 Adrian Sabău et al. 11 T ⎛ 0
Page 148 and 149:
136 Adrian Sabău et al. No experim
Page 150 and 151:
138 Adrian Sabău et al. calculated
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160: Bul. Inst. Polit. Iaşi, t. LVIII (
Page 163: Bul. Inst. Polit. Iaşi, t. LVIII (
Page 166 and 167: 154 Marius Receanu et al. where: qr
Page 168 and 169: 156 Marius Receanu et al. In Fig. 2
Page 170 and 171: 158 Marius Receanu et al. the ambie
Page 173 and 174: BULETINUL INSTITUTULUI POLITEHNIC D
Page 184 and 185: 172 Mariana Lupchian Propulsion eng
Page 186 and 187: 174 Mariana Lupchian Fig. 1 - The p
Page 200 and 201: 188 Costică Atanasiu et al. comput
Page 202 and 203: 190 Costică Atanasiu et al. γ= ε
Page 204 and 205: 192 Costică Atanasiu et al. The sa
Page 206 and 207: 194 Costică Atanasiu et al. Fig. 1
Page 208 and 209: 196 Costică Atanasiu et al. elasti
Page 212 and 213: 200 Ovidiu Niţă et al. aluminium
Page 214 and 215: 202 Ovidiu Niţă et al. a b Fig. 5
Page 216 and 217: 204 Ovidiu Niţă et al. căreia ac
Page 218 and 219: 206 Ovidiu Niţă and Vasile Braha
Page 226 and 227: 214 Marian Teodor Popescu et al. 2.
Page 228 and 229: 216 Marian Teodor Popescu et al. Sp
Page 230 and 231: 218 Marian Teodor Popescu et al. Th
Page 242 and 243: 230 Victor Cotoros and Emil Budescu
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
Page 283 and 284:
Page 285 and 286:
Page 287 and 288:
Page 289 and 290:
Page 291 and 292:
Page 293 and 294:
Page 295 and 296:
Page 297 and 298:
PC Cell calibration Bul. Inst. Poli
Page 299 and 300:
Page 301 and 302:
Page 303 and 304:
Page 305 and 306:
Page 307 and 308:
Page 309 and 310:
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
Page 317:
show all

buletinul institutului politehnic din iaşi - Universitatea Tehnică ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?