4.1 Differentiate between polymorphism andisomerism.

Polimorfisme adalah dimana dua atau lebih struktur kristal yang mungkin sebagai

bahan yang diberikan komposisi. Isomer adalah suatu polimer rumus molekul yang

sama – yang berarti bahwa mereka terdiri dari jumlah yang sama dari jenis atom

yang sama – tetapi memiliki struktur atau pengaturan yang berbeda dalam ruang.

4.2 On the basis of the structures presented in this chapter, sketch mer structures for the following polymers: (a) polyvinyl fluoride,(b) polychlorotrifluoroethylene, and (c) polyvinyl alcohol.

4.30 The density and associated percent crystallinityfor two polytetrafluoroethylene materialsare as follows:_ (g/cm3) Crystallinity (%)2.144 51.32.215 74.2(a) Compute the densities of totally crystallineand totally amorphous polytetrafluoroethylene.(b) Determine the percent crystallinity of aspecimen having a density of 2.26 g/cm3.

4.31 The density and associated percent crystallinityfor two nylon 6,6 materials are asfollows:_ (g/cm3) Crystallinity (%)1.188 67.3

1.152 43.7(a) Compute the densities of totally crystallineand totally amorphous nylon 6,6.(b) Determine the density of a specimenhaving 55.4% crystallinity

7.29 A cylindrical specimen of aluminum havinga diameter of 0.505 in. (12.8 mm) and a gaugelength of 2.000 in. (50.800 mm) is pulled intension. Use the load–elongation characteristicstabulated below to complete problemsa through f.

7.30 A specimen of ductile cast iron having arectangular cross section of dimensions4.8 mm _ 15.9 mm (_ _ in. _ _ in.) is deformedin tension. Using the load-elongation datatabulated below, complete problems athrough f.

7.64 (a) A 10-mm-diameter Brinell hardness indenterproduced an indentation 1.62 mm indiameter in a steel alloy when a load of 500kg was used. Compute the HB of this material.(b) What will be the diameter of an indentationto yield a hardness of 450 HB when a500 kg load is used?

7.68* Below are tabulated a number of RockwellB hardness values that were measured on asingle steel specimen. Compute average andstandard deviation hardness values.

9.26 Tabulated below are data that were gatheredfrom a series of Charpy impact tests on aductile cast iron:

9.27 Tabulated as follows are data that were gatheredfrom a series of Charpy impact tests ona tempered 4140 steel alloy:

9.33 The fatigue data for a brass alloy are givenas follows:Stress Amplitude Cycles to(MPa) Failure310 2 _ 105

223 1 _ 106

191 3 _ 106

168 1 _ 107

153 3 _ 107

143 1 _ 108

134 3 _ 108

127 1 _ 109

(a) Make an S–N plot (stress amplitude versuslogarithm cycles to failure) using thesedata.(b) Determine the fatigue strength at 5 _105 cycles.(c) Determine the fatigue life for 200 MPa.

9.35 The fatigue data for a ductile cast iron aregiven as follows:Stress Amplitude Cycles to[MPa (ksi)] Failure248 (36.0) 1 _ 105

236 (34.2) 3 _ 105

224 (32.5) 1 _ 106

213 (30.9) 3 _ 106

201 (29.1) 1 _ 107

193 (28.0) 3 _ 107

193 (28.0) 1 _ 108

193 (28.0) 3 _ 108

(a) Make an S–N plot (stress amplitude versuslogarithm cycles to failure) using thedata.(b) What is the fatigue limit for this alloy?(c) Determine fatigue lifetimes at stress amplitudesof 230 MPa (33,500 psi) and 175MPa (25,000 psi).(d) Estimate fatigue

9.47 The following creep data were taken on analuminum alloy at 400_C (750_F) and a constantstress of 25 MPa (3660 psi). Plot thedata as strain versus time, then determinethe steady-state or minimum creep rate.Note: The initial and instantaneous strain isnot included