1. Describe the mechanism of crack propagation for both ductile and brittle modes of fracture. 3. Define fracture toughness.
6. Briefly describe the phenomenon of crazing.
8. Define fatigue and specify the conditions under which it occurs. 9. From a fatigue plot for some material, determine (a) the fatigue lifetime, and (b) the fatigue strength.
QUESTIONS AND PROBLEMS
Example Problem 9.1； Design Example 9.1
9.3 What is the magnitude of the maximum stress that exists at the tip of an internal crack having a radius of curvature of 2.5 × 10-4 mm and a crack length of 2.5 × 10-2 mm when a tensile stress of 170 MPa is applied?
9.3求曲率半径为2.5 × 10-4 mm和裂纹长度2.5 × 10-2 mm的内部裂纹尖端最大应力幅值，施加拉伸应力为170 MPa。
9.16 A specimen of a 4340 steel alloy having a plane strain fracture toughness of 45 MPa
m is exposed to a stress of 1000 MPa. Will this
specimen experience fracture if it is known that the largest surface crack is 0.75 mm long? Why or why not? Assume that the parameter Y has a value of 1.0.
9.16 4340钢合金试件平面应变断裂韧性为45 MPa
m，受应力1000
MPa，如果已知最大的表面裂纹长0.75 mm，试件会断裂吗？为什么会断裂或不断裂？假设参数Y 的值为1.0。
9.26 Tabulated below are data that were gathered from a series of Charpy impact tests on a ductile cast iron:
Temperature (℃) Impact Energy (J) 温度 -25 -50 -75 -85 -100 -110 -125 -150 -175 冲击功 124 123 115 100 73 52 26 9 6 (a) Plot the data as impact energy versus temperature.
(b) Determine a ductile-to-brittle transition temperature as that temperature corresponding to the average of the maximum and minimum impact energies.
(c) Determine a ductile-to-brittle transition temperature as that
temperature at which the impact energy is 80 J.
9.26 下表中收集的数据是从一系列球铁却贝冲击试验得到的： (a)把数据作图，冲击功对温度
(b)确定最大和最小冲击功的平均值对应的韧性—脆性转变温度。 (c)确定对应于冲击功为80 J的温度作为塑性—脆性转变温度。
9.33 The fatigue data for a brass alloy are given as follows: Stress Amplitude Cycles (MPa) 310应力幅值 Failure 2×105失效循to 环数 223 191 168 153 143 134 127 1×106 3×106 1×107 3×107 1×108 3×108 1×109 (a) Make an S–N plot (stress amplitude versus logarithm cycles to failure) using these data.
(b) Determine the fatigue strength at 5 × 105 cycles. (c) Determine the fatigue life for 200 MPa.
9.33给出黄铜疲劳数据如下：
(a)用这些数据作出S–N曲线图（应力幅值对失效循环的对数作图）。 (b)确定循环数为5 × 105时的疲劳强度。 (c)确定200 MPa时的疲劳寿命。
9.44 List four measures that may be taken to increase the resistance to fatigue of a metal alloy.
9.44列出四个可采取的增加金属合金疲劳抗力的措施。
Design Problems 设计题
9.D6 (a) For the thin-walled spherical tank discussed in Design Example 9.1, on the basis of critical crack size criterion [as addressed in part (a)], rank the following polymers from longest to shortest critical crack length: nylon 6,6 (50% relative humidity), polycarbonate, polyethylene terephthalate, and polymethyl methacrylate. Comment on the magnitude range of the computed values used in the ranking relative to those tabulated for metal alloys as provided in Table 9.2. For these computations, use data contained in Tables B.4 and B.5 in Appendix B. (b) Now rank these same four polymers relative to maximum allowable pressure according to the leak-before-break criterion, as described in the (b) portion of Design Example 9.1. As above, comment on these values in relation to those for the metal alloys that are tabulated in Table 9.3.
9.D6 (a) 在设计举例9.1中讨论的薄壁球罐，根据临界裂纹尺寸判据[如(a)部分所讨论的]将下列高分子按照临界裂纹从最长到最短排列：尼龙6,6 (50% 相对湿度)，聚碳酸酯、聚乙烯、对苯二酸盐(或酯)、聚甲基丙烯酸甲酯。相对于表9.2所列的金属合金评价计算值的数量级范围。使用附录B中表B.4 and B.5的数据进行计算。
(b) 现在根据破坏前泄露的准则，按最大允许压力排列这四种高分子，如同设计举例9.1的(b)部分，同上，与表9.3列出的金属合金的值相比，评价这些值。
第13章 材料的类型及应用
IMPORTANT TERMS AND CONCEPTS 重要术语和概念 Abrasive (ceramic) Alloy steel Brass Bronze Calcination Cast iron Cement 磨粒（陶瓷） 合金钢 黄铜 青铜 煅烧 铸铁 水泥 可锻铸铁 非铁合金 普通碳钢 高温陶瓷 比强度 Devitrification Ductile (nodular) iron Ferrous alloy Glass–ceramic Gray cast iron High-strength, low-alloy (HSLA) steel Stainless steel Temper designation White cast iron Whiteware Wrought alloy 不锈钢 热处理制度 白口铁 白色陶瓷 锻造合金 晶化 球墨铸铁 铁基合金 玻璃-陶瓷 灰铸铁 高强低合金钢 Malleable iron Nonferrous alloy Plain carbon steel Refractory (ceramic) Specific strength
Learning Objectives
1. Name four different types of steels and, for each, cite compositional differences, distinctive properties, and typical uses.
2. Name the four cast iron types and, for each, describe its