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Fatigue Life Design of Mechanical Structure
- The keywords of fatigue do not include ( )
- The correct statement is as follows ( )
- Damage tolerance design is ( )
- Fatigue behavior and life predictions are more complicated at high temperatures because of ( )
- The feature of excess deformation does not include ( )
- Fine grain size in room temperature usually means ( )
- The feature of impact or dynamic loading does not include ( )
- Non-detective inspection techniques include ( )
- A mean stress may relax fully or partially due to ( )
- The elastic stress concentration factors are often obtained by ( )
- Which is the feature of small crack ( )
- The number of beach marks is related to ( )
- Which is not the characteristic of real fatigue Limit ( )
- The hysteresis loops at high temperatures are ( )
- In general, fatigue resistance for a given metal in an air environment tends to ( ) as the temperature increases
- The concepts of linear elastic fracture mechanics (LEFM) for crack growth include ( )
- The following mechanical properties are usually obtained from monotonic tension test( )
- For Infinite-life design, the correct statement is as follows ( )
- Understanding of fracture toughness include ( )
- The characteristics of ductile fracture include ( )
- The S-N behavior can be affected by many factors ( )
- Some necessary points about the estimation of crack growth life with mean stress must be again noted ( )
- Understanding of strain approach includes ( )
- The reason about fatigue failure usually occurring on the surface ( )
- The characteristics of fatigue include ( )
- Cyclic stabilization is usually reasonably complete within 10 to 40 percent of the total life. ( )
- Plane strain fracture toughness is 对 material property and regardless of thickness. ( )
- Twice the value of plastic stress is regardless of the plastic relaxation. ( )
- Higher frequencies typically allow more environmental interaction to occur. ( )
- A larger fraction of life for crack growth occurs at lower stress levels. ( )
- The number of beach marks is the same for different fracture surfaces. ( )
- Stress relaxation is the same as the cyclic softening. ( )
- Most materials exhibit an decrease in fatigue resistance with increasing temperature. ( )
- Stress ratio of -1 means fully reversed load . ( )
- Fine-grain materials tend to give lower fatigue resistance, while coarse-grain materials give higher creep resistance. ( )
- A crystallite is a small or even microscopic crystal which forms. ( )
- Crack growth rates are initially high but decrease, with the decreasing crack length. ( )
- Only the plastic portion of the strain-life curve is modified to account for the surface finish effects. ( )
- The mechanism of crack initiation in the very high cycle region has been roughly understood. ( )
- The deformation of the material at the notch root is often inelastic involving plastic strain. ( )
A:Cyclic loading B:Deformation C:Progressive D:Crack
AI参考:正确答案是D:Crack。关键词疲劳不包括裂缝(D),疲劳的关键词包括周期性载荷(A)、变形(B)和渐进性(C)。因此,本题的正确答案是D。'
A:Life can be ignored in unstable growth region B:Paris law for near threshold region C:larger effect in stable crack growth D:Crack growth rate is faster in near threshold region
答案:is odd function.
A:Anti-crack measures B:Nominal stress C:Crack cannot occur D:Nominal strain
AI参考:答案:C推理过程:损伤容限设计就是设计使得结构或构件在规定的服役期中,在预期的交通荷载、环境因素和制造安装等因素的作用下,不发生或只发生轻微裂纹、裂痕或小的损伤,不致影响其安全使用。因此答案为C。'
A:Creep deformation B:Time-dependent process C:Cycle-dependent process D:Complex interaction between creep and fatigue
AI参考:在高温下的疲劳行为和寿命预测由于蠕变和疲劳之间的复杂相互作用而变得更加复杂。因此,正确答案是D:复杂相互作用。高温下的疲劳行为和寿命预测涉及到多种因素,包括蠕变、疲劳、温度、材料特性等。这些因素之间存在复杂的相互作用,因此预测高温下的疲劳行为和寿命需要更复杂的分析和计算。选项A、B和C与高温下的疲劳行为和寿命预测没有直接关系。'
A:Plasticity B:The most common failure mode C:Maximum tensile stress criterion D:Yielding
AI参考:正确答案是D:Yielding。Excess deformation feature不包括屈服(yielding),屈服是材料发生塑性变形,但仍保持原有平衡状态的现象。选项A和B是塑性变形的一些特征,选项C是最大拉应力准则的一种表现形式。因此,正确答案是D。'
A:Low fatigue strength B:Higher fatigue strength C:Short fatigue life D:High crack growth rate
答案:Higher nucleation rate with lower growth rateAI参考:正确答案是B:更高的疲劳强度。选项中只有B选项与“细粒度”有关,因为细粒度通常意味着材料具有更高的强度和耐久性,所以选项B“更高的疲劳强度”是正确的答案。其他选项A、C、D都与“细粒度”无关。'
A:Fracture B:Lower tensile toughness/ ductile C:Short time/ period D:High strain rate
AI参考:正确答案是 B:Lower tensile toughness/ ductile。冲击或动态加载的特征不包括较低的拉伸韧性和塑性(B选项)。冲击或动态加载通常会导致材料产生裂纹并迅速扩展,因此需要材料具有较高的拉伸韧性和塑性以抵抗这种破坏。选项A(Fracture)和D(High strain rate)都与冲击或动态加载有关,而选项C(Short time/ period)则与加载时间有关,与冲击或动态加载的特征不符。因此,正确答案是B选项。'
A:Drilling a hole B:Ultrasonic testing C:Fatigue testing D:Microscope observation
AI参考:正确答案是D:Microscope observation。非探测检查技术包括显微镜观察。选项A、B、C都是探测检查技术,选项D是正确的。'
A:Plastic deformation B:Environment C:Surface condition D:Residual stress
AI参考:正确答案是D: Residual stress(残余应力)。选项A是塑性变形,选项B是环境因素,选项C是表面条件,这些都是可能导致应力变化的物理现象,但不是本题中答案的来源。残余应力是可能导致应力变化的主要因素,所以答案是D。这个概念可以应用在材料科学、机械工程、建筑等领域。'
A:Fracture surface observation B:Fatigue test C:Strain - life D:Finite element method
答案:is primarily caused by the burning of fossil fuels by humans.
A:Constant threshold value B:Discontinuity C:Regardless of crack size D:Naked-eye visible
答案:pensionAI参考:正确答案是C:Regardless of crack size。小裂缝的特征是无论裂缝大小都存在,因此选项C“无论裂缝大小”是正确的。选项A“恒定的阈值”、选项B“不连续性”和选项D“肉眼可见”都与小裂缝的特征不符。'
A:Surface condition B:Defect C:Environment D:Slip
AI参考:正确答案是C:环境。海滩上的标记数量与环境有关,而与表面状况、缺陷和滑坡无关。因此,选项C是正确答案。'
A:High temperature B:Fully reversed uniaxial fatigue test C:Standard, highly polished, unnotched specimen D:Group method
答案:All of the above.
A:Discontinuous B:Easy C:Constant D:Regular
A:Decrease first, and then Increase B:Increase first, and then decrease C:Increase D:Decrease
AI参考:In general, fatigue resistance for a given metal in an air environment tends to **increase first, and then decrease** as the temperature increases. 答案为B。在一般情况下,在空气环境中给定金属的抗疲劳性能随着温度的升高而增加,然后减少。这个答案基于对材料科学和金属疲劳的基本理解。在高温环境下,金属的强度和弹性会增加,这有助于提高其抗疲劳性能。然而,随着温度的进一步升高,金属的强度和弹性会逐渐降低,这会导致抗疲劳性能下降。因此,答案为B:在温度逐渐上升的过程中,疲劳抗力首先增加,然后减少。'
A:Initial crack size B:Stress intensity factor C:Stress concentration D:Stain
AI参考:正确选项为:AB。线性弹塑性断裂力学(LEFM)中的概念包括初始裂纹尺寸(A)和应力强度因子(B)。选项C和D与断裂力学不相关。因此,正确选项为AB。'
A:Percent reduction in area B:Modulus of elasticity C:Fatigue limit D:Ultimate tensile strength
AI参考:通常,以下力学性能可以从单轴拉伸试验中得到:B:弹性模量 D:拉伸极限强度。所以,选项B和D是正确的。选项A和C并不常见于拉伸试验中。因此,正确选项为B:Modulus of elasticity 和 D:Ultimate tensile strength。'
A:Especially for notched members B:The oldest criterion C:Mason-Coffin model D:Fatigue limit is difficult to define
AI参考:对于无限寿命设计,正确的陈述如下:C: Mason-Coffin model(选项C)Mason-Coffin模型是一种用于评估疲劳寿命的经典模型,特别适用于缺口构件的设计。因此,选项C是正确的。选项A、B、D都与无限寿命设计的核心概念不符。选项B的“The oldest criterion”可能指的是最古老的标准或准则,但与无限寿命设计的概念不相关。选项D的“Fatigue limit is difficult to define”虽然提到了疲劳极限的定义问题,但并不是无限寿命设计的核心要点。'
A:Depends on material, strain rate, environment, thickness and crack length B:Critical value of K C:K at the last cycle of a fatigue fracture D:Used to obtain the critical crack size for fracture
A:Low strength/ high ductile metals B:Micro-void coalescence (dimpling) C:Substantial plasticity D:High energy absorption
A:Frequency B:Surface condition C:Size effect D:Microstructure
AI参考:对于这个问题,正确的选项应该是【D:Microstructure】。microstructure指的是微观结构,它包括了材料中的晶粒大小、晶粒形状、晶界数量、相组成等因素。这些因素都会影响材料的导热性能,因此会影响S-N行为。而选项A、B、C虽然也与材料性能有关,但它们并不是影响S-N行为的直接因素。因此,选项D是正确答案。'
A:What value of ΔK will cause fracture? B:Does corrosion or temperature play an important role? C:How do we integrate this equation? D:Which crack growth rate equation should be used?
A:Strain approach is very suitable for fatigue of notched members. B:The strain-based approach to fatigue problems is widely used. C:Strain has a good quantity for correlating with low cycle fatigue. D:Strain is hardly measured.
AI参考:正确选项为【ABCD】理解疲劳问题的方法包括:应变法非常适合于缺口构件的疲劳,基于应变的疲劳问题解决方法被广泛应用,应变是用来与低循环疲劳相关的良好量度,应变很难被测量。因此,选项ABCD都是正确的理解疲劳问题的方法的内容。'
A:Inelastic deformation is easier at the surface B:Surface condition is smooth C:Slip steps are able to develop on the surface D:The stress or strain on the surface is usually maximum
A:Monotonic tension B:Constant or variable amplitude C:Repeated loading D:Crack nucleation/growth
AI参考:正确选项是:B:Constant or variable amplitude疲劳的特征包括:持续或变化的振幅(B选项正确)。疲劳通常是由于材料在周期性应力或应变的作用下,材料内部产生的微小裂纹逐渐扩展的结果。因此,疲劳的特征之一就是裂纹的萌生和扩展。而选项A中的单调拉应力不是疲劳的主要特征,选项C中的重复加载也是疲劳的一种表现形式,但不是其主要特征。选项D中的裂纹扩展也不是疲劳的主要特征,它更多地与材料脆性有关。因此,B选项是正确的答案。'
A:错 B:对
A:对 B:错
A:对 B:错
AI参考:答案是B:错。塑料应力与塑料松弛的乘积是恒定的,因此塑料应力增加两倍,塑料松弛并不随之增加,所以乘积是不变的。因此,这个判断题是错误的。"
A:错 B:对
A:错 B:对
AI参考:答案:B.对。 根据题目中的描述,裂纹增长的大部分生命发生在较低的应力水平下,因此选项B“对”是正确的。"
A:错 B:对
AI参考:答案是B:对。海滩划痕的数量对于不同的骨折表面应该是相同的。这个结论是根据生物学、医学、考古学等多个领域的科学研究得出的。海滩划痕是用来判断骨组织是否存在骨折或断裂的标志之一,其数量和位置在不同骨折表面上应该是相同的。因此,这个判断题的答案是B,即“对”。"
A:错 B:对
A:对 B:错
A:对 B:错
AI参考:答案:B:错。 负号通常表示反向,因此负1的压力负载不是完全相反的,而是反相或负值。因此,此题是错误的。"
A:对 B:错
AI参考:答案:B:错。 根据题干中的描述,细粒材料通常具有较低的疲劳抵抗力和较高的蠕变抗力,而粗粒材料通常具有较高的蠕变抗力。因此,选项B是正确的,而选项A是错误的。"
A:错 B:对
AI参考:答案:B:对。 晶粒(cristallite)是指晶体形成的小的或微细的晶体。因此,这是一个正确的选项。"
A:对 B:错
AI参考:答案是B:错。 根据题目描述,crack growth rates(裂纹增长速率)的初始值很高,但随着裂纹长度的减小而减小。这表明裂纹增长速率会随着裂纹长度的减小而降低,而不是持续增加或保持不变。因此,这个说法是错误的,答案为B。"
A:错 B:对
A:对 B:错
A:错 B:对