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1、 实现汽车轻量化的关键因素为了提高车辆的燃油经济性和车辆变速的快捷性，就要降低车辆重量。实现汽车轻量化的关键是在车身的制造中大量使用轻型材料，如铝合金、复合材料、高分子材料、具有表面镀层不导电有机保护层的板料等，而难于用电焊对这些材料进行良好联接，且车辆及工程机械等机械产品所处的工况是恶劣的振动状态，疲劳失效是连接破坏的基本普遍现象，所以它的联接设计和工艺就要求更高以满足疲劳寿命和疲劳强度提高的迫切需求，虽然自冲铆接疲劳强度较点焊高，但继续提高其疲劳强度有重要的现实意义。In order to improve the promptness of vehicle fuel economy and
2、 vehicle speed, to reduce vehicle weight. Automobile lightweight is the key to the extensive use of lightweight materials in the production of car body, such as aluminum alloy, composite materials, polymer materials, has a surface coating is not conductive organic covering layer of sheet metal, etc.
3、, and difficult to use welding for these materials with good connection 1, and vehicles and engineering machinery and other machinery products are state of the vibration of the working condition is bad, the fatigue failure is the basic common connection failure, so its connection design and process
4、requires higher fatigue life and fatigue strength to meet the urgent demand, while the impact riveting fatigue strength is relatively high spot welding, but we will continue to increase its fatigue strength has important practical significance. 自冲铆接技术是采用一个铆钉连接两个或更多部件的方法，它实行冲铆一次完成。半空心铆钉自冲铆接工艺的铆接过程铆钉在
5、冲头的作用下，穿透上层板料，在凹模和铆钉外形共同作用下空心铆钉尾部在下层金属中张开形成喇叭口形状。自冲铆接除了可连接上述点焊所难于连接的材料外，自冲铆接和点焊相比还具有许多点焊所不具备的优点：能连接不同材料，能和粘接复合连接，无发光，发热少，疲劳强度较高，快捷等。Since a riveting technology is to use a method of rivet connection of two or more components (see figure 1), it implements the rivet at one time. Half from hollow rivet
6、 riveting process of rivet riveting process under the action of the punch, penetrates the upper plate, the die shape under the action of common hollow rivets and rivet tail open formation in the lower metal bell shape. Since the flush riveted in addition to the above spot welding can connect the out
7、side material is difficult to connect, since the riveting and welding compared also has many advantages: what spot welding does not have to connect different materials, and adhesive compound connection, no light, less heat, high fatigue strength, fast, etc. 图1空心铆钉自冲铆接接头剖面图From figure 1 hollow rivet
8、riveting joint section 1自冲铆接疲劳破坏方式1 since the riveted joint fatigue failure mode 自冲铆接的疲劳扩展最易在铆接孔处扩展，且在宏观上裂纹扩展方向垂直于载荷方向，且裂纹宏观方向通过铆接孔中心，在裂纹扩展末期的瞬断时形成剪切唇，剪切唇与载荷成大约45o，如图2（a）所示，这其实是由于强度不足所致。Since flush riveted fatigue most easily spread in the rivet hole expansion, and on the macroscopic crack propagati
9、on direction is perpendicular to the loading direction, and through the macro direction of crack riveting holes center, formed in the crack propagation when the end of the transient breaking shear lips, shear lips and load into about 45 o, as shown in figure 2 (a), it is due to insufficient strength
10、. （a）(a) （b）（c）(b) (c) 图2自冲铆接板料的疲劳破坏Figure 2 punching riveting sheet metal fatigue failure 有的时候自冲铆接疲劳裂纹不在铆接孔发生，而有可能在铆接孔附近靠近铆钉头部的地方萌生和扩展，这主要由于铆钉在受载时会对板料有一个弯曲作用，如图2（b）所示。在有的时候，比如自冲铆接和粘接复合连接时，或材料缺陷情况下，疲劳萌生和扩展还可能发生在板料的其他部位，如图2（c）所示。Sometimes from riveting fatigue crack does not occur riveting holes, and
11、 possible near the rivet hole near the rivet head initiation and propagation, this is mainly because of the rivet when loading of bending sheet metal has a role, as shown in figure 2 (b). In sometimes, such as the riveting and adhesive composite connections, or material defects, the fatigue initiati
12、on and extension may also occur in other parts of the sheet metal, as shown in figure 2 (c). 2自冲铆接微裂纹的产生2 since the riveting micro cracks 铆钉可用钢材或硬铝等制作，一般经热处理来适当提高其韧、硬度，这主要取决于被铆接材料特性如强度、硬度、厚度等。被铆接的材料常有钢板、铝板或铝合金、塑料、铜或铜合金、高分子材料及复合材料等，一般其硬度不能太高，否则铆钉将难刺穿上板料，酱油若采用更高硬度的铆钉，但这样铆钉在刺入板料和张开时易开裂，且增大了刺入力。Rivets a
13、vailable steel or hard aluminum production, usually by heat treatment to improve its toughness and hardness appropriate, depending on is riveting material properties such as strength, hardness, thickness, etc. By riveting material is steel, aluminum or aluminum alloy, plastic, copper or copper alloy
14、s, high polymer material and composite material, etc., generally the hardness can not too high, otherwise the rivet will be difficult to put on the sheet, if USES the higher hardness of the rivet, but such rivets in Pierce plate and easy to crack, when I opened and increases the Pierce force. 由于铆钉刺进
15、板料时，板料内部强度、硬度、结构、相分布、原子结合力不均，晶粒、晶界性状不一等原因导致板料的铆钉孔孔壁有毛刺、微裂纹，这些将是导致自冲铆接失效的重要扩展源。Because the rivet in sheet metal, sheet metal strength, hardness, internal structure, phase distribution, uneven atomic bonding force, grain, grain boundary character different causes of sheet metal rivet distributed wall
16、have burr, micro cracks, these will be important extended source leading to the invalid since the punching riveting. 下面阐述裂纹不在铆接孔中产生的情况。金属中常见的有面心立方晶格、体心立方晶格、密排六方晶格等多种结构，它们具有多种滑移系和滑移方向，晶体是各向异性的。在其受力时可沿着受载最大或最弱的、抗力最小的晶面和晶向滑移，矿车在每一次滑移时晶面和晶向都有可能不同，这样就有可能导致产生侵入沟、挤出脊、晶格畸变或位错堆积等缺陷，导致出现微裂纹。Here in this paper
17、, the crack of rivet hole is formed in. Metal face centered cubic lattice, are so common in body centered cubic lattice, close the six-party lattice and various structures, they have a variety of slip system and sliding direction, crystals are anisotropic. In its maximum stress along when loading or
18、 crystal of the weakest, least resistance to slip, and at each slip crystal when the wafer is likely to be different, so it may lead to invade the ditch, extrusion ridge, lattice distortion and dislocation pile up defects (see figure 3), resulting in micro cracks. Figure 3 metal surface extrusion ri
19、dge and intrusion groove 由于材料在成形时温度高低不是很均匀、化学成分也不可能非常均匀（如钢中的碳元素）、表面和内部散热不均、化学成分偏析或偏聚也不均匀等原因，可能导致多种晶体结构同时存在，不过可能有一种或几种结构为主，况且材料一般都是含有多种元素，则原子间作用力或键的作用力将不同，其对内、外界环境和作用载荷改变而应力的变化也不同，酿酒设备这也将导致最薄弱处出现微裂纹；每种结构、成分的机械性能（如硬脆度、强度等）和形状、结构就不同，受载时材料内部的微观部分的受力肯定不一样（如应力集中等）；那么由以上各原因，经过反复不断的受载则位错或微裂纹将在最薄弱处发生。Because
20、 material in shape when the temperature is not very uniform, chemical composition could not very uniform (such as the carbon steel), uneven surface and internal heat, chemical composition segregation, or partial is uneven, could lead to a variety of crystal structures exist at the same time, but may
21、 have one or more of the following structures is given priority to, besides material is generally contain a variety of elements, the force of atomic inter-atomic forces or key will be different, its internal and external environment and load change and the stress change is different, this will also
22、lead to the weakest place in micro cracks; Each structure, the composition of the mechanical properties (such as brittleness, intensity, etc.) and shape, the structure is different, loading the material microscopic part of the internal force must be different, such as stress concentration, etc.); So
23、 by all reasons mentioned above, after repeated loading is dislocation or micro crack will occur at the weakest point. 一般金属材料都是多晶体构成的，如果结晶时温度不太均匀、散热不均匀、冷却不均匀或其他添加元素、杂质干扰等情况，金属内可能出现两种或多种晶格，微观受载不均就位错增加而出现微裂纹。每种晶格分别存在一个个小晶体内，这样一些小晶体常排列方向各异，各小晶体间以不规则的、畸变的结构连接，形成晶界或亚晶界，晶界或亚晶界强度和硬度较高17，但其方向、排列、结构、强度等各异，且存
24、在位错，在受到交变载荷、冲击载荷、循环载荷、受力不均匀、应力集中等情况时，由于变形不协调、不均匀或附加载荷等，相对较弱的晶界和亚晶界可能发生更大的位错，或小孔洞，甚至破裂成微裂纹；也可能因小晶体内的微观或显微局部强度不够，当载荷长时间作用时，某些小缺陷就不断扩展成微裂纹，然后微裂纹经很多次扩展就穿晶破裂。Generally is composed of polycrystalline metal materials, if the crystallization temperature is not uniform, the uneven heat dissipation, cooling u
25、neven or add other elements, interference of impurities, etc., within may appear two or more metal lattice, uneven microstructure under load in place increases with the micro cracks appear wrong. Each period of small crystal lattice, respectively, is so small crystal orientation of each different, o
26、ften among small crystals with irregular connection, the distortion of the structure, formation of grain boundary or the grain boundary and grain boundary or the grain boundary strength and hardness is taller. 17, but its direction, arrangement, structure and strength of each different, and there is
27、 a fault, under alternating load, impact load and cycle load, force is not uniform, stress concentration, and so on and so forth, due to uneven deformation coordination, or additional load, such as grain boundary and the boundary of relative weakness may be greater dislocation, or small holes, even
28、burst into micro cracks; May also be because of the small crystals in the micro or microscopic local strength is not enough, when the load for a long time, some small defects have been extended to micro cracks, micro cracks and through many times extension is transgranular fracture. 金属材料内部常有其他金属或非金属
29、元素。如钢材中添加的碳、硅、硫、磷、铬、镍等等元素，这些元素往往固溶于基体中（如在钢材中这些元素会固溶于铁晶格中形成固溶体）或形成金属化合物等，且铝合金中可能有、S等相，铜合金中可能有、等相，还可形成金属化合物如渗碳体等17，载荷在微观不均，位错增加，微裂纹将在薄弱处产生；由于化学成分不完全均匀，各种成分在进行物理化学变化时所处的条件也不完全毫无差别，这些相可能同时存在，且可能方向、位置及形状等较为杂乱，微观受载不均，位错堆积，微裂纹将在薄弱处产生；而且比如常用的退火、正火的钢材由于化学元素是否均匀、是否偏聚偏析、热处理加热快慢、加热是否均匀、降温速度、降温是否均匀等影响可能导致材料中同时存在
30、铁素体、珠光体、渗碳体等各种相、结构，而各种相的强度、硬度、韧性、伸长率等不一，这样当材料受到外载时，在微观中的每个相的各个部分的微观变形及受力就不一样，这使得最薄弱处出现微裂纹；且由于加温、降温等在材料内部和外部差别不一等情况，可导致材料内部应力大小不一，甚至出现有的地方是拉应力而有的地方是压应力，且可能应力大小差别较大，薄弱处也将出现微裂纹；在应力集中或局部受力超过相的强度极限等情况下，相特别是其尖端可能破裂或者和相邻的相之间产生更长更宽的位错以及压破相邻的相，而后出现微裂纹；如渗碳体等硬脆相在应力集中和局部过载时易脆断，或者珠光体等较强韧相压破相邻的弱相，而出现微裂纹；以及在晶界原子结构
31、畸变处累积位错，这样晶界处可能产生微裂纹，特别是那些局部的尖锐的板条状渗碳体；且由于金属材料成形时的相变和温度改变不均等可能造成应力集中或初始位错等。所有以上情况经反复加载就成了微裂纹。Metal material often has other metallic or non-metallic elements inside. Such as adding of carbon steel, silicon, sulfur, phosphorus, chromium, nickel and so on elements, these elements are often fixed disso
32、lved in the matrix (e.g., these elements in steel will be formed in the solid dissolves in iron lattice solid solution) or metal compounds, etc., and aluminum alloy might be alpha, theta and S phase, there may be alpha, the delta in the copper alloy, beta phase, also can form metal compounds such as
33、 cementite 17, uneven load at the micro, dislocation increases, the micro cracks in the weak place; Due to incomplete homogeneous chemical composition, various elements in the physical and chemical changes of the conditions is not entirely without difference, may exist at the same time, the phase an
34、d the possible direction, position and shape more cluttered, the uneven microstructure under load, the dislocation accumulation, micro cracks in the weak place; Commonly used steel annealing, normalizing and such as uniform due to the chemical elements, whether partial poly segregation, heat treatme
35、nt heating speed, heating is uniform, cooling speed, cooling and uniform effect may lead to material exist in ferrite, pearlite and cementite phase, structure, and various phase have different strength, elongation, toughness and hardness, so when the material under external load, each phase in the m
36、icrostructure of the microscopic deformation and stress of all parts is different, making it the weakest micro cracks appeared; And due to the material such as heating, cooling, internal and external difference is differ, and so on and so forth, internal stress can lead to material sizes, and appear
37、ed in some places even and in some places is compressive stress, tensile stress and stress size difference is bigger, weak micro cracks will also appear; In stress concentration and ultimate strength of local stress exceeds phase, phase especially the tip may be broken or between adjacent phase and
38、is longer and wider dislocation crushed adjacent phase, then the micro cracks appeared; Such as cementite hard brittle phase in the stress concentration and local overload brittle broken, broken or more strength pearlite phase pressure adjacent weak phase, and micro cracks appeared; Atomic structure
39、 and the grain boundary distortion cumulative dislocation, the micro cracks may be produced that grain boundary, especially those local sharp board strips cementite; And because the metal material forming the phase change and temperature change when inequality may cause stress concentration and the initial dislocation, etc. All of the above situation after repeated loading is a micro crack.