热振耦合环境TC4钛合金铆接结构振动疲劳对比试验研究

Experimental study on vibration fatigue of TC4 titanium alloy riveted structure in thermal vibration coupling environment

钛合金材料在飞机结构设计中有着广泛的应用,在恶劣的振动和热耦合环境中容易发生热振耦合疲劳破坏,振动疲劳破坏严重影响飞机的飞行安全。为了获得热振耦合环境下较优的钛合金结构设计细节形式,设计了热振耦合振动疲劳试验件和试验系统,在150℃温度条件下进行了TC4钛合金材料蒙皮+不同结构形式支撑和不同铆钉形式(半圆头铆钉和平头抽芯铆钉)铆接试验件进行振动疲劳试验。对试验结果数据统计归纳、对比,得出:同结构类型试验件,宽度相同、铆钉(抽钉)数量相同,平头抽钉连接试验件固有频率相对较高;而试验件宽度相同、铆钉类型相同、铆钉数量不同,铆钉数较多的试验件固有频率较高;半圆头铆钉连接件破坏多数表现为铆钉脱落,抽芯铆钉连接件破坏表现为蒙皮裂纹;抽芯铆钉相比半圆头铆钉连接件,其振动疲劳寿命较长;试验分别用6倍铆钉直径间距和4倍铆钉直径间距抽芯铆钉连接结构作对比,6倍铆钉直径间距试验件振动疲劳寿命较长。这些试验结论可以作为飞机结构设计中薄壁结构设计的重要参考。

Titanium alloy materials are widely used in aircraft structures.Thermal vibration coupling fatigue failure is easy to occur in harsh thermal vibration coupling environment.These fatigue failure threaten the aircraft safety.For obtaining better structure detail of thin-walled structure,the thermal vibration coupled vibration fatigue test pieces and test system were designed,and the vibration test of TC4 titanium alloy skin+support structure with different forms of and different rivets(semicircular head rivet and pull core rivet)was carried out at 150℃.The results of vibration fatigue test are summarized and compared:For the pieces with the same forms structure,same width and same rivet number,the nature frequency of the connection structure of pull core rivets is higher than that of semicircular head rivet.For the pieces with the same forms structure、same width and same rivet type,the nature frequency of the connection structure with bigger rivet number is higher than that with smaller rivet number.Most of the damage of the semicircular head rivet connector is the fall off the rivet,and the failure of the pull core rivet connector is skin crack.The vibration fatigue life of pull core rivets connector is longer than that of semicircular head rivets connector.The connection structure of pull core rivets with 6 times rivet diameter spacing and 4 times rivet diameter spacing were tested for comparison,and it is shown that the vibration fatigue life of the test piece with 6 times rivet diameter spacing is longer.These results can be used as an important reference for titanium alloy thin-walled structure of aircraft.