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首页> 外文会议>39th aerospace mechanisms symposium >Space Shuttle Orbiter Atlantis Liquid Oxygen Pre-Valve Detent Roller Cracking Investigation
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Space Shuttle Orbiter Atlantis Liquid Oxygen Pre-Valve Detent Roller Cracking Investigation

机译：航天飞机轨道飞行器亚特兰蒂斯液氧预阀棘轮开裂研究

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During routine inspections of the Space Shuttle's Main Propulsion System Liquid Oxygen (LO_2) pre-valve, the mechanism provided to maintain the valve in the open position was found cracked. The mechanism is a Vespel roller held against the valve visor by a stack of Belleville springs. The roller has been found cracked 3 times. All three instances were in the same valve in the same location. There are 6 pre-valves on each orbiter, and only one has exhibited this problem. Every-flight inspections were instituted and the rollers were found to be cracked after only one flight. Engineers at Marshall Space Flight Center, Johnson Space Center, and Kennedy Space Center worked together to determine a solution. There were several possible contributors to the failure: a misaligned visor, an out-of-specification edge with a sharp radius, an out-of-specification tolerance stack up of a Belleville spring stack that caused un-predicted loads on the Vespel SP-21 roller, and a dimple machined into the side of the roller to indicate LO_2 compatibility that created a stress riser. The detent assembly was removed and replaced with parts that were on the low side of the tolerance stack up to eliminate the potential for high loads on the detent roller. After one flight, the roller was inspected and showed fewer signs of wear and no cracks.
机译：在对航天飞机的主推进系统液氧（LO_2）预阀进行例行检查时，发现将阀保持在打开位置的机构破裂。该机构是一个Vespel滚轮，通过一堆Belleville弹簧紧靠着阀瓣。发现滚筒破裂3次。所有三个实例均位于同一位置的同一阀门中。每个轨道飞行器上有6个前置阀，只有一个显示出此问题。进行了每次飞行检查，仅一次飞行后，发现滚筒破裂。马歇尔航天飞行中心，约翰逊航天中心和肯尼迪航天中心的工程师共同努力，确定了解决方案。造成这种故障的原因可能有多种：遮阳板未对准，半径较大的边缘超出规格范围，Belleville弹簧堆栈超出规格公差范围，从而导致Vespel SP-上的负载意外21个滚子，并在滚子侧面加工了一个凹痕，以表明LO_2的兼容性会产生应力上升。拆卸了制动组件，并更换了公差叠层低端的零件，以消除在制动辊上产生高负载的可能性。一次飞行后，对滚筒进行了检查，并显示出较少的磨损迹象和无裂纹。

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