为了纪念巴勃罗·罗德里格斯，本报告介绍了两项试验性初步研究的结果，这些研究调查了外部弯矩对两种类型的ASME NPS 4性能的影响。150级螺栓法兰接头:一个带焊颈法兰，一个带搭接法兰。专门设计了一个试验台，以使法兰接头承受纯弯矩。在试验过程中，将接头泄漏率、垫片接触应力分布、螺栓载荷和法兰旋转记录为施加弯矩的函数。 法兰接头在三种不同的初始螺栓应力水平下进行了测试:25、37.5和50 ksi（172、259和345 Mpa）。在整个试验过程中使用了单一类型的垫片，即初始厚度为1/16英寸的NBR/石棉板。（1.6毫米）。试验期间对两种法兰接头泄漏率的分析表明，弯矩对接头密封性的影响相对较小。还发现，当装配过程中使用较高的初始螺栓载荷时，接头能够更好地抵抗弯矩载荷。然而，施加弯矩可能会导致螺栓荷载大幅松弛，尤其是在焊接颈法兰装配时，螺栓初始应力较低，为25 ksi。 螺栓荷载松弛与垫片的永久变形有关，该变形是由弯曲力矩局部施加在垫片上的额外压缩应力引起的。如果螺栓荷载的松弛程度足够高，当接头承受反向弯矩荷载时，可能会出现严重泄漏情况。在进行的一些试验中，在四个位置测量了垫片接触应力分布，并在垫片正下方放置了一个箔式传感器。在焊颈法兰中，垫片应力分布的变化有点像承受弯矩的空心圆筒中的纵向应力。 在搭接法兰中，垫片应力分布更为复杂。还分析了垫片宽度上的应力变化。在焊颈法兰中，整个垫片宽度上的应力似乎是均匀的，而在搭接法兰中，垫片外径处存在一个高应力区。研究了在计算垫片最小接触应力时，用等效内压代替弯矩效应的问题。从与现有试验结果的比较来看，该方法似乎会给出保守的结果。 然而，对于精确的接头密封性计算来说，这可能过于简单，因为该方法没有考虑法兰刚度对垫片应力分布的影响。

Dedicated in Memory of Pablo RodriguezThis report presents the results of two experimental pilot studies that investigate the effect of external bending moments on the behavior of two types of ASME NPS 4 in. Class 150 bolted flanged joints: one with weld neck flanges, and one with lap joint flanges. A test rig has been specifically designed to submit the flanged joints to pure bending moments. During the tests, the joint leak rate, the gasket contact stress distribution, the bolt loads, and the flange rotations were recorded as a function of the bending moment applied. The flanged joints were tested under three different initial bolt stress levels: 25, 37.5 and 50 ksi (172, 259 and 345 Mpa). A single type of gasket was used throughout the tests, an NBR/asbestos sheet having an initial thickness of 1/16 in. (1.6 mm). The analysis of the leak rates of the two types of flanged joints during the tests shows that the bending moment has a relatively small effect on the tightness of the joints. It was also found that the joint better resists bending moment loading when a high initial bolt load is used during the assembly. However, substantial bolt load relaxation can result from the application of a bending moment especially in the case of weld neck flanges assembled with a low initial bolt stress of 25 ksi. Bolt load relaxation has been linked to the permanent deformation of the gasket caused by the additional compressive stress applied locally to the gasket by the bending moment. If the relaxation of the bolt loads is sufficiently high, a gross leakage condition can occur when the joint is subjected to a reverse bending moment loading. In some of the test performed, the gasket contact stress distribution was measured at four locations with a foil sensor placed directly under the gasket. In the weld neck flange the gasket stress distribution varies somewhat like the longitudinal stress in a hollow cylinder subjected to a bending moment. In the lap joint flange the gasket stress distribution is more intricate. The stress variation across the gasket width was also analyzed. In the weld neck flange, the stress seems to be uniform across the gasket width, while in the lap joint flange a highly stressed zone exits at the outside diameter of the gasket. The replacement of the bending moment effect by an equivalent internal pressure in the calculation of the minimum gasket contact stress was investigated. From a comparison with the available test results, it appears that this method will give conservative results. However, this could be too simplistic for accurate joint tightness calculations, since, this method does not take into account the effect of the flange rigidity on the gasket stress distribution.