The main parameter that influences the bending strength of timber from tropical hardwood is the slope of grain. Although, in the grading rules, a specific threshold value is given, in these hardwoods, the global slope of grain is very difficult to quantify by visual assessment. The slope of grain measured after testing gives a better indication, but still it can only poorly describe the Hankinson relations. By rewriting the Hankinson relations, the slope of grain can be determined from the bending strength test values and from the MOE test value, both in combination with the density values and constants derived by non-linear regression analysis. These two values correlate very well, and the average value is designated as the theoretical slope of grain. With the theoretical slope of grain, five test samples of the tropical wood species okan were evaluated, and slope of grain values of 0.3 were observed, where 0.1 is the limit value. Because all pieces passed the visual grading method as applied in practice, slope of grain values should be incorporated in the strength class assignment test program, when these qualities cannot be ruled out for coming on the market. The (dynamic) modulus of elasticity can be used to evaluate the occurrence of the desired range of slope of grain values in the test samples.

影响热带硬木木材弯曲强度的主要参数是谷物的坡度。尽管在分级规则中给出了特定的阈值，但是在这些硬木中，通过视觉评估很难对谷物的整体坡度进行量化。经过测试后测得的谷物的斜率可以更好地说明问题，但仍然只能很好地描述汉金森关系。通过改写汉金森关系，可以根据弯曲强度测试值和MOE测试值，以及密度值和非线性回归分析得出的常数，来确定晶粒的斜率。这两个值具有很好的相关性，并且将该平均值指定为晶粒的理论斜率。随着谷物的理论斜率，对五个热带木种冈的测试样品进行了评估，观察到的谷值斜率为0.3，其中极限值为0.1。由于所有部件均通过了实际应用的视觉分级方法，因此当不能排除这些品质时，应在强度等级分配测试程序中纳入晶粒度的斜率。（动态）弹性模量可用于评估测试样品中晶粒值的期望斜率范围的出现。