ASTM E647-00 and ISO 7539-6 are the appropriate standards, if that is what you are looking for.

There are two main issues in dealing with the mixed mode fatigue (or fracture problems). The first one is the loading fixture. Depending upon the specimen geometry that you choose (CT or TPB for example), you should have an appropriate loading fixture to induce mode mixity. You might get some help from literature on designing the fixture (often you might not get ready made fixture from the market and you have to design & fabricate on your own). The second issue is with crack length measurement. Potential drop methods (DCPD for example) has been successfully used for mixed mode problems. You may buy a standard pulsed DCPD from market (Matelect for example). If your test frame offers an additional strain transducer and software provides a provision to directly use the DCPD system, then you can use the system on the fly (modern dynamic test frames come with this feature). In case you are using an old system and such direct use of DCPD is not available, then you can use the DCPD as stand alone and have to measure the crack lengths intermittently. By the way, you have to calibrate the DCPD system prior to use and refer to any standard literature (or the DCPD product manual) for how to go about it.

Hope this helps.

@Sivaprasad, thank you very much for the answer.

Mixed mode crack growth can be studied also using specimens fabricated such that crack plane/ orientation is inclined to the loading axis.

I agree with Dr. Sasikala....this is could be another way to study mixed mode fatigue/fracture. The problem, however, with this approach is that if you want to pre-crack the specimen (usually a fatigue pre-crack is growth normal to the loading axis), it is difficult since the notch is already at an angle. Nevertheless, some people adopt this method. Irrespective of whether you use an angled notch specimen or a fixture design that would introduce mixed mode, you require crack measurement procedure as posted earlier...