What are the difficulties in translation of phrasal verbs? The following matters can be encountered

99. What criteria for linguistic classification of PhUs do you know?
The central problem is the criteria of distinguishing them from free word groups. Shakhmatov and Fortunatov singled out the following criteria: stability, idiomaticity, function and context.
Criterion of stability means that the components of phraseological units follow each other in the definite constant order, there can be no substitution for them. This view point has been criticized, since many phraseological units lack absolute stability and admit variations.
Criterion of idiomaticity is based on the lack of motivation. Vinogradov singled out the degrees of idiomaticity: a phraseological unit is based on a phraseological fusion, which is non-motivated at all, e.g. to kick the bucket. Free word groups can be perceived through the metaphorical or metonymical meaning, e.g. to wash one’s dirty linen in public. Phraseological collocations are stable set word groups which still have a clear motivation but strictly limited vocabulary, e.g. to shrug one’s shoulder. This view point has been criticized, for there is no distinct boarder line between phraseological units and word groups on one hand and word groups and phraseological collocations – on the other.
Criterion of function presupposes that phraseological units are grammatically and stylistically inseparable, in a sentence they behave like a single syntactic form, e.g. He wrote it in a long run. This view point has been criticized, as the same phraseological units may be inseparable in 1 type of syntactic context, but quite separable in another, i.g. take care - care was taken.
According to the criterion of context phraseological units have a fixed meaning (unlike free word groups). Амосова subdivided them into phraseological units and phraseological idioms. Phraseological units are 2 member groups in which 1 of the members has a specific meaning dependent on the 2nd member (small hours = early).
Fortunatov and Shakhmatov paid much attention to the syntactic analysis of phraseological units. Their classification is known as structural.
Vinogradov’s classification is synchronic. It is based on the motivation of the unit, i.e. the relationship between the meaning of the whole and the meaning of its component parts. The degree of motivation is correlated with the rigidity, indivisibility and semantic unity of the expressions. It suggests 3 types of phraseological units: phraseological fusions, phraseological units, phraseological combinations.